In order to evaluate the characteristics of photocatalysts such as TiO2, it is important to separately estimate the oxidation and reduction reaction rates, since the overall reaction rate is limited by the rate-determining step. In this study, photoelectrochemical techniques were applied to thin films of crystalline oriented anatase TiO2 with polycrystalline aggregations deposited on the transparent conductive oxide (TCO) glass substrate, fabricated by the electrophoretic deposition (EPD) in a strong magnetic field. The influence of the plane orientation on the photocatalytic reaction rates was discovered for both oxidation and reduction with respect to current through the electrochemical measurements. The maximum photocurrent for the (001) plane orientation is three times higher than that for the (100) plane orientation, and is comparable with that of the random orientation. The rate of the anodic reaction determines the rate of the overall photocatalytic reaction, therefore affecting the photopotential.

The influence of the crystalline orientation of the TiO2 photoanode on the photo-electrochemical characteristics was investigated to reveal the primary factors responsible for improving the photoelectric conversion efficiency of a dye-sensitized solar cell. It was observed that the photocurrent depended on the plane orientation, whereas the dependence of the photopotential on the open circuit was almost constant. The rate of the photoanodic reaction was attributed to the dye adsorption, depending on the surface energy of each oriented plane of the TiO2. The cathodic reaction on TiO2 during open circuit is likely to determine the rate of the entire electrochemical reaction.

The role of MgAl2O4 spinel particle dispersion for attaining high-strain-rate superplasticity (HSRS) was examined in tetragonal ZrO2. Microstructural examination shows that the dispersed spinel particles provide the following positive factors to ZrO2 simultaneously: (i) stable fine grain size by retarding grain growth due to pinning effect; and (ii) enhanced accommodation due to accelerated lattice diffusivity caused by the dissolution of aluminum and magnesium into ZrO2 from the spinel particles, and accelerated relaxation of stress concentrations exerted by grain boundary sliding through dislocation motion. These positive factors make it possible to attain HSRS in ZrO2.

We report magnetic properties of [Ca2CoO3-δ]0.62CoO2 (Ca349) powders with various average size and the Bi- and Sr-doping effects on thermoelectric properties for the magnetically grain-aligned and densified Ca349 thick films. Magnetic anisotropy at 300 K depended on the initial average size of Ca349 powders and decreased with the decrease in the size. This presumably suggests that distortion of crystal structure was induced by a ball-milling process and led to the change of magnetic anisotropy. On the Bi- and Sr-doping effects, an obvious enhancement of thermoelectric properties did not emerge in the case of the Sr-doping, whereas the enhancement was observed for the Bi-doped Ca349 thick films. However, a drastic decrease of magnetic anisotropy was caused by the Bi-doping. For usage of the p-type layer in multilayered thermoelectric module, tuning of the Bi-doping levels in which both enhancement of thermoelectric properties and a certain level of magnetic anisotropy are achieved is required.

We report thermoelectric (TE) properties of mono-layer thick films of p-type [Ca2CoO3-δ]0.62CoO2 (Ca349) and n-type compounds of Ca0.9La0.1MnO3 (Mn113) and LaNi0.98Mo0.02O3 (Ni113) for the improvement of TE performance in multi-layered TE modules. In the case of magnetically aligned Ca349 film, the improvement of TE properties due to the reduction of resistivity (ρ) was achieved by optimization of hot-pressing temperature and ρ was sensitive to relative density of the Ca349 layer. For the decrease in ρ of the n-type layers, two different approaches, the choice of Ni113 as a n-type compound and usage of fine powders of Mn113, were attempted. Both approaches were effective for reducing ρ even in the sintering at ∼900°C.

Porous Al2O3/Al catalyst supports were fabricated using a mixture of Al(OH)3 and Al powders, followed by pressureless sintering at a temperature of 600 °C in vacuum. Different pressures were used to prepare green compacts. High compaction pressure led to a high surface area and good mechanical and electrical properties for the sintered specimens. However, when the Al content in the sintered specimen exceeded a definite value, high compaction pressure decreased the surface area abruptly. Scanning electron microscopy observations revealed that agglomeration in the starting mixture has a significant effect on the microstructure of the sintered specimens. High compaction pressure greatly eliminated the agglomerates and led to a uniform microstructure for the sintered specimens. However, when the Al content in the starting mixture was too high, Al particles in the compacts prepared by the high pressure were largely sintered due to the high compact density so that most of the pores were closed. The present study indicates that a suitable compaction pressure is critical to obtaining superior Al2O3/Al supports.

We report the preparation of grain-aligned [Ca2CoO3−δ]0.62CoO2 (Ca349) thick films and the conversion of the easy axis of magnetization from the a-axis to the c-axis. The thick films were fabricated by a simultaneous usage of electrophoretic deposition and magnetic alignment methods (MEPD) at high deposition rate with the order of 10 mm/min. Moreover, a multi-layered thick film of Al2O3/Ca349/Al2O3/Ca0.9La0.1MnO3/Al2O3 was also fabricated by the MEPD method by the optimization of condition of each suspension. The conversion of the easy axis was performed crystallochemically for a [Bi2Sr2O4]0.55CoO2 (BiSr222) compound with the easy axis parallel to the a-axis in order to fabricate c-axis grain-oriented bulks by the magnetic alignment method. The substitution of Ca for Sr in the [(Bi0.5Pb0.5)2Sr2O4] block layer induced the change of the easy axis into the c-axis direction, and the magnetic anisotropy was increased by the partial substitution of rare earth elements of Pr, Nd, Tb and Dy for Ca. Using a compound of [(Bi0.5Pb0.5)2(Ca0.8Pr0.2)2O4]0.55CoO2, we have successfully prepared the c-axis grain-aligned bulk by the magneto-scientific method. Our present results indicate that the magneto-scientific method is one of the useful and realistic processes for production of thermoelectric modules.

The role of MgAl2O4 spinel particle dispersion in high-strain-rate superplasticity (HSRS) of tetragonal ZrO2 was examined by characterizing microstructural changes during deformation. The dispersed spinel particles elongate with strain along tensile direction and the elongation tends to be pronounced with increasing strain rate. In the elongated spinel particles, intragranular dislocations lying along the elongated direction were observed, suggesting that the elongation relates to the dislocation motion. The flow behavior characterized by a stress exponent of ≈ 2.0 suggests that grain boundary sliding (GBS) is the predominant flow mechanism. The dislocation-induced plasticity in the spinel particles may assist the relaxation of stress concentrations exerted by GBS, leading to HSRS in tetragonal ZrO2.

The electrophoretic deposition of single-crystalline α-alumina particles dispersed in aqueous media was performed in a strong magnetic field of 10 T. The α-alumina particles in the stable suspension were aligned due to their anisotropic diamagnetic susceptibility and then deposited on a cathodic substrate. The orientation of the α-alumina crystallites was confirmed by x-ray diffraction of the sintered specimen.

The characteristics of electrophoretic deposition (EPD) of positively charged particles onto a cathode were investigated using aqueous alumina and zirconia suspensions. The deposition was performed using several kinds of metal substrates at different current densities. For most substrate materials, a large number of macropores appeared in the deposit, and their size increased with the current density due to gas bubble formation. However, no macropores were formed in the deposit on a palladium substrate, regardless of the current density. The green density and sintering properties of the EPD deposits on a palladium substrate from aqueous suspensions were the same as from slip casting. Bubble-free zirconia/alumina laminate composites were also fabricated by EPD from aqueous suspensions.

Bi, Y, and Al-doped antimonic acids with the empirical formula (1-x)Sb2O5·xM2O3·nH2O (M =Al, Bi and Y; 0 ≤ x ≤ 1) have been prepared by the direct reaction of an aqueous H2O2 solution with metal alkoxides. The electrical properties have been investigated by ac and dc conductivity measurements using a polycrystalline compactdisc as a sample, in connection with the water adsorption behavior. The (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y) materials exhibit a solid solution of cubic antimonic acid (Sb2O5·nH2O) with Bi2O3 and Y2O3 in the range of x = 0 – 0.1, and the ionic transference numbers of the materials are all over 0.98. The proton conductivity of (1-x)Sb2O5·xM2O3·nH2O (M = Bi and Y; x = 0.1) at room temperature increases to over 10-3 Scm-1 with an increase in the relative humidity. The conductivity is closely affected by the water adsorption behavior, which seems to be related to the introduction of oxygen vacancies.

Three types of antimonic acid (Sb2O5 · nH2O) films, (111)-oriented and nonoriented polycrystalline films of cubic Sb2O5 · nH2O and amorphous Sb2O5 · nH2O films, were prepared on quartz glass substrates with a spin-coating technique using aqueous slurries, which were formed by reacting H2O2 with metallic Sb powder or Sb(O-n-C3H7)3. The morphologies and structures of the films were observed, and the electrical conductivity of the films was determined at 20 °C in the relative humidity range 9–100%. The electrical conductivity of the (111)-oriented film, which increases from 1.69 × 10−5 to 2.89 × 10−3 S cm−1 as the relative humidity changes from 11 to 85%, is approximately one order of magnitude larger than those of the nonoriented and amorphous films.

Dependence of the contents and the states of residual carbon in YBa2Cu3O7−x powders synthesized by the sol-gel method on heating conditions, and effects of residual carbon on the superconducting properties were investigated. The carbon content of the powder heated at 950 °C for 20 h was reduced to 0.02%. It has been found that a large number of carbonaceous materials in the starting materials that are used in the sol-gel method does not affect the carbon content of synthesized superconducting powders. The volume of diamagnetism was increased and the Tc,onset was raised as the carbon contents were reduced to 0.04%. These properties were further improved by O2–HIP treatment at 500 °C.

YBa2Cu3O7−x superconducting films have been prepared on a YSZ ceramic substrate through the sol-gel method using metal alkoxides of Y, Ba, and Cu. A homogeneous solution containing the three metal alkoxides was prepared by dissolving the copper alkoxide, which is otherwise insoluble, in diaminoalcohol. The gel film, formed by dipping the substrate into the sol of 80 °C and withdrawing it up, was converted to a ceramic film consisting of YBa2Cu3O7−x phase by sintering at 850 °C for 30 min. The resulting film of about 10 μm in thickness showed zero resistivity (Tc end) at 54 K. Cold isostatic pressing of the film before sintering remarkably improved the Tc end to 85 K.