Luminescent properties of a novel afterglow phosphor Sr3Al2O5Cl2:Eu2+, Ce3+

A series of Eu2+ and Ce3+ doped/co-doped Sr3Al2O5Cl2 afterglow phosphors that presented various bright colors were successfully synthesized via high temperature solid state reaction. The structure and luminescence properties of the obtained samples were characterized by X-ray powder diffraction (XRD), photoluminescence (PL) spectra and decay curves as well as the thermoluminescence (TL) glow curves. The XRD results showed that all the phase could be indexed to the orthorhombic structure with the space group P212121. After being exposed to a 254 nm or 365 nm mercury lamp, blue/yellow-orange afterglow emissions with broad bands peaking around 620 nm/435 nm, which were ascribed to the characteristic 4f65d–4f7/5d1–4f1 transitions of Eu2+/Ce3+, could be observed in phosphors of Sr3Al2O5Cl2:Eu2+/Sr3Al2O5Cl2:Ce3+, respectively. Because of the overlap spectral range between the Sr3Al2O5Cl2:Eu2+ and Sr3Al2O5Cl2:Ce3+ phosphors, the energy transfer (ET) from Ce3+ to Eu2+ occurred. The related ET process was discussed in detail. Moreover, the incorporation of Ce3+ could significantly prolong the afterglow duration of Sr3Al2O5Cl2:Eu2+ phosphor, which was due to the increase of trap concentration. Consequently, 6 h of the afterglow duration could be observed in Sr3Al2O5Cl2:1.0%Eu2+, 0.5%Ce3+ sample, exhibiting much longer than that of Sr3Al2O5Cl2: 1.0%Eu2+ (3 h). From the afterglow decay curves and the fitting results, the optimal concentration of Ce3+ for the enhanced afterglow property was experimentally determined to be 0.5%.