[in Japanese]

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Structure-controlled and crystal-oriented magnetostrictive SmFe₂ was synthesized by unidirectional solidification of Sm-7Fe in microgravity of 10^-3g for 1.43s. The product was composed of sheet-dendrite of SmFe₂ sandwiched between Fe-rich layers and was oriented toward <111> along cooling direction. The magnetostriction of product to the cooling (solidification) direction was 3200ppm.

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Organic–inorganic hybrid system offers a novel route for the spontaneous formation of ordered structures ranging from nano to micro meter scale. We used the sol-gel processing to deposit such photo monomer–titania-polymer hybrid films and obtained periodic microstructures through wrinkling process induced by photopolymerization. An accurate control of photo-chemical processes taking place in the coating films enables us to realize the self-organized formation of nano/micro ordered structure. It is expected for these surface patterned films to be used as highly functional photonic devices, bio-sensing systems and so on.

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[in Japanese]

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Highly photoluminescent glass beads incorporating CdTe nanocrystals (NCs) were prepared via a two-step preparation procedure: (Step 1) formation of thin SiO2 layer on the CdTe NCs; (Step 2) encapsulation of the SiO2-coated CdTe NCs into glass beads by a reverse micelle method. The size of the glass beads can be controlled from 30 nanometers to 2 micrometers by changing the injection speed of the SiO2-coated CdTe NCs solution in Step 2. A red-emitting bead with 30 nm in diameter encapsulated roughly 14 NCs with retaining their initial PL efficiency (65%) in colloidal solution. Possible reasons for the retention of high PL efficiency during incorporation are proper pH control, protection of the NC surface in Step 1, and short reaction time.

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AgNO3-polyethylene glycol aqueous solution was deposited by inkjet printing on a soda-lime silicate glass substrate as a dot-array, in which the size of the dots was about 100 micrometer. Then, the glass substrate was heat-treated at 300 oC for 12 hours. The substrate was transparent and colorless after the heat-treatment. However, a yellow-colored dot-array appeared after a second heat-treatment at 550 oC for 30 minutes. This shows that the silver ions were selectively incorporated into the glass substrate where the solution was applied resulting in the formation of periodical compositional modification in the surface of the glass substrate.

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Optical waveguides were fabricated in the LiTaO₃ (LT) single crystal by irradiating focused femtosecond laser. The laser induced structures in three kinds of materials (two different compositions of LT, and congruent LiNbO₃ for compare) were studied. The cross sections of the structures and waveguiding behaviors were strongly dependent on the kind of the material, focusing depth, repetition frequency, and pulse duration. The waveguide with comparatively less polarized light dependancy was formed in congruent LT at pulse duration of 64fs, repetition rate of 250kHz, pulse energy of 2.0μJ, focusing depth of 50μm, and scanning speed of 500μm/s.

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Oxyfluoride glasses with a small amount of NiO are prepared using a melt quenching technique. The spatially selected crystallization of CaF₂ crystals is induced on the glass surface by irradiations of laser with a wavelength of λ=1080nm. Lines including CaF₂ crystals are patterned by laser irradiations with a power of P=1.7W and a scan speed of S=2μm/s, and crystallization of CaF₂ crystals were confirmed from X-ray diffraction (XRD) analysis. Dots and lines consisting of CaF₂ crystals on an ErF₃-doped oxyfluoride glass are also patterned by laser irradiations with some laser irradiation conditions, and Er³⁺ ions into CaF₂ crystals is confirmed by micro-photo luminescence spectrum measurements.

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[in Japanese]

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Periodic pillar patterns with submicrometer to micrometer repetitions, which are applicable for various optical devices, were fabricated from organic-inorganic hybrid materials by photolithography. The photosensitive hybrid materials were irradiated periodically by UV light or laser and the unirradiated portions were removed by alcohol. After rinse, the pillar patterns were obtained. The pillar patterns depended on the pillar height, the distance between neighboring pillars and kinds of the rinse liquids. Especially, top-gathering periodic pillar patterns, in which the pillars are gathered at the top, were obtained by self-organization during the evaporation of the remover or the rinse liquids.

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Thermal conduction is one of the fundamental thermodynamic properties of materials. However, that of oxide glasses at low temperature has not been studied enough. In this study, thermal conductivity of Na₂O-B₂O₃ glasses in the range of temperature from about 150K to room temperature was measured by means of a transient heating method. As a result, the increase of the alkali content in this glass system is found to increase the thermal conductivity and the thermal diffusivity, together with the decrease in phonon mean free path.

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[in Japanese]

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Deformation of the glasses in the system of Na2O-Al2O3-SiO2 was investigated by molecular dynamics simulation method. The fracture time of the glasses increased with increasing content of network former (Si+Al), while the fracture strain showed a maximum at an optimum content of network former. However, both the fracture time and the strain of the Na2O-Al2O3-SiO2 glasses were smaller than those of Na2O-SiO2 glass at the same network former content because the bond strength of Al-O pair was weaker than that of Si-O pair.

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Glass is densified under a high compressive stress. Densification of glass also occurs under a sharp diamond indenter. Although indentation-induced densification of some silicate glasses has been reported, there is less information on the densification of other types of glasses. In this study, indentation-induced densification of binary sodium borate glasses was investigated. The volume change in Vickers indent by annealing attributes to the relaxation of densified volume under the indenter. For all binary sodium borate glasses, large shrinkage of Vickers indentation was observed after annealing, and the densification of sodium borate glasses was evidenced. The volume change in Vickers indent on sodium borate glass is more than 70 %. The ratio of densified volume to total indentation volume depends a little on the glass composition.

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The structural models for SiO2, GeO2-SiO2, Al2O3-SiO2, Al2O3-GeO2-SiO2 glasses doped with Er3+ ions were prepared by means of the molecular dynamics technique. The absorption and emission spectra of the Er3+ ions were calculated from the structural models. The structural models were classified into SiO2, GeO2-SiO2 systems and Al2O3-SiO2, Al2O3-GeO2-SiO2 systems from the atomic arrangement around the Er3+ ion and the shape of the optical spectra. The oxygen coordination number of the Er3+ ion was about 5 in the SiO2 and GeO2-SiO2 systems. On the other hand, it increased to 6 with an increase of the Al2O3 content in Al2O3-SiO2 and Al2O3-GeO2-SiO2 systems. In the calculated distribution curve of the Er-O pairs the sharp peak at 2.3 Å was attributed to Si-O-Er bonds in the structural models for the SiO2 and GeO2-SiO2 systems. The first peak in the structural models for Al2O3-SiO2 and Al2O3-GeO2-SiO2 systems was broadened because the part of Si-O-Er bonds was replaced by the SiAl-O-Er bonds at 2.65 Å. It was found that the different shape in the calculated emission spectrum was obtained as well as the difference of the atomic arrangement around the Er3+ ions.

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[in Japanese]

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Pr³⁺ doped perovskites, SrTiO₃:Pr, were synthesized, and the Raman scattering of the specimens were performed in order to determine the width of crystal-field splitting of Pr³⁺. The extra peak at around 110cm-1 for Raman spectra was growing with increased Pr³⁺ concentration at SrTiO₃:Pr (Pr= 0-4%). The extra peak at around 140cm^-1 was found in the Raman spectra for SrTiO₃:Pr (Pr=5-8%). The luminescent properties were also investigated. The emission intensities of Pr³⁺ from the excited ³P₀ level to the ground ³H₄ level were changed with Pr³⁺ concentration.

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We investigated photoluminescenct property of sintered porous silica doped with rare metal under VUV excitation. It was found that all the emission originated from f-f transition in trivalent rare earth were enhanced with the addition of Rb or Cs ions. The emission intensity was greatly dependent on the species of porous silica and sintering temperature.

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The authors have actualized white-electroluminescent devices with nanocrystalline red phosphors and Ba₂TiSi₂O₈ ceramics sheet. Nanocrystalline Y₂O₃:Eu³⁺ and CaTiO₃:Pr were used as red phosphor layers. These phosphors were synthesized by an ion crosslinked method using carboxymethyl cellose and high concentration sol-gel method, respectively. And Ba₂TiSi₂O₈ ceramics sheet which shows blue-green emission were prepared by sintering of BaTiO₃ thick film on SiO₂ substrate. Electroluminescent properties of the device which had a structure of ITO glass/red phosphor layer/Ba₂TiSi₂O₈ sheet/Ag electrode were investigated under high ac field of 1 kHz. The device emitted white emission corresponding to a color coordinate near ideal white.

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We report the fabrication of flexible organic light-emitting diodes (OLEDs) using transparent clay films with heat-resistance and high gas barrier properties. Indium tin oxide (ITO) thin films were deposited as anode layers at high temperature using rf magnetron sputtering method. The ITO films deposited at temperatures greater than 300°C exhibit high optical transparency (>90%) in the visible region with a low electrical resistivity of 4×10^-4 Ωcm. Flexible OLEDs with structure of clay film/ITO/TPD/Alq₃/Al showed a turn-on voltage of around 7.2 V, a luminance efficiency of 2.7 cdA^-1, and a luminance of 100 cdm^-2 at 11.5 V. Results showed that the clay film is an excellent candidate for transparent flexible substrates.

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The PDP technology enables high resolution output on large screens, while maintaining a thin profile. The panels use self-emission technology, making PDP TVs easy on the eyes, and particularly suited for displaying moving images. The development of home information appliances, of which the core of the large screen FPD TVs, has been rapidly proliferating high-definition digital broadcasts and broadband technology. The PDP that provides vivid and high-resolution pictures including abundant information has been receiving high evaluations as the best suited imaging device for displaying images on a thin and large screen. In this lecture, I title it "Ceramic technology to support the screen technology of the plasma television" and introduce the outline about glass materials constituting plasma display panel and an example of the glass materials development of the plasma display panel use.

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About 20 years has passed since a liquid crystal display television (LCD-TV) appeared. Now, we caught up with a cathode-ray tube (CRT) display in the point of visual quality, and, besides, the image which one had experienced was expressed more naturally. Display characteristics of the latest LCD-TVs and adopted technologies were reviewed. Also, future trend of LCD-TVs and requirements for materials were discussed.

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[in Japanese]

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Faraday rotation properties of Eu_1-xMn_xO-Al₂O₃-SiO₂ glasses were investigated for x = 0 and 0.02 at 632.8 nm at 15 ~ 250 K in pulsed magnetic fields. For x = 0, the Verdet constant V, that is defined by Faraday Angle = VBL (B : magnetic fields, L: sample length) was gradually varied up to 150 K and rapidly decreased above it. On the other hand, the sample of x = 0.02 exhibited less temperature dependence and its Verdet constant was higher at 250 K than for x = 0. This is attributable to antiferro-coupling between Eu²⁺ and Mn²⁺ ions, which was supported by the negative Curie temperature in the magnetization behavior for x = 0.02.

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[in Japanese]

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We investigated third-order optical nonlinearities (χ⁽³⁾) by Z-scan technique for various heavy-metal oxide (MO_X) doped tellurite glasses (TlO_0.5-TeO₂ matrix; M = Ti, Zn, Ga, Pb and Bi) as well as their relative Raman scattering spectra. As a result, the real part of χ⁽³⁾ was varied with the Raman shift positions (660~760cm^-1) for the peaked Raman intensities, indicating that intermediate structures TeO₃₊₁ close to trigonal bipyramids (tbp) were preferable to increasing Re(χ⁽³⁾).

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Ca-Ir-O compounds in various molar ratio of Ir to Ca (R_Ir/Ca) from 0.2 to 1.2 were prepared by spark plasma sintering (SPS) and the effect of compositions on phase structure, Seebeck coefficient, electrical conductivity and thermal conductivity were investigated. All specimens had density around 70% of theoretical density. Three stable phase compounds of Ca₄IrO₆, Ca₂IrO₄ and CaIrO₃ and a metastable phase of CaIrO₃ (m-CaIrO₃) were identified. Only a single phase of Ca₂IrO₄ were obtained at R_Ir/Ca = 0.5. The Seebeck coefficient of Ca-Ir-O compounds at room temperature was around 10 to 150 Sm^-1and increased with increasing temperature, exhibiting a semiconducting behavior for all samples. The Seebeck coefficient at R_Ir/Ca = 0.4 to 0.7 slightly increased with increasing temperature showing negative values. The Seebeck coeeficient at R_Ir/Ca = 0.9 to 1.2 showed positive values and decreased with increasing temperature at below 600 K and increased at higher than 600 K. The thermal conductivity was around 0.7 to 2.7 Wm^-1K^-1 at room temperature and slightly decreased with increasing temperature. The highest ZT was 0.006 at R_Ir/Ca = 1.2 (1023 K).

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Y heavy doped (Sr, Y)TiOx was fabricated by plasma spray technique and its thermoelectric properties were evaluated. Y was successfully replaced Sr up to 25% and a uniform solid solution was made. The increase in Y content produced the increase in the electric conductivity and the decrease in the thermal conductivity. But Seebeck coefficient also decreased with increasing Y content. As a result, ZT value did not exceed 0.1 at any Y content. However, it was demonstrated that a plasma spray technique worked well for over dosing an additive element.

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[in Japanese]

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AgSbO₃ ceramics were prepared by solid state reactions and tartrate processes. And their electrical conductivity and Seebeck coefficient were measured. Sb excess made lattice constants large and Ag excess make Ag metal deposition. Tartrate process of CuO-added AgSbO₃ made electrical conductivity high and absolute value of Seebeck conductivity low, which was explained by homogeneity of powders prepared by tartrate process and substitution of Cu for Ag site was efficient.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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During the microwave reforming, only a catalyst layer is preferentially heated from the inside for a short time, and so it becomes possible to quickly reform with a simple setup and provide a high energy efficiency. The full conversion of 100% was obtained at low temperatures and high gas space velocities SV. The activation energies for the microwave process were not affected by SV, and were low values that averaged 18.1 kJ/mol. The advantages of the microwave method over conventional method then became clear.

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Recently, the efficient production method of hydrogen from water has been desired. In this study, dense zeolite membranes were fabricated on porous alumina substrates by "Secondary growth way", and their hydrogen generation properties were investigated at 450 degrees Celsius. As a result, the hydrogen generation from water by the zeolite membrane had lasted for more than 24 hours.

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The mixed gas of CH₄ (50 %) and CO₂ (50 %) was fed into the porous compacts of alimina-supported Ni (30 vol%) catalyst heated at 673-973 K. Hydrogen was produced by the reaction of the mixed gas (CH₄ + CO₂ → 2CO + 2H₂). A part of produced CO decomposed to CO₂ and C (2CO → CO₂ + C) below 873 K. As a parallel reaction, the decomposition of CH₄ occured in the wide temperature range from 673-973 K. The carbon deposition suppressed the flow of outlet gas.

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[in Japanese]

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[in Japanese]

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Metal-organic precursors have been designed and synthesized for the development of novel Si-based ceramic materials. Amorphous Si-C-N ceramics with enhanced thermal stability, Si3N4-based nanocomposites, and amorphous silica-based composite membranes with nanometer-sized particles having hydrogen affinity have been successfully synthesized by controlling the crystallization and microstructure development of the precursor-derived Si-based multicomponent amorphous ceramics.

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Porous ceramics with cylindrical pores were fabricated by unidirectional solidification under hydrogen atmosphere. In the case of alumina, the pores are formed at solid-liquid interface due to hydrogen gas solubility gap between solid and liquid phases during the solidification. Since the hydrogen solubility in the molten alumina increases with increasing hydrogen partial pressure, the porosity of the solidified samples increases with increasing hydrogen partial pressure. On the other hand, the average pore size decreases with increasing total pressure due to decreasing volume of pores according to Boyle's law.

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[in Japanese]

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[in Japanese]

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Oxidation behavior of nano Ni-dispersed Al2O3 composites was studied at high temperature ranging from 1200 to 1350C in air. Dispersed Ni particles were oxidized into NiAl2O4 in Al2O3 matrix. Growth of oxidized zone of the composite was rate-controlled by oxygen diffusion at grain boundary in an oxidized zone. Voids and surface NiAl2O4 layer were formed in the oxidized zone due to outward diffusion of cations. Surface cracks developed by the Vicker's indentation disappeared by heat treatment in air at temperature higher than 1100C. The crack healing of the composite was caused by filling-up of oxidation products in cracks by the outward diffusion of cations.

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[in Japanese]

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The layer by layer (LBL) method will be the most efficient techniques to prepare well-dispersed nanocomposite powders. The LBL method has been established to produce several types of functional ceramics as one of the simplest and the most versatile processing techniques for fabricating nanocomposite powders. In this study, ZrO2- Al2O3 nanocomposite particles were synthesized by coating nano- Al2O3 sol on the surface of ZrO2 particles to produce a well-dispersed ZrO2- Al2O3 composite by adopting the layer-by-layer (LBL) technique. As a result the superior microstructure and mechanical characteristic of 3Y-TZP based Al2O3.

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The effect of chemical composition of Y₂O₃-MgO-SiO₂-based intergranular glass on high temperature deformation of alpha-Si₃N₄ was studied by compression tests at elevated temperatures. All spark plasma sintered Si₃N₄ had the same initial microstructures and the same amount of glass phase, which was different in composition only. The flow stress was not proportional to the original viscosity of Y₂O₃-MgO-SiO₂ glass, probably, because the chemical composition of the glass changed during sintering. The difference in the chemical composition of glass altered the microstructural evolution at elevated temperatures, thus, peculiar stress-strain curves were observed in the deformation tests.

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Mono-phase and hexagonal plate-like Al4SiC4 powder was successfully synthesized using a mixture of Al(OH)3, SiO2 and carbon via a carbothermal reduction process. Two-step reaction was compartmentally observed during the calcination; the carbothermal reduction of SiO2 between 1300 and 1600oC and that of Al2O3 above 1500oC. The mechanisms which were responsible for the synthesis of the ternary carbide (Al4SiC4) powder were discussed.

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[in Japanese]

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[in Japanese]

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