title: Examination of the mixed-alkali effect in (Li,Na) disilicate glasses by nuclear magnetic resonance and conductivity measurements.
abstract: 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.
authors: Chemical Laboratory, University of Kent, Canterbury, UK.
authors: F
authors: F
authors: Ali
authors: A V
authors: AV
authors: Chadwick
authors: G N
authors: GN
authors: Greaves
authors: M C
authors: MC
authors: Jermy
authors: K L
authors: KL
authors: Ngai
authors: M E
authors: ME
authors: Smith
mesh_terms: D004553:Electric Conductivity; D005898:Glass / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy