Effect of MnO2 addition on microstructure and electrical properties of ZnO–V2O5-based varistor ceramics

The microstructure and electrical properties of ternary system ZnO–0.5 mol% V2O5–MnO2 ceramics sintered were investigated in accordance with MnO2 content by sintering at 900 °C. For all samples, the microstructure of the ternary system ZnO–V2O5–MnO2 ceramics consisted of mainly ZnO grain and secondary phase Zn3(VO4)2. The incorporation of MnO2 to the binary system ZnO–V2O5 ceramics was found to restrict the abnormal grain growth of ZnO. The breakdown field in the E–J characteristics increased from 175 to 992 V/cm with the increase of MnO2 content. The incorporation of MnO2 improved non-ohmic properties by increasing non-ohmic coefficient. The highest non-ohmic coefficient (27.2) in the ternary system ZnO–0.5 mol% V2O5–MnO2 was obtained for MnO2 content of 2.0 mol%.