Platinum/Quartz based surface acoustic wave device for monotonic long-term wireless temperature sensing up to 450 ℃

Abstract Surface acoustic wave (SAW) devices have been widely applied for passive wireless sensing in harsh environment. However, the current SAW temperature sensors cannot achieve long-time thermal stability, low cost and easy fabrication process at the same time. In this research, a wireless passive high-temperature SAW temperature sensing system based on Pt/quartz structure has been proposed, which has excellent thermal stability, low cost, and simple process flow. Temperature-frequency coefficients (TCFs) of Pt and Al electrodes based SAW devices with different thicknesses were studied through theoretical analysis, indicating that the temperature-frequency response curve of Al electrode based SAW device is not significantly influenced by the electrode thickness, while Pt electrode based SAW device exhibits a non-monotonic temperature-frequency curve, and the turnover temperature is increasing with decreasing Pt electrode thickness. For a measuring temperature range from room temperature to 450 ℃, 40 nm Pt electrode thickness is chosen for a monotonic temperature-frequency response. Thermal stability tests show that Pt electrodes remain intact after 450 °C treatment, whereas Al electrodes develop agglomerations and voids. Moreover, only Pt IDT-based SAW devices survived long-term high-temperature exposure, and a passive wireless temperature sensing system was established and a full-scale error of less than 2% F.S. was achieved, demonstrating the potential of Pt/Quartz based SAW sensor for long-time temperature monitoring.