Cation distribution and crystallographic characterization of the spinel oxides MgCr Fe2−O4 by neutron diffraction

Zakaria, A.K.M.; Nesa, Faizun; Khan, Murad Ali; Datta, T. K.; Aktar, Sanjida; Liba, Samia Islam; Hossain, Shahzad; Das, Amitabh; Kamal, I.; Yunus, S.M.; Eriksson, Sandra

doi:10.1016/j.jallcom.2015.01.179

Cited by 11 publications

(6 citation statements)

References 12 publications

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“…The degree of inversion is sensitive to the combination and nature of the two TM cations and the synthesis conditions. Characterization techniques, including X‐ray diffraction (XRD), neutron powder diffraction, Mössbauer spectroscopy, X‐ray absorption fine structure (XAFS), etc . are generally used to determine the distribution of cations in the spinel lattice.…”

Section: Introductionmentioning

confidence: 99%

Significance of Engineering the Octahedral Units to Promote the Oxygen Evolution Reaction of Spinel Oxides

et al. 2019

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electrolyzer are oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. The OER at the anode, proceeding through 4e − transfer and generates more than one intermediates, is much more kinetically sluggish than the 2e − transfer HER. [1] Lowering the energy barrier of OER is the key to the enhancement of overall water splitting efficiency. The state-of-the-art OER electrocatalysts, such as iridium-and ruthenium-based materials, are not sustainable choices due to the high cost and element scarcity. Transition metal (TM) oxides, with wide variety of physical and electronic properties, are considered as promising low-cost alternatives. [2] Spinel-type oxides have been extensively investigated as OER electrocatalysts and have presented outstanding catalytic performances. [2b,3] The crystal structure of spinel is made up of oxygen anions arranged in a cubic close-packed lattice with metallic ions filling the tetrahedral and octahedral interstices. Of all the 96 interstices between the oxygen anions in one cubic unit cell, 64 are four oxygencoordinated tetrahedral sites and 32 are six oxygen-coordinated octahedral sites. In the spinel lattice, only half of the octahedral interstices and one-eighth of the tetrahedral interstices are filled with metal cations. The remaining unoccupied interstitial sites make spinel a very open structure to accommodate the migration of cations. [4] For binary spinel AB 2 O 4 , the distribution of The clean energy carrier, hydrogen, if efficiently produced by water electrolysis using renewable energy input, would revolutionize the energy landscape. It is the sluggish oxygen evolution reaction (OER) at the anode of water electrolyzer that limits the overall efficiency. The large spinel oxide family is widely studied due to their low cost and promising OER activity. As the distribution of transition metal (TM) cations in octahedral and tetrahedral site is an important variable controlling the electronic structure of spinel oxides, the TM geometric effect on OER is discussed. The dominant role of octahedral sites is found experimentally and explained by computational studies. The redox-active TM locating at octahedral site guarantees an effective interaction with the oxygen at OER conditions. In addition, the adjacent octahedral centers in spinel act cooperatively in promoting the fast OER kinetics. In remarkable contrast, the isolated tetrahedral TM centers in spinel prohibit the OER mediated by dual-metal sites. Furthermore, various spinel oxides preferentially expose octahedral-occupied cations on the surface, making the octahedral cations easily accessible to the reactants. The future perspectives and challenges in advancing fundamental understanding and developing robust spinel catalysts are discussed.

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Section: Introductionmentioning

confidence: 99%

Significance of Engineering the Octahedral Units to Promote the Oxygen Evolution Reaction of Spinel Oxides

et al. 2019

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“…Ni solubility is shown to momentarily increase below 1573 K, and then the Ni content rebounds due to rejection of Ni ions into the liquid as the Ni‐free phases predominantly form during cooling. Unsaturated Mn, Ti, Ca, and Si above 1523 K are not involved in the formation of spinel, while unsaturated Fe in liquid is absorbed in the spinel and then is disordered on both tetrahedral and octahedral sites, representing Fe partitioning between spinel and silicate melts based on Gibbs energy minimization . Mn, Ca, Si, and Fe are saturated between 1523 K and 1573 K, and Ti is saturated between 1473 K and 1523 K. The melilite and Ca 3 Si 2 O 7 formation temperatures in the present system, 1549 K and 1524 K, are within the saturation temperature range of Mn, Ca, Si, and Fe, and CaTiO 3 formation temperature; 1519 K corresponds to the saturation temperature range of Ti.…”

Section: Resultsmentioning

confidence: 75%

“…Spinel is in contact with liquid with a lower Cr content as the temperature decreases since Cr in liquid becomes depleted as the Cr‐concentrated spinel growth proceeds. Previous studies have shown that Cr ions have an octahedral site preference, and if the majority of octahedral sites are occupied by Cr ions in the Cr‐rich spinel of the present system and an overall decrease in Cr occurs, octahedral sites previously occupied by Cr ions can be substituted by Fe and Ni ions. In spite of the slight decrease in the Fe solubility in the liquid at lower temperatures, the Fe content in the spinel phase increases with lower temperatures.…”

Section: Resultsmentioning

confidence: 99%

Understanding the solidification of stainless steel slag and dust mixtures

2017

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The solidification of a multicomponent stainless steel slag and dust composite has been studied by thermodynamic calculations using Factsage and analyses of samples using EPMA and Rietveld refinement of synchrotron X-ray powder diffraction after various cooling rates. At an apparent cooling rate of 1 K/min, the content of spinel (10.6 wt%) was less than thermodynamically calculated (16.6 wt %), largely because of difficulties in the diffusion of depleted ions (including Cr, Mn, and Ni) in the liquid with very gradual compositional gradients. Melilite showed a uniform but distorted crystal structure of P2 1 2 1 2 and its content (48.9 wt%) was larger than the calculated result (32.3 wt%). At apparent cooling rates of 10 K/min and 50 K/min, a slight decrease in spinel and a significant decrease in melilite were observed, and the spinel was divided into two regions with an identical space group of Fd 3m but with distinguished composition and lattice parameters. However, the amorphous proportion consistently increased with the cooling rate from 29.4 wt% at 1 K/min to 69.6 and 92.9 wt% at 10 K/min and 50 K/min respectively. K E Y W O R D Shazardous waste, phase transformations, spinels, X-ray methods

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“…Paper [8] presents results of crystallographic studies and Raman spectroscopy of ferrite of MgCr x Fe 2−x O 4 (0≤x≤1) system and works [9,10] have revealed crystal-chemical and magnetic properties of the MgCr x Fe 2-х O 4 system ferrites obtained by the ceramic technology from a mixture of oxides. Magnesium chromite with lattice parameter of 8.3347 Å and average particle size of 85-124 nm was synthesized from solutions of metallic nitrates in a stochiometric ratio by hydrothermal method at various pH, temperature and time values [11].…”

Section: Analysis Of the Published Data And Problem Statementmentioning

confidence: 99%

“…Electrical resistivity of nanoferrites of MgCr x Fe 2−x O 4 (0≤x≤1) system obtained by gel-citrate method was measured by authors of work [13]. However, no data on studies of magnetic microstructure by Mössbauer spectroscopy were given in papers [8][9][10][11][12][13].…”

Section: Analysis Of the Published Data And Problem Statementmentioning

confidence: 99%

Mössbauer studies of spinellides of Mg(FeXCr2-X)O4 system obtained by the hydroxide co-precipitation method

Luсas

Moklyak

Yaremiy

et al. 2017

EEJET

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Cation distribution and crystallographic characterization of the spinel oxides MgCr Fe2−O4 by neutron diffraction

Cited by 11 publications

References 12 publications

Significance of Engineering the Octahedral Units to Promote the Oxygen Evolution Reaction of Spinel Oxides

Significance of Engineering the Octahedral Units to Promote the Oxygen Evolution Reaction of Spinel Oxides

Understanding the solidification of stainless steel slag and dust mixtures

Mössbauer studies of spinellides of Mg(FeXCr2-X)O4 system obtained by the hydroxide co-precipitation method

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