A high-entropy β-type disilicate for advanced thermal protective coatings: Integrating low infrared emissivity, low thermal conductivity, and high CMAS corrosion resistance

The development of high-performance infrared radiation ceramic materials with low emissivity, while also featuring low thermal conductivity and excellent corrosion resistance, is an urgent need for emerging industrial and aerospace applications. This study develops a novel high-entropy rare-earth disilicate, (Lu_1/6Yb_1/6Sc_1/6Er_1/6Y_1/6Ho_1/6)₂Si₂O₇ ((6RE_1/6)₂Si₂O₇). The phase-pure (6RE_1/6)₂Si₂O₇ ceramic exhibits exhibits a low infrared emissivity of 0.415 (3-5 μm) at room temperature, a phenomenon attributed to oxygen vacancy-enhanced conduction. It achieves a low thermal conductivity of 1.85 W m⁻¹ K⁻¹ at 1073 K, and is primarily due to severe lattice distortion from cationic heterogeneity. When exposed to CMAS at 1300 °C, it develops a thin, continuous barrier layer of a multicomponent cyclosilicate (Ca₃RE₂(Si₃O₉)₂), that reaches a thickness of only 25 μm after 48 h and effectively inhibits infiltration. The high-entropy design successfully integrates low emissivity, suppressed thermal transport, and superior corrosion resistance in a single-phase material.