Transport and magnetic properties of bismuth metaloxide ceramic (Bi–Pb)–Sr–Ca–Cu–O

Transport properties of single-phase metaloxide bismuth ceramics with Tc = 110 K and jc = 20–340 A/cm2 are studied. It is found that cavities surrounded by low-porosity regions are formed in the samples during their synthesis and annealing. These formations produce a step in the temperature dependence of the diamagnetic response, the position of this step depending strongly on low magnetic field of order of 1 Oe. It is shown that the critical current density is mainly determined by the binding force between intergranular contacts inside the cavities. The temperature dependence of the critical current for samples prepared under different thermal treatments is studied.

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