High-Performance\nShear Mode Ultrasonic Transducer\nOperating at Ultrahigh Temperature Fabricated with Bi<sub>12</sub>SiO<sub>20</sub> Piezoelectric Crystal

Shear\nmode ultrasonic waves are in high demand for structural health\nmonitoring (SHM) applications owing to their nondispersive characteristics,\nsingular mode, and minimal energy loss, especially in harsh environments.\nHowever, the generation and detection of a pure shear wave using conventional\npiezoelectric materials present substantial challenges because of\ntheir complex piezoelectric response, involving multiple modes. Herein,\nwe introduce a high-quality piezoelectric crystal Bi<sub>12</sub>SiO<sub>20</sub> (BSO), exhibiting a robust piezoelectric response (<i>d</i><sub>14</sub> = 45.1 pC/N) and a pure vibration mode. Thereafter,\nwe developed a BSO-based shear mode ultrasonic transducer and conducted\nfinite element simulations and experiments. Results indicated that\nthe proposed transducer excels in exciting and receiving pure shear\nwaves with a high signal-to-noise ratio across a wide operating frequency\nrange. Remarkably, the proposed transducer demonstrates efficacy ranging\nfrom 25 to 800 °C, which exhibits an exceptionally high operating\ntemperature. These excellent attributes, coupled with cost-effectiveness,\nrender this crystal highly promising for practical SHM applications.