SILVA, V. J.; http://lattes.cnpq.br/9578629554234816; SILVA, Valmir José da.
Resumo:
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.