Electron/hole and ion transport in La1−xSrxFeO3−δ

Патракеев, М.В.; Bahteeva, J. A.; Митберг, Э. Б.; Леонидов, И. А.; Кожевников, В. Л.; Poeppelmeier, Kenneth R.

doi:10.1016/s0022-4596(03)00040-9

Cited by 219 publications

(141 citation statements)

References 24 publications

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“…2 is shifted to the left hand side, increasing the amount of oxygen vacancies and thus the ionic conductivity. 23,24 Concurrently, oxygen release causes a reduction of the iron, which decreases the concentration of electron holes. This also increases the electron concentration (i.e.…”

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.…”

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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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confidence: 99%

mentioning

confidence: 99%

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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“…The stacks were subjected to electrochemical impedance spectroscopy and conversion/polarisation experiments while the gas composition was monitored by a mass spectrometer (MS) and a chemiluminiscense detector (CLD). The cell stacks differed from each other in the way they were impregnated: one stack had no impregnation, one stack was impregnated with KNO 3 and one stack was impregnated with K 2 O. LSF was chosen as electrode material, since LSF as a mixed conductor [18] [19] has been evaluated to be a promising material for intermediate temperate solid oxide electrodes [20] while CGO was chosen as an electrolyte, as CGO has superior oxygen ion-conductivity below 600 °C when compared to yttria stabilized zirconia [21]. KNO 3 /K 2 O was chosen for impregnation, as potassium is known to act both as a NO x -storage compound [22] and also to improve simultaneous NO x and soot removal [23,24], the latter being of interest for future development of the electrochemical deNO x technique.…”

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NO x conversion on porous LSF15–CGO10 cell stacks with KNO3 or K2O impregnation

Traulsen

Bræstrup

2012

J Solid State Electrochem

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In the present work it was investigated how addition of KNO 3 or K 2 O affected the NO x conversion on LSF15-CGO10 (La 0.85 Sr 15 FeO 3 -Ce 0.9 Gd 0.1 O 1.95 ) composite electrodes during polarisation. The LSF15-CGO10 electrodes were part of a porous 11-layer cell stack with alternating layers of LSF15-CGO10 electrodes and CGO10 electrolyte. The KNO 3 was added to the electrodes by impregnation, and kept either as KNO 3 in the electrode or thermally decomposed into K 2 O before testing. The cell stacks were tested in the temperature range 300-500 °C in 1000 ppm NO, 10% O 2 and 1000 ppm NO + 10% O 2 . During testing the cells were characterized by electrochemical impedance spectroscopy (EIS) and the NO conversion was measured during polarization at -3 V for 2 h. The concentration of NO and NO 2 was monitored by a chemiluminiscence detector, while the concentration of O 2 , N 2 and N 2 O was detected on a mass spectrometer. A significant effect of impregnation with KNO 3 or K 2 O on the NO x conversion was observed. In 1000 ppm NO both impregnations caused an increased conversion of NO into N 2 in the temperature range 300-400 °C with a current efficiency up to 73%. In 1000 ppm NO + 10% O 2 no formation of N 2 was observed during polarisation, but the impregnations altered the conversion between NO and NO 2 on the electrodes. Both impregnations caused increased degradation of the cell stack, but the exact cause of the degradation has not been identified yet.

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“…The homogeneity regions substantially depend on the oxygen content and, therefore, the conditions of processing/receiving, the influence of which increases with increasing content of strontium. For example, at a temperature of 1300 °C-installed the homogeneity regions were as follows: orthorhombic cell with space group Pbnm exists in the range of compositions 0 ≤ х ≤ 0.2, the rhombohedral cell (R3c) is at 0.4 ≤ х ≤ 0.7, cubic (Pm3m) is at 0.8≤х≤1 [65,66]. Thermogravimetric studies allowed us to assess the thermal stability of La 1-x Sr x FeO 3-d in an atmosphere of 95 % Не+5 % Н 2 , which decreases with increasing content of strontium [66].…”

Section: Phase Equilibrium In Systems With T = Fementioning

confidence: 99%

“…For example, at a temperature of 1300 °C-installed the homogeneity regions were as follows: orthorhombic cell with space group Pbnm exists in the range of compositions 0 ≤ х ≤ 0.2, the rhombohedral cell (R3c) is at 0.4 ≤ х ≤ 0.7, cubic (Pm3m) is at 0.8≤х≤1 [65,66]. Thermogravimetric studies allowed us to assess the thermal stability of La 1-x Sr x FeO 3-d in an atmosphere of 95 % Не+5 % Н 2 , which decreases with increasing content of strontium [66].Numerous studies of properties of compounds with the general formula M 2 LnFe 3 O 8+d (M = Ca, Sr) [67][68][69][70][71], (which otherwise can be represented as Ln 0.33 M 0.67 FeO 3-d ), obtained, as a rule, at Cherepanov V. A., Gavrilova L. Ya., Volkova N. E., Urusova A. S., Aksenova T. V., Kiselev E. Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals.…”

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Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals. A short overview of

et al. 2015

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Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals. A short overview of.Review is dedicated studies of phase equilibria in the systems based on rare earth elements and 3d transition metals. It's highlighted several structural families of these compounds and is shown that many were found interesting properties for practical application, such as high conductivity up to the superconducting state, magnetic properties, catalytic activity of the processes of afterburning of exhaust gases, the high mobility in the oxygen sublattice and more.Keywords: phase equilibrium; manganites; isobaric-isothermal diagrams; solid solutions © Cherepanov V. A., Gavrilova L. Ya., Volkova N. E., Urusova A. S., Aksenova T. V., Kiselev E., 2015 IntroductionThe studies of phase equilibria in the systems based on rare earth elements and 3d transition metals and thermodynamic parameters of the oxide phases formed in these systems was initiated by Vladimir Mikhailovich Zhukovsky in 1977 under the direct supervision of Alexander Nikolaevich Petrov, as the development of contractual issues, conducted with an experienced company GIREDMET. The works on the study of the system Sm-Co-O and properties of oxide phases formed in system were then extended to other rare earth elements (REE) [1][2][3][4][5][6][7][8] and 3d transition metals [9][10][11][12][13]. A characteristic feature of these systems is the formation of oxide phases with perovskite structure AVO 3 and related. The partial substitution of rare earth elements in alkaline earth metals (AEM) leads to significant change of properties and they found a wide range of interesting for practical applications of the properties such as high conductivity up to the superconducting state, magnetic properties, catalytic activity of the processes of afterburning of exhaust gases and a variety of redox reactions, high mobility in the oxygen sublattice and more. In addition, partial substitution in the A-sublattice under constant 3d-cation in the systems Ln-T-O allows to stabilize the structure, which Cherepanov V. A., Gavrilova L. Ya., Volkova N. E., Urusova A. S., Aksenova T. V., Kiselev E. in the given conditions (temperature and oxygen pressure) are thermodynamically unstable. Therefore, further development of investigations of phase equilibria and thermodynamic stability of complex oxides were targeting the systems Ln-M-T-O (where Ln = REE, M = Ca, Sr, Ba; T = Mn, Fe, Co, Ni, Cu). When a certain percentage of similarity (in all possible formation of a phase with perovskite structure LnTO 3±d ) these systems still have a noticeable and distinctive features depending on the nature of the components. Phase equilibrium in systems with T = MnThe significant difference of perovskite phases in the manganese-containing systems Ln-Mn-O is that the oxygen content in them exceeds the stoichiometric air LnMnO 3+d . In fact, the oxygen sublattice is complete and the non-stoichiometry is realized by vacancy disordering ...

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Electron/hole and ion transport in La1−xSrxFeO3−δ

Cited by 219 publications

References 24 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

NO x conversion on porous LSF15–CGO10 cell stacks with KNO3 or K2O impregnation

Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals. A short overview of

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Electron/hole and ion transport in La1−xSrxFeO3−δ

Cited by 219 publications

References 24 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

NO x conversion on porous LSF15–CGO10 cell stacks with KNO3 or K2O impregnation

Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals. A short overview of

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Product

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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