Microstructure, lattice parameters, and superconductivity of YBa/sub 2/(Cu/sub 1-//sub x/Fe/sub x/)/sub 3/O/sub 7-//sub delta/ for 0less than or equal toxless than or equal to0. 33
Iron was substituted for copper in YBa/sub 2/(Cu/sub 1-//sub x/Fe/sub x/)/sub 3/O/sub 7-//sub delta/ for 0less than or equal toxless than or equal to0.33. Superconducting transition temperatures and lattice parameters have been determined as a function of Fe content. The orthorhombic distortion ..delta..a/sub 0/ = 2(b-a)/(a+b) decreased to zero near x = 0.03. Beyond x = 0.03 the structure appears tetragonal. For compositions 0less than or equal toxless than or equal to0.15 the superconducting critical temperature T/sub c/ decreased smoothly from T/sub c/ = 90 K to below 4.2 K. Transmission electron microscopy (TEM) revealed that the spacing between the twin boundaries decreased from /similar to/200 nm for x = 0 to /similar to/20 nm for x = 0.02 before the twins disappeared for x> = 0.03. The sharp streaks in TEM diffraction patterns were interpreted as due to the twin boundary layers whose thickness varied from /similar to/1 nm for the pure to /similar to/2 nm for the Fe (x = 0.02) containing specimen. A tweed structure in the TEM image and associated diffuse streaks along the <110> directions in electron diffraction pattern appeared for x>0.015. This observation suggests that the structure consists of fine (<5 nm) orthorhombic domains, each domain having the twinlike crystallographic relation with its neighbors. Rietveld refinement of powder neutron diffraction for x = 0.10 and 0.167 determined that Fe substituted primarily on the Cu ''chain'' site, and for every two atoms of Fe substituted, approximately one extra oxygen is incorporated in the Cu-O plane.
- Research Organization:
- Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973
- OSTI ID:
- 6407748
- 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
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
IMPURITIES
IRON COMPOUNDS
IRON OXIDES
LATTICE PARAMETERS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PARAMETRIC ANALYSIS
PHYSICAL PROPERTIES
QUANTITY RATIO
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES