INTRINSIC DEFECTS IN ZnO VARISTOR CERAMICS

The relationship between dielectric loss factor D (tanδ) and frequency for ZnO-Sb2O3-BaO and ZnO-Bi2O3-Sb2O3-BaO varistor ceramics has been investigated. A new dielectric loss peak was found near by 2MHz at room temperature for the sample in the absence of Bi2O3, the corresponding electron trapping level was about 0.18 eV, it was considered that the loss peak resulted from intrinsicdefect Zni . It was assumed that the formation of intrinsic defect Zni was restricted by ion Bi, it was consistent with experimental fact that the degradation properties of varistor ceramics under the long duration load voltage are improved with the increasing amount of Bi2O3.