Crystal structures, charge and oxygen-vacancy ordering in oxygen deficient perovskites SrMnOx (x&lt;2.7)

Suescun, Leopoldo; Chmaissem, O.; Mais, J.; Dąbrowski, B.; Jorgensen, J. D.

doi:10.1016/j.jssc.2007.03.020

Cited by 49 publications

(67 citation statements)

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“…This annealing condition does not induce a transformation from cubic SrMnO 3 to hexagonal SrMnO 3 . 6 The prepared samples were characterized by XRD with Cu K␣ radiation ͑ = 1.5406 Å͒. O-K and Mn-L 2,3 edge EEL spectra were obtained with crushed polycrystalline particles supported on holey carbon films by an EEL spectrometer ͑EELS, Model 766 Enfina, Gatan Inc.͒ attached to a STEM ͑JEM-2100F, JEOL Ltd.͒, which was operated at 200 kV.…”

Section: Methodsmentioning

confidence: 99%

“…5 To obtain cubic SrMnO 3 , a certain annealing condition of temperature and oxygen partial pressure is necessary in order to avoid the formation of hexagonal SrMnO 3 . 6 Cubic SrMnO 3 does not contain oxygen vacancies and the linkage of the oxygen octahedrons does not contain distortions, and thus the oxidation state of Mn is 4+. On the other hand, pseudocubic SrMnO 3−␦ and orthorhombic SrMnO 2.5 have a distorted linkage of oxygen octahedrons.…”

Section: Introductionmentioning

confidence: 99%

“…The manner of the linkage and the distortion of the oxygen octahedrons are varied by the presence of oxygen vacancies. 4,6,7 The variation of the Mn oxidation states in SrMnO 3−␦ is very attractive from a viewpoint of mixed valences of manganese oxides. For example, perovskite manganites of La x A 1−x MnO 3 ͑A being a divalent cation͒ show remarkable properties such as colossal magnetoresistance ͑CMR͒ due to the correlation between magnetism and electronic states.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Kobayashi

Tokuda

Mizoguchi

et al. 2010

Journal of Applied Physics

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The oxidation state of Mn in cubic SrMnO 3 and orthorhombic SrMnO 2.5 was investigated by electron energy loss ͑EEL͒ spectroscopy. Change in the oxidation state of Mn produced some spectral changes in the O-K edge as well as in the Mn-L 2,3 edge EEL spectra. This study demonstrated that the oxidation state of Mn and the amount of oxygen vacancies in cubic SrMnO 3 and orthorhombic SrMnO 2.5 could be quantified by analyzing the features of the O-K edge spectrum and the Mn L 3 / L 2 ratio in the Mn-L 2,3 edge spectrum. Our quantitative analysis showed that the spectral changes in the Mn-L 2,3 edge were mainly caused by the oxidation state of Mn, whereas those in the O-K edge could be sensitive to both the oxidation state of Mn and to lattice distortions.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Kobayashi

Tokuda

Mizoguchi

et al. 2010

Journal of Applied Physics

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“…For the (8) octahedra, the four bonds in the aÀc plane with an average distance of 1.92 Å are significantly shorter than the two bonds out of the plane, 2.22 Å, whereas for the tetrahedra, the four bond lengths range from 1. 12,13 There does not appear to be a simple, straightforward explanation for the remarkable absence of tetrahedral chains in the long-range sense, which is equivalent to the destruction of oxide vacancy order, in proceeding from Ca 2 FeMnO 5 to Sr 2 X-ray diffraction and refers to the average structure. Our NPDF and M€ ossbauer results show that the local structure is more Figure 5.…”

Section: ' Introductionmentioning

confidence: 99%

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Ramezanipour¹,

Greedan²,

Siewenie

et al. 2011

Inorg. Chem.

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Local and average structures and magnetic properties of of Sr2FeMnO5+y, y = 0.0, 0.5. comparisons with Ca2FeMnO5 and the effect of the A-site cation Ramezanipour, Farshid; Greedan, John E.; Siewenie, Joan; Proffen, Th.; Ryan, Dominic H.; Grosvenor, Andrew P.; Donaberger, Ronald L.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. Oxygen-deficient perovskites can have a variety of structures depending on different factors including the degree of anion deficiency and the composition. In this article, the focus is on oxygen-deficient perovskites with the formula A 2 BB 0 O 5+x . The oxygen vacancies can order to form the brownmillerite structure in which the B cations are octahedrally coordinated, forming corner-sharing layers, and the B 0 cations are tetrahedrally coordinated, forming corner-sharing chains. (Figure 1). This longrange vacancy ordering results in a supercell that generally has dimensions with respect to the cubic perovskite cell constant, a p , of a br ≈ 2 1/2 a p , b br ≈ 4a p , and c br ≈ 2 1/2 a p . A number of different space group symmetries are observed, depending on subtle differences in the ordering of the tetrahedral chains within the unit cell. The chains can show either a right-handed (R) or lefthanded (L) orientation and the correlation between the intraand interlayer chain orientations and the resulting space groups are summarized in ABSTRACT: Sr 2 FeMnO 5+y was synthesized under two different conditions, in air and in argon, both of which resulted in a cubic, Pm3m, structure with no long-range ordering of oxygen vacancies. The unit cell constants were found to be a 0 = 3.89328(1) Å for argon (y = 0.0) and a 0 = 3.83075(3) Å for air (y = 0.5). In contrast, Ca 2 FeMnO 5 retains long-range brownmillerite oxygen vacancy ordering for either air or argon synthesis. Remarkably, Sr 2 FeMnO 5.0 oxidizes spontaneously in air at room temperature. A neutron pair distribution function (NPDF) study of Sr 2 FeMnO 5.0 (Ar) showed evidence for local, brownmillerite-like ordering of oxygen vacancies for short distances up to 5 Å. M€ ossbauer spectroscopy results indicate more than one Fe site for Sr 2 FeMnO 5+y (Ar and air), consistent with the noncubic local structure found by NPDF analysis. The isomer shifts and quadrupole splittings in both air-and argon-synthesized materials are consistent with the 3+ oxidation state for Fe in sites with coordination number four or five. This is confirmed by an L-edge XANES study. Mn is almost entirely in the 3+ state for Sr 2 FeMnO 5.0 (Ar), whereas Mn 4+ is predominantly present for Sr 2 FeMnO 5.5 (air). Magnetic susceptibility data show zero-fieldcooled/field-cooled (ZFC/FC) divergences near 50 K for the Ar sample and 25 K for the air sample, whereas Ca 2 FeMnO 5 is longrange G-type antiferromagnetically ordered at 407(2) K. Hyperfine magnetic splitting, observed in temperature-dependent M€ ossbauer measurements, indicates short-range magnetic correlations that persist up to 150 K for Sr 2 FeMnO 5.0 (Ar) and 100 K for Sr 2 FeMnO 5.5 (air), well above the ZF...

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“…13 Various oxygenvacancy order patterns are formed, depending on the choice of A and B cations and the oxygen vacancy level. Examples include ¤ = 1/8 (SrFeO 2.875 ), 11 ¤ = 1/5 (CaVO 2.8 ), 14 ¤ = 1/4 (SrFeO 2.75 ), 11 ¤ = 2/5 (SrMnO 2.6 ), 15 and ¤ = 1/2 (LaNiO 2.5 ). …”

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Hydride Reductions of Transition Metal Oxides

Yamamoto

Kageyama

2013

Chemistry Letters

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Low-temperature reactions are a powerful approach to generate new transition metal oxides that are inaccessible by conventional high-temperature reactions. In this review, we describe the recent progress of the topochemical reduction method using metal hydrides for transition metal oxides, in particular, focusing on structural modifications (relations), chemical and physical properties, and the factors that direct selective and rational preparations. The hydride reduction has been so far extensively applied to 3d transition metal perovskite oxides, yielding highly reduced products with unusual coordination environment (e.g., FeO 4 square-planar coordination), and extremely low-valent metal centers (e.g., Mn(I) and Co(I)). Non-perovskite oxides like pyrochlore and hexagonal perovskite can be also reduced. Moreover, this method allows access to oxyhydride materials (LaSrCoO 3 H 0.7 and BaTiO 3¹x H x ) that are promising for use as hydride ion conductors. Morphology-controlled oxides (thin film-and nano-oxides) are useful targets for hydride reduction, opening new possibilities for extending functions. Ç IntroductionTransition metal (TM) oxides like spinel and perovskite oxides represent a variety of exotic and useful chemical and physical properties that include magnetoresistance, multiferroics, superconductivity, photocatalysis, thermoelectricity, and so on.17 These properties are closely related to the valence, spinstate, coordination of transition metal centers, and how they are connected to form an extended network. In order to achieve improved or new properties, cation chemistry has been often executed. For example, tuning the MnOMn bridging angle in LaMnO 3 by rare-earth substitution induces a large multiferroic responce.8 However, conventional solid-state synthesis at high temperature produces only thermodynamically stable products and permits limited access to structural modifications.Low-temperature reactions have attracted recent attention owing to its kinetics-driven nature, providing, in principle, rational and predictable design of structures and compositions as a metastable product. Ion-exchange reaction is such a process, which is found in minerals (e.g., clay), and is also of technological and industrial importance since nearly a century ago. Intercalation (deintercalation) reactions involve reactive species to be inserted into (extracted from) a host compound. The important feature in these soft chemical reactions is that the structural framework remains unchanged when comparing the starting and final compounds during the reaction. Therefore, if a suitable reaction condition (precursor material, reactant, temperature, etc.) is chosen, one may obtain a desired structure and composition with novel functionalities.TM perovskite ABO 3 oxides (Figure 1a) have high tolerance to oxygen deficiency (ABO 3¹¤ ), as found in SrFeO 3¹¤ and LaNiO 3¹¤ . 11,12 Increase of the oxygen content in the perovskiterelated cuprate YBa 2 Cu 3 O 7¹¤ (0¯¤¯1) gives rise to drastic change in the ground states, from ...

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Crystal structures, charge and oxygen-vacancy ordering in oxygen deficient perovskites SrMnOx (x<2.7)

Cited by 49 publications

References 20 publications

Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation

Hydride Reductions of Transition Metal Oxides

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Crystal structures, charge and oxygen-vacancy ordering in oxygen deficient perovskites SrMnOx (x<2.7)

Cited by 49 publications

References 20 publications

Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Quantitative analyses of oxidation states for cubic SrMnO3 and orthorhombic SrMnO2.5 with electron energy loss spectroscopy

Local and Average Structures and Magnetic Properties of Sr2FeMnO5+y, y = 0.0, 0.5. Comparisons with Ca2FeMnO5 and the Effect of the A-Site Cation

Hydride Reductions of Transition Metal Oxides

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Local and Average Structures and Magnetic Properties of Sr₂FeMnO_5+y, y = 0.0, 0.5. Comparisons with Ca₂FeMnO₅ and the Effect of the A-Site Cation