Preparation of lead free KNLNTS piezoelectric ceramics by molten salt synthesis and its application

Lead-free (K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.10Sb_0.04)_O3 (KNLNTS) piezoelectric ceramics were synthesized by the NaCl-KCl (NaCl/KCl=1/1) molten salt synthesis (MSS) method. The KNLNTS ceramics was fabricated successfully by sintering at 1100degC to 1200degC. The results show that the KNLNTS powder particle size increased form 50 nm to 200 nm and the shape changed from cubic structure to plated-like structure with time increasing. Compared to the solid mixed oxide (SMO) process, the MSS can get powders with (100) grain orientation and without aggregation in less time. The density of the KNLNTS ceramics sintered at 1150degC reached a maximum value of 4.69 g/cm3. The ceramics sintered at 1150 square by MSS method shows a maximum Piezoelectric coefficient of about 250 pC/N and a maximum electromechanical coupling factor kp of 37.6%. A novel rocking head type piezoelectric ultrasonic motor was fabricated using the lead-free ceramics as the actuator. The Doppler Laser Vibrometer (Polytec 300-F) was used to measure the vibration characteristic of the ultrasonic motor. The resonant frequency of first bending mode is about 129.6 kHz. The output torque was 32 uNm, and the maximum revolution speed was 330 rpm at 100 Vp-p driving voltage.