Synthesis and crystal structure of calcium dizinc iron(III) tris(orthophosphate), CaZn2Fe(PO4)3

Abstract

Single crystals of the title compound, CaZn2Fe(PO4)3, were synthesized by conventional solid-state reaction. In the asymmetric unit, all atoms are located in fully occupied general positions of the P21/c space group. The zinc atoms are located on two crystallographically independent sites with tetrahedral and distorted triangular-based bipyramidal geometries. Two edge-sharing triangular bipyramidal ZnO5 units form a dimer, which is linked to slightly deformed FeO6 octahedra via a common edge. The resulting chains are interconnected through PO4 tetrahedra to form a layer perpendicular to the b axis. Moreover, the remaining PO4 and ZnO4 tetrahedra are linked together through common vertices to form tapes parallel to the c axis and surrounding a chain of Ca2+ cations to build a sheet, also perpendicular to the b axis. The stacking of the two layers along the b axis leads to the resulting three-dimensional framework, which defines channels in which the Ca2+ cations are located, each cation being coordinated by seven oxygen atoms.