CaRuO₃ (CRO) thin films were prepared on SrTiO₃ (STO) single-crystal substrates by laser ablation, and their microstructures and the effect of lattice misfit on electrical conductivity were investigated. Pseudo-cubic (001), (110) and (111) oriented CRO thin films were grown epitaxially with the in-plane relationships on (001), (110) and (111) STO substrates at an oxygen pressure of 13 Pa and a substrate temperature of 973 K, respectively. Epitaxial (001) thin films showed a flat and smooth surface with a terrace and step structure whereas (110) CRO thin film had a faceted pyramid-like structure. The (111) CRO thin film had a rough terrace and step structure with trigonal texture. The lattice expansion of CRO would cause the decrease of the electrical conductivity. Epitaxial (111) CRO thin films has good lattice consistency with (111) STO substrate, and exhibited the highest electrical conductivity of 1.5×10⁵ S·m^-1 among the (001), (110) and (111) CRO thin films.

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We fabricated resistive-type oxygen sensors having a Ce_0.9Zr_0.1O₂ thick film as a sensing material and a Zr_0.8Y_0.2O_2-δ thick film as a temperature compensating material for the first time, and measured the resistance of the two thick films and the output of the sensors in model exhaust gas which was a combustion gas of propane. Then, we considered whether the sensor could be used as a “lambda sensor,” which can identify whether the air-to-fuel ratio of exhaust gas is rich or lean region. As a result, we confirmed that the resistance of the Ce_0.9Zr_0.1O₂ thick film was low and high in the case of rich and lean regions, respectively. The activation energy of the resistance of the Ce_0.9Zr_0.1O₂ film was 0.41 and 1.20 eV in rich and lean regions, respectively, and the mean value of them was 0.8 eV. The resistance of the Zr_0.8Y_0.2O_2-δ thick film in rich was almost the same as that in lean. The activation energy was 0.92 and 0.98 eV in rich and lean, respectively, and similar to the mean value of the activation energies of the Ce_0.9Zr_0.1O₂ film in rich and lean. This result shows that the combination of the Ce_0.9Zr_0.1O₂ and Zr_0.8Y_0.2O_2-δ films is better for the “lambda sensor.” The electrode structures of the sensor were optimized so that the mean value of the resistances of the Ce_0.9Zr_0.1O₂ film in rich and lean was the same as the resistance of the Zr_0.8Y_0.2O_2-δ film. The difference in output of the resistive oxygen sensor having the optimized electrode between rich and lean regions was more than 0.7 V, when the source voltage was 1.0 V. The output dramatically changed on the stoichiometric air-fuel ratio. From above-mentioned results, we conclude that the resistive oxygen sensors fabricated in this study are able to be used as “lambda sensors.”

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Titania/nitrogen-doped titania (TiO₂/TiO_2-xN_y) composite was prepared by mechanical milling in liquid medium and the phase composition, specific surface area, photo chemical properties, and photocatalytic activities were characterized. TiO₂/TiO_2-xN_y composites showed excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide and acetaldehyde. It is suggested that the doped nitrogen in TiO_2-xN_y acts as the acceptor of photoinduced holes on TiO₂ to depress the recombination of the electron-hole and improve the photocatalytic activity.

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For the fabrication of ceramic micro-scale patterns over a wide area, the Micro-molding in Capillaries (MIMIC) method is can be used by applying low solid loading colloidal suspensions of nanopowders. However, to uniformly form thick films from low solids loading suspensions, it is necessary that the additional spontaneous process of concentrating the suspensions in the molds occurs and is successfully accomplished, after the ordinary MIMIC process caused by capillary action. This concentration of suspension occurs as a result of inflow of the suspension from the entrance along with solvent evaporation from the exit of the mold. Therefore, the suspension preparation is important in order that the particles flow in due to the flow of the solvent. In this study, we determined the required condition of the suspension preparation by fabricating films from aqueous and ethanol-based suspensions of TiO2 nanopowders. By comparing the uniformity of the fabricated films and the particle distributions of the suspensions, it was found that the condition required for uniform patterning over a wide area is to disperse the nanoparticles into their primary size.

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This paper reports a dense textured single Ca-α-sialon fabricated by strong magnetic field alignment (SMFA) during non-aqueous slip casting of α-Si₃N₄, CaCO₃, Al₂O₃ and AlN starting powders, followed by reaction pressureless sintering at 1800°C. XRD analysis reveals that the orientation of the α-Si₃N₄ crystals occurs with the c-axis perpendicular to the magnetic field during slip casting. It is shown that the formation of the single Ca-α-sialon is complete within 5 min and nearly complete densification is achieved within 60 min. SEM observation reveals that the textured Ca-α-sialon is featured by the long-axis (c-axis) of large elongated grains perpendicular to the magnetic field. The texturing mechanism is attributed to the heterogeneous nucleation and epitaxially elongated growth on the initially oriented α-Si₃N₄ seeds. The prolonged sintering leads to a higher orientation as a result of the promoted grain growth.

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A laminated solid-reference electrode of BiCuVO_x (Bi₂Cu_0.1V_0.9O_5.35)/perovskite-oxide (La_0.6Sr_0.4Co_0.78Ni_0.02Fe_0.2O₃) was developed for a NASICON (Na₃Zr₂Si₂PO₁₂; Na⁺ conductor)-based potentiometric CO₂ sensor. The fabricated electrochemical cell expressed as, CO₂, O₂/Au (sensing electrode)/Li₂CO₃-BaCO₃ (auxiliary phase)/NASICON/BiCuVO_x/BiCuVO_x-perovskite-oxide (reference electrode)/O₂, responded well to changes in CO₂ concentration (100-400 ppm) at 450°C under high humid conditions (88%RH). The potential of the developed reference electrode was stable and exhibited little interference by water vapor. Furthermore, the reference electrode potential did not response to CO₂ even after the BiCuVO_x layer was contaminated with carbonate, indicating a good stability of BiCuVO_x against CO₂. The sensor device attached with the laminated solid-reference electrode showed a good warming-up characteristic, i.e., the electromotive force (EMF) of the device reached a steady and constant value when the sensor operation is re-started even after the sensor was exposed to humid air containing CO₂ at room temperature.

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A transparent smooth superhydrophilic silica coating has been developed by coating a polyethylene terephthalate (PET) substrate with microporous silica and immersing the microporous silica coating in water at 80°C. The microporous precursor sol for coating was synthesized from tetramethoxysilane under neutral conditions by accelerating the rate of the condensation with hydroxyacetone. Immersing the coating in water is an important process for removing not only the methoxy group, but also the hydroxyacetone to form the hydrophilic surface.

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Unique core-shell-structured micron spheres of Si-SiC consisting of a layer of silicon carbide nanocrystallites and a silicon single-crystal core were synthesized by thermal plasma in-flight carburization of silicon micron powders in Ar-H₂-CH₄ plasma. Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) revealed the formation of silicon carbide particles on the surface of Si particles, and transmission electronic microscopy (TEM) showed a uniform distribution of SiC nano-sized grains (~80 nm) at a depth of 500 nm beneath the surface of the composite spheres. Micron voids and nano pores were observed at the SiC-Si interface and in the Si matrix. The formation of long and thick SiC nanotubes was observed in the Si matrix near the SiC-Si interface. The mechanism of carburization reactions and the growth of silicon carbide layers and SiC nanotubes are discussed.

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Composite materials with europium (III) ion-doped zirconia (ZrO₂:Eu³⁺) infiltrated SnO₂ inverse opal have been prepared by the liquid phase infiltration (LPI) process. The absolute reflectance spectra measurement for ZrO₂:Eu³⁺ infiltrated SnO₂ inverse opal showed photonic stop band due to three-dimensionally (3D) ordered structure. Photonic stop band of ZrO₂:Eu³⁺ infiltrated SnO₂ inverse opals was shifted to longer wavelength compared with SnO₂ inverse opals due to the increase of average refractive index. The ZrO₂:Eu³⁺ infiltrated SnO₂ inverse opal showed stronger emission intensity than ZrO₂:Eu³⁺ thin film without 3D ordered structure.

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Two strontium cyanamide polymorphs (trigonal low temperature phase and orthorhombic high temperature phase) were prepared by firing strontium acetate in ammonia flowing at 600-850°C. Trigonal low temperature phase irreversibly changed to orthorhombic high temperature phase by post annealing. The two structures differed in SrN₆ octahedon linkage and (NCN)^2- arrangement. The structural change was discussed in relation to repulsion between strontium cations and SrN₆ octahedron linkage by corner or edge sharing.

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Bioactive organic-inorganic hybrids can be used as biomaterials for bone substitution because they exhibit osteoconduction and other functions due to their organic components, such as flexibility and bioabsorbability. In this study, we synthesized uniform organic-inorganic hybrids from triethoxysilane-functionalized poly(tetramethylene oxide) (Si-PTMO), tetraethoxysilane (TEOS) and calcium chloride (CaCl₂) via the sol-gel process. The starting composition of Si-PTMO/TEOS molar had a weight ratio ranging from 20/80 to 90/10. The CaCl₂ concentration was kept constant at a CaCl₂/TEOS molar ratio of 0.15. Uniform and transparent hybrids were obtained with a Si-PTMO/TEOS compositional range from 20/80 to 90/10. The potential bioactivity was evaluated by determining the formation of a bone-like apatite layer in simulated body fluid (SBF). Formation of a bone-like apatite layer was observed on the surface of the organic-inorganic hybrids when they were prepared from starting compositions of Si-PTMO/TEOS with weight ratios ranging from 20/80 to 50/50. An appreciable quantity of the calcium silicate is required to produce bioactive organic-inorganic hybrids.

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Green density of the samples prepared from wet-jet milled slurries was much higher than that of the samples prepared from conventional ball milled slurries indicating that the former method results in closer packing of particles. Due to this close packing, ceramics could be sintered at a lower temperature with little grain growth. Furthermore, ceramics densified to 97% of its theoretical density at 1450°C had a 3-point bending strength of 733 MPa, which is equivalent to that of the Al₂O₃ ceramics prepared by pressure assisted sintering. Wet-jet milling method works well for the dispersion of the particles before molding them into green bodies.

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A layered organic/inorganic hybrid thin film, which consists of MoO₃ with poly(5,6,7,8-tetrahydro-1-naphthylamine) (PTHNA), which is used as an aldehyde gas sensor, was investigated by X-ray diffraction (XRD) analysis and gas-sensing properties analysis. The (PTHNA)_xMoO₃ hybrid thin film shows distinct increasing resistance response to acetaldehyde and little response to formaldehyde in ppb level whereas typical organic/MoO₃ hybrids show larger response to formaldehyde than to acetaldehyde or almost equal responses to formaldehyde and acetaldehyde in ppb level.

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A solid-in-oil-in-water (S/O/W) emulsion-solvent evaporation method was applied to encapsulate protein-loaded hydroxyapatite (HAp) granules (D₅₀=19.5 μm) with a biodegradable polymer of poly (lactic-co-glycolic acid) (PLGA). After loading bovine selum albumin (BSA), the HAp granules were mechanically dispersed in oil phase (PLGA dissolved in CH₂Cl₂), and then the suspension was dropped into water containing an emulsion stabilizer of polyvinyl alcohol (PVA). Stirring of the dropped suspension in the water phase produced S/O/W emulsions. The emulsions were diluted with excess water to facilitate removal of the organic solvent (CH₂Cl₂) from the oil phase. After the evaporation of CH₂Cl₂, the particulate materials were separated, washed and vacuum-dried. The resultant particles had very smooth PLGA surface with spherical shape, and their mean particle size was about several microns larger than that of the HAp granules. Fluorescently-labeled confocal laser scanning microscopy (CLSM) revealed that the protein-loaded HAp granules were encapsulated in the PLGA microsphere.

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The double catalyst structure on two microheaters of a thermoelectric device was suggested to improve selectivity of the hydrogen for the mixed gas of H₂ and CO. Thermoelectric hydrogen sensor (THS) burns and detects both of H₂ and CO when these were mixed. Moreover, if we can eliminate the heat contribution of CO, only the H₂ concentration can be estimated ever for these mixture gases. The noble structure of double catalysts, a CO selective Au/Co₃O₄ catalyst and a H₂ selective Pt/Al₂O₃, integrated on the two microheaters were fabricated and its gas sensing performance was investigated.

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Porous ceramic materials are generally used for templates in synthesis of new porous carbon materials by template method. In the synthesis procedure, template materials are finally dissolved by acid or alkaline solution. Improvement of carbon content in the carbon materials by the process is expected to be effective for advancement of porosity and specific surface areas of the specimens, therefore realization of elimination of templates to a maximum extent is assumed to be desirable. In this report, we have prepared several porous carbon materials by the use of natural soils or clays for templates, and improved their carbon content by ammonium chloride (NH₄Cl) treatment. However, their specific surface areas demonstrate a tendency to decrease contrary to the expectation. The result suggests that the original carbon specimens are rather effective in porosity, and the residue of templates can also play a useful part for specific surface areas of the carbon materials. This effect is attractive for improvement of synthesis process of porous carbon materials, which have high specific surface area, from viewpoints of practical applications.

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Preparation of fire red cadmium sulfo- selenide pigments based on zircon via solid-state reactions encountered with some difficulties. Undesirable reactivity and inadequate homogeneity of components are two important problems, which counteracted on completely covering of color agents by zirconium silicate and so stable production of these materials. It has shown that by using a sol-gel method the above-mentioned problem will be eliminated and a desirable color shade can be obtained. In the sol-gel process, at first a precipitatant was prepared by mixing of Se (dissolved in sodium sulfide solution) and a cadmium sulfate-zirconium acetate solution. Gelation was occurred by adding a diluted sodium silicate solution into the washed and dried precipitant. The mineralizer was lithium fluoride, which was added to the washed/dried gel. Calcinations of the later compound were done at about 950°C. The experiments showed that the relative volume of zircon to cadmium sulfo selenide has an important role on a complete encapsulation of colorants and so on quality of pigment. According to our experiment, the optimum relative volume of colorant agent to zircon was determined as bout 40/60.

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Al₄SiC₄ has been reported to be a good additive for carbon-containing refractories. The present study investigated various factors influencing the synthesis of Al₄SiC₄ by heating mixtures of Al₂O₃, SiO₂ and graphite in an argon atmosphere. The formation of Al₄SiC₄ began from a temperature between 1450°C and 1500°C. The formed quantity of Al₄SiC₄ increased as the heating temperature was raised. As the heating time was extended, the Al₄SiC₄ increased to its greatest amount and then it hardly changed. SiC and Al₄O₄C were also formed as mediums and were decreased as the heating time was extended. The optimum molar ratio of C, Al₂O₃ and SiO₂ was 8:2:0.8 and at that time pure Al₄SiC₄ was formed. The formation mechanism of Al₄SiC₄ was also discussed.

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Fine-sized LiCoO₂ powders were prepared by solid-state reaction method using nano-sized Co₃O₄ powders. Nano-sized Co₃O₄ powders with regular morphology and narrow size distribution were obtained by spray pyrolysis method. The fine-sized LiCoO₂ powders had slightly aggregated morphology and narrow size distribution even without milling process. The mean size of the LiCoO₂ powders increased from 280 nm to 500 nm when the post-treatment temperature was changed from 500°C to 800°C. On the other hand, the LiCoO₂ powders prepared by conventional spray pyrolysis method at preparation conditions of high production rate had irregular morphology and broad size distribution. The initial discharge capacities of the fine-sized LiCoO₂ powders prepared by solid-state reaction method and the commercial product with micron size were each 151 mAh/g and 133 mAh/g. The discharge capacities of the fine-sized LiCoO₂ powders dropped from 151 to 135 mAh/g after 50 th cycle at a current density of 0.1 C.

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Charge density is an important film characteristic that determines the quality of film surface passivation. In this study, a prediction model of charge density was constructed by using a neural network and generic algorithm. For a systematic modeling, plasma enhanced chemical vapor deposition process of silicon nitride films was characterized by means of a statistical experimental design. Effects of parameters under various radio frequency (rf) powers were examined under various plasma conditions. An increase in charge density was observed with increasing rf power over the entire range of SiH₄ flow rate as well as at lower N₂ flow rates or pressures. The effect of SiH₄ flow rate on charge density was opposite to that for N₂ flow rate given rf powers. For the variations in N₂ or SiH₄ flow rate, charge density seemed to be strongly correlated to N/Si ratio. Under the variations in pressure or N₂ flow rate, maintaining a lower pressure was beneficial in achieving a higher charge density. A pronounced rf power effect at smaller grain size was expected.

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Structure of electrically conductive xBaO·(90-x)V₂O₅·10Fe₂O₃ glasses (x=20, 30 and 40), NTA glass^TM, was investigated by ⁵⁷Fe-Mössbauer spectroscopy, Fourier-transform infrared spectroscopy(FT-IR), X-ray diffractometry (XRD), differential thermal analysis (DTA) and scanning electric micrography (SEM). A remarkable increase in the electric conductivity (σ) was observed from 1.6×10^-5 to 1.1×10⁰ S cm^-1 after annealing NTA glass^TM with ‘x’ of 20 at 500°C for 1000 min. Precipitation of a small amount of BaFe₂O₄ and BaV₂O₆ phases was confirmed by XRD, indicating that the sample still has a glassy phase even after prolonged isothermal annealing. An activation energy for the crystallization (E_a) was estimated to be 2.3±0.2 eV, indicating that the crystallization of the vanadate glasses is involved in a cleavage of Fe-O bond having binding energy of 2.6 eV, not of the V-O bond of which binding energy is known to be 3.9-4.9 eV. A consistent result was obtained in the FT-IR spectra, showing that the absorption band attributed to a stretching vibration of Fe-O bond of FeO₆ octahedra appeared after the annealing. By applying ‘T_g-Δ rule’, i.e., a linear relationship between glass transition temperature and quadrupole splitting of the Mössbauer spectra, it proved that Fe^III plays a role of a network former (NWF) like V^IV and V^V in NTA glass^TM. A constant isomer shift of 0.40±0.01 mm s^-1 and a decrease of quadrupole splitting from 0.70±0.02 to 0.53±0.02 mm s^-1 were observed in the Mössbauer spectra after the isothermal annealing. These results suggest that σ of NTA glass^TM is enhanced as a result of structural relaxation, i.e., reduced local distortion of the network composed of Fe^IIIO₄, VO₄ and VO₅ units.

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Powder neutron diffraction experiments with Rietveld analyses were carried out on pure and Ta-substituted Zn₂TiO₄ at room temperature to investigate the defect structure together with the oxide ion conduction mechanism. The refined structure of pure-Zn₂TiO₄ agreed well with the previously reported inverse spinel-type structure with cubic symmetry. For Zn_2-x/2Ti_1-xTa_xO₄ solid solutions of cubic phase, the tantalum substitution as well as the vacancy formation was made at the octahedral cation site, while the tetrahedral cation site was occupied by zinc ions without any significant deficiency. Essentially the similar results were attained in the tetragonal phase obtained by long-term annealing. By evaluating the occupation factors of tentatively introduced oxide ion interstitials at various positions, oxide ion conduction was supposed to be made with the interstitialcy diffusion mechanism, where displacement of a regular oxide ion toward the cation vacancy enabled the migration of other oxide ions through the oxide ion vacancy at which the displaced oxide ion had been initially.

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Aqueous 5 vol% suspensions with 30 nm SiC particles at pH 7.0 were filtrated at a constant pressure of 0.1-10 MPa to form the compacts of 18-37% of theoretical density. The packing density became higher at a higher pressure. The filtration kinetics deviated from the filtration theory established for the suspension containing well dispersed particles. A new filtration model for a flocculated suspension was developed. The experimental results were well explained by the developed theory except for the final stage of consolidation. When the deformation ability of flocculated particles was reduced, the difference of the consolidation behavior between the experiment and the derived theory became larger.

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Rare-earth cobalt ruthenium oxides Ln₂CoRuO₆ (Ln=La, Pr, Nd, Sm, Eu and Gd) having the double perovskite-type structure were prepared at 1673 K in air. Rietveld analysis of the X-ray diffraction patterns revealed that the oxides crystallized in monoclinic cells with space group P2₁/n (No. 14). Co/Ru disorder up to 10% was observed at each of the octahedral site in GdCoRuO₆. Ln₂CoRuO₆ oxides were p-type semiconductors with Seebeck coefficient of 180-290 μV·K^-1 at 400 K and 72-79 μV·K^-1 at 1073 K. The power factors at 1073 K were 1.9-4.3×10^-6 W·K^-2·m^-1.

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The microwave dielectric properties of Al₂O₃-TiO₂ ceramics were studied. The large negative temperature coefficient of the resonant frequency (τ_f) of Al₂O₃ ceramics was improved by adding rutile (TiO₂), which has a large positive τ_f. In order to achieve τ_f of nearly zero, the post annealing treatment is necessary for the dense Al₂O₃-TiO₂ ceramics sintered at more than 1300°C, because Al₂TiO₅ secondary phase appears during sintering. The previous study reported that the post-annealing treatment decomposed Al₂TiO₅ into Al₂O₃ and TiO₂. However, a brief post-annealing accompanied to reduction of Qf. This study tries to make clear influence of the annealing on the decomposition and the microstructure as well as the microwave dielectric properties. Particularly, we focus on effect of starting particle sizes of TiO₂ on the annealing process. It was found that difference in the starting particle size affected both decomposition process and grain growth during annealing. In the case that the small starting particle size (0.05 μm), Al₂TiO₅ phase was lightly decomposed by post annealing treatment for one time. The grains gradually grew as time of the post annealing treatment, resulting in increase of Qf. In the case of the large starting particle size (0.5 μm), Al₂TiO₅ phase remained slightly by post annealing treatment for one time and the grain size maintained without grain growth. The residual Al₂TiO₅ might bring the reduction of Qf and the Qf values maintain overall by mean of no grain growth.

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