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Volume 51, Issue 12
Displaying 1-9 of 9 articles from this issue
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Hideaki Matsubara2004 Volume 51 Issue 12 Pages 833-838
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have successfully developed a computer simulation technique to design microstructural development such as sintering and grain growth of nano/micro-size particles by using the Monte Carlo (MC). The MC simulations were performed for the array of two- or three-dimensional lattices. Plural mechanisms of mass transport were introduced in the MC simulations of sintering and grain growth in ceramic systems, which involve a liquid phase and second solid particles. The MC simulation was applied to the microstructural development of sintering and grain growth at the solid state and in the presence of a liquid phase. The compound effects of the second particle, liquid phase and anisotropy were successfully analyzed by the MC simulations in order to design complex and important microstructures in ceramics. The MC simulations are useful for microstructural design on a lot of materials of grains and particles.View full abstractDownload PDF (5795K) -
Yoshinori Fujikawa, Yuji Umeda, Fumikazu Yamane2004 Volume 51 Issue 12 Pages 839-844
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTransmission Electron Microscopy and Scanning Transmission Electron Microscopy were applied to study sintering process of the X7R MLCC materials, BaTiO3-MgO-Y2O3-(BaCa)SiO3. Though the materials were porous at the intermediate state of sintering process, the Ar-ion beam milling technique was employed for specimen preparation of electron microscopy. Succeeding in preparation, structural changes in microscopic scale have become visible. It has found that at rather low firing temperatures where the materials would not show any shrinkage in the macroscopic scale, the additives such as yttria, were already active. It was confirmed that thin Y layers of a few nanometers in thickness were formed at the surface of BaTiO3 Particles. The macroscopic shrinkage could progress, as yttria or calcia begins to diffuse toward the inner part of BaTiO3 particles. After the shrinkage, so-called core-shell structures could be observed.View full abstractDownload PDF (4722K) -
[in Japanese]2004 Volume 51 Issue 12 Pages 846
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (73K) -
Saburo Sano, Michihito Horiba, Takuma Endo, Akihiro Tsuzuki, Kiichi Od ...2004 Volume 51 Issue 12 Pages 847-851
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSolid-state electrochemical reduction was applied for yttria partially stabilized zirconia. The reduction was done by applying a DC voltage to the sample in a vacuum furnace at a temperature range from 400 to 700°C. The sample was reduced since oxygen is released at anode but oxygen is not supplied at cathode in vacuum. The reduced yttria partially stabilized zirconia changed the color to black, and the electric conductivity was increased. Apparent electric conductivity-quantity of electricity graph showed a crooked point. It was thought that the main part of electric conductivity changed form ionic to electronic at the point. Highly oxygen depleted yttria partially stabilized zirconia showed high electric conductivity even at room temperature. The Vickers hardness remained constant on electrochemical reduction, but the 3 points bending strength was degraded about 30% after the reduction.View full abstractDownload PDF (1902K) -
Haruki Ryoken, Isao Sakaguchi, Takeshi Ohgaki, Yutaka Adachi, Tadashi ...2004 Volume 51 Issue 12 Pages 852-858
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThin films of Zinc Oxide (ZnO) and Mg-alloyed Zinc Oxide ((Zn, Mg)O) were deposited with a pulsed laser deposition method. The oxygen diffusion was evaluated in their films. All of the prepared sample were single-phase having c-axis orientation from results of XRD analysis. The observed diffusion profile of oxygen isotope did not correspond with the calculated values under an assumption with a double layer model near surface of (Zn, Mg)O films. Boltzmann-Matano analysis leaded to a result that the oxygen diffusivity increased with increasing the depth for surface in (Zn, Mg)O films. On the contrary, undoped-ZnO films had similar diffusivity of oxygen ions to the single crystal. These results indicate that the defect concentration of (Zn, Mg)O film increased by the substitution of Mg for Zn in ZnO.View full abstractDownload PDF (622K) -
Yuko Sawaki, Mikio Kishimoto2004 Volume 51 Issue 12 Pages 859-863
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe synthesized the complex composed of indium tin oxide (ITO) and zinc oxide (ZnO) particles. The ITO was precipitated on the surface of the ZnO particles formed from the chlorides of In and Sn ion. The complex of ITO and ZnO particles was obtained through the hydrothermal treatment of the precursory, heattreatment in air and reduction in hydrogen gas. The complex was confirmed to have a core-shell structure with the ZnO core coated by ITO layer. The film prepared using the complex showed supherior transpararency at the wave range of visible. The film using the complex of ITO/ZnO of 35/65 wt% showed UV absorption property reducing the UV under 400 nm to the strength lower than 7% maintaining the surface resistivity of about 50kΩ/??.View full abstractDownload PDF (3455K) -
Masahiro Ito, Takashi Takeda, Hiroki Tamura, Shinichi Kikkawa2004 Volume 51 Issue 12 Pages 864-868
Published: December 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSDouble perovskite Sr2FeMoO6 was prepared by using gelation of (NH4)6Mo7O24⋅4H2O from aqueous solution in presence of Sr2+ and Fe3+ nitrates, The dried gel was pulverised and fired at 700°C for 6 hrs. It was fired again in H2/Ar=3% flow for 3 hrs in temperature range of 850-1000°C. The products were slightly contaminated with impurities of α-Fe and FeMoO4. They were annealed at 1000-1200°C in sealed tube. Inner part of the annealed sample at 1100°C showed magnetoresitance effect of 8.3% at room temperature with a comparable amount of impurity. Ordering of Fe3+ and Mo5+ was also enhanced.View full abstractDownload PDF (349K) -
Tomohiko Nakajima, Yutaka Ueda2004 Volume 51 Issue 12 Pages 869-874
Published: December 15, 2004
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe structures and electromagnetic properties of A-site ordered/disordered perovskite manganites, RBaMn2O6/R0.5Ba0.5MnO3(R=Y and rare earth elements), have been investigated. RBaMn2O6 exhibits remarkable features; (1) the charge/orbital order (CO) transition at relatively higher temperatures far above 300K, (2) a new stacking variation of the CE-type CO with a 4-fold periodicity along the c-axis, (3) the presence of structural transition possibly accompanied by dx2-y2 orbital order, (4) electronic phase separation. These novel structural and electromagnetic properties are discussed in terms of the structural characteristic that the MnO2 square sub-lattice is sandwiched by two types of rock-salt layers, RO and BaO with different lattice sizes, which introduces a strong frustration to the MnO2 sub-lattice. In R0.5Ba0.5MnO3 with a primitive cubic perovskite cell, on the other hand, the magnetic glassy states are dominant as the ground state. A peculiar behavior, the steplike ultrasharp magnetization and resistivity changes, has been observed in Pr0.5Ba0.5MnO3.View full abstractDownload PDF (549K) -
Kaoru Ikeuchi, Sadayuki Kuniyoshi, Toyokazu Nishimura, Masahiro Yasuka ...2004 Volume 51 Issue 12 Pages 875-880
Published: December 15, 2004
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSA series of layered perovskites Ban+1SnnO3n+1 with n=integer was selected as a model oxide to elucidate correlation between the dimensionality of electrical conduction and the thermoelectric power factor. La-doped sintered bodies of Ba2-xLaxSnO4 (n=1), Ba3-xLaxSn2O7 (n=2), and Ba1-xLaxSnO3 (n=∝) were prepared by oxalate coprecipitation method and their electrical conductivity and Seebeck coefficient were measured at high temperatures. For the layered perovskites with n=1 and n=2, single phases of Ba2-xLaxSnO4 and Ba3-xLaxSn2O7 with x=0.0-0.2 were obtained, in which the La atoms were doped into the rock-salt-type Ba site, but the conductivities were in insulating region, suggesting the localization of doped electrons. The doped perovskite Ba0.95La0.05SnO3 with n=∝ showed n-type degenerate semiconducting behavior and the thermoelectric power factors were in the order of 10-7 Wm-1 K-2, which should be increased by the improvement of sinterability.View full abstractDownload PDF (390K)
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