Transport Properties of Bi2212 Round Wires Grown in High Magnetic Fields

The transport critical current density J
_c
is one of the most important properties for practical applications of high-T
_c
superconductors. The J
_c
properties of high-T
_c
superconductors are highly dependent on the microstructural texturing of the superconducting phase. In order to improve the grain alignment of the superconducting phase melt-processing in high magnetic fields is a very effective method based on the anisotropy of magnetic susceptibility. For Bi-based superconducting bulks and tapes, there have been many studies using the in-field melt-processing and large J
_c
enhancements due to the texture improvement are observed. In this study, we employed melt-processing in high magnetic fields for the Ag/Bi2212 round wires, which are much superior to thin tapes in fabricating superconducting magnets. Since the J
_c
properties of Ag/Bi2212 are very sensitive to the maximum temperature of the heat treatment, we performed the melt-processing under various maximum processing temperatures. During the heat treatment, a magnetic field of 0 T or 5 T was applied using a cryocooled superconducting magnet. For the wires heat-treated under a magnetic field, small increase of the J
_c
values were observed. From the results of the detailed analysis of the E - J properties, we found that there are possible microstructural changes due to the in-field process. It is suggested that the in-field heat-treatment is very effective for not only J
_c
enhancement but also the n-value improvement for Bi2212 conductors.