High-temperature monoclinic α-SrHfF 6 , and isostructural α-SrZrF 6 : associating Hf 2 F 12 bipolyhedra and SrF 8 snub disphenoids.

The structure of the high-temperature monoclinic variety α-SrHfF6 (strontium hafnium hexafluoride) [and of isostructural α-SrZrF6 (strontium zirconium hexafluoride)] associates Hf2 F12 bipolyhedra and SrF8 snub disphenoids, forming zigzag twisted [SrF6 ]n layers. The distribution of the Hf and Sr polyhedra forms a three-dimensional framework which can be related to the family of anion-excess ReO3 -related superstructures. α-SrHfF6 corresponds to a new ABX6 type and is compared to the other main families already described. A partial amorphization of this structure is observed in samples quenched from the melt.