Piezoelectric and dielectric properties of Bi0.5Na0.5TiO3–Bi0.5Li0.5TiO3 lead-free ceramics

(1 − x)Bi_0.5Na_0.5TiO₃–xBi_0.5Li_0.5TiO₃ lead-free ceramics have been prepared by a conventional solid-state reaction method, and their piezoelectric and dielectric properties have been studied. X-ray diffraction studies reveal that Li⁺ diffuses into the Bi_0.5Na_0.5TiO₃ lattices to form a solid solution with a pure perovskite structure. The addition of Bi_0.5Li_0.5TiO₃ effectively lowers the sintering temperature of the ceramics and greatly assists in the densification of the ceramics. The ceramic with x = 0.075 possesses the optimum piezoelectric properties: piezoelectric coefficient d ₃₃ = 121 pC/N and planar electromechanical coupling factor k _P = 18.3%. After the partial substitution of Li⁺ for Na⁺ in the A-sites of Bi_0.5Na_0.5TiO₃, the ceramics exhibit more relaxor characteristic, which is probably resulted from the cation disordering in the 12-fold coordination sites. The depolarization temperature T _d shifts to low temperature with the substitution level x of Li⁺ for Na⁺ increasing.