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

Abstract

The main purpose of this study is to develop resistance temperature sensors which can work at high temperature. A 2μm 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 3nm. The vertical electrical resistance of thin films deposited on Pt-coated Al2O3 ceramic substrates was more than 2GΩ at room temperature and 100kΩ 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.