Anomalous Trapped Exciton and d鈥揻 Emission in Sr4Al14O25:Eu2+

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• 作者：Danuta Dutczak ; Cees Ronda ; Thomas J眉stel ; Andries Meijerink
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：March 6, 2014
• 年：2014
• 卷：118
• 期：9
• 页码：1617-1621
• 全文大小：378K
• 年卷期：v.118,no.9(March 6, 2014)
• ISSN：1520-5215

文摘

The photoluminescence and time-resolved emission for Eu²⁺ in Sr₄Al₁₄O₂₅ has been investigated in the temperature range 4 to 500 K. The Eu²⁺ emission changes in a peculiar way with temperature. At low temperature two emission bands are observed at 490 and 425 nm, which are attributed to emission from Eu²⁺ on the 7- and 10-coordinated sites. Upon raising the temperature, an unexpectedly large blue shift to 400 nm is observed for the 425 nm emission band. To explain these observations, the 400 and 425 nm emission bands are assigned to d鈥揻 and trapped exciton emission, for Eu²⁺ on the 10-coordinated site. The trapped exciton emission is characterized by a short (0.5 渭s) decay time. The temperature dependence of the emission is explained by a configurational coordinate diagram in which the Eu²⁺ trapped exciton state is at a slightly lower energy than the lowest energy 4f⁶5d state. Upon raising the temperature, the 4f⁶5d state is thermally populated and emission from this state is observed, and because of the smaller lattice relaxation (smaller Stokes shift), a large blue shift from 425 to 400 nm is observed.