Structure and crystal chemistry of the high-T(c) superconductor YBa2Cu3O(7-x)
Abstract
High-resolution neutron powder diffraction data for the high-T(c) superconductor YBa2Cu3O(7-x) with x = 1.5 are presented. The results agree with those of Hazen with respect to cation positions, but the location of one set of oxygen defects is substantially different and necessitates the lowering of lattice symmetry from tetragonal to orthorhombic, in agreement with separate findings. In constrast to the 35 K superconductor La(1.85)Ba(0.15)CuO4, the corner-linked CuO4 planar groups are connected not only as sheets in the a-b plane but also as chains parallel to the b-axis. The average copper valence is 2.23(5). From bond valence arguments, it is inferred that the Cu(2+) and Cu(3+) ions preferentially occupy square pyramidal and square planar sites respectively. Crystal chemical considerations suggest that these structural features may be involved in the superconducting mechanism.
- Publication:
-
Nature
- Pub Date:
- May 1987
- DOI:
- 10.1038/327310a0
- Bibcode:
- 1987Natur.327..310D
- Keywords:
-
- Copper Oxides;
- Crystal Defects;
- Crystal Structure;
- High Temperature Superconductors;
- Yttrium Compounds;
- Barium Compounds;
- Chemical Properties;
- Critical Temperature;
- Solid-State Physics