Oxygen nonstoichiometry, thermo-chemical stability and lattice expansion of La0.6Sr0.4FeO3−δ

Kühn, Melanie; Hashimoto, Shinichi; Sato, Kazuhisa; Yashiro, Keiji; Mizusaki, Junichiro

doi:10.1016/j.ssi.2011.05.013

Cited by 133 publications

(199 citation statements)

References 28 publications

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“…19 Additional measurements on macroscopic electrodes in humidified hydrogen without gas change confirmed the stability, see Fig. 12, inset.…”

Section: Resultsmentioning

confidence: 62%

“…We obtain 103 F/cm 3 , when normalizing to the total LSF64 volume. This is much less than C chem in air and a defect chemical interpretation is possible based on the data reported by Kuhn et al 19 The corresponding calculation is in analogy to that for oxidizing conditions, with 10 −23 bar pO 2 at 620…”

Section: Resultsmentioning

confidence: 86%

“…[3][4][5] Therefore, generally other compositions such as (La,Sr)(Cr,Mn)O 3 , [6][7][8][9] (La,Sr)(Cr,V)O 3 , 10,11 (La,Sr)(Cr,Ru)O 3 , 12,13 or La and Fe doped SrTiO 3 14,15 are tested under reducing conditions. 16 Although Sr-doped LaFeO 3-δ (LSF) is a typical SOFC cathode material, it is also rather stable in reducing conditions, [17][18][19] with La 0.6 Sr 0.4 FeO 3-δ decomposing below 10 −27 bar pO 2 at 600…”

mentioning

confidence: 99%

“…19,20 Several studies were performed on the defect chemistry and transport properties of LSF [21][22][23][24][25][26][27][28][29][30][31] [2] Fe 4+ states can be interpreted as electron holes (h • ) and those determine the electronic conductivity at high oxygen partial pressure as they are the majority mobile charge carrier. [20][21][22] Towards lower oxygen partial pressures (and/or higher temperatures) the equilibrium of Eq.…”

mentioning

confidence: 99%

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Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Kogler

Nenning

Rupp

et al. 2015

J. Electrochem. Soc.

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Owing to its mixed ionic and electronic conductivity and high thermochemical stability, La 0.6 Sr 0.4 FeO 3-δ (LSF64) is an attractive electrode material in solid oxide fuel/electrolysis cells (SOFCs/SOECs). Well defined thin film microelectrodes are used to compare the electrochemical properties of LSF64 in oxidizing and reducing conditions. The high electronic sheet resistance in hydrogen can be overcome by the use of an additional metallic current collector. With the sheet resistance being compensated, the area specific electrode resistance is similar in humidified hydrogen and oxygen containing atmospheres. Analysis of the chemical capacitance and the electrode resistance for current collectors on top and beneath the LSF64 thin film allow mechanistic conclusions on active zones and bulk defect chemistry. Cyclic gas changes between reducing and oxidizing conditions, performed on macroscopic LSF64 thin film electrodes with top current collector, reveal a strong degradation of the surface kinetics in synthetic air with very fast recovery in reducing atmosphere. Additional in-situ high-temperature powder XRD on LSF64 demonstrates the formation of small amounts of iron oxides in humidified hydrogen at elevated temperatures. Solid oxide fuel cells (SOFCs) are in the process of gaining more and more commercial success as highly efficient power generation systems. They transform the chemically bound energy of a fuel to electrical energy. Solid oxide electrolysis cells (SOECs) are the counter parts of SOFCs as they use electrical energy, e.g. excess energy from the grid, to form fuel by electrolysis. Owing to their very high efficiencies, also SOECs are promising devices in future energy technologies. 1Currently Ni/YSZ cermet electrodes are the standard electrodes in SOF/ECs for reducing conditions, but they are known to suffer from several problems, like sulfur poisoning (in SOFC operation), sintering, redox cycle stability etc.2 To find an alternative to Ni/YSZ could therefore be favorable for both SOFCs and SOECs.Electrodes in SOE/FCs have to meet numerous requirements: thermochemical stability over a wide oxygen partial pressure range, high catalytic activity for oxygen exchange reactions, compatibility with adjacent cell components, sufficiently high electronic and ionic conductivity, etc. Perovskite-type oxides such as LaMnO 3 , LaCoO 3 and LaFeO 3 based materials are used in state-of-the-art SOF/EC electrodes in oxygen atmosphere. Often they are mixed ionic and electronic conductors (MIECs), which is advantageous in SOF/ECs as the whole electrode surface area may become active in the oxygen exchange reaction. Employing such MIECs also in reducing atmosphere could be highly attractive. However, Sr-doped LaMnO 3 and LaCoO 3 are only stable under comparatively high oxygen partial pressures and thus not suited for the use in hydrogen. Fe 4+ states can be interpreted as electron holes (h • ) and those determine the electronic conductivity at high oxygen partial pressure as they are the majority mobile charge carrie...

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“…19 Additional measurements on macroscopic electrodes in humidified hydrogen without gas change confirmed the stability, see Fig. 12, inset.…”

Section: Resultsmentioning

confidence: 62%

Section: Resultsmentioning

confidence: 86%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Kogler

Nenning

Rupp

et al. 2015

J. Electrochem. Soc.

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“…Journal of the Ceramic Society of Japan 123 [6] 501-506 2015 JCS-Japan specimens, indicating that magnetic character of LnFeO 3 (Ln = La, Pr, Nd, Sm) are antiferromaginetic. Figure 6 shows isomar shift, ¤ and internal magnetic field, H i of LnFeO 3 estimated from Mössbauer spectra as a function of tolerance factor.…”

Section: )23)mentioning

confidence: 99%

Dependence of crystal symmetry, electrical conduction property and electronic structure of LnFeO<sub>3</sub> (Ln: La, Pr, Nd, Sm) on kinds of Ln<sup>3+</sup>

Niwa

Sato

Watanabe

et al. 2015

J. Ceram. Soc. Japan

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Dependence of crystal symmetry, electrical conductivity, chemical state of Fe and optical property of LnFeO 3 (Ln: La, Pr, Nd, Sm) on kinds of Ln 3+ was investigated. All the LnFeO 3 showed orthorhombic structure, with which order of high crystal symmetry was LaFeO 3 > PrFeO 3 > NdFeO 3 > SmFeO 3 . Using tolerance factor, the order was successfully explained. The electrical conductivity of all the specimens could be explained by using small polaron hopping model. With increasing crystallite symmetry, electrical conductivity increased and activation energy for hopping conduction decreased. This can be ascribed to larger overlapping of Fe3d orbital and O2p orbital on nearly linear FeOFe bond in LnFeO 3 with higher crystal symmetry. The larger overlapping of Fe3d orbital and O2p orbital in LnFeO 3 with higher crystal symmetry can also be an origin of larger spinspin interaction detected by Mössbauer spectroscopy and larger optical band gap observed by diffuse reflectance spectroscopy. Since chemical state of Fe, evaluated by Mössbauer spectroscopy, in LnFeO 3 is fundamentally constant at +3 regardless of kinds of Ln 3+ , carrier concentration of LnFeO 3 was revealed to be constant. It is concluded that the predominant factor which determine the electrical property of LnFeO 3 is mobility affected by crystal symmetry.

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Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

Wang

Syed

Ning

et al. 2021

Adv Funct Materials

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Nanostructured functional oxides play an important role in enabling clean energy technologies and novel memory and processor devices. Using thin‐film La0.6Sr0.4FeO3 (LSF) as a model system, the novel utility of exsolution in fabricating self‐assembled metal oxide nanocomposites with tunable functionalities is shown. Exsolution triggers the formation of metallic iron (Fe0) nanoparticles, Ruddlesden–Popper domains, and nm‐scale percolated Fe‐deficient channels in LSF. Combining multimodal characterization with numerical modeling, the chemical, magnetic, and electrical properties of the exsolution‐synthesized nanocomposite at different stages of Fe0 exsolution as well as during redox cycling are assessed. After exsolution, the electronic conductivity of the nanocomposite LSF increased by more than two orders of magnitude. Based on numerical analysis representing all the constituents, it is expected that this increase in conductivity originates mainly from the Fe‐deficient percolating channels formed during exsolution. Moreover, the exsolved nanocomposite is redox‐active even at moderate temperatures. Such redox capabilities can enable dynamic control of the nanocomposite functionality by tailoring the oxygen non‐stoichiometry. This concept is demonstrated with a continuous modulation of magnetization between 0 and 110 emu cm−3. These findings point out that exsolution may serve as a platform for scalable fabrication of complex metal oxide nanocomposites for electrochemical and electronic applications.

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Oxygen nonstoichiometry, thermo-chemical stability and lattice expansion of La0.6Sr0.4FeO3−δ

Cited by 133 publications

References 28 publications

Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Dependence of crystal symmetry, electrical conduction property and electronic structure of LnFeO<sub>3</sub> (Ln: La, Pr, Nd, Sm) on kinds of Ln<sup>3+</sup>

Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

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Oxygen nonstoichiometry, thermo-chemical stability and lattice expansion of La0.6Sr0.4FeO3−δ

Cited by 133 publications

References 28 publications

Comparison of Electrochemical Properties of La0.6Sr0.4FeO3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Comparison of Electrochemical Properties of La0.6Sr0.4FeO3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Dependence of crystal symmetry, electrical conduction property and electronic structure of LnFeO<sub>3</sub> (Ln: La, Pr, Nd, Sm) on kinds of Ln<sup>3+</sup>

Exsolution Synthesis of Nanocomposite Perovskites with Tunable Electrical and Magnetic Properties

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Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions

Comparison of Electrochemical Properties of La_0.6Sr_0.4FeO_3-δThin Film Electrodes: Oxidizing vs. Reducing Conditions