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Synthesis and characterization of the micro-mesoporous anode materials and testing of the medium temperature solid oxide fuel cell single cells

Author Kadi Tamm
Source
Time of Publication: 2013
Remark Dissertation
Link

Polymorphism and properties of Bi2WO6 doped with pentavalent antimony

Authors E.P. Kharitonova, D.A. Belov, A.B. Gagor, A.P. Pietraszko, O.A. Alekseeva, V.I. Voronkova
Source
Journal of Alloys and Compounds
Time of Publication: 2014
Abstract Antimony-containing solid solutions isostructural with bismuth tungstate, Bi2WO6, have been prepared in air as polycrystalline samples by solid-state reactions and as single crystals by unseeded flux growth. The antimony in the solid solutions is in a pentavalent state and substitutes for tungsten in the structure of Bi2WO6. The Bi2W1–xSbxO6–y solid solutions have been shown to exist in the composition range 0 ⩽ x ⩽ 0.05. We have examined the effect of Sb5+ doping on the polymorphism and properties of Bi2WO6. In contrast to undoped Bi2WO6, antimony-substituted bismuth tungstate does not completely transform into its high-temperature, monoclinic phase at 960 °C and remains two-phase up to temperatures approaching its melting point. Antimony substitution for tungsten has a weak effect on the temperatures of the ferroelectric phase transitions. Heterovalent substitution of Sb5+ for W6+ is accompanied by the formation of extra oxygen vacancies and an increase in the electrical conductivity of the solid solutions by one to two orders of magnitude relative to undoped Bi2WO6.
Keywords Aurivillius phases; Bi2WO6; Ceramics; Phase transitions; Electrophysical properties; Differential scanning calorimetry
Remark Available online 3 January 2014
Link

Effect of Ni Concentration on Phase Stability, Microstructure and Electrical Properties of BaCe0.8Y0.2O3-δ - Ni Cermet SOFC Anode and its application in proton conducting ITSOFC

Authors Pooja Sawant, S. Varma, M.R. Gonal, B.N. Wani, Deep Prakash, S.R. Bharadwaj
Source
Electrochimica Acta
Time of Publication: 2013
Abstract In this work we have studied the effect of Ni concentration on phase stability, microstructure and electrical properties of BaCe0.8Y0.2O3-δ (BCY)-Ni cermet SOFC anode. It has been seen that Ni forms composite with BCY without forming any solid solution in both oxidized and reduced state. Also, microstructural analysis reveals the effect of Ni on porosity and triple phase boundaries necessary for electrochemical reactions during cell operation. Electrical conductivity values obtained from dc four probe technique in H2 atmosphere increase with an increase in Ni content. Composites with low vol% of Ni contents i.e. 19% (Ni19) and 26% (Ni26) show predominantly semiconductor-like behaviour whereas higher vol% viz. 35% (Ni35), 45% (Ni45) and 56% (Ni56) composites show electronic conductivity behaviour. This confirms that electronic conduction occurs through metallic Ni phase. Also, anode supported single cell for proton conducting SOFC has been fabricated using Ni35 composition and its current-potential characteristics measured at different temperatures.
Keywords Cermet; X-ray diffraction; Electrical conductivity; Four probe; Single Cell
Remark Available online 25 December 2013
Link

Cathode compatibility, operation, and stability of LaNbO4-based proton conducting fuel cells

Authors Anna Magrasó, Marie-Laure Fontaine, Rune Bredesen, Reidar Haugsrud, Truls Norby
Source
Solid State Ionics
Time of Publication: 2013
Abstract Cathodes compatible with Ca-doped LaNbO4 (LCNO) and the operation of a complete proton conducting fuel cell based on this electrolyte are presented. The best performing cathode was a 50 vol.% La0.8Sr0.2MnO3 (LSM)–50 vol.% LCNO composite, with an overall area specific resistance (ASR) of ~ 10 Ω cm2 at 800 °C in wet air. Pt and La0.8Sr0.2(Cr0.5Mn0.5)O3-based cathodes exhibit higher ASRs. The performance of a complete Ni–LCNO//LCNO//LSM–LCNO fuel cell shows a high open circuit voltage but with relatively low performance, in agreement with the modest proton conductivity of LaNbO4-based materials and cathode performances. The cell exhibits stable operation with CO2 containing atmosphere on the cathode side, confirming the chemical robustness of LaNbO4-based electrolytes.
Keywords Proton conducting fuel cells; Manufacturing; Impedance spectroscopy; LaNbO4; Characterization; Cathode performance
Remark Available online 22 December 2013;
Link

Determination of Oxygen Diffusion Coefficients in La1-xSrxFe1-yGayO3-δ Perovskites Using Oxygen Semi-Permeation and Conductivity Relaxation Methods

Authors P. M. Geffroy, Y. Hu, A. Vivet, T. Chartier and G. Dezanneau
Source
Journal of the Electrochemical Society
Volume: 161, Issue: 3, Pages: F153-F160
Time of Publication: 2014
Abstract This paper reports new evidence that oxygen surface exchange and bulk diffusion in a mixed conductor can be simultaneously determined via the oxygen semi-permeation method. Herein, we report the use of an original apparatus for oxygen activity measurements at both membrane surfaces to evaluate the oxygen surface exchange and bulk diffusion coefficients. Oxygen surface exchange and bulk diffusion in the La1-xSrxFe1-yGayO3-δ perovskite series are also determined and compared with the results from three different methods: isotopic exchange, conductivity relaxation, and oxygen semi-permeation. Although the thermodynamic conditions for these methods are not exactly the same, the values obtained for the oxygen surface exchange and bulk diffusion coefficients are in good agreement.
Remark Link

Entwicklung protonenleitender Werkstoffe und Membranen auf Basis von Lanthan-Wolframat für die Wasserstoffabtrennung aus Gasgemischen

Author J Seeger
Source
Book of its own
Time of Publication: 2013
Remark Link

Porous La 0.6 Sr 0.4 CoO 3-δ thin film cathodes for large area micro solid oxide fuel cell MEMS power generators

Authors I. Garbayo, V. Esposito, S. Sanna, A. Morata, D. Pla, L. Fonseca, N. Sabaté, A. Tarancón
Source
Journal of Power Sources
Time of Publication: 2013
Abstract Porous La0.6Sr0.4CoO3-δ thin films were fabricated by pulsed laser deposition for being used as a cathode for micro solid oxide fuel cell applications as MEMS power generators. Symmetrical La0.6Sr0.4CoO3-δ/yttria-stabilized zirconia/La0.6Sr0.4CoO3-δ free-standing membranes were fabricated using silicon as a substrate. A novel large-area membrane design based on grids of doped-silicon slabs. Thermo-mechanical stability of the tri-layer membranes was ensured in the intermediate range of temperatures up to 700şC. In-plane conductivity of ca. 300 S/cm was measured for the cathode within the whole range of application temperatures. Finally, area specific resistance values below 0.3 Ωˇcm2 were measured for the cathode/electrolyte bi-layer at 700şC in the exact final micro solid oxide fuel cell device configuration, thus presenting La0.6Sr0.4CoO3-δ as a good alternative for fabricating reliable micro solid oxide fuel cells for intermediate temperature applications.
Keywords Micro Solid Oxide Fuel Cell, thin film cathode, self-supported electrolyte
Remark DOI: 10.1016/j.jpowsour.2013.10.038

Nanocrystalline Sm0.5Sr0.5CoO3−δ synthesized using a chelating route for use in IT-SOFC cathodes: microstructure, surface chemistry and electrical conductivity

Authors Rares Scurtu, Simona Somacescu, Jose Maria Calderon-Moreno, Daniela Culita, Ion Bulimestru, Nelea Popa, Aurelian Gulea, Petre Osiceanu
Source
Journal of Solid State Chemistry
Time of Publication: 2013
Abstract Nanocrystalline Sm0.5Sr0.5CoO3−δ powders were synthesized by a chelating route using different polyfunctional HxAPC acids (APC=aminopolycarboxylate; x= 3, 4, 5). Different homologous aminopolycarboxylic acids, namely nitrilotriacetic (H3nta), ethylenediaminetetraacetic (H4edta), 1,2-cyclohexanediaminetetracetic (H4cdta) and diethylenetriaminepentaacetic (H5dtpa) acid, were used as chelating agents to combine Sm, Sr, Co elements into a perovskite structure. The effects of the chelating agents on the crystalline structure, porosity, surface chemistry and electrical properties were investigated. The electrical properties of the perovskite-type materials emphasized that their conductivities in the temperature range of interest (600–800 °C) depend on the nature of the precursors as well as on the presence of a residual Co oxide phase as shown by XRD and XPS analysis. The surface chemistry and the surface stoichiometries were determined by XPS revealing a complex chemical behavior of Sr that exhibits a peculiar „surface phase” and „bulk phase” chemistry within the detected volume (<10 nm).
Keywords Cathode; Perovkites; Electrical Conductivity; XPS; IT-SOFC
Remark Available online 5 November 2013
Link

Effects of temperature, triazole and hot-pressing on the performance of TiO2 photoanode in a solid-state photoelectrochemical cell

Authors Kingsley O. Iwu, Augustinas Galeckas, Spyros Diplas, Frode Seland, Andrej Yu. Kuznetsov,Truls Norby
Source
Electrochimica Acta
Time of Publication: 2013
Abstract The photocurrent of hydrogen generating solid-state photoelectrochemical cell utilising a polybenzimidazole proton-conducting membrane and gaseous anode reactants has been enhanced by operation at higher temperatures. With a bias of 0 V for example, photocurrent increased from 15 to 30 μA/cm2 on moving from 25 °C to 45 °C. The increase in photocurrent, which was limited by the dehydration of the cell, was shown to have contribution from improved electrode kinetics. Modification of TiO2 surface with triazole, a conjugated heterocyclic compound, led to significant increase in photocurrent - up to 4 fold increase at 0 V and 25 °C. This was attributed to improved separation of photogenerated charge carriers, as confirmed by correspondingly increased carrier lifetimes from 50 ns to 90 ns for triazole-modified TiO2. Assembly of the photoelectrochemical cell by hot-pressing induced a ̴ 0.3 eV red shift in optical absorption edge of TiO2, in agreement with a shift of its valence band maximum to higher binding energy.
Keywords Solid-state; photoelectrochemical; XPS; carrier lifetime; triazole
Remark Available online 28 October 2013
Link

Synthesis and Investigation of Porous Ni–Al Substrates for SolidOxide Fuel Cells

Authors A. A. Solov’ev, N. S. Sochugov , I. V. Ionov , A. I. Kirdyashkin , V. D. Kitler , A. S. Maznoi , Yu. M. Maksimov , and T. I. Sigfusson
Source
Materials of power engineering and radiationresistant materials
Time of Publication: 2013-10
Abstract Selfpropagating hightemperature synthesis (SHS) is applied for the production of porous supporting Ni–Al bases of solidoxide fuel cells. The effect of synthesis onditions and the composition of source powders on the phase composition, microstructure, gas permeability, corrosion resistance, and other proper ties of obtained Ni–Al samples is investigated. The possibility is shown for the formation of solidoxide fuel cells (SOFCs) on the surface of porous Ni–Al plates. The cells have the structure Ni–ZrO3:Y2O3 anode/ZrO3:Y2O3 electrolyte/La0.8Mn0.2SrO3 cathode and provide a specific power of 400 mW/cm2 at a temperature of 800°C.
Keywords selfpropagating hightemperature synthesis, Ni–Al, solidoxide fuel cells, ZrO3:Y2O3 electrolyte, magnetron sputtering.
Remark Link

Galliosilicate glasses for viscous sealants in solid oxide fuel cell stacks: Part III: Behavior in air and humidified hydrogen

Authors T. Jin, M.O. Naylor, J.E. Shelby, S.T. Misture
Source
International Journal of Hydrogen Energy
Time of Publication: 2013
Abstract Optimized boro-galliosilicate glasses were selected to evaluate their viscous sealing performance in both air and humidified hydrogen atmospheres. Selected low-alkali and alkali-free glasses show excellent performance, with viscous behavior maintained for more than 1000 h in wet hydrogen. Candidate sealants were thermally treated at 850 and 750 °C for up to 1000 h in contact with alumina coated 441 stainless steel (Al-SS) and 8 mol% yttria-stabilized zirconia (8YSZ). Each sealant crystallizes appreciably by 1000 h, and their coefficients of thermal expansion range from 10.2 to 11.7 × 10−6 K−1, 100–400 °C. The remnant amorphous phases in most of the partially crystallized sealants show softening points near or below the target operating temperatures, thus enabling viscous sealing. Humidified hydrogen in general increases the rate of crystallization but does not change the crystalline phases formed or interactions with 8YSZ. For the low-alkali GaBA series, wet H2 enhances the interfacial interaction between potassium in the glass phase and the protective alumina coating on the stainless steel.
Keywords Solid oxide fuel cell; Sealing glass; Galliosilicate; Thermal expansion; Hydrogen
Remark Available online 25 October 2013
Link

Porous La0.6Sr0.4CoO3-δ thin film cathodes for large area micro solid oxide fuel cell MEMS power generators

Authors I. Garbayo, V. Esposito, S. Sanna, A. Morata, D. Pla, L. Fonseca, N. Sabaté, A. Tarancón
Source
Journal of Power Sources
Time of Publication: 2013
Abstract Porous La0.6Sr0.4CoO3-δ thin films were fabricated by pulsed laser deposition for being used as a cathode for micro solid oxide fuel cell applications as MEMS power generators. Symmetrical La0.6Sr0.4CoO3-δ/yttria-stabilized zirconia/La0.6Sr0.4CoO3-δ free-standing membranes were fabricated using silicon as a substrate. A novel large-area membrane design based on grids of doped-silicon slabs. Thermo-mechanical stability of the tri-layer membranes was ensured in the intermediate range of temperatures up to 700°C. In-plane conductivity of ca. 300 S/cm was measured for the cathode within the whole range of application temperatures. Finally, area specific resistance values below 0.3 Ωˇcm2 were measured for the cathode/electrolyte bi-layer at 700°C in the exact final micro solid oxide fuel cell device configuration, thus presenting La0.6Sr0.4CoO3-δ as a good alternative for fabricating reliable micro solid oxide fuel cells for intermediate temperature applications.
Remark Available online 18 October 2013
Link

Nano Coated Interconnects for SOFC (NaCoSOFC)

Authors Jan Froitzheim, Anna Magraso, Tobias Holt, Mats W Lundberg, Hannes Falk Windisch, Robert Berger, Rakshith Nugehalli Sachitanand, Jörgen Westlinder, Jan-Erik Svensson and Reidar Haugsrud
Source
ECS Transactions
Volume: 57, Issue: 1, Pages: 2187-2193
Time of Publication: 2013
Abstract The NaCoSOFC project is focused on the development of nano coatings for SOFC interconnects. The project is sponsored by the Nordic Top Level Research Initiative and has four project partners: Sandvik Materials Technology which is producing coated interconnects, Chalmers University of Technology and the University of Oslo that characterize samples with respect to e.g. corrosion, Cr evaporation and ASR as well as Topsoe Fuel Cell that is testing the developed interconnects in its stacks. The developed coatings are based on a combination of Co with RE elements and exhibit high corrosion resistance, 10 fold decrease in Cr evaporation and ASR values that are approximately 50% of the uncoated material.
Remark Link

Nano Coated Interconnects for SOFC (NaCoSOFC)

Source
Time of Publication: 2013

Application of FIB-TOF-SIMS and FIB-SEM-EDX Methods for the Analysis of Element Mobility in Solid Oxide Fuel Cells

Authors Rait Kanarbik, Priit Möller, Indrek Kivi and Enn Lust
Source
ECS Transactions
Volume: 57, Issue: 1, Pages: 581-587
Time of Publication: 2013
Abstract The solid oxide fuel cell single cells with porous Pr0.6Sr0.4CoO3-δ and La0.6Sr0.4CoO3-δ (PSCO, LSCO respectively) cathodes on compact Ce0.9Gd0.1O2-δ|Zr0.85Y0.15O2-δ or Ce0.9Gd0.1O2-δ|Zr0.85Sc0.15O2-δ bi-layered electrolytes deposited onto Ni-Zr0.85Y0.15O2-δ (Ni-ZYO) or Ni- Ce0.9Gd0.1O2-δ (Ni-CGO) supporting anode were prepared for ion (element) mobility studies. Focused ion beam - time of flight - secondary ion mass spectrometry (FIB-TOF-SIMS) method in addition to FIB-SEM, SEM-EDX and XRD methods has been used for analysis of mass-transfer (interlayer diffusion) of cathode electrode elements, demonstrating that during PSCO and LSCO sintering at 1100°C on to CGO|ZYO or CGO|ZScO bilayered electrolyte, noticeable mass-transfer of Sr2+ cations through the partially microporous CGO has been verified using FIB-TOF-SIMS and SEM-EDX methods. The single cells have been additionally studied using cyclic voltammetry, electrochemical impedance and chronoamperometry methods and high power densities have been demonstrated.
Remark Link

Chromium Poisoning of La2NiO4+δ Cathodes

Authors Soo-Na Lee, Alan Atkinson and John A. Kilner
Source
ECS Transactions
Volume: 57, Issue: 1, Pages: 605-613
Time of Publication: 2013
Abstract It has been reported that Sr-containing materials (such as LSCF) are susceptible to Cr-poisoning by the formation of SrCrO4 and therefore there is interest in Sr-free cathodes such as La2NiO4+δ (LNO). In this study, La2NiO4+δ electrodes were deposited symmetrically onto Ce0.9Gd0.1O1.95 electrolytes by screen printing. The LNO electrodes were solution impregnated with targeted amounts of chromium and then characterised by impedance spectroscopy (520- 800°C). XRD of LNO/Cr2O3 powder mixtures annealed at 900°C showed that there is a reaction between them. Nevertheless, the impedance results indicate that LNO is less prone to chromium deactivation than LSCF.
Remark Link

Effect of Steam-to-Carbon Ratio on Degradation of Ni-YSZ Anode Supported Cells

Authors Hossein Madi, Stefan Diethelm, Jan Van herle and Nathalie Petigny
Source
ECS Transaction
Volume: 57, Issue: 1, Pages: 1517-1525
Time of Publication: 2013
Abstract Internal steam reforming (IR) of methane was investigated on Ni-YSZ anode supported cells, looking in particular at the effect of the steam to carbon (S/C) ratio on the degradation rate. The cells were fed with different H2O/CH4 mixtures during 100 hours sequences, alternating with sequences of dry H2 feeding. V-I characterization was performed before and after each sequence, and EIS measurements were performed regularly. A marked degradation was observed during the IR sequences while it was negligible under dry H2 feed. The observed degradation, attributed to carbon deposition on the anode active sites, was partially reversible for S/C >1.5, whereas it became irreversible at lower S/C.
Remark Link

Synthesis, properties and phase transitions of pyrochlore- and fluorite-like Ln2RMO7 (Ln=Sm, Ho; R=Lu, Sc; M= Nb, Ta)

Authors A.V. Shlyakhtina, D.A. Belov, K.S. Pigalskiy, A.N. Shchegolikhin, I.V. Kolbanev, O.K. Karyagina
Source
Materials Research Bulletin
Time of Publication: 2013
Abstract We have studied the new compounds with fluorite-like (Ho2RNbO7 (R = Lu, Sc)) and pyrochlore-like (Sm2ScTaO7) structure as potential oxide ion conductors. The phase formation process (from 1200 to 1600 °C) and physical properties (electrical, thermo mechanical, and magnetic) for these compounds were investigated. Among the niobate materials the highest bulk conductivity is offered by the fluorite-like Ho2ScNbO7 synthesized at 1600 °C: 3.8 × 10−5 S/cm at 750 °C, whereas in Sm system the highest bulk conductivity, 7.3 × 10−6 S/cm at 750 °C, is offered by the pyrochlore Sm2ScTaO7 synthesized at 1400 °C. In Sm2ScTaO7 pyrochlore we have observed the first-order phase transformation at ∼650–700 °C is related to rearrangement process in the oxygen sublattice of the pyrochlore structure containing B-site cations in different valence state and actually is absent in the defect fluorites. The two holmium niobates show Curie–Weiss paramagnetic behavior, with the prevalence of antiferromagnetic coupling. The magnetic susceptibility of Sm2ScTaO7 is a weak function of temperature, corresponding to Van Vleck paramagnetism.
Keywords Pyrochlore; Fluorite; Phase transition; Ionic conductivity; Thermo mechanical analysis; Dielectric permittivity; Loss tangent; Magnetic susceptibility
Remark Available online 11 October 2013
Link

Proton Conductivity in Solid Solution 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4) and Ca(1−x)LaxW(1−y)TayO4

Authors Camilla K. Vigen, Reidar Haugsrud
Source
Journal of the American Ceramic Society
Time of Publication: 2013
Abstract The conductivity of nominal CaWO4, CaW0.99Ta0.01O4–δ, 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4–δ), and Ca0.9La0.1WO4+δ has been studied by means of a.c. impedance measurements. Proton conductivity was observed for CaW0.99Ta0.01O4–δ, which displayed exothermic hydration with enthalpy and entropy of –82 kJ/mol and –120 J/molK, respectively. The proton mobility in CaW0.99Ta0.01O4–δ was low, with enthalpy and preexponential factor of mobility of 82 kJ/mol and 0.7 cm2K/Vs. The high enthalpy of mobility is interpreted to reflect association between the acceptor dopant and protonic defects, whereas the low preexponential factor of mobility may reflect a lower proton concentration than assumed. Rietveld refinement indicated low solubilities of La on Ca-site and Ta on W-site. Proton conductivity was also observed in undoped CaWO4, however, not in Ca0.9La0.1WO4+δ. The conductivity of 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4–δ) behaved much like that of undoped LaNbO4, likely due to a very low acceptor dopant concentration.
Remark Article first published online: 1 OCT 2013. DOI: 10.1111/jace.12587
Link

The Investigation of E-beam Deposited Titanium Dioxide and Calcium Titanate Thin Films

Authors Kristina BOČKUTĖ, Giedrius LAUKAITIS, Darius VIRBUKAS, Darius MILČIUS
Source
MATERIALS SCIENCE (MED´IAGOTYRA)
Volume: 19, Issue: 3, Pages: 245-249
Time of Publication: 2013
Abstract Thin titanium dioxide and calcium titanate films were deposited using electron beam evaporation technique. The substrate temperature during the deposition was changed from room temperature to 600 °C to test its influence on TiO2 film formation and optical properties. The properties of CaTiO3 were investigated also. For the evaluation of the structural properties the formed thin ceramic films were studied by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of thin TiO2 ceramics were investigated using optical spectroscope and the experimental data were collected in the ultraviolet-visible and near-infrared ranges with a step width of 1 nm. Electrical properties were investigated by impedance spectroscopy.It was found that substrate temperature has influence on the formed thin films density. The density increased when the substrate temperature increased. Substrate temperature had influence on the crystallographic, structural and optical properties also.
Keywords electron beam evaporation; titanium oxide; calcium titanate; optical properties
Remark DOI: http://dx.doi.org/10.5755/j01.ms.19.3.1805
Link

Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6–xWO12–y

Authors Janka Seeger, Mariya E. Ivanova, Wilhelm A. Meulenberg, Doris Sebold, Detlev Stöver, Tobias Scherb, Gerhard Schumacher, Sonia Escolástico, Cecilia Solís, and José M. Serra
Source
Inorganic Chemistry
Publisher: ACS Publications, Time of Publication: 2013
Abstract Mixed proton–electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic–electronic conductivity. Lanthanum tungstate La6–xWO12–y (with y = 1.5x + δ and x = 0.5–0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6–xWO12–y and for all substituted La6–xWO12–y compounds was measured in the temperature range of 400–900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM.
Keywords ProGasMix
Remark lanthanum tungstate
La6–xWO12–y
Link

Synthesis and Characterization of Nonsubstituted and Substituted Proton-Conducting La6–xWO12–y

Authors Janka Seeger, Mariya E. Ivanova, Wilhelm A. Meulenberg, Doris Sebold, Detlev Stöver, Tobias Scherb, Gerhard Schumacher, Sonia Escolástico, Cecilia Solís, and José M. Serra
Source
Inorg. Chem.
Time of Publication: 2013
Abstract Mixed proton–electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic–electronic conductivity. Lanthanum tungstate La6–xWO12–y (with y = 1.5x + δ and x = 0.5–0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La6–xWO12–y and for all substituted La6–xWO12–y compounds was measured in the temperature range of 400–900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM.
Remark DOI: 10.1021/ic401104m; Publication Date (Web): September 3, 2013
Link

Defects and Transport Properties in TiNb2O7

Authors Wen Xing, Liv-Elisif Kalland, Zuoan Li, Reidar Haugsrud
Source
Journal of the American Ceramic Society
Time of Publication: 2013
Abstract The electrical conductivity of TiNb2O7 was characterized as a function of temperature, inline image and inline image. The total conductivity was independent of inline image in the low oxygen partial pressure regime, while a dependency of inline image was observed at higher oxygen partial pressures. The conductivity increased with increasing inline image under oxidizing conditions below 700°C. Mixed electronic and protonic conduction was indicated by H/D isotope exchange and transport number measurements. A defect model based on interstitial type of hydration was established and fitted to the conductivity data allowing for determination of physicochemical parameters of hydration and electron migration.
Remark Article first published online. DOI: 10.1111/jace.12558
Link

CO2 removal at high temperature from multi-component gas stream using porous ceramic membranes infiltrated with molten carbonates

Authors M.-L. Fontaine, T.A. Peters, M.T.P. McCann, I. Kumakiri, R. Bredesen
Source
Energy Procedia
Volume: 37, Pages: 941–951
Time of Publication: 2013-09
Abstract This work reports on the investigation of CO2 selective membranes for pre-combustion and post- combustion processes, in which CO2 is extracted from multi-component gas streams at intermediate temperature (400 – 600 °C). The dual-phase membranes developed in this work are designed as a porous oxide ion conducting ceramic matrix, which is infiltrated with a molten carbonate phase. Both ex-situ and in-situ characterization methods were used to study disk shaped and tubular membranes. The gas transport properties of disk-shaped membranes were further investigated under various operating conditions relevant for both post-combustion and pre-combustion applications.
Keywords Membrane; CO2 separation; molten carbonate; dual-phase membrane; ionic conductor
Remark Link

Preparation and electrical properties of Li–Si–Al–O–N ceramics

Authors Eiichirou Narimatsu∗, Takashi Takeda, Toshiyuki Nishimura, Naoto Hirosaki
Source
Journal of Asian Ceramic Societies
Volume: 1, Pages: 191–196
Time of Publication: 2013
Abstract Ceramic samples were synthesized by hot pressing mixtures of Li3N, Si3N4, AlN, Al2O3, and Li2CO3withnominal compositions of LiSi2−xAlxOxN3−x(x = 0–0.75) at 20 MPa and 1773–2073 K in a N2atmosphere of0.10 MPa. The samples prepared with nominal compositions, x = 0.25 and 0.50, showed electronic con-ductivities of 2.2 and 4.2 S m−1at room temperature with activation energies of 3.8 and 3.9 kJ mol−1,respectively. Electronic conductive parts were detected in the sample of x = 0.50 by conductive atomicforce microscopy (AFM). In this sample, a glassy thin layer, having a Si/Al atomic ratio of 3.8, was observedbetween the grains of LiSi2−xAlxOxN3−xsolid solution by high-resolution transmission electron microscopy(HRTEM). It was expected that the glassy phase of grain boundaries is an electronic conductive pathwaybesides the conductive parts observed by AFM.
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