An electron diffraction study of superconducting oxides Ba1−xPbxBiO3 and Ba1−yPbyBiO3

1990 ◽  
Vol 48 (4) ◽  
pp. 82-83
Author(s):  
Yasumasa Koyama ◽  
Manabu Ishimaru
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Study ◽  
Perovskite Structure ◽  
Electron Diffraction Study ◽  
Structural Disorder ◽  
Oxide Superconductors ◽  
Mechanism Of Superconductivity ◽  
Superconducting Oxides ◽  
Characteristic Features

Before the discovery of superconductivity in La-Ba-Cu-O by Bednorz and Müller, it has been known that BaPb1−xBixO3 (BPB) exhibits superconductivity below about 13 K. In particular, because Ba1−yKyBiO3 (BKB) was found to be a superconductor with Tc of about 30 K, the Ba-oxides become more important in order to understand the mechanism of superconductivity of the oxide superconductors. Characteristic features for the Ba-Oxides are that their crystal structure is basically the cubic perovskite structure and there is not a Cu-O layer which is responsible for the superconductivity in the oxide superconductors having the Cu-O layer, such as Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O. That is, the O(2p)-[Pb(6s), Bi(6s)] hybridized orbitals would play an important role in the case of the Ba-oxides. In the present work, in order to understand features of the crystal structure of the Ba-oxides, including a structural disorder, the details of the structure have been examined by means of electron diffraction.

scholarly journals An electron diffraction study of the structure of thin films of normal paraffins

1947 ◽  
Vol 188 (1014) ◽  
pp. 414-426 ◽  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Stainless Steel ◽  
Electron Diffraction ◽  
Film Thickness ◽  
Diffraction Study ◽  
Electron Diffraction Study ◽  
Film Structure ◽  
Copper Surfaces

Thin films of the normal paraffins tetracosane (C 24 H 30 ), triacontane (C 30 H 62 ) and tetratriacontane (C 34 H 70 ) have been examined by electron diffraction when deposited on stainless steel, copper or collodion. Both the reflexion and the transmission techniques have been employed. The results of rubbing the films have been ascertained, and the orientations observed have been explained in terms of the crystal structure of the normal paraffins. Films of the three paraffins have been heated upon stainless steel and upon copper surfaces, and curves derived relating the temperature at which the ordered film structure breaks down, to the film thickness. These results suggest that this temperature corresponds in the case of a monolayer to a transition of the film structure from a condensed to an expanded type.

An electron diffraction study of Bi2Sr2(GdxCa1−x)0.8Cu2O8+δ

1990 ◽  
Vol 5 (8) ◽  
pp. 1625-1638 ◽  
Author(s):  
J. Kulik ◽  
Y. Y. Xue ◽  
Y. Y. Sun ◽  
M. Bonvalot
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Study ◽  
Wave Vector ◽  
Electron Diffraction Study ◽  
Reciprocal Space ◽  
Incommensurate Modulation

The compound Bi2Sr2(GdxCa1−x)0.8Cu2O8+δ is examined by electron diffraction for several values of x. The incommensurate modulation which has been reported for x - 0 persists for all values of x with the wave vector increasing as x increases. A secondary modulation with a wave vector equal to one-half that of the primary is observed for x  0.85. This modulation manifests itself through satellite reflections that are highly streaked normal to the (001) planes and that flank certain select positions in reciprocal space. The appearance of this secondary modulation is accompanied by a change in the average crystal structure from B-centered to F-centered orthorhombic.

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