ISOTHERMAL MELT PROCESSING OF BI2SR2CACU2O-GAMMA ROUND WIRE

Isothermal melt processing (IMP) has been used to process oxide-powder-in-tube (OPIT) Bi2Sr2CaCu2Oy (Bi-2212) round wire with high critical current densities. Isothermal melt processing is a process in which the melting and solidification steps are carried out at the same temperature by melting in an inert atmosphere and solidifying in a high oxygen partial pressure. For each particular oxidizing atmosphere used during IMP, the highest critical currents were found in wires processed in the temperature range between 790 degrees C to 820 degrees C. The highest critical current densities obtained in 1.0, 0.75, and 0.5 mm diameter wires at 4 K and self-field were 4.3 X 10(4), 6.0 X 10(4), and 7.9 x 10(4) A/cm(2), respectively. Transport measurements on a 0.75 mm wire revealed that critical current densities in excess of 3 X 10(4) A/cm(2) could be achieved at 4 K in applied magnetic fields of 9 T. Anisotropy measurements and SEM analysis were used to examine the radial alignment of the Bi-2212 grain colonies within the wires.