Percolation in superconducting cuprates; Resistivity and critical currents

Journal Article · Mon May 01 04:00:00 EDT 1989 · International Journal of Modern Physics B; (USA)

DOI:https://doi.org/10.1142/S0217979289000531· OSTI ID:7171690

Halbritter, J ^[1]

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1. Kernforschungszentrum Karlsruhe GmbH (Germany, F.R.)

Weak links in metallic cuprates yield complicated percolative conduction networks enhancing the intrinsic resistivity {rho}{sup i}(T) = {alpha}{sup i} + {rho}{sup i}{sub 0L} to: {rho}(T) = {Sigma}{sub {rho}b} + p({alpha}{sup i}T + {rho}{sup i}{sub 0L}) with {rho}{sub b} describing the weak links and a geometrical factor p {ge} 1. In most cases single crystals and epitaxial films show insulating intragrain weak links yielding p {approx} 3 and {Sigma}{sub {rho}b{much gt}} {rho}{sup i} (100K), like good sintered YBa{sub 2}Cu{sub 3}O{sub x}. Rarely are the intrinsic values {alpha}{sup i} {approx} 0.5 {mu}{Omega}cm/K and {rho}{sup i} (100 K) {approx} 50 {mu}{Omega}cm observed. In the superconducting state the intrinsic resistivity {rho}{sup i}(T) vanishes and then the critical transport current density j{sub c}(B,T) is given by the superconducting aspects of conducting weak links: j{sub c}(B,T) = {Sigma}p{sub s}(B,T) min (j{sub CJ}, j{sub CG}, j{sub CP}). Here, j{sub CJ}(j{sub CG}) stands for Josephson junctions at intergrain (intragrain) weak links and j{sub CP} for pinning. p{sub 5}(B,T) stands for current path systems changing with B-field and temperature. j{sub CJ} and j{sub CG} depend crucially on the care in preparation and alignment of the a-b-planes, where the current flows, but values j{sub CJ}(0.77 K) {approx} 10{sup 3} A/cm{sup 2} and j{sub CG}(0.77 K) {approx} 10{sup 5} A/cm{sup 2} seem typical. Weak links are related to planar defects where large and small angle grain boundaries are dominant. j{sub CP} is shadowed by j{sub CJ} and j{sub CG} but j{sub CP} {approx} 10{sup 6} a/CM{sup 2} are inferred from experiment. The time-, temperature-, B-field and voltage-dependencies of the current in- and in the transition to- the superconducting state are analyzed. Evidence is presented for arrays of microbridges being electrically the planar defects.

• OSTI ID: 7171690
• Journal Information: International Journal of Modern Physics B; (USA), Journal Name: International Journal of Modern Physics B; (USA) Vol. 3:5; ISSN 0217-9792; ISSN IJPBE
• Country of Publication: United States
• Language: English

Related Subjects

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Cermets
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
CHARGE TRANSPORT
COOPER PAIRS
COPPER COMPOUNDS
COPPER OXIDES
CRITICAL CURRENT
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CURRENT DENSITY
CURRENTS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
GRAIN BOUNDARIES
JOSEPHSON JUNCTIONS
JUNCTIONS
MAGNETIC FLUX
MATHEMATICAL MODELS
MICROSTRUCTURE
NUCLEAR MODELS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTIVITY
TEMPERATURE DEPENDENCE
TETRAGONAL LATTICES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TUNNELING
WEAK-COUPLING MODEL
YTTRIUM COMPOUNDS
YTTRIUM OXIDES