Synthesis and luminescence properties of Ca5-x(PO4)3Br: xEu2+-A novel blue-emitting bromapatite phosphor for near-ultraviolet-pumped white light-emitting diodes

A series of novel Ca5-x(PO4)3Br: xEu2+ (x = 0.01-0.10) blue phosphors were synthesized via the conventional solid state reaction and their luminescence properties were reported. The Ca5-x(PO4)3Br: xEu2+ phosphors could be excited efficiently in the wavelength range of 320-440 nm and displayed an intense asymmetric blue emission band around 458 nm under 365 nm excitation. The concentration quenching of Eu2+ in the Ca5(PO4)3Br host was investigated in detail. The optimum doping concentration of Eu2+ was determined to be 0.07 and the energy transfer mechanism was certified to be the dipole-dipole interaction. Moreover, the CIE chromaticity coordinates for the composition-optimized Ca4.93(PO4)3Br: 0.07Eu2+ were located in the blue region at (x = 0.1450, y = 0.0840), whose color purity was close to that of the commercial blue phosphor BaMgAl10O17: Eu2+. All these results gave an indication that Ca5-x(PO4)3Br: xEu2+ phosphors could serve as a promising blue-emitting candidate for near-UV-pumped white light-emitting diodes.