Low-temperature ac properties of metal-oxide varistors

Abstract

Low‐temperature (3.5<Tf in the range 30<f5 Hz. A loss peak and dispersion in ε observed at 4 °K are identified as resulting from the two‐phase structure of the ZnO varistor (Maxwell‐Wagner model). We find the zinc oxide grain resistivity ρ_ZnO∼10⁶ Ω cm in a typical commercial varistor at 4.2 °K. The physical origin of a second loss peak observed in measurements around room temperature is discussed. We show the latter dispersion is not interpretable using a Maxwell‐Wagner model for an inhomogeneous conductor.