Abstract
Bimorph piezoelectric actuators were subjected to cyclic electric loading with bias DC voltage V_b=0, 50, 100V. When specified number of cycles was preceded, electric loading was interrupted and resonance and anti-resonance frequencies were measured by an impedance analyzer. In addition, displacement of the actuator due to DC voltage was measured by a laser displacement meter. Electromechanical coupling coefficient k_<3l> and piezoelectric constant d_<31> were calculated from resonance and anti-resonance frequencies and the relationship between DC voltage and displacement of actuator. Degradation of bimorph piezoelectric actuators due to cyclic electric loading with positive bias voltage was indicated. Moreover, variation in material properties of piezoelectric ceramics used in actuators under cyclic electric loading was indicated, too. When the positive bias voltage was superposed on AC electric loading, piezoelectric ceramics below the center electrode was depoled, and it was found that the degradation of actuators was caused by the variation in piezoelectric material properties due to the domain switching.
