Properties Of High-temperature Superconductors Research Articles

Unified EOS incorporating the finite strain theory for explaining thermo elastic properties of high temperature superconductors, nanomaterials and bulk metallic glasses

In the present research paper, we have proposed a novel EOS, which is based on the concepts of finite strain theories for predicting the thermo elastic properties of various materials viz. bulk metallic glasses, nanomaterials, and high temperature superconductors. Development of the present EOS involved deriving an innovative mathematical framework that considers the effects of finite strain, enabling the prediction of essential properties like pressure and bulk modulus under different compression ratios. For validity and applicability of the proposed EOS, we have conducted an extensive analysis by comparing the calculated thermo elastic properties with existing theoretical models or equation of sates and experimental data available in the literature. The present comparison revealed a remarkable agreement between our predictions and the observed values for a wide range of compression of nanomaterials, bulk metallic glasses, and superconductors. Our research not only introduces a comprehensive equation of state for these advanced materials but also demonstrates its effectiveness in accurately capturing their unique thermodynamic behavior. This present derived EOS can serve as a valuable tool to predict and understand the response of nanomaterials, bulk metallic glasses, and superconductors to varying pressure conditions, aiding the design and development of innovative applications in fields such as materials science, nanotechnology, and condensed matter physics.

AC Loss in High-Temperature Superconducting Bulks Subjected to Alternating and Rotating Magnetic Fields.

High-temperature superconductor (HTS) bulks have demonstrated extremely intriguing potential for industrial and commercial applications due to their capability to trap significantly larger magnetic fields than conventional permanent magnets. The magnetic field in electrical rotating machines is a combination of alternating and rotational fields. In contrast, all previous research on the characterization of electromagnetic properties of HTS have solely engrossed on the alternating AC magnetic fields and the associated AC loss. This research paper gives a thorough examination of the AC loss measurement under various conditions. The obtained results are compared to the finite element-based H-formulation. The AC loss is measured at various amplitudes of circular flux density patterns and compared with the AC loss under one-dimensional alternating flux density. The loss variation has also been studied at other frequencies. The findings in this research paper provide more insights into material characterization, which will be useful in the design of future large-scale HTS applications.

The superconducting properties of YBa2Cu3Oy ceramics fabricated using ultrahigh dilution technology

YBa2Cu3Oy (Y-123) is one of the most intensively studied high-temperature superconductors (HTS) and has great potential for applications in electronics. Its superconducting properties significantly depend on the oxygen index (y), the peculiarities of the atomic crystal and microgranular structure, the type and concentration of contaminating atoms. Therefore, of particular interest are the techniques of HTS synthesis that significantly affect the superconducting properties, as well as modifications of these techniques. The aim of this study was to investigate the effect of ultrahigh dilution (UHD) technology on the Y-123 HTS properties.We applied UHD technology to treat Y2O3·4BaO2·6CuO composition (before and/or after calcination) and used solid-phase reaction to obtain batches of ceramic samples of the Y-123 phase. Main characteristics of the synthesized HTS specimens (the orthorhombic unit cell parameters, temperature dependence of electrical resistance, Meissner effect, and critical current density) were studied.X-ray phase analysis demonstrated that the samples were practically single-phase and consisted of the Y-123 phase. Depending on the treatment method, the modifying effect varied. Positive and most significant results were demonstrated for specimens obtained from precursor powder mixture treated with UHD. For some of such specimens an increase in the temperature of the beginning of the transition to the superconducting state by 3.8 K, the Meissner effect by 9%, and the density of the intergranular critical current by 35% were observed. We conclude that UHD technology can be used to improve properties of HTS. However, methodology for implementation of UHD technology should depend on which specific superconductor property needs to be changed.

Ferromagnetism and Superconductivity in CaRuO3/YBa2Cu3O7-δ Heterostructures.

The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. We investigated the influence of ferromagnetic CaRuO3 on the properties of YBa2Cu3O7-x (YBCO) superconducting thin films when the layers are either in direct contact or separated by a barrier layer of 5 nm SrTiO3. Detailed measurements of the magnetic moment of the superconductor and ferromagnet as a function of temperature and magnetic field have been performed using SQUID magnetometry. Magnetometry and relaxation measurements show that the modification of the superconducting properties of YBCO strongly depends on the interaction with the ferromagnetic layer on top. The barrier layer has a significant impact on both the supercon-ducting properties of the YBCO film and the ferromagnetic ordering of CaRuO3. The physical properties mentioned above were discussed in correlation with the materials’ structure determined by XRD analysis.

Experimental Electromagnetic Characterization of High Temperature Superconductors Coils Located in Proximity to Electromagnetically Active Materials

The electromagnetic properties of high temperature superconductors (HTS) are characterized with the explicit intent to improve their integration in electric power systems. A tape and a coil made of Bismuth Strontium Calcium Copper Oxide (BSCCO) are considered in the presence of electromagnetically active materials in order to mimic properly the electromagnetic environment typical of electrical machines. The characterization consists of the determining the critical current and the AC losses at different values of the frequency and the transport current. The effects induced by the proximity of the active materials are studied and some related experimental issues are analyzedc.

Magnetic Characteristic Analysis of High Temperature Superconductors by the Elemental Operator Model

In this paper, to accurately analysis the magnetic properties of high temperature superconductor, a superconductor hysteresis model is proposed. Based on the physical mechanism, the hysteresis loop of high temperature superconductor can be decomposed into an antimagnetic curve and a paramagnetic loop. The calculated and measured results of silver-sheathed Bi2223 superconducting tape samples under external magnetic field are compared to show the effectiveness and accuracy of the presented method.

Unusual symmetries of the order parameter in cuprates

The BCS superconducting theory, introduced by J. Bardeen, L. Cooper and R. Schriffer in 1957, succeeded in describing and satis-factorily explaining the nature of superconductivity for low-temperature superconductors. However, the BCS theory cannot explain the properties of high-temperature superconductors, discovered by J. G. Bednorz and K. A. Müller in 1986. Although scientists have found a lot of new superconductors and their transition temperatures are constantly increasing, most high-temperature superconductors are found by experiment and so far no theory can fully explain their properties. Many previous studies have suggested that the order parameter in high-temperature copper-based superconductors (cuprate superconductors - cuprates) is in the form of d-wave symmetry, but recent results show that the order parameter has an extended s-wave symmetry (extended s wave). Studying the symmetric forms of order parameters in cuprate can contribute to understanding the nature of high-temperature superconductivity. In this article, the authors present an overview of the development of high-temperature supercon-ductors over the past 30 years and explains unusual symmetries of the order parameter in copper-based superconductors. The com-petition of three coupling mechanisms of electrons in cuprates (the mechanism of coupling through coulomb repulsion, electron-phonon mechanism and spin-fluctuation mechanism) affects the unusual symmetry of the order parameter. The solution of the self-consistency equation in simple cases has been found and the ability to move the phase within the superconducting state has been shown.

Memristive Properties of Oxide-based High-Temperature Superconductors

The study of memristive properties or effect of resistive switchings in four classes of high-temperature superconductors (HTSC), namely Bi2Sr2CaCu2O8+y (BSCCO), YBa2Cu3O7−y (YBCO), Ba0.6K0.4BiO3−y (BKBO), and Nd2−xCexCuO4−y (NCCO), is presented. The purpose of this study is to reveal functional properties of HTSC which become apparent in the effects under discussion, prospects of usage of HTSC-based memristors in applications, and search for new mechanisms of strongly correlated nature to realize new-generation memristors (Tulina 1). The properties are as follows: undergoing the metal-insulator transition at oxygen doping, transport anisotropy, and existence of charge reservoirs through which doping of conductive copper–oxygen layers is carried out. These are the main functional properties of HTSC which allows their usage in memristors. By the example of study of bipolar effect of resistive switching in HTSC-based heterojunctions, it is shown how one can form memristor structures based on HTSC using their functional properties.

An evaluation of thermal conductivity of high-temperature superconductors

This paper deals with the transport properties of high temperature superconductors. The transport properties are temperature dependence of thermal conductivity of high Tc superconductor. We have taken two different high Tc superconductors in our studies namely La2-nSrnCuO4 and YBa2Cu3O7-δ. These superconductors bear transition temperature from 38K to 110K. Transport properties basically concerns with the movement of the classic carriers in the solid. In the case of superconductors the carriers are super electrons which move in the vicinity of a different excitation of the solid created by the impurity which has been dropped in the system. It was believed that as in the case of noble metal or low Tc superconductors (Tc from 1K to 24K) phonons has dominant role in different transport properties. From the investigation this has been ruled out. Phonons does play role in the high Tc superconductor only above Tc. The studies of thermal conductivities of high Tc superconductors indicate that the phonons contributions are larger near Tc and smaller far away.

Linked cluster theory in the spin polaron problem

The Linked Cluster Theory in the spin polaron formulation is investigated in this paper using the finite temperature (Matsubara) Green’s function method. We use a representation where holes and spins are described as spinless fermions and normal bosons, respectively. An analytic expression of the thermodynamic potential of high-temperature superconductors in the superconducting state was obtained using the Linked Cluster theory and an expression for its normal state by setting the energy gap to zero. The expression of the thermodynamic potential enabled us to calculate two bulk thermodynamic properties of high-temperature superconductors, entropy and specific heat, both in the normal and superconducting states.

Synthesis and study the Structural and electrical and mechanical properties of High Temperature Superconductor Tl0.5Pb0.5Ba2Can-1Cun-xNixO2n+3-δ Substituted with nickel oxide for n=3

on this research is to study the effect of nickel oxide substitution on the pure phases superconductor Tl0.5Pb0.5Ba2Can-1Cun-xNixO2n+3-δ (n=3) where x=(0,0.2,0.4,0.6,0.8.and 1.0). The specimens in this work were prepared with used procedure of solid state reaction with sintering temperature 8500C for 24 h .we used technical (4-prob)to calculated and the critical temperature Tc . The results of the XRD diffraction analysis showed that the structure for pure and doped phases was tetragonal with phases high-Tc phase (1223),(1212) and low-Tc phase (1202) and add to the presence of some impure phase. It was noted the value a=b,c the parameter of the lattice increment with the increment of Ni content. The increment of (NiO) concentration effects electrical resistivity, dielectric constant and the hardness.

Use of slag (CaO-Al2O3-SiO2-MgO) droplet as a catalyst to grow MgO whiskers through VLS mechanism

Abstract MgO whiskers have a variety of potential applications like nanoelectronics, sensing devices and to improve mechanical properties of high temperature superconductors like MgB2, and MgO-C refractory used in the steel industry. The growth of whiskers is known to be catalyzed by the presence of a liquid droplet at the whisker tip, generally known as the vapor-liquid-solid (VLS) growth mechanism. Several metallic systems like Au, Mg-Si, Al-Mg and Ni have been used as a catalyst. In this work, it was found that a CaO-Al2O3-MgO-SiO2 mixture (a typical ladle slag used in steelmaking) can facilitate the growth of MgO whiskers. This was first observed, in this work, during a steel-slag equilibrium experiment conducted in a confocal laser scanning microscope (CLSM) using an MgO crucible. MgO whiskers observed after the experiment had a slag droplet on the tip of whiskers. Subsequently, targeted experiments were conducted to find the possible sources of magnesium vapor and the usability of slag to grow whiskers in MgO-C refractory. Results show that the slag can facilitate the growth of MgO whiskers in an MgO-C pellet.

Thallium-based high-temperature superconductors for beam impedance mitigation in the Future Circular Collider

CERN has recently started a design study for a possible next-generation high-energy hadron–hadron collider (Future Circular Collider—FCC-hh). The FCC-hh study calls for an unprecedented center-of-mass collision energy of 100 TeV, achievable by colliding counter-rotating proton beams with an energy of 50 TeV steered in a 100 km circumference tunnel by superconducting magnets which produce a dipole field of 16 T. The beams emit synchrotron radiation at high power levels, which, to optimize cryogenic efficiency, is absorbed by a beam-facing screen, coated with copper, and held at 50 K in the current design. The surface impedance of this screen has a strong impact on beam stability, and copper at 50 K allows for a limited beam stability margin only. This motivates the exploration of whether high-temperature superconductors (HTS), the only known materials possibly having a surface impedance lower than copper under the required operating conditions, would represent a viable alternative. This paper summarizes the FCC-hh requirements and focuses on identifying the best possible HTS material for this purpose. It reviews in particular the properties of Tl-based HTS, and discusses the consequent motivation for developing a deposition process for such compounds, which should be scalable to the size of the FCC components.

9th International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials (PASREG2015)

The 9th International Workshop on Processing and Applications of Superconducting (RE)BCO Large Grain Materials (PASREG 2015) was held at the University of Liege, Belgium on September 02- 04, 2015, as a satellite conference of the European Conference on Applied Superconductivity (EUCAS 2015). The Chairman was Philippe Vanderbemden; Benoît Vanderheyden, David Cardwell, and Herbert C. Freyhardt served as Co-Chairmen. PASREG 2015 was the ninth in a series of international workshops previously held in Cambridge, UK (1997), Morioka, Japan (1999), Seattle, USA (2001), Jena, Germany (2003), Tokyo, Japan (2005), Cambridge, UK (2007), Washington D.C., USA (2010), and Tainan, Taiwan (2012).PASREG 2015 covered novel and important processing aspects of bulk High Temperature Superconductors (HTS) as well as bulk MgB2. Besides processing, the workshop highlighted advanced material characterization technologies and activation techniques, which revealed the superior superconducting properties of bulk HTS and MgB2. Novel developments and innovative applications involving bulk superconductors complemented the discussion and exchange of information. The workshop was attended by 63 participants from 19 different countries. A total of 50 contributions were presented, of which 31 were presented in oral form and 19 were presented as posters.Together with a ‘Special Issue’ of Superconductor Science and Technology, these proceedings gather a selection of original research papers presented at the workshop (including both oral and poster presentations). We greatly acknowledge all the effort of the authors.Philippe VanderbemdenBenoît VanderheydenHerbert FreyhardtDavid Cardwell

Note: Effective measurement of retained I(c) in evaluating electromechanical properties of high temperature superconductor tapes by the voltage tap clipping technique.

In this note, the effectiveness of voltage tap clipping technique was assessed in evaluating the electromechanical properties of high temperature superconductor (HTS) tapes in the aspect of practical device applications. In the four-probe transport I(c) measurement, instead of directly soldering the voltage lead wires onto the HTS samples, they were tapped to the sample by either just clipping or soldering them to the clips. This technique facilitated the simultaneous and repeated retained I(c) measurement test for multiple samples. Finally, the critical double bending diameter of HTS tapes and the electrical properties of jointed and striated coated conductor tapes could be easily determined.

A technique and installation for studying electrophysical properties of high-temperature superconductors

This paper presents an experimental exploration of the electrophysical properties of high-temperature superconductors that is based on the determination of the constitutive equation parameters for the combined model with two sources of electromagnetic field: current density and magnetization. It involves a series of experiments in different external magnetic fields and various transition modes to the superconducting state that allows the individual field sources to be distinguished. Since conditions that would enable us to maintain a homogenous current density distributions and magnetization under varying external magnetic induction in the HTSs are not available, the magnetic field parameters and its sources in the samples are determined via computational and experimental methods, in which the magnetic field parameters in the sample are calculated using their values out of the sample. A special laboratory installation equipped with the required measuring tools and magnetic system to create a controlled external magnetic field with the magnetic flux density of 1.5 T is constructed for the practical implementation of the experimental research technique.

Modeling of electrophysical properties of bulk high-temperature superconductors in calculations of magnetic systems

Advanced macroscopic models of electrical properties of materials that are represented by a set of transport and associated currents and identified, respectively, by the resistive current model and nonlinear hysteretic magnetization model are proposed in order to calculate magnetic systems with the bulk high-temperature superconductor (HTS) elements. Such models allow a more accurately reproduced behavior of superconductors in the electromagnetic field of simply and multiply connected domains in various HTS transition regimes to the superconducting state. The paper presents the results of the compared combined and resistive models of the HTS properties. The proposed models enable us to reproduce the nonlinear, anisotropic, and hysteretic properties of superconductors in a wide range of parameter variation on a macroscopic scale and can be recommended for their application in numerical analysis of electromagnetic fields. The results of the calculations allow the parameter determination methods for the combined model from the experimental data to be substantiated.

Magnetic and magnetostrictive properties of finite superconducting cylinders containing a cavity

To improve the mechanical properties of high temperature superconductors due to the intrinsic brittleness and defects is a central problem for the application of the superconductors. This paper presents an analysis of mechanical behavior for the finite cylindrical type-II superconductors containing an ellipsoidal cavity in an applied magnetic field. After the Bean's critical state model and the method of minimum magnetic energy variation are employed, the dependences of the magnetic properties and magnetoelastic behaviors on the sizes of the cavity and superconducting sample are obtained. The results display that the induced current and magnetic field distributions in such sample are quite different from the case of a cylinder or ring, and a vertical flipping behavior of the magnetostriction curves is found in the magnetization process when the radial wall thickness changes through a critical value. Meanwhile, the overall maxima of the stress components during field descent are enhanced by a factor of 2 or more relative to those in a finite cylinder without any cavity.

Magnetoresistance of Superconducting Granules and Grain Boundaries in Ceramic YBa2Cu3O7−δ High-Temperature Superconductors in Weak Magnetic Fields

The objective of the work is to establish the contribution of superconductive granules and grain boundaries (weak links) in magnetoresistance ρ value of YBa2Cu3O7−δ granular high-temperature superconductor (HTS) at T<Tc. The current-voltage characteristics (CVCs) \(E(j)_{H_{\mathrm{ext}} = \mathrm{const}}\) of YBa2Cu3O6.95 ceramic samples were measured in Hext (0≤Hext≤≈500 Oe) magnetic fields. The CVCs \(E(j)_{H_{\mathrm{trap}} = \mathrm{const}}\) of the samples magnetized in Htreat magnetic fields were measured at Hext=0. Based on the CVCs, \(\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}\), ρ(Hext)j=const and \(\rho(j)_{H_{\mathrm{treat}} = \mathrm{const}}\) dependences were reestablished. The comparative analysis of \(\rho(j)_{H_{\mathrm{ext}} = \mathrm{const}}\) and ρ(Hext)j=const dependences indicates the magnetic field redistribution between grain boundaries and superconductive granules influence on transport and galvanomagnetic properties of granular HTS. The superconductive grain magnetoresistance ρg was established to be significantly lower than ρJ value of Josephson medium.

Setup for studying nonlinear magnetic properties of high-temperature superconductors with the aid of magnetization harmonics

A setup for measuring cophasal and quadrature components of higher harmonics of an electromotive-force signal of the response of a high-temperature superconductor makes it possible to study nonlinear magnetic properties of superconductors in variable magnetic fields of up to 1 kOe and constant magnetic fields of up to 10 T in the temperature range of 5–300 K. This setup was used to measure the temperature dependences of the absolute values of the real and imaginary parts of the first and third harmonics of the magnetization of textured Yba2Cu3O7 − x polycrystalline samples in the temperature range of 77–220 K at various values of variable and constant magnetic fields. An analysis of resulting data made it possible to reveal the presence of different dynamical modes of the magnetic flux in YBa2Cu3O7 − x that were dominant in different temperature ranges. The nonlinearity of the magnetization of YBa2Cu3O7 − x (the appearance of higher harmonics) was observed up to temperatures in the range of T = 103–112 K, which were substantially higher than the temperature of the transition of this compound to a superconducting state. The observed feature in the magnetization of YBa2Cu3O7 − x was associated with the emergence of a pseudogap state in this compound.