Effects of Thermal Annealing for Barium and Silicon-added Bismuth Based Zinc Oxide Varistors on Electrical Properties and Grain Boundary Structure

In order to fabricate varistors with low varistor voltage, the effects of thermal annealing of Co-Mn-Ba-Si-added Bi based ZnO varistors on electrical properties and the grain boundary structure were investigated. The varistor voltage for the Bi-Co-Mn-Ba-Si-added ZnO varistor decreased in half by thermal annealing for a short time. The resistance to electrical degradation was most improved by the addition of SiO2 and thermal annealing for 10-20 min. It is suggested that the composition of Bi and Si in the sheet-like deposit is changed by varying the annealing time and the resistance to electrical degradation is improved by both addition of SiO2 as well as thermal annealing for short time.