The iron phosphate CaFe₃(PO₄)₃O

Abstract

A new iron phosphate, calcium triiron(III) tris­(phosphate) oxide, CaFe3(PO4)3O, has been isolated and shown to exhibit a three-dimensional structure built by FeO6 octa­hedra, FeO5 trigonal bipyramids and PO4 tetra­hedra. The FeOx (x = 5, 6) polyhedra are linked through common corners and edges, forming [Fe6O28]∞ chains with branches running along [010]. Adjacent chains are connected by the phosphate groups via common corners and edges, giving rise to a three-dimensional framework analogous to those of the previously reported SrFe3(PO4)3O and Bi0.4Fe3(PO4)3O structures, in which the Ca2+ cations occupy a single symmetry non-equivalent cavity.

Crystal Growth and Structure of the New Ferrimagnetic Oxyphosphate PbFe3O(PO4)3

“…It was found to be isostructural with AFe 3 O-(PO 4 ) 3 (A = Ca, [15] Sr). [16] In the 3D structure, there are three crystallographically nonequivalent transition metal cation sites (Figure 1, a) 6 ] octahedra in such a way as to form a "millipede" with b/2-translated "legs".…”

“…These millipedes are connected to each other by tetrahedral phosphate groups, which yields layers parallel to the b direction (Figure 1, a). These layers are linked to each other to form the 3D structure through three crystallographically nonequivalent phosphate tetrahedra (Figure 1, b [15] Sr). [16] The ratio of the sum of the ionic radii of A 2+ and oxygen ions to the average A-O bond lengths is very close to 1 for the three compounds.…”