Modèles d'arrangements anioniques locaux dans les solutions solides à structure fluorine stabilisée par dopage Na 0.5- xY 0.5+ xF 2+2 x
Electron, X-ray, and neutron diffuse scattering measurements have been performed on single crystals of the Na 0.5- xY 0.5+ xF 2+2 x solid-solutions having a doped stabilized fluorite structure. The localization and the shape of the diffuse scattering agree with a description of the local structure using a tridimensional arrangement of microdomains. A model of the fluorine local order agreeing with the refinements of the average structure is proposed. It assumes that all the interstitial atoms are trapped in thermally stable [NaY 3F 12] 2- clusters diluted in a fluorite matrix. The high inelastic contribution to the diffuse scattering indicates that the fluorine sublattice of the fluorite structure is strongly affected by anharmonic vibrations.