Afterglow emission of Er3+, Ho3+ and Tm3+ in gadolinimn oxysulfide

The new Er3+, Ho3+ and Tm3+ doped gadolinium oxysulfide phosphors with the long afterglow emission were synthesized by solid-state reaction method. The synthesized phosphors were characterized by X-ray diffraction. The excitation and photoluminescence spectra, afterglow spectra and afterglow decay curve were examined by fluorescence spectroscopy. The afterglow spectra of Gd2O2S:Er3+, Mg, Ti showed typical transitions of Er3+ at 528 (H-2(11/2) -> I-4(15/2)), 548 (S-4(3/2) -> I-4(15/2)) and 669 nm (F-4(9/2) -> I-4(15/2)). In the afterglow spectra of Gd2O2S: Ho3+, Mg, Ti, typical transitions of Ho3+ at 546 nm (S-5(2) -> I-5(8)), 651 and 661 nm (F-5(5) -> I-5(8)) were observed. In Gd2O2S:Tm3+, Mg, Ti, the afterglow emission at 800 nm ((1)G(4) -> H-3(5)) of Tm3+ was seen. The mechnism and model of afterglow energy transfer were proposed.