In this paper

spectral difference between nanocrystalline yttria doped with europium (Y

2

O

3

:Eu

3+

) and the bulk ones was reported. Besides a 580.6nm line similar to that in the bulk Y

2

O

3

:Eu

3+

a new broad excitation line at 579.9nm was observed in the excitation spectra of nanocrystals (NCs). The 579.9nm peak relative to the 580.6nm one decreases a little as temperature increases. The fluorescent lifetime excited by 579.9nm line became slightly shorter than that of the 580.6nm line. We suggest that in nanocrystalline Y

2

O

3

:Eu

3+

the broader 579.9nm excitation peak originates from the luminescence of Eu

3+

ions near the surface

and the 580.6nm one from the internal Eu

3+

ions. The surface to volume ratio is quite small (1%) in the micrometer particles

while it increases significantly as the particle size decreases to several nanometers. This will lead the surface effects to be effective. As well known

the energies of electrons in 4f states of rare earth ions are affected by the crystal field. In nanocrystals

rare earth ions near the particle surface are at the sites microscopically inequivalent with those close to the center. Their energy levels may shift

and the degenerated spectral lines in the bulk sample may split. Due to the appearance of numerous surface defects the crystal field in the surface of nanoparticles degenerates and the emission of 5D

o

7

Fj

shifts. Because the local environments surrounding Eu

3+

ions near the surface are more disordered and surface defects may act as nonradiative transition channels

the width of the 579.9nm line is broader and the fluorescent lifetime becomes shorter.