Energy transfer and tunable photoluminescence of Sr 6 Gd 2 Na 2 (PO 4 ) 6 F 2 :Tb 3+ , Eu 3+ phosphors for near-UV white LEDs

A series of apatite-type Sr 6 Gd 2 Na 2 (PO 4 ) 6 F 2 :Tb 3+ , Eu 3+ phosphors have been successfully synthesized by the high-temperature solid-state reaction method. Phase structures were examined based on X-ray diffraction, the results indicated that the obtained Sr 6 Gd 2 Na 2 (PO 4 ) 6 F 2 :Tb 3+ , Eu 3+ samples were well crystallized without impurity phase. The photoluminescence emission and excitation spectra and the decay curves were investigated in detail. The main energy transfer from Tb 3+ to Eu 3+ was verified to compliance with the dipole-quadrupole mechanism. The luminescence colors of the Sr 6 Gd 2 Na 2 (PO 4 ) 6 F 2 :Tb 3+ , Eu 3+ phosphors can be easily tuned from green light (0.2570, 0.3766) to white light (0.3674, 0.2813) by adjusting the proportion of Tb 3+ and Eu 3+ ions. The investigations indicated that the Sr 6 Gd 2 Na 2 (PO 4 ) 6 F 2 :Tb 3+ , Eu 3+ phosphors can be used as a qualified candidate for application in white light-emitting diodes.