Eu3+ and Yb3+ codoped Gd2O3 single phase nanophosphor: An enhanced monochromatic red emission through cooperative upconversion and downconversion

Single phase cubic Gd2O3 nanophosphor codoped with Eu3+ and Yb3+ ions has been synthesized through solution combustion route. Structural properties have been investigated using x-ray diffraction (XRD) and transmission electron microscopy (TEM). The as-synthesized Gd2O3 phosphor shows amorphous nature which changes to crystalline single cubic phase on annealing. Optical properties have been investigated through absorption, photoluminescence, and lifetime measurements. Intense red emission (D-5(0)-> F-7(2)) is observed both from cooperative upconversion (Yb3++Yb3+-> Eu3+ on 976 nm excitation) as well as through downconversion process (on 355 nm excitation). The unusual and rarely reported emissions from the higher lying D-5(J) (J=2, 3, and 4) to F-7(J) (J=0, 1, 2, 3, and 4) levels are also observed with 976 nm excitation. Nearly twenty two times enhancement in the intensity of the hypersensitive transition (D-5(0)-> F-7(2)) along with an increase in the decay time (770 mu s) is observed for the sample annealed at 1200 degrees C on 355 nm excitation. These observations have been explained satisfactorily. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3373628]