Network former mixing (NFM) effects in alkali germanotellurite glasses

Network former mixing (NFM) effects on ionic conductivities have been characterized in ternary germa-notellurite glasses of composition (A(2)O)(0.3)[(TeO2)(x)(GeO2)(1-x)](0.7) (A = Li, Na), revealing an interesting cation dependence. While the results demonstrate a weak positive NFM effect in the Li-containing system, the electrical conductivities of the Na-containing systems correspond to the weighted average values observed in their binary endmembers. The structural origins of these differing effects have been explored by Raman scattering and Te-125 solid-state NMR spectroscopy, indicating no significant differences in the structural organization of these materials. Overall, the data suggest that the concentration of heteroatomic con-nectivities is relatively low. For the Li-containing system, an analysis of the motional narrowing effects observed in temperature-dependent static Li-7 NMR spectra confirms the existence of a weak positive NFM effect at the local atomic level. Accordingly, the absence of an NFM effect for the Na-containing system is corroborated by low-temperature Na-23 spin-echo decay spectroscopy, showing very similar network modifier distributions in those glasses. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The effects of Network former mixing (NFM) on ionic conductivities in ternary germa-notellurite glasses containing Li and Na have been characterized, showing a weak positive NFM effect in the Li-containing system and no NFM effect in the Na-containing system. Structural origins of these effects were explored using Raman scattering and solid-state NMR spectroscopy, indicating relatively low concentrations of heteroatomic connectivities in these materials.