Influence of Mn doping on microstructure and DC-accelerated aging behaviors of ZnO–V2O5-based varistors

The microstructure, electrical properties, dielectric characteristics, and DC-accelerated aging behavior of the ZnO–V2O5–MnO2 system sintered were investigated for MnO2 content of 0.0–2.0 mol% by sintering at 900 °C. For all samples, the microstructure of the ZnO–V2O5–MnO2 system consisted of mainly ZnO grain and secondary phase Zn3(VO4)2. The incorporation of MnO2 to the ZnO–V2O5 system was found to restrict the abnormal grain growth of ZnO. The nonlinear properties and stability against DC-accelerated aging stress improved with the increase of MnO2 content. The ZnO–V2O5–MnO2 system added with MnO2 content of 2.0 mol% exhibited not only a high nonlinearity, in which the nonlinear coefficient is 27.2 and the leakage current density is 0.17 mA/cm2, but also a good stability, in which %ΔE1 mA = −0.6%, %Δα = −26.1%, and %Δtan δ = +22% for DC-accelerated aging stress of 0.85E1 mA/85 °C/24 h.