ZnO varistor ceramics prepared by the reduction-reoxidation method

Multilayer ceramic components with base metal inner electrodes should be sintered in a reducing or protective atmosphere to avoid oxidation of the base metal, and then re-oxidized in air or oxygen to control their electrical properties. It is called reduction-reoxidation method. In this article, ZnO varistors were firstly prepared by the reduction-reoxidation method. Electrical performances of ZnO varistors sintered in air and nitrogen (N2 99.8%) were compared with those prepared by the reduction-reoxidation method. ZnO varistor ceramics sintered in N2 at 1000 °C and then re-oxidized in air at 750 °C for 2 h exhibited excellent electrical properties such as a high nonlinear coefficient of 47.9 and a low leakage current of 0.06 μA/cm2, which is promising for producing multilayer ZnO varistors with base metal electrodes.