Pinning mechanism in (Bi,Pb)-2223 polycrystalline samples prepared with Al2O3 nano-particles

Nano-size Al2O3 (40 nm) addition effect on the polycrystalline (Bi,Pb)-2223 system properties was studied by XRD, SEM, TEM/EDX and electrical measurements. Samples with 0.0 and 0.2.wt% Al2O3 are synthesized in air by solid state reaction. Nanometer Al2O3 particles were added during the final sintering cycle of a multi-step preparation process. Analysis of magnetoresistivity has shown that the dissipation phenomenon follows the thermally activated flux creep model. Both onset temperature of dissipation, effective activation energy U, critical current density Jc behaviour in applied magnetic field and volume pinning force density Fp are enhanced by addition of 0.2wt.% Al2O3. Enhancement of the vortices flux pinning in doped samples is mainly originated from the surface normal-like pinning centers