Synchrotron XRD Measurements of Thermal Barrier Coating Configurations With Rare Earth Elements for Phosphor Thermometry

The development of temperature sensing Thermal Barrier Coating (TBC) systems by phosphor thermometry has significant potential to achieve accurate non-destructive temperature measurement in the coating. The doping of coatings using rare earth elements is a viable option to enable the temperature measurement by the virtue of their luminescence. While facilitating the temperature sensing, however, the thermo-mechanical and thermo-chemical stability of the coating must be maintained under extreme operating conditions. In this work, TBC configurations including a doped layer placed at the top or the bottom of the top coat have been fabricated via Air Plasma Spray (APS) using Yttria-Stabilized Zirconia (YSZ) that contains Europium (Eu) dopant. The TBC configurations have been characterized using high energy synchrotron X-ray diffraction (XRD) at both room temperature and high temperature. The TBC samples have been subjected to a single cycle thermal load during XRD data collection. The residual strain in the top coats of the TBCs have been quantified using XRD data. Residual strain in the top coat of the regular TBC configuration has been measured to be in the range of −0.8 × 10−4 to −1.0 × 10−4 for out-of-plane strain (e11) and 0.5 × 10−4 to 2.0 × 10−4 for in-plane strain (e22). The doped layer above the top coat was found to most significantly affect the spatial strain distribution across depth in the YSZ layer by increasing the strain magnitudes closer to the bond coat. However, the difference in strain distribution due to doped layers was found to be less than 1.0 × 10−4, which is close to the experimental limit. Thus, the doped layer did not significantly alter the overall residual strain states of the coating.