Stability of the Tl-1223 phases
- Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)
- Argonne National Laboratory, Argonne, Illinois 60439 (United States)
The thermodynamic stability of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{ital y}}(1223) and substitutionally related phases has been studied by performing extended high-temperature anneals in a two-zone furnace. This approach allows for independent control of each of the thermodynamic variables: the oxygen and thallous oxide partial pressures [P(O{sub 2}) and P(Tl{sub 2}O)], the sample temperature, and the sample composition. P(Tl{sub 2}O) determines which of several superconducting phases form in the unsubstituted Tl{endash}Ba{endash}Ca{endash}Cu{endash}O system. TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{ital y}} is stable only within a narrow window of P(Tl{sub 2}O). Partially replacing Tl with Pb and Ba with Sr substantially increases the stability of the 1223 phase. The composition (Tl{sub {ital x}}Pb{sub 0.5})(Sr{sub 1.6}Ba{sub 0.4})Ca{sub 2}Cu{sub 3}O{sub 9{minus}{ital y}} yields only the 1223 phase under two-zone conditions when P(Tl{sub 2}O) exceeds a lower bound. The stability of Pb- and Sr-substituted 1223 relative to the 1212 phase are related to the substitutional stoichiometry, rather than P(Tl{sub 2}O). {copyright} {ital 1996 Materials Research Society.}
- Research Organization:
- Sandia National Laboratory
- DOE Contract Number:
- AC04-94AL85000; W-31109-ENG-38
- OSTI ID:
- 286327
- Journal Information:
- Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 7 Vol. 11; ISSN JMREEE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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