Fostered Thermomagnetic Stabilities and Boosted Mechanical Reliability Related to High Trapped Field in Composite Bulk YBa₂Cu₃O_7−δ Cryomagnets

Abstract

In the quest of YBa2Cu3O(7-δ) (Y123) bulk superconductors providing strong magnetic fields without failure, it is of paramount importance to achieve high thermal stabilities to safeguard the magnetic energy inside them during the trapping-field process, and sufficient mechanical reliability to withstand the stresses derived from the Lorenz force. Herein, we experimentally demonstrate a temperature rise induced by dissipative flux motion inside an Y123 thin-wall superconductor, and a significant thermal exchange in a composite bulk Y123 cryomagnet realized by embedding this superconductor with high thermal-conductivity metal network. It resulted in stimulating the maximum trapped field Bm, which reached 6.46 T on 15.9 mm-diameter single disk superconductor after magnetization by field cooling to 17 K under 7 T, leading to an improvement of 18% compared to the thin-wall superconductor. The composite cryomagnet particularly revealed the potential to trap stronger fields if larger magnetic activation is available. By virtue of the pore-free and crack-free microstructure of this cryomagnet, its strength σR was estimated to be 363 MPa, the largest one obtained so far for Y123 bulk superconductors, thus suggesting a striking mechanical reliability that seems to be sufficient to sustain stresses derived from trapped fields stronger than any values hitherto reported.

Film thermal stability correlation with seeding modes in the growth of YBa2Cu3O7−δcrystals

“…Then the precursor powders were pressed into bulks with 20 mm diameter and 10 mm thickness. The seed was a c-axis-oriented NdBCO/YBCO/MgO thin film (NdBCO film seed) (Kenfaui et al, 2015;, which was placed at the centre on the upper surface of the bulk to induce crystal growth.…”

“…The YBa 2 Cu 3 O 7À (YBCO or Y123) high-temperature superconductor has attracted a significant amount of attention since it was discovered in 1987 (Campbell & Cardwell, 1997;Werfel et al, 2012;Krabbes et al, 2006). Single crystals with a large size and high quality are extremely important for device applications (Bean, 1962;Ren et al, 1993;Morita et al, 1998;Fuchs et al, 2000;Tomita & Murakami, 2003;Babu et al, 2005;Treimer et al, 2012;Kenfaui et al, 2013Kenfaui et al, , 2015Grissonnanche et al, 2014) and fundamental studies (Krabbes et al, 2006;Headings et al, 2011). Of all the methods for growing YBCO single crystals, the self-flux technique (Krauns et al, 1994) is popularly used for producing small crystals.…”

“…In this MMG method, the NdBCO film seed (Kenfaui et al, 2015; has been preferentially exploited owing to its superheating capacity and commercial availability (Xu, Chen et al, 2012). The most important advantage of using this thin film as the seed material is its capacity to endure a high maximum processing temperature (T max ), which is good for inducing the growth of large-sized REBCO (RE = Nd, Sm, Gd) crystals with a high peritectic temperature (T p ), e.g.…”

Proposal of an effective mechanical reinforcement structure for a REBaCuO disk bulk pair by full metal encapsulation to achieve a higher trapped field over 20 T

“…Both the fracture strength and Young's modulus of the REBaCuO bulk were increased with decreasing contents of voids [17][18][19]. For the void-free and crack-free microstructure of YBaCuO bulk superconductors, its mechanical strength was estimated to be higher than 300 MPa, suggesting a possible trapped field of over 30 T without fracture [20].…”

Towards a sustainable fabrication of cryomagnets: Melting‐driving approaches for recycling failed REBa2Cu3Ox bulks

“…REBa 2 Cu 3 O x (RE123 or REBCO, RE = rare earth elements) superconducting bulks, possessing high critical current density ( J c ) and high trapped magnetic field, have great potential in large‐scale application on power sector and engineering . As potentially applicable cryomagnets, the world records in the trapped field of 17.24 T at 29 K for YBCO, and more recently 17.6 T at 26 K for GdBCO have been successfully achieved .…”