Effects of Gd3+ and Lu3+ co-doping on the long afterglow properties of yellowish-orange phosphor Y2O2S:Ti4+, Mg2+

A new long afterglow phosphor Y2O2S:Ti4+, Mg2+ co-doped with Gd3+ and Lu3+ was synthesized by solid-state reaction in inert gas ambient. Its properties were systematically analyzed by X-ray diffraction (XRD), luminescence spectra, afterglow decay curves and thermoluminescence (TL) spectra. It was found that the long afterglow performance of Y2O2S:Ti4+, Mg2+ such as brightness and persistent time was largely improved when co-doped with Gd3+ and Lu3+. By analyzing the TL curve the activation energy E were calculated to be 0.64 eV for 388 K peak and 0.98 eV for 508 K peak, and the trap intensity related to 388 K peak is much stronger than that related to 508 K peak. The mechanism of the long afterglow was also discussed in this paper.