FLUX-PINNING IN MELT-GROWN NDBA2CU3OY AND SMBA2CU3OY SUPERCONDUCTORS

REBa2Cu3Oy superconductors with rare earth (RE) ions with large radii (RE: La, Nd, Sm) exhibit relatively low T(c) due to the presence of RE -Ba solid solution. We have found that this solid solution can be supp ressed if these superconductors are melt processed in a reduced oxygen atmosphere. We have also found that critical current densities of the se superconductors are higher than those of melt processed YBa2Cu3Oy w ith fine Y2BaCuO5 inclusions in a high field region. The irreversibili ty line was also shifted toward the higher H-T region. We believe that flux pinning in these superconductors is ascribable to a finely distr ibuted RE(Ba1-x, REx)2Cu3Oy phase in a good superconductive matrix.