Electrical Properties and Relaxor Phase Evolution of Li-Modified BNT-BKT-BT Lead-Free Ceramics

By conventional ceramics sintering technique, the lead-free 0.85Bi(0.5)Na(0.5(1-x))Li(0.5x)TiO(3)-0.11Bi(0.5)K(0.5)TiO(3)-0.04BaTiO(3) ( x = 0-0.15) piezoelectric ceramics were obtained and the effects of Li dopant on the piezoelectric, dielectric, and ferroelectric properties were studied. With increasing Li addition, the temperature-dependent permittivity exhibited the normal ferroelectric-to-ergodic relaxor ( FE-to-ER) transition temperature ( TFE-ER, abbreviated as TF-R) decreasing down to room temperature. The increasing Li content also enhanced the diffuseness of the FE-to-ER transition behavior. For composition with x = 0.15, a large unipolar strain of 0.37% ( d(33)* = S-max/E-max = 570 pm/V) was achieved under 6.5 kV/mm applied electric field at room temperature. Both unipolar and bipolar strain curves related to the temperature closely, and when the temperature reached the TF-R, the normalized strain d(33)* achieved a maximum value ( e.g., for x = 0.10, d(33)* = 755 pm/V) owing to the electric-field-induced ER-to-FE state transition.