1,721,034 research outputs found
Electrochemical response of several cathode configurations prepared with Ba0.5Sr0.5Co0.8Fe0.2O3-δ and Ce0.9Gd0.1O1.95 for IT-SOFC
Full text linkThe electrochemical response of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) electrodes prepared by an acetic acid-based gel route has been investigated by impedance spectroscopy (IS) as a function of temperature (400 ≤ T ≤ 900 °C) and oxygen partial pressure (1 × 10−3 ≤ pO2 ≤ 1 atm). Several electrode configurations were studied using Ce0.9Gd0.1O1.95 (GDC) as the electrolyte. These consisted of one BSCF layer (cell A), a BSCF layer with an intermediate porous GDC layer (cell B), and graded electrodes using a composite BSCF+GDC, with variations in the surface area of GDC (cells C and D). The optimum heat treatment for the electrode assemblages was determined to be around 850–900 °C. Analysis of the impedance spectra shows that at T ≥ 600 °C a low frequency (LF) contribution, associated to the gas phase diffusion is systematically the rate-limiting step. All the electrodes show an intermediate frequency (IF) arc related to mixed processes. For cells A and B, the IF response is related to the oxide ion transfer at the electrode/electrolyte surface and the charge transfer at the electrode surface, while for cells C and D the mixed process involves the charge transfer and the molecular oxygen dissociation at the electrode surface.Fil: Setevich, Cristian. Universidad Nacional del Sur. Departamento de Física; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Prado, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Física; ArgentinaFil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin
Structural properties and electrical conductivity of perovskite-type oxides in SOFCs
No full textStructural properties and electrical conductivity of Sr2MgMoO6 (SMMO) and Sr2MgMo0.9TM0.1O6-δ (TM = Co, Mn) compounds were analyzed for establishing the usefulness of these materials as Solid oxide fuel cells (SOFC) anode. SMMO and SMMTM were synthesized through combustion-solution method and annealing in air at temperatures between 1000 and 1200 °C. SMMO and SMMCo with triclinic structures, and SMMMn with tetragonal structure at room temperature showed a cubic symmetry at 800 °C, which are apparently coking-resistant. Mn-doping in SMMO is detrimental for electrical conductivity in diluted-H2 environment, whilst the highest conductivity value was recorded for Co-containing sample on Mo-site of SMMO double perovskite. On the other hand, the oxygen reduction reaction of Pr2-xNdxNiO4+δ, (x=0, 0.3, 1 and 1.7) SOFC cathodes deposited on La0.9Sr0.1Ga0.8Mg0.2O2.85 electrolyte was studied by electrochemical impedance spectroscopy. The obtained results showed that the chemical reactivity between Pr2-xNdxNiO4+δ oxides with electrolyte materials is a serious drawback in their use as cathode in SOFC.Fil: Montenegro Hernández, Alejandra. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Dager, P.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Caneiro, Alberto. YPF - Tecnología; ArgentinaFil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentin
Increasing Conductivity in Proton Conductors BaCeO3-d doped with Pr
Full text linkIn this work we explore the effect of partial substitution of Ce forPr ions in BaCe1-xPrxO3-δ (0 ≤ x ≤0.8) perovskites with the aim of increasing the oxygen vacancies concentration and H+ charge carriers. The oxides were obtained by Pechini combustion method and sintered at 1350°C. The Pr incorporation improves the capability of to obtain dense samples at this temperature. Crystal structure were studied by X-ray diffraction, while morphology by SEM. The conductivity was studied by Electrical Impedance Spectroscopy (EIS) under 20 % O2/Ar and 10 % H2/Ar, both with 2% humidity. We found that the Pr content diminished the lattice parameters, increase the sintering capacity and the conductivity under wet oxidant atmosphere, but it decreases the stability under reducing atmosphereFil: Basbus, Juan Felipe. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin
X-ray absorption study of the Fe and Mo valence states in Sr2FeMoO6
Full text linkWe studied the Fe and Mo valence states in Sr2FeMoO6 using X-ray absorption spectroscopy. The exper- imental results were analyzed using atomic multiplet plus crystal field calculations. The analysis indi- cates that the Fe ions present a fairly ionic Fe3+ (3d5) valence, and that the Mo ions are in a strongly covalent Mo5+ (4d1) state. The presence of Fe ions in a 2+ valence state can be excluded from the Fe-L2,3 spectrum. These results can be understood taking into account the relative energy of the d-levels, the relative strength of the M d?O p mixing, and the exchange stabilization of the Fe3+ ion.Fil: Martins, H.P.. Universidade Federal Do Parana; BrasilFil: Prado, F.. Universidad Nacional del Sur; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Vicentin, F.C. . Laboratório Nacional de Luz Síncrotron; BrasilFil: Chaves, D.S.. Laboratório Nacional de Luz Síncrotron; BrasilFil: Mossanek, R.J.O. . Universidade Federal Do Parana; BrasilFil: Abbate, M.. Universidade Federal Do Parana; Brasi
Validation of Nd2NiO4+δ as Oxygen Electrode Material for Intermediate Temperature Solid Oxide Cells with LSGM Electrolyte
Full text linkThe oxygen reduction reaction (ORR) was studied by Electrochemical Impedance Spectroscopy (EIS) for Nd2NiO4+δ (NNO) electrodes deposited on La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolyte. The influence of NNO microstructure on the electrochemical performance was evaluated. The EIS measurements were carried out as a function of temperature (500<T<750ºC) and oxygen partial pressure (10-4<pO2<1atm). Three contributions associated with the ORR were identified: at high (HF), medium (MF) and low frequencies (LF). The HF contribution was associated with oxygen ion transfer trough electrode/electrolyte interphase. The MF contribution was attributed to oxygen ions diffusion within the NNO. The LF contribution was related to O2-dissociative adsorption for NNO obtained by chemical routes, where the particle sizes are smaller. If NNO were obtained by Solid State Reaction, the LF element was associated with a convolution of dissociative adsorption and gas diffusion processes.Fil: Montenegro Hernandez, Alejandra. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
High temperature properties of the n = 2 Ruddlesden-Popper phases (La,Sr)3(Fe,Ni)2O7-δ
Full text linkThe crystal chemistry and mixed conductor properties of the n = 2 member of the Ruddlesden-Popper (R-P) phases Sr3-xLaxFe2-yNiyO7-δ with 0 ≤ x ≤ 0.3 and 0 ≤ y ≤ 1.0 have been studied at high temperature. High-temperature X-ray diffraction and thermogravimetric measurements of the equilibrium pO2 (10- 5 ≤ pO2 ≤ 1 atm) in the temperature range 400 ≤ T ≤ 1000 °C indicate that the Sr3FeNiO7-δ phase is able to accommodate a large oxygen non-stoichiometry (δ ∼ 1.5) without structural transformations. The electrical conductivity and oxygen permeability increase with the substitution of Ni for Fe in the range 550 ≤ T ≤ 1000 °C. The electrical transport of the Sr3FeNiO7-δ phase is thermally activated and the activation energy decreases with the substitution of Ni for Fe for a given oxygen content. The increase in the oxygen permeation flux with increasing Ni content is due to an increasing oxygen non-stoichiometry and a lower activation energy for permeation.Fil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Prado, Fernando Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Manthiram, A.. University of Texas at Austin; Estados Unido
Synthesis and preliminary study of pure and Zr-doped YMnO3 compounds as Solid Oxide Fuel Cells electrode
Full text linkThe Y1−xZrxMnO3series (0 ≤ x ≤ 0.30) has been studied to be used as possible SOFC electrode material. These compounds adopt a layered structure of hexagonal symmetry in which the manganese cations are located in trigonal bi-pyramidal coordination of oxygen atoms, different from that of the classical perovskite. The synthesis of the materials has been carried out by solid state reaction and X-ray diffraction technique reveals that pure phases can be obtained until x∼0.10. For x ≥ 0.10, an additional YSZ phase is formed, similar to the SOFC electrolyte material. HT-XRD technique and thermogravimetric analysis of pure or Zr-doped YMnO3indicate that, in diluted dry H2for T > 600 °C, these compounds are unstable, what precludes their use as anode material. On the other hand, reactivity studies at high temperature (T = 1300 °C) between Y1−xZrxMnO3(x = 0, 0.05 and 0.1) and 8YSZ show a chemical compatibility in which the formation of an electrically insulating phase does not take place, but a crossed diffusion of Y3+/Mn3+and Zr4+at the interface between both materials. Thermomechanical compatibility in air between YSZ and Y1−xZrxMnO3is also demonstrated from RT to 850 °C.Fil: Moreno Botello, Zulma Liliana. Universidad Industrial Santander; Colombia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Roussel, Pascal. Instituto Pasteur; Francia. Centre National de la Recherche Scientifique; Francia. Universite Lille; FranciaFil: Gauthier, Gilles. Universidad Industrial Santander; Colombi
Defect structure and electrical conductivity of the ruddlesden-popper phases Sr3FeMO6+δ (M = Co, Ni)
Full text linkIn this work, we report a systematic study of the oxygen nonstoichiometry, high-temperature thermodynamics, and transport properties of the perovskite-related mixed conductor Sr3FeMO6+δ (M = Co, Ni). Thermogravimetry was used to determine the oxygen content change (6+δ) as a function of temperature (T) and equilibrium oxygen partial pressure (pO2) within the range 1 × 10-5 atm < pO2 < 1 atm and 400 °C ≤ T ≤ 1000 °C. From the experimental values of the oxygen chemical potential (μo2), we determined both the partial molar enthalpy (ho2) and the partial molar entropy (so2) for the composition range 5.9 <6+δ < 6.6. Thermodynamic data were fitted using a straightforward defect model. The model was deduced from the mass action law assuming oxygen-vacancy formation and involving different fractions of localized and delocalized charge carriers in iron sites and the metal transition M3d-O2p band, respectively. Electrical resistivity measurements as a function of pO2 at constant temperature were performed in the 650 °C ≤ T ≤ 1000 °C temperature range for Sr3FeCoO6+δ and Sr3FeNiO 6+δ compounds. The activation energy values for the electrical-transport process at constant oxygen content values were obtained from the combination of electrical conductivity and thermogravimetry data. The electrical conductivity data are discussed within the frame of large polaron behavior in agreement with the thermodynamic data. © 2006 American Chemical Society.Fil: Mogni, Liliana Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Prado, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin
Síntesis y caracterización de Nd₁.₈₅Ce₀.₁₅Cu₁₊ᵟOy
Full text linkEn este trabajo se prepararon muestras de Nd₁.₈₅Ce₀.₁₅Cu₁₊ᵟOy preparadas por reacción de estado sólido (RES), descomposición de nitratos (DN) y mediante la técnica de solidificación de disoluciones líquidas -liquid-mix- (TSDL). Las mismas fueron caracterizadas a través de RX, SEM, EDS y magnetización dc. Los distintos resultados indican que las muestras preparadas por TSDL se obtuvo la formación de la fase T' a una temperatura de síntesis menor que la correspondiente a los otros métodos; además, la distribución de Ce en estas muestras ser más homogénea y la transición al estado superconductor la más angosta. Las preparación de muestras por reacción de estado sólido, técnica generalmente utilizada, con transiciones superconductoras angostas, requirió una temperatura de síntesis superior a la del punto eutéctico, existente en el sistema Nd₁.₈₅Ce₀.₁₅O₃ - CuO, para obtener una mayor homogeneidad en la distribución de Ce. Por otro lado la descomposición de nitratos permite la obtención de muestras de mejor calidad que por reacción de estado sólidoIn this work samples of Nd₁.₈₅Ce₀.₁₅Cu₁₊ᵟOy were prepared by solid state reaction (SSR), nitrate decomposition method (NDM) and liquid-mix method (LMM) and characterized by XRD, SEM, EPMA, DTA and d.c. magnetization. The results indicate that in LMM samples the T' structure is obtained at the lowest temperature. Besides, this samples have a very narrow superconducting transition due to a better distribution of the Ce content. In SSR samples it is necessary a synthesis temperature higher than the eutectic one, existing in the binary Nd₁.₈₅Ce₀.₁₅O₃ - CuO phase diagram, to get good superconducting transition through a better Ce homogeneity. On the other hand, NDM samples are better than SSR onesFil: Serquis, Adriana Cristina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche. Instituto Balseiro (CNEA-CAB). Río Negro. ArgentinaFil: Prado, Fernando Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche. Instituto Balseiro (CNEA-CAB). Río Negro. ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche. Instituto Balseiro (CNEA-CAB). Río Negro. Argentin
Neutron powder diffraction study at high temperature of the Ruddlesden-Popper phase Sr3Fe2O6 + δ
Full text linkThe crystal and oxygen defect structure of the n = 2 Ruddlesden-Popper phase Sr3Fe2O6 + δ have been studied by in situ high temperature neutron powder diffraction in the temperature range 20 ≤ T ≤ 900 °C in air. The analysis of the neutron diffraction data revealed the presence of structural oxygen vacancies on both the O(1) sites linking the octahedra along the c axis and the O(3) sites in the FeO2 planes of the perovskite layers. The oxygen vacancies on the O(3) site increase with temperature up to ∼ 0.25 per formula unit at T = 900 °C. This result supports previously proposed oxygen ion diffusion mechanism in Sr3Fe2O6 + δ that involves the migration of vacancies from an O(3) site to an adjacent O(1) site. The total linear expansion along the c axis αc = 17.7(5) · 10- 6 K- 1 mainly affects the perovskite block while the width of the rock salt layers remains stable with temperature. The total volumetric expansion αV / 3 = 20(1) · 10- 6 K- 1 is around the average of the TEC values (14.8-27.1 K- 1) reported for the perovskite system La1 - xSrxCo1 - yFeyO3 - δ.Fil: Prado, Fernando Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Mogni, Liliana Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Cuello, G.J.. Institut Laue Langevin; FranciaFil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin
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