Synthesis and characterization of ZnO based varistor ceramics: effect of sintering temperatures

Abstract

Purpose The purpose of this paper is to investigate the effects of the sintering temperature on the microstructural, morphological and electrical characteristics of Zinc oxide (ZnO)-based varistors. Design/methodology/approach This study used a conventional method to design and produce ZnO varistors by sintering ZnO powder with small amounts of various metal oxides. Furthermore, the effect of sintering temperature on varistor properties of (Bi, Co, Cr, Sb, Mn)-doped ZnO ceramics was investigated in the range of 1280–1350 °C. Findings The obtained results showed an EB value of 2109.79 V/cm, a Vgb value of 0.831 V and a nonlinear coefficient (α) value of 19.91 for sample sintered at temperature of 1300 °C. In addition, the low value of tan δ at low frequency range confirmed that the grain boundaries created in 1300 °C sintering temperature were obviously good. Originality/value Based on the previous research on the ZnO-based varistors, a thorough study was carried out on these components to improve their electrical characteristics. Thus, it is necessary that those varistors have low leakage current and low value of dissipation factor to ensure their good quality. High breakdown fields and nonlinearity coefficients are also required in such kind of components. The effect of sintering temperature on the varistor properties of the new compositions (zinc, bismuth, manganese, chrome, cobalt, antimony and silicon oxides)-doped ZnO ceramics was studied in the range of 1280–1350 °C. Also, the microstructure and the phase evolution of the samples sintered at various temperatures (1280 °C, 1300 °C, 1320 °C and 1350 °C) were investigated according to X-ray diffraction and scanning electron microscope measurements.

An Ultralow Concentration of Cr2O3 Dopants‐Driven Lower Temperature Sintering ZnO‐Based Varistor Ceramics

“…The XRD profile presented in Figure offers a comprehensive depiction of the impact of varying sintering temperatures on the evolution of the spinel phase. [ 20 ] Figure 1a shows the XRD pattern of the ZnO‐based varistor ceramic doped with Cr 2 O 3 content of 0.1 mol% under different sintering temperature conditions, which clearly shows that the least amount of spinel phase can be formed when the sintering temperature is at 950 °C. The peaks in the range of 32–36° are indicative of the spinel phase, as elucidated in the magnified pattern delineated in Figure 1b, the XRD intensity of the spinel phase increases gradually with the sintering temperature.…”