Structure and piezoelectric properties of (1-x)K0.5Na0.5NbO3-xLiBiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1-x)(K0.5Na0.5)NbO3-xLiBiO3 [(1-x)KNN-xLB] (x=0, 0.0005, 0.002, 0.004, 0.006, 0.008, 0.010) were prepared by an traditional solid-state reaction. The microstructure and electrical properties of the ceramics were investigated. The results show that all (1-x)KNN-xLB ceramics possess pure perovskite structure when x=0.01, no trace of any secondary phase is detected, and the phase structure of the ceramics transits abnormally from orthorhombic to cubic. With the increase of the LB content, the size of grain gradually becomes small, the piezoelectric constant d33 and the planar electromechanical coupling coefficient kp first increases and then decreases. The d33 and kp of the ceramics reach their maximum values 115 pC/N at x=0.002 and 0.2701 at x=0.001, respectively. The dielectric constant er of the ceramics firstly increases evidently and then decreases with the increase of x, the maximum value 871.8 is obtained at x=0.006.