A Rare Earth Hafnate (Gd _0.5 Dy _0.5 ) ₄ Hf ₃ O ₁₂ Ceramic Prepared via Ultrafast High‐Temperature Sintering for Thermal Barrier Coatings Application: Thermophysical Properties, High‐Temperature Stability, and CMAS Corrosion Behavior

Developing novel thermal barrier coating (TBC) materials is crucial for addressing the increasing service temperature of aero‐engines. Herein, a rare‐earth hafnate (Gd _0.5 Dy _0.5 ) ₄ Hf ₃ O ₁₂ (GDH) with a defective fluorite structure was successfully fabricated within 7 min via ultrafast high‐temperature sintering technology, and its thermophysical properties, high‐temperature stability, and CaO‐MgO‐Al ₂ O ₃ ‐SiO ₂ (CMAS) corrosion resistance at 1250°C were systematically investigated. The doping of Dy ³⁺ introduces extra point defects and lattice distortions, thereby enhancing phonon scattering while preserving a high concentration of oxygen vacancies. The GDH ceramic exhibits a high coefficient of thermal expansion (11.8 × 10 ⁻⁶ /K at 1500°C) and low thermal conductivity (1.83 W m ⁻¹ K ⁻¹ at 1300°C). After annealing at 1500°C for 60 h, GDH exhibits excellent phase stability and suppressed grain growth due to internal lattice distortion. During CMAS corrosion at 1250°C, a dense reaction layer composed of two corrosion products, HfO ₂ and apatite, was formed, which hinders the further penetration of molten CMAS and enhances corrosion resistance. Furthermore, GDH maintained structural stability after 20 h of exposure to CMAS at 1250°C. In conclusion, the prepared GDH exhibits excellent overall performance and holds significant potential as a next‐generation TBC material.