Effect of small changes in sintering temperature on varistor properties and degradation behavior of V–Mn–Nb–Gd co-doped zinc oxide ceramics

Abstract

The effect of small changes in sintering temperature on microstructure, electrical properties, dielectric characteristics, and degradation behavior of V–Mn–Nb–Gd co-doped zinc oxide ceramics was investigated. With the increase of sintering temperature, the densities of the sintered pellets decreased from 5.54 to 5.42 g/cm3 and the average grain size increased from 4.1 to 11.7 μm. The breakdown field (E1 mA) decreased noticeably from 7138 to 920 V/cm with the increase of sintering temperature. The varistor ceramics sintered at 900 °C exhibited excellent nonohmic properties, which were 66 for the nonohmic coefficient and 77 μA/cm2 for the leakage current density. Concerning stability, the varistors sintered at 900 °C exhibited the strongest accelerated degradation characteristics, with ΔE1 mA =–9.2% for DC accelerated degradation stress of 0.85 E1 mA at 85 °C for 24 h.