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arXiv · 1111.6767

Towards the Realization of Higher Connectivity in MgB2 Conductors: In-situ or Sintered Ex-situ?

A. Yamamoto·H. Tanaka·J. Shimoyama·H. Ogino·K. Kishio·T. Matsushita
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Abstract

The two most common types of MgB2 conductor fabrication technique - in-situ and ex-situ - show increasing conflicts concerning the connectivity, an effective current-carrying cross-sectional area. An in-situ reaction yields a strong intergrain coupling with a low packing factor, while an ex-situ process using pre-reacted MgB2 yields tightly packed grains, however, their coupling is much weaker. We studied the normal-state resistivity and microstructure of ex-situ MgB2 bulks synthesized with varied heating conditions under ambient pressure. The samples heated at moderately high temperatures of ~900°C for a long period showed an increased packing factor, a larger intergrain contact area and a significantly decreased resistivity, all of which indicate the solid-state self-sintering of MgB2. Consequently the connectivity of the sintered ex-situ samples exceeded the typical connectivity range 5-15% of the in-situ samples. Our results show self-sintering develops the superior connectivity potential of ex-situ MgB2, though its intergrain coupling is not yet fulfilled, to provide a strong possibility of twice or even much higher connectivity in optimally sintered ex-situ MgB2 than in in-situ MgB2.

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A. Yamamoto, H. Tanaka, J. Shimoyama, H. Ogino, K. Kishio, T. Matsushita. 2012-01-07. Towards the Realization of Higher Connectivity in MgB2 Conductors: In-situ or Sintered Ex-situ?. https://doi.org/10.1143/jjap.51.010105

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