Melt processing and high performance of binary (Nd, Sm)-Ba-Cu-O superconductors

Binary (Nd, Sm)-Ba-Cu-O superconductors with T_c of 96 K and a high irreversibility field up to 8 T have been fabricated in air via a newly developed technique. The initial composition was controlled by using binary (Nd, Sm)₂BaO₄ as an addition. In comparison with both NdBaCuO and YBaCuO melt-textured superconductors, the present composition showed a remarkable enhancement of critical current densities in an intermediate field regime (1-3 T). Microstructural observations and compositional analysis showed that the distributions of Nd and Sm in the (Nd, Sm)-123 matrix were homogeneous while the atomic ratio between these two rare earth elements was inconsistent with that in the nominal composition. These new characteristics were thought to cohere with the different solubilities between Nd and Sm in the liquid phase. Finally, trapped magnetic field mapping showed a single-domain shape of the trapped field, which indicated the growth of a single grain in the samples.