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 mu m. The sintered density of pellets increased from 5.50 to 5.54 g/cm(3) 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/cm(2). (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.