Novel tunable red to yellow emitting (Ca, Ba)4(PO4)2O:Eu2+ phosphor for blue-excited white light emitting diodes

A novel tunable red to yellow emitting phosphor, (Ca, Ba) 4 (PO 4 ) 2 O:Eu 2+ is reported that displays a broad emission from 500 to 800   nm, and its emitting color can be adjusted from red to yellow by changing Ba 2+ doping concentration. X-ray powder diffraction (XRD) analysis confirmed the phase formation. Excitation and emission spectra, and concentration dependence of emission intensity of the phosphor were investigated. The results showed that the emission peak wavelength take blue-shifted from 640 to 545   nm and the color hue can be tuned from red to yellow with increasing Ba 2+ concentration. When single-phase (Ca 3.85 Ba 0.10 )(PO 4 ) 2 O:0.05Eu 2+ phosphor is pumped by a blue InGaN light-emitting diode, we obtain white light with color rending index ( R a ) between 84.0 and 90.6 and color temperatures between 4000 and 5500   K, which suggests that this material is competitive as a color conversion material for solid state lighting.