The observation of quantum confinement enhancement of the luminescence of nanocystalline (Y0.95Tb0.05)2O3 synthesized by alkalide reduction

Nanocrystalline (Y0.95Tb0.05)2O3 has been synthesized by sub-ambient homogenous reduction using alkalide solutions, subsequent oxidation and annealing. As synthesized, the material consists of free flowing, agglomerates of ill-defined, amorphous or subnanocrystalline nanoparticles. Samples annealed at 500 deg C or greater are crystalline, consisting of agglomerated nanocrystals. The nanocrystals grow from an average of ~1-2 nm to 19 nm and the agglomerates break-up as the annealing temperature is raised from 500 to 1000 deg C. The nanocrystalline product displays luminescence typical of the Tb3+ ion. The photoluminescence intensity of the green 5D4-7F4 transition increases with increasing annealing temperature, reaching a maximum of 4% for the nanophosphor annealed at 1000 deg C. Evidence of quantum confinement luminescence enhancement is observed for the nanocrystallites annealed at 500 deg C, but the quantum efficiency is low, presumably due to their very small size and consequent rapid surface recombination. The results of this study suggest that nanocrystallites of (Y0.95Tb0.05)2O3 with a large quantum confinement fluorescence enhancement may be accessible by appropriate annealing in the temperature range 500-600 deg C.