Si-29 T-1 relaxation in alkali silicate glasses: a method for detecting glass-in-glass phase separation

High resolution nuclear magnetic resonance (NMR) has been used to measure r elaxation times, T-1, in alkali silicate glasses. Two-component relaxation was observed in lithium silicate glasses. In glasses close to the sodium di silicate composition, the relaxation was one component but, with decreasing sodium content, this becomes two component. In heat-treated sodium silicat e glasses two components appear to grow from the single component and the e xtent of growth depends upon the heal-treatment temperature and time. The r esults for all systems are explained in terms of phase separation and all i nsight into the Q " distribution is also presented. (C) 2001 Elsevier Scien ce B.V. All rights reserved.