Effect of Sintering Temperature on the Microstructure and Electrical Characteristics of Low Clamping Voltage Zinc Oxide- Based Ceramic Varistor

摘要

Pelletized samples of polycrystalline zinc oxide ceramics doped with 2mol% MnO2 and 3mol% PbO were prepared by the conventional method of ceramic processing. The requisite composition was obtained by the direct mixing of constituent phases (DMCP) technique. Sintering was carried out at various temperatures ranging from 650oC to 850oC. The effects of sintering on the non-linear characteristics of the doped ceramic samples were investigated. The threshold or breakdown voltages were found to decrease as sintering temperature increased. Microstructural investigation revealed improved homogeneity and increased grain sizes with increasing sintering temperature. The random distribution of secondary phases also featured prominently. These findings were observed to correlate with the evolution of electrical characteristics while the sample sintered at 850oC exhibited the best electrical response suitable for varistor behaviour.