Giant electric field-induced strain and structure evolution of NaTaO₃-modified 0.94(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃ Pb-free ceramics

To acquire giant electric field-induced strain in non-Pb materials is attracting a great deal of attention in the past decade. In the current investigation, the crystal and domain structures as well as the electrical performances of (1-x) (0.94Bi_0.5Na_0.5TiO₃-0.06BaTiO₃)-xNaTaO₃ (BNBT-xNT) specimens were systematically studied to achieve enhanced strain. The introduction of NT makes the phase structure transit from rhombohedral-tetragonal to pseudo-cubic structure. The original domain structure of BNBT is destroyed, and the disorder degree of the local structure increases. Simultaneously, the remnant polarization, coercive field, and piezoelectric coefficients were significantly decreased. The transition from ferroelectric to ergodic relaxation can be effectively modified, thus lowering the transition zone to room temperature. Finally, the BNBT-3NT ceramics achieve marked strain coefficients at room temperature, with a maximum strain of 0.394% under 65 kV/cm and a d₃₃* of 606 pm/V.