Design, Fabrication, and Performance Optimization of a High-Temperature Thin Film Heat Flux Sensor with a Composite Protective Layer

As aerospace technology continues to advance, real-time monitoring of heat flux density has become increasingly important. However, most heat flux sensors (HFSs) are unable to withstand high temperatures without water cooling, resulting in their sensitive layer films being exposed to severe oxidation or sublimation. This paper proposes a composite protective layer thin-film heat flux sensor (TFHFS) based on an ITO/In₂O₃ thermopile. An Al₂O₃-YSZ protective layer is deposited on top of the sensitive layer to mitigate sublimation failures caused by prolonged exposure to high temperatures. Test results indicate that the temperature resistance of the TFHFS with the protective layer is significantly enhanced, enabling it to withstand a maximum temperature of 1200 °C, with response and recovery times of 1.2 s and 1.3 s, respectively. Furthermore, the fabricated TFHFS exhibited excellent repeatability and high-temperature stability. However, the reliability of the leads in the designed TFHFS requires further enhancement in future studies.