Broadband-excited and green-red tunable emission in Eu 2+ -sensitized Ca 8 MnTb(PO 4 ) 7 phosphors induced by structural-confined cascade energy transfer.

Novel green-red color-tunable Ca 8 (Mg,Mn)Tb(PO 4 ) 7 :Eu 2+ phosphors have been synthesized via the traditional solid-state method. Since Tb 3+ /Mn 2+ ions are the parent ions in the lattice, the structural confinement occurs when the sensitizer Eu 2+ is introduced into the Ca 8 (Mg,Mn)Tb(PO 4 ) 7 :Eu 2+ structure. The distance from Eu 2+ to Tb 3+ /Mn 2+ is confined in the 5 Å range, which induces a highly efficient energy transfer process. At Eu 2+ 350 nm excitation, Ca 8 MgTb(PO 4 ) 7 :Eu 2+ shows dominant Tb 3+ green emission with almost-vanished Eu 2+ emission. Red emission is clearly observed as Mn 2+ ions doping into Ca 8 MgTb(PO 4 ) 7 :Eu 2+ , and color-tuning from green to red is realized by varying the Mn 2+ contents. Eu 2+ -Tb 3+ -Mn 2+ cascade energy transfer process is in effect due to short Eu 2+ -Tb 3+ /Mn 2+ and Tb 3+ -Mn 2+ distances, which is verified by PL and decay variations. Meanwhile, the Ca 8 (Mg,Mn)Tb(PO 4 ) 7 :Eu 2+ phosphor indicates good thermal stability and maintained the 45% emission level at 150 °C, which demonstrates their potential applications in white light LEDs.