Dielectric and ferroelectric properties of Ta-modified Bi3.25La0.75Ti3O12 ceramics

B-site modified Bi3.25La0.75Ti3-xTaxO12 ceramics were prepared by the conventional solid-state reaction method. The influence of Ta2O5 on microstructure and electric properties of the ceramics was investigated. The results demonstrated that Ta5+ ions were dissolved into the perovskite lattice and homogeneously distributed in the matrix without forming any minority phase. The conduction mechanism and dielectric response behavior were transformed with Ta substation, which is triggered by varied structural distortion characteristics and defect diploes. The Curie temperature decreased gradually with increasing Ta content and a relaxor-like behavior was observed for x = 0.09 sample. The internal bias field is decreased with Ta doping, because the substitution of Ta5+ at B-site contributes to release the involved oxygen vacancies in defect diploes. Moreover, further increasing Ta content causes a reduction in the oxygen vacancies located at lattice misfits, resulting in a decrease of coercive fields. An improved ferroelectric properties were obtained for x = 0.09 sample with a relatively lower coercive field and a larger spontaneous polarization.