Characterization of bismuth silicon oxide for high temperature ultrasound sensing

Clean energy production continues to grow as an international priority. Solar and nuclear power plants are being designed to operate at high temperatures, and some Generation IV nuclear plants are expected to operate at or above 850 °C. Monitoring of such structures requires advanced sensors able to survive in environments that would easily destroy conventional sensors. Bismuth Silicon Oxide (Bi₁₂SiO₂₀; BSO) is gaining attention as a robust piezoelectric material that can survive in extreme temperatures. In this work, we present a high temperature impedance and phase characterization of BSO transducers up to 600 °C. We also conducted experiments with 5.1 × 5.1 × 1 mm³ BSO face-shear transducers to generate quasi-shear horizontal waves in 3 mm thick steel bars. We performed high temperature acoustic transmission and receiving tests at temperatures up to 650 °C. BSO retains its material properties well until around 500 °C before experiencing major rises in capacitance and dielectric loss (measured at 100 kHz). The BSO transducers also experienced a shift in transmitting frequency from 209-213 kHz at room temperature to approximately 195 kHz at 650 °C. BSO was able to recover its material properties as environmental temperature decreased, and a cooldown test revealed that all properties returned to normal ranges when the sample was cooled. BSO was also able to perform continuously as an ultrasonic emitter and receiver on structural steel from room temperature to 650 °C. Additionally, we conducted multiple defect detection tests using an artificial damage, and BSO was able to detect damage-induced waves up to 600 °C with ≤10 % error. These findings suggest BSO is a material capable of performing high temperature ultrasonic sensing with durability and survivability.