Electrically and Optically Active Nonstoichiometric Metal Oxides

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This research is the continuation of a very productive program under Professor H. L. Tuller at the Massachusetts Institute of Technology. Under the prior support by the National Science Foundation, Professor Tuller and his colleagues published more than eighteen significant papers in scientific journals on topics such as mixed electrical conduction in nonstoichiometric oxides, electronic structure of grain boundaries and interfaces in polycrystalline zinc oxide, defects and charge transport in stabilized tantalum oxide, electrical and optical properties of magnesia and alumina, thermodynamics and transport properties in mixed cerium and uranium oxides, and metal oxide sensors. The current research will emphasize defect formation, interaction, and transport in nonstoichiometric metal oxides in both single and polycrystalline forms. The program will include both experimental and theoretical efforts. Electrically-active ceramic interfaces (which form the basis of a variety of advanced electronic devices) will be studied with the goal of modifying and controlling the chemistry of these interfaces, characterization of their electronic transport properties, and interpreting the correlation between the two. Oxygen defect concentration as a function of depth from the surface will be determined with complex impedance techniques and through a unique new method based upon photoelectrochemical etching. Solid state diffusional techniques will be used to establish the oxygen ion configuration as a function of composition. Electronic ceramics are technologically important to the semiconductor industry, the sensor industry, and for fuel cells, catalysts, and high temperature batteries. Understanding of the defect structure and electrical charge transport is crucial to the performance of these materials. Training of students to do research in this critical area is a key part of this research program.