Crystalline structure and electrical performance of Bi2O3-modified 0.95BaTiO3-0.5Sr(Al0.5Ta0.5)O3 ceramics

To solve the poor sintering behavior of 0.95BaTiO₃-0.05Sr(Al_0.5Ta_0.5)O₃ (BT-SAT) sample, in this paper, various weight ratios of Bi₂O₃ powder is used as a sintering aid and dopant to construct the BT-SAT + xwt%Bi₂O₃(BT-SAT + x%Bi, x = 0, 0.5, 1, 2, and 3) ceramic system. The impacts of Bi₂O₃ concentration on the ceramic density, crystalline structure, and electrical properties of BT-SAT samples were investigated and discussed. In contrast to the undoped sample, the addition of Bi₂O₃ can dramatically improve the ceramic density and electrical performance of BT-SAT samples. The BT-SAT + x%Bi samples display a tetragonal and cubic double-phase coexistence feature, which has been confirmed by the X-ray diffraction (XRD), Raman, and Rietveld refinement results. The substitution-site of Bi cations is dependent on the doping level. For lower doping content, Bi cation tends to replace A-sites, leading to a lattice shrinkage, while it will also replace B-sites to regulate charge balance and lattice deformation in heavily doped samples, thereby enhancing the dynamic response of oxygen octahedron and optimizing the dielectric properties by defect engineering. In addition, the enhanced dielectric relaxation of the ceramic sample is realized by the formation of local ordered fields due to the presence of defect dipoles, giving rise to the thin and tilted ferroelectric P-E loops, thereby significantly improving the energy storage efficiency of the BT-SAT + x%Bi ceramics.