A comparative study on degradation characteristics of ZnO nanoparticles-Bi2O3-Mn2O3varistors at various ambient sintering processes

In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to produce high-density ZnO varistor ceramics, which were doped with Bi2O3 and Mn2O3 through a conventional ceramic processing method. Electron probe microanalysis was performed to analyze the elemental content in the microstructures of the ceramics. Different sintering ambient conditions were found to have marginal effects on the microstructure, varistor voltage, and degradation characteristics, although these conditions strongly affected the nonlinear exponents and leakage currents of the varistor samples. The strong solid-state reaction during sintering process may be attributed to the high surface area of the 20 nm ZnO sintered at different sintering ambient conditions, those sintered in oxygen ambient exhibited the highest nonlinearity and had a nonlinear exponent of 58.8 and leakage current of 577.2 µA. Moreover, their grains had the highest Zn and lowest O elemental contents among the four samples. Meanwhile, sintering ambient considerably affected the stability against DC- accelerated aging stress, which, similar to sintering ambient, was high in following order: oxygen, air, nitrogen, and argon in sintering atmosphere.