Phase transition, microstructure, and dielectric properties of Li/Ta/Sb co-doped (K, Na)NbO3 lead-free ceramics

Li/Ta/Sb co-doped lead-free (K0.4425Na0.52Li0.0375)(Nb0.93−xTaxSb0.07)O3 (abbreviated KNLNSTx) piezoelectric ceramics, with Ta-doping ratio of x ranging from 0.0275 to 0.0675, were synthesized using the conventional solid-state reaction method at the sintering temperature of 1130 °C. The effects of Ta content on the microstructure, dielectric properties, and phase transition behavior of the prepared ceramics were systematically investigated. The X-ray diffraction results show that all KNLNSTx ceramics formed a secondary phase, which is assigned to the tetragonal tungsten-bronze type (TTB) structure phase, and showed a phase transition from an orthorhombic symmetry to a tetragonal symmetry across a composition region of 0.0375