[Zurück]

M. Eisterer, J. Emhofer, S. Sorta, M. Zehetmayer, H. W. Weber:
"Connectivity and critical currents in polycrystalline MgB₂";
Superconductor Science and Technology, 22 (2009), 034016; S. 1 - 7.

Current transport in polycrystalline magnesium diboride is highly non-uniform (percolative) due to the presence of secondary phases and also due to the instrinsic anisotropy of the material. The influence of secondary phases on the transport properties of MgB₂ was investigated. Bulk samples were prepared from a mixture of MgB₂ and MgO powders by the <i> ex </i> situ technique in order to vary the MgO content systematically. The samples were characterized by resistive and magnetization measurements. The reduced MgB₂ fraction is modeled by a reduced effective cross section (connectivity), which was assessed directly by the experiments. The presence of MgO also increases the percolation threshold, which reduces the zero resistivity (or irreversibility) field.

http://dx.doi.org/10.1088/0953-2048/22/3/034016

http://publik.tuwien.ac.at/files/PubDat_174448.pdf