Properties of 1-3 PZT/Epoxy Composites for Ultrasonic Transducer Applications

The aim of this paper is to present the measured properties of dice-and-fill 1-3 composites. Instead of using the conventional reflection technique, the acoustic impedance is determined by the product of velocity and density; the velocity of sound in the composite is measured by using the echo-shift method and checked by the resonant method. The characteristic acoustic impedance values determined by these two methods are in close agreement. No significant variation of velocity with respect to frequencies for thin samples can be observed in the frequency range from . 5 MHz up to 7 . 5 UHz. It is also found that all composites have thickness resonance frequencies ft lower than the original ceramic disc and ft decreases as the width of the PZT columns in the composite increases. Effect of volume percentages of ceramic, and column width size on the coupling constants kf and kp are also discussed. By reducing the thickness of the composite by lapping, it is observed that when the sample is comparatively thick (thickness greater than the ceramic column width) the resonant frequency varies linearly with the inverse of the thickness l/t. However when the thickness is less than the ceramic column width the frequency increases only gradually as the value of l / t increases.