Quantum efficiency of silica-coated rare-earth doped yttrium silicate

The photoluminescent properties of rare earth-activated white-emitting Y2SiO5:Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol-gel, were studied. The synthesized phosphor samples were post-annealed at 1373 K and 1623 K in order to obtain the X1-Y2SiO5 and X2-Y2SiO5 phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380-450 nm region originating from 5d-4f transitions in Ce3+ ions and a well-defined green emission of Tb3+ ions located at 545 nm corresponding to 5D4→7F5 electronic transitions. Thereafter, Y2SiO5:Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y2SiO5:Ce,Tb phosphor.