Enhanced flux pinning properties in Bi-2212 high temperature superconductors with nano-sized precipitates

Al doped Bi-2212 superconducting bulks with large amounts of nano-sized precipitates have been fabricated by spark plasma sintering (SPS) and subsequent annealing under oxygen. Due to the interferences of Al doping, alkali earth cuprates (AEC, (Ca, Sr)xCuyOz) have precipitated and formed the nanoparticles distributed uniformly in the Bi-2212 matrix. The influences of these precipitates and Al doping on the microstructures, transport and superconducting properties, especially the flux pinning properties have been systematically investigated. The point flux pinning mechanism has been obviously enhanced with the appearance of precipitates. The effects of these nano-sized precipitates on the enhancements of flux pinning properties in Bi-2212 bulks under magnetic field have been proved by both the increased activation energy and the improved flux pinning force.