Synergism effect of Pb doping and microstructure optimization on the superconducting properties of Bi-2212 ceramics

Bi-2212 is one of the most competitive high-temperature superconducting materials for the fabrication of high field magnet, but its superconducting transmission mechanism is not clear yet. To further investigate the effects of both weak connections and magnetic flux pinning on the current transition process, polycrystalline bulks of Bi₂Sr₂CaCuO_8+δ (Bi-2212) with different chemical compositions and microstructures were prepared with the introduction of Pb doping and spark plasma sintering process. Both XRD and SEM indicated that nearly single phase Bi-2212 bulks with high (00l) texture could be achieved with spark plasma sintering. The texture degree of Bi-2212 bulks was positively correlated with T_cj and T_p, and negatively related to ΔT, indicating that the increase of texture degree could improve the intergranular connectivity. Besides, it was found that grain size had a stronger impact on the self-field J_c than texture degree by analyzing the relationship between full-width at half maximum of (008) and self-field J_c. In addition, by analyzing the flux pinning properties, it indicated that Pb doping could enhance the point pinning property, while the improving textural structure could enhance the surface pinning property.