The behavior of solid oxide electrolysis cell was investigated as follows.
(1) The asymmetry of i-V performance indicated the existence of the parallel reaction path in the hydrogen evolution reaction.
(2) It is possible to operate the cell at high water decomposition rate (>82%) without a remarkable interference of concentration polarization maintaining the effective electronic conductance of the electrode.
(3) The polarization behavior revealed that the operation current density of 2A/cm² can well be achieved within the optimum cell voltage of 1.48V at 1273K.
(4) The degradation rate of LSM anode was decreased by improving the initial polarization resistance.
(5) The degradation of LSC anode was accelerated by Sr.
(6) The use of ceria-based electrolyte as an intermediate layer is effective in decreasing the degradation rate of LSM anode. The complete inhibition of the degradation could be achieved by avoiding the direct contact between LSM and YSZ.

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A suspension of C₃AH₆-NaOH was prepared by adding -37g of Ca(OH)₂ with stirring into 2l of aqueous solution in which -27g of NaAlO₂ is dissolved. The CaCO₃ fibers having aspect ratios of -20 with diameters of -3μm were obtained by blowing CO₂ gas into the suspension at 80-85°C. Successive CO₂-gas-blowing at 25-30°C leads to precipitation of the fine particles of Al(OH)₃ on the surface of the CaCO₃ fibers, so that the CaCO₃ fibers coated with fine particles of Al(OH)₃ were obtained. By heating them at 500°C, the CaCO₃ fibers coated with fine particles of activated alumina with large specific surface area of -120m²/g were also obtained. These coated layers firmly adhered to the CaCO₃ fibers.

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This paper presents a reduction in the Rayleigh scattering intensity in VAD silica glass with annealing and its relation to the fictive temperature, T_F, estimated from the shift in the infra-red (IR) absorption peak, an overtone mode of the Si-O-Si stretching vibration. An 18% decrease was observed in the scattering intensity for a sample annealed at 950°C for 156h. The decrease appears to be mainly due to the T_F reduction. The T_F reduction rate for a dehydrated sample was higher than that for an undehydrated sample. This is explained by the interaction between termination units (-OH and -Cl) and the glass network.

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Several simulations were performed in order to estimate the effects of the nonuniformity of the SiC ceramic semiconductor microstructure on the electrical conductivity. The boundary potential model was used to express the electrical characteristics of the grain boundaries and the calculations were performed using the three-dimensional equivalent circuit in the simulations. These simulations show that the nonuniformity of the acceptor concentration or of the trap concentration at the grain boundary greatly affects the electrical conductivity of the SiC ceramic semiconductor. This is explained by the percolation theory. The influence of these nonuniformities should be carefully considered in order to design or to produce related devices.

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A compact of spherical silica with alkali metal oxide addition was fired within a temperature range from 600 to 1200°C for 6h in air. The crystallization and phase transformation behavior of sintered spherical silica were examined by XRD, IR, DTA, density and shrinkage measurements and SEM. The following results were obtained. (1) The silica phases formed in the sintered compacts depended on the kind and amount of added alkali metal oxide and on the firing temperature. (2) The phase transformation behavior of sintered spherical silica proceeded as follows: amorphous silica→keatite→quartz→cristobalite→tridymite. (3) Through SEM observation, it was found that molten phase formed in the sintered compacts with alkali metal oxide. The molten phase is hypothesized to be a factor determining the crystallization and phase transformation of sintered spherical silica.

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Semiconducting (Ba_0.9Sr_0.1)TiO₃ ceramics with 0.1mol% Sb₂O₃ and 0.05mol% Ta₂O₅ were prepared by changing sintering temperature and heating rate. Microstructure, specific resistivity at room temperature, magnitude of PTCR effect and breakdown voltage of the obtained ceramics were investigated. Abnormal grain growth was observed from 1300°C and became remarkable at the temperature regime between 1320°C and 1360°C. The specific resistivity at room temperature decreased and the magnitude of PTCR effect increased with increasing the degree of abnormal grain growth. When the heating rate is increased from 180°C/h to 500°C/h at the temperature regime between 1300°C and 1360°C, the grain size of the samples decreased from 44μm to 18μm. The specific resistivity at room temperature increased from 5Ωcm to 7.5Ωcm by decreasing average grain size. However, both the magnitude of PTCR effect and the resistivity in the grain evaluated by the complex impedance measurement were independent of the grain size. The breakdown voltage increased from 31V/mm to 60V/mm with decreasing the grain size from 44μm to 18μm. There was the linear relationship between the breakdown voltage and the reverse of the grain size, and the breakdown voltage of a grain boundary was estimated 0.78V from the slope of this relationship. In this study, it was revealed that the heating rate is one of the critical factors for properties of (Ba, Sr)TiO₃ ceramics. Rapid heating at a proper temperature regime is a preferable condition for the ceramics with fine microstructure, which results in the improvement of their breakdown voltage without significant increase of the specific resistivity at room temperature.

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Morphological control of Sn²⁺ doped calcium carbonate phosphors by crystallizing amorphous calcium carbonate formed from aqueous solution reaction of CaCl₂-(NH₄)₂CO₃-SnCl₂ system and its fluorescence property were investigated. Amorphous calcium carbonate changed into spherical and platelike vaterites at 15-50°C and needlelike aragonite above 60°C. In order to obtain calcite, a suspension of vaterite formed at 20°C by crystallizing amorphous calcium carbonate was kept at 90°C for 120min. The content of Sn²⁺ in platelike vaterite crystal was Sn/CaCO₃ mol% of approximately 0.4 and was about 4 times as compared with that of rhombohedral calcite crystal. The emission spectrum of rhombohedral calcite phosphors with Sn²⁺ of 0.04mol% showed bright blue fluorescence at 465nm. Its optimum excitation wavelength was wavelength of ultraviolet irradiation at 255nm.

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Phase-separated glass specimen was prepared from a fluorine containing sodium borosilicate glass by heat treatment at 500°C, which consisted of borate-rich glass phase and silica-rich glass phase. For this phase-separated glass specimen, the leaching process was investigated. The leaching process consisted of two stages. In the first stage, soluble components of B₂O₃, Na₂O and NaF were leached out from the borate-rich phase and this leaching proceeded in a diffusion-controlled process. In the second stage, silica-gel which precipitated in pores during leaching was leached out and this leaching proceeded in a reaction-controlled process. Activation energies were calculated for the first stage as 33.5kJ/mol and 32.7kJ/mol from the data of thickness of leached layer and weight loss, and for the second stage as 22.6kJ/mol, 24.5kJ/mol and 29.1kJ/mol from the data of pore size distribution, weight loss and Si content of leaching solution.

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The lead leaching from overglaze decoration was greatly reduced after soaking in 4% acetic acid for 10 to 24h. The effectiveness of the treatment in reducing the lead leaching was confirmed. Most overglaze decorations showed no change in gloss or color after the treatment with acetic acid. The reduced gloss in some overglaze decorations after the treatment could be recovered by reheating at 300 to 500°C. The low level of lead leaching achieved by the treatment was retained even after reheating up to 800°C. For studying the mechanism of lead leaching, the surface of overglaze decoration was observed by optical microscopy and EPMA. It was observed that particular regions in the overglaze decoration releasing large amounts of lead were eroded by acetic acid.

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A series of praseodymium manganites, Pr_1-xA_xMnO₃ (A=Ca, Sr, Ba, 0≤x≤1.0), were examined for their electrode-catalytic activities as incorporated into a gas diffusion-type oxygen reduction electrode working in an alkaline solution. Among the oxides tested, Pr_0.6Ca_0.4MnO₃ gave the highest electrode performance (320mA·cm^-2 at -150mV vs. Hg/HgO) in 8mol·dm^-3 KOH aqueous solution at 60°C under air flow. The electrode performances were found to be well correlated with the activities of the oxides for the 4-electron reduction of oxygen (O₂+2H₂O+4e^-→4OH^-) evaluated from a rotating ring-disk electrode analysis. The oxidation state of Mn ions of the oxides was investigated by means of iodometry, X-ray photoelectron spectroscopy, temperature-programmed oxygen desorption and electron spin resonance. The results obtained suggest that the active sites for the 4-electron reduction of oxygen involve Mn³⁺ ions and that their activities increase profoundly as the Mn³⁺ ions neighbor Mn⁴⁺ to form Mn³⁺-Mn⁴⁺ pairs. The electrode loaded with Pr_0.6Ca_0.4MnO₃ was confirmed to continue to work rather stably for a test period of 200h under the galvanostatic condition of 300mA·cm^-2, the oxide being kept intact as revealed by X-ray diffraction analysis after the test. The same electrode was shown to exhibit a promising performance when incorporated into a zinc-air cell.

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A method for an estimation of the compositional fluctuation area in ternary solid solutions was developed. An elliptic area of the compositional fluctuation which is defined by constants, A, B and φ, was assumed in a ternary diagram. The maximum and minimum lattice spacings in the assumed area were figured out for several lattice planes. Values of (Δd/d)_i^cal, fluctuations of the lattice spacings, were calculated from these values. Values of β, which is the net width of the X-ray diffraction peak of the sample, were measured and the values of β cosθ were plotted against sinθ. Theoretically, each plot is on a line whose section at sinθ=0 is fixed by the crystallite size of the sample and whose slope is Δd/d. The section was determined by the least square method using (Δd/d)_i^cal estimated from the assumed elliptic area. Then ∑e_i², a sum of squares of the difference between the calculated value of β cosθ and the observed one, was determined. The values of ∑e_i² were evaluated for various values of A, B and φ systematically. The values of A, B and φ which give the minimum value of ∑e_i² were finally determined. The area which is settled by the values of A, B and φ determined thus is the compositional fluctuation area. The compositional fluctuation areas such determined agreed with those determined by the method reported previously. By this method, the compositional fluctuation area can be determined without data of diffractions whose dependence of lattice spacing on composition is the same, while it could not be determined by the previous method.

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The hydrothermal hot-pressing method is a very usefull technique for solidifying various inorganic materials. The authors have tried to apply some cementitious materials to this process. A commercially available alumina cement is used and the effects of addition of sodium phosphate and silica fume are examined to increase the strength of solidified alumina cement. The reaction temperature is 250°C, and the reaction time is 60min. The maximum tensile strength of the solidified bodies reached at about 24MPa when alumina cement is replaced by 2.5mass% of silica fume and modified with 10mass% of sodium metaphosphate.

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Casting slips of silicon carbide without sintering additives were prepared by the use of a cationic cellulose derivative (CCD) as a deflocculant. The effects of CCD addition on the degree of dispersion, flow behaviors and moldability of the slips along with those on the sintered bodies were investigated. The optimum amounts of CCD for good dispersion based on the mechanisms both of steric stabilization and positive electrification by the adsorbed layer of CCD increased with increasing pH values, because CCD molecules bond electrostatically to the negatively charged sites formed by ionization of the surface silanol groups of SiC. The slips well-dispersed in the presence of CCD exhibited flow curves close to Newtonian and/or pseudoplastic flow with a low viscosity and were found to be satisfied both in moldability and mold release, while the SiC slips deflocculated without CCD show the intrinsic flow of dilatancy. The resulting fired bodies proved to have the values of apparent density much lower than those of the sintered bodies of which green bodies were shaped by the use of high solid content slips without CCD, indicating that not only the interparticle structures formed in the slips but also the presence of CCD affects the sintering stages.

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Preparation of silicon oxide films was tried by chemical vapor deposition (CVD) at substrate temperatures (T_sub) from 298 to 308K and pressures in CVD chamber (P_chm) from 4 to 13kPa. Fluorotriethoxysilane (FTES) and water which were vaporized in thermostatic oil baths were used as source materials. Dense films were obtained at T_sub below 303K and P_chm above 6.7kPa, and the deposition rate was seriously affected by the bath temperature to evaporate water. Deposited films were examined by infrared reflection spectroscopy and X-ray photoelectron spectroscopy, and it was found that the deposits contained fluorine. The relation between current density and electric field of dense films was also examined.

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La-doped (Ba, Sr)TiO₃ ceramics were prepared by using high purity starting materials to clarify the influence of Sr addition on the semiconducting behavior of BaTiO₃. No sintering aids such as SiO₂ and excess TiO₂ were used. Resistivity at room temperature, grain growth and Curie temperature (T_C) were studied as functions of Sr content. The addition of Sr within a range of 20mol% enhanced grain growth, and the room-temperature resistivity decreased with increasing Sr content. The decreasing rate of T_C in Ba_0.8-xLa_xSr_0.2TiO₃ was smaller than that in Ba_1-xLa_xTiO₃ with La content (x), but the total amount of La incorporated into the grains is considered not to be noticeably influenced by Sr addition. The present result may suggest that the addition of Sr increases the ratio of the concentration of La incorporated into the lattice compensated with free electrons to the total content of La doped. The addition of further amounts of Sr caused an increase in the total resistivity.

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Synthesis process of the barium plumbate thin films by metal alkoxide method was improved to obtain the high quality films. The precursor solution was prepared using Ba metal and Pb(OⁱPr)₂ as raw materials, and 2-methoxyethanol as a solvent. The perovskite thin films with flat surface were formed by firing the films at a temperature higher than about 450°C immediately after coating the precursor solution on the MgO(100) substrate in the relatively dry atmosphere. The typical specific resistivity of films post-annealed at 550°C was about 1.2×10^-2Ωcm.

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The oxidation behavior of three kinds of Si-Ti-C-O fibers, TF1(18), TF2(12) and TF2(18), was investigated. TF2(12) with 12mass% of oxygen content and TF2(18) with 18mass% oxygen content synthesized from a polytitanocarbosilane (PTC2) with lower polyborodiphenylsiloxane content, had higher tensile strength after heat treatment at 1000°C in air than TF1(18) with 18mass% oxygen content synthesized from an another polytitanocarbosilane (PTC1). After heat treatment at 1000°C for 500h, an oxide layer was formed on each fiber's surface. The oxide layer on TF1(18) was cristobalite, and a lot of cracks was observed on it, whereas that on TF2(12) and TF2(18) contained amorphous material. The free carbon content in TF1(18) was higher value than that of another two fibers.

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The dependence of the conductivity of the Li(Fe_xAl_1-x)₅O₈ solid solution on its composition was investigated. The abrupt increase in the conductivity and decrease in the activation energy were observed between x=0.4 and 0.5 of Li(Fe_xAl_1-x)₅O₈. The composition x=0.415, which corresponds to the percolation threshold expected from the percolation theory, is within this range (x=0.4-0.5). The conductivities of the compositions above the percolation threshold were revealed to increase as (p-p_SC)^2.0(p_SC=0.311). Consequently, the abrupt increase in the conductivity is attributed to the formation of the conducting or percolation path of Fe ions among the B-sites of the spinel.

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Ba₂NaNb₅O₁₅ (BNN) thin films were prepared on Pt and fused quartz substrated using the sol-gel process with Ba(CH₃COO)₂, NaNO₃ and Nb(O(CH₂)₃CH)₅ as starting materials and CH₃COOH and CH₃OC₂H₄OC₂H₄OH as solvents.
BNN single-phase thin films, prepared using the heat treatment at 800°C for 1h, were optically transparent down to 30nm. A relatively good ferroelectric hysteresis loop was observed, from which the remanent polarization of 3.5μC/cm² and the coercive field of 21.6kV/cm were estimated.
Study of the electrical and optical properties of the BNN thin films is now in progress.

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