Influence of Er(3+) concentration on the photoluminescence characteristics and excitation mechanism of Gd2O3:Er(3+) phosphor synthesized via a solid-state reaction method.

An Er(3+) -doped phosphor of Gd2O3(Gd2O3:Er(3+)) was prepared using a conventional solid-state reaction method. The structure and particle size were determined from X-ray powder diffraction measurements. The average particle size of the phosphor was in between 20 and 50 nm. The particle size and structure of the phosphor were further confirmed by transmission electron microscopy (TEM) analysis. Luminescence spectra were recorded under excitation wavelengths of 275, 380, 515 and 980 nm. The visible upconversion and downconversion luminescence spectra of the Gd2O3:Er(3+) phosphor were investigated as a function of Er(3+) ion concentration. The upconverted emission at 980 nm excitation shows enhanced red emission with respect to green emission as the dopant concentration increased. Similar results were observed for downconversion emission under 275 and 380 nm excitation wavelengths. The mechanisms responsible for populating the (4)S3/2 and (4)F9/2 levels, for green and red emissions, respectively, are different for different excitations and for different concentrations of Er(3+).