Novel Na3Sc2(PO4)3:Ce3+,Tb3+ phosphors for white LEDs: Tunable blue-green color emission, high quantum efficiency and excellent thermal stability

In this paper, Ce3+ and Tb3+ singly doped as well as Ce3+/Tb3+ co-doped Na3Sc2(PO4)(3) phosphors were synthesized by the traditional solid-state method and their crystal structure, morphology, luminescence properties, temperature-dependent emission spectra and quantum efficiency were investigated in detail. The Ce3+ singly doped sample exhibited intense blue emission under 320 nm excitation. The Na3Sc2(PO4)(3):Tb3+ phosphors showed four emission bands in the wavelength range of 450-650 nm with a maximum at about 542 run. Furthermore, efficient energy transfer from Ce3+ to Tb3+ ions occurred in Ce3+ and Tb3+ co-doped Na3Sc2(PO4)(3) phosphors, and the electric dipole-dipole interactions was responsible for the energy transfer mechanism. By adjusting Tb3+ doping concentration in Na3Sc2(PO4)(3):Ce3+,Tb3+ phosphors, their emission colours can be tuned appropriately from deep blue (0.171, 0.050) to green (0.299, 0.593), and the intensity of green emission reached the maximum at 10 mol% Tb3+. The Na3Sc2(PO4)(3):0.03Ce(3+),0.1Tb(3+) sample possessed high internal quantum efficiency of 65% and also excellent thermal stability with an activation energy of 0,245 eV. The relative emission intensity of Na3Sc2(PO4)(3):0.03Ce(3+),0.1Tb(3+) at 423 K was found to be about 85.6% of its initial value at 303 K. These results indicate the potential of Na3Sc2(PO4)(3):Ce3+,Tb3+ compounds as candidates for color converters in phosphor-converted white light-emitting diodes.