Variation of Fluorescence Lifetimes and Judd-Ofelt Parameters between Eu³⁺ Doped Bulk and Nanocrystalline Cubic Lu₂O₃

The luminescent properties of 1 mol % Eu 3+ -doped cubic Lu 2 O 3 nanocrystals prepared by a combustion synthesis route were investigated. The visible emission spectrum of the europium doped Lu 2 O 3 nanocrystals indicate that the structural environment surrounding the dopant Eu 3+ ion is distorted when compared to a bulk sample with a micrometer particle size. From the resulting emission spectra, the Ω 2 and Ω 4 Judd-Ofelt intensity parameters were calculated. The lifetimes of the 5 D 0 excited state for both the C 2 and C 3i sites were found to be nearly double that found for a similarly doped sample with larger particle size (bulk sample). This behavior is attributed to a change in the refractive index of the nanocrystalline material that in turn modifies the oscillator strength of the 4f ↔ 4f transitions.