This work reports on the research and development of high temperature (HT) thin electrodes for use in acoustic wave sensor platforms up to 1000degC. Previously developed thin film platinum (Pt) electrodes limits HT operation due to a de-wetting phenomena, which results in loss of Pt film electrical continuity and device failure above 650mnplus750degC. To address the problem, co-deposition of Pt/rhodium (Pt-Rh) alloys with zirconia (ZrO2) was used to fabricate HT-stable thin film surface acoustic wave interdigitated electrodes on langasite substrates. The resulting devices showed stable operation for over five months at 800degC. As temperature sensors, these devices have a sensitivity of 9.1 KHz/degC @800degC. In addition, ceramic silicon-alumina-nitrogen (SiAlON) overlayers were investigated to protect the sensor surface. The resulting devices enable harsh environment temperature and pressure sensors, for applications such as monitoring of jet engines, atmospheric re-entrance, and space exploration.
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