Effect of temperature on the luminescence processes of SrAl2O4:Eu2+

Aitasalo, T.; Hölsä, Jorma; Jungner, H.; Krupa, J.C.; Lastusaari, Mika; Legendziewicz, J.; Niittykoski, Janne

doi:10.1016/j.radmeas.2004.01.031

Cited by 85 publications

(57 citation statements)

References 12 publications

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“…Upon lowering the temperature a second, blue, emission band becomes visible (λ max = 445 nm). Although less well studied as the green emission band, its presence has been reported earlier in several papers [16,17,26]. In the figure, the temperature dependency of both blue and green emission upon excitation with 370 nm is visible.…”

Section: A Photoluminescence Of Sral 2 O 4 :Eudysupporting

confidence: 53%

“…There still remains strong debate about the chemical nature of the trapping centers. More specifically for SrAl 2 O 4 :Eu,Dy it is not agreed upon whether the Dy 3+ codopant acts as an electron trap, thereby becoming Dy 2+ [15][16][17]38]. Based on the shape of the TL glow curves, it is clear that SrAl 2 O 4 :Eu,Dy contains different trap centers, with different associated trap depths.…”

Section: Discussionmentioning

confidence: 99%

“…Detailed knowledge of the underlying mechanism of persistent luminescence is lacking, more specifically on the trapping and detrapping processes. First of all, it is still unclear whether the traps are related to host defects, the trivalent codopant, or a combination of both [15][16][17]. Different opinions also exist on the trapping and detrapping routes, regarding the role of the conduction band and whether tunneling processes also play a role [18,19].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Trapping and detrapping inSrAl2O4:Eu,Dypersistent phosphors: Influence of excitation wavelength and temperature

2014

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SrAl 2 O 4 :Eu,Dy is presumably the best known persistent luminescent phosphor. At room temperature, its green emission remains visible for hours after switching off the excitation. It is known that upon lowering the temperature of the phosphor a second photoluminescence emission band arises in the blue part of the visible spectrum, although its origin is still the subject of discussion. In this paper we thoroughly study the origin of both emission bands in SrAl 2 O 4 :Eu,Dy and we attribute this to europium ions substituting for the two different Sr sites in the phosphor's monoclinic host lattice. The photoluminescence properties, the thermal quenching behavior, and photoluminescence lifetime of both emission bands are investigated. A lanthanide energy level scheme is constructed for both sites. Using an integrated approach, i.e., combining charging, afterglow, and thermoluminescence measurements in the same run, we study the charging or trap filling processes in SrAl 2 O 4 :Eu,Dy upon excitation with site selective excitation wavelengths and at different temperatures. We show that trap filling is a thermally activated process when the green emitting center is excited at 435 nm.Furthermore, we also demonstrate that the distribution of filled traps after charging depends strongly on the excitation wavelength and thus on which Eu 2+ center has been excited. This suggests trapping of the electron close to the ionized Eu 2+ ion, without full delocalization to the conduction band during the trapping process. Finally, the quantum efficiency of the persistent luminescence is estimated at 65 (+/−10)%.

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Section: A Photoluminescence Of Sral 2 O 4 :Eudysupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trapping and detrapping inSrAl2O4:Eu,Dypersistent phosphors: Influence of excitation wavelength and temperature

2014

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“…Aitasalo et al [2] measured the lifetime of the green and blue emitting sites with 1.23 μs and 0.43 μs respectively at 20 K using a sample doped with 0.5 mol%. At this temperature the green emission showed a mono exponential decay.…”

Section: Introductionmentioning

confidence: 99%

Thermal and concentration dependent energy transfer of Eu^2+ in SrAl_2O_4

Bierwagen

Yoon

Gartmann³

et al. 2016

Opt. Mater. Express

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SrAl 2 O 4 doped with europium and dysprosium is a powerful and widely used afterglow material. Within this material strontium is found in two crystallographic different sites. Due to the similar ion radii and same charge, Eu 2+ -ions can occupy both sites, resulting in two different Eu 2+ -ions, one emitting in the blue and one in the green spectral range. The blue emission is thermally quenched at room temperature. In this paper we investigate the energy transfer between different Eu ions depending on the concentration and temperature using two different approaches: lifetime measurements and integrated intensity. We find an activation energy for the thermal quenching of the blue emission of 0.195 ± 0.023 eV and a critical radius for the energy transfer of 3.0 ± 0.5 nm. These results can help in designing better afterglow materials due to the fact that with energy transfer parts of the lost emission in the blue region at room temperature can be converted to the green site.

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“…At room temperature only one asymmetric emission band is 59,60 In Fig. 19 the temperature dependence of the emission bands is depicted.…”

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confidence: 99%