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ST386 - Reduction of Internal Porosity in Bi2Sr2CaCu2Ox Round Wires with Overpressure Processing

Reduction of Internal Porosity in Bi2Sr2CaCu2Ox Round Wires with Overpressure Processing
 
 M. R. Matras, J. Jiang, E. Hellstrom, N. Craig, T. Kametani,
U. Trociewitz, P. Chen, D. Larbalestier
 
Applied Superconductivity Center, National High Magnetic Field Laboratory, 
Florida State University, Tallahassee, FL-32310, USA
 
Abstract — Bi2Sr2CaCu2Ox is the only cuprate superconductor that can be made into multi-filament round wires. Bi-2212 wires are made using the powder in tube process. The main obstacle to high engineering critical current density (JE) is the low packing density (25%) of the 2212 powder within the filament which leads to gas-filled filament size bubbles acting like barrier against current transport. We reduced this internal porosity by applying an external over-pressure (OP) during the heat treatment to compensate the internal gas expansion and densify the filaments up to 98 % at an OP of 50 atm. The densification occurs at 821°C within 10 min. With an OP of 100 atm, JE increased to 917 A/mm2 at 4.2 K, 5 T, compared to a JE around 200 A/mm2 at 4.2 K, 5 T when long samples are heat treated in 1 atm. Bi-2212 is now a good candidate for magnet application above 20 T.
 
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), October 2014.
Reference No. ST386; Category 5. ASC 2014 presentation and extended abstract 4MPo1D-07;
2nd Prize in Best Student Paper Contest, Materials. Not submitted to IEEE Trans. Appl. Supercond..