Mechanisms of Mono‐Vacancy and Oxygen Permeability in Y 2 SiO 5 Orthosilicate Studied by First‐Principles Calculations

Understanding the mechanisms of native point defects and oxygen‐vacancy diffusion in Y 2 SiO 5 is important to evaluate its performance as environmental and thermal barrier coating ( ETBC ). In the present first‐principles calculations, we show that oxygen vacancy is the predominant vacancy species and prefers to form on the oxygen lattice sites inside SiO 4 tetrahedra instead of on the interstitial non‐silicon‐bonded oxygen site. The calculated defect formation energy and concentration of mono‐vacancies in Y 2 SiO 5 obviously depend on the chemical potential of each element. The results suggest that it is possible to tailor the vacancy species in Y 2 SiO 5 by controlling the chemical environment in material synthesis. Finally, theoretical simulation revealed that the self‐diffusion of oxygen vacancy has high energy barriers in Y 2 SiO 5 , which is comparable to those in SiO 2 and Al 2 O 3 . The result demonstrates low oxygen permeability in Y 2 SiO 5 and further strengthens its promising applications as ETBC material.