Tunable luminescence of broadband-excited and narrow line green emitting Y 2 SiO 5 :Ce 3+ , Tb 3+ phosphor

Cerium and terbium activated white emitting yttrium silicate phosphors (Y2−x−yCexTbySiO5) having average size between 96 and 123 nm were synthesised by a gel-combustion, and their phase and crystal structures, morphologies and ultraviolet (UV)-visible spectroscopic properties were studied. All rare earth doped yttrium silicate (YSO) phosphors are well crystallized powders containing only monoclinic X2-Y2SiO5 phase. No significant changes in the cell parameters were observed with increasing of Tb amount as ionic radii of Tb3+ (0.923 Å) and Y3+ (0.9 Å) have almost the same. Under different excitations, YSO:Ce3+ exhibits blue emission due to the 5d–4f transitions of Ce3+ ions. The series of emission states at different wavelengths of YSO:Tb3+ associated to f–f transition of Tb3+ ion were detected from luminescence measurements. The emission observed at 544 nm (green) corresponding to 5D4 → 7F5 of Tb3+ is strongest one. Incorporation of variable amounts of Tb3+ in the YSO host lattice determines the modification of emission colour from blue through light blue and eventually to bluish green. A possible energy transfer mechanism taking place from Ce3+ to Tb3+ was also discussed in terms of excitation and emission spectra.