Size-dependent energy transfer and spontaneous radiative transition properties of Dy3+ ions in the GdVO4 phosphors

Bulk and nanosized GdVO4:Dy3+ phosphors were prepared via a simple co-precipitation process, and their crystal structure, morphology, and spectral properties were studied. It is found that electric dipole-dipole interaction was hindered in the nanosized samples based on the analysis of the dependence of luminescent intensity on the Dy3+ doping concentration. The decay time of the F-4(9/2) level in the nanosized GdVO4:2 mol% Dy3+ sample is determined to be longer than that in the 0.3 mol% Dy3+ doped bulk sample. Moreover, the fluorescent lifetime of this level in the nanosized sample is strongly dependent on the index of refraction of the medium surrounding the nanoparticles, and a 0.68 filling factor was obtained. The intrinsic radiative lifetimes and internal quantum efficiencies of the F-4(9/2) level of Dy3+ in the nanosized and bulk samples were obtained, which indicate that the internal quantum efficiency of nanosized sample is higher than that of the bulk sample, but the external quantum efficiency is lower.