The crystallization in the welding region for Y–Ba–Cu–O bulk superconductors

Abstract

We have studied the effect of crystal orientation on the microstructure at joining regions between two blocks of Y–Ba–Cu–O bulk superconductors using Er–Ba–Cu–O sintering plate. The (1 0 0)/(1 0 0) joint suffered from the segregation of second phase and residual liquid phase, which reduced the critical current. In contrast, the (1 1 0)/(1 1 0) joint was free from the segregation of second phase and residual liquid phase. Microstructural observation showed that many triangular crystals were formed from the back melt zone in the (1 1 0)/(1 1 0) joint. On the other hand, the growth front was parallel to the (1 0 0) surfaces in the (1 0 0)/(1 0 0) joint. Such a difference in the growth morphology was responsible for the difference in the superconducting properties of the joints.