Microstructures and electrical properties of ZnO–V2O5–MnO2 varistors with low-temperature sintering

The microstructures and electrical properties of 95 at.%ZnO + xV2O5 + (5−x)MnO2 varistors (x = 1, 2, 3, 4, 5 at.%) sintering at 900 °C were investigated. The microstructure of all the samples consisted of ZnO grain with β-Zn3(VO4)2 and γ-Zn3(VO4)2 as minority secondary phases. The average grain size decreased from 10.4 to 4.5 μm with the decrease of V2O5 mol fraction and it is attributed that ZnO grains could probably grow rapidly in the presence of a rich liquid phases related to V2O5 concentrations. The breakdown voltage increases from 6444 to 1446 V/cm with increase of V2O5 mol fraction due to the decrease of the average grain size. The samples containing 2 at.% V2O5 and 3 at.% MnO2 varistors exhibited the best nonlinear properties, with present nonlinear coefficient (20.8).