Interfacial charge between ZnO varistor ceramics and inorganic insulating materials and its role

The interfacial charge distribution between ZnO varistor ceramics and inorganic insulating materials was investigated by means of thermally stimulated current and pulsed electroacoustic methods. It was found that the interfacial charge density depends largely on inorganic insulating materials, a large amount of charges exist at the interface between ZnO varistor ceramics and polyester polyurethane, but almost no charge exists at the interface between ceramics and polyester modified silicone. The interfacial charges that exist between ZnO varistor ceramics and inorganic coating lower largely the steep impulse flashover voltage of ZnO varistor blocks.