Research On BNT Based Lead-free Piezoelectric Ceramics For Ultrasonic Motors

Piezoelectric ceramics are kinds of advanced functional materials based on their mutual transfer between mechanical energy and electric energy. They are the key parts of ultrasonic motors. At present, lead based piezoelectric ceramics are widely used for ultrasonic motors .The development and study of lead-free piezoelectric materials have been more and more urgent because of the environment problem.In this dissertation, the Bi1/2Na1/2TiO3(abbreviated as BNT) based ceramics samples were prepared by the conventional solid-state reaction and by citric-gel processes.The optimum preparation condition were investigated. (Bi0.972Na0.852K0.12-xLix)0.5TiO3-0.028BaTiO3(abbreviated as BNT-BKT-BT+xLi)ceramic samples wre also prepared by the two metholds. Microstructures were studied according x-ray diffraction, scanning electron microscope, etc. Dielectric, piezoelectric, ferroelectric, mechanical properties and mechanical quantity factor were measured by d33 meter, impedance analyzer, high resistance system and ferroelectric parameter meter etc. Li+ doping effects and mechanisms were analyzed and discussed. After comparison, it was found that the ceramics with composition BNT-BKT-BT+0.03Li were the optimal piezoelectric property among all the samples fabricated. BNT-BKT-BT+0.03Li ceramics were supplied on ultrasonic motors designed in Precision Driving Laborotary of NUAA.The ultrasonic motors run well and it indicated that lead-free piezoelectric ceramics were promising to be used for actuation purpose after sufficient modification.