Integrated ferroelectric monomorph transducers for acoustic imaging

Millimeter-sized ferroelectric monomorph sonar transducers have been built using sol-gel PZT on micromachined silicon wafers. Second generation 8×8 transducer arrays have been built and tested in water in the frequency range of 0.3 to 2 MHz. Improvements to the sol-gel process have yielded high-quality, crack-free PZT films up to 12 μm in thickness, which leads directly to higher sensitivity and figure of merit for acoustic transducers. 4-μm thick films had longitudinal piezoelectric coefficient d₃₃=140-240 pC/N, remanent polarization=28 μC/cm², coercive field=30 kV/cm, and dielectric constant=1400. Test results are presented, including frequency response, beam patterns, and sensitivity. High-resolution acoustic images have been generated using these transducers with 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)