Abstract
Bi2Sr2CaCu2Ox (Bi-2212) single-filamentary and multi-filamentary wires were fabricated by powder in tube (PIT) process and sintered under the over pressure heat treatment (OPHT) process. The thermal behavior, microstructure, phase composition, and superconducting properties of wires were characterized by thermal gravimetric analysis, scanning electron microscopy, X-ray diffraction, and four-probe method, respectively. The inclined grain microstructure and randomly orientated grains were observed directly in single-filamentary wire. The performance of Bi-2212 mono-filamentary wire was extremely lowered than that of multi-filamentary wire, which could be ascribed to poor microstructure and texture. The inhomogeneous melting behavior of single-filamentary wire was responsible to the poor microstructure and the randomly orientated grains. Furthermore, high engineering critical current density (Je) of 1224 A/mm2 and critical current density (Jc) of 4896 A/mm2 were obtained in 666-filament Bi-2212 wire with good grain orientation and microstructure. It revealed that the grain orientation might be a major current-limiting factor. Therefore, the multi-filamentary architecture with good texture was critical for the improvement of performance Bi-2212 wires during OPHT process.
