Novel Multilayer SAW Temperature Sensor for Ultra-High Temperature Environments

Abstract

Performing high-temperature measurements on the rotating parts of aero-engine systems requires wireless passive sensors. Surface acoustic wave (SAW) sensors can measure high temperatures wirelessly, making them ideal for extreme situations where wired sensors are not applicable. This study reports a new SAW temperature sensor based on a langasite (LGS) substrate that can perform measurements in environments with temperatures as high as 1300 °C. The Pt electrode and LGS substrate were protected by an AlN passivation layer deposited via a pulsed laser, thereby improving the crystallization quality of the Pt film, with the function and stability of the SAW device guaranteed at 1100 °C. The linear relationship between the resonant frequency and temperature is verified by various high-temperature radio-frequency (RF) tests. Changes in sample microstructure before and after high-temperature exposure are analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The analysis confirms that the proposed AlN/Pt/Cr thin-film electrode has great application potential in high-temperature SAW sensors.

Langasite as Piezoelectric Substrate for Sensors in Harsh Environments: Investigation of Surface Degradation under High-Temperature Air Atmosphere

“…Many issues regarding electrodes, packaging, interconnections, antennas, etc. are still to be fixed so that higher temperature measurements can be reached [ 12 , 13 ]. Moreover, as for any semiconductor crystal, the electrical resistivity of LGS decreases with the temperature, which unfavorably impacts the quality factor of SAW resonators [ 14 ].…”

“…Moreover, because LGS maintains its piezoelectric properties at very high temperatures and because good-quality wafers are commercially available, LGS is currently one of the very few piezoelectric materials that allow the development of SAW sensors for applications above 600 °C, in particular under an air atmosphere. Thus, research work on LGS as a potential substrate for hash environment applications continues to mobilize scientists, as evidenced by the many recent published papers [ 12 , 13 , 16 , 17 , 18 , 19 , 20 ]. In fact, most of the studies dedicated to LGS based SAW sensors are essentially focused on either the development of thin film electrodes able to withstand very elevated temperatures to be combined with LGS crystals [ 8 , 9 , 12 , 13 ], the frequency–temperature behavior of various cuts [ 16 , 19 ], or the optimization of the sensor design in order to compensate for the decrease of the quality factor at high temperatures [ 17 ].…”

“…Thus, research work on LGS as a potential substrate for hash environment applications continues to mobilize scientists, as evidenced by the many recent published papers [ 12 , 13 , 16 , 17 , 18 , 19 , 20 ]. In fact, most of the studies dedicated to LGS based SAW sensors are essentially focused on either the development of thin film electrodes able to withstand very elevated temperatures to be combined with LGS crystals [ 8 , 9 , 12 , 13 ], the frequency–temperature behavior of various cuts [ 16 , 19 ], or the optimization of the sensor design in order to compensate for the decrease of the quality factor at high temperatures [ 17 ]. Finally, apart from this main application as a HT piezoelectric substrate, LGS material is foreseen to play other roles in the SAW domain.…”

Three-Dimensional Finite Element Analysis and Characterization of Quasi-Surface Acoustic Wave Resonators

“…Surface acoustic wave (SAW) devices are one of the most popular microelectromechnical systems (MEMS) devices at high frequency and super high frequency, which have been widely used in filters, actuators and sensors applications [ 1 , 2 , 3 , 4 ]. SAW devices are usually fabricated based on lithium niobate (LiNbO 3 ) piezoelectric substrate and have demonstrated excellent performance of high-quality factor ( Q ) as well as large effective coupling coefficient [ 5 , 6 , 7 , 8 ].…”

An Experimental and Theoretical Study of Impact of Device Parameters on Performance of AlN/Sapphire-Based SAW Temperature Sensors

“…There have been reports of AlN-based SAW temperature sensors on Si [5,6], sapphire [7,8], and silicon carbide [9,10], but AlN/sapphire-based sensors have attracted the most attention because of their good thermal stability, high acoustic velocity, high quality factor (Q) and low cost. Until now, most studies have focused on improving the working temperature of AlN-based SAW sensors [11][12][13]; however, the basic performance of these sensors still requires further improvement for their commercialization. As a result, a systematic study on the impact of device structure on the performance of AlN/sapphire-based SAW temperature sensors, which has rarely been reported, is necessary to further improve the performance of these devices.…”