The thermally stimulated current in zinc oxide varistors with TiO 2 additives

To contribute more information on the conduction mechanism in ZnO varistors, a study of ZnO varistors with TiO₂ additives was conducted. The properties of ZnO varistors are found to depend on the grain structure of ZnO. The mechanism of nonlinear conduction of ZnO may be explained on the basis of the grain structure. The TSC (thermally stimulated current) spectrum was measured to study the trapped carriers in ZnO varistors. Four peaks of TSC may be distinguished on the spectrum of TSC. The origin of the first, second, and third TSC peaks was attributed to the detrapping of the trapped electrons in the shallow trap, donor level, and deep trap, respectively. The origin of the fourth peak was attributed to the process of depolarization of the donor ions in the depleted layer. Adding TiO₂ to ZnO varistors caused the leakage current to increase