Optimizing electromechanical properties of KNN-based piezoelectric ceramics through regulation of lattice distortion

With the rapid development of broadband transducers, there is an increasing demand for enhanced electromechanical properties in lead-free piezoelectric ceramics. In this study, the strategies to enhance the electrical properties of ceramics were explored by doping BaZrO3 into 0.96(K0.48Na0.52)Nb0.96Sb0.04O3-0.04(Bi0.5Ag0.5)ZrO3 ceramics, inducing lattice distortion (c/a) and regulating the phase structure. The ceramics doped with 1.5 mol% BaZrO3 demonstrate excellent electrical performance, with a piezoelectric coefficient (d33) of 545 pC/N, a relative dielectric constant (εr) of 4126, and an electromechanical coupling factor (kp) of 54.1 %. The reduced c/a ratio and rhombohedral-orthorhombic-tetragonal phase structure reduce the polarization energy barrier and promote the ordered arrangement of ferroelectric dipoles, thereby enhancing the comprehensive performance of the ceramics. Lastly, the electrical impedance of ceramics is studied in detail and reveals the main conduction mechanism in the microscopic region. This research provides new insights into optimizing the electrical properties of ceramics through microstructural manipulation and demonstrates the potential application of KNN-based ceramics in high performance piezoelectric transducers.