SYNTHESIS AND THERMAL-STABILITY OF DENSE POLYCRYSTALLINE AG, CD, AND PB BETA'' BETA-ALUMINAS

Ag, Cd, and Pb β″ β-alumina ceramic tubes were prepared by ion exchange of sintered Li2O-stabilized Na β″-alumina containing ∼19% β-phase. X-ray diffraction patterns of these materials are presented. Thermal stability of substituted β″ β-aluminas was investigated by heating the materials to 760, 960 and 1075°C. A gradual degradation of the β″-phase to the β-phase was observed. This depends not only on the temperature, but also on the chemical character of the mobile ion. Thus, while Cd appears to stabilize the β″-phase, Pb seems to increase the rate of the β″-phase degradation. Ag and Cd β-aluminas were also prepared by ion exchange and their XRD patterns are included. © 1990.