嶺重 温

The two types of c-axis-aligned polycrystals of lanthanum silicate oxyapatite (LSO) doped with K2O and Al2O3 were prepared by the templated grain growth method with different template/matrix mass ratios of 11.1/88.9 and 5.9/94.1. The template particles, K2O- and F-doped plate-like LSO crystals with developed {001} faces, and the matrix powder, mainly Al2O3-doped LSO, were those used in a previous study with the template/matrix mass ratio of 20.0/80.0. Considering the ionic conductivity and orientation degree of the three types of textured polycrystals, the intermediate mixing ratio of 11.1/88.9 was found to be optimal among the three, with the texture fraction of {0 0 l}apatite being 0.74. Thus, the random grain oriented polycrystal was prepared with the same bulk chemical composition as the control sample. As the temperature increased from 773 to 823 K, the bulk oxide-ion conductivity (σb) of the textured polycrystal increased from 1.04 × 1013 to 1.71 × 1013 S cm11 and the activation energy of conduction (Ea) was 0.61 eV. The σb value of the random grain oriented polycrystal increased steadily from 3.80 × 1015 to 5.26 × 1014 S cm11 with increasing temperature from 773 to 973 K (Ea = 0.92 eV). Comparing the σb values at the same temperatures, the former was 27.5 (773 K) and 21.2 (823 K) times higher than the latter. The chemical formula of the doped LSO in the textured polycrystal was determined from the average composition to be (La9.59K0.09□0.32)(Si5.50Al0.38□0.12)O26, where □ denotes vacancies in La and/or Si sites. The major chemical composition of the coexisting interstitial material was estimated to be 29.8 mol % La2O3, 44.9 mol % SiO2, and 25.3 mol % Al2O3. The mole fractions were determined by the lever rule to be 0.9824 for doped LSO and 0.0176 for interstitial material.

The disk-shaped sintered compacts consisting mainly of c-axis-aligned lanthanum silicate oxyapatite (LSO) polycrystals doped with K2O and Al2O3 were prepared by templated grain growth method. The tabular single crystals of K2O- and F-doped LSO were used as template particles, and the Al2O3-doped LSO as matrix powder. The chemical formula derived from the average chemical composition of the constituent LSO crystal grains was (La9.60K0.16□0.24)Σ=10(Si5.48Al0.38□0.14)Σ=6O26, where □ denotes vacancies in La and/or Si sites. One of the doped LSO grains was examined by single-crystal X-ray diffraction to confirm that the crystal structure was isomorphous to those previously reported. Other coexisting phases were 0.16 mol% LaAlO3 and 0.34 mol% SiO2-rich interstitial material (probably in a liquid state at high temperature). With increasing temperature from 773 to 1073 K, the total oxide-ion conductivity (σtotal) along the grain-alignment direction steadily increased from 1.31 × 10−4 to 3.21 × 10−3 S cm−1, each value of which was, at the same temperature, more than 7.7 times larger than that of the randomly grain-oriented polycrystal with the same bulk chemical composition. The larger σtotal-value of the former polycrystal would be due to the significantly higher oxide-ion conductivity along the c-axis direction of the doped LSO. A solid oxide fuel cell (SOFC) using the textured polycrystal as the electrolyte was constructed and tested for power generation. The maximum power density was satisfactorily high at 873 K, indicating that the c-axis-aligned polycrystals of doped LSO would be potentially applicable as electrolytes for the SOFCs operating at medium to low temperatures.

Ba0.6La0.4F2.4 (BLF) is one of the promising candidates for solid-state electrolytes in fluoride-ion batteries owing to the wide electrochemical potential window. Compared with a BLF single crystal, the microstructure-modified BLF polycrystals by mechanochemical synthesis have improved the F− ion conductivity. However, the fundamental mechanism of the F− ion conductivity enhancement is still unclear because of the lack of structural and chemical analysis at the atomic level. Here, we investigate the microstructure of the mechanochemically synthesized BLF, using atomic-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. We find that the La-rich tysonite nano-precipitates are formed in the BLF fluorite matrix. The observed unique microstructure in BLF realized by mechanochemical synthesis would be the origin of the F− ion conductivity enhancement.

Among the three inequivalent fluorides in tysonite CeF3(F1, F2, and F3 in the ratio of 12:4:2 per unit cell), we show by 19F solid-state NMR that F1 is solely responsible for the ion conductivity in Ce1-xSrxF3-x(x = 0.001) at 0 °C. It is further shown that the observed conductivity can be explained quantitatively by using the Nernst-Einstein relation with the F1-F1 exchange rate (ca. 6 × 105s-1) estimated from lineshape analysis with the carrier-F1 concentration. As for an alternative method to obtain the hopping rate of a carrier, we adopt the AC impedance method, for which the identity of the "carrier" is rather elusive. The observed AC impedance gives the carrier hopping rate of 3.5 × 107s-1, which is ca. 60 times of the F1-F1 exchange rate determined by NMR. The slower F1-F1 hopping rate is ascribed to the result of the long-time average of the faster carrier hopping rate. For the AC impedance analysis, the concentration of the carrier to realize the observed conductivity is much larger than that of the fluoride ion vacancy introduced by Sr doping. For explanation, we postulate that what influences AC impedance includes not only the vacancy but also fast-exchanging fluoride ions around the vacancy.

There has been a long-standing controversy over ion conducting pathways in tysonite. To unravel the pathways in CeF3, high-resolution MAS NMR spectra of 19F in CeF3 at −40–240 °C are analyzed on the bases of the calculated dipolar coupling tensor between 19F and paramagnetic electron spins at Ce3+ to assign the three spinning-sideband manifolds for the three crystallographically inequivalent sites (F1, F2, and F3). Clearly resolved sideband manifolds for F1∼F3 at 240 °C indicate that ion exchange among the three sites is not fast enough to affect the 19F spectrum, whereas F1 motion is suggested by its broader linewidth. Further, we show that addition of only 0.1% Sr2+ in CeF3 (Ce1-xSrxF3-x (x = 0.001)) brings significant effects on F-ion mobility. While some of the F2 ions remain at the F2 site, most of the F3 ions undergo exchange motion between F1 at 240 °C. The preference of the exchange pathways in CeF3 is thus consistent with that postulated for LaF3, that is, F1–F1 exchange occurs first followed by F1–F3, and F1–F2 exchange is most restricted.

Electrochemical impedance spectroscopy (EIS) enables the examination of the electrochemical nature of electrodes and electrochemical cells by applying an alternating voltage (or current) and measuring the resulting current (or voltage). The resistance and capacitance components of the electrode can be evaluated by applying an AC voltage and changing the frequency. In particular, analysis using the equivalent circuit can determine important parameters related to the electrochemical reaction of the electrode, such as the charge transfer resistance, electric double-layer capacitance, and Warburg impedance. Moreover, the internal resistance of the cell can be divided into resistances caused by the positive electrode, negative electrode, and electrolyte. Because of these advantages, EIS is a powerful technique used for basic research, such as in identifying the rate-determining step of an electrochemical reaction, and also for applied research, such as characterizing electrochemical devices (e.g., batteries and capacitors). In this paper, the concept of impedance, which represents the relationship between the AC voltage and current, is first explained; then, the AC characteristics of various circuit elements used in equivalent circuits, which are essential for understanding EIS, are described. Finally, treatments of more complex circuits based on transmission-line models (TLMs), which are used to represent equivalent circuits of porous electrodes, are presented. Analyses based on TLMs are the foundation for understanding electrodes for practical applications because porous electrodes are usually used in electrochemical devices.

Electrochemical impedance spectroscopy (EIS) is widely used for the analysis of various electrochemical devices, as it can quantitatively evaluate the main kinetic parameters related to electrochemical phenomena by analysis using equivalent circuits. This paper describes practical applications of EIS, along with EIS measurement and analysis methods for solid electrolytes, Li-ion batteries (LIBs), and electric double-layer capacitors (EDLCs). In all applications, it is necessary to properly measure the impedance data for an adequate equivalent circuit analysis. Therefore, after presenting the backgrounds of EIS applications in the Section 1 (Introduction), the experimental cautions in the measurements are discussed in detail in Sections 2– 4. Section 2 (“EIS for Solid Electrolytes”) presents practical examples of measurements for accurate data, as the EIS analysis of solid electrolytes requires impedance data in the high-frequency range above 1 MHz. Section 3 (“EIS for Lithium-Ion Batteries”) describes a method of separating the internal resistance into the resistances of the positive and negative electrodes and electrolyte resistance, as the output power capabilities of LIBs are frequently evaluated based on an internal resistance. In particular, a symmetrical cell technique enabling measurements of the impedance data only for the positive or negative electrode is demonstrated. As described in Section 4 (“EIS for Electric Double-Layer Capacitors”), the excessive and unwanted impedances arising from instruments and cells must be suppressed as much as possible for appropriately measuring the correct EIS of EDLCs, because the resistance of EDLCs is very small. Therefore, the experimental setup that should be considered in EIS measurements for EDLCs leading to disturbed impedance data is discussed, along with the effects of this scenario on the impedance data. Finally, we summarize our conclusions in Section 5 (Summary).

In order to operate a battery, current must flow smoothly not only in the external circuit but also inside the battery to form a “current loop”. Between electrodes, in many cases, electrons and ions carry charges in the external circuit and inside the battery, respectively. Therefore, it is necessary to minimize the electrode reaction resistance and the ion migration resistance between the electrodes in order to develop highly efficient batteries. For the latter, the key technology is the development of electrolyte materials with excellent ionic conductivity in addition to shorten the distance between the electrodes. In this paper, we use fluoride ion (F−) conductors as an example to explain design guidelines for solid electrolyte materials that contribute to the development of high energy density batteries. In addition, applying the mechanochemical synthesis will be discussed since it has advantages to obtain novel materials that cannot be synthesized by existing methods.

Fluoride-ion-conducting compounds are key materials for solid electrolytes in all-solid-state fluoride shuttle batteries (FSBs) and widely regarded as promising rechargeable batteries. However, their ionic conductivities are still insufficient to allow room-temperature operation. Particularly, the transportation of F ions through solid-state ionic devices is yet to be fully understood. We studied the electrochemical, thermal, and structural features of BaF2-SnF2solid electrolytes by means of AC impedance, differential scanning calorimetry, X-ray diffraction, and neutron diffraction experiments. The substitution of Ba by Sn atoms increased the electrical conductivity of BaF2-SnF2to 107-109times that of BaF2; particularly, (BaF2)0.47(SnF2)0.53exhibited the highest electrical conductivity (σ = 4.1 × 10-3S/cm at room temperature) with the lowest activation energy (Ea= 17.9 kJ/mol). Structural analysis revealed that (BaF2)0.47(SnF2)0.53consists of a tetragonal structure (T-phase) and residual amounts of the cubic structure (C-phase). The T-phase could be refined on the basis of a [−SnSnMMSnSn−]-layered structure (M= BaxSn1-x) with three nonequivalent fluorine sites: F1, F2, and F3. The anisotropic displacement of F3 was more pronounced toward F1; thus, the “-F1-F3-F1-”zigzagnetwork between theMand Sn layers plays a key role in two-dimensional fast F-ion diffusion.

An oxide ion (O2−) conducting membrane cell, based on lanthanum silicate oxyapatite (La9.33+xSi6O26+1.5x, LSO), exhibiting low ohmic and polarization resistances in the intermediate-temperature region (~873 K) was developed. As a solid electrolyte, highly conductive Mg-doped LSO, La9·8(Si5·7Mg0.3)O26.4 (MDLS), modified with another kind of non-conductive lanthanum silicate, La2SiO5 was employed. Two kinds of silicate layers were successively spin-coated on a Ni-MDLS porous anode support, followed by thermal treatment aimed at improving ionic conductivity as well as densification of MDLS through solid state reactive diffusion. In addition, the Gd-doped CeO2, (Ce0.9Gd0.1)O1.95 (GDC) electrolyte layer, which plays an important role to prevent a reaction between the electrolyte and cathode materials, was spin-coated on the modified MDLS electrolyte. Finally, the cathode layer of porous (La,Sr)(Co,Fe)O3-δ was screen printed on the electrolyte layers. The resulting cell obtained from this study showed good fuel cell performance with a maximum power density of 94 mW cm−2 at 873 K, when operated with argon-diluted hydrogen and pure oxygen gasses.

All-solid-state fluoride shuttle batteries (FSBs) have the potential to become the next generation of rechargeable batteries. However, there are gaps in the fundamentals of developing all-solid-state FSBs. For example, the mechanism by which the F- ions travel through a working device is not yet fully understood. In this work, we use a cutting-edge neutron diffractometer and a suite of analysis programs to perform Rietveld refinements. We employ the maximum entropy method to experimentally determine the F- ion diffusion pathways in the superior solid electrolyte with a fluorite-type structure, namely, Ba0.6La0.4F2.4. We show that the excessive F- ions, located at the specific interstitial sites, migrate to the neighboring F- ion sites based on the interstitialcy diffusion mechanism at the operating temperature for all-solid-state FSBs. Understanding the diffusion mechanism of F- ions plays a key role in the development of solid electrolytes for all-solid-state FSBs, particularly for those that can operate at room temperature.

Fluorine-intercalated graphite, CxF with x = 2.8, was tested for the cathode active material of an all-solid-fluoride-ion shuttle battery. The addition of copper fluoride facilitated the discharge reaction of CxF. It was discharged up to 0.4 V vs. Pb and the resulting carbon was charged up to 1.6 V, regenerating C-F bonding. A highest capacity of 230 mAh g−1 was delivered when 80 wt% (67 mol%) of CuF2 was added and utilization of CxF reached 98%.

Lanthanum silicate oxyapatite (LSO) attracts attention as an alternative electrolyte material for the intermediate-temperature solid oxide fuel cells (SOFCs). However, controlling factors of its conductivity and activation energy values have not been well identified. In this study, its conducting properties were reinvestigated in detail aiming at obtaining highly conductive LSO specimen. In addition, an anode-supported electrochemical cell using LSO-based electrolyte was developed and operated at 873 K.

Effects of dopant content and synthesis temperature on phase relations and conducting behavior of lanthanum silicate, La9.33+xSi6O26+1.5x (LSO) electrolytes were investigated. The La-excess-type Fe-doped LSO, La10(Si5.5Fe0.5)O26.75 synthesized at 1973 K showed lower grain boundary as well as grain interior resistances, and then, had high total conductivity (6.9 × 10−3 S cm−1 at 873 K and 3.6 × 10−5 S cm−1 at 573 K). In addition, the chemical instability owing to a high lanthanum activity in the La-excess-type LSO (x = 0.67) specimen could be eliminated by incorporating iron into the specimen. The synchrotron radiation microbeam X-ray diffraction technique revealed that this specimen contains a small amount of new secondary phase, which differs from the situation found in a highly conductive but chemically unstable Al-doped LSO specimen with the same x value and the same synthesis temperature.

The preparation of In2O3 crystals in phase separated structure of sodium borosilicate (Na2O-B2O3-SiO2) glass was successfully obtained by melt quenching method and its electrical conductivity was successfully clarified. Sodium borosilicate glass is phase separated into silica (SiO2) phase and sodium borate phase (Na2O-B2O3). The sodium borate phase mainly contains ionic bondings, and the generation and growth of crystals can easily occur in this phase for its high solubility of various kinds of ions. In this study, a glass ceramics was prepared by precipitating In2O3 crystals in the sodium borate phase of the sodium borosilicate glass. After acid leaching of the sodium borate phase, the In2O3 X-ray diffraction peaks that were observed after crystallization treatment disappeared, indicating that In2O3 crystals were selectively precipitated in the sodium borate phase. By decreasing the proportion of the sodium borate phase which was achieved via controlling the amount of B2O3 in the glass, In2O3 crystals precipitated continuously in this phase, resulting in an increase in the electrical conductivity from 3.30 × 10−5 S/cm to 6.56 × 10−5 S/cm at 500 °C and a decrease in the activation energy from 36.6 kJ/mol to 27.0 kJ/mol, respectively. Furthermore, the electrical conductivity increased by Sn doping and introduction of oxygen vacancies via H2 reduction into the In2O3 crystal lattice.

Crystal structures of oxyapatite-type lanthanum silicate (LSO), La9.667Si6O26.5, and Al- and Mg-doped LSOs; La9.667(Si5.8Al0.2)O26.4 and La9.667(Si5.5Mg0.5)O26.0, were refined using synchrotron powder X-ray diffraction (SXRD) data to investigate the origin of enhanced oxide ion (O2 -) conducting behavior with Si-site doping. It was found that temperature factors of oxygen atoms largely increased with slight Al- or Mg-doping into the Si-site of LSO. Especially, that for the 2a-site oxygen located on the c axis (O4) was enhanced by doping. In addition, that for the 12i-site oxygen, O3, the constituent of an SiO4 tetrahedron in the LSO lattice increased with doping anisotropically toward O4. It was suggested that the ionic movement perpendicular to the c axis via SiO4 tetrahedron was activated by cation (M) doping, and that contributed to the ion conduction in addition to the fast ion channel along c axis.

This paper describes a new approach to novel protonconducting organic?inorganic nanohybrid materials by surface modification of a large amount of SiOH groups on nanoporous glass with silane coupling reagent containing double SH groups, based on pore surface analysis and first principle calculations.

Dense films of an oxygen-excess-type solid electrolyte (OESE) based on Mg-doped lanthanum silicate (MDLS) were fabricated and applied to electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). To obtain dense MDLS films on NiO-MDLS porous substrates, a conventional spin-coating technique using the MDLS printable paste, obtained by mixing nano-sized MDLS particles and a dispersant, was employed. The Ni-MDLS anode supported single cells were then fabricated by printing porous cathode layer onto the electrolyte film surface. By optimizing fabrication conditions of an MDLS film and cathode, the highly active cathode/OESE interface (ASR = 0.23 Ω cm2at 873 K) were successfully obtained, which resulted in high power density of 0.166 W cm-2at 873 K in the fuel cell test when operated with argon-diluted hydrogen and pure oxygen as the fuel and the cathode gas, respectively.

An oxygen-excess-type lanthanum silicate (LSO) solid electrolyte with high chemical stability as well as high ion conductivity was developed by optimizing the chemical composition, La9.333 + x(Si6 - yAl y)O26 + 1.5x - 0.5y. It was found that La 10(Si5.8Al0.2)O26.9 (x = 0.667, y = 0.2) exhibited the highest conductivity among them, and addition of a small amount of iron was effective for the improvement of its chemical stability. The LSO specimen of x = 0.667 and y = 0.2 with iron addition (0.5 mol%) was chemically stable and had a conductivity of 5.6 × 10- 2 S cm- 1 under air at 1073 K, while its electronic conductivity was less than 2.0 × 10- 4 S cm- 1 at the same temperature. The oxygen tracer diffusion coefficient, DO* of this material was determined as 2.0 × 10- 8 cm2 s- 1 at 1073 K. © 2014 Elsevier B.V.

Apatite-type lanthanum silicate based films have attracted significant interests to use as an electrolyte of solid oxide fuel cells (SOFCs) working at intermediate temperature. We have prepared Mg doped lanthanum silicate (MDLS) films on NiO-MDLS cermet substrates by spin coating and sintering of nano-sized printable paste made by beads milling. Changes in crystal structure and microstructure of the paste films with the sintering temperature have been investigated to show that porous network structure with a grain growth evolves up to 1300°C, whereas densification occurred above 1400°C. Anode supported SOFCs using the pasted MDLS films were successfully fabricated: an open circuit voltage of 0.91V and a maximum power density of 150mWcm-2 measured at 800°C were obtained with the electrolyte film sintered at 1500°C. © 2013 Elsevier Ltd.

Electrical measurements of conducting and dielectric materials under high pressures (in the order of GPa) reveal important information regarding orbital overlaps, electronic states, changes in transition temperatures, and activation volumes (ΔV). In this study, we demonstrate a new method for high-pressure impedance measurements, up to 4 GPa, utilizing an indentation-induced local stress field. The current system does not require any pressure mediums or pressure calibrations. The ΔV for O2 - ion conduction in 10 mol% Y2O3-doped zirconia at 500 C was estimated to be 3.0 cm3 mol- 1. ΔV increased with increasing temperatures from 500 to 600 C. The technique also allows the concurrent determination of the effective elastic modulus by fitting the experimental data obtained from the indentation load-depth profile curve with the Hertzian elastic model. The experimental values were consistent with the theoretical values. © 2013 Elsevier B.V.

The relationship between the local structure and oxide ionic conduction of Nd2NiO4+δ possessing the K2NiF4 structure was investigated. Various oxygen nonstoichiometry samples of Nd2NiO4+δ prepared with different annealing oxygen partial pressures were examined. The local structure related to oxide ionic conduction was determined by the Nd K-edge extended X-ray absorption fine structure. The oxide ionic conductivity and surface exchange coefficient were estimated using electronic conductivity relaxation methods. The activation energy for the oxide ionic conductivity was found to have a direct correlation to the surface exchange coefficient. The bottleneck size for oxide ion conduction was strongly correlated to the oxide ionic conduction of interstitial oxygen and the oxygen surface exchange rate.

The oxygen chemical potential of dense Nd2NiO4+δ thin films on Zr0.92Y0.08O1.96 electrolyte was investigated by operando X-ray absorption spectroscopy (XAS) measurements. Operando XAS at the Ni K-edge was measured under an applied voltage and various oxygen partial pressures at high temperature to simulate the operating conditions of solid oxide fuel cells (SOFCs). The absorption edge energy under various polarizations is similar to those measured under equivalent oxygen partial pressures under open circuit condition. Thus, the oxygen chemical potential changes drastically at the electrode/gas interface and the rate-determining step of this model system is the surface reaction. This study provides direct evidence for the rate-determining step of the SOFC cathode reaction.

Ionic conductivity and proton transport number (tH) of borosilicate and phosphosilicate glasses were measured at 500°C for intermediate temperature fuel cells. A borosilicate glass (Na2O-B2O3-SiO2) shows tH = 0.04, which increases to 0.2 by doping 3mol% of P2O5 component. On the other hand, a phosphosilicate glass (Na2O-P2O5-SiO2) shows tH = 0.6 at the same condition. It was found that the Al2O3 doping is indispensable in order to improve both the tH and the chemical durability of the phosphosilicate glasses, and a glass with tH = 1.0 can be obtained for a mixed alkali glass (Na2O-K2O-P2O5-SiO2). In the case of non-alkali phosphosilicate glasses (SnO-B2O3-P2O5-SiO2), a SnP2O7 phase-dispersed dense glass-ceramic was successfully obtained with Sn/P = 0.52, and the glass ceramic also shows tH = 1.0 at 500°C. By increasing the amount of SnO2 and decreasing P2O5 components, Sn-rich Sn2.5P3O12 phase was precipitated, and the glass-ceramics show a possibility of proton/electron mixed conductivity.

pH responsive porous glass of which pore radius was ca. 4 nm was successfully obtained by its surface modification with COOH group on its pore surface. Surface modification with COOH group was performed by the hydrolysis of CN group on its pore surface. Its response speed of acetone in 3 mol/L aqueous solution under acidic condition (pH = 2.8) was twice as large as that under basic condition (pH = 10.8). This was caused by COOH group state on its pore surface with pH. It shrinks under acidic condition, whereas expands under basic condition as if the gate of pore of the porous glass opened and closed with changing pH. The amount of COOH group on its pore surface was approximately 2.5 μmol/m2.

In order to study the grain boundary's (GB's) blocking effect in lanthanum silicate electrolyte, high density Al-doped apatite-type lanthanum silicate was synthesized and characterized by impedance spectroscopy, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Microstructural characterization indicated that the GB's blocking effect was an intrinsic effect. Further microanalysis shows that the GB region is rich in La and poor in Si in comparing with the grain interior (GI). Our discussion suggested that the chemical variation from GI to GB, on the one hand, could degrade the GB region's conductivity; on the other hand, it introduced a strong space-charge effect at GBs. The latter was believed to play a dominant role in the GB's blocking effect. © 2013 American Chemical Society.

Three functional siliconalkoxides (RSi(OC2H5) 3, RTES), phenyltriethoxysilane (PhTES), methyltriethoxysilane (MeTES), and 1,4-bis(triethoxysilyl)benzene (BTEB)-tetraethoxysilane (Si(OC 2H5)4, TEOS) coatings [xA-(100-x)TEOS (x=0-80, mol%), A=PhTES, MeTES, BTEB] were prepared by sol-gel process, and the effects of plastics substrates on both the distribution of organic component in the coatings and its adhesion on plastics substrates were discussed. Polyethylene terephthalate (PET) and polycarbonate (PC) with phenyl group and polyethylene (PE), polypropylene (PP) and polyvinylchloride (PVC) without phenyl group were employed as plastics substrates. The distribution of organic component was monitored by total reflection (ATR) fourier transform infrared (FTIR) measurements. Before the solidification of the coating sol, the organic component for good adhesion migrated on coatings/substrate interface side by the interaction between organic component and substrate. This interaction may be caused by π/π electron interaction, CH3/π electron interaction and CH3/CH3 van der Waals interaction. The migration of phenyl group on plastics substrate with phenyl group was larger than that on plastics substrate without phenyl group, while the migration of methyl group on plastics substrate without phenyl group was larger than that on plastics' substrates with phenyl group. Thus, the chemical structure of substrate affected phase separation behavior in the coatings. Adhesion of PhTES-TEOS and BTEB-TEOS coatings on PET and PC increased drastically at larger than x=60. On the other hand, no adhesion was observed for all the MeTES-TEOS coatings. © 2012 Elsevier Ltd and Techna Group S.r.l.

The development of new methods for the formation of noble-metal-free fuel cell catalysts is currently important in order to provide active catalysts and to realize fuel cell advancements. We attempted the one-pot physical-chemical vapor deposition of iron phthalocyanine (FePc) on the surface of high-surface-area carbon particles as the substrate. This method enabled loading of FePc on the carbon material and concurrent heat treatment, resulting in the formation of carbon-carbon composite nanoparticles with a catalytic activity for the cathodic oxygen reduction, which functioned in a cathode in the polymer electrolyte fuel cell. The increasing temperature rate during the heat treatment, arranging the FePc-substrate configuration and simply adjusting their ratio controlled the amount of the loading and the thickness of the carbonaceous film, which was demonstrated by the transmission electron microscope images and the pore structure analysis. The catalytic activity was dependent on these parameters. The partial retention of the center structure of the FePc (Fe-Nx moiety) in the carbonaceous thin film was indicated by the Fe-K edge extended X-ray absorption fine structure. The results of this study also showed the possibility of coating various kinds of nanoparticles with functional carbonaceous thin films. © 2013 Elsevier Ltd.

The redox reaction of Li1.16Ni0.15Co 0.19Mn0.50O2 positive electrode material during the charging and discharging processes was investigated by using spectroscopic methods, i.e. in situ hard X-ray absorption near edge structure (XANES) at transition metal K-edges and ex situ soft XANES at oxygen K- and transition metal L-edges. The spectral changes of constituent elements during the initial charging to 4.5 V vs. Li/Li+ are quite similar to those of conventional layer-structured positive materials, such as LiNi 1/3Mn1/3Co1/3O2. Ni2+ and Co3+ ions are fully oxidized to Ni4+ and Co4+, while Mn4+ remains unchanged. Ligand oxygen ions also take part in charge compensation. In the process of charging to 4.8 V via the plateau voltage region, no significant spectral change appears except partial reduction of Ni and Co ions in spite of lithium extraction. By discharging to 2.0 V the spectra of each element return to those of the pristine material. © 2012 Elsevier B.V. All rights reserved.

A fast proton conducting glass with proton transport number tH = 1 was successfully prepared by using conventional melting method. In-situ FTIR (Fourier transform infrared) measurements under hydrogen atmosphere, temperature of 300°C and applying 1 V between Pt electrodes were carried out in order to monitor the proton concentration. The electrode reaction on Pt in these conditions is similar to that under intermediate-temperature fuel cell operation. It was found from the in-situ FTIR measurements that the absorbance around 2900 cm-1 increases clearly after applying 1 V, whereas no significant change was observed around 3400 cm-1. Proton infiltration into the glass is discussed based on the in-situ FTIR and impedance results. © 2013 Materials Research Society.

Anode supported solid oxide fuel cells (SOFCs) utilizing apatitetype Mg-doped lanthanum silicate (MDLS) electrolytes obtained from nano-sized printable paste coated on NiO-MDLS substrates were fabricated. With optimizing fabrication conditions of MDLS films, anode and cathode materials, the performance was largely improved, and the high performance SOFC based on apatite-type electrolyte was successfully developed for the first time. © The Electrochemical Society.

The c-axis oriented apatite-type silicates were fabricated in simple ways: fabrication of melt-quenched glass and its crystallization. It was found that a degree of c-axis orientation was affected by many factors such as crystallization temperature and kind of powder materials, in which the precursor glass embedded during crystallization. The performance of a solid oxide fuel cell (SOFC) using the crystallization glass as an electrolyte was also investigated at temperatures of 600 to 800°C. © The Electrochemical Society.

Binary xMO·(100 - x)P2O5 (mol%; M = Ca, Mg) glasses were prepared using a conventional melting method, and the proton conduction mechanism in the glasses was investigated. The proton conductivities of the glasses were measured under various hydrogen (H2) gas concentrations from 0 to 100 vol.% using Pt electrodes. The CaO·P 2O5 glasses show higher proton conductivities than MgO·P2O5 ones. Fourier-transform infrared (FTIR) measurements showed that protons dissociated from H2 gas at the Pt electrodes are incorporated into the glasses, and the proton conductivity increases as a result of an increase in the carrier (proton) concentration. There is a good linear relationship between the peak wavenumber of PO nb (Onb indicates non-bridging oxygen) and the proton conductivity measured in a 100 vol.% H2 atmosphere. Furthermore synchrotron radiation X-ray diffraction (SRXRD) and FTIR results suggest that the π-electron of PO double bond is localized significantly in MgO·P2O5 compared with CaO·P 2O5 glasses, which is the origin of higher proton conductivity in CaO·P2O5 glasses. © 2013 Published by Elsevier B.V.

Ultrathin layers of positively charged poly(diallyl dimethylammonium) choloride (PDDA) and negatively charged poly(sodium 4-styrenesulfonate) (PSS) were deposited on SiO2/polyethylene glycol hybrid membranes via layer-by-layer assembly technique, and carbon dioxide absorption/separation properties were investigated. Quartz crystal microbalance (QCM) measurements revealed that both PDDA and PSS nanocoatings have a good affinity for CO 2 absorption. PDDA-deposited film shows about two times higher CO2 ideal gas selectivity compared with unmodified silica film. © 2013 Materials Research Society.

Electrochemical oxygen reduction behavior for a half cell composed of a mixed ionic and electronic conducting (MIEC) oxide and an oxygen excess-type solid electrolyte was investigated. A perovskite-type MIEC oxide, (La 0.6Sr 0.4)(Co 1-yFe y)O 3-δ (LSCF), was employed as a base material for an electrode catalyst of oxygen reduction reaction. As an electrolyte, Al-doped lanthanum silicate [La 10(Si 5.8Al 0.2)O 26.9 (ALSO)] was used, which is a new class of oxide ion conductors with apatite-type structure. The evaluated polarization resistance, R pol, for the reaction largely depended on y, and the minimum resistance was obtained for y = 0.2. The R pol value was 0.3 Ω cm 2 at 1073 K in ambient air [P(O 2) = 2.1 × 10 4 Pa] for y = 0.2. To improve the performance, introduction of silver nano-particles onto the LSCF particles was studied. With the Ag-modification, R pol at 1073 K could be minimized toward 0.08 Ω cm 2. The cathodic overpotential of the electrode evaluated from DC polarization at 1073 K was 18 mV at 0.1 A cm -2. Highlights: (La 0.6Sr 0.4)(Co 0.8Fe 0.2)O 3 was good cathode for lanthanum silicate electrolytes. By Introducing Ag nanoparticles to LSCF, electrode property was largely improved. Ag-modified LSCF showed quite small activation energy for polarization resistance. © 2012 Elsevier B.V. All rights reserved.

Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES•(100 - x)TEOS (mol%)] (x = 0-80) were prepared using methanol (Film A) or 1-propanol (Film B) as a solvent on polycarbonate (PC) substrate, and the effect of alcohol solvents on both the adhesion and distribution of phenyl groups were studied. The alcohol evaporation rates for Films A and B were monitored by using quartz crystal microbalance (QCM). QCM measurements revealed that the migration of phenyl group to the PC substrate side was strongly related with the alcohol solvent. Transmission fourier transform infrared measurements for these films suggest that a phase-separation between SiO 2 and PhSiO 3/2 networks occur during the alcohol evaporation. © 2012 Springer Science+Business Media, LLC.

A carbonaceous thin film containing Fe and N was formed on a basal plane of highly oriented pyrolytic graphite (HOPG) from iron phthalocyanine (FePc). Hybrid physical-chemical vapor deposition (HPCVD) in a single vessel through a simple heat treatment at atmospheric pressure enabled the formation and was found to be a facile and versatile method. The catalytic activity of the thin film for O2reduction was as high as dispersed Pt on a flat glassy carbon (GC) surface in an acidic electrolyte, implying high potential of the carbonaceous materials as well as the formation method. © 2011 Elsevier B.V. All rights reserved.

The electrical conduction mechanism of mixed conductive perovskite oxides, La0.6Sr0.4Co0.8Fe0.2O 3-δ, for cathode materials of solid oxide fuel cells has been investigated from electronic structural changes during oxygen vacancy formation. La0.6Sr0.4Co0.8Fe0.2O 3-δ was annealed under various oxygen partial pressures p(O2)s at 1073 K and quenched. Iodometric titration indicated that the oxygen nonstoichiometry of La0.6Sr0.4Co 0.8Fe0.2O3-δ depended on the annealing p(O2), with more oxygen vacancies introduced at lower than at higher p(O2)s. X-Ray absorption spectroscopic measurements were performed at the O K-, Co L-, Fe L-, Co K-, and Fe K-edges. The valence states of the Co and Fe ions were investigated by the X-ray absorption near edge structure (XANES) at the Co and Fe LIII-edges. While the Fe average valence was almost constant, the valence of the Co ions decreased with oxygen vacancy introduction. The O K-edge XANES spectra indicated that electrons were injected into the Co 3d/O 2p hybridization state with oxygen vacancy introduction. Both absorption edges at the Co and Fe K-edge XANES shifted towards lower energies with oxygen vacancy introduction. The shift at the Co K-edge resulted from the decrease in the Co average valence and that at the Fe K-edge appeared to be caused by changes in the coordination environment around the Fe ions. The total conductivity of La0.6Sr0.4Co0.8Fe 0.2O3-δ decreased with decreasing p(O2), due to a decreasing hole concentration. © 2011 The Owner Societies.

The relationship between the local structural changes and the oxide ion diffusion in La0.6Sr0.4FeO3-δ was investigated. The oxygen vacancy concentration in La0.6Sr 0.4FeO3-δ was varied by annealing under various oxygen partial pressures. Local structural changes of La0.6Sr 0.4FeO3-δ with the introduction of oxygen vacancies were studied by the extended X-ray absorption fine structure (EXAFS) analysis. Oxygen vacancies are preferentially introduced near the La ions and local distortion around the oxygen vacancies is induced. The oxygen vacancy diffusion coefficient, Dv was calculated by means of electrical conductivity measurement. Dv decreased with increasing local distortion around the oxygen vacancy. Activation energies for Dv strongly depended on the bottle-neck size calculated from the result of EXAFS. © 2011 The Royal Society of Chemistry.

a- and 6-axis-oriented (Bi3.25Nd0.75)Ti3O12 (BNT) films, 2.4 - 2.8 μm thick, were fabricated on conductive IrO2 (101)/Al2O3 (012) and Nb:TiO2 (101) [Nb = 0, 0.05, and 0.79 mass%] substrates by high-temperature sputtering. A BNT film grown on an IrO2 (101)/Al2O3 (012) substrate had low crystallinity [full width at half maximum (FWHM): ΔΘ = 2.83°], low degrees of a- and 6-axis orientations [«(h00/0k0) = 49.2%] and dense microstructure in which a- and b-axis-oriented crystals existed locally in the film, while a BNT film grown on a Nb:TiO2 (101) substrate with 0.79 mass% Nb showed high crystallinity (ΔΘ = 0.57°), a high a(h00/0k0) (99.9%) and a porous microstructure comprised of many nanoplate-like crystals. The BNT film grown with a heteroepitaxial relationship to the underlying Nb:TiO2 substrate is shown to have a symmetric loop shape, with a remanent polarization (2Pr) of 29 μC/cm2 and a coercive field (2Ec) of 297 kV/cm.

3.0-μm-thick a- and 6-axis-oriented (Bi3 25Nd0.75)Ti3O12 (BNT-0.75) films were fabricated on conductive Nb:TiO2 (101) (Nb = 0, 0.048, 0.46, 0.79 mass%) single crystal substrates by high-temperature sputtering. BNT films grown on undoped TiO2 substrates have no orientation, whereas BNT films deposited on Nb:TiO2 substrates with 0.46-0.79 mass% Nb show strong (/i00/0fc0) diffractions and grow with a heteroepitaxial relationship to the underlying Nb:TiO2 substrates. The BNT-0.75 film deposited on a Nb:TiO2 (101) substrate with 0.79 mass% Nb exhibited the peculiar shape of approximately 100- to 150-nm-thick nanoplates. We speculate that the driving force for producing a plate-like structure for BNT films is the large anisotropy of the linear expansion coefficients for Bi4Ti3O12, and the comparatively small lattice matching between the Nb:TiO2 substrate and the BNT film.

The electronic structural changes of La0.6Sr 0.4CoO3-δ cathodes with oxygen vacancy formation by reducing oxygen partial pressures, p(O2)'s were investigated in detail using X-ray absorption spectroscopy to understand metallic-like electronic conduction mechanism. The oxygen nonstoichiometry of La 0.6Sr0.4CoO3-δ was controlled by annealing the samples under various p(O2)'s and quenched to room temperature. Co K-edge X-ray absorption near edge structure (XANES) spectra revealed that the Co average valence decreased with decreasing p(O2), which was also confirmed by iodometric titration. The Co L-edge XANES spectra were hardly changed with changing p(O2)-s. Meanwhile, the peak area of the O K-edge XANES spectra strongly depended on p(O2). This result revealed the strong hybridization between the O 2p and Co 3d states. It was concluded the introduction of oxygen vacancies narrowed the hybridized orbital of O 2p and Co 3d states, resulted in a decrease in the mobility as well as the concentration of electron holes with decreasing p(O2). © 2011 American Chemical Society.

Electronic as well as ionic conducting properties for oxyapatite-type solid electrolytes based on lanthanum silicate, La9.333 + xSi 6O26 + 1.5x (LSO) were investigated in the oxygen-excess region (x > ca. 0.3). We have found that the oxygen excess-type LSO (OE-LSO), namely La10Si6O27 on weighted basis, exhibited high conductivity, and substitution of the Si-site of LSO with some dopants (Mn+) had a positive effect toward the conducting property. Furthermore, it was also found that addition of a very small amount of iron ions into the M-doped OE-LSO, La10(Si6-yMn+y)O27-(2-0.5n)y, improved its conductivity. On the other hand, replacement of the La-site with various ions for La10(Si 6-yMn+y)O27-(2-0.5n)y did little to improve conductivity. The electronic transport numbers for Al-doped OE-LSO with Fe-addition, (1-α){La10(Si5.8Al0.2)O 26.9}-α(FeOγ), evaluated with the Hebb-Wagner polarization method were very low: i.e., 1.1 × 10- 3 and 2.9 × 10- 3 under P(O2) = 1.1 × 104 Pa at 1073 K for α = 0.00 and 0.005, respectively. Conductivity for each sample was unchanged under humidified atmosphere at 1073 K sustained for over 50 h, revealing that both compositions were chemically stable. It was concluded that 0.995{La10(Si5.8Al0.2)O 26.9}-0.005(FeOγ) is suitable for the fuel cell electrolytes because of its high and almost pure ionic conductivity, and its good chemical stability under humidified as well as reducing conditions. © 2010 Elsevier B.V. All rights reserved.

Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES•(100 - x)TEOS (mol%)] (x = 0 - 80) were prepared on polycarbonate (PC) substrate, and adhesion, surface hardness and distribution of phenyl groups were studied. The coatings with more than 60 mol% of PhTES showed good adhesion (≈ 100%), and the pencil hardness of PC substrate (4B) improved to 2B or B after the coatings. Bulk gels with the same compositions were also prepared, and distribution of phenyl groups were estimated using fourier transform infrared (FT-IR) spectroscopy (KBr method for bulk gels and attenuated total reflection (ATR) method for coatings). A significant difference for the distribution of phenyl groups was clearly observed between bulk gels and coatings, suggesting PC substrate affects the distribution of phenyl groups in coatings. The adhesion and FTIR results revealed that there is an interaction caused by π-electrons between benzene rings on PC substrate and phenyl groups of PhTES-TEOS coatings. It was found that the adhesion was strongly correlated with the phenylsilsesquioxane networks formed around PC substrate side. © 2010 Springer Science+Business Media, LLC.

A fast-proton-conducting porous tubular glass electrolyte was prepared by surface modification of glass, and the direct methanol fuel cell performance of the glass electrolyte was measured. The glass electrolyte showed very low methanol permeability of 2.1 × 10-7 cm2 s -1 compared with the polymer electrolyte Nafion® (2.3 × 10-6cm2s-1). An open-circuit voltage of approximately 0.7V was obtained at room temperature, which corresponds to 15 V when the tubes are stacked in a 6.5 cm3 portable cell. © 2011 The Chemical Society of Japan.

Na2O-B2O3-SiO2 and Na 2O-P2O5-SiO2 glasses show a spinodal phase separation to SiO2 rich and Na2OB2O 3 or Na2OP2O5 rich phases by heating. Herein we report for the first time the application of phosphosilicate glasses to fuel cells operated at moderate temperature. The glass was prepared by conventional melting method. The mixed-alkali glass showed 100 proton transport at 400-500C. Two crucial aspects, the first is the enhancement of proton transport number by mixing two types of alkali metal oxides, and the second is proton infiltration into the glass under hydrogen (fuel cell) atmosphere, are reported. © 2011 The Electrochemical Society.

Apatite-type lanthanum silicates are promising electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) because of the high oxide-ion conductivity and excellent transport properties. High sintering temperature in making thin and dense lanthanum silicate ceramics, however, is the most serious obstacle to the practical use of this material to SOFC electrolytes. In this study, we have succeeded in fabricating anode supported SOFC using plasma-sprayed Mg doped lanthanum silicate (MDLS) films as an electrolyte. The films were deposited on the NiO-MDLS substrates by atmospheric DC plasma spraying, followed by post heat treatments in a reduced atmosphere. During the heat treatments, the films were fully crystallized and the NiO-MDLS substrates reduced to the porous anodes of Ni-MDLS, which were confirmed by X-ray diffraction and scanning electron microscopy. The maximum power densities of the cell using (La0.6Sr0.4)(Co0.2Fe 0.8)O3-δ cathode increased to 79.9, 45.4 and 21.6 mW cm- 2 at 800, 700 and 600 °C, respectively, compared to the Pt paste cathode, though the open circuit voltages of 0.90-0.97 V were similar for both cathodes. © 2010 Elsevier B.V. All rights reserved.

Influences on electrical property and phase relationship of oxyapatite-type solid electrolytes based on lanthanum silicate (LSO) were investigated by addition of a small amount of transition metal elements. It was revealed that a very small amount of 3d-transition metal additives into the La-excess-type, i.e., oxygen-excess-type Al-doped LSO, La10(Si5.8Al 0.2)O26.9, changed its electrical conductivity. Some metals such as iron and chromium showed a positive effect for an increase in conductivity. The specimen with a nominal composition of 0.995{La 10(Si5.8Al0.2)O26.9}-0.005(FeO γ), showed the maximum electrical conductivity among the specimens measured in this study. Formed phases of oxygen-excess-type Al-doped LSO based materials were found to be altered even by addition of a small amount of transition metal oxides. La-rich impurity phases such as La(OH)3 and La2SiO5 are usually detected in the oxygen-excess-type LSO, whereas no formation of La-rich impurity phases was confirmed in the case of iron addition. These results suggest that the enhancement of electrical conductivity by iron addition is due to a disappearance of the La-rich impurity phases as insulators and/or an increase in the concentration of oxygen interstitial carriers within the LSO phase. © 2010 Elsevier B.V. All rights reserved.

Porous glasses with the surface area of ≊300m2/g were prepared utilizing the spinodal-type phase separation of Al2O 3-doped Na2OB2O3SiO2 glasses. The proton conductivity under humidified conditions and their relations to the amount of doped Al2O3 were investigated. The proton conductivity of the glass doped with 2mol% of Al2O3 was about 6 times higher than that of the undoped glass. Fourier transform infrared (FTIR) measurements revealed that the absorption by the strongly hydrogen-bonded OH groups increased with increasing the amount of Al 2O3. Bond overlap populations (BOPs), which are directly related to the strength of the covalent bond, between the surface OH groups and an absorbed water molecule were calculated based on a firstprinciples theory (DVXα). The BOP values between O and H of the surface OH groups decreased by the Al2O3 doping. Substitution of Si atoms of the SiOSi silica networks with Al atoms, and formation of the AlOHSi bonds effectively improved the proton conductivity under humidified conditions. © 2010 The Ceramic Society of Japan.