Millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. First generation transducer arrays with diaphragms varying in size from 0.2 to 2 mm were tested. Second generation 8 X 8 arrays have also been built and tested in water in the frequency range of 0.3 to 2 MHz.Improvements to the sol-gel process have yielded highquality, crack-free PZT films up to 12 pm in thickness, which leads directly to higher sensitivity and figure of merit for acoustic transducers. The longitudinal piezoelectric coefficient d33 is 140 to 240 pC/N, measured through a double beam laser interferometer. Remanent polarization of 28 pC/cm2, a coercive field of 30 kV/cm, and dielectric constant of 1400 were measured on 4-pm thick films. Test results are presented, including frequency response, beam patterns, and sensitivity.High-resolution acoustic images have been generated using these transducers and a four-element underwater acoustic lens. Potential applications for these transducers include high-frequency imaging sonars, medical ultrasound, ultrasonic communication links, and flaw detection (NDT).

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