Study on brazing of high temperature superconducting YBCO bulks with YBCO-based and YbBCO-based filler

The brazing of high-temperature superconducting YBCO bulks was performed using YBCO-based and YbBCO-based brazing filler. The levitation force of the superconducting base bulks and the brazed joints after oxygenation was measured to evaluate the superconducting properties. The microstructure of YBCO base bulks and the brazed joints was also analyzed. The results indicated that the density of levitation force of the joints reached up to 79.4% of the original YBCO bulks under the technological conditions in this study. It was proved that brazing technology can be used to achieve the dimension-increment of superconducting YBCO bulks. Microstructure analysis shows that aggregation of Y211 or (Y, Yb) 211 appeared in the brazing seam and has negative effects on superconductivity of the joints.