Conformally Large-Area Single-Crystal Piezocomposites with High Performance for Acoustic Transducers.

Large-area and conformal piezoelectric elements are highly desired for acoustic transducers to possess a large power source level and wide detecting range. To date, single-crystal piezocomposites attract much attention on enhancing the power source level and bandwidth for next-generation acoustic transducers, owing to their higher piezoelectric and electromechanical coupling properties compared to traditional piezocomposites. Unfortunately, it is still challenging to achieve large-area and conformal single-crystal piezocomposites because of the fragile nature, large anisotropy, and the limited grown size of piezoelectric single crystals. Here, we successfully fabricate the conformally large-area single-crystal piezocomposite with an area of 160 × 50 mm2 and a bending angle of 162° by a modified 3D-printing-assisted inserting method. The single-crystal piezocomposite exhibits a high thickness electromechanical coupling factor kt of 85% and a large piezoelectric coefficient d33 of 1150 pC/N, surpassing those of the reported large-area piezocomposites. The influence of the volume fraction and curvature radius of single-crystal PCs and acoustic transducers was investigated. Furthermore, we designed an acoustic transducer based on the conformal single-crystal piezocomposite. Benefiting from the excellent piezoelectric and electromechanical properties of the single-crystal piezocomposite, the transducer indicates a high maximum transmitting voltage response of 171.8 dB. Especially, its bandwidth (-3 dB) achieves 60 kHz with a resonant frequency of 292 kHz, which is about 1.8 times superior to the conformal acoustic transducer based on the ceramic piezocomposite with a similar resonant frequency. This work may benefit the future design and fabrication of high-performance and complex-shape piezoelectric composites as key materials for next-generation transducers.

High-Performance Curved Piezoelectric Single-Crystal Composites via 3D-Printing-Assisted Dice and Insert Technology for Underwater Acoustic Transducer Applications.

Piezoelectric single-crystal composites (PSCCs) have been studied and applied because of their improved resolution and power source level performance in underwater acoustic transducer applications relative to traditional piezoelectric ceramic composites (PCCs). Currently, the methods to fabricate curved PSCCs are mostly derived from PCCs, including molding with flexible backing, molding with heating, and molding with the casting rubber method. Unfortunately, the methods mentioned above are not suitable for preparing curved PSCCs for underwater acoustic transducer applications because of their brittleness, the large anisotropy of piezoelectric single crystals, and the high thickness (>2 mm) of PSCCs for achieving the low operating frequency (<700 kHz). In the present work, we proposed a preparation method, 3D-printing-assisted dice and insert technology, and successfully prepared curved PSCCs with high performance. Although the PSCCs have a low volume fraction of single crystals in this work (∼33%), a high thickness electromechanical factor kt of 86% and a large piezoelectric coefficient d33 of 1550 pC/N were achieved in the curved 1-3 PSCCs, which are superior to other reported PSCCs and PCCs with nearly the same volume fraction of single crystals and piezoelectric ceramics. This work presents a paradigm for fabricating curved PSCCs for underwater acoustic transducers, and this method shows the potential for large-area, special-shaped PSCCs, which are key materials for next-generation underwater acoustic transducers.