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

Authors

  • Bin Liu,

    1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
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  • Jiemin Wang,

    1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
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  • Fangzhi Li,

    1. Division of Functional Materials and Nano-Devices, Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, China
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  • Luchao Sun,

    1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
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  • Jingyang Wang,

    Corresponding author
    • Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
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  • Yanchum Zhou

    Corresponding author
    1. Science and Technology of Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials and Processing Technology, Beijing, China
    • Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
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    • Fellow, The American Ceramic Society

Authors to whom correspondence should be addressed. e-mails: jywang@imr.ac.cn and yczhou714@gmail.com

Abstract

First-principles method is used to study the native point defects in Y2SiO5 and Y2Si2O7 silicates. The calculated defect formulation energies show similar native point defect behaviors in Y2SiO5 and Y2Si2O7: the oxygen Frenkel defect is predominant; and it is followed by the cation antisite and Schottky defects. The possible chemical potential range of each constituent is further considered in the calculation of defect formation energy. Oxygen interstitial (Oi) and oxygen vacancy (VO) are the predominant native point defects under O-rich and O-poor condition, respectively. In addition, the mechanisms of accommodating composition deviations from stoichiometric Y2SiO5 and Y2Si2O7 are investigated. For Y2SiO5, Y2Si2O7 impurity may appear, together with the defects of SiY antisite, Oi interstitial, and/or VY vacancy when SiO2 is excess; while YSi antisite appears together with Yi interstitial and/or VO vacancy in Y2SiO5 when Y2O3 is excess. For Y2Si2O7, the main process is the formation of SiY antisite accompanied by Oi interstitial and/or VY vacancy when SiO2 is excess; but Y2SiO5 impurity forms, together with YSi antisite, VO vacancy, and/or Yi interstitial in Y2Si2O7 when Y2O3 is excess. We expect that the results are useful to control of processing conditions and further to optimization of performance of the two silicates.

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