The afterglow time of typical red-emitting phosphors is much shorter than those of green-or blue-emitting phosphors which afterglow time were longer than 1000 min. This study reports on the effect of initial Eu/Ca atomic ratio on the afterglow properties of a red-emitting CaS: Li+, Eu2+, Pr3+ phosphor. The resulting phosphor exhibited red-emission at 645 nm originating from Eu2+ ions upon visible light irradiation, and gave some afterglow after visible light irradiation. The afterglow time was affected by initial Eu/Ca atomic ratio. Trap depth of TL peak was calculated from Hoogenstraaten method. The afterglow time of CaS: Li+, Eu2+, Pr3+ phosphor was changed by the 1st trap depth change due to initial Eu/Ca atomic ratio.

Keywords: Red afterglow; Calcium sulfide; Visible light; Thermoluminescence; Trap depth