Tunable blue-green color emitting phosphors Sr3YNa(PO4)3F:Eu2+, Tb3+ based on energy transfer for near-UV white LEDs

A series of Eu2+ and Tb3+ doped Sr3YNa(PO4)3F phosphors have been synthesized via a high temperature solid state reaction method. Eu2+ activated Sr3YNa(PO4)3F phosphors can be efficiently excited by light in the range of 220-420 nm, which matches well with the commercial n-UV LEDs, and show intense blue emission centered at 456 nm. The optimal doping concentration of Eu2+ is determined to be 1 mol%. The concentration quenching mechanism of Eu2+ in SYNPF host is mainly attributed to the dipole-dipole interaction. Energy transfer from Eu2+ to Tb3+ is observed when Eu2+ and Tb3+ are co-doped into Sr3YNa(PO4)3F host. Under excitation of 380 nm, the emission color can be varied from blue to green along with the increase of Tb3+ doping concentration. Based on decay curves, the energy transfer from the Eu2+ to Tb3+ ions is demonstrated to be a dipole-dipole mechanism. According to thermal quenching study by yoyo experiments of heating-cooling, Sr3YNa(PO4)3F:Eu2+, Tb3+ shows good thermal stability. The thermal quenching mechanism is also discussed. The results indicate that as-prepared samples might be of potential application in w-LEDs