Structure and ac conductivity of K-for-Na ion-exchanged sodium borate glasses

Abstract

This work addresses structural and ionic transport properties of ion-exchanged borate glasses at temperatures below the glass transition, T g . Analysis of the infrared reflectance spectra of the K-for-Na ion-exchanged glass 0.3Na 2 O-0.7B 2 O 3 revealed short-range order structural changes, pointing towards the occurrence of alkali ion-induced sub-T g structural relaxations of the borate structure leading to the establishment of suitable sites for the guest K ions. The conductivity spectra of the ion-exchanged glasses are dominated by two distinct dc responses before the dispersive regime. The low-frequency response is due to the development of a highly resistive ion-exchange layer where K and Na ions coexist, whereas the dynamics of Na ions in the core of the glass determine the high-frequency response. The structure and dynamics of the ion-exchange layer were shown to resemble those of the melt-quenched mixed K-Na borate glasses.