FDS+Evac models and cryogenic and oxygen deficiency emergency management for underground facilities in Gran Sasso National Laboratories

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012093x ◽

1992 ◽

Vol 50 (1) ◽

pp. 106-107

Author(s):

H.W. Zandbergen ◽

M.R. McCartney

Keyword(s):

Electron Microscopy ◽

Copper Oxide ◽

Grain Boundaries ◽

Atomic Structure ◽

Oxygen Deficiency ◽

Surface Layers ◽

Layer Sequence ◽

Surface Reconstructions ◽

Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

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Crystal chemistry of high-Tc superconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178720 ◽

1990 ◽

Vol 48 (4) ◽

pp. 1118-1119

Author(s):

Maryvonne Hervieu

Keyword(s):

Oxygen Deficiency ◽

Large Family ◽

Copper Oxides ◽

High Tc Superconductors ◽

High Tc ◽

Single Mechanism ◽

Square Planar ◽

History Of ◽

Bismuth Cuprates ◽

New Compounds

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.

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