High Temperature SAW Sensors on LiNbO3 Substrate with SiO2 Passivation Layer

The surface acoustic wave (SAW) device can be used to measure temperature wirelessly, which is highly adaptable to the use in aero-engines high-temperature test scenarios where wired-sensors is not suitable for its difficulty in signal transfers. Herein, this paper presents a SAW sensor capable of achieving high-temperature measurement up to 800 °C with a good repeatability. The sensor is built on 41°Y LiNbO3 substrate with a SiO2 passivation. With the protection of SiO2 layer, the volatilization of platinum is effectively prevented to ensure SAW’s stability at a higher temperature. At the same time, SiO2 layer also protects the lithium niobate substrate, according to our verification result of XRD and EDS. Both crystal orientation and chemical composition of LiNbO3 substrate have been maintained after high-temperature testing. The temperature coefficient factor TCF is −2.98KHz/°C for our passivated SAW devices with a good linearity and repeatability.