Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Award type：Award from Japanese society, conference, symposium, etc.  Country：Japan

Country：Japan

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

Perovskite oxides, ABO3, are potential catalysts for the oxygen evolution reaction, which is important in the production of hydrogen as a sustainable energy resource. Optimizing the chemical composition of such oxides by substitution or doping with additional elements is an effective approach to improving the activity of such catalysts. Here, we characterized the crystal and electronic structures of fluorine-doped La0.5Sr0.5CoO3−δ particles using scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). High-resolution STEM imaging demonstrated the formation of a disordered surface phase caused by fluorine doping. In addition, spatially resolved EELS data showed that fluorine anions were introduced into the interiors of the particles and that Co ions near the surfaces were slightly reduced by fluorine doping in conjunction with the loss of oxygen ions. Peak fitting of energy-loss near-edge structure data demonstrated an unexpected nanostructure in the vicinity of the surface. An EELS characterization comprising elemental mapping together with an energy-loss near-edge structure analysis indicated that this nanostructure could not be assigned to Co-based materials but rather to the solid electrolyte BaF2. Complementary structural and electronic characterizations using STEM and EELS as demonstrated herein evidently have the potential to play an increasingly important role in elucidating the nanostructures of functional materials.

DOI： 10.1093/jmicro/dfad031

Other Link： https://academic.oup.com/jmicro/article-pdf/73/1/22/56611404/dfad031.pdf

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

As a promising cathode material for high-energydensity Li-ion batteries, Ni-rich layered oxide cathode active chemical performance degrades rapidly upon charge/discharge cycles probably due to electrochemical/thermochemical instabilities. While cationic doping in the transition-metal site has been regarded as an effective strategy to enhance the electrochemical performance, the true impact of cation doping is not well understood. To quantitatively assess the impact of cationic doping, in this work, the electrochemical performance and lattice oxygen stability of LiNi0.82Co0.18O2, isovalent Al3+-doped LiNi0.82Co0.15Al0.03O2, and high-valent Ti4+-doped LiNi0.82Co0.15Ti0.03O2 were investigated. Despite significant improvements in electrochemical performance by Al3+ and Ti4+ doping, it was revealed that these cation dopings had no discernible effect on the lattice oxygen stability. Such information suggests that the electrochemical enhancement by Al3+/Ti4+ doping is not attributed to the stabilization of lattice oxygen. This work highlights the importance of independent and quantitative experimental evaluations on kinetic electrochemical properties and thermodynamic stability of lattice oxygen to establish rational guidelines for doping strategy toward high-energy-density and reliable cathode-active materials.

DOI： 10.1021/acsaem.2c04141

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.22-00114

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

In this work, high-temperature ionic logic gates composed of ion rectifying YSZ/La₂NiO_4+δ junctions are demonstrated.

DOI： 10.1039/d2ra00710j

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsenergylett.2c00353

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Aiming development of the fast anion conductors, we proposed a new material design using flexible molecular cation as a host cation, and demonstrated it with fluoride ion conduction in NH₄MgF₃ and (NH₄)₂MgF₄ based materials. Dominant fluoride ion conduction with relatively high conductivities of 4.8 × 10^–5 S cm⁻¹ and 8.4 × 10^–6 S cm⁻¹ were achieved at 323 K in (NH₄)₂(Mg_0.85Li_0.15)F_3.85 and NH₄(Mg_0.9Li_0.1)F_2.9, respectively. It is implied that the molecular cation in the host lattice can assist the anion conduction. Our findings suggest molecular cation-containing compounds can be attractive material groups for fast anion conductors.

DOI： 10.1038/s41598-022-09835-0

Other Link： https://www.nature.com/articles/s41598-022-09835-0

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Lattice defects significantly affect the mechanical properties of crystalline metal oxides. The materials for the components of solid oxide fuel cells (SOFCs) are no exception, and hence understanding of the interplay between lattice defects and the mechanical properties of components is important to ensure the mechanical stability of SOFCs. Herein, we performed an in situ evaluation of the temperature and P(O2) dependence of the elastic moduli of La2NiO4 (LN214), a candidate for the cathode material of SOFCs, using the resonance method to understand the influence of interstitial oxygen on its elastic properties. Above 873 K, both the Young’s and shear moduli of LN214 slightly decreased with increasing P(O2), suggesting that these elastic moduli are correlated with interstitial oxygen concentration and decreased with increasing interstitial oxygen. We analyzed the influence of interstitial oxygen on the Young’s modulus of LN214, based on numerically obtained lattice energy. The P(O2) dependence of the Young’s modulus of LN214 was found to be essentially explained by variation in the c-lattice constant, which was triggered by variation in interstitial oxygen concentration. These findings may contribute to a better understanding of the relationship between lattice defects and mechanical properties, and to the improvement of the mechanical stability of SOFCs.

DOI： 10.3390/met11121889

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.21-00033

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/aenm.202101005

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/aenm.202101005

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsaem.0c02447

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>The oxygen vacancy containing Li-rich cathode Li_1.2Ni_0.13Co_0.13Mn_0.54O_2−δ showed excellent energy density retention.</p>

DOI： 10.1039/d0ta09521d

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsaem.0c01303

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

Designing composite electrodes with optimal microstructure, composition, and choice of active material (AM) as well as solid electrolyte (SE) is critically important for the development of high-performance solid-state batteries (SSBs). To optimize AM loading, which includes loading amount, composition, and dispersion state, and to maximize AM utilization in composite SSB electrodes, we need to precisely understand how the AM loading affects electrochemical reactions taking place in the electrodes. Here, using computed tomography combined with X-ray absorption near edge structure spectroscopy (CT-XANES), we performed operando three-dimensional (3D) observations of electrochemical reactions in composite SSB electrodes with different AM loading amounts to understand the influence of the AM loading on the electrochemical reactions. In the composite electrode with higher AM loading amount, the lower reacted regions were mainly found at the inner parts of the aggregated AM regions. It was suggested that such a reaction distribution resulted from the slow intergranular ion transport between AM particles. In the composite electrode with lower AM loading amount, the electrochemical reaction progressed more homogeneously compared to the one with higher loading. This is probably because the lower AM loading mitigated the AM aggregation and decreased the number of high-resistance AM-AM interfaces that Li ions must pass through. Such a reaction distribution formation due to the slow ion transport between the AM particles can be a serious restriction in composite SSB electrodes. This is in marked contrast to conventional liquid-based lithium ion battery (LIB) electrodes, in which a majority of AM particles can directly exchange Li ions with the surrounding liquid electrolyte. Therefore, the optimal design for composite SSB electrodes can significantly differ from that for liquid-based LIBs. Our analysis technique can provide valuable information to rationally design optimal composite electrodes, and hence we expect that this technique contributes to the further development of high-performance SSBs.

DOI： 10.1021/acsaem.0c01186

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s41918-020-00062-7

Other Link： http://link.springer.com/article/10.1007/s41918-020-00062-7/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.tsf.2019.137433

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The protonation mechanism in Mn-doped CaZrO3 (CZM), which involves a direct hydrogen dissolution from the surrounding H-2 gas, was investigated by thermogravimetry (TG) and X-ray absorption spectroscopy (XAS). The TG results implied the formation of oxygen vacancies in a H-2 atmosphere. The Mn Kedge XAS spectra indicated a reduction of the Mn ions and local structure variations around the Mn ion, but the Zr K-edge spectra were independent of the surrounding atmosphere. The amount of oxygen vacancies was smaller with respect to the reduction of the Mn ions, suggesting direct dissolution of hydrogen. Unlike many typical perovskite-type proton conductors, protonation by direct dissolution of hydrogen and not hydration was the predominant reaction in Mn-doped CaZrO3. Our experimental results demonstrated that the hydration reaction was suppressed because the oxygen vacancy was stable in the distorted ZrO6 symmetry in the CaZrO3 crystal host, whereas protonation proceeded by the direct dissolution of hydrogen being stabilized near the Mn ions in the interstitial sites at the distorted MnO6 octahedral symmetry. The experimental results showed that the structural configurations around dopants play important roles in the stabilization of protons in perovskite-type CZM materials. We demonstrated a new group of proton conductors that can overcome issues with conventional proton conductors by utilizing the direct hydrogen dissolution reaction.

DOI： 10.1021/acs.jpcc.9b03897

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The cover feature of Batteries &amp; Supercaps, Vol. 2 Issue 8

DOI： 10.1002/batt.201900018

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsami.9b03053

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Herein, high-valence-state Mn(v) oxide, barium manganate(v) (Ba-3(MnO4)(2)), is examined as an anode electrocatalyst of a H+-conducting solid oxide steam electrolysis cell (H-SOEC). Ba-3(MnO4)(2) comprises C-3v-symmetric MnO43- oxo-anions with three long Mn-O bonds and one short Mn-O bond at room temperature. Ba-3(MnO4)(2) caused a conductivity jump by one order of magnitude at approximately 600 degrees C owing to the antiferromagnetic/paramagnetic phase transition, accompanied by a shape change of the tetrahedral MnO43- anions from C-3v to T-d symmetry, as confirmed by the electrical conductivity measurements and the extended X-ray absorption fine structure at an elevated temperature. Hence, the Ba-3(MnO4)(2) base anode of the H-SOEC exhibited improved performance, with anode polarization resistances being lower than those of Sm0.5Sr0.5CoO3, a well-known H-SOEC anode material. Impedance analysis in terms of oxygen and water partial pressure revealed that the superior performance of the Ba-3(MnO4)(2) base anode can be attributed to the extended reaction area. Since abundant unoccupied 3d states of the high-valence-state Mn5+ cations are favorable for charge transfer interactions with water electron donors, thereby facilitating water adsorption, the oxygen evolution reaction could occur directly over the electrode surface, and thus the reaction sites were not limited to the gas-electrode-electrolyte triple phase boundary.

DOI： 10.1039/c9qi00253g

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

In this study, dense sintered polycrystalline compacts (relative density: >95%)of Tysonite-type fluoride ion conductor, La Ba F , with different grain sizes were prepared by applying the spark plasma sintering method, and their electrical conductivities were evaluated in order to understand the influence of microstructures on the ionic conductivity. The conductivity of the prepared compacts increased when increasing the sintering temperature up to 1273 K, and showed the highest value, e.g. 7.1 × 10 S cm at 300 K, which was much higher than the reported values for sintered compacts of the same material. These were because the application of the spark plasma sintering technique enabled us the high densification of the sintered compacts and the increase in the sintering temperature enhanced the grain growth resulting in the decrease in the grain boundary resistance. The inhibitory effect of grain boundary on the ionic conduction was not significant when the density of the polycrystalline compacts was sufficiently high. On the other hand, when the sintering temperature was higher than 1273 K, small pores were formed along the grain boundaries and the conductivity was degraded with increasing the sintering temperature. Such a decrease in the conductivity could be interpreted by the increase in the grain boundary resistance due to the pore formation by the high temperature sintering. This work demonstrated that, for sintering polycrystalline (La,Ba)F -based fluoride ion conductors, there is an optimum preparation condition to achieve the optimum microstructure i.e. high density, large grain size, and clean grain boundary, for high fluoride ion conduction. 0.93 0.07 2.93 3 −5 −1

DOI： 10.1016/j.ssi.2019.05.023

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. The electrochemical properties of the composite electrodes of LaNi 0.6 Fe 0.4 O 3−δ -Ce 0.9 Gd 0.1 O 1.95 in various compositions were measured by electrochemical impedance spectroscopy as a function of temperature and p(O 2 ). The enhancement of area-specific conductivity, σ E , was found higher than that of the single-phase porous LaNi 0.6 Fe 0.4 O 3−δ electrode. σ E greatly depends on their volume ratio, where σ E increases with the increase of the volume fraction of Ce 0.9 Gd 0.1 O 1.95 phase up to 50%. Above 50% of the volume ratio, σ E decreases which could be due to the loss of its surface area density and connectivity between LaNi 0.6 Fe 0.4 O 3−δ particles. The enhancement degree of σ E was evaluated using the transmission line model for the porous-mixed ionic and electronic electrodes. The calculated model is close to the measured σ E , showing that the enhancement of σ E is not only because of the enhancement of ionic conducting pathways but also possibly due to the decrease of the surface reaction resistivity upon contact with the Ce 0.9 Gd 0.1 O 1.95 .

DOI： 10.1016/j.ssi.2018.12.023

Scopus

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c8ta12484a

Language：English   Publishing type：Research paper (scientific journal)  

In sheet-type all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte, composite electrodes consist of active material, solid electrolyte, conductive additive material, and binder. Thus, they form a three-dimensional ionic and electronic conduction pass. In composite electrodes, the reaction inhomogeneity derived from their morphology exerts a remarkable effect on battery performance. In this study, we prepared sheet-type composite electrodes for all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte using different binder materials with different solvents and investigated the reaction distribution within the electrodes using the 2D-imaging X-ray absorption spectroscopy. Thus, we demonstrated that the dominant factor of the reaction distribution formation is the ionic conduction, depending on the structure of the composite electrode, and that the structure is influenced by the combination between the binder and the solvent used in the preparation of the sheet-type composite electrode.

DOI： 10.1021/acs.jpcc.8b09569

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10008-018-4102-0

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this study, the efficiency of ionic transport through proton-conducting ceramic electrolytes for energy conversion applications was discussed while considering the energy losses caused by the mixed ionic and electronic conduction and by the ionic transport resistance. It was shown that high energy efficiency cannot be expected with an extremely thin electrolyte because of the significant energy loss due to the internal current leakage. In the case of a fuel cell with a BaZr0.8Y0.2O3- electrolyte operating at 873 K, the maximum energy efficiency was estimated to be only 82% when the product of the external current density and the electrolyte thickness was 1.7 x 10(-3) A cm(-1). The energy efficiency for the ionic transport in BaZr0.8Y0.2O3- was compared with those for typical oxide ion conductors, i.e. yttria stabilized zirconia and Ce0.9Gd0.1O1.95-, under various fuel cell operating conditions. BaZr0.8Y0.2O3- can provide higher energy efficiency than the oxide ion conductors at lower temperatures and under higher current conditions. For the efficient operation of fuel cells using a proton-conducting ceramic as an electrolyte, lower operating temperatures below 873 K is preferable from the viewpoint of energy loss in the electrolyte. The influence of the partial conductivity variation on the energy efficiency was also discussed. It was shown that not only the increase of ionic conductivity but also the decrease of electronic conductivity could improve the energy efficiency if the electrolyte thickness can be optimized. This means that decreasing electronic conductivity as well as increasing proton conductivity can be an effective strategy to develop highly efficient proton conductors for energy conversion applications.

DOI： 10.1039/C8TA05373A

Web of Science

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The effect of A-site cation ordering on the cathode performance and chemical stability of A-site cation ordered LaBaCo2O5+δ and disordered La0.5Ba0.5CoO3-δ materials are reported. Symmetric half-cells with a proton-conducting BaZr0.9Y0.1O3-δ electrolyte were prepared by ceramic processing, and good chemical compatibility of the materials was demonstrated. Both A-site ordered LaBaCo2O5+δ and A-site disordered La0.5Ba0.5CoO3-δ yield excellent cathode performance with Area Specific Resistances as low as 7.4 and 11.5 Ω·cm2 at 400 °C and 0.16 and 0.32 Ω·cm2 at 600 °C in 3% humidified synthetic air respectively. The oxygen vacancy concentration, electrical conductivity, basicity of cations and crystal structure were evaluated to rationalize the electrochemical performance of the two materials. The combination of high-basicity elements and high electrical conductivity as well as sufficient oxygen vacancy concentration explains the excellent performance of both LaBaCo2O5+δ and La0.5Ba0.5CoO3-δ materials at high temperatures. At lower temperatures, oxygen-deficiency in both materials is greatly reduced, leading to decreased performance despite the high basicity and electrical conductivity. A-site cation ordering leads to a higher oxygen vacancy concentration, which explains the better performance of LaBaCo2O5+δ. Finally, the more pronounced oxygen deficiency of the cation ordered polymorph and the lower chemical stability at reducing conditions were confirmed by coulometric titration.

DOI： 10.3390/ma11020196

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The electrical conductivity (sigma) and oxygen diffusivity of the typical Ruddlesden-Popper oxide Sr3Fe2O7-delta were investigated with the variation of oxygen partial pressure, P(O-2), and temperatures, and thus the results were discussed based on its defect structure. The a increases with the increase of P(O-2) and a positive slope of log sigma depend on P(O-2) is close to 1/4 with the small polaron conduction, where the mobility mu(p) are between 0.01 and 0.0(2) cm(2) V-1 s(-1) regardless of temperature and P(O-2). Oxygen diffusivity derived from the electrical conductivity relaxation (ECR) after an abrupt change of P(O-2) increased with the increase P(O-2) and temperature. A new pulse isotope O-18-O-16 exchange (PIE) at 623-773 K was carried in order to rapidly determine the tracer oxygen surface reaction coefficient. The numerical relationship of oxygen diffusivity measured by ECR and PIE measurements was successfully established by the ambipolar diffusion theory and defect chemical analysis.

DOI： 10.1016/j.ceramint.2017.08.211

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Relevant factors affecting an oxygen reduction reaction (ORR) in a heterostructure electrode comprising a Ce09Gd0.1O1.95 porous layer on LaNi0.6Fe0.4O3 (-) (delta) film electrode were evaluated using electrochemical impedance spectroscopy and isotope depth profile analyses. Despite the LaNi0.6Fe0.4O3 (-) (delta) film - porous Ce0.9Gd0.1O1.95 electrode having higher interfacial conductivity, sigma(E), compared to a bare LaNi0.6Fe0.4O3 (-) (delta) film electrode, sigma(E) behavior as a function of p(O-2) was similar to each measured temperature. This exhibits a good correlation with the isotopic oxygen depth profile analysis where the evaluated surface oxygen exchange coefficient, k*, showed enhancement compared to bare LaNi0.6Fe0.4O3 (-) (delta) film and exhibited the same behavior on p(O-2). Based on the analyses, there are two plausible reasons for this enhancement: (a) the formation of triple phase boundaries at the junction of LaNi0.6Fe0.4O3 (-) (delta) film, porous Ce0.9Gd0.1O1.95, and gas phase, where the incorporation process during an ORR process takes place via the porous Ce0.9Gd0.1O1.95; and (b) a modification of the subsurface layer just below the film surface where the presence of diffused Ce and Gd appears to accelerate the ORR process.

DOI： 10.1016/j.ssi.2017.10.007

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In order to elucidate the electronic conduction mechanism and defect chemical model of LaNi0.4Fe0.6O3 - delta at high temperatures, electrical conductivity (sigma), Seebeck coefficient (S), and oxygen vacancy concentration (delta) of LaNi0.4Fe0.6O3 (-) (delta) were measured as a function of oxygen partial pressure (p(O-2)) and temperature. Relatively large a and small positive S values are observed, which indicates the contribution of ionic conduction is negligibly small to thermoelectric power and the major electronic carrier is a hole. From the analysis of a and S, it is expected that the LaNi0.4Fe0.6O3 - delta has small polaron hopping conduction mechanism where an electron is localized on the Fe. The slope of delta vs p(O-2) shows a minimum value near the stoichiometric composition and the delta increases as p(O-2) reduces and temperature increases. The relationship between delta vs. log p(O-2) is analyzed by a localized electron model and the behavior of the oxygen nonstoichiometry of LaNi0.4Fe0.6O3 (-) (delta) can be explained.

DOI： 10.1016/j.ssi.2017.08.014

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

It is well known and accepted that oxygen nonstoichiometry, the deviation of oxygen content from the stoichiometric composition, significantly affects electrochemical properties of functional oxides. Therefore, it is important to understand the defect formation mechanism and the influences of defect species on electrochemical properties. In this paper, layered perovskite type La2NiO4-based oxides were investigate'd as a model system. Oxygen nonstoichiometry was evaluated by thermogravimetry and coulometric titration and analyzed based on defect chemistry. To understand the governing factor for interstitial oxygen formation, thermochemical deformation and electronic structural variation were evaluated by in -situ X-ray diffraction measurement and soft X-ray absorption spectroscopy. While La2NiO4+delta can deform flexibly to accept interstitial oxygen, more than 90% of interstitial sites are not occupied under equilibrium state. This strongly indicates the restriction due to crystal structure is not dominant for interstitial oxygen formation. Ni L-edge and 0 K-edge spectra reveal that lattice oxygen works as a sink/source of electronic carrier for the interstitial oxygen formation. These analyses indicate that the interstitial oxygen formation in La2NiO4+delta is mainly limited by the electronic structural restriction. This hypothesis is supported by the fact that electron doping increases the equilibrium concentration of interstitial oxygen. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.85.552

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Proton concentration in BaZr0.9Y0.1O3- (delta) was measured by highly-accurate thermogravimetry as functions of temperature and p(H2O), and thermodynamic properties of the proton dissolution were discussed. Apparent Gibbs free energy change of the proton dissolution reaction changes with proton concentration even at a constant temperature. This means the proton dissolution in BaZr0.9Y0.1O3- (delta) is not ideal-solution-like. The deviation from the ideal solution became more significant with increasing temperature i.e. decreasing the proton concentration. This indicated the interaction between oxygen vacancies or electron hole, dopant-defect interaction, or lattice deformation may cause the proton dissolution in BaZr0.9Y0.1O3- (delta) especially at higher temperature. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2017.02.004

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La2NiO4+ dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773K under an atmospheric pressure of 100ppm O-2/He, 0.1% O-2/He, and 1% O-2/He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni3d-O2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study.

DOI： 10.1002/cssc.201700237

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

In this work, we directly observed the reaction distribution formed in a composite cathode of the all-solid-state lithium-ion battery (ASSLIB) LiCoO2/Li2.2C0.8B0.2O3|Li2.2C0.8B0.2O3|PEO|Li during charging by using the two-dimensional X-ray absorption spectroscopy (2D-XAS) at Co K-edge. The two-dimensional mapping of the state of charge in a composite cathode indicated that the reaction distribution was formed during charging process in the in-plane direction due to the disconnection in electron pathway at cracks. It was experimentally confirmed that the 2D-XAS technique was a useful tool for evaluating the reaction distribution in a composite cathode of an ASSLIB and investigating the influence factors for the formation of the reaction distribution. (C) 2017 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.16253

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Two-dimensional X-ray absorption spectroscopy was carried out to observe the reaction distribution in a LiCoO2 composite electrode from the shift of the peak top energy in Co K-edge X-ray absorption spectra. The influence of ionic transportation to the inhomogeneous reaction was evaluated by using the model electrode, which sandwiched the LiCoO2 composite electrode between an aluminum foil and a polyimide ion blocking layer. When the model electrode was charged with the currents of 6, 9, and 12 mA cm(-2), the observed capacities were 51, 20, and 12 mAh g(-1) and the charged areas visualized from the shift of the peak top energy in Co K-edge X-ray absorption spectra were formed within ca. 700, 500, and 200 mu m from the edge of the electrode, respectively. The observed reaction distribution indicated that the electrochemically active region decreases with increasing the current density because of the large potential loss of the electrochemical processes.

DOI： 10.1021/acs.jpcc.6b12133

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Change of the lithium chemical potential in a crystalline LiCoO2 with the application of a mechanical stress was discussed based on the results of electromotive force (emf) measurements between preferentially-oriented LiCoO2 films on Li0.33La0.55TiO3 solid electrolytes under mechanical stress. [001]-oriented LiCoO2 films with different degrees of orientation were prepared, and it was investigated how the direction of mechanical stress to the crystal lattice affects emf. It is found that emf emerged when mechanical stress was applied. The magnitude of emf under stress was dependent not only on the magnitude of applied stress but also the degree of the film orientation. This clearly demonstrated that the crystal orientation, i.e. the direction of mechanical stress to the crystal, affects the lithium chemical potential. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2016.10.011

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

High-temperature proton conductors gained ever-increasing interest as electrolyte materials alternative to oxygen-ion conductors due to their high conductivity associated with low activation energy at reduced temperatures. In this study, we reported our findings on chemically stable, easily sintered and highly proton-conductive BaZrO3 oxides with Bi2O3 and In2O3 co-addition as electrolyte materials for proton conducting solid oxide fuel cells (H-SOFCs). Among the composition series, BaZr0.75In0.2Bi0.05O3-delta (BZIB5) exhibited the improved sinterability and good conductivity. Correspondingly, high-temperature gravimetry results indicated that the concentrations of protonic defect and oxygen vacancy strongly depended on P(H2O) and temperature rather than P(O-2). Importantly, single cells with 12-mu m-dense BZIB5 electrolyte films were successfully fabricated, and achieved high performance with the maximum power density of 0.34 Wcm(-2) at 700 degrees C. The encouraging results demonstrated that BZIB5 is a promising candidate as the electrolyte material for high performance H-SOFCs. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jeurceramsoc.2016.05.027

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The oxygen nonstoichiometry of large oxygen-deficient Ruddlesden-Popper oxides LaxSr3-xFe2O7- (LSFO7-x) (x=0, 0.25, 0.5) was measured by the high-temperature gravimetry and the coulometric titration. In the composition series, the P(O-2) dependencies exhibited typical plateaus at =(2-[LaSr]2. Meanwhile, La0.5Sr2.5Fe2O7- showed the smallest oxygen nonstoichiometry and was the most thermochemically stable compound against P(O-2), temperature, and the La content. Based on the defect equilibrium model and the statistical thermodynamic calculation derived oxygen nonstoichiometric data, the substitution of La for Sr-site can promote the forward reaction of oxygen incorporation, the backward reaction of the disproportionation of the charge carriers, and oxygen redistribution between the O1 and O3 sites, resulting in the reduction of oxygen-deficient and the lower decomposition P(O-2). The obtained thermodynamic quantities of the partial molar enthalpy of oxygen, hO-hO degrees and the partial molar entropy of oxygen, sO-sO degrees, calculated from the statistical thermodynamic calculation are in good agreement with those using the Gibbs-Helmholtz equation.

DOI： 10.1111/jace.14410

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

In-situ simultaneous measurement technique of soft X-ray absorption and X-ray emission spectroscopy, which was available for atmospheric pressure and high temperature, was developed. This technique is expected to provide direct information about electronic structures, both occupied and unoccupied pDOS, of functional materials under controlled atmospheric and temperature conditions. In this work, this technique was applied to simultaneously measure O K-edge X-ray absorption and X-ray emission spectra of LaCoO3-based oxides under various oxygen partial pressure and temperatures. Clear O K-edge spectra could be obtained even in 1 bar of 100 ppm O-2-He, 0.1%O-2-He and 1%O-2-He atmospheres below 873 K. The changes of the O K-edge X-ray absorption and X-ray emission spectra due to the changes of oxygen partial pressure and temperature were discussed in terms of changes of defect concentrations and spin states of the oxides. Availability of the developed in-situ simultaneous spectroscopic technique was successfully demonstrated. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.84.793

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The oxygen nonstoichiometry of the perovskite-type oxide, LaNi0.6Co0.4O3-delta, was measured at various temperatures and oxygen partial pressures (p(O-2)) by high temperature gravimetry and coulometric titration. The oxygen nonstoichiometry appeared independent of p(O-2) in the range of 10(-4) bar &gt; p(O-2), which was in good agreement with the tendency of lattice parameter determined by the high-temperature X-ray diffraction (HT-XRD). The oxygen nonstoichiometry behavior was analyzed using the defect equilibrium model assuming delocalized electron. In addition, the diffusion coefficient, D*, and the surface reaction rate constant, k*, were obtained by the isotope exchange and secondary ion mass spectrometry. The Dv estimated from the D* showed similarity with those reported for other perovskite oxides which supported the reliability of delta determined in this work. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2016.05.005

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Oxygen nonstoichiometry in the Ruddlesden-Popper type oxides LaxSr3 (-) xFe2O7 - (delta) (x = 0, 0.25 and 0.5) was determined by means of the high temperature gravimetry and the coulometric titration. The measurements were carried out in the temperature range between 773 and 1073 K and the P(O-2) range between 10(-40) and 1 bar. The P(02) dependencies of the oxygen nonstoichiometry exhibited typical plateaus at delta similar to 1.0 for Sr3Fe2O7 (- delta), delta similar to 0.875 for La0.25Sr2.75Fe2O7 (- delta), and delta similar to 0.75 for La0.5Sr2.5Fe2O7 - (delta), where the average oxidation state of iron is 3+. In the LaxSr3 (-) xFe2O7 - (delta) series, La0.5Sr2.5Fe2O7 - (delta) showed the smallest oxygen nonstoichiometry and was the most thermochemically stable compound against on P(O-2), temperature, and the La content. Thermodynamic quantities of the partial molar enthalpy of oxygen, h(O) - h(O)degrees, and the partial molar entropy of oxygen, s(O) - s(O)degrees, were calculated from measured nonstoichiometric data. The behavior of oxygen nonstoichiometry and thermodynamic quantities indicates that the ideal-solution-like defect formation is established (La,Sr)(3)Fe2O7 in the oxygen deficient region. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2016.01.016

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this paper we try to tailor the chemical stability of cobalt-rich perovsldte Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) by B-site doping Sb. The chemical stability of Ba0.5Sr0.5Co0.8Fe0.1Sb0.1O3-delta (BSCFS) was investigated by studying the oxygen nonstoichiometry, crystal structure and oxidation state by means of coulometric titration, high temperature X-ray diffraction (HT-XRD) and soft-X-ray absorption spectroscopy (s-XAS) in Various oxygen pressure (p(O-2)) and temperatures. The results prove that chemical stability of BSCFS is successfully improved in intermediate temperature solid oxide fuel cell working condition owing to Co valence change which is controlled by high valence cation doping. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2016.01.018

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Two LiCoO2 dense film electrodes were prepared on both surfaces of a lithium ion-conducting glass ceramics, and electromotive force measurements were, preformed between the film electrodes under mechanical compressive and tensile stresses by four-point bending tests. Electromotive force appeared immediately after applying the stress and disappeared after releasing the stress. The larger stress was applied, the larger electromotive force was observed. These results clearly demonstrated that the lithium chemical potential in the LiCoO2 electrode varies under mechanical stress. The influence of the mechanical stress on the lithium chemical potential was discussed based on the relation between the CoO2 interlayer distance and the lithium concentration in LiCoO2. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2015.09.009

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We analyzed the X-ray absorption spectra (XAS) of Co 2p orbital in LaCoO3 by using density functional theory method to understand the temperature effect on the electronic structures, especially low-spin (LS), intermediate-spin (IS), and high-spin (HS) states of Co3+ ion. We considered the lattice change, thermal excitation of electrons, and displacement of atoms from equilibrium position in LaCoO3 as a temperature effect in this study. We observed negligible change in the shape of Co 2p XAS of LaCoO3 for each LS, IS, and HS state associated with the lattice expansion due to temperature increase, while different spectral features for LS, IS, and HS states were observed. The change of spectra observed by in situ XAS measurement of LaCoO3 at Co L-II- and L-III-edges would be due to the increase in HS and decrease in LS and IS at higher temperature. In addition, the geometry change by thermal displacement of atomic position was analyzed by using first-principles molecular dynamics calculation. Our results indicated that the electronic structure is sensitively changed by the change of Co-O bond distance due to the displacement of atoms from the equilibrium position at studied temperature when the spin state was IS. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

DOI： 10.1016/j.ssi.2015.08.017

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The interstitial oxygen formation mechanism in La2NiO4-based oxides was studied using soft X-ray absorption spectroscopy. When the interstitial oxygen concentration increased, the pre-edge peak of O K-edge spectra increased while Ni L-edge spectra was almost invariant. These spectral changes strongly suggest the significant contribution of ligand oxygen to interstitial oxygen formation by providing/accepting electronic charge carriers. The variation of the integrated peak intensity of the O K-edge strongly suggests that interstitial oxygen formation is determined by the equilibrium unoccupied pDOS of ligand oxygen. From this hypothesis, we propose that modulating the electronic structure is the key to control the capability of interstitial oxygen formation in La2NiO4-based oxides.

DOI： 10.1039/c5cp05993c

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

Effects of mechanical stress on lithium chemical potential in electrodes and electrolytes for all-solid-state lithium ion batteries were investigated. Dense film electrodes of LiCoO2 or LiMn2O4 were symmetrically deposited on both surfaces of a plate of various solid state lithium ion conductors, such as Li0.29La0.57TiO3, Li2La3Zr2O12 and Li1+x+yAlx(Ti,Ge)(2-x)SiyP3-yO12. Mechanical stress was applied to the specimen by four points bending tests while measuring electromotive force (EMF) between the two electrodes. EMF proportional to the applied stress was observed. EMF was significantly dependent on the electrode material, but was almost independent of the electrolyte material. These results indicated that lithium chemical potential varied under mechanical stress both in the electrode and electrolyte but the influence of mechanical stress appeared more notably in the electrode than the electrolyte. The lithium chemical potential changes in the electrode and the electrolyte under mechanical stress were discussed based on the idea of local equilibrium. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.83.894

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Electrochemical properties of LaNi0.6Fe0.4O3-delta film electrodes were measured by electrochemical impedance spectroscopy as functions of temperature, T, oxygen partial pressure, p(O-2), and thickness of the film electrode to determine the rate determining step of the oxygen reduction process. From its chemical capacitance, the oxygen reduction process was limited on the surface, which had good agreement with the isotope exchange depth profile measurement. It was also confirmed that the different thickness of the film electrode showed the total capacitance completely belong to the oxygen nonstoichiometric change of the LNF film electrodes. (C) 2015 The Electrochemical Society. All rights reserved.

DOI： 10.1149/2.0391514jes

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Oxygen nonstoichiometry of the Ruddlesden-Popper oxide Sr3Fe2O7-delta was measured at intermediate temperatures (773-1073 K) by coulometric titration and high temperature gravimetry. The oxygen non-stoichiometric behavior was analyzed using the defect equilibrium model with localized electrons. From the defect chemical analysis, estimated oxygen vacancy concentration at the O3 sites increases and at the O1 sites decreases with the increasing temperature. This characteristic behavior is considered to be caused by the redistribution of oxygen and vacancies between the O1 and O3 sites. The obtained thermodynamic quantities of the partial molar enthalpy of oxygen, h(o) - h(o)degrees, and the partial molar entropy of oxygen, s(o) - s(o)degrees, calculated from the Gibbs-Helmholtz equation are in good agreement with those from the statistical thermodynamic calculation based on the defect equilibrium model, indicating that the proposed defect equilibrium model is reasonable.

DOI： 10.1039/c4cp05719h

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In order to understand the behaviour of the crystal lattice deformation induced by the interstitial oxygen formation in La-2(Ni0.9M0.1)O4+delta (M = Fe, Co, and Cu), thermogravimetry, coulometric titration, and high temperature X-ray diffraction measurements were carried out in the temperature range between 873 and 1173 K and the P(O-2) range between 10(-24) and 1 bar. Compared with non-doped La2NiO4+delta, La-2(Ni0.9Fe0.1)O4+delta and La-2(Ni0.9Co0.1)O4+delta have more interstitial oxygen while La-2(Ni0.9Cu0.1) O4+delta has less. The crystal structure at high temperatures was analyzed assuming the tetragonal symmetry, I4/mmm, for all compositions. With increasing interstitial oxygen concentration, the lattice parameter perpendicular to the perovskite layer increased and that parallel to the perovskite layer decreased. Consequently, the change of the cell volume by the interstitial oxygen formation was small, meaning that macroscopic chemical expansion was small. Chemical and thermal deformation behaviour could be explained by assuming a linear relation of the lattice constants to T and delta. Apparent and true thermal expansion coefficients and chemical expansion coefficient were calculated and compared with oxygen deficient perovskite-and fluorite-type oxides. It was found that the chemical expansion coefficients of La2NiO4-based oxides which are induced by the formation/annihilation of interstitial oxygen are smaller than those of perovskite- and fluorite-type oxides which are induced by the formation/annihilation of oxygen vacancies.

DOI： 10.1039/c5ta01504a

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

To evaluate the electrochemical and electronic properties of strained film specimen, La1-xSrxCoO3-delta (x = 0.4, 0.5) films were evaluated by means of electrochemical impedance spectroscopy and electrical conductivity measurement. Dense polycrystalline La1-xSrxCoO3-delta films were fabricated on a polycrystalline Ce0.9Gd0.1O1.95 substrate by a pulsed laser deposition technique. Obtained film was (001) oriented in the pseudo-cubic perovskite unit cell and tensile strained along out-of-plane direction. It was confirmed that oxygen nonstoichionnetric behavior of the film was different from that of bulk La1-xSrxCoO3-delta and analyzed by assuming localized and itinerant electronic states. Localized electron model with Co2+, Co3+ and Co4+ shows good agreement with observed oxygen nonstoichiometry of the film. The electrical conductivity of La1-xSrxCoO3-delta films show positive temperature coefficient like semiconductors although that of the bulk La1-xSrxCoO3-delta shows a negative temperature coefficient like metals. This indicates localized electron for the La1-xSrxCoO3-delta film and itinerant electron for the bulk La1-xSrxCoO3-delta. Although detail mechanism of the strain effect is not fully understood, both oxygen nonstoichiometric and electronic conduction behaviors of the film could be explained by assuming localized electronic state. Plausible electronic structure of the film was proposed and compared with that of bulk La1-xSrxCoO3-delta. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.82.884

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The orthorhombic-tetragonal structural phase transition behaviors of Pr2NiO4 (+) (delta) and Nd2NiO4 (+ delta) were investigated by DSC and TG-DTA under controlled oxygen partial pressure, P(O-2), and their difference was discussed. A discrete weight variation originating from the variation of oxide ion content, Delta delta, was observed during the phase transition in both Pr2NiO4 (+) (delta) and Nd2NiO4 (+) (delta). The Delta delta of Pr2NiO4 (+) (delta) was larger than that of Nd2NiO4 (+) (delta), and the Delta delta of Pr2NiO4 (+) (delta) increased with decreasing P(O-2), while that of Nd2NiO4 (+) (delta) was independent on P(O-2), suggesting that not only the valence of Ni but also that of Pr changed during the phase transition in Pr2NiO4 (+) (delta) (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2014.03.031

Web of Science

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Reaction distribution in the composite electrode of LiCoO2, an acetylene black and an organic binder was evaluated by two-dimensional X-ray absorption spectroscopy (XAS). The valence change of Co ion in LiCoO2 due to the Li de-intercalation during charging was evaluated as the change of the absorption energy of Co K-edge. To demonstrate the reaction distribution due to ionic transportation in the composite cathode, a composite electrode laminated by an aluminum foil and a polyhnide film was fabricated in this study. After charging, clear shifts of the absorption energy was observed. The reaction distribution was evaluated by evaluating the peak top energy of Co K-edge as a function of the distance from the edge of the laminated cathode. Two-dimensional mapping of the reaction distribution revealed that the electrochemically active area expands about 700 mu m from the edge of the electrode under the charging condition of 0.2 C. This is consistent with a result of electrochemical charging test showing only 42% of the theoretical capacity with the current rate of 0.2 C. (C) 2013 Elsevier BM. All rights reserved.

DOI： 10.1016/j.ssi.2013.10.013

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The effects of Nb doping on the chemical stability of Ba0.5Sr0.5Co0.8Fe0.2O3 - delta based solid solutions under high oxygen partial pressure (p(O-2)) and CO2-containing atmospheres were studied. BSCF and Ba0.5Sr0.5Co0.9Nb0.1O3 - delta (BSCN) and Ba0.5Sr0.5Co0.8Fe0.1Nb0.1O3 (- delta) (BSCFN) were prepared and investigated by using TG-DTA analysis under p(O-2) = 1 and 10(-3) bar with or without CO2. The results showed that the Nb substitution effectively improved the chemical stability under high oxidation condition and also improved the CO2-tolerance of BSCF-based materials. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2014.01.045

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In this study, in situ soft X-ray absorption spectroscopy (soft XAS) technique, which enables us to analyze electronic structures of oxides at elevated temperatures while controlling atmospheric conditions, was developed. The technique was applied to investigate the electronic structures of La0.6Sr0.4CoO3 (- delta). X-ray absorption spectra at the Co L-edges and the O K-edge were measured in the temperature range from room temperature to 873 K and the p(O-2) range from 10(-4) to 10(-2) bar. The developed in situ soft XAS technique is found to be effective for evaluating electronic structures of oxides under controlled temperature and p(O-2). (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2014.01.005

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

High temperature X-ray diffraction measurements in controlled partial pressures of oxygen are used to study the thermal expansion and point defect induced expansion, known as chemical expansion, of Zr0.2Ce0.8O2 - delta powder. The coefficient of thermal expansion agrees with previous values for undoped ceria. The coefficient of chemical expansion, on the other hand, is significantly less than in ceria, in agreement with a previous study by this group on Zr0.2Ce0.8O2 - delta. Contrary to previous studies of chemical expansion in ceria, with increasing 6, the chemical expansion coefficient increased, approaching the value for undoped ceria for large 6. This behavior is discussed in terms of availability of Zr for defect association. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2014.03.026

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The oxygen nonstoichiometry and the crystal structure of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) were investigated by using coulometric titration, high-temperature gravimetry and in situ HT-XRD. The chemical stability diagram of BSCF was established as a function of temperature between room temperature and 1373 K and oxygen partial pressure, p(O-2), between 1 and 1 x 10(-21) bar. The results showed that the cubic BSCF had poor chemical stability both under highly oxidative conditions at low temperatures and highly reductive conditions at high temperatures. The phase analysis of the decomposition products showed that the chemical instability of BSCF was mainly owing to the oxidation/reduction of trivalent Co ions.

DOI： 10.1039/c3cp54810d

Web of Science

Language：English  

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© The Electrochemical Society. In this study, Cr-poisoning in a SOFC mixed conducting cathode was investigated. To examine the influence of the electrode reaction systematically, a model patterned thin film electrode was used. La0.6Sr0.4CoO3-δ was chosen as the model cathode material. The LSC model electrode was exposed to Cr-containing oxygen at 973 K under a cathodic polarization. The Cr content in the feed gas was controlled by setting the temperature of a Cr-source at 973 K or 773 K. The degradation of the electrode performance was observed under both conditions. Deposits observed on the electrode surface were SrCrO4 for the higher Cr-concentration in the feed gas. On the other hand, deposits were Sr-compounds without detectable amount of Cr for the lower Cr-concentration. These results may indicate that not only the Cr-deposition but also the decomposition of the electrode material could be considerable causes for the Cr-poisoning in mixed conducting cathodes depending on the Cr-concentration.

DOI： 10.1149/09101.1231ecst

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Event date： 2024.3

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Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：徳島県徳島市 徳島大学常三島キャンパス   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya   Country：Japan  

Event date： 2022.9

Language：English   Presentation type：Oral presentation (general)  

Venue：Nagoya   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神奈川県横浜市 神奈川大学みなとみらいキャンパス   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神奈川県横浜市 神奈川大学みなとみらいキャンパス   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：神奈川県横浜市 神奈川大学みなとみらいキャンパス   Country：Japan  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：愛知県名古屋市   Country：Japan  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Poster presentation  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Poster presentation  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.7

Language：English   Presentation type：Oral presentation (general)  

Venue：Boston, U.S.   Country：United States  

Event date： 2022.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2021.10

Language：English   Presentation type：Poster presentation  

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン  

Event date： 2021.3

Language：English   Presentation type：Oral presentation (general)  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.3

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2021.1

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.12

Language：Japanese   Presentation type：Poster presentation  

Event date： 2020.12

Language：English   Presentation type：Poster presentation  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.11

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (general)  

Event date： 2020.10

Language：English   Presentation type：Oral presentation (invited, special)  

Event date： 2020.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

オンライン開催

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2020.3

Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2020.3

Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2020.1

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Florida   Country：United States  

Event date： 2020.1

Language：English   Presentation type：Poster presentation  

Venue：Sapporp   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：JAPAN 仙台市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京  

Presentation type：Oral presentation (general)  

Venue：JAPAN 秋田県仙北市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 福岡  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：甲府  

Presentation type：Oral presentation (general)  

Venue：JAPAN 仙台市  

Presentation type：Poster presentation  

Venue：岐阜県下呂市  

Presentation type：Oral presentation (general)  

Venue：仙台  

Presentation type：Oral presentation (general)  

Venue：仙台  

Language：English   Presentation type：Oral presentation (general)  

Venue：Kyoto  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：United States Hollywood,Florida  

Presentation type：Oral presentation (invited, special)  

Venue：United States New Orleans  

Presentation type：Oral presentation (general)  

Venue：Italy Padua  

Presentation type：Poster presentation  

Venue：JAPAN 仙台市太白区秋保  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Poster presentation  

Venue：Norway Oslo  

Presentation type：Oral presentation (general)  

Venue：Kyoto  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Ohio, U.S.  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：PyeongChang, Korea  

Presentation type：Oral presentation (general)  

Venue：U.K. Glasgow, Scotland  

Presentation type：Oral presentation (general)  

Venue：JAPAN 札幌市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 横浜市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 伊豆熱川温泉  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Presentation type：Oral presentation (general)  

Venue：U.K. Glasgow, Scotland  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京都八王子市（首都大学東京 南大沢キャンパス）  

Presentation type：Poster presentation  

Venue：JAPAN 東京都（日本大学 文理学部）  

Presentation type：Poster presentation  

Venue：JAPAN 仙台市 東北大学片平キャンパスさくらホール  

Presentation type：Poster presentation  

Venue：JAPAN 横浜  

Presentation type：Oral presentation (general)  

Venue：JAPAN 伊豆熱川温泉  

Presentation type：Oral presentation (general)  

Venue：JAPAN 名古屋市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 花巻市  

Presentation type：Oral presentation (general)  

Venue：United States Keystone, Colorado  

Presentation type：Oral presentation (general)  

Venue：JAPAN Toyama  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tsukuba-city Ibaraki  

Presentation type：Poster presentation  

Venue：Kyoto  

Presentation type：Poster presentation  

Venue：Okinawa  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tokyo  

Presentation type：Oral presentation (general)  

Venue：JAPAN 軽井沢  

Presentation type：Oral presentation (invited, special)  

Venue：Canada Quebec  

Language：English   Presentation type：Oral presentation (general)  

Venue：Okinawa  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：Kyoto  

Presentation type：Oral presentation (general)  

Venue：United States Honolulu  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (invited, special)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：JAPAN 横浜市  

Presentation type：Oral presentation (general)  

Venue：Italy Como  

Presentation type：Oral presentation (invited, special)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tokyo  

Presentation type：Oral presentation (general)  

Venue：Italy Padua  

Language：English   Presentation type：Oral presentation (general)  

Venue：PyeongChang, Korea  

Presentation type：Oral presentation (invited, special)  

Venue：United States Las Vegas  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Poster presentation  

Venue：Okinawa  

Presentation type：Oral presentation (general)  

Venue：United States San Francisco  

Presentation type：Oral presentation (invited, special)  

Venue：Italy Montecatini Terme  

Presentation type：Poster presentation  

Venue：JAPAN 仙台市 東北大学片平キャンパスさくらホール  

Presentation type：Oral presentation (invited, special)  

Venue：United States Chicago, Illinois  

Presentation type：Oral presentation (general)  

Venue：Norway Oslo  

Presentation type：Oral presentation (general)  

Venue：JAPAN 姫路市  

Presentation type：Oral presentation (invited, special)  

Venue：JAPAN Sendai  

Language：English   Presentation type：Poster presentation  

Venue：Shizuoka  

Presentation type：Oral presentation (general)  

Venue：United States San Francisco  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都  

Presentation type：Oral presentation (general)  

Venue：United States San Francisco  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：United States Honolulu  

Language：English   Presentation type：Poster presentation  

Venue：Yokohama  

Presentation type：Oral presentation (invited, special)  

Venue：United States Boston  

Presentation type：Oral presentation (general)  

Venue：Republic of Korea Seoul  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Venue：Italy Padua  

Language：English   Presentation type：Poster presentation  

Venue：Arcachon, France  

Language：English   Presentation type：Oral presentation (general)  

Venue：PyeongChang, Korea  

Language：English   Presentation type：Oral presentation (general)  

Venue：Sommarøy, Norway  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Venue：Singapore Singapore  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tokyo  

Presentation type：Oral presentation (invited, special)  

Venue：United States Pittsburgh  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：Thailand Bangkok  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：United States Keystone, Colorado  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tokyo  

Presentation type：Oral presentation (general)  

Venue：United States Ohio, Columbus  

Presentation type：Oral presentation (general)  

Venue：Tokyo  

Presentation type：Oral presentation (general)  

Venue：France Nantes  

Presentation type：Oral presentation (general)  

Venue：Sendai  

Presentation type：Oral presentation (invited, special)  

Venue：Sendai  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：Norway Trondheim  

Presentation type：Oral presentation (general)  

Venue：JAPAN Toyohashi  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Language：English   Presentation type：Poster presentation  

Venue：PyeongChang, Korea  

Presentation type：Oral presentation (general)  

Venue：Italy Como  

Presentation type：Oral presentation (general)  

Venue：JAPAN 山形県天童市  

Language：English   Presentation type：Poster presentation  

Venue：PyeongChang, Korea  

Language：English   Presentation type：Poster presentation  

Venue：Okinawa  

Presentation type：Oral presentation (general)  

Venue：JAPAN Tsukuba-city Ibaraki  

Presentation type：Oral presentation (general)  

Venue：France Arcachon  

Presentation type：Poster presentation  

Venue：Kyoto  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Language：English   Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Presentation type：Oral presentation (general)  

Venue：France Arcachon  

Language：English   Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Venue：United States Honolulu  

Presentation type：Oral presentation (general)  

Venue：United States Hollywood,Florida  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Tokyo  

Presentation type：Oral presentation (general)  

Venue：United States Hollywood,Florida  

Language：English   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：京都  

Presentation type：Oral presentation (general)  

Venue：JAPAN 名古屋市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 指宿市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 伊豆熱川温泉  

Presentation type：Oral presentation (general)  

Venue：JAPAN 伊豆熱川温泉  

Presentation type：Oral presentation (general)  

Venue：JAPAN 宮崎  

Presentation type：Oral presentation (general)  

Venue：JAPAN 宮崎  

Presentation type：Poster presentation  

Venue：JAPAN 仙台  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：JAPAN 札幌市  

Presentation type：Oral presentation (invited, special)  

Venue：United States Ohio  

Presentation type：Oral presentation (general)  

Venue：United States Sandiego  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Presentation type：Oral presentation (general)  

Venue：JAPAN 横浜市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Language：English   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：JAPAN 京都  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京  

Presentation type：Oral presentation (general)  

Venue：JAPAN 札幌市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡  

Presentation type：Oral presentation (general)  

Venue：JAPAN 横浜市  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Language：English   Presentation type：Oral presentation (general)  

Venue：Sendai, Miyagi  

Language：English   Presentation type：Oral presentation (general)  

Venue：Cancun, Mexico  

Language：English   Presentation type：Poster presentation  

Venue：PyeongChang, Korea  

Presentation type：Oral presentation (general)  

Venue：United States Florida  

Presentation type：Oral presentation (invited, special)  

Venue：United States Salt lake city,UＴＡＨ  

Language：English   Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Venue：JAPAN Sendai  

Language：English   Presentation type：Poster presentation  

Language：English   Presentation type：Oral presentation (general)  

Venue：PyeongChang, Korea  

Presentation type：Oral presentation (general)  

Venue：Italy Padua  

Presentation type：Poster presentation  

Venue：JAPAN 東京都（日本大学 文理学部）  

Presentation type：Oral presentation (general)  

Venue：JAPAN 東京都八王子市（首都大学東京 南大沢キャンパス）  

Presentation type：Poster presentation  

Venue：JAPAN 仙台  

Language：English   Presentation type：Oral presentation (general)  

Venue：Miyazaki  

Language：English   Presentation type：Oral presentation (general)  

Venue：Xuzhou, China  

Language：English   Presentation type：Oral presentation (general)  

Venue：福岡  

Language：English   Presentation type：Poster presentation  

Venue：宮城県仙台市  

Language：English   Presentation type：Oral presentation (general)  

Venue：甲府  

Presentation type：Oral presentation (general)  

Venue：Tokyo  

Presentation type：Oral presentation (general)  

Venue：Kyoto  

Presentation type：Poster presentation  

Venue：Okinawa  

Presentation type：Poster presentation  

Venue：Okinawa  

Presentation type：Oral presentation (general)  

Venue：United States Keystone, Colorado  

Presentation type：Oral presentation (general)  

Venue：JAPAN 大阪  

Presentation type：Oral presentation (general)  

Venue：United States Ohio, Columbus  

Presentation type：Oral presentation (general)  

Venue：United States Keystone, Colorado  

Presentation type：Poster presentation  

Venue：Tokyo  

Presentation type：Oral presentation (general)  

Venue：Germany Heidelberg  

Presentation type：Oral presentation (general)  

Venue：JAPAN 横浜市