Double-Mode Miniature Cantilever-Type Ultrasonic Motor Using Lead-Free Array-Type Multilayer Piezoelectric Ceramics

We studied the following to improve the characteristics of the lead-free ultrasonic micromotor. A double-mode miniature cantilever-type ultrasonic motor was fabricated using array-type multilayer piezoelectric ceramics (A-MLPC) of (Sr,Ca) 2 NaNb 5 O 15 (SCNN) such as lead-free piezoelectric materials, and the electrical driving properties were investigated. The A-MLPC integrated multilayer piezoelectric ceramics (MLPC) arrayed in a 2 × 2 matrix. By using A-MLPC, double-mode bending vibration of the stator vibrator can be realized easily, and the quality factor of the vibrator increased. Furthermore, with the improvement of the piezoelectric properties of the SCNN, the electromechanical coupling coefficient of the vibrator increased. As a result, we succeeded in improving the driving properties of the motor. In particular, the driving voltage of SCNN motor decreased to 1/10 of the previous study, and this motor is similar to Pb(Zr,Ti)O 3 –Pb(Ni,Nb)O 3 –Pb(Zn,Nb)O 3 (PZT) one in terms of properties by applying 3 times higher voltage than that required for the PZT one. The SCNN motor started to rotate at 0.3 V p–p and showed such characteristics as revolution speed of 730 rpm, torque of 0.7 µN m, and efficiency of 3.5% at 1.6 V p–p . It appeared that the SCNN motor was able to rotate by a lithium-ion cell used in the mobile equipment without an amplifier circuit.