BaNb_2O_6掺杂Na_(1/2)Bi_(1/2)TiO_3无铅压电陶瓷的介电弛豫

Dielectric behavior of BaNb_2O_6 doped Na_(1/2)Bi_(1/2)TiO_3 lead-free piezoelectric ceramics

采用传统陶瓷制备方法,制备了无铅新压电陶瓷材料(1-x)Na1/2Bi1/2TiO3-xBaNb2O6。研究了BaNb2O6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-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随BaNb2O6掺杂量的增加而增加。该体系陶瓷表现出与典型弛豫铁电体明显不同的弛豫行为,低掺杂量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,而高掺杂的陶瓷材料在室温和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产生介电弛豫的机理。

The dielectric properties and relaxation of BaNb2O6 doped Na1/2Bil/2TiO3 lead -free piezoelectric ceramics were investigated. X -ray diffraction shows that BaNb2O6 diffuses into the lattice of Na1/2 Bi1/2TiO3 to form a solid solution with perovskite - type structure. The temperature dependence of dielectric constant εr reveals that the solid solution has two dielectric abnormal peaks. The thermal variation of the permittivity is well described by a law 1/ε -1/εm = C（T-Tm）^γ and the diffuse coefficient γ value increases with the increasing concentration of BaNb2O6. All samples exhibited relaxor characteristics different from classic relaxor ferroelectrics. The samples with low doping level of BaNb2O6 exhibits obvious frequency dependence only near the low temperature dielectric abnormal peak Tf, and the samples with a high doping level of BaNb2O6 exhibits 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.