The trap states in the Sr2MgSi2O7 and (Sr,Ca)MgSi2O7 long afterglow phosphor activated by Eu2+ and Dy3+

The excellent long afterglow phosphor Sr2MgSi2O7:Eu2+,Dy3+ with the blue light and (Sr,Ca)MgSi2O7:Eu2+,Dy3+ emitting blue-green afterglow for more than 20 h under the UV excitation were prepared. The trap states in the samples are studied by thermoluminescence (TL) and photo-stimulated luminescence (PSL). The results of TL and PSL exhibit plenty of traps which are responsible for the long afterglow. TL study shows that a broad band appears at 330 and 357 K for (Sr,Ca)MgSi2O7:Eu2+,Dy3+ with the thermal depth of trap ETL = 0.66 eV and for Sr2MgSi2O7:Eu2+,Dy3+ with the thermal depth of trap ETL = 0.75 eV, respectively. PSL spectra reveals that the trapped carries also can be released by optical stimulation with the EPSL = 1.56-1.94 eV. The relation between TL and PSL can be explained by the configuration coordinate mode.