Effect of chromium and manganese co-doping on the vacuum voltage-withstanding properties of alumina ceramics

MnO₂ ranging from 0 to 1.5wt% was considered to be mixed with 95wt% alumina powders doped with 0.5wt% Cr₂O₃. Effects of incorporation of MnO₂ on performance of alumina ceramic material phase, microstructure, sintering properties, resistivity, dielectric constant and the vacuum pressure resistance were researched. The results show that, MnO₂ doped into the Al₂O₃ lattice, which promote the sintering and grain growth of 95% alumina ceramic and improve the uniformity and density of the microstructure. With the increase of doping amount of MnO₂, the resistivity of the material decreases significantly, and the dielectric constant is slightly reduced. The effect of chromium and manganese doping on the vacuum voltage withstanding properties of alumina ceramics is closely related to the incorporation of MnO₂. In the case of 0.5wt% Cr₂O₃ doping, the flashover voltage of the sample doped with MnO₂ ranging from 1 to 1.5wt% is higher than the sample undoped with MnO₂. The flashover voltage of the sample doped with 1.5wt% MnO₂ is the highest, and reaches 54 kV/cm.