Effect of concentration on the luminescence of Eu3+ ions in nanocrystalline La2O3

Nanocrystalline powders with various Eu3+ concentration (from 1 to 10 mol %) doped La2O3 were prepared via a combustion route. Their structure and morphology were characterized using X-ray diffraction (XRD) and High-resolution transmission electron microscopy. The emission spectra of the as-synthesized samples show that the strongest emission position is centered at 626 nm corresponding to 5D0→7F2 transition of Eu3+ ions and the intensity change of 626 nm emission is considered as a function of ultraviolet (240 nm) irradiation time. The excitation spectra at 626 nm monitoring indicate that the charge transfer state band is varies with different Eu3+ ion concentration. These results are attributed to the surface defects of the nanocrystals.