Microstructural evolution in infiltration‐growth processed MgB2 bulk superconductors

The study reports phase and microstructural evolution in MgB2 bulk superconductors fabricated by an infiltration and growth (IG) process. Three distinct stages, (1) intermediate boride formation, (2) bulk liquid Mg infiltration, and (3) MgB2 layer formation, were identified in IG process after detai...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2017-06, Vol.100 (6), p.2451-2460
Main Authors: Bhagurkar, Ashutosh G., Yamamoto, Akiyasu, Dennis, Anthony R., Durrell, John H., Aljohani, Talal A., Nadendla, Hari B., Cardwell, David A.
Format: Article
Language:English
Subjects:
Beta rays
Borides
Boron
Crack propagation
Critical current density
Evolution
Grain boundaries
Infiltration
infiltration and growth
Magnesium compounds
MgB2
Microstructure
Superconductors
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Summary:The study reports phase and microstructural evolution in MgB2 bulk superconductors fabricated by an infiltration and growth (IG) process. Three distinct stages, (1) intermediate boride formation, (2) bulk liquid Mg infiltration, and (3) MgB2 layer formation, were identified in IG process after detailed examination of series of samples prepared with varied heating conditions. The intermediate phase Mg2B25, isomorphous to β‐boron, was detected prior to MgB2 phase formation in stage (1). Due to volume expansion involved in stage 1, cracks formed in the β‐boron particles and propagated radially inwards during stage 3. The growing MgB2 particles sintered simultaneously with formation of grain boundaries during the process, as evidenced by the measured hardness and critical current density in these samples. From our observations, we estimate the total time needed for complete transformation to MgB2.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.14792