An Investigation on the Luminescence and Ce3+→Eu2+ Energy Transfer in Ca9Y(PO4)7:Ce3+,Eu2+ Phosphor

A series of Ce 3+ - and Eu 2+ -coactivated Ca 9 Y(PO 4 ) 7 phosphors were synthesized by high temperature solid-state reactions. The Ca 9 Y(PO 4 ) 7 :Ce 3+ ,Eu 2+ phosphor showed two emission bands under 292 nm excitation: the one observed at 342 nm was attributed to the 4 f 0 5 d 1 → 4 f 1 transition of Ce 3+ ion emission, and the other found at 492 nm was assigned to the 4 ƒ 6 5 d 1 → 4 f 7 transition of Eu 2+ ions. Through an effective resonance-type energy transfer, the Ca 9 Y(PO 4 ) 7 :Ce 3+ ,Eu 2+ phosphors exhibit a systematically varied hues from ultraviolet to blue-greenish and the relative intensity of ultraviolet and blue-greenish emissions can be tuned by properly tuning the relative dopant composition of Ce 3+ /Eu 2+ . The energy transfer from a sensitizer Ce 3+ to an activator Eu 2+ in Ca 9 Y(PO 4 ) 7 host matrix was studied and demonstrated to be a resonant type via a dipole-dipole mechanism based on the decay lifetime analysis. Furthermore, we have calculated the critical distance for Ce 3+ → Eu 2+ energy transfer to be about 30.7 Å by both concentration quenching and spectral overlap methods.