Microstructural properties of Bi_(1.65)Pb_(0.35)Sr_2Ca_2Cu_3O_(10+δ) and Bi_(1.65)Pb_(0.35)Sr_2CaCu_2O_(8+δ) ceramic samples through transport measurements: a comparative study

摘要

We have studied in detail the dependence of the electrical resistivity as a function of temperature of Bi_(1.65)Pb_(0.35)Sr_2Ca_2Cu_3O_(10+δ) ((Bi,Pb)-2223) and Bi_(1.65)Pb_(0.35)Sr_2CaCu_2O_(8+δ) ((Bi,Pb)-2212) ceramic samples. Both types of samples were obtained by a solid-state reaction method and pressed uniaxially at different compacting pressures ranging from 90 to 600 MPa before the last heat treatment. From electrical resistivity measurements as a function of temperature, we were able to separate contributions arising from both the grains' misalignment and microstructural defects, by using a current-conduction model. The results suggest that in both compounds the texture degree and the connectivity between grains are improved with increasing compacting pressures. It was found that in the (Bi,Pb)-2223 samples, even in those obtained at low compacting pressures, the grains exhibit a preferential orientation. A similar effect, but less pronounced, was observed in the (Bi,Pb)-2212 samples. In both cases, the behavior is different to the one reported in YBCO ceramic samples, in which the grains exhibit random orientation.