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

Abstract

A series of Ce3+- and Eu2+-coactivated Ca9Y(PO4)7 phosphors were synthesized by high temperature solid-state reactions. The Ca9Y(PO4)7:Ce3+,Eu2+ phosphor showed two emission bands under 292 nm excitation: the one observed at 342 nm was attributed to the 4f 05d1 → 4f 1 transition of Ce3+ ion emission, and the other found at 492 nm was assigned to the 4ƒ65d1 → 4f 7 transition of Eu2+ ions. Through an effective resonance-type energy transfer, the Ca9Y(PO4)7:Ce3+,Eu2+ 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 Ce3+/Eu2+. The energy transfer from a sensitizer Ce3+ to an activator Eu2+ in Ca9Y(PO4)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 Ce3+ → Eu2+ energy transfer to be about 30.7 Å by both concentration quenching and spectral overlap methods.