Flux Pinning Mechanism and Critical Current Density in High-Temperature Superconductors

The major limitation of Bi-system superconductor applications is the intergrain weak links and weak flux pinning capability producing low critical current density of the Bibased phases. In order to enhance these characteristics and other superconducting properties, effective flux pinning centers are introduced into high temperature superconductors. In this work, different weight percentages of ZnO nano oxide were introduced at the final stage of the Bi1.8Pb0.4Sr2Ca2Cu3O10-y superconductor preparation process. Phase characterization was completed by X-ray diffraction (XRD). Exact constitution of the samples was determined using particle induced X-ray emission (PIXE). Granular and microstructure were investigated using scanning electron microscopy (SEM). Electrical resistivity as function of the temperature was carried to evaluate the relative performance of samples, and finally, E-J characteristic curves were obtained at 77K. Using 0.4 ZnO weight percentage, the electrical and granular properties were greatly enhanced, indicating more efficient pinning mechanisms. A critical current density of 949 A/cm2 was obtained which represents more than twice the value obtained for the pure sample (Jc= 445 A/cm2).

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Anisotropic critical current density and flux pinning mechanism of Fe1+yTe0.6Se0.4 single crystals

Superconductor Science and Technology ◽

10.1088/1361-6668/ac3632 ◽

2021 ◽

Author(s):

Yongqiang Pan ◽

Nan Zhou ◽

Bencheng Lin ◽

Jinhua Wang ◽

Zengwei Zhu ◽

...

Keyword(s):

Critical Current Density ◽

Single Crystals ◽

Critical Current ◽

Current Density ◽

Flux Pinning ◽

Magnetic Hysteresis ◽

Magnetic Hysteresis Loop ◽

Pinning Force ◽

Magnetization Relaxation ◽

Pinning Mechanism

Abstract Fe1+yTe0.6Se0.4 has considerable application potential due to its large critical current density (J c) and high upper critical magnetic field (H c2). However, the uncertainty of the anisotropy of J c and the unclear flux-pinning mechanism have limited the application of this material. In this study, the J c in three directions were obtained from magnetic hysteresis loop measurements. A large anisotropy of J c ab /J c c ~ 10 was observed, and the origin of the anisotropy was discussed in details. Flux pinning force densities (F p) were obtained from J c, and a non-scaling behavior was found in the normalized pinning force f p[F p/F p-max] versus the normalized field h[H/H c2]. The peaks of pinning force shift from a high h to a low h with increasing temperature. Based on the vortex dynamics analysis, the peak shift was found to originate from the magnetization relaxation. The J c and F p at critical states free from the magnetic relaxation were regained. According to the Dew-Hughes model, the dominant pinning type in Fe1+yTe0.6Se0.4 clean single crystals was confirmed to be normal point pinning.

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Crystal Growth of High Temperature Superconductors

MRS Bulletin ◽

10.1557/s0883769400064204 ◽

1988 ◽

Vol 13 (10) ◽

pp. 56-61 ◽

Cited By ~ 31

Author(s):

H.J. Scheel ◽

F. Licci

Keyword(s):

High Temperature ◽

Critical Current Density ◽

Single Crystals ◽

Critical Current ◽

Current Density ◽

Large Scale ◽

High Temperature Superconductivity ◽

High Temperature Superconductors ◽

Superconducting Transition ◽

Theoretical Understanding

The discovery of high temperature superconductivity (HTSC) in oxide compounds has confronted materials scientists with many challenging problems. These include the preparation of ceramic samples with critical current density of about 106 A/cm2 at 77 K and sufficient mechanical strength for large-scale electrotechnical and magnetic applications and the preparation of epitaxial thin films of high structural perfection for electronic devices.The main interest in the growth of single crystals is for the study of physical phenomena, which will help achieve a theoretical understanding of HTSC. Theorists still do not agree on the fundamental mechanisms of HTSC, and there is a need for good data on relatively defect-free materials in order to test the many models. In addition, the study of the role of defects like twins, grain boundaries, and dislocations in single crystals is important for understanding such parameters as the critical current density. The study of HTSC with single crystals is also expected to be helpful for finding optimum materials for the various applications and hopefully achieving higher values of the superconducting transition temperature Tc than the current maximum of about 125 K. It seems unlikely at present that single crystals will be used in commercial devices, but this possibility cannot be ruled out as crystal size and quality improve.

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