(Gd_1/7Dy_1/7Ho_1/7Er_1/7Tm_1/7Yb_1/7Lu_1/7)₂Si₂O₇ high-entropy disilicate: A promising environmental barrier coating material

The unique combination of a series of thermal properties and water-oxygen corrosion resistance is crucial for high-entropy disilicates serving as environmental barrier coating materials. Here, we report a novel (Gd_1/7Dy_1/7Ho_1/7Er_1/7Tm_1/7Yb_1/7Lu_1/7)₂Si₂O₇ high-entropy disilicate (7HERED) that simultaneously possesses excellent match of coefficient of thermal expansion with SiC_f/SiC composites across 473–1973 K, ultralow thermal conductivity (1.5 Wm⁻¹ K⁻¹ at 1273 K), superior high-temperature stability up to 1973 K, and water-oxygen corrosion resistance at 1673 K. Such superior properties are attributed to the high-entropy and lattice-distortion effects. Our 7HERED shows great potential as a next-generation environmental barrier coating material.