Single crystal structural study of Sr7Y6F30(O): an example of anion-rich fluorite derived structure with a cuboctahedron cluster

A bright colorless anion-rich compound was obtained by heating a pellet of homogeneous mixture of well dried SrF2 and YF3 (in 7:6.1 ratio) at 1300 °C in a stream of dry argon atmosphere followed by cooling to 900 °C in 12 h. Crystal structure of this new compound was elucidated from single crystal X-ray diffraction data (wR2 = 0.074). This oxide-fluoride composition Sr7Y6F30O was proposed on the basis of structural analysis of the product. It crystallizes in the rhombohedral lattice, space group Rimage (No. = 148) with a = 14.498(2) and c = 9.926(2) Å, Z = 3, (i.e., 9.001 Å and α = 107.30°, Z = 1, in rhombohedral setting). The yttrium atoms are square anti-prismatically coordinated by eight fluorine. Six of these square anti-prisms are octahedrally arranged and connected via common corners to form Y6F36+1 clusters with a central F12 cuboctahedron, which occupy an additional anion inside in it.