Solid electrolytes with oxygen ion conduction

Abstract

Oxygen ion conductors constitute an important class of solid electrolytes and have been extensively studied from scientific and technological standpoint. Most of the oxygen ion conductors (eg. those based on ZrO₂, ThO₂, CeO₂ and Bi₂O₃) have a perfect or distorted fluorite type structure. Some oxides with a perovskite type structure also exhibit oxygen ion conduction. All these materials show enhanced conductivity when doped with aliovalent impurities. The defect structure of these materials and the resulting transport properties (electrical conductivity, diffusion and transference number) are discussed as a function of temperature, oxygen partial pressure and composition. Some of the important measurement methods are briefly surveyed. Interface phenomena receive attention as they affect transport behaviour at the electrode - electrolyte combination. Defect interactions in these massively defective solids are presented through an analysis of theoretical models. Finally, some of the important applications of the oxygen ion conductors in fuel cells, oxygen probes and pumps and electrochemical decomposition of water are indicated.