Ferroelectric thin film ultrasonic micromotors

Ferroelectric thin films of lead zirconate titanate (PZT) of morphotropic phase-boundary composition have been fabricated by a sol-gel spin-on technique for application to a new family of flexure-wave piezoelectric micromotors characterized by low speed and high torque. The high relative dielectric constant (1300) and breakdown strength (1 MV/cm) of the films lead to high stored energy densities. The piezoelectric coefficients d/sub 33/ and d/sub 31/ were measured to be 220 pC/N and -88 pC/N, respectively; the electromechanical coupling factors calculated from these data were k/sub 33/=0.49, k/sub 31/=0.22, and k/sub p/=0.32. The development of the piezoelectric ultrasonic micromotors from the PZT thin films and the architecture of the stator structure are described. Nonoptimized prototype micromotors show rotational velocities of 100-300 rpm and net normalized torques in the pN-m/V/sup 2/ range.<>