Network former mixing effects in alkali germanotellurite glasses: A vibrational spectroscopic study

Alkali germanotellurite glasses of composition 0.3M2O-0.7[(1-x)GeO2-xTeO2], M=Li, Na and 0≤x≤1, were investigated by Raman and infrared vibrational spectroscopic techniques to search for the origins of the alkali ion-dependent network former mixing (NFM) effect in these ion-conducting glasses. The vibrational spectra measured on mixed network-former glasses, and the spectral comparison between equimolar-mixed glasses (x=0.5) and pellet-mixtures of the endmember glasses, 0.3M2O-0.7GeO2 and 0.3M2O-0.7TeO2, provided evidence for the formation of hetero-atomic Ge-O-Te linkages and structural rearrangements in the germanate and tellurite components of glass. The mixing-induced structural rearrangements were expressed in terms of chemical equilibria between the network-building units and were used to make qualitative predictions for changes in the network cross-linking density and the related network-strain energy, as well as in the binding energy part of the activation energy for ion conduction. Thus, it is proposed that the mixing-induced structural modifications in the germanate and tellurite parts of glass cause the cancelation of changes in the binding energy and the network-strain energy contributions to the activation energy for ion transport. These qualitative predictions were discussed in the context of the previously found absence of an NFM effect for M=Na and the presence of a weak positive NFM effect for M=Li.

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Recommended citation: N.S. Tagiara, K.I. Chatzipanagis, Henrik Bradtmüller, A.C.M. Rodrigues, D. Möncke, E.I. Kamitsos, “Network Former Mixing Effects in Alkali Germanotellurite Glasses: A Vibrational Spectroscopic Study ”, Journal of Alloys and Compounds, 2021, 882, 160782.