Giant strain in Nb-doped Bi0.5(Na0.82K0.18)0.5TiO3 lead-free electromechanical ceramics

The effect of Nb substitution on the crystal structure, ferroelectric, and electric field induced strain properties of Bi0.5(Na82K0.18)0.5TiO3 (BNKT) ceramics has been investigated. The coexistence of rhombohedral and tetragonal phases was found in undoped BNKT ceramics, however, Nb doping induced a phase transition to a pseudocubic phase with high electrostriction coefficients. When 3 mol% Nb was substituted on Ti ions, the electric field induced strain was markedly enhanced up to Smax/Emax = 641 pm/V, which is higher than those previously reported on non-textured lead-free electromechanical ceramics.