Temperature dependence of the local structure of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ with varying oxygen content: An x-ray-absorption study

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.6555· OSTI ID:6408453

Boyce, J B; Bridges, F; Claeson, T; Nygren, M

The local structure of YBa/sub 2/Cu/sub 3/O/sub y/ determined using x-ray-absorption fine structure (XAFS) agrees well with the long-range order given by diffraction results for both oxygen-rich, orthorhombic (y = 6.98 and 6.87) and oxygen-deficient, tetragonal (y = 6.15) compounds. The x-ray-absorption near-edge structure supports the conclusion that, as y = 7 goes to y = 6, the O is removed from the chains and the chain Cu atoms, Cu(1), becomes monovalent with a linear O-Cu-O structural configuration and a 3d/sup 10/ electronic configuration, as in Cu/sub 2/O. For the XAFS analysis, structural standards were determined, and these standards worked well not only for the Cu first-neighbor O environment but also for the Cu second-neighbor metal-atom environment out to 4 A. A detailed multipeak analysis reproduced the XAFS spectra well and yielded structural parameters that agree with diffraction. The temperature dependence of the structural parameters shows only a smooth variation, with no significant anomalies. The Cu-X distances have a negligible to a small positive change with temperature, consistent with the lattice expansion. The exception is the Cu-Ba distances which change substantially; the Cu(1)-Ba distance increases and the Cu(2)-Ba distance decreases. This indicates that the Ba moves away from the Cu(1)-O chains and toward the Cu(2)-O planes with increasing temperature and that anharmonicity plays a role. This motion is larger for the oxygen-depleted compound than for the fully oxygenated material. The in-plane Cu-O first-neighbor vibrations exhibit no significant softening with temperature.

• Research Organization: Xerox Palo Alto Research Center, Palo Alto, California 94304
• OSTI ID: 6408453
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 39:10; ISSN PRBMD
• 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
ABSORPTION SPECTROSCOPY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
ELECTRONIC STRUCTURE
HIGH TEMPERATURE
LOW TEMPERATURE
MEDIUM TEMPERATURE
ONE-DIMENSIONAL CALCULATIONS
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
PEROVSKITES
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
QUANTITY RATIO
SPECTROSCOPY
STOICHIOMETRY
STRUCTURAL CHEMICAL ANALYSIS
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
TETRAGONAL LATTICES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TWO-DIMENSIONAL CALCULATIONS
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES