Size-dependent electronic transition rates in cubic nanocrystalline europium doped yttria

In cubic nanocrystalline as well as polycrystalline Y2O3:Eu3+ prepared by combustion, the radiative transition rate of 5D1–7F1 and the nonradiative relaxation rate of 5D1–5D0 were obtained by measuring the temperature-dependence of emission intensity and lifetime. The results indicate that the radiative and nonradiative rates both increase with decreasing particle size. The increase of radiative transition rate was attributed to the lower symmetry surrounding the Eu3+ ions, while the increase of nonradiative relaxation rate to the additional nonradiative relaxation channels caused by surface defects.