Effect of Pt Addition on Microstructure and Superconducting Properties for Filamentary (Nd,Sm,Gd)-Ba-Cu-O Superconductors

The filamentary (Nd0.33Sm0.33Gd0.33)(1.18)-Ba2.12Cu3.09Oy (NSG123) superconductors chemically doped with nominal Pt concentrations from 0 to 0.5 at% were fabricated by a solution spinning method. We investigated effects of the amount of Pt addition and cooling rate from partial melting temperature of 1050 degrees C during OCMG processing on superconducting properties and microstructure of filamentary samples. Pure NSG123 filaments cooled at 20 degrees C/h-50 degrees C/h showed the J(c) vale higher than 2.0 x 10(4) A/cm(2) at 77 K and 0 T. Although the sample treated at fast cooling rate of 60 degrees C/h exhibited the J(c) value of about 3.0 x 10(3) A/cm(2) at most, the NSG123 doped with 0.05 at% Pt cooled at 60 degrees C/h showed high J(c) value of 2.0 x 10(4) A/cm(2) at 77 K and 0 T. The field dependence of transport J(c) value was also investigated at 77 K for samples cooled at 60 degrees C/h. The J(c) value of 0.8 x 10(4) A/cm(2) was maintained up to magnetic field of 5 T for the 0.05 at% Pt doped sample. The size of (Nd, Sm, Gd)(2)BaCuO5 particles in NSG123 matrix was reduced from about 3 to 0.5 mu m with increasing Pt concentration from 0 to 0.5 at%. In addition, the connectivity in microstructure was improved with increasing Pt concentration. It was found that both J(c)-B properties and the microstructure for the sample treated at fast cooling were effectively improved by Pt doping.