Nb2O5 doping effect on electrical properties of ZnO–V2O5–Mn3O4 varistor ceramics

The microstructure and electrical properties of ternary ZnO–V2O5–Mn3O4 varistor ceramics modified with Nb2O5 were systematically investigated for different amounts of Nb2O5. The average grain size for Nb2O5-doped ceramics was larger than Nb2O5-free ceramics and it was in the range of 6.64–7.27 μm. The sintered density of pellets increased from 5.50 to 5.54 g/cm3 as the Nb2O5 amount increased. The breakdown field increased from 947 to 4521 V/cm with an increase in the amount of Nb2O5, whereas a further addition caused it to decrease up to 4374 V/cm at 0.25 mol%. The varistor ceramics doped with 0.05 mol% Nb2O5 exhibited the best nonlinear properties, in which the nonlinear coefficient is 47 and the leakage current density is 0.14 mA/cm2.