Thermodynamics and Microstructure of Oxides

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This research is the renewal of a special Creativity Extension Award. The prior grant was highly productive resulting in more than twenty publications in refereed scientific journals with more than five addition being prepared. A summary of the significant accomplishments includes determination that the defect structure in barium titanate dielectrics was very dependent upon the processing of the material with little difference in stoichiometry noted; the defect structure of beta alumina solid electrolytes has both long range order and long range disorder which depends upon the stoichiometry and the thermal history; the mixed ion effect in beta alumina was explained and shown to be related to the defect structure (conductivity varies by as much as several thousand times for the same material); solid electrolytes with more control of the structure and properties were synthesized using ion exchange techniques. The renewal grant will emphasize research on increased understanding of the critical chemical factors affecting the structure and properties of oxide ceramics and on synthesis of new oxides using this understanding. Materials being investigated include layered transition metal oxides, copper oxides, and lanthanide beta alumina. Analytical techniques used include high resolution electron microscopy, x- ray diffraction, Raman spectroscopy, infrared spectroscopy, thermal analysis, and electronic characterization (conductivity, dielectric loss, magnetic susceptibility). The materials being investigated have technological importance because of their potential application in thermal batteries, lasers, high temperature superconductors, dielectrics for communications etc.