Superior CMAS corrosion resistance of high-entropy rare-earth disilicate environmental barrier coating for SiC coated C/C composites

High-entropy rare-earth silicates are promising candidate materials for enhanced calcium‑magnesium-aluminosilicate (CMAS) resistance as next-generation environmental barrier coatings (EBCs). In this study, CMAS corrosion behaviors of plasma-sprayed high-entropy disilicate (Yb_0.2Lu_0.2Er_0.2Tm_0.2Sc_0.2)₂Si₂O₇ ((5RE_0.2)₂Si₂O₇) and Yb₂Si₂O₇ coatings were comparatively investigated at 1500 °C, to clarify the effect of high-entropy engineering on enhancing the CMAS corrosion resistance. After corrosion at 1500 °C for 1 h, the corrosion layer thickness of the (5RE_0.2)₂Si₂O₇ coating was 50 ± 12 μm, while that of the Yb₂Si₂O₇ coating reached 90 ± 15 μm. When the corrosion time was extended to 20 h, the Yb₂Si₂O₇ coating completely failed, but the (5RE_0.2)₂Si₂O₇ coating still maintained protective effect. The (5RE_0.2)₂Si₂O₇ coating exhibited superior corrosion resistance compared with the Yb₂Si₂O₇ coating, primarily attributed to the sluggish diffusion effect of high-entropy materials and reduced average rare-earth ion radius. A dense reaction layer interlaced with apatite and garnet was formed, effectively limiting the further penetration of CMAS. This work provides valuable insights for designing high-entropy coatings with exceptional anti-CMAS corrosion performance.