Luminescent properties of the Sr2.97−xBaxMgSi2O8:Eu2+0.01, Dy3+0.02 with different Sr/Ba ratio

The long afterglow phosphor materials Sr2.97−xBaxMgSi2O8:Eu0.012+, Dy0.023+ (x = 0, 0.5, 1, 1.5, 2) were prepared by the high temperature solid-state reaction method. The crystal phases of these phosphors were examined using X-ray powder diffraction. Slight shifts of the peaks in the structure, which indicate a small change of the interplanar crystal spacing, were observed for each different x's. As a result of decreasing Sr/Ba ratio, the interplanar spacing becomes widened. The emission peaks of the phosphors indicated on the emission spectra range from 434 to 464 nm under the ultraviolet excitation. By gradually increasing the value of x, the blue shift occurs when x ≤ 1.5 while the slight red shift occurs when x > 1.5. It is probably due to the interfering effect of 5d energy level of Eu2+ and the strength of the crystal field which is subjected to the repulsion between the 5d electrons and electron of the ligand and the attraction that exists between Eu2+ and the ligand. The thermoluminescence curves depict the depth of the trap, where the Dy3+ ion generates, and this leads directly to the long afterglow of the phosphors. As the proportion of Ba in the composition increases, the attenuation time of the long-lasting phosphors shortens. The result of the experiment proves that the luminescent properties of the phosphors can be adjusted with different Sr/Ba ratio.