Acoustic wave sensors, particularly surface acoustic wave (SAW) devices, have been one of the most studied options for high temperature applications. Although they present the big advantage of simple wireless interrogation, they also have disadvantages. These disadvantages include the destructive agglomeration of their metallic thin electrodes. To overcome these issues, AlN-based solidly mounted resonators (SMRs) appear as promising alternatives. Our previous studies have shown they sustain temperatures as high as 1000 degrees C, however their in-situ performance at high temperature during a long period of time has not been performed yet. With this work we continue our previous investigations and we test in real time the performance of SMRs at 400 degrees C during 7 hours.
