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Pb-doped Bi-2212: Homogeneity Area, Oxidation and Effect on jc

Published online by Cambridge University Press:  18 March 2011

A. Veresov ,
M. Pulkin ,
A. Knotko ,
V. Putlayev  and
E. K. H. Salje
A. Veresov
Affiliation:
Department of Materials Sciences, Moscow Sate University, Moscow 119899, RUSSIA Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
M. Pulkin
Affiliation:
Department of Materials Sciences, Moscow Sate University, Moscow 119899, RUSSIA
A. Knotko
Affiliation:
Department of Chemistry, Moscow Sate University, Moscow 119899, RUSSIA
V. Putlayev
Affiliation:
Department of Chemistry, Moscow Sate University, Moscow 119899, RUSSIA
E. K. H. Salje
Affiliation:
Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
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Abstract

The most promising way to improve jc in superconductors is likely to be a creation of small precipitates in the material during decomposition of supersaturated solid solution. It was recognised recently that Pb-doping of 2212 could have beneficial effect on jc. Bi2.1−xPbxSr2CaCu2O8+d (x=0.1…0.7) was prepared at different temperatures and oxygen partial pressure (pO2=10−3 – 0.21 atm) via nitrate route. The effect of pO2 and Pb-doping on Bi-2212 phase formation was explored with XRD, SEM/EPMA and TEM/SAED. The limit of Pb solubility in Bi-2212 was found to increase with a decrease in pO2 and corresponded to a decrease in x=0.3 at pO2 = 0.21 atm (850 °C) and x=0.6 at pO2 ∼ 10−3 atm (750 °C). TEM study of the as-synthesized solid solutions revealed significant nanoscale inhomogeneity attributed to Pb-segregation. For the samples with x > 0.3 the inhomogeneity quite often looked like a well- ordered wave with the period of about 10 nm. The samples of (Bi,Pb)-2212 processed under pO2 conditions were oxidized at 600–750°C in air for 0.5–60 h in order to cause precipitation of secondary phases from the supersaturated solid solution. Thermogravimetrical study (TG) of the oxidation gave a strong evidence of two stages composing the process. It was found that jc was enhanced by a factor of 2 after annealing at 650°C (i.e. during the first stage of oxidation).

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 659: Symposium II – High-Temperature Superconductors-Crystal Chemistry, Processing & Properties , 2000 , II9.6
Copyright
Copyright © Materials Research Society 2001

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References

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