Robust hydrophone with hydrothermal PZT thick-film vibrator and titanium front layer for use in high-power ultrasound fields

Novel robust hydrophones were fabricated by depositing hydrothermally synthesized lead zirconate titanate polycrystalline film on the back-side surface of a titanium plate. These hydrophones were resistant to damage during the measurement of the high-intensity acoustic field formed by a high-intensity focused ultrasound transducer driven continuous wave, for driving power of up to 50 W, and to the acoustic field of an ultrasonic cleaner with generation of inertial acoustic cavitation. The sensitivity of the robust hydrophone was linear up to about 8 MPa. We confirmed the linearity of response for the hydrophone at high acoustic pressure. The fabricated robust hydrophone showed receiving sensitivity across a wide frequency range. Furthermore, we observed the output waveforms of the fabricated robust hydrophone with distortion due to non-linear propagation in water. These results indicate that our hydrophone can detect broadband acoustic signals emitted by oscillating and collapsing acoustic cavitation bubbles. However, the flat tip of the hydrophone disturbed the acoustic field, as shown by the results of sonochemiluminescence in luminol solution. This means that the setting position should be considered for measurements at higher acoustic power.