Microstructure, phase transition and electrical properties of LiSbO₃-doped (K_0.49Na_0.51)NbO₃ lead-free piezoelectric ceramics

Microstructure, phase transition and electrical properties of (1 − x)K_0.49Na_0.51NbO₃ − xLiSbO₃ (x = 0–0.08) lead-free piezoceramics prepared by the conventional solid-state sintering method were investigated with an emphasis on the effects of LiSbO₃ doping amount x. SEM results showed that the ceramic became denser by increasing LiSbO₃ doping amount x. Being indexed by XRD profiles, the ceramics changed from an orthorhombic perovskite structure to a tetragonal one across a composition region of 0.04 ≤ x≤0.05. The sample of LiSbO₃ doping amount x = 0.05 in tetragonal side of the region had the maximum values of piezoelectric constant (d ₃₃ = 256 pC/N) and planar electromechanical coupling coefficient (k _p = 42.7%). Meanwhile, this ceramic sample showed other good properties such as ε _r = 1,463, tgδ = 0.036, Q _m = 48, P _r = 19.8 μC/cm², E _c = 1.9 kV/mm and T _c = 340 °C, which indicated it was a promising lead-free piezoelectric material for ultrasonic transducer applications.