| Abstract
| - The effect of temperature on the alkali environment in melts and in glasses has been investigated in Lithiumdiborate system by neutron diffraction with isotopic substitution of Li. In situ high-temperature measurementshave been performed in glassy and liquid states (1273 K), by use of a vanadium furnace. A well-definedenvironment extends up to 4 Å around Li in the glass as well as in the melt. However, several structuraldifferences are observed between the melt and the glass. The mean Li−O distance is shortened by −0.02 Åin the melt, and the distribution of Li−B correlations is reduced in width and intensity. As the structure ofthe glass at 300 K retains that of the melt quenched at Tg, the present neutron diffraction data indicate acontinuous reorganization process between the supercooled melt and the liquid state. These temperature-induced structural changes are related to the increased modifying role of Li in diborate melt. Together withthe boron coordination change, these modifications imply a non-Arrhenian behavior in transport propertiessuch as ionic diffusion and melt fragility.
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