The Pr3+ spectra of Czochralski-type crystals were investigated by using absorption, site-selective excitation and emission and fluorescence decay methods, and were shown to have a complex structure. As well as the spectra which were attributed to Pr3+ in dodecahedral c-sites (D2 local symmetry), the effect of Pr3+ in other sites was also significant. An attempt was made to link the most intense lines to structural defects. Thus, 3 of the most intense satellite lines were attributed to a Pr3+(c) ion that was perturbed by a nearby non-stoichiometric defect (Gd3+ in octahedral a-sites) whose concentration was estimated to be about 7%. The spectra of perturbed Pr3+ centers exhibited additional lines which were associated with a reduction in local symmetry. Two other lines were attributed to Pr3+(c)-Pr3+(c) pairs. The 3P0 emission decays were almost exponential, with similar lifetimes, except for one which exhibited very strong quenching. This line was attributed to strongly coupled Pr3+(c)-Pr3+(c) nearest-neighbor pairs.

A.Lupei, H.Gross, P.Reiche: Journal of Physics - Condensed Matter, 1995, 7[28], 5701-12