Research at the SMRL
Jonathan F. Stebbins
Professor and Department Chair
Department of Geological and Environmental Sciences
stebbins "at" stanford.edu
Allwardt, J.R., Stebbins, J.F., and Frost, D.J.. (accepted) "The effect of composition, compression, and decompression on the structure of high-pressure aluminosilicate glasses: An investigation utilizing 17O and 27Al NMR" In Chen, J., Q. Wang, Y., Duffy, T., Shen, G., and Dobrzhinetskaya, L., Eds. Frontiers in High Pressure Research: Geophysical Applications.
T. O. Sandland, L.-S. Du , J. Webster and J.F. Stebbins (in press) "Structure of Cl-Containing Silicate and Aluminosilicate Glasses: A 35Cl MAS NMR study" Geochim. Cosmochim. Acta.
L.-S. Du and J. F. Stebbins (2004) "Calcium and Strontium Hexaluminates: NMR Evidence that "Pentacoordinate" Cation Sites Are Four-Coordinated" J. Phys. Chem. B. 108, 3681-3685.
L.-S. Du, J.R. Allward, B.C. Schmidt and J.F. Stebbins (2004) "Pressure-Induced Structures Changes in a Borosilicate Glass-Forming Liquid: boron coordination, non-bridging oxygens, and network ordering" J. Non-Cryst. Solids 337, 196-200.
Allwardt, J.R., Stebbins, J.F., Frost, D.J., Schmidt, B.C. (2003) "The effect of modifier cations on the amount of five- and six-coordinated aluminum present in high-pressure aluminosilicate glasses" Bayerisches Forschunsintitut fur Experimentelle Geochemie und Geophysik, Universitat Bayreuth, Annual Report, 3.7i.
Allwardt, J.R., Stebbins, J.F., and Schmidt, B.C. (2003) "Structural mechanisms of compression and decompression in high-pressure K2Si4O9 glasses" Bayerisches Forschunsintitut fur Experimentelle Geochemie und Geophysik, Universitat Bayreuth, Annual Report, 3.7h.
Stebbins, J.F., Kojitani, H., Akaogi, M. and Navrotsky, A. (2003) "Aluminum substitution in MgSiO3 perovskite: Investigation of multiple mechanisms by 27Al NMR" Am. Mineral. 88, 1161-1164.
Lee, SK; Stebbins, JF; Weiss, CA; Kirkpatrick, RJ (2003) "17O and 27Al MAS and
3QMAS NMR study of synthetic and natural layer silicates" CHEMISTRY OF MATERIALS
Lee, SK; Stebbins, JF (2003) "The distribution of sodium ions in aluminosilicate glasses:
A high-field Na-23 MAS and 3Q MAS NMR study" GEOCHIMICA ET COSMOCHIMICA ACTA
Kroeker, S.K., Rice, D., and Stebbins, J.F. (2002) "Disordering during melting: An
17O NMR study of crystalline and glassy CaTiSiO5 (titanite)" Am.
Mineral. 87 572-579.
Stebbins, J.F., Du, L.-S., Kroeker, S., Neuhoff, P., Rice, D., Frye, J., Jakobsen,
H.J. (2002) "New opportunities for high-resolution solid-state NMR spectroscopy of
oxide materials at 21.1 and 18.8 Tesla fields" Sol. St. NMR
Stebbins, J.F. and Du, L.-S. (2002) "Chloride ion sites in silicate and aluminosilicate
glasses: a preliminary study by 35Cl solid-state NMR" Am.
Mineral. 87 359-363.
Kroeker, S. and Stebbins, J.F. (2001) "Three-coordinated boron-11 chemical shifts
in borates" Inorg. Chem. 40 6239-6246.
Kroeker, S., Neuhoff, P.S. and Stebbins, J.F. (2001) "Enhanced resolution and
quantitation from "ultrahigh" field NMR spectroscopy of glasses" J.
Non-Cryst. Solids 293-295 440-445.
Stebbins, J.F., Oglesby, J.V., and Kroeker, S. (2001) "Oxygen triclusters
in crystalline CaAl4O7 (grossite) and calcium aluminosilicate glasses: 17O
NMR" Am. Mineral. 86, 1307-1311.
Stebbins, J.F., Kroeker, S. and Andrault, D. (2001) "The mechanism of solution
of aluminum oxide in MgSiO3 perovskite" Geophys. Res.
Lett. 28, 615-618.
Stebbins, J.F., Kroeker, S., Lee, S.K. and Kiczenski, T.J. (2000) "Quantification
of five- and six-coordinated aluminum in aluminosilicate and fluoride-containing
glasses by high-field, high-resolution 27Al NMR" J. Non-Cryst. Solids
Enhanced resolution and quantitation from "ultrahigh" field NMR spectroscopy
Kroeker, S., Neuhoff, P.S. and Stebbins, J.F. (2000) " J. Non-Cryst.
Solids 293-295 440-445.
The utilization of higher magnetic fields for nuclear magnetic resonance
(NMR) (e.g., 14.1 and 18.8 T) can enhance both resolution and sensitivity
in studies of disordered materials. When used in conjunction with fast magic
angle spinning (MAS), high-field NMR can yield structural information not
always available from NMR experiments of glasses at lower fields. Examples
include site distinction of multiple boron groupings in 11B MAS
NMR spectra of borate glasses, the spectroscopic observation of low concentrations
of five- and six-co-ordinate aluminum species in 27Al MAS NMR spectra
of aluminosilicate glasses, and new insight into magnesium co-ordination environments
in silicate glasses using 25Mg MAS NMR. Also presented are
17O MAS NMR spectra of a zeolite in which high-field experiments
permit resolution and quantification of bound molecular water. Comparisons
of spectral data collected at 18.8 T with those at lower fields demonstrate
these principles and indicate the potential of high-field MAS NMR applications
to amorphous solids.
Figure Caption. Magnesium-25 MAS NMR spectra of (a) CaMgSi2O6 and (b)
K2MgSi5O12 glasses at 14.1 and 18.8 T.
Figure Caption. Oxygen-17 MAS NMR spectra of analcime acquired at 9.4, 14.1 and 18.8 T.
Expansions of the vertical scale by the indicated factors highlight
low-intensity features. Dashed lines point out corresponding lineshape singularities
for the water signal. Spinning sidebands are denoted by dots.
Quantification of five- and six-coordinated aluminum in aluminosilicate and
fluoride-containing glasses by high-field, high-resolution 27Al NMR
Stebbins, J.F., Kroeker, S., Lee, S.K. and Kiczenski, T.J. (2000) J. Noncryst. Solids
Aluminum cation sites with five (Al) or six ( Al) anion neighbors are
minor species in aluminosilicate glasses that are interesting in models of structure,
diffusion, and viscous flow. Using 27Al NMR, we present the first direct evidence
for Al in a calcium-aluminosilicate glass without excess aluminum over
charge-balancing cations, and quantify small concentrations of both
Al and Al in several fluoride-containing aluminosilicate glasses. NMR
techniques that enhance resolution by decreasing the effects of second-order quadrupolar broadening,
including triple-quantum magic-angle spinning (3QMAS), analysis of spinning sidebands, and data
collection at very high external magnetic fields (14.1 and 18.8 T), are particularly
effective in accurately observing such species.
Figure Caption. 27Al MAS spectra of glass sample An + F at the external magnetic
fields shown. Vertical scales (not shown) represent the intensity in arbitrary
units, normalized to the maximum peak height in each spectrum.
Figure Caption. 27Al MAS spectra at 18.8 T for glasses as labeled. Vertical scale
expansions of 4 or 8 times are shown for each.