Photoluminescent properties of Ln 2O 3:Eu 3+ (Ln = Y, Lu and Gd) prepared by hydrothermal process and sol–gel method

Abstract

Nanorods and microparticles Eu 3+-doped Ln 2O 3 (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 5D 0– 7F 2 transition (612 nm) under ultraviolet excitation. Compared with Eu 3+-doped Ln 2O 3 (Ln = Y, Lu and Gd) by the sol–gel method, the Ln 2O 3:Eu by the hydrothermal process showed smaller lattice constants, a little lower O 2−–Eu 3+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 Gd 2O 3:1%Eu < Y 2O 3:1%Eu < Lu 2O 3:1%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 Y 2O 3:Eu and Lu 2O 3:Eu obtained by the two different preparation methods mainly originated from the changes of their lattice constants.