White-Emitting Tuning and Energy Transfer in Eu2+/Mn2+-Substituted Apatite-Type Fluorophosphate Phosphors

Herein, a series of Eu2+&Mn(2+)substituted fluorophosphates Ca6Gd2Na2(PO4)(6)F-2 phosphor with apatite structure have been synthesized and investigated by the powder X-ray diffraction, photoluminescence spectra, fluorescence decay curves, thermal quenching, and chromaticity properties. Particularly, both Eu2+ and Mn2+ emissions at the two different lattice sites 4f and 6h in Ca6Gd2Na2(PO4)(6)F-2 matrix have been identified and discussed. The dual energy transfer of Eu2+Mn2+ and Gd3+Mn2+ in Ca6Gd2Na2(PO4)(6)F-2:Eu2+,Mn2+ samples have been validated and confirmed by the photoluminescence spectra. The dependence of color-tunable on the activator concentration of Mn2+ was investigated to realize white light emission. By varying the doping concentration of the Mn2+ ion, a series of tunable colors including pure white light and candle light are obtained under the excitation of 350nm. Moreover, the fluorescence decay curves have been fitted and analyzed using the Inokuti-Hirayama theoretical model to estimate the Eu-Mn interaction mechanism. We also investigated temperature-dependent photoluminescence quenching characteristics according to the Arrhenius equation. Preliminary studies on the properties of the phosphor indicated that the obtained phosphors might have potential application as a single-component white-emitting phosphor for UV-based white LEDs.