Structural role of Nd3+ and Al3+ cations in SiO2 glass : a 29Si MAS-NMR spin-lattice relaxation, 27Al NMR and EPR study

High field strength cations such as rare earth ions are known to show strong clustering when incorporated in minor quantities (hundreds to up to a few thousands of ppm) in highly polymerized silicate liquids and glasses. In this study, formation, distribution and growth of such clusters in Nd2O3-doped SiO2 glasses have been detected by monitoring the effect of changing Nd2O3 concentration on 29Si magic-angle spinning nuclear magnetic resonance (MAS-NMR) spin-lattice relaxation rates. The results indicate the presence of clusters of Nd ions even at the lowest doping level of 300 ppm of Nd2O3 by weight. Once the Nd2O3 concentration reaches 1400 ppm, no new clusters are found to form on further addition of Nd2O3 and only the growth of existing clusters is observed. These observations have significance for both dipolar resonant energy transfer among Nd ions and for fluorescence quenching. Electron paramagnetic resonance spectroscopy and 29Si MAS-NMR spin-lattice relaxation studies indicate that, on doping SiO2 glass with Al2O3, paramagnetic defect sites are created. 29Si relaxation results also show that, on co-doping the Nd2O3-doped glasses with Al2O3, a completely homogeneous distribution of the Nd ions is obtained at an Al:Nd atomic ratio of 10:1.

[1]  M. Monerie,et al.  Modeling of pair-induced quenching in erbium-doped silicate fibers , 1993 .

[2]  H. Carr,et al.  The Principles of Nuclear Magnetism , 1961 .

[3]  C. W. Ponader,et al.  Rare earth elements in silicate systems: I. Effects of composition on the coordination environments of La, Gd, and Yb , 1989 .

[4]  G. Waychunas,et al.  EXAFS study of the coordination environment of aluminum in a series of silica-rich glasses and selected minerals within the Na2OAl2O3SiO2 system , 1985 .

[5]  T. Yokoyama,et al.  Silica glass doped with Nd and Al prepared by sol-gel method. Change in the state of aluminium in the formation process , 1991 .

[6]  Eiichi Fukushima,et al.  Experimental pulse NMR : a nuts and bolts approach , 2018 .

[7]  David N. Payne,et al.  Local structures of rare-earth ions in glasses: the ‘crystal-chemistry’ approach , 1993 .

[8]  D. Freude,et al.  Multinuclear solid-state NMR studies of Brønsted sites in zeolites , 1993 .

[9]  Donald R Uhlmann,et al.  Glass--science and technology , 1980 .

[10]  J. Stebbins.  Effects of temperature and composition on silicate glass structure and dynamics: SI-29 NMR results , 1988 .

[11]  R. Denning.  Luminescence in Inorganic Solids , 1981 .

[12]  Ian M. Thomas,et al.  Optical properties and laser demonstrations of Nd-doped sol-gel silica glasses , 1992 .

[13]  É. Lippmaa,et al.  Structural studies of calcium aluminosilicate glasses by high resolution solid state 29Si and 27Al magic angle spinning nuclear magnetic resonance , 1985 .

[14]  K. L. Brower.  Structural and trapping characteristics of a new A1 defect in vitreous silica , 1978 .

[15]  Takashi Handa,et al.  Aluminum or phosphorus co‐doping effects on the fluorescence and structural properties of neodymium‐doped silica glass , 1986 .

[16]  M. Tomozawa,et al.  Phase separation in rare-earth-doped SiO2 glasses , 1993 .

[17]  P. Gaskell,et al.  Medium-range order in the cation distribution of a calcium silicate glass , 1991, Nature.

[18]  C. Dobson,et al.  Studies of rare-earth stannates by trin-119 MAS NMR. The use of paramagnetic shift probes in the solid state , 1989 .

[19]  A. Räuber,et al.  Motional effects in the trapped-hole center in smoky quartz , 1971 .

[20]  K. Kawamura,et al.  The structural groups of alkali silicate glasses determined from 29Si MAS-NMR , 1991 .

[21]  Sapoval,et al.  NMR determination of the fractal dimension in silica aerogels. , 1990, Physical review letters.