Microstructural and electrical properties of multicomponent varistor ceramics with PbO–ZnO–B2O3 glass addition

Zinc oxide based ceramics are widely used materials in varistors because of their excellent nonlinearity. Traditionally these ceramics are sintered at high temperatures (about 1,100–1,300°C). In this work a novel zinc oxide-based material with a low sintering temperature (900–1,000°C) was investigated. This material can be used in varistors consisting of several ceramic layers with embedded silver/palladium thick-film electrodes. This paper explains the research procedure employed with this novel varistor material, including the effect of sintering aid addition on the final electrical properties and fired microstructure. The electrical properties achieved are compared to the values measured from the original zinc oxide composition without sintering aid addition. Especially the I–V characteristics, nonlinearity coefficient α, breakdown voltage Vbk and leakage current density JL are investigated. The sintering properties are also reported. It was found that by adding 10 wt.% of glass and using a 900 °C sintering temperature, the material had good varistor characteristics, as Vbk = 378 V/mm, α = 33 and JL = 15 μA/cm2. The investigated varistor material can be applied to protect electrical circuits against surges.