Abstract
The effects of calcination conditions on the electrical properties of BaTiO3-based PTC thermistorshave been studied. Samples quenched from 1350°C showed significantly lower resistivity than those quenched from 1300°C. Over the same temperature range, a large amount of oxygen was evolved and a divergence between grain and grain boundary resistance was observed. The grain boundary phase is mainly composed of Ba, Ti and Si, and is Ti-poor and Si-rich compared with the grain composition. It was shown that the occurence of Ba-Si-Ti phases at the grain boundaries depends on calcining conditions. It is thought that the grain boundary phase plays an important role in causing semiconductivity in the samples, and therefore in controlling their electrical properties.
