[in Japanese]

View full abstract

Viscoelastic slurries involving ceramic nanoparticles have been developed to apply direct-writing technique. Influences of slurry compositions on rheological properties of slurries and the forming ability were investigated, and then the slurry design was fixed. The slurry design was also applied for fabrication of a current collector of the SOFC electrode.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

In the percolation process, the resistivity changes abruptly at a certain mixing ratio of conductor to insulator. In this study, we first applied this percolation principle to chemical sensor. By using montmorillonite as insulator and carbon as conductor, we successfully fabricated a humidity sensor whose resistivity increases in a humid atmosphere and decreases in a dry atmosphere. The resistivity change is due to the volume change of montmorillonite by water adsorption and desorption. A new type of chemical sensor based on the percolation principle is proposed.

View full abstract

[in Japanese]

View full abstract

In this study, we demonstrated the use of organic-inorganic nanohybrid films as sensitive coating for odor detection. Among them, the TiO2/PAA films showed high sensitivity and selectivity to ammonia less than 1ppm, whereas no noticeable changes were observed for ethanol, toluene, and chloroform.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Recently, the new energy generation system such as a fuel cell using hydrogen or bio-ethanol gases has been taken much notice. Thus, a high-performance gas sensor which can detect these gases with high sensibility is required. On the other hand, the electrophoretic deposition (EPD) process is known to be simple and easy process for preparing a porous thin film on a complex formed substrate. In this study, in order to fabricate a combustion type high-performance gas sensor, porous titania thin films loading Pd and Pt fine particles were prepared by using an EPD process and a subsequent photo deposition one. The microstructure and the sensor characteristic to flammable gas of the obtained porous titania thin films were examined.

View full abstract

[in Japanese]

View full abstract

The semiconductor-type H2S sensor using cerium oxide as a sensing material was developed. The resistance of Cerium Oxide decreases quickly to low concentration H2S, and is excellent also in reproducibility. Therefore, the highly sensitive H2S sensor which is easy to use is realizable.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

YBa2Cu3O7-x (Y123) layers with BaZrO3 nano-sized rods were fabricated by pulsed laser deposition using zirconium oxides mixed Y123 targets on Hastelloy tape with a textured buffer layer (CeO2/Gd2Zr2O7). Both cross-sectional and plan-view transmission electron microscopy (TEM) specimens of the Y123 layers were prepared by focused ion beam and standard ion thinning. Then the nanostructural characterizations of the layer were carried out by TEM to investigate the size, the orientation and the distribution of the nano-rods in the Y123 layer.

View full abstract

[in Japanese]

View full abstract

Layered cobalt oxides have attracted much attention due to their good thermoelectric property. Recently, Ca_0.33CoO₂ thin films have been made successfully by the reactive solid-phase epitaxy method and the following ion-exchange treatment of Na_xCoO₂ film on sapphire c(0001) plane. The as-prepared Ca_0.33CoO₂ film forms the root(3)a x root(3)a ordered structure. However, it changes to the 2a x root(3)a ordered structure after annealing at 400^oC in air though Ca concentration keeps the same as before. Such 2a x root(3)a ordered structure can be easily distinguished from the root(3)a x root(3)a ordered structure by the inbetween contrast of Ca pairs in HAADF-STEM image. The intensity fluctuation of Ca pairs indicates the existence of many Ca-vacancies in this structure, which rationalizes the metal-insulator transition corresponding to the variation of Ca ordering.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The high-spin to low-spin transition is expected to be accompanied with some volume reductions and thus considerable changes in the elastic property. We propose two different models of the elastic properties across the spin crossover with/without elastic anomaly. Marked softening appears across the spin crossover in the first model due to gradual volume reductions, whereas simple hardening is found in the second one. To clarify which model is physically more appropriate, we make a numerical model to simulate dynamical fluctuations of the spin state and investigate its stress responses.

View full abstract

[in Japanese]

View full abstract

This paper focuses on the atomic and electronic structure of the interesting thermoelectric superlattices , SrTiO3/Nb doped SrTiO3/SrTiO3 and SrTiO3/Nb doped SrTiO3/BaTiO3 superlattices. They were fabricated on the (001) LaAlO3 substrate by pulsed laser deposition (PLD) method. Z-contrast HAADF image and ELNES were taken by STEM equipped with a spherical aberration-corrector and parallel electron energy loss spectrometer. The electronic structure and ELNES of the superlattice were calculated by using a first principles PAW method and a first principles relativistic multi-electron method. It was found that Nb preferentially solve to Ti site, and Ti in the Nb doped layer have extra electron, and it causes the 2DEG formation. Details on the STEM-ELNS and first principles calculations will be present.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

We investigated the crystal and electronic structures of Li(Ni,Mn)O₂ by Rietveld analysis and first-principles calculations. Cathode property depended on the composition and heat treatment. From the result of Rietveld analysis, the fitting between experimental data and calculation data was good. So, the structure parameter is enough to use theoretical calculations. By the first-prinsiples calculation, the band of Ni and Mn overlapped with that of O, and the hybrid orbital was built from DOS. The covalent bond of Ni-O is considered to be stronger than that of Mn-O since the overlap of Ni-O band is larger.

View full abstract

The local structure of oxygen defect in yittria stabilized zirconia (YSZ) oxide ionic conductor has been investigated by O-17 solid state MAS-NMR. We have quantitatively determined the coordination number of oxygen ions around Y ion in YSZ with Y-89 solid state MAS-NMR With increasing the Yttria content, O-17 NMR spectra changed peak shape and the chemical shift . The observed spectral change was interpreted in terms of the oxygen local structure and the defect formation.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Oxide ion conductor is an improtant material for electrolyte. In this study, oxide ion conductivity in LaGaO₃ and Pr₂NiO₄ based perovskite oxide will be introduced. In case of LaGaO₃, fast oxide ion conductivity is assigned to the large mobility of oxygen vacancy due to the large free volume. On the other hand, clusterization of oxygen vacancy is observed at lower dopant level comparing with that of considered. In case of Pr₂NiO₄ perovskite related oxide, oxide ion conductivity is occurred by using interstitial oxygen and increasing the amount of interstitial oxygen is effective for increasing the oxide ion conductivity.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

A fundamental issue with microtubular Solid Oxide Fuel Cells (SOFCs) is improvement of the mechanical properties of the cell. Fabricated using extrusion and co-firing techniques, the 0.8 mm diameter tubes are composed of NiO doped ceria (GDC) as an anode (support tube), GDC as an electrolyte and La_0.8Sr_0.2Co_0.6Fe_0.4O₃ (LSCF) GDC as a cathode. The mechanical properties of SOFCs are analyzed through burst testing, c-ring testing, and micro- and nano-indentation testing. This paper will relate the processing methods to mechanical properties for fabrication of the micro-tubes.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

Materials design for fuel cell electrodes are considered, based on thermochemical calculations, electrochemical characterizations, and microstructural observation. Principles to improve chemical durability of solid oxide fuel cells (SOFCs) as well as polymer electrolyte fuel cells (PEFCs) are discussed.

View full abstract

In this study, the effect of small amount of Bi component on the sintering characteristics and electrical performance of scandia stabilized zirconia (Zr_0.89Sc_0.1Ce_0.01O_1.95, ScSZ) has been investigated. Bi addition of > 1 mol% enhanced the sintering characteristics of ScSZ and it seems to be related to the rich phase of Zr and Sc. The electrical conductivity of ScSZ with 3 mol% addition in air was almost the same as that of ScSZ.

View full abstract