Dielectric, ferroelectric, and field-induced strain properties of Ta-doped 0.99Bi_0.5(Na_0.82K_0.18)_0.5TiO ₃-0.01LiSbO₃ ceramics

Ta-doped 0.99Bi_0.5(Na_0.82K_0.18) _0.5TiO₃-0.01LiSbO₃ (BNKTT-LS) ceramics were prepared through a conventional mixed oxide solid-state sintering route. Partial substitution of Ta for Ti decreased the dielectric constant and depolarization temperature. The dielectric curves, polarization and strain hysteresis loops demonstrated that the incorporation of Ta stabilized the canonical relaxor phase of BNKT-LS ceramics leading to the degradation of piezoelectric and ferroelectric responses. The destabilization of field-induced ferroelectric order at x = 0.013 was accompanied by substantial enhancement in strain level. A unipolar field-induced strain of 0.39 % with a normalized strain (S _max/E _max = d 33 â̂ -) of 650 pm/V was achieved at a driving field of 6 kV/mm. The observed large strain can be attributed to the non-ergodic relaxor phase at zero electric field that transformed into an ergodic relaxor phase under the influence of the applied electric field.