期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 656, 期 -, 页码 172-180出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2015.09.253
关键词
MgB2 superconductor; Polycrystalline bulk; Self-sintering; Microstructural connectivities; Electron microscopy
资金
- Japan Society for the Promotion of Science (JSPS) [22102002, 25286027, 24656368]
- Nanotechnology Support Project of Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan
- Japan Science and Technology Agency
- PRESTO
- Grants-in-Aid for Scientific Research [24656368, 25286027] Funding Source: KAKEN
We have performed combined high-resolution microstructural and grain orientation analyses to understand the key microstructural factors associated with high intergranular transport current in polycrystalline bulk forms of MgB2. The ex-situ method can produce MgB2 with relatively high packing factors; nevertheless, the connectivity of MgB2 fabricated by the ex-situ method (ex-situ MgB2) was less than that of in-situ MgB2. The poor connections between MgB2 grain aggregates cause the low connectivity of ex-situ MgB2. Plate-like pores are present between the aggregates of MgB2 grains in ex-situ MgB2; these pores remain even after prolonged self-sintering at high temperatures. In addition, MgB2 crystals decompose to MgB4 in sintering for a long period. Moreover, MgO particles are formed between MgB2 grain aggregates and inhibit interaggregate connections. In contrast, in-situ MgB2 fabricated at the same sintering conditions exhibits spherical pores between MgB2 grains, resulting in a uniform pore distribution and intergranular connection. These problems must be addressed to further enhance the connectivity in ex-situ MgB2. (C) 2015 Elsevier B.V. All rights reserved.
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