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12 April 2000 Performance of high-frequency PZT fiber composite and PbTiO3 transducers
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Fine scale 1 - 3 fiber composites and PbTiO3 are promising materials for high frequency (greater than 30 MHz) ultrasonic transducers because of their high thickness coupling coefficients and good mechanical flexibility. This work focus on improvements in the fiber composite and PbTiO3 ceramic transducer performance through innovative tuning techniques and optimized materials selection. For the fiber composite transducers, a 45% volume fraction of PZT fibers with 17 micrometer fiber diameter was selected to obtain high coupling (approximately 0.60) and ensure pure thickness vibration mode at high frequency. Microballoons mixed with epoxy formed a low acoustic impedance backing material and parylene was deposited as a front matching layer. The PbTiO3 ceramic was first processed to provide high density and then polished to the required thickness. Conductive epoxy was then chosen as backing and parylene was deposited as a front matching layer. The focus for both transducers was achieved by spherical shaping. The fiber composite transducers with center frequency around 40 MHz showed 6 dB bandwidth as high as 100%, and round-trip insertion losses near -36 dB. Compared to fiber composite transducers, the PbTiO3 ceramic transducers can work at much higher frequencies (near 90 MHz). In a similar frequency range as fiber composite transducers, they showed improvement sensitivity as marked by an insertion loss around -24 dB. In addition, they still displayed good bandwidth as a result of electrical tuning.
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Jian-Zhong Zhao, Richard J. Meyer Jr., Timothy A. Ritter, and K. Kirk Shung "Performance of high-frequency PZT fiber composite and PbTiO3 transducers", Proc. SPIE 3982, Medical Imaging 2000: Ultrasonic Imaging and Signal Processing, (12 April 2000);

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