Beam-focused SH wave transducer based on YSr3(PO4)3 piezoelectric crystal for high temperature structural health monitoring

Guided-wave-based structural health monitoring (SHM) technology is of great importance for real-time inspection of high-temperature structures. The fundamental shear horizontal (SH0) wave is believed to be an ideal wave mode for developing SHM systems due to its nondispersive characteristics. However, currently very limited SH0 wave transducers can be used for SHM of high-temperature structures due to the limitation of materials. Herein, a novel YSr3(PO4)3 (YSP) piezoelectric crystal in the space group I4¯3d was grown. Experiments show that the face-shear piezoelectric coefficient d14 (d14 = d25 = d36) is 9.7 pC/N and varies little from 25 to 800 °C. Then a beam-focused SH0 wave piezoelectric transducer is developed based on face-shear-mode YSP wafers. Both finite element simulations and experimental results indicate that the YSP-based transducer can excite pure SH0 wave and focus the wave energy along two opposite main directions. Especially, the obtained SH0 wave beam is highly concentrated with a small divergence angle of less than 30°, originating from the high working frequency range from 300 to 400 kHz. The excellent temperature stability of the as-grown YSP crystal makes the proposed SH0 wave piezoelectric transducer very suitable for SHM of high-temperature structures.