Preparation and characterization of (Yb _0.25 Lu _0.25 Sc _0.25 Tm _0.25 ) ₂ Si ₂ O ₇ as a potential environmental barrier coating

Abstract A novel high‐entropy rare‐earth disilicate (Yb _0.25 Lu _0.25 Sc _0.25 Tm _0.25 ) ₂ Si ₂ O ₇ ((4RE _0.25 ) ₂ Si ₂ O ₇ ) was proposed as an advanced environmental barrier coating (EBC) materials in this work. The (4RE _0.25 ) ₂ Si ₂ O ₇ powders were synthesized using the solid‐state sintering method. Based on the X‐ray diffraction (XRD) and scanning electron microscope/energy‐dispersive spectroscopy analysis, the uniform solid solution was detected in the (4RE _0.25 ) ₂ Si ₂ O ₇ , which had a monoclinic β‐phase structure in the space group of C2/m. The lattice parameter of the structure was derived based on the Rietveld refinement analysis to the XRD results. The coefficient of thermal expansion of the bulk (4RE _0.25 ) ₂ Si ₂ O ₇ was similar to that of the SiC‐SiC ceramic matrix composite substrate of the environmental barrier coating. In addition, this (4RE _0.25 ) ₂ Si ₂ O ₇ bulk material had a very low thermal conductivity, which was beneficial for the application of environmental barrier coatings. The hot water‐vapor corrosive experiments were conducted in an environment of 90% air and 10% H ₂ O at 1300°C. The results indicated a better water‐vapor corrosion performance than the commercialized Yb ₂ Si ₂ O ₇ EBC materials. The (4RE _0.25 ) ₂ Si ₂ O ₇ material prepared in this work showed great potential to work as the environmental barrier coating.