Piezoelectric Composite Materials for Ultrasonic Transducer Applications. Part II: Evaluation of Ultrasonic Medical Applications

TLDR

The study measured acoustic impedance of PZT‑polymer composites using three techniques, modeled its dependence on PZT volume fraction and frequency, calibrated voltage responses with time‑delay spectrometry, and molded the composites into curved shapes via a simple thermal process to fabricate focused transducers. The composites exhibited acoustic impedance between 3–10 M rayl, a receiving‑mode figure of merit three times that of pure PZT, and a 20 % PZT composite’s figure of merit increased 50 % with a lucite impedance transformer, while focused transducers produced the reported axial and lateral beam profiles.

Abstract

Abstmct-The electro-acoustic properties of Lead zirconate titanate (PZT) rod-polymer composites relevant for ultrasonic transducer applications are reported. Acoustic impedance of the composite materials was measured by three different techniques in the frequency range 0.33.5 MHz. Dependence of the acoustic impedance as a function of volume fraction of PZT and frequency was also modeled theoretically. Time-delay spectrometry was employed to calibrate the free-field transmitting and receiving voltage responses of the composite materials. The acoustic impedance of the composite materials was in the range of 3-10 M rayl. The figure of merit in the receiving mode of composite materials was three times that of PZT. The figure of merit for a 20percent PZT composite (2 = 7.3 M rayl) was further enhanced by 50 percent using a single-layer impedance transformer of lucite (2 =3.3 M rayl). These composite materials were molded into curved shapes by simple thermal process to fabricate focused transducers. The axial and lateral beam profiles of focused composite transducers are presented.