A XANES investigation of the network-modifier cations environment before and after the Na+/K+ ion-exchange in silicate glasses
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μ-XANES is used to study the modifications in the alkali and alkaline-earth environments induced by the Na +/K + ion-exchange process in various Na –silicate glasses. The results indicate that the ion-exchange process induces a shortening of the Na–O, Ca–O and Mg–O bond distances. The contraction of the Na–O, Ca–O and Mg–O coordination shell allows a better accommodation of the K + cations in the glass network and thereby leads to partial relaxation of the stress developed by the Na +/K + ion-exchange. Nevertheless, despite the stress relaxation process, the K + environment in the ion-exchanged glass is not equivalent to the one in Na,K–silicate as-melted glasses. Hence, this study clearly shows that the ion swapping forced K + cations to occupy smaller sites which are not achievable via the melt quench route for glasses with the same K amount.