Reversibility in electric field-induced transitions and energy storage properties of bismuth-based perovskite ceramics

The effects of temperature and electric field-induced structural modifications on the energy storage properties of 0.95[0.94Bi _0.5Na _0.5TiO ₃-0.06BaTiO ₃]-0.05K _0.5Na _0.5NbO ₃ (BNT-BT-5KNN) ceramics were investigated. X-ray diffraction performed on unpoled and poled ceramics in the temperature range 25-500°C suggested an increment in the rhombohedral phase intensity peaks and in the tetragonal distortion after electrical poling. The rhombohedral phase content reduced with increasing temperature in both unpoled and poled ceramics. In the unpoled ceramic, the rhombohedral phase eventually disappeared, while it survived in the poled specimen up to 500°C. The stabilization of the rhombohedral ferroelectric phase by dc poling produced remarkable differences in the temperature dependence of permittivity, loss, currentpolarizationelectric field loops and energy density. As a consequence of a reversible transition induced by an alternating electric field, competitive energy densities (0.39-0.51Jcm ^-3 in the range 25-175°C) with those of lead-based and lead-free bulk ceramics recently developed was obtained, indicating bismuth-based perovskites as potential lead-free systems for energy storage applications.