Luminescence of bulk and nanocrystalline cubic yttria

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.