Measurement of LiNbO_3 Rectangular Plate Under Large Vibration Velocity of the First Longitudinal and Second Flexural Modes

摘要

We have studied a miniature ultrasonic motor using a piezoelectric single-crystal LiNbO_3. The crystal vibrator retains superior characteristics even when the vibrational velocity is large. On the other hand, a vibrator using a resonance mode shows no signs of an operating limit and fractures itself when the vibrational velocity exceeds the limit. Such behavior causes a problem in controlling the achievement of a large output power from the motor. Therefore we must investigate the vibrational characteristics at a high vibration level and at the fracture limit. In this study, the samples were examined for their vibrational characteristics at a high driving level and at the fracture limit. First, the characteristics of the resonance vibration of the first longitudinal and second flexural modes in an X128°-rotated Y-cut rectangular plate were measured. Second, to evaluate the difference caused by the cut angle of the X-rotation, the characteristics for the first longitudinal mode of X128°-, XI35°-, X140°- and X155°-rotated Y-plates were measured; additionally, for each rotation-angle plate, we measured the characteristics of the rectangular plates whose longer side was directed along the x- or z'-axis. In this paper, we describe the experimental results for the high-power characteristics and the fracture limits.