The preferential incorporation of Er3+ ions into the PbF 2 nanocrystals during the ceraming process of oxyfluoride glass was analyzed using electron energy loss spectroscopy analysis. Concentrations of Er3+ ions were considerably higher in PbF 2 nanocrystals compared to those in the glass matrix. Changes in lineshapes of absorption spectra from Er3+: I-4(15/2) -> I-4(13/2) transition and lifetimes of the excited-state Er3+ (S-4(3/2) level) ions also supported the incorporation of Er3+ ions into PbF 2 nanocrystals.