We have prepared (Nd0.33Eu0.33Gd0.33)Ba2Cu 3Oy ('NEG') superconductors by means of melt-processing under a partial oxygen pressure of 0.1%. In these samples, we achieved a large critical current density, Jc, of 6.8 × 104 A/cm2 at T = 77 K and in an applied magnetic field, Ha = 2.5 T. Furthermore, the irreversibility field, Hirr, exceeds 7 T at 77 K for fields applied parallel to the c-axis of the sample. As additional pinning sites, we introduced up to 40 mol% (Nd,Eu,Gd)2BaCuO5 (NEG-211) particles plus Pt in analogy to YBa2Cu3Oy (YBCO) melt-processed superconductors. Microstructural observations clarified that the Pt addition was effective in reducing the size of NEG-211 second-phase particles, which led to a dramatic increase in Jc as compared to melt-processed YBa2Cu3Oy and NdBa2Cu3Oy (NdBCO). A pronounced secondary peak effect was observed in all magnetization curves obtained at 77 K, however, there is a considerable change in the shape of the magnetization loops as a function of NEG-211 content, which demonstrates the pinning provided by the NEG-211 particles in addition to the δTc-pinning caused by fluctuation in the transition temperature, Tc, like in ordinary NdBa2Cu3Oy superconductors.
ASJC Scopus subject areas