Effet Jahn-Teller coopératif dans le systéme Mn3O4Mn2SnO4

Noguès, M.; Poix, P.

doi:10.1016/0022-4596(74)90091-7

Cited by 30 publications

(9 citation statements)

References 3 publications

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“…There are two different distances (Cr 3+ -O) 6 equal to 0.198 and 0.199 nm (Ivanov & Talanov, 1995b). Similar experimental data obtained for other crystals (for Mn spinels, see Nogues & Poix, 1974, 1972 confirm the proposed mechanism of tetragonal distortion of the spinel. It is of interest that the formation of a tetragonally elongated tetrahedron leads to the formation of a tetragonal shortened octahedron (Fig.…”

Section: Stratification Of Wyckoff Positionsupporting

confidence: 85%

Tilting structures in spinels

Таланов¹,

Широков²

2012

Acta Cryst Sect A

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The possible distortions in the spinel structure resulting from rotation of the tetrahedra and octahedra have been investigated by a group-theoretical method. The possibility of the existence of 28 phases of rotation of the tetrahedra and five phases of rotation of the octahedra has been shown. In all these phases the polyhedra are equivalent, but their orientation can be different. Among the phases of the tetrahedra rotation there is one phase of pure rotation, i.e. not accompanied by additional (not rotation) distortions of the structure. Of the five phases of the rotation of the octahedra three phases can be obtained only by pure rotation of the octahedra.

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Section: Stratification Of Wyckoff Positionsupporting

confidence: 85%

Tilting structures in spinels

Таланов¹,

Широков²

2012

Acta Cryst Sect A

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“…The patterns show that the Zn(II) phases formed are not pure Zn(II)Mn(III) 2 O 4 , but exhibit XRD reflections at 2θ positions intermediate between those of hetaerolite (Zn(II)Mn(III) 2 O 4 ) and hausmannite (Mn(II)Mn(III) 2 O 4 ). Hausmannite and hetaerolite both have normal spinel structures with Mn(III) occupying the octahedral site, but the tetrahedral site is occupied by Zn(II) in hetaerolite, and by Mn(II) in hausmannnite. , We have previously shown that reaction of Mn(II) with birnessite at pH 8.0 and 8.5 readily produces hausmannite according to: The structural similarity of hausmannite and hetaerolite and the ease with which they precipitate in our experimental systems makes Mn(II)-for-Zn(II) substitution likely during precipitation of hetaerolite in the presence of Mn(II). Such substitutions would account for the XRD results suggesting formation of a hetaerolite:hausmannite solid solution (Figure ), and explain the high level of Mn(II) sorption observed in the ternary system (Figure b).…”

Section: Exafs and Powder Xrd Datamentioning

confidence: 75%

Impacts of Aqueous Mn(II) on the Sorption of Zn(II) by Hexagonal Birnessite

Lefkowitz

Elzinga

2015

Environ. Sci. Technol.

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We used a combination of batch studies and spectroscopic analyses to assess the impacts of aqueous Mn(II) on the solubility and speciation of Zn(II) in anoxic suspensions of hexagonal birnessite at pH 6.5 and 7.5. Introduction of aqueous Mn(II) into pre-equilibrated Zn(II)-birnessite suspensions leads to desorption of Zn(II) at pH 6.5, but enhances Zn(II) sorption at pH 7.5. XAS results show that Zn(II) adsorbs as tetrahedral and octahedral triple-corner-sharing complexes at layer vacancy sites when reacted with birnessite in the absence of Mn(II). Addition of aqueous Mn(II) causes no discernible change in Zn(II) surface speciation at pH 6.5, but triggers conversion of adsorbed Zn(II) into spinel Zn(II)1-xMn(II)xMn(III)2O4 precipitates at pH 7.5. This conversion is driven by electron transfer from adsorbed Mn(II) to structural Mn(IV) generating Mn(III) surface species that coprecipitate with Zn(II) and Mn(II). Our results demonstrate substantial production of these reactive Mn(III) surface species within 30 min of contact of the birnessite substrate with aqueous Mn(II). Their importance as a control on the sorption and redox reactivity of Mn-oxides toward Zn(II) and other trace metal(loid)s in environments undergoing biogeochemical manganese redox cycling requires further study.

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“…[23b] Literature reports also indicate that the tetrahedral site is preferred by Zn 2+ in various spinel oxides, such as ZnMn 2 O 4 and ZnCo 2 O 4 . [15,23b] The FT spectra of Mn and Co (Figure b,c) look similar to that of either octahedral‐Co in ZnCo 2 O 4 or octahedral‐Mn in ZnMn 2 O 4 , confirming the unchanged coordination environment of Mn and Co on substitution. Thus, the Mn and Co cations are occupying the octahedral sites in all the spinel ZnCo x Mn 2− x O 4 ( x = 0.0–2.0) oxides synthesized here.…”

mentioning

confidence: 70%

“…Interactions could be direct between TM cations (e.g., B–B) via t 2g orbital overlap, and by superexchange between TM cations mediated through oxygen anions (e.g., A–O–B, B–O–B) . Since Zn 2+ has a strong preference for tetrahedral sites and its d orbital is fully occupied (3d 10 ), catalytic contribution from the tetrahedra and A–O–B interactions via corner sharing tetrahedra/octahedra is not possible. Therefore, this study facilitates an exclusive investigation of the effect of edge‐sharing [Co x Mn 1− x O 6 ] octahedra in the spinel ZnCo x Mn 2− x O 4 oxides.…”

mentioning

confidence: 99%

Superexchange Effects on Oxygen Reduction Activity of Edge‐Sharing [Co_xMn₁₋_xO₆] Octahedra in Spinel Oxide

et al. 2018

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Mn-Co containing spinel oxides are promising, low-cost electrocatalysts for the oxygen reduction reaction (ORR). Most studies are devoted to the design of porous Mn-Co spinels or to strongly coupled hybrids (e.g., MnCo O /N-doped-rmGO) to maximize the mass efficiency. The lack of analyses by metal oxide intrinsic activity (activity normalized to catalysts' surface area) hinders the development of fundamental understanding of the physicochemical principles behind the catalytic activities. A systematic study on the composition dependence of ORR in ZnCo Mn O (x = 0.0-2.0) spinel is presented here with special attention to the role of edge sharing [Co Mn O ] octahedra in the spinel structure. The ORR specific activity of ZnCo Mn O spans across a potential window of 200 mV, indicating an activity difference of ≈3 orders of magnitude. The curve of composition-dependent ORR specific activity as a function of Co substitution exhibits a volcano shape with an optimum Mn/Co ratio of 0.43. It is revealed that the modulated e occupancy of active Mn cations (0.3-0.9), as a consequence of the superexchange effect between edge sharing [CoO ] and [MnO ], reflects the ORR activity of edge sharing [Co Mn O ] octahedra in the ZnCo Mn O spinel oxide. These findings offer crucial insights in designing spinel oxide catalysts with fine-tuned e occupancy for efficient catalysis.

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Effet Jahn-Teller coopératif dans le systéme Mn3O4Mn2SnO4

Cited by 30 publications

References 3 publications

Tilting structures in spinels

Tilting structures in spinels

Impacts of Aqueous Mn(II) on the Sorption of Zn(II) by Hexagonal Birnessite

Superexchange Effects on Oxygen Reduction Activity of Edge‐Sharing [Co_xMn₁₋_xO₆] Octahedra in Spinel Oxide

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Effet Jahn-Teller coopératif dans le systéme Mn3O4Mn2SnO4

Cited by 30 publications

References 3 publications

Tilting structures in spinels

Tilting structures in spinels

Impacts of Aqueous Mn(II) on the Sorption of Zn(II) by Hexagonal Birnessite

Superexchange Effects on Oxygen Reduction Activity of Edge‐Sharing [CoxMn1−xO6] Octahedra in Spinel Oxide

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Superexchange Effects on Oxygen Reduction Activity of Edge‐Sharing [Co_xMn₁₋_xO₆] Octahedra in Spinel Oxide