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

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.