Nihon Kessho Gakkaishi

[title in Japanese]

1987Volume 29Issue 6 Pages 349
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.349

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High Temperature Superconduction Oxides

Shinobu HIKAMI

1987Volume 29Issue 6 Pages 350-352
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.350

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Brief introduction to the high temperature superconducting oxides which have been discovered is presented. And also possible mechanisms for the superconductivity are surveyed.

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Growth and Properties of High-T_c Oxide-Superconductor Crystals

Humihiko TAKEI, Hiroyuki TAKEYA

1987Volume 29Issue 6 Pages 353-359
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.353

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Crystal growth and physical properties of oxide superconductor YBa₂Cu₃Ox are reviewed. Flake crystals, which are obtained by a solution growth technique where excess CuO is used as a solvent, display a low temperature superconducting transition below 60K. On the other hand, block crystals, which are prepared using a solid-liquid reaction at peritectic temperature Tp, show a sharp transition above 90K in the as-grown state. A clear anisotropy in the upper critical field is observed in the block crystals. Twinning structures are also discussed in terms of a strain releasing model in the tetragonal-orthorhombic transformation near 600°C.

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Preparation and Properties of Superconducting Oxede Thin Films

Toshiaki MURAKAMI, Youichi ENOMOTO, Minoru SUZUKI

1987Volume 29Issue 6 Pages 359-364
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.359

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Preparation and properties of superconducting oxide thin films are described. (La_1-xSr_x) ₂ CuO₄ (LSCO) and Ba₂YCu₃O_7-σ (BYCO) can be epitaxially grown on (100) and (110) SrTiO₃ single crystal substrates by magnetron sputtering method. Anisotropic properties of BYCO are measured by using thin films deposited on the (110) plates. The critical current density along the CuO layers has reached 1.8×10⁶A/cm² at 77.3k. This current density is adequate for device applications.

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Crystal Structures of High-T_c Superconductors and Related Compounds

Fujio IZUMI, Izumi NAKAI

1987Volume 29Issue 6 Pages 365-373
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.365

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The structures of high-T_c superconducting oxides are classified into two groups: K₂NiF₄ and oxygen-deficient triperovskite types. The crystal chemistry of these two types of superconductors and related compounds is explained on the basis of coordination polyhedra and oxidation states of Cu, metal-oxygen bond lengths, and coordination numbers of metals.

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High Resolution Transmission Electron Microscopy of High T_c Superconducors

Yoshio MATSUI

1987Volume 29Issue 6 Pages 374-381
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.374

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High T_c superconducting oxide, Ba₂YCu₃O_v, and some related compounds are examined by means of high resolution transmission electron microscopy. Twin structure, planar defects, microdomain structure, out-of-phase domain structures etc are observed in these compounds. Structural changes, including orthorhombic-to-tetragonal phase transition, are observed when the specimen is heated by electron beam or by the heating-stage. Super-lattice reflections or diffuse scatterings are sometimes observed in the electron diffraction patterns of these materials.

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Local Structure and Valence States in Ba₂YCu₃O_y

Hiroyuki OYANAGI, Hideo IHARA

1987Volume 29Issue 6 Pages 382-389
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.382

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The role of oxygen vacancies in superconducting properties of Ba₂YCu₃O_y (6.22<_y<6.96) has been investigated by EXAFS and XANES on the Cu K-edge. Fourier transform analysis of EXAFS shows that oxygen vacancies influence the local structure through (1) the disappearance of O1-Cu1-O1 chain and displacement of atomic positions along the c-axis, (2) the Cu-O vibrational properties and (3) introducing structural disorder between the CuO₂ planes. Cu XANES spectra show that Cu valency in Ba₂YCu₃O_y is essentially 2+ with some 3+ contribution. Oxygen vacancies create Cu1⁺for _y<6.7 at which high T_c (90K) degrades to low T_c (50-60K) superconducting states.

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Analysis of the Lattice Dynamics in High T_c Superconductors by the Neutron Scattering Method

Atsushi MASAKI

1987Volume 29Issue 6 Pages 389-397
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.389

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The results of the neutron scattering experiments of three kinds of superconducting oxides, BaPb_1-xBi_xO₃, (La_1-xSr_x) ₂CuO₄, and YBa₂Cu₃O_x, are reviewed. The phonon structures of superconducting compositions are compared with those of nonsuperconducting ones. In each oxide system, the phonons in the high-energy region are softened and become broad in the superconducting materials in contrast with the nonsuperconducting materials. In particular, in BaPb_1-xBi_xO₃ case, the obtained spectrum is in good agreement with our previous FIR experimental results.

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Structure Factor Determination by the Pendellösung-Beats Measurement Using White Radiation

Toshihiko TAKAMA

1987Volume 29Issue 6 Pages 398-405
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.398

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This paper describes the new techniques of measuring the Pendellosung beats using white radiation with the energy-dispersive diffraction method. Two techniques have been developed in the author's laboratory on the basis of the dynamical diffraction theory, in which the intensity of a Laue spot diffracted from a parallel-sided single crystal is successively measured at different Bragg angles, i.e., with different wavelengths. In the fast method, the integrated intensity diffracted from the whole exit area is measured and in the second case, the measurement is made only at the center of the Borrmann fan. A discussion is made on the advantage points as well as on the accuracy of these methods in the structure factor determination.

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The Structure of an Icosahedral Al-Mn Quasicrystal

Akiji YAMAMOTO

1987Volume 29Issue 6 Pages 406-414
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.406

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This article reviewes the section method which is convenient to understand all the quasiperiodic structures including the modulated and quasicrystal structures on the same basis. A model construction of an icosahedral Al - Mn quasicrystal is examplified by use of this method. This model explains the X -ray and neutorn powder diffraction patterns of an icosahedral A1₄Mn.

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[title in Japanese]

[in Japanese]

1987Volume 29Issue 6 Pages 415-417
Published: November 30, 1987
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.5940/jcrsj.29.415

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