Construction of new morphotropic phase boundary in 0.94(K0.4−xNa0.6BaxNb1−xZrx)O3–0.06LiSbO3 lead-free piezoelectric ceramics

0.94(K0.4−xNa0.6BaxNb1−xZrx)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 kP = 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.