ABSTRACT Nonlinear optical 4-aminopyridinium monophthalate (4 ...
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ABSTRACT
Nonlinear optical 4-aminopyridinium monophthalate (4-APMP) single
crystals were grown by the slow evaporation technique using methanol as
the solvent. Single crystal X-ray diffraction confirmed that the grown crystal
belonged to the orthorhombic system. The presence of functional groups
was qualitatively determined by FTIR. The optical absorption studies
revealed very low absorption over the entire visible region. The fluorescence
spectrum at 430 nm indicated blue light emission. The thermal stability of the
grown crystal was found to be approximately 197.2˚C. Microhardness
studies revealed that the hardness number was 4.89. The second harmonic
generation (SHG) efficiency of the grown crystal was found to be 1.1 times
that of KDP crystals.
Amino acid-doped sodium acid phthalate (NaAP) crystals were
successfully grown by the slow evaporation technique at room temperature.
The effect of amino acids on the growth and properties of NaAP was
investigated thoroughly. Single crystal X-ray diffraction was carried out on the
grown crystals to identify the structural and lattice parameters. The presence
of dopants in NaAP single crystals was determined qualitatively by FTIR.
The optical transparency for the doped crystals was observed using optical
absorption. The mechanical strength of the grown crystals was determined
by Vickers microhardness measurements. The SHG efficiency for the grown
crystals was determined using the Kurtz powder technique.
Nonlinear optical single crystals of diglycine barium chloride
monohydrate (DGBCM) were grown by the slow evaporation solution growth
technique from a mixture of an aqueous solution of glycine and barium
chloride in the ratio 2:1 at room temperature. The grown crystals were
characterized by various techniques such as single crystal X-ray diffraction,
FTIR, UV-Vis-NIR spectra, Vickers hardness testing, thermogravimetric
analysis, and fluorescence spectra. Their SHG efficiency was measured by
the Kurtz and Perry powder technique using a Nd:YAG laser, and the results
were discussed in detail.
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ACKNOWLEDGEMENT
First of all, I am truly grateful to my supervisor
Dr. S. Krishnan, Assistant Professor of Physics, B. S. Abdur Rahman
University, Chennai who has been tremendously cooperative throughout my
research.
My sincere thanks to the Doctoral Committee members
Dr. R. Gopalakrishnan, Associate Professor of Physics, Anna University,
Chennai-25 and Dr. S.S.M. Abdul Majeed, Professor and Head, Department
of Polymer Technology, B. S. Abdur Rahman University, Chennai for their
critical comments and suggestions for my research work.
I am thankful to Dr. I. B. Shameem Banu, Dean (School of Physical
and Chemical Sciences) and Professor of Physics, B. S. Abdur Rahman
University, Chennai.
I express my heartfelt thanks to Dr. I. Raja Mohamed, Professor and
Head, Department of Physics, B. S. Abdur Rahman University, Chennai.
I place a record of thanks to The Principal, and the management of
Sri Ramanujar Engineering College, Chennai, for giving an opportunity to
teaching as an Assistant Professor in the Department of Physics, in this
esteemed institution.
It is my great pleasure to thank Dr. G. Vinitha, Assistant Professor of
Physics, School of Basic sciences, VIT University, Chennai.
I sincerely thank to Dr. P. Samuel, Assistant Professor, Department of
Physics, Ramco College of Engineering, Palayamkottai.
I am whole heartedly thank to Mr. G.V. Vijayaraghavan, Assistant
Professor (Sel. Grade), Department of Physics, B. S. Abdur Rahman
University, Chennai, for his constant support and encouragement throughout
my research work.
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I am always thankful to Dr. R. Indirajith, Assistant Professor,
Department of physics, B. S. Abdur Rahman University, Chennai, for his
tireless and moral support throughout my research work.
I am deeply indebted to Dr. M. Basheer Ahamed, Mr. S. Sathik
Basha, Mrs. U. Majitha Parvin, Mr. Md. Sheik Sirajuddeen, Dr. S. Begam
Elavarasi, Dr. J. Thirumalai, Dr. Jahir Abbas Ahmed and all non
teaching staff, Department of Physics, B. S. Abdur Rahman University,
Chennai, for their constant encouragement and support.
I am also thankful to Mr. T. Thilak, Mr. G. Shanmuganadhan,
Mr. R. Krishnan and all research scholars in the department of physics,
B. S. Abdur Rahman University, Chennai, for their help and support rendered
towards my research work.
I am truly grateful to Dr. G. Pasupathi, Assistant Professor of Physics,
Department of Physics, A.V.V.M. Sri Pushpam College, Thanjavur.
I wholeheartedly express my immense gratitude to my beloved
parents Mr. M. Gangatharan, Mrs. G. Kanniammal, my lovable wife
Mrs. Sudha, my cute son Jr. M. S. Thamizh, my uncle Mr. S. Balamurugan
and my Lovable sisters Mrs. Mala and her gifted son
Jr. B. M. Prahatheeshwaran, and Miss. Malar for their unlimited love,
boundless affection and support and blessings.
I thankfully remember to my uncle Mr. G. Vijayamohan, who is like
my father, my aunt Mrs. V. Senthamarai, who is like my mother and his
family for their huge support and encouragement to complete my research.
I must mention the huge encouragement received from my wonderful
B. Tech IT (2010-14) students of Sri Ramanujar Engineering College.
Finally, I thank all those who helped me directly or indirectly to
complete the research work in time.
G. MARUDHU
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APPENDIX 1
BASIC CONCEPTS
A 1.1 CRYSTAL GROWTH
Crystal growth is a major stage in the crystallization process and
consists of adding new atoms, ions, or polymer strings into the characteristic
arrangement of a crystalline Bravais lattice.
A 1.1.1 Crystals
A crystal is a solid material whose constituent atoms, molecules, or
ions are arranged in an orderly repeating pattern extending in all three spatial
dimensions.
A 1.1.2 Lattice
A lattice is an array of points in space, in which the environment about
each point is the same, i.e., every point has identical surroundings to that of
every other point in the array.
A 1.1.3 Unit cell
The smallest geometric structure, which is repeated to derive the
actual crystal structure. This represents the characteristics of the entire
crystal.
A 1.2 SYMMETRY
Symmetry is a common natural occurrence and appears in art forms,
architecture, natural patterns (snowflakes, flower petals, honeycombs,
skeletons, etc.). Symmetry implies some (a) regularity, (b) proportion, and
(c) the resulting beauty.
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A 1.2.1 Point group
A representation of the ways that the macroscopic symmetry elements
(operations) can be self-consistently arranged around a single, immobile
geometric point. There are 32 unique manners in which this can be done,
and thus, there are 32 point groups.
A 1.2.2 Space group
Symmetry operations can only be combined in a finite number of ways
in three dimensions. The 230 possibilities are called space groups.
A 1.3 CRYSTAL SYSTEMS
There are seven crystal systems, as shown in Table A.1.1.
A 1.4 NUCLEATION
Nucleation is the first step in growing a single crystal from a mother
solution. This is achieved by taking the saturated solution to the
supersaturated state [133]. The formation of nuclei or embryos in the
solution is often termed the centre of crystallization. Nucleation may occur
spontaneously or may be induced artificially [134]. The fundamental process
of nucleation can be classified into two categories, homogeneous and
heterogeneous.
In homogeneous nucleation, the parent material contains no
impurities. In heterogeneous nucleation, the parent material contains
impurities. Here, the foreign particles induce crystallization within the parent
material, which is faster than homogeneous nucleation. The advantage of
heterogeneous nucleation is a short processing time to crystallization with
simplicity, as it is common to add foreign substances such as string or rock to
the solution. Heterogeneous nucleation can occur through several methods.
Some of the most typical ways are either small inclusions or cuts in the
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container, thereby providing a nucleating site for the crystal and speeding up
the growth of the crystal. To achieve a moderate number of medium sized
crystals, a container with few scratches works better.
Table A.1.1: Seven Crystal Systems
Additionally, adding small seed crystals to a supersaturated solution
can provide nucleating sites. The addition of only one seed crystal leads to a
large single crystal [135].
S.
no System
Bravais
lattice
Unit cell
Characteristics
Characteristic
symmetry
elements
1. Cubic
Simple
Body-centred
Face-centred
a = b = c
α = β = γ = 900
Four 3-fold rotation
axes (along cube
diagonal)
2. Tetragonal Simple
Body-centred
a = b ≠ c
α = β = γ = 900
One 4-fold rotation
axis
3. Orthorhombic
Simple
Base-centred
Body-centred
Face-centred
a ≠ b ≠ c
α = β = γ = 900
Three mutually
orthogonal 2-fold
rotation axes
4. Monoclinic Simple
Base-centred
a ≠ b ≠ c
α = β = 90 0 ≠ γ
One 2-fold
rotation axis
5. Triclinic Simple a ≠ b ≠ c
α ≠ β ≠ γ ≠ 900 None
6. Trigonal Simple a = b = c
α = β = γ ≠ 900
One 3-fold rotation
axis
7. Hexagonal Simple
a = b ≠ c
α = β = 900
γ = 1200
One 3-fold rotation
axis
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Some important features of the growth process are the arrangement,
the origin of growth, the interface form (important for the driving force) and
the final size. When the origin of growth is in one direction for all of the
crystals, then the material becomes highly anisotropic (different properties in
different directions). The interface form determines the additional free energy
for each crystal volume. The final size of the crystal is important for the
mechanical and physical properties [136].
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APPENDIX 2
PREPARATION METHODS
A 2.1 GROWTH METHODS FOR CRYSTALS
The growth of single and bulk crystals is classified under fundamental
physical and physicochemical mechanisms. Phase change transitions are
significant for crystal growth techniques. We have classified crystal growth
methods into three main categories.
Melt growth (growth from molten liquid to solid)
Vapour growth (growth from vapour to solid)
Solution growth (growth from liquid to solid)
We briefly describe all three crystal growth methods in upcoming papers [36,
137].
A 2.1.1 Melt Growth
Melt growth is a method of crystal growth, in which a solid is
crystallized from a molten liquid state. There are a variety of techniques to
grow suitable materials into well shaped crystals. Some growth techniques,
such as crystal pulling, zone refining, and float zone, have been thoroughly
studied for common electronic materials to not only refine but also enhance
their applicability and to apply them to new materials. Melt growth is a
technique involving crystallization through fusion and resolidification of a pure
material, where a liquid becomes a solid below its freezing point. Melt growth
is further classified into various sub-techniques, as follows:
Bridgman technique
Czochralski technique
Verneuil technique
Zone melting technique
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The leading significant factors to be considered during the growth of crystals
from melts are as follows:
Volatility or dissociability
Chemical reactivity
Melting point
The advantages of this method are as follows: [137]
No impurities found during growth process
Growth rate much greater than other methods
Commercially more familiar than ever
Has more sub techniques than ever
A 2.1.2 Vapour Growth
A suitable technique in crystal growth is the vapour phase method,
which is used in electronic and optoelectronic industries. This method can be
classified into two categories: physical vapour deposition (PVD) and chemical
vapour deposition (CVD) [137]. The simple experimental setup consists of a
closed horizontal tube with feed material and transporter. This tube is placed
between the two double zone furnaces with temperatures T1 and T2. The
transport material is deposited in the growth zone from the vapour phase.
With a further endothermic and exothermic reaction, the growth rate of the
crystallization is increased. Cadmium sulphide and cerium telluride crystals
have been grown by this method. Some of the studies that have investigated
the growth of crystals by CVD and PVD have reported SiC crystals grown by
PVD [138]. Additionally, growth and characterization of CuInTe2 crystals by
CVD have been reported [139]. The special features of this method are
modelling, mass-transport yield, productivity, and growth stability [140].
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A 2.1.3 Solution Growth
The most common method for growing crystals is the solution growth
method, which is simple and can be used to grow perfect crystals without
much difficulty. In this method, crystals are grown from solution at a
particular temperature that is not the melting point. The dissolved amount of
constituent substance crystallizes via saturation. This process can be
classified under slow cooling and slow evaporation techniques [137]. The
solution growth methods are classified according to the temperature range
and nature of solvents. The methods are below:
1. High temperature solution growth
2. Hydrothermal growth
3. Gel growth
4. Low temperature solution growth
A 2.1.3.1 High Temperature Solution Growth
In this method, a solid (molten salt/flux) is used as the solvent instead
of a liquid, and the growth occurs well below the melting point of the solute.
This technique can be applied to incongruent melting materials. Mixed
crystals of a solid solution can also be grown by the choice of optimum
growth parameters.
This technique can be used for the crystallization of oxide
compounds, which generally have high melting points as well as phase
transitions below the melting point [141, 142].
A 2.1.3.2 Hydrothermal Growth
Hydrothermal growth means that high pressure, as well as high
temperature, is used to solubilize otherwise insoluble materials, such as
quartz, calcite, alumina, and antimony sulfoiodide, in water.
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The hydrothermal technique is well suited for materials that otherwise
require high temperature crystallization because the temperature is low
during growth compared to the melting point of the material. The well-known
example is quartz, which was reported by Brice [13].
The main advantages of hydrothermal growth over solution methods are as
follows:
Growth of low temperature polymorphs of refractory materials
Suited to growing large quantities of single crystals
Prepares high quality and very homogeneous single crystals
Some of the disadvantages of this technique are as follows:
Frequent incorporation of OH- ions into the crystal, which makes them
unsuitable for many applications
Due to high pressure, it is not possible to observe the growth process
Unsuitable to be employed for preliminary exploratory materials in
research
A 2.1.3.3 Gel Growth
The growth of a variety of crystals having immense importance in
applications and theoretical studies has been achieved by the gel technique
[143]. The importance of gel growth is attributed to its simplicity and
effectiveness in growing single crystals of compounds that cannot easily be
grown by other methods. Crystal growth in gels is a promising technique for
growing single crystals of substances that are slightly soluble in water and
that cannot be grown conveniently from a melt or vapour. The gel method
has also been applied to study crystal formation in urine. Recently, crystals
of biological macromolecules (proteins) have been grown by this method.
One of the novel organic NLO materials, thiourea with quinine sulphate
dehydrate (TQS), was grown by the gel method by Lekshmi P. Nair. This
crystal exhibited 1.4 times higher NLO efficiency than KDP [54]. In recent
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years, tartarate crystals were grown by the silica gel method [144, 145].
Nonlinear optical γ-glycine crystals were the first crystals to be grown by the
gel method [146].
A 2.1.3.4 Low Temperature Solution Growth
The growth of crystals from aqueous solutions is one of the oldest
methods of crystal growth. The method of crystal growth from low
temperature aqueous solutions is extremely popular in the production of
many technologically important crystals. Low temperature solution growth is
the most widely used method for the growth of single crystals when the
starting materials are unstable at high temperatures [147]. This method is
not restricted to only water soluble materials but can also be used for
materials that are insoluble in water but can be brought into solution by using
complexes. The mechanism of crystallization from solution is governed by
the interactions of ions or molecules of the solute and solvent; these
interactions are based on the solubility of the substance and the
thermodynamic parameters of the process, including temperature, pressure
and solvent concentration [148].
The advantages of crystal growth from low temperature solution are
the ambient temperatures required and the simple and straight forward
equipment design, which provides good control to a precision of +0.01oC.
Due to the precise temperature control, supersaturation can be accurately
controlled. In general, this method involves seeded growth from a saturated
solution. The driving force, i.e., the super saturation, is achieved either by
lowering the temperature or evaporating the solvent. Additionally, the
efficient stirring of solutions reduces fluctuations to a minimum. The low
temperature solution growth technique is well suited to materials suffering
from decomposition as a melt or solid at high temperatures.
This method is widely used to grow bulk crystals, which have high
solubility and variation in solubility with temperature [149, 150]. Growth of
crystals from solution at room temperature has many advantages over other
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growth methods, even though the rate of crystallization is slow. Because
growth is carried out at room temperature, the structural imperfections in
solution grown crystals are relatively small [151]. Among the various
methods of growing single crystals, solution growth at low temperature
occupies a prominent place because of its versatility and simplicity. After
undergoing so many modifications and refinements, the process of solution
growth now yields good quality crystals that can be used for a variety of
applications.
Low temperature solution growth can be subdivided into the following
methods:
Temperature gradient method
Slow cooling method
Slow evaporation method
A 2.1.3.4.1 Temperature Gradient Method
The temperature gradient method relies on the transport of the
material from a hot region, containing the source material to be grown, to a
cooler region where the solution is supersaturated. The main advantages of
this method are as follows:
o Economy of solvent and solute
o Crystals grow at a fixed temperature
o Relative insensitivity to changes in temperature
A 2.1.3.4.2 Slow Cooling Technique
In this method, super saturation is produced by a change in
temperature usually throughout the whole crystallizer. The crystallization
process is carried out in such a way that the point on the temperature
dependence of the concentration moves into the metastable region along the
saturation curve in the direction of lower solubility. Because the volume of
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the crystallizer is finite and the amount of substance placed in it is limited, the
supersaturation requires systematic cooling. It is achieved by using a
thermostated crystallizer, and the volume of the crystallizer is selected based
on the desired size of the crystals and the temperature dependence of the
solubility of the substance. This method is mostly used for materials with
high solubility and a large positive temperature coefficient [152]. Recently,
single crystals of nonlinear optical L-lysine alanine mono hydrochloride
dihydrate were grown by the slow cooling technique [153].
A 2.1.3.4.3 Slow Evaporation Technique
The experimental setup for the slow cooling and slow evaporation
methods are almost identical. In the latter method, the saturated solution is
kept at a particular temperature and provisions are made for evaporation.
The basic apparatus (Mason jar crystallizer) is used for the solution growth
technique (Figure. A.2.1). This method is based on the concepts of solubility
and supersaturation. In this method, an excess of a given solute is
established by utilizing the difference between the rates of evaporation of the
solvent and the solute. In contrast to the cooling method, in which the total
mass of the system remains constant, in the solvent evaporation method, the
solution loses particles, which are weakly bound to other components;
therefore, the volume of the solution decreases. In almost all cases, the
vapour pressure of the solvent above the solution is higher than the vapour
pressure of the solute. Therefore, the solvent evaporates more rapidly, and
the solution becomes supersaturated. Usually, it is sufficient to allow the
vapour formed above the solution to escape freely into the atmosphere.
Typical growth conditions involve temperature stabilization to approximately
+0.005oC and rates of evaporation of a few mm3/hr. [152].
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Figure A.2.1: Mason jar crystallizer
Solution growth is the easiest, simplest and least expensive method.
The growth of crystals from an aqueous solution is one of the oldest methods
of crystal growth. This method is extremely popular in the production of
many technologically important crystals. Growth from solution is used
extensively to purify and grow single crystals of a number of inorganic,
organic and semiorganic materials. Furthermore, crystals grown from
solutions are faceted and exhibit excellent optical transparency.
High quality single crystals of NLO NaAP were grown by the slow
evaporation method, which exhibited a relative NLO efficiency 1.56 times that
of KDP [154]. Additionally, diglycine barium chloride monohydrate, a
nonlinear optical material grown by slow evaporation, exhibited SHG
efficiency 2.18 times greater than that of KDP [155]. Here, the slow
evaporated NLO crystals exhibit much higher optical transmittance, good
mechanical strength, and better thermal stability and are thus suitable for
device applications. Hence, we chose this technique to present novel
materials in this research work. This method is potentially very useful for
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growing bulk crystals of ammonium dihydrogen phosphate (ADP) and
potassium dihydrogen phosphate (KDP) [156, 157]. Much attention has been
paid to understand the growth mechanism of this process, and this was
developed by various works of scientists, such as Bennema, Chernov and
others, during the past several decades [150, 158].
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APPENDIX 3
CHARECTERIZATION TECHNIQUES
A 3.1 STRUCTURAL CHARACTERIZATIONS
A 3.1.1 Single Crystal X- Ray Diffractometer
Single crystal X-ray diffraction is mainly concerned with the excitation
of atoms by the removal of an electron from an inner shell. The excitation is
followed by the transfer or an electron from an outer shell to an inner shell
with consequent emission of energy in the form of X-rays, which are photons
with high energy and short wavelengths on the order of a few Angstroms to
several Angstroms. There are three methods to determine the structure of
compounds. One method uses the fact that X-rays emitted by an excited
element have a wavelength characteristic of that element and its intensity is
proportional to the number of excited atoms. The excitation can be carried
out in several ways, either by direct bombardment of the material with an
electron (direct emission of X-ray) or by irradiation of the material with X-rays
utilizing the different absorption of X-rays by different materials (absorption
analysis). A third method makes use of X-rays in analytical work by the
diffraction of X-rays from the planes of a crystal (diffraction analysis).
A 3.1.2 Powder X-Ray Diffractometer
In general, to determine the molecular structure of new materials, a
single crystal X-ray diffractometer is used. Powder X-ray diffractometer is
used for phase identification and quantitative phase analysis. The
experimental geometry used in the powder diffraction method is shown in
Figure A.3.1. [http://www.ammrf.org.au/myscope/xrd/background/ Australian
Microscopy & Microanalysis Research Facility Website]
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The basic three components of an X-ray diffractometer are as follows:
X-Ray source
Specimen
X-ray detector
Figure A.3.1: Powder X-ray Diffractometer
The angle between the plane of the specimen and the X-ray source is
, the Bragg angle. The angle between the projection of the X-ray source and
the detector is 2. For this reason, the X-ray diffraction patterns produced
with this geometry are often known -2 (theta-two theta) scans. In the - 2
geometry the X-ray source is fixed and the detector moves through a range
of angles.
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The radius of the focusing circle is not constant but increases as the
angle 2 decreases. The 2 measurement ranges typically from 0 to
approximately 170. In an experiment, it is not necessary to scan the whole
range of detector angles. A 2 range from 30 to 140 is an example of a
typical scan. The choice of range depends on the crystal structure of the
material (if known). For an unknown specimen, a large range of angles is
often used because the positions of the reflections are not known.
The diffractometer circle is shown in Fig A.3.1. It is different from the
focusing circle. The diffractometer circle is centred at the specimen, and
both the X-ray source and the detector lie on the circumference of the circle;
the radius of the circle is fixed. The diffractometer circle is also referred to as
the goniometer circle. The goniometer is the central component of an X-ray
diffractometer and contains the specimen holder.
A 3.1.3 Fourier Transform Infrared Spectroscopy (FTIR)
Fourier transform infrared spectroscopy is a simple mathematical
technique used to resolve a complex wave into its frequency components. It
is one of the most influential tools for identifying organic, inorganic,
polymeric, crystalline and coordination compounds.
The IR region of the electromagnetic spectrum is considered to cover
the range from 50 to 12500 cm-1 approximately. It is generally subdivided
into three region – near IR (12500-4000 cm-1), middle IR (4000-400 cm-1) and
far IR (400-50 cm-1) [158]. The middle IR is the region most commonly
employed for laboratory investigations, as it covers most of the vibrational
transitions.
The conventional infrared spectrometers are not of much use in the far
IR, which has made this energy limited region more accessible. They have
also been made to measure in the middle IR region ranging between 400 and
4000 cm-1. Conventional spectroscopy, known as frequency domain
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spectroscopy, records the changes in radiant power as a function of
frequency. In time domain spectroscopy, the changes in radiant power are
recorded as a function of time. In Fourier transform spectroscopy [Fig.A.3.2
from DOI:10.4236/ojapps.2014.43012] a time domain plot is converted to a
frequency domain spectrum. The actual calculation of the Fourier transform
of such systems is done by means of high speed computers [159, 160].
Figure. A.3.2: Schematic diagram of a FTIR spectrometer
A 3.2 OPTICAL CHARACTERIZATIONS
A 3.2.1 UV-Vis-NIR Spectrometer
A UV-Vis-NIR spectrometer (Fig.A.3.3) measures the energy
[DOI:10.4236/jcpt.2014.42013] absorbed when electrons are promoted from
the ground state to higher energy levels. In the ground state, the spins of the
electrons in each molecular orbital are essentially paired. In the higher state,
if the spins of the electrons are paired, then it is called an excited singlet
state [161, 162]. In contrast, if the spins of the electrons in the excited state
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are parallel, it is called an excited triplet state. The UV-Vis-NIR spectrum is
simply a plot of the wavelength of light absorbed versus the absorption
intensity (absorption or transmittance) and is conveniently recorded by
plotting molar absorptivity (ε) against wavelength (nm).
Figure A.3.3: Schematic representation of a UV-Vis-NIR spectrophotometer
A 3.2.2 Fluorescence Spectrometer
Fluorescence spectroscopy is a type of electromagnetic
spectroscopy that analyses fluorescence from a sample. It involves using a
beam of light, usually ultraviolet light, to excite the electrons in molecules of
certain compounds and causes them to emit light typically, but not
necessarily, in the visible range. A complementary technique is absorption
spectroscopy. Molecules have various states referred to as energy levels.
Fluorescence spectroscopy is primarily concerned with electronic and
vibrational states. Generally, the species being examined has a ground (low
energy) electronic state of interest and an excited (higher energy) electronic
state. Within each of these electronic states are various vibrational states.
In fluorescence spectroscopy, the species is first excited by
absorbing a photon from its ground electronic state to one of the various
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excited vibrational states. Collisions with other molecules cause the excited
molecule to lose vibrational energy until it reaches the lowest vibrational state
among the excited electronic states. This process is often visualized with
a Jablonski diagram.
The molecule then drops down to one of the various vibrational levels
of the ground electronic state again, emitting a photon in the process. As
molecules may drop down into any of several vibrational levels in the ground
state, the emitted photons will have different energies and thus frequencies.
Therefore, by analysing the different frequencies of light emitted in
fluorescence spectroscopy, along with their relative intensities, the structure
of the different vibrational levels can be determined.
For atomic species, the process is similar; however, because atomic
species do not have vibrational energy levels, the emitted photons are often
at the same wavelength as the incident radiation. This process of re-emitting
the absorbed photon is "resonance fluorescence", and while it is
characteristic of atomic fluorescence, it is seen in molecular fluorescence as
well.
In a typical experiment, the different wavelengths of fluorescent light
emitted by a sample are measured using a monochromator, which holds the
excitation light at a constant wavelength. This is called an emission
spectrum. An excitation spectrum is the opposite, whereby the emission light
is held at a constant wavelength, and the excitation light is scanned through
many different wavelengths (via a monochromator). An emission map is
measured by recording the emission spectra resulting from a range of
excitation wavelengths and combining them all together. This is a
three-dimensional surface data set, where emission intensity is a function of
excitation and emission wavelengths, and is typically depicted as a contour
map.
Fluorescence spectroscopy is used in, among other areas,
biochemical, medical, and chemical research fields for analysing organic
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compounds. There has also been a report of its use in differentiating
malignant, bashful skin tumours from benign ones.
A 3.3 THERMAL CHARACTERIZATIONS
A 3.3.1 Thermal Analysis
The term “thermal analysis” refers to a group of techniques in which
some physical or chemical property of a system is measured as a function of
temperature. All materials, as they experience changes in temperatures,
undergo changes in their physical and chemical properties. These changes
can be detected by suitable transducers that convert the changes into
electrical signals, which are collected and analysed to give thermograms
showing the property change as a function of temperature.
A 3.3.2 Thermogravimetric Analysis
Thermogravimetric analysis (TGA) addresses the change in the mass
of a substance, continuously monitored as a function of temperature or time
when the substance is heated or cooled at a controlled rate [163, 159]. It
provides information on the thermal stability of the sample at different
temperatures and pressures of the environmental gases.
A 3.3.3 Differential Thermal Analysis
Differential thermal analysis (DTA), often considered an addition to
TG, is, in fact, more versatile and yields data of a considerably more
fundamental nature. The technique is simple, as it involves the
measurements of the temperature difference between the sample and an
inert reference material as both are subjected to identical thermal regimes in
an environment heated or cooled at a constant rate. The origin of the
temperature difference in the sample lies in the energy difference between
the products and the reactants or between the two phases of a substance.
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This difference is manifested as enthalpy changes, either exothermic or
endothermic [164].
A 3.3.4 Differential Scanning Calorimetry
In differential scanning calorimetry (DSC), the sample reference
materials are also subjected to a closely controlled programmed temperature.
In the event that a transition occurs in the sample, however, thermal energy
is added to or subtracted from the reference containers to maintain both
sample and reference at the same temperature [159].
A 3.4 MECHANICAL CHARACTERIZATIONS
A 3.4.1 Microhardness
The hardness of a material is the resistance it offers to indentation by
a much harder body. It may be termed as a measure of the resistance
against lattice destruction or the resistance to permanent deformation or
damage [165]. Hardness properties are basically related to the crystal
structure of the material. Microhardness studies on crystals provide an
understanding of the plastic behaviour of the crystal [166].
Hardness is a technique in which a crystal is subjected to relatively
high pressure within a localized area. With a suitable choice of an indenter
material and relatively simple equipment construction, hardness tests can be
easily carried out on any crystalline material under various conditions of
temperature and pressure. The deformation is local, so several trials can be
made on a single specimen of small dimensions and can be reproduced by
maintaining the relative orientation between the specimen and indenter.
A 3.4.1.1 Vickers Hardness Measurement
Among the various methods of hardness measurements, the most
common and reliable method is the Vickers hardness test method. In this
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method, a micro indentation is made on the surface of a specimen with a
diamond indenter (Fig.) Smith and Sandland [96] have proposed that a
pyramid be substituted for a ball to provide geometrical similitude under
different values of load.
Hardness is generally defined as the ratio of the load applied to the
surface area of the indentation. The Vickers hardness number is calculated
from the relation
(A 3.1)
where P is the applied load in kg and d is the diagonal length of the
indentation mark in mm. Hardness values are always measured from the
observed size of the impression remaining after a loaded indenter has
penetrated and been removed from the surface.
Thus, the observed hardness behaviour is the summation of a
number of effects involved in the material response under indentation
pressure during loading and depends on the final measurement of the
residual impression.
The importance of microhardness studies lies in the possibility of
making an indirect estimate of the mechanical properties of materials, such
as yield strength and toughness, which have a specific correlation to
hardness.
A 3.5 SECOND HARMONIC GENERATION
Second harmonic generation (SHG, also called frequency doubling)
was the first NLO effect ever observed, where a coherent input generates a
coherent output [167, 168]. SHG is a NLO process in which photons
interacting with a nonlinear material are effectively “combined” to form new
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photons with twice the energy and therefore twice the frequency and half the
wavelength. Two incident photons are converted into one emerging photon
with exactly twice the energy (half the wavelength). No excitation of
molecules occurs, so all energy is conserved. Second harmonics can be
generated by NLO materials with a non-centrosymmetric molecular structure.
The simplest case for analysis of SHG is a plane wave of amplitude
E() traveling in a nonlinear medium. When light interacts with the medium,
the electromagnetic field takes on a specific orientation, or polarization P.
This overall polarization is actually the combined product of several
components, including the incident light as well as different harmonic
frequencies that are generated through interactions with the medium. The
intensity of each of these components depends on the electric field (E) and
the susceptibility () for that particular harmonic frequency such that the
overall polarization can be rewritten as the power series in Equation A 3.2,
where 0 is the permittivity of free space.
P = 0 (1) E + (2) E2 + (3) E3 + … (A 3.2)
The susceptibility is governed by properties of the medium of
interaction, in this case a crystal. Similar to other interesting properties such
as piezoelectricity, pyro electricity, ferroelectricity and optical activity, SHG is
imparted by the absence of a centre of symmetry in the crystal structure of a
material [169]. This lack of inversion symmetry is the most important
requirement for SHG because it defines the second order NLO susceptibility,
(2), as a non-zero term (in centrosymmetric materials, (n) = 0 for all terms
where n is even). The magnitude of the susceptibility is determined by
detailed structural features and the direction in which the light interacts with
NLO active features (e.g., the orientation of the crystal). SHG is less than
50% efficient and in most cases occurs at efficiencies less than 30% [170];
higher order NLO effects occur with even lower efficiencies. Because of this,
the third harmonic is typically generated by the more efficient process of sum
frequency mixing of the second harmonic with the fundamental frequency
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[171]. Likewise, generation of the fourth harmonic is more efficiently
achieved by two consecutive SHG events rather than a direct fourth
harmonic generation.
Figure A.3.4: Second harmonic generation (SHG) instrument
A 3.5.1 Kurtz and Perry Powder SHG Technique
Nonlinear optics plays a major role in photonics and optoelectronics.
Extensive exploration of potential inorganic, organic and semiorganic NLO
materials has been carried out. Powder SHG testing offers the possibility of
assessing the nonlinearity of new materials.
Kurtz and Perry proposed a powder SHG method for comprehensive
analysis of the second order nonlinearity. This is an important method for
characterizing a material before going through the long process of growing
large optical quality crystals. The schematic diagram of the Kurtz powder
technique for SHG measurement using an Nd: YAG laser is shown in the Fig.
A.3.4 [Dept. of Physics, B.S. Abdur Rahman University] [172, 173].
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TECHNICAL BIOGRAPHY
Mr. G. Marudhu (RRN. 1090206) was born on 6th March 1983, in
Vandavasi, Tamil Nadu. He completed his schooling in Govt. Higher
Secondary School at Vandavasi. He received his B.Sc. degree in Physics
from Govt. Arts College at Cheyyar, University of Madras in 2003. He
completed his M.Sc. in Physics at A.V.V.M. Sri Pushpam College at Poondi,
Thanjavur, Barathidasan University in 2007. He completed his B.Ed. degree
in Physical Science from Paulson’s Teacher Training College at
Pulichapallam, Vanur, Thiruvalluvar University in 2008. He received his
M.Phil. degree in Physics from A.V.V.M. Sri Pushpam College at Poondi,
Thanjavur, Barathidasan University in 2009. He has six years of experience
in the teaching field. Currently, he is working as an assistant professor in Sri
Ramanujar Engineering College at Chennai. He is pursuing his Ph.D. in
Physics in the Department of Physics in B.S. Abdur Rahman University at
Chennai. His research area is “growth and characterization of NLO crystals
for optoelectronic device applications.” He has published two papers in peer-
reviewed international journals and has presented three papers at national
conferences. His e-mail address is [email protected], and his contact
number is 9566751751.
Photo
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iv
B.S.ABDUR RAHMAN UNIVERSITY
(B.S. ABDUR RAHMAN INSTITUTE OF SCIENCE & TECHNOLOGY) (Estd. u/s 3 of the UGC Act. 1956)
www.bsauniv.ac.in
BONAFIDE CERTIFICATE
Certified that this thesis GROWTH AND CHARACTERIZATION OF
NONLINEAR OPTICAL 4-APMP, AMINO ACIDS DOPED NaAP AND
DGBCM SINGLE CRYSTALS is the bonafide work of MARUDHU. G
(RRN: 1090206) who carried out the thesis work under my supervision.
Certified further, that to the best of my knowledge the work reported herein
does not form part of any other thesis report or dissertation on the basis of
which a degree or award was conferred on an earlier occasion on this or any
other candidate.
SIGNATURE SIGNATURE
Dr. S. KRISHNAN Dr. I. RAJA MOHAMED RESEARCH SUPERVISOR PROFESSOR & HEAD Assistant Professor (Sr.Gr) Department of Physics Department of Physics B. S. Abdur Rahman University B. S. Abdur Rahman University Chennai – 600 048 Chennai – 600 048
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1. INTRODUCTION
1.1 INTRODUCTION TO CRYSTAL GROWTH
Many modern technological devices would not exist without the use of
synthetic single crystals, obtained by the technique for preparing and
producing bulk single crystals known as crystal growth [1]. Crystal growth
has consistently been a key aspect in some of the most important advances
of the past 80 years. Crystal growth is an applied science that underpins a
number of the world’s major industries because the accomplishments of most
of the extraordinary modern day technologies are very much attributed to the
development of microelectronic, optoelectronic and optical devices made
from artificial crystals [2, 3]. The most in demand research area in the field of
physics is crystal growth; currently, it addresses how to grow crystals and
what their properties are, as well as how they can be suitably fabricated for
device applications. The above questions were answered by developing
novel nonlinear optical (NLO) crystals for a wide range of applications such
as optical switching, frequency conversion and electro-optic modulation [4].
The crystalline quality of NLO crystals must be improved to be able to
fabricate large single crystals for fruitful applications [5]. Here, crystal
engineering involves the development of new crystalline materials with
superior properties, functions and applications, e.g., polarized materials for
NLO applications and materials tailored with magneto-photo properties such
as luminescence for electronic applications and molecular sensors [6]. In
chemistry, the compositions of crystals are based on atomic and molecular
concepts. In particular, X-ray diffraction has been used to reveal the internal
structure of single crystals.
Materials science is primarily concerned with the fundamental
understanding of the internal structure, properties and processing of
materials and is ultimately responsible for many of the recent technological
innovations [7]. Thus, crystals are considered the pillars of modern
technology. In recent years, crystals have been used in the development of
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photonics technology, which uses both electrons and photons to carry, store
and process information [8-12]. Crystals are also typically used in laser
technology, optoelectronics, photovoltaic devices, infrared detectors and
other technologically important scientific applications [13-15].
A single crystal or monocrystalline solid is a material in which the
crystal lattice of the entire sample is continuous with no grain boundaries.
This allows the material to exhibit unique properties, in particular mechanical,
optical and electrical properties, which can be anisotropic depending on the
crystal structure. Anisotropic crystals can be obtained if the origin of the
crystal growth is along a single direction. The additional free energy for each
crystal growth volume can be determined from the interface types and the
final size of the crystal and is an important factor for the mechanical
properties. Anisotropy is useful in single crystals of silicon, used in
semiconductor industries, especially in semiconductor fabrication and
functioning field effect transistors, for altering local electrical properties. The
importance of single crystals in various applications is evident from the recent
advancements in the fields of semiconductors; polarizers; transducers;
infrared detectors; ultrasonic amplifiers; ferrites; magnetic garnets; solid state
lasers; nonlinear optic, piezoelectric, acousto-optic, and photosensitive
materials; and crystalline thin films used in microelectronics and hardware
industries [16-18]. Hence, to achieve high performance devices, high quality
single crystals are needed. The growth and characterization of single
crystals for device fabrication have created a great stimulus due to their
significance for both academic and applied research.
1.2 IMPORTANCE OF NLO CRYSTALS
The appropriate development of crystal growth is nonlinear optics,
which means the extension of the motion of the linear propagation of an
electromagnetic field. In mathematics, this is based on Maxwell’s equations,
in which the polarization of a medium is expressed in terms of a power series
[19]. In recent years, great efforts have been made in the field of nonlinear
optics through investigating several classes of materials, including organic,
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inorganic, and semiorganic, which are expected to be important for
optoelectronics, frequency conversion effects, high speed information
processing, optical advantages such as optical data storage technology, etc.
[20, 21] Here, NLO materials are a special criteria class of the materials,
which have a huge impact on laser and information technology and industrial
applications because of their ability to change the frequency of an incoming
laser beam by modifying its amplitude and phase [22]. Therefore, lasers
alone cannot be used widely in modern science and technology without NLO
crystals [23]. Hence, the development of NLO crystals with better linear
optical (LO) and NLO properties, wider spectral transmission and phase-
matching range is obviously essential for further broadening the applications
of lasers such as image applications, frequency multipliers, mixers,
parametric oscillators, and other functions in the deep-UV, far IR, and even
THz spectral regions [24].
Finally, our aim is to develop novel materials with large nonlinearities
that exhibit exceptional properties such as a wide transparency range, fast
response in data processing, and high damage threshold [25-27]. For this,
we grew and fabricated application-oriented crystals by mixing various
materials into grown NLO materials. Some materials could allow the entry of
light depending on the orientation at room temperature, i.e., receiving high
energy of photons in the blue and green range from incident infrared light
through a NLO crystal [28-30]. Some of the familiar crystals that exhibit the
property of frequency conversion over the entire UV and visible regions are
KTP, LBO, BBO, KDP, KNbO3, LiNbO3, AgGaS2, AgGaSe2, etc. These
crystals are selected based on their optical, mechanical, and physical
properties, such as transmission, damage threshold, and efficiency of the
nonlinear effect, phase matching range and laser beam quality [31, 32].
In the current decade, many researchers have focused on the growth
and characterization of aminopyridine groups to establish NLO behaviour
[33]. The slow evaporation technique is used to grow NLO crystals with good
optical transparency, better orientation, defect-free structures, and good
mechanical and thermal stability [34].
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1.3 INORGANIC CRYSTALS
Inorganic materials are preferred for NLO applications over organic
materials. The single crystals of pure inorganic materials, such as quartz,
lithium niobate (LINbO3), potassium dihydrogen phosphate (KDP), potassium
titanyl phosphate (KTP), and urea, exhibit excellent NLO properties. These
are the pure inorganic materials used in second harmonic generating
devices, parametric oscillators, etc. [35-39]. Some of the familiar properties
of inorganic host materials are large mechanical strength, excellent thermal
stability, good transmittance, and high electro-optic coefficients as well as
high degree of chemical inertness [40-43]. The most familiar single crystals
of KDP exhibit superior NLO properties and have been used as reference
materials for comparison with other crystalline materials. The transmittance,
hardness and dielectric constants are improved by growing KDP crystals
using the Sankaranarayanan-Ramasamy method compared with the normal
slow evaporation method [44, 45]. NLO materials such as lithium sulphate,
potassium lithium niobate and lithium triborate have peculiar advantages
such as a large damage threshold, high phase matching angle, wider
transparency range and chemical stability. Additionally, lithium sulphate
monohydrate has been classified as a promising material for Raman laser
frequency converters [46]. We have been growing several inorganic
materials that exhibit high transparency, good chemical stability and tensile
strength as well as second harmonic generation (SHG), frequency
conversion, optical parametric amplification (OPA), optical parametric
oscillation (OPO), optical emission [47] and electro-optical applications.
However, in these systems, the nonlinear responses are undoubtedly related
to individual bond polarizabilities. Due to a lack of extended π electron
delocalization, the inorganic materials have modest optical nonlinearities.
Due to the difficulty of synthesizing towards particular directions, newer
materials are currently being explored, and this has led to a new class of
NLO materials [48].
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1.4 ORGANIC CRYSTALS
Organic materials exhibit excellent NLO properties because of their
electronic structure with π conjugated systems between donors and
acceptors [49, 50]. This is due to non-centrosymmetry leading to huge NLO
efficiency, exhibited by organic materials on the order of 10 to 100 times
larger than that of inorganic NLO materials through macroscopic second
order NLO response [51]. These materials exhibit excellent properties such
as optoelectric coefficients, large second-order NLO coefficients, small
dielectric constants, molecular designing, faster optical responses, and ultra-
fast responses to external electric fields. [52]. Hence, organic materials are
superior to their inorganic counterparts in terms of crystal preparation, device
fabrication, and production of better devices with large nonlinearities, i.e.,
they have wide applications in areas such as information storage, optical
communication, optical data storage, optoelectronics, laser technology, and
telecommunications [53]. Moreover, they can be in bulk and single form for
NLO device fabrication. Additionally, they are important for frequency
modulation device applications, such as frequency conversion, integrated
circuitry, optical switching, and terahertz wave generation with detection [54].
The slow evaporation technique is one of the simplest techniques for growing
high quality organic single crystals [55]. Recently, Paul M. Dinakaran had
grown 4-Bromo 4-nitrostilbene (BONS) single crystals that exhibited a peak
NLO efficiency of 67 times greater than the reference KDP crystal [25].
Another organic host crystal L-phenylalanine-4-nitrophenol (LPAPN)
demonstrated a high NLO efficiency of 1.2 times that of KDP [50]. One of the
newest organic NLO materials is thiourea with quinine sulphate dehydrate
(TQS) grown by the gel method by Lekshmi P. Nair. This exhibited 1.4 times
higher NLO behaviour than the KDP reference crystal [54]. Redrothu
Hanumantharao had grown l-threonine formate, which had an SHG efficiency
of 1.21 times that of reference KDP [56]. Even though organic materials
have many advantages, they exhibit some drawbacks, as they have a low
laser damage threshold, low optical transparency, etc. [57].
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1.5 SEMIORGANIC CRYSTALS
The inability of organic materials to grow to large crystal sizes
impedes device fabrication, which has led to the discovery of a new class of
crystals called semi organics to satisfy technological requirements [58, 59].
The most promising candidates among metal-organic compounds have
attracted researchers in recent years due to their various properties such as
NLO response, magnetism, and luminescence, as well as applications in
photography and drug delivery [6] due to the combination of organic and
inorganic components. Hence, they have shown large NLO behaviour and
also favourable properties such as high optical transparency over the entire
visible region, a large laser damage threshold value, low deliquescence, high
resistance, and low angular sensitivity [4, 21].
In semiorganic materials, the organic ligand is ionically bonded with
the inorganic host, which promotes exceptional mechanical strength and
chemical stability [42]. Because of this, semiorganic materials are promising
for many other applications such as frequency conversion, light amplitude
and phase modulation and phase conjugation [60]. One significant example
of semiorganic hosts is alkali hydrogen phthalate single crystal, which is used
in long-wave X-ray spectrometers. Several semi organics are used as
substrates for depositing thin films of organic NLO samples, and their
centrosymmetric or non-centrosymmetric forms depend on how the cations
are arranged in the chemical bonding during crystal growth [52] and are thus
suitable for the fabrication of optoelectronic devices [61]. Moreover, metal–
organic complexes offer higher environmental stability combined with greater
diversity of tunable electronic properties by virtue of the coordinated metal
centre [6]. Furthermore, organic ligands combined with inorganic hosts
thereby become semiorganic crystals, which lead to more attractive
applications such as SHG, THG, optical bistability, laser remote sensing,
optical disc data storage, laser driven fusion, medical and spectroscopic
image processing, colour displays and optical communication [33].
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Recently, Soma Adhikari grew L-leucine hydrobromide (LEHBr) single
crystals, which demonstrated a peak NLO efficiency 4 times greater than that
of reference KDP [61]. Another semiorganic host crystal, bis (thiourea) silver
(I) nitrate (TuAgN), exhibited a better NLO efficiency of 0.85 times that of
KDP [58]. Another NLO material, 2-aminopyridine bis thiourea zinc sulphate,
was grown by the slow evaporation method. This exhibited higher NLO
behaviour than KDP [33].
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2. LITERATURE OVERVIEW
2.1 INTRODUCTION
Currently, most of the published research has focused on semiorganic
crystals to enhance the nonlinear optical properties. Due to familiar
properties of both inorganic and organic hosts, until now, semiorganic
materials have been grown for more familiar broad applications, such as
frequency modulation, data storage technology, fibre optic communication,
optical modelling, and electro-optic modulations, because of their good
mechanical strength, high optical transmittance, large damage threshold,
chemical stability, etc. [62].
2.2 4-AMINOPYRIDINIUM MONOPHTHALATE (4-APMP) SINGLE
CRYSTAL
Pyridine and its derivatives of 4-aminopyridine are used as proton
acceptors. 4-Aminopyridine (4-NH2Py) has an amine group present in the
para-position of the nitrogen of the heterocycle. The phthalic acid is an
aromatic dicarboxylic acid group, which has two carboxylic groups in the
ortho positions so that it can act in bidentate ligand (COO-, COO-)
coordination, thereby acting as a donor in the nucleation process. In donor-
acceptor series, the organic ligands are favourable for growing NLO crystals
by the slow evaporation technique, in which one of the pyridine derivatives of
2-aminopyridine is combined with some of the organic ligands such as
benzoic acid, malic acid, etc. Work has been published on the well-known 2-aminopyridinium benzoate [63] and 2-aminopyridinium malate [64] single
crystals, which provides better information on the structural, functional,
optical, thermal, and mechanical properties, dielectric behaviour and
enhancements to the NLO properties. However, there are currently no
reports on the above properties for 4-aminopyridine combined with phthalic
acid, i.e., 4-aminopyridinium monophthalate single crystals produced by the
slow evaporation method. In the present work, the structural, optical,
thermal, mechanical and fluorescence properties of 4-aminopyridinium
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monophthalate single crystals grown by slow evaporation are reported for the
first time.
2.3 AMINO ACID DOPED SODIUM ACID PHTHALATE (NaAP) SINGLE
CRYSTALS
The most significant phthalic acid families are potassium acid
phthalate (KAP) and sodium acid phthalate (NaAP) single crystals, which are
used for various scientific applications such as substrates for organic thin film
NLO materials [65], standards in volumetric analysis, etc. [66] Generally,
KAP crystals are discussed much more in the literature, while very limited
information is available on NaAP single crystals. These phthalate family
materials exhibit large optical transmission with low absorption over the entire
UV-visible region, superior thermal stability in the presence of moisture and
good mechanical hardness; moreover, photo-electric devices can be
fabricated to take advantage of their SHG behaviour [154]. One research
group has used zinc, an inorganic metal, as a dopant in NaAP single crystals
for the improvement of optical, thermal and dielectric properties [52].
Rigorous literature surveys reveal that amino acids are not used as dopants
in NaAP crystals. Hence, L-alanine, L-arginine and glycine are added as
dopants to NaAP single crystals. In the present work, we discuss the optical
and mechanical properties of pure and doped NaAP single crystals grown by
the slow evaporation technique.
2.4 DIGLYCINE BARIUM CHLORIDE MONOHYDRATE (DGBCM) SINGLE
CRYSTAL
Glycine is a simple and effective amino acid with a zwitterionic
structure. Its complexes with inorganic materials have attracted the attention
of many researchers [67]. Furthermore, they show high optical nonlinearity
as well as the chemical flexibility of organic materials and physical
ruggedness of inorganic materials [6]. Glycine zinc sulphate, glycine oxalic
acid, glycine nitrate, and glycine lithium sulphate are the stoichiometric ratio-
based NLO crystals. At an appropriate ratio of 2:1, glycine can be combined
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with familiar inorganic materials, such as zinc chloride, cadmium chloride,
calcium bromide, and magnesium sulphate, and organic materials, such as
picric acid, oxalic acid and hydrochloric acid. These combinations have
enabled developments in bulk growth and have provided new structural,
optical, thermal, mechanical, dielectric and NLO properties. Here, we
mention that some of the diglycine derivatives, such as diglycine zinc chloride
(DGZC) NLO single crystals [68], diglycine cadmium chloride (DGCC) single
crystals [69], calcium dibromide bis (glycine) tetrahydrate single crystals [62],
diglycine hydrobromide NLO crystal [70], bisglycine oxalate single crystals
[71], and diglycine picrate single crystals [72], were grown by the slow
evaporation method. In the series of glycine derivatives we have
investigated, the familiar one is diglycine barium chloride single crystal, which
is a nonlinear optical semiorganic crystal with non-centrosymmetry belonging
to the orthorhombic crystal system. Some of the researchers who have
investigated this material have produced significant studies [73]. Studies
from the current decade are discussed in Chapter 6. The growth of diglycine
barium chloride monohydrate single crystals has been investigated to
improve their optical, mechanical and NLO properties for fabrication tailored
towards device applications.
2.5 CONCLUSION
From the above discussions, it is clear that growth, optical, thermal,
and mechanical studies of 2-aminopyridinium benzoate and 2-aminopyridinium malate single crystals have been conducted that use the
slow evaporation method. A rigorous literature survey reveals that nonlinear
optical 4-aminopyridinium monophthalate single crystals obtained from slow
evaporation were not reported elsewhere. Likewise, the addition of zinc to
NaAP single crystals has been reported elsewhere. However, amino acid-
doped (L-alanine, L-arginine and glycine) NaAP single crystals obtained by
slow evaporation have been reported for the first time by us. Additionally, the
growth and theoretical, optical, and mechanical properties of diglycine barium
chloride monohydrate single crystals obtained by slow evaporation have
been reported and published [155]. All of the above mentioned compounds
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were subjected to various characterizations, and the results were discussed
in detail.
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3. EXPERIMENTAL
3.1 INTRODUCTION
This chapter addresses the crystal growth technique, in particular the
slow evaporation solution growth technique. This technique is used to grow
a crystal in a simple manner and provide improvements in purity.
Additionally, this technique can produce organic, inorganic and semiorganic
NLO crystals at ambient temperature in different solvents. Hence, we chose
this technique to grow our crystals, including 4-aminopyridinium
monophthalate, amino acid-doped NaAP and diglycine barium chloride
monohydrate single crystals.
4-Aminopyridinium monophthalate (4-APMP) crystals based on
organic materials were subjected to many characterization studies to
measure their structural, vibrational, optical and mechanical properties.
Other work on semiorganic materials, such as amino acid-doped NaAP, has
demonstrated modifications to the optical and mechanical behaviours. The
final works were on diglycine barium chloride monohydrate (DGBCM) crystal
semiorganic materials; characterizations of these materials were carried out
to improve their physical properties. Hence, the experimental methods used
for the various types of crystals are briefly discussed in this chapter.
3.2 MATERIALS
4-aminopyridine
Phthalic acid
Sodium bicarbonate
L-alanine
L-arginine
Glycine
Barium chloride dihydrate
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3.3 GLASSWARE AND APPARATUS
Magnetic stirrer
Magnetic pellets
Beakers
Whatmann filter paper
Tissue paper
Petri dish
Digital weight balance
3.4 MATERIAL SYNTHESIS
3.4.1 SYNTHESIS OF 4-AMINOPYRIDINIUM MONOPHTHALATE
The title compound was synthesized by dissolving (AR grade)
4-aminopyridine and phthalic acid in methanol in a 1:1 molar ratio. After
continuous stirring, the supersaturated solution was filtered with Whatmann
filter paper and kept it in a dust free atmosphere. The saturated solution was
allowed to dry at room temperature by the slow evaporation technique. After
a period of 30 days, optically transparent and defect free crystals with
dimensions of 15 × 3 × 2 mm3 were grown, and the photograph of the grown
crystal is shown in Fig. 3.1. The chemical reaction of the synthesized
materials is given as follows:
C5H6N2 + C8H6O4 → C13H12N2O4
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Figure 3.1: Photograph of as grown 4-APMP crystal
3.4.2 SYNTHESIS OF AMINO ACID-DOPED SODIUM ACID PHTHALATE
The amino acid-doped NaAP single crystals were prepared by doping
1 mol%, 3 mol%, and 5 mol% of each amino acid (AR grade L-alanine,
L-arginine, and glycine) into NaAP in double distilled water at ambient
temperature and stirring thoroughly for five hours. The impurities were
removed by successive recrystallization. The supersaturated solutions were
filtered using Whatmann filter paper and were kept in dust free atmosphere.
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Figure 3.2: Photograph of pure NaAP crystal
Figure 3.3: Photograph of NaAP crystal doped with 1 mol% L-alanine
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Figure 3.4: Photograph of NaAP crystal doped with 3 mol% L-alanine
Figure 3.5: Photograph of NaAP crystal doped with 5 mol% L-alanine
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Figure 3.6: Photograph of NaAP crystal doped with 1 mol% L-arginine
Figure 3.7: Photograph of NaAP crystal doped with 3 mol% L-arginine
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Figure 3.8: Photograph of NaAP crystal doped with 5 mol% L-arginine
Figure 3.9: Photograph of NaAP crystal doped with 1 mol% Glycine
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Figure 3.10: Photograph of NaAP crystal doped with 3 mol% Glycine
Figure 3.11: Photograph of NaAP crystal doped with 5 mol% Glycine
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All 9 mixtures were allowed to undergo slow evaporation. L-alanine,
L-arginine, and glycine-doped NaAP crystals with different concentrations
were obtained within the periods of 22, 20, and 21 days, respectively. The
photographs of the doped NaAP crystals are shown in Figs. 3.2 - 3.11.
3.4.3 SYNTHESIS OF DIGLYCINE BARIUM CHLORIDE MONOHYDRATE
Diglycine barium chloride Monohydrate (DGBCM) salt was
synthesized by dissolving (AR grade) glycine and barium chloride dihydrate
in a 2:1 molar ratio in double distilled water. The supersaturated solution of
DGBCM was prepared and filtered using Whatmann filter paper. The filtered
solution was tightly closed with a thin plastic sheet, so that the rate of
evaporation could be minimized. After a period of 25 days, a colourless,
transparent crystal with dimensions of 10 x 8 x 2 mm3 was obtained and is
shown in Fig. 3.12.
(NH2CH2COOH)2 + BaCl2. 2H2O → Ba (NH2CH2COOH)2 Cl2. H2O
Figure. 3.12: Photograph of as grown DGBCM crystal
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3.5 CHARACTERIZATIONS
There was various characterization techniques used to analyse the
grown crystals. A single crystal X-ray diffractometer was used to determine
the structure of the grown crystals. Fourier transform interferometry
confirmed the presence of functional groups in the crystalline materials.
Spectroscopic methods are widely used for qualitative and quantitative
analyses of chemical compounds. The UV-Vis-NIR spectrum gave the
optical transmittance and absorption of the grown crystals. The fluorescence
spectrum showed excitation and emission wavelengths for the crystalline
materials. Thermal analysis was used for studying the thermal stability of the
grown crystals. The Vicker’s hardness measurement was used for
investigating the mechanical behaviour of the grown crystals. The Kurtz and
Perry powder technique was used to find the SHG efficiency of the grown
crystals.
3.6 CONCLUSION
The various types of grown crystals were successfully prepared by the
slow evaporation solution growth technique. They exhibited superior
transparency without major imperfections. Hence, they were selected to
undergo further characterization, and the exhibited properties for each crystal
are reported in the upcoming chapters.
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4. STRUCTURAL, OPTICAL, FLUORESCENCE, MECHANICAL
AND THERMAL PROPERTIES OF NONLINEAR OPTICAL
4-AMINOPYRIDINIUM MONOPHTHALATE SINGLE CRYSTAL
4.1 INTRODUCTION
In recent years, nonlinear optical materials (NLO) have attracted many
researchers due to its wide applications in the field of telecommunication,
optoelectronic and optical information storage devices [74-81]. Organic NLO
materials exhibits much larger NLO efficiencies compared to their inorganic
counterpart, thus promises to meet future requirements for ultrahigh
bandwidth photonic devices [82-84]. Organic materials have been known for
their potential applications in semiconductors, superconductors and nonlinear
optical devices [85]. Hence, Organic NLO crystals with high second
harmonic generation efficiency and transparency in UV-Vis region are
required for numerous device applications. In the present work, single
crystals of 4-Aminopyridinium monophthalate have been grown from
aqueous solution by slow evaporation technique and the grown crystals were
subjected to various characterizations such as single crystal XRD, FTIR, UV,
Fluorescence, thermal and mechanical analysis and the results were
discussed in detail.
4.2 RESULTS AND DISCUSSION
4.2.1 Single crystal X-ray diffraction analysis
The grown crystal having dimensions 0.35 x 0.30 x 0.25 mm3 was
subjected to single crystal XRD analysis using Enraf Nonius CAD 4/MACH 3
single crystal X-ray diffractometer using Mo Kα radiation (λ = 0.71073 Å).
The crystal structure of the title compound was solved by the direct method
using the program SIR-92 (WINGX) [86]. Data were collected in frames
using oscillation method with µ ranging between 2.59 and 25.00 θ. Full
matrix least-squares refinement was done using SHELXL-97 (WINGX)
computer program [87, 88].
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Figure. 4.1: Molecular structure of 4-APMP crystal
Table 4.1 gives the details of the crystal and experimental data.
Figure. 4.1 represents the ORTEP (Oak Ridge Thermal Ellipsoid Plot)
diagram of the molecule with atom numbering with the unit cell projected
down the b-axis. There are two molecules of the title compound in the
asymmetric unit. The phthalate ion is getting attached to 4-Aminopyridine
molecules. Further, the analysis reveal that the title crystal belongs to
orthorhombic system with non-centrosymmetric space group P212121 and the
lattice parameters are a = 5.340 Å, b = 8.223 Å, c = 27.366 Å,
α = β = γ = 90◦ and V = 1201.66 Å3.
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Table 4.1: Crystal data and structure refinement for 4-APMP crystal
CRYSTAL DATA
Formula C13 H12 N2 O4
Formula weight [g / mol] 260.25
Crystal color, habit Pale yellow, Rod
Crystal system Orthorhombic
Crystal size [mm] 0.35 x 0.30 x 0.25 mm3
Space group P212121
Z 4, 1.439 Mg / m3
Unit cell parameters
a = 5.340 (10) Å
b = 8.223 (2) Å
c = 27.366 (8) Å
α = 90º, β = 90º, γ = 90º
Volume [Å3] 1201.66(5) A^3
F (000) 544
µ [mm-1] 1.064
DATA COLLECTION
Diffractometer ENRAF NONIUS CAD 4/MACH 3
Radiation MoKα
Wavelength [Å] 0.71073
Temperature [K] 293(2)
θ min ; θ max [º] 2.59 to 25.00 deg.
Total reflections measured 5415 / 2122
R int 0.0187
Range h = -6→6, k = -9→9, l = -32→31
REFINEMENT
Refinement method Full-matrix least squares
No. of reflection 5415
No. of parameters 185
Final R(F) [ I>2σ (I)] reflections 0.0308
w R [F2] 0.0740
Goodness-of-fit on F2 1.064
Absolute structure parameter 0.3 (11)
Δρ (min; max) [eÅ-3] -0.124 ; 0.154
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4.2.2 FTIR Spectral Study
Fourier transform infrared spectrum (FTIR) of the 4-APMP crystal was
recorded in the range of 400-4000cm-1 using Perkin Paragon-500 through
KBr pellet technique and is shown in Figure. 4.2. A broad band at 3350 cm-1
is due to NH2 symmetric stretching. The peaks at 1928 and 955 cm-1 are
assigned to C-C-C ring breathing. The C – H in plane is found to be at 1157,
1026 and 620 cm-1. The peaks at 833 and 732 cm-1 is due to C – H out of
plane. All these assignments illustrate the presence of 4-Aminopyridinium
monophthalate and the assignments were shown in the Table 4.2.
Figure. 4.2: FTIR spectrum of the grown crystal
4.2.3 Optical Absorption Spectral Studies
An optical absorption spectrum of the grown crystal was carried out
between from 200 to 800 nm using VARIN CARY 5E UV-VIS-NIR
spectrophotometer and is shown in Figure. 4.3. The optical studies reveal
very low absorption in the entire visible region, which is one of the desired
properties for the device fabrication. The UV cut off wavelength of the crystal
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was found to be around 335 nm. This very low absorption in the entire visible
region suggests its suitability for second harmonic generation.
Table. 4.2: FTIR analysis of the grown crystal
Wavenumbers (cm-1) Band Assignment
3350 NH2 Symmetric stretching
1928 C-C-C ring breathing
1644 C - C stretching
1371 C – NH2 stretching
1157 C – H in plane bending
1026 C – H in plane bending
955 C-C-C ring breathing
833 C – H out of plane
732 C – H out of plane
620 C – H in plane
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Figure. 4.3: Optical absorption spectrum the grown crystal
4.2.4 Fluorescence Studies
The Fluorescence gives information about excitation of molecule
brought by absorption of photon. It may be expected in molecules that will be
aromatic or contain multiple conjugated double bonds with a high degree of
resonance stability. The emission spectrum of the grown single crystal of
4-Aminopyridinium monophthalate was recorded in the range of 350-600 nm
using Varian Carry Eclipse Fluorescence spectrometer and is shown in
Figure. 4.4. The sample was excited at 335 nm. The broad peak ranges from
400 to 600 nm with a maximum at 430 nm which indicates that 4-APMP
crystal has blue color of fluorescence emission.
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Figure. 4.4: Emission Spectrum of 4-APMP crystal
4.2.5 Thermal analysis
The thermal stability of the title crystal was carried out by
thermogravimetric (TG) and differential thermal analysis (DTA) studies using
NETZSCH STA 409 C analyzer in the nitrogen atmosphere at the heating
rate of 10 ◦C/min in the temperature range between from 25 to 400 ºC and
the resultant thermogram is shown in the Figure. 4.5. The TGA curve shows
that there is a loss of weight in the range between 96 ◦C and 306 ◦C in
association with a sharp endothermic peak in DTA, which can be ascribed to
the absorption of energy for breaking of bonds at the initial stage of
decomposition. The TGA illustrates that there is no loss below 197.2 ºC,
thus assigned as the melting point of the crystal. From the results of DTA,
this is observed that there is no transformation inside the structure was
observed before melting point of 197.2◦C. Thus from the thermal studies, the
crystal can retain its texture up to 197.2º C, which proves its suitability for the
fabrication of nonlinear optical devices.
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Figure. 4.5: TG/DTA spectrum of the title crystal
4.2.6 Microhardness studies
The mechanical hardness studies for the grown crystal were carried
out by a Leitz Wetzler Microhardness tester with a diamond pyramidal
indenter. The indentations were made using a Vickers pyramidal indenter for
various loads from 25 to 100g in the steps of 25g with a constant indentation
period of 25 s for all loads. Vicker’s hardness number (Hv) is calculated using
the relation
2
2
1.8544/v
PH kg mm
d (4.1)
Where P is applied load in kg and d the diagonal length in mm. The variation
of Hv with applied load P is shown in Figure. 4.6. From the graph it becomes
clear that the hardness value increases with increasing load, thus satisfying
the normal indentation effect.
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Figure. 4.6: Plot of load (P) vs. Hv
A plot of log p versus log d (Figure. 4.7) yields a straight line graph
and its slope gives the work hardening index n, and is found to be 4.89,
according to Meyer’s relation
1
nP K d (4.2)
Figure. 4.7: Plot of Log d vs. log P
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Where K1 is the standard hardness value, which can be found out from the
plot of P versus dn (Figure. 4.8).
Figure. 4.8: Plot of dn vs. Load P
Since the material takes some time to revert to the elastic mode after
every indentation, a correction χ is applied to the d value and Kick’s law is
related as
2
2 ( )P K d x (4.3)
From Equations. (2) and (3), we get
1/2
/2 2 2
1 1
n K Kd d x
K K
(4.4)
The slope of dn/2 versus d yields (K2/K1)1/2 and the intercept is a
measure of χ and is shown in Figure. 4.10. The fracture toughness (Kc) is
given by
Kc = P/ βc 3/2 (4.5)
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Figure. 4.9: Plot of d vs. dn/2
Where C is the crack length measured from the centre of the
indentation mark to the crack tip, P is the applied load and geometrical
constant β = 7 for Vicker’s indenter. The brittleness index (B) is given by
β = Hv / Kc (4.6)
Yield strength σv of the material can be found out using the relation
2
12.5(2 )1 (2 )
2.9 1 (2 )
n
vv
H nn
n
(4.7)
The stiffness constant gives an idea about the nature of
bonding between successive atoms. This property of the material by virtue of
which it can absorb maximum energy before the fracture occurs. For various
loads the stiffness constant is calculated using Wooster’s empirical relation
[89]
C11 = Hv7/4 (4.8)
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Figure. 4.10: P vs σv
The variation of stiffness constant plotted with load is shown in Figure.
4.11. All the determined mechanical parameters are shown in the Table. 4.3.
Figure. 4.11: P vs C11
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4.2.7 NLO studies
The powder SHG efficiency of the grown crystal was studied using
Q-switched Nd: YAG laser by employing the Kurtz and Perry powder
technique. The Nd: YAG laser emits fundamental wavelength of 1064 nm.
The output from Nd: YAG laser was used as source and it was illuminated to
the crystal powder. Pulse energy was 850 mj /second and pulse width was
about 9 ns, also repetition rate was 10 Hz. The SHG radiation at 532 nm
green light was obtained through photomultiplier tube. Hence the output
power of the grown crystal was 9.681 mj for the input power of 0.68 j, and the
powder SHG efficiency obtained is 1.1 times than that of well-known
reference material (KDP crystal).
Table 4.3: Microhardness value obtained on the 4-APMP Crystal
Hardness Parameters Values
n 4.89
K1 in kg/m 121.43
K2 in kg/m 48.86
Hp 64.9
Hv 28.25
Pm 100
Ps 25
Kc (MNm-3/2) 0.0282
β (m-1/2) 10.017 x 102
σv (MPa) 929.32 x 102
C11 (Pa) 346.16
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4.3 CONCLUSION
A novel nonlinear optical 4-Aminopyridinium monophthalate have
been grown by slow evaporation solution growth technique. The grown
crystal belongs to orthorhombic system. The presence of functional groups
was confirmed by FTIR analysis. The optical absorption studies reveal very
low absorption in the entire visible region. The title material has blue color
fluorescence emission at 430 nm. The thermal stability of the title compound
is found to be 197 °C. From Vickers hardness studies, work hardening
coefficient n is 4.89, thus confirms the exceptional hardness of the crystal.
Kurtz Perry powder method, used to confirm the SHG of the crystal, having
SHG efficiency 1.1 times that of KDP. All these studies confirm that the
grown crystal is the potential candidate for the fabrication of nonlinear optical
devices.
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5. OPTICAL AND MECHANICAL STUDIES ON AMINO ACID DOPED
SODIUM ACID PHTHALATE (NaAP) SINGLE CRYSTALS
5.1 INTRODUCTION
Nonlinear optical materials have attracted many researchers due to its
potential applications in the field of photonics, lasers, electro - optic switches
and frequency conversion etc. [90-100]. During the past decade, number of
organic and inorganic materials with high nonlinear susceptibilities has been
synthesized. However, their device applications have been impeded by the
inadequate optical transmittance, poor optical quality and low laser damage
threshold [101]. The molecules in pure organic crystals are often bonded by
weak Vander Waals forces of hydrogen bonds, which result in poor
mechanical robustness. In the case of inorganic NLO materials, they have
excellent mechanical and thermal properties but relatively modest optical
susceptibilities due to the lack of π – electron delocalization [102-105, 42].
Phthalic acid family crystals are potential nonlinear optical materials and are
widely used in variety of applications [106]. Sodium acid phthalate is an
excellent material for SHG applications [107, 108]. In the present work,
attempts were made to grow amino acids (L-alanine, L-arginine, Glycine)
doped sodium acid phthalate by slow evaporation technique. Effect of
dopants is significant, because of the influence of doping on intrinsic defects
[109-114]. The results and characterization reveal that the presence of
dopants enhances optical, mechanical properties etc.
5.2 RESULTS AND DISCUSSION
5.2.1 Single crystal X-ray diffraction analysis
The amino acid doped sodium acid phthalate crystals were subjected
to single crystal X-ray diffraction analysis using by ENRAF NONIUS CAD4
single crystal X-ray diffractometer. The lattice parameters are measured and
are shown in Table 5.1. All the grown crystals belong to orthorhombic crystal
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system having space group of B2ab which is in good agreement with that of
the literature [107, 108].
Table 5.1: Lattice parameters for Pure and doped crystals
compound
Name
Crystal
system
Space
group Unit cell parameters Volume
NaAP (pure) Orthorhombic B2ab a = 6.60 Å, b = 9.08 Å,
c = 25.84 Å, α = β = γ = 90° V = 1548 Å3
NaAP + 1mole%
L-alanine
Orthorhombic B2ab a = 6.73 Å, b = 9.24 Å,
c = 26.25 Å, α = β = γ = 90° V = 1631 Å3
NaAP + 3mole%
L-alanine Orthorhombic B2ab
a = 6.74 Å, b = 9.23 Å,
c = 26.28 Å, α = β = γ = 90° V = 1635 Å3
NaAP + 5mole%
L-alanine Orthorhombic B2ab
a = 6.77 Å, b = 9.28 Å,
c = 26.35 Å, α = β = γ = 90° V = 1655 Å3
NaAP + 1mole%
L-arginine Orthorhombic B2ab
a = 6.78 Å, b = 9.29 Å,
c = 26.38 Å, α = β = γ = 90° V = 1661 Å3
NaAP + 3mole%
L-arginine Orthorhombic B2ab
a = 6.77 Å, b = 9.30 Å,
c = 26.39 Å, α = β = γ = 90° V = 1662 Å3
NaAP + 5mole%
L-arginine Orthorhombic B2ab
a = 6.87 Å, b = 9.45 Å,
c = 26.76 Å, α = β = γ = 90° V = 1737 Å3
NaAP + 1mole%
Glycine Orthorhombic B2ab
a = 6.68 Å, b = 9.19 Å,
c = 26.06 Å, α = β = γ = 90° V = 1600 Å3
NaAP + 3mole%
Glycine Orthorhombic B2ab
a = 6.74 Å, b = 9.28 Å,
c = 26.29 Å, α = β = γ = 90° V = 1644 Å3
NaAP + 5mole%
Glycine Orthorhombic B2ab
a = 6.81 Å, b = 9.38 Å,
c = 26.62 Å, α = β = γ = 90° V = 1701 Å3
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5.2.2 FTIR studies
The presence of functional groups and vibrational frequencies of pure
and doped NaAP single crystals identified by FTIR spectroscopy. The
recorded spectrum of the grown crystals were carried out between the range
400-4000 cm-1 using Perkin - Elmer spectrum one and is shown in Figures.
5.1- 5.3. An absorption band in the range 538-858 cm-1 appears due to C-H
out-of-plane deformations of the aromatic ring. The spectral band attributed
at 1118 cm-1 is due to C-H in-plane deformation of the aromatic ring. The
C-O stretching vibrations obtained as peak at 1354 cm-1. The peak at 1613
cm-1 assigned due to C-C skeletal aromatic ring vibrations. The carboxyl
group C=O vibrations appear near 1696 cm-1. All these assignments are in
very good agreement with NaAP crystals that of the reported values [108].
The L-alanine dopants assigned at 2867 cm-1 due to NH3+ asymmetric
stretching mode and 1468 cm-1 assigned for deprotonated carboxylic group
(COO-) characteristic absorption band. In the L-arginine dopants the peaks
at 3501 cm-1 NH2 asymmetric stretching vibrational mode, C-H stretching of
CH2 vibrations assigned at 2468 cm-1, the minute peak at 1466 cm-1 due to
NH2 symmetric bending mode.
And the Glycine dopants identified at 3161 cm-1 due to NH3+
Asymmetric stretching vibrational mode, C-O symmetric stretching mode
assigned at 1467 cm-1, and the peak at 1125 cm-1 for NH3+ rocking mode for
out plane bending respectively. From the above assignments verified that
amino acids were presence as dopants in NaAP single crystals.
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Figure. 5.1: FTIR Spectra of L-alanine doped NaAP crystals
Figure. 5.2: FTIR Spectra of L-arginine doped NaAP crystals
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Figure. 5.3: FTIR Spectra of Glycine doped NaAP crystals
5.2.3 UV-Vis-NIR spectral analysis
The UV-Vis-NIR spectrum of the grown crystals was recorded in the
range 300-800 nm using Perkin Elmer Lambda 35 UV-Vis spectrophotometer
and the resultant spectra is shown in Figures. 5.4, 5.5, and 5.6. The optical
absorption studies reveal that amino acids doped NaAP crystals show good
transparency in entire visible region and the UV cut off wavelength is found to
be around 313 nm, 320 nm and 317 nm for L-alanine, L-arginine and Glycine
doped NaAP crystals respectively. Moreover it is observed that the
absorbance decreases with increase in the doping concentration for all the
three dopants. This proves that the presence of dopants enhance the optical
property of the material. The very low absorbance in the entire visible region
suggests its suitability for the fabrication of optoelectronic devices [115].
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Figure. 5.4: Absorption spectra of L-alanine doped NaAP crystals
Figure. 5.5: Absorption spectra of L-arginine doped NaAP crystals
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Figure. 5.6: Absorption spectra of Glycine doped NaAP crystals
The optical absorption coefficient (α) was calculated from the
transmittance using the following relation,
1 1log
t T
(5.1)
Where T is transmittance and t is thickness of the crystal.
Owing to the direct band gap, the crystal under study has an
absorption coefficient (α) obeying the following relation for high photon
energies (hν);
1/2( )gA h E
h
(5.2)
Where Eg is optical band gap of the crystal and A is a constant.
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Figure. 5.7: Plot of (αhν) 2 vs. (hν) for pure and L-alanine
doped NaAP crystals
Figure. 5.8: Plot of (αhν) 2 vs. (hν) for pure and L-arginine
doped NaAP crystals
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Figure. 5.9: Plot of (αhν) 2 vs. (hν) for pure and Glycine
doped NaAP crystals
The plot of variation of (αhν) 2 vs. hν is shown in Figures. 5.7, 5.8, 5.9.
Eg is evaluated by the extrapolation of the linear part and the band gap for
pure NaAP crystal is found to be 4.050 eV. But for L-alanine doped NaAP
the band gap values are 4.070, 4.075 and 4.077 eV respectively for 1mole%,
3mole%, 5mole% concentrations. Similarly, for L-arginine doped NaAP, Eg is
found to be 4.048, 4.051 and 4.052 eV respectively for 1mole%, 3mole%,
5mole% concentrations. Whereas for glycine doped NaAP the values are
4.054, 4.063 and 4.066 eV respectively for 1mole%, 3mole%, 5mole%
concentrations.
5.2.3.1 Determination of optical constants
The optical behaviour of materials is important to determine its usage
in optoelectronic devices. Knowledge of optical constants of a material such
as optical band gap and extinction coefficient is quite essential to examine
the material’s potential opto-electronic applications. Further, the optical
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properties may also be closely related to the material’s atomic structure,
electronic band structure and electrical properties. The extinction coefficient
(K) for the grown crystals can be determined using formula
4K
(5.3)
The plot of K vs. photon energy (hν) is shown in the Figures. 5.10-
5.12. It is observed that the K decreases with increase in energy.
The reflectance (R) in terms of photon energy (Figures. 5.13-5.15) is
derived from the relation,
R (5.4)
Figure. 5.10: Extinction Coefficient of L-alanine doped NaAP crystals
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Figure. 5.11: Extinction Coefficient of L-arginine doped NaAP crystals
Figure. 5.12: Extinction Coefficient of Glycine doped NaAP crystals
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Figure. 5.13: Reflectance of L-alanine doped NaAP crystals
Figure. 5.14: Reflectance of L-arginine doped NaAP crystals
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Figure. 5.15: Reflectance of Glycine doped NaAP crystals
The optical conductivity (σop) is a measure of the frequency response
of the material when irradiated with light (Figures. 5.16-5.18)
σop = (5.5)
Where c is the velocity of light.
Figure. 5.16: Optical Conductivity of L-alanine doped NaAP crystals
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Figure. 5.17: Optical Conductivity of L-arginine doped NaAP crystals
Figure. 5.18: Optical Conductivity of Glycine doped NaAP crystals
Also, the electrical conductivity has been determined for the grown crystals
by optical method using the relation
σelec = 2λσop/α (5.6)
and the electrical conductivity is shown in Figures. 5. 19-5.21.
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Firgure. 5.19: Electrical Conductivity of L-alanine doped NaAP crystals
Firgure. 5.20: Electrical Conductivity of L-arginine doped NaAP crystals
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Firgure. 5.21: Electrical Conductivity of Glycine doped NaAP crystals
5.2.4 Microhardness measurements
The title crystals were carried out to Vickers microhardness tests using
Leitz Wetzler Microhardness tester with a diamond pyramidal indenter. A
diamond indenter was pressed the plane of pure and doped NaAP crystals
under the known load 25 –100g and the resulting indentation was measured.
The indentation time was 25s for all trials. The Vickers hardness number
was calculated using the relation
Hv = 1.8544 (P/d2) kg/mm2 (5.7)
Where P is the applied load in kg and d is the diagonal length of the
indentation impression mm2. The variation of it Hv when the applied load P is
shown in Figures. 5.22-5.24. The microhardness value is gradually increases
after load 50g which is lightly increased in the range of load from 25 to 100g
for different mole% of L-alanine doped NaAP crystals. The same results
were observed for different mole% of L-arginine and Glycine doped NaAP
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crystals. Thus we can conclude that the presence of dopants increases the
hardness of the material.
Figure. 5.22: Hardness number of L-alanine doped NaAP crystals
Figure. 5.23: Hardness number of L-arginine doped NaAP crystals
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Figure. 5.24: Hardness number of Glycine doped NaAP crystals
5.2.5 Nonlinear Optical studies
The second harmonic generation efficiency of pure and amino acid
doped sodium acid phthalate single crystals were studied using Q-switched
Nd: YAG laser by Kurtz powder test. The fundamental radiation of 1064 nm,
with pulse energy was 850 mj per second, pulse width of 9ns, and repetition
rate was 10Hz of infrared light beam focused on the powder samples of
amino acids doped NaAP crystals. The SHG efficiency of the doped crystal
is found to be lesser than that of KDP crystal. The relative SHG efficiency for
different doping concentration is shown in the Figure. 5.25.
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Figure. 5.25: SHG efficiency of Doped amino acid crystals
5.3 CONCLUSION
Single crystals of amino acid doped sodium acid phthalate single
crystals were grown by slow evaporation solution growth technique at room
temperature. Single crystal X-ray diffraction analysis reveals that the title
crystals belong to orthorhombic system having space group B2ab. The
functional groups of the presence of dopants revealed with parent material.
The optical absorption spectra reveal that the amino acid dopants enhanced
the optical properties of the materials. The mechanical hardness study
reveals that the hardness increases with increase in the doping
concentration. The SHG efficiency is found to be lesser than that of KDP
crystal. All these studies confirm that the amino acid doped NaAP crystal
could be considered as a potential candidate for the fabrication of
optoelectronic devices.
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6. STRUCTURAL, OPTICAL, MECHANICAL, THERMAL AND
FLUORESCENCE PROPERTIES OF NONLINEAR OPTICAL DIGLYCINE
BARIUM CHLORIDE MONOHYDRATE (DGBCM) SINGLE CRYSTAL
6.1 INTRODUCTION
The Nonlinear optical (NLO) materials have attracted many
researchers due to their wide applications in the area of photonics, lasers,
electro-optic switches and frequency conversion [116, 90-95]. In recent
years, complexes of amino acids with organic and inorganic acids possess
excellent nonlinear optical properties [61, 117-121]. Amino acids are
interesting materials for NLO applications, as this contains an asymmetric
carbon atom which makes them optically active and most of them crystallize
in non-centrosymmetric space groups. Also, amino acids exist as zwitterionic
nature, favours exceptional crystal hardness, making them ideal for the
fabrication of NLO devices [122, 123]. In addition, amino acid mixed
inorganic compounds are widely used in device fabrication because of their
high nonlinear optical coefficient and high degree of chemical inertness [124].
Hence in the present work, our aim is focused towards the growth of
Diglycine barium chloride monohydrate, a semi organic nonlinear optical
crystal, by slow evaporation solution growth technique. The grown crystals
were subjected to various characterisations and were discussed in detail.
6.2 RESULTS AND DISCUSSION
6.2.1 Single crystal X-ray diffraction analysis
The single crystal X – ray diffraction analysis for the grown crystals
was carried out using ENRAF NONIUS CAD-4 X-ray diffractometer to
determine the cell parameters. The results indicate the DGBCM
[Ba (NH2CH2COOH)2 Cl2. H2O] crystal belongs to orthorhombic crystal
system and space group Pbcn. The calculated unit cell parameter values are a = 8.26 Å, b = 9.29 Å, c = 14.82 Å, α = β = γ = 90o and V = 1139 Å3. Which
are in very good agreement with that of the reported values [125-127].
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The valence electron plasma energy, p is given by
2/1)(8.28 MZp (6.1)
Where Z = ((4 × ZC) + (12 × ZH) + (5 × ZO) + (1 × ZBa) + (2 × ZN) + (2 × ZCl)) =
58 is the total number of valence electrons, ρ is the density and M is the
molecular weight of the grown crystal. Explicitly p dependent Penn gap
and the Fermi energy [128], is given by
2/1)1(
p
pE
(6.2)
And
3/4)(2948.0 pFE (6.3)
Polarizability α obtained using the relation [129]
324
2
0
2
0
2
10396.0]3)(
)([ cm
M
ES
S
pp
p
(6.4)
Where, S0 is a constant for a particular material which is given by
2
0 ]4
[3
1]
4[1
F
p
F
p
E
E
E
ES (6.5)
The value of α so obtained agrees with that obtained using Clausius-
Mossotti equation which is given by,
)2
1(
4
3
aN
M (6.6)
All these calculated data for the grown crystal are shown in the Table 6.1.
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Table 6.1: Some theoretical parameters on DGBCM crystals
6.2.2 FTIR studies
The FTIR study on the grown crystal was carried out between the
range 400 – 4000 cm-1 using Perkin-Elmer spectrum one and the resultant
spectrum is shown in the Figure. 6.1. The broadband around 3478 cm-1 is
due to NH asymmetric stretching. A peak at 2587 indicates the presence of
NH3+ stretching vibrations. The peaks at 1480 and 1111 cm-1 is due to the
NH3+ group of glycine molecule. The carboxylate group of the glycine
molecule is found to be around 671 and 1582 cm-1. The peaks at 896 and
1326 cm-1 are attributed to CCN and COO- stretching groups respectively.
All these assignments are in very good agreement with that of the reported
values [126, 127].
Parameters Values
Plasma energy (eV) 18.20
Penn gap energy (eV) 2.65
Fermi energy (eV) 14.11
Polarizability (cm3)
By Penn analysis 5.38 X 10-23
By Claussius- Mosotti equation 5.41 X 10-23
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Figure. 6.1: FTIR spectrum of the grown crystal
6.2.3 Optical absorption studies
The optical absorption spectrum of the DGBCM crystals was recorded
in the range 200-1200 nm using Perkin Elmer Lambda 35 UV-Vis
spectrophotometer and is shown in Figure. 6.2. It is observed that the lower
cut off wavelength is around 240 nm and the crystal is found to be
transparent in the entire visible region, thus suggesting its suitability for the
fabrication of second harmonic generation devices. The optical absorption
coefficient (α) was calculated from the transmittance using the following
relation,
1 1log
t T
(6.7)
Where T is transmittance and t is thickness of the crystal.
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Figure. 6.2: Optical absorption spectrum of the grown crystal
Owing to the direct band gap, the crystal under study has an
absorption coefficient (α) obeying the following relation for high photon
energies (hν);
1/2( )gA h E
h
(6.8)
Where Eg is optical band gap of the crystal and A is a constant. The plot of
variation of (αhν) 2 vs. hν is shown in Figure. 6.3. Eg is evaluated by the
extrapolation of the linear part and the band gap is found to be 5.19 eV.
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Figure. 6.3: Plot of (hν) vs. (αhν) 2
6.2.3.1 Determination of optical constants
The optical behaviour of materials is important to determine its usage
in optoelectronic devices. Knowledge of optical constants of a material such
as optical band gap and extinction coefficient is quite essential to examine
the material’s potential opto-electronic applications. Further, the optical
properties may also be closely related to the material’s atomic structure,
electronic band structure and electrical properties. The extinction coefficient
(K) for the grown crystals can be determined using formula [130, 131]
4K
(6.9)
The plot of K vs. photon energy (hν) is shown in the Figure. 6.4. It is
observed that the K decreases with increase in energy. The refractive index
(n) can be derived from the following relations,
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2( 1) 3 10 3
2( 1)
R R Rn
R
(6.10)
Figure. 6.4: Plot of extinction coefficient (K) vs. photon energy (hν)
Figure. 6.5: Plot of photon energy (hν) vs. Refractive index (n)
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The dependence of refractive index (n) as a function of photon energy
is shown in the Figure. 6.5. Initially, it is observed that the refractive index
decreases with increase in the photon energy. Later it becomes constant for
the all values of energy.
6.2.4 Microhardness studies
The microhardness of DGBCM crystal was carried out by a Leitz
Wetzler Microhardness tester with a diamond pyramidal indenter. The
indentations were made using a Vickers pyramidal indenter for various loads
from 25 to 100g in the steps of 25g with a constant indentation period of 25 s
for all loads. Vicker’s hardness number (Hv) were calculated using the
relation
2
2
1.8544/v
PH kg mm
d (6.11)
Where P is applied load in kg and d is the diagonal length in mm. The
variation of Hv with applied load P is shown in Figure. 6.6. From the graph it
becomes clear that the hardness value increases with increasing load, thus
satisfying the normal indentation effect.
Figure. 6.6: Plot of P vs. Hv
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A plot of log p versus log d (Figure. 6.7) yields a straight line graph
and its slope gives the work hardening index n, and is found to be 2.89,
according to Meyer’s relation
1
nP K d (6.12)
Where K1 is the standard hardness value, which can be found out from the
plot of P versus dn (Figure. 6.8). Since the material takes some time to revert
to the elastic mode after every indentation, a correction χ is applied to the d
value and Kick’s law is related as
2
2 ( )P K d x (6.13)
From Equations. (12) and (13), we get
1/2
/2 2 2
1 1
n K Kd d x
K K
(6.14)
Figure. 6.7: Plot of Log d vs. log P
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Figure. 6.8: Plot of dn vs. Load P
The slope of dn/2 versus d yields (K2/K1)1/2 and the intercept is a
measure of χ and is shown in Figure. 6.9. The fracture toughness (Kc) is
given by
Kc = P/ βc 3/2 (6.15)
Figure. 6.9: Plot of d vs. dn/2
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Where C is the crack length measured from the centre of the indentation
mark to the crack tip, P is the applied load and geometrical constant β = 7 for
Vicker’s indenter. The brittleness index (B) is given by
β = Hv / Kc (6.16)
Yield strength σv of the material can be found out using the relation
2
12.5(2 )1 (2 )
2.9 1 (2 )
n
vv
H nn
n
(6.17)
All the determined mechanical parameters are shown in the Table 6.2.
Table 6.2: Microhardness value obtained on the DGBCM Crystal
Hardness Parameters Values
n 2.89
K1 in kg/m 0.0319 x 10-2
K2 in kg/m 2.177 x 10-4
Hp 48.45
Hv 31
Pm 100
Ps 25
Kc (MNm-3/2) 0.013239
β (m-1/2) 2.341 x 103
σv (MPa) 701.31
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6.2.5 TGA/DTA studies
The thermal analysis was carried out for the grown crystals using by
NETZSCH STA 409C analyzer in nitrogen atmosphere at heating rate of
20 oC per minute from 25 oC to 400 oC and is shown in Figure. 6.10. From
DTA curve, the first endothermic peak at 171.7oC indicates the starting point
for the decomposition of the material, thus confirms that the materials can
retain its texture till 171.7oC. Another endothermic broad peak obtained at
312.6 oC illustrates the liberation of volatile substances like ammonia and
carbon dioxide in the compound. The TG analysis shows that the 34.9 % of
weight loss takes place during this transition. From the analysis, it is
observed that the material is stable up to 171.7˚C without any intermediate
loss.
Figure.6.10: TG/DTA analysis of the title crystal
6.2.6 Fluorescence studies
The Fluorescence spectrum was recorded to DGBCM crystal sample
using Varian Cary Eclipse Fluorescence spectrometer at room temperature.
The sample was excited at 240 nm and the spectra was recorded in the
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range from 200 to 700 nm is shown in Figure. 6.11. A high intense peaks at
418 nm and 489 nm are observed and shows that DGBCM exhibits blue and
bluish green fluorescence. Either different low intensity peaks can be
intrinsic defects of crystal.
Figure. 6.11: Fluorescence spectrum of the DGBCM crystal
6.2.7 Second harmonic generation study
The second harmonic generation efficiency (SHG) was determined for
the DGBCM crystal using a Q-switched high energy Nd: YAG laser emitting
1064 nm radiation. The emission of green radiation by the sample was
confirmed and the SHG efficiency of DGBCM is 2.18 times more than that of
the KDP single crystal. The comparative SHG efficiencies of some semi
organic crystals relative to KDP are shown in Table. 6.3. [132].
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Table. 6.3: Comparative of SHG efficiencies of NLO crystals relative to KDP
Name of the samples SHG efficiency
KDP 1.0
γ-glycine
L – Tyrosine Hydrochloride
L – Alanine Lithium Chloride
L – Alanine Acetate
L – Alanine Chloride
L – Alanine Bromide
Bis thiourea Lithium chloride
Bis thiourea cadmium zinc chloride
1.5
0.15
0.43
0.30
0.20
0.30
0.90
1.10
Diglycine barium chloride Monohydrate*
(Current Study) 2.18
6.3 CONCLUSION
Single crystal of Diglycine barium chloride monohydrate, a semi
organic NLO material, has been grown by slow evaporation solution growth
technique. The single XRD analysis confirmed that the grown crystals
belong to orthorhombic system having space group Pbcn. FT-IR analysis
confirms the presence of all the functional groups in the crystal lattice. The
optical absorption spectrum reveals that the crystal has good optical
transmittance in the visible IR region, also has high optical band gap energy.
Micro hardness test reveals that the material has good mechanical stability
and good yield strength. The thermogravimetric (TGA) and differential
thermal analysis (DTA) reveals that the material has high thermal stability.
The fluorescence spectrum shows that the grown crystals emit blue
fluorescence. The nonlinear optical study confirms that the SHG efficiency of
DGBCM is 2.18 times higher than KDP crystals. All these studies confirm
that the diglycine barium chloride monohydrate, a semiorganic nonlinear
optical material, is a potential candidate for the fabrication of nonlinear optical
devices.
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7. CONCLUSION
The summary of the results of the present study and conclusions
drawn are presented below.
A novel NLO 4-aminopyridinium monophthalate crystal was grown by
the slow evaporation solution growth technique. The grown crystal belongs
to the orthorhombic system. The presence of functional groups was
confirmed by FTIR analysis. The optical absorption studies revealed very
low absorption over the entire visible region. The title material had a blue
fluorescence emission at 430 nm. The thermal stability of the title compound
was found to be 197 ◦C. From Vickers hardness studies, the work hardening
coefficient n was found to be 4.89, thus confirming the exceptional hardness
of the crystal. The Kurtz Perry powder method was used to confirm the SHG
behaviour of the crystal, and SHG efficiency was found to be 1.1 times that of
KDP. All of these studies confirmed that the grown crystal is a promising
candidate for the fabrication of NLO devices.
Amino acid-doped NaAP single crystals were grown by slow
evaporation solution growth at room temperature. Single crystal X-ray
diffraction analysis revealed that the title crystals belonged to the
orthorhombic system with space group B2ab. The presence of functional
groups was determined qualitatively using FTIR analysis. The optical
absorption spectra revealed that the amino acid dopants enhanced the
optical properties of the materials. The mechanical hardness study revealed
that the hardness increased with increasing doping concentrations. The
SHG efficiency was compared with that of KDP. All of these studies
confirmed that the amino acid-doped NaAP crystal could be considered a
promising candidate for the fabrication of optoelectronic devices.
Single crystal diglycine barium chloride monohydrate, a semiorganic
NLO material, was grown by the slow evaporation solution growth technique.
The single crystal XRD analysis confirmed that the grown crystals belonged
to the orthorhombic system with space group Pbcn. FTIR analysis confirmed
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70
the presence of all of the functional groups in the crystal lattice. The optical
absorption spectrum revealed that the crystal had good optical transmittance
in the visible IR region as well as a high optical band gap energy.
Microhardness tests revealed that the material had good mechanical stability
and good yield strength. The thermogravimetric (TGA) and differential
thermal analyses (DTA) revealed that the material had high thermal stability.
The fluorescence spectrum showed that the grown crystals emitted bluish-
green fluorescence. The NLO study confirmed that the SHG efficiency of
DGBCM was 2.18 times higher than that of KDP. All of these studies
confirmed that diglycine barium chloride monohydrate, a semiorganic NLO
material, is a promising candidate for the fabrication of NLO devices.
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8. SCOPE OF FURTHER WORK
In the future, attempts will be made to grow bulk single crystals (4-
APMP, SAP and DGBCM) along their growth axes to investigate their
growth rate, transparency and nonlinear optical properties such as
nonlinear coefficients, threshold frequency, phase matching behaviour,
other higher harmonic generations and ferroelectric hysteresis studies,
etc.
A systematic study on solution pH will shed more light on the habit
morphology, growth rate and physical properties.
Additionally, attempts can be made to grow application oriented crystals
using the Sankaranarayanan – Ramasamy (SR) method.
Advanced microscopic techniques, such as AFM and TEM, can be used
to characterize the grown samples.
The etching behaviour on the growth planes can be done using various
organic solvents to estimate the dislocation density and lattice
inhomogeneity and to identify the growth mechanism.
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GROWTH AND CHARACTERIZATION OF
NONLINEAR OPTICAL 4-APMP, AMINO ACIDS
DOPED NaAP AND DGBCM SINGLE CRYSTALS
A THESIS
Submitted by
G. MARUDHU
Under the guidance of
Dr. S. KRISHNAN
in partial fulfilment for the award of the degree of
DOCTOR OF PHILOSOPHY in
PHYSICS
B.S.ABDUR RAHMAN UNIVERSITY (B.S. ABDUR RAHMAN INSTITUTE OF SCIENCE & TECHNOLOGY)
(Estd. u/s 3 of the UGC Act. 1956) www.bsauniv.ac.in
MARCH 2015
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iii
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120
LIST OF INTERNATIONAL PUBLICATIONS
[1] Marudhu G, Krishnan S, Thilak T, Samuel P, Vinitha G, and
Pasupathi G, “Growth, thermal and optical studies on nonlinear
optical material Diglycine Barium Chloride Monohydrate (DGBCM)
single crystal”, Journal of Nonlinear Optical Physics & Materials,
Vol. 22, pp. 1-13, 2013.
[2] Marudhu G, Krishnan S, and Vijayaragavan G. V, “Optical, theoretical
and mechanical studies on sodium acid phthalate crystal”, Optik,
Vol. 125, pp. 2417-2421, 2014.
LIST OF PAPERS COMMUNICATED IN INTERNATIONAL JOURNALS
[1] Marudhu G, Krishnan S, and Vijayaragavan G. V, “Optical and
mechanical studies on Amino acids doped Sodium acid phthalate
(NaAP) single crystals by slow evaporation method” to Journal of
Optoelectronics and Advanced Materials-Rapid Communications.
[2] Marudhu G, Krishnan S, and Palanichamy M, “Growth, structural,
optical, thermal and mechanical studies on 4-Aminopyridinium
monophthalate: A novel nonlinear optical crystal” to Journal of Optics
and Laser Technology.
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LIST OF PRESENTATIONS IN NATIONAL CONFERENCE/SEMINAR
[1] Marudhu G, Thilak T and Vinitha G, “Growth and Characterization of
KDP crystals in different pH values by Solution Growth method” in the
Padiga Valarchi Ariviyal Karutharangu, conducted by Anna University,
Chennai, held on 18-19 October, 2010.
[2] Marudhu G, Krishnan S, Vinitha G and Vijayaragavan G. V, “Growth,
optical, thermal and mechanical properties of nonlinear optical sodium
acid phthalate single crystal by slow evaporation technique” in the
XVIII NATIONAL SEMINAR ON CRYSTAL GROWTH (XVIII NSCG-
2014), conducted by SSN Engineering College, Chennai-603 110,
held on 24-26 October, 2014.
[3] Marudhu G and Krishnan S, “Growth and Characterizations of
Nonlinear Optical Diglycine Barium Chloride Monohydrate (DGBCM)
single crystal” in the Second National conference on Recent advances
in materials (NCRAM-2014), conducted by B.S.Abdur Rahman
University, Chennai, held on 03-04 September, 2014.
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TABLE OF CONTENTS
CHAPTER NO. TITLE PAGE NO.
ACKNOWLEDGEMENT v
ABSTRACT vii
LIST OF TABLES xii
LIST OF FIGURES xiii
LIST OF SYMBOLS xvii
1. INTRODUCTION 1
1.1 INTRODUCTION TO CRYSTAL GROWTH 1
1.2 IMPORTANCE OF NLO CRYSTALS 2
1.3 INORGANIC CRYSTALS 4
1.4 ORGANIC CRYSTALS 5
1.5 SEMIORGANIC CRYSTALS 6
2. LITERATURE OVERVIEW 8
2.1 INTRODUCTION 8
2.2 4-AMINOPYRIDINIUM MONOPHTHALATE
(4-APMP) SINCLE CRYSTAL 8
2.3 AMINO ACID DOPED SODIUM ACID
PHTHALATE (NaAP) SINGLE CRYSTALS 9
2.4 DIGLYCINE BARIUM CHLORIDE
MONOHYDRATE (DGBCM) SINGLE
CRYSTAL 9
2.5 CONCLUSION 10
3. EXPERIMENTAL 12
3.1 INTRODUCTION 12
3.2 MATERIALS 12
3.3 GLASSWARE AND APPARATUS 13
3.4 MATERIAL SYNTHESIS 13
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CHAPTER NO. TITLE PAGE NO.
3.4.1 SYNTHESIS OF 4-AMINOPYRIDINIUM
MONOPHTHALATE 13
3.4.2 SYNTHESIS OF AMINO ACID DOPED
SODIUM ACID PHTHALATE 14
3.4.3 SYNTHESIS OF DIGLYCINE BARIUM
CHLORIDE MONOHYDRATE 20
3.5 CHARACTERIZATIONS 21
3.6 CONCLUSION 21
4. STRUCTURAL, OPTICAL,
FLUORESCENCE, MECHANICAL AND
THERMAL PROPERTIES OF NONLINEAR
OPTICAL 4-AMINOPYRIDINIUM
MONOPHTHALATE SINGLE CRYSTAL 22
4.1 INTRODUCTION 22
4.2 RESULTS AND DISCUSSION 22
4.2.1 Single crystal X-ray diffraction analysis 22
4.2.2 FTIR Spectral Study 25
4.2.3 Optical Absorption Spectral Studies 25
4.2.4 Fluorescence Studies 27
4.2.5 Thermal analysis 28
4.2.6 Microhardness studies 29
4.2.7 NLO studies 34
4.3 CONCLUSION 35
5. OPTICAL AND MECHANICAL STUDIES
ON AMINO ACID DOPED SODIUM
ACID PHTHALATE (NaAP) SINGLE
CRYSTALS 36
5.1 INTRODUCTION 36
5.2 RESULTS AND DISCUSSION 36
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CHAPTER NO. TITLE PAGE NO.
5.2.1 Single crystal X-ray diffraction analysis 36
5.2.2 FTIR studies 38
5.2.3 UV-vis-NIR spectral analysis 40
5.2.3.1 Determination of Optical Constants 44
5.2.4 Microhardness measurements 51
5.2.5 Nonlinear Optical studies 53
5.3 CONCLUSION 54
6. STRUCTURAL, OPTICAL, MECHANICAL,
THERMAL AND FLUORESCENCE
PROPERTIES OF NONLINEAR OPTICAL
DIGLYCINE BARIUM CHLORIDE
MONOHYDRATE (DGBCM)
SINGLE CRYSTAL 55
6.1 INTRODUCTION 55
6.2 RESULTS AND DISCUSSION 55
6.2.1 Single crystal X-ray diffraction analysis 55
6.2.2 FTIR studies 57
6.2.3 Optical absorption studies 58
6.2.3.1 Determination of Optical Constants 60
6.2.4 Microhardness studies 62
6.2.5 TGA/DTA studies 66
6.2.6 Fluorescence studies 66
6.2.7 Second harmonic generation study 67
6.3 CONCLUSION 68
7. CONCLUSION 69
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CHAPTER NO. TITLE PAGE NO.
8. SCOPE FOR FURTHER WORK 71
REFERENCES 72
APPENDIX 1
(BASIC CONCEPTS) 95
APPENDIX 2
(PREPARATION TECHNIQUES) 99
APPENDIX 3
(CHARACTERIZATION TECHNIQUES) 108
TECHNICAL BIOGRAPHY 118
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LIST OF TABLES
TABLE
NO. TITLE PAGE NO.
4.1 Crystal data and structure refinement for 4-APMP 24
4.2 FTIR analysis of the grown crystal 26
4.3 Microhardness value obtained on the 4-APMP crystal 34
5.1 Lattice parameters for Pure and doped crystals 37
6.1 Some theoretical parameters on DGBCM crystals 57
6.2 Microhardness value obtained on the DGBCM crystal 65
6.3 Comparative of SHG efficiencies of NLO crystals
relative to KDP 68
A.1.1 Seven Crystal Systems 97
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LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
3.1 Photograph of as grown 4-APMP crystal 14
3.2 Photograph of Pure NaAP crystal 15
3.3
Photograph of NaAP crystal doped with 1 mol%
L-alanine 15
3.4
Photograph of NaAP crystal doped with 3 mol%
L-alanine 16
3.5
Photograph of NaAP crystal doped with 5 mol%
L-alanine 16
3.6
Photograph of NaAP crystal doped with 1 mol%
L-arginine 17
3.7
Photograph of NaAP crystal doped with 3 mol%
L-arginine 17
3.8
Photograph of NaAP crystal doped with 5 mol%
L-arginine 18
3.9 Photograph of NaAP crystal doped with 1 mol% Glycine
18
3.10 Photograph of NaAP crystal doped with 3 mol% Glycine
19
3.11 Photograph of NaAP crystal doped with 5 mol% Glycine 19
3.12 Photograph of as grown DGBCM crystal 20
4.1 Molecular structure of 4-APMP crystal 23
4.2 FTIR spectrum of the grown crystal 25
4.3 Optical absorption spectrum the grown crystal 27
4.4 Emission Spectrum of 4-APMP crystal 28
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FIGURE NO. TITLE PAGE NO.
4.5 TG-DTA spectrum of the title crystal 29
4.6 Plot of load (P) vs. Hv 30
4.7 Plot of Log d vs. log P 30
4.8 Plot of dn vs. Load P 31
4.9 Plot of d vs. dn/2 32
4.10 P vs. σv
33
4.11 P vs C11
33
5.1 FTIR Spectra of L-alanine doped NaAP crystals
39
5.2 FTIR Spectra of L-arginine doped NaAP crystals 39
5.3 FTIR Spectra of Glycine doped NaAP crystals 40
5.4 Absorption spectra of L-alanine doped NaAP crystals
41
5.5 Absorption spectra of L-arginine doped NaAP crystals 41
5.6 Absorption spectra of Glycine doped NaAP crystals 42
5.7 Plot of (αhν) 2 vs. (hν) for pure and L-alanine doped
NaAP crystals 43
5.8 Plot of (αhν) 2 vs. (hν) for pure and L-arginine doped
NaAP crystals 43
5.9 Plot of (αhν) 2 vs. (hν) for pure and Glycine doped
NaAP crystals 44
5.10 Extinction Coefficient of L-alanine doped NaAP crystals 45
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FIGURE NO. TITLE PAGE NO.
5.11 Extinction Coefficient of L-arginine doped NaAP crystals 46
5.12 Extinction Coefficient of Glycine doped NaAP crystals 46
5.13 Reflectance of L-alanine doped NaAP crystals 47
5.14 Reflectance of L-arginine doped NaAP crystals 47
5.15 Reflectance of Glycine doped NaAP crystals 48
5.16 Optical Conductivity of L-alanine doped NaAP crystals 48
5.17 Optical Conductivity of L-arginine doped NaAP crystals 49
5.18 Optical Conductivity of Glycine doped NaAP crystals 49
5.19 Electrical Conductivity of L-alanine doped NaAP
crystals 50
5.20 Electrical Conductivity of L-arginine doped NaAP
crystals 50
5.21 Electrical Conductivity of Glycine doped NaAP crystals 51
5.22 Hardness number of L-alanine doped NaAP crystals 52
5.23 Hardness number of L-arginine doped NaAP crystals 52
5.24 Hardness number of Glycine doped NaAP crystals 53
5.25 SHG efficiency of doped amino acid crystals 54
6.1 FTIR spectrum of the grown crystal 58
6.2 Optical absorption spectrum of the grown crystal 59
6.3 Plot of (hν) vs. (αhν) 2 60
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FIGURE NO. TITLE PAGE NO.
6.4 Plot of extinction coefficient (K) vs. photon energy (hν) 61
6.5 Plot of photon energy (hν) vs. Refractive index (n) 61
6.6 Plot of P vs. Hv 62
6.7 Plot of Log d vs. log P 63
6.8 Plot of dn vs. Load P 64
6.9 Plot of d vs. dn/2 64
6.10 TG/DTA analysis of the title crystal 66
6.11 Fluorescence spectrum of the DGBCM crystal 67
A.2.1 Mason jar crystallizer
106
A.3.1 Powder X-ray Diffractometer 109
A.3.2 Schematic diagram of a FTIR spectrometer 111
A.3.3 Schematic representation of a UV-Vis-NIR
spectrophotometer 112
A.3.4 Second Harmonic Generation (SHG) Instrument 118
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LIST OF SYMBOLS AND ABBREVIATIONS
XRD - X-ray diffraction
FTIR - Fourier Transform Infrared
KBr - Potassium Bromide
UV - Ultraviolet
NIR - Near Infrared
TGA - Thermogravimetric Analysis
DTA - Differential Thermal Analysis
NLO - Nonlinear Optics
SHG - Second Harmonic Generation
Nd : YAG - Neodymium Yttrium Aluminium Garnet
Eg - Energy gap
h - Planck’s constant
σelec - Electrical conductivity
n - Refractive index
K - Extinction coefficient
P - Polarization
HV - Vickers hardness number
nm - Nanometre
Å - Angstrom
KDP - Potassium Dihydrogen Phosphate