New Oxygen Ion Conductors

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Abstract 9523157 Zur Loye In the previous funding period, it was shown that new oxide ion conductors containing intrinsic oxygen vacancies can be readily synthesized by creating intergrowth structures and, furthermore, that such intergrowths can exhibit very high oxide ion conductivities above an order-disorder transition. Although the exact mechanism for this order-disorder transition is not yet fully understood, it appears that by appropriate choices of structure type and elemental compositions such transitions can be induced in many types of intergrowth structures containing intrinsic oxygen vacancies. This approach of creating intergrowth structures for the synthesis of new oxide ion conductors is a general one, and can be extended to other systems. During the proposed funding period, major emphasis will be placed on investigating the precise structural changes that occur during the order-disorder transitions and on extending this work to include brownmillerite/rock salt intergrowths and on modifying a class of materials which is structurally related to the Aurivillius phase. It is expected that new oxygen ion conductors will be synthesized and that their oxygen ion conductivity and their stability in both reducing and oxidizing conditions will be determined. The new materials will be synthesized by high temperature solid state methods and structurally characterized by Rietveld refinement of powder X-ray or neutron diffraction data. Their chemical and physical properties will be determined by standard electrical and analytical techniques. %%% The objective of the proposed research is to synthesize new oxide ion conductors and to characterize their structures, conductivities and chemical stabilities. Oxide ion conductors have many important applications in the areas of solid oxide fuel cells, oxygen sensors, oxygen pumps and partial oxidation catalysts. Although this class of materials has been known for a long time, there still exists the general need to develop new oxide ion conductors that exhibit high conductivities and that are chemically stable under both oxidizing and reducing conditions.