Flux pinning by Al-based nano particles embedded in polycrystalline (Bi,Pb)-2223 superconductors

The effect of nano-size Al2O3 (40 nm) addition on the microstructure and pinning properties of polycrystalline (Bi,Pb)-2223 was analyzed. The Al2O3 content in samples varied from 0.0 to 1.0 wt.% of the total mass of the sample. Phase analysis by X-rays diffraction (XRD), granular structure examination by scanning electron microscopy (SEM), microstructure investigation by transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS), critical current density dependence on applied magnetic field Jc(B) and electrical resistivity as a function of temperature ρ(T) were carried out to evaluate the relative performance of samples. Using the right amount of Al2O3 addition (0.2 wt.%), the flux pinning ability of (Bi,Pb)-2223 has been enhanced. The pinning force analysis and microstructure observations indicated that the sharp interface between nanometer scale Al-rich particles and the (Bi,Pb)-2223 phase provided effective normal surface pinning centers.