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Published references for ProboStat™

These publications have a reference to ProboStat™ or other NorECs products

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Porous Ca3Co4O9 with enhanced thermoelectric properties derived from Sol–Gel synthesis

Authors Michael Bittner, Lailah Helmich, Frederik Nietschke, Benjamin Geppert, Oliver Oeckler, Armin Feldhoff
Source
Journal of the European Ceramic Society
Time of Publication: 2017
Abstract Highly porous Ca3Co4O9 thermoelectric oxide ceramics for high-temperature application were fabricated by sol–gel synthesis and subsequent conventional sintering. Growth mechanism of misfit-layered Ca3Co4O9 phase, from sol–gel synthesis educts and upcoming intermediates, was characterized by in-situ X-ray diffraction, scanning electron microscopy and transmission electron microscopy investigations. The Ca3Co4O9 ceramic exhibits a relative density of 67.7%. Thermoelectric properties were measured from 373 K to 1073 K. At 1073 K a power factor of 2.46 μW cm−1 K−2, a very low heat conductivity of 0.63 W m−1 K−1 and entropy conductivity of 0.61 mW m−1 K−2 were achieved. The maintained figure of merit ZT of 0.4 from sol–gel synthesized Ca3Co4O9 is the highest obtained from conventional, non-doped Ca3Co4O9. The high porosity and consequently reduced thermal conductivity leads to a high ZT value.
Keywords Thermoelectricity; Thermal conductivity; Porosity; Oxide; Ca3Co4O9
Remark https://doi.org/10.1016/j.jeurceramsoc.2017.04.059
Link

Electrochemical performance of Co3O4/CeO2 electrodes in H2S/H2O atmospheres in a proton-conducting ceramic symmetrical cell with BaZr0.7Ce0.2Y0.1O3 solid electrolyte

Authors Tz. Kraia, S. Wachowski, E. Vllestad, R. Strandbakke, M. Konsolakis, T. Norby, G.E. Marnellos
Source
Solid State Ionics
Time of Publication: 2017
Abstract The electrochemical performance of Co3O4/CeO2 mixed oxide materials as electrodes, when exposed to H2S/H2O atmospheres, was examined employing a proton conducting symmetrical cell, with BaZr0.7Ce0.2Y0.1O3 (BZCY72) as the solid electrolyte. The impact of temperature (700–850 C) and H2S concentration (0–1 v/v%) in steam-rich atmospheres (90 v/v% H2O) on the overall cell performance was thoroughly assessed by means of electrochemical impedance spectroscopy (EIS) studies. The performance of the Co3O4/CeO2 electrode was significantly enhanced by increasing the H2S concentration and temperature. The obtained results were interpreted on the basis of EIS results and physicochemical characterization (XRD, SEM) studies of fresh and used electrodes. Notably, it was found that the mass transport processes, mainly associated with the adsorption and diffusion of the intermediate species resulting by the chemical and half-cell reactions taking place during cell operation, dominate the electrode polarization resistance compared with the charge transfer processes. Upon increasing temperature and H2S concentration, the electrode resistance is substantially lowered, due to the in situ activation and morphological modifications of the electrode, induced by its interaction with the reactants (H2S/H2O) and products (H2/SO2) mixtures.
Keywords H2S-tolerant electrodes; Cobalt-ceria oxides; BZCY72
Remark https://doi.org/10.1016/j.ssi.2017.04.010
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Thermal stability and enhanced thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47 (0 < x < 5)

Authors G. Cerretti, M. Schrade, X. Song, B. Balke, H. Lu, T. Weidner, I. Lieberwirth, M. Panthfer, T. Norby and W. Tremel
Source
Journal of Materials Chemistry A
Time of Publication: 2017
Abstract Thermoelectric materials are believed to play a fundamental role in the energy field over the next years thanks to their ability of directly converting heat into usable electric energy. To increase their integration in the commercial markets, improvements of the efficiencies are needed. At the same time, cheap and non-toxic materials are required along with easily upscalable production cycles. Compounds of the tetragonal tungsten bronze (TTB) series Nb8−xW9+xO47 fulfill all these requirements and are promising materials. Their adaptive structure ensures glass-like values of the thermal conductivity, and the substitution on the cation side allows a controlled manipulation of the electronic properties. In this contribution we report the stability study of the two highly substituted samples of the series, Nb5W12O47 (x = 3) and Nb4W13O47 (x = 4), when subjected to thermal cycling. Moreover, we show the results of the thermoelectric characterization of these samples. The two compounds have not been affected by the thermal treatment and showed an improvement of the thermoelectric performances up to a zT = 0.2 above 1000 K.
Remark Link

Influence of (Zn,Co)O/ZnO) interface amounts on ionic conduction performance of (Zn1-x,Cox)O (x=0.01, 0.05 and 0.10)

Authors Shalima Shawuti, Musa Mutlu Can, Mehmet Ali Glgn, Satoru Kaneko, Endo Tamio
Source
Composites Part B: Engineering
Time of Publication: 2017
Abstract We investigated the effect of dopant Co atoms into ZnO lattice, on ionic conduction at internal grain and/or through the grain boundary. Influence of dopant Co amount on resistivity was associated with enhanced activation energies of ionic conductivity through the grain boundaries. The change in the activation energy indicated that the mechanism of ionic conduction through the boundaries can be manipulated with Co amount in the lattice. Three conductance mechanisms were identified from the Cole-Cole Plots in order to understand the relaxation mechanism and activation energies of ionic transportations. Formed activation energy, 395 meV, by increasing Co dopant amount up to 10 mol% was attributed to enhanced ionic conductivity through enhancing (Zn,Co)O/ZnO) interface amounts at the grain boundaries. Furthermore, increased activation energy were also enhanced the electronic stability at high temperatures due to decrease in electronic conductivity compared to undoped ZnO.
Keywords Ionic activation energy; Oxide semiconductors; Impedance spectroscopy
Remark https://doi.org/10.1016/j.compositesb.2017.04.020
Link

Development of novel metal-supported proton ceramic electrolyser cell with thin film BZY15–Ni electrode and BZY15 electrolyte

Authors M. Stange, E. Stefan, C. Denonville, Y. Larring, P.M. Rrvik, R. Haugsrud
Source
International Journal of Hydrogen Energy
Volume: 42, Issue: 19, Pages: 13454–13462
Time of Publication: 2017
Abstract Metal supports for planar MS-PCEC were manufactured using tape-casting of low-cost ferritic stainless steel. A coating protecting the metal support against oxidation was applied by vacuum infiltration and a buffer layer of La0.5Sr0.5Ti0.75Ni0.25O3–δ (LSTN) was further deposited to smoothen the surface. The BaZr0.85Y0.15O3–δ–NiO (BZY15–NiO) cathode and the BaZr0.85Y0.15O3–δ (BZY15) electrolyte were applied by pulsed laser deposition (PLD) at elevated substrate temperatures (at 700 C and 600 C, respectively). The main challenges are related to the restrictions in sintering temperature and atmosphere induced by the metal support, as well as strict demands on the roughness of substrates used for PLD. Reduction treatment of the half cells confirmed that NiO in the BZY15–NiO layer was reduced to Ni, resulting in increased porosity of the BZY15–Ni cathode, while keeping the columnar and dense microstructure of the BZY15 electrolyte. Initial electrochemical testing with a Pt anode showed a total resistance of 40 Ωcm2 at 600 C. Through this work important advances in using metal supports and thin films in planar PCEC assemblies have been made.
Keywords Proton ceramic electrolyser cell (PCEC); Tape casting; Thin film deposition; Metal supports
Remark https://doi.org/10.1016/j.ijhydene.2017.03.028
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Energetically benign synthesis of lanthanum silicate through “silica garden” route and its characterization

Authors Kavita Parmar, Santanu Bhattacharjee
Source
Materials Chemistry and Physics
Volume: 194, Pages: 147–152
Time of Publication: 2017
Abstract Lanthanum silicate synthesis through “silica garden” route has been reported as an alternative to energy intensive milling procedure. Under optimum conditions lanthanum chloride crystals react with water glass (sodium silicate) to produce self generating hollow lanthanum silicate precipitation tube(s) (LaSPT). The micro tubes are irregular, thick, white coloured and amorphous but are hierarchically built from smaller tubules of 10–20 nm diameters. They retain their amorphous nature on being heated up to 600 C beyond which crystallization starts. The major phase in the LaSPT heated at 900 C is La2Si2O7. “As synthesized” LaSPT is heterogeneous and comprises non stoichiometric phases. The exterior and interior surfaces of these tubes are remarkably different in their morphology and chemical composition. LaSPT sintered at 1200 and 1300 C show fair amount of ionic conductivity.
Keywords Silica garden; Lanthanum silicate; Synthesis; Characterization
Remark https://doi.org/10.1016/j.matchemphys.2017.03.021
Link

Effect of Pt catalyst and external circuit on the hydrogen permeation of Mo and Nb co-doped lanthanum tungstate

Authors Yong Cao, Bo Chi, Jian Pu, Li Jian
Source
Journal of Membrane Science
Volume: 553, Pages: 336–341
Time of Publication: 2017
Abstract In this contribution, the hydrogen permeation properties of 30% Mo and 15% Nb co-doped La5.4WO11.1-δ (LWNM30) with/without Pt catalyst and external circuit were investigated. It was found that the surface reaction was the limiting factor in the hydrogen permeation process of LWNM30, and could be improved by using Pt as catalyst. The applied external circuit could also increase the hydrogen flux of LWNM30, and two followed effects might be responsible: the external circuit could transfer the electrons and promote the diffusion process; the external circuit could remove the charge layer on the surface and enhance the surface reaction rate.
Keywords Lanthanum tungstate; Hydrogen permeation; Pt catalyst; Mo and Nb; External circuit
Remark Link

Magnetron-sputtered La0.6Sr0.4Co0.2Fe0.8O3 nanocomposite interlayer for solid oxide fuel cells

Authors A. A. Solovyev, I. V. Ionov, A. V. Shipilova, A. N. Kovalchuk, M. S. Syrtanov
Source
Journal of Nanoparticle Research
Time of Publication: 2017
Abstract A thin layer of a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) is deposited between the electrolyte and the La0.6Sr0.4Co0.2Fe0.8O3/Ce0.9Gd0.1O2 (LSCF/CGO) cathode layer of a solid oxide fuel cell (SOFC) by pulsed magnetron sputtering using an oxide target of LSCF. The films were completely dense and well adherent to the substrate. The effects of annealing in temperature range from 200 to 1000 C on the crystalline structure of the LSCF films have been studied. The films of nominal thickness, 250–500 nm, are crystalline when annealed at temperatures above 600 C. The crystalline structure, surface topology, and morphology of the films were determined using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. To study the electrochemical characteristics of the deposited-film, solid oxide fuel cells using 325-nm LSCF films as interlayer between the electrolyte and the cathode have been fabricated. The LSCF interlayer improves the overall performance of the SOFC by increasing the interfacial area between the electrolyte and cathode. The electrolyte-supported cells with the interlayer have 30% greater, overall power output compared to that achieved with the cells without interlayer. The LSCF interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. Our results demonstrate that pulsed magnetron sputtering provides a low-temperature synthesis route for realizing ultrathin nanocrystalline LSCF film layers for intermediate- or low-temperature solid oxide fuel cells.
Keywords (La,Sr)(Co,Fe)O3 Magnetron sputtering Nanocomposite Interlayer Solid oxide fuel cells Nanostructured thin films Energy conversion
Remark DOI: 10.1007/s11051-017-3791-0
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Ferroelectric crystal Ca9Yb(VO4)7 in the series of Ca9R(VO4)7 non-linear optical materials (R = REE, Bi, Y)

Authors Bogdan I. Lazoryak, Sergey M. Aksenov, Sergey Yu. Stefanovich, Nikolai G. Dorbakov, Dmitriy A. Belov, Oksana V. Baryshnikova, Vladimir A. Morozov, Mikhail S. Manylov and Zhoubin Lin
Source
Journal of Materials Chemistry C
Time of Publication: 2017
Abstract The crystal structure, thermal, dielectric and second harmonic generation (SHG), and nonlinear optical activity data for whitlockite-type Ca9Yb(VO4)7 single crystals were obtained on one and the same sample produced by means of the Czochralski method. The crystal structure refinement has revealed that Yb3+ cations substitute for Ca2+ ions only in the M1, M2 and M5 positions of the whitlockite-type structure. Dielectric, differential thermal analysis and SHG data have shown that Ca9Yb(VO4)7 belongs to the family of high-temperature Ca3(VO4)2 ferroelectrics with Curie temperature Tc = 1221 K, where the symmetry changes from R3c to R[3 with combining macron]c. At higher temperatures a previously unknown complementary phase transition is discovered at T2 = 1276 K and is associated with the symmetry change during heating from R[3 with combining macron]c to R[3 with combining macron]m. Unlike other whitlockites, two phase transitions in Ca9Yb(VO4)7 are separated by a broad interval (ΔT = 55 K) which allows one to register two phase transitions by DSC and dielectric measurements. According to the thermal type both transitions are classified as first-order transformations and their structural mechanisms are considered. Inhomogeneity in the cation distribution is argued to have a crucial influence on the optical quality and ferroelectric domain structures of Ca9Yb(VO4)7 and other whitlockite-type laser crystals.
Remark Link

Status report on high temperature fuel cells in Poland – Recent advances and achievements

Authors J. Molenda, J. Kupecki, R. Baron, M. Blesznowski, G. Brus, T. Brylewski, M. Bucko, J. Chmielowiec, K. Cwieka, M. Gazda, A. Gil, P. Jasinski, Z. Jaworski, J. Karczewski, M. Kawalec, R. Kluczowski, M. Krauz, F. Krok, B. Lukasik, M. Malys, A. Mazur, A. Miele
Source
International Journal of Hydrogen Energy
Volume: 42, Issue: 7, Pages: 4366–4403
Time of Publication: 2017
Abstract The paper presents recent advances in Poland in the field of high temperature fuel cells. The achievements in the materials development, manufacturing of advanced cells, new fabrication techniques, modified electrodes and electrolytes and applications are presented. The work of the Polish teams active in the field of solid oxide fuel cells (SOFC) and molten carbonate fuel cell (MCFC) is presented and discussed. The review is oriented towards presenting key achievements in the technology at the scale from microstructure up to a complete power system based on electrochemical fuel oxidation. National efforts are covering wide range of aspects both in the fundamental research and the applied research. The review present the areas of (i) novel materials for SOFC including ZrO2-based electrolytes, CeO2-based electrolytes, Bi2O3 based electrolytes and proton conducting electrolytes, (ii) cathode materials including thermal shock resistant composite cathode material and silver-containing composites, (iii) anode materials, (iv) metallic interconnects for SOFC, (v) novel fabrication techniques, (vi) pilot scale SOFC, including electrolyte supported SOFC (ES-SOFC) and anode supported SOFC (AS-SOFC), (vii) metallic supported SOFC (MS-SOFC), (viii) direct carbon SOFC (DC-SOFC), (ix) selected application of SOFC, (x) advances in MCFC and their applications, (xi) advances in numerical methods for simulation and optimization of electrochemical systems.
Keywords SOFC; MCFC; Experiments; Simulations; Fabrication techniques
Remark https://doi.org/10.1016/j.ijhydene.2016.12.087
Link

Surface Protonics Promotes Catalysis

Authors R. Manabe, S. Okada, R. Inagaki, K. Oshima, S. Ogo & Y. Sekine
Source
Nature Scientific Reports
Volume: 6, Pages: Article number: 38007
Time of Publication: 2016
Abstract Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.
Keywords Catalytic mechanisms, Energy, Heterogeneous catalysis, Surface spectroscopy
Remark doi:10.1038/srep38007
Link

Sm6-xMoO12-δ (x = 0, 0.5) and Sm6WO12 – Mixed electron-proton conducting materials

Authors A.V. Shlyakhtina, S.N. Savvin, N.V. Lyskov, D.A. Belov, A.N. Shchegolikhin, I.V. Kolbanev, O.K. Karyagina, S.A. Chernyak, L.G. Shcherbakova, P. Nez
Source
Solid State Ionics
Time of Publication: 2017
Abstract Samarium molybdates Sm6-xMoO12-δ (x = 0, 0.5) and samarium tungstate Sm6WO12 – potential mixed electron-proton conductors have been studied by X-ray diffraction, Raman spectroscopy, SEM and impedance spectroscopy (in ambient air and in dry and wet air). Solid solutions differing in structure have been obtained in the Sm2O3-MoO3 system at 1600 C. The samarium molybdate Sm6MoO12 has the fluorite structure (Fm3m). The less samarium rich solid solution Sm5.5MoO11.25 crystallizes in a rhombohedral (View the MathML sourceR3) structure. The morphotropic transformation is due to the change in the chemical composition of the solid solution with decreasing Sm3 + concentration. The total conductivity of the cubic fluorite phase Sm6MoO12 at 750 C in air (1.48 10− 3 S/cm, Ea = 1.22 eV) is an order of magnitude higher than that of rhombohedral Sm5.5MoO11.25 (2.34 10− 4 S/cm, Ea = 1.11 eV). At low temperatures (T < 500 C), the Arrhenius plot of total conductivity for Sm6MoO12 and Sm5.5MoO11.25 in air deviates from linearity, suggesting that there is a proton contribution to its conductivity at these temperatures, like in the case of the Sm5.4Zr0.6MoO12.3 zirconium-doped molybdate. Below ~ 500 C, Sm6MoO12 fluorite and fluorite-like Sm6WO12 have identical Arrhenius plots of conductivity in ambient air. The region of dominant proton conductivity is wider for Sm6WO12 than Sm6MoO12, reaching temperatures as high as 750 С for the former. The absolute values of total conductivity obtained for samarium tungstate and molybdate at 400 С in wet air are virtually identical and close to 3 10− 6 S/cm, which suggests the conductivity of both compounds is dominated by protons at low temperatures and the proton transport numbers are similar.
Keywords Phase transition; Fluorite; Fluorite-like phase; Proton-conducting membranes; Proton conductivity; Electron conductivity
Remark http://dx.doi.org/10.1016/j.ssi.2017.01.020
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The effect of Zr-substitution in La1‐xSrxCo0.2M0.6Zr0.2O3‐δ (M = Fe, Mn) on the crystal structure, thermal expansion and electronic transport properties

Authors Vegar ygarden, Tor Grande
Source
Solid State Ionics
Volume: 301, Pages: 53–58
Time of Publication: 2017
Abstract The effect of Zr-substitution on the evolution of crystal structure, thermal expansion and the electronic transport properties is reported for La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ (0.1 ≤ x ≤ 1.0) and La1‐xSrxCo0.2Mn0.6Zr0.2O3-δ (x = 0.1, 0.2, 0.25, 0.3). La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ was found to be single-phase for the compositions investigated. The electrical conductivity of La1‐xSrxCo0.2Fe0.6Zr0.2O3‐δ demonstrated a maximum for x = 0.5, while the area specific resistance was shown to decrease significantly with increasing Sr-content due to an increased concentration of oxygen vacancies. No signs of oxygen vacancy ordering were observed. The area specific resistance of La0.3Sr0.7Co0.2Fe0.6Zr0.2O3‐δ at 600 C is close to an order of magnitude lower than reported values for La0.4Sr0.6Co0.2Fe0.8O3‐δ. The series La1‐xSrxCo0.2Mn0.6Zr0.2O3‐δ was found as multiphase materials. The stability of both series is discussed with respect to the red-ox properties of the transition metals.
Keywords Perovskite; Zr-substitution; X-ray diffraction; Electrical conductivity; Thermal expansion
Remark http://dx.doi.org/10.1016/j.ssi.2017.01.011
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Co- and Ce/Co-coated ferritic stainless steel as interconnect material for Intermediate Temperature Solid Oxide Fuel Cells

Authors Hannes Falk-Windisch, , Julien Claquesin, Mohammad Sattari, Jan-Erik Svensson, Jan Froitzheim
Source
Journal of Power Sources
Volume: 343, Pages: 1-10
Time of Publication: 2017
Abstract Chromium species volatilization, oxide scale growth, and electrical scale resistance were studied at 650 and 750 C for thin metallic Co- and Ce/Co-coated steels intended to be utilized as the interconnect material in Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Mass gain was recorded to follow oxidation kinetics, chromium evaporation was measured using the denuder technique and Area Specific Resistance (ASR) measurements were carried out on 500 h pre-exposed samples. The microstructure of thermally grown oxide scales was characterized using Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-Ray Analysis (EDX). The findings of this study show that a decrease in temperature not only leads to thinner oxide scales and less Cr vaporization but also to a significant change in the chemical composition of the oxide scale. Very low ASR values (below 10 mΩ cm2) were measured for both Co- and Ce/Co-coated steel at 650 and 750 C, indicating that the observed change in the chemical composition of the Co spinel does not have any noticeable influence on the ASR. Instead it is suggested that the Cr2O3 scale is expected to be the main contributor to the ASR, even at temperatures as low as 650 C.
Keywords Interconnect; Solid oxide fuel cell; Corrosion; Cr vaporization; Area specific resistance; Coating
Remark http://dx.doi.org/10.1016/j.jpowsour.2017.01.045
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Characterization of laser-processed thin ceramic membranes for electrolyte-supported solid oxide fuel cells

Authors J.A. Cebollero, R. Lahoz, M.A. Laguna-Bercero, J.I. Pea, A. Larrea, V.M. Orera
Source
International Journal of Hydrogen Energy
Time of Publication: 2017
Abstract By laser machining we have prepared thin and self-supported yttria stabilized zirconia (YSZ) electrolytes that can be used in electrolyte-supported solid oxide fuel cells for reducing the operation temperature. The membranes, which are supported by thicker areas of the same material, have an active area of ∼20 μm in thickness and up to 8 mm in diameter. Buckling limits the maximum size of the thin areas to below 1 mm, the overall effective active area being formed by multiple thin areas bounded by ribs. Electron Backscattering Diffraction experiments determined that there are not significant strains inside the membranes and that the heat-affected zone is confined to a shallow layer of ∼1–2 μm. The bending strength of the membranes decreases by ∼26% as a result of the surface microcracking produced by the laser machining. The membranes have a roughness of ∼2.5 μm and are coated by a layer of nanoparticles produced by the laser ablation. This coating and small roughness is not detrimental for the cathodic polarization of the cells. Conversely, the cathode polarization resistance decreases ∼5% in the 650–850 C temperature range.
Keywords SOFC; Solid electrolytes; Laser machining; Self-supporting ceramic membranes
Remark http://dx.doi.org/10.1016/j.ijhydene.2016.12.112
Link

Tuning of nonlinear optical and ferroelectric properties via the cationic composition of Ca9.5–1.5xBixCd(VO4)7 solid solutions

Authors N.G. Dorbakov, O.V. Baryshnikova, V.A. Morozov, A.A. Belik, Y. Katsuya, M. Tanaka, S.Yu. Stefanovich, B.I. Lazoryak
Source
Materials & Design
Volume: 116, Pages: 515–523
Time of Publication: 2017
Abstract Ca9.5–1.5xBixCd(VO4)7 (0 ≤ x ≤ 1) solid solutions with the whitlockite-type structure (SG R3c) were synthesized by a standard solid-state method in air. Structures of Ca9.5–1.5xBixCd(VO4)7 (x = 0.167, 0.5, 0.833) were refined by the Rietveld method from synchrotron powder X-ray diffraction data. Nonlinear optical properties of the whitlockite-type compounds can be designed and increased by an order of magnitude through appropriate isovalent and aliovalent substitutions for Ca2+ cations. Dielectric and temperature second harmonic generation investigations revealed the presence of a reversible ferroelectric phase transition in the range from 1331 K to 1055 K. The phase transition temperature monotonically decreases while nonlinear optical activity of Ca9.5–1.5xBixCd(VO4)7 strongly increases with increasing Bi3+ content.
Keywords Vanadates; Ferroelectric properties; Nonlinear optical properties; Crystal structure
Remark http://dx.doi.org/10.1016/j.matdes.2016.11.107
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The structural and electrical properties of samarium doped ceria films formed by e-beam deposition technique

Authors Darius Virbukas, Giedrius Laukaitis
Source
Solid State Ionics
Time of Publication: 2016
Abstract Sm2O3-doped CeO2 (Sm0.15Ce0.85O1.925, SDC) thin films were formed by e-beam evaporation method. Thin films were formed evaporating micro powders (particle size varied from 0.3 to 0.5 μm). The influence of deposition rate on formed thin film structures and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersion spectrometry (EDS), and atomic force microscopy (AFM). The deposition rate of formed SDC thin films was changed from 2 to 16 /s. The electrical properties were investigated as a function of frequency (0.1–106 Hz) at different temperatures (473–873 K). The formed SDC thin ceramic films repeat the crystallographic orientation of the initial powders using different substrates and different deposition rate. It was determined that crystallites size and samarium concentration are decreasing by increasing the deposition rate. The crystallites size decreased from 17.0 nm to 10.4 nm when SDC thin films were deposited on Alloy 600 (Fe-Ni-Cr), and decreased from 13.7 nm to 8.9 nm when were used optical quartz substrate. The best ionic conductivity σtot = 1.66 Sm− 1 at 873 K temperature, activation energy ΔEa = 0.87 eV (σg = 1.66 Sm− 1, σgb = 1.66 Sm− 1) was achieved when 2 /s deposition rate was used. The grain size (in the formed SDC thin films) was ~ 83 nm in this case.
Keywords Electron beam deposition; Samarium doped ceria oxide (SDC); Solid oxide fuel cells (SOFC); Ionic conductivity
Remark http://dx.doi.org/10.1016/j.ssi.2016.12.003
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Interstitial oxygen as a source of p-type conductivity in hexagonal manganites

Authors Sandra H. Skjrv, Espen T. Wefring, Silje K. Nesdal, Nikolai H. Gauks, Gerhard H. Olsen, Julia Glaum, Thomas Tybell & Sverre M. Selbach
Source
Nature Communications
Time of Publication: 2016
Abstract Hexagonal manganites, h-RMnO3 (R=Sc, Y, Ho–Lu), have been intensively studied for their multiferroic properties, magnetoelectric coupling, topological defects and electrically conducting domain walls. Although point defects strongly affect the conductivity of transition metal oxides, the defect chemistry of h-RMnO3 has received little attention. We use a combination of experiments and first principles electronic structure calculations to elucidate the effect of interstitial oxygen anions, Oi, on the electrical and structural properties of h-YMnO3. Enthalpy stabilized interstitial oxygen anions are shown to be the main source of p-type electronic conductivity, without reducing the spontaneous ferroelectric polarization. A low energy barrier interstitialcy mechanism is inferred from Density Functional Theory calculations to be the microscopic migration path of Oi. Since the Oi content governs the concentration of charge carrier holes, controlling the thermal and atmospheric history provides a simple and fully reversible way of tuning the electrical properties of h-RMnO3.
Remark doi:10.1038/ncomms13745
Link

Oxygen ion conductivity in samarium and gadolinium stabilized cerium oxide heterostructures

Authors Marius Zienius, Kristina Bockute, Darius Virbukas, Giedrius Laukaitis
Source
Solid State Ionics
Time of Publication: 2016
Abstract Gadolinium (GDC) and samarium (SDC) doped ceria were investigated in terms of multilayer systems, evaporated by e-beam technique on optical quartz, Alloy600 and sapphire substrate. GDC-SDC heterostructures of 1.3 μm thicknesses, composed of 1, 2, 3, 5 and 7 layers and they were investigated by structural and ionic conductivity techniques. Bragg peaks show nanocrystalline state of Gd and Sm doped ceria thin films. XRD patterns show fluorite type structure with space group Fm3m. The XRD analysis of thin films, deposited on quartz substrate, reveals the increase of (220) peak with increasing number of layers. The decrease of (111) peak is slightly notable, also. Thin film heterostructures have a face-centered cubic cell with the following lattice parameters, such as 5.4180 nm for GDC of and of 5.4245 nm for SDC. The scanning electron microscopy cross sectional analysis of three-layered structure clearly indicates the interfaces of different material. There are no visually distinct discontinuities in higher layer structures (5–7 layers). Total conductivity increases linearly with increasing of temperature, but decreases with the increase of number of layers. The highest total ionic conductivity at 1214 K temperature for SDC and GDC thin monolayers was 1.62 S/m and 1.02 S/m, respectively. The activation energy increases with the increase of number of layer as well.
Keywords Multilayer electrolyte; SDC; GDC; e-Beam deposition
Remark http://dx.doi.org/10.1016/j.ssi.2016.11.025
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A multistep model for the kinetic analysis of the impedance spectra of a novel mixed ionic and electronic conducting cathode

Authors A. Donazzi, M. Maestri, G. Groppi
Source
Electrochimica Acta
Time of Publication: 2016
Abstract A one-dimensional, heterogeneous and dynamic model is applied to kinetically analyze impedance experiments performed on a novel NdBa0.9Co2O5.6 (NBC) MIEC cathode. The model simulates the spectra in the time domain by accounting for the gas diffusion inside the electrode pores, and for the solid state diffusion of oxygen vacancies inside the bulk of the cathodic material. A detailed kinetic scheme is applied to describe the oxygen reduction mechanism, which includes steps for adsorption and desorption, first and second electronation at the gas/electrode interface, and ion transfer at the electrode/electrolyte interface. The kinetic investigation is based on impedance spectra collected on symmetric NBC/GDC/NBC cells, at open circuit voltage, between 550 and 700C, and 5–100% O2 molar fraction. The vacancies diffusion coefficient and the kinetic parameters of the reaction steps are fitted to describe the data. At the highest temperatures, a sensitivity analysis reveals that the rate determining step is the first electronation of the oxygen adatom, while the second electronation and the interfacial ion transport are kinetically irrelevant. Overall, the model allows to individuate the key parameters for capturing the kinetics of a MIEC cathode.
Keywords EIS; perovskites; kinetics; modeling
Remark http://dx.doi.org/10.1016/j.electacta.2016.11.072
Link

Stability of NASICON materials against water and CO2 uptake

Authors M. Guin, S. Indris, M. Kaus, H. Ehrenberg, F. Tietz, O. Guillon
Source
Solid State Ionics
Time of Publication: 2016
Abstract The stability in ambient conditions of a scandium-based NASICON material, Na3.4Sc2Si0.4P2.6O12, was investigated using impedance spectroscopy, thermogravimetry/differential scanning calorimetry (TG/DSC) and multinuclear magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). The presence of H2O and CO2 in samples stored in ambient air could be evidenced as well as its impact on the ionic conductivity of the samples. The detected amounts of water and CO2 in the samples had no influence on the measured conductivities at room temperature, which confirmed the absence of protonic conduction in hydrated samples. A loss of conductivity during heating of hydrated samples was due to a loss of contact between the ceramic and the electrode used for the conductivity measurement. The recommendation for handling of NASICON-type materials is therefore: samples require storage in an Ar-filled glove box or in a dry environment to avoid artefacts during high temperature measurements. Nevertheless, the stability of the NASICON-type materials is confirmed since their conductivity is not affected by the moisture.
Keywords Ionic conductivity; NASICON; Sodium; Scandium; ProGasMix
Remark http://dx.doi.org/10.1016/j.ssi.2016.11.006
Link

AgI thin films prepared by laser ablation

Authors Svetlana V. Fokina, Eugene N. Borisov, Vladimir V. Tomaev, Ilya I. Tumkin, Yuri S. Tveryanovich
Source
Solid State Ionics
Volume: 297, Pages: 64–67
Time of Publication: 2016
Abstract High quality and uniform morphology AgI films consisting of crystal grains about 30 nm in size were obtained by the laser (XeCl) ablation method. The designed silver iodide films have crystalline structure, optical and electrical properties corresponding to stoichiometric compound films. We have demonstrated that the laser ablation method commonly used for the preparation of thin films and nanolayered structures with the defined thickness can be successfully used for the deposition of AgI superionic conductor layers as well. The films were studied by XRD, EDA, optical absorption, photoluminescence, and impedance spectroscopies.
Keywords Thin films; Laser ablation; Conductivity; Optical band gap; Luminescence; Morphology; Excitons; XRD; Electron microscopy
Remark http://dx.doi.org/10.1016/j.ssi.2016.10.004
Link

Development of Temperature - Stable Relaxor Dielectrics for High Energy Density Capacitor Applications

Author Connor S. McCue
Source
Time of Publication: 2016
Remark THESIS
Link

Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC

Authors A.A. Solovyev, A.V. Shipilova, I.V. Ionov, A.N. Kovalchuk, S.V. Rabotkin, and V.O. Oskirko
Source
Journal of Electronic Materials
Volume: 45, Issue: 8, Pages: 3921-3928
Time of Publication: 2016
Solid oxide fuel cell, CGO, YSZ, bilayer electrolyte, magnetron sputtering, pulse electron-beam treatment
Remark Link

Thermodynamic properties of the Ba0.75Sr0.25TiO3 nanopowders obtained by hydrothermal synthesis

Authors C.F. Rusti, V. Badilita, A.M. Sofronia, D. Taloi, E.M. Anghel, F. Maxim, C. Hornoiu, C. Munteanu, R.M. Piticescu, S. Tanasescu
Source
Journal of Alloys and Compounds
Volume: 693, Pages: 1000–1010
Time of Publication: 2017
Abstract The paper is devoted to the investigation of the thermodynamic properties of nanostructured Ba0.75Sr0.25TiO3 perovskite material synthesized by hydrothermal method. The thermodynamic parameters obtained by a couple of measurements in both isothermal and dynamic regimes (drop calorimetry, solid-oxide electromotive force measurements, differential scanning calorimetry and thermogravimetry), allow for the investigations of the thermodynamic stability in a large temperature range from room temperature to 1273 K. The influence of the oxygen stoichiometry on the thermodynamic properties was examined using a coulometric titration technique coupled with electromotive force measurements. The results are discussed based on the strong correlation between the thermodynamic parameters and the charge compensation of the material system. X-ray powder diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were used for the microstructure and morphology analyses. The variation of the thermal expansion and electrical conductivity associated with the structural changes has been evidenced by thermomechanical measurements and impedance spectroscopy, respectively. Through a combined analysis of all the results, new features related to the understanding of the strong interplay between the thermodynamic properties, microstructure, thermal expansion and electrical conductivity in the hydrothermally prepared Ba0.75Sr0.25TiO3 perovskite material have been revealed.
Keywords Nanostructured materials; Chemical synthesis; Thermodynamic properties; Electromotive force, EMF; Calorimetry; X-ray diffraction
Remark http://dx.doi.org/10.1016/j.jallcom.2016.09.215
Link
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