Intra- and inter-configurational luminescence spectroscopy of Pr3+ -doped YPO4 nanophosphors

Nanopowders of YPO4 phosphors with different Pr3+doping were successfully prepared by a sol gel method under different synthesis conditions. The crystallite size and strain show a strong dependence on the Pr3+ doping concentration and on the annealing temperature. By annealing at 300 °C one can obtain the xenotime structure of the pure YPO4. The crystallite size can be controlled by controlling the annealing temperature and it increases with increasing the annealing temperature. The room temperature inter-configurational 4f2 ↔ 4f5d and intra-configurational 4f2↔ 4f2 emission-excitation transitions spectra are measured and investigated. Upon 4f2 → 4f5d excitation transition, all the samples present broad intense emission bands attributed to 4f5d → 4f2 emission transitions and peaks in red region assigned to 1D2→3H4 transition as photon cascade emission phenomena (PCE). The presence of only 1D2→3H4 transition is discussed. In addition, the 1D2 energy level lifetimes as well as the refractive indexes were determined and discussed.