Characterisation of SnO 2–CoO–MnO–Nb 2O 5 ceramics

Abstract

Varistors based on SnO 2 have attracted increasing interest in recent years. However, the combined effect of CoO–MnO on SnO 2 ceramics is still unclear. In this study, the non-Ohmic behaviour of the 98.95 mol%SnO 2–0.5 mol%CoO–0.5 mol%MnO–0.05 mol%Nb 2O 5 system, the microstructures and the influence of sintering temperature were investigated. The samples were prepared by the mixed oxide route, and were sintered at temperatures in the range 1250–1450 °C. SEM observation and EDS analysis revealed that the ceramics have a two-phase microstructure comprising SnO 2 primary grains and a Mn, Co rich secondary phase of small particles. The sintered density of the samples increased with the increase in sintering temperature. The maximum non-linear coefficient ( α = 10) was obtained at a sintering temperature of 1350 °C.