Effect of antimony oxide on the electrical properties and stability of ZnO varistors

The nonlinear current-voltage characteristics, depression angle and stability of ZnO varistors were investigated as a function of valence and amount of antimony oxide. The nonlinear properties were improved, the depression angle decreased, and the stability under continuous dc bias increased with decreasing valence of the antimony ion. However, the nonlinear properties became worse with an increasing amount of antimony oxide for any valence. The relaxation time was insensitive to the valence of the antimony ion and the amount of antimony oxide, while the increased antimony oxide content enhanced the electrical stability as a function of time. Spinel particles formed by the reaction of antimony oxide and ZnO, were suggested as playing an important role in the improvement of electrical properties and stability by stressing the junction between two ZnO grains.