Saturday , January 16 2021

Unprecedented high irreversible magnetic fields of non-toxic copper oxide superconductors: promising superconducting materials for high power applications over liquid nitrogen temperatures



A very important characteristic of a superconductor is that it can generate a huge magnetic field when it is made into a magnet because it can carry non-radiative superconducting currents. This property can be applied to medical treatment, fusion control, high energy accelerators, new generation magnetic levitation. In order for a superconductor to deliver a non-radiative superfluid, Hirr(tea), very important. This phase line actually separates the state diagram into zero and finite resistive dissipation. In general, if superconductors can deliver higher non-radiative overcurrents with irreversible magnetic fields, they will have better prospects for applications.

Superconductors are in a superconducting state below the transition temperature. teaaspirate, So a higher superconductor teaaspirate Potential applications are better. Liquid nitrogen is an easily manufactured, low cost cryogen with a boiling temperature of about 77.3K. It is very important if we find a superconductor with Taspirate Liquid nitrogen boiling temperature and high irreversible magnetic field. Some compounds of the Y-system in the cuprate series[YBa[YBa[YBa[YBa2Cuthreeo7δ (Y-123), teaaspirate≈90K], Bi-based[Bi[Bi[Bi[Bi2Sr2calcium2Cuthreeo10+δ (Bi-2223), teaaspirateAbout 110K], Hg based[HgBa[HgBa[HgBa[HgBa2calciumthreeCu4o10+δ (Hg-1234), teaaspirate≈124K], And T1-based[T1[Tl[T1[Tl2bar2calcium2Cuthreeo10+δ (Tl-2223), teaaspirate≈125]The system shows a superconducting transition temperature of over 77K. However, in the case of Hg and Tl based systems, the toxic elements Hg and Tl strongly limit the high-power applications of these materials. Non-toxic Bi-based systems also have a transition temperature in excess of 100K, but a highly layered structure and a large anisotropy do not allow a high irreversible field at liquid nitrogen temperatures. Irreversible field and superconducting current densities decrease rapidly as temperature rises. Temperate temperature zone. Y-based YBa2Cuthreeo7δ (YBCO) is a non – toxic, highly irreversible material and is considered a promising material in applications. However, it is extremely difficult to produce long superconducting wire with a short consistent length. Until now, large-scale applications can not be realized.

Professor Hai-Hu Wen of the Department of Physics at Nanjing University is a non-toxic copper oxide superconductor (Cu, C) Ba2calciumthreeCu4o11 years or olderD Wow teaaspirate= 116K at high pressure and high temperature. Systematic resistance and magnetization measurements show the most irreversible magnetic fields in the liquid nitrogen temperature range. This work has recently been published. Science Advances 4, eaau0192 (2018) September 28, 2018

Figure 1 shows the temperature-dependent resistance of sample 1 under different magnetic fields. Resistivity criterion of 1% ρyen(teaaspirate) Is selected, the determined irreversible field is about 82K to 15T. In fact, higher values ​​of irreversible fields are found in other samples. Improved weak connections between polycrystalline samples can lead to higher irreversible lines.

Figure 1. Temperature dependence of magnetoresistance and resistance of samples. (a)

Temperature dependence of the resistivity under different magnetic fields of 0 to 15 T. The insertion shows the temperature dependence of the magnetosensitivity measured in the ZFC and FC modes under 10 Oe magnetic field. (ratio) The same data in (A) of the rounding scale. The blue horizontal dashed line represents the criterion for resistivity 1% ρ.yen(teaaspirate), Is used to determine irreversible lines.

Figure 2 shows a comparison of the irreversible lines for our sample and other curate systems (including polycrystalline samples, film / single crystals with H // c). From the data we see that the (Cu, C) Ba irreversibility field2calciumthreeCu4o11 years or olderD Is the highest in the temperature range from 77K to 116K. We use the highlighted area to indicate the area of ​​the sample where there is a limited supercurrent (or zero / weakly resistive dissipation) of the sample compared to YBCO. It can be seen that there is a large area beyond the irreversible line of YBCO. The samples are capable of delivering non-acidic overcurrents, which is highly likely to be applied at temperatures higher than liquid nitrogen temperatures, which stimulates the study of copper oxide superconductors, resulting in large-scale applications.

Figure 2. The irreversibility line of another cuprate system.

(Cu, C) -1234 (this study, Sample 1 and Sample 2), YBCO 1 and YBCO 2 (single crystal, H || c Bi-2223 (thin film, blue triangle), Bi-2223 (single crystal, cyan diamond), (T1, Pb) -1223 (pink triangle). The highlighted area represents the zero dissipation area above the YBCO boundary. The dotted black line shows the tendency of the irreversible line of YBCO. teaaspirate = 91K

It should be emphasized that this sample was made by high-pressure synthesis. The present results show very good intrinsic properties for the application of non-toxic substances (Cu, C) Ba2calciumthreeCu4o11 years or olderD And related systems. It is highly desirable to try new methods with lower pressure or thin film deposition to make superconducting wires / tapes based on this promising material.

Professor Hai-Hu Wen, Ph.D student Yue Zhang is the first author of this paper, and Professor Hai-Hu Wen and Professor Xiyu Zhu have independently created this work.

Article link: http: //advances.sciencemag.org/content/advances/4/9/eaau0192.full.pdf

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