Topotactic Electrochemical Redox Reactions of the Defect Perovskite SrCoO<sub>2.5+<i>x</i></sub>

Nemudry, A. P.; Rudolf, and P.; Schöllhorn, R.

doi:10.1021/cm950504+

Cited by 122 publications

(145 citation statements)

References 19 publications

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“…[22,28] We compared the unit cell volume of these annealed films to that of the as-grown P-SCO ozone films (see Figure S3 for θ-2θ scans), which have essentially stoichiometric concentrations of oxygen. [23,29,30] As seen in Fig. 1b, the unit cell volume of the P-SCO ozone films increased monotonically with strain for all but the ε = 4.2% film, which may be due to a slight change in oxygen stoichiometry.…”

Section: Structural Analysis Of Annealed Bm-sco and P-sco Filmsmentioning

confidence: 79%

“…[26] Supporting Information Supporting Information is available from the Wiley Online Library or from the author. [29,30,34,37] From this combined data set, x is found to range from just below 3 to 2.75 as tensile strain increases from ε = 1% to ε = 4.2% , and e) while those of annealed P-SCO are displayed on the right panels in b), d), and e). We note that the growth in highly oxidizing ambient using ozone could improve the oxygen stoichiometry.…”

Section: Characterization Of Structural and Physical Propertiesmentioning

confidence: 95%

“…Quantification of the oxygen non-stoichiometry is given in Figure 3. The estimates of oxygen deficiency were obtained from comparing structural data (unit cell volume) [29,30] and spectroscopic peak shifts (O-K and Co-L edges) [34,37] to previous studies.…”

Section: Oxygen Stoichiometry Changes Probed By X-ray Absorption Specmentioning

confidence: 99%

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Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Petrie

Mitra

Jeen

et al. 2016

Adv Funct Materials

213

160

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The ability to manipulate oxygen anion defects rather than metal cations in complex oxides is facilitating new functionalities critical for emerging energy and device technologies.However, the difficulty in activating oxygen at reduced temperatures hinders the deliberate control of an important defect, oxygen vacancies. Here, strontium cobaltite (SrCoO x ) is used to demonstrate that epitaxial strain is a powerful tool for manipulating the oxygen vacancy concentration even under highly oxidizing environments and at annealing temperatures as low as 300 °C. By applying a small biaxial tensile strain (2%), the oxygen activation energy barrier decreases by ~30%, resulting in a tunable oxygen deficient steady-state under conditions that would normally fully oxidize unstrained cobaltite. These strain-induced changes in oxygen stoichiometry drive the cobaltite from a ferromagnetic metal towards an antiferromagnetic insulator. The ability to decouple the oxygen vacancy concentration from its typical dependence on the operational environment is useful for effectively designing oxides materials with a specific oxygen stoichiometry.2

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Section: Structural Analysis Of Annealed Bm-sco and P-sco Filmsmentioning

confidence: 79%

Section: Characterization Of Structural and Physical Propertiesmentioning

confidence: 95%

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Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Petrie

Mitra

Jeen

et al. 2016

Adv Funct Materials

213

160

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“…Conversely, it has also been shown that SrCoO 3 can be transformed into SrCoO 2.5 in H 2 atmosphere by using the reduction process. Interestingly, the oxidation process provokes semireversible transformation of SrCoO 2.5 back into SrCoO 3 [11]. The previous experimental results [9] showed that SrCoO 3 is FM metallic with relatively high Currie temperature of about 305 K for δ = 0.…”

Section: Introductionmentioning

confidence: 84%

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO₃ for different space groups: first-principles study

Muhammady

Sutjahja

2017

Materials Science-Poland

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We report structural, electronic, and magnetic properties of SrCoO 3 in Pm3m and P 4 /mbm space groups, which are calculated by using generalized gradient approximation corrected with on-site Coulomb repulsion U and exchange energies J. The cubic lattice parameter a and local magnetic moments of Co (µ Co ) are optimized by varying U at Co 3d site. Employing ultrasoft pseudopotential, the values of U = 8 eV and J = 0.75 eV are the best choice for Pm3m space group. We found the value of µ Co = 2.56 µ B , which is consistent with the previous results. It was also found that Co 3d, hybridized with O 2p, is the main contributor to ferromagnetic metallic properties. Besides, norm-conserving pseudopotential promotes a, which is in good agreement with experimental result. However, it is not suitable for P4/mbm space group. By using ultrasoft pseudopotential, the value of U = 3 eV (J = 0.75) is the most suitable for P4/mbm group. Ferromagnetic metallic properties, Jahn-Teller distortion, and reasonable lattice parameters have been obtained. This study shows that U has significant contribution to the calculated properties and also points out that P4/mbm space group with US-PP is suitable to describe experimental results.

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“…Hence, it serves as a kind of prototype for the recently highlighted functional oxides of mixed-valent (III/IV) cobalt. With the proper choice of process parameters it can be obtained as different types of metastable single phases with orthorhombic (0:5 < < 0:6), 1,2 tetragonal (0:1 < < 0:25) 2,3 or cubic ( % 0) [3][4][5] symmetry. Synthesis of the oxidized phases usually goes through the orthorhombic brownmillerite phase SrCoO 2:5 , 1 which has ordered oxygen vacancies such that the structure is composed of alternately stacked layers of corner-sharing CoO 4 tetrahedra and CoO 6 octahedra.…”

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confidence: 99%

Chemical Oxidation of SrCoO3−δ

et al. 2007

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Various chemical oxidants were investigated for their capability to oxidize brownmillerite SrCoO 2:5 to perovskite SrCoO 3À . Among the oxidants tested, KMnO 4 /HCl was found to be the strongest to yield SrCoO 3À with % 0:06.The perovskite SrCoO 3À system is known for its wide range of oxygen nonstoichiometry. Hence, it serves as a kind of prototype for the recently highlighted functional oxides of mixed-valent (III/IV) cobalt. With the proper choice of process parameters it can be obtained as different types of metastable single phases with orthorhombic (0:5 < < 0:6), 1,2 tetragonal (0:1 < < 0:25) 2,3 or cubic ( % 0) 3-5 symmetry. Synthesis of the oxidized phases usually goes through the orthorhombic brownmillerite phase SrCoO 2:5 , 1 which has ordered oxygen vacancies such that the structure is composed of alternately stacked layers of corner-sharing CoO 4 tetrahedra and CoO 6 octahedra. For the oxidation of SrCoO 2:5 , electrochemical [3][4][5] and high-pressure 2,6 techniques have been employed. Possibility to utilize chemical ways for the control of oxygen content was brought up by Nemudry et al.3 who oxidized SrCoO 2:5 by immersing the sample into an aqueous solution of Br 2 and NaOH. Compared to the other methods chemical oxidation requires only a very simple experimental set up. In the present work, several other chemical oxidizing agents are utilized.The SrCoO 2:5 precursor was prepared from Co and SrCO 3 powders, dissolved in stoichiometric amounts in 3 M HNO 3 solution and then chelated by EDTA/NH 3 solution containing EDTA in 50% excess. The solution was dried, burned and then calcined at 900 C. The calcination product was ground and pressed into pellets for the final heat treatment in air at 1000 C for 40 h, followed by quenching to room temperature. The X-ray diffraction pattern for the product revealed a singlephase brownmillerite with an oxygen content of 2.50 per formula unit, as determined by iodometric titration.For the oxidation experiments, the SrCoO 2:5 pellets were crushed and ground. Four different oxidizing media were employed: (1) aqueous solution of 0.2 M KMnO 4 and HCl in various concentrations, (2) aqueous solution of Na 2 S 2 O 8 saturated at room temperature, (3) 1:1 dispersion of Br 2 and H 2 O, and (4) aqueous solution of 0.3 M Br 2 and 5 M NaOH. The experiments were carried out for 50-mg samples in 2-mL plastic vials except for experiment (4), which was carried out for a 200-mg sample in a 20-mL glass tube. Immersion time varied from 1 to 24 h. Temperature was controlled using a water or an ice bath and a thermometer. After the oxidation treatment, the sample powder was washed with deionized water plus ethanol [(1) and (2)] or CH 3 CN plus ethanol [(3) and (4)] and subsequently dried in air at room temperature.X-ray diffraction (XRD) patterns were collected for the samples with a Rigaku RINT2550 diffractometer equipped with a rotating Cu anode. Software JANA 2000 was used in the profile-fitting mode for the lattice-parameter refinements [in space groups, I4=mmm (SrCoO 3À ) and P...

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Topotactic Electrochemical Redox Reactions of the Defect Perovskite SrCoO_2.5+x

Cited by 122 publications

References 19 publications

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO₃ for different space groups: first-principles study

Chemical Oxidation of SrCoO3−δ

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Topotactic Electrochemical Redox Reactions of the Defect Perovskite SrCoO2.5+x

Cited by 122 publications

References 19 publications

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Strain Control of Oxygen Vacancies in Epitaxial Strontium Cobaltite Films

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO3 for different space groups: first-principles study

Chemical Oxidation of SrCoO3−δ

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Topotactic Electrochemical Redox Reactions of the Defect Perovskite SrCoO_2.5+x

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO₃ for different space groups: first-principles study