Optical and Electrical Properties of SrAl[sub 2]O[sub 4]:Eu[sup 2+]

Abbruscato, Victor J.

doi:10.1149/1.2408226

Cited by 243 publications

(156 citation statements)

References 6 publications

(8 reference statements)

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“…[5][6][7][8][9] Since the work by Matsuzawa et 26 For each of these compounds the model of Matsuzawa et al 1 is used to explain the mechanism. Experiments to elucidate the mechanism by means of thermoluminescence, 3,4 electron paramagnetic resonance ͑EPR͒, 14 and photoconductivity 1,2,5 were all interpreted in support of that mechanism. Hölsa and coworkers [27][28][29][30][31][32] are some of the few who disagree with the mechanism.…”

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confidence: 79%

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Mechanism of Persistent Luminescence in Eu[sup 2+] and Dy[sup 3+] Codoped Aluminate and Silicate Compounds

Dorenbos

2005

J. Electrochem. Soc.

386

265

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A mechanism of persistent luminescence that was proposed in 1996 for SrAl 2 O 4 :Eu 2+ ;Dy 3+ has been widely adopted to explain afterglow in many Eu 2+ and Dy 3+ codoped aluminates and silicates. The mechanism involves the thermally activated release of a hole from Eu 2+ in its excited 5d state to the valence band which is subsequently trapped by Dy 3+ . In this work the location of the lanthanide energy levels relative to the valence and conduction band of various compounds is presented. It is shown that the mechanism of persistent luminescence cannot be correct. An alternative model that involves the ionization of the 5d electron to conduction band states and subsequent trapping by Dy 3+ is proposed. The level schemes are consistent, both qualitatively and quantitatively, with many observations regarding persistent luminescence. They also provide insight into the mechanism of thermal quenching of Eu 2+ 5d-4f emission. proposed the same mechanism for CaGa 2 S 4 :Eu 2+ . In mechanisms of persistent luminescence, luminescence quenching, and electroluminescence, the thermally activated ionization or field ionization of either electrons to the conduction band or holes to the valence band is an important aspect. To understand these mechanisms it is necessary to accurately know the location of the impurity states relative to the conduction band and the valence band. The problem is that hitherto this information has not been available, leading to mechanisms that rely on speculative ideas.Recently new methods have become available that make it possible to determine the absolute location of the lanthanide impurity levels. In this work we apply these methods to reconsider the mechanism of persistent luminescence and luminescence quenching. It is shown that the mechanism proposed by Matsuzawa et al. Results and DiscussionLevel schemes for CaGa 2 S 4 and SrAl 2 O 4 .-The method to determine the absolute location of the lowest 4f state and the lowest 5d state of divalent and trivalent lanthanide ions in compounds was presented in detail in previous papers and is not repeated here. 36,37Instead only the information used to construct the level schemes in the electroluminescence phosphor CaGa 2 S 4 and the persistent luminescence phosphor SrAl 2 O 4 is presented. Recently Bessiere et al. 38 determined the level scheme for CaGa 2 S 4 . The result is reproduced in Fig. 1 where zero energy is at the top of the valence band. E ex = 4.35 eV is the energy of exciton creation, i.e., a bound electron-hole pair. The energy E VC needed to create a free electron in the conduction band is at 4.9 eV. The lowest 4f and lowest 4f5d levels of the divalent and the trivalent lanthanides are drawn in the scheme as function of the number n in the 4f n state of the trivalent lanthanide. SrGa 2 S 4 has the same crystal structure as CaGa 2 S 4 and also approximately the same bandgap value. We therefore regard the level scheme for CaGa 2 S 4 also as representative for that of SrGa 2 S 4 .Ultraviolet and vacuum ultraviolet ͑VUV͒ studies by Kamada ...

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confidence: 79%

“…The first report on the persistent luminescence properties of SrAl 2 2 the following mechanism was proposed. After excitation of Eu 2+ to the 5d state, a hole is released to the valence band that is subsequently trapped by Dy 3+ .…”

mentioning

confidence: 99%

Mechanism of Persistent Luminescence in Eu[sup 2+] and Dy[sup 3+] Codoped Aluminate and Silicate Compounds

Dorenbos

2005

J. Electrochem. Soc.

386

265

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“…Eu 2+ -doped phosphors usually show intense broad band PL with a short decay time of the order of tens of nanoseconds [7]. The emission of Eu 2+ is very strongly dependent on the host lattice and can occur from the ultraviolet to the red region of the electro-magnetic spectrum [8][9][10][11][12][13]. This is because the 5 ↔ 4 transition is associated with the change in electric dipole, and the 5 excited state is affected by crystal field effects.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Dejene

Kebede

2012

Open Physics

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Europium-doped barium aluminate (BaAlxOy:Eu2+) phosphors were obtained at low temperatures (500°C) using the solution — combustion of corresponding metal nitrate-urea solution mixtures. The particle size and morphology and the structural and luminescent properties of the synthesized phosphors were examined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Electron diffraction spectroscopy (EDS) and photoluminescence (PL). It was found that the change in Ba: Al molar ratios showed greatly influence not only on the particle size and morphology, but also on their PL spectra and crystalline structure. The structure of BaAlxOy nanophosphors changes from a hexagonal Ba2Al10O17 phase for samples with 6:100 molar ratios to a hexagonal BaAl2O4 one with an increase in Ba content. The peak of the emission band occurs at a longer wavelength (around 615 nm) with a decrease in Ba concentration but displays a broad blue-green emission band composed from two emissions with the maximum at 495 and 530nm coming from Eu2+ in two sites for increasing Ba content. The blue-green emission is probably due to the influence of 5d electron states of Eu2+ in the crystal field because of atomic size variation causing crystal defects while the red emission is due to f - f transitions. These findings clearly demonstrate the possibility of fine tuning the colour emission.

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“…in 1997 [9]. Efficient luminescence in the blue to green (450-520 nm) was also reported from Eu [10,11]. Recently, a much brighter and longer persistent blue-green phosphor; Sr 4 Al 14 O 25 :Eu 2+ ,Dy 3+ has been reported and in commercial use [12][13][14][15][16].…”

Section: +mentioning

confidence: 99%

Design of Long Persistent White Phosphorescence in a Composite Phosphor Via Energy Transfer Mechanism

Luitel¹,

Chand²,

Torikai

et al. 2015

IJMSA

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Abstract:A high quality composite phosphor powder of warm to cool white emission and long afterglow phosphorescence was reported by the process of energy transfer in a composite phosphor. The composite phosphor particles include at least two types of phosphor particles viz. a blue white persistent component and yellow fluorescent component. The blue white extremely long persistent component transfers its afterglow to the yellow fluorescent component in the composite phosphor followed by the color mixing process to generate the white afterglow. The composite phosphor is designed in such a way that the excitation spectrum of the fluorescent component was overlapped as much with the afterglow emission of the persistent component. The composite phosphor emission spectrum can be well tuned from warm to cool white depending on the proportions of the composite phosphors and energy transfer extent. Phosphor includes powders, ceramics and resin composites.

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Optical and Electrical Properties of SrAl[sub 2]O[sub 4]:Eu[sup 2+]

Cited by 243 publications

References 6 publications

Mechanism of Persistent Luminescence in Eu[sup 2+] and Dy[sup 3+] Codoped Aluminate and Silicate Compounds

Mechanism of Persistent Luminescence in Eu[sup 2+] and Dy[sup 3+] Codoped Aluminate and Silicate Compounds

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Design of Long Persistent White Phosphorescence in a Composite Phosphor Via Energy Transfer Mechanism

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