Effects of BN on phase compositions and electrical properties of ZnO-Bi2O3 varistors prepared by the reduction-reoxidation method

A reduction-reoxidation method is frequently used for preparing multilayer ceramic components with base metal inner electrodes (BME). However, ZnO varistors has been hardly prepared by the reduction-reoxidation method because that ZnO is easy to be reduced. We proposed that Boron nitride (BN) as an anti-reduction additive in this paper, which obviously prevented ZnO-Bi2O3 from reducing when sintering in a reducing atmosphere. For the BN-added samples, the B-containing phase formed during the sintering process promoted the liquid-phase sintering process of ZnO and prevented the composition loss of them. BN-added samples sintered in a reducing atmosphere (N2(99.5%)-H2(0.5%)) at 1000 °C for 2 h and re-oxidized in air at 850 °C for 2 h exhibited excellent nonlinear properties with nonlinear coefficient of 43.3 and leakage current of 0.12 μA/cm2. This is promising for producing BME ZnO-based multilayer varistors (MLVs).