YSZ/Al2O3 multilayered film as insulating layer for high temperature thin film strain gauge prepared on Ni-based superalloy

The insulating layer plays a vital role to provide adequate electrical insulation for developing sputtered thin film sensors on Ni-based turbine blades of aircraft engine running at high temperature environment. Here, the multilayered YSZ/Al2O3 thin film as insulating layer was deposited by reactive sputtering. The prepared multilayered film exhibited improved insulation property as compared to the single Al2O3 thin film, the insulation resistance of the four-layered YSZ/Al2O3/YSZ/Al2O3 film increased roughly two orders of magnitude. During thermal cycle tests, the four-layered film insulating layer showed stable electrical insulation and no shorts to substrate occurred up to 800 ℃. Subsequently, the PdCr thin film strain gauge using the four-layered film as insulating layer was fabricated on Ni-based substrate and performed very well with highly sensitive resistance-strain response, stable apparent strain output and no drift error at elevated temperatures, indicating the feasibility and validity of the four-layered YSZ/Al2O3/YSZ/Al2O3 film as insulating layer for high temperature thin film sensors.