Hydrothermal Synthesis, Cubic Structure, and Luminescence Properties of BaYF5:RE (RE = Eu, Ce, Tb) Nanocrystals

BaYF5 nanocrystals with a mean size of about 24 nm have been prepared via a facile hydrothermal method without the assistance of any surfactant for the first time. The structure investigation reveals that the as-synthesized BaYF5 nanocrystals are cubic structures instead of the reported tetragonal structures found via a Rietveld refinement method with GSAS, a Rietveld refinement package. The XRD and SEM analyses demonstrate that the size and morphology of the products are insensitive to the variation of experimental conditions. The photoluminescence properties of the Eu3+, Ce3+, and Tb3+ single-doped as well as Ce3+-Tb3+ codoped BaYF5 nanocrystals were characterized. The results reveal that the existence of the Ce3+ ions can dramatically enhance the emission intensity of the Tb(3+)ions, due to an efficient energy transfer from the Ce3+ to Tb3+ ions in the BaYF5:Ce3+,Tb3+ nanocrystals. The critical energy transfer distance between the Ce3+ and Tb3+ ions was calculated by methods of concentration quenching and spectral overlapping. Analysis and calculation reveal that the dipole-quadrupole interaction should be mainly responsible for the energy transfer and the accurate oscillator strength ratio of the electric quadrupole to dipole transitions for the Tb3+ ion is about 10(-3).