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Iono-molecular Separation with Composite Membranes

Authors ABBAS ABDUL KADHIM KLAIF RIKABI, MARIANA BALABAN (CHELU), IULIA HARABOR, PAUL CONSTANTIN ALBU, MIRCEA SEGARCEANU, GHEORGHE NECHIFOR
Source
REV.CHIM.
Volume: 9 Time of Publication: 2016
Abstract The fast development of these methods in the recent years has been possible due to new materials developing, the boom of nanomaterials in the development of composite and hybrid materials and also due to developing of new techniques and technologies. This paper presents the composite membranes based on polysulfone and performance nanomaterials: polyaniline and magnetic nanoparticles synthesis and characterization. Composite membranes (PSf-PANI and PSf-magnetite) have been produced by phase inversion by immersion - precipitation from a polysulfone in N-methyl pyrrolidone dispersion solution in which were dispersed polyaniline or magnetic nanoparticles. The prepared composite membranes were morphologically and structurally characterized using techniques and specific measurments: FT-IR, SEM, AFM, UV VIS, DSC, dielectric spectroscopy, solvents permeation and bovine serum albumin retention.Membranes pore size indicate their use in micro and ultrafiltration (12% in the case of PSF membrane and 12% for PSf - PANI) or in the field of microfiltration and membrane sensor, 12% for magnetite - PSF membrane. The results show that water flows at 3-4 bar pressure, are increasing in the order: PSf membrane < PSf –magnetite membrane PSf –magnetite membrane > PSf-PANI membrane. In the case of alcohols flow, hydrocarbon chain has influence on flows and this correlates with hydrophily of membranes. Following bovine serum albumin retention tests, PSf-PANI membrane has the best performance (R> 95%), which correlates with the higher permeate flows.
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Structural and electrochemical characterization of BaCe0.7Zr0.2Y0.05Zn0.05O3 as an electrolyte for SOFC-H

Authors Ahmed Afif, Nikdalila Radenahmad, Chee Ming Lim, Quintin Cheok, Md. Aminul Islam, Seikh Mohammad Habibur Rahman, Abul Kalam Azad
Source
IOP Conf. Series: Materials Science and Engineering
Volume: 121 Time of Publication: 2016
Abstract As a potential electrolyte for proton-conducting solid oxide fuel cells (SOFC-Hs)and to get better protonic conductivity and stability, zinc doped BCZY material has been found to be promising. In this study, we report a new composition of proton conductors BaCe0.7Zr0.2Y0.05Zn0.05O3 (BCZYZn5) which was investigated using XRD, SEM and conductivity measurements. Rietveld refinement of the XRD data revel a cubic perovskite structure with Pm-3m space group. BaCe0.7Zr0.2Y0.05Zn0.05O3 shows cell parameter a = 4.3452(9) Ĺ. Scanning electron microscopy images shows that the grain sizes are large and compact which gives the sample high density and good protonic conductivity. The total conductivity in wet atmosphere is significantly higher than that of dry condition and the conductivity was found to be 0.276 x 10-3 Scm-1 and 0.204 x 10-3 Scm-1 at 600°C in wet and dry Ar, respectively. This study indicated that perovskite electrolyte BCZYZn5 is a promising material for the next generation intermediate temperature solid oxide fuel cells (IT-SOFCs).
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Enhanced O2 Flux of CaTi0.85Fe0.15O3−δ Based Membranes by Mn Doping

Authors Polfus, J. M., Xing, W., Riktor, M., Sunding, M. F., Dahl, P. I., Hanetho, S. M., Mokkelbost, T., Larring, Y., Fontaine, M.-L. and Bredesen, R.
Source
Journal of the American Ceramic Society
Volume: 99, Issue: 3, Pages: 1071–1078
Time of Publication: 2016
Abstract Dense symmetric membranes of CaTi0.85−xFe0.15MnxO3−δ (x = 0.1, 0.15, 0.25, 0.4) are investigated in order to determine the optimal Mn dopant content with respect to highest O2 flux. O2 permeation measurements are performed as function of temperature between 700°C–1000°C and as function of the feed side math formula ranging between 0.01 and 1 bar. X-ray photoelectron spectroscopy is utilized to elucidate the charge state of Mn, and synchrotron radiation X-ray powder diffraction (SR-XPD) is employed to investigate the structure symmetry and cell volume of the perovskite phase at temperatures up to 800°C. The highest O2 permeability is found for x = 0.25 over the whole temperature and math formula ranges, followed by x = 0.4 above 850°C. The O2 permeability for x = 0.25 reaches 0.01 mL(STP) min−1 cm−1 at 925°C with 0.21 bar feed side math formula and Ar sweep gas. X-ray photoelectron spectroscopy indicates that the charge state of Mn changes from approx. +3 to +4 when x > 0.1, which implies that Mn mainly improves electronic conductivity for x > 0.1. The cell volume is found to decrease linearly with Mn content, which coincides with an increase in the activation energy of O2 permeability. These results are consistent with the interpretation of the temperature and math formula dependency of O2 permeation. The sintering behavior and thermal expansion properties are investigated by dilatometry, which show improved sinterability with increasing Mn content and that the thermal expansion coefficient decreases from 12.4 to 11.9 × 10−6 K−1 for x = 0 and x = 0.25, respectively.

Fabrication and characterization of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)-Ce0.9Gd0.1O1.95 (GDC) composite thick film for anode supported solid oxide fuel cells

Authors Atul P. Jamale, C. H. Bhosale, L. D. Jadhav
Source
Journal of Materials Science: Materials in Electronics
Volume: 27, Issue: 1, Pages: 795–799
Time of Publication: 2016
Abstract Nowadays, the commercialization of solid oxide fuel cell (SOFC) is impeded by the chemical compatibility and polarization losses in association with electrode/electrolyte interface. Thus, to minimize these difficulties, the thick film of LSCF-GDC (50:50 wt%) composite was deposited onto GDC electrolyte to form perfect LSCF-GDC/GDC structure. The chemically compatibility of LSCF-GDC upon sintering of 1000 °C was confirmed from the X-ray diffraction studies. Typically, the film with 15 μm thickness possesses the porous structure, availing the free path for oxygen diffusion. The electrochemical impedance analysis of symmetric cell with LSCF-GDC as an electrode implies the relaxation of charge transfer and electrochemical reduction reaction with temperature. The NiO-GDC (30:70 wt%) supported SOFC with GDC and LSCF-GDC as an electrolyte and cathode, respectively was tested for their performance. The cell generates the maximum powder density of 315 μWcm−2 at 500 °C.
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Materials development: general discussion

Authors Raymond Gorte, John Vohs, Theis L. Skafte, Robert Kee, John Varcoe, Ian Metcalfe, Sune Dalgaard Ebbesen, Guntae Kim, Dehua Dong, San Ping Jiang, Ming Li, Tatsumi Ishihara, John Břgild Hansen, Beatriz Molero-Sanchez, Steven McIntosh, Helena Téllez, Alex Mo
Source
Faraday Discussions
Volume: 182, Pages: 307
Time of Publication: 2015
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The Band Gap of BaPrO3 Studied by Optical and Electrical Methods

Authors Matthias Schrade, Anna Magrasó, Augustinas Galeckas, Terje J. Finstad, and Truls Norby
Source
Journal of the American Ceramic Society
Volume: 99, Issue: 2, Pages: 492–498
Time of Publication: 2016
Abstract We report on measurements of the electrical and optical properties of BaPrO3. The temperature dependences of the electrical conductivity σ and the Seebeck coefficient α of polycrystalline samples were studied over a wide temperature range (300°C–1050°C). At lower temperatures, the observed charge transport can be described as thermally activated hopping of electron-based small polarons with an activation energy of 0.37 eV. An observed change in temperature dependence of both σ and α around 700°C was observed and interpreted as a transition from extrinsic to intrinsic carrier transport. The intrinsic conduction can be modeled with an apparent electrical band gap of ~2 eV. Optical absorption and emission spectroscopy in the UV–VIS–NIR range revealed a series of characteristic absorption thresholds and the type of optical transitions was identified by combining transmittance and diffuse-reflectance spectroscopy methods. An absorption edge of indirect type with onset at 0.6 eV is attributed to small polaron effects. The higher lying absorption thresholds of direct origin positioned at around 1.8 and 3.8 eV are correlated with thermal activation parameters from electrical measurements and discussed in terms of the band gap of BaPrO3.
Remark DOI: 10.1111/jace.13961
Link

Copper Iron Conversion Coating for Solid Oxide Fuel Cell Interconnects

Authors Jan Gustav Grolig, Patrik Alnegren, Jan Froitzheim, Jan-Erik Svensson
Source
Journal of Power Sources
Volume: 297, Pages: 534-539
Time of Publication: 2015
Abstract A conversion coating of iron and copper was investigated with the purpose of increasing the performance of Sanergy HT as a potential SOFC interconnect material. Samples were exposed to a simulated cathode atmosphere (air, 3 % H2O) for durations of up to 1000 h at 850 °C. Their performance in terms of corrosion, chromium evaporation and electrical resistance (ASR) was monitored and compared to uncoated and cobalt-coated Sanergy HT samples. The copper iron coating had no negative effects on corrosion protection and decreased chromium evaporation by about 80%. An Area Specific Resistance (ASR) of 10 mΩcm2 was reached after 1000 h of exposure. Scanning Electron Microscopy revealed well adherent oxide layers comprised of an inner chromia layer and an outer spinel oxide layer.
Remark https://doi.org/10.1016/j.jpowsour.2015.06.139
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New alluaudite-related triple molybdates Na25Cs8R5(MoO4)24 (R = Sc, In): synthesis, crystal structures and properties

Authors Aleksandra A. Savina, Sergey F. Solodovnikov, Dmitry A. Belov, Zoya A. Solodovnikova, Sergey Yu. Stefanovich, Bogdan I. Lazoryak and Elena G. Khaikina
Source
New Journal of Chemistry
Volume: 41, Pages: 5450
Time of Publication: 2017
Abstract New triple molybdates Na25Cs8R5(MoO4)24 (R = Sc, In) were prepared as powders and ceramics by solid state reactions, and their single crystals were also obtained from melts by spontaneous сrystallization. The structures were determined by single crystal XRD analysis. The electrical conductivity of ceramics was measured by impedance spectroscopy. The crystal structures were determined in monoclinic sp. gr. P21/c, a = 14.0069(3) Ĺ,b = 12.6498(3) Ĺ, c = 28.6491(6) Ĺ, b = 90.007(1)1 (Sc) and a = 14.0062(2) Ĺ, b = 12.6032(2) Ĺ, c = 28.7138(4) Ĺ,b = 90.001(1)1 (In). Together with triclinic Na25Cs8Fe5(MoO4)24, the titled compounds form a distinctive family of pseudo-orthorhombic alluaudite-related structures with the parent sp. gr. Pbca. Its structural features are alluaudite-like polyhedral layers composed of pairs of edge-shared (R, Na)O6 and NaO6 octahedra connected by bridging MoO4 tetrahedra. The layers are joined together by means of interlayer MoO4 tetrahedra, thus forming open 3D frameworks with cavities filled with Cs+ and Na+ ions. The manner of stacking layers is somewhat different from the alluaudite type. The compounds undergo phase transitions at 668 (Sc) and 725 (In) K accompanied by an abrupt increase of electrical conductivity presumably Na+-ionic in nature. Above these transitions, the conductivity is as high as 10(3) Scm(-1), which makes Na25Cs8R5(MoO4)24 (R = Sc, In) promising solid state electrolytes.
Remark DOI: 10.1039/c7nj00202e
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Enhanced Flexible Thermoelectric Generators Based on Oxide–Metal Composite Materials

Authors Benjamin Geppert, Artur Brittner, Lailah Helmich, Michael Bittner, Armin Feldhoff
Source
Journal of Electronic Materials
Volume: 46, Issue: 4, Pages: 2356–2365
Time of Publication: 2017
Abstract The thermoelectric performance of flexible thermoelectric generator stripes was investigated in terms of different material combinations. The thermoelectric generators were constructed using Cu-Ni-Mn alloy as n-type legs while varying the p-type leg material by including a metallic silver phase and an oxidic copper phase. For the synthesis of Ca3Co4O9/CuO/Ag ceramic-based composite materials, silver and the copper were added to the sol–gel batches in the form of nitrates. For both additional elements, the isothermal specific electronic conductivity increases with increasing amounts of Ag and CuO in the samples. The amounts for Ag and Cu were 0 mol.%, 2 mol.%, 5 mol.%, 10 mol.%, and 20 mol.%. The phases were confirmed by x-ray diffraction. Furthermore, secondary electron microscopy including energy dispersive x-ray spectroscopy were processed in the scanning electron microscope and the transmission electron microscope. For each p-type material, the data for the thermoelectric parameters, isothermal specific electronic conductivity σ and the Seebeck coefficient α, were determined. The p-type material with a content of 5 mol.% Ag and Cu exhibited a local maximum of the power factor and led to the generator with the highest electric power output Pel.
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Protonic Conduction in TiP2O7

Authors V. Nalini, T.Norby, A.M. Anuradha
Source
Solid State Ionics: Advanced Materials for Emerging Technologies
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Crystal structure and proton conductivity of BaSn 0.6 Sc 0.4 O 3  d : insights from neutron powder di ff raction and solid-state NMR spectroscopy

Authors Francis G. Kinyanjui, Stefan T. Norberg, Christopher S. Knee, Istaq Ahmed, Stephen Hull, Lucienne Buannic, Ivan Hung, Zhehong Gan, Fr ́ed ́eric Blanc, Clare P. Grey and Sten G. Eriksson
Source
J.Mater.Chem.A
Volume: 4, Issue: 14, Pages: 5088-5101
Time of Publication: 2016
Abstract The solid-state synthesis and structural characterisation of perovskite BaSn1−xScxO3−δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm[3 with combining macron]m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. 119Sn and 45Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn4+ and Sc3+ local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). 17O NMR spectra on 17O enriched BaSn1−xScxO3−δ materials show the existence of Sn–O–Sn, Sn–O–Sc and Sc–O–Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3−δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O–D bond distance of 0.96(1) Ĺ and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10−4 to 1.1 × 10−3 S cm−1 between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.
Remark DOI: 10.1039/c5ta09744d
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Microstructural design of CaMnO3 and its thermoelectric proprieties.

Author Natalia Maria Mazur
Source
dissertation
Time of Publication: 2015
Remark Norwegian University of Science and Technology, Department of Materials Science and Engineering
Link

Effect of Firing Temperature on the Kinetics of Oxygen Reduction in La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) Cathodes for Solid Oxide Fuel Cells

Author Brage Braathen Kjeldby
Source
dissertation
Time of Publication: 2015
Remark Norwegian University of Science and Technology, Department of Materials Science and Engineering
Link

DC-bias dependent impedance spectroscopy of BaTiO3–Bi(Zn1/2Ti1/2)O3 ceramics

Authors Nitish Kumar, Eric A. Patterson, Till Frömling and David P. Cann
Source
J. Mater. Chem. C
Volume: 4, Pages: 1782-1786
Time of Publication: 2016
Remark DOI: 10.1039/C5TC04247J
Link

Surface Protonics Promotes Catalysis

Authors R. Manabe, S. Okada, R. Inagaki, K. Oshima, S. Ogo & Y. Sekine
Source
Nature Scientific Reports 6
Time of Publication: 2016
Abstract Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.
Remark doi:10.1038/srep38007
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Structural- and Compositional Investigations of Grain Boundaries in Y-Doped BaZrO3 A proton-conducting electrolyte for electrochemical applications

Author Adrian Lervik
Source
Master’s Thesis
Time of Publication: 2016
Remark University of Oslo
Link

Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes

Authors I.Kalaitzidou, M. Makri, D. Theleritis, A. Katsaounis, C.G. Vayenas
Source
Surface Science
Volume: 646, Pages: 194-203
Time of Publication: 2016
Abstract The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing and decreases with increasing . These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively.
Keywords Electrochemical promotion of catalysis, Ion conducting support, Hydrogenation of CO2, Ruthenium catalyst, Rules of promotion, Metal–support interactions
Remark https://doi.org/10.1016/j.susc.2015.09.011
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Defect mechanisms in BaTiO3-BiMO3 ceramics

Authors Nitish Kumar, Eric A. Patterson, Till Frömling, Edward P. Gorzkowski, Peter Eschbach, Ian Love, Michael P. Müller, Roger A. De Souza, Julie Tucker, Steven R. Reese and David P. Cann
Source
Journal of the American Ceramic Society
Time of Publication: 2018
Abstract Often, addition of BiMO3 to BaTiO3 (BT) leads to improvement in resistivity with a simultaneous shift to n-type conduction from p-type for BT. In considering one specific BiMO3 composition, that is, Bi(Zn1/2Ti1/2)O3 (BZT), several prospective candidates for the origin of this n-type behavior in BT-BZT were studied—loss of volatile cations, oxygen vacancies, bismuth present in multiple valence states and precipitation of secondary phases. Combined x-ray and neutron diffraction, prompt gamma neutron activation analysis and electron energy loss spectroscopy suggested much higher oxygen vacancy concentration in BT-BZT ceramics (>4%) as compared to BT alone. X-ray photoelectron spectroscopy and x-ray absorption spectroscopy did not suggest the presence of bismuth in multiple valence states. At the same time, using transmission electron microscopy, some minor secondary phases were observed, whose compositions were such that they could result in effective donor doping in BT-BZT ceramics. Using experimentally determined thermodynamic parameters for BT and slopes of Kröger-Vink plots, it has been suggested that an ionic compensation mechanism is prevalent in these ceramics instead of electronic compensation. These ionic defects have an effect of shifting the conductivity minimum in the Kröger-Vink plots to higher oxygen partial pressure values in BT-BZT ceramics as compared to BT, resulting in a significantly higher resistivity values in air atmosphere and n-type behavior. This provides an important tool to tailor transport properties and defects in BT-BiMO3 ceramics, to make them better suited for dielectric or other applications.
Remark DOI: 10.1111/jace.15403, Version of Record online: 8 JAN 2018
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The Effect of Ni Doping on the Performance and Electronic Structure of LSCF Cathodes Used for IT-SOFCs

Authors Alessandro Longo, Leonarda F. Liotta, Dipanjan Banerjee, Valeria La Parola, Fabrizio Puleo, Chiara Cavallari, Christoph J. Sahle, Marco Moretti Sala, and Antonino Martorana
Source
J. Phys. Chem.: C
Time of Publication: 2017
Abstract We investigated the effect of nickel doping on the electronic structure and performance of nanostructured La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ prepared by the one-pot sol–gel method. The commercial undoped La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF0.8) was used as reference. Moreover, for comparison, Ni (3 mol %) was deposited by wetness impregnation over the La0.6Sr0.4Co0.2Fe0.8O3−δ. We show by in situ X-ray absorption spectroscopy at 900 °C under air flow that nickel enters the B perovskite site of the material and favors the stabilization of the cobalt oxidation state, as evidenced by the delay in the decrease of the average Co valence with respect to undoped samples. Our results are further supported by in situ X-ray Raman spectroscopy (XRS) that allowed us to monitor the temperature evolution of the O K-edge. XRS evidences that nickel-doped LSCF shows unmodified O2p-TM3d density of states, which proves that the Co oxidation state is preserved. Electrochemical impedance spectroscopy measurements were carried out over half-cell systems consisting of LSCF-based materials deposited onto a Ce0.8Gd0.2O2−δ electrolyte. The improvement of the electrochemical performances of the Ni-doped La0.6Sr0.4Co0.2Fe0.8–0.03Ni0.03O3−δ sample with respect to a reference Ni-impregnated LSCF is attributed to the stabilization of the TM-O6 structural units, which were recently proposed as the functional units for oxygen reduction.
Remark DOI: 10.1021/acs.jpcc.7b07626
Link

Protonic Conductors for Intermediate Temperature Fuel Cell Electrolytes: Superprotonic CsH2PO4 Stabilization and in-Doped SnP2O7 Structure Study

Author Heber Jair Martinez Salinas
Source
Dissertation
Time of Publication: 2017
Remark The University of Texas at El Paso
Link

Optimisation of growth parameters to obtain epitaxial Y-doped BaZrO3 proton conducting thin films

Authors A. Magrasó, B. Ballesteros, R. Rodríguez-Lamas, M.F. Sunding, J. Santiso
Source
Volume: 314, Pages: 9–16
Time of Publication: 2018
Abstract We hereby report developments on the fabrication and characterization of epitaxial thin films of proton conducting Y-doped BaZrO3 (BZY) by pulsed laser deposition (PLD) on different single crystal substrates (MgO, GdScO3, SrTiO3, NdGaO3, LaAlO3 and sapphire) using Ni-free and 1% Ni-containing targets. Pure, high crystal quality epitaxial films of BZY are obtained on MgO and on perovskite-type substrates, despite the large lattice mismatch. The deposition conditions influence the morphology, cell parameters and chemical composition of the film, the oxygen partial pressure during film growth being the most determining. Film characterization was carried out using X-ray diffraction, transmission electron and atomic force microscopies, wavelength dispersive X-ray spectroscopy and angle-resolved X-ray photoelectron spectroscopy. All films show a slight tetragonal distortion that is not directly related to the substrate-induced strain. The proton conductivity of the films depends on deposition conditions and film thickness, and for the optimised conditions its total conductivity is slightly higher than the bulk conductivity of the target material (3 mS/cm at 600 °C, in wet 5% H2/Ar). The conductivities are, however, more than one order of magnitude lower than the highest reported in literature and possible reasoning is elucidated in terms of local and extended defects in the films.
Keywords BaZrO3; Thin film; Electrolyte; Proton conductivity; SOFC; PC-SOFC
Remark https://doi.org/10.1016/j.ssi.2017.11.002
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Improvement of thermoelectric properties of lanthanum cobaltate by Sr and Mn co-substitution

Authors Ashutosh Kumar, D. Sivaprahsam, Ajay D. Thakur
Source
Journal of Alloys and Compounds
Volume: 735, Pages: 1787–1791
Time of Publication: 2018
Abstract We report thermoelectric (TE) properties of Sr and Mn co-substituted LaCoO3 system from room temperature to 700 K. Sr-substitutions at La and Mn at Co site in LaCoO3 improves the electrical conductivity (σ). Thermal conductivity (κ) of all the samples increases with the increase in temperature but decreases with the substitution in LaCoO3. An estimation of the electronic thermal conductivity (κe) suggests a dominant phonon contribution to thermal conductivity in this system. A maximum value of the figure of merit is 0.14 at 480 K for La0.95Sr0.05Co0.95Mn0.05O3.
Keywords Powders: solid-state reaction; Thermal conductivity; Electrical conductivity; Perovskites
Remark https://doi.org/10.1016/j.jallcom.2017.11.334
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Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells

Authors F.J. Garcia-Garciaa, F. Yubero, A.R. González-Elipe, R.M. Lambert
Source
International Journal of Hydrogen Energy
Volume: 43, Issue: 2, Pages: 885–893
Time of Publication: 2018
Abstract Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-doped-ceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 °C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au-doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H2O mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Nisingle bondAu surface alloy that inhibited carbonisation and poisoning of the active nickel surface.
Keywords SOFC; Ultrathin film anodes; Magnetron sputtering; Gadolinia doped ceria; Carbon-tolerant; Gold doping
Remark https://doi.org/10.1016/j.ijhydene.2017.11.020
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Electrical properties of polycrystalline materials from the system Cu-As-Ge-Se under high pressure condition

Authors V E Zaikova, N V Melnikova, A V Tebenkov , A A Mirzorakhimov, O P Shchetnikov, A N Babush kin and G V Sukhanova
Source
Journal of Physics: Conference Series
Volume: 917 Time of Publication: 2017
Abstract The paper deals with electrical properties of polycrystalline materials (GeSe)x(CuAsSe2)1-x(x= 0.5 and 0.7) under high pressure (up to 45 GPa) conditions. The phenomenon of negative magnetoresistance was observed for studied materials.
Remark doi :10.1088/1742-6596/917/8/082009
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Asymmetric tubular CaTi0.6Fe0.15Mn0.25O3-δ membranes: Membrane architecture and long-term stability

Authors Wen Xing, Marie-Laure Fontaine, Zuoan Li, Jonathan M. Polfus, Yngve Larring, Christelle Denonville, Emmanuel Nonnet, Adam Stevenson, Partow P. Henriksen, Rune Bredesen
Source
Journal of Membrane Science
Volume: 548, Pages: 372-379
Time of Publication: 2018
Abstract Three architectures of asymmetric tubular oxygen transport membranes (OTM) based on CaTi0.6Fe0.15Mn0.25O3-δ were fabricated with various thicknesses of the tubular porous supports and the dense membrane layers. This was achieved by a two-step firing method combining water based extrusion and dip-coating. The oxygen flux of the tubular membranes was characterized as a function of temperature and oxygen partial pressure on both feed and sweep sides for the different architectures. The flux exhibits different functional dependencies with respect to the oxygen partial pressure gradient and the membrane architecture. Numerical simulations using a Dusty-gas model were conducted to evaluate the effect of the porous support microstructure and thickness on oxygen partial pressure gradient inside the porous media. Results from this work were used to establish dependency of the flux with respect to bulk transport properties of the material, surface kinetics and architecture of the porous support. Furthermore, long-term stability of the produced tubular asymmetric membrane operated in CO2-containing atmospheres was assessed over half a year. The membrane exhibited a stable oxygen flux without showing significant flux degradation.
Keywords OTM, Asymmetric tubular membrane, Oxygen flux, CaTiO3, Long-term stability
Remark https://doi.org/10.1016/j.memsci.2017.11.042
Link
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