Short-range order and diffusion processes in the Na1-xBixF1+2x anion-excess solid solution

Malika El Omari (1) , Mohamed El Omari (1) , A. Abaouz (1) , A. Yacoubi (1) , Jean-Maurice Réau (2) , Jean Sénégas (2)

1 Department of Chemistry, Faculty of Science
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The F− diffusion processes within the anion-excess solid solution Na1−xBixF1+2x with fluorite-type structure have been studied by 19F-NMR investigation. Two types of fluoride ions, Fn and F′, are distinguished in the 19F-NMR spectra of rigid lattice at low temperature (T=175 K) and the distribution of fluoride ions among the two sites is determined by deconvolution of the experimental spectra. The short-range order in these materials is analogous to the clustering process observed in the K1−xBixF1+2x solid solution. It corresponds to an order between cubic entities and cubooctaedral clusters. Two diffusion mechanisms are identified on both sides of a Tr temperature. The first one at TTr to an F− exchange between cubic and cubooctaedral clusters.

Mots clés: Diffusion; NMR; Fluorite-type structure; Clustering

Domaines: Matériaux

Malika El Omari, Mohamed El Omari, A. Abaouz, A. Yacoubi, Jean-Maurice Réau, et al.. Short-range order and diffusion processes in the Na1-xBixF1+2x anion-excess solid solution. Materials Letters, 2002, 53 (3), pp.138-144. ⟨10.1016/S0167-577X(01)00462-1⟩. ⟨hal-00818186⟩