High Oxygen Ion Conductivity Research Articles

Processing SCNT(SrCo0.8Nb0.1Ta0.1O3-δ)-SCDC(Ce0.8Sm0.05Ca0.15O2-δ) composite into semiconductor-ionic membrane fuel cell (SIMFC) to operate below 500 °C

High power density performance at intermediate (600 °C–450 °C) temperatures (IT) must be considered in the development of solid oxide fuel cell (SOFC). A niobium and tantalum co-doped perovskite material SCNT (SrCo0.8Nb0.1Ta0.1O3-δ) can be used as a cathode for IT-SOFC due to its (H+/O2−/e−) triple conduction and promising catalysis activity. In this work, the SCNT was composited with ionic conductor SCDC(Ce0.8Sm0.05Ca0.15O2-δ) and processed as electrolyte membrane into semiconductor-ionic membrane fuel cell (SIMFC), which delivered an appreciable performance at IT, i.e., a peak power output of 1016 mW/cm2 at 550 °C and 401 mW/cm2 at 450 °C, respectively. The high performance mainly originated from the (H+/O2−) dual-ion conduction of SCNT as well as the high oxygen ion conductivity of SCDC, the SCNT-SCDC electrolyte layer adjacent to cathode have promoted the oxygen reduction reaction (ORR) with some extent because of the excellent catalysis activity of SCNT. Moreover, the on-line generated carbonate suppressed the electronic conductivity and resulted in the attractive density of SCNT-SCDC electrolyte to further contribute to the desired cell performance.

Characterizing transport mechanism of cathodic oxygen ions in SOFC by molecular dynamics

This paper investigates the oxygen ion conductivity (OIC) of cathodic materials in Solid Oxide Fuel Cells (SOFCs) by molecular dynamics simulation. Although the oxygen diffusion coefficient (ODC) is known to be one of the major factors associated with the ion conductivity of cathodic materials in the SOFC, other major process factors are remained to be further investigated so that the related oxygen ion conductivity can be fully characterized and enhanced. In order to search for significant factors that affect the OIC in cathode, the characteristics of doping effect and temperature change are simulated via Molecular Dynamics approach and the results are presented in details in this study. Based upon the modeling results, it is realized that the OIC at 773 K can be greatly improved by using the catalyst of Gd1-xBaxCoyFe1-y (GBCF). And also, the highest OIC at 973 K can be greatly enhanced by using the catalyst of La1-xSrxCoyFe1-y (LSCF).In addition, the modeling results also indicate that both the doping ratio and operating temperature are of significant factors for both ODC and OIC. Although ODC is a metrics that can be used to evaluate the mobility of oxygen ions inside the catalyst for cathode materials, it does not comprehend the characters of materials. In order to be able to fully characterize the conductivity of cathodic materials in SOFC, significant factors of OIC including the lattice structure of materials, the concentration of oxygen vacancy, and the operating temperature are fully explored in this paper for detailed system characterization.The modeling results clearly indicate that as the working temperature increasing from 773K to 973K, the largest OIC change is given by LSCF, and the smallest OIC change is provided by GBCF. Also, the ODC curve of the GBCF possesses highest ODC values in medium working temperature range due to large numbers of oxygen vacancy generated by the cathode.

X-ray nanodiffraction studies of ionically controlled nanoscale phase separation in cobaltites

Complex oxide heterostructures provide access to emergent functional and structural phases which are not present in the bulk constituent materials. In this Rapid Communication, we focus on ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{CoO}}_{3}$ (LSCO)/Gd heterostructures due to the high oxygen ion conductivity, as well as the coupled magnetic and electronic properties of LSCO, which are strongly dependent on the oxygen stoichiometry. This combination of properties enables the ionic control of the functional properties of LSCO thin films through the presence of oxygen getter layers such as Gd. We utilize x-ray nanodiffraction to directly image the nanoscale morphology of LSCO thin films as they are progressively transformed from the equilibrium perovskite phase to the metastable brownmillerite (BM) phase with increasing Gd thickness. Our studies show the coexistence of perovskite and BM phases with a critical oxygen vacancy concentration threshold which leads to the formation of extended BM filaments. In addition to lateral phase separation, we observed phase separation within the film thickness possibly due to pinning of the perovskite and BM phases by the substrate/LSCO and LSCO/Gd interface, respectively. Our studies provide a nanoscale survey of the phase separation in the cobaltites and shed light on the formation of the metastable BM phase.

The effect of A-site sublattice order on the electrical properties of Na0.5Bi0.5TiO3 compound

The A-site sublattice order of the Na0.5Bi0.46K0.04TiO2.96 (NBT-K4) compound was changed by the isovalent Na+ ions partly substituting K+ ions. The Na0.5+xBi0.46K0.04−xTiO2.96 (x = 0, 0.01 and 0.02) samples were prepared. By the AC impedance test, the grain conductivity of the Na0.52Bi0.46K0.02TiO2.96 (x = 0.02) samples is 8.23 × 10−4 S/cm at 623 K, which is around 1.65 times higher than that of NBT-K4 sample at the same tested temperature. By anatomizing relaxation spectroscopy, when the Na-doped content x in the NBT-K4 compound increases from 0 to 2 mol%, the activation energy E decreases from 0.64 to 0.57 eV. Accompany with the rise of the Na-doped content in the NBT-K4 compound, although the mobile oxygen vacancy content decreases, the oxygen vacancy diffusivity are strengthened. The higher oxygen vacancy jumping rates and lower oxygen relaxation activation energies were found in the Na-doped NBT-K4 samples, which causes the higher grain conductivity in the Na0.5+xBi0.46K0.04−xTiO2.96 (x = 0.01 and 0.02) samples. There is the higher oxygen-ion conductivity and lower activation energy in the relative A-site order of Na-doped NBT-K4 compound, which is consistent with the first principle simulation results. The investigation provides a new way to design a high oxygen-ion conductivity NBT-based oxide ion conductors and related materials.

Phase transition of doped LaFeO3 anode in reducing atmosphere and their power generation property in intermediate temperature solid oxide fuel cell

In general, transition metal-doped La0.6Sr0.4FeO3 (LSF) has been used as a cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs) because of its high mixed electronic−ionic conductivity and catalytic properties. Recently, some research groups have been investigating the doped LSF as an anode material. In this study, we evaluated the influence of dopant in LSF on anodic properties of LSF in SOFCs. Whereas Mn-doped LSF showed typical perovskite oxide structure even after reduction in hydrogen at high temperature, the LSF and Co-doped LSF exhibited phase transition partially to LaSrFeO4 and exsolution of metal particles after reduction. The phase transition and metal exsolution occurred at temperature higher than 1008 K in a reducing atmosphere. Despite the partial phase transition, the cell using Co-doped LSF anode exhibited fairly high power density of 1.33 W/cm2 at 1173 K with the lowest polarization resistance. These results may originate from the high oxygen-ion conductivity of LaSrFeO4–La(Sr)Fe(Co)O3 and the high hydrogen oxidation property of the Co–Fe particles on ceramic anode surface.

Investigation of Sr, Mg codoped Na0.5Bi0.5TiO3 oxide ion conductor prepared by spark plasma sintering

The spark plasma sintering and conventional sintering methods were used to prepare the Sr/Mg–codoped Na0.5Bi0.48Sr0.02Ti0.96Mg0.04O2.95 (NBT-SM) compounds. By the AC impedance spectrum test, the grain and total conductivity of NBT-SM sample sintered by the spark plasma sintering method (NBT-SM-SPS) at 673 K can reach 1.23 mS/cm and 0.478 mS/cm, respectively. The grain conductivity of NBT-SM-SPS sample is around 4.2 times higher than that of NBT-SM sample prepared by the conventional sintering method (NBT-SM-CS). There is higher mobile oxygen vacancy concentration and vacancy mobility capability in the NBT-SM-SPS sample, which is the reason that there is higher oxygen ion conductivity in NBT-SM-SPS sample. The aging behavior investigation was carried out at 573 K. After 48 h aging, there is around 12.3% degradation of the grain conductivity in the NBT-SM-SPS sample. The conductivity degradation should result from the decrease of the oxygen vacancy mobility capability and mobile vacancy concentration.

Gd0.2Ce0.8O1.9/Y0.16Zr0.84O1.92 nanocomposite thin films for low temperature ionic conductivity

Gd0.2Ce0.8O1.9/Y0.16Zr0.84O1.92 (GDC/YSZ) nanocomposite is synthesized by a novel hybrid chemical route, where colloidal crystalline GDC nanoparticles from continuous hydrothermal synthesis are dispersed into a metalorganic YSZ matrix precursor. The result is a mixture of metal oxides in which GDC nanoparticles are finely distributed in a continuous metalorganic polymeric matrix to be crystallized after calcination. The GDC nanoparticles reduce the temperature necessary to obtain crystalline YSZ, which is already formed at 400 °C. The nanocomposite reveals structural stability up to 800 °C when treated in both air and reducing atmosphere, showing the onset of diffusion below 1000 °C. The diffusional processes are largely dependent on the nanometric grain size, with Zr4+ diffusing abruptly towards GDC in air at 1000 °C and GDC/YSZ interdiffusion being hindered in reducing environment despite the onset temperature of 900 °C.The nanocomposite precursor is an inkjet-printable reactive water-based material, suitable for the deposition of thin films with a thickness below 100 nm after calcination at 750 °C. The crystal structure of the film reveals no interaction between GDC and YSZ but a microstrain (0.3% tensile strain for YSZ). The thin film microstructure shows a compact layer with 94% density.The nanocomposite shows high oxygen ionic conductivity at low temperatures (>5⋅10-3 S⋅cm-1 at 500 °C), low activation energy (0.55 eV), and dominant oxygen ionic conductivity even in reducing conditions (pO2 < 10–25 atm). We show that these properties arise from the large interface between the components of the composite, due to the embedding of the GDC nanoparticles in the YSZ matrix, while ZrO-CeO intermixing can be avoided and no n-type conductivity is observed even at low oxygen activities and high temperatures.

Coordination Numbers in Sm-Doped Ceria Using X-ray Absorption Spectroscopy

Sm-doped ceria has one of the highest ionic conductivities reported for rare earth-doped cerium oxides. The high oxygen-ion conductivity can be attributed to the creation of oxygen vacancies by doping and weak defect interactions between oxygen vacancies and dopants. Especially, oxygen vacancies in the nearest neighborhood to dopants decrease the conductivity due to trapping and blocking. In this work, the local structure around the Ce cations is investigated using the extended X-ray absorption fine structure. The resulting coordination numbers of cerium coordinated by oxygen are only marginally larger than in a random oxygen vacancy distribution, explaining the large ionic conductivity.

The effect of Fe‐acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3

AbstractNa1/2Bi1/2TiO3 (NBT) based ceramics are amongst the most promising lead‐free ferroelectric materials. It was expected that the defect chemistry and the effect of doping of NBT would be similar to that observed for lead based materials, however, acceptor doping does not lead to ferroelectric hardening. Instead, high oxygen ionic conductivity is induced. Nevertheless, for solid solutions with BaTiO3 (BT), which are more relevant with respect to ferroelectric applications, such a drastic change of electrical properties has not been observed so far. To rationalize the difference in defect chemistry between NBT and its solid solution 94(Na1/2Bi1/2TiO3)–0.06 BaTiO3 (NBT–6BT) compositions with different concentrations of Fe‐dopant were investigated. The study illustrates that the materials exhibit very similar behavior to NBT, and extraordinarily high oxygen ionic conductivity could also be induced in NBT–6BT. The key difference between NBT–6BT and NBT is the range of the dependence of ionic conductivity with dopant concentration. Previous studies of NBT–6BT have not reached sufficiently high dopant concentrations to observe high conductivity. In consequence, the same defect chemical model can be applied to both NBT and its solid solutions. This will help to rationalize the effect of doping on ferroelectric properties of NBT‐ceramics and defect chemistry related degradation and fatigue.

First-principles prediction of high oxygen-ion conductivity in trilanthanide gallates Ln3GaO6

ABSTRACT We systematically investigated trilanthanide gallates (Ln3GaO6) with the space group Cmc21 as oxygen-ion conductors using first-principles calculations. Six Ln3GaO6 (Ln = Nd, Gd, Tb, Ho, Dy, or Er) are both energetically and dynamically stable among 15 Ln3GaO6 compounds, which is consistent with previous experimental studies reporting successful syntheses of single phases. La3GaO6 and Lu3GaO6 may be metastable despite a slightly higher energy than those of competing reference states, as phonon calculations predict them to be dynamically stable. The formation and the migration barrier energies of an oxygen vacancy (V O) suggest that eight Ln3GaO6 (Ln = La, Nd, Gd, Tb, Ho, Dy, Er, or Lu) can act as oxygen-ion conductors based on V O. Ga plays a role of decreasing the distances between the oxygen sites of Ln3GaO6 compared with those of Ln2O3 so that a V O migrates easier with a reduced migration barrier energy. Larger oxygen-ion diffusivities and lower migration barrier energies of V O for the eight Ln3GaO6 are obtained for smaller atomic numbers of Ln having larger radii of Ln3+. Their oxygen-ion conductivities at 1000 K are predicted to have a similar order of magnitude to that of yttria-stabilized zirconia.

Long-term conductivity stability of acceptor-doped Na0.54Bi0.46TiO3−δ

Sodium bismuth titanate (NBT) based compounds have drawn significant attention because of high oxygen-ion conductivity which makes them a promising electrolyte candidate for solid oxide fuel cells. The present work investigates the long-term conductivity stability of Na0.54Bi0.46TiO3−δ doped with acceptor cations such as Mg2+ and Ga3+ in 5% H2-95% N2 environment at 600 °C for 100 h. In-situ conductivity measurement performed using impedance spectroscopy indicates a significant loss in the conductivity in the first 20 h of ageing. Following which, the conductivity appears to be stable for the next 20 h. However, a sudden gain in conductivity is seen after 40 h of ageing in reducing conditions. XRD analysis indicates the formation of Bi2O3 based compound which on further ageing decomposes to metallic Bi. SEM analysis reveals the change in grain morphology during the course of ageing with the microstructure of 100 h aged sample is shown to contain several ruptured grains. XPS results indicate the partial reduction of Ti4+ to Ti3+ which possibly leads to high n-type electronic conductivity in aged samples. The conductivity loss is attributed to the decomposition of the perovskite phase while the sudden conductivity increase after 40 h of ageing is explained through n-type electronic conduction inside the NBT lattice.

Information content of the voltage vs. current curve of a solid oxide fuel cell

Relationships are derived by means of which data on the ionic and electronic conductivity of the electrolyte employed in a fuel cell can be calculated from the U-I curves of the cell, provided that certain conditions in regard to the extent of electrode polarization are met. The capability and limitations of the resulting equations are demonstrated on the basis of known data on the ionic conductivity of gadolinia doped ceria. By applying the relationships to recently published performance data of fuel cells with CuFeO2 as electrolyte or as part of a composite electrolyte, the partial conductivities of this oxide are quantified for the first time. The results prove that CuFeO2, known to be a good mixed ionic-electronic conductor, exhibits unexpectedly high oxygen-ion conductivity under the operating conditions of a fuel cell.

Oxygen vacancy-assisted high ionic conductivity in perovskite LaCoO3−δ (δ = 1/3) thin film: A first-principles-based study

Synthesising a solid state material with high oxygen-ionic conductivity is a challenge. In this work, an integrated method of density functional theory and first-principles molecular dynamics (FPMD) simulations has been performed to investigate the oxygen-ionic conductivity in the LaCoO3−δ films. We demonstrated that, in the strained epitaxial LaCoO3−δ films, O vacancy superstructures release strain and produce the high oxygen-ionic conductivity with an activation barrier of 0.65±0.1 eV. We found that the oxygen hopping occurs in the oxygen-deficient regions of CoO mainly. We proposed a possible oxygen-ionic diffusion highway with an energy barrier of 0.55 eV by using the transition state calculations. Thus, the oxygen-deficient regions are the keys to the high oxygen-ionic conductivity in the LaCoO3−δ thin films.

Study the Structural and Optical behaviour of Conducting Polymer based nanocomposites: ZrO2-Polypyrrole Nanocomposites

Conducting polymer provides an intriguing type of environment for various inorganic structures resulting in the generation of exciting properties in the composite owing to the mutual interactions between the two and this provides interesting dimensions for the development of new multifunctional devices. ZrO2 ceramic is one of the most investigated materials for its outstanding mechanical properties ionic, conduction properties and due to its high oxygen ion conduction. In order to achieve novel properties of ZrO2 nanoparticles, nanocomposites of ZrO2 with Polypyrrole (PPy) were prepared through in-situ method using ZrO2/pyrrole dispersions. Firstly, ZrO2 nanoparticles were synthesized by co-precipitation method and then embedded in pyrrole solution for polymerization. The structural and optical properties of ZrO2/PPy nanocomposites were investigated comprehensively by X-Ray diffraction (XRD), UV-visible spectroscopy and Fourier-transform infrared spectroscopy (FTIR). XRD and FTIR highlight the presence of tetragonal phase of ZrO2 nanoparticles in nanocomposites, whereas UV-Visible and PL spectra indicate the presence of different electronic levels.

Compatibility Analysis of Chromites in Dual-Phase Composites for Oxygen Transport Membranes

An oxygen transport membrane (OTM) is a promising way of supplying oxygen from air to high temperature processes, such as gasification.[1] Several studies have demonstrated that mixed ionic-electronic conducting (MIEC) perovskites with composition AxSr1-xCoyFe1-yO3-d (A=La, Ba) have high oxygen-ionic and electronic conductivity, which are the basic requirements for an OTM material. However, these perovskites have a limited pO2 operation range, suffering irreversible chemical decomposition at pO2 values below 10-12. [2] YCrO3-based perovskites show high electronic conductivity and thermo-chemical stability both at high temperatures (~1000 ºC) and in reducing environments (pO2 ~10-20 atm). [3,4] Hence, chromites in combination with highly stable ionic-conductors (e.g. ceria or zirconia-based materials) as dual-phase composites are alternative OTM materials. However, their chemical compatibility and stability together with ion-conductors in reducing conditions, as well as their oxygen permeation in different atmospheres, needs to be further investigated. This study analyses the stability of dual-phase composites consisting of 30 vol.% perovskite Y0.8Ca0.2Cr0.8Co0.2O3 (YCCC) and 70 vol.% ionic conductors Ce0.9Gd0.1O1.95 (CGO10) or (Sc2O3)0.1(Y2O3)0.01(ZrO2)0.89 (10Sc1YSZ) as OTM materials. These dual-phase composites were sintered in air between 1200 ºC and 1450 ºC to analyze the effect of temperature on the composites, and stability tests were made by exposing the composites to humidified 5% H2/N2 at 850 ºC. SEM-EDS, XRD and thermal analyses were performed to characterize the composites and identify possible secondary phases that could detriment their performance. Oxygen flux tests were performed using 1 mm thick pellets in air/N2, air/CO2 and air/H2-3%H2O gradients at temperatures up to 950 ºC. In 10Sc1YSZ-containing samples, densification was inhibited in the studied temperature range, which might be related to evaporation of transition metals from the perovskite B site, Ca mobility and possible reactions with Zr. Metal evaporation was slightly intensified after reducing conditions, resulting in relative densities <80%. Chromium depletion from the composite and formation of Cr2O3 crystals was observed in samples sintered at 1450 ºC. On the other hand, CGO10-based composite reached ~ 90% of relative density at 1200 ºC, though CaCrO4 formation, probably related to Ca excess in the perovskite, was identified. Nevertheless, higher stability towards reducing conditions was observed. Initial oxygen permeation tests performed in dense CGO10-YCCC composite pellets show fluxes up to 0.4 Nml·cm-2·min-1 at 950ºC in air/N2 gradient. The CGO10-YCCC dual-phase composite is therefore a promising material, which is now under further optimization and development as a tubular, multilayer OTM. [1] Julbe, A. et. al. Catalysis Today, 104 (2005), 102-113 [2] Niedrig, C. et al. Journal of The Electrochemical Society, 160 (2) F135-F140 (2013). [3] Gupta, S. et al. Materials Science and Engineering, 90 (2015), 1–36. [4] Suvorov, S.A. et al. Refractories and Industrial Ceramics, 45-2 (2004), 94-99.

Structural, morphological and electrical characterization of ceria-based nanostructured thin films obtained by ultrasonic spray pyrolysis

In this work, the synthesis and the structural, morphological and electrical characterization of Ce1−xSmxO2−δ solid solution, with x=0, 0.10, 0.15, 0.20, 0.25 and 0.30mol, are reported. Nanocrystalline, homogeneous, and adherent samarium doped cerium oxide thin films were deposited onto glass (Pyrex®) substrates by a simple and cost effective ultrasonic spray pyrolysis system, at a low substrate temperature of 450°C and further annealing treatment at 500°C for 2h. For all the samples, X-ray diffraction results showed the formation of single phase and well crystalline thin films, with cubic fluorite type structure. Scanning electron microscopy analyses showed homogeneous surfaces for all the samples; from SEM micrographs crystallite sizes were found to be in the range 23–37nm. From atomic force microscopy, surface roughness in the range of 20–95nm was measured and the formation of smooth films with an average grain size of 45nm was observed. For the best sample in the solid solution, high oxygen ion conductivity of 1.71×10−1Scm−1, at 450°C, was determined by impedance spectroscopy, with an activation energy of 0.93eV. Results suggest that these films may have a potential application as electrolytes in intermediate temperature solid oxide fuel cells, IT-SOFC.

Zirconia Doped Ceria Cathodic Interlayer By Atomic Layer Deposition for Low Temperature Solid Oxide Fuel Cell

Solid oxide fuel cell (SOFC) has the advantages of high energy conversion efficiency, fuel flexibility, and environment friendliness. However, conventional SOFC also has limitations in applying to various fields due to the high operating temperature of 800-1000℃. Therefore, low temperature SOFC (LT-SOFC) (≤ 500 ℃), which can be operated at relatively low temperature, are being widely researched these days. Operation losses of LT-SOFCs, however, have to be minimized to maintain the performance even at low temperature; especially, at low temperature, the activation loss at cathode is the dominant loss due to sluggish oxygen reduction reaction (ORR). The adoption of cathode interlayer such as doped ceria has been researched as an effective method to dramatically lower the cathodic activation loss in LT-SOFCs. In this study, we used zirconia-ceria composite cathodic interlayer fabricated by atomic layer deposition (ALD) to improve the performance of SOFC at low temperature. Ceria-based materials with high oxygen ion conductivity and high oxygen surface exchange coefficient at relatively low temperatures have been widely used as cathodic interlayers for LT-SOFCs, but the relatively low chemical stability has been the practical issue. Zirconia doped ceria (ZDC), on the contrary, is known to have better catalytic properties than pure ceria with even improved chemical stability. We show that the performance of LT-SOFC can be significantly enhanced by using ZDC as cathodic interlayer. The ZDC interlayer was deposited on the cathode side surface of yttria stabilized zirconia (YSZ) electrolyte using ALD. ALD is beneficial in depositing ultra-thin film with the capability to precisely control the composition and the thickness of films. Each interlayer of 20 nm-in-thickness was deposited with different ratios of zirconia and ceria; the molar ratio of zirconia was varied at 0, 30, 50, 80, and 100 mol%, respectively. The composition of the interlayer was analyzed by X-ray Photoelectron Spectroscopy (XPS) and the electrochemical performance was measured at 450℃ by using current-voltage characterization and electrochemical impedance spectroscopy (EIS). The maximum power density of the cell with the ZDC interlayer improved by 50% compared to that of the reference cell without the interlayer, which is even higher those of the cells with zirconia-only or ceria-only interlayers. In addition, the activation resistance of the cell with ZDC was decreased by ~50% in comparison with the cell without interlayers as shown in EIS measurements.

Generating an electron-blocking layer with BaMn1-xNixO3 mixed-oxide for Ce0.8Sm0.2O2−δ-based solid oxide fuel cells

Doped ceria (DCO) has high oxygen ionic conductivity, but the electronic conduction due to the reduction of Ce4+ to Ce3+ degrades its usage as an electrolyte material for solid oxide fuel cells. Inserting an electron-blocking layer is an attractive strategy to deal with this problem. In order to generate a Ba-containing electron blocking layer for DCO-based single cells, we applied BaMn1-xNixO3 (x = 0, 0.25, 0.5) mixed-oxide as an anode precursor material, and studied the solid reactions of it with NiO and SDC under the cell preparation conditions. XRD analysis indicates that the BaMn1-xNixO3 precursors are primarily BaMnO3/BaNiO3-δ mixed-oxides. It is found that BaMn1-xNixO3 reacts with SDC to form BaCeO3 and a novel Ba2(NiMnCe)2O6 double perovskite. SEM/EDS analyses reveal that BaCeO3 tends to accumulates at the anode-electrolyte interface, as well as to fill the closed pores in the SDC electrolyte. A 4 μm-thick electron-blocking layer with BaCeO3 as the main component effectively eliminates the internal-short-circuit and enhances the performance of the cell. The open circuit voltage and peak power density of the cell with such an electron-blocking layer are 1.010 eV and 621 mW cm−2 respectively at 650 °C.

An Efficient Electron-Blocking Interlayer Induced by Metal Ion Diffusion for SOFC Based on Y-Doped Ceria Electrolyte.

To suppress the internal electronic leakage at ceria-based electrolyte, a novel electron-blocking layer consisting of doped BaCe0.8Y0.2O3-δ was fabricated in situ at the interface of Ba-containing anode and Y-doped ceria electrolyte. The anode-supported full cell based on Y0.2Ce0.8O1.9 (YDC20) electrolyte presents a remarkable peak power density of 814 mW/cm2 as well as an open-circuit voltage of 1.0 V at 650 °C, which are much higher than those of the cells with Gd0.1Ce0.9O1.95 (GDC10) electrolyte (453 mW/cm2 at 650 °C) and BaCe0.8Y0.2O3-δ|Y0.2Ce0.8O1.9 (BCY|YDC20) bilayered electrolyte (419 mW/cm2 at 650 °C). The efficient promotion of the electron-blocking interlayer with high oxygen ionic conductivity is considered as the main reason for the improved performance of YDC20-based solid oxide fuel cell. The composition and the microstructure of the electron-blocking interlayer are further analyzed by scanning electron microscope and transmission electron microscope characterizations.

Dense lanthanum silicate oxyapatite ceramics obtained by uniaxial pressing and slip casting

Lanthanum silicate oxyapatite (LSO) is a promising ion conductive ceramic material, which has higher oxygen ion conductivity at intermediate temperatures (600-800?C) compared to yttria-stabilized zirconia. Its mechanical properties, though important for any of its applications, have been scarcely reported. In this study, we compare apparent densification, open porosity and Vickers hardness of samples conformed by uniaxial pressing and slip casting and fired up to 1600?C. Colloidal processing was optimized for slip casting in order to get high green densities. At sintering temperatures higher than 1400?C, both processing routes yielded comparable densities, although uniaxially pressed samples show slightly better mechanical properties, evidencing that slip cast ones already underwent a grain growth process.