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

Abstract

Textured rods of Bi-2212 based materials with nominal compositionsBi2Sr2CaCu2O8+δ,Bi2Sr2CaCu2O8+δ+1 wt% Ag,Bi1.6Pb0.4Sr2CaCu2O8+δ,and Bi1.6Pb0.4Sr2CaCu2O8+δ+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 werecharacterized. Pb doping results in the decrease of the transport critical current density,Jc,t (from 4.4 × 107 to 6 × 106 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 thecritical current density and mechanical strength. In this regard we have observed an increase ofJc,t (65 K) from4.4 × 107 for Bi-2212 to7.2 × 107 A m−2 for Bi-2212/Agand from 6 × 106 forBi(Pb)-2212 to 8 × 106 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 isobserved, which would explain the improved superconducting properties of these samples.