Fabrication and Characterization of High Sensitivity Ultrasonic Transducers with Functionally Graded Design

In this paper, a PZT/epoxy piezo-composite transducer with functionally graded design was proposed, which facilitated high sensitivity and broad bandwidth. The functionally graded piezocomposite was fabricated using a modified dice and fill method. Finite-element simulation was performed to study the vibration modes of the piezocomposite and to predict the transducer performances. To evaluate the performances experimentally, the proposed and conventional transducer based on monolithic PZT ceramic with similar dimension was fabricated and characterized systematically. We determined that the functionally graded transducer has a slightly higher center frequency (5.37 MHz), broader −6-dB bandwidth (22.5%), and a much lower insertion loss (−13.57 dB) compared to the conventional transducer (5.26 MHz, 18.3%, and −17.72 dB, respectively). The experimental results are in good agreement with the simulation ones. This preliminary investigation suggests that the functionally graded design is a promising approach to enhance the performance of ultrasonic transducers in high-sensitivity applications.