Microstructure in High-Density Wires Prepared by an Internal Mg Diffusion Method

• Published in: IEEE transactions on applied superconductivity Vol. 21; no. 3; pp. 2668 - 2671
• Main Authors: Shimada, Y, Kubota, Y, Hata, S, Ikeda, K, Nakashima, H, Matsumoto, A, Togano, K, Hur, J, Kumakura, H
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2011; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Crystals; Diffraction; Heat treatment; Microstructure; Powders; reaction-induced diffusion process; Scanning electron microscopy; Silicon carbide; Wire; Wires; {\rm MgB}_{2} wire
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2010.2091097

Several reaction-induced diffusion processes to fabricate high-density MgB 2 materials are developed, and the critical current density ( J c ) has been notably enhanced. In this study, microstructure in high-density MgB 2 wires fabricated by an internal Mg diffusion (IMD) process has been investigated. The inner reacted region of the wire heat-treated at 640°C for 1 h shows dense polycrystalline MgB 2 of 20-200 nm in grain sizes. Fine MgO and Mg 2 Si particles of 10-30 nm in sizes are dispersed in this region. On the other hand, the outer region near the Ta sheath is composed of unreacted B and SiC powders, fine MgO particles and small voids. Sizes of voids in the IMD MgB 2 wire are small compared with the PIT MgB 2 wire. Oxidation of Mg in the IMD process forms fine dispersion of MgO which may be effective for flux pinning.