Published references
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These publications have a reference to ProboStat™ or other NORECS products
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ID=234| Author |
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Book of its own
Time of Publication: 2013
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| 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
ID=233| Authors |
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| Source |
Journal of Power Sources
Time of Publication: 2013
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| 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 Ω·cm2 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. |
| 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
ID=228| Authors |
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Journal of Solid State Chemistry
Time of Publication: 2013
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| 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
ID=226| Authors |
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Electrochimica Acta
Time of Publication: 2013
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| 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
ID=225| Authors |
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Materials of power engineering and radiationresistant materials
Time of Publication: 2013-10
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| 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
ID=224| Authors |
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International Journal of Hydrogen Energy
Time of Publication: 2013
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| 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
ID=223| Authors |
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| Source |
Journal of Power Sources
Time of Publication: 2013
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| 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 Ω·cm2 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)
ID=222| Authors |
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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)
ID=221| Source |
Time of Publication: 2013
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Application of FIB-TOF-SIMS and FIB-SEM-EDX Methods for the Analysis of Element Mobility in Solid Oxide Fuel Cells
ID=220| Authors |
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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
ID=219| Authors |
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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
ID=218| Authors |
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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)
ID=217| Authors |
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Materials Research Bulletin
Time of Publication: 2013
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| 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
ID=216| Authors |
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Journal of the American Ceramic Society
Time of Publication: 2013
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| 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
ID=215| Authors |
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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
ID=214| Authors |
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Inorganic Chemistry
Publisher: ACS Publications,
Time of Publication: 2013
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| 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
ID=213| Authors |
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Inorg. Chem.
Time of Publication: 2013
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| 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
ID=212| Authors |
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Journal of the American Ceramic Society
Time of Publication: 2013
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| 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
ID=211| Authors |
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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
ID=209| Authors |
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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. |
Effects of Nb5+, Mo6+, and W6+ dopants on the germanate-based apatites as electrolyte for use in solid oxide fuel cells
ID=208| Authors |
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| Source |
International Journal of Hydrogen Energy
Volume: 38,
Issue: 27,
Pages: 12015–12023 Time of Publication: 2013-09 |
| Abstract | Rare information is available in the literature on the cell performance of the solid oxide fuel cells (SOFCs) using apatites known for their good electrical conductivity as electrolyte materials. In this study, La9.5Ge5.5Nb0.5O26.5, La9.5Ge5.5Mo0.5O26.75, and La9.5Ge5.5W0.5O26.75 ceramics were prepared and characterized. The results indicated that the La9.5Ge5.5Nb0.5O26.5 and La9.5Ge5.5W0.5O26.75 ceramics reported hexagonal phase, while the La9.5Ge5.5Mo0.5O26.75 ceramic demonstrated triclinic symmetry. Among the apatities evaluated, La9.5Ge5.5Nb0.5O26.5 sintered at 1450 °C showed the best conduction with an electrical conductivity value of 0.045 S/cm at 800 °C. Button cells of NiO–SDC/La9.5Ge5.5Nb0.5O26.5/LSCF–SDC were built and revealed good structural integrity. The total ohmic resistance (R0) and interfacial polarization resistance (RP) of the cell read 0.428 and 0.174 Ω cm2 and 0.871 and 1.164 Ω cm2, respectively at 950 and 800 °C. The maximum power densities (MPD) of the single cell at 950 and 800 °C were respectively 0.363 and 0.095 W cm−2. Without optimizing the anode and cathode as well as hermetic sealing of the cell against the gas, the study found the performance of the single cell with the pure La9.5Ge5.5Nb0.5O26.5 as its electrolyte material superior to those of the SOFC cells with a YSZ electrolyte of comparable thickness shown in the literature. |
| Keywords | Solid oxide fuel cell; Apatite; Impedance; Cell performance |
| Remark | Link |
Transformation from insulating p-type to semiconducting n-type conduction in CaCu3Ti4O12-related Na(Cu5/2Ti1/2)Ti4O12 ceramics
ID=207| Authors |
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| Source |
Journal of Applied Physics
Volume: 114,
Issue: 3,
Pages: 034106 - 034106-8 Time of Publication: 2013-07 |
| Abstract | A double doping mechanism of Na+ + ½ Ti4+ → Ca2+ + ½ Cu2+ on the general formula Ca1-xNax(Cu3-x/2Tix/2)Ti4O12 has been used to prepare a series of isostructural CaCu3Ti4O12 (CCTO)-type perovskites. A complete solid solution exists for 0 ≤ x ≤ 1 and all compositions exhibit incipient ferroelectric behaviour with higher than expected intrinsic relative permittivity. Although CCTO ceramics typically exhibit n-type semiconductivity (room temperature, RT, resistivity of ∼10–100 Ω cm), Na(Cu5/2Ti1/2)Ti4O12 (NCTO) ceramics sintered at 950 °C consist of two insulating bulk phases (RT resistivity > 1 GΩ cm), one p-type and the other n-type. With increasing sintering temperature/period, the p-type phase transforms into the n-type phase. During the transformation, the resistivity and activation energy for electrical conduction (Ea ∼ 1.0 eV) of the p-type phase remain unchanged, whereas the n-type phase becomes increasingly conductive with Ea decreasing from ∼ 0.71 to 0.11 eV with increasing sintering temperature. These changes are attributed to small variations in stoichiometry that occur during high temperature ceramic processing with oxygen-loss playing a crucial role. |
| Remark | Link |
New double molybdate Na9Fe(MoO4)6: Synthesis, structure, properties
ID=206| Authors |
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| Source |
Journal of Solid State Chemistry
Volume: 205,
Pages: 149–153 Time of Publication: 2013-09 |
| Abstract | A new double molybdate Na9Fe(MoO4)6 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, X-ray fluorescence analysis, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na9Fe(MoO4)6 were obtained and its structure was solved (the space group RView the MathML source3¯, a=14.8264(2), c=19.2402(3) Å, V=3662.79(9) Å3, Z=6, R=0.0132). The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)3. The basic structure units are polyhedral clusters composed of central FeО6 octahedron sharing edges with three Na(1)О6 octahedra. The clusters share common vertices with bridging МоО4 tetrahedra to form an open 3D framework where the cavities are occupied by Na(2) and Na(3) atoms. The compound melts incongruently at 904.7±0.2 K. Arrhenius type temperature dependence of electric conductivity σ has been registered in solid state (σ=6.8×10−2 S сm−1 at 800 K), thus allowing considering Na9Fe(MoO4)6 as a new sodium ion conductor. |
| Keywords | Sodium–iron molybdate; Crystal structure; Solid-state electrolyte |
| Remark | Link |
Study of bulk and grain-boundary conductivity of Ln2+xHf2−xO7−δ (Ln = Sm-Gd; x = 0, 0.096) pyrochlores
ID=205| Authors |
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| Source |
Journal of Electroceramics
Volume: 24,
Issue: 4,
Pages: 300-307 Time of Publication: 2010-06 |
| Abstract | The electrical conductivity of new solid electrolytes Eu2.096Hf1.904O6.952 and Gd2Hf2O7 have been compared with those for different pyrochlores including titanates and zirconates Ln2+xМ2−xO7−δ (Ln = Sm-Lu; M = Ti, Zr; x = 0−0.81). Impedance spectroscopy data demonstrate that Eu2.096Hf1.904O6.952 and Gd2Hf2O7 synthesized from mechanically activated oxides have high ionic conductivity, comparable to that of their zirconate analogues. The bulk and grain-boundary components of conductivity in Sm2.096Hf1.904O6.952 (Тsynth = 1600°С), Eu2.096Hf1.904O6.952 and Gd2Hf2O7 (Тsynth = 1670°С) have been determined. The highest bulk conductivity is offered by the disordered pyrochlores prepared at 1600°C and 1670°C: ~1.5 × 10−4 S/cm for Sm2.096Hf1.904O6.952, 5 × 10−3 S/cm for Eu2.096Hf1.904O6.952 and 3 × 10−3 S/cm for Gd2Hf2O7 at 780°С, respectively. The conductivity of the fluorite-like phases at the phase boundaries of the Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x ~ 0.286) solid solutions, as well as that of the high-temperature fluorite-like phases Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.286), is lower than the conductivity of the disordered pyrochlores Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.096). |
| Remark | Link |
Ionic conduction in glasses in the MnNbOF5-BaF2-BiF3 system
ID=204| Authors |
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| Source |
Russian Journal of Inorganic Chemistry
Volume: 58,
Issue: 4,
Pages: 387-391 Time of Publication: 2013-04 |
| Abstract | The electrical conductivity of oxyfluoride glasses in the MnNbOF5-BaF2-BiF3 system in the temperature range 299–550 K was studied by impedance spectroscopy. It was shown that the conductivity is mainly caused by fluoride ions forming fluorobismuth polyhedra in the glass structure, being as high as 7.46 × 10−3 S/cm (533 K) in the 20MnNbOF5-30BaF2-50BiF3 system reaches, which is at the level of the best values for fluoride glasses. |
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