Direct jointing of Ba–Sr–Ca–Cu–O superconducting glass-ceramics by welding

Superconducting glass-ceramics in the Bi–Sr–Ca–Cu–O (BSCCO) system were found to be successfully joined together by welding with an LNG-O2 flame. Two edge portions of the glass- ceramics to be joined were set in close contact to each other and melted by the high-temperature flame. After the welding, the joined portion was annealed with a soft flame, so that no crack formed in the product. The directly joined product was converted into a superconductor with Tc≂90 K by a postheating at ∼830 °C. Its critical current density Jc, was almost the same as the of the original glass-ceramic. This technique is very important for fabrication of large-sized superconducting apparatus such as current leads or magnetic shields.