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Updated: Jun 20, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Free volume anomalies in mixed-cation glasses revealed by positron annihilation lifetime spectroscopy (PALS)
Malcolm D Ingram1, Steven J Pas, Cornelia Cramer
1Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, Scotland, UK AB24 3UE.
Abstract:
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.
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