A trapped magnetic field of 3 T in homogeneous, bulk MgB sub(2) superconductors fabricated by a modified precursor infiltration and growth process

• Published in: Superconductor science & technology Vol. 29; no. 3; pp. 35008 - 35015
• Main Authors: Bhagurkar, A G, Yamamoto, A, Anguilano, L, Dennis, A R, Durrell, J H, Babu, N Hari, Cardwell, D A
• Format: Journal Article
• Language: English
• Published: 01.03.2016
• Subjects: Borides; Bulk sampling; Infiltration; Magnesium compounds; Microstructure; Precursors; Superconductors; Wetting
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/29/3/035008

The wetting of boron with liquid magnesium is a critical factor in the synthesis of MgB sub(2) bulk superconductors by the infiltration and growth (IG) process. Poor wetting characteristics can therefore result potentially in non-uniform infiltration, formation of defects in the final sample structure and poor structural homogeneity throughout the bulk material. Here we report the fabrication of near-net-shaped MgB sub(2) bulk superconductors by a modified precursor infiltration and growth (MPIG) technique. A homogeneous bulk microstructure has subsequently been achieved via the uniform infiltration of Mg liquid by enriching pre-reacted MgB sub(2) powder within the green precursor pellet as a wetting enhancer, leading to relatively little variation in superconducting properties across the entire bulk sample. Almost identical values of trapped magnetic field of 2.12 T have been measured at 5 K at both the top and bottom surfaces of a sample fabricated by the MPIG process, confirming the uniformity of the bulk microstructure. A maximum trapped field of 3 T has been measured at 5 K at the centre of a stack of two bulk MgB sub(2) samples fabricated using this technique. A steady rise in trapped field was observed for this material with decreasing temperature down to 5 K without the occurrence of flux avalanches and with a relatively low field decay rate (1.5%/d). These properties are attributed to the presence of a fine distribution of residual Mg within the bulk microstructure generated by the MPIG processing technique.