Effect of ageing on the electrical resistivities of (Ba0.69Pb0.31)TiO3 PTCR ceramic thermistors

The electrical resistivity of (Ba0.69Pb0.31)TiO3 PTCR ceramic thermistors aged at temperatures of 175, 200, 250 and 300 °C, respectively, were measured. When the samples were aged at temperatures of 175 and 200 °C, room-temperature resistivity decreased at the initial ageing stage, and then increased with the ageing time. The samples displayed a monotonous rise of the room-temperature resistivity when the ageing treatments were performed at 250 and 300 °C. PTCR effects showed different characteristics after different ageing treatments. These ageing characteristics were analyzed by considering interior oxidation and reduction reactions.