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Issue 15, 2020
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Red luminescent Eu2+ in K2MgH4 and comparison with KMgH3

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The engineering of covalency and crystal field is a key point for the control of the 5d energy level of Eu2+. The hydride ion exhibits strong covalency, which results in a large 5d energy shift by the nephelauxetic effect compared to their fluoride analogues. In this study, the Eu2+-doped K2MgH4 Ruddlesden–Popper (n = 1) perovskite was prepared and its optical properties were investigated. Red luminescence due to the 4f65d1 → 4f7 transition was observed at 670 nm by UV excitation of the K2MgH4:Eu2+ sample. Compared with yellow Eu2+-luminescence at 565 nm of the KMgH3 cubic perovskite, which has almost the same chemical composition as K2MgH4, the additional red-shift of the luminescence in K2MgH4:Eu2+ is caused by the strong crystal field splitting in the unique 9-fold coordinated site in addition to the large nephelauxetic effect by hydride ions. Using a hydride model system that allows for a clear distinction between crystal field splitting and nephelauxetic effect, we successfully demonstrated the design concept for the 5d energy shifting by covalency and crystal field in Eu2+-doped K2MgH4. Also, the thermal quenching process of K2MgH4:Eu2+ by the ionization process was discussed in comparison to KMgH3:Eu2+ on the basis of the energy diagram.

Graphical abstract: Red luminescent Eu2+ in K2MgH4 and comparison with KMgH3

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Supplementary files

Article information

25 Nov 2019
03 Mar 2020
First published
04 Mar 2020

J. Mater. Chem. C, 2020,8, 5124-5130
Article type

Red luminescent Eu2+ in K2MgH4 and comparison with KMgH3

J. Ueda, T. Wylezich, N. Kunkel and S. Tanabe, J. Mater. Chem. C, 2020, 8, 5124
DOI: 10.1039/C9TC06459A

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