The research on lead-free piezoelectric ceramics has been one of the importantfields worldwide for years for the sustainable development of the world.In recent years,the author and his group concentrated their work on perovskite lead-free piezoelectric ceramics,especially on(Bi_(1/2)Na_(1/2))TiO_(3)(BNT)-and K_(1/2)Na_(1/2)NbO_(3)(KNN)-based ceramics.In this paper,the researches of the composition design on BNT-and KNN-based lead-free piezoelectric ceramics,the effects of doping on the properties of these ceramics,the study of the temperature stability of these ceramics,and the fabrication technique used in the author's group for these ceramics are reviewed,and the further considerations and some prospects to be resolved in coming years from the viewpoint of the device applications of these ceramics are suggested.
Lead-free piezoelectric ceramics （1-y）Bi0.5（Na1-xLix）0.5TiO3-yBaTiO3 with x=0-0.125 and y=0.02-0.12 were fabricated by a solid-state reaction process, and their dielectric, piezoelectric and ferroelectric properties were investigated. The results show that the addition of Li^＋ significantly improves the sintering performance and piezoelectric properties of the ceramics. X-ray diffraction （XRD） patterns indicate that the ceramics possess pure perovskite structure. At room temperature, the ceramics provide high piezoelectric charge constant d33 （up to 210 pC/N）, high planar electromechanical coupling factor kp （34.5%）, large remanent polarization Pr （up to 40 μC/cm^2）, and low coercive field Ec （3.0 kV/mm）, which indicates that （1-y）Bi0.5（Na1-xLix）0.5TiO3-yBaTi03 is a good lead-free piezoelectric ceramic.
