Atmospheric plasma sprayed high-entropy (Lu_1/6Yb_1/6Sc_1/6Er_1/6Y_1/6Ho_1/6)₂Si₂O₇ coating: A promising material with synergistic low infrared emissivity and thermal conductivity

To address the demand for high-temperature infrared stealth, 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) coating was fabricated via atmospheric plasma spraying. The coating exhibited a single-phase monoclinic structure with uniform element distribution. It demonstrated low infrared emissivity in the 3−5 μm band, with values of 0.497 at room temperature and 0.479 at 400 °C. This low emissivity is attributed to the increased charge carrier concentration resulting from oxygen vacancies, as confirmed by X ray photoelectron spectroscopy (XPS) analysis. Furthermore, the coating achieved a low thermal conductivity of 0.51 W m−1 K−1 at 1173 K, benefiting from severe phonon scattering caused by the high-entropy composition. The coating also possessed a good bonding strength of 31.98 MPa. This work demonstrates that the high-entropy strategy is effective in developing silicate coatings with synergistic low emissivity and low thermal conductivity for advanced infrared stealth applications.