A Novel Top‐Seeded Infiltration Growth Technique for Fabricating Y–Ba–Cu–O Single‐Grain Superconductor Nano‐Composites

Abstract

Top-seed infiltration and growth technique (TSIG) is proposed to fabricate Y-Ba-Cu-O (YBCO) single-grain superconductor nano-composites, in which a solid source composition of nano-Y 2 O 3 + BaCuO 2 and a liquid source composition of Y 2 O 3 + 10BaO + 16CuO are employed. As can be seen, this novel technique uses just one source of precursor powder of BaCuO 2 , so it is more simplified and efficient. Microstructural observation indicates that fine Y 2 BaCuO 5 (Y-211) inclusions with a size from dozens of nanometers to about one hundred nanometers are successfully introduced in YBa 2 Cu 3 O 7 -X (Y-123) superconducting matrix, which can act as more effective pinning centers for improving the bulk performance. Superconducting property measurement shows that, a maximum trapped field of 0.36044 T is present at the center of the sample after magnetization by a permanent magnet (B = 0.5 T). These results prove that our proposed TSIG technique is a practical method for fabricating YBCO bulk superconductor nano-composites with high performance.

Significant Improvement of Superconducting Properties in Nano‐NiFe2O4‐Doped Y–Ba–Cu–O Single‐Grain Superconductor

“…The performance improvement contributed by nano‐NiFe 2 O 4 doping is very clear, as that observed in levitation force. On the other hand, however, compared with the trapping ability (0.3604 T) of the sample fabricated using a presintering treatment, the trapped field (0.2754 T) of the undoped sample here is much lower, and the 0.2 wt% nano‐NiFe 2 O 4 ‐doped sample just exhibits a comparable trapping performance (0.3628 T), even though its levitation force (33.93 N) is much higher than that sample (28.54 N). In the conventional TSIG technique, it has been proved that the presintering helps to control the porosity of Y‐211 preforms, and finally results in low porosity and high density in final bulks, which are very associated with the J c and trapped magnetic field results of the samples .…”

“…In the conventional TSIG technique, it has been proved that the presintering helps to control the porosity of Y‐211 preforms, and finally results in low porosity and high density in final bulks, which are very associated with the J c and trapped magnetic field results of the samples . In the novel TSIG technique we reported earlier, a presintering treatment at 850°C for 10 h is adopted to promote partial phase transformations of Y 2 O 3 and BaCuO 2 toward Y‐211 phase in SSP pellet, and also to expel the residual gas and increase the preform density/compactness. As is indicated here, this processing is important for obtaining high trapped field performance in the final bulk and should be retained in the whole process flow, even though it prolongs the heat‐treatment cycle.…”

“…The arranged sample was heated fast to 1035°C at a rate of 240°C/h and held for 1 h to ensure complete infiltration of liquid from LSP to SSP, then cooled to 1005°C at a rate of 60°C/h, then cooled slowly at a rate of 0.33°C/h to 975°C, and finally furnace‐cooled to room temperature. It should be noticed that, different from the processing we reported earlier, the presintering stage at 850°C for 10 h is cut off in this study, in order to test whether the presintering contributes to the growth and properties of the final bulk and whether this stage is essential in the whole process flow. After completion of the TSIG process, the bulk sample was annealed in a flowing oxygen for 200 h at temperatures ranging from 450°C to 400°C.…”

“…Introduction of refined second‐phase particles in Y‐123 matrix has been proved to be an effective route to improve the δ l ‐type pinning, and the pinning force is very related to the distribution density and mean size of the inclusions. In our previous study, a novel top‐seeded infiltration growth (TSIG) technique has been proposed to fabricate YBCO superconductor nanocomposites, in which a large amount of Y‐211 nanoinclusions are observed in Y‐123 matrix, which can act as effective δ l ‐type pinning centers and improve the bulk performance. While, on the basis of that work, it is still desirable to develop new method to introduce stronger δ T c ‐type pinning to enhance the bulk performance further.…”

BiFeO3 nanoparticle doping effect on the growth and properties of Y–Ba–Cu–O superconductors

“…In the subsequent work, a new solid source with a composition of RE 2 O 3 + xBaCuO 2 was proposed to replace the RE-211 solid phase, and single-grain, high-quality SmBCO [9], GdBCO [10] and YBCO [11] bulks or rings have been successfully fabricated using this 'RE + 011' method. If the RE 2 O 3 nanopowder is employed, a large number of RE-211 inclusions will be in situ formed and composited in the REBa 2 Cu 3 O 7-δ (RE-123) matrix, which improves the performance further [12,13]. After this processing, only one type of precursor powder (i.e.…”