Long persistent alkali-earth silicate phosphors doped with Eu2+,Nd3+

Phosphors of SrnMgSi2O5+n(1⩽n⩽2) singly doped with Eu2+ or doubly doped with Eu2+ and Nd3+ were prepared by using a solid state chemical reaction method. X-ray diffraction spectra revealed that the SrnMgSi2O5+n(1⩽n⩽2) compounds have the same crystal structure as Sr2MgSi2O7. The samples showed a strong blue emission at 470nm. Their excitation bands are from 250to450nm which were assigned to the 5d-4f transitions of Eu2+. Energy transfer between Eu2+ ions in inequivalent sites was found. Temperature dependence of photoluminescence was studied. A decrease of luminescence intensity and a blueshift of the emission spectra with increasing temperature were observed in both SrMgSi2O6:Eu2+ and Sr2MgSi2O7:Eu2+. Persistent afterglow was detected in the samples. The Eu2+ blue afterglow emission could be greatly enhanced by codoping trivalent rare earth ions, such as Nd3+. Thermoluminescence measurements revealed that doping with Nd3+ created a much large number of traps and hence enhanced the afterglow.