Color-tunable phosphor of SrYNa(PO)F:Tb interionic cross-relaxation energy transfer.

A series of color-tunable SrYNa(PO)F:Tb phosphors with a fluorapatite structure were synthesized by a traditional high-temperature solid state reaction. The emitting color tuning from blue to green can be observed by gradually increasing Tb concentrations, which is attributed to the enhanced cross-relaxation (CR) between Tb ions, as described by (D, F)-(D, F). The CR process is analyzed based on the Dexter and Inokuti-Hirayama model, which is assigned to the electric dipole-dipole interaction. The energy transfer critical distance between Tb ions is evaluated to be 18.1 Å. In addition, the thermal quenching mechanism of SrYNa(PO)F:Tb is also investigated. At the general working temperature of an LED (423 K), the luminescence intensity still maintains 81% and 92% with the Tb concentration of 10 and 30 mol%, respectively, indicating an excellent thermal quenching performance of Tb. Due to the good optical and thermal properties, the SrYNa(PO)F:Tb phosphor can be used as a promising green emitting phosphor candidate in the field of white light applications.