Efficient Diffusion Bonding between BSCCO Superconducting Multifilamentary Tapes

To improve the joining efficiency of Bi-Sr-Ca-Cu-O ( BSCCO) superconducting tapes, a new diffusion bonding technology with a direct uniaxial pressing at high temperature was developed to join 61-filament tapes. It was observed that bonding parameters such as bonding pressure and holding time, significantly affected the critical current ratio (CCRo). A peak CCRo value of 89 % for the lap-joined tapes was achieved at 3 MPa for 2 h when bonding temperature was 800 °C. Compared with the conventional diffusion bonding technology, this new technology remarkably shortened the fabrication period and improved the superconductivity of the joints. The bonding interface and microstructures of the joints were evaluated and correlated to the CCRo. An uniaxial pressing at high temperature was beneficial to interface bonding, and there was an optimal pressure value for the CCRo.

AC Loss Properties in Bi2223 Multifilamentary Tapes with Enhanced Transverse Resistivity by Introducing Oxide Barriers

Bi2223 multifilamentary tapes with enhanced transverse resistivity by introducing Ca2CuO3 and SrZrO3 as interfilamentary barriers were prepared and their AC loss properties were examined under AC external magnetic field. To improve the deformation properties of these oxide powders, 20-30wt% Bi2212 powders were mixed with them. The mixed oxide powders were introduced among the twisted Bi2223 filaments by using dip-coating method. AC loss properties under AC parallel or perpendicular field were measured and compared with the results for the tape without barriers. The loss measurements were carried out by changing both the amplitude and the frequency of external field. Based on the experimental results, the effect of barrier introduction on the loss reductions was discussed.