Fluorite-pyrochlore structured high-entropy oxides: Tuning the ratio of B-site cations for resistance to CMAS corrosion

As gas turbine inlet temperatures continue to rise, new thermal barrier coating (TBC) materials must be developed urgently. This work investigated molten silicate corrosion, thermal conductivity, and high-temperature phase stability of a new class of high-entropy oxides (HEO) as potential protective coating materials. With composition tuning, high-entropy RE2B2O7 (RE= Gd, Sm, Y, Pr, La; BCe, Zr) can be transformed from pyrochlore to fluorite structures. They all exhibited phase stability when annealed at 1600 ℃ for 10 h and very low thermal conductivity (1.21–1.39 W·m−1·K−1) compared to conventional materials with better thermal protection. In addition, the CMAS corrosion resistance behavior of all samples at 1300 °C and 1500 °C was investigated, and it was found that the infiltration thickness decreased with increasing Ce content (down to ∼10 µm for 5 h at 1500 °C). The RE2Ce2O7 had the most substantial CMAS resistance, forming a dense barrier layer composed of uniformly fine crystal grains during the reaction. The results of this study establish the foundation for future applications of RE2B2O7 in thermal protection systems.