Fast ion conductors: future trends

Abstract

The characteristics of various fast ion conductors (FICs) are reviewed with an emphasis on correlating their structural and transport properties. This approach leads toward an improved understanding of the cause of fast ion conduction in solids and suggests avenues for future research and applications. All three categories of fast ion conductors—extrinsic, intrinsic and amorphous—are briefly reviewed. Special attention is focused on (a) some of the newer, intrinsically disordered oxygen conductors such as α-Ta 2O 5 and the pyrochlore system Gd 2(Zr xTi 1−x) 2O 7, (b) amorphous cation conductors both organic and inorganic and (c) two-phase composite systems. Some of the more promising new FICs are discussed in relation to applications which will probably become increasingly important before the end of the century including fuel cells, batteries, sensors, electrochemical pumps and smart windows.