Piezoelectric Properties of K_(0.47)Na_(0.47)Li_(0.06)NbO_3-NaSbO_3 Lead-Free Ceramics for Ultrasonic Transducer Applications

摘要

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.