The large electro-strain in BNKT-BST-100xTa lead-free ceramics

0.94Bi_0.5(Na_0.78K_0.22)_0.5Ti_1-xTa_xO₃-0.06Ba_0.95Sr_0.05TiO₃ (BNKT-BST-100xTa, for x = 0,0.005, 0.010, 0.015, 0.020 and 0.025) lead-free ceramics were fabricated by the solid-state reaction technique. Microstructure, dielectric, ferroelectric and fatigue performances of BNKT-BST-100xTa ceramics had been systemically studied. The XRD patterns confirmed that Ta⁵⁺ ions had completely dissolved into the lattice of BNKT-BST-100xTa ceramics. Meanwhile, the temperature of R3c-PNRs (T_s) was found to shift towards room temperature in dielectric permittivity curves with the introduction of Ta⁵⁺ ions. In addition, the highest unipolar strain of 0.32% with the corresponding normalized strain of 458 pm/V was obtained for x = 0.020 under the applied electric field of 70 kV/cm. The large electro-strain was cause by intrinsic effect of the crystal and the external electric field. Moreover, the excellent strain fatigue resistance indicated the prepared ceramics are promising candidates for actuators and stress sensors.