Molten carbonate remained a topic of intense research in electrochemical sciences, particularly where it co-exists with ceramic phases in composites. Various models and assumptions were developed to explain the behavior of carbonate. In fact, most explanations, such as superionic diffusion along the interface, are yet challenged in research, which needs right justification or overwriting the story to nullify those claims. Here, we attempt to develop our understanding of carbonate conductivity based on the well-established concept of changing ionic mobility in vicinity of ceramic surface, which depends on extension of interface (area) among ceramic and molten phases and surface defect conc. and molten carbonate wettability of ceramic. Therefore, to discuss the behavior of carbonate, in present work, the solid/molten interface area was expanded in Ce0.9Gd0.1O1.95(CGO)NaLiCO3(NLC), where NLC varied from 3 to 40 vol%. In initial experiments, the CGO matrices of fixed 30 vol% porosity were impregnated at 650-800 degrees C to find the optimum temperature. Then, all CGO matrices of 10-40 vol % porosities were impregnated at optimum temperature. The SEM micrographs showed NLC impregnation changes the microstructure of composites from partially soaked CGO grains to the grains suspended in pool of NLC melt. The composite conductivity measurements were performed at temperature starting from 200 degrees C, where only ceramic phase is active, to 700 degrees. As well, on basis of matching activation energies and eutectic points, three distinct conductivity regions were recognized in Arrhenius.

In addition to the years of trials and innovations delivered in ceramic processing for high CO2 separation of membranes, acceleration of additional flux of oxide ions through the molten phase of the ceramic-salt composite has been a seeking complementary but most interesting topic of the research. The previous examinations on carbonate, nitrate, hydroxide salts, etc., with an additive, were independently carried out, and their merits were addressed. However, the unavailability of collective information and data on nitrate, hydroxide, and carbonate hinders the true comparison in optimizing the best competitor. In scope of the above drawback, the current study is dedicated to review the impact of nitrate, hydroxide, and carbonate salts together at a fixed Li-to-Na cationic molarity of 52:48. All assessments were performed in the asymmetric membrane geometry of the composite under identical synthesis and testing protocols, where 40 vol % porous support and similar to 10 mu m-thick matrices were prepared from Ce0.9Gd0.1O2-delta. However, the molten nitrate, hydroxide, and carbonate salts were impregnated, respectively, to the top thick-film matrix at 350 degrees C, 460 degrees C (in argon), and 650 degrees C (in air), i.e., 150 degrees C above the corresponding eutectic temperatures.

Rare earth doped oxides have been intensively promoted for the last two decades to embrace the high-performance target of a ceramic–carbonate composite CO2-separation membrane, with countless incidents of exsolution.

In this study, the effects of Bi and Fe on the optical and electrical qualities of BaTiO3 made with the sol-gel method are examined. On the one hand, UV-visible spectroscopy is used to study the sample's optical behavior. This shows that the band gap energy is lower with Bi and Fe doping than with pure BaTiO3. On the other hand, an impedance spectroscopy investigation is carried out to reveal the conduction processes in the frequency range of 102 to 107 Hz and the temperature range of 450-650 K. This examination is carried out to investigate the conduction mechanisms. The conduction mechanism in the elaborated material is best described by the Overlapping Large Polaron Tunnelling model (OLPT), where the exponent s drops with temperature until reaching a minimal value, at which point it grows again. In addition, the Summerfield scaling method is used to investigate the relationship between conductivity and temperature. When the scaled curves are combined into one master curve, it shows that the time-temperature superposition principle (TTSP) is true and that Koop's concept about how the dielectric constant change with frequency is valid. So, the results give us new information about the optical and dielectric qualities of the functional barium titanate ceramics based on Bi and Fe.

The present work explores the impact of Fe insertion on the physical properties of Ba0.95Bi0.05Ti1-xFexO3 (x = 0.025, 0.050, and 0.075) prepared via sol gel method. The resulting samples crystallize in the tetragonal structure with space group P4mm and their morphological features point out the variation of the microstructure with Fe content. In turn, the dielectric constant versus temperature plot reveals the existence of two transition phases: the first one is ferroelectric-paraelectric transition phase (TF-P) and the second one is ferroelectric orthorhombic - ferroelectric tetragonal phase (TO-T). Analysis of conductivity curves using Jonscher’s augmented equation (for x = 0.025) and Jonscher’s power law (for x = 0.075) suggests the Non-Overlapping Small Polaron Tunneling (NSPT) model as a conduction mechanism.

This work provides an overview on established achievements and debatable findings involving Ca, Gd or Sm-doped ceria-based electrolytes, using Li2CO3, LiNO3 and Na2CO3 as sintering aid or as second phase. The performance of these materials is discussed considering the characteristics of the oxides and of the salts or derived second(ary) phases (e.g., alkali metal oxides and hydroxides, eutectic mixtures), extensively surveyed to identify influential parameters with respect to processing and electrical performance (e.g., melting and boiling points, thermal decomposition, hydrolysis). The analysis of published data highlights the possible contribution of additional charge carriers to the total conductivity, besides oxide-ion vacancies. Claimed bulk and grain boundary conductivity enhancements are deeply discussed, as well as advantages and limitations of impedance spectroscopy as characterization tool. Irrespective of controversial reasons, reports on unusual improvements of grain boundary conductivity sustain the possibility of advanced grain boundary engineering to enhance the performance of these materials.

The least surface electrode resistance is a key in maturing low-temperature solid oxide fuel cells (SOFCs). The current article addresses the effect of crystallinity on electrode kinetics of La0.6Sr0.4Co0.2Fe0.8O3-delta using annealing in 650-1000 degrees C range. Increased polaron activity and hence conductivity due to in-situ crystallization in 273-380 degrees C range, with highest conductivity of 9.62 Scm(-1), is evidenced the strain induced in low temperature annealed electrodes were higher sourcing the driving force for diffusion of carriers in thin films. To understand this effect comprehensively, the thin film surfaces were studied for degree of crystallinity, elemental atomic distribution, in- and cross-plane electrical performances.

Alkali metal nitrates were successfully used as starting chemicals in the production of composite CO2 separation membranes. The easy conversion of nitrates into carbonates after high temperature annealing in CO2 is confirmed using techniques like FTIR (Fourier transform infrared) or selective NO3- electrodes. This conversion shows a step like increase at temperatures in the order of 600 ?, consistent with target utilization temperatures for these membranes. A second but equally relevant consequence of this novel route is the formation of significant concentrations of oxide ions in the molten phase, able to boost the membrane performance, where the ceramic phase modest oxide ion conductivity is rate determining. At 650 ?, a CO2 separation flux enhancement in the order of 60% was reached using nitrates as starting chemicals. A deep analysis of the oxide ion content in molten phases using a variety of analytical techniques, confirmed the specific features of the nitrates as starting chemicals but also showed that even when carbonates are used as precursors, the role of oxide ions in the molten phase can increase significantly the membrane performance.

Composite membranes for CO2 separation based on CGO (Gd-doped ceria) and the eutectic mixture of Na and Li carbonates, with distinct salt content (around 20 and 40 vol%) and microstructures (starting oxide grain size in the 170-220 nm range), were prepared and tested up to 250 h, at 650 degrees C, under distinct atmospheres (CO2 gradient or fully immersed in CO2 or Ar), to elucidate degradation mechanisms. Substantial oxide grain growth (50-65%) was observed during endurance tests of membranes with higher and lower oxide content, respectively. These relative changes were unable to explain the observed stability, higher for membranes with lower salt content. Combined microstructural, structural and electrochemical analyses of samples revealed that the solu-bility of metal oxides in the molten phase plays a crucial role. While ceria is poorly soluble, Gd oxide dissolves easily under acidic conditions (high CO2, membrane feed side) but precipitates under low CO2 (sweep side). Grain growth with formation of regions with distinct Gd content (core-shell CGO grains) explain the degradation of the oxide scaffold. This information provides important guidelines on membrane design, pointing towards oxide scaffolds with large and well percolated grains, also moderate acidity of the molten phase, to improve membrane stability.

In this study, Ba0.95Bi0.05Ti1-xFexO3 was elaborated using sol gel method. The samples were sintered at 1000°C for 2 hours. They were characterized using X-ray diffraction, Scanning Electron Microscope and impedance complex spectroscopy. The prepared samples were crystallized in a tetragonal structure with space group P4mm. The average crystallite size calculated by Debye-Scherrer were found in nanoscale dimension and increases by introduction of strain. From SEM micrograph, the grain size was estimated to be in microscale dimension which indicates the presence of many grains. The incorporation of Fe3+ into Ti4+sites is proved by the apparition of several peaks corresponding to Fe-O in the characteristic band Ti-O. The dielectric constant versus temperature plot revealed the existence of two transition phases: the first one is ferroelectric-paraelectric transition phase (TF-P) and the second is transition from ferroelectric orthorhombic to ferroelectric tetragonal phase (TO-T). Dielectric and complex impedance have been studied at temperatures ranging from 450K to 650K. Jonscher’s augmented equation for x=0.025 and Jonscher’s power law for x=0.075 were used to fit ac conductivity. To represent the conduction mechanism of both compounds, the Non-Overlapping Small Polaron Tunneling (NSPT) model is appropriate.

The structural role of V in 28Li(2)O-72SiO(2) (in mol%) lithium silicate glass doped with 0.5 mol% V2O5 was assessed using Si-29 and V-51 Nuclear Magnetic Resonance (NMR), Fourier-transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopy techniques. Despite the low amount of V2O5 used, the structural information obtained or deduced from the statistical analysis of the NMR data could explain the evolution of glass properties after V2O5 addition. The XPS results indicated that all vanadium exists in 5+ oxidation state. Both the Si-29 NMR and FTIR data point toward an increase in the polymerization of the silicate network, caused by the V2O5 acting as network former, capable to form various QVn tetrahedral units (for n = 0, 1, and 2) in the glasses. These QVn units, which are similar to phosphate units, scavenge the Li+ ions and cause the silicate network to polymerize. However, in an overall balance, the entire glass network is depolymerized due to the additional nonbridging oxygens contributed by the vanadium polyhedra. The addition of vanadium causes the network to expand and increases the ionic conductivity.

The commercially ubiquitous liquid electrolytes for lithium-ion batteries have several shortcomings in terms of safety. Therefore, development of solid electrolytes, especially those that are glass-based, has been gaining increasing interest in recent times. However, the fundamental understanding of the changes in the glass structure and the corresponding changes in the properties due to the addition of dopants is necessary for the development of glasses. Therefore, here, we report a study on the role of vanadium on the glass structure, ionic conduction, crystallization behavior, and other properties of lithium silicate-based glasses (23Li(2)O-2.64K(2)O-2.64Al(2)O(3)-71.72SiO(2)) as a solid electrolyte for high-temperature Li-ion battery applications. Furthermore, we proposed a mathematical model to describe/quantify the ion-conducting channels' connectivity in glasses. The experimental glass structures were assessed using Si-29, V-51, Al-27 nuclear magnetic resonance, Fourier transform infrared, and ultraviolet-visible spectroscopy techniques. The ionic conductivity was measured by impedance spectroscopy, and the crystallization behavior was studied by optical microscopy and X-ray diffraction. Furthermore, molecular dynamics simulations were also used to gain structural insights of the glasses. In the designed compositions, the addition of vanadium decreased the overall concentration of Li+ ions. However, the results revealed that the ionic conductivity improved with the addition of vanadium in spite of a decrease in the number of charge carriers. This suggests that vanadium makes the pathways easier for the conducting ions. Thus, we conclude that vanadium modifies the conduction channels to promote better hoping of the ions from one site to another.

Oxide + salt composites can be used in CO2 and NOx separation membranes, where high oxide-ion conductivity is crucial to improve performance. Pursuing this goal, the stability of three different bismuth oxide-based electrolytes (Cu + V, Y and Yb-doped) against molten alkali carbonates (Li, Na, K) or nitrates (Na, K) was tested firing them in the 450-550 degrees C temperature range, and with endurance tests up to 100 h. A well-known ceriabased composite was used as reference (CGO - Ce0.9Gd0.1O1.95). Oxides and composites were studied by X-ray diffraction, scanning electron microscopy and impedance spectroscopy (in air, 140-650 degrees C temperature range). Bi2Cu0.10V0.90O5.35 easily reacts with molten salts. Bi0.75Y0.25O1.5 and Bi0.75Yb0.25O1.5 have higher stability against molten carbonates and complete stability against molten nitrates. The Y-doped oxide stability against the molten carbonates was enhanced changing the molten salt composition (Y2O3 additions) and using lower firing temperatures. Above all, composites based on Y or Yb-doped Bi2O3 with molten alkali nitrates showed impressive 6x or 3x higher electrical conductivity at 290 degrees C, in air (4.88 x 10(-2) and 2.41 x 10(-2) S cm(-1), respectively) than CGO-based composites (7.72 x 10(-3) S cm(-1)), qualifying as promising materials for NOx separation membranes.

Pure NiO or lithiated NiO with distinct Li/Ni atomic proportions (50/50—LN55 and 30/70—LN37) were tested as protective barrier layers (PBLs) to enhance the stability of LaCoO3 (LC) electrodes in cells with composite electrolytes (CEs) consisting of Gd‐doped ceria (CGO) and a eutectic mixture of Na and Li carbonates (NLCs). PBLs and LC layers were sequentially deposited by screen printing before firing at 700°C and 550°C, respectively, to yield symmetrical cells (LC|PBL|CE|PBL|LC). Electrochemical testing involved impedance spectroscopy measurements in air in the 500°C to 650°C range. Scanning electron microscopy combined with energy‐dispersive X‐ray spectroscopy (SEM/EDS) revealed that distinct PBLs possess uneven wetting tendency, with impact on the role of LC layers. The best electrode performance (0.55 Ω cm2 electrode area specific resistance at 550°C in air) was observed using the LN37 PBL, stable throughout endurance tests up to 200 hours. Possible electrode mechanisms consistent with experimental evidence suggest an active role of the molten phase as an intermediate provider of O2− transport between the electrode and CGO.

Due to sluggish oxygen reduction reactions, development in the solid oxide fuel cell (SOFC) field is stagnant. Two solutions, increasing the active surface or use of precious materials, can stimulate the oxygen reduction kinetics on electrodes. Thus, to gain both these benefits, the present article addressed the synthesis of high surface-area mixed oxide ionic-electronic conductor La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) using chemistry of the propellant glycine-nitrate reaction. In this study, different fuel to oxidant ratios (psi), 2.0, 2.6, and 3.0 were used to control the exothermicity of reaction and powder properties. The maximum reaction temperature of 1337 K at psi = 3.0 resulted in coarsened powder. In contrast, comparatively less exothermicity of reaction at psi = 2.0 resulted in powder with substantial Brunauer-Emmett-Teller surface area of 10.97 m(2) g(-1), with maximum powder compaction achieved at sintering of 1273 K. With optimal direct current in-plane electrical conductivity of 341 S cm(-1), H-2-temperature-programmed reduction showed excellent catalytic activity for the sample obtained at psi = 2.0. The electrochemical performance comparisons of electrodes in two different cell geometries - with and without a gold catalytic current collecting layer (Au-CCCL) - revealed the least polarization and cell resistance in the cell with Au-CCCL. The electrode area specific resistance and cell conductivity using Au-CCCL were 0.097 Omega cm(-2) and 0.15 S cm(-1), respectively.

The optimization of the performance of electrodes (oxide-based) for composite electrolytes (Ce0.9Gd0.1O1.95 + (Li0.52Na0.48)(2)CO3) is addressed in this work acting mostly on the electrode chemical nature (eg, LaCoO3, Li0.43NiO2, or LiNiO2), thickness (single and multiple screen-printed layers), and cell layer concept (with/without barrier layers between electrode and electrolyte). The cell performance and stability were analyzed by electrochemical impedance spectroscopy, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. LaCoO3 electrodes deposited on the electrolyte using an intermediate barrier layer showed a promising area specific resistance of 0.22 Omega.cm(2) at 600 degrees C. This optimized cell processing route was adopted as reference to study the endurance performance of distinct electrode materials up to 100 hours in air, at 550 degrees C, where lithiated NiO showed the best stability.

Nowadays, the commercialization of solid oxide fuel cell (SOFC) is impeded by the chemical compatibility and polarization losses in association with electrode/electrolyte interface. Thus, to minimize these difficulties, the thick film of LSCF-GDC (50:50 wt%) composite was deposited onto GDC electrolyte to form perfect LSCF-GDC/GDC structure. The chemically compatibility of LSCF-GDC upon sintering of 1000 °C was confirmed from the X-ray diffraction studies. Typically, the film with 15 μm thickness possesses the porous structure, availing the free path for oxygen diffusion. The electrochemical impedance analysis of symmetric cell with LSCF-GDC as an electrode implies the relaxation of charge transfer and electrochemical reduction reaction with temperature. The NiO-GDC (30:70 wt%) supported SOFC with GDC and LSCF-GDC as an electrolyte and cathode, respectively was tested for their performance. The cell generates the maximum powder density of 315 μWcm−2 at 500 °C.

Standard electrolyte materials (ceramic oxide-ion conductors and eutectic mixtures of alkaline carbonates) used in Solid Oxide and Molten Carbonate Fuel Cell technologies can be combined to produce composite CO2 separation membranes for a variety of applications. The model performance of these membranes is reviewed highlighting critical design and performance parameters. This model is used to build diagrams where actual membrane permeation data can be benchmarked against an ideal performance, providing immediate guidance on likely kinetic limitations. A complementary pictorial tool is also described to assess the electrical microstructure of these composites before permeation tests. The added value from combination of such diagrams in process control or membrane development is discussed.

The solution combustion synthesis is a novel approach to synthesize the nanocrystalline materials with an unexpectedly high surface to volume ratio. Thus, in present paper, La0.6Sr0.4Co0.8Fe0.2O3−δ powders have been synthesized by solution combustion synthesis route at different fuel to oxidant ratio (ψ) and its effect on different physiochemical properties have been studied. The mode of propagation of combustion reaction changed from smoldering to volume with increasing ψ. The thermal analysis shows that exothermicity increased with ψ resulting into enhanced agglomeration as confirmed from particle size distribution. Typically, the size of agglomerate varies from 0.59 to 1.56μm. The XRD and FT-IR patterns reveal that the phase pure La0.6Sr0.4Co0.8Fe0.2O3−δ is formed at the ψ=2. The TEM particles size is 25nm. La0.6Sr0.4Co0.8Fe0.2O3−δ powder shows the higher catalytic activity at about 426°C.