Enhancement of critical current density in (Nd, Eu, Gd)-Ba-Cu-O superconductors

We have achieved a large critical current density (J(c)) of 70 000 A/cm(2) at 77 K in 2.3 T and a large irreversibility field exceeding 7 T at 77 K fo r the fields parallel to the c axis in (Nd, Eu, Gd)-Ba-Cu-O in which 40 mol % (Nd, Eu, Gd)(2)BaCuO5 (NEG211) second phase particles are finely disperse d in the (Nd, Eu, Gd)Ba2Cu3Oy matrix and prepared by the melt process under oxygen partial pressure of 0.1%. Microstructural observations clarified th at Pt addition was effective in reducing the size of NEG211 second phase pa rticles, which led to a dramatic increase in J(c). A clear secondary peak e ffect was observed in the magnetization curve, suggesting that field-induce d pinning is active in parallel with the pinning by NEG211 particles. (C) 1 999 Elsevier Science S.A. All rights reserved.