Report
Materials Science
Materials science or materials engineering is an interdisciplinary field that deals
with the study of matter and applying their properties to various areas in science
and engineering. This field deals with the structure of matter at the atomic or
molecular scale and the properties that it possesses on the macroscopic level. Its
interdisciplinary nature is evidenced in the application of various concepts centered
in physics and chemistry. Materials science has extended applications in forensic
science and failure analysis, the later being closely linked with the collapse of
structures and even aviation accidents. It is therefore quite clear that this field of
study opens the door to deep understanding and offers explanatory power for many
of the things we encounter in our contemporary society. Many of the pressing
scientific problems today exist because of limitations in this field; therefore,
breakthroughs in material science will inevitably have significant impacts on the
development of future technologies.
Background
The aspect of materials science that I have explored this summer involves ceramic
oxides containing various ionic deficiencies in a special structure that is referred to
as perovskite (ABO3) where various elements are able to assume the A or B
position. The research involved various compositions of Lanthanum, Strontium,
Chromium and Iron (LSCF) where the percentages of these elements where varied
and the resulting structure examined. In the perovskite structure referenced above,
Lanthanum and Strontium occupied the A position and Chromium and Iron
occupied the B position. Other examples of this type of structure are pyrochlore
(A2B2O7) and brownmillerite (A2B2O5). These materials exhibit interesting and
intriguing properties. Some of these include superconductivity, ferro-electricity
and charge ordering. The most relevant application of the use of these materials is
there use and importance to micro electric devices which is crucial in our time with
the advancement of nanotechnology. In addition, synthetic perovskites have been
identified as inexpensive base materials for photovoltaics, demonstrating a
conversion efficiency of as much as 15%. There were three procedures used in
preparing the compounds. The first was referred to as co-precipitation, the second
was sol-gel and the third was solid state sintering. The structure is later examined
by X-ray diffraction and compared to a data base in order to verify the type of
structure that has been created.
Procedures
Co-precipitation of ZrO2-Sc2O3
A mass of 0.5644g of Sc2O3 was measured on weighing paper. Then the mass was transferred to a
200 mL beaker. Next , 20 mL of 90% concentrated HNO3 was added to dissolve the sample. Next,
the sample was then placed on heating plate at 100°C and stirred until oxides dissolved (< 1 hr)
Afterwards, 250 mL of Zr nitrate solution (15.1 g Zr/L) was placed in a 1000 mL beaker and the
dissolved Sc2O3 is added to the Zirconium solution and mixed. The pH is now measured to record
its acidity, the acidity will usually be very low almost zero on the pH scale. In order to move the
pH up to the basic side, Ammonium is now added to allow the nitrates to precipitate;
the pH is monitored until it reaches between 9 and 10
The solution is then filtered using a vacuum aid into an Erlenmeyer flask. The filtered compound is
allowed to dry in air
The dried compound is placed in a crucible where it is then calcined at 1000°C for 10 hrs in a box
furnace. Afterwards, the sample is then grounded in a mortar with acetone added
Finally, X-ray diffraction is then performed to examine structure of the compound which was formed
Sol-gel
The above composition was synthesized from La2O3 (Lanthanum III Oxide), Sr(NO3)2
(Strontium II Nitrate), Fe(NO3)3 9H2O (Iron III Nitrate) and Cr(NO3)3 9H2O (Chromium III Nitrate).
The Lanthanum oxide was dissolved in hot nitric acid and the nitrates were dissolved in deionized water separately. Afterwards, the solutions were mixed. Then, an excess of citric acid
and ethylene glycol were added. The mixture was then placed in a water bath at 80°C being
stirred constantly for 6 hrs to evaporate the water and obtain a gel. This gel is then dried at 200
°C and pre calcined at 350°C for 3 hours. Afterwards, the powder is claimed at 900°C for 2
hours. Finally, x-ray diffraction is performed again to verify structure.
Solid State sintering
Sc2O3 (Scandium III Oxide) and ZrO2 (Zirconium Oxide) are pulverized in a crucible and placed in
an aluminum jar with ¼ to 1/8 inch aluminum balls with isopropyl alcohol to facilitate their
complete mixture with each other. The mixture is then placed in a planetarium ball milling for
12 hours at 250 rpm (10 min mixing 15 min break). When completed, the compound will be at
1000°C for 24-48 hrs. XRD performed to investigate structure.
Conclusion
As referenced above, each procedure terminates in an x-ray diffraction laser run where the
created compound is placed in the diffraction equipment and the following image is produced
The rings represent the characteristic peak produced by the diffracted ray which ought to be
consistent with the materials that make up the compound and the particular final geometric
shape.
Acknowledgements
Dr Hong’s Research group (Maria Mora)
Journal of Membrane Science 320 (2008)
Wikipedia