OXYGEN-ION CONDUCTION AND STRUCTURAL DISORDER IN CONDUCTIVE OXIDES

Defect-free crystals do not conduct ions. Increasing disorder initially translates into enhanced atomic transport. Heavily defective crystals, however, often exhibit successively lower levels of atomic diffusivity as the defect level is increased. This dilemma may be addressed by considering that highly disordered solids tend towards order. Interesting insights may be obtained by considering compounds with related structures which can be induced to go through order-disorder transitions either by change in temperature or composition. A number of such systems will be considered including materials with structures related to the fluorite and perovskite structures. The significance of these considerations on the application of such materials in solid state electrochemical devices will also be addressed as are the key contributions made by Arthur S. Nowick and co-workers towards our understanding of defect-dopant interactions in such systems.