BaFe0.4Sn0.6O3/BaBiO3负温度系数复合热敏陶瓷阻抗分析

以BaBiO₃为导电相,BaFe_0.4Sn_0.6O₃为高阻相,采用固态反应法制备了不同BaBiO₃含量的BaFe_0.4Sn_0.6O₃/BaBiO₃负温度系数(NTC)热敏复合陶瓷.为获得在渗流阈值(即BaBiO₃含量为12 mol%)前后复合陶瓷的内部导电机理,对复合陶瓷进行了阻抗分析.分

Impedance analysis of BaFe0.4Sn0.6O3/BaBiO3 composite negative temperature coefficient ceramics

The BaFe_0.4Sn_0.6O₃/BaBiO₃ composite negative temperature coefficient (NTC) thermistor ceramics were prepared by conventional solid-state reaction method. The raw materials used are composed of conductive BaBiO₃ phase and high resistive BaFe_0.4Sn_0.6O₃ phase. The conductive mechanism of thermistor ceramics before and after the percolation threshold (containing 12 mol% of BaBiO₃), is investigated by impedance analysis. For compositions with 5 mol%—8 mol% of BaBiO₃, the contribution to the conductivity is mainly due to the grain boundary (R_b), grain (R_g), and grain shell (R_s) existing in the BaFe_0.4Sn_0.6O₃. In the range of 10 mol%—12 mol% of BaBiO₃, the grain (R_bg) and grain boundary resistance (R_bb) corresponding to the BaFe_0.4Sn_0.6O₃ melted with BaBiO₃ in composite ceramic, are also main factor governing the resistance magnitude, the values of which are lower than the other main sources like R_b, R_g, and R_s. For composition x=0.15, the values of R_bb and R_bg are higher than that of R_b, R_g and R_s. For BaBiO₃ contents around 20 mol%, the resistance is mainly determined by the values of R_bb and Rbg. In addition to the electrode-specimen interface, all of the components in composite ceramic show NTC feature. The NTC composite ceramics with different BaBiO₃ contents show nonideal Debye-like behavior, and the conduction mechanism of the composite ceramics is of the localizing type.