Color-tunable properties and energy transfer in Ba3GdNa(PO4)3F:Eu2+, Tb3+ phosphor pumped for n-UV w-LEDs

• The Ba3GdNa(PO4)3F:Eu2+, Tb3+ phosphor exhibits a broad excitation band.
• The energy transfer between Eu2+ and Tb3+ takes place in Ba3GdNa(PO4)3F:Eu2+, Tb3+.
• The Ba3GdNa(PO4)3F:Eu2+, Tb3+ emission color adjusts from blue to green.

A series of Eu2+ and Eu2+/Tb3+ co-doped Ba3GdNa(PO4)3F phosphors have been synthesized via a high temperature solid-state reaction. The relative intensity of PL spectra of Ba3GdNa(PO4)3F:xEu2+ increases with increasing x value, and reaches a maximum at x=0.04. Ba3GdNa(PO4)3F:Eu2+, Tb3+ phosphors exhibit a broad excitation band ranging from 220 to 450 nm, which matches perfectly with the characteristic emission of n-UV light-emitting diode (LED) chips. Upon 365 nm excitation, the Ba3GdNa(PO4)3F:Eu2+, Tb3+ phosphors show two dominating bands peaked at 466 and 543 nm, which are assigned to the 4f7→4f65d1 transition of the Eu2+ ions and the 5D4→7F5 transition of the Tb3+ ions, respectively. In view of the energy transfer mechanism between Eu2+ and Tb3+, the Ba3GdNa(PO4)3F:Eu2+, Tb3+ emission color can adjust from blue to green, and their chromatic coordinates (x, y) vary from (0.16, 0.135) to (0.254, 0.398). The critical distance was also calculated to be 16.90 Å. The above results indicate that the Ba3GdNa(PO4)3F: Eu2+, Tb3+ phosphors are a candidate for blue–green components in the application of n-UV w-LEDs.