Effect of cooling rate on electrical properties, impulse surge and dc-accelerated aging behaviors of ZPCCD-based varistors

Abstract

The effect of cooling rate on nonlinear electrical properties, and stability against impulse surge and dc-accelerated aging stress of ZPCCD-based varistors was investigated. The cooling rate relatively slightly affects the microstructure, whereas it did not significantly modify the densification process. The nonlinear coefficient increased with the increase of cooling rate up to 240 °C/h, whereas the further fast cooling rate caused it to decrease. The samples cooled at 240 °C/h exhibited the highest nonlinearity, in which the nonlinear coefficient is 61.6 and the leakage current density is 6.8 μA/cm2. The aging was not significantly affected by the specified impulse surge stress, whereas it was greatly affected by dc-accelerated aging stress. The samples cooled at 120 °C/h exhibited the highest stability, in which the variation rate of breakdown field is −5.5% and the variation rate of nonlinear coefficient is −29.1% under continuous stress composed of the specified impulse surge and dc-accelerated aging stress of 0.95 E B/150 °C/24 h.