J. Phys. IV France 07 (1997) C1-541-C1-542
Metal-Spinel Composites (M0xFe01-x)α-(MyFe3-y)1-α with M=Co, Ni Synthesis and Physical PropertiesS. Läkamp, T. Bouakham and G. Pourroy
Institut de Physique et Chimie des Matériaux de Strasbourg, Groupe des Matériaux Inorganiques, 23 rue du Loess, 67037 Strasbourg cedex, France
Composite materials made up of cobalt-iron alloy (or nickel -iron alloy) and Co (or Ni) doped magnetite are synthesized in an aqueous media. The procedure employed is a low temperature reaction in alkaline KOH solution which involves the disproportionation of Fe(II) into Fe0 and Fe(III) and a reduction of Co(II) or Ni(II). The composition of the final product depends on the initial and final concentrations of reagents and KOH. Pure cobalt - containing composites are obtained in a narrow range of KOH concentration. The metallic phases have the α-Fe (b.c.c. structure) or α-Mn structure, and the lattice parameter of the cobalt - containing magnetite lies between 8.396(2)Å and 8.405(2)Å. Nickel - containing composites without hydroxides are obtained for higher KOH concentrations, 14-15 mol/liter. For lower and higher KOH concentration, hydroxides or amorphous phases precipitate. The coercive field increases when [Co]/[Fe] increases.
© EDP Sciences 1997