MICROSTRUCTURAL CHARACTERISATION OF Bi2212 WIRE PRODUCED BY MELT PROCESSING BY EBSD

摘要

Bi2212 is the only high temperature superconductor that can be produced in the form of round wire, and is therefore studied for use in very high field magnets. Bi2212 superconducting wires are made of hundreds of filaments in an Ag matrix using the powder in tube (PIT) process. In this PIT technique, pure Bi2212 powder particles are inserted in the Ag matrix and then the multifilament wire is drawn down to a diameter of about 1 mm. The required superconducting properties are obtained when the wire is heated up to approximately 890 ℃, in order to melt the Bi-2212 particles, and then cooled down slowly. Two wires in the "as received" and "heat treated" states were characterized in the SEM by EDS in order to point out any difference in composition of the Bi2212 phase before and after heat treated induced melting and quantify 2nd phase elements like Bi-2201. EBSD analyses were performed in both wires in order to identify the different phases present, to determine grain size distribution and to detect any texture arising from the fabrication process. The first EBSD analyses carried out confirm the presence of texture and allow the sample preparation process to be further refined in order to get higher indexing rates.