Giant strain response and structure evolution in (Bi0.5Na0.5)0.945−x(Bi0.2Sr0.7□0.1)xBa0.055TiO3 ceramics

The microstructure, electric-field-induced strain, polarization, and dielectric permittivity in (Bi0.5Na0.5)0.945−x(Bi0.2Sr0.7□0.1)xBa0.055TiO3 (BNBT–xBST) (0 ≤ x ≤ 0.08) electroceramics are investigated. An irreversible transition from rhombohedral and monoclinic coexistence phase to single rhombohedral phase is indicated with the remnant strain Sr = 0.330% at x = 0. As the BST content increases, the ferroelectric order is disrupted resulting in a degradation of the remnant polarization, coercive field, and the ferroelectric-to-relaxor transition temperature (TF–R). The coexistence of ferroelectric relaxor and ferroelectric phase is observed for the optimum composition x = 0.02 at ambient temperature with a large strain of 0.428% at 60 kV/cm (normalized strain Smax/Emax = 713 pm/V). The large strain is contributed by both ferroelectric domain reorientation behavior and the reversible relaxor to ferroelectric phase transition.