Showing papers by "Kunihito Koumoto published in 1996"
TL;DR: In this paper, homologous compounds of (ZnO){sub m}In{sub 2}O{sub 3} (m = integer) with layered structures were synthesized by reaction-sintering a mixed powder of ZnO and In {sub 2]O{Sub 3} at 1,823 K for 2 h in air, and their thermoelectric properties were measured at 500 to 1,100 K.
Abstract: Homologous compounds of (ZnO){sub m}In{sub 2}O{sub 3} (m = integer) with layered structures were synthesized by reaction-sintering a mixed powder of ZnO and In{sub 2}O{sub 3} at 1,823 K for 2 h in air, and their thermoelectric properties, i.e., electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured at 500 to 1,100 K. Their thermoelectric figure of merit depended on the composition, and an optimum value of m apparently existed giving the largest figure of merit.
205 citations
Abstract: Factors affecting stacking fault formation during the synthetic fabrication of {beta}-SiC were investigated in the present study. Two main reaction routes in the carbothermal reduction of SiO{sub 2}--solid-solid and solid-gas reactions--led to the formation of {beta}-SiC, depending on the vapor pressure of the SiO gas. The {beta}-SiC formed by the solid-gas (carbon-SiO gas) reaction showed a whisker morphology with a high stacking fault density (SFD), whereas that formed by the solid-solid (Si-carbon) reaction exhibited spherical particles with a low SFD. The average size of the synthesized particles decreased with decreasing reaction temperature and time, and their stacking fault content, measured by X-ray diffraction, was higher than the true value, possibly because of a size effect. The stacking fault density increased with increase in the heating rate because of an increased reaction rate.
124 citations
TL;DR: In this article, the first stage for thin film preparation of copper indium disulfide (CuInS 2 ), an electrodeposition technique of thin films in the CuS system was investigated from a new viewpoint.
107 citations
TL;DR: Langmuir monolayers of DHP were confirmed to induce oriented crystallization of HAp in the present study as mentioned in this paper, and both electrostatic and stereochemical interactions at the inorganic-organic interface were of vital importance for the oriented growth of hap crystals.
Abstract: Langmuir monolayers of DHP were confirmed to induce oriented crystallization of HAp in the present study. Both electrostatic and stereochemical interactions at the inorganic-organic interface were of vital importance for the oriented growth of HAp crystals. Organic surfaces with highly ordered functional groups would in general have potential to catalyze inorganic crystallization in a controlled manner through molecular recognition.
22 citations
TL;DR: In this article, a p-type bismuth telluride was fabricated by plasma sintering using milled powders of (Bi2Te3)0.75+Se2.0mass, whose thermoelectric properties did not exhibit anisotropy due to their isotropic microstructure without grain orientation.
Abstract: Semiconducting ceramics of p-type bismuth telluride was fabricated by plasma sintering using milled powders of (Bi2Te3)0.25(Sb2Te3)0.75+Se2.0mass%. The figure of merit and compressive strength were as large as 2.7×10-3K-1(25°C) and 6MPa, respectively. Their thermoelectric properties did not exhibit anisotropy due to their isotropic microstructure without grain orientation. The power factor increased with increasing sintering temperature and pressure, and was independent of the sintering time. Thermoelectric properties apparently have been generated possibly due to enhanced cleaning and activity of milled powder by spark plasma effect.
7 citations
TL;DR: In this article, the compressive strength of p-and n-type bismuth telluride ceramics was investigated by hot-pressing, and the figure of merit was shown to be 2.6×10-3K-1 (p-type) and 2.1MPa (n-type).
Abstract: Semiconducting ceramics of p- and n-type bismuth telluride fabricated from the milled powders of (Bi2Te3)0.25(Sb2Te3)0.75+Te 2.0mass% and (Bi2Te3)0.95(Bi2Se3)0.05+HgBr2 0.07mass% with low impurity oxygen having figures of merit were as large as 2.6×10-3K-1 (p-type) and 2.0×10-3K-1 (n-type) at 25°C, respectively, have been developed by hot press. The figure of merit showed a maximun when the grain size was 5 and 10μm because thermal conductivity apparently became the lowest possibly due to enhanced phonon scattering at grain boundaries. The compressive strength of p- and n-type obeyed Hall-Petch type which was directly proportional to (-1/2) the power of grain size, and showed 8.8 and 6.1MPa whose figure of merit was maximum, respectively.
4 citations
TL;DR: In this article, Zn metal was vacuum deposited at room temperature onto cadmium stearate Langmuir-Blodgett (LB) films with surfaces of either hydrophilic head groups or hydrophobic tail groups.
2 citations
TL;DR: In this article, the crystal structure and morphology of polycrystalline Si films were investigated by x-ray diffraction and atomic force microscopy, and it was found that the grains with almost the same size are uniformly distributed within the film, and their shapes in a top view become rectangular.
Abstract: The crystal structure and morphology of polycrystalline Si films deposited using a plasma‐enhanced chemical vapor deposition method, have been investigated by x‐ray diffraction and atomic force microscopy. When the 〈110〉‐oriented films were prepared at 690 °C with a hydrogen dilution ratio H2/SiH4=3 and rf power of 20 W, it was found that the grains with almost the same size are uniformly distributed within the film, and their shapes in a top view become rectangular. The longer sides of rectangles stand in line in the direction of gas flow (the plasma also spreads in this direction), indicating that the gas‐flow direction and the plasma assist the growths of essentially three‐dimensionally oriented grains.
2 citations
TL;DR: In this article, bismuth (Bi) metal was vacuum-deposited on cadmium stearate Langmuir-Blodgett (LB) films with surfaces of either hydrophilic head groups or hydrophobic tail groups at room temperature.
Abstract: To investigate the possibility of the control over crystal growth on oriented organic film surfaces, bismuth (Bi) metal was vacuum-deposited on cadmium stearate Langmuir-Blodgett (LB) films with surfaces of either hydrophilic head groups or hydrophobic tail groups at room temperature. Interaction in both geometric and chemical senses between organic functional groups and evaporated metal seems critical for its growth. Different growth manner of Bi was observed on different surfaces in the initial stage of deposition ; A very low deposition rate, 0.01 nm/s, resulted in the large crystals grown on the hydrophilic surfaces, while fine particles formed on the hydrophobic surfaces. Time dependence of the average size of fine particles (∝t1/3) indicated high diffusivity of Bi adatoms on the hydrophobic surface, while crystallization of Bi on the hydrophilic surface possibly implied their strong chemical interactions.
1 citations
1 citations
26 Mar 1996
TL;DR: In this article, homologous compounds of (ZnO)mIn/sub 2/O/sub 3/ (m=integer) with layer structures were synthesized by reaction-sintering the powder mixtures of ZnO and In/sub 1.5 µm O 2 O 3 µm 1 µm 2 µm in air for 2 h in air.
Abstract: Thermoelectric materials with high Z's have been searched for recently among semiconducting oxide ceramics for the purpose of power generation at high temperatures in an air atmosphere. Metallic oxides consisting of non-transition metal elements which mould possibly have large band widths and high carrier mobility have been the target materials. One possible oxide group is that having In/sub 2/O/sub 3/ as a main component. In the present study, homologous compounds of (ZnO)mIn/sub 2/O/sub 3/ (m=integer) with layer structures were synthesized by reaction-sintering the powder mixtures of ZnO and In/sub 2/O/sub 3/ at 1823 K for 2 h in air. Their thermoelectric characteristics, i.e. electrical conductivity, Seebeck coefficient, and thermal conductivity were measured at 500-1000 K. Their Z depended on the composition and the microstructure.