Hydrothermal Synthesis And Magnetic Properties Of Co_xfe_(1_x)/co_yla_zfe_(3-y-z)o_4 Composites

摘要

A series of iron-cobalt alloy and cobalt-ferrite composites doped with La~(3+) (Co_xFe_(1-x)/Co_yLa_zFe_(3-y-z)O_4) in which the Fe-Co alloy has either a bcc or a fcc structure and the oxide is a spinel phase, have been synthesized by using the disproportionation of Fe (OH)_2 and the reduction of Co (Ⅱ) by Fe~0 in a concentrated and hot KOH solution. when x≤ 0.1, the structures of the Fe_xCo_(1-x) alloy and cobalt-ferrite are fcc structure; and when x ≥ 0.25, the structures of the Fe_xCo_(1-x) alloy is bcc structure. The fcc structure of alloy is favored for [KOH] close to 9 N, Co(Ⅱ)/ Fe(Ⅱ) ratios between 0.5 and 0.9 and short reaction time of synthesis. And the bcc structure of the alloy is favored for [KOH] close to 1 N, Co(Ⅱ)/Fe(Ⅱ) ratios between 0.1 and 0.5 and long reaction time of synthesis. A low [KOH] favors nucleation leading to octahedral of 1 μm. And [KOH] of 9-12 N favors particle growth. The metal occurs in square particles of 100-150 nm included within the spinel. Powder X-ray diffraction (XRD), thermal gravity analysis (TGA) and different thermal analysis (DTA), scanning electron microscope (SEM), transmission electron micrograph (TEM) and vibrating sample magnetometer (VSM) were employed characterize the crystallite sizes, structure, morphology and magnetic properties of the composites. And the effect of the Co(Ⅱ)/ Fe(Ⅱ) ratio (0 ≤ Co/Fe ≤ 1), concentration of KOH, reaction time and substitution Fe~(3+) ions by La~(3+) ions on structure, magnetic properties of the composites were investigated.