19F NMR study of the fluorite‐Type Ca1−xThxF2+2x solid solution

Abstract

AbstractAn investigation is made by 19F NMR of the disordered fluorite‐related solid solution Ca1−xThxF2+2x (0 ≦ x ≦ 0.18). The existence is shown of different fluoride sublattices at low temperatures and the setting‐up of partial exchanges between them at increasing temperature. The identity of these sublattices with those identified by neutron diffraction is discussed. The NMR study allows to confirm the formation of clusters of 1:0:3 type in Ca1−xThxF2+2x. The results obtained are so in good agreement with the composition dependence of the ionic conductivity properties and are satisfying with respect to the model of the processes of clustering proposed for the anion excess CaF2‐type solid solutions: indeed, within Ca1−xThxF2+2x, the F‴ interstitial fluoride ions seem to play the main role in the long‐range motions.