Improvement in the nonlinear electrical characteristics of SnO2 ceramic varistors with Dy2O3 additive

The effects of Dy2O3 on the microstructure and electrical properties of the SnO2 based varistor system were investigated. It was found that Dy2O3 significantly affects the grain size and electrical properties of the SnO2-based varistors. The sample with 1.00 mol% Dy2O3 has the best nonlinear electrical property and the highest nonlinear coefficient (α = 26.3) among all samples. By SEM, TEM and EDS images, it was found dysprosium segregates at the grain boundary, which is responsible for “p-type characteristics” of the grain boundaries. The reason that grain size decreases with increasing Dy2O3 concentration is given. The reason why the varistor sample has the excellent nonlinearity is explained.