Effects of cold isostatic pressing on and high pulse current characterization in long bar Bi(Pb)SrCaCuO ceramics

Detailed measurements on the transport critical current dependence resulting from cold isostatic pressing are presented. Long bars (diameter 5 mm, length 120 mm) of ceramics were formed by the application of an isostatic pressure between 0.3 and 1 GPa followed by sintering at during 90 h. The critical current at 77 K rapidly increases from 24 A to 57 A and 95 A at 65 K for the samples pressed to 0.3 and 1 GPa, respectively. The pressure induces better connection between grains and the material density increases. The homogeneity of the bars has been characterized by measuring the critical current and normal state resistivity along the samples. Also, these bars have been submitted to high pulse current during 1.25 ms to avoid problems from ohmic heating at the electrical contacts. We observed two regimes (superconducting recovery and resistive) following the pulse current amplitude. These bars are interesting candidates for technological applications at liquid nitrogen temperature (77 K).