Effects of composition on phase structure, microstructure and electrical properties of (K_0.5Na_0.5)NbO₃-LiSbO₃ ceramics

Lead-free piezoelectric ceramics with the composition of (1 - x)(K_0.5Na_0.5)NbO₃-xLiSbO₃ [(1 - x)KNN-xLS] have been synthesized by conventional solid-state sintering process and without cold isostatic pressing (CIP). A morphotropic phase boundary (MPB) between orthorhombic and pseudocubic phases was found in the composition range of 0.06 ≤ x < 0.10. Analogous to Pb(Zr, Ti)O₃, the density, dielectric and piezoelectric properties were enhanced for the composition near the MPB. The 0.94KNN-0.06LS ceramics show excellent electrical properties, which are as follows: ρ = 4.44 g/cm³, ε_r = 708 (10 kHz), tan δ = 0.037 (10 kHz), d₃₃ = 171 pC/N, k_p = 0.38 and T_c = 365 °C. Dielectric study revealed that the dielectric relaxor behavior was induced by increasing LS content. In addition, 0.94KNN-0.06LS ceramics also exhibited relatively good ferroelectric properties with remanent polarization (P_r) of 18.9 μC/cm² and coercive field (E_c) of 9.38 kV/cm. The results show that KNN-LS ceramics have the potential to be one of the leading lead-free piezoelectric materials for electromechanical transducers applications in the future.