Effect of AlN/Al2O3 Thin-Film Protective Layer on the High-Temperature Performance of ITO Thin-Film Strain Gauge

When an ITO thin-film strain gauge is applied on turbine engine blades, a protective layer must be included to prevent the oxidation of the ITO thin-film sensitive material. In this study, an AlN/Al2O3 composite film is prepared as a protective layer on an alumina ceramic sheet using the pulsed laser deposition (PLD) technique to cover the ITO-sensitive material film. Subsequently, the films are microscopically characterized, and the high-temperature performance of the ITO thin film strain gauge is verified. The results indicate that the AlN/Al2O3 film is dense and crack-free, and that the ITO thin-film strain gauge with the AlN/Al2O3 film acting as the protective layer demonstrates a minimum resistance temperature coefficient of −521 ppm/°C, minimum resistance drift rate (Dr) of 0.0117/h, and good cycle repeatability at 1100 °C when compared to an ITO strain gauge without a protective layer and a strain gauge prepared using a single Al2O3 film protective layer. Furthermore, its strain characteristic test at 800 °C showed an average gauge factor (GF) of 8.12.