The filamentary (Nd0.33Sm0.33Gd0.33) 1.18-Ba2.13Cu3.09Oy (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 °C during OCMG processing on superconducting properties and microstructure of filamentary samples. Pure NSG123 filaments cooled at 20°C/h-50 °C/h showed the Jc vale higher than 2.0 × 104 A/cm2 at 77 K and 0 T. Although the sample treated at fast cooling rate of 60 °C/h exhibited the Jc value of about 3.0 × 103 A/cm2 at most, the NSG123 doped with 0.05 at% Pt cooled at 60 °C/h showed high Jc value of 2.0 × 10 4 A/cm2 at 77 K and 0 T. The field dependence of transport Jc value was also investigated at 77 K for samples cooled at 60 °C/h. The Jc value of 0.8 x 10 4A/cm2 was maintained up to magnetic field of 5 T for the 0.05 at% Pt doped sample. The size of (Nd, Sm, Gd)4BaCu05 particles in NSG123 matrix was reduced from about 3 to 0.5 μim 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 Jc-B properties and the microstructure for the sample treated at fast cooling were effectively improved by Pt doping.
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