Ex situ XRD, TEM, IR, Raman and NMR spectroscopy of crystallization of lithium disilicate glass at high pressure

摘要

The structure of Li2O center dot 2SiO(2) (LS2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 degrees C) respectively, using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si-O-Si bond angle similar to 7 degrees 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 Q(4) species with (Q(4))Si-O-Si(Q(4)) bond angles of similar to 157 degrees. This is the first reported occurrence of Q(4) species with such large bond angles in alumina free alkali silicate glass. No five- or six-coordinated Si are found. (c) 2006 Elsevier B.V. All rights reserved.