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-Versatile apparatus for thermoelectric characterization of oxides at high temperatures
ID=285| Authors |
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Review of Scientific Instruments
Volume: 85,
Pages: 103906 Time of Publication: 2014 |
| Abstract | An apparatus for measuring the Seebeck coefficient and electrical conductivity is presented and characterized. The device can be used in a wide temperature range from room temperature to 1050 °C and in all common atmospheres, including oxidizing, reducing, humid, and inert. The apparatus is suitable for samples with different geometries (disk-, bar-shaped), allowing a complete thermoelectric characterization (including thermal conductivity) on a single sample. The Seebeck coefficient α can be measured in both sample directions (in-plane and cross-plane) simultaneously. Electrical conductivity is measured via the van der Pauw method. Perovskite-type CaMnO3 and the misfit cobalt oxide (Ca2CoO3) q (CoO2) are studied to demonstrate the temperature range and to investigate the variation of the electrical properties as a function of the measurement atmosphere. |
| Remark |
http://dx.doi.org/10.1063/1.4897489 Link |
Electrochemical behavior of the pyrochlore- and fluorite-like solid solutions in the Pr2O3–ZrO2 system. Part I
ID=284| Authors |
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Solid State Ionics
Time of Publication: 2014
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| Abstract | We have studied the structure, microstructure, and electrochemical properties in air of (Pr2 − xZrx)Zr2O7 + x/2 (x = 0.15, 0.32, 0.78), Pr2Zr2O7, and Pr2(Zr2 − xPrx)O7 − x/2 (x = 0.1, 0.4, 1) materials. The solid solutions were prepared through coprecipitation followed by heat treatment of the precursors at 1550 °C for 4 h. According to XRD data, the extent of the pyrochlore-like Pr2 ± xZr2 ± xO7 ± x/2 solid solutions at 1550 °C is ~ 6 mol.%, which is considerably smaller than that in the NdZrO and SmZrO systems at this temperature. Among the pyrochlores, the highest bulk conductivity was offered by the (Pr2 − xZrx)Zr2O7 + x/2 (x = 0.15): 7.15 × 10− 3 S/cm at 800 °C (Ea = 0.66 eV). The pyrochlore-like Pr2(Zr2 − xPrx)O7 − x/2 (x = 0.1) had lower conductivity (3.97 × 10− 3 S/cm at 800 °C). The highest bulk conductivity among the materials studied was found in the Pr2O3-rich fluorite-like Pr2(Zr2 − xPrx)O7 − x/2 with x = 1: ~ 0.217 S/cm at 800 °C (Ea = 0.0.31 eV). The temperature-dependent conductivity of the Pr2O3-rich fluorite-like solid solutions Pr2(Zr2 − xPrx)O7 − x/2 with x = 0.4 and 1 had a break at 560 °C, suggesting a change in the mechanism of ion transport at this temperature. |
| Remark |
DOI: 10.1016/j.ssi.2014.09.035 Link |
Thermal Depolarization in the High-Temperature Ternary Piezoelectric System xPbTiO3–yBiScO3–zBi(Ni1/2Ti1/2)O3
ID=283| Authors |
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Journal of the American Ceramic Society
Time of Publication: 2014
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| Abstract | In the high-temperature ternary perovskite piezoelectric system xPbTiO3–yBiScO3–zBi(Ni1/2,Ti1/2)O3 (PT–BS–BNiT), the addition of bismuth to the A site and nickel to the B site leads to compositions that exhibit diffuse relaxor-like behavior. For these, depolarization temperature, not Curie point, is the critical value of temperature. Depolarization temperature (Td) is defined as the temperature at which the steepest loss in polarization occurs. This temperature is observed in poled materials through two different methods: loss tangent measurements and in situ d33. Across the ternary system, multiple dielectric anomalies occurred which was observed in dielectric tests where the dielectric peak broadens and becomes frequency dependent as BNiT content increased. For different compositions, the value of Td ranged between 275°C–375°C. Values for the piezoelectric coefficient increased with temperature up to d33 = 1000 pC/N during in situ d33. High temperature (up to 190°C) and high field (up to 40 kV/cm) were also applied to test ferroelectric properties in these regimes. |
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DOI: 10.1111/jace.13268 Link |
Characterization and Modeling of La 1 − x Sr x CoO 3 − δ Solid Oxide Fuel Cell Cathodes Using Nonlinear Electrochemical Impedance Techniques
ID=282| Author |
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Time of Publication: 2014
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Dissertation Link |
Structural and electrical study of samarium doped cerium oxide thin films prepared by e-beam evaporation
ID=281| Authors |
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Solid State Ionics
Time of Publication: 2014
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| Abstract | Samarium doped cerium oxide (Sm0.15Ce0.85O1.925, SDC) thin films were grown on the Alloy 600 (Fe–Ni–Cr) and optical quartz (SiO2) substrates using e-beam deposition technique. Formed SDC thin films were characterized using different X-ray diffraction (XRD) techniques, scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and impedance spectroscopy. The deposition rate of formed SDC thin films was changed from 2 Å/s to 16 Å/s. XRD analysis shows that all thin films have a cubic (FCC) structure and repeat the crystallographic orientation of the initial powders evaporated with different deposition rate and on different substrates. The crystallite size increases from 7.7 nm to 10.3 nm and from 7.2 nm to 9.2 nm on Alloy 600 substrate and optical quartz (SiO2) substrate respectively as the thin film deposition rate increases. SEM images indicate a dense and homogeneous structure of all formed SDC thin films. The ionic conductivity depends on thin films density and blocking factor. The best ionic conductivity (σg = 1.34 Sm− 1 and σgb = 2.29 Sm −1 at 873 K temperature, activation energy ΔEg = 0.91 eV and ΔEgb = 0.99 eV) was achieved for SDC thin films formed at 4 Å/s deposition rate. It was found that the highest density (5.25 g/cm3) and the lowest relaxation time in grain (τg = 9.83 × 10− 7 s), and the lowest blocking factor (0.39) is in SDC thin films formed at 4 Å/s deposition rate. The deposition rate influences the stoichiometry of the formed SDC thin ceramic films. |
| Keywords | Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity |
| Remark |
DOI: 10.1016/j.ssi.2014.09.036 Link |
Electrical conductivity and TG-DSC study of hydration of Sc-doped CaSnO3 and CaZrO3
ID=280| Authors |
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Solid State Ionics
Volume: 267,
Pages: 61–67 Time of Publication: 2014 |
| Abstract | Correlations linking hydration thermodynamics to materials parameters can be of vital importance for further development of proton conducting oxides. However, the currently proposed correlations are troubled by scattering limiting their predictive power. As such, the present contribution has investigated Sc-doped CaSnO3 and CaZrO3 in an attempt to further elucidate the trends in the thermodynamics of hydration for perovskites. Conductivity and impedance spectroscopy on 5 and 10% Sc-doped CaSnO3 demonstrated that it is primarily an oxygen ion conductor with a small protonic contribution at lower temperatures (below 500 °C) under wet conditions. Simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC), TG-DSC, was applied to measure the standard molar hydration enthalpy of CaSn1−xScxO3−δ and CaZr1−xScxO3−δ (x = 0.05, 0.10, 0.15 and 0.20) as a function of the Sc concentration. The hydration enthalpy becomes increasingly negative with increasing Sc substitution, which is discussed on the basis of changes in electronegativity, basicity and tolerance factor. |
| Keywords | Defects; Protons; Hydration; Thermodynamics; Perovskites |
| Remark |
DOI: 10.1016/j.ssi.2014.09.006 Link |
Synthesis, crystal structure and properties of alluaudite-like triple molybdate Na25Cs8Fe5(MoO4)24
ID=279| Authors |
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Journal of Solid State Chemistry
Volume: 220,
Pages: 217–220 Time of Publication: 2014 |
| Abstract | A new triple molybdate Na25Cs8Fe5(MoO4)24 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na25Cs8Fe5(MoO4)24 were obtained and its structure was solved (the space group P View the MathML source1¯, a=12.5814(5), b=13.8989(5), c=28.4386(9) Å, α=90.108(2), β=90.064(2), γ=90.020(2)°, V=4973.0(3) Å3, Z=2, R=0.0440). Characteristic features of the structure are polyhedral layers composed of pairs of edge-shared FeO6 and (Fe, Na)O6 octahedra, which are connected by bridging МоО4 tetrahedra. The layers share common vertices with bridging МоО4 tetrahedra to form an open 3D framework with the cavities occupied by the Cs+ and Na+ cations. The compound undergoes first-order phase transformation at 642 K and above this phase transition, electrical conductivity reaches 10−3–10−2 S cm−1. Thus, Na25Cs8Fe5(MoO4)24 may be considered as a promising compound for developing new materials with high ionic conductivity. |
| Keywords | Triple molybdate; Sodium; Synthesis; Crystal structure; Phase transition; Ionic conductivity |
| Remark |
DOI: 10.1016/j.jssc.2014.09.004 Link |
Hydrogen permeability of SrCe0.7Zr0.25Ln0.05O3−δ membranes (Ln=Tm and Yb)
ID=278| Authors |
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Journal of Membrane Science
Volume: 473,
Pages: 327–332 Time of Publication: 2015 |
| Abstract | Zr substituted acceptor doped SrCeO3 materials were synthesized by citric acid route and characterized by XRD and SEM. The hydrogen flux of the materials was measured as a function of temperature and hydrogen partial pressure on the feed side. The hydrogen permeability for SrCe0.7Zr0.25Tm0.05O3−δ and SrCe0.7Zr0.25Yb0.05O3−δ is similar under our measurement window and shows the same hydrogen partial pressure dependency. Under short circuit condition, the hydrogen permeability increased significantly by more than one order of magnitude indicating that the hydrogen transport is limited by electronic conduction under open circuit conditions. The observed data were discussed by applying defect chemistry and the conventional ambipolar transport theory. After the hydrogen permeation measurements, the indication of kinetic cation de-mixing was found by XRD analysis. |
| Keywords | Co-substitution of B site; Hydrogen flux; Permeability; Acceptor doping; SrCeO3 |
| Remark |
DOI: 10.1016/j.memsci.2014.09.027 Link |
Superior electrochemical performance and oxygen reduction kinetics of layered perovskite PrBaxCo2O5+δ (x = 0.90–1.0) oxides as cathode materials for intermediate-temperature solid oxide fuel cells
ID=277| Authors |
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| Source |
International Journal of Hydrogen Energy
Time of Publication: 2014
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| Abstract | The layered perovskite PrBaxCo2O5+δ (PBxCO, x = 0.90–1.0) oxides have been synthesized by a solid-state reaction technique, and evaluated as the potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Room temperature X-ray diffraction patterns show the orthorhombic structures which double the lattice parameters from the perovskite cell parameter as a ≈ ap, b ≈ ap and c ≈ 2ap (ap is the cell parameter of the primitive perovskite) in the Pmmm space group. There is a good chemical compatibility between the PBxCO cathode and the Ce0.9Gd0.1O1.95 (CGO) electrolyte at 1000 °C. The electrical conductivity and thermal expansion coefficient of PBxCO are improved due to the increased amount of electronic holes originated from the Ba-deficiency. The results demonstrate the high electrochemical performance of PBxCO cathodes, as evidenced by the super low polarization resistances (Rp) over the intermediate temperature range. The lowest Rp value, 0.042 Ω cm2, and the cathodic overpotential, −15 mV at a current density of −25 mA cm−2, are obtained in the PrBa0.94Co2O5+δ cathode at 600 °C in air, which thus allow to be used as a highly promising cathode for IT-SOFCs. A CGO electrolyte fuel cell with the PrBa0.94Co2O5+δ cathode presents the attractive peak power density of ∼1.0 W cm−2 at 700 °C. Furthermore, the oxygen reduction kinetics of the PrBa0.94Co2O5+δ cathode is also studied, and the rate-limiting steps for oxygen reduction reaction are determined at different temperatures. |
| Remark |
DOI: 10.1016/j.ijhydene.2014.09.041 Link |
Organic–Inorganic Hybrid Membranes Based on Sulfonated Poly(ether ether ketone) and Tetrabutylphosphonium Bromide Ionic Liquid for PEM Fuel Cell Applications
ID=276| Authors |
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European Journal of Inorganic Chemistry
Time of Publication: 2014
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| Abstract | Ionic liquids (ILs), with their inherent ionic conductivity and negligible vapor pressure, can be exploited in proton exchange membrane (PEM) fuel cells for which thermal management is a major problem and the cell operation temperature is limited by the boiling point of water. In this work, sulfonated poly(ether ether ketone) (SPEEK) membranes were modified by the incorporation of tetrabutylphosphonium bromide ([P4 4 4 4]Br) by solvent-casting. Electrochemical impedance spectroscopy (EIS) was used to study the electrical properties of the modified membranes. Simultaneous TGA and FTIR studies were used to evaluate the thermal stability and chemical structure of the modified membranes, respectively. 1H NMR spectroscopy was applied to probe the changes in the chemical environment due to the interaction between the ionic liquid and the polymer. Mechanical properties were studied by dynamic mechanical analysis. The temperature-dependent behavior of the viscosity of the [P4 4 4 4]Br ionic liquid was observed to obey the Vogel–Fulcher–Tammann (VFT) equation, and was correlated to the ion-conducting properties of the IL-doped SPEEK membranes. |
| Remark |
DOI: 10.1002/ejic.201402558 Link |
Crystal Structure and electrical properties of complex perovskite solid solutions based on (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3
ID=275| Authors |
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Journal of Electroceramics
Time of Publication: 2014
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| Abstract | Ceramics based on the perovskite solid solution (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3 were prepared using conventional solid state synthesis. The crystal structure, electrical, and optical properties were examined. According to diffraction data, a single perovskite phase could be identified up to the composition x = 0.09. As the Bi (Zn0.5Ti0.5) O3 content increased the crystal structure transitioned from orthorhombic to pseudocubic symmetry. Furthermore, dielectric data showed that the dielectric maximum shifted to lower temperatures with the addition of Bi (Zn0.5Ti0.5) O3. Polarization hysteresis data revealed a slim linear loop across the whole range of solid solutions. Optical data also showed a decrease in the optical band gap from 3.4 eV for pure NaNbO3 to 2.9 eV for the x = 0.09 composition. Using impedance spectroscopy, an electrically inhomogeneous microstructure was observed for compositions with increased Bi (Zn0.5Ti0.5) O3 content. Finally, the substitution of Ta on the B-site was shown to shift the dielectric maximum to temperatures as low as 100 K. |
| Remark |
DOI 10.1007/s10832-014-9953-x Link |
A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3
ID=274| Authors |
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Nature Materials
Volume: 13,
Pages: 31-35 Time of Publication: 2014 |
| Abstract | Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors1, 2, 3, 4, 5, 6, 7, 8, 9. Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material; however, it is often reported to possess high leakage conductivity that is problematic for its piezo- and ferroelectric applications10, 11, 12, 13, 14, 15. Here we report this high leakage to be oxide ion conduction due to Bi-deficiency and oxygen vacancies induced during materials processing. Mg-doping on the Ti-site increases the ionic conductivity to ~0.01 S cm−1 at 600 °C, improves the electrolyte stability in reducing atmospheres and lowers the sintering temperature. This study not only demonstrates how to adjust the nominal NBT composition for dielectric-based applications, but also, more importantly, gives NBT-based materials an unexpected role as a completely new family of oxide ion conductors with potential applications in intermediate-temperature SOFCs and opens up a new direction to design oxide ion conductors in perovskite oxides. |
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doi:10.1038/nmat3782 Link |
Thermoelectric Properties of A-site Deficient Lanthanum Substituted Strontium Titanate
ID=273| Author |
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Time of Publication: 2014
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| Remark | Link |
Grain Size Dependent Comparison of ZnO and ZnGa2O4 Semiconductors by Impedance Spectrometry
ID=272| Authors |
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Electrochimica Acta
Time of Publication: 2014
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| Abstract | We investigated the electrical properties of ZnGa2O4 via AC (alternating current) Impedance Spectroscopy method comparing with ZnO reference material. Experimentally, AC electrical conductivity of ZnO and ZnGa2O4 were found to be a function of temperature and grain size; i.e., the increase in grain size of the ZnO led a decrease in room temperature conductivity from 1.35 × 10−7 S cm−1 to 9.9 × 10−8 S cm−1. The temperature dependent resistivity variation of ZnGa2O4 and ZnO were similar to each other with varied responding temperature. Likewise, the conductivity for ZnGa2O4 decrease from 2.2 × 10−8 S cm−1 to 3.8 × 10−9 S cm−1 upon an increase in grain size from ∼0.5 μm to 100 μm, accordingly. In addition, a rise in temperature caused an increase in conductivity and led to a corresponding shift in the relaxation time towards the lower values. The semicircles in Nyquist plots disappeared at temperature above 250 °C and 700 °C for ZnO and ZnGa2O4, respectively. The AC measurements were also correlated with the size dependent activation energies (171 meV for 0.5 μm ZnO and 1200 meV for 0.5 μm ZnGa2O4). |
| Keywords | Activation energy; Nyquist plots; AC Impedance spectrometry; Oxide semiconductors |
| Remark |
DOI: 10.1016/j.electacta.2014.08.084 Link |
Effect of thermobaric treatment on the structure and properties of CaCu3Ti4O12
ID=271| Authors |
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Bulletin of the Russian Academy of Sciences: Physics
Volume: 78,
Issue: 8,
Pages: 719-722 Time of Publication: 2014 |
| Abstract | CaCu3Ti4O12 is prepared by means of solid-state sintering. The effect of thermobaric treatment (P = 8.0 GPa and T = 1100°C) and partial replacement of titanium by vanadium on the microstructure and dielectric properties of CaCu3Ti4O12 are investigated. |
| Remark | Link |
Conductivity and oxygen reduction activity changes in lanthanum strontium manganite upon low-level chromium substitution
ID=270| Authors |
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Solid State Ionics
Volume: 266,
Pages: 19-24 Time of Publication: 2014 |
| Abstract | On the timescale of solid oxide fuel cell (SOFC) system lifetime requirements, the thermodynamically predicted low-level substitution of chromium on the B-site of (La,Sr)MnO3 could be a source of cathode degradation underlying more overt and well-known chromium poisoning mechanisms. To study this phenomenon in isolation, electronic conductivity (σ) and electrochemical oxygen reduction activity of the (La0.8Sr0.2)0.98CrxMn1−xO3 model series (x = 0, 0.02, 0.05 or 0.1) were measured in air between 850 and 650 °C. Depending on the extent of chromium substitution and the measurement temperature, electrochemical impedance spectroscopy (EIS) results could be deconvoluted into a maximum of three contributions reflecting possible limiting processes such as oxide ion transport and dissociative adsorption. Chromium substitution resulted in lowered σ (from 174 S cm− 1 (x = 0) to 89 S cm− 1 (x = 0.1) at 850 °C) and a steady rise in associated activation energy (Ea) (from 0.105 ± 0.001 eV (x = 0) to 0.139 ± 0.001 eV (x = 0.1)). From EIS analyses, ohmic and polarisation resistances increased, whilst Ea for the overall oxygen reduction reaction also increased from 1.39 ± 0.04 eV (x = 0) to 1.48–1.54 ± 0.04 eV upon chromium substitution. |
| Keywords | Solid oxide fuel cell; Lanthanum strontium manganite; Chromium poisoning; Electronic conductivity; Electrochemical impedance spectroscopy |
| Remark | Link |
The effect of calcination temperature on the electrochemical properties of La0.3Sr0.7Fe0.7Cr0.3O3−x (LSFC) perovskite oxide anode of solid oxide fuel cells (SOFCs)
ID=269| Authors |
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Sustainable Energy Technologies and Assessments
Volume: 8,
Pages: 92-98 Time of Publication: 2014 |
| Abstract | A series of perovskite structure anode materials, LSFC, was successfully prepared by a glycine combustion process and further calcined at different temperatures. The electrochemical properties of anodes prepared at various calcination temperatures (1100 °C, 1200 °C and 1300 °C) were investigated. The calcination temperature had no significant influence on the morphology of the material but showed obvious influences on the particle sizes and electrochemical properties of the materials. Higher calcination temperature results in sharper X-ray diffractometer (XRD) diffraction peaks of the materials with larger particle sizes and higher electrical conductivity. However materials calcined at higher temperature had much smaller BET surface area resulting in lower triple phase boundary (TPB). The electrochemical performance test exhibited that LSFC anode material sintered at 1100 °C exhibited the smallest area specific resistance (ASR) value in H2 at operating temperatures from 700 to 900 °C. For proton conducting SOFCs (PC-SOFCs) fed by syngas, the cell with anode calcined at 1100 °C also showed highest power density output of 120 mW/cm2 at 750 °C, which was almost three times higher than that of the cell with anode calcined at 1300 °C. |
| Keywords | Solid oxide fuel cell; Calcination temperature; Electrochemical properties; Perovskite |
| Remark | Link |
Oxygen interstitial and vacancy conduction in symmetric Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions
ID=268| Authors |
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Inorganic Materials
Volume: 50,
Issue: 10,
Pages: 1035-1049 Time of Publication: 2014 |
| Abstract | We have compared (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm) pyrochlore-like solid solutions with interstitial oxide ion conduction and Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm) pyrochlore-like solid solutions with vacancy-mediated oxide ion conduction in the symmetric systems Nd2O3-ZrO2 (NdZrO) and Sm2O3-ZrO2 (SmZrO). We have studied their structure, microstructure, and transport properties and determined the excess oxygen content of the (Sm2 − x Zr x )Zr2O7 + x/2 (x = 0.2) material using thermal analysis and mass spectrometry in a reducing atmosphere (H2/Ar-He). The Ln2 ± x Zr2 ± x O7 ± x/2 (Ln = Nd, Sm) solid solutions have almost identical maximum oxygen vacancy and interstitial conductivities: (3–4) × 10−3 S/cm at 750°C. The lower oxygen vacancy conductivity of the Ln2(Zr2 − x Ln x )O7 − δ (Ln = Nd, Sm; 0 < x ≤ 0.3) solid solutions is due to the sharp decrease in it as a result of defect association processes, whereas the interstitial oxide ion conductivity of the (Ln2 − x Zr x )Zr2O7 + x/2 (Ln = Nd, Sm; 0.2 ≤ x < 0.48) pyrochlore-like solid solutions is essentially constant in a broad range of Ln2O3 concentrations. |
| Remark | Link |
MICROWAVE SINTERING OF Sr AND Mg-DOPED LANTHANUM GALLATE (LSGM) SOLID ELECTROLYTES
ID=267| Authors |
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Romanian journal of materials
Time of Publication: 2014-01
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| Abstract | Sr2+ and Mg2+ simultaneously doped lanthanum gallate (LSGM) powders, prepared by a modified Pechini route using polyvinyl alcohol (PVA) as polymeric alcohol, were densified using an activated microwave technique at 2.45 GHz, to develop a dense stable electrolyte for application in intermediate temperatures solid oxide fuel cells (IT-SOFC). Thermal behaviour of precursors was investigated by means of differential thermal analysis combined with thermogravimetric analysis (DTA/TGA). The powders and sintered samples were characterized using scanning electron microscopy and energy dispersive analysis (SEM-EDAX), X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The thermal expansion coefficient (TEC) and ionic conductivity of the sintered samples were also evaluated. Fine, homogeneous and high density pellets of almost pure LSGM phase were obtained after sintering at 14000C for a short period time in an activated microwave field. Using activated microwave field, due to the volumetric in situ heating, the sintering process is highly specific and instantaneous, leading to a faster kinetics compared to the conventional process (electric oven). With an optimized sintering schedule, a fine grained and dense microstructure of the samples were obtained. |
| Remark | Link |
Magnetron formation of Ni/YSZ anodes of solid oxide fuel cells
ID=266| Authors |
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Russian Journal of Electrochemistry
Volume: 50,
Issue: 7,
Pages: 647-655 Time of Publication: 2014 |
| Abstract | Physico-chemical and structural properties of nanocomposite NiO/ZrO2:Y2O3 (NiO/YSZ) films applied using the reactive magnetron deposition technique are studied for application as anodes of solid oxide fuel cells. The effect of oxygen consumption and magnetron power on the discharge parameters is determined to find the optimum conditions of reactive deposition. The conditions for deposition of NiO/YSZ films, under which the deposition rate is maximum (12 μm/h), are found and the volume content of Ni is within the range of 40–50%. Ni-YSZ films reduced in a hydrogen atmosphere at the temperature of 800°C have a nanoporous structure. However, massive nickel agglomerates are formed in the course of reduction on the film surface; their amount grows at an increase in Ni content in the film. Solid oxide fuel cells with YSZ supporting electrolyte and a LaSrMnO3 cathode are manufactured to study electrochemical properties of NiO/YSZ films. It is shown that fuel cells with a nanocomposite NiO/YSZ anode applied using a magnetron sputtering technique have the maximum power density twice higher than in the case of fuel cells with an anode formed using the high-temperature sintering technique owing to a more developed gas-anode-electrolyte three-phase boundary. |
| Remark | Link |
Full ceramic micro solid oxide fuel cells: towards more reliable MEMS power generators operating at high temperatures
ID=265| Authors |
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Energy Environ. Sci.
Time of Publication: 2014
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| Abstract | Batteries, with a limited capacity, have dominated the power supply of portable devices for decades. Recently, the emergence of new types of highly efficient miniaturized power generators like micro fuel cells has opened up alternatives for continuous operation on the basis of unlimited fuel feeding. This work addresses for the first time the development of a full ceramic micro solid oxide fuel cell fabricated in silicon technology. This full-ceramic device represents a new generation of miniaturized power generators able to operate at high temperatures, and therefore able to work with a hydrocarbon fuel supply. Dense yttria-stabilized zirconia free-standing large-area membranes on micromachined silicon were used as the electrolyte. Thin-film porous electrodes of La0.6Sr0.4CoO3−δ and gadolinia-doped ceria were employed as cathode and anode materials, respectively. The electrochemical performance of all the components was evaluated by partial characterization using symmetrical cells, yielding excellent performance for the electrolyte (area specific resistance of 0.15 Ω cm2 at temperatures as low as 450 °C) and the electrodes (area specific resistance of the cathode and anode below 0.3 Ω cm2 at 700 °C). A micro solid oxide fuel cell with an active area of 2 mm2 and less than 1 micrometer in thickness was characterized under fuel cell conditions, using hydrogen as a fuel and air as an oxidant. A maximum power density of 100 mW cm−2 and 2 mW per single membrane was generated at 750 °C, having an open circuit voltage of 1.05 V. Impedance spectroscopy of the all-ceramic membrane showed a total area-specific resistance of [similar]3.5 Ω cm2. |
| Remark |
DOI: 10.1039/C4EE00748D Link |
Proton conductivity of hexagonal and cubic BaTi1−xScxO3−δ (0.1 ≤ x ≤ 0.8)
ID=264| Authors |
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Dalton Transactions
Time of Publication: 2014
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| Abstract | BaTi1−xScxO3−δ (x = 0.1–0.8) was prepared via solid state reaction. High resolution X-ray powder diffraction was used to characterise the synthesised materials. It was found that low substitution (x = 0.1 and 0.2) of Ti4+ for Sc3+ gives a hexagonal perovskite structure, whereas high substitution (x = 0.5–0.7) results in a cubic perovskite structure. Thermogravimetric analysis revealed significant levels of protons in both as-prepared and hydrated samples. Electrical conductivity was measured by AC impedance methods under oxygen, argon and under dry and humid, both H2O and D2O, conditions for BaTi1−xScxO3−δ (x = 0.2, 0.6 and 0.7). In the temperature range of 150–600 °C, under humid conditions, the conductivity is significantly higher than that under the dry conditions. The increase in conductivity is especially prominent for the cubic phases, indicating that protons are the dominant charge carriers. The proton conductivity of hexagonal BaTi0.8Sc0.2O3−δ is approx. two orders of magnitude lower than that of the more heavily substituted cubic phases. Conductivity is also found to be higher in dry O2 than in Ar in the whole temperature range of 150–1000 °C, characteristic of a significant contribution from p-type charge carriers under oxidising atmospheres. Greater Sc3+ substitution leads to a higher proton concentration and the highest proton conductivity (σ [similar] 2 × 10−3 S cm−1 at 600 °C) is found for the BaTi0.3Sc0.7O3−δ composition. |
| Remark |
DOI: 10.1039/C4DT01280A Link |
Protons in acceptor doped langasite, La3Ga5SiO14
ID=263| Authors |
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Solid State Ionics
Volume: 264,
Pages: 76–84 Time of Publication: 2014 |
| Abstract | The electrical and defect chemical properties of acceptor doped langasite have been investigated over wide ranges of pH2O, pO2 and temperature. All compositions are pure proton conductors up to 800 °C in wet atmospheres and mixed oxide ion-p-type conductors at higher temperatures. The enthalpy of mobility of protons is 75 ± 3 kJ/mol, while that of oxygen vacancies is 125 ± 7 kJ/mol. The standard enthalpy and entropy of hydration are -100 ± 3 kJ/mol and -157 ± 5 J/mol K, respectively. Langasite based sensors may therefore be affected by dissolution of protons from H2O in the bulk crystal lattice up to temperatures as high as 1000 °C. |
| Keywords | Langasite; Piezoelectric; DFT; Defects; Hydrogen; Conductivity |
Solid-State Synthesis and Properties of Relaxor (1−x)BKT–xBNZ Ceramics
ID=261| Authors |
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| Source |
J. of American Ceramic Society
Time of Publication: 2014
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| Abstract | Conventional solid-state synthesis was used to synthesize dense and phase pure ceramics in the (1−x) Bi0.5K0.5TiO3–xBi0.5Na0.5ZrO3 (BKT–BNZ) system. Structural characterization was done using X-ray diffraction at both room temperature and elevated temperatures, identifying a transition from tetragonal xBi0.5Na0.5ZrO3 (xBNZ, x = 0–0.10) to pseudo cubic xBNZ for x = 0.15–0.80. Dielectric properties were investigated with respect to both temperature (RT = 600°C) and frequency (1–106 Hz). Relaxor-like behavior was retained for all the materials investigated, evident by the broadening of the relative dielectric permittivity peaks at transition temperatures as well as frequency dispersion at their maximum. The maximum dielectric constant at elevated temperature was found for 0.15 BNZ. Electric field-induced strain and polarization response were also investigated for several compositions at RT and the largest field-induced strain was observed for the 0.10 BNZ ceramics. The composition range with best performance coincides with the transition from tetragonal to cubic crystal structure. |
| Remark |
DOI: 10.1111/jace.13066 Link |
Ceramic–carbonate dual-phase membrane with improved chemical stability for carbon dioxide separation at high temperature
ID=260| Authors |
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| Source |
Solid State Ionics
Volume: 263,
Pages: 172–179 Time of Publication: 2014 |
| Abstract | This study examines membrane synthesis, structural stability, permeation properties, and long-term permeation stability of a new dense dual-phase membrane of composition La0.85Ce0.1Ga0.3Fe0.65Al0.05O3 − δ (LCGFA)–carbonate for high temperature CO2 separation. Porous ceramic supports made by sintering pressed powder at a temperature below its densification temperature resulted in a desired support with an open porosity ranging between 40 and 50%. The dual-phase membranes was prepared by direct infiltration of the ceramic supports in molten carbonate at 600 °C, resulting in a four order of magnitude decrease in permeance when compared to the support. LCGFA–carbonate membranes are stable when exposed to gases ranging from gas mixtures containing N2 and various concentrations of CO2 to simulated syngas, and exhibit a stable long term CO2 permeation flux of 0.025 mL·min− 1·cm− 2 for more than 275 h at 900 °C. The CO2 permeation results show exponential dependence to increasing system temperature as well as a linear dependence to logarithmic change in CO2 partial pressure gradients across the membrane in the CO2 pressure range studied. |
| Keywords | Ceramic–carbonate; Carbon dioxide permeation; Dual-phase membrane; Perovskite |
| Remark | Link |
