A new view on impulse degradation of ZnO-based ceramics

The electrical and dielectric properties of a commercial ZnO-based varistor ceramics were measured in the process of 8/20mus impulse current degradation with a current density of 1725A/cm². The characteristic of U-I in the pre-breakdown region was mainly investigated. It was found that the varistor voltage U_1mA will first increase rapidly with the times of impulse, and then remain stable and finally decrease sharply. Furthermore, a new loss peak emerges in the dielectric spectra after 600 times of impulse degradation, which suggests a new trapping behavior introduced in the degradation process. It was also found that the non-linear coefficient was more sensitive to the degradation process than varistor voltage U_1mA. These phenomena were not reported before.