Ex Situ XRD, TEM, IR, Raman and NMR Spectroscopy of Crystallization of Lithium Disilicate Glass at High Pressure

Abstract

The structure of Li2O · 2SiO2 (LS2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 °C, respectively, using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si-O-Si bond angle about 7° lower than that found in glass processed at 4.5 GPa. At 4.5 GPa, lithium disilicate crystallizes from the glass, while at 6 GPa new high pressure form of lithium metasilicate crystallizes. This new phase, while having lithium metasilicate crystal symmetry, contains at least four different Si sites. NMR results for 6 GPa indicate the presence of Q4 species with (Q4)Si-O-Si(Q4) bond angles of about 157°. This is the first reported occurrence of Q4 species with such large bond angles in alumina free alkali silicate glass. No five- or six-coordinated Si are found.

Department(s)

Materials Science and Engineering

Sponsor(s)

United States. National Aeronautics and Space Administration
National Science Foundation (U.S.)

Keywords and Phrases

FTIR Measurements; Raman Scattering; Crystals; Medium-Range Order; Nuclear Magnetic (And Quadrupole) Resonance; Pressure Effects; Short-Range Order; Silicates; X-Ray Diffraction

International Standard Serial Number (ISSN)

0022-3093; 1873-4812

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 Elsevier, All rights reserved.

Publication Date

01 Oct 2006

Link to Full Text

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