采用固相反应法制备了施主掺杂浓度不同的Nb2O5（分别为0.1mol%、 0.3mol%、 0.5mol%、 0.7mol%）掺杂(Ba, Bi,Na)TiO3基PTCR陶瓷. 对其微观结构及电性能进行研究发现：随着Nb2O5掺杂浓度的增加，陶瓷晶粒尺寸先变大后变小，室温电阻率也随之先减小后增大，说明Nb2O5的掺杂量存在一个临界施主掺杂浓度. 当Nb2O5施主掺杂量为临界施主掺杂浓度0.5mol%时，获得了居里温度Tc为 183℃、室温电阻率ρ为1.06×103Ω·cm、升阻比ρmax/ρmin为1.0×104的高温无铅PTCR陶瓷. 通过交流复阻抗谱分析，探讨了Nb2O5施主掺杂在该PTCR陶瓷中的作用机理.
(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(ρ25) of 1.06×103Ω·cm, the Curie temperature (Tc) of 183℃, and the resistivity jump (ρmax/ρmin) of 1.0×104. 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.
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