Abstract
Broadband yellowish emission from Sr5(PO4)3Cl:Yb3+,Mn2+ phosphors at room temperature is demonstrated upon 976 nm excitation. Two kinds of Yb3+-Mn2+ dimers with different structural geometry are proposed according to the substitution of Mn2+ for different coordinated Sr2+ ion. The upconversion luminescence at 506 nm and 585 nm are originated from the |2F5/2, 2F5/2> −> |2F7/2, 2F7/2> transition of Yb3+-Yb3+ dimers and the |2F7/2, 4T1(4G)> -> |2F7/2, 6A1(6S)> transition of Yb3+-Mn2+ dimers, respectively. From the analysis of crystal structure and measured spectra, the UC mechanism of Mn2+ ions in Sr5(PO4)3Cl:Yb3+,Mn2+ phosphors is deduced to be ground state absorption (GSA)/excited state absorption (ESA) process based on the dimer model. The abnormal photon number deviated from the double photons process can be explained by the large ESA rate of intermediate state and additional depletion of emitting state within the Yb3+-Mn2+ dimers. The obtained results provide a better understanding of the intrinsical UC luminescence of Mn2+ ions at room temperature.
Published Version
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