Microstructure and Electrical Properties of K0.5Na0.5NbO3-LiSbO3-BiFeO3-x %molZnO Lead-Free Piezoelectric Ceramics

Lead-free piezoelectric ceramics {0.996[(0.95(K0.5Na0.5)NbO3-0.05LiSbO3]-0.004BiFeO3}-xmol%ZnO were prepared through a conventional ceramics sintering technique. The effect of ZnO content on structure, microstructure, and piezoelectric properties of KNN-LS-BF ceramics was investigated. The results reveal that ZnO as a sintering aid is very effective in promoting sinterability and electrical properties of the ceramics sintered at a low temperature of 1,020 °C. The ceramics show a single-perovskite structure with predominant tetragonal phase, and coexistence of orthorhombic and tetragonal phases is observed for x = 2.5–3.0. The addition of ZnO causes abnormal grain growth. A dense microstructure is also obtained at x = 2.0 because the relative density reaches up to 94.6 %. The morphotropic phase boundary and dense microstructure lead to significant enhancement of the piezoelectric properties. The ceramic with x = 1.5 exhibits optimum electrical properties as follows: d33 = 280 pC/N, kp = 46 %, Qm = 40.8, Pr = 25 μC/cm2, Ec = 1.2 kV/mm, and Tc = 340 °C.