Effect of composite rare earth doping on the flash sintered zinc oxide varistor ceramics

With the development trend of device miniaturization, the demand for varistor ceramics with high break field is becoming more and more important. To enhance the high-voltage performance and improve the nonlinear coefficient of zinc oxide varistor ceramics, the technical advantages of rare earth and flash sintering were innovatively proposed to effectively improve the varistor performance, and their microstructure and electrical properties were systematically studied. The results indicate that rare earth doping affected the formation of liquid phase and thus reduced the electrical conductivity during flash sintering, which decreased the conductivity in the early stage of flash sintering. Moreover, the pinning effect from rare earth doping to ZnO grains inhibited grain growth, which leads to a smaller grain size. The breakdown field of 0.2 mol % Y₂O₃ + 0.2 mol % Sc₂O₃ composite doped sample has been significantly improved to 1880 V/mm, with a nonlinear coefficient of 42.5 and the leakage current of 0.5 μA. It also exhibits a high dielectric constant of 267 on 1 kHz, and better dielectric frequency stability compared to others.