کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5399335 | 1505896 | 2015 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Electronic structure and energy level schemes of RE3+:LaSi3N5 and RE2+:LaSi3N5âxOx phosphors (RE=Ce, Pr, ND, Pm, Sm, Eu) from first principles
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موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
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چکیده انگلیسی
First principles calculations of rare earth (RE)-doped LaSi3N5 host lattice are performed to obtain the electronic structure, the band gap (BG), and the character of electronic transitions. Doping with both trivalent and bivalent RE cations is inspected. RE 4f states form two bands of occupied and unoccupied states separated by ~5Â eV. In RE3+-doped compounds 4f states are shifted by ~6Â eV to more negative energies compared with RE2+-compounds. This stabilization causes that RE3+ 4f bands are in a different position relative to the valence band and the conduction band than RE2+ 4f bands and therefore different electronic transitions apply. BG of RE3+-compounds decreases from ~4.6Â eV (Ce) to ~1.5Â eV (Eu). Except for Ce3+, exhibiting the 4fâ5d transition, other RE3+-compounds show the charge transfer of the pâ4f character. BG of RE2+-compounds increases from ~0.80Â eV (Ce, Pr) to ~0.95Â eV (Nd, Pm), ~1.43Â eV (Sm), and ~3.28Â eV (Eu) and the electronic transition is of the 4fâ5d character. The energy level scheme constructed from ab initio calculated electronic structures agrees well with the experimental energy level diagram. The agreement demonstrates the reliability of the hybrid functional HSE06 to describe correctly bands of nonbonding RE 4f electrons.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Luminescence - Volume 164, August 2015, Pages 131-137
Journal: Journal of Luminescence - Volume 164, August 2015, Pages 131-137
نویسندگان
Ismail A.M. Ibrahim, Zoltán LenÄéÅ¡, Pavol Å ajgalÃk, Lubomir Benco,