Effects of Niobiuma2Doping on the Structure and Electrical Properties of (Ba,Bi,Na)TiO3-based PTCR Ceramics

(Ba, Bi, Na)TiO3-based PTCR Ceramics (BBNMT) doped with Nb2O5 (0.1mol%, 0.3 mol%, 0.5mol%, 0.7mol%) were prepared by the solid state reaction method and annealing in the reduction atmosphere. The microstructures and electrical properties of BBNMT were investigated. The results show that with the increase of Nb2O5 contents, the grain size increases firstly and then decreases, which indicates that there exists an optimal content of Nb2O5. The low resistivity PTC ceramic materials are obtained when the content of Nb2O5 is 0.5mol% with the room temperature resistivity(| SUB>25) of 1.06 03| ¤cm, the Curie temperature (Tc) of 183 and the resistivity jump (| SUB>max/| SUB>min) of 1.0 04. By analyzing the impedance spectroscopy, the influence of the grain phase, grain boundary phase and °shell phase ± on the resistivity are discussed, the interaction mechanism of Nb2O5 donor in PTCR ceramics are also studied.