Energy transfer between Eu2+ and Mn2+ in long-afterglow phosphor CaAl2O4:Eu2+, Nd3+, and Mn2+

Long-afterglow phosphor CaAl2O4:Eu2+, Nd3+, and Mn2+ were prepared by the solid-state synthesis method. The CaAl2O4:Eu2+, Nd3+, and Mn2+ phosphors show two emission bands peaking at around 440 and 545 nm, originating from the allowed f-d transition of Eu2+ and the forbidden T41-A61 transition of Mn2+, respectively, under ultraviolet excitation at 340 nm. Spectroscopy and afterglow decay time measurements demonstrate that energy transfer from Eu2+ to Mn2+. The different colors between photoluminescence and afterglow was analyzed and observed based on energy transfer. Moreover, effects of Mn2+ doping on the afterglow properties of CaAl2O4:Eu2+, Nd3+ are explored and explained by thermoluminescence technique.