IMPACT OF RARE EARTH OXIDES ON THE STRUCTURE AND ELECTRICAL PROPERTIES OF ZnO-Bi2O3−BASED VARISTOR CERAMICS: A COMPARATIVE ANALYSIS OF Y2O3 AND CeO2

Zinc oxide (ZnO)-based varistor ceramics, incorporating varying amounts of Y2O3/CeO2, were fabricated through a twostep solid-state reaction method involving pre-calcination and subsequent sintering processes. ZnO powder and corresponding additives served as raw materials in the production. The investigation of phase composition, microstructure, and electrical properties employed techniques such as X-ray diffractometry (XRD), scanning electron microscopy (SEM), and direct current electrical measurement. The findings revealed that varistor ceramics sintered at 950°C, using powder pre-calcined at 800°C and doped with an appropriate amount of Y2O3, exhibited enhanced electrical properties. Conversely, the introduction of varying concentrations of CeO2 did not contribute to the improvement of the electrical characteristics. The CeO2-doped samples displayed lower breakdown voltages and nonlinear coefficients compared to the undoped sample (M0). The addition of Y2O3 proved effective in improving the nonlinear coefficient but resulted in a decrease in the breakdown voltage withstand capability of the samples. A Y2O3 content of 0.5% was identified as a suitable compromise, balancing both factors. Notably, ZnO varistors doped with 0.5 mol% Y2O3 demonstrated optimal comprehensive electrical properties, featuring a breakdown field of 620 V/mm and a nonlinear coefficient of 45. These results suggest that Y2O3 doping holds promise as a viable strategy for achieving varistor ceramics with outstanding electrical performance.