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    ABSTRACT: Copper based oxide glasses are especially interesting for the possibility of ionic-electronic mixed conduction, which has potential applications in energy and switching devices. Accordingly, lithium metaphosphate glasses are investigated within the (100-x) Li2O - xCu2O - 50P2O5 series, where Li+ ions are gradually replaced by copper ions. Based on the changes in glass transition temperature and thermal stability via structural modification, the glasses are shown to be predominantly ionic conductors. In fact, they exhibit signs of classic mixed mobile ion effect (MMIE), a hallmark of ion conduction in glass, which would be due to Li+ and Cu+ ions in the present case.
    Journal of Non-Crystalline Solids 01/2014; 383:137-140. · 1.72 Impact Factor
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    ABSTRACT: Lithium vanado-phosphate glasses have been designated as possible cathode material for the next generation of solid state batteries, due to their high conductivity and mixed electronic–ionic conducting behaviours, which derive from the small polaron hopping between the vanadium ions with different valence state and the lithium ion diffusion. Therefore, the understanding of the behaviour of these glasses at the atomistic level can be an important aspect in designing compositions for these applications. To reach this goal, the structure and lithium ion diffusion behaviour in lithium vanado-phosphate glasses with mixed V4 + and V5 + ions were studied using molecular dynamics simulations. The results show that vanadium oxide generally plays an intermediate role in glass structure while there are subtle details depending on its concentration and oxidation states. The phosphorus network is depolymerized by the content of vanadium oxide, but phosphorus ions always contribute to the glass network, interposing to vanadium polyhedra. The V4 + 5 + 2 5 2 5
    Journal of Non-Crystalline Solids 11/2014; 403:53–61. · 1.72 Impact Factor
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    ABSTRACT: Transition metal containing glasses have unique electrical properties and are therefore often used for electrochemical applications, such as in batteries. Among oxide glasses, vanadium tellurite glasses exhibit the highest electronic conductivity and thus the high potential for applications. In this work, we investigate how the dynamic and physical properties vary with composition in the vanadium tellurite system. The results show that there exists a critical V2O5 concentration of 45 mol %, above which the local structure is subjected to a drastic change with increasing V2O5, leading to abrupt changes in both hardness and liquid fragility. Electronic conductivity does not follow the expected correlation to the valence state of the vanadium as predicted by the Mott-Austin equation but shows a linear correlation to the mean distance between vanadium ions. These findings could contribute to designing optimum vanadium tellurite compositions for electrochemical devices. The work gives insight into the mechanism of electron conduction in the vanadium tellurite systems.
    The Journal of Physical Chemistry B 12/2014; · 3.38 Impact Factor

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Jun 3, 2014