Improvement of passive component like multilayer ceramic capacitor (MLCC) has supported advancement in performance of mobile electronic equipment such as mobile phones. Nowadays these MLCC are composed of below 1μm thick active layers. But to fabricate thinner than 1μm dielectric layer is very difficult for conventional ceramic process. Therefore there is much expectation for the process technologies for further thinning such as sputtering method. In this presentation, we introduce the characteristics of sputter deposited thin films.

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SrRuO3 thin films were fabricated on SrTiO3 (100) substrate by RF magnetron spatter method as the bottom electrode. Dielectric/Conductive hybrid thin films that SrRuO3 molecular layers were introduced into the SrTiO3 thin films were prepared by molecular beam epitaxy (MBE) on SrRuO3 bottom electrode. RHEED oscillations indicated that two-dimensional layer-by-layer growth were achieved. The capacitance and dielectric loss were measured by impedance analyzer. Hybrid thin films showed larger capacitance than normal SrTiO3 thin films.

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A dielectric film with high capacity is expected for the performance improvement and stabilization of electronics. In this study, we focus electrophoretic deposition method as an easy-to-use film-forming process and examined an optimal preparation condition of the Ba1-xSrxTiO3(BST) dielectric film. As a result, it was found that a BST film deposited for 2sec at 80V with 10g/l binder-free BST slurry were significantly dense and homogeneous. After a heat-treatment at 800^oC for 30min in air, the deposited film showed 1.85% of dielectric loss. The obtained film with ultrafine BST slurry was relatively thin and uniform.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Nonstoichiometric BaTiO3 powder was synthesized by conventional solid-state reaction at 1200oC for 4h. The results showed that the solubility limit of barium and titanium ions in nonstoichiometric BaTiO3 was 0.98 < Ba/Ti < 1.02. Within the solubility limit, the crystallite size of the as-calcined BaTiO3 powder decreased drastically in the vicinity of Ba/Ti = 1.01 ~ 1.00. When Ba/Ti ratio decreased to 1.00 ~ 0.98, the decrease of crystallite size enhanced the internal stress, which makes the tetragonality decreased.

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In this study, barium titanate (BaTiO3, BT) and strontium titanate (SrTiO3, ST) nanocube particles were successfully prepared by solvothermal method. Size of the obtained BT and ST nanoparticles was around 20 nm, and their crystal structures were assigned to cubic m-3m symmetry. Using these nanocubes, their selective interconnections were investigated.

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In this study, barium titanate (BaTiO3, BT)/strontium titanate (SrTiO3, ST) complex nanoparticles were prepared by solvothermal method using new titanium chelate complex compounds (Ti(AcAc)2(i-Pro)2). First, preparation condition of BT nanoparticles was investigated as functions of temperature, Ba/Ti atomic ratio, solvents and so on. As a result, formation mechanism of BT nanoparticles was proposed in this study. For ST nanoparticles, similar investigation was performed. Finally, on the basis of proposed formation mechanism, formation of BT/ST complex nanoparticles were investigated.

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The formation of ternary oxides containing Sn²⁺ is difficult to prepare due to the disproportionation of Sn ²⁺ to Sn and Sn⁴⁺. In this paper, using a microwave-assisted solvothermal (MS) process and a solvothermal (RS) process using a rolling sealed tube reactor. Ba _1-x Sn _x TiO ₃ (x=0.00, 0.02, 0.05 and 0.10) nanopowders were successfully synthesized and characterized. The powders obtained using MS process show much smaller particle size (40-60nm) than those obtained using RS process(40-140nm), but showed more ignition loss than the latter. The corresponding ceramic body obtained using MS process show higher dielectric constant than latter.

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[in Japanese]

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Barium titanate (BaTiO3) ceramics with various grain sizes were prepared by a conventional sintering method, a two-step sintering method, and a rate-control sintering method. The dielectric permittivity of the ceramics increased with decreasing grain size down to 1 μm. On the other hand, at grain size below 1 μm, the dielectric permittivity decreased with decreasing grain size. It was clarified that the grain size dependence of the permittivity was due to the domain size effect.

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[in Japanese]

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Complex permittivity spectra of a-axis and c-axis of the barium titanate single crystal were directly measured by the THz ellipsometer and the improved analysis program. Those spectra were also obtained by analysis method using four-parameter-semi-quantum model and polarized reflectivity spectra. As the result of analysis, the calculated ellipsometry constants and polarized reflectivity spectra showed good agreements for the observed value. Complex permittivity spectra measured by the ellipsometer was consistent with those obtained by reflectivity analysis. Infrared active phonons were also observed. Therefore complex permittivity spectra determined by four-parameter-semi-quantum model have the same accuracy as those directly measured by ellipsometer.

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Electronic structure in ZnO was characterized by hard x-ray photoelectron spectroscopy in order to develop controlling of electric conductivity in ZnO for optoelectronic applications.

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Functions of III-nitride/ZnO heterostructures are attracting attention, and these heterostructures have been studied theoretically and experimentally with the aim of using them to fabricate optoelectronic devices composed of III-nitride/ZnO heterojunctions. The crystalline polarity of III-nitride and ZnO is another important issue in the development of optoelectronic devices fabricated using III-nitride and ZnO. Since a wurtzite-type structure lacks inversion symmetry, III-nitride and ZnO are permanently polarized along the c-axis of their lattice and exhibit pyroelectricity and piezoelectricity. Such polarization in III-V nitride semiconductors affects the properties of LEDs and transistors. III-nitride films were grown on the c-face of ZnO single crystals by molecular beam epitaxy, and their interfacial structure and polarity is discussed based on the structural similarity between the ZnO-based homologous structure and the III-nitride/ZnO interface.

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[in Japanese]

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We report the growth of ZnO nanowires on quartz glass substrates by a simple electric current heating (ECH) method. The effect of substrate temperature on structural, surface morphological and optical properties of ZnO nanocrystals have been systematically studied. X-ray diffraction result showed the presence of hexagonal wurtzite ZnO phase in the grown crystals. The SEM observation revealed the aligned ZnO nanowires were grown on the substrate. The change in morphology of ZnO crystals with different substrate temperatures will be discussed in detail.

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We have reported morphology property of micro meter size ZnO crystal by electrochemical deposition method using Zn(NO3)2 aqueous solution. The effects of growth parameters, such as Zn(NO3)2 concentration, current density and cathodic potential, with respect to the morphology of ZnO crystals were studied. In this report, to purpose nano size crystals, preparation of ZnO on CNT by electrochemical deposition method were carried out. Scanning electron microscopy and transmission electron microscopy indicate that nanocrystals on CNT have been obtained.

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You can't get both at the same time; cation-exchangeable d⁰ perovskites possess interesting interlayer chemistry, but lack the electronic and magnetic functionalities that many mixed valence dⁿ (n>0) perovskites are privileged to. To bridge this gap, the insulating, cation-exchangeable layered perovskite RbLaNb₂O₇ was treated with PTFE powder under inert conditions to yield the corresponding reduced fluorinated perovskite. Upon fluorination, the B-site cations are reduced to yield a mixed valence. Electronic transport measurements on the air-stable RbLaNb₂O₆F reveal room temperature conductivity (195 Ω·cm) via a 2D/E-S variable range hopping mechanism, while the material still retains its capacity for cation exchange/intercalation.

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[in Japanese]

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Na₅YSi₄O₁₂-type glass-ceramic Na⁺-superionic conductors (Na₅YXSi) were prepared by crystallization of glasses. In the present study, polycrystalline Na5YXSi glass-ceramics have been obtained with X = B, Al, Ti, Te, Ge, P, V and Mo. The effects of X elements on the crystallization of the phase and the microstructural effects on the conduction properties of the glass-ceramics were discussed, and the crystallization kinetics of the glasses was examined by DTA analysis.

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[in Japanese]

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The proton conductive membrane for the intermediate temperature fuel cell was fabricated using phosphoric acid treated gypsum and silicone based materials. The ionic conductivity of the membrane was estimated to be 1.6×10^-5 S/cm by AC impedance measurement at 165°C. The conductivity of the membrane rose continuously with the rise of temperature beyond 100°C. This suggests that the proton conduction in the membrane does not require water molecules and the membrane might be used in intermediate temperature fuel cell without water supply.

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Intermediate temperature ion conducting electrolytes have been investigated by solidification of ionic liquids into solid state titania matrix. The quasi-solid electrolytes showed high ion conductivity at elevated temperatures due to the presence of ionic liquids channels in the 3-dimensional TiO2 matrix.

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In the last few decades, perovskite type oxides have been widely investigated as high temperature proton conductor. We focused on La_1-xBa_1+xGa_1-yMg_yO_4-δ (LBGM) and LaSrGa_1-yMg_yO_4-δ (LSGM) in this work, and examined their electrical conduction properties and crystal and electronic structures. In order to clarify these structures, we measured powder neutron diffraction patterns of the materials and analyzed the patterns with Rietveld method. As a result, it was found that LBGM had single phases and their phases were orthorhombic (S. G.:P2₁2₁2₁) at the temperature range from room temperature to 900K.

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Porous glasses with approximately 4 nm in diameter pores were prepared utilizing a spinodal-type phase separation of Na2O-B2O3-SiO2 glass, and effects of doped Al2O3 components on proton conductivity were investigated. Compared with the porous glass without Al2O3 component, small amounts of Al2O3-doped glasses showed higher proton conductivities under humidified conditions. Proton conductivity of the porous glasses are discussed in relation to the amounts of doped Al2O3 and hydrogen bonding structure.

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[in Japanese]

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SiC membranes synthesized from precursor polymers have an excellent thermal and corrosion resistances and the structure is amorphous with nano-hole which has gas permeability. Therefore, the membranes are expected as a hydrogen separation filter that can be used in the severe environment. However, the improvement of the amount of the hydrogen penetration and the separation ratio is required. In this research, the possibility of controlling the gas penetration of the SiC membranes by EB crosslinking technique was examined.

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Spinel precursor sol was synthesized by addition of aluminum isopropoxide into the magnesium nitrate solution at 80C. After removal of alcohol, water was added to the sol to control a concentration of the sol. The resultant sol was transparent and slightly cloudy. The sol could be coated and spinel phase was detected after heating at 400C. D-value of the formed phase was not that of gamma-alumina but that of Al2MgO4. The sol was coated on aluminum titanate (AT) ceramics and corrosion in molten aluminum alloy was examined.

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Corrosion mechanism of aluminum titanate (AT) ceramics used in molten aluminum alloy for aluminum casting was investigated thermodynamically. The corrosion progressed not only in the direct contact region with the molten alloy, but also through space between the ceramic surface and alloy.

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[in Japanese]

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Aluminum/Sapphire hetero interfaces were characterized using HRTEM and TEM-EDX. Step structures of sapphire at the interface were found to be a general characteristic in the formation of the interface. During liquid-phase bonding, addition of silicon in aluminum played a critical role in reducing the step growth at the interface. Silicon was found to preferentially segregate at the interface. It was discovered that silicon precipitates at the interface form an epitaxial relationship with sapphire. The strong preferential segregation of silicon at the interface combined with the stable orientation relationship of its precipitates with sapphire, suggest the strong bond in liquid-phase bonded aluminum/sapphire interfaces.

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For the preparation of transparent submicrometer alumina via pressureless sintering, uniform green compacts were formed by controlling the particle size distribution of alumina powders and gravitational sedimentation of slurries. The microstructure and transparent properties of sintered alumina ceramics were investigated. The submicrometer alumina with a total forward transmission of 78% were obtained by pressureless sintering in air at 1250 C for 4 h.

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[in Japanese]

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When a synthesized powder of Al4SiC4 was heated using the PECS (Pulse Electric Current Sintering) technique at 1900C for 5 min under an applied pressure of 60 MPa, the Al4Si2C5 body with 98% in relative density was formed. However, Al4C3 was also considered to be formed in the dense body. According to the XRD analysis, Al4C3 was not detected in the sample. In this study, formation mechanism of the dense Al4Si2C5 body using an Al4SiC4 powder material was discussed on the basis of chemical thermodynamics. Furthermore, thermal stability of the formed Al4Si2C5 was examined in Ar atmosphere.

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