The interplay of surface stability and oxygen vacancy dynamics in RE2Si2O7‐based environmental barrier coatings

Abstract Surface structure and relevant oxygen vacancy play an important role in the application of RE 2 Si 2 O 7 for environmental barrier coatings, in which the oxygen vacancies in RE 2 Si 2 O 7 may influence their thermal and optical properties. In this work, the structure and thermodynamics of (0 0 1) and (1 1 0) surfaces of RE 2 Si 2 O 7 ( RE = Yb, Lu) are studied via first‐principles calculations to reveal the underlying mechanism of the surface formation and the associated oxygen vacancy behavior. The (1 1 0) surface is preferred energetically, being in good agreement with the experiential results. It is uncovered that the weak chemical bond broken dominates the decrease of the surface energy, together with the contribution from the polyhedral distortion. Furthermore, the [O 3 Si–O–SiO 3 ] site is found to be the preferred site for oxygen vacancies on (1 1 0) surface. The formation energies of oxygen vacancies on the (1 1 0) surfaces are lower than those in the bulk, suggesting their segregation on the surfaces. These findings provide essential insights into the surface excitation and oxygen vacancy behaviors of RE 2 Si 2 O 7 , which could shield light on the experimental improvement of the thermal, mechanical, and corrosion properties for RE 2 Si 2 O 7 ‐based environmental barrier coating materials.