The Effects of Addition of Al on Electrical Degradation of ZnO Varistors

Abstract

The effects of addition of Al on the electrical degradation of the Bi, Mn, and Al added ZnO varistors and the Bi, Co, and Al added ZnO varistors were investigated by V-I, C-V, ICTS, and XPS methods. The optimum quantity of Al additive to prevent the electrical degradation is approximately 5ppm in the case of Bi-Mn-Al added ZnO varistor and approximately 10ppm in the case of Bi-Co-Al added ZnO varistor. For each optimum quantity of Al content for Bi-Mn-Al or Bi-Co-Al added varistor, the distribution of values of the energies of the trap levels became narrowest. On the other hand, values of the full width at half maximum of Mn-2p and Co-2p orbits became largest.