Nano-powders Y₂O₃ with various particle sizes and different doping concentrations of Ln(Ln=Tb,Tm,Eu) were prepared by using a combustion technique.The bulky powders doped with concentrations corresponding to nano-powders were obtained by annealing the nano-powders at high temperature.The emission spectra,XRD spectra and TEM were used in the present study.The concentration quenching of luminescent centers and energy transfer between luminescent centers in Y₂O₃:Ln nanocrystal powders were investigated.It was found that the behaviors of luminescence concentration quenching for 5D 4→ 7F 5:Tb³⁺ and 5D 0→ 7F 2:Eu³⁺ in nano-powders are similar to that in bulky powders.On the contrary,the quenching concentrations for 5D 3→ 7F 5:Tb³⁺ and 1D 2→ 3H 4:Tm3+ are distinctly higher than that in bulk powders.This owes to the size confinement effect:the interface of nanocrystal particles can stop a portion of the energy transfer,which happens in the bulk ones,between luminescent centers.The size confinement effect can bring different influences to the different types of energy transfer.For instance,it will restrain the energy transfer (governed by electric dipole-dipole interaction) between the ions in long distances,and will hardly affect the energy transfer (governed by exchange interaction) between the ions locating at near intervals.