The Influence of Ba-Ti Ratio on the Electrical Properties and Microstructures of the BaM-0.007Sm0.007TiO3 Based Ceramics Fired in Reducing Atmosphere
Electrical properties, positive temperature coefficient of resistivity (PTCR), and microstructures of (Bam-0.007Sm0.007)TiO3(BST) with different Ba-site/Ti-site (A/B) ratio sintered in a reducing atmosphere and reoxidized in air are investigated. The results reveal that the room temperature resistivity of the semiconducting BST ceramics first decreases and then increases with increasing of A/B ratio (m), particularly when m is equal to 1.006, the semiconducting BST ceramics which have been sintered in a reducing atmosphere and reoxidized at 800°C exhibit significant PTCR effect with a resistance jumping ratio of 3 orders magnitude, and achieve a lower room temperature resisitivity of 80.8 Ω∙cm, in addition, the grain size distribution of the Ti-excess specimens is much better than that of the Ba-excess ones.