Synthesis, structure and optical properties of europium doped calcium barium phosphate - a novel phosphor for solid-state lighting

A new phase, Ca6BaP4O17, was found in the CaO-BaO-P2O5 phase diagram and its Eu2+-doped derivative was evaluated as a possible phosphor for solid-state lighting. Ca6BaP4O17 was prepared by conventional solid-state synthesis and its structure was solved ab initio from high-resolution, synchrotron X-ray powder diffraction data. The bandgap of Ca6BaP4O17 was estimated to be 5.79 eV. Under excitation with UV to blue light, Ca6BaP4O17:Eu2+ shows strong yellow emission with the peak position at 553 nm. A white LED, which was fabricated with an InGaN blue chip and Ca6BaP4O17:Eu2+, achieved a luminous efficacy of 31 lm W-1 with a color-rendering index of 78 around the correlated color temperature of 6500 K.