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Insights on ion and polaron dynamics in phosphate glasses from model-free conductivity scaling

A deep understanding of electrical transport in mixed conductive glasses is necessary for the development of these materials as cathodes in battery technologies. In this study, we report on the dynamics of polarons and ions in six glass series of composition WO3/MoO3-Li2O/Na2O/Ag2O-ZnO-P2O5 by examining their frequency-dependent conductivity using simple model-free scaling procedures proposed by Summerfield and Sidebottom. The validity of Sidebottom scaling for each glass confirms that the time-temperature superposition principle is satisfied implying that the basic conduction mechanism for individual glass does not change with temperature. However, Summerfield scaling is not valid for all glasses. Deviation observed for purely ionic Li2O glass and mixed Li2O-WO3/MoO3 glasses where Li+ conductivity dominates, originates from the specific interaction of Li+ ions with the local glass network. In addition, the deviation is also observed for particular WO3-based glasses in which the contribution of ionic conductivityis comparable to polaronic one. The cause of this phenomenon lies in the significant amount of both types of charge carriers and their different thermally activated mobility. We show how very fine differences in conductivity spectra, deduced solely from the experimental data, contain valuable insights into the dynamics of mixed ionpolaron transport.

conductivity ; phopshate glass ; ion-polaron ; model-free scaling

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