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Multicomponent rare earth phosphates hold immense potential as next-generation environmental barrier coatings (EBCs), offering enormous possibilities and flexibility by controlling and varying their components and fractions to tailor their performance. In this work, the key material parameters (e.g., ionic size and ionic size disorder) and the elements governing their thermal‒mechanical properties and resistance against calcium‒magnesium‒aluminosilicate (CMAS) corrosion were elucidated. The thermal conductivities of multicomponent rare-earth phosphates correlate well with cation size disorder, but no clear trend is identified for the coefficient of thermal expansion (CTE). Er-containing compositions display low CTEs and high fracture toughness. Rapid formation of a dense interfacial layer occurs for most CAMS corrosion-resistant compositions when tested at 1300 °C, e.g., (Lu0.2Yb0.2Er0.2Y0.2Gd0.2)PO4 and (Lu0.2Yb0.2Er0.2Dy0.2Gd0.2)PO4. These multicomponent phosphates also display the least recession upon molten CMAS attack at 1400 °C without significant volumetric swelling, which is superior to their single-component counterparts and state-of-the-art EBCs based on rare-earth disilicates. In contrast, Sc-containing multicomponent phosphates display inferior performance against CMAS corrosion and penetration. A mechanistic understanding and understanding of the kinetics of the interfacial interaction at higher temperatures, as well as the key parameters governing their thermomechanical properties and CMAS corrosion, are valuable for designing data-driven materials of multicomponent phosphates for EBC applications.
Bryce et al. (Fri,) studied this question.