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 excit ation energy of activation centers in Y2SiO5 : Pr3+, Lu2SiO5 : Pr3+, and Gd 2SiO5 : Pr3+ was performed. An analysis of the low-temperature optical spec tra showed that the energy parameters and the character of field splitting of the D-1(2) and H-3(4) activator ion terms were substantially different i n crystals of different crystallographic types. The pseudosymmetry effect w as observed in splitting of the D-1(2) and H-3(4) terms of Pr3+ ions situat ed in nonequivalent crystal lattice cation sites of Y2SiO5 and Lu2SiO5 . Ac tivator ions nonuniformly populated nonequivalent cation sites of the Y2SiO 5 crystal lattice. At high activator ion concentrations (>1 at. %), lumines cence decay in Y2SiO5 could not be described by a simple exponential time d ependence. The complex luminescence decay law was caused by activator ion e xcitation energy migration and capture by acceptors. The role of energy acc eptors was played by activator ion dimers. (C) 2001 MAIK "Nauka/Interperiod ica".