Mechanism of cluster dissolution of Yb-doped high-silica lanthanum aluminosilicate glass: Investigation by spectroscopic and structural characterization

To investigate clusters of Yb ions and the effectiveness of lanthanum co-doping in dispersing and isolating Yb ions in silica glass, Yb-doped high-silica lanthanum aluminosilicate (LAS) glass with compositions Yb2O3-Al2O3-La2O3-SiO2 was prepared by the solegel method combined with high temperature sintering. The glass structure and spectroscopic properties of Yb-doped high-silica LAS glass were studied in detail to explore the mechanism of cluster dissolution. Al-27 and Si-29 solid-state nuclear magnetic resonance (SSNMR) spectra were introduced to study the spatial distribution of the Yb ions in the glass. The spinning sideband patterns of the Al-27 and Si-29 NMR spectra showed that part of the Yb3+ ions in the vicinity of aluminium atoms transferred to Si ions with increasing La2O3 concentration. The results of two-dimensional hyperfine sublevel correlation (2D-HYSCORE) electron paramagnetic resonance (EPR) spectroscopy led to the conclusion that the vicinity of Yb3+ ions are mostly aluminum atoms for glass doped with Al and aluminum and silicon atoms for glass co-doped with Al and La. It was also found that Yb clusters exist in the form of Yb-O-Yb bonds in high-concentration Yb-doped silica glass and that co-doping with La can replace these bonds with Yb-O-La linkages to reduce the number of Yb3+ pairs. The fluorescence intensity and fluorescence lifetime of Yb increase steadily with increasing La2O3 concentration, which also indicates that the addition of La in silica glass can dissolve the Yb clusters. The results show that co-doping high-silica LAS glasses with La3+ ions is an ideal way to increase Yb solubility and decrease clustering. (C) 2016 Elsevier B.V. All rights reserved.