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Defects and Persistent Luminescence in Eu -Doped SrAl 2 O 4 by Khang Hoang is a Physics and Astronomy article available to read on EtoBox.

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We investigate native point defects and rare-earth (co)dopants in monoclinic SrAl 2 O 4 using hybrid density-functional defect calculations. Europium (Eu) and dysprosium (Dy) are found to be mixed valence and energetically most favorable at the Sr lattice sites. However, unlike Eu, where both Eu 2+ and Eu 3+ can be realized in synthesis, Dy is stable predominantly as Dy 3+ and the divalent Dy 2+ may only be photogenerated under irradiation. On the basis of an analysis of Eu-related band-defect (including charge-transfer) and interconfigurational 5d-4f optical transitions, we assign the characteristic broad blue (445-nm) and green (520-nm) emission bands in Eu 2+ -doped SrAl 2 O 4 to the 4f 6 5d 1 → 4f 7 transition in Eu 2+ incorporated at the Sr1 and Sr2 sites, respectively. Strontium interstitials (Sr i ; not oxygen vacancies, in contrast to what is commonly believed) and substitutional Dy impurities (Dy Sr ) can act as efficient electron traps for room-temperature persistent luminescence. This work calls for a reassessment of certain assumptions regarding specific carrier trapping centers made in all mechanisms previously proposed for the persistent luminescence in Eu-and (Eu,Dy)

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Author

Khang Hoang

Publisher

American Physical Society (APS)

Published

2023

Language

EN

Field

Physics and Astronomy (Physical Sciences)