Solid State Synthesis of Mixed Metal Oxides

Anibal Tornésa,1 & Abneil D. Aliceab,2

a University of Puerto Rico at Cayey, RISE Program, Department of General Sciencesb University of Puerto Rico at Cayey, RISE Program, Department of Chemistry

A B S T R A C TThe search for a perpetual energy source has been the goal of every material chemist. Mixing and matching elements to obtain new compounds is the base of every innovative application in the chemistry field. The importance of our research goes beyond obtaining crystals, it consists of characterizing plausible compounds which might have superconductivity characteristics and other applicable properties. The problem that we are facing is to determine if certain elements might provide useful structures to apply in the technologically dependent world we live in and suffice the energy crisis that surrounds us. Our hypothesis states that even though oxygen is present, after heat application, oxide crystals will form and their characterization will provide magnetism, optical, and even electronic properties. After reacting ternary compounds in a high temperature furnace and analyzing them in a microscope we managed to obtain compact structures which merely provided oxide powders with crystal structures. This finding of oxide powder alludes to our hypothesis and demonstrated that it was partially proved, because the oxide powder has a crystal structure, yet it does not have enough potential to be characterized for all the properties we stated.

1. Introduction

Solid-state synthesis is a branch of material chemistry which consists of mixing and matching solids in

order to obtain new compounds which could have unique properties useful for the technologically dependent world

we live in. During our investigation we principally worked with metals in their solid powdered form and

synthesized what are known as mixed-metal oxide, these are metal compounds with intrinsic oxygen within them.

When superconductors such as high purity silicon were implemented in the industrialization process, this ¨eternal

energy source¨ gained the scientific community's acceptance. In recent years, electrochemical capacitors, also

known as supercapacitors, have received a large amount of attention as an important power storage device due to

their high power density, fast recharge capability and long cycle life (Chen et al. 2015).

If we take a moment to think about the amount of possible compounds the periodic table holds, we will

surely be wasting our time since the possibilities are infinite. This is why the research had to follow an extremely

strict protocol since we dealt with a numerous amount of highly reactive metals, as a precaution and minimization

of the elements the maximum weight we had of reactives is 30 mg. This environmentally favorable protocol will

help decrease the ecological footprint we might have when disposing of the different compounds formed. When

reactants are mixed in carbon coated silica tubes and put into a GSL-1100x high temperature vacuum tube furnace

at temperatures over (1,000 °C), one of the powder state solids liquefies first and mixes with its adjacent solid,

forming compounds (Cotton et al. 1995).

We expect that after this reactions occur, a series of analysis will be run to determine if our synthesis can

provided crystal structures products. Also by observing the product color make inferences about what it might or

might not be its oxide states. If the investigation provide positive results it could continued into the characterization

step, which would let us determine the specific properties of the compound and would let us determined if it might

provide magnetism, optical, and even electronic properties which could help derive the next-generation of

“superconductors”.

2. Materials & Methods

2.1 Reactant Selection

Our research began with a comprehensive study of the reactant selection. After doing a broad analysis of

our elements peculiar oxidation states, fusion points, and the minimum amount of milligrams they might need to

react as shown in (Fig 1.1), we determined to work with ternary and quaternary compounds. These two divisions,

principally from groups 13-15 on the periodic table aided us to determine how intrinsic oxygen reacts in them.

Chosen elements for reactions

Ternary Quaternary

1 In : 1 Sb 1 S : 1 Bi : 1 In

1 In : 1 Bi 1 Pb : 1 Sn : 1 S

2 In : 1 Sn 2 In : 1 Sn : 1S

2 In : 1 Pb 2 In : 1 Sn : 2 S

(Fig 1.1)

2.2 Silica tube preparation

The elements we used will be inserted into different silica tubes, passed under heat alignment and carbon

coating protocols. The original tube was 4 feet long and split into 4 halves of 12 inches each with a crystal cutter so

they would fit in the fume hood. This split was done using an oxygen acetylene torch which provided a blue flame

usually used for welding. This split and tube alignment was done in order to then put our reactions in, but first we

carbon coated each 6 inch tube. Carbon coating is a process which will help inhibit light from reacting with our

compounds and the same compounds from reacting with the tube.

2.3 Stoichiometric Weight Conversion

In order to decrease the ecological footprint we mentioned at the beginning of this paper, we had a limit of

30 mg from the heaviest weighting element in the ratio. According to the mass and ratio of each element in the

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compound, the 30 mg limit will establish the weight of the other elements in the reaction, except for oxygen as

shown in (Fig 1.2). This step requires mathematical stoichiometric conversion efficiency, considering ratios and

precise molar masses since the weighing could give place to a significant percent of human error, and in

consequence the reaction might not take place effectively.

Ternary Milligram (mg) reason Quaternary Milligram (mg) reason

1 In : 1 Sb 30 mg Sb + 28 mg In 1 S : 1 Bi : 1 In 5mg + 30mg + 20mg

1 In : 1 Bi 30 mg Bi + 16 mg In 1 Pb : 1 Sn : 1 S 30mg + 20mg + 5mg

2 In : 1 Sn 30 mg In + 16 mg Sn 2 In : 1 Sn : 1S 30mg + 16mg + 4mg

2 In : 1 Pb 30 mg In + 27 mg Pb 2 In : 1 Sn : 2 S 30mg + 16mg + 8mg

(Fig 1.2)

2.4 GSL-1100x application

The fusion points of the

elements we put together to form

compounds go over (1,000 °C), which

is why we used a special GSL-1100x

high temperature vacuum tube furnace.

Depending on the reactions we deposit

in, the calibration will vary since not

every compound similar fusion points.

The heat is distributed during a period

of about one week max in the order of

heating and cooling to provide a space

for crystal formation. Figure 1.3,

obtained from the MTI operation

manual portrays a general overview of

the calibration and adaptable heat the

furnace may go through.

(Fig 1.3) MTI Operation Manual

3. Results and Discussion

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The reaction were taken from the furnace and used dissecting microscope techniques to observe compact

structures, before considering that they were crystals we went on to attempt and break them. With the use of the

microscope and tweezers we decomposed the structures and confirmed that it was just compacted powder.

According to tabulated powder results and their oxidation numbers, we determined that each structure complied to

its peculiar color. Indium appears in all the ternary reactions, nevertheless we may observe how the elements

different oxidation numbers may be determined by color. Due to the reaction between low melting mixed metal

oxides there is a transference of electrons which are represented by their oxidation numbers as shown in (Fig 1.4).

Ternary Reaction Results

Solid Products Element Oxidation Number

1 In: 1 Sb

1 Sb +3

2 In : 1 Sn

1 Sn +2

1 In : 1 Bi

1 Bi +3

2 In : 1 Pb

1 Pb +2

(Fig 1.4)

The way the heat is distributed is diagrammed in (Fig 1.5) shown below, in the the first few days the temperature

increase 10 degrees per minute until it reaches the target temperature. This target temperature is based on the

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melting points of the different reactants inside the tubes. Once the furnace reaches this target temperature it remain

at this temperature for two days. When the two day counting concludes, the furnace temperature decreases 5

degrees per minute until it reaches the room temperature again. This way the metals can react in a better way with

each other when liquified. After the room temperature has been reached we may go on to observe the products

achieved in each one of our silica tubes.

(Fig 1.5)

From a chemical perspective of what was occurring in the furnace we might conclude the following, crystal

formation consist of two basic steps; homogenization and a maximum melting point accompanied by a constant

cooling curve. Out of the four compounds we worked with, only one of them turned out to react as loose oxide

powder, whilst the other three compacted themselves.. Permitting an even more constant temperature will permit a

better structure homogenization and a paulatine slope decrease might even provide more space for a stable crystal

structure formation.

Our hypothesis was partially proved, we were not able to find any type of crystals from the ternary

reactions shown in Figure 1.4, yet the visible structures we observed are just homogenized powder. Future work

will have to take into consideration a more constant calibration curve and a more comprehensive analysis of proper

compounds to mix, we suggest the use of bioinformatics to decrease this trial and error percent. Taking into

consideration work done by (Koscielski et al.2012) we may confirm that for future studies, the use of radioactive

compounds would be more efficient than dealing with oxides. Yet radioactive compounds produce high quantities

of energy, but have not proven to be sustainable enough for the planet. Hence dealing with these metal compounds,

would leave a less significant ecological footprint and would therefore provide clean energy; an appropriate

suggestion would be to include oxygen isolation chambers since their crystal product might show to be more pure.

Cited Literature:

Chen S, Xue M, Li Y, Zhu L, Zhang D, Fang Q, Qiu S. 2015. Porous ZnCo2O4 nanoparticles derived from a new mixed-metal organic framework for supercapacitors. Royal Society of Chemistry (RSC) (2) . [2014 Oct 17,

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cited 2015 April 29] 2:177-183. DOI: 10.1039/c4qi00167b

Cotton FA, Wilkinson G, Gaus PL. 1995. Basic Inorganic Chemistry. 3rd edition. New York. John Wiley & Sons, Inc.

Koscielski L, Ringe E, Van Duyne R, Ellis D, Ibers J. 2012. Single-Crystal Structures, Optical Absorptions, and Electronic Distributions of Thorium Oxychalcogenides ThOQ (Q=S, Se, Te). American Chemical Society (ACS)/ [2012, cited 2015 May 1] 51: 8112−8118. DOI:10.1021/ic300510x

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