Enhancement of critical current density of (Pb,Sn)-doped Bi-2212 superconductors at high temperature

The magnetic properties of ceramic samples of Bi2-2x(PbSn)(x)Sr2CaCu2Oy (x = 0, 0.1, 0.2, 0.3 and 0.4) superconductors have been investigated using a vibrating sample magnetometer from 20 to 50 K and up to 8 T. Phase analysis shows that most of the (Pb,Sn) dopant enters the Bi-2212 lattice and occup ies Pi sites. The current-carrying scale-length analysis has been determine d from the reverse leg of the magnetization hysteresis loops and compared t o the actual dimensions of the sample. Magnetization hysteresis loops of th e (PbSn)-doped sample exhibit strong pinning behaviour in the higher temper ature range. The effect of (Pb,Sn) doping on intragranular critical current J(c) was found to be enhanced by one order of magnitude at 50 K. We discus s the experimental results within a model of (PbSn) duster pinning in block ing layers. Doping by (PbSn) clusters into the Bi-O layers provides effecti ve pinning centres, as well as a large reduction of the resistivity anisotr opy. (C) 2001 Published by Elsevier Science B.V.