A New Long Phosphorescent Phosphor with High Brightness, SrAl2 O 4 : Eu2 +  , Dy3 +

Matsuzawa, T.; Aoki, Y.; Takeuchi, Nobuyuki; Murayama, Yoshihiko

doi:10.1149/1.1837067

Cited by 1,970 publications

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“…Its luminescent properties were first described by Blasse and Bril 49 and Palilla et al 50 in 1968, but in 1996 Matsuzawa et al mentioned its persistent luminescence. 2 An afterglow duration of up to 10 h is mentioned in literature. 6,51,52 The host material has a monoclinic crystal structure, 53 but when prepared with a combustion or sol-gel method, a hexagonal or orthorhombic phase is sometimes obtained.…”

Section: Trap Depth Distribution In Caal 2 O 4 :Eundmentioning

confidence: 99%

“…This remarkable property has been known since ancient times, 1 but research into persistent luminescence has seen a dramatic increase since the discovery of the bright and long-lasting green afterglow of SrAl 2 6 ).…”

Section: Introductionmentioning

confidence: 99%

“…A trap depth of around 0.6-0.7 eV is often stated as ideal for persistent luminescence. 2 Clearly, knowing the number and depth of these energy levels is crucial when trying to understand the mechanism of persistent luminescence, and when developing new afterglow materials. Unfortunately, the trap system often consists of multiple levels with similar depths, or even continuous distributions of energy levels.…”

Section: Introductionmentioning

confidence: 99%

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Revealing trap depth distributions in persistent phosphors

et al. 2013

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Persistent luminescence or afterglow is caused by a gradual release of charge carriers from trapping centers. The energy needed to release these charge carriers is determined by the trap depths. Knowledge of these trap depths is therefore crucial in the understanding of the persistent luminescence mechanism. Unfortunately, the trap depths in persistent phosphors are often difficult to evaluate in an accurate and reliable way. The existing analysis methods are mostly based on single experiments, or they ignore the possibility of a continuous distribution of trap depths. We present a procedure to accurately probe the activation energies, even in the presence of a continuous distribution of energy levels. By performing a series of thermoluminescence experiments with varying excitation duration and at varying excitation temperature, and employing the initial rise analysis method, the depth and shape of such a distribution can be estimated. As an example, we investigated the trap system in the violet persistent phosphor CaAl 2 O 4 :Eu,Nd, and show that it consists of a Gaussian-shaped distribution of trap depths. The maximal density of traps lies in the region around 0.9 eV, but the distribution extends to 0.7 eV on the shallow side and 1.2 eV on the deep side. The described procedure can be used to obtain a clear view of the trap system in other persistent phosphors as well. This can lead to a better understanding of the nature of these trapping centers, and the role they play in the persistent luminescent mechanism.

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Section: Trap Depth Distribution In Caal 2 O 4 :Eundmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revealing trap depth distributions in persistent phosphors

et al. 2013

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“…The question of how to deal with glow-peaks that are not adjacent but embedded within one another is not posed often enough and is the subject of this report on SrAl 2 O 4 :Eu 2+ ,Dy 3+ , a well-known phosphor (Matsuzawa et al, 1996). Evidence for such collocation has been reported by Chithambo and Niyonzima (2014) in Sr 2 SiO 4 :Eu 2+ and by Mokoena et al (2015) for Ca 5 (PO 4 ) 3 OH:Gd 3+ ,Pr 3+ .…”

Section: Introductionmentioning

confidence: 97%

“…The glow-curve of SrAl 2 O 4 :Eu 2+ , Dy 3+ e.g. (Matsuzawa et al, 1996) consists of a glow-peak with a wide expanse of the order of 100 o . Previous kinetic analyses of the peak e.g.…”

Section: Introductionmentioning

confidence: 99%

Thermoluminescence of SrAl2O4:Eu2+, Dy3+: Kinetic analysis of a composite-peak

Chithambo

Wako

Finch

2017

Radiation Measurements

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The kinetic analysis of thermoluminescence of beta-irradiated SrAl 2 O 4 :Eu 2+ ,Dy 3+ is reported.The glow-curve is dominated by an apparently-single peak. It has been demonstrated using a number of tests including partial dynamic-heating, isothermal heating, phosphorescence and, the effect of fading, that the peak and the glow-curve consists of a set of closely-spaced peaks. In view of the peak being complex, its first few components were abstracted and analysed and for comparison, the peak was also analysed assuming it is genuinely single. In the latter, the order of kinetics is calculated to be intermediate between first and second-order and not first-order as predicted by qualitative tests such as the − or − procedures. A model based on density of energy states has been used to account for and reconcile the qualitative and quantitative results. The activation energy is found as ~1 eV, consistent with the value expected of Dy 2+ , the presumed electron trapping state of the Dy 3+ electron trap. The thermoluminescence is subject to thermal quenching with an activation energy of 0.520 ± 0.002 eV. The luminescence is ascribed to 5d→4f 7 Eu 2+ transitions whereas the thermal quenching is presumed to occur from an alternative level of the degenerate 5d energy level of the Eu 2+ cation.

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