2015

Solid State Synthesis of Mixed Metal Oxides

Ramón B. Colón Rivera1 and Ann M. González Piñeiro2

1 University of Puerto Rico, Cayey, Department of Natural Sciences

2 University of Puerto Rico, Cayey, Department of Chemistry

ABSTRACT

New compound synthesis is a very important application in the chemistry material field.

In this investigation metals from groups 13-15 in the periodic table were used to accomplish the

major purpose of the research. Ternary and quaternary reactions were selected as part of our

experimentation and eco-friendly protocols were included in the experimentation. We expect to

see crystal formation and eventually characterize it. Our hypothesis was partially proved.

Although we had negative outcomes it is incorrect to say that the hypothesis was not proved

because powder is a miniature particle with crystal structure.

INTRODUCTION

Dr. Lucasz Koscielski was an inorganic chemistry professor who was committed to the

solid state synthesis of new compounds in order to find novel ways of conducting energy without

increasing our planet’s pollution. Solid state synthesis is a branch of material chemistry which

consists of mixing and matching solids in order to obtain new compounds with useful properties.

In his laboratory, metals from groups 13-15 in the periodic table were used.

Our research work consisted in trying new combinations of metal oxides in order to

synthesize new compounds. It seemed really easy, but it was not. Solid state synthesize is a try

and error methodology in which metals combination are endless. Ternary and quaternary

reactions were selected as part of our experimentation. Eco-friendly protocols were included in

the experimentation to minimize radiation or contamination. That is why a maximum of 30mg of

the heaviest element was permitted. A high temperature furnace was used to complete the

reactions having in mind the melting points of the elements.

Our hypothesis established that a successful synthesis could be achieved. To evidence a

success it was necessary to observe a crystal production. If positive outcomes were observed,

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characterization and new mixed metals combinations can be done as future work. Hopefully the

results will help to develop new technologies.

MATERIALS AND METHODS

Reactant Selection:

Ternary and quaternary compounds from groups 13-15 of the periodic table were chosen

to react. An extensive study of the elements properties such as oxidation states and melting

points was done. The ternary and quaternary combinations selected are showed in Table 1.

Stoichiometric calculations were completed in order to determine the minimum of milligrams

that could be added by element. Intrinsic oxygen unable us to determine with certainty the

possible synthesized compound.

Table 1: Elements Combinations for Reactions

Ternary Quaternary

5 In : 3 Sb 1 Co : 2 In : 1 S

5 Sn : 3 Pb 1 Co : 1 Bi : 1 S

5 Bi : 3 Pb 1 In : 2 Co : 2 S

1 Bi : 2 Pb 1 In : 1 Bi : 1 S

Silica tube preparation:

Before the experimentation was started the silica tubes passed through two different

protocols: heat alignment and carbon coating. The initial silica tube was four feet long. It was

split with a crystal cutter into four halves of twelve inches each one in order to fit in the fume

hood. Then, each twelve inches piece was divided in two halves using an oxygen acetylene torch

which is really powerful and commonly used in welding. Carbon coating was the next step; it is a

process which help to inhibit light from reacting with the compound in study and the compound

from reacting with the tube. Acetone was heated inside each tube in three occasions until the

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walls turned black. Once the tubes were ready each mixture of elements were inserted in

different silica tubes.

Conversion using Stoichiometric Relations:

Working with toxic compounds is a possibility that we can encounter in the

experimentation. In order have an eco-friendly response towards this situation we established

that we will be using a maximum of 30mg per element. Depending in the molar mass and the

ratio selected for each reaction, the quantities of each element will vary. That is why a

stoichiometric conversion is necessary before loading the reactions. The final quantities of each

element are showed in Table 2.

Table 2: Final Quantities for each Reaction

Ternary Quantity (mg) Quaternary Quantity (mg)

5 In : 3 Sb 30mg In + 19mg Sb 1 Co : 2 In : 1 S 8mg Co + 30mg In + 4mg S

5 Sn : 3 Pb 29mg Sn + 30mg Sn 1 Co : 1 Bi : 1 S 8mg Co + 30mg Bi + 5mg S

5 Bi : 3 Pb 30mg Bi + 18mg Pb 1 In : 2 Co : 2 S 29mg In + 30mg Co + 16mg S

1 Bi : 2 Pb 15mg Bi + 30mg Pb 1 In : 1 Bi : 1 S 16mg In + 30mg Bi + 2mg S

GSL-1100x Furnace:

A special GSL-1100x high temperature furnace is used to heat the reactions. This

powerful furnace is needed because the melting points of metals usually stands between 200ºC

and 1000 ºC. Depending on the melting points of the elements present in the reaction a heating

curve is prepared. An example of a heating curve is showed in Figure 1. This curve can vary

since the melting points of all the elements aren’t the same. The reactions are under heat until the

temperature of the highest melting points is accomplished. Then a constant temperature period

will let the reactants to mix and react. At the end a slow process of cooling will provide crystal

formation.

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RESULTS AND DISCUSSION

After one week in the furnace the reactions were completed. We proceeded to break the

silica tubes in order to spread the product in different petri dishes and analyze the results using a

dissecting microscope. We were looking for crystals, but we found powder. The results of the

ternary compounds can be found in Figures 2-5. In Figure 4 and 5 powder attached to the tube

wall was observed. First we thought we have found crystals, but after consulting with our mentor

we concluded that crystal formation was not seen. Compacted powder in the wall of the silica

tube may be a result of a poor carbon coating procedure. Oxidation reactions were distinguished

by the change in color of some of the elements. That could be explained because of the intrinsic

oxygen present during the reaction. Oxygen cannot be quantified and as a consequence it reacts

freely with the metals producing a change in color.

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Figure 1: Example of a Heating Curve

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We confronted some limitations that included time and lack of appropriate equipment.

Because of the limited time we were not able

to run the quaternary reactions. Also, we supposed that negative results were observed as a

consequence of the inappropriate conditions in which the reactions were run. In order to avoid

limitations and achieve positive results we proposed for future work to repeat the experiment

increasing the quality of the carbon coating and using the appropriate equipment. We also want

to try new ternary and quaternary combinations until a new compound is synthesized and

characterized.

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Figure 3: 5 Sn : 3 PbFigure 2: 5 In : 3 Sb

Figure 5: 1 Bi : 2 PbFigure 4: 5 Bi : 3 Pb

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Our hypothesis was partially proved. Although we had negative outcomes it is incorrect

to say that the hypothesis was not proved because powder is a miniature particle with crystal

structure. We found crystals, but not the ones that we were looking for.

REFERENCES

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