Ultrafast and slow Mn2+ luminescence in lithium tetraborate
•Sensitized Mn2+ luminescence is studied in lithium tetraborate.•Existence of complex luminescence centres is proposed.•Slow or ultrafast Mn2+ luminescence decays occur depending on the excitation energy.•Mechanisms for excitation transfer and luminescence decay acceleration are proposed. Sub-nanose...
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Veröffentlicht in: | Journal of alloys and compounds 2021-11, Vol.883, p.160852, Article 160852 |
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Hauptverfasser: | , , , , , , , , , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | •Sensitized Mn2+ luminescence is studied in lithium tetraborate.•Existence of complex luminescence centres is proposed.•Slow or ultrafast Mn2+ luminescence decays occur depending on the excitation energy.•Mechanisms for excitation transfer and luminescence decay acceleration are proposed.
Sub-nanosecond luminescence of Mn2+ in Mn-, Sn/Mn-, and Cu/Mn-doped Li2B4O7 ceramics is observed under laser excitation. Picosecond pulsed laser radiation (350–370 nm) generates the frequency-doubled radiation directly in a single microcrystal selected in a ceramic sample, with this secondary radiation falling within the impurity-induced VUV excitation bands of doped Li2B4O7. These excitation bands are attributed to the creation of an impurity-bound intra-anionic exciton in MeiO4–BO3–MnLi complex centres (Mei = Mn, Sn, or Cu). The exciton, in turn, interacts with a nearby Mn2+ ion due to mixing of the Mn2+ excited states with the excitonic states. Exciton annihilation involves Mn2+ energy levels as transient states and causes a sub-nanosecond radiative transition which is accelerated, being accompanied by rearrangement of the surrounding atoms. Excitation within the lower-energy bands is related to the other part of the complex luminescence centre, this is metal-to-ligand intra-anionic charge transfer, which makes an electron accessible to MnLi, while the hole is transferred only during relaxation of the excited structure. Mn2+ radiative transitions are not forced in the latter case, and slow Mn2+ luminescence decay is observed. |
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ISSN: | 0925-8388 1873-4669 |
DOI: | 10.1016/j.jallcom.2021.160852 |