Environmental barrier coatings with thermomechanical robustness against calcium-magnesium-aluminum-silicate deposits are in high demand. The aim of this work is to clarify the influence of Sc³⁺ on crystallization behavior of Yb-based coatings against CMAS deposits. The reaction products of solid solutions with compositions traversing the Sc₂O₃-Yb₂O₃ system indicate that Sc³⁺ tend to form [BO₆] coordination polyhedron in crystal structure to promote the formation of garnet and diopside, while Yb³⁺ occupy 7, 8 and 9-coordinate sites to crystallize apatite and silicocarnotite. The transformation of crystalline products from apatite/silicocarnotite to garnet/diopside greatly improves the efficiency of CMAS melt consumption and facilitates the prevention of its further penetration and corrosion. Based on the commonality of cation occupancy in crystallography, an A(CaO+YbO1.5)-B(ScO1.5+MgO+AlO1.5)-T(SiO₂) pseudo-ternary phase diagram is established, which has a great potential to describe phase equilibrium in coating-deposit systems and can provide guidance for compositional design of corrosion-resistant coatings.
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Zhang et al. (2024) studied this question.
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