Partial Melting in Filamentary NSG123 Superconductors Under Various Oxygen Atmospheres

Precursor filaments with starting composition (Nd_0.33,Sm_0.33,Gd_0.33) : Ba : Cu = 1.18 : 2.12 : 3.09 were prepared by a solution spinning method. Samples were partially melted at temperature range of 1020-1090degC in flowing 0.1%O₂ + Ar, 1%O₂ + Ar and 20%O₂ + Ar and then oxygenated in pure 100%C>2 gas. The T_c value decreased from 91.3 K to 88.8 K with increasing oxygen concentration in atmosphere gas. A transport J_c value higher than 104 A/cm at 77 K and 0 T was showed over a wide temperature range of 1030-1080degC in 0.1%O₂ + Ar and 1040-1090degC in 1%02 + Ar. Especially, the 0.1%O₂ + Ar sample partially melted at 1050degC and the 1%02 + Ar sample at 1060degC exhibited the highest J_c value of 2.7 x 104 A/cm² and 2.5 x 104 A/cm², respectively. The transport J_c value of the sample melted in flowing 0.1%O² + Ar was maintained higher than 2.4 x 10³ A/cm² at 77 K in applied magnetic fields up to 17 T. On the other hand, the maximum J_c value at 77 K and 0 T for the sample treated in 20%O₂ + Ar melted at 1080degC showed 5.4 X 103 A/cm² at most, and the superconductivity was disappeared at magnetic field of 7 T.