Potential color tunable SrLaNa(PO)F:Eu/Tb/Mn phosphor induced by Eu → Tb and Tb → Mn energy transfer for WLEDs.

Color tunable SrLaNa(PO)F:Eu,Tb and SrLaNa(PO)F:Tb,Mn phosphors were prepared by a high temperature solid state reaction. The crystal structure, luminescence properties, and energy transfer mechanism of the samples were investigated in detail. The Eu doped phosphors can be efficiently excited in the range from 250 to 410 nm, which matches well with the commercial n-UV LED chips. Utilizing the energy transfer from Eu to Tb ions, tunable colors from blue to green were obtained under the irradiation of 405 nm. The mechanism of the Eu → Tb energy transfer was demonstrated to be a dipole-quadrupole interaction in terms of the experimental results and analysis of the photoluminescence spectra and decay curves of the phosphors. Moreover, the thermal stability and quantum efficiency of the Eu and Tb co-doped phosphors were studied. For the SrLaNa(PO)F:Tb,Mn samples, tunable green-orange emissions were obtained by changing the relative ratio of Tb and Mn ions under 230 nm irradiation. The investigation results suggest that color tunable phosphors with potential for WLEDs were obtained utilizing the energy transfer process.