Microstructure and properties of ZnO-Bi2O3-based varistor ceramics via flash sintering

Purpose This paper aims to study the effects of MnO2 on the ZnO–Bi2O3-based varistor prepared via flash sintering (FS) Design/methodology/approach MnO2-doped ZnO–Bi2O3-based varistors were successfully prepared by the FS with a step-wise increase of the .current in 60 s at the furnace temperature <750°C under the direct current electric field of 300 V cm−1. The FS process, microstructure and the electrical performance of ZnO–Bi2O3-based varistors were systematically investigated. Findings The doping of MnO2 significantly decreased the onset temperature of FS and improved the electrical performance of FS ZnO varistor ceramic. The sample with 0.5 mol% MnO2 doping shows the highest improvement, with the nonlinear coefficient of 18, the leakage current of 16.82 µA, the threshold voltage of 459 V/mm and the dielectric constant of 1,221 at 1 kHz. Originality/value FS is a wonderful technology to enhance ZnO varistors for its low energy consumption, and a short sintering time can reduce grain growth and inhabit Bi2O3 volatilize, yet few research studies work on that. In this research, the authors analyzed the FS process and improved the electrical characteristics through MnO2 doping.