Examination of the mixed-alkali effect in (Li,Na) disilicate glasses by nuclear magnetic resonance and conductivity measurements

✍ Scribed by F. Ali; A.V. Chadwick; G.N. Greaves; M.C. Jermy; K.L. Ngai; M.E. Smith

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 998 KB
• Volume: 5
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1016/0926-2040(95)00033-m

✦ Synopsis

Results from 29Si, 23Na and 7Li magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy, 7Li NMR relaxation and electrical conductivity in a series of [Li(1-x).Nax]2O.2SiO2 (disilicate) glasses are used to investigate the mixed-alkali effect. From the 29Si NMR spectra there is relatively little change of the network with alkali composition. 23Na and 7Li NMR linewidths and shifts change continuously as a function of composition, indicating that the alkali ions are intimately and uniformly mixed rather than separated into lithium and sodium-rich domains. The activation energy from electrical conductivity shows a distinct maximum at the central composition (x = 0.5), whereas the local activation energy for lithium motion determined from NMR shows only a smaller but monotonic increase as the lithium-content decreases.