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.