The influence of calcination temperature on the PTCR effect in (Ba_x-0.002Sm_0.002) TiO₃ ceramics prepared by the reduction sintering-reoxidation method

We investigate the effect of calcination temperature on the positive temperature coefficient of resistivity (PTCR) characteristics in (Ba_x-0.002Sm0.002)TiO₃ ceramics that were fired at 1250 °C for 30 min in a reducing atmosphere and reoxidized at 800 °C for 1 h in air. The results indicate that the room-temperature resistivity first decreased and then increased as calcination temperature increased from 1000 °C to 1200 °C. Moreover, the critical calcination temperature of 1150 °C is experimentally determined. The samples have a low room-temperature resistivity of 38.4 Ω·cm and exhibit a significant PTCR effect with a resistance jump of 2.1 orders of magnitude. Furthermore, the room-temperature resistivity of the S7 samples doped with a small amount of Mn(NO₃)₂ is much higher than that of the S3 specimens not doped with Mn(NO₃)₂ in our work.