Hydrothermal synthesis and crystal structure of SrAl2(PO4)2F2: A new three-dimensional framework with channels delimited by a helical anionic border

Abstract

The new compound SrAl₂(PO₄)₂F₂ has been synthesised by a hydrothermal method (700°C, 195 MPa, 24 h). The structure was determinated by X-ray diffraction on single crystal. SrAl₂(PO₄)₂F₂ crystallises in the non-centrosymmetric space group P2₁2₁2₁ (N^o19) with a = 12.026(1) Å, b = 12.199(1) Å, c = 4.666(1) Å, V = 684.6(5) ų and Z = 4. Its structure is built up from corner-linkage between octahedral and tetrahedral units. The resulting tridimensional framework exhibits channels along [001] delimited by oxygen anions helically distributed. The Sr²⁺ cations are inserted inside the channels.