Abstract
Relations between PTC effect and reactions observed in DTA were investigated in the temperature range of 25 to 1400°C on the specimens prepared by adding SiO2 or Si3N4 to Y-doped BaTiO3. Two kinds of eutectic reactions were observed in DTA, i.e. reaction A at 1184-1238°C, and B at 1290-1327°C. Resistivity was measured on the specimens quenched before and after these reactions took place. Compared to the specimen quenched after reaction A, remarkable reduction in PTC effect was observed in the specimen quenched before reaction A. Quenching from much higher temperature, i.e. above reaction B temperature, however, gave a larger PTC effect. Microstructures of boundary phases suggested that Ti-rich phase (Ba6Ti17O40) played an important role on the appearance of PTC effect.
