Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 6: Diffusion I
MM 6.1: Vortrag
Montag, 25. Februar 2008, 10:15–10:30, H 0111
Fast ionic mobility in cryolite studied by quasielastic neutron scattering — •Sandro Jahn1, Jacques Ollivier2, and Franz Demmel3 — 1GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam — 2Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France — 3ISIS Facility, Chilton, OX11 0QX, UK
The relation between ionic mobility and conductivity at high temperature of the perovskite fluoride cryolite, Na3AlF6, is studied by quasielastic neutron scattering (QENS). Up to T=880 ∘C the conductivity is dominated by jump diffusion of Na ions. At higher temperatures, a considerable broadening of the QENS spectra and the development of a liquid-like diffraction peak is observed. In the temperature range between T=880 ∘C and the melting point (Tm=1013 ∘C), the presence of about one percent of partial melt, that is expected from the phase diagram, causes a high mobility of almost all F ions of the system. The Q-dependence of the line width suggests a set-in of translational diffusion of fluorines at this temperature. This additional degree of translational movements could reason the jump-like increase in the ionic conductivity observed macroscopically.