Redox thermodynamics and phase composition in the system SrFeO3δ — SrMnO3δ

Vieten, Josua; Bulfin, Brendan; Senholdt, Marion; Roeb, Martin; Sattler, Christian; Schmücker, Martin

doi:10.1016/j.ssi.2017.06.014

Cited by 61 publications

(51 citation statements)

References 54 publications

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“…B-site substitution only increased the redox capacity for B’ = Co, and the redox capacities for B’ = Cr, Cu, and Mn were significantly reduced. The B’ = Mn and Cu redox capacities were consistent with previously published literature [ 26 , 27 ]. The results showed no significant dependence with x or y on the redox capacity except for B’ = Cr, which reduced the overall Δ m / m initial from 1.78% (Δδ = 0.21) to 1.37% (Δδ = 0.16) as y increased from 0.10 to 0.20.…”

Section: Resultssupporting

confidence: 91%

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

et al. 2020

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An A‑ and B‑site substitutional study of SrFeO3−δ perovskites (A’xA1−xB’yB1−yO3−δ, where A = Sr and B = Fe) was performed for a two‑step solar thermochemical air separation cycle. The cycle steps encompass (1) the thermal reduction of A’xSr1−xB’yFe1−yO3−δ driven by concentrated solar irradiation and (2) the oxidation of A’xSr1−xB’yFe1−yO3−δ in air to remove O2, leaving N2. The oxidized A’xSr1−xB’yFe1−yO3−δ is recycled back to the first step to complete the cycle, resulting in the separation of N2 from air and concentrated solar irradiation. A-site substitution fractions between 0 ≤ x ≤ 0.2 were examined for A’ = Ba, Ca, and La. B-site substitution fractions between 0 ≤ y ≤ 0.2 were examined for B’ = Cr, Cu, Co, and Mn. Samples were prepared with a modified Pechini method and characterized with X-ray diffractometry. The mass changes and deviations from stoichiometry were evaluated with thermogravimetry in three screenings with temperature- and O2 pressure-swings between 573 and 1473 K and 20% O2/Ar and 100% Ar at 1 bar, respectively. A’ = Ba or La and B’ = Co resulted in the most improved redox capacities amongst temperature- and O2 pressure-swing experiments.

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Section: Resultssupporting

confidence: 91%

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

et al. 2020

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“…By oxygen partial pressure swing between air and helium at 600 • C,~1 wt% oxygen capacity was achieved for oxygen production [39]. Recently, SrFeO 3 based oxygen sorbents have received many research interests, owing to its large oxygen capacity and low operating temperature [40][41][42]. The versatile structure of SrFeO 3 offers many opportunities to introduce dopants at A and/or B site to further tuning the redox property [43][44][45].…”

Section: Introductionmentioning

confidence: 99%

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

et al. 2020

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Chemical looping air separation (CLAS) is a promising technology for oxygen generation with high efficiency. The key challenge for CLAS is to design robust oxygen sorbents with suitable redox properties and fast redox kinetics. In this work, perovskite-structured Sr 1-x Ca x Fe 1-y Co y O 3 oxygen sorbents were investigated and demonstrated for oxygen production with tunable redox properties, high redox rate, and excellent thermal/steam stability. Cobalt doping at B site was found to be highly effective, 33% improvement in oxygen productivity was observed at 500 • C. Moreover, it stabilizes the perovskite structure and prevents phase segregation under pressure swing conditions in the presence of steam. Scalable synthesis of Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 oxygen sorbents was carried out through solid state reaction, co-precipitation, and sol-gel methods. Both co-precipitation and sol-gel methods are capable of producing Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 sorbents with satisfactory phase purity, high oxygen capacity, and fast redox kinetics. Large scale evaluation of Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 , using an automated CLAS testbed with over 300 g sorbent loading, further demonstrated the effectiveness of the oxygen sorbent to produce 95% pure O 2 with a satisfactory productivity of 0.04 g O2 g sorbent −1 h −1 at 600 • C.

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“…Perovskites of the general composition A 2 + M 3/4 + O 3-δ with δ = 0-0.5 constitute stable phases for many different alkali earth metals A and transition metals M. The large variety of possible phases can be even extended by solid solution formation, as many of these perovskites form stable mixed phases in a large range of mixture ratios. [7] SrFeO 3-δ is a simple, grossly non-stoichiometric perovskite oxide, which is well known for its oxygen non-stoichiometry and mixed + III/ + IV Fe valence, which makes it a suitable oxygen carrier for thermochemical air separation. [8] To a small extent, iron cations in this phase can be exchanged by copper cations, forming solid solutions, i. e. SrFe 0.95 Cu 0.05 O 3-δ , as demonstrated previously by the authors.…”

Section: Introductionmentioning

confidence: 99%

Redox Behavior of Solid Solutions in the SrFe_1‐xCu_xO_3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation

et al. 2018

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Perovskite oxides with temperature and oxygen partial pressure dependent non‐stoichiometry δ, such as SrFeO3‐δ or its Cu‐doped variants, can be applied as redox materials for two‐step thermochemical processes, i. e. to reversibly store oxygen and thereby thermal energy, or separate air using concentrated solar power. We studied the redox state of Cu in SrFe1‐xCuxO3‐δ samples using in‐situ X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption (XAS) measurements in oxygen atmospheres using synchrotron radiation, and characterized these materials through thermogravimetric analysis. By this means, we show how spectroscopic and thermogravimetric data are correlated, suggesting that Cu and Fe are reduced simultaneously for x=0.05, whereas the reduction of samples with x=0.15 is mainly driven by a change in the Fe oxidation state. Furthermore, we studied the re‐oxidation kinetics of reduced SrFe1‐xCuxO3‐δ, revealing very high reaction speeds with t1/2=13 min at 150 °C for SrFeO3‐δ. Our results indicate that SrFe1‐xCuxO3‐δ solid solutions can be applied for oxygen storage and air separation with high capacity at relatively low temperatures, which allows an efficient thermochemical process.

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Redox thermodynamics and phase composition in the system SrFeO3δ — SrMnO3δ

Cited by 61 publications

References 54 publications

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Redox Behavior of Solid Solutions in the SrFe_1‐xCu_xO_3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation

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Redox thermodynamics and phase composition in the system SrFeO3δ — SrMnO3δ

Cited by 61 publications

References 54 publications

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

An A- and B-Site Substitutional Study of SrFeO3−δ Perovskites for Solar Thermochemical Air Separation

Sr1-xCaxFe1-yCoyO3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Redox Behavior of Solid Solutions in the SrFe1‐xCuxO3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation

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Sr_1-xCa_xFe_1-yCo_yO_3-δ as facile and tunable oxygen sorbents for chemical looping air separation

Redox Behavior of Solid Solutions in the SrFe_1‐xCu_xO_3‐δ System for Application in Thermochemical Oxygen Storage and Air Separation