Probing lattice defects in Sr2MgSi2O7:Eu2+,Dy3+

The Sr2MgSi2O7:Eu2+,Dy3+ materials were prepared with a solid state reaction and their microscopic structure (at 295 K only) and luminescence were studied at selected temperatures between 150 and 295 K. Undisturbed Sr crystal planes were common in the TEM images of the undoped Sr2MgSi2O7 material, whereas with Eu2+ doping more disturbed planes were observed even in the nanometer scale. With Dy3+ co-doping, a large number of small lattice domains created by the discontinuities in the crystal structure was observed. The domains with different orientations seem to be centered around point defects. The decay curves of Sr2MgSi2O7:Eu2+,Dy3+ showed fast (ms scale) persistent luminescence. The intensity of persistent luminescence increased considerably between 200 and 250 K while remaining constant in the ranges of 150-200 and 250-295 K. The changes were used to study the depth of the traps. In general, Dy3+ co-doping was found to deepen the traps.