Nanocrystalline europium doped yttria was synthesized using a chemical vapor technique. The powder was characterized by x-ray diffraction, transmission electron microscopy, and ultraviolet spectroscopy. For the first time it was possible to obtain single phase Y2O3:Eu nanoparticles crystallized in the cubic structure with an average particle size of only 10 nm. The reflection, excitation, and emission spectra were studied. The nanoparticles show blue shifted absorption bands with respect to coarse grained material.

The luminescence of nanocrystalline cubic yttria has been measured for 300 and 80 K. A blueshift and a broadening of the absorption edge, both depending on the particle size were found. The energy of the radiation emitted due to the recombination of a bound exciton does not depend on particle size. The observations are not caused by quantum or phonon confinement. Using a quantum mechanical configurational coordinate diagram an explanation can be given. Hydrostatic pressure increasing the phonon energy of the excited state of the bound exciton, or an increase of the exciton-phonon coupling may generate the size dependent optical properties of nanocrystalline yttria.

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