Characterisation of SnO2-CoO-MnO-Nb2O5 ceramics

Varistors based on SnO2 have attracted increasing interest in recent years. However, the combined effect of CoO-MnO on SnO2 ceramics is still unclear. In this study, the non-Ohmic behaviour of the 98.95 mol%SnO2-0.5 mol%CoO-0.5 mol%MnO-0.05 mol%Nb2O5 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 SnO2 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.