Development of Cardiac Phased Array With Large-Size PZN-5.5 %PT Single Crystals

In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃, also called PZN-PT], has been enhanced with improvements in size, consistency, and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This article mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254-mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about −46 dB, while a crosstalk between the adjacent elements was less than −31 dB. The wire phantom can be distinctly imaged with the phased array, and the axial and lateral resolutions were measured to be 660 and $1299 \mu \text{m}$ , respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.