141 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
No full textThe 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
Disorder effects in the S1⁄41 antiferromagnetic spin ladder CaV2O4
No full textWe study the physical properties of the antiferromagnetic spin ladder CaV2O4 (CVO) and the Y-doped related compound Ca0.9Y0.1V2O4. In the latter, X-ray diffraction demonstrates the segregation of a small amount of a vanadium–perovskite impurity phase, leading to the formation of V vacancies within the main CVO-type structure. The 1D character of this calcium–vanadite enhances the influence of the vacancies on the electric and magnetic properties of Ca0.9Y0.1V2O4. Electrical transport is characterized by a variable-range hopping mechanism determined by the charging energy of nm-sized segments of V chains delimited by V vacancies, i.e. a Coulomb gap is formed at the Fermi level. These vacancies also locally affect the magnetic correlations, breaking the long-range AFM order observed in CaV2O4 and producing exchange bias when the Y-doped sample is cooled with an applied magnetic field.Fil: Guitarra, S.R.. Universidad San Francisco de Quito; EcuadorFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Niebieskikwiat, Dario Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad San Francisco de Quito; Ecuado
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
No full textIn 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
No full textWe 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
No full textThe 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
No full textThe 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
No full textThe 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
High temperature properties of Sr2MgMo0.9TM0.1O6−δ (TM = Mn, Co and Ni)
No full textHigh temperature properties of Sr2MgMo0.9TM0.1O6−δ (SMMTM; TM = Mn, Co and Ni) and Sr2MgMo2O6 (SMMO) compounds were studied for evaluating SMMTM materials as SOFC electrodes. SMMTM and SMMO compounds were synthesised by the combustion method, followed by annealing in air at temperatures between 1000 and 1200 °C. Rietveld structural analysis of XRD patterns showed that the TM-dopants substitute Mo cations with a solubility limit of 10% of Mo. SMMTM compounds are thermodynamically stable in 10%H2-Ar until 900 °C. Electrical conductivities of SMMTM under reducing atmosphere were three orders of magnitude higher than in air. Although the partial replacement of Mo by Mn or Ni in Sr2MgMoO6−δ decreases the electrical conductivity in both atmospheres, an increase of conductivity in 10%H2 atmosphere was observed for SMMCo compound. Whilst the area specific resistance (ASR) are not significantly affected by Mo-substitution in reducing atmospheres, the ASR of SMMTM materials as cathodes are improved.Fil: Dager Caballero, Paola Katherine. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Soria, Sergio Raul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Oxygen vacancies effect on phase separation in Pr0.5Ca0.2Sr0.3MnO3-δ
No full textWe study the effect of the introduction of a controlled amount of oxygen vacancies on the magnetic and transport properties of the phase separated manganite Pr0.5Ca0.2Sr0.3MnO3−δ, for δ=0 and 0.01. This compound presents a paramagnetic to ferromagnetic (FM) transition below TC∼240 K, and then to a charge-ordered (CO) and antiferromagnetic (AFM) phase at TCO∼175 K. However, below TCO an appreciable FM component (∼20%) still survives, related to a FM volume immersed within the CO/AFM matrix. At low temperatures, in the mainly CO phase, the introduction of oxygen vacancies enhances the FM ordering, with the consequent decrease of resistivity and magnetoresistance (MR). On the contrary, in the FM phase (in the range TCO<T<TC) the magnetization is reduced and the resistivity and MR increase. These results are discussed in the frame of percolative transport in metal–insulator mixtures, and frustrated double exchange interaction due to the interruption of some Mn–O–Mn chains.Fil: Niebieskikwiat, Dario Gabriel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); ArgentinaFil: Sanchez, Rodolfo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentin
- …
