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Role of Silver in Yba2Cu3AgXO7-δ Composite Superconductors

Published online by Cambridge University Press:  28 February 2011

L. Ganapathi ,
Ashok Kumar  and
J. Narayan
L. Ganapathi
Affiliation:
Department of Materials Science and EngineeringNorth Carolina State UniversityRaleigh, N. C. 27695‐7916
Ashok Kumar
Affiliation:
Department of Materials Science and EngineeringNorth Carolina State UniversityRaleigh, N. C. 27695‐7916
J. Narayan
Affiliation:
Department of Materials Science and EngineeringNorth Carolina State UniversityRaleigh, N. C. 27695‐7916
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Abstract

Superconducting properties and microstructures of the YBa2Cu3AgxO7‐δ composites have been studied as a function of silver content, 0 ≤ x ≤ 6, using a variety of techniques.The superconducting transition temperature,Tc, of these composites was found to be the same, ∼ 90 K, for the above range of compositions. The composites with x > 3 are found to have resistivity behavior identical to silver metal above the superconducting transition temperature. The peritectic transformation temperature of the 123 material in the composite is lowered. Alloy formation between Ag and Cu is proposed to take place triggering the peritectic transformation at lower temperatures. The silver is observed in the form of precipitates at very low concentrations of silver, indicating that silver does not substitute for copper in YBa2Cu3AgxO7. Lattice parameters of the composites were found to be invariant throughout the above composition range. The addition of Ag2O in the starting composition seems to stabilize the stoichiometric YBa2Cu3AgxO7 by way of decomposition to Ag and O, also, the better diffusion of oxygen through silver in comparison with that through the superconductor helps the regeneration of superconductivity in the composite superconductor. As a result, the incorporation of oxygen and recovery of superconducting properties is enhanced in the silver composites.For values of x > 3 small quantities of 211 phase were detected along the grain boundaries, which makes the residual composition poor in copper resulting in the formation of non‐superconducting 211 phase.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 169: Symposium M – High Temperature Superconductors: Fundamental Properties and Novel Materials Processing , 1989 , 1267
Copyright
Copyright © Materials Research Society 1990

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References

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