A cylindrical micro ultrasonic motor using PZT thin film deposited by single process hydrothermal method (phi2.4 mm, L=10 mm stator transducer).

A micro ultrasonic motor using PZT (lead zirconate titanate) thin film has been improved by a single process hydrothermal method. The hydrothermal method is a unique method for depositing PZT thin film in a solution. An earlier reported hydrothermal method consisted of two linked processes. Our new method, however, has only a single process. Hence, less distribution of chemical components of the PZT film contributes to a higher efficiency of the stator transducer. The piezoelectric factor d(31) was -30 pC/N for this new method, which is six times larger than that of the previous method. The output torque of the micro ultrasonic motor fabricated by the single process hydrothermal method was measured. The output torque was 7.0 microNm, and the maximum revolution speed was 880 rpm at 15 Vp-p driving voltage.