FeIVdisproportionation (2FeIV→FeIII+ FeV) in AFeO3(ACa, Sr) perovskite lattices studied by119Sn diamagnetic probe Mössbauer spectroscopy

Demazeau, G.; Fabritchnyi, P.B.; Fournes, L.; Darracq, S.; Presniakov, Igor A.; Похолок, К. В.; Gorkov, V. P.; Etourneaua, J.

doi:10.1039/jm9950500553

Cited by 12 publications

(5 citation statements)

References 23 publications

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“…Disproportionation by the iron charge state has been reported [13] previously when SrFeO 3−δ was doped with 1% Sn 4+ and charge states of Fe 3+ , Fe 4+ and Fe 5+ were observed. The reason suggested for the disproportionation was that in a material in which the lattice parameters are determined by the parent SrFeO 3−δ phase, strains caused by substituting Fe 4+ by a larger Sn 4+ ion are mitigated by adjacent unit cells incorporating a smaller Fe 5+ ion with the concomitant formation of Fe 3+ ions (some of which are already present because of oxygen deficiency) to retain electrical neutrality.This demonstration of disproportionation on incorporation of such a low level of tin would suggest inherent instability in the parent compound.…”

Section: Discussionsupporting

confidence: 65%

“…In the work reported here the tin content greatly exceeds the 1% level of doping in the previous work [13] but the same process may still operate with unit cells incorporating the smaller Fe 5+ ions being adjacent to cells with the larger Sn 4+ ion. However the results recorded here from materials with larger amounts of tin failed to show evidence for the presence of Fe 4+ and thereby indicate complete disproportionation of Fe 4+ to Fe 3+ and Fe 5+ .…”

Section: Discussionmentioning

confidence: 55%

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Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

Berry

Bowfield

Coomer

et al. 2009

J. Phys.: Condens. Matter

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Perovskite-related compounds of composition SrFe(1-x)Sn(x)O(3-δ) (x = 0.31, 0.54) have been prepared. X-ray powder diffraction shows that the materials adopt orthorhombic unit cells. The lattice parameters increase with the incorporation of increasing amounts of tin, which is shown by x-ray absorption near edge structure investigation to be present as Sn(4+). (57)Fe Mössbauer spectroscopy indicates that iron in these phases is present as Fe(5+) and Fe(3+) and that the materials adopt the compositions SrFe(0.69)Sn(0.31)O(2.94) and SrFe(0.46)Sn(0.54)O(2.88). We propose that the disproportionation of Fe(4+) in SrFeO(3-δ) to Fe(5+) and Fe(3+) in SrFe(1-x)Sn(x)O(3-δ) is driven by the reduction of local lattice strain. The materials have been fluorinated by reaction with poly(vinylidene fluoride) to give products of composition SrFe(0.69)Sn(0.31)O(2.31)F(0.69) and SrFe(0.46)Sn(0.54)O(2.54)F(0.46). The increased iron to oxygen or fluorine distances as revealed by the extended x-ray absorption fine structure are associated with the reduction of Fe(5+) to Fe(3+) as evidenced by (57)Fe Mössbauer spectroscopy. The (57)Fe Mössbauer spectra recorded from the fluorinated materials at low temperature show the coexistence of magnetic sextet and non-magnetic doublet components corresponding to networks of Fe(3+) coupled through oxide ions. The Sn(4+) ions disrupt the coupling and the size of the networks. The magnetic susceptibility measurements and Mössbauer spectra recorded between 4.2 and 300 K are used to model the magnetic properties of these materials, with the larger networks appearing to possess random spin orientations consistent with spin glass-type materials.

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Section: Discussionsupporting

confidence: 65%

Section: Discussionmentioning

confidence: 55%

Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

Berry

Bowfield

Coomer

et al. 2009

J. Phys.: Condens. Matter

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“…This has previously been observed by substituting the larger Sn 4+ ions in place of Fe 4+ ions in SrFeO 3Àd , which causes lattice strain that can be mitigated by incorporating smaller Fe 5+ ions. 56,57 In this case the situation is most likely reversed with the smaller Si 4+ ions causing signicant local strain resulting in the Si 4+ being surrounded by the large Fe 3+ ions to relieve the strain with the adjacent cells incorporating the smaller Fe 5+ ions. The untted 57 Fe Mössbauer spectra from SrFe 0.9 Si 0.1 O 3Àd between 300 and 15 K (Fig.…”

Section: Neutron Diffraction Structural Studymentioning

confidence: 99%

Investigation into the effect of Si doping on the performance of SrFeO3−δ SOFC electrode materials

et al. 2013

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In this paper we report the successful incorporation of silicon into SrFeO 3Àd perovskite materials for potential applications as electrode materials for solid oxide fuel cells. It is observed that Si doping leads to a change from a tetragonal cell (with partial ordering of oxygen vacancies) to a cubic one (with the oxygen vacancies disordered). Annealing experiments in 5% H 2 /95% N 2 (up to 800 C) also showed the stabilization of the cubic form for the Si-doped samples under reducing conditions, suggesting that they may be suitable for both cathode and anode applications. In contrast to the cubic cell of the reduced Si doped system, reduction of undoped SrFeO 3Àd leads to the formation of a brownmillerite structure with ordered oxide ion vacancies. SrFe 0.90 Si 0.10 O 3Àd and SrFe 0.85 Si 0.15 O 3Àd were analysed by neutron powder diffraction, and the data confirmed the cubic cell, with no long range oxygen vacancy ordering. Mössbauer spectroscopy data were also recorded for SrFe 0.90 Si 0.10 O 3Àd , and indicated the presence of only Fe 3+ and Fe 5+ (i.e. disproportionation of Fe 4+ to Fe 3+ and Fe 5+) for such doped samples. Conductivity measurements showed an improvement in the conductivity on Si doping. Composite electrodes with 50% Ce 0.9 Gd 0.1 O 1.95 were therefore examined on dense Ce 0.9 Gd 0.1 O 1.95 pellets in two different atmospheres: air and 5% H 2 /95% N 2. In both atmospheres an improvement in the area specific resistance (ASR) values is observed for the Si-doped samples. Thus the results show that silicon can be incorporated into SrFeO 3Àd-based materials and can have a beneficial effect on the performance, making them potentially suitable for use as cathode and anode materials in symmetrical SOFCs.

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“…As shown in Figure 3, the valence state of iron in SrRu 1-x Fe x O 3 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) is determined to be Fe(III) with the isomer shifts, δ = 0.24, 0.26, 0.27, 0.28, and 0.30 mm/s, respectively. [6][7][8] As above mentioned, the magnetic and transport properties of the CaMn 1-x Ru x O 3 (0 < x ≤ 0.8) were studied by Maignan et al, 3 and they explained that the inducement of ferromagnetism and metallicity in the anti-ferromagnetic CaMnO 3 matrix is due to the valence combination (Ru 5+ creating Mn 3+ ), which allows double exchange through the hybridization between Ru and Mn e g orbital. In our system, as Fe 3+ species are introduced into the SrRuO 3 lattice according to the formula of SrRu pression and Sr-O bonds under tension.…”

Section: Resultsmentioning

confidence: 99%

The Variation of Structure and Transporting Property in SrRu_1-xFe_xO₃

2003

Bulletin of the Korean Chemical Society

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The ruthenium based perovskite oxide, SrRuO 3 has been intensively studied due to its diverse electronic and magnetic properties. The structure of SrRuO 3 is orthorhombic (a = 5.573 Å, b = 5.538 Å, c = 7.856 Å), which is similar to that of rare earth orthoferrite, GdFeO 3 , but it can be considered as pseudo-cubic (a p = 3.93 Å). However, the electrical property of both compounds is contradictory to each other, namely a good conductor for SrRuO 3 and an insulator for GdFeO 3 . This might be due to the different electron configurations as GdFeO 3 adopts the high spin t 2g 3 e g 2 of Fe 3+and SrRuO 3 the low spin t 2g 4 e g 0 of Ru 4+ . Recently, the electronic structural variation of ARuO 3 (A = Ca, Sr, and Ba) has been discussed using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Rietveld fitting of the XRD data.1 The ionic radii of A cations (Ca=1.34 Å, Sr=1.44 Å, and Ba=1.61 Å) induces the distorted orthorhombic, particularly hexagonal symmetry for Ba compound. Moreover, the variation in Ru-O and Ru-Ru bond distances has a great influence on the electrical and magnetic properties of these compounds.Some reports on the partial substitution of metal cations in Ru sites of ARuO 3 . (A=Sr, Ca) have been issued. SrTi 1-xRu x O 3-δ (0 ≤ x ≤ 1) deposited films are cubic or pseudocubic over the whole composition range with the lattice parameters increasing continuously with the concentration of Ru 4+ , which correspondingly results in the conductivity variation from insulating to metallic behavior.2 The magnetic and transport properties of CaMn 1-x Ru x O 3 (0 < x ≤ 0.8) were studied by Maignan et al. using resistivity and ac-susceptibility measurements, and they explained that the inducement of ferromagnetism and metallicity in the antiferromagnetic CaMnO 3 matrix is due to the valence combination (Ru 5+ creating Mn 3+ ), which allows double exchange through the hybridization between Ru and Mn e g orbitals.

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Fe^IVdisproportionation (2Fe^IV→Fe^III+ Fe^V) in AFeO₃(ACa, Sr) perovskite lattices studied by¹¹⁹Sn diamagnetic probe Mössbauer spectroscopy

Cited by 12 publications

References 23 publications

Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

Investigation into the effect of Si doping on the performance of SrFeO3−δ SOFC electrode materials

The Variation of Structure and Transporting Property in SrRu_1-xFe_xO₃

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FeIVdisproportionation (2FeIV→FeIII+ FeV) in AFeO3(ACa, Sr) perovskite lattices studied by119Sn diamagnetic probe Mössbauer spectroscopy

Cited by 12 publications

References 23 publications

Fluorination of perovskite-related phases of composition SrFe1−xSnxO3−δ

Fluorination of perovskite-related phases of composition SrFe1−xSnxO3−δ

Investigation into the effect of Si doping on the performance of SrFeO3−δ SOFC electrode materials

The Variation of Structure and Transporting Property in SrRu1-xFexO3

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Product

Resources

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Fe^IVdisproportionation (2Fe^IV→Fe^III+ Fe^V) in AFeO₃(ACa, Sr) perovskite lattices studied by¹¹⁹Sn diamagnetic probe Mössbauer spectroscopy

Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

Fluorination of perovskite-related phases of composition SrFe_1−xSn_xO_3−δ

The Variation of Structure and Transporting Property in SrRu_1-xFe_xO₃