Structure, properties and corrosion resistance of high entropy (Y0.2 Gd0.2 Dy0.2 La0.2Sm0.2) TaO4 ceramic materials.

In order to meet the urgent demand of new thermal barrier coating materials for a new generation of aero-engines,a high entropy rare earth tantalate (Y_0.2Gd_0.2Dy_0.2La_0.2Sm_0.2)TaO₄ material,abbreviated as (5RE_0.2) TaO₄, was developed using high-purity oxides (Y₂O₃, Gd₂O₃, Dy₂O₃, Sm₂O₃, La₂O₃, Ta₂O₅) as raw materials according to the stoichiometric ratio, and insulating at 1 200 - 1 750 °C for 5 h for a solid phase reaction. The phase composition, microstructure, thermal properties, mechanical properties, and CMAS (CaO-MgO-Al₂O₃-SiO₂) corrosion resistance of the material were studied. The results show that: (1) the (5RE_0.2)TaO₄ ceramic material has a monoclinic structure with obvious ferroelastic domain; (2) the material fired at 1 750 °C exhibits extremely low thermal conductivity (1.65 W ⋅ m^-1 ⋅ K^-1,600 °C) and high thermal expansion coefficient (10.2 x 10^-6 K^-1,1 200 °C); (3) due to the unique ferroelastic toughening effect,the fracture toughness of the (5RE_0.2)TaO₄ material fired at 1 750 °C reaches 2.4 MPa ⋅ m¹²; (4) (5RE_0.2)TaO₄ reacts with CMAS melt forming a reaction layer, showing excellent corrosion resistance. [ABSTRACT FROM AUTHOR]