Effect of sintering temperature on microstructure and nonlinear electrical characteristics of ZnO varistor

Abstract

The nonlinear properties of ZBMCCS-based varistors, which are composed of ZnO–Bi2O3–MnO2–Cr2O3–Sb2O3–Co3O4 and SiO2 are studied inrelation to sintering temperature, in the range of 1280–1350[Formula: see text]C. The samples are investigated for grain morphology by using scanning electron microscope (SEM). These samples were examined by using X-ray diffraction patterns (XRD) and DC electrical measurements. X-ray diffraction analysis of the samples show the presence of ZnO, Zn2SiO4 willemite phase and Co[Formula: see text]Sb[Formula: see text]O4 spinel phases.The average grain size of ZnO increased as the sintering temperature increased from 2.57 to 6.84 [Formula: see text]m. In the examined temperature range, the breakdown field decreased from 2992 to 127[Formula: see text]V/cm with the increase of sintering temperature. This system gives a relatively high nonlinearity coefficient [Formula: see text] (at a sintering temperature of 1280[Formula: see text]C) with a low leakage current of 0.21[Formula: see text]mA/cm2.