Effects of Zr and Y Addition on the Electrical Degradation Characteristics of ZnO Varistors
The effects of the addition of Y or both Y and Zr to Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistors on the varistor voltage and the tolerance characteristics of electrical degradation were investigated. The deterioration of the tolerance characteristics of electrical degradation by the addition of Y was probably caused by an increase in the number of willemite (Zn2SiO4)-type particles or a decrease in the number of spinel (Zn2.33Sb0.67O4)-type particles, but this deterioration was reduced by adding Zr. Moreover, the reduction in the average ZnO grain size due to the addition of Y was a major factor in the increased varistor voltage, and the ZnO grain growth was inhibited by the formation of an un-known compound after adding Y. The varistor voltage of a varistor with 2 mol% added Y increased by approximately 50% compared to a varistor with no Y added.
Shinobu Fujihara and Tadashi Takenaka
Y. Akiyama et al., "Effects of Zr and Y Addition on the Electrical Degradation Characteristics of ZnO Varistors", Key Engineering Materials, Vol. 445, pp. 237-240, 2010