Effects of heat treatment on degradation in the electrical properties of ZnO ceramics after DC pre-stress were investigated from the viewpoint of the time dependence of the leakage current under DC pre-stressing, the voltage-current (
V-I) characteristics, and the thermally stimulate current (TSC) before and after the DC pre-stressing.
For none heat-treated sample, the leakage current increases with the increase of the DC pre-stressing time. In this sample, the degradation of the
V-I characteristics observed and the new TSC peak observed at high temperature region after DC pre-stressing. The magnitude of this TSC peak is greater than that of the other TSC peaks. On the other hand, in the heat-treated sample at 600°C, the leakage current decreases with the increase of the DC pre- stressing time. The current in
V-I characteristics decreases after the DC pre-stressing.
From these results, it is suggested that the effect of DC pre-stressing on the electrical properties for ZnO ceramics is changed remarkably by the heat treatment after sintered ZnO ceramics. These phenomena will be associated with the phase transition of the Bi
2O
3-rich intergranular layer by heat treatment after sintered ZnO ceramics.
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