Fast ionic mobility in cryolite studied by quasielastic neutron scattering

Quasielastic neutron scattering (QENS) has been used to study the relation between ionic mobility and conductivity at high temperature of the perovskite fluoride cryolite, Na3AlF6. 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. 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.