Comparison of electrical properties of ZnO-Bi2O3-based ceramics prepared by conventional and spark plasma sintering (SPS) methods

Abstract

ZnO-Bi2O3-metal oxide systems are successfully utilized as varistors due to their non-linear I-V behavior. The electrical properties of ZnO-based varistors strongly depends on grain boundary phase composition and microstructural features. In this study, ZnO-based varistors containing different amount of CuO (0-2 mol%) were sintered by conventional and spark plasma sintering (SPS) methods, which resulted different I-V characteristics. While the samples sintered by SPS method were observed to have smaller grain size, more homogenous microstructure and higher density, grain boundary thickness reduced due to removal of bismuth, which was the result of high vacuum environment during sintering step. Since the barrier thickness of SPSed samples decreased, a lower breakdown electrical field (E-b) value was recorded in comparison to conventionally sintered samples. It was also detected that E-b values of both conventional and SPS samples increased with increasing CuO content.