Multicomponent (Gd _x1 Ho _x2 Yb _x3 Lu _x4 ) ₂ Si ₂ O ₇ Disilicates: Compositional Modulation and CMAS Corrosion Resistance at 1300°C

ABSTRACT Multi‐rare‐earth‐principle‐component disilicates ((nRE x ) 2 Si 2 O 7 ) are advanced candidates for the environmental barrier coatings (EBCs) materials, wherein the multicomponent design strategy is used to achieve synergistic optimization on various material properties. In this study, two (nRE x ) 2 Si 2 O 7 materials, that is, β‐(Gd 0.15 Ho 0.15 Yb 0.35 Lu 0.35 ) 2 Si 2 O 7 and γ‐(Gd 0.15 Ho 0.35 Yb 0.35 Lu 0.15 ) 2 Si 2 O 7 with distinct polymorphic structures are designed by exquisitely tuning the relative ratio of the four constituent rare‐earth elements. The two samples exhibit good stability of β or γ phase, low thermal conductivity, and coefficients of thermal expansion in good compatibility with the silicon carbide fiber‐reinforced silicon carbide ceramic matrix composites. The corrosion depth of β‐(Gd 0.15 Ho 0.15 Yb 0.35 Lu 0.35 ) 2 Si 2 O 7 and γ‐(Gd 0.15 Ho 0.35 Yb 0.35 Lu 0.15 ) 2 Si 2 O 7 samples after the completeness of CMAS corrosion process at 1300°C are approximately 428.33 and 239.70 µm, respectively. Such different corrosion behaviors have been attributed to the increased concentration of active elements (e.g., Ho), which serves multiple functions by accelerating apatite formation, consuming molten CMAS, decreasing the Ca/Si ratio, and significantly mitigating the activity of corrosion reactions. These results are expected to enlighten the synergistic optimization of thermo‐physical properties and corrosion resistance of (nRE x ) 2 Si 2 O 7 materials by compositional modulation, and provide important guidelines for the design and screening of advanced EBC materials.