Flux Pinning Characteristics in Superconducting Bi-(2212) Single Grains with Normal Particles

The temperature and magnetic field dependence of the critical current density, Jc, in the melt processed Bi2Sr2Ca1Cu2Oy superconductors, (2212), with normal particles was measured. Although Jc at 4.2K was about one order of magnitude larger than in the polycrystalline (Bi,Pb)2Sr2Ca2Cu3Oz, its temperature dependence seemed to be enhanced by the existance of weak links. The irreversibility magnetic fields were represented as [1-(T/Tc)2]n with the exponent n=5.44 at low temperatures and n=1.5 in high temperatures. Discussion is given on the dominant pinning centers by comparing the results and the theoretical predictions based on the flux creep.