Mechanisms of Mono‐Vacancy and Oxygen Permeability in Y₂SiO₅ Orthosilicate Studied by First‐Principles Calculations

Abstract

Understanding the mechanisms of native point defects and oxygen‐vacancy diffusion in Y2SiO5 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 SiO4 tetrahedra instead of on the interstitial non‐silicon‐bonded oxygen site. The calculated defect formation energy and concentration of mono‐vacancies in Y2SiO5 obviously depend on the chemical potential of each element. The results suggest that it is possible to tailor the vacancy species in Y2SiO5 by controlling the chemical environment in material synthesis. Finally, theoretical simulation revealed that the self‐diffusion of oxygen vacancy has high energy barriers in Y2SiO5, which is comparable to those in SiO2 and Al2O3. The result demonstrates low oxygen permeability in Y2SiO5 and further strengthens its promising applications as ETBC material.

Investigation of Native Point Defects and Nonstoichiometry Mechanisms of Two Yttrium Silicates by First‐Principles Calculations

“…predicted that Y 2 Si 2 O 7 is a damage tolerant silicate and proved it by experimental study of mechanical properties . Very recently, the present authors showed the mechanisms of monovacancy and extremely low oxygen permeability in Y 2 SiO 5 by first‐principles calculation . In this article, we focus on all possible native point defects and mechanisms of nonstoichiometry of Y 2 SiO 5 and Y 2 Si 2 O 7 .…”

“…To pace the first step to study the mechanism of defects, one need to determine the preferred position of an isolated native point defect for the later case. In our previous work about the monovacancy in Y 2 SiO 5 , the most stable vacancy sites of oxygen and yttrium are reported at the O 1 and Y 1 sites, respectively . To determine the possible interstitial site, we follow the calculation strategy used in Ref.…”

“…To conveniently clarify the relations described by Eqs. , three independent variables, , , and , together with one induced variable are adopted to a ternary chemical potential diagram which is similar to our previous article . The detail descriptions will be presented in Section III (2) and III (3) .…”

Mechanism of Intrinsic Point Defects and Oxygen Diffusion in Yttrium Aluminum Garnet: First‐Principles Investigation

“…Previous first‐principles investigation of point defects in YAG used the same primitive cell and obtained reasonable results . Furthermore, this distance is supposed to be large enough to exclude self‐interaction of many point defects in the first‐principles calculations …”

Synthesis of Al₃BC₃ particulates by carbo-thermal reduction process—Parameter optimization and mechanism analysis

“…15) Li et al reported the synthesis of bulk Al 3 BC 3 by reactive hot pressing and proposed the synthesis mechanism as solid-solid reactions. 14) Metal carbides have been prepared by the carbo-thermal reduction of metal oxides, direct reaction between metal elements and carbon, and the gas phase reaction of metal-containing gases and appropriate hydrocarbons. 17) Among the processes, carbo-thermal reduction of metal oxides is the most commonly used route for industrial production due to inexpensive raw materials and simple process.…”