Screening rare-earth aluminates as promising thermal barrier coatings by high-throughput first-principles calculations

Thermal barrier coatings (TBCs) play an important role in gas turbines to protect the turbine blades from the high-temperature airflow damage. In this work, we use first-principles calculations to investigate a specific class of rare-earth (RE) aluminates, including cubic-REAlO₃ (c-REAlO₃), orthorhombic-REAlO₃ (o-REAlO₃), RE₃Al₅O₁₂, and RE₄Al₂O₉, to predict their structural stability, bonding characteristics, and mechanical and thermal properties. The polyhedron structures formed by the Al–O bonds are stronger and exhibit rigid characteristics, whereas the polyhedra formed by the RE–O bonds are relatively weak and soft. The alternating stacking of AlO₄ tetrahedra, AlO₆ octahedra, and RE–O polyhedra, as well as the selection of RE elements, shows intensive influences on the expected mechanical and thermal properties. The B, G, and E of these four types of aluminates decrease in the order of c-REAlO₃ > o-REAlO₃ > RE₃Al₅O₁₂ > RE₄Al₂O₉. REAlO₃ and RE₄Al₂O₉ are brittle and quasi-ductile ceramics, respectively, whereas RE₃Al₅O₁₂ is tailorable. The minimum thermal conductivity is in the range of 1.4–1.5 W m⁻¹ K⁻¹ for c-REAlO₃, 1.3–1.4 W m⁻¹ K⁻¹ for o-REAlO₃, 1.25–1.35 W m⁻¹ K⁻¹ for RE₃Al₅O₁₂, and 0.8–0.9 W m⁻¹ K⁻¹ for RE₄Al₂O₉. RE₄Al₂O₉ with low thermal conductivity and damage tolerance is predicted to be the potential candidates for next-generation TBC materials.