MELT PROCESSING FOR OBTAINING NDBA2CU3OY SUPERCONDUCTORS WITH HIGH-TC AND LARGE JC

A reduced oxygen atmosphere during melt processing turned out to be critical for the fabrication of NdBa2Cu3Oy (Nd123) superconductors possessing high superconducting transition temperature (T(c)) with a sharp transition and large critical current density (J(c)) at 77 K. In a dc magnetization measurement, Nd123 superconductors melt processed in flowing a mixture gas Of 1% 02 in Ar exhibited the T(c) of about 95 K and the transition width of 1.5 K with the applied field of 10 Oe. A four-probe measurement showed the zero resistive transition T(c) (R=0) of about 95 K. An anomalous peak effect in the magnetization hysteresis (M-H) loops was commonly observed and lead to large magnetic J(c) of 2 X 10(4) A/CM2 at 77 K and 2 T for the applied field H parallel to the c axis of a sample (H parallel-to c). This achievement is attributable to a preferential formation of high T(c) phase (x<0.l) among the Nd1+xBa2-xCU3Oy solid solutions in a reduced oxygen atmosphere.