Degradation characteristics of low-voltage ZnO varistor manufactured by chemical coprecipitation processing

The chemical coprecipitation processing has been developed to manufacture low-voltage ZnO varistor. The emphasis of the process is mainly on improving the stability against AC degradation stress and pulse degradation so as to obtain high quality component. It was found that the higher electrical field (Eb = 87.5 V/mm) and nonlinear coefficient (α = 32.5) can be obtained on the sintered sample prepared with this method compared with sample of identical overall composition prepared by conventional ceramic processing route. The improvement in electrical properties may be explained by the homogeneous distribution of various dopant in the mixed powder and the chemically more uniform structures.