High temperature sensors fabricated on Al2O3 ceramic and nickel-based superalloy substrates

The main purpose of this study is to develop resistance temperature sensors which can work at high temperature. A 2 μm thick Al2O3 thin film was deposited as an electrical insulating film on Pt-coated Al2O3 ceramic substrates and nickel-based superalloy substrates by Dual Ion Beam Sputtering Deposition (DIBSD). The results of atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photon electron spectroscopy (XPS) analyses reveal that the Al2O3 films were dense, smooth and pinholes free with roughness around 3 nm. The vertical electrical resistance of thin films deposited on Pt-coated Al2O3 ceramic substrates was more than 2 GΩ at room temperature and 100 kΩ even at around 800 °C. Both resistance temperature sensors (RTSs) fabricated on Al2O3 ceramic substrate and that on nickel-based superalloy substrates showed a linear relation up to 1000 °C. The RTS on the ceramic substrates showed stable after 4 thermal cycles while RTS on the superalloy substrates showed a good repeatability of heating and cooling curves even after experiencing a high temperature environment as high as 1000 °C.