Preparation of grain-aligned bulk (2223) B(Pb)SCCO superconductor with improved J_c by hot-texturing

Bulk Bi₁₈₄Pb_0.34Sr_1.81Ca_2.03Cu _3.06oO_x superconductors with relative density in the range 88-90% were prepared by high cold pressing + pressureless sintering and subsequently hot forged to increase the extent of grain orientation. It has been found that the final density of the samples exceeds 95% and the orientation factor increases up to ≈ 80%. The introduction of a short high-temperature treatment (T = 885 °C) promotes the extrusion of secondary phases, leaving in the sample only the (2223) as a superconducting phase and islands of Ca-Sr-Cu-0 and CuO. The annealing at 400 °C in oxygen was found essential to recover the oxygen content, lost during densification and texturing treatments, and to increase the T& value up to 100-105 K. The employment of pressureless sintered samples (PLS) together with the step at 885 °C implies the release of the disorder near sub-grain boundaries usually found in hot-pressed samples. As a consequence of these features, textured PLS samples show a Jc value at 77 K one order of magnitude higher with respect to the simple PLS sample. The use of sol-gel powder impi'oves the densification and texturing of the superconductor even for shorter treatment times. Since Jc of this sample is ≃ 700 A/cm², the addition to the treatment of the step at 885 °C is highly promising in the view to reach a further increase of critical current density.