Synthesis and up-conversion white light emission of RE3+-doped lutetium oxide nanocubes as a single compound

Uniform and dispersive Lu2O3:Yb3+/Er3+/Tm3+ nanocubes have been successfully synthesized by hydrothermal process with subsequent calcination at 900 °C. The as-formed RE3+-doped lutetium oxide precursor via the hydrothermal process, as a template, could transform to RE3+-doped Lu2O3 with their original cubic morphology and slight shrinkage in the size after post-annealing process. The formation mechanism for the lutetium oxide precursor cubes has been proposed. Under single wavelength diode laser excitation of 980 nm, the as-obtained Lu2O3:3%Yb3+/0.5%Er3+/0.3%Tm3+ nanocubes show nearly equal intensities of blue (Tm3+: 1G4 → 3H6), green (Er3+: (2H11/2, 4S3/2) → 4I15/2), and red (Er3+: 4F9/2 → 4I15/2) emissions, which produces bright white light emission, clearly visible to the naked eyes. The main pathways to populate the upper emitting states come from the energy-transfer processes from Yb3+ to Tm3+/Er3+, respectively. The chromaticity coordinate of the Lu2O3:3%Yb3+/0.5%Er3+/0.3%Tm3+ sample is calculated to be about x = 0.3403 and y = 0.3169, which falls exactly within the white region of 1931 CIE diagram and is very close to the standard equal energy white light illuminate (x = 0.33 and y = 0.33), pointing out its potential use as a white light source under 980 nm laser diode excitation.