Singular Nature of Preferential Conducting Paths at High Electric Fields in ZnO‐Based Varistors

Abstract

The ac electrical response of ZnO‐based varistors was monitored as a function of frequency (50 Hzf2 MHz) and electric field (60% ElmA/cm2EElmA/cm2, ElmA/cm2 in the critical field at 1 mA/cm2) at room temperature, and these data were represented in the complex impedance (Z*) plane. The finite depression angle observed in this plane was rationalized in terms of nonuniformity in the measured reactance between the terminals. The singular nature of the series‐parallel combination of the uniform conducting paths between the electrodes was suggested when this depression angle diminished to 0° at high electric fields (EElmA/cm2).