Tri-chromatic Emission from a Single-phase Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ Phosphor for White-light-emitting Diodes

A series of single-phase Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ phosphors were successfully synthesized by high-temperature solid state reaction and their crystal structure and luminescence properties were investigated. The chromaticity coordinates of the as-prepared phosphors under 375 nm excitation can be tuned effectively, from the light blue (0.260, 0.213) to red (0.638, 0.337) and eventually to white (0.407, 0.373) via resonant type energy transfer and appropriate choice of color combination. Furthermore, the states occupation of the dopant ions and the energy transfer mechanisms Eu2+ → Tb3+ and Tb3+ → Eu3+ have been investigated and discussed, emphasizing on spectral content and thermal stability of Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ emission under 375 nm excitation. The results indicate that the Na5Y4(SiO4)4F:Eu2+,Tb3+,Eu3+ phosphors have a potential application in UV-based White LED devices.