Flux Pinning in Melt-Grown NdBa₂Cu₃O_y and SmBa₂Cu₃O_y Superconductors

TLDR

REBa₂Cu₃O_y superconductors with large rare‑earth ions such as La, Nd, and Sm exhibit relatively low Tc because of a RE–Ba solid solution. Melt processing in a reduced oxygen atmosphere suppresses this solid solution, raising critical current densities above those of melt‑processed YBa₂Cu₃O_y with fine Y₂BaCuO₅ inclusions, shifting the irreversibility line to higher H‑T, and attributing enhanced flux pinning to a finely distributed RE(Ba₁₋ₓ,REₓ)₂Cu₃O_y phase.

Abstract

REBa 2 Cu 3 O y 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 suppressed if these superconductors are melt processed in a reduced oxygen atmosphere. We have also found that critical current densities of these superconductors are higher than those of melt processed YBa 2 Cu 3 O y with fine Y 2 BaCuO 5 inclusions in a high field region. The irreversibility line was also shifted toward the higher H-T region. We believe that flux pinning in these superconductors is ascribable to a finely distributed RE(Ba 1- x , RE x ) 2 Cu 3 O y phase in a good superconductive matrix.