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

摘要

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 occupies Pi sites. The current-carrying scale-length analysis has been determined from the reverse leg of the magnetization hysteresis loops and compared to the actual dimensions of the sample. Magnetization hysteresis loops of the (PbSn)-doped sample exhibit strong pinning behaviour in the higher temperature 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 discuss the experimental results within a model of (PbSn) duster pinning in blocking layers. Doping by (PbSn) clusters into the Bi-O layers provides effective pinning centres, as well as a large reduction of the resistivity anisotropy. (C) 2001 Published by Elsevier Science B.V. [References: 27]