Electron-transport mechanisms of oxide ceramics exhibiting high-speed voltage-pulse-induced resistivity changes were characterized with regard to nanostructure and defect formation. La-doped SrTiO₃ single crystals with Ag top electrodes and Pt bottom electrodes exhibited bipolar resistive switching but retained the low-resistivity state for only 3 or 4 h because of unstable deep-level trap states at the metal-semiconductor interface. Crystalline (Pr_0.7Ca_0.3)MnO₃ thin films sandwiched by Pt electrodes showed metallic conductivity and consequently never showed electric-pulse-induced resistivity changes, but insulative amorphous (Pr_0.7Ca_0.3)MnO₃ thin films showed monopolar resistivity switching that suggested the formation of nanoscale filament paths with nanodomain switches. The TiO₂ anatase nanolayer formed on a TiN thin film exhibited high-speed electric-pulse-induced bipolar resistivity changes thought to be due to a Mott transition caused by o^2- migration and the formation and annihilation of V_O^•• in 2.5-nm-thick anatase layer.

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In this paper, the effects of heating temperature and soaking time on the synthesis of magnesium aluminum oxynitride (MgAlON) by spark plasma sintering (SPS) were investigated. Results showed that the content of N decreased while that of O increased with the increasing of temperature, because of the reaction between Mg₃N₂ and H₂O when the sample heated below 1500°C. Owing to the rapid warming up rate and the reaction between graphite and H₂O, the variation of chemical composition was lowered in the sample heated at higher temperature. During the heating process, shrinkage started above 1000°C and expansion was observed above 1600°C. Moreover, open pores were not detected in the sample heated at 1500°C for 1 min and single phase MgAlON without pores could be obtained when heated at 1700°C for 10 min. With the increasing of the content of Mg and the decreasing of N, all the thermal characteristics were increased and the cold bending strength was decreased, which may provide a standard data about the cold bending strength and the thermal characteristics of MgAlON with different composition.

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Fine-sized, spherical BaMgAl₁₀O₁₇:Eu²⁺ phosphor particles with filled morphologies were prepared by flame spray pyrolysis. Precursor particles prepared by flame spray pyrolysis at a low-temperature diffusion flame and a short particle residence time within the diffusion flame were of large size and had hollow structures. On the other hand, precursor particles prepared at optimum preparation conditions were fine sized, had filled structures, and narrow size distributions. The melting of large-sized intermediate particles with hollow structures within the high-temperature diffusion flame formed fine-sized, spherical precursor particles with filled structures. The BaMgAl₁₀O₁₇:Eu²⁺ phosphor particles prepared by flame spray pyrolysis at optimum preparation conditions were fine-sized and had regular morphologies after post-treatment at 1400°C. The mean size of the BaMgAl₁₀O₁₇:Eu²⁺ phosphor particles was 1.0 μm. The photoluminescence intensity of fine-sized, spherical BaMgAl₁₀O₁₇:Eu²⁺ phosphor particles with filled structures was higher than that of large-sized phosphor particles with hollow structures excited by the vacuum ultraviolet light at the wavelength, 147 nm.

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The addition of aluminum fluoride to gibbsite retarded the phase change to boehmite by chemisorption of hydrogen fluoride on gibbsite particles. In the specimen with addition of aluminum fluoride, the spinel type phase transformed directly to α-Al₂O₃, without passing through κ- and θ-Al₂O₃ phases. The formed α-Al₂O₃ consisted of clear, hexagonal plate-like particles about 1 μm, Without taking over a relic of the gibbsite particle. The formation of automorphic crystals suggests that a surface diffusion also contributes to the mechanism of this material transport in addition to the vapor phase transport.

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Formation kinetics of chemically vapor-deposited carbon on mesoporous silica was examined for its porous texture, activation energy and thermodynamic factors. The carbon was deposited by CVD using benzene, hexane and toluene. The amount of carbon in these hybrids increased with deposition in temperature and time. The increase of carbon resulted in decreases of their specific surface area and pore size. The density of carbon within mesopores in the hybrid prepared from benzene and toluene was around 0.6 and 1.9 g/cm³, respectively. For the hybrid modified with hexane, carbon was prone to enclose particles of the mesoporous silica. The activation energies of carbonization were estimated to be less than 100 kJ/mol for benzene and toluene; however, the energy from hexane was 279 kJ/mol. These energies imply that mesopores accelerate carbonization from benzene and toluene to form carbon within mesopores, and carbon was deposited on MPS particles for hexane. The estimated change of formation free energy (ΔG_f) of hexane was smaller than those of benzene and toluene over the temperature range of these experiments. From these estimated ΔG_f, hexane molecules tend to carbonize more quickly before introduction into mesopores than benzene and toluene. Eventually the lower ΔG_f of hexane presumably possibly gives a large amount of deposited carbon on the surface of the mesoporous silica particles.

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Frequency dependences of dielectric constant (ε_r′) for 9 mol% Y₂O₃ doped ZrO₂ (YSZ) single crystal which is a typical oxide-ion conductor was successfully explained by the superimposition of both electrolyte-electrode interfacial and Debye-type polarizations. Three kinds of Debye-type polarizations were observed at fairly high temperatures. The two polarizations were ascribed to defect associates, (Y_Zr′-V_O^••)^•, which were observed in the tan δ spectra. The third polarization in the high frequency region was ascribed to a long range migration of oxygen vacancy, which was observed in the M″ spectra. The σ_ac dispersion was also explained by the Debye-type polarizations.

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Use of moderator materials in a fast breeder reactor is effective for transmutation technology, and ¹¹B₄C is one of the candidates. Up to now, the behavior of ¹⁰B₄C as the control rod material is well known, but that of ¹¹B₄C has hardly been investigated. In this paper, irradiation effects of ¹¹B₄C pellet irradiated in the experimental fast reactor JOYO were studied. From the experimental results, it was observed that no macro-cracks were recognized but bubble nucleation was found in the grain and along the grain boundaries of ¹¹B₄C. Furthermore, it was shown that the thermal conductivity of ¹¹B₄C was higher than that of ¹⁰B₄C. During the annealing from room temperature to 1400°C, two recovery stages were found on thermal conductivity. It was suggested that the recovery of B₄C was related to the volume and distribution of helium bubbles. Since the ¹¹B₄C pellet was mechanically more stable compared with the ¹⁰B₄C pellet under irradiation, it was shown that ¹¹B₄C had high applicability for a moderator material.

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Silica and silica/polymethylmethacrylate (PMMA) hybrid thin films 0.15-0.9 μm in thickness were deposited on polybutyleneterephthalate (PBT) substrates by dip-coating followed by heat-treatment at 170° or 180°C, using perhydropolysilazane (PHPS) and tetraethylorthosilicate (TEOS) as a silica source. A contamination test was carried out using curry as a contaminant; the curry was placed on the thin film samples, heated at 150°C, and then removed with neutral detergent, followed by microscopic observation and color difference measurement. Coating with silica either using TEOS or PHPS was effective in suppressing the contamination, where the latter was found to be more effective than the former. Although the as-prepared silica and silica/PMMA hybrid thin films were crack-free, the films tended to be cracked when subjected to the contamination test, which was more significant for those prepared at higher substrate withdrawal speeds. The cracking tendency, however, was found to decrease when silica was hybridized with PMMA, and no cracks were observed on the contamination test for the sample prepared at PMMA/PHPS mass ratios higher than 1.2. The degree of contamination was minimized at a PMMA/PHPS mass ratio of 0.8, where excellent adhesion was also found between the film and the substrate.

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According to XRD analysis, when sprayed amosite was heated at over 900°C for 3 h, amosite crystal was not detected in the sample. In contrast, a part of the needlelike amosite grains were not detected in the sprayed amosite using a phase-contrast microscope analysis after heating at 500°C for 3 h. Then the color of the needlelike amosite grains changed to red, because Fe₂O₃ (hematite) was precipitated at the surface of the amosite grains. The grindability of the needlelike amosite grains was improved with an increase of the heating temperature. When the sprayed amosite was heated at 1100°C for 3 h, a fine powder with under aspect ratio of 3 was obtained after grinding.

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12SrO•7Al₂O₃ (S12A7) is a meta-stable phase in the system of SrO-Al₂O₃ and has the isostructure with 12CaO•7Al₂O₃ (C12A7), which is composed of sub-nanometer-sized cages with oxygen ions loosely encaged in the cages. This letter reports fabrication of polycrystalline thin films of insulating and metallic S12A7 electride thin films. The as-crystallized film was an electrical insulator, while light-induced persistent electronic conduction with a conductivity of~1×10^-3 S•cm^-1 at 300 K was realized in proton-implanted films. Higher conductivities of~270 S•cm^-1 were attained in the films subjected to a reduction treatment using an oxygen deficient amorphous film deposition. These behaviors are similar to those observed on C12A7. The present results suggest that S12A7 is another candidate material to explore electronic functions originating from a nanoporous structure embedded in a crystal structure.

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