Piezoelectric Properties of K 0.47 Na 0.47 Li 0.06 NbO 3 –NaSbO 3 Lead‐Free Ceramics for Ultrasonic Transducer Applications

Lead‐free piezoelectric ceramics (1− x )K 0.47 Na 0.47 Li 0.06 NbO 3 – x NaSbO 3 have been prepared by a conventional solid‐state sintering technique. Our results reveal that NaSbO 3 diffuses into the K 0.5 Na 0.5 NbO 3 lattices to form a solid solution with a perovskite structure. After the addition of NaSbO 3 , both the paraelectric cubic–ferroelectric tetragonal and ferroelectric tetragonal–ferroelectric orthorhombic phase transition temperatures decrease. Coexistence of the orthorhombic and tetragonal phases is formed in the ceramics with x =0.04–0.10 at room temperature. In addition to the increase of the Na + /K + ratio and the strong covalence of Sb, the piezoelectricity of the ceramics is improved. For the ceramic with x =0.09, the piezoelectric properties become optimum, giving a piezoelectric coefficient d 33 of 305 pC/N, and electromechanical coupling factors k p and k t of 0.51. The ceramics also exhibit excellent performance in transducer applications, indicating that the ceramics are ready for replacing lead‐containing ceramics in practical applications.