Dual energy transfers and color tunable emission in Eu2+/Tb3+/Mn2+-triactivated Mg21Ca4Na4(PO4)18 phosphors

A series of single-composition Mg21Ca4Na4(PO4)18: Eu2+,Tb3+,Mn2+ phosphors have been synthesized via a combustion-assisted synthesis technique. The crystal structure, luminescence properties, and energy transfers (ET) from Eu2+ to Tb3+ and/or Mn2+ ions are discussed in detail. The ETEu-Tb and ETEu-Mn processes in the Mg21Ca4Na4(PO4)18 host are demonstrated to be resonant types via dipole-dipole interaction and quadrupole-quadrupole interaction, respectively. Additionally, the emitting colors of Mg21Ca4Na4(PO4)18: Eu2+, Tb3+, Mn2+ samples can be tuned from blue to blue-green via the ETEu-Tb process and from blue to reddish purple via the ETEu-Mn process. Finally, the tunable white light emission with high quantum yields (>50%) was realized by precise control of the concentrations of Eu2+, Tb3+, and Mn2+ ions. The results suggest the developed phosphors can find applications in the field of ultraviolet irradiation pumped white-LEDs.