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[in Japanese]
2004 Volume 46 Issue 1 Pages
1
Published: February 27, 2004
Released on J-STAGE: September 30, 2010
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Takashi KAMIYAMA, Hiroshi SAWA, Yoshio MATSUI
2004 Volume 46 Issue 1 Pages
2
Published: February 27, 2004
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Yuji NOGUCHI, Masaru MIYAYAMA
2004 Volume 46 Issue 1 Pages
3-8
Published: February 27, 2004
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Ferroelectric memories have attracted much attention because of the invaluable advantage of nonvolatile and high-speed read-write functions. The current status of ferroelectric memory materials is briefly reviewed, and the effects of oxygen vacancies analyzed by first-principles band-structure calculations are described. We show that the defect engineering of cation vacancies as well as oxygen vacancies is effective in controlling the polarization properties of layered ferroelectrics.
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Ryoji KANNO, Masahiro MURAYAMA
2004 Volume 46 Issue 1 Pages
9-15
Published: February 27, 2004
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New lithium ionic conductor, thio-LISICON (LIthium Super Ionic CONductor) is reviewed. The thio-LISICON has a general composition of Li
4-x M1-yM'
yS
4, where the
M and
M' are Ge, Si or P, Al, Ga, respectively. In the thio-LISICON family, Li
3.25Ge
0.25P
0.75S
4 showed the highest conductivity of 2.2 × 10
-3 Scm
-1 at 25 °C among the materials synthesized, and the conductivity value is comparable to or even higher than liquid-electrolytes. The thio-LISICON has a structure similar to the γ-Li
3PO
4 type. Materials relationships to the oxides LISICON family is indicated. The advantages of the solid electrolyte to all solid-state lithium battery are discussed.
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Yasushi IDEMOTO, Yuka ITO, Nobuyuki KOURA
2004 Volume 46 Issue 1 Pages
16-20
Published: February 27, 2004
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We investigated the relation between crystal structure, electronic states and electrode performance of LiMn
2-xM
xO
4 (M = Zn, Ni etc.) as cathode materials for lithium ion secondary batteries. The cycle performance is improved by substitution of Mn with M. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. The electron density distribution was obtained by XRD using MEM/Rietveld method. From the results, the stability of the host structure is important for cycle performance.
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Yuzuru MIYAZAKI
2004 Volume 46 Issue 1 Pages
21-26
Published: February 27, 2004
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Crystal structure of the thermoelectric compound known as “Ca
3Co
4O
9” has been determined using a 3+1 dimensional superspace group approach. The cobaltite has been revealed to be a misfit layer compound which consists of two monoclinic subsystems of [CoO
2] and [Ca
2CoO
3] . The [CoO
2] subsystem has a CdI
2- type triangular lattice of cobalt, while the [Ca
2CoO
3] subsystem compises a three-layered ordered rock salt-type slab. Since the both subsystems have incommensurate
b-axis lengths, the structure formula is expressed as [Ca
2CoO
3]
pCoO
2, where
p=
bCoO2/
bCa2CoO3. Due to the potential interaction between the subsystems, atomic displacive modulation is observed for each atom. The most significant modulation has been found in the Co-O layer of the [Ca
2CoO
3] subsystem.
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Ichiro TERASAKI
2004 Volume 46 Issue 1 Pages
27-31
Published: February 27, 2004
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The layered cobalt oxides show large thermopower, low resistivity, and low thermal conductivity, and are a promising material for thermoelectric power generation. They share the CdI
2-type hexagonal CoO
2 layer as a common unit, where large entropy of kBlog6 is stored on Co
4+ ion. They show large anisotropy between the in-and out-of-plane directions depending on the block layers. Lattice thermal conductivity is smaller for heavier ions. Some of them show a characteristic misfit structure, which induces a significant in-plane anisotropy.
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Toshiharu FUKUNAGA
2004 Volume 46 Issue 1 Pages
32-37
Published: February 27, 2004
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Recently mechanical alloying (MA) has been employed to synthesize various kinds of materials. The MA of graphite under Ar gas atmosphere transformed the hexagonal graphite into nanostructured graphite which has a lot of dangling bonds. In case of the mechanical alloying of the graphite under D
2 gas atmosphere, deuterium was absorbed by the solid-gas reaction. The radial distribution function
RDF (r) derived by neutron diffraction experiments informed us the location of deuterium in the nano-structured graphite. One is the C-D covalent bond and the other is deuterium located between layers of the graphite.
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Yumiko NAKAMURA, Etsuo AKIBA
2004 Volume 46 Issue 1 Pages
38-42
Published: February 27, 2004
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Metal hydride is one of key materials for developing fuel-cell vehicles, which is most demanded for reduction of CO
2 emission. In this report, our recent work relating to crystal structure and nano-structure of metal hydrides studied by ‘
in situ’ X-ray and neutron diffraction for clarifying the mechanism of hydriding reaction of metal hydride will be described.
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Junichi TAKAHASHI, Hisanori YAMANE
2004 Volume 46 Issue 1 Pages
43-47
Published: February 27, 2004
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Silicon nitride-based ceramics having high functional mechanical properties are described with respect to phase relationships between Si
3N
4 and the grain boundary phases of rare-earth silicon-oxynitrides. The crystal structures of La
4Si
2O
7N
2 (La-J-phase) and Lu
4Si
2O
7N
2 (Lu-J-phase) have been determined by time-of-flight neutron powder diffractometry. The local structures of Si
2 (O, N)
7 ditetrahedra including O and N atom distribution in the rare-earth silicon-oxynitrides are revealed.
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Masahiro HIRANO, Hideo HOSONO
2004 Volume 46 Issue 1 Pages
48-52
Published: February 27, 2004
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Realization of novel functions in transparent oxides utilizing intrinsic nanostructures in their crystal structures are discussed by taking layered compounds, InGaO
3 (ZnO)
m and LnCuOS/Se as examples. The layered structure forms“natural superlattice”or“multi-quantum well”, providing distinct features due to the electron confinement to the nano-sized layers including efficient blue emission and large nonlinear optical susceptibility associated with“room temperature exciton”and degenerated p-type conduction by“modulation doping”. These features allow for realizing emerging devices such as all optical switches and high mobility transparent field effect transistor.
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Ryotaro MATSUDA, Susumu KITAGAWA
2004 Volume 46 Issue 1 Pages
53-58
Published: February 27, 2004
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Coordination Polymers (CPs) are opening up a new field in porous materials. A large number of CPs have been so far synthesized and characterized because of their versatile applicability to gas storage, molecular sieves, size- or shape-selective catalysis, and ion exchange. Moreover, CPs, in spite of their crystalline form, are suitable for creating flexible and dynamic porous frameworks, which are hardly realized by inorganic zeolites and carbon materials. We described here the several unique structures and functions of CPs.
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Yuji OHASHI
2004 Volume 46 Issue 1 Pages
59-64
Published: February 27, 2004
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Recently the time-resolved X-ray analysis has been applied to organic crystals. Two-dimensional detector and low temperature technique made it possible to analyze the metastable species produced in the crystal by photoirradation. The structures of the diplatinum complexes at the excited state have been analyzed with the same technique. The time-resolved analysis using the combination of the pulsed X-rays from synchrotron radiation and the exciting pulsed photons from laser has been developed. The structural changes in the processes of photoexcitation and the photo-induced phase transition in the time scale less than 1 ns have been made clear.
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Hiroshi ABE, Yasushi ISHII, Yoshie MATSUO
2004 Volume 46 Issue 1 Pages
65-72
Published: February 27, 2004
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We have reviewed recent studies on atomic short-range order (SRO) in Al-Ni-Co decagonal quasicrystals by anomalous X-ray scattering. Anisotropic distributions of diffuse scattering around Bragg reflections are analyzed in context of phasonic diffuse scattering. Phason strains also cause peak broadening of Bragg reflections. Both chemical and topological distortions are responsible for the order-disorder phase transitions. In addition, a decrease of the Bragg intensity at high temperatures and the anomalous Debye-Waller factor are explained as consequences of the phason flip.
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Kazuma HIROTA
2004 Volume 46 Issue 1 Pages
73-78
Published: February 27, 2004
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Review is given on recent neutron scattering studies of the prototypical relaxor Pb (Mg
1/3Nb
2/3) O
3 (PMN), particularly focusing on diffuse scattering from polar nanoregions (PNRs) . Inconsistency between the relative intensities of diffuse scattering and those of the lowest-energy transverseoptic phonons in PMN has remained unsolved for a decade. A simple model consisting of two components δ
cm and δ
shift, which has been proposed to solve the contradiction, is introduced in this article.
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Yutaka UEDA, Masahiko ISOBE, Tomohiko NAKAJIMA
2004 Volume 46 Issue 1 Pages
79-84
Published: February 27, 2004
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The relation between structures and electromagnetic properties is reviewed on vanadium oxides with the trellis lattice and the A-site ordered perovskite manganites. These compounds show novel phase transitions in which the charge, orbital and spin degrees of freedom are coupled with the lattices. For example, a quarter filled ladder system α'-NaV
2O
5 undergoes a charge order transition at 35 K, accompanied by lattice dimerization and spin gap formation, and under high pressure it shows various stacking sequences of the zigzag-type in-plane charge-order along the c-axis, so-called “Devils Flowers”. On the other hand, the novel properties of the A-site ordered perovskite manganites are closely related to the most remarkable structural property that the MnO
2 layer is sandwiched by two types of rock salt layers with very different lattice sizes.
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Takahiro MURANAKA, Jun AKIMITSU
2004 Volume 46 Issue 1 Pages
85-89
Published: February 27, 2004
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Since the discovery of high-
Tc superconductor MgB
2 by our group, a large number of experimental and theoretical works has been performed. The superconductivity in this simple binary alloy is essentially explained within a framework of BCS theory from both sides. It is considered that the high-
Tc superconductivity at 40 K in MgB
2 is caused by the metallic nature of the two dimensional sheets formed by B atoms and the presence of strong electron-phonon interactions which together with the high vibrational frequencies of the light B atoms ensure a high transition temperature. The main problems in this stage are the possibility in application of MgB
2 and whether high-
Tc superconductors exist in boride and carbide systems. In this paper, we review the physical properties of MgB
2 which has been cleared until now.
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Hirofumi MATSUHATA, Chul-Ho LEE, Chihiro SEKINE, Ichimin SHIROTANI, To ...
2004 Volume 46 Issue 1 Pages
90-93
Published: February 27, 2004
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A structural change has been found in PrRu
4P
12 accompanied by a metal-insulator transition at about 60 K by electron diffraction. At room temperature the structure of Filled-Skutterudite type compound PrRu
4P
12 belongs to space group Im3 (No.204), and is a metal. At about transition temperature new and weak reflections appear at h + k + 1= 2n + 1 positions. Space group and structure of the low temperature phase is discussed to be P23 (No. 195) or Pm3 (No.200) . The origin of the transition was discussed.
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Kazuyuki MATSUHIRA
2004 Volume 46 Issue 1 Pages
94-97
Published: February 27, 2004
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Pyrochlore oxides have attracted much interest because their crystal structures include the corner-sharing tetrahedra. This represents an ideal system for studying the effect of geometrical frustration in the limit of low disorder. Recently, a new class of magnetic state known as“spin ice”is discovered in the pyrochlore rare-earth oxides. Recent our study reveals a new macroscopically degenerate ground state in the spin ice induced by a magnetic field. This is called“kagomé ice”.
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Masaya UCHIDA, Daisuke AKAHOSHI, Yoshio MATSUI, Yoshinori TOKURA
2004 Volume 46 Issue 1 Pages
98-102
Published: February 27, 2004
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The crystal structure, magnetic and electrical properties of A-site-ordered perovskite manganites Ln
1/2Ba
1/2MnO
3 (Ln=rare earth) were investigated. In the ordered Ln
1/2Ba
1/2MnO
3 (Ln = Sm-Y), a new charge/orbital ordering pattern was found. Electron diffraction studies revealed a series of superlattice reflections with modulation vectors at q
2 = (1/2, 1/2, 1/2) as well as at q
1= (1/4, 1/4, 0) in the tetragonal setting (a
p × a
p × 2a
p, a
p being the cubic perovskite lattice parameter) . Together with the results of the resonant X-ray scattering, a model for the three-dimensional charge/orbital ordering is proposed.
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[in Japanese], [in Japanese], [in Japanese], [in Japanese], [in Japane ...
2004 Volume 46 Issue 1 Pages
103-105
Published: February 27, 2004
Released on J-STAGE: September 30, 2010
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