Published references
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These publications have a reference to ProboStat™ or other NORECS products
All 1-25 26-50 51-75 76-100 101-125 126-150 151-175 176-200 201-225 226-250 251-275 276-300 301-325 326-350 351-375 376-400 401-425 426-450 451-475 476-500 501-525 526-550 551-575 576-600 601-625 626-650 651-675 676-Triode operation for enhancing the performance of H2S-poisoned SOFCs operated under CH4–H2O mixtures
ID=310| Authors |
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| Source |
Solid State Ionics
Volume: 277,
Pages: 65–71 Time of Publication: 2015 |
| Abstract | Performances of Solid Oxide Fuel Cells (SOFCs) were investigated in triode operation mode under methane steam reforming in the presence of H2S. Both the catalytic performances for methane steam reforming and the electrochemical properties for the electrochemical oxidation of hydrogen of a Ni/GDC anode drastically dropped in the presence of 1 ppm H2S. Poisoned catalytic sites are different from those for the hydrogen electrochemical oxidation. Triode operation, i.e. application of moderate negative currents between the anode and an auxiliary electrode, can improve electrochemical properties, as a result of a local production of H2 coming from H2O electrolysis. Some specific triode operations were found to achieve a thermodynamic efficiency close to the unity to avoid any energy overconsumption. |
| Keywords | SOFC; Triode operation; H2S poisoning; Ni/GDC anode |
| Remark |
doi:10.1016/j.ssi.2015.05.003 Link |
High-temperature anion and proton conduction in RE3NbO7 (RE = La, Gd, Y, Yb, Lu) compounds
ID=309| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 35,
Issue: 11,
Pages: 3051–3061 Time of Publication: 2015 |
| Abstract | The oxide-ion and proton conduction properties of RE3NbO7 (RE = La, Gd, Y, Yb, Lu) compounds were investigated. For the bigger rare-earth cation, i.e. La3+, the compound crystallises in a weberite-type structure and the oxide-ion conductivity is low owing to the lack of intrinsic oxygen vacancies. Consequently, the resultant proton incorporation and conductivity in La3NbO7 are also low. For small rare-earth cations, i.e. from Gd3+ to Lu3+ and for RE = Y, materials adopt a fluorite-like structure confirmed from X-ray powder diffraction. In this latter case, materials include intrinsic oxygen vacancies leading to a higher oxygen conductivity. For these compounds, a proton incorporation takes place at low temperature under wet conditions giving rise to proton conductivity. Nevertheless, both oxygen and proton conductivities are low in these materials, which can be explained by the ordering of oxygen vacancies observed by Transmission Electron Microscopy. |
| Keywords | Protonic ceramic fuel cell; Rare-earth niobate; Combustion synthesis; Fluorite-type structure; Electrical properties |
| Remark |
doi:10.1016/j.jeurceramsoc.2015.04.014 Link |
Proton transport properties of the RE3Ga5MO14 (RE = La, Nd and M = Si, Ti, Sn) langasite family of oxides
ID=308| Authors |
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| Source |
Solid State Ionics
Volume: 275,
Pages: 29–34 Time of Publication: 2015 |
| Abstract | Hydration and proton transport properties of novel, intrinsically acceptor doped compositions within the RE3Ga5MO14 family of oxides have been addressed by means of measurements of the electrical conductivity. Oxygen vacancies and protons charge compensate the acceptor in dry and wet atmospheres, respectively, and all compositions display significant proton conductivity below 1000 °C. The hydration thermodynamics is affected by M-ion substitution, and becomes more favorable in the order Si < Ti < Sn. The enthalpy of proton mobility is also strongly dependent on the M-ion; M = Si, Ti and Sn exhibit enthalpies of proton mobility of 76 ± 3, 61 ± 1 and 80 ± 2 kJ mol− 1, respectively. |
| Keywords | Langasites; Conductivity; Defects; Acceptor; Hydration; Protons |
| Remark |
doi:10.1016/j.ssi.2015.03.014 Link |
Diffusion of Nd and Mo in lanthanum tungsten oxide
ID=307| Authors |
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| Source |
Solid State Ionics
Volume: 274,
Pages: 128–133 Time of Publication: 2015 |
| Abstract | Cation diffusion in functional oxides exposed to electrochemical gradients may lead to kinetic demixing or decomposition and, consequently, determine the life-time of the functional component. Here we present chemical diffusion coefficients of Nd and Mo in the mixed proton–electron conductor lanthanum tungsten oxide, La28 − xW4 + xO54 + 3x/2 (LWO), measured at 1000 to 1200 °C in both oxidizing and reducing atmospheres. The bulk diffusivities of Nd and Mo were similar at all temperatures investigated and did not change significantly from oxidizing to reducing conditions. On these bases it is suggested that bulk diffusion of both Nd and Mo occurs via the La2 site on which both cations reside. Based on the low activation energy for bulk transport (~ 200 kJ∙mol− 1) at temperatures below 1200 °C it is proposed that the cation defect concentrations are, in effect, frozen in. Preferential diffusion of Nd along the grain boundaries was rationalized based on space charge effects and depletion of W6 + and Mo6 + near the positively charged grain boundary core. Potential implications of kinetic demixing or decomposition of LWO membranes are also evaluated based on the present results. |
| Keywords | Lanthanum tungstate; Cation diffusion; SIMS; Degradation; Tracer diffusion |
| Remark |
doi:10.1016/j.ssi.2015.03.011 Link |
Crystal structure and high-temperature properties of the Ruddlesden–Popper phases Sr3−xYx(Fe1.25Ni0.75)O7−δ (0≤x≤0.75)
ID=306| Authors |
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| Source |
Journal of Solid State Chemistry
Volume: 227,
Pages: 45–54 Time of Publication: 2015 |
| Abstract | Ruddlesden–Popper n=2 member phases Sr3−xYxFe1.25Ni0.75O7−δ, 0≤x≤0.75, have been investigated by X-ray and neutron powder diffraction, thermogravimetry and Mössbauer spectroscopy. Both samples as-prepared at 1300 °C under N2(g) flow and samples subsequently air-annealed at 900 °C were studied. The as-prepared x=0.75 phase is highly oxygen deficient with δ=1, the O1 atom site being vacant, and the Fe3+/Ni2+ ions having a square pyramidal coordination. For as-prepared phases with lower x values, the Mössbauer spectral data are in good agreement with the presence of both 5- and 4-coordinated Fe3+ ions, implying in addition a partial occupancy of the O3 atom sites that form the basal plane of the square pyramid. The air-annealed x=0.75 sample has a δ value of 0.61(1) and the structure has Fe/Ni ions in both square pyramids and octahedra. Mössbauer spectroscopy shows the phase to contain only Fe3+, implying that all Ni is present as Ni3+. Air-annealed phases with lower x values are found to contain both Fe3+ and Fe4+. For both the as-prepared and the air-annealed samples, the Y3+ cations are found to be mainly located in the perovskite block. The high-temperature thermal expansion of as-prepared and air-annealed x=0.75 phases were investigated by high-temperature X-ray diffraction and dilatometry and the linear thermal expansion coefficient determined to be 14.4 ppm K−1. Electrical conductivity measurements showed that the air-annealed samples have higher conductivity than the as-prepared ones. |
| Keywords | Ruddlesden–Popper structure; Oxygen non-stoichiometry; Crystal structure; Mössbauer spectroscopy; Electrical conductivity; Thermal expansion |
| Remark |
doi:10.1016/j.jssc.2015.03.018 Link |
Atmosphere dependence of anode reaction of intermediate temperature steam electrolysis using perovskite type proton conductor
ID=305| Authors |
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| Source |
Journal of Solid State Electrochemistry
Volume: 19,
Issue: 6,
Pages: 1793-1798 Time of Publication: 2015 |
| Abstract | The effect of oxygen partial pressure on anode reaction of steam electrolysis using SrZr0.5Ce0.4Y0.1O3-α (SZCY-541) proton conducting electrolyte was investigated by AC impedance measurement in this work. The anode reaction was enhanced by increasing oxygen partial pressure, and this result was opposite to the expectation from the conventional anode reaction (water splitting reaction). The increase in the electrode reaction conductivity with oxygen chemical potential was proportional to PO21/4 at 600 °C and at higher oxygen partial pressure region of 700 and 800 °C, suggesting the possibility that the enhancement is caused by the increase in hole concentration on the electrolyte surface near the anode. |
| Remark | Link |
FD Electrolysis: Co-electrolysis of steam and CO2 in full-ceramic symmetrical SOECs: A strategy for avoiding the use of Hydrogen as a safe gas
ID=304| Authors |
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| Source |
Faraday Discussions
Time of Publication: 2015
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| Abstract | The use of cermets as fuel electrodes for solid oxide electrolysis cells requires permanent circulation of reducing gas, e.g. H2 or CO, so called safe gas, in order to avoid oxidation of the metallic phase. Replacing metallic based electrodes by pure oxides is therefore proposed as an advantage for the industrial application of solid oxide electrolyzers. In this work, full-ceramic symmetrical solid oxide electrolysis cells have been investigated for steam/CO2 co-electrolysis. Electrolyte supported cells with La0.75Sr0.25Cr0.5Mn0.5O3-δ reversible electrodes have been fabricated and tested in co-electrolysis mode using different fuel compositions, from pure H2O to pure CO2, at temperatures of 850°C – 900°C. Electrochemical impedance spectroscopy and galvanostatic measurements have been carried out for the mechanistic understanding of the symmetrical cells performance. The content of H2 and CO in the product gas has been measured by in-line gas micro-chromatography. The effect of employing H2 as a safe gas has been also investigated. Maximum density currents of 750 mA/cm2 and 620 mA/cm2 have been applied at 1.7 V for pure H2O and for H2O:CO2 ratios of 1:1, respectively. Remarkable results were obtained for hydrogen-free fuel compositions, which confirmed the interest of using ceramic oxides as a fuel electrode candidate to reduce or completely avoid the use of safe gas in operation minimizing the contribution of the reverse water shift reaction (RWSR) in the process. H2:CO ratios close to two were obtained for hydrogen-free tests fulfilling the basic requirements for synthetic fuel production. An important increase of the operation voltage was detected under continuous operation leading to a dramatic failure by delamination of the oxygen electrode. |
| Remark |
Accepted Manuscript, DOI: 10.1039/C5FD00018A Link |
Doping strategies for increased oxygen permeability of CaTiO3 based membranes
ID=303| Authors |
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| Source |
Journal of Membrane Science
Volume: 482,
Pages: 137–143 Time of Publication: 2015 |
| Abstract | Oxygen permeation measurements are performed on dense samples of CaTi0.85Fe0.15O3−δ, CaTi0.75Fe0.15Mg0.05O3−δ and CaTi0.75Fe0.15Mn0.10O3−δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O2 permeability of CaTi1−xFexO3−δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700 and 1000 °C with feed side oxygen partial pressures between 0.01 and 1 bar. The O2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10−3 ml min−1 cm−1 at 900 °C and 0.21 bar O2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x=0.2. While the O2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O2 permeability, i.e., oxygen vacancies and electronic charge carriers. |
| Keywords | Dense ceramic oxygen membrane; Ambipolar transport; Mixed ionic-electronic conduction; CaTiO3; Calcium titanate |
| Remark |
doi:10.1016/j.memsci.2015.02.036 Link |
Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Evolution of electrical properties
ID=302| Authors |
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| Source |
Journal of Power Sources
Volume: 284,
Pages: 321–327 Time of Publication: 2015 |
| Abstract | AISI 441 coated with a double layer coating of 10 nm cerium (inner layer) and 630 nm cobalt was investigated and in addition the uncoated material was exposed for comparison. The main purpose of this investigation was the development of a suitable ASR characterization method. The material was exposed to a simulated cathode atmosphere of air with 3% water at 850 °C and the samples were exposed for up to 1500 h. We compared two methods of ASR measurements, an in-situ method where samples were measured with platinum electrodes for longer exposure times and an ex-situ method where pre-oxidized samples were measured for only very short measurement times. It was found that the ASR of ex-situ characterized samples could be linked to the mass gain and the electrical properties could be linked to the evolving microstructure during the different stages of exposure. Both the degradation of the electric performance and the oxygen uptake (mass gain) followed similar trends. After about 1500 h of exposure an ASR value of about 15 mΩcm2 was reached. The in-situ measured samples suffered from severe corrosion attack during measurement. After only 500 h of exposure already a value of 35 mΩcm2 was obtained. |
| Keywords | ASR; Interconnect; AISI 441; SOFC; Corrosion; Platinum |
| Remark |
doi:10.1016/j.jpowsour.2015.03.029 Link |
Steam-promoted CO2 flux in dual-phase CO2 separation membranes
ID=301| Authors |
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| Source |
Journal of Membrane Science
Volume: 482,
Pages: 115–119 Time of Publication: 2015 |
| Abstract | Steam dissolving into molten carbonates through the formation of hydroxide ions could contribute to the permeation of CO2 in dual-phase membranes under certain conditions. In this work, ceria (CeO2) supported dual-phase membranes was fabricated and the effect of steam on the transport properties has been investigated by means of flux measurements. The results show an approximate 30% increase of the CO2 flux when 2.5% steam is introduced to the feed side, while an approximate 250–300% increase of the CO2 flux is observed when introducing the same amount of steam to the sweep side. These phenomena and transport mechanisms are explained by the theory of ambipolar permeation of CO2 via various combinations of charged species. |
| Keywords | Dual-phase; CO2 separation membrane; Steam; Flux |
| Remark |
doi:10.1016/j.memsci.2015.02.029 Link |
Electrical conductivity and thermopower of (1 − x) BiFeO3 – xBi0.5K0.5TiO3 (x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition
ID=300| Authors |
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| Source |
Physical Chemistry Chemical Physics
Volume: 17,
Issue: 14,
Pages: 9420-9428 Time of Publication: 2015 |
| Abstract | Ferroelectric BiFeO3 has attractive properties such as high strain and polarization, but a wide range of applications of bulk BiFeO3 are hindered due to high leakage currents and a high coercive electric field. Here, we report on the thermal behaviour of the electrical conductivity and thermopower of BiFeO3 substituted with 10 and 20 mol% Bi0.5K0.5TiO3. A change from p-type to n-type conductivity in these semi-conducting materials was demonstrated by the change in the sign of the Seebeck coefficient and the change in the slope of the isothermal conductivity versus partial pressure of O. A minimum in the isothermal conductivity was observed at [similar]10−2 bar O2 partial pressure for both solid solutions. The strong dependence of the conductivity on the partial pressure of O2 was rationalized by a point defect model describing qualitatively the conductivity involving oxidation/reduction of Fe3+, the dominating oxidation state of Fe in stoichiometric BiFeO3. The ferroelectric to paraelectric phase transition of 80 and 90 mol% BiFeO3 was observed at 648 ± 15 and 723 ± 15 °C respectively by differential thermal analysis and confirmed by dielectric spectroscopy and high temperature powder X-ray diffraction. |
| Remark |
DOI: 10.1039/C5CP00266D Link |
Structure and conductivity of acceptor doped La2BaZnO5 and Nd2BaZnO5
ID=299| Authors |
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| Source |
Solid State Ionics
Volume: 272,
Pages: 160–165 Time of Publication: 2015 |
| Abstract | The effect of calcium substitution on the structure and electrical conductivity of Ln2 − xCaxBaZnO5 − δ, Ln = La and Nd, has been studied. Differing trends with respect to dependence of the unit cell volume were observed as a function of Ca substitution. For both series of materials the limit of Ca substitution was estimated to be x ≈ 0.2. The electrical conductivity was studied in the temperature range of 1000–350 °C using electrochemical impedance spectroscopy in argon and oxygen atmospheres and via isotherms between 400 and 1000 °C as function of oxygen pressure and the water vapour pressure. A marked increase in conductivity of approx. two orders of magnitude was explained by the presence of oxygen vacancies in the calcium doped samples. At pO2 < 10− 12 atm the x = 0.15 materials are predominantly oxygen ion conductors, and La1.85Ca0.15BaZnO5 − δ displays a peak conductivity of 0.002 S cm− 1 at 1000 °C. The materials display a rise in conductivity in oxidizing conditions, indicating a significant p-type contribution. |
| Keywords | Oxide ion conductor; Mixed conductor; Synthesis; Impedance spectroscopy; SOFC |
| Remark |
doi:10.1016/j.ssi.2015.02.001 Link |
Dual atmosphere study of the K41X stainless steel for interconnect application in high temperature water vapour electrolysis
ID=298| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 40,
Issue: 15,
Pages: 5305–5312 Time of Publication: 2015 |
| Abstract | High temperature water vapour electrolysis (HTE) is one of the most efficient technologies for mass hydrogen production. A major technical difficulty related to high temperature water vapour electrolysis is the development of interconnects working efficiently for a long period. Working temperature of 800 °C enables the use of metallic materials as interconnects. High temperature corrosion behaviour and electrical conductivity of a commercial stainless steel, K41X (AISI 441), were tested in HTE dual atmosphere (95%O2-5%H20/10%H2-90%H2O) at 800 °C. The alloy exhibits a very good oxidation resistance compared to single atmosphere tests. However, a supplied electrical current significantly changes the nature of the oxides that form during the test. A very good Area Specific Resistance (ASR) parameter was measured in dual atmosphere, much lower than the values obtained in single atmosphere tests. |
| Remark |
doi:10.1016/j.ijhydene.2015.01.116 Link |
Solid oxide fuel cells with (La,Sr)(Ga,Mg)O3-δ electrolyte film deposited by radio-frequency magnetron sputtering
ID=297| Authors |
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| Source |
Journal of Power Sources
Volume: 281,
Pages: 258–264 Time of Publication: 2015 |
| Abstract | In this study, solid oxide fuel cells (SOFCs) containing a high quality La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) film deposited on anode supported substrate using RF magnetron sputtering are successfully prepared. The anode substrate is composed of two functional NiO/Sm0.2Ce0.8O2-δ (SDC) composite layers with ratios of 60/40 wt% and 50/50 wt% and a current collector layer of pure NiO. The as-deposited LSGM film appears to be amorphous in nature. After post-annealing at 1000 °C, a uniform and dense polycrystalline film with a composition of La0.87Sr0.13Ga0.85Mg0.15O3-δ and a thickness of 3.8 μm is obtained, which was well adhered to the anode substrate. A composite LSGM/La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) layer, with a ratio of 30/70 wt%, is used as the cathode. The SOFC prepared reveals a good mechanical integrity with no sign of cracking, delamination, or discontinuity among the interfaces. The total cell resistance of a single cell with LSGM electrolyte film declines from 0.60 to 0.10 Ω cm2 as the temperature escalates from 600 to 800 °C and the open circuit voltage (OCV) ranges from 0.85 to 0.95 V. The maximum power density (MPD) of the single cell is reported as 0.65, 1.02, 1.30, 1.42, and 1.38 W cm−2 at 600, 650, 700, 750, and 800 °C, respectively. The good cell performance leads to the conclusion that RF magnetron sputtering is a feasible deposition method for preparing good quality LSGM films in SOFCs. |
| Keywords | Solid oxide fuel cell; Sputtering; Electrolyte; Doped lanthanum gallate |
| Remark |
doi:10.1016/j.jpowsour.2015.01.185 Link |
Phase equilibria in the Cs2MoO4–ZnMoO4–Zr(MoO4)2 system, Crystal structures and properties of new triple molybdates Cs2ZnZr(MoO4)4 and Cs2ZnZr2(MoO4)6
ID=296| Authors |
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| Source |
Volume: 81,
Pages: 93–99 Time of Publication: 2015 |
| Abstract | Subsolidus phase relations in the Cs2MoO4–ZnMoO4–Zr(MoO4)2 system were determined and two new compounds, Cs2ZnZr(MoO4)4 and Cs2ZnZr2(MoO4)6, were obtained. The structure of Cs2ZnZr(MoO4)4 (a=5.7919(1) Å, c=8.0490(3) Å; space group P View the MathML source3¯m1; Z=0.5; R=0.0149) belongs to the layered glaserite-like KAl(MoO4)2 structure type where the octahedral Al3+ positions are statistically occupied by 0.5 Zn2++0.5 Zr4+. The second triple molybdate, Cs2ZnZr2(MoO4)6 (a=13.366(1) Å, c=12.253(3) Å, space group R View the MathML source3¯, Z=3, R=0.0324), is isostructural to Cs2MnZr2(MoO4)6 and Cs2M2Zr(MoO4)6 (M=Al, Fe) and contains a mixed 3D framework built of МоO4 tetrahedra and (Zn, Zr)O6 octahedra sharing common vertices. Cesium cations are located in large channels of the framework. The latter compound undergoes a first-order phase transition at 723 K with considerable increasing its ionic conductivity. |
| Keywords | Cesium; Zinc; Zirconium; Triple molybdates; Crystal structure; X-ray diffraction; IR and Raman spectra; Conductivity |
| Remark |
doi:10.1016/j.jpcs.2015.01.015 Link |
Binder Jetting: A Novel Solid Oxide Fuel-Cell Fabrication Process and Evaluation
ID=295| Authors |
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| Source |
JOM
Volume: 67,
Issue: 3,
Pages: 660-667 Time of Publication: 2015 |
| Abstract | With an ever-growing concern to find a more efficient and less polluting means of producing electricity, fuel cells have constantly been of great interest. Fuel cells electrochemically convert chemical energy directly into electricity and heat without resorting to combustion/mechanical cycling. This article studies the solid oxide fuel cell (SOFC), which is a high-temperature (100°C to 1000°C) ceramic cell made from all solid-state components and can operate under a wide range of fuel sources such as hydrogen, methanol, gasoline, diesel, and gasified coal. Traditionally, SOFCs are fabricated using processes such as tape casting, calendaring, extrusion, and warm pressing for substrate support, followed by screen printing, slurry coating, spray techniques, vapor deposition, and sputter techniques, which have limited control in substrate microstructure. In this article, the feasibility of engineering the porosity and configuration of an SOFC via an additive manufacturing (AM) method known as binder jet printing was explored. The anode, cathode and oxygen ion-conducting electrolyte layers were fabricated through AM sequentially as a complete fuel cell unit. The cell performance was measured in two modes: (I) as an electrolytic oxygen pump and (II) as a galvanic electricity generator using hydrogen gas as the fuel. An analysis on influence of porosity was performed through SEM studies and permeability testing. An additional study on fuel cell material composition was conducted to verify the effects of binder jetting through SEM–EDS. Electrical discharge of the AM fabricated SOFC and nonlinearity of permeability tests show that, with additional work, the porosity of the cell can be modified for optimal performance at operating flow and temperature conditions. |
| Remark |
DOI 10.1007/s11837-015-1296-9 Link |
Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system
ID=294| Authors |
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| Source |
Journal of Membrane Science
Volume: 479,
Pages: 39–45 Time of Publication: 2015 |
| Abstract | Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes. |
| Keywords | Hydrogen separation; Dense ceramic membrane; Ceramic–ceramic composite; Lanthanum tungstate; Lanthanum chromite |
| Remark |
doi:10.1016/j.memsci.2015.01.027 Link |
Bi1−xNbxO1.5+x (x=0.0625, 0.12) fast ion conductors: Structures, stability and oxide ion migration pathways
ID=293| Authors |
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| Source |
Journal of Solid State Chemistry
Volume: 225,
Pages: 383–390 Time of Publication: 2015 |
| Abstract | A combined experimental and computational study of Bi1−xNbxO1.5+x (x=0.0625 and 0.12) has been carried out using laboratory X-ray, neutron and electron diffraction, impedance measurements and ab-initio molecular dynamics. We demonstrate that Bi0.9375Nb0.0625O1.5625, previously reported to adopt a cubic fluorite-type superstructure, can form two different polymorphs depending on the synthetic method: a metastable cubic phase is produced by quenching; while slower cooling yields a stable material with a tetragonal √2×√2×1 superstructure, which undergoes a reversible phase transition into the cubic form at ~680 °C on subsequent reheating. Neutron diffraction reveals that the tetragonal superstructure arises mainly from ordering in the oxygen sublattice, with Bi and Nb remaining disordered, although structured diffuse scattering observed in the electron diffraction patterns suggests a degree of short-range ordering. Both materials are oxide ion conductors. On thermal cycling, Bi0.88Nb0.12O1.62 exhibits a decrease in conductivity of approximately an order of magnitude due to partial transformation into the tetragonal phase, but still exhibits conductivity comparable to yttria-stabilised zirconia (YSZ). Ab-initio molecular dynamics simulations performed on Bi0.9375Nb0.0625O1.5625 show that oxide ion diffusion occurs by O2− jumps between edge- and corner-sharing OM4 groups (M=Bi, Nb) via tetrahedral □M4 and octahedral □M6 vacancies. |
| Keywords | Functional oxides; Fast ion conductors; Complex superstructures |
| Remark |
doi:10.1016/j.jssc.2015.01.006 Link |
Functional properties of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ proton conductors where X is an alkaline earth cation
ID=292| Authors |
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| Source |
Journal of the European Ceramic Society
Volume: 35,
Issue: 4,
Pages: 1239–1253 Time of Publication: 2015 |
| Abstract | Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. |
| Keywords | Proton-conducting ceramic materials; Hydrogen transport ceramic membranes; Rare earth ortho-niobates; Acceptor-doped lanthanum niobates |
| Remark |
doi:10.1016/j.jeurceramsoc.2014.11.009 Link |
Hydrogen permeation, water splitting and hydration kinetics in Nd5.4Mo0.3W0.7O12−δ
ID=291| Authors |
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| Source |
Journal of Membrane Science
Volume: 476,
Pages: 105–111 Time of Publication: 2015 |
| Abstract | To investigate transport properties of Mo-substituted Nd5.4Mo0.3W0.7O12−δ for hydrogen separation application, hydrogen fluxes of Nd5.4Mo0.3W0.7O12−δ have been measured in both dry and wet sweep gases. The fluxes in dry sweep gas show lower temperature dependence at high temperatures than at low temperatures. Comparing the hydrogen permeability among rare earth tungstates, it has been revealed that the larger the RE-site cation radius, the higher the hydrogen permeation. Water splitting effect for the wet sweep gas has been confirmed by mass spectrometry. Oxygen surface kinetics under oxidizing conditions has been studied by ToF-SIMS measurements, and is significantly faster under wet conditions than dry. Hydration kinetics has been studied by conductivity relaxation measurements under reducing conditions for the first time, showing a two-fold non-monotonic behavior. |
| Keywords | Hydrogen permeation; Hydration kinetics; Water splitting; Oxygen surface kinetics; Nd5.4Mo0.3W0.7O12−δ |
| Remark |
doi:10.1016/j.memsci.2014.11.013 Link |
Savitha Thayumanasundaram, Vijay Shankar Rangasamy, Niels De Greef, Jin Won Seo andJean-Pierre Locquet
ID=290| Author |
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| Source |
European Journal of Inorganic Chemistry
Volume: 2015,
Issue: 7,
Pages: 1290–1299 Time of Publication: 2014 |
| Abstract | Polymer blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were prepared with different molar ratios by a solvent-casting technique. The XRD patterns of the blends show that the degree of crystallinity of the PVA membranes decreases with the addition of PAA owing to the formation of interpenetrating polymer chains. The vibrational spectra of the blend membranes reveal the formation of strong hydrogen bonding between PVA and PAA. Dynamic mechanical analysis (DMA) reveals that the storage modulus of a 25 mol-% PAA sample is comparable to that of pure PVA and, therefore, confirms the mechanical stability of the blend membranes. Significant changes in the peak areas and chemical shifts of the PVA hydroxyl signal (δ = 4–5 ppm) in the 1H NMR spectra of the blend membranes confirm the strong hydrogen bonding between the OH groups of PVA and PAA. The ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) with 0.2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was added to the polymer blend to prepare flexible, nonvolatile hybrid polymer electrolytes for lithium-ion batteries. A maximum ionic conductivity of 1 mS cm–1 is observed at 90 °C for the membrane with 70 mol-% IL. |
| Keywords | Polymers;Ionic liquids;Hybrid membranes;Hydrogen bonds;Lithium batteries |
| Remark |
DOI: 10.1002/ejic.201402603 Link |
Pure and Mn-doped La4SrTi5O17 layered perovskite as potential solid oxide fuel cell material: Structure and anodic performance
ID=289| Authors |
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| Source |
Journal of Power Sources
Volume: 274,
Pages: 806–815 Time of Publication: 2015 |
| Abstract | Pure and 5% Mn doped layered perovskites La4SrTi5O17, members of the La4Srn-4(Ti,Mn)nO3n+2 series with n = 5, have been synthesized and investigated as anode materials for Solid Oxide Fuel Cells. The use of XRD, neutron and electron diffraction techniques allows clarifying some divergences concerning the structural characterization within the family, not only in air but also in anodic-like N2/H2(97/3) atmosphere. The electrical conductivity of both compounds is very low in air but those values increase by two orders of magnitude in diluted hydrogen. The study of catalytic properties for methane steam reforming as well as in-depth analysis of the SOFC anodic behaviour of both materials are described, for which a microstructure optimization of the electrode allows to demonstrate the potential interest of the lamellar materials upon the classical three-dimensional cubic-like LSTs. |
| Keywords | SOFC; Anode; Layered perovskite; Titanate; Methane steam reforming; Electrochemical impedance spectroscopy |
| Remark |
doi:10.1016/j.jpowsour.2014.10.131 Link |
Electrochemical performance and carbon deposition resistance of Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ anode materials for solid oxide fuel cells fed with syngas
ID=288| Authors |
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| Source |
Journal of Power Sources
Volume: 254,
Pages: 483–487 Time of Publication: 2015 |
| Abstract | Ce-doped La0.7Sr0.3Fe0.5Cr0.5O3-δ (Ce-LSFC) perovskite anode catalysts for solid oxide fuel cells are successfully synthesized by a modified combustion method for the first time. The pure perovskite structure without formation of CeO2 is obtained when the content of Ce ≤ 10%. Compared with La0.7Sr0.3Fe0.5Cr0.5O3-δ anode, Ce-LSFC anode not only shows much higher catalytic activity towards the oxidation of syngas with less carbon deposition, but also displays better regeneration from coking. The enhanced performance is attributed to the more available oxygen vacancies in lattice and better oxygen mobility after doping with Ce. |
| Keywords | SOFC; Ce-doped LSFC; Perovskite |
| Remark |
doi:10.1016/j.jpowsour.2014.10.090 Link |
Visualization of conduction pathways in a lanthanum lithium titanate superionic conductor synthesized by rapid cooling
ID=287| Authors |
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| Source |
Solid State Ionics
Volume: 268,
Issue: A,
Pages: 76-81 Time of Publication: 2014 |
| Abstract | Three-dimensional structure and conduction pathways of the lithium ions in 7Li0.4La0.53TiO3 quenched with liquid nitrogen were studied using reverse Monte Carlo modeling and the bond valence sum approach using neutron diffraction data. The lithium ions were primarily located in the region between the off-center positions of the A-sites and bottlenecks defined by four coordinating oxygen ions. The bottlenecks in the predicted conduction pathways of the lithium ions were classified into three types (I, II, and III) by their size. The type II bottlenecks were the most accessible to lithium-ion migration and more than 70% of the bottlenecks were type II. |
| Keywords | Lithium-ion conductor; Lanthanum lithium titanate; Local structure; Neutron diffraction; Reverse Monte Carlo modeling; Bond valence sum |
| Remark |
doi:10.1016/j.ssi.2014.09.030 Link |
Functional properties of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ proton conductors where X is an alkaline earth cation
ID=286| Authors |
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| Source |
Journal of the European Ceramic Society
Time of Publication: 2014-12
|
| Abstract | Lanthanum niobates with general formulas of La0.99X0.01Nb0.99Al0.01O4−δ and La0.99X0.01Nb0.99Ti0.01O4−δ (X = Mg, Ca, Sr or Ba) were synthesized via the conventional solid state reaction. Specimens with relative density above 96% were produced after sintering. Structural and phase composition studies revealed predominant monoclinic Fergusonite structure for the majority of samples. SEM and TEM studies elucidated the effect of the used dopant combinations on grain growth, micro-crack formation and secondary phase formation. Results from microstructural study were correlated to the grain interior and grain boundary conductivities for selected samples (La0.99Sr0.01Nb0.99Al0.01O4−δ and La0.99Sr0.01Nb0.99Ti0.01O4−δ). The majority of co-doped niobates exhibited appreciable protonic conductivity under humid atmospheres at intermediate temperatures. Sr- or Ca-doped compounds displayed the highest total conductivities with values for LSNA equal to 6 × 10−4 S/cm and 3 × 10−4 S/cm in wet air and in wet 4% H2–Ar (900 °C), respectively. Additionally, thermal expansion was studied to complete functional characterization of co-doped LaNbO4. |
| Keywords | Proton-conducting ceramic materials, Hydrogen transport ceramic membranes, Rare earth ortho-niobates, Acceptor-doped lanthanum niobates, ProGasMix |
| Remark | Link |
