Sr2MgSi2O7中本征缺陷和镧系离子的热力学稳定性和转变能级

Thermodynamic Stabilities and Transition Levels of Native Defects and Lanthanide Ions in Sr2MgSi2O7

利用基于标准PBE0泛函的杂化密度泛函理论计算了Sr2MgSi2O7中本征缺陷、缺陷复合对及镧系离子的缺陷形成能、热力学转变能级以及光跃迁能级,以研究它们在Sr2MgSi2O7∶Eu2+,Dy3+的热致发光和长余辉发光过程中所起的作用。PBE0计算的形成能结果表明,缺陷VO、SrMg、MgSr和SrMg-MgSr较容易在还原气氛下制备的Sr2MgSi2O7材料中生成。基于PBE0计算的基质带隙(7.18 eV)和缺陷形成能,获得了上述较易形成的缺陷与复合对以及镧系离子的热力学转变能级和光跃迁能级。根据理论计算结果与实验所确定的陷阱深度的直接对比,电中性及带一个负电荷的氧空位与Dy3+离子可以作为该材料中的电子陷阱,从而有助于其热致发光和长余辉发光。本研究的目的是利用第一性原理研究方法深入理解Sr2MgSi2O7∶Eu2+,Dy3+的热致发光和长余辉发光机理,从而作为实验研究手段的一种有效补充。

The formation energies and thermodynamic/optical transition energy levels of native defects,defect complexes and lanthanide ions in the Sr2MgSi2O7(SMSO)are calculated from hybrid density functional theory(DFT)with the standard PBE0 functional in order to study their contributions to the thermoluminescence(TL)and long-lasting luminescence(LLL)of the material SMSO∶Eu2+,Dy3+.The PBE0-calculated formation energies reveal that the defects/complex VO,SrMg,MgSr and SrMg-MgSr are relatively easily generated in the SMSO samples prepared under reducing atmospheres.The thermodynamic and optical transition energy levels of the easily generated defects/complex above and the lanthanide ions in the host are derived from the PBE0-calculated band gap(of 7.18 eV)and formation energies.Based on their comparison with the experimental results of trap depths of the SMSO∶Eu2+,Dy3+,the neutral and singly negatively charged VO and Dy3+ions(at Sr sites)are supposed to act as the electron traps.The aim of this study is to deeply understand the mechanisms of the TL and LLL in the long afterglow material SMSO∶Eu2+,Dy3+by using first-principles calculations,which can be adopted as the effective supplement of the experiment.