The Effect of Trasition of Valence State of Additives Electrical Degradation of ZnO Varistors

Abstract

The correlation between electrical degradation and valence states of additives in the Bi2O3 and MnO2(Bi-MnO2) or Mn2O3(Bi-Mn2O3) added ZnO varistors and Bi2O3 and CoO(Bi-CoO) or Co3O4(Bi-Co3O4) added varistors was investigated by ICTS and XPS measurements. The results of ICTS and XPS measurements showed that Mn as the additive contributes differently to the factors of degradation in the cases of Bi-MnO2 and Bi-Mn2O3 added ZnO and Co as the additive contributes similarly to the factors of degradation in the cases of Bi-CoO and Bi-Co3O4 added ZnO. The recovery of varistor characteristics of Bi-Mn-Co added ZnO added Co3O4 after degradation was more remarkable than that of the sample added CoO by the thermal annealing. The results of ICTS measurements showed that the interface states changed for Bi-Mn-Co added ZnO after the thermal annealing. XPS spectra of the Co-2p3/2 orbit and Mn-2p3/2 orbit for Bi-Mn-Co added ZnO showed different binding energies after degradation.