Effects of copper oxide on the microstructural morphology and electrical properties of tin oxide-based varistor ceramics

Abstract

The effects of copper oxide additive on the densification, microstructural morphology and nonlinear electrical properties of tin oxide-based varistors are investigated. It is found that copper oxide significantly improves the densification of tin oxide ceramics, while excess copper reduces the densification. Copper oxide partially centralizes at the grain boundaries and partially evaporates at sintering, while tantalum improves the conductivity of the grains. All the samples have excellent nonlinear electrical properties and the sample doped with 0.25 mol% CuO possesses the highest density, the highest nonlinearity coefficient (α = 37.7) and the lowest leakage current density (JL = 12.6 µA cm−2) among all the samples. The copper oxide intergranular insulating layer separates the two semiconductive tin oxide grains and forms barriers.