OptikOptikOptik 121 (2010) 773

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Abstract

crystal have poor mechanical, thermal properties and

and EDAX of this material has already been reportedby Shankar et al. [5]. In this paper, we present the crystalgrowth, thermal and optical characterization of the

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Corresponding author. Tel.: +91422 2692461;

single crystal of TCCM. Further the birefringence ofTCCM has been measured in the visible region.

0030-4026/$ - see front matter r 2009 Elsevier GmbH. All rights reserved.

doi:10.1016/j.ijleo.2008.09.041

fax: +91422 2693812.

E-mail address: mades_saamy@yahoo.co.in (P. Maadeswaran).1. Introduction

In recent years there has been considerable interest onthe synthesis of semiorganic nonlinear optical materialswith good second-order nonlinearities having potentapplication in telecommunication, optical computingand optical data storage devices [1]. Of which particularinterest are the materials generating highly efcientsecond harmonic blueviolet light by using laser diodes.Materials with large second-order optical nonlinearities,short transparency cutoff wavelength and stable physi-co-chemical performances are needed in order to realizemany of these applications [2]. Most organic NLO

susceptible to damage during processing. Also it isdifcult to grow large size optical quality crystals ofthese materials for device application. SemiorganicNLO crystal have good thermal, mechanical propertiesand large nonlinear coefcient [3,4]. In this respect,thiourea and its derivates are interesting materials forNLO application. Thiosemicarbazide cadmium chloridemonohydrate (TCCM) is a semiorganic NLO materialwith molecular formula (CdNH2NHCSNH2)Cl2 H2Oand has second harmonic generation (SHG) efciencygreater than KDP. The solubility, single crystal X-raydiffractometry (XRD), Fourier transfer infrared (FTIR)A semiorganic nonlinear optical material (thiosemicarbazide cadmium chloride monohydrate) (TCCM) wassynthesized and single crystals was grown from aqueous solution by slow evaporation method at ambient temperature.Crystal of average size up to 5 4 3mm3 were harvested and characterized by powder X-ray diffractometry (XRD)and Fourier transfer infrared (FTIR) technique to conrm the identity of the compound formed. The thermal stabilitywas analyzed by TG/DTA. The birefringence values (Dn) were determined in the wavelength region 5406500 (A. Thesecond harmonic generation (SHG) from the materials was conrmed using Nd:YAG laser.r 2009 Elsevier GmbH. All rights reserved.

Keywords: Characterization; Growth from solution; Semiorganic; Nonlinear optical crystals; BirefringenceGrowth, thermal, optical and birefrinnonlinear optical thiosemicarbazide c(TCCM) single crystals

P. Maadeswaran, S. Thirumalairajan, J. C

Department of Physics, Sri Ramakrishna Mission Vidyalaya Co

Received 19 March 2008; accepted 24 September 2008Optics777

nce studies of semiorganicmium chloride monohydrate

drasekaran

of Arts and Science, Coimbatore 641 020, Tamil Nadu, India

www.elsevier.de/ijleo

2. Material synthesis and crystal growth

All starting materials were of AR grade and thesynthesis and growth process were carried out in aqueoussolution. The TCCM has been synthesized by takingcadmium chloride monohydrate and thiosemicarbazidein a 1:1 equimolar ratio. The calculated amounts ofthiosemicarbazide and cadmium chloride were dissolvedin double distilled water using a magnetic stirrer. TCCMsalt was synthesized according to the reaction:

CdCl2 H2ONH22NH2CS2NH2! CdNH2NHCSNH2Cl2 H2O

4000400 cm employing a Nicolet IR 200 FTIR

1.75mJ. The SHG was conrmed by the emission ofgreen radiation.

3. Results and discussion

3.1. Elemental analysis

To ascertain that the TCCM material obtainedis surely that of the desired compound, elementalanalysis was carried out on the sample. The resultof the elemental analysis shows that the compoundcontain the following percentage of elements: C 4.122%(4.107%), H 2.305% (2.393%), N 14.39% (14.37%)and S 10.39% (10.96%). The microanalysis of thecrystallized material shows good agreement with thecalculated values given in parenthesis.

3.2. Powder X-ray diffraction studies

Powder X-ray diffraction pattern is shown in Fig. 2.The observed d values for different 2y values of thecorresponding reective planes for the crystal aregiven in Table 1. The sample was scanned at a rateof 1 degmin1 in the range 101501. The sharp and welldened Braggs peaks at specic 2y angles testimonies

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23.9 2.653

26.1 2.421

P. Maadeswaran et al. / Optik 121 (2010) 773777774spectrometer in order to reveal the metal complexescoordination. The optical properties of the crystals wereexamined between 200 and 400 nm using JASCO(spectrophotometer model V 530). The birefringenceof HCCMH was measured in the visible region byinterference method. The powdered sample was illumi-nated using Q-switched Nd:YAG laser emitting funda-mental wavelength of 1064 nm with a power output ofThe solution was kept in undisturbed condition.After 15 days, transparent and needle shaped crystalsof TCCM were found. The crystals obtained werebright, colorless with an average size of 5 4 3mm3.The purity of the synthesized salt was improved bysuccessive recrystallization process. The photograph ofthe as-grown crystal is shown in Fig. 1.

2.1. Analysis techniques

Elemental analysis was carried out using Vario EL IIIElementar. Elemental analyzer was used to verify itsstoichimetry. A JEOL JDX series instrument was usedto obtain the X-ray powder diffraction pattern. Thermalstability was identied with using SDT Q600V 8.3 Build101 (universal V 4.3A TA instruments) in nitrogenatmosphere by a heating rate of 20 degmin1. The FTIRspectra were recorded in the wave number range of

1Fig. 1. Photograph of single crystals of TCCM.27.7 2.021

34.2 1.825

46.5 1.325the crystalline nature and purity of the crystal TCCM.

Fig. 2. Powder XRD pattern of TCCM crystal.

Table 1. X-ray powder diffraction data of TCCM.

2y (deg) Experimental d value

11.2 5.123

11.9 4.654

12.3 4.125

17.2 3.854

20.3 3.354

22.5 2.965

3.3. FTIR spectrum studies

The middle infrared FTIR analysis of TCCM wascarried out between 4000 and 450 cm1 [5]. Thecharacteristic vibrational frequencies of the functionalgroups present in the TCCM crystals were assignedand tabulated (Table 2) and the spectrum is shown inFig. 3. The broad envelope between 2100 and 3800 cm1

was obtained. Intense sharp peak was observedat 3187.61 cm1 due to OH vibration. Multiple nestructures at the lower energy mode of the envelopeindicate strong hydrogen bonding interaction of asym-metric NH3

+. Asymmetric band NH3+ (1642.32 cm1)

and its symmetric band (1458.38 cm1) are also clearlyseen in the crystal [6]. Since the stretching vibrations ofthe OH bonds in water molecules and the deformationvibrations of NH2

+ and NH3+ groups were present,

it is difcult to determine the presence or absenceof water molecules on the basis of the FTIR spectrum.This band shifted into 1610.99 cm1 region indicatingthat sulfur is involved in metal coordination. The intenseband near 1610.99 cm1 and bands in the region1377.811080.29 cm1 are close to absorption bands ofthiosemicarbazide. The former band connected withdeformation vibration of NH2 and NH groups and latermay be assigned to CQS and CN groups. The narrow

1

the vibration of the Cl groups. These values are closelyagreed with the reported values [5].

3.4. Optical absorption studies

Fig. 4 shows the UV spectrum of the compoundscanned between 200 and 400 nm. There is no absorp-tion band in the region 245 and 400 nm. Hence thecrystal of TCCM is expected to be transparent to all theUV-visible radiation between these two wavelengths [7].

3.5. Thermal analysis

The TG and DTA thermogram of TCCM is shown inFig. 5. The sharp weight loss observed at 144 1C isattributed to the loss of lattice water. From the DTAcurve it is observed that the material is stable up to144 1C and above which the material begins to attain anendothermic transition and begins to decompose. Thesharpness of this endothermic peak shows good degreeof crystallinity. The initial mass of the material is2.7950mg. The graph also reveals that the material isfully decomposed at 325 1C. It is seen that at variousgaseous friction, NH2 are liberated lead by a signicant

ARTICLE IN PRESSP. Maadeswaran et al. / Optik 121 (2010) 773777 775bands at 684.85, 749.37, 1080.29 cm and wide splitbands at 1458.38, 1377.81, 1208.52 cm1 correspond to

Table 2. FTIR data of TCCM crystals.

Wavenumber (cm1) Assignments

3187.61 OH stretching vibration

1642.32 Asymmetric stretching band NH3+

1610.99 Deformation of NH2 groups

1458.38 Symmetric stretching band NH3+

1377.81 CQS stretching vibration1080.29 CN stretching vibrationFig. 3. FTIR spectrum of TCCM.decomposition of the compound. The TG curve showsthe corresponding weight losses at various stages.The characterized absorption band is observed only at237 nm.

Fig. 4. UV spectrum of TCCM.Fig. 5. TG/DTA spectrum of TCCM.

The authors express their gratitude to Prof. P.K. Das,IPC Department, IISc, Bangalore for extending laserfacilities to measure SHG efciency.

References

[1] X.Q. Wang, D. Xu, D.R. Yuan, Y.P. Tian, W.T. Yu, S.Y.

Sun, Z.H. Yang, Q. Fang, M.K. Lu, Y.X. Yan, F.Q.

Meng, S.Y. Guo, G.H. Zhang, M.H. Jiang, Synthesis,

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cadmium tetrathiocyanate, Mater. Res. Bull. 34 (1999)

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[2] S. Dhanuskodi, K. Vasantha, X-ray diffraction spectro-

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NLO material: lithium bis L-malato borate, Spectrochim.

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Wavelength ()

/ Opt3.6. NLO property studies

The SHG intensity of the grown crystal was measuredusing the Kurtz and Perry powder technique [8,9].The powdered form of TCCM crystal was taken for thismeasurement and densely packed between two trans-parent glass slides. A Q-switched Nd:YAG laser(1064 nm) has been used. The input pulse energy of1.75mJ was incident on the crystalline powder, whichis mounted on the geiometa state. The SHG signalof TCCM was detected by photomultiplier tube anddisplayed on a storage oscilloscope. For this measure-ment, the powdered form of KDP was used as areference. The present experimental result shows thatSHG conversion efciency of KDP is 55mV and TCCMis 75mV.

3.7. Birefringence

Birefringence (Dn) is dened as the anisotropy in amaterials refractive index with respect to the polariza-tion state of light propagating through it. The birefrin-gence materials are used in many optical device such ascalculator, glan polarizer, beam splitter, etc. [1012].Anisotropic crystals have crystallographically distinct

axes and interact with light by a mechanism whichdepends on the orientation of the crystalline latticewith respect to incident angle. When the light entersthe optical axis of anisotropic crystal, it behaves in amanner similar to the interaction with isotropic crystaland passes through a non-equivalent axis; it is refractedinto two rays polarized with the vibration directionsoriented at right angles to one another, traveling atdifferent velocities. This phenomenon is termed asdouble refraction or birefringence and it exhibits agreater or lesser degree in all anisotropic crystal.The birefringence of TCCM was measured using the

channel spectrum method with a high power halogenlamp (500W) as a source. The polarizer and analyzerwere placed in crossed position and the crystal wasplaced in its optic axis perpendicular to the incidentray. The transmitted light components from the analyzerinterfere and an interference pattern was observedthrough the high resolution spectrometer. For eachband, the corresponding minimum deviation angle wasnoted. Then the wavelength of corresponding deviateddark band was obtained from the calibration graph ofstandard wavelength (mercury) spectrum. The birefrin-gence was calculated as

Dn l2=l1 l2 l1=twhere t is the thickness of the crystal [13].A graph is drawn between birefringence (Dn) and

wave length (l) and it is shown in Fig. 6. It is quite clearfrom the plot that the birefringence value lies in the

P. Maadeswaran et al.776range 0.120.07 in the wavelength range of 54006500 (AAcknowledgments4. Conclusions

A semiorganic NLO material TCCM has beensynthesized and crystals were grown by slow evapora-tion method. The elemental analysis of the complexcrystal conrms the stoichiometry. The sharp well-dened peaks conrm the crystalline nature of thematerials. The functional groups have been conrmedfrom the FTIR analysis. UV-visible analysis wascarried out to determine the lower cut-off wavelengthat 237 nm. The thermal stability of the materials hasbeen established by TG/DTA. The birefringence valuewas found to be higher than KDP. The SHG efciencyof the powdered sample was found to be 75mV (KDP55mV). From the results, it can be speculated thatthe TCCM crystal is a potential candidate for NLOapplications.indicating TCCM (0.12) is more birefringent than KDP(0.10).

Fig. 6. Birefringence as a function of wavelength for TCCM.0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

5540

Bire

fring

ence

(n)

5620 5710 5820 5910 5990 6120 6205 6300 6410

ik 121 (2010) 773777Acta, Part A 61 (2005) 17771782.

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[7] C.N.R. Rao, Ultra violet and visible spectroscopy of

organic compound, Prentice-Hall of India Pvt. Ltd., New

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[8] S.K. Kurtz, T.T. Perry, A powder technique for the

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[10] W.A. Wooster, Experimental Crystal Growth, Cam-

bridge, 1957.

[11] D.W. Fischer, M.C. Ohmer, P.G. Schunemann, T.M.

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[12] J. Ramajothi, S. Dhanuskodi, Crystal growth, thermal

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ARTICLE IN PRESSP. Maadeswaran et al. / Optik 121 (2010) 773777 777

Growth, thermal, optical and birefringence studies of semiorganic nonlinear optical thiosemicarbazide cadmium chloride monohydrate (TCCM) single crystalsIntroductionMaterial synthesis and crystal growthAnalysis techniques

Results and discussionElemental analysisPowder X-ray diffraction studiesFTIR spectrum studiesOptical absorption studiesThermal analysisNLO property studiesBirefringence

ConclusionsAcknowledgmentsReferences