Preparation and luminescence properties of green-light-emitting afterglow phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Green-light-emitting long-lasting phosphorescence phosphor, Eu2+ activated calcium magnesium chlorosilicate Ca8Mg(SiO4)4Cl2, has been prepared by a modified solid-state reaction method using Ca2SiO4:Eu2+ as a precursor. Its properties have been discussed and analyzed utilizing XRD, photoluminescence, excited-state decay curve and long-lasting phosphorescence decay curve. Upon UV light excitation, the emission spectrum of Ca8Mg(SiO4)4Cl2:Eu2+ phosphor is composed of two separate bands centered at 425 nm and 505 nm, respectively. Furthermore, after irradiation by a 320-nm UV light for 3 min, the 2% Eu2+-doped Ca8Mg(SiO4)4Cl2 phosphor emits intense green-light-emitting afterglow from the 4f65d1→4f7 transition of Eu2+, and its afterglow can be seen with the naked eye in the dark clearly for more than 3 h after removal of the excitation source. The disappearance of the high-energy 425 nm band in the afterglow emission spectrum is explained by its different crystallographic sites. The afterglow decay curve of the Eu2+-doped Ca8Mg(SiO4)4Cl2 phosphor contains a fast decay component and another slow decay one. The possible mechanism of this long-lasting phosphorescence phosphor is also discussed based on the experimental results.