Cation distribution and valence in synthetic Al–Mn–O and Fe–Mn–O spinels under varying  conditions

Stokes, Thomas N.; Bromiley, Geoffrey; Gatta, G. Diego; Rotiroti, Nicola; Potts, N. J.; Saunders, Kate

doi:10.1180/mgm.2018.109

Cited by 9 publications

(8 citation statements)

References 54 publications

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“…The rising edge position (determined from the first-derivative maximum of the main absorption edge) was shifted toward higher values in comparison to Mn 0.5 Fe 2.5 O 4 . This indicates more oxidized Mn in the abiotic magnetite samples than in the measured Mn-ferrite reference, which has been shown to contain 25% Mn(III) and 75% Mn(II), − , while the biological magnetite overlapped the Mn-ferrite reference, which suggests a similar valence for Mn. Therefore, based on the shift of the absorption edge position, the Mn(III)/Mn total ratios in the abiotic and biologic magnetites were taken as 0.3 (i.e., higher than that of the Mn-ferrite reference) and 0.25 (i.e., similar to that of the Mn-ferrite reference), respectively.…”

Section: Resultsmentioning

confidence: 86%

“…K-edge XAS for Mn-doped abiotic magnetite (Figure A) has near-edge structural features that resemble a Mn 0.5 Fe 2.5 O 4 reference (where Mn is a mixture of Mn(II) located in tetrahedral sites and Mn(III) in octahedral sites). − Comparison with Mn-based oxides shows an oxidation state between Mn(II) and Mn(III) but closer to MnO. This is reflected by the position of the main rising edge (Figure S5).…”

Section: Resultsmentioning

confidence: 97%

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Crystal–Chemical and Biological Controls of Elemental Incorporation into Magnetite Nanocrystals

et al. 2023

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Magnetite nanoparticles possess numerous fundamental, biomedical, and industrial applications, many of which depend on tuning the magnetic properties. This is often achieved by the incorporation of trace and minor elements into the magnetite lattice. Such incorporation was shown to depend strongly on the magnetite formation pathway (i.e., abiotic vs biological), but the mechanisms controlling element partitioning between magnetite and its surrounding precipitation solution remain to be elucidated. Here, we used a combination of theoretical modeling (lattice and crystal field theories) and experimental evidence (high-resolution inductively coupled plasma–mass spectrometry and X-ray absorption spectroscopy) to demonstrate that element incorporation into abiotic magnetite nanoparticles is controlled principally by cation size and valence. Elements from the first series of transition metals (Cr to Zn) constituted exceptions to this finding, as their incorporation appeared to be also controlled by the energy levels of their unfilled 3d orbitals, in line with crystal field mechanisms. We finally show that element incorporation into biological magnetite nanoparticles produced by magnetotactic bacteria (MTB) cannot be explained by crystal–chemical parameters alone, which points to the biological control exerted by the bacteria over the element transfer between the MTB growth medium and the intracellular environment. This screening effect generates biological magnetite with a purer chemical composition in comparison to the abiotic materials formed in a solution of similar composition. Our work establishes a theoretical framework for understanding the crystal–chemical and biological controls of trace and minor cation incorporation into magnetite, thereby providing predictive methods to tailor the composition of magnetite nanoparticles for improved control over magnetic properties.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 97%

Crystal–Chemical and Biological Controls of Elemental Incorporation into Magnetite Nanocrystals

et al. 2023

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“…4A, inset). Near-edge features of Mn-doped magnetite correspond more so with a Mn-ferrite reference (Mn0.5Fe2.5O4) 22 indicating similar chemical and structural environment. However, weaker pre-edge and post-edge features (6562 eV) potentially originate from the dilute and inhomogenous nature of the dopant metal in the magnetite lattice compared to the Mn-ferrite reference.…”

Section: Crystal Field Constraints On Element Incorporation Into Magnetite and Coordination Of 3d Metals In Magnetitementioning

confidence: 75%

Crystal-chemical and biological controls of trace and minor element incorporation into magnetite nanocrystals

Amor

Faivre

Chevrier

2021

Preprint

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Magnetite nanoparticles possess numerous fundamental, biomedical and industrial applications, many of which depend on tuning the magnetic properties. This is often achieved by the incorporation of trace and minor elements into the magnetite lattice. Such incorporation was shown to depend strongly on the magnetite formation pathway (i.e., abiotic vs biological), but the mechanisms controlling element partitioning between magnetite and its surrounding precipitation solution remain to be elucidated. Here, we used a combination of theoretical modelling (lattice and crystal field theories) and experimental evidence (high-resolution inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy) to demonstrate that element incorporation into abiotic magnetite nanoparticles is controlled principally by cation size and valence. Elements from the first series of transition metals (Cr to Zn) constituted exceptions to this finding as their incorporation appeared to be also controlled by the energy levels of their unfilled 3d orbitals, in line with crystal field mechanisms. We then show that element incorporation into biological magnetite nanoparticles produced by magnetotactic bacteria (MTB) cannot be explained by crystal-chemical parameters alone, which points to the biological control exerted by the bacteria over the element transfer between MTB growth medium and the intracellular environment. This screening effect generates biological magnetite with a purer chemical composition than the abiotic materials formed in a solution of similar composition. Our work establishes a theoretical framework for understanding the crystal-chemical and biological controls of trace and minor cation incorporation into magnetite, thereby providing predictive methods to tailor the composition of magnetite nanoparticles for improved control over magnetic properties.

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“…Since the valence state also affects the properties of the spinel, it is fundamental to estimate the average valence state when present mixed spinels. By intensity ratios of X-Ray diffraction planes sensitive to cation distribution; which is an easiest and more reliable technique rather than neutron diffraction, Mossbauer spectroscopy or X-Ray photoelectron spectroscopy [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…In batteries one aspect that might dictate the electrochemical behavior of the spinel in the electrochemical cell is the cation distribution of the atoms in the structure since a redox couple and the valence of the transition metals tends to change to lower or higher average valence. Then, to study the cation distribution of these spinels we developed a 2 more accurate method to approximate the cation distribution based on the works of Bertaut et al, Ashish and Hiren, Siva Ram Prasad et al and Lakhani et al [3,9,12].…”

Section: Introductionmentioning

confidence: 99%

Modified Bertaut Method to Determine Cation Distribution and Valence State in Powders of Spinels Through X-ray Diffraction

Hernandez de la Cruz,

Mani Gonzalez

2024

Preprint

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In this work a new method is proposed to tackle down the multiple objective optimization problem of the calculation of cation distribution in spinels structure, through the difference of intensity ratios between experimental and calculated intensities of cation sensitive Bragg planes, by introducing a new factor, Rabs, in Bertaut method. This factor is introduced as the sum of absolute R factors, and it is minimized by varying cation distribution. To test this method aluminate manganese spinel where synthesized though modified Pechini method and characterized though XRD. The results show to be in agreement with literature for the aluminum inversion in tetrahedral sites, which is near to the reported value of 10%. Also, it was noticed that the manganese atoms are present in octahedral sites with a mixed valence state of +2 and +3. Which might be an indicator that oxygen vacancies are present in the structure, so the vacancies value of oxygen is proposed considering the total charge of cations and thus proposing the value of 3.678 mol per formula unit of the spinel, thus having the next stoichiometry considering normalized Al and Mn, MnAl2O3.678. Finally, the last cation distribution proposed was [Mn0.867^(+2) Al0.129^(+3) ][Mn0.034^(+2) Mn0.098^(+3) Al1.871^(+3) ] O3.678 with a Rabs factor value of 0.6466, which considers the cation distribution and oxygen vacancies.

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Cation distribution and valence in synthetic Al–Mn–O and Fe–Mn–O spinels under varying conditions

Cited by 9 publications

References 54 publications

Crystal–Chemical and Biological Controls of Elemental Incorporation into Magnetite Nanocrystals

Crystal–Chemical and Biological Controls of Elemental Incorporation into Magnetite Nanocrystals

Crystal-chemical and biological controls of trace and minor element incorporation into magnetite nanocrystals

Modified Bertaut Method to Determine Cation Distribution and Valence State in Powders of Spinels Through X-ray Diffraction

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