Experimental and theoretical analysis on the charge transfer band of Y2O3:Eu nanocrystals

Nanocrystalline cubic Y2O3:Eu were prepared by combustion reaction. The crystal structure and morphology were analyzed by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The luminescent properties of the powder were investigated. The charge transfer band position showed redshift from 241 to 251 nm, which was related to the change of the local surroundings of Eu3+ ions in nanocrystalline Y2O3:Eu. The ground-state electronic structure and charge transfer transition of both the bulk and nanocrystalline cubic Y2O3:Eu crystals were calculated by the ab initio self-consistent relativistic DV-Xα (discrete variational Xα) method. A complete 35-ion cluster was selected to simulate the local coordination surroundings of Eu doped in Y2O3 bulk crystals while five additional incomplete clusters were also selected to simulate the local surroundings of Eu ions in nanocrystals. It could be found that the charge transfer energies of the nanocrystalline Y2O3:Eu were less than that of the bulk counterpart, which was consistent with the redshift phenomenon of the CT band in the excitation spectrum of the nanocrystalline Y2O3:Eu.