Photoluminescence and afterglow luminescence properties of a green-emitting Na2BeGeO4:Mn2+ phosphor

Recently, developing free rare-earth (RE) doped afterglow phosphors has received great attentions in the lighting field. In this work, we prepare and report a RE-free phosphor, Na 2 BeGeO 4 :Mn 2+ , which can simultaneously emit the green fluorescence and afterglow luminescence upon excitation at UV light. Our results reveal that the as-prepared samples crystallize in orthorhombic type with the space group of Pmn 2 1 (31). The green emission is a broad band centered at 525 nm, corresponds to the 4 T 1 ( 4 G)- 6 A 1 ( 6 S) transition of Mn 2+ ions. After exposing to a 254 nm UV lamp for 10 min, the green afterglow luminescence seen with naked eyes can last more than 5 h. Together with the structural analysis and thermoluminescence (TL) spectra, the afterglow luminescence mechanism is also discussed in this work.