Hydrothermal polycrystalline PZT thick film transducer for high intensity ultrasound radiation at over 20 MHz

A high intensity and high frequency ultrasound radiation ultrasonic transducer was fabricated by the hydrothermal deposition technique of lead zirconate titanate polycrystalline thick film. This ultrasonic transducer had a 45 micron meters thick hydrothermal PZT layer on a 50 micron meters thick titanium substrate, and an active area was 5 mm X 5 mm. The piezoelectric constant d33 of this PZT thick film was 44 pm/V and the acoustic impedance was about 8 Mrayl. This prototype ultrasonic transducer radiated a sound pressures of over 100 kPa at over 20 MHz in degassed water using a thickness vibration mode of the PZT film. The radiated sound pressures was measured using a commercial hydrophone that was proofed of the receiving sensitivity at 1 MHz to 60 MHz. The hydrophone was held 40 mm in front of a surface of the prototype transducer. This measuring point was a central ultrasonic beam axis from the prototype transducer. An applied voltage to the prototype ultrasonic transducer was 40 V at ten cycles burst waveform of sine wave when measuring the radiated sound pressure. Additionally, when a driving signal was 20 MHz continuous sine waves, cavitations and an acoustic streaming was generated along a line of the central ultrasonic beam axis. The observation of generated cavitations when the continuous high intensity ultrasonic radiation from the transducer was conducted with the KI oxidation method. The cavitations was measured by measuring the oxidation reaction from the generating of cavitations in a KI solution. A volume of the KI solution for the measurement of cavitations was 50 ml.