Effects of non-stoichiometry on crystallinity, photoluminescence and afterglow properties of Sr2MgSi2O7:Eu2+, Dy3+ phosphors

Eu2+, Dy3+ co-doped Sr2MgSi2O7 phosphors with deficient, stoichiometric or excess amounts of silicon are prepared by solid-state reaction. XRD and SEM results indicate that all the samples studied are found to be free from impurities and samples with SiO2 excess possess better crystallinity and larger grain size. Photoluminescence reveals that the position of Eu2+ emission is not changed with various compositions. However, both photoluminescence intensity and afterglow properties are increased by an incorporation of excess SiO2 and are decreased by SiO2 deficiency. The thermoluminescence results show that the corresponding increase or decrease in afterglow is associated with trap density, but no change in trap depth. The underlying reason of photoluminescence and afterglow enhancement is discussed.