Red luminescent Eu2+ in K2MgH4 and comparison with KMgH3. Issue 15 (18th March 2020)

• Record Type: Journal Article
• Authors: Ueda, Jumpei; Wylezich, Thomas; Kunkel, Nathalie; Tanabe, Setsuhisa
• Is Part Of: Journal of materials chemistry. Volume 8:Issue 15(2020)
• Page Start: 5124
• Page End: 5130
• Publication Date: 2020-03-18
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc06459a
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A Ruddlesden–Popper ( n = 1) hydride perovskite, K2 MgH4 :Eu 2+, shows longer wavelength luminescence compared with the KMgH3 :Eu 2+ simple perovskite by crystal field engineering. Abstract : The engineering of covalency and crystal field is a key point for the control of the 5d energy level of Eu 2+ . 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 Eu 2+ -doped K2 MgH4 Ruddlesden–Popper ( n = 1) perovskite was prepared and its optical properties were investigated. Red luminescence due to the 4f 6 5d 1 → 4f 7 transition was observed at 670 nm by UV excitation of the K2 MgH4 :Eu 2+ sample. Compared with yellow Eu 2+ -luminescence at 565 nm of the KMgH3 cubic perovskite, which has almost the same chemical composition as K2 MgH4, the additional red-shift of the luminescence in K2 MgH4 :Eu 2+ 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 Eu 2+ -doped K2 MgH4 . Also, the thermal quenching process of K2 MgH4 :Eu 2+ by the ionization process was discussed in comparison to KMgH3 :Eu 2+ on the basis of the energy diagram.