Spectroscopic studies of solvothermally derived LaF3:Nd nanocrystals

LaF3:Nd (0.5-10.7 mol%) nanocrystals were solvothermally synthesized and their optical properties were studied. Judd-Ofelt parameterization of the absorption spectra gave a radiative decay time of 846 micros for the 4F3/2 excited state to the four emission channels. Measured fluorescence decay curves for 5 different Nd3+ concentrations were fit with double exponential functions. The decrease in fluorescence decay time shows that concentration quenching is appreciable as the Nd3+ concentration increases. The 0.5 mol% Nd3+ concentration shows a decay time of 800 micros and a radiative quantum efficiency of 95%. For all dopant concentrations, heat-treatment (800 degrees C, 2 h) substantially increased the emission intensity by 2 to 3-orders of magnitude. This emission intensity increase is attributed to reduction in hydroxyls and homogenization of the Nd3+ coordination environment through improved crystalline perfection of the LaF3:Nd lattice.