Synthesis, Crystal and Magnetic Structures of the Sodium Ferrate (IV) Na4FeO4 Studied by Neutron Diffraction and Mössbauer Techniques

✍ Scribed by C. Jeannot; B. Malaman; R. Gérardin; B. Oulladiaf

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 571 KB
• Volume: 165
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9520

✦ Synopsis

The alkali sodium ferrate (IV) Na 4 FeO 4 has been prepared by solid-state reaction of sodium peroxide Na 2 O 2 and wustite Fe 1؊x O, in a molar ratio Na/Fe‫,4؍‬ at 4003C under vacuum. Powder X-ray and neutron di4raction studies indicate that Na 4 FeO 4 crystallizes in the triclinic system P؊1 with the cell parameters: a‫)2(0184.8؍‬ A s , b‫)1(8867.5؍‬ A s , c‫)1(2265.6؍‬ A s , ‫؍‬ 124.662(2)3, ‫,3)2(848.89؍‬ ‫3)2(167.101؍‬ and Z‫.2؍‬ Na 4 FeO 4 is isotypic with the other known phases Na 4 MO 4 (M‫؍‬Ti, Cr, Mn, Co and Ge, Sn, Pb). The solid solution Na 4 Fe x Co 1؊x O 4 exists for x‫180؍‬ and we have followed the evolution of the cell parameters with x to determine the lattice parameters of the triclinic cell of Na 4 FeO 4 . A three-dimensional network of isolated FeO 4 tetrahedra connected by Na atoms characterizes the structure. This compound is antiferromagnetic below T N ‫61؍‬ K. At 2 K the magnetic cell is twice the nuclear cell and the magnetic structure is collinear ( Fe ‫)21(63.3؍‬ B at 2 K). This black compound is highly hygroscopic. In water or on contact with the atmospheric moisture it is disproportionated in Fe 3؉ and Fe 6؉ . The MoK ssbauer spectra of Na 4 FeO 4 are 5tted with one doublet ( ‫؊؍‬ 0.22 mm/s, ‫14.0؍‬ mm/s at 295 K) in the paramagnetic state and with a sextet at 8 K. These parameters characterize Fe 4؉ highspin in tetrahedral FeO 4 coordination.

2002 Elsevier Science (USA)