Stebbins Group Research


Jonathan F. Stebbins

Professor and Department Chair
Department of Geological and Earth Sciences

(650) 723-1140
stebbins@pangea.stanford.edu

Group Home Page



Publications:

Stebbins, J.F., Kroeker, S. and Andrault, D. (2000) "The mechanism of solution of aluminum oxide in mantle perovskite (MgSiO3)" Geophys. Res. Lett. (submitted 8/29/00).

Kroeker, S., Neuhoff, P.S. and Stebbins, J.F. (2000) "Enhanced resolution and quantitation from "ultrahigh" field NMR spectroscopy of glasses" J. Noncryst. Solids (submitted 7/18/00).

(Details Below) 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. Noncryst. Solids 275, 1-6. PDF


Presentations:

(Upcoming:) American Geophysical Union 2000 Fall Meeting, San Francisco, California, December 15-19, 2000.

2000 Varian Worldwide Users Conference, Stanford, California, April 6-8, 2000.

42nd Rocky Mountain Conference on Analytical Chemistry, Broomfield, Colorado, U. S. A., July 30-August 1, 2000.

8th International Conference on the Structure of Non-Crystalline Materials, Aberystwyth, Wales, U. K., August 6-11, 2000.

Glass and Optical Materials Division Meeting of the American Ceramic Society, Corning, New York, October 1-4, 2000.


Details:

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 275, 1-6. PDF

Abstract:
Aluminum cation sites with five ([5]Al) or six ([6] 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 [5]Al in a calcium-aluminosilicate glass without excess aluminum over charge-balancing cations, and quantify small concentrations of both [5]Al and [6]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.

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. 27Al MAS spectra at 18.8 T for glasses as labeled. Vertical scale expansions of 4 or 8 times are shown for each.