Melting and vaporization of the 1223 phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O)
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
- Oak Ridge National Lab., TN (United States)
The melting and vaporization of the 1223 [(Tl,Pb):(Ba,Sr):Ca:Cu] oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods and post-quenching characterization techniques. Vaporization rates, thermal events, and melt compositions were followed as a function of thallia loss from a 1223 stoichiometry. Melting and vaporization equilibria of the 1223 phase are complex, with as many as seven phases participating simultaneously. At a total pressure of 0.1 MPa the 1223 phase was found to melt completely at (980 {+-} 5) C in oxygen, at a thallia partial pressure (p{sub tl2O}) of (4.6 {+-} 0.5) kPa, where the quoted uncertainties are standard uncertainties, i.e., 1 estimated standard deviation. The melting reaction involves five other solids and a liquid. Stoichiometries of the participating phases have been determined from microchemical analysis, and substantial elemental substitution on the 1212 and 1223 crystallographic sites is indicated. The 1223 phase occurs in equilibrium with liquids from its melting point down to at least 935 C. The composition of the lowest melting liquid detected for the bulk compositions of this study has been measured using microchemical analysis. Applications to the processing of superconducting wires and tapes are discussed.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 419652
- Journal Information:
- Journal of Research of the National Institute of Standards and Technology, Journal Name: Journal of Research of the National Institute of Standards and Technology Journal Issue: 5 Vol. 101; ISSN 1044-677X; ISSN JRITEF
- Country of Publication:
- United States
- Language:
- English
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