The very important property of the superconductor is that it can carry a non-dissipative superconducting current, so it can produce a huge magnetic field when it makes a superconductor into a magnet. This property can be used for treatment, controlled nuclear fusion, high energy accelerator, new generation of maglev transport, etc., For a superconductor carrying a non-dispersive supercenter, the boundary, namely, a line of irreversibility Hirr(T), is very crucial. This phase line actually separates the phase diagram into zero and the final resistive dissipation. Typically, if a superconductor can carry a higher dispersive supercurrent with a higher magnetic field of irreversibility, it will have a better perspective for applications.
The superconductor goes into a superconducting state below the transition temperature Tc, so the superconductor is higher Tc it has better potential applications. Liquid nitrogen is easily produced and low cost oxygen with a boiling temperature of about 77.3 K. It is very crucial for applications if we find superconductors with Tc outside the flow temperature with liquid nitrogen and a magnetic field of a large irreversible state. In the family of couples, some units I-based[IBa[YBa[ИБа[YBa2Cu3ABOUT7–δ (I-123), Tc≈90K], Bi-based[Wouldbe[Wouldbe[Би[Bi2Sr2Ca2Cu3ABOUT10+δ (Bi-2223), Tc≈110K], Hg-based[HgBa[HgBa[ХгБа[HgBa2Ca3Cu4ABOUT10+δ (Hg-1234), Tc≈124K], and Tl-based[Tl[Tl[Тл[Tl2Ba2Ca2Cu3ABOUT10+δ (Tl-2223), Tc≈125]systems show superconducting temperatures over 77K. However, for systems based on Hg and Tl, Hg and Tl toxic elements strongly limit the application of large strengths of these materials. The non-toxic Bi-based system also has a transition temperature exceeding 100 K, but a very layered structure and huge anisotropy do not allow a high field of irreversibility at liquid nitrogen temperatures: the field of irreversibility and superconductivity of the superconducting current rapidly decreases with increasing temperature in a moderate temperature region. I-based IBa2Cu3ABOUT7–δ (IBCO), which is non-toxic and has a high irreversibility field, is considered to be a promising material for use. But it is extremely difficult to produce a long superconducting wire for a short coherent length, so far it can not realize large applications.
The group of professors Hai-Hu Ven in the Department of Physics of the University of Nanjing successfully synthesized the non-toxic bipartite superconductor (Cu, C) Ba2Ca3Cu4ABOUT11+d with Tc= 116K under high pressure and high temperature. Systemic measurements of resistance and magnetization show that it has the largest magnetic field of irreversibility in the region of liquid nitrogen temperature. This paper was published recently in Science Advances 4, eaau0192 (2018) September 28, 2018.
Figure 1 shows the temperature dependence of the sample 1 under different magnetic fields. If the resistance criterion is 1% ρn(Tc) selected, marked with a blue horizontal dashed line, a certain irreversibility field is 15 T to about 82K. In fact, even the higher irreversibility field values are found in the second sample. If weak bonds between polycrystalline samples improve, the irreversibility line may be even higher.
Figure 1. Temperature dependence of the resistance and magnetization of the sample 1. (A)
Temperature dependence of resistance under different magnetic fields from 0 to 15 T. The insert shows the temperature dependence of the magnetic sensitivity measured in the ZFC and FC modes under a magnetic field of 10 Oe. (B) The same data in (A) in the semilogarithmic scale. A blue horizontal cracks represent a resistance criterion of 1% ρn(Tc), which is used to determine the irreversibility line.
Figure 2 shows a comparison of the irreversibility lines for our samples and other cuprate systems (including polycrystalline samples, film / one crystal with H // c). From the data, we can see that the irreversibility field (Cu, C) Ba2Ca3Cu4ABOUT11+d is the highest in the temperature range from 77 K to 116 K. We use a prominent surface to denote a region with the final supercurrent (or zero / low resistance swelling) of our sample compared to IBCO. It can be seen that there is a large area outside the IBCO irreversibility line where the samples can carry an undisputed supercurrent, providing a great potential for applications above the liquid nitrogen temperature, which can stimulate the superratewater cuprate research and ultimately lead to large-scale applications.
Figure 2. Non-return lines of different coupler systems.
The irreversibility lines for (Cu, C) -1234 (this paper, sample 1 and sample 2), IBCO 1 and IBCO 2 (monocrystals, H || c axis), Bi-2223 (thin film, blue triangle), Bi-2223 (one crystal, cyan diamond) and (Tl, Pb) -1223 (pink triangles). The marked surface denotes the zero-dissipation area above the IBCO boundary. The line of the black dash shows the trend of the irreversibility line of IBCO with Tc = 91 К.
It should be emphasized that the present samples are made through high-pressure synthesis. The present results show very good properties for the use of non-toxic materials (Cu, C) Ba2Ca3Cu4ABOUT11+d and related systems. It is very desirable to try new methods with low pressure or thin film application to make superconducting wire / strip based on this promising material.
This work was independently completed by a group of professors Hai-Hu Ven, Doctor PhD Iue Zhang was the first author of the paper, Professor Hai-Hu Ven and Xiu Zhu are the appropriate authors.
Link articles: http: //advances.sciencemag.org/content/advances/4/9/eaau0192.full.pdf
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