Hydrothermal syntheses, structures, and magnetic properties of (NH4)2NaVF6 and Na3VF6

The single crystals of perovskite fluorides (NH4)2NaVF6 and Na3VF6 were synthesized under mild hydrothermal conditions. The structures of the compounds were determined by means of single-crystal and powder X-ray diffraction analyses, respectively. (NH4)2NaVF6 has a cubic elpasolite-type structure and crystallizes in the space group View the MathML sourceFm3¯m with lattice constant a=8.495(0) Å. Rietveld refinement indicates that Na3VF6 has a monoclinic structure and is in space group P21/n. The compounds were characterized by scanning electron microscopy, thermogravimetric and differential thermal analysis, and variable temperature magnetic susceptibility. With the temperature decreasing, the magnetic studies of the compounds showed the magnetic ordering was related to the crystallographic features and isolated magnetic units.