Oxygen deficiency and formation of a new ordered perovskite-based structure Sr(Sr0.5Sb0.5)O3−y

Saïdi, Mohamed; Morán, E.; Amador, Ulises; Gallardo‐Amores, J. M.; Abboudi, Mostafa; Asskali, Abderrahman

doi:10.1016/s1466-6049(00)00103-3

Cited by 6 publications

(7 citation statements)

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“…Sb has been very often found to occupy the B position of a perovskite structure in a pentavalent oxidation state, with a spherical symmetry (4d 10 5s 0 5p 0 ) which is well-suited for the required octahedral oxygen coordination of this site. [22][23][24][25][26][27] On the other hand, the increment of the Co oxidation state with the Sb doping level could be explained by the concomitant increase of the oxygen content as evidenced not only by XANES results but also by thermogravimetric and neutron powder diffraction measurements (Table 1). This is also in agreement with the huge tendency of Sb to be located at a fully oxygenated octahedron, as required for the spherical symmetry of Sb 5+ .…”

Section: Crystal Structurementioning

confidence: 98%

Evolution of cobalt spin states and magnetic coupling along the SrCo1−xSbxO3−δ system: correlation with the crystal structure

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Retuerto

Jiménez-Villacorta

et al. 2011

Phys. Chem. Chem. Phys.

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The oxides of the SrCo(1-x)Sb(x)O(3-δ) perovskite family have been recently designed, characterized and described as cathode materials for solid-oxide fuel cells with competitive power performance in the temperature range 750-850 °C. They feature a number of interesting properties including a good electronic conductivity, low electrode polarization resistance and adequate thermal expansion; the crystal structure adopts a 3C corner-linked perovskite network with a considerable number of oxygen vacancies. This paper reports on the effects of Sb-doping on the crystal structure features, the Co oxidation state and magnetic properties related to the presence of spin-state transitions in the Co cations. A phase transition was observed from the tetragonal P4/mmm space group for x≤ 0.15 to the cubic Pm ̅3m space group in the x = 0.2 composition from neutron powder diffraction data. For the tetragonal phases the oxygen vacancies were found to be ordered and localized in the axial O2 and equatorial O3 atoms surrounding the Co2 positions. A noticeable distortion of CoO(6) octahedra is observed for x = 0.05 and 0.1, exhibiting a charge-ordering with a mixed oxidation state of Co(3+/4+) at Co1 sites and Co(3+) at Co2 positions: the Jahn-Teller Co(3+) in an intermediate-spin configuration is responsible for the octahedral distortion. Increasing Sb contents promotes a higher average oxidation state of cobalt, from a valence of 3.2+ for x = 0.05 to 3.4+ for x = 0.2, inducing a decrease of the oxygen vacancies and favouring a random distribution over a Pm ̅3m cubic symmetry. All the samples present an antiferromagnetic behaviour with a G-type (k = 0) magnetic structure. The increase of the Sb content induces the weakening of the crystal field (Δ(cf)) in the octahedral environment promoting the Co spin-transition from the intermediate-spin to the high-spin configuration, as evidenced by the decrease of the octahedral distortion, increment of the unit-cell volume and enhancement of the ordered magnetic moment.

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Section: Crystal Structurementioning

confidence: 98%

Evolution of cobalt spin states and magnetic coupling along the SrCo1−xSbxO3−δ system: correlation with the crystal structure

Aguadero

Retuerto

Jiménez-Villacorta

et al. 2011

Phys. Chem. Chem. Phys.

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“…The other features were again very reminiscent of a perovskite phase, but it proved very difficult to find a reasonable Rietveld simulation (generated from known structural parameters) to the data. The major peaks were eventually and very tentatively assigned according to a close visual match to the peaks of oxygen-deficient perovskite-type phases exhibited by, for example, Sr(Sr 0.5 Sb 0.5 )O 3 - y . The peaks indexed in Figure are assigned to a phase with an orientation based on a distorted perovskite type lattice, although this should be used only for comparison purposes rather than as an absolute assignment.…”

mentioning

confidence: 99%

“…It is highly unusual for any material to form a perovskite phase containing the same type of atoms in both A- and B-type sites. However, there are some data in the literature that in certain materials Sr 2+ can share A- and B-site locations . There are, however, no reports of a perovskite of effective formula M 2 O 3 (although this may be more correctly described by the formula M 2 O 3 - x ).…”

mentioning

confidence: 99%

“…The major peaks were eventually and very tentatively assigned according to a close visual match to the peaks of oxygen-deficient perovskite-type phases exhibited by, for example, Sr(Sr 0.5 Sb 0.5 )O 3-y . 21 The peaks indexed in Figure 4 are assigned to a phase with an orientation based on a distorted perovskite type lattice, although this should be used only for comparison purposes rather than as an absolute assignment.…”

mentioning

confidence: 99%

“…However, there are some data in the literature that in certain materials Sr 2+ can share A-and B-site locations. 21 There are, however, no reports of a perovskite of effective formula M 2 O 3 (although this may be more correctly described by the formula M 2 O 3-x ). Thallium has been reported as occupying B-type perovskite sites 22 in BaTl 0.5 Sb 0.5 O 3 but is more normally associated with filling of the A-sites because of the relatively large size of Tl 3+ ions.…”

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Synthesis and Characterization of a Novel Perovskite-like Phase of Thallium Oxide

Lyons

Morris

2002

Crystal Growth & Design

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Investigations directed toward the preparation of the common IA3 phase of thallium oxide by thermal decomposition of thallium nitrate has led to the synthesis of novel and previously undescribed thallium oxide phases under controlled conditions. An unexpected material with a perovskite-like MMO 3 (M ) Tl 3+ ) structure was formed. Two other thallium oxide phases that appear to be highly anion deficient were also discovered. It is argued that the perovskite phase is produced by the reaction of Tl 2 O 3 (cubic IA3 rare-earth structure) with Tl 2 O formed by thermal decomposition and the oxidation of a Tl 5 O 4 Tl product of reaction. These materials show temperature-dependent insulating and conducting properties.Thallium is generally regarded as toxic, but various thallium compounds have been used for the treatment of ringworm and other skin infections 1 and as a chemical tracer in diagnosis, particularly in cardiology. 2 Thallium compounds are also used for X-ray imaging 3 and infrared detection. 4 Its medical use is limited by a very narrow window between therapeutic and toxic behavior. Thallium is a very important ingredient of many hightemperature oxide superconductors, 5 due to the wide range of stoichiometry over which superconductivity is observed in such thallium-doped materials. 6 All of these superconducting compounds adopt structures based around the perovskite IA3 structure. 7 Tl 3+ ions normally adopt the A-site in perovskite structures as, for example, in TlNiO 3 8 and (Tl,Pb)-(Sr,Ba)O 3 . 9 In pyrochlore structures thallium ions may also adopt sites between the distorted MO 6 octahedra. 10 The superconducting thallium-containing materials are typically thallium barium calcium cuprates of general formula Tl 2 Ba 2 Ca n-1 Cu n O 4n+2 , in which the calcium and copper (and oxygen) form perovskite-like blocks and the thallium forms Tl 2 O 2 layers which adopt a layered rock salt like structure between the perovskite blocks. 11 The thallium sites exist in these layers in an arrangement that (in ideal structures) can be considered as a bilayer. In this bilayer the first layer consists of thallium ions in a square-planar arrangement similar to that found for the A site in perovskites (i.e., a square-planar arrangement of oxygen ions around the thallium cation). The second layer below it consists of a layer of thallium cations adopting the B-site arrangement from which the usual cations have been removed and an additional oxygen ion placed in the square-planar arrangement of B-type site thallium ions. The structural analysis of these materials is difficult because of the complexity of the systems, the large unit cells observed and distortions of the square-planar arrangement which are known. 12 Rietveld analysis of powder X-ray diffraction data is traditionally used for structural determination, although this technique, for these complex structures, is relatively insensitive to different substitutional arrangements (for example, substitution of thallium rather

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Oxides: Solid‐State Chemistry

McCarroll

Ramanujachary

2005

Encyclopedia of Inorganic Chemistry

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This article is an overview of the solid‐state chemistry of oxides. It starts with a brief description of the periodic trends associated with compounds of oxygen and is followed by a discussion of the principle of the closest packing of spheres that can be used to describe ionic structures. An in depth description of several structure types, important in solid‐state oxide chemistry, follows, and covers the important binary structures as well as several ternary structures including the Perovskite, Spinel, Garnet, Pyrochlore, and Scheelite structures. Selected special topics in solid‐state oxide chemistry include a discussion of crystallographic shear structures, defect oxides, and tungsten and molybdenum bronzes, intergrowth structures of which the high‐temperature superconductor YBa 2 Cu 3 O 7 is an example. The importance of structure‐property relations in oxides is illustrated by a discussion of metal–metal bonds in oxides, electronic conduction in a variety of oxides, and the catalytic properties of defect scheelites. A lengthy discussion is devoted to the various means used by solid‐state chemists to synthesize oxides not only as bulk polycrystalline phases but as single crystals and thin films as well that are so important to electronic applications. The article concludes with a discussion of several important practical applications of oxides including magnetic oxides, oxide sensors, luminescent materials, ferroelectrics, CMR oxides, optical materials, ceramics, and refractory materials as well as a brief overview of other important uses. Because this is a survey article, in depth discussion of many properties of oxides is not possible. However, many of these topics are covered in depth in other parts of the Encyclopedia and the reader will find the cross references helpful. A substantial list of references also provides a gateway to the solid‐state literature.

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Oxygen deficiency and formation of a new ordered perovskite-based structure Sr(Sr0.5Sb0.5)O3−y

Cited by 6 publications

References 20 publications

Evolution of cobalt spin states and magnetic coupling along the SrCo1−xSbxO3−δ system: correlation with the crystal structure

Evolution of cobalt spin states and magnetic coupling along the SrCo1−xSbxO3−δ system: correlation with the crystal structure

Synthesis and Characterization of a Novel Perovskite-like Phase of Thallium Oxide

Oxides: Solid‐State Chemistry

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