Investigation on the grain features of PbO-doped ZnO and ZnO varistors

Abstract

The effects of lead oxide (PbO) on the grain characteristics of zinc oxide ceramics and zinc oxide varistors were surveyed in this study. PbO was added to two ZnO systems in varying concentrations of 1 mol%, 5 mol% and 10 mol%. The first system was made up of only ZnO while the second system is the ZnO-Bi₂O₃-Sb₂O₃ system. The addition of PbO caused grain boundaries to fuse together during the sintering process, leading to an increased grain size. Addition of a small amount of PbO to the systems causes the grains to become disordered, increasing the porosity. However, as more PbO is added, the grains become more fused together, producing less grain boundaries per unit area. This leads to a decrease in the porosity of the samples.