YAG:Ce3+ piezo-spectroscopy: A high-sensitive method used for stress characterization of thermal barrier coating

The internal residual stress of thermal barrier coating (TBC) induced during the preparation and service process is the kernel cause of internal and interfacial failure and even the structure damage and destruction. Therefore, the accurate characterization of the internal stress is of great significance for TBC property and life evaluation. Fluorescence piezo-spectroscopic technology has been used to realize the nondestructive measurement of the TBC internal stress. However, the sensitivity of the existing Eu³⁺/Cr³⁺ fluorescence, namely, the piezo-spectroscopic coefficient, is normally <10 cm⁻¹/GPa. There is still an urgent need to develop a sensitive method or material of piezo-spectroscopy for the precision measurement of the TBC internal stress. This paper used Ce³⁺ as a sensing medium to detect stress. YAG:Ce³⁺ was applied as the top-coating material of TBC. Then, calibration experiments of the piezo-spectroscopic coefficient were carried out. The results demonstrated that the obtained Ce³⁺ piezo-spectroscopic coefficient can be up to 4.48 cm⁻¹/MPa, almost three magnitudes larger than other existing fluorescence piezo-spectroscopic technologies.