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

• Published in: Solid state nuclear magnetic resonance Vol. 5; no. 1; pp. 133 - 143
• Main Authors: Ali, F., Chadwick, A.V., Greaves, G.N., Jermy, M.C., Ngai, K.L., Smith, M.E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 01-10-1995
• Subjects: 23Na nuclear magnetic resonance; 29Si nuclear magnetic resonance; 7Li nuclear magnetic resonance; Alkali disilicates; Electric Conductivity; Electrical conductivity; Glass - chemistry; Glasses; Magic-angle spinning; Magnetic Resonance Spectroscopy; Mixed-alkali effect; Electrical conductivity; 23Na nuclear magnetic resonance; Magic-angle spinning; Alkali disilicates; Glasses; 7Li nuclear magnetic resonance; Mixed-alkali effect; 29Si nuclear magnetic resonance
• ISSN: 0926-2040; 1527-3326
• DOI: 10.1016/0926-2040(95)00033-M

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)
· Na
x
]
2O · 2SiO
2 (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.