CLABAU, Frédéric; ROCQUEFELTE, Xavier; JOBIC, Stéphane; DENIARD, Philippe; WHANGBO, Myung-Hwan; GARCIA, Alain; LE MERCIER, Thierry

doi:10.1021/cm050763r

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CLABAU, Frédéric
Institut des Matériaux Jean Rouxel [IMN]

ROCQUEFELTE, Xavier
Institut des Matériaux Jean Rouxel [IMN]

JOBIC, Stéphane
Institut des Matériaux Jean Rouxel [IMN]

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Chemistry of Materials. 2005, vol. 17, n° 15, p. 3904-3912

American Chemical Society

Résumé en anglais

The existing mechanisms proposed to explain the phosphorescence of SrAl2O4:Eu2+,Dy3+ and related phosphors were found to be inconsistent with a number of important experimental and theoretical observations. We formulated a new mechanism of phosphorescence on the basis of the facts that the d orbitals of Eu2+ are located near the conduction band bottom of SrAl2O4, that the Eu2+ concentration decreases during UV excitation, and that trace amounts of Eu3+ are always present in these phosphors. In our mechanism, some Eu2+ ions are oxidized to Eu3+ under UV, and the released electrons are trapped at the oxygen vacancy levels located in the vicinity of the photogenerated Eu3+ cations. The phosphorescence arises from the recombination of these trapped electrons around the photogenerated Eu3+ sites with emission at 520 nm. The codopant Dy3+ enhances the phosphorescence by increasing the number and the depth of electron traps, and the codopant B3+ enhances the phosphorescence by increasing the depth of electron traps. We also probed the origin of another emission at 450 nm of SrAl2O4:Eu2+ that occurs at low temperatures. Our analysis indicates that this emission is caused by a charge transfer from oxygen to Eu3+ cations and is associated with a hole trapping.< Réduire

Mots clés en anglais

Luminescent properties

Persistent luminescent

Strontium aluminate

Yttrium oxysulfide

Gel method

Eu2+

Afterglow

Crystals

Red

Orange

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Mechanism of phosphorescence appropriate for the long-lasting phosphors Eu2+-doped SrAl2O4 with codopants Dy3+ and B3+

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