Transport critical current of aligned polycrystalline Y sub 1 Ba sub 2 Cu sub 3 O sub 7 minus. delta. and evidence for a nonweak-linked component of intergranular current conduction

Journal Article · Sat Sep 01 00:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.346533· OSTI ID:6429985

Ekin, J W ^[1]; Hart, Jr, H R; Gaddipati, A R ^[2]

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1. National Institute of Standards and Technology, Electromagnetic Technology Division, Boulder, CO (USA)
2. GE Corporate Research and Development, Schenectady, NY (USA)

A study of grain alignment and its effect on the dc transport critical current in fine-grained bulk Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is reported in magnetic fields from 10{sup {minus}4} T to 26 T. Two features distinguish the critical current density {ital J}{sub {ital c}} of aligned bulk Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} from unaligned material. First, the effective critical field where the intergranular {ital J}{sub {ital c}} approaches zero is about four times higher (30 T) for aligned samples with field parallel to the {ital a}, {ital b} planes, than it is for polycrystalline unaligned samples (7 T). Second, the nearly field independent plateau value of {ital J}{sub {ital c}} between 10 mT and 1 T is one to two orders of magnitude higher than typical plateau values of {ital J}{sub {ital c}} in unaligned bulk-sintered Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, for field parallel to the {ital a}, {ital b} planes. A low-field ({lt}10 mT) weak-link decrease in {ital J}{sub {ital c}} with magnetic field is still observed, but it is much smaller than for unaligned material. These data clearly demonstrate that alignment alone significantly reduces the {ital weak}-{ital link} problem in fine-grained polycrystalline samples with low-aspect-ratio (4:1) grains (unlike melt-grown samples where there has been some ambiguity as to the relative importance of alignment versus large grain growth). Furthermore, the results provide strong evidence that there are two parallel components of {ital intergranular} current conduction, one consisting of weak-linked material, the other behaving like intrinsic intragranular material that is not weak-linked. A comparison with unaligned Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} indicates that the volume fraction of such nonweak-linked material is significantly enhanced by grain alignment, but still only 0.01%--0.1% of the grain boundary area.

• OSTI ID: 6429985
• Journal Information: Journal of Applied Physics; (USA), Vol. 68:5; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CRITICAL CURRENT
COPPER OXIDES
YTTRIUM OXIDES
CRITICAL FIELD
GRAIN ORIENTATION
HIGH-TC SUPERCONDUCTORS
MAGNETIC FIELDS
POLYCRYSTALS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL STRUCTURE
CRYSTALS
CURRENTS
ELECTRIC CURRENTS
MICROSTRUCTURE
ORIENTATION
OXIDES
OXYGEN COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties