Study on Ultrasound Transducers With Alternating Current Poled Pb(Mg_1/3Nb_2/3) O₃-xPbTiO₃ Single Crystals

Alternating current poling (ACP) has been investigated, showing dramatic enhancement of the piezoelectric and dielectric properties of PMN-PT and PINPMN- PT single crystals. However, reported studies have been mainly focused on material or simulation studies. In this work, we investigated ultrasound (US) transducers with ACP Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals and compared the key specifications of ACP single crystal transducers with those of conventional direct current poling (DCP) single crystal prototypes. Based on the measured material properties, single-layer US transducers were first designed with a center frequency of 10 MHz with the Krimholtz, Leedom, and Matthae (KLM) model. Then, the prototypes were fabricated using ACP and DCP single crystals. After that, the performances of two different kinds of transducers were characterized by comparison of sensitivity, pressure output, bandwidth, and imaging quality. At last, the ACP transducer durability was tested with long working hours, which showed a low and recoverable decrease in the transducer's performance. With an aperture size of $2 \times 2$ mm2, ACP transducers showed a better electrical impedance, 14% improvement in loop sensitivity, and 66% improvement in pressure output compared with DCP transducers. For the imaging test, although the ACP transducers showed comparable resolution with the DCP transducers for the in vitro wire phantom imaging, the ACP transducers showed 3 dB signal-to-noise ratio (SNR) improvement under the same input. These findings suggest that ACP single-crystal transducers are promising for diagnostic and therapeutic applications.