Akiyasu Yamamoto et al 2007 Supercond. Sci. Technol. 20 658 doi:10.1088/0953-2048/20/7/012
Akiyasu Yamamoto1, Jun-ichi Shimoyama1, Kohji Kishio1 and Teruo Matsushita2
Show affiliationsNormal-state conductivity in polycrystalline MgB2 bulk samples having a systematically varied packing factor was studied. The packing factor dependence of phonon term resistivity Δρ(T) = ρ(T)−ρ0 was found to be well explained by the three-dimensional site percolation model. The low packing density of the samples and the wet impurity phases at grain boundaries are suggested to be the main causes of poor electrical connectivity in MgB2. Our model enables quantitative evaluations of the intrinsic resistivity inside the grains, the fraction of the active grains that can carry current and the anisotropy of the grains in polycrystalline samples. The model predicts that the anomaly suppressed connectivity in rather weak-link-free MgB2 can be understood under a scenario of a percolation problem.
74.25.Fy Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
61.72.Mm Grain and twin boundaries
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
Issue 7 (July 2007)
Received 3 April 2007, in final form 2 May 2007
Published 4 June 2007
Akiyasu Yamamoto et al 2007 Supercond. Sci. Technol. 20 658
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