The nature of activation centers in Y2SiO5:Pr3+, Gd2SiO5:Pr3+, and Lu2SiO5:Pr3+ crystals

A complex study of the energy spectra and relaxation channels for the excitation energy of activation centers in Y2SiO5:Pr3+, Lu2SiO5:Pr3+, and Gd2SiO5:Pr3+ was performed. An analysis of the low-temperature optical spectra showed that the energy parameters and the character of field splitting of the 1D2 and 3H4 activator ion terms were substantially different in crystals of different crystallographic types. The pseudosymmetry effect was observed in splitting of the 1D2 and 3H4 terms of Pr3+ ions situated in nonequivalent crystal lattice cation sites of Y2SiO5 and Lu2SiO5. Activator ions nonuniformly populated nonequivalent cation sites of the Y2SiO5 crystal lattice. At high activator ion concentrations (>1 at %), luminescence decay in Y2SiO5 could not be described by a simple exponential time dependence. The complex luminescence decay law was caused by activator ion excitation energy migration and capture by acceptors. The role of energy acceptors was played by activator ion dimers.