Preparación y caracterización de ferritas de MnZn a partir de mezclas de ZnFe2O4 y MnFe2O4.

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

Bariloche, Argentina

Jornada; Jornadas SAM-CONAMET-SIMPOSIO MATERIA 2003; 2003

Asociación Argentina de Materiales – Sociedad Chilena de Metalurgia y Materiales

MnZn ferrites are widely used ceramic materials in the fabrication of transformers, frequency filters, magnetic recording heads, etc., due to their excellent properties as high saturation magnetization, high initial permeability, high resistivity and low losses. The magnetic properties of these ferrites are affected by starting compositions, additives and sintering conditions as well as the synthesis method. These materials are obtained by means of the traditional ceramic method, which comprises a solid-state reaction by calcination of oxides and/or carbonates, a forming step and a final sintering at high temperature (T > 1300ºC). In this work, the synthesis of MnxZn1-xFe2O4 ferrites with three different compositions (x = 0.5, 0.65 and 0.85) is carried out starting from previously prepared MnFe2O4 and ZnFe2O4. Zn ferrite was obtained by mechanochemical activation of a Zn-Fe2O3 mixture and ulterior thermal treatment in air atmosphere. On the other hand, Mn ferrite was prepared by mechanochemical activation of a MnO-Fe2O3 mixture and ulterior calcination under inert atmosphere. Both ceramic powders were well-mixed, compacted and submitted to thermal treatments at 1100ºC under N2 atmosphere during several holding times. The obtained materials were characterized by X-ray diffraction, differential and gravimetric thermal analyses, vibrating sample magnetometry and scanning electron microscopy. Also the densities of the sintered materials for the three studied compositions. were determined. The formation of mixed ferrites for each composition was observed, with densities between 80 and 85% of the corresponding theoretical values. These materials reached high saturation magnetization values (very close to the theoretical ones) and low coercivities. Finally, the effect of the processing parameters on the properties and morphology of the synthesized materials are discussed.