J. Phys. I France
Volume 1, Numéro 5, May 1991
Page(s) 721 - 741
DOI: 10.1051/jp1:1991165
J. Phys. I France 1 (1991) 721-741

The crystal structure of RESr $\mathsf{_{2}}$GaCu $\mathsf{_{2}}$O $\mathsf{_{7}}$

G. Roth1, P. Adelmann1, G. Heger2, R. Knitter3 and Th. Wolf4

1  Kernforschungszentrum Karlsruhe, Institut für Nukleare Festkörperphysik, P.O. Box 3640, D-7500 Karlsruhe, Germany
2  Laboratoire Léon Brillouin laboratoire commun CEA-CNRS, CEN Saclay, F-91191 Gif-sur-Yvette, France.
3  Kernforschungszentrum Karlsruhe, Institut für Material- und Festkörperforschung III, P.O. Box 3640, D-7500 Karlsruhe, Germany
4  Kernforschungszentrum Karlsruche, Institut für Technische Physik, P.O. Box 3640, D-7500 Karlsruhe, Germany

(Received 20 December 1990, accepted 5 February 1991)

The crystal structure of RESr 2GaCu 2O 7 (with RE=Er...La and Y) has been studied by powder neutron, powder X-ray and single crystal X-ray diffraction. These compounds crystallize in space group Ima2 with approximate lattice parameters $a\approx 22.8$Å  $\approx 2\cdot c$ (1-2-3), $b\approx 5.5$Å  $\approx\sqrt{2}\cdot b$ (1-2-3) and $c\approx 5.4$Å  $\approx\sqrt{2}\cdot a$ (1-2-3) and 4 formula units per cell. Like the high- $T_{\rm c}$ superconductor YBa 2Cu 3O 7 ("1-2-3") the structure contains double layers of Cu-O 5-pyramids separated by Y or trivalent rare earth ions. The Cu-O4 square planar chains of 1-2-3, however, are replaced by Ga-O4 tetrahedral chains running along the diagonal of the basal plane of the 1-2-3 subcell. The role of Ba to fill the large voids in 1-2-3 is played by Sr in these compounds. The structure forms with Y and all trivalent rare earth ions from Er through La with the exception of Ce. The oxygen stoichiometry is fixed to O 7 and the compounds are semiconducting. They can be p-doped by partially replacing RE by divalent earth alkali ions, thus reducing the resistivity drastically. However, despite their strong similarity to 1-2-3, particularly with respect to the Cu-O 5-pyramidal bilayers, combined with the possibility of p-doping all attempts to make these compounds metallic or even superconducting have failed so far.

© Les Editions de Physique 1991

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.