Properties of Pb-Stabilized Bi-Oxide Superconductors

Abstract

The initial magnetization curve of B_1.5Pb_0.5Sr₂Ca₂Cu₃O_x superconductor with the T_c of 105 K was measured. The lower critical field, H_cl, was 6 Oe at 77 K, which was much smaller than that of YBa₂Cu₃O_7-y (52 Oe). The volume fraction of the 105 K phase was estimated to be about 80 %.

Grinding the powder in an attrition mill resulted in a slight increase in Tc, although the densification of the sintered body did not ocurr. By hot-pressing at a pressure of 39 MPa at 800 °C in vacuum of 5 x 10^-5 Torr for 2 h, the bulk density of the hot-pressed sample reached 6.21 g/cm³ , which was higher than 95 % of the theoretical density, and the T_c was 72 K. The grains were oriented with the c-axis along the pressing axis. After annealing at 835 °C in air for 40 h, the T_c was improved to be 108 K and the critical current density at 77 K was found to be 731 A/cm².