Performance and applications of quench melt-growth bulk magnets

Abstract

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 Jc 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.

Reliable 4.8 T trapped magnetic fields in Gd–Ba–Cu–O bulk superconductors using pulsed field magnetization

“…The peak trapped field, BT, surpasses comprehensively the field generated by conventional PMs, e.g. NdFeB, at temperatures below 70 K [4][5][6][7]. Large, single-grain GdBCO-Ag samples [8] and uranium-doped and irradiated YBCO samples have been shown to exhibit maximum trapped fields exceeding 2 T at liquid nitrogen temperature [9].…”

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

“…At T = 10 K, bulk Bi2Sr2CaCu2O8 (BSCCO-2212) tubes can be used for shielding fields up to 1 T [19]. Solenoid magnets made of bulk melt-textured YBCO prepared by various techniques [20][21][22][23][24][25][26] show significant potential for magnetic shielding. There are very few reports, however, describing their shielding performances.…”

Optimized performance of an all-REBaCuO hybrid trapped field magnet lens (HTFML) with liquid nitrogen cooling

“…The values of Jc1 and Jc2 of the EuBaCuO TFM cylinder were determined in order to reproduce the experimental trapped field by FCM or ZFCM for the TFM-B, which consists of the EuBaCuO TFM cylinder [17]. The Jc1 and Jc2 values of the GdBaCuO magnetic lens were estimated to be slightly higher than those of the EuBaCuO TFM cylinder because of the fact that the trapped magnetic field of a QMG-GdBaCuO disk bulk with 60 mm in OD and 20 mm in H at 77 K was slightly higher than that of QMG-EuBaCuO disk bulk with the same size [27]. Isothermal conditions were assumed in the simulation, such that the temperature of the TFM cylinder and magnetic lens was set to a constant 300 K or 77 K during the magnetizing process, as shown in Fig.…”