Bismuth(V) iron(III) tris(phosphate) oxide

Abstract

Bi(V)(0.4)Fe(3)(III)O(PO(4))(3) crystallizes with two Fe atoms (one on an inversion centre and one on a mirror plane) displaying octahedral geometry and a third Fe atom (on a mirror plane) with trigonal bipyramidal coordination. Fe atoms are seen in oxygen-bridged chains. Bi(V) atoms are found in the interstitial sites between these chains. Bi shows sevenfold coordination, with Bi-O distances between 2.357 (7) and 2.529 (6) A.

The iron phosphate CaFe3(PO4)3O

“…As a part of a systematic exploration of the A 2 O-MO-Fe 2 O 3 -P 2 O 5 (A = alkali metal, M = divalent cation) in a search of new iron phosphates with interesting structures and subsequently intriguing properties, we describe here the structure of CaFe 3 (PO 4 ) 3 O, extracted from a mixture of nominal composition LiCaFe 3 (PO 4 ) 4 . This compound is isostructural to the previously reported iron phosphates Bi 0.4 Fe 3 (PO 4 ) 3 (Benabad et al, 2000) and SrFe 3 (PO 4 ) 3 O (Morozov et al, 2003). Its structure, shown in figure 1, is built from a three-dimensional arrangement based on two crystallographically distinct FeO 6 octahedra, one symmetry non equivalent FeO 5 polyhedron and three symmetry distinct PO 4 tetrahedra.…”

“…The interest in iron phosphates has increased following the discovery of LiFePO 4 with olivine-type structure, which is the most promising electrode material for Li-ion batteries, see: Padhi et al (1997). The title compound is isostructural to the iron phosphates Bi 0.4 Fe 3 (PO 4 ) 3 (Benabad et al, 2000) and SrFe 3 (PO 4 ) 3 O (Morozov et al, 2003). For ionic radii, see: Shannon (1976).…”