Electrical Behavior of Nb-doped Bi_4Ti_3O_(12) 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.