Nb_2O_5 doping effect on electrical properties of ZnO-V_2O_5-Mn_3O_4 varistor ceramics

摘要

The microstructure and electrical properties of ternary ZnO-V_2O_5-Mn_3O_4 varistor ceramics modified with Nb_2O_5 were systematically investigated for different amounts of Nb_2O_5. The average grain size for Nb_2O_5-doped ceramics was larger than Nb_2O_5-free ceramics and it was in the range of 6.64-7.27 ìm. The sintered density of pellets increased from 5.50 to 5.54 g/cm~3 as the Nb_2O_5 amount increased. The breakdown field increased from 947 to 4521 V/cm with an increase in the amount of Nb_2O_5, 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% Nb_2O_5 exhibited the best nonlinear properties, in which the nonlinear coefficient is 47 and the leakage current density is 0.14 mA/cm~(-2).