Synthesis and magnetic properties of zinc ferrite using mechanochemical and thermal treatments

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

Viña del Mar, Chile

Workshop; International Workshop: Frontiers in Materials Science; 2002

Soft magnetic ferrites such as Franklinite (ZnFe2O4) are materials with a wide application in electronic and telecommunication industries. In order to prepare Franklinite, reactive mixtures of Zn-Fe3O4 (with a molar ratio of 3:2) were mechanochemically activated during different milling times in an oscillating mill, under air atmosphere. The physicochemical and structural evolution of these samples was studied by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The high-energy ball milling produced the amorphization of crystalline structures and the oxidation of metallic Zn. However, no any new phase was formed in the range of used miling times (up to 30 minutes). Thermal treatments for 30 minutes of the non-activated sample (ZF0) and the sample activated for 30 minutes (ZF30) were performed at several temperatures between 400 and 1000°C. The analysis of these heated mixtures showed an increased reactivity of sample ZF30 with respect to ZF0, yielding Franklinite from 400°C on. The thermal treatments at 400 and 500°C as a function of time revealed a non-expected magnetic behavior for sample ZF0. This was explained on the basis of the formation of a solid solution ZnxFe1-xFe2O4, which did not occur in the activated mixture. In order to interpret these facts, a diffusional model of the reactions is proposed.