Pairs and nonequivalent Pr3+ sites in GGG

摘要

Abstract: Spectral data on Pr$+3$PLU$/ ion in Czochralski grown GGG Gd$-3$/Ga$-5$/O$-12$/) crystals are analyzed. Pr$+3$PLU$/ spectra, investigated by high resolution absorption, site selective excitation and emission contain besides the main lines assigned to Pr$+3$PLU$/ in dodecahedral c-sites, at least four other types of non-equivalent centers. Three satellites have been assigned to Pr$+3$PLU$/ in dodecahedral c-sites perturbed by a non-stoichiometric defect, Gd$+3$PLU$/ in octahedral sites, whose concentration was estimated from absorption. A reduction of local symmetry is observed from the spectra. It is connected with X-ray measurements that show forbidden $LFBC@222$RTBC reflections in cubic ideal garnets, but with similar small intensities. Other lines are assigned to Pr$+3$PLU$/(c)- Pr$+3$PLU$/(c) near pairs, one of them showing a very strong quenching of $+3$/P$-0$/ emission. Some of the mechanisms of $+3$/P$-0$/ emission quenching and their influence on quantum efficiency are discussed.!16