Construction of new morphotropic phase boundary in 0.94(K_0.4−xNa_0.6Ba_xNb_1−xZr_x)O₃–0.06LiSbO₃ lead-free piezoelectric ceramics

0.94(K_0.4−xNa_0.6Ba_xNb_1−xZr_x)O₃–0.06LiSbO₃ ceramics were prepared by conventional technique, and the effect of BaZrO₃ on the phase transitions, dielectric, ferroelectric, and piezoelectric properties of the ceramics were investigated. The phase transitions for the ceramics were determined by the temperature dependence of dielectric properties and X-ray diffraction patterns. BaZrO₃ changes the symmetry of the ceramics from tetragonal dominant phase with x = 0–0.06 to rhombohedral phase with x = 0.07–0.09. The phase transition near room temperature for the composition with x ~ 0.06 is different from previously reported phase transition between orthorhombic and tetragonal phases. It is suggested that a new morphotropic phase boundary (MPB) is constructed with both rhombohedral–orthorhombic and orthorhombic–tetragonal phase transitions near room temperature, and the enhanced piezoelectric properties (d₃₃ = 344 pC/N and k_P = 32.4% with x = 0.06) are obtained. The results indicate that the construction of new MPB is of significance for further development of KNN-based ceramics.