Single-Crystal X-Ray Structure Analysis of New Oxide-Superconductor Bi₂(Sr_1-xLn_x)₂(Gd_1-yCe_y)₂Cu₂O_10+z

Abstract

The crystal structure of Bi2(Sr1-xLnx)2(Gd1-yCey)2Cu2O10+z(Ln=Gd with x=0.1, y=0.23 and z=0.16 or Ln=Ce with x=0.1, y=0.13 and z=0.16) was determined using the X-ray intensity data of a single crystal. The chemical composition was determined by electron microprobe analysis. The crystal data are as follows: orthorhombic, space group Cmmb, a=5.435(2), b=5.446(1), c=17.826(5) Å, final R factor Rw=0.053 for 640 independent observed reflections. The structure is composed of stacking of the Bi-O double layer, a Cu-O sheet of CuO5pyramids, and the fluorite-like Ln2O2layer. Sr is located between the Cu-O sheet and the Bi-O double layer. The crystal has a commensurate type superstructure with unit cell dimensions b×9 and c×2 of the subcell: a=5.426(7), b=49.06(2), c=35.66(2) Å. Precession photographs showed orthorhombic symmetry and systematic absences suggested condensed symbols C*c*for the space group of the superlattice. The modulation of the structure was well reflected on the anisotropic motions of the thermal ellipsoids of the component atoms in the average structure. © 1990 IOP Publishing Ltd.