The Size Confinement Effect for Ln3+ (Ln = Tm or Eu) Concentration Quenching and Energy Transfer in Y2O3 Nanocrystals

Y2O3:Ln (Ln = Tm or Eu) nano-powders with different particle sizes and various doping concentrations were prepared by using a combustion method. The bulk powders doped with the same concentrations were obtained by annealing the nano-powders at high temperatures. Emission spectra of the phosphors were measured. The crystal structure and morphology of the phosphors were characterized by XRD (X-ray diffraction) and FE-SEM (field emission scanning electron microscopy), respectively. The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y2O3:Ln nanocrystal powders were investigated. It is found that the behavior of luminescent concentration quenching for Eu3+ D-5(0) -> F-7(2) in nano-powders is similar to that in bulk powders. On the contrary, the quenching concentration for Tm3+ D-1(2) -> H-3(4) is distinctly higher than that in bulk powders. This owes to the size confinement effect which will restrain the electric dipole dipole interaction as a long-rang interaction (e.g., energy transfer between Tm3+ ions), and will hardly affect the exchange interaction which is a short-rang interaction (e g., energy transfer between Eu3+ ions).