Novel single-phase white-emitting phosphor Sr6Gd2Na2(PO4)6F2:Eu2+,Mn2+: band gap, luminescence, and energy transfer

White-emitting phosphors Sr6Gd2Na2(PO4)6F2:Eu2+,Mn2+ (SGNPF:Eu2+,Mn2+) were synthesized under a weak reductive atmosphere. Phase purity was examined based on XRD patterns, and results showed that the obtained SGNPF:Eu2+,Mn2+ phosphors were well crystallized with no impurity phase. The emission spectra of SGNPF:Eu2+,Mn2+ phosphor exhibited broad blue and broad yellow emission bands with two peaks at approximately 460 and 560 nm under 300 nm excitation. The energy transfer process from Eu2+ to Mn2+ was verified through luminescence spectra and fluorescence decay curves. The energy transfer from Eu2+ to Mn2+ in SGNPF was demonstrated to be a resonant type via a dipole–dipole mechanism. Adjusting the relative contents of Eu2+ and Mn2+ could change the emitting colors of SGNPF:Eu2+,Mn2+ phosphors from blue and azure to white, and the ideal white light-emitting phosphor SGNPF:0.05Eu2+,0.25Mn2+ with color coordinate (0.29, 0.31) was obtained. All investigations indicated that the SGNPF:Eu2+,Mn2+ phosphors exhibit great potential as a single component white-emitting phosphor for white light-emitting diodes.