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.
Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, Scotland, UK AB24 3UE.
Malcolm D
MD
Ingram
Steven J
SJ
Pas
Cornelia
C
Cramer
Yong
Y
Gao
Anita J
AJ
Hill
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