The correlation between electrical degradation and valences state of additives in the ZnO (Zinc oxide-based) varistors added Cr{sub}2O{sub}3 or V{sub}2O{sub}3 besides Bi{sub}2O{sub}3 and MnO{sub}2 or CoO were investigated by an ICTS and an XPS measurements. The results of ICTS measurement showed that the factor of degradation for Bi and Co added samples is concerned with the decrement of the interface states density. The factor of degradation of samples added Bi and Mn is concerned with the shallowing of the interface states level. XPS spectra of Mn-2p orbit for sample added Bi and Mn was measured and analyzed at least square method. It is found that XPS spectra of Mn-2p orbit has new peak after electrical degradation and the disappearance of this new peak by thermal annealing. It is conjectured that the some of valence state of Mn may be affected by drift of O{sup}(2-) ions under the applied voltage and changed to different valence state. Results of XPS spectra of Cr-2p orbit for the all samples added Cr showed that Cr-2p{sub}(3/2) orbit had same binding energy after electrical degradation. Both of the α and XPS spectra of V-2p{sub}(1/2) orbit for the sample added Bi{sub}2O{sub}3, CoO and V{sub}2O{sub}3 did not change after electrical degradation. On the other hand, XPS spectra of V-2p{sub}(1/2) orbit for sample added Bi{sub}2O{sub}3, MnO{sub}2 and V{sub}2O{sub}3 was shifted to high energy side by about 1eV. In this case α is drastically decreased compared with that for sample added Bi{sub}2O{sub}3, CoO and V{sub}2O{sub}3. These results of XPS spectra showed the valence state for additives such as Cr and V may affect to electrical degradation of ZnO varistors.
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