Formation of Porosity and Its Effects on the Uniformity of Jc in Bi-2212/Ag Tapes
The uniformity of Bi-2212 tape has been studied by using multiple potential taps, Magneto-Optical (MO) imaging and microstructure observation. The major defect, porosity, has been identified in the melt processed tapes. The current sharing into the Ag sheath due to the existence of defects causes a linear section on the V-I curve. The cause of the porosity formation is believed to be due to the gas release, such as CO2, when 2212 reforms from the liquid phase. Some other factors which can influence the porosity formation, such as packing density, packing atmosphere and pre-heat treatment of billets have also been examined.
KeywordsPacking Density Bubble Formation Precursor Powder Porosity Formation Oxide Core
Unable to display preview. Download preview PDF.
- 1.W. Zhang, E. E. Hellstrom, M. Polak and D. C. Larbalestier, “Important issues for melt processing long lengths of BSCCO-2212 tapes”, Advances in Cryogenic Engineering-Materials, 42: 787 (1995).Google Scholar
- 2.M. Polak, W. Zhang, A. Polyanskii, A. E. Pashitski, E. E. Hellstrom and D. C. larbalestier, “The effects of the maximum processing temperature on the microstructure and electrical properties of melt processed Ag-sheathed Bi2Sr2CaCu20x tape”, IEEE Tran. on Appl. Supercond. 7: 1537 (1997).Google Scholar
- 4.M. Polak, W. Zhang, J. Parrell, X. Y. Cai, A. Polyanskii, E. E. Hellstrom, D. C. Larbalestier, “Transfer lengths and the origin of linear components in the voltage-current curves of Ag-sheathed BSCCO composites, Accepted for publication in Supercond. Sci. Technol., 1997.Google Scholar
- 5.W. Zhang and E. E. Hellstrom, “The influence of carbon content on phase formations in BSCCO-2212 system”, 234: 137 (1994).Google Scholar