DTA study for clarifying the role of silver in the formation of Bi-2223 phase in Ag-Sheathed tapes
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The role of silver in catalysing and promoting the textured growth of 2223 phase in Ag-sheathed (Powder In Tube) tapes, starting from a precursor «bi-component» powder, constituted by Bi-2212 and other mixed oxides, was investigated in detail by means of DTA and X-ray analyses at the different stages of the annealing of the tapes. By monitoring the reaction it was possible to show how the presence of silver modifies the thermal behaviour of the reactants. The reduction of the temperature at which a liquid phase is formed is believed to be the key mechanism through which the presence of silver enhances the overall conversion to 2223 phase. This temperature decrease was shown (for the first time, to our knowledge) to be active only as long as some precursor (unreacted) powder was present, and not on fully reacted 2223 phase. Further investigation on 2212 phase and the other mixed oxides, separately analysed by DTA, clarified that only the thermal behaviour of the former was modified by the presence of silver. An explanation based on oxygen unbalancing in the material possibly induced, at the annealing temperature, by the presence of silver, is suggested: as a consequence of the very high solubility of oxygen in silver at high temperature, O2 would be «pumped off» the superconducting 2212 phase, with the result of lowering its melting point.
PACS85.25.Ly Superconducting magnets and magnetic levitation devices superconducting cables and conductors
PACS74.70.Vy Superconducting perovskites and related structures
PACS01.30.Cc Conference proceedings
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- P. Metra and S. Ashworth: Power Technology International (Sterling Pubblication Ltd., 1994), p. 49.Google Scholar
- G. Szabo Miszenti, L. Gherardi, P. Caracino and P. Metra: Applied Superconductivity, edited by H. C. Freyhardt, Vol. 2 (DGM Informations GmbH, Oberursel, 1993), pp. 1609–1612.Google Scholar
- R. B. Poeppel, et al.: Processing and microstructural development of Ag-clad Bi−SrCSCuO tapes, in Proceedings of the V U.S/ Japan Workshop on High T c Superconductors, November 9–13, 1992, Tsukuba, Japan, p. 63.Google Scholar
- P. V. P. S. S. Sastry: II Conference on Solid State Chemistry and Superconductivity (UMIST), Manchester, September 20–22, 1993.Google Scholar
- J. Bock and E. Preisler: High Temperature Superconductors, edited by H. C. Freyhardted et al. Vol. 1 (DGM Information GmbH, Oberursel, 1991), p. 215.Google Scholar