COMPOSITE SOLID ELECTROLYTES IN THE AGI-AL2O3 SYSTEM

The ionic conductivity of AgI-Al2O3 composites was investigated. The c omposites were produced by mechanically mixing the components in a hig h-energy planetary mill, followed by sintering at temperatures from 35 0 to 600-degrees-C. It is shown that this procedure allows one to obta in strong composite pellets with up to 90 vol % Al2O3. The maximum con ductivity from 0.001 to 0.0015 S/cm was found in the composites with 4 0 - 50 vol % of the oxide. The behavior that the composites show with respect to temperature and concentration is accurately described by a percolation model of the conductor-surface conductor-insulator type at high temperatures, and of the insulator-surface conductor-insulator t ype at low temperatures. Upon prolonged sintering, the silver iodide o f the composites separates into two phases: the bulk phase, which is i dentical to pure AgI in properties, and the surface state, which is re sponsible for the high ionic conductivity of the composites.