Síntese por reação de combustão, sintetização e caracterização de ferritas Ni-Zn dopadas com cromo.

Abstract

In this work Ni-Zn ferrites doped with chromium o f nominal composition given by Ni0 j5Zno.5Fe2.xCrx04 (x = 0.00; 0.10; 0.15 and 0.20 mol o f C r 3 + ) were prepared for combustion reaction using urea as fuel and using as container a vitreous silica crucibles. The effect of Cr3 + on the characteristics powders and samples sintered at 1200°C/2h with heating rate of 5°C/min were investigated. The resulting powder and sintered samples were characterized by X rays diffraction, scanning electronic microscopy (SEM) and magnetic measures. The temperature and flame average time were measured during the synthesis and the powders were characterized by adsorption with N 2 (BET). The sintered samples were also characterized by the green density measures, apparent density and apparent porosity. The results showed that both powders and sintered samples compositions presented only the formation of the inverse spinel phase Ni-Zn- Cr ferrites. The crystallite size varied for the powder from 22 to 23 nm. The specific superficial area for the powder varied from 43.5 to 29.2 m2/g. The results obtained by SEM for the powder in all the studied compositions, showed the formation of agglomerates of nanoparticles. Already for the samples sinterized an increase was observed in the apparent porosity and grains size around 1.2 ± 0.5 um for the FCr0.05 and FCrO.20 systems. Through the magnetic parameters was possible to verify so much for the powder as for the sintered samples that all the systems presented a behavior o f soft magnetic materials. The saturation magnetization decreased from 53 to 42.4 emu/g and 76 for 64 emu/g for the powder and sintered samples, respectively.