Size-dependent excitation spectra and energy transfer in Tb3+-doped Y2O3 nanocrystalline

Nanocrystal Y2O3 powders with different grain sizes and various doping concentrations of Tb3+ were prepared by an autocombustion reaction. The size and surface effects on the 4f-5d transitions and energy transfers between Tb3+ ions were studied by using x-ray diffraction, transmission electron microscopy, fluorescent spectra, and luminescent decay. It was found that the excitation spectra are composed of two parts: one is the contribution from the Tb3+ at/near the nanoparticle surfaces; another is from the Tb3+ inside the nanoparticles. The study on the concentration quenching and luminescent decay indicated that the energy transfers depopulating the D-5(3) and D-5(4) level were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively. The size confinement greatly affects the energy transfer quenching the emission from the D-5(3) level, but slightly affects the energy transfer quenching the emission from the D-5(4) level. (C) 2007 American Institute of Physics.