Free volume anomalies in mixed-cation glasses revealed by positron annihilation lifetime spectroscopy (PALS).
PALS experiments reveal a minimum in ortho-positronium (o-Ps) lifetimes and a maximum in the corresponding intensities that emerge when mixed-cation (Li/Na) borate glasses are heated from ambient temperatures up to 473 K. These free volume 'anomalies' appear to be a true manifestation of the mixed alkali effect (MAE). They are consistent with a mechanism of ion transport involving cooperation between hops of unlike cations, resulting in increased disturbance of the glass network. The result lends support to the dynamic structure model.
Ingram
Malcolm D
MD
Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, Scotland, UK AB24 3UE.
Pas
Steven J
SJ
Cramer
Cornelia
C
Gao
Yong
Y
Hill
Anita J
AJ
D001881:Borates / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D005898:Glass; D008672:Metals, Alkali / Q000737:chemistry; D013057:Spectrum Analysis; D013499:Surface Properties; D013696:Temperature
D001881:Borates; D002412:Cations; D008672:Metals, Alkali