Synthesis and critical current density promotion for Nb-doped 2212-BPSCCO HTc-superconducting materials

Although BPSCCO superconducting regime has very low stability under high oxygen pressures as reported in the literature, we managed to synthesize relatively pure 2212-BPSCCO and their Nb-doped samples having general formula Bi_1−xNb_xPbSr₂CaCu₂O₈, where x = 0.1, 0.2, 0.4 and 0.6 mole, respectively, at moderate oxygen pressure (∼30 bar). The superconducting measurements proved that the best recorded T_c ∼ 69 K was for the undoped 2212-BPSCCO, while the lowest T_c ∼ 58 K was recorded for the maximum doped sample x = 0.6 mole indicating that superconductive transition temperatures T_cs decrease regularly with increasing Nb-dopant concentration from x = 0.1 to 0.6, respectively. The lattice parameter c exhibited a slight length compression as Nb-dopant ratio increases from 0.1 to 0.6 mole, respectively. From SE-microscopic analysis, the average grain size was estimated and found in between 0.44 and 1.6 μm which is considered relatively high to that reported in the literature. The measured J_c’s values were found to be enhanced remarkably as Nb-dopant concentration increases.