Emission-tunable phosphors Ca9MgM′ (PO4)7: Eu2+,Mn2+ (M′=Li, Na, K) for white light-emitting diodes

A series of single-composition phosphors Ca9MgM′(PO4)7:xEu2+, yMn2+ (CMM′ P:Eu2+, Mn2+; M′=Li, Na, K; 0.003≤x≤0.03; 0 ≤y≤0.1) were synthesized by solid state reactions. Upon excitation at 337 nm, phosphors Ca9MgM′ (PO4)7: Eu2+ exhibit strong blue emissions centered at 417 (Ca9MgLi(PO4)7:Eu2+), 457 (Ca9MgNa(PO4)7:Eu2+), and 453 (Ca9MgK(PO4)7:Eu2+) nm respectively, which correspond to the 4f65d1→4f7 transitions of Eu2+ ions, Through an effective resonance-type energy transfer, CMM′P:Eu2+,Mn2+ phosphors exhibit a series of colors by adjusting the concentration of Mn2+. The result indicates that CMM′P:Eu2+,Mn2+ can be potentially used as a UV excited phosphor for white light-emitting diodes (LEDs).