Requirements to achieve high in-field critical current density at 30 K in heavily-doped (Gd,Y)Ba₂Cu₃Oxsuperconductor tapes

Critical current densities ( J c ) above 15 MA cm −2 have been achieved at 30 K, 2.5 T ( B || c ) in (Gd,Y)–Ba–Cu–O tapes with 20–25 mol.% Zr addition. The optimal compositions of Gd + Y, Ba + Zr and Cu to achieve lift factor in critical current above 6 at 30 K, 2.5 T ( B || c ) have been determined by development of a composition map of the performance of heavily-doped (Gd,Y)–Ba–Cu–O tapes. An inverse relationship is found between the critical current density at 77 K, 0 T and the lift factor in critical current at 30 K, 2.5 T ( B || c ). It is discovered that a J c of 15 MA cm −2 at 30 K, 2.5 T ( B || c ) is achievable only in tapes with a J c between 2.5 and 3.8 MA cm −2 at 77 K, 0 T.