Microstructural developments and electrical properties of novel coarse-grained SnO2 varistors obtained by CuO addition for low-voltage applications

Abstract

This research focused on making novel low-voltage SnO2 varistors by CuO addition on conventional high-voltage SnO2 varistors. Moreover, the withstand surge capability of samples was studied. The results showed that CuO addition enhances grain growth of SnO2 and coarse-grained SnO2 varistors with simple microstructures were acquired in 1 mol% CuO-doped sample. This coarse-grained SnO2 varistor presented a high nonlinear coefficient (23) and low leakage current density (23 µA/cm2) with low breakdown field value of 0.6 kV/cm. Despite the large grain size, the low residual voltage ratio (2.3) was obtained for this sample compared to the CuO-free sample. The decrease in grain electric resistivity by CuO addition is responsible for the low residual voltage ratio observed in coarse-grained SnO2 varistors. Furthermore, it was found that withstanding surge current density and disruptive discharge current density of 1 mol% CuO-doped sample were 1.2 kA/cm2 and 1.4 kA/cm2, respectively, which is superior for low-voltage applications.