Luminescence properties and energy transfer of Ce3+/Tb3+ co-doped Ca6Ba(PO4)4O phosphor for near-UV pumped light-emitting diodes

A series of Ca6-x-yBa(PO4)(4-x-y)(SiO4)(x+y)O:xCe(3+), yTb(3+) phosphors was synthesized via a high-temperature solid-state method. Charge balance was realized via the collaborative substitution of a Ca2+/Ce3+(Tb3+)P5+/Si4+ couple with the pure phase. On excitation at 365 nm, the emission spectra of the as-obtained phosphor contained both the asymmetrical broad band Ce3+ emissions and the line-type Tb3+ emissions. Energy transfer occurred from Ce3+ to Tb3+ and the mechanism was ascribed to a resonant type via a non-radiative dipole-dipole interaction. The critical distance of the energy transfer was calculated via the concentration quenching method. The hues of the studied phosphors could be adjusted by the relative ratios of the Ce3+ and Tb3+ ions. The phosphors have good thermal stability and a high quantum efficiency and therefore may have potential applications in near-UV pumped white light-emitting diodes.