Investigation on the diffuse phase transition of (K_(0.5)Na_(0.5))_(1-x)Li_xNb_(1-y)Sb_yO_3 lead-free piezoelectric ceramics

(K0.5Na0.5)1-xLixNb1-ySbyO3(KNLNSx-y,x=0-10mol%,y=2mol%-8mol%) lead-free piezoelectric ceramics have been synthesized by conventional mixed oxide method.The effects of Li and Sb substitutions on the characteristic of the diffuse phase transition of the ceramics were investigated.The results indicate that during the sintering Li+ and Sb5+ diffuse into the K0.5Na0.5NbO3 lattices forming a solid solution with perovskite structure;with the increasing amount of Li,the characteristic of the diffuse phase transition of the KNLNSx-5 ceramics decreases;and with the increasing amount of Sb the characteristic of the diffuse phase transition of the KNLNS2-y ceramics increases.At the temperature higher than the Curie temperature of the ceramics,the thermal variation of the dielectric constant of the KNLNSx-y ceramics is well described by the modified Curie-Weiss law;and the related mechanisms for the diffuse phase transition of the ceramics were also discussed.