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

Abstract

Nanocrystalline (Y_0.95Tb_0.05)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 °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 °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 °C. Evidence of quantum confinement luminescence enhancement is observed for the nanocrystallites annealed at 500 °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 (Y_0.95Tb_0.05)₂O₃ with a large quantum confinement fluorescence enhancement may be accessible by appropriate annealing in the temperature range 500–600 °C.