Synthesis and Luminescent Characterization of Eu2+/Dy3+-Doped Sr2MgSi2O7 Powders

Eu2+/Dy3+-doped Sr2MgSi2O7 powders were synthesized using a solid-state reaction method with flux (NH4Cl). The broad photoluminescence (PL) excitation spectra of Sr2MgSi2O7:Eu2+ were assigned to the 4f(7)-4f(6) 5d transition of the Eu2+ ions, showing strong intensities in the range of 375 to 425 nm. A single emission band was observed at 470 nm, which was the result of two overlapping subbands at 468 and 507 nm owing to Eu(I) and Eu(II) sites. The strongest emission intensity of Sr2MgSi2O7:Eu2+ was obtained at the Eu concentration of 3 mol%. This concentration quenching mechanism was attributable to dipole-dipole interaction. The Ba2+ substitution for Sr2+ caused a blue-shift of the emission band; this behavior was discussed by considering the differences in ionic size and covalence between Ba2+ and Sr2+. The effects of the Eu/Dy ratios on the phosphorescence of Sr2MgSi2O7:Eu2+/Dy3+ were investigated by measuring the decay time; the longest afterglow was obtained for 0.01Eu(2+)/0.03Dy(3+).