The inherent brittleness and low sustainability of YBa2Cu3O7–x (YBCO) bulk superconductor seriously impede its wide applications. It is a great challenge to achieve toughening of this material and maintain its invariable superconductivity at the same time. Here, we fabricate bulk YBCO composite superconductor with a density of 2.15 g cm−3, which consists of interlocking dual network construction and shows high toughness and durability. The results show that its unit normalized fracture energy at 77 K reaches 638.6 kN m−2, which is ∼14.8 times that of YBCO bulk prepared by the top-seeded melt textured growth (TSMTG) method. Its critical current shows no degradation during the toughening process. Moreover, after 10 000 cycles, the sample does not fracture with the decay of critical current at 4 K of 14.6% whereas the TSMTG sample fractures only after 25 cycles.
Superconducting YBa 2 Cu 3 O 7− x (YBCO) bulks have demonstrated promising applications in quasi-permanent magnets, levitation, etc. Recently, the applications of bulk superconductors have been proposed, such as in portable, ultralight superconducting devices. These applications require bulk superconductors with lightweight, complex morphology, and good processability. However, the traditional fabrication method of YBCO bulks requires prolonged supplemental oxygenation and produces limited geometries with many randomly distributed cracks. This, combined with the inherent brittleness of the ceramic material, seriously impedes its wide application. In this study, a YBCO bulk with a multiscale hierarchical geometric configuration is constructed by a direct-ink-writing-based 3D-printing process. The 3D-printed YBCO green bodies exhibit a robust structure after directional freezing, which promotes intimate contact between the precursor particles in the deposited layers. This technology offers the advantage of a low shrinkage of 13.6 vol% after sintering at 920 °C. The 3D-printed bulks show lightweight, highly crystalline, and good electromagnetic properties compared with those produced by traditional cold-pressed sintering. Importantly, the multilevel void structure with a large specific surface area significantly reduces the oxygenation time and retains superconductivity. The proposed 3D-printing process can be adopted for the industrial production of superconducting bulk with complex geometries for novel applications.
Liu Yuting,Chen Yiming,Liang Jianlin,Zhao Jianyuan,Li Kang,Zhao Weiwei
In this study, we explored the impact of ionic liquid gating on YBa 2 Cu 3 O 7−x superconductivity. We observed that direct contact of YBa 2 Cu 3 O 7−x and the ionic liquid N-diethyl-N-methyl-N-(2methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) results in irreversible electrochemical reactions, despite the application of a relatively low gate voltage at 220 K. Capping a thin layer of boron nitride (BN) on YBa 2 Cu 3 O 7−x enabled a reversible modulation of carrier density at 300 K. Benefiting from the higher ion mobility of ionic liquid at 300 K, this modification led to more than a one-time increase in carrier density, a 3-time improvement in voltage modulation efficiency, and a reversible tuning of the superconducting temperature. These findings suggest that using a BN capping layer holds promise for enhancing the stability and efficiency of devices using ionic liquid gating.
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