Temperature Dependence of the Intergranular Critical Current Density in Uniaxially Pressed Bi1.65Pb0.35Sr2Ca2Cu3O10+δ Samples

We have studied the normal and superconducting transport properties of Bi1.65Pb0.35Sr2Ca2Cu3O10+δ (Bi-2223) ceramic samples. Four samples, from the same batch, were prepared by the solid-state reaction method and pressed uniaxially at different compacting pressures, ranging from 90 to 250 MPa before the last heat treatment. From the temperature dependence of the electrical resistivity, combined with current conduction models for cuprates, we were able to separate contributions arising from both the grain misalignment and microstructural defects. The behavior of the critical current density as a function of temperature at zero applied magnetic field, J c (T), was fitted to the relationship J c (T)∝(1−T/T c ) n , with n≈ 2 in all samples. We have also investigated the behavior of the product J c ρ sr , where ρ sr is the specific resistance of the grain-boundary. The results were interpreted by considering the relation between these parameters and the grain-boundary angle, θ, with increasing the uniaxial compacting pressure. We have found that the above type of mechanical deformation improves the alignment of the grains. Consequently the samples exhibit an enhance in the intergranular properties, resulting in a decrease of the specific resistance of the grain-boundary and an increase in the critical current density.