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Phase Relations of the Bi-2201–CuO Pseudobinary Join as a Function of Oxygen Pressure

Published online by Cambridge University Press:  18 March 2011

James K. Meen ,
Karoline Müller ,
Celia Salmeron  and
Don Elthon
James K. Meen
Affiliation:
Department of Chemistry and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, U.S.A.
Karoline Müller
Affiliation:
Department of Chemistry and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, U.S.A.
Celia Salmeron
Affiliation:
Department of Chemistry and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, U.S.A.
Don Elthon
Affiliation:
Department of Chemistry and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204, U.S.A.
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Abstract

Phase relations on the join Bi-2201–CuO have been determined as a function of P(O2). Most of the major changes that occur between P(O2) of 1 and 0.01 atm occur in the most oxidizing part of the range. Stoichiometric Bi-2201 occurs only at the most oxidizing conditions and in a narrow temperature range near the solidus. In the Bi-2201–CuO system, the ternary phase that forms has higher Bi:Sr and Cu:Sr than Bi-2201. That phase, Sr14Cu24Oy, and CuO occur in the subsolidus and the invariant point at which they coexist with liquid is a ternary eutectic. The liquid is more Sr-rich than the Bi-2201–CuO join. Decrease in P(O2) produces a change in the Bi- 2201 solid solution so that stoichiometric Bi-2201 does not occur. At P(O2) ≤0.5 atm, all Bi- 2201 solid solutions have Bi:Cu<2 but Bi:Sr near unity and Sr14Cu24Oy does not form. Small amounts of a phase believed to be Bi9Sr11Cu5Ox form under these conditions and the primary phase field of that phase crosses the pseudobinary join and minimum melting is at a ternary tributary reaction point. The liquid there is more Bi-rich than the join. Further decrease in P(O2) causes a continued freezing point depression and enlargement of the CuO primary phase field so that the compositions of multiply-saturated liquids move away from the CuO apex.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 659: Symposium II – High-Temperature Superconductors-Crystal Chemistry, Processing & Properties , 2000 , II2.4
Copyright
Copyright © Materials Research Society 2001

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References

REFERENCES

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