Optical spectroscopy of nanocrystalline cubic Y2O3 : Er3+ obtained by combustion synthesis

We report the emission and upconversion spectra and the lifetimes of Er3+ doped Y2O3 nanocrystalline and bulk samples. We found that when the nanocrystal and bulk samples of Y1.80Er0.20O3 were excited at 815 nm, the overall emission intensity was stronger for the bulk sample. However, the relative intensity of the (H-2(11/2), S-4(3/2))-->I-4(15/2)/F-4(9/2)-->I-4(15/2) transitions is 2:3 and 3:2 for the nanocrystal and bulk sample, respectively. The decay times obtained for the nanocrystalline samples are in general significantly faster than those observed for the bulk sample. We attribute this to the adsorption of CO2 on the surface of the nanocrystalline samples. The effect of Er3+ concentration on the decay time of the nanocrystalline samples is also discussed.