Nb掺杂Bi4Ti3O12层状结构铁电陶瓷的电行为特性研究

采用固相烧结工艺制备了Nb⁵⁺掺杂的Bi₄Ti₃O₁₂层状结构铁电陶瓷.运用XRD 和AFM对Bi₄Ti_3-xNb_xO_12+x/2材料的微观结构进行表征,发现所制备的陶瓷均具有单一的正交相结构,抛光热腐蚀表面晶粒的显微形貌表现为随机排列的棒状结构.通过对材料直流电导率与温度关系的Arrhenius拟合,分析丁Bi₄Ti_3-xNb_xO_12+x/2的导电机理. Nb⁵⁺掺杂提高了材料的介电常数,但居里温度随掺杂含量的增加呈线性下降趋势.DSC结果显示Bi₄Ti_3-xNb_xO_12+x/2材料在居里温度处经历了一级铁电相变.样品的铁电性能测试结果表明, Nb⁵⁺掺杂Bi₄Ti₃O₁₂提高了材料的剩余极化Pr,这主要是由于^_Nb5+取代Ti⁴⁺大大降低了材料中氧空位的浓度,使得氧空位对畴的钉扎作用减弱的缘故.

Electrical Behavior of Nb-doped Bi4Ti3O12 Layer-structured Ferroelectric Ceramics

Nb5+-doped Bi4Ti3O12 layer-structured ferroelectric ceramics were prepared by the solid-state reaction technology. Microstructures of Bi4Ti3-xNbxO12+x/2 materials were characterized by XRD and SEM. The results show that Bi4Ti3-xNbxO12+x/2 material has a single orthorhombic structure. The grains of polished and thermally etched surfaces reveal a needle-like structure. Electronic conductor mechanism of Bi4Ti3-xNbxO12+x/2 was analyzed by the Arrhe-nius fit of direct current conductivity vs temperature. Dielectric constants of Bi4Ti3-xNbxO12+x/2 ceramics increase by Nb5+ doping. The Curie temperatures decrease linearly with the increase of Nb5+ concentration. DSC results show that Bi4Ti3-xNbxO12+x/2 materials undergo the first-order ferroelectric phase transition at the Curie point. Nb5+ doping Bi4Ti3O12 ceramics results in an increase remanent polarization (Pr) according to ferroelectric test results. The reason is that Nb5+ substituting for Ti4+ decreases the concentration of oxygen vacancies. The effect of oxygen vacancies on domain pinning is reduced significantly.