Abstract
The electrical properties of ZnO ceramics were studied from their voltage-current characteristics, thermally stimulated current (TSC), and heat-treatment effects.
ZnO ceramic samples with a few mol% of insulating oxide components were prepared. After sintering at 1, 200°C in air, some of them were heat-treated at various temperatures between 450°C and 900°C in air.
In the voltage-current curves, the current varies as a function of applied DC voltage, according to the relation; I=kVa, where α is the nonlinear exponent. The nonlinear exponent α decreased with the heat-treatment temperature in the low temperature resion, and it became the lowest around 600-750°C. But they almost recovered at 900°C.
Three TSC peaks (designated by P1, P2 and P3 from low temperature side) were observed in the nonheat-treated sample. The sample heat-treated at 600°C and 750°C showed only the P1 and P2 peaks, the P3 peak increased in magnitude with the increase of the biasing temperature Tb, and it shifted toward high temperature side.
These results suggest that the electrical properties of ZnO ceramics will be associated with the phase transition of the Bi2O3-rich intergranular by heat-treatment.
