Influence of SrCO3‐doping on the microstructure and electrical properties of ZnO–(Bi2O3/Sb2O3) varistor ceramics

The objective desired is the elaboration of varistors based on zinc oxide-doped by the addition of SrCO3 with a different quantity of 1, 2, 3 and 4 mol% SrCO3, such that the base quantity is 0.5 mol% of Bi2O3, 0.5 mol% of Sb2O3 and 99 mol% of ZnO. The varistors were sintered at the temperature 1000–1200 °C in a solid way, the microstructural characteristics are carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) where we could determine several secondary phases such as Zn2.33Sb0.67O4, Bi3Sb3Zn2O14, Bi6Sr2O11, Bi2O3 and Sb2O3 have been formed. These latter were the result of a competition between diffusion and segregation of oxides into the grain core and the grain boundaries of matrix. High SrCO3 content was originally the segregation of the Bi2O3, Sb2O3 oxides and of solid solution (Bi6Sr2O11) in the grain boundaries. Grain size, relative density, electrical permittivity (ε′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\upvarepsilon }^{\mathrm{^{\prime}}}$$\end{document}), loss factor (tanδ) and leakage current (IL) are reduced when increasing the amount of SrCO3, on the other hand, the non-linearity coefficient (α) and electric voltage (Vb) increased, the sample with the highest amount of SrCO3 presents a better coefficient of non-linearity 29.37 and 1020 V in comparison with others varistors. In all of these results it can be said that the addition of SrCO3 was given an improvement on the electrical property, dielectric and microstructure of the base varistor. The obtained varistor would be very promising in low-voltage power transmission systems.