La2O3掺杂(Na0．5 Bi0．5)0．94 Ba0.06 TiO3无铅压电陶瓷的介电弛豫研究

Study of Dielectric Relaxor of La_2O_3 Doped (Na_(0.5)Bi_(0.5))_(0.94)Ba_(0.06)TiO_3 Lead-free Piezoelectric Ceramics

采用固相合成法制备了La2O3掺杂(Na0.5Bi0.5)0.94Ba0.06TiO3无铅压电陶瓷。研究了La2O3掺杂对(Na1/2Bi1/2)TiO3陶瓷晶体结构、介电性能与介电弛豫行为的影响。XRD分析表明,在所研究的组成范围内陶瓷材料均能够形成纯钙钛矿固溶体。材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm。修正的居里-维斯公式较好的描述了陶瓷弥散相变特征,弥散指数随La2O3掺杂量的增加而增加。掺杂量较低的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随掺杂量的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性。并根据宏畴-微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理。

The dielectric properties and relaxation of La2O3 doped （Na0. 5Bi0. 5）0. 94Ba0.06 TiO3 lead-free piezoelectric ceramics were investigated. X-ray diffraction showed that La ions diffused into the lattice of （Na0. 5Bi0. 5）0.94Ba0.06 TiO3 to form a solid solution with perovskite-type structure. The temperature dependence of dielectric constant G revealed that the solid solution exist two dielectric abnormal peaks Tf and Tm. The thermal variation of the permittivity was well described by a law 1/ε--1/εm=C（T- Tm）^α and the diffuse coefficient α value increased with increasing concentration of La2O3. All samples exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with a low doping level of La2O3 exhibited obvious frequency dependent only near Tf and the samples with a high doping level of La2O3 exhibited obvious frequency dependence between room temperature and Tf. The mechanism of relaxor behavior was also discussed according to the macro-domain to micro-domain transition theory.