Long-time polarization currents in metal-oxide varistors

Abstract

The low‐frequency (10⁰–10⁻⁴ Hz) behavior of metal‐oxide varistors is obtained from analysis of the charging and discharging currents which flow upon the application and removal of a step voltage. These results are compared to data for the complex dielectric constant ε=ε′−iε^″ obtained using an ac bridge in the frequency range 10¹–10⁻¹ Hz. The presence of long‐time polarization currents dominates the low‐field low‐temperature (T?0°C) dc response of these devices. When the varistor microstructure is taken into account the curves of ε^″ (ω) versus frequency are consistent in slope and magnitude with other published data obtained on a wide variety of dielectric materials.