1. Scientific Manuscript 2014
Abstract
There is strong interest in the unique
properties of inorganic solids that can be
utilized for a whole array of
technological applications such as
functioning as semiconductors and
catalysts. High temperature synthesis
will be utilized as the means for
obtaining novel inorganic solid phase
materials, specifically mixed-metal
oxides. Although widely used, this
procedure has to be categorized as a
trial and error based method. Products
are predicted through established
stoichiometry of the reactants. Further
characterization by means of X-ray
crystallography will provide with the
exact composition and stoichiometry of
the inorganic solid. Due to some
limitations, the reactions and products
were predicted but the synthesis part of
the project was not carried out.
1. Introduction
Modern electronic technology is
completely dependent on the properties
that specific solid substances exhibit.
One of the most active research fields in
our technological era is Solid State
Chemistry. This branch, also called
materials science, focuses on
synthesizing new metal compounds that
may result in crystalline solids. There is
strong interest in the unique magnetic,
electrical, optical, and catalytic
properties of these inorganic solids that
can be utilized for a whole array of
technological applications. Inorganic
materials are used to manufacture
devices such as semiconductors, which
are the devices that serve as the
foundation for all solid state electronic
such as transistors, silicon chips, photo
cells, and others (Cotton et. al 1995).
Solid state synthesis is usually carried
out in two distinct ways. One common
method involves mixing the reactants in
their liquid form (or aqueous solution,
depending on the solvent) so that a
chemical reaction takes place and the
solid product precipitates. The second
method, which is the one that will be
utilized during our research, is one of
the simplest and most widely used
procedures (Cotton et. al 1995). It
consists of using high temperature
reactions that require mixing two or
more finely powdered starting materials,
placing the mixture inside a sealed
container and then heating this same
container in a specialized oven at
>500˚C in order to obtain inorganic
compounds, especially in crystalline
form. Although simple and widely used,
this method has various shortcomings
that must be addressed. The main
disadvantage is that it is usually
challenging to predict the stoichiometry
of the product(s), resulting in an almost
Solid-State Synthesis of Mixed-Metal Oxides
Paola G. Caballero León1
, Anthony Hernández Rivera2
1
Department of Chemistry, RISE Program, University of Puerto Rico at Cayey
2
Department of Biology, RISE Program, University of Puerto Rico at Cayey

2. Scientific Manuscript 2014
trial and error based method. For this
reason, this specific branch of research
is often described as mostly exploratory
science. Having calculated a total of 10
reactions from groups 14/15, 14/14,
15/15 using the available finely
powdered starting materials available at
the laboratory, we now plan to
synthesize inorganic compounds and
analyze if the final products resemble
one of the possibilities that were initially
calculated. The stoichiometry of one of
the reactions with metals from group 14
and 15 was established so that one of
the products would have a pyrochloric
structure. A mixed metal oxide
compound with a pyrochloric structure
has a stoichiometry of A2B2O7, in which
the letters A and B represent two metals
(Jones and Knight 1997). According to
Salamat et al. (2011) solids with
pyrochloric have important dielectric
properties that make them essential in
the production of thin film devices and
are being used for microwave
applications. Most importantly we aim to
obtain solid inorganic compounds as our
final product, ideally in crystalline form,
that exhibit magnetic, electrical or other
unique properties that have variety of
technological applications.
2. Materials and Methods
2.1.Predicting Products
Two metals- Sn, Sb, Bi, or Pb -
were chosen as the primary reactants.
The stoichiometry of the metals was
established for further calculations. For
example, 4Sn: 3Bi is a reaction where
the stoichiometry of the reactants is 4
atoms of Sn for each 3 atoms of Bi.
Once the stoichiometry was determined,
all possible products were predicted. In
order to do this, the oxidation number of
each reactant was taken under
consideration. In the previous example,
Sn has two possible oxidation numbers:
+2 and +4. On the other hand, Bi only
has the oxidation number +3. Therefore,
there are only two possible products for
such reaction: 4Sn+2:3Bi+3 and 4Sn+4:
3Bi+3. The positive charges were
summed up to determine how many
oxygen atoms are needed in order to
predict a neutral compound. The oxygen
atoms from the air react with the
reactants. Oxygen has an oxidation
number of -2. This negative charge will
balance out the positive charges from
the metals. In the first combination of
the example, the sum of the positive
charges is (+8) + (+6) for a total charge
of +14. Therefore, seven oxygen atoms
are required because (7) x (-2) is equal
to -14. The overall charge of the
predicted compound is then (+14) + (-
14) which is equal to 0, in other words, it
is neutral.
Once the whole array of possible
products was predicted from simple
stoichiometry, the amount of the
reactants to be loaded was calculated.
The mass of the heaviest element was
calculated from 20 mg of the lightest
element and the established
stoichiometry. With these calculations,
the reaction mixture can be properly
prepared.
2.2.Preparation of Silica Tubes

3. Scientific Manuscript 2014
A long silica tube was cut into eight
12 inch smaller tubes. Each of these
tubes was divided into two smaller tubes
with the use of an acetylene flame.
Afterwards, the bottom part of each tube
was molded with the acetylene flame so
that it was completely sealed. Three
drops of acetone were added to the
tube. With the use of a Bunsen burner,
the bottom of the tube was heated up
until the acetone evaporated and a
single carbon layer formed on the inside
of the tube. The process was repeated
three times in order to obtain a three
layer carbon lining, each one higher
than the last. This serves to isolate the
reactants from the silica and ensure the
reaction happens as predicted.
Subsequently, the reactants were added
to the tube and stored for further
processing.
2.3.High Temperature Reaction
Once the finely powdered reactants are
added to the tube, the mixture will be
subject to a high temperature reaction in
order to obtain novel mixed metal oxide
crystals. Basically, the mixture is
heated up in an oven designed to
withstand high temperatures until both
reactants change to their liquid phases.
This part of the process can last for a
period of three weeks. Afterwards, the
solution is cooled down slowly, to permit
the formation of crystals. Although the
procedure is rather simple, it is also time
consuming. Due to some limitations, this
part of the project was not carried out.
3. Results
3.1.Predicting Products
Ten reactions were calculated using
metals from groups 14 and 15. The
stoichiometry for each reaction was
determined and the products were
predicted. The predicted products for
the mixing of same group metals (14/14
and 15/15) are summarized in table 1.
Group 14/14
1) 9Sn: 15Pb
Reactants Products
9Sn+2
, 15Pb+2
Sn9Pb15O24
9Sn+2
, 15Pb+4
Sn9Pb15O39
9Sn+4
, 15Pb+2
Sn9Pb15O33
9Sn+4
, 15Pb+4
Sn9Pb15O48
2) 3Sn: 5Pb
Reactants Products
3Sn+2
, 5Pb+2
Sn3Pb5O8
3Sn+2
, 5Pb+4
Sn3Pb5O11
3Sn+4
, 5Pb+2
Sn3Pb5O13
3Sn+4
, 5Pb+4
Sn3Pb5O16
3) 13Sn: 6Pb
Reactants Products
13Sn+2
, 6Pb+2
Sn13Pb6O19
13Sn+2
, 6Pb+4
Sn13Pb6O25
13Sn+4
, 6Pb+2
Sn13Pb6O32
13Sn+4
, 6Pb+4
Sn13Pb6O38
Group 15/15
4)7Sb: 21Bi
Reactants Products
7Sb+3
, 21Bi+3
Sb7Bi21O42
7Sb+5
, 21Bi+3
Sb7Bi21O49
5) 11Sb: 3Bi
Reactants Products
11Sb+3
, 3Bi+3
Sb11Bi3O21

4. Scientific Manuscript 2014
11Sb+5
, 3Bi+3
Sb11Bi3O32
The predicted products for the mixing of
mixed group metals (14/15) are
summarized in table 2.
Group 14/15
1) 7Bi:9Sn
Reactants Products
7Bi+3
, 9Sn+2
Bi14Sn18O39
7Bi+3
, 9Sn+4
Bi14Sn18O57
2) 13Pb:23Bi
Reactants Products
13Pb+2
, 23Bi+3
Pb26Bi46O95
13Pb+4
, 23Bi+3
Pb26Bi46O121
3) 33Pb:21Sb
Reactants Products
33Pb+2
, 21Sb+3
Pb66Sb42O129
33Pb+2
, 21Sb+5
Pb66Sb42O171
33Pb+4
, 21Sb+3
Pb66Sb42O195
33Pb+4
, 21Sb+5
Pb66Sb42O237
4)12Sn: 17Sb
Reactants Products
12Sn+2
, 17Sb+3
Sn24Sb34O75
12Sn+2
, 17Sb+5
Sn24Sb34O109
12Sn+4
, 17Sb+3
Sn24Sb34O99
12Sn+4
, 17Sb+5
Sn24Sb34O133
5) 2Sn:2Bi
Reactants Products
2Sn+2
, 2Bi+3
Bi2Sn2O5
2Sn+4
, 2Bi+3
Bi2Sn2O7
3.2.High Temperature Reaction
There were some limitations that
impeded us to obtain results. The main
obstacle was that the oven’s lid was not
available. Therefore, the oven was non-
functional and none of the reactions
could be loaded for further processing.
The secondary obstacle was the time
constraint to carry out the project, which
was partially completed.
4. Future Work
Due to time constraints and a non-
operational oven we will put on hold our
project until the appropriate parts of the
oven arrive and are installed. After this
we intend to load our respective
reactions using the finely powdered
starting materials available at the
laboratory, elements: Sn, Pb, Sb, and Bi
(groups 14/15, 14/14, and 15/15). We
will then proceed to synthesizing new
solid inorganic compounds in
accordance with the established
reactions.
5. Acknowledgements
We would like to give special thanks to
RISE Program for this great research
project that has once more enabled us
to gained invaluable laboratory and
research experience. Also we highly
appreciate our research mentor Dr.
Lukasz Koscielski and Teaching
Assistant (TA) Gerardo Ramos.
Literature Cited
Table 2: Mixed
Metal Oxide
reactions from
groups 14/15
and the
respective
predicted
compounds.

5. Scientific Manuscript 2014
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Salamat A, Hector AL, McMillan PF,
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