Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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A.L.Rollet, V.Sarou-Kanian, C.Bessada, 'Measuring self-diffusion coefficients up to 1500K: a powerful tool to investigate the dynamics and the local structure of inorganic melts', Inorg. Chem. 48 10972-10975 (2009) doi:10.1021/ic9010086

Self-diffusion is a fundamental property of liquid dynamics that also provides important structural information. To explore the dynamics in inorganic melts with high liquidus temperature, we propose a new setup based on Pulsed Field Gradient NMR combined with laser heating that makes possible in situ self-diffusion coefficients measurements up to 1500K. Applied to several corrosive molten fluorides in a wide range of compositions and temperature, we have evidenced the different key parameters of their motion along with their structural characteristics. In alkali fluorides, the self-diffusion coefficient of fluorine depends slightly on the composition compared to the temperature, displaying these systems as an ideal bath of polarisable hard spheres. In contrast, self-diffusion in rare earth and alkali fluorides mixtures presents a complicated balance between temperature and the network-forming process of the ionic long-lived units. These results open wide perspectives in the study of high temperature liquids.