The influence of Pb and Ag doping on the Jc(H, T) dependence and the mechanical properties of Bi-2212 textured rods

Textured rods of Bi-2212 based materials with nominal compositions Bi2Sr2CaCu2O8+delta, Bi2Sr2CaCu2O8+delta + 1 wt% Ag, Bi1.6Pb0.4Sr2CaCu2O8+delta, and Bi1.6Pb0.4Sr2CaCu2O8+delta + 3 wt% Ag were fabricated using a laser floating zone (LFZ) melting method. The electrical, magnetic, and mechanical properties of the resulting rods after annealing were characterized. Pb doping results in the decrease of the transport critical current density, J(c,t) (from 4.4 x 10(7) to 6 x 10(6) A m(-2) at 65 K and self-field) as well as in the worsening of the mechanical properties, by about 35% compared to the undoped samples. In contrast, Ag doping results in the improvement of both the critical current density and mechanical strength. In this regard we have observed an increase of J(c,t) (65 K) from 4.4 x 10(7) for Bi-2212 to 7.2 x 10(7) A m(-2) for Bi-2212/Ag and from 6 x 10(6) for Bi(Pb)-2212 to 8 x 10(6) A m(-2) for Bi(Pb)-2212/Ag. These described effects are related to the microstructural observations, since Pb doping dramatically reduces the texture while Ag doping improves it. Moreover, for samples with Ag addition, an intergrowth of Bi-2223 inside the Bi-2212 grains is observed, which would explain the improved superconducting properties of these samples.