Photoluminescent properties of Ln2O3:Eu3+ (Ln = Y, Lu and Gd) prepared by hydrothermal process and sol–gel method

Nanorods and microparticles Eu3+-doped Ln2O3 (Ln = Y, Lu and Gd) have been successfully prepared through a hydrothermal method followed by a subsequent calcinations process and the sol–gel technology, respectively. The samples were systematically characterized by powder X-ray diffraction (XRD), field emission-scanning microscopy (FE-SEM), and photoluminescent spectra (PL). They all showed a strong red emission corresponding to 5D0–7F2 transition (612 nm) under ultraviolet excitation. Compared with Eu3+-doped Ln2O3 (Ln = Y, Lu and Gd) by the sol–gel method, the Ln2O3:Eu by the hydrothermal process showed smaller lattice constants, a little lower O2−–Eu3+charge transfer (CT) energy and weaker photoluminescent emission intensity. For all of the samples prepared through any one of the two methods, the CT energy increased in the sequence Gd2O3:1%Eu < Y2O3:1%Eu < Lu2O3:1%Eu. The CT energies for the samples have been further investigated from the chemical bond viewpoint. The calculated results show that the shifts of the charge transfer bands for the Y2O3:Eu and Lu2O3:Eu obtained by the two different preparation methods mainly originated from the changes of their lattice constants.