An entropy‐stabilized disilicate for advanced T/EBC: Synergistic thermal and corrosion resistance

A low thermal conductivity, compatible thermal expansion coefficient, and excellent resistance to calcium–magnesium–aluminum–silicate (CMAS) corrosion are critical requirements for thermal/environmental barrier coatings (T/EBC) applied to silicon‐based ceramics. Rare earth disilicates are considered among the most promising ecological barrier coating materials due to their superior resistance to water vapor corrosion. However, the relatively high thermal conductivity and poor resistance to CMAS corrosion limit the practical application. In this work, a single‐phase high‐entropy rare earth disilicate (Lu 1/5 Yb 1/5 Sc 1/5 Er 1/5 Y 1/5 ) 2 Si 2 O 7 ((5RE 1/5 ) 2 Si 2 O 7 ) was successfully synthesized via a solid‐state reaction. It exhibits a low thermal conductivity of 1.92 W⋅m −1 ⋅K −1 at 1273 K, a thermal expansion coefficient (4.89 × 10 −6 /°C) matching that of SiC f /SiC ((4.5–5.5) ×10 −6 /°C), high hardness and elastic modulus (11.22 and 184.6 GPa, respectively, at 25°C), and exceptional CMAS corrosion resistance, forming a reaction layer of only 28 µm after 48 h at 1300°C. The enhanced comprehensive performance is attributed to the synergistic combination of multiple rare‐earth cations with different ionic radii within the high‐entropy structure, highlighting its great promise as a next‐generation T/EBC material.