A Caltech Library Service

Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses

Kelsey, Kimberly E. and Stebbins, Jonathan F. and Mosenfelder, Jed L. and Asimow, Paul D. (2009) Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses. American Mineralogist, 94 (8-9). pp. 1205-1215. ISSN 0003-004X.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present the first direct observation of high-coordinated Si and Al occurring together in a series of high-pressure sodium aluminosilicate glasses, quenched from melts at 6 GPa. Using ^(29)Si MAS NMR, we observe that a small amount of Al does not have a significant effect on the amount of ^VSi or ^(VI)Si generated, but that larger Al concentrations lead to a gradual decrease in both these species. ^(27)Al MAS NMR spectra show that samples with small amounts of Al have extremely high mean Al coordination values of up to 5.49, but that larger Al concentrations cause a gradual decrease in both ^VAl and ^(VI)Al. Although mean Al and Si coordination numbers both decrease with increasing Al contents, the weighted combined (Al+Si) coordination number increases. Silicon and Al resonances shift in frequency with increasing pressure or changing Al concentration, indicating additional structural changes, including compression of network bond angles. Increases in the ^(23)Na isotropic chemical shifts indicate decreases in the mean Na-O bond lengths with increasing pressure, which are more dramatic at higher Al contents. Recovered glass densities are about 10 to 15% greater than those of similar ambient pressure samples. However, the density increases due to the combined coordination changes of Al and Si are estimated to total only about 1 to 2%, and are roughly constant with composition despite the large effects of Al content on the individual coordinations of the two cations. Thus, effects of other structural changes must be significant to the overall densification. Apparent equilibrium constants for reactions involving the generation of high-coordinated species show systematic behavior, which suggests an internal consistency to the observed Si and Al coordination number shifts.

Item Type:Article
Related URLs:
URLURL TypeDescription
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2009 Mineralogical Society of America. Manuscript received December 19, 2008. Manuscript accepted April 24, 2009. We are grateful to Bob Jones for microprobe analyses, to NSF for funding under grants numbered EAR-0408410 (support for Kelsey and Stebbins) and OCE-0550216 (support for Mosenfelder and Asimow), and to J. Puglisi and C. Liu for access to the 18.8 T NMR spectrometer at the Stanford Magnetic Resonance Laboratory.
Funding AgencyGrant Number
Subject Keywords:NMR; aluminosilicate; glass; high pressure; coordination; aluminum; silicon; sodium
Issue or Number:8-9
Record Number:CaltechAUTHORS:20090908-083706628
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15661
Deposited By: George Porter
Deposited On:14 Sep 2009 20:51
Last Modified:03 Oct 2019 01:01

Repository Staff Only: item control page