Fundamental Study of Miniature Membrane-Type Hydrophone Using Hydrothermally Synthesized Lead Zirconate Titanate

  • Kazuho Yoshimura, Department of Biomedical Engineering, Graduate School of Engineering, Toin University of Yokohama, Japan
  • Norimichi Kawashima, Department of Biomedical Engineering, Graduate School of Engineering, Toin University of Yokohama, Japan
  • Shinichi Takeuchi, Department of Biomedical Engineering, Graduate School of Engineering, Toin University of Yokohama, Japan
  • Takeyoshi Uchida, National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Japan
  • Tsuneo Kikuchi, National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Japan
  • Minoru Kurosawa, Tokyo Institute of Technology, Japan

    • The acoustic field distribution should be measured with a hydrophone to confirm the safeness of ultrasound diagnostic equipments or to estimate the performance of those. Our hydrothermally synthesized lead zirconate titanate (PZT) poly-crystalline film can be deposited on a tiny or complex-shaped titanium (Ti) substrate. Furthermore, it is thought that ultrasound probes with ultrawide frequency characteristics of their receiving sensitivity can be fabricated with the hydrothermally synthesized PZT film. We fabricated the miniature needle-type hydrophones with a small aperture by deposition of a hydrothermally synthesized PZT film on thin Ti wires and measured their performance. However, unnecessary back echo from the end of Ti wire was observed in our needle-type hydrophones and unnecessary peaks and dips appeared in the frequency characteristics of receiving sensitivities of our needle-type hydrophones. We think that such peaks and dips were caused by the resonance of the radial vibration mode. Miniature membrane-type hydrophones with disk type unimorph piezoelectric element were fabricated by deposition of a hydrothermally synthesized PZT film on Ti foil in order to avoid from back echo and peaks and dips in the frequency characteristics of receiving sensitivities. As a result, back echo was not observed in the membrane-type hydrophone. And received ultrasound waveform with our membrane-type hydrophone were similar to the applied electrical pulse waveform. Therefore, it is expected that our membrane-type hydrophone has smooth and wide frequency characteristics of receiving sensitivity without unnecessary peaks and dips. We will report the manufacturing process and measured results of their performance in this paper.