ISSN:
1434-6036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract A superconducting (T c=40K) high-pressure phase recently discovered in the system of perovskite type YBaCuO structures is investigated by high-resolution transmission electron microscopy and electron diffraction in order to find its crystal structure. A structure model is proposed on the basis of a comparison between the observed images and image simulations based on crystal chemical considerations. The new phase has aB-centered orthorhombic cell with a monoclinic primitive cell. The primitive cell is composed of two subunits. The first of these is identical with the unit cell of orthorhombic YBa2Cu3O7−x (1-2-3 structure) withT c=92K. In contrast to the first subunit, the second one contains two adjacent Cu−O chains but is identical otherwise. This second subunit has been observed as one type of planar defect in the 1-2-3 structure. It is therefore concluded, that other stacking polytypes composed of these two different units could exist. The structure of the new phase is compared to the structures of the other known high-T c superconductors. The chemical formula for the new phase can be written as Y2Ba4Cu7O14+x, with x≈0.5±0.2.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01314269
