Influência da substituição do Mn2+ pelo Fe2+ na morfologia de ferritas Mn-Zn e sua caracterização eletromagnética.

Abstract

In the branch of magnetic ceramics, Mn-Zn ferrites are the most important commercially, due the high magnetic saturation and application possibility in high frequencies with low magnetic losses. However these ceramic presented magnetic properties very sensitive and the microstructure depends fundamentally of the processing conditions. Thus, the goal of this work was to study the influence of the substitution of Mn2 + by Fe2 + in the electromagnetic properties of ferrites of the type (Mnl\_xZnl\\Fel+ Fe;+ ](94 to x = 0.05; 0.1 e 0.2 mols of Fe2 + , prepared for synthesis by combustion reaction in the proportions of 1:14, 1:21 and 1:25 of total reagents (TR):100ml of distilled water. The resulting powders were characterized by XRD, BET, granulometric distribution, SEM, TEM and electromagnetic measuments. The results showed that the increase of proportion TR:H2 0 provided the formation of monophase powders and that the addition of Fe2 + in the system caused in general a considerable reduction at the maximum temperature combustion flame. The crystallite size, lattice parameters, particle size and the medium diameter of the agglomerates decreased with the increase of the Fe2 + ions content in substitution to the Mn2 + ions. The obtained powders for all the systems presented porous aspect, constituted by agglomerates no dense of small spherical particles, of varied size (large distribution), in the form of irregular foams. The increase in the concentration of Fe2 + ions caused a light increase in the saturation magnetization values, in the coercive field and in the loss area for hysteresis and a small decrease in the absorption capacity. The Mn-Zn ferrites obtained in this work were very promising for use as absorbers of electromagnetic radiation in the narrow band, specifically in the X band ( 8 - 1 2 GHz), with larger absorption of 68,3%.