Effects of non-stoichiometry and substitution on photoluminescence and afterglow luminescence of Sr4Al14O25:Eu2+, Dy3+ phosphor

The effects of nonstoichiometry and cationic substitution on photoluminescence and afterglow characteristics of strontium aluminate phosphor (Sr4Al14O25:Eu2+, Dy3+) were investigated. Photoluminescence intensity of both the strontium-deficit and -rich phosphors was enhanced, but no definite correlation was observed between the afterglow intensity and non-stoichiometry. The photoluminescence emission maxima were either blue or green shifted in case of non-stoichiometric phosphors, whereas the afterglow emission maxima were not affected by the non-stoichiometry. Substitution of strontium by calcium resulted in white afterglow emission at higher calcium concentration. The emission centers in case of photoluminescence and afterglow emission appear to be different. Addition of silver significantly enhanced the afterglow intensity due to increased trap density.