Luminescence and energy transfer mechanism in Sr9Sc(PO4)7: Ce3+, Mn2+ phosphor

A series of Ce3+ and Mn2+ co-doped Sr9Sc(PO4)7 phosphors have been synthesized by high temperature solid state reaction and their luminescence properties are investigated. The obtained phosphors exhibit a broad excitation band ranging from 240 to 350 nm and two emission bands centered at about 370 and 610 nm upon 310 nm excitation, resulting from the 5d-4f transitions of Ce3+ and the d-d forbidden transition of Mn2+, respectively. Energy transfer mechanism from Ce3+ to Mn2+ in Sr9Sc(PO4)7 host matrix was studied and demonstrated to be a resonant type via a dipole-dipole mechanism based on the decay lifetime data. Furthermore, we have calculated the critical distance for Ce3+→Mn2+ energy transfer to be about 6.12 Å by the spectral overlap method. Through effective energy transfer, a color-tunable emission varied from blue to reddish orange can be realized by adjusting the ratio of Ce3+ to Mn2+. Our results indicate the novel Sr9Sc(PO4)7: Ce3+, Mn2+ phosphor can be a promising candidate for a color-tunable phosphor applied in a UV white light emitting diodes.