Magnetic and structural study of mechanochemical reactions in the Al-Fe3O4 system

PABLO M. BOTTA; PAULA G. BERCOFF; ESTEBAN F. AGLIETTI; HÉCTOR R. BERTORELLO; JOSÉ M. PORTO LÓPEZ

JOURNAL OF MATERIALS SCIENCE

Año: 2002 vol. 37 p. 2563 - 2568

0022-2461

The solid state reaction between Al and Fe3O4 (magnetite) using mechanochemical activation of powder mixtures under Ar atmosphere is studied. The phase evolution during the reaction is analyzed by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), differential thermal analysis (DTA) and scanning electron microscopy (SEM). At 37 minutes of high-energy ball-milling the disappearance of reactive phases and the production of a-Fe, FeAl2O4 and a-Al2O3 is observed, together with significant changes in the magnetic behavior of the system. The composition and properties of samples heated up to 1200°C are also investigated. The behavior of the saturation magnetization Ms is interpreted on the basis of the formation of a variable composition spinel phase Fe [Alx Fe2-x] O4 with 0£ x £ 2 and a canting effect due to the presence of Al3+ ions in the spinel structure