White light emission from rare earth activated yttrium silicate nanocrystalline powders and thin films

We present a potential rare earth activated white-emitting nanocrystalline phosphor powders produced by combustion synthesis and report their luminescent properties and thin films deposited by pulsed laser ablation. Effects of varying the atomic concentration of rare earth dopants in Y2SiO5:Ce-x,.Tb-y (0.0065 < x < 0.0085, 0.010 < y < 0.040), along with morphological, microstructural and photoluminescence (PL) properties were investigated in order to produce white-light emission close to D-65 with optimized luminescent efficiency. Characteristic electronic transitions measured from photoluminescence spectra at gimel(cm) = 544 nm (D-5(4) -> F-7(5)) in Tb3+ and gimel(cm) = 418 nm (5d -> F-2(7/2)) in Ce3+ show that an inductive energy transfer occurs when Tb3+ ions absorbs the energy from Ce3+ upon excitation with long-UV photons (gimel(exe) = 358-380 nm). The optimal concentration for the best luminescence intensity has been obtained in Y2SiO5:Ce-0.0075,Tb-0.025, and the closest to daylight white emission was found with a composition of Y2SiO5:-Ce-0.0075,Tb-0.040. These activated phosphors with two rare earth ions in the yttrium silicate host (Y2SiO5) represent an efficient way to produce white-light emission close to D65 with chromaticity coordinates of x = 0.225 and y = 0.320. (c) 2004 Elsevier B.V. All rights reserved.