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-Characterization of laser-processed thin ceramic membranes for electrolyte-supported solid oxide fuel cells
ID=387| Authors |
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| Source |
International Journal of Hydrogen Energy
Time of Publication: 2017
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| 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
ID=386| Authors |
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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 Link |
The structural and electrical properties of samarium doped ceria films formed by e-beam deposition technique
ID=385| Authors |
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Solid State Ionics
Time of Publication: 2016
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| 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 Å/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 Å/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 Link |
Interstitial oxygen as a source of p-type conductivity in hexagonal manganites
ID=384| Authors |
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| Source |
Nature Communications
Time of Publication: 2016
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| 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
ID=383| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2016
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| 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 Link |
A multistep model for the kinetic analysis of the impedance spectra of a novel mixed ionic and electronic conducting cathode
ID=382| Authors |
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| Source |
Electrochimica Acta
Time of Publication: 2016
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| 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 700°C, 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
ID=381| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2016
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| 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
ID=380| Authors |
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| 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
ID=379| Author |
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| Source |
Time of Publication: 2016
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| Remark |
THESIS Link |
Magnetron-Sputtered YSZ and CGO Electrolytes for SOFC
ID=378| Authors |
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| 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
ID=377| Authors |
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| 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 |
Enhanced bulk conductivity of A-site divalent acceptor-doped non-stoichiometric sodium bismuth titanate
ID=376| Author |
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| Source |
Fan Yang, Patrick Wu, Derek C. Sinclair
Time of Publication: 2016
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| Abstract | Bismuth-deficient sodium bismuth titanate (nominally Na0.5Bi0.49TiO2.985, NB0.49T) is a good oxide-ion conductor. Here we report the influence of A-site divalent ions, M2 + = Ca2 +, Sr2 + and Ba2 +, on the electrical properties of NB0.49T. A-site divalent doping for Bi3 + enhances the bulk (grain) conductivity by ~ one order of magnitude without changing the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on the doping mechanism Bi3 + + ½ O2 − → M2 +. Among these three dopants, Sr2 + is the most effective in increasing the bulk conductivity due to a combination of its smaller mismatch in ion size with Bi3 +, its intermediate polarisability and lower bond strength to oxygen compared to Ca2 + and Ba2 +. Doping strategies for further improvements to bulk conductivity of NBT materials are discussed based on these results. Comparison with other oxide-ion conductors and initial stability test under reducing atmosphere show the doped non-stoichiometric NBT materials are promising for low and intermediate temperature applications. |
| Keywords | Sodium bismuth titanate; Oxide-ion conductors; Doping; Non-stoichiometry |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.09.016 Link |
Effect of high pressures and temperatures on the structure and properties of CaCu3Ti4O12
ID=375| Authors |
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| Source |
Inorganic Materials
Volume: 52,
Issue: 10,
Pages: 1051–1054 Time of Publication: 2016 |
| Abstract | We have prepared ceramic CaCu3Ti4O12 samples by solid-state reaction and investigated the effect of high-pressure/high-temperature processing (p = 8.0 GPa, t = 1100°C) on the structure and electrical properties of CaCu3Ti4O12. |
| Keywords | High pressures and temperatures, microstructure, dielectric properties, CaCu3Ti4O12 |
| Remark |
DOI: 10.1134/S0020168516100083 Link |
Evaluation of La0.75Sr0.25Cr0.5Mn0.5O3 protective coating on ferritic stainless steel interconnect for SOFC application
ID=374| Authors |
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| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
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| Abstract | Ferritic stainless steel (SS) interconnect used for intermediate temperature solid oxide fuel cell has issues associated with the growth of oxide scale on the surface and evaporation of chromium species to the cathode leading to increase in polarization resistance and hence, overall cell resistance. Protective coating is essentially applied over the SS surface to restrict the above phenomena. In the present investigation, strontium doped lanthanum manganese chromite (LSCM) of composition La0.75Sr0.25Cr0.5Mn0.5O3 has been explored as a possible protective coating material on ferritic SS interconnect surface. For this application, fine LSCM powder was synthesized by solution polymerization method. Terpineol based slurry of LSCM was formulated and used for coating on ferritic SS surface by screen printing. LSCM coated ferritic SS was exposed to moist oxygen at 800 °C for 300 h and area specific resistance (ASR) of the coating was found to be as low as 2.0 mΩ cm2 after exposure. Microstructure of LSCM coating and the chromium oxide film was investigated using SEM and EDS. The results indicate that LSCM can form an effective protective coating on ferritic stainless steel for SOFC interconnect application. |
| Keywords | Interconnect; Protective coating; LSCM; SOFC |
| Remark |
http://dx.doi.org/10.1016/j.ijhydene.2016.08.143 Link |
Solid oxide carbonate composite fuel cells: Size effect on percolation
ID=373| Authors |
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| Source |
International Journal of Hydrogen Energy
Time of Publication: 2016
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| Abstract | In the studies of solid oxide carbonate composite fuel cell, percolation behaviour of the two phases was investigated as a function of particle size of the oxide phase. The ratio of amount of samarium doped ceria (SDC; Sm0.2Ce0.8O) to Na2CO3 was varied to determine an optimum ionic conductivity as function of oxide particle size. The roles of both phases in the composite electrolyte were investigated. SDC particles were mixed in different amounts of Na2CO3 to obtain composites with carbonate ratios from 1 wt% to 50 wt%. Micro-structural investigations showed that Na2CO3 phase served as the matrix in the micro-structure gluing the oxide particles together. The lowest and the highest carbonate ratios caused low conductivities in the composite as in these samples the 3D connectivity of both phases were disrupted. Low conductivity at both ends of the mixture composition could be interpreted as none of the components of the composite dominated the ionic conductivity. The highest conductivity was obtained at 10 wt% Na2CO3 amount in the composite electrolyte when nano-sized SDC (5–10 nm) oxide powders were used. Two different particle sizes of SDC powders were used to show that the optimum phase ratio, i.e. percolation of both phases, is function of particle size as well. The conductivity in the composite showed percolation behaviour with respect to the two constituent phases. |
| Keywords | Composite electrolyte; SOFC; Interface; Percolation; Carbonate; Impedance |
| Remark |
http://dx.doi.org/10.1016/j.ijhydene.2016.07.208, in press Link |
Insights into the enhancement of oxygen mass transport properties of strontium-doped lanthanum manganite interface-dominated thin films
ID=372| Authors |
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| Source |
Solid State Ionics
Time of Publication: 2016
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| Abstract | Strontium-doped lanthanum manganite thin films were deposited by pulsed laser deposition on yttria-stabilized zirconia single crystals for a comprehensive electrochemical characterization of the material acting as a cathode. A physically-meaningful electrical model was employed to fit the electrochemical impedance spectroscopy results in order to extract the main oxygen mass transport parameters as a function of the temperature and oxygen partial pressure. The oxygen diffusion and surface exchange coefficients extracted from the analysis showed several orders of magnitude of enhancement with respect to the bulk values reported in the literature and an unexpectedly low dependence with the oxygen partial pressure. Different observations were combined to propose a mechanism for the enhanced incorporation of oxygen in interface-dominated thin films mainly based on the high concentration of oxygen vacancies expected in the grain boundaries. |
| Remark |
http://dx.doi.org/10.1016/j.ssi.2016.08.009 Link |
Formation of solid solutions in the CdSe–PbSe system under the action of high pressures and temperatures
ID=371| Authors |
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| Source |
Russian Journal of Inorganic Chemistry
Volume: 61,
Issue: 8,
Pages: 1013–1018 Time of Publication: 2016 |
| Abstract | A method was proposed for producing solid solutions in the CdSe–PbSe systems, which is based on heat and high pressure treatment. X-ray powder diffraction analysis showed the formation of substitutional solid solutions CdxPb1–xSe with the NaCl structure, which contained 20, 40, 60, and 80 mol % cadmium selenide. The solid solutions were characterized by scanning electron microscopy, impedance spectroscopy, gas pycnometry, and Raman spectroscopy. |
| Remark |
DOI: 10.1134/S0036023616080052 Link |
Comparison of characteristics of solid oxide fuel cells with YSZ and CGO film solid electrolytes formed using magnetron sputtering technique
ID=370| Authors |
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| Source |
Russian Journal of Electrochemistry
Volume: 52,
Issue: 7,
Pages: 662–668 Time of Publication: 2016 |
| Abstract | The work describes the methods of manufacturing single cells of solid oxide fuel cell (SOFC) with thin–film YSZ and CGO electrolytes and also with the bilayer YSZ/CGO electrolyte. Formation of YSZ and CGO films on the supporting NiO–YSZ anode of SOFC was carried out using the combined electron–ionic–plasma deposition technique. The microstructure and phase composition of the formed coatings are studied and also comparative analysis of electrochemical characteristics of single fuel cells with different electrolytes is performed. It is shown that the maximum power density of 1.35 W/cm2 at the temperature of 800°C is obtained for the cell with bilayer YSZ/CGO electrolyte. However, the highest performance at lower working temperatures (650–700°C) is characteristic for the fuel cell with single–layer CGO electrolyte; its power density is 600–650 mW/cm2. |
| Keywords | Solid oxide fuel cell, CGO, YSZ, bilayer electrolyte, magnetron sputtering, pulsed electron–beam treatment |
| Remark |
DOI: 10.1134/S102319351607017X Link |
Nanolayered solid electrolyte (GeSe2)30(Sb2Se3)30(AgI)40/AgI: A new hypothesis for the conductivity mechanism in layered AgI
ID=369| Authors |
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| Source |
Solid State Ionics
Volume: 294,
Pages: 82–89 Time of Publication: 2016 |
| Abstract | Using the laser ablation method, films comprised of alternating layers of AgI and (GeSe2)30(Sb2Se3)30(AgI)40 glass were obtained. Individual layer thickness amounts to 10 ÷ 15 nm, and the total number of layers is about 100. X-ray diffraction (XRD) and film conductivity measurements were carried out during several cycles of heating up to 200 °C and cooling to room temperature. It was established that after three cycles of thermal processing specific lateral conductivity of the film is equal to 0.3 S cm− 1 and conductivity activation energy is equal to 0.07 eV at room temperature. Attempts to explain such a high conductivity value based on XRD results did not yield satisfactory results. However, our first-principle calculations within the density functional theory (DFT) showed that in the free layer composed of four AgI planes a rearrangement occurs, resulting in formation of the stable structure of two silver planes on the inside and two iodine planes on the outside (I–Ag–Ag–I). Rearrangement of similar stack of eight or twelve atomic planes results in formation of two or three I–Ag–Ag–I layers loosely bound to each other, accordingly. This suggests that increase in specific conductivity growth of multilayer film as a consequence of cyclic heating and cooling may be connected with AgI stratification on its boundary with chalcogenide glass and following stabilization of layered phases mentioned above. The existence of an empty space between the layers that is constrained by iodine ion planes should facilitate silver ion diffusion along the layers. |
| Keywords | Glass-composite; Laser-ablation method; Ionic conductivity; AgI polymorphs; DFT calculations |
| Remark |
doi:10.1016/j.ssi.2016.07.004 Link |
Tin–Zinc oxide composite ceramics for selective CO sensing
ID=368| Authors |
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| Source |
Ceramics International
Time of Publication: 2016
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| Abstract | Composite metal oxide gas sensors were intensely studied over the past years having superior performance over their individual oxide components in detecting hazardous gases. A series of pellets with variable amounts of SnO2 (0–50 mol%) was prepared using wet homogenization of the component oxides leading to the composite tin-zinc ceramic system formation. The annealing temperature was set to 1100 °C. The samples containing 2.5 mol% SnO2 and 50 mol% SnO2 were annealed also at 1300 °C, in order to observe/to investigate the influence of the sintering behaviour on CO detection. The sensor materials were morphologically characterized by scanning electron microscopy (SEM). The increase in the SnO2 amount in the composite ceramic system leads to higher sample porosity and an improved sensitivity to CO. It was found that SnO2 (50 mol%) - ZnO (50 mol%) sample exhibits excellent sensing response, at a working temperature of 500 °C, for 5 ppm of CO, with a fast response time of approximately 60 s and an average recovery time of 15 min. Sensor selectivity was tested using cross-response to CO, methane and propane. The results indicated that the SnO2 (50 mol%)-ZnO (50 mol%) ceramic compound may be used for selective CO sensing applications. |
| Keywords | SnO2–ZnO; Composites; Sensors; Selective detection of CO |
| Remark |
doi:10.1016/j.ceramint.2016.07.102 Link |
Synthesis and electrical properties of new perovskite-like AMn3V4O12 (A = Ca, Ce, and Sm) compounds
ID=367| Authors |
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| Source |
Bulletin of the Russian Academy of Sciences: Physics
Volume: 80,
Issue: 6,
Pages: 620–623 Time of Publication: 2016 |
| Abstract | AMn3V4O12 (A = Ca, Ce, and Sm) compounds with a perovskite structure are synthesized at high pressures and temperatures. The crystalline structure of these compounds (space group Im3¯Z = 2) is determined via X-ray analysis. If ions in the A sublattice are changed in the order Ca2+–Sm3+–Ce3+, the valence is redistributed from Ca2+Mn32+V44+O12 to Sm3+Mn32+V43.75+O12, and to Ce3+Mn32+V43.75+O12. The temperature dependences of the electrical resistivity are studied. |
| Remark | Link |
Tailoring transport properties through nonstoichiometry in BaTiO3–BiScO3 and SrTiO3–Bi(Zn1/2Ti1/2)O3 for capacitor applications
ID=366| Authors |
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| Source |
Journal of Materials Science
Volume: 51,
Issue: 20,
Pages: 9404–9414 Time of Publication: 2016 |
| Abstract | The ceramic perovskite solid solutions BaTiO3–BiScO3 (BT–BS) and SrTiO3–Bi(Zn1/2Ti1/2)O3 (ST–BZT) are promising candidates for high-temperature and high-energy density dielectric applications. A-site cation nonstoichiometry was introduced in these two ceramic systems to investigate their effects on the dielectric and transport properties using temperature- and oxygen partial pressure-dependent AC impedance spectroscopy. For p-type BT–BS ceramics, the addition of excess Bi led to effective donor doping along with a significant improvement in insulation properties. A similar effect was observed on introducing Ba vacancies onto the A-sublattice. However, Bi deficiency registered an opposite effect with effective acceptor doping and a deterioration in the bulk resistivity values. For n-type intrinsic ST–BZT ceramics, the addition of excess Sr onto the A-sublattice resulted in a decrease in resistivity values, as expected. Introduction of Sr vacancies or addition of excess Bi on A-site did not appear to affect the insulation properties in air. These results indicate that minor levels of nonstoichiometry can have an important impact on the material properties, and furthermore it demonstrates the difficulties encountered in trying to establish a general model for the defect chemistry of Bi-containing perovskite systems. |
| Remark |
DOI: 10.1007/s10853-016-0186-z Link |
Leaching effect in gadolinia-doped ceria aqueous suspensions for ceramic processes
ID=365| Authors |
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| Source |
Journal of Power Sources
Volume: 326,
Issue: 15,
Pages: 70–77 Time of Publication: 2016 |
| Abstract | Gadolinium doped ceria (CGO) is a commonly used electrolytic material for Solid Oxide Fuel Cells (SOFCs) and for this reason different shaping methods for its deposition are reported in literature. Most of these processes are based on the use of organic-based CGO suspensions, but water-based processes are acquiring increasingly interest for their economical and environmental friendly properties. In this paper we reported how the components of water-based suspension and some unexpected process parameters can deeply affect the functional properties of the final powder. In particular, we observed that CGO powders are strongly affected by ionic leaching induced by furoic acid used as dispersant: the extent of this leaching was related to the dispersant concentration and suspension’s ball-milling-time; the phenomenon was confirmed by ICP-AES analyses on suspensions surnatant. Most importantly, ionic leaching affected the electrical properties of CGO: leached powder showed a higher ionic conductivity as a consequence of a partial removal of Gd ions at the grain boundaries. This work is therefore pointing out that when considering water-based suspensions, it is extremely important to carefully consider all the process parameters, including the organic components of the ceramic suspension, as these could lead to unexpected effects on the properties of the powder, affecting the performance of the final shaped material. |
| Keywords | Gadolinium doped ceria; Water-based suspensions; Furoic acid; Ionic leaching; Electrical conductivity |
| Remark |
doi:10.1016/j.jpowsour.2016.06.069 Link |
Structural, textural, surface chemistry and sensing properties of mesoporous Pr, Zn modified SnO2–TiO2 powder composites
ID=364| Authors |
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| Source |
Ceramics International
Volume: 43,
Issue: 13,
Pages: 14992–14998 Time of Publication: 2016 |
| Abstract | Mesoporous Zn and Pr modified SnO2-TiO2 mixed powders (Sn:Ti:Zn:Pr contents 60:20:15:5) have been prepared by a modified sol–gel method involving Tripropylamine (TPA) as chelating agent, TritonX100 as template and Polyvinylpyrrolidone as dispersant and stabilizer, respectively. The obtained gels have been dried at different temperatures and calcined in air at 600 and 800 °C, respectively. Phase identification of the synthesized samples and their evolution with the calcination temperature has been performed by X-ray diffraction. N2 adsorption/desorption isotherms were found to be characteristic for mesoporous materials, showing relatively low values for the specific surface area (15–32 m2 g−1) and nanometric sized pores. In case of the sample calcined at 800 °C, a bimodal pore size distribution can be observed, with maxima at 20 and 60 nm. SEM results demonstrate a porous nanocrystalline morphology stable up to 800 °C. The surface chemistry investigated by XPS reveals the presence of the elements on the surface as well as the oxidation states for the detected elements. At 800 °C a diffusion process of Sn from surface to the subsurface/bulk region accompanied by a segregation of Ti and Zn to the surface is noticed, while Pr content is unchanged. The sensing properties of the prepared powders for CO detection have been tested in the range of 250–2000 ppm and working temperatures of 227–477 °C. |
| Keywords | SnO2; TiO2; Sol–gel; Mesoporous materials; CO detection |
| Remark |
doi:10.1016/j.ceramint.2016.06.146 Link |
New promising NASICON material as solid electrolyte for sodium-ion batteries: Correlation between composition, crystal structure and ionic conductivity of Na3 + xSc2SixP3 − xO12
ID=363| Authors |
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| Source |
Solid State Ionics
Volume: 293,
Pages: 18–26 Time of Publication: 2016 |
| Abstract | In the search for novel sodium-ion conductors to be used in batteries for grid application, the thoroughly studied class of NASICON materials is of great interest due to compositional diversity and high ionic conductivity. The solid solution Na3 + xSc2(SiO4)x(PO4)3 − x with 0.05 ≤ x ≤ 0.8 was investigated for the first time. The various compositions were synthesized by solid state reaction and their crystallographic and electrical properties were measured. As a result, one of the best sodium-conductive NASICON materials to date was obtained for x = 0.4 (σNa,Total = 6.9 × 10− 4 S cm− 1 at 25 °C). Furthermore, the importance of the sodium concentration and size of lattice parameters on the ionic conductivity were investigated. The bulk ionic conductivity was correlated with the structural parameters along the conduction pathway of the sodium ions and confirm the key influence of the interatomic Na–O distances on sodium ion transport. |
| Keywords | Ionic conductivity; NASICON; Sodium; Scandium; Solid electrolyte; Battery |
| Remark |
doi:10.1016/j.ssi.2016.06.005 Link |
