High temperature sensing technology for applications up to 1000°C

This work reports on the research and development of high temperature (HT) thin electrodes for use in acoustic wave sensor platforms up to 1000°C. 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 650∓750°C. 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 800°C. As temperature sensors, these devices have a sensitivity of 9.1 KHz/°C @800°C. 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.