Structural and Mössbauer study of nanoparticles CoFe2O4 prepared by sol-gel auto-combustion and subsequent sintering

Al-Maashani, Mohammed; Gismelseed, A. M.; Khalaf, Kadhim A.M.; Yousif, A. A.; Al-Rawas, A. D.; Widatallah, H. M.; Elzain, M. E.

doi:10.1007/s10751-018-1491-5

Cited by 27 publications

(7 citation statements)

References 14 publications

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“…The high-field part of HMF distribution associated with component 2 is attributed mainly to the oxide shell composed of iron and/or iron-cobalt oxides in a form of crystallites that are strongly distorted, primarily due to the proximity of both surfaces (inner and outer) of the oxide layer. However, the mean HMF values of this component are clearly smaller than typical of most crystalline Fe and Fe-Co oxides [ 31 , 32 , 33 , 34 ]. This can indicate the fine-grained character of these crystallites.…”

Section: Resultsmentioning

confidence: 99%

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

et al. 2021

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Thermal treatment is a post-synthesis treatment that aims to improve the crystallinity and interrelated physical properties of as-prepared materials. This process may also cause some unwanted changes in materials like their oxidation or contamination. In this work, we present the post-synthesis annealing treatments of the amorphous Fe1−xCox (x = 0.25; 0.50; 0.75) Wire-like nanochains performed at 400 °C in two different atmospheres, i.e., a mixture of 80% nitrogen and 20% hydrogen and argon. These processes caused significantly different changes of structural and magnetic properties of the initially-formed Fe-Co nanostructures. All of them crystallized and their cores were composed of body-centered cubic Fe-Co phase, whereas their oxide shells comprised of a mixture of CoFe2O4 and Fe3O4 phases. However, the annealing carried out in hydrogen-containing atmosphere caused a decomposition of the initial oxide shell layer, whereas a similar process in argon led to its slight thickening. Moreover, it was found that the cores of thermally-treated Fe0.25Co0.75 nanochains contained the hexagonal closest packed (hcp) Co phase and were covered by the nanosheet-like shell layer in the case of annealing performed in argon. Considering the evolution of magnetic properties induced by structural changes, it was observed that the coercivities of annealed Fe-Co nanochains increased in comparison with their non-annealed counterparts. The saturation magnetization (MS) of the Fe0.25Co0.75 nanomaterial annealed in both atmospheres was higher than that for the non-annealed sample. In turn, the MS of the Fe0.75Co0.25 and Fe0.50Co0.50 nanochains annealed in argon were lower than those recorded for non-annealed samples due to their partial oxidation during thermal processing.

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Section: Resultsmentioning

confidence: 99%

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

et al. 2021

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“…Rare earth ions will have a great influence on the magnetocrystalline anisotropy of ferrite [ 23 , 24 , 25 , 26 ]. Mg-Zn ferrite is important in soft magnetic materials and semiconducting magnetic materials [ 27 , 28 , 29 ]. Because Mg-Zn ferrite has low eddy current losses, high resistivity and high cost effective, it is widely used in computer memory, recording heads and loading coils [ 30 ].…”

Section: Introductionmentioning

confidence: 99%

Mössbauer and Structure-Magnetic Properties Analysis of AyB1−yCxFe2−xO4 (C=Ho,Gd,Al) Ferrite Nanoparticles Optimized by Doping

et al. 2023

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AyB1−yCxFe2−xO4 (C=Ho,Gd,Al) ferrite powders have been synthesized by the sol-gel combustion route. The X-ray diffraction of the CoHoxFe2−xO4 (x = 0~0.08) results indicated the compositions of single-phase cubic ferrites. The saturation magnetisation of CoHoxFe2−xO4 decreased by the Ho3+ ions, and the coercivity increased initially and then decreased with the increase of the calcination temperature. The Mössbauer spectra indicated that CoHoxFe2−xO4 displays a ferrimagnetic behaviour with two normal split Zeeman sextets. The magnetic hyperfine field tends to decrease by Ho3+ substitution owing to the decrease of the A–B super-exchange by the paramagnetic rare earth Ho3+ ions. The value of the quadrupole shift was very small in the CoHoxFe2−xO4 specimens, indicating that the symmetry of the electric field around the nucleus is good in the cobalt ferrites. The absorption area of the Mössbauer spectra changed with increasing Ho3+ substitution, indicating that the substitution influences the fraction of iron ions at tetrahedral A and octahedral B sites. The X-ray diffraction of Mg0.5Zn0.5CxFe2−xO4(C=Gd,Al) results confirmed the compositions of single-phase cubic ferrites. The variation of the average crystalline size and lattice constant are related to the doping of gadolinium ions and aluminum ions. With increasing gadolinium ions and aluminum ions, the coercivity increased and the saturation magnetization underwent a significant change. The saturation magnetization of AlMg0.5Zn0.5FeO4 ferrite reached a minimum value (MS= 1.94 mu/g). The sample exhibited ferrimagnetic and paramagnetic character with the replacement with Gd3+ ions, that sample exhibited paramagnetic character with the replacement with Al3+ ions, and the isomer shift values indicated that iron is in the form of Fe3+ ions.

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“…Contrary to the “normal” spinel structure of Co 3 O 4 , the single cation oxide Fe 3 O 4 forms an “inverse” spinel structure, where the divalent Fe 2+ cations occupy half of the octahedrally coordinated B-sites . While the degree of inversion is described by a single parameter for binary spinel compounds, the mixed-metal oxides Co 3− x Fe x O 4 exhibit a complex cation distribution that is analyzed by combinations of scattering and Mössbauer spectroscopy measurements. − However, the superparamagnetic limit and the absorption by the cobalt ions may limit these studies to larger nanoparticles, low temperatures, and significant iron fractions. Alternatively, X-ray absorption spectroscopy (XAS) allows the element-specific measurement of the local and electronic structures of Co 3− x Fe x O 4 nanoparticles. − Here, measurements at the Co–K and Fe–K edges are suitable for a wide range of compositions, small particle sizes, high temperatures, and variable sample environments.…”

Section: Introductionmentioning

confidence: 99%

Atom Pair Frequencies as a Quantitative Structure–Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt–Iron–Spinel

et al. 2022

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The purpose of this study is to find a direct and quantitative correlation of the structure of Co 3−x Fe x O 4 nanoparticles with catalytic performance in 2-propanol oxidation. Eight nanocrystalline samples with varying iron contents are synthesized, and quantitative information regarding their structure is obtained from nitrogen physisorption, X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) analyzed by reverse Monte Carlo simulations. The catalytic performance is tested in 2-propanol oxidation in the gas phase. Overall, catalytic conversion data as a function of temperature are deconvoluted to obtain conversion and half-conversion temperatures as quantitative parameters for the different catalytic reaction channels. The crystal structure is described by a spinel structure with interstitial cation defects. These defects result in a reduced electronic state of the nanoparticles. The defect density depends on the cationic composition. We also observe a complex cationic distribution on tetrahedral and octahedral sites, which is strongly influenced by the overall cationic composition. In the catalytic tests, the samples exhibit a low-temperature pathway, which is deactivated in subsequent runs but can be recovered by an oxidative treatment of the catalyst. We find that the frequency of cation pairs Co O −Co O and Co O −Co T of the individual samples correlates directly to their catalytic activity and selectivity.

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Structural and Mössbauer study of nanoparticles CoFe2O4 prepared by sol-gel auto-combustion and subsequent sintering

Cited by 27 publications

References 14 publications

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

Evolution of Structural and Magnetic Properties of Fe-Co Wire-like Nanochains Caused by Annealing Atmosphere

Mössbauer and Structure-Magnetic Properties Analysis of AyB1−yCxFe2−xO4 (C=Ho,Gd,Al) Ferrite Nanoparticles Optimized by Doping

Atom Pair Frequencies as a Quantitative Structure–Activity Relationship for Catalytic 2-Propanol Oxidation over Nanocrystalline Cobalt–Iron–Spinel

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