Flux motion, proximity effect, and critical current density in YBa sub 2 Cu sub 3 O sub 7 minus. delta. /silver composites

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

DOI:https://doi.org/10.1103/PhysRevB.42.6181· OSTI ID:6226403

Jung, J; Mohamed, M A; Cheng, S C; Franck, J P ^[1]

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1. Department of Physics, University of Alberta, Edmonton, Alberta (Canada)

We report on studies of magnetic and transport properties, as well as on characterization of defects in the pure YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}/Ag(10 and 30 wt. %) composites. The studies of magnetic properties include the diamagnetic shielding, the Meissner effect, the trapped field (for both zero-field-cooling (ZFC) and field-cooling (FC) cases), and their dependence on applied magnetic field, temperature, and time. High- and low-magnetic-field hysteresis loops were measured and the intragrain magnetic'' critical current density was calculated. The studies of transport properties include the resistivity and intergrain transport'' critical-current-density measurements. Distribution, spacing, and size of intragrain twin boundaries were investigated. The results show the degradation of superconducting properties if silver is added to YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} during the sintering process, except the enhancement of the intergrain critical current density {ital J}{sub CT} in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}/Ag(10 wt. %) composite. The activation energy for intergranular flux creep of 1.6 and {approximately}0.3 eV was found for the pure YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}/Ag composites, respectively. The results did not show any relationship between {ital J}{sub CT}, the activation energy, and the number of pinning centers (the trapped field) in these samples. It is suggested that the proximity junctions superconductor--normal-metal--superconductor built up by intergranular silver, and not flux pinning, are responsible for the increase of {ital J}{sub CT}. Defect characterization by transmission electron microscopy revealed that silver does not affect the structure of twin boundaries inside the grains of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}.

• OSTI ID: 6226403
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 42:10; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COMPOSITE MATERIALS
COPPER COMPOUNDS
COPPER OXIDES
CRITICAL CURRENT
CRYSTAL STRUCTURE
CURRENTS
ELECTRIC CURRENTS
ELEMENTS
FLUX QUANTIZATION
GRAIN BOUNDARIES
LOW TEMPERATURE
MAGNETIC PROPERTIES
MAGNETIZATION
MATERIALS
MEISSNER-OCHSENFELD EFFECT
METALS
MICROSTRUCTURE
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PEROVSKITE
PEROVSKITES
PHYSICAL PROPERTIES
PROXIMITY EFFECT
SILVER
SUPERCONDUCTING COMPOSITES
TEMPERATURE DEPENDENCE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRANSPORT THEORY
TWINNING
VERY LOW TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES