Effect of sintering atmosphere on Ni/PTC composites ceramics

In order to prepare lead-free BaTiO₃-based PTC (positive temperature coefficient) with low room temperature resistivity, metal Ni is added to BaTiO₃-based PTC samples that contain 5, 8, 10, 12, 15, 20 wt% of Ni. The sintering temperature is from 1240 °C to 1260 °C. The sintering atmosphere of Ni/PTC composites ceramics was studied. Two sintering atmospheres were adopted in this experiment; full reducing sintering atmosphere and part reducing sintering atmosphere. Controlling the dose of graphite powder can make these two reducing atmospheres. The experiment data show that the optimal sintering atmosphere is a part-reducing atmosphere. Under on the conditions mentioned above, the room temperature resistivity of the samples can drop to under 10 Ω cm and the PTC jump can reach 10³, which represents a good PTC characteristic.