Luminescence and energy transfer of Ce3+-Eu2+ in Ca9Al(PO4)7

A series of Ce3+, Eu2+ and Ce3+-Eu2+ doped Ca9Al(PO4)7 phosphors are synthesized by a high temperature solid-state method. Under 291 nm excitation, Ca9Al(PO4)7:Ce3+ has one emission band at 356 nm, which is attributed to 4f05d1→4f1 transition of Ce3+. Under 305 nm excitation, Ca9Al(PO4)7:Eu2+ presents one emission band at 445 nm, which is assigned to 4f65d1→4f7 transition of Eu2+. Energy transfer from Ce3+ to Eu2+ in Ca9Al(PO4)7 is validated and proved to be a resonant type via a quadrupole-quadrupole interaction. Critical distance (R c) of Ce3+ to Eu2+ in Ca9Al(PO4)7 is calculated to be 1.264 nm. Moreover, the emission intensity of Ca9Al(PO4)7:Ce3+, Eu2+ can be tuned by properly adjusting the relative doping composition of Ce3+/Eu2+.