Fabrication of Ultrasonic Transducers with KNbO₃ Piezoelectric Single Crystal for Detecting Harmonic Signals

Abstract

An ultrasonic transducer with a circular aperture has been designed and fabricated for the development of a harmonic imaging system with high sensitivity. The transducer consists of two piezoelectric elements; one is made from Pb(Zr, Ti)O 3 (PZT) ceramics for transmitting a finite-amplitude ultrasonic pulse, and the other is made from a KNbO 3 (KN) piezoelectric single crystal for receiving second harmonic signals generated in a nonlinear medium. They are arranged coaxially. Using this transducer, acoustic characteristics were measured and the observation of sponge phantom images was performed. Compared with other transducers with PZT and PbTiO 3 (PT) ceramics, we have confirmed that higher sensitivity and stronger correlation between the sensitivity and figure-of-merit can be obtained. Additionally, the third harmonic detection has been demonstrated.