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Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum.

Ding B, Han C, Zheng L, Zhang J, Wang R, Tang Z - Sci Rep (2015)

Bottom Line: The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied.When La(3+) occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands.This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Micro-nano Measurement, Manipulation and Physics (Ministry of Education), Department of Physics, Beihang University, Beijing 100191, China.

ABSTRACT
The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La(3+) into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La(3+) into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La(3+) is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La(3+) occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La(3+) occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.

No MeSH data available.


The defect formation energies of (a) VO(i), VO(i) + LaYk (k = 1,2, and 3) and (b) VO(ij), VO(ij) + LaYk in oxygen-rich conditions.
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f5: The defect formation energies of (a) VO(i), VO(i) + LaYk (k = 1,2, and 3) and (b) VO(ij), VO(ij) + LaYk in oxygen-rich conditions.

Mentions: To obtain the deep understanding of luminescence origin, the first principle method is often applied to derive electronic structures of luminescent materials62. The appearance of four- and five-coordination tungsten atom numbers from the pure to different-concentration La3+-doped samples indicates that the oxygen vacancy concentration increases gradually with incorporation of La3+ into the samples. Hence, we first establish a perfect 1 × 2 × 1 Y2WO6 supercell, and then one or two oxygen atoms next to tungsten are removed to constitute single and twin oxygen vacancies together with replacing the nearest Y atom with a La atom (these models are labeled as LaYk + VO(i) and LaYk + VO(ij) with k = 1, 2, and 3 and i, j = 1, 2, 3, 4, 5, and 6, i ≠ j). Under oxygen-rich atmosphere, the defect formation energies (Eformation) of various models when oxygen vacancy locates at different sites are plotted in Figure 5. As illustrated in Figure 5(a), for the models containing one oxygen vacancy, the variation rules of Eformation are the same for the undoped and La3+-doped models expect for the model with VO(6). Their average values are calculated as 2.1593, 2.2175, 2.0334, and 2.2521 eV for pure and La3+-doped models when La substitutes for Y at three sites. Comparing these two average Eformation for VO(i) and LaY2 + VO(i) models, it can be found that when La3+ replaces Y2, the formation energy is reduced. This indicates that La3+ enters into the Y2 site most easily, and doping La3+ into Y2WO6 can really promote the formation of oxygen vacancies.


Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum.

Ding B, Han C, Zheng L, Zhang J, Wang R, Tang Z - Sci Rep (2015)

The defect formation energies of (a) VO(i), VO(i) + LaYk (k = 1,2, and 3) and (b) VO(ij), VO(ij) + LaYk in oxygen-rich conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4377636&req=5

f5: The defect formation energies of (a) VO(i), VO(i) + LaYk (k = 1,2, and 3) and (b) VO(ij), VO(ij) + LaYk in oxygen-rich conditions.
Mentions: To obtain the deep understanding of luminescence origin, the first principle method is often applied to derive electronic structures of luminescent materials62. The appearance of four- and five-coordination tungsten atom numbers from the pure to different-concentration La3+-doped samples indicates that the oxygen vacancy concentration increases gradually with incorporation of La3+ into the samples. Hence, we first establish a perfect 1 × 2 × 1 Y2WO6 supercell, and then one or two oxygen atoms next to tungsten are removed to constitute single and twin oxygen vacancies together with replacing the nearest Y atom with a La atom (these models are labeled as LaYk + VO(i) and LaYk + VO(ij) with k = 1, 2, and 3 and i, j = 1, 2, 3, 4, 5, and 6, i ≠ j). Under oxygen-rich atmosphere, the defect formation energies (Eformation) of various models when oxygen vacancy locates at different sites are plotted in Figure 5. As illustrated in Figure 5(a), for the models containing one oxygen vacancy, the variation rules of Eformation are the same for the undoped and La3+-doped models expect for the model with VO(6). Their average values are calculated as 2.1593, 2.2175, 2.0334, and 2.2521 eV for pure and La3+-doped models when La substitutes for Y at three sites. Comparing these two average Eformation for VO(i) and LaY2 + VO(i) models, it can be found that when La3+ replaces Y2, the formation energy is reduced. This indicates that La3+ enters into the Y2 site most easily, and doping La3+ into Y2WO6 can really promote the formation of oxygen vacancies.

Bottom Line: The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied.When La(3+) occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands.This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Micro-nano Measurement, Manipulation and Physics (Ministry of Education), Department of Physics, Beihang University, Beijing 100191, China.

ABSTRACT
The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La(3+) into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La(3+) into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La(3+) is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La(3+) occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La(3+) occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.

No MeSH data available.