Piezoelectric properties and dielectric relaxation of La3+-doped Na0.5Bi0.5TiO3 based lead-free ceramics

La3+ doped 0.97Na0.5Bi0.5TiO3 - 0.03K0.5Na0.5NbO3 binary lead-free piezoceramic systems were prepared by the cold isostatic pressing and air-proof sintering techniques. The effects of La3+ addition on the phase structure, microstructure and dielectric and piezoelectric properties were investigated. X-ray diffraction patterns indicate that all ceramics samples (0.015x0.105) are single perovskite phase. By using the cold isostatic pressing technique, the growth of grains is suppressed and the piezoelectric pro-perties are enhanced. All samples possessed the characteristics of diffuse phase transition and frequency dispersion, showing that the ceramics are typically relaxor ferroelectrics. With the increasing of La3+ doping amount, the ferroelectric-antiferroelectric transition temperature decreases, while the Curie temperature increases. At the same time, the dielectric constant, dielectric loss and piezoelectric constant all gradually decrease and the relaxor characteristics become more obvious.