Broadband-excited and green-red tunable emission in Eu-sensitized CaMnTb(PO) phosphors induced by structural-confined cascade energy transfer.

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