Micromachined high frequency ferroelectric sonar transducers

摘要

Millimeter-sized ferroelectric monomorph sonar transducers havenbeen built using sol-gel PZT on micromachined silicon wafers. Firstngeneration transducer arrays with diaphragms varying in size from 0.2 ton2 mm were tested. Second generation 8×8 arrays have also beennbuilt and tested in water in the frequency range of 0.3 to 2 MHz.nImprovements to the sol-gel process have yielded high-quality,ncrack-free PZT films up to 12 Μm in thickness, which leads directlynto higher sensitivity and figure of merit for acoustic transducers. Thenlongitudinal piezoelectric coefficient d33 is 140 to 240npC/N, measured through a double beam laser interferometer. Remanentnpolarization of 28 ΜC/cm2, a coercive field of 30 kV/cm,nand dielectric constant of 1400 were measured on 4-Μm thick films.nTest results are presented, including frequency response, beam patterns,nand sensitivity. High-resolution acoustic images have been generatednusing these transducers and a four-element underwater acoustic lens.nPotential applications for these transducers include high-frequencynimaging sonars, medical ultrasound, ultrasonic communication links, andnflaw detection (NDT)