Ferroelectric thin films for piezoelectric micromotors

The dielectric and piezoelectric properties of lead zirconate titanate (PZT) thin films were investigated to examine its viability for application to a new family of flexure-wave piezoelectric micromotors, characterized by low speed and high torque. Stored energy densities higher than the air-gap electrostatic actuators accrue from high relative dielectric permittivity (1300) and breakdown strength (1 MV/cm) of the films. The piezoelectric longitudinal and transverse strain coefficients were measured by a nonresonance technique through a modified Mach-Zehnder laser interferometer; at a dc bias of 75 k V/cm, d33 was measured to be 220 pC/N; evaluation of the film as a bimorph yielded a value of —88 pC/N for d31 at 200 kV/cm ac field. The electromechanical coupling factors calculated thereupon were k33 = 0.49, k31 = 0.22, and kp = 0.37. The development of the piezoelectric ultrasonic micromotors from the PZT thin films, and the architecture of the stator structures are described. Nonoptimized prototype micr...