Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (18) Citing Articles via Google Scholar Google Scholar Articles by Dubinsky, E. V. Articles by Stebbins, J. F. Search for Related Content GeoRef GeoRef Citation

Quench rate and temperature effects on framework ordering in aluminosilicate melts

Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115, U.S.A.

Correspondence: ^* E-mail: evd{at}pangea.stanford.edu

The effect of temperature on the structure of LiAlSiO₄ and NaAlSiO₄ liquids has been studied by ¹⁷O 3QMAS NMR spectroscopy using glass samples prepared with different fictive temperatures. The abundance of Al-O-Al and Si-O-Si bridging O linkages increases with increasing fictive temperature, indicating that the reaction 2 Al-O-Si Al-O-Al + Si-O-Si shifts to the right with increasing temperature in the liquid. The observed temperature dependence of Al-O-Al species abundance allows us to estimate the H of this reaction to be 28.8 ± 11.3 kJ/mol for NaAlSiO₄ glasses and 31.7 ± 13.3 kJ/mol for LiAlSiO₄ glasses. Extrapolating our results to higher temperature, we estimate that 13–18% of the bridging O atoms occur as Al-O-Al in NaAlSiO₄ and 15–25% in LiAlSiO₄ at ~2000 K, as compared to 25% Al-O-Al predicted by a statistically random bridging O distribution in compositions with an Al/Si ratio of 1. Using the experimental data to estimate the contribution to configurational heat capacity from Al/Si disordering in NaAlSiO₄ liquid, we find that redistribution of bridging O species with increasing temperature produces a negative dC_P/dT above the glass transition and therefore cannot account for the observed positive dC_P/dT. We discuss a generalized mechanism for structural rearrangement characterized by a small initial species concentration at T_g and a large H, which produces a positive dC_P/dT.

Key Words: NMR spectroscopy • ¹⁷O 3QMAS NMR • alkali aluminosilicate glasses, melts • melt structure • enthalpy • configurational heat capacity • framework cation • order-disorder • Al/Si • bridging oxygen • non-bridging oxygen • network former • termperature effect • fictive temperature • quench rate

This article has been cited by other articles:

				K. E. Kelsey, J. F. Stebbins, J. L. Mosenfelder, and P. D. Asimow Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses American Mineralogist, August 1, 2009; 94(8-9): 1205 - 1215. [Abstract] [Full Text] [PDF]

				K. E. Kelsey, J. F. Stebbins, L.-S. Du, J. L. Mosenfelder, P. D. Asimow, and C. A. Geiger Cation order/disorder behavior and crystal chemistry of pyrope-grossular garnets: An 17O 3QMAS and 27Al MAS NMR spectroscopic study American Mineralogist, January 1, 2008; 93(1): 134 - 143. [Abstract] [Full Text] [PDF]

				G. Calas, G. S. Henderson, and J. F. Stebbins Glasses and Melts: Linking Geochemistry and Materials Science Elements, October 1, 2006; 2(5): 265 - 268. [Abstract] [Full Text] [PDF]

				G. S. Henderson, G. Calas, and J. F. Stebbins The Structure of Silicate Glasses and Melts Elements, October 1, 2006; 2(5): 269 - 273. [Abstract] [Full Text] [PDF]