ملخص: Structural phase transitions were detected in Na3TiOF5, Na3CoF6 and Na3InF6 by micro-DTA and X-ray diffraction. Optical measurements were performed on single crystals. Ferroelastic domains were observed for the low-temperature phases.The three compounds are isostructural with phases of general formula Na3MF6 (M = 3d transition or IIIb elements). At high temperature, all these compounds exhibit the cubic Fm--m symmetry which is the prototype phase. The ferroelastic Curie temperature was related to the size and the electronic configuration of the cation Mn+.ResumeDes transitions de phases structurales ont ete mises en evidence par micro-ATD et diffraction X a haute temperature pour trois composes de structure cryolite: Na3TiOF5, Na3CoF6 et Na3InF6. Des monocristaux ont ete elabores. Des domaines ferroelastiques ont ete visualises au microscope en lumiere polarisee.Ces trois composes sont isostructuraux d'une serie de composes de formulation Na3MF6 (M = elements 3d et IIIb) presentant a haute temperature une variete prototype de symetrie cubique. La valeur de la temperature de Curie ferroelastique a ete discutee en fonction de la taille et de la structure electronique du cation Mn+.

لغة: فرنسية