Observation of temperature-dependent site disorder in YBa sub 2 Cu sub 3 O sub 7 minus. delta. below 150 degree C

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.42.6305· OSTI ID:6001363

Veal, B W; Paulikas, A P; You, H; Shi, H; Fang, Y; Downey, J W ^[1]

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1. Materials Science Division, Argonne National Laboratory, Argonne, IL (USA)

We have observed annealing effects in both single-crystal and ceramic samples of oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} that occur at temperatures as low as 0 {degree}C. Oxygen stoichiometries were controlled by quenching, from 520 {degree}C, samples equilibrated in a controlled O{sub 2}-N{sub 2} atmosphere. For single crystals, transition temperatures with any desired value between 0 and 92 K, and transition widths less than 2 K, were readily obtained with appropriate variation of {delta}. After quenching, superconducting transition temperatures of the reduced samples rise, as much as 15 K, when aged in ambient atmosphere for several days; the sample composition does not change with aging. With low-temperature aging, structural changes also occur; e.g., orthorhombicity increases. These effects are attributed to oxygen-vacancy ordering that occurs in the chain region of the structure. The rise in {Tc} with aging (ordering) is attributed to increased hole doping in the planes that results from an increased population of two-coordinated (monovalent) copper atoms. For samples with reduced stoichiometries, the degree of disorder can be reversibly controlled with secondary quenches in the temperature range 0--120 {degree}C. For stoichiometries 7{minus}{delta}{approx equal}6.5, an approximate activation energy of 0.96 eV was obtained for the annealing process. This low-temperature annealing behavior, occurring in samples of constant composition, provides a remarkably simple and effective way to study the relationship between superconductivity, structure, and associated electronic properties.

• OSTI ID: 6001363
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 42:10; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
BARIUM COMPOUNDS
BARIUM OXIDES
CERAMICS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
HEAT TREATMENTS
HIGH-TC SUPERCONDUCTORS
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POINT DEFECTS
STOICHIOMETRY
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES