The application of Eu3+ photoluminescence piezo-spectroscopy in the LaMgAl11O19/8YSZ:Eu double-ceramic-layer coating system

A non-destructive inspection technique based on the relationship between the stress and peak position of 5D0 → 7F2 transition of Eu3+ ions in 8YSZ has been developed to measure the residual stress in TBCs. A LaMgAl11O19/8YSZ:Eu (LaMA/8YSZ:Eu) double-ceramic-layer coating was prepared by atmospheric plasma spraying. Thermal cycling test was conducted and the residual stress in the 8YSZ:Eu layer was analyzed with the application of the Eu3+ photoluminescence piezo-spectroscopy. There existed both compressive and tensile stresses in the 8YSZ:Eu layer of the as-sprayed LaMA/8YSZ:Eu coating with an average tensile stress value of 55 MPa. As thermal cycling test going on, the compressive stress disappeared and the tensile stress increased gradually. In addition, the application of 8YSZ:Eu luminescence sublayer could also be used to indicate the spallation and damage degree of LaMA/8YSZ:Eu coating.