Structural optimization and high-temperature performance characterization of LGS surface acoustic wave sensors: simulation and experimental research

Abstract SAW wireless sensing technology holds broad application prospects in the field of high-temperature monitoring. LGS piezoelectric crystals serve as ideal SAW sensor substrate materials due to their excellent high-temperature stability. However, sensor performance is affected by multiple factors, necessitating structural optimization to achieve stable high-temperature wireless sensing. This paper investigates the effects of LGS crystal tangential orientation, electrode metallization rate, electrode thickness, and protective layer structure on sensor performance through numerical calculations and experimental studies. The Al ₂ O ₃ /Pt/LGS structured SAW sensor is fabricated experimentally and analyzed for high-temperature performance degradation. A wireless sensor system based on digital frequency estimation technology is constructed to validate the wireless transmission performance of sensors. The results showed that LGS (0, 138.5°, 27°) exhibits a monotonically decreasing frequency-temperature characteristic across the range of 25 °C to 600 °C, with the highest wave velocity. Temperature sensitivity and turnover temperature decrease significantly with increasing electrode thickness and metallization rate, while the effect of metallization rate is relatively minor. After adding the protective layer, the performance of the SAW sensor has significantly improved. The Al ₂ O ₃ protective layer effectively maintains sensor performance below 700 °C. However, when the aging temperature is above 700 °C, the Pt electrode develops pitting and fractures, leading to performance degradation. The wireless measurement system successfully achieves precise signal readings within the range of 25 °C–600 °C. The research findings provide crucial theoretical foundations and data support for the design and optimization of high-performance SAW sensors.