Investigation of Structural, Sintering Kinetics, and Electrical Properties of (ZnO–Bi2O3) Based Ceramic Varistors System Doped with ZrO2

This investigation focused on the impact of ZrO2 doping on phase formation, microstructure, sintering kinetics, and electrical properties of ZnO-based ceramic varistors, with ZrO2 content ranging from 0.0 to 1.0 mol %. The varistors enriched with various amounts of ZrO2 were prepared via a conventional solid-state reaction route and sintered at 1200°C for 2 h. Microstructural analysis was conducted using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The capacity of ZrO2 to enhance the sintering process is well demonstrated through thermal analysis kinetics by determining the Arrhenius parameters. Electrical properties and current–voltage (I–V) characteristics were assessed using a DC parameter instrument. The results reveal that ZrO2 doping inhibits ZnO grain growth by anchoring grain boundaries and promotes the formation of the spinel phase (Zn4Ni3Sb2O12)0.333. ZrO2 addition effectively improves the sintering process. The activation energy of ZnO varistors, which are doped with ZrO2, is significantly lower compared to undoped varistors. Doping with ZrO2 enhances the nonlinear exponent (α) of the varistors up to 0.25 mol %, leading to increased varistor voltage and reduced leakage current. For instance, at 0.25 mol % ZrO2, the nonlinear exponent (α) reaches a peak of 41, with a varistor voltage of approximately 320 V mm–1. Conversely, varistors containing 1.0 mol % ZrO2 exhibit a lower voltage (210 V mm–1) and α below 25. The findings suggest that the proposed varistor composition and processing method are promising for low-voltage power transmission systems.