Preparation and luminescence properties of Ba2P2O7:Dy3+, Ce3+ phosphors.

In this paper, Ba2-x-yP2O7:xDy3+,yCe3+ phosphors are synthesized by calcining the precursor via chemical co-precipitation. The phase structure, excitation and emission spectra, thermal stability, the chromatic performance of phosphors, and energy transfer from Ce3+ to Dy3+ are studied and discussed. The results indicate the samples keep a stable crystal structure as a high-temperature σ-Ba2P2O7 phase with two different coordination of Ba2+ sites. Ba2P2O7:Dy3+ phosphors can be effectively excited by 349 nm n-UV light and emit 485 nm blue light and a relatively stronger yellow light peaking at 575 nm, corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+, implying that Dy3+ mainly occupies the non-inversion symmetric sites. By contrast, Ba2P2O7:Ce3+ phosphors exhibit a broadband of excitation peaking at 312 nm, and two symmetrical emission peaks at 336 nm and 359 nm from 5d1→4F5/2 and 5d1→4F7/2 transitions of Ce3+, showing Ce3+ should merely be presumed to occupy Ba1 site. After Dy3+ and Ce3+ are co-doped, Ba2P2O7:Dy3+, Ce3+ phosphors exhibit the enhanced characteristic blue and yellow emission of Dy3+ with nearly equal intensity under excitation at 323 nm, meaning Ce3+ co-doping increases the symmetry of Dy3+ site as well as the sensitizer. Simultaneously, energy transfer from Dy3+ to Ce3+ is found and discussed. The thermal stability of co-doped phosphors was characterized and briefly analyzed. The color coordinates of Ba2P2O7:Dy3+ phosphors fall in the yellow-green region near the white light, while the emission moves towards the blue-green region after the Ce3+ is co-doped.