Influence of Pores on the Homogeneity, Microstructure and Current-Carrying Performance of Bi-2212 Superconducting Wires

Multi-filament Bi<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>Sr<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>CaCu<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8+δ</sub> (Bi-2212) wires were prepared using the powder-in-tube method. The wires were subjected to different heat treatment conditions, including atmospheric opening and sealing, as well as high-pressure opening and sealing. Optical microscopy (OM), scanning electron microscopy (SEM) and current-carrying performance tests were conducted on the wires. By comparing the microstructure, phase composition, and current-carrying performance of the four samples, it was observed that the influence of internal gases on the filament structure and performance was significant. The Bi-2212 wires treated under 50 atm pressure exhibited minimal diameter fluctuations, no leakage, and dense filament structures, resulting in the highest current-carrying performance. Therefore, one of the key factors in improving the overall performance of Bi-2212 wires is to suppress internal pressure in long-length wires and reduce the presence of bubbles in the filaments.