The Long Afterglow Of Eu2+-Activated La2o2s

The new Eu3+ doped lanthanum oxysulfide phosphors, which have the orange-red long afterglow emission, were synthesized by solid-state reaction method. The synthesized phosphors were characterized by X-ray diffraction. The excitation and emission spectra, afterglow spectra and afterglow decay curves were examined. XRD confirmed the phosphor as pure phase La2O2S. The phosphors showed typical transitions D-5(J) (J=0,1) --> F-7(J) (J=0,1,2,3,4) of Eu3+. The photoluminescence spectra and afterglow spectra presented the regular alteration with various Eu3+ concentration, due to cross relaxation between energy levels of Eu3+. In addition, we studied the effects of activator concentration and dopants species on the afterglow property. The data showed afterglow result was the best with 2% Eu3+ and doped with Mg2+ and Zr4+. A prominent phosphorescence can be seen in this phosphor after illuminated with UV light.