Performance and applications of quench melt-growth bulk magnets

This paper describes the progress in quench melt-growth. (QMG) bulk magnets, developed by. the Nippon Steel & Sumitomo Metal Corporation, which consist. of single crystalline RE123 phase and finely dispersed RE211 particles. QMG bulks. can trap high magnetic fields. The. field-trapping ability of QMG bulks is largely increased with an improvement in its. J(c) and size, promising the. realization of. various applications such as flywheel energy-storage systems, ship motors, NMR/MRI spectrometers, wind-power generators and so on. Intensive research has revealed that the optimal RE element is different depending on application requirements. Gd-QMG bulk. is. the most promising material for several high-field engineering applications. The trapped magnetic field of Gd-QMG bulk 60 mm in diameter at 77 K is twice as large as that of Y-QMG bulk with a similar size due to its. excellent Jc properties. The large Gd-based QMG bulks up to 150 mm in diameter are. fabricated by incorporating the RE compositional gradient method. Compact NMR/MRI spectrometers are one of the promising applications of bulk superconductors. Eu-QMG bulks are suitable for NMR magnets. NMR applications require extremely homogeneous magnetic fields. In the Eu-system, the small paramagnetic moment of a Eu ion compared to a Gd ion improves the field homogeneity in the bulk. For the application of current leads, Dy-based QMG is available by utilizing a low thermal conductivity.