Intrinsic properties of dispersion-strengthened HfO₂–Al₂O₃–SiO₂ material as an EBC bond coat

To address the challenges of insufficient thermal resistance and high-temperature stability in current environmental barrier coating (EBC) bond coats above 1500 °C, this study successfully synthesized HfO₂–Al₂O₃–SiO₂ powders with a dispersion-strengthened structure for EBC bond coat raw material for spraying through a solid-phase synthesis method using HfO₂, Al₂O₃, and SiO₂ sol. The dispersion-strengthened structure with a microstructure of oxides (HfO₂ and Al₂O₃) dispersed in silicates (mullite and HfSiO₄) can be achieved by systematically adjusting the component molar ratios, synthesis temperature, and time. The synthesized raw powders underwent subsequent high-temperature hot-pressing sintering to form ceramic bulks, allowing for a comprehensive characterization of the intrinsic material properties, including thermal conductivity, coefficient of thermal expansion, mechanical performance, oxidation resistance at 1600 °C, and water‒oxygen corrosion resistance at 1300 °C. The investigation elucidates the property evolution and related mechanisms, conclusively demonstrating the viability of the HfO₂–Al₂O₃–SiO₂ system as an EBC bond coating material. Additional chemical compatibility tests with SiO₂ at 1500 °C further validated the dispersion-strengthened structure. Notably, oxidation resistance testing at 1600 °C revealed that Al₂O₃ could better capture SiO₂ generated by the decomposition of HfSiO₄ to form mullite, thus enhancing the high-temperature stability of the HfO₂–Al₂O₃–SiO₂ material, benefiting from its dispersion-strengthened structure. The present study establishes a robust theoretical foundation for the development of EBC bond coatings with exceptional high-temperature endurance exceeding 1500 °C.