Enhancement of J(c) by 211 particles in ternary (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy melt-processed superconductors

(Nd0.33Eu0.33Gd0.33)(2)BaCuO5 (NEG-211) particles are added to ternary (Nd0 .33Eu0.33Gd0.33)Ba2Cu3Oy (NEG) bulk, melt-processed superconductors. By mea ns of transmission electron and polarized light microscopy, we found that t wo types of 211 particles are formed; large NEG-211 and submicron-sized par ticles containing mostly Gd in the rare earth site are formed which can act as effective flux pinning sites. The critical current density at zero fiel d increases monotonously as a function of the NEG-211 concentration, but th e secondary peak vanishes above 40 mol % 211 addition. As a result, a criti cal current density of 68 000 A cm(-2) at 77 K and 2.5 T applied field is a chieved with at 40 mol % 211 additions. (C) 2000 American Institute of Phys ics. [S0003-6951(00)04301-1].