Comparison of acoustical fields radiated from PZT piezoceramic and piezocomposite highly focused transducers

The present report compares acoustical fields radiated in water from two focused transducers of the same geometrical parameters (aperture diameter 100 mm, focal length 100 mm, resonance frequency 1 MHz), but made of different materials (PZT piezoceramic and piezocomposite). Both continuous wave and pulsed regimes of transducer excitation were used. A discrepancy between the O´Neil theory (1949) and experiment was noticed, which was essential in the case of the PZT radiator and of little importance for the piezocomposite source. It is shown that this disagreement is accounted for by Lamb waves propagating in the piezoceramic transducer material. O´Neil theory is not applicable to describe the pressure field, as long as the effect of Lamb waves is not taken into account for PZT transducers. On the contrary, O´Neil theory is able to describe approximately the pressure field of highly focused piezocomposite transducers