Abstract
Advanced environmental barrier coatings (EBCs) with a periodic layered structure consisting of two kinds of oxide materials such as Y2Ti2O7 (YT) and Al2O3, which have a large difference in refractive index, can be expected to effectively reflect thermal energy, in addition to preventing oxidation of an underling SiC/SiC composite. In the present study, a test sample containing layers of YT and Al2O3 was fabricated, and its thermal reflection properties were investigated based on measured and simulated optical reflection spectra. In the wavelength region from 500 to 2500 nm, the measured reflectance was found to be lower than the calculated value, which is thought to be due to the porosity of the YT layers produced by the sol-gel technique. Therefore, it can be expected that if all the layers in the EBC were dense, it would exhibit thermal reflection properties that were as good as those predicted by the calculations. In addition, proper arrangement of dopants in alumina layers, based on the calculated flux distribution for oxygen and Al, was thought to enhance the oxygen shielding capability and structural stability of the EBC.
