Structure-property relationships for RBa/sub 2/Cu/sub 3//O/sub x/ phases. [R = Y, La, Nd, Er]

Conference · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6198625

Torardi, C C; McCarron, E M; Subramanian, M A; Horowitz, H S; Michel, J B; Sleight, A W

The structures of several 1-2-3 compounds, e.g., YBa/sub 2/Cu/sub 3/O/sub 7/, have been refined from powder neutron diffraction data collected at 298/sup 0/K. Orthorhombic symmetry was found for the superconducting phases NdBa/sub 2/Cu/sub 3/O/sub 6.85/, YBa/sub 2/Cu/sub 3/O/sub 6.91/, and ErBa/sub 2/Cu/sub 3/O/sub 6.99/. The short Cu-O distance of about 1.85 A decreases with increasing size of the rare earth cation, but the average Cu-O distance in the chains remains nearly constant. Refinement of a reduced YBa/sub 2/Cu/sub 3/O/sub 7-x/ phase shows that a tetragonal YBa/sub 2/Cu/sub 3/O/sub 6/ composition can be achieved before structural collapse. This phase is semiconducting and not superconducting. We have also prepared a sample of YBa/sub 2/Cu/sub 3/O/sub 7/ with the tetragonal 1-2-3 structure where oxygens have not ordered in a way to produce the linear (Cu-O)/sub n/ chains. This form of YBa/sub 2/Cu/sub 3/O/sub 7/ is not superconducting above 4.2/sup 0/K. The structure of La/sub 1.6/Ba/sub 1.6/Cu/sub 3/O/sub 7.33/ with the tetragonal 1-2-3 structure was refined and again there are no linear (Cu-O)/sub n/ chains and no superconductivity. On the basis of these six structural refinements, we tentatively conclude that the (Cu-O)/sub n/ chains are required for superconductivity. 5 refs., 1 fig., 4 tabs.

• Research Organization: Du Pont de Nemours (E.I.) and Co., Wilmington, DE (USA). Central Research and Development Dept.; Brookhaven National Lab., Upton, NY (USA)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 6198625
• Report Number(s): BNL-40072; CONF-870802-16; ON: DE87014440
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ATOMS
BARIUM COMPOUNDS
BARIUM OXIDES
BOND LENGTHS
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
DIMENSIONS
ELEMENTS
ERBIUM COMPOUNDS
ERBIUM OXIDES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LENGTH
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
NEUTRON DIFFRACTION
NONMETALS
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SCATTERING
STOICHIOMETRY
SUPERCONDUCTORS
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES