Bi_(0.5)Ba_(0.5)FeO_3陶瓷的电性能及阻抗分析

Electrical properties and impedance analysis of Bi_(0.5)Ba_(0.5)FeO_3 ceramic

以传统的固相反应法制备了Bi0.5Ba0.5FeO3陶瓷,并采用X射线衍射仪、扫描电子显微镜、直流阻温测试仪和交流阻抗分析仪测试了Bi0.5Ba0.5FeO3陶瓷的微结构和电性能.分析结果表明:Bi0.5Ba0.5FeO3陶瓷具有立方钙钛矿结构,颗粒尺寸约1.0μm;在16—280℃范围内,Bi0.5Ba0.5FeO3陶瓷表现出明显的负温度系数热敏效应,其热敏常数、活化能分别为6490K及0.558eV;介电温谱揭示,在280℃下Bi0.5Ba0.5FeO3陶瓷材料没有出现相变行为.对于交流阻抗谱,采用3个串联的RQ(R与Q为并联)等效部件来拟合分析,拟合结果表明拟合数据与实验数据高度匹配,且这3个等效部件分别代表晶界、晶粒和晶壳的贡献.3个部件中,晶粒对陶瓷电阻阻值的影响最大,晶壳贡献次之,晶界最小,且3个部件电阻值都显示出负温度系数效应.在25—115℃范围内,电学模量虚部峰频与阻抗虚部峰频始终不匹配,意味着Bi0.5Ba0.5FeO3陶瓷体内部一直表现出局域导电机理.

Ba0. 5 Bi0. 5FeO3 ceramic was fabricated by conventional solid-state reaction method. The microstructures and electrical properties were characterized by X-ray diffraction, scanning electron microscopy, direct current （ DC ） resistance-temperature measurement and alternative current （ AC） impedance analysis. According to the analysis,Ba0. 5 Bi0. 5 FeO3 ceramic is a cubic perovskite-type compound,and its grain size is about 1. 0 μm. In the measured temperature range of 16—280 ℃ ,Ba0. 5 Bi0. 5 FeO3 ceramic shows obvious negative temperature coefficient thermistor characteristic,and the thermistor constant and activation energy of the ceramic are 6490 K and 0. 558 eV,respectively. The temperature dependence of dielectric constant reveals that below 280 ℃ no phase transition occurs. The AC impedance characteristic in the ceramic can appropriately be modeled in terms of an equivalent electrical circuit comprising of a series combination of three parallel RQ components in connection with the grain,grain shell and grain boundary effects. The fitting results are in good agreement with the experimental data. The components of grain,grain shell and grain boundary,showing NTC characteristic,have the order of resistive contribution of Rg Rs Rgb. In the temperature range 25—115 ℃ ,the significant mismatch between the peaks of parameters Z″（ω） （imaginary part of impedance） and M″（ω） （imaginary part of electric modulus） suggests a development of persistent localized conduction in Ba0. 5Bi0. 5FeO3ceramic.