SUPPRESSION OF ACCEPTOR SOLUBILITIES IN BATIO3 DENSIFIED IN HIGHLY REDUCING ATMOSPHERES

The solubilities of acceptor impurities are strongly suppressed when B aTiO3 is densified in highly reducing atmospheres. This is evidenced b y a shift in the minimum in the equilibrium electrical conductivity to higher oxygen activities, a decrease in the ionic contribution to the conductivity, and a decrease in the leakage current and the rate of l eakage current degradation under temperature-voltage stress. The norma l solubility is restored by subsequent anneals in air that result in s ubstantial grain growth, and the properties then revert to those of Ba TiO3 sintered in air. The solubility suppression is attributed to a ma ss-action interaction between the processes that generate oxygen vacan cies, those that result from the compensation of acceptor centers, and those that result from reduction.