Piezoelectric Composite Materials for Ultrasonic Transducer Applications. Part I: Resonant Modes of Vibration of PZT Rod-Polymer Composites

Abstmcr-The objective of the present work was to gain a deeper mensions of the transducer are much smaller than the understanding of the behavior of lead zirconate titanate (PZT) polymer composites for applications such as ultrasonic medical diagnosis in the megahertz frequency range. These composites were originally devel-oped for low-frequency hydrophone applications. The PZT rod-poly-mer composites have been prepared with five to 30 volume percent PZT using mm and mm rods. In a disc of PZT rod-polymer com-posite material, there are three principal types of resonance: the planar mode, the thickness mode, and various lateral modes caused by the reg-ular periodicity of the PZT rod in the composite. These resonance modes have been studied with the following techniques: electrical impedance measurement as a function of frequency and laser probe dilatometry of the dynamic displacement function of frequency and position in the composite lattice. The observed resonance behavior is found to be a result of lateral interactions in the composite through the epoxy me-dium. The effect of temperature on the electromechanical properties of the composite has also been investigated. Implications f these results for optimizing the design of ultrasonic transducers are discussed. I