Influence of sintering method on the PTCR effect and microstructures of Sm2O3-doped BaTiO3-based ceramics sintered in a reducing atmosphere

This study investigated the effects of sintering temperature and cooling rates on the positive temperature coefficient of resistance (PTCR) effect and microstructures of Ba1.022-xSmxTiO3 (BST) ceramics sintered at 1200 °C−1260 °C for 30 min in a reducing atmosphere and reoxidized at 700 °C−900 °C for 1 h. The sintering temperature and cooling rates influenced the PTCR effect and microstructure of the BST samples. The resistivity of the samples at room temperature initially decreased and then increased with the increase in the content of Sm2O3. A high sintering temperature resulted in low resistivity of the BST ceramics. Meanwhile, the resistivity of the specimens at room temperature increased with the increase in cooling rates. Furthermore, a rapid cooling rate exerted a significant PTCR effect. The samples exhibited a resistance jump greater than 3.0 orders of magnitude and a low room-temperature resistivity. The behaviour of the microstructure of the as-fired BST ceramics cooled at different rates was also investigated.