A blue emitting phosphor Li 2 Sr 0.9 Mg 0.1 SiO 4 :Ce 3+ , with long persistence, was synthesized via a hightemperature solid phase method. According to the X-ray diffraction analysis result, the introduction of Mg 2+ and Ce 3+ ions has no influence on the structure of the host material. Typical 5d-2 F 5/2 and 5d-2 F 7/2 transitions of Ce 3+ ions were detected by PL spectra, which corresponded to the CIE chromaticity coordinates of x ¼ 0.1584, y ¼ 0.0338. An optimal doping concentration of Ce 3+ was determined as of 0.4 at%. Furthermore, the Li 2 Sr 0.9 Mg 0.1 SiO 4 :Ce 3+ phosphor showed a typical triple-exponential afterglow behavior when the UV source was switched off. The highest lifetime of the electrons within the material reached a value of 73.9 s. Thermal stimulated luminescence study indicated that the afterglow of Li 2 Sr 0.9 Mg 0.1 SiO 4 :Ce 3+ was due to the recombination of the electrons with holes released from the traps generated by the doping of Ce 3+ ions in the Li 2 Sr 0.9 Mg 0.1 SiO 4 host. The afterglow mechanism of Li 2 Sr 0.9 Mg 0.1 SiO 4 :Ce 3+ is illustrated and discussed in detail on the basis of the experimental results. Fig. 6 Schematic graph of phosphorescence mechanism. B represent hole; C represent electron.Fig. 5 TSL curve of the Li 2 Sr 0.9 Mg 0.1 SiO 4 :0.004Ce 3+ phosphor.This journal is