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Basic material and critical current density relevant parameters for practical superconductors
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Large-scale superconducting electric power industry devices depend critically on wires with high critical current densities at temperatures where cryogenic losses are tolerable. This restricts choice to two high temperature cuprate superconductors, (Bi,Pb)2Sr2Ca2Cu3Ox and YBa2Cu3Ox, and possibly to MgB 2, recently discovered to superconduct at 39K....
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Context 1
... properties, crystal structure and anisotropy Figure 2 presents the important magnetic field-temperature (H-T) phase diagram for the three actual (Nb-Ti, Nb 3 Sn and Bi-2223) and two potential (YBCO and MgB 2 ) conductor materials. Their differ- ent phase diagrams result from their distinctly different physical parameters and crystal structures, as shown in Fig. 3 and Table 2. All five are type II superconductors for which bulk superconductivity exists up to an upper critical field H c2 (T), which can exceed 100 T for Bi-2223 and YBCO. ...
Context 2
... low irreversibility field prevents use of Bi-2223 at 77 K in any significant field (although power cables are possible) and provides one of the key arguments for developing a second-generation HTS technology based on YBCO, for which H*(77K) ~ 7 T. The structural origin of these important superconducting anisotropies is illustrated in Fig. 3 and Table 2. Nb-Ti, normally Nb47-50wt%Ti, is a body-centred cubic, solid-solution alloy with short electron mean-free-path, high resistivity and coherence length (4K)5 nm. ...
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... behaviour of HTS materials is in strong contrast to metallic LTS and MgB 2 , in which grain boundaries are not only transparent to current, but also significantly contribute to flux pinning, increasing the overall J c as the grain size decreases 26,28,48 . Although Table 2 might suggest that HTS grain boundaries are weak links because of their short coherence length, in fact a value of (77K) of ~4 nm for YBCO is actually longer than for Nb 3 Sn at 4 K. Moreover, low carrier density makes grain boundaries in (Ba,Pb)BiO 3 also weak-linked, even though (4K) ~ 7 nm for this compound 49,50 . ...
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Citations
... T HE coated conductor architecture was developed to exploit the potential of low-cost high temperature superconductors with excellent performance [1], [2]. Prior to low-cost industrial production, the coated conductor architecture which consist of superconducting REBa 2 Cu 3 O 7-δ (REBCO, RE = Rare Earth or yttrium) compound as a thin film on cube-textured Ni based alloy tapes was developed by Chemical Solution Deposition (CSD) methods [3], [4]. ...
Chemical solution deposition (CSD) approach was introduced in this work to simplify and to optimize the trifluoracetic based
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... Hysteresis loops M(H) seems to be rotated clockwise that indicates the presence of a paramagnetic contribution. Obtained critical current values are corresponding to the data reported by earlier HE compound [14] and conventional Y-123 and R-123 [20,21]. Content courtesy of Springer Nature, terms of use apply. ...
High-entropy single-phase superconducting oxide Y0.2Nd0.2Eu0.2Sm0.2Ho0.2Ba2Cu3Oy was synthesized. For samples with different values of oxygen content thermogravimetry, x-ray diffraction and magnetic properties were measured. Orthorombitity, critical temperature, and critical current grow with oxygen nonstoichiometry value y and corresponds to those for “low-entropy” YBa2Cu3Oy-type superconductors. The increase of the oxygen content leads to a decrease of “buckling” CuO2 layers and does not lead to a decrease in the Ba–O distance.
... YBa 2 Cu 3 O 7-δ (YBCO) films with biaxial texture are capable of transmitting large current. The flexible and cheap metal substrates are conducive to the preparation of large-scale superconducting tapes, which can be applied to electric power applications and have a good industrial application prospect [1][2][3][4]. At present, typical vacuum deposition approaches, such as pulsed laser deposition [5] and metal organic chemical vapor deposition [6], usually have high quality but high cost; by contrast, the non-vacuum and economical metal organic deposition (MOD) with accurate composition control and high raw material utilization is one of the preferred deposition methods [7]. ...
YBa2Cu3O7-δ (YBCO) thin films were fabricated rapidly on LaMnO3/MgO/Y2O3/Al2O3/Hastelloy substrate by the self-built induction heating system. The growth rate can be more than 60 nm/s, which is much higher than the traditional Metal Organic Deposition (MOD) method. The effects of heating rate, oxygen partial pressure and growth temperature on the texture and morphology of YBCO films were studied, as well as the analysis of properties. The results of X-Ray Diffraction and Scanning Electron Microscopy demonstrated that rapid heating can effectively reduce the residual of BaCO3 particles. The faster heating rate results in a faster YBCO growth rate, easier c-axis oriented grains growth and denser morphology. Moreover, the growth temperature and atmosphere window of YBCO films were obtained in the rapid heating condition. Meanwhile, the YBCO nucleation and growth models were established. This work realized the rapid crystallization of YBCO films by induction heating system and improved understanding of the nucleation mechanism of YBCO on the flexible metal substrate with buffer layers, which is extremely attractive for the industrialization development of Fluorine Free-MOD superconducting films in the future.
... At such high current densities J, once a vortex gets depinned from a defect, it can move with very high velocity v and dissipate much power. This phenomenon is critical for many applications, such as high-field magnets [6][7][8], THz radiation sources [9,10], or resonator cavities for particle accelerators [11,12]. Yet, the extreme dynamics of curvilinear elastic vortices driven by very strong currents close to the depairing limit J ∼ J d has not been well understood. ...
... 6. r i (β ) calculated at γ = 0.01, 0.05, 0.1, α 0 = 10 4 , and l/λ = 3.Figures 7(a) and 7(b) show the effect of the pin position on the field dependence of r i (β ) calculated at α = 1 and γ = 0.01 and 1. ...
We report numerical simulations of large-amplitude oscillations of a trapped vortex line under a strong ac magnetic field $H(t)=H\sin\omega t$ parallel to the surface. The power dissipated by an oscillating vortex segment driven by the surface ac Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass and a nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient $\eta(v)$. We show that the LO decrease of $\eta(v)$ with the vortex velocity $v$ can radically change the field dependence of the surface resistance $R_i(H)$ caused by trapped vortices. At low frequencies $R_i(H) $ exhibits a conventional increases with $H$, but as $\omega$ increases, the surface resistance becomes a nonmonotonic function of $H$ which decreases with $H$ at higher fields. The effects of frequency, pin spacing and the mean free path $l_i $ on the field dependence of $R_{i}(H) $ were calculated. It is shown that, as the surface gets dirtier and $l_i$ decreases, the anomalous drop of $ R_{i}(H) $ with $H$ shifts to lower fields which can be much smaller than the lower critical magnetic field. Our numerical simulations also show that the LO decrease of $\eta(v)$ with $v$ can cause a vortex bending instability at high field amplitudes and frequencies, giving rise to the formation of dynamic kinks along the vortex. Measurements of $R_i(H)$ caused by sparse vortices trapped perpendicular to the surface can offer opportunities to investigate an extreme nonlinear dynamics of vortices driven by strong current densities up to the depairing limit at low temperatures. The behavior of $R_i(H)$ which can be tuned by varying the rf frequency or concentration of nonmagnetic impurities is not masked by strong heating effects characteristic of dc or pulse transport measurements.
... Apart from the critical temperature (T c ), the critical current density (J c ) is the most relevant parameter of a superconductor which is directly related to its possible use in practical applications [6][7][8]. J c in a superconductor is determined by the critical temperature, electronic structure, and the flux pinning mechanism governed by the microscopic defects that are generated naturally or artificially during the growth of the superconducting films. The upper limit of the J c is determined by splitting of the paired electrons that carry the supercurrent (the so-called Cooper pairs), and Ginzburg-Landau gave an equation to estimate the depairing current density (current density at which splitting of Cooper pairs takes place) J d [9]: ...
... The reversible portion of this phase diagram refers to the vortex-liquid state in which vortex movements due to thermal fluctuation are so high that the ordered vortex lattice state (referred by irreversible portion of the phase diagram) is destroyed [18,19]. Thus, the irreversibility line or the melting line demarcates the solidliquid phases of the vortex matter and it is highly desired to shift this line toward higher H-T regime by artificial pinning center (APC) technology [6,8,20,21]. Figure 3 shows the comparison of the irreversibility lines of various superconductors which include superconducting alloys, metallic compounds, MgB 2 , and high temperature superconductors (HTS). The coated conductor technology employing APC incorporation in superconducting REBCO matrix is set to usher new frontiers of superconductivity applications between a wide temperature range of 5-77 K. Following subsections present different properties of YBCO superconductor. ...
The lossless transmission of direct electrical currents in superconductors is very often regarded as an “energy superhighway” with greatly enhanced efficiency. With the discovery of high temperature superconductors (HTS) in the late eighties, the prospect of using these materials in efficient and advanced technological applications became very prominent. The elevated operating temperatures as compared to low temperature superconductors (LTS), relaxing cooling requirements, and the gradual development of facile synthesis processes raised hopes for a broad breakthrough of superconductor technology. The impact of superconductor technology on the economy and energy sectors is predicted to be huge if these are utilized on a large scale. The development of superconducting tapes with high critical current density (Jc) is crucial for their use in transmission cables. Many countries these days are running projects to develop wires from these HTS materials and simultaneously field trials are being conducted to assess the feasibility of this technology. These HTS wires can carry electrical currents more than 100 times larger than their conventional counterparts with minimal loss of energy. The increased efficiency of HTS electric power products may result in greatly reduced carbon emissions compared to those resulting from using the conventional alternatives. In order to use the thin films of YBa2Cu3O7−δ (YBCO) and REBCO [RE (rare-earth) = Sm, Gd, Eu etc.], members of the HTS family, for future technological applications, the enhancement of Jc over wide range of temperatures and applied magnetic fields is highly desired. The enhancement of Jc of YBCO and REBCO films has been successfully demonstrated by employing different techniques which include doping by rare-earth atoms, incorporating nanoscale secondary phase inclusions into the REBCO film matrix, decoration of the substrate surface etc. which generate artificial pinning centers (APCs). In this review, the development of the materials engineering aspect that has been conducted over the last two decades to improve the current carrying capability of HTS thin films is presented. The effect of controlled incorporation of APCs through various methods and techniques on the superconducting properties of YBCO and REBCO thin films is presented, heading toward superior performance of such superconducting thin films.
... Nevertheless, none of them is able to convince the community of superconductivity with its physical pictures and rigorous derivations to reach a consensus on the origin and mechanism of superconductivity. With the findings of the superconductors with higher transition temperature, such as YBCO, and new types of superconductors, such as C 60 , 19 MgB 2 (Ref. 20) and Pnictides, 21-28 the confusion does not disappear at all. ...
The methods that have been used to deal with a many-particle system can be basically sorted into three types: Hamiltonian, field theory and phenomenological method. The first two methods are more popular. Traditionally, the Hamiltonian method has been widely adopted in the conventional electronic theory for metals, alloys and semiconductors. Basically, the mean-field approximation (MFA) that has been working well for a weakly coupled system like a metal is employed to simplify a Hamiltonian corresponding to a particular electron system. However, for a strongly coupled many-particle system like a cuprate superconductor MFA should in principle not apply. Therefore, the field theory on the basis of Green’s function and the Feynman diagrams must be invoked. In this method, one is however more familiar with the random phase approximation (RPA) that gives rise to the same results as MFA because of being short of the information for higher-order terms of interaction.
For a strongly coupled electron system, it is obvious that one has to deal with higher-order terms of a pair interaction to get a correct solution. Any ignorance of the higher-order terms implies that the more sophisticated information contained in those terms is discarded. However, to date one has not reached a consensus on how to deal with the higher-order terms beyond RPA.
We preset here a method that is termed the diagrammatic iteration approach (DIA) and able to derive higher-order terms of the interaction from the information of lower-order ones on the basis of Feynman diagram, with which one is able to go beyond RPA step by step. It is in principle possible that all of higher-order terms can be obtained, and then sorted to groups of diagrams. It turns out that each of the groups can be replaced by an equivalent one, forming a diagrammatic Dyson-equation-like relation. The diagrammatic solution is eventually “translated” to a four-dimensional integral equation. The method can be applied to a layered 2D system that is a model system of cuprate superconductors and others such as atomic, nuclear, heavy-fermion systems, etc.
... Due to the improvements of high temperature superconducting tapes (HTS) with high critical current (100 A) [1], power applications such as HTS power cables have been being studied in many countries [2,3,4]. Since 2006, we started to study the HTS cable for DC transmission since there is no AC loss in comparison with that for AC transmission [5]. ...
We have successfully constructed a 200 m high temperature superconducting (HTS) cable test facility for DC transmission in 2010. This coaxial power cable is composed of two superconducting (SC) conductors of DI-BSCCO tapes spirally surrounding a copper former. The tapes are arranged closely to make the magnetic field lines surrounding the cable uniformly. The number of tapes in each conductor is different because of their different radii. Previously, we have investigated the dependence of critical current (I-c) on the gap between the tapes in order to optimize the cable configuration for DC transmission. This paper report the investigation of I-c distributions in the multi-layer conductors which consist of 2, 3 and 4 tapes with a tape-on-tape structure by setting currents in each tape separately. The I-c measurement is performed with four-probe method at 77 K. The I(c)s of the tapes in the different structures are measured and compared with that of the single one. The enhancement and degradation of I-c are observed due to magnetic field interaction and magnetic shielding between the tapes in the multi-layer conductors. We will present the experimental results and show the dependence of the Ic distribution in the multi-layer conductors on the structures and transport currents in the neighboring tapes. (C) 2012 Published by Elsevier B. V. Selection and/or peer-review under responsibility of the Guest Editors.
... A PPLICATION of high temperature superconductor (HTS) thin films with a flexible tape shape to the superconducting magnets operated at 77 K in a fascinating trial [1], [2]. Practical applications of HTS require high critical current density under high magnetic field at 77 K. ...
We have reported superconducting properties of Sm1+xBa2-xCu3Oy (SmBCO; x = 0.08) thin films prepared by the low temperature growth technique (LTG). LTG process is consisted of two steps as follows; a seed layer is deposited at 830℃ on MgO(100), and then upper layer is deposited at 740－780℃ on the seed layer. In order to investigate the effect of the fluctuations Sm/Ba composition ratio in the SmBCO matrix, we deposited upper layer with the Sm/Ba composition of x = 0-0.12. The SmBCO films with x = 0.04 and 0.08 show critical current density (Jc) at 77 K of up to 5×10^6 A /cm2 under 0 T and 1×10^5 A /cm2 under 5 T for B//c at 77 K, respectively. The Jc of x = 0.12 film dropped more sharply compared with the cases of x = 0.04 and 0.08 films. From the microstructure analysis, it was found that the main phase of x = 0.12 film was Sm-rich (Sm1.1Ba1.9Cu3Oy) phase, while that of x = 0.04 and 0.08 films was stoichiometry. We speculated that the low-Jc of x = 0.12 film in the magnetic fields was ascribed to the low physical meters of Tc and irreversibility field of the Sm-rich SmBCO main phase. IEEE Transactions on Applied Superconductivity 15(2), 2005, p.3078-3081
... On the application point of view, the small scale applications of MgB 2 are not promising due to two band superconductivity with a dominant small energy gap [4,5]. On the other hand, the large scale applications are promising and the MgB 2 superconductor wire technology is getting mature to be available in the market to replace Nb-Ti and Nb 3 Sn [6]. The brittleness of MgB 2 , as in Nb 3 Sn and HTS, does not allow it to be used as a stand alone material. ...
MgB2/Mg composites were prepared to improve mechanical properties of brittle superconducting MgB2. MgB2 and Mg powders were mixed at different weight ratios and uniaxially pressed in a cylindrical dye at 0.5 GPa and at various temperatures for two hours to prepare MgB2/Mg composites. X-ray diffraction, SEM and EDX were used for phase identification and microstructural characterization. In addition to the main MgB2 and Mg phases, the microstructural studies have indicated the presence of a minor amounts of second phases, namely MgO and B-rich compounds. The surface morphology, grain size and porosity ratio of the samples prepared under various temperatures were also investigated. The resistivity measurements were performed in the range of room temperature to 15 K. The effect of excess Mg and secondary phases on critical temperature of MgB2/Mg composites were studied.
... Yet, clean MgB 2 has so far offered no clear advantages as compared to existing practical highfield superconductors because of rather low upper critical fields, H c2 ⊥ (0) ≈ 3.5 T and H c2 || (0) ≈ 18 T perpendicular and parallel to the ab plane of MgB 2 single crystals [8][9][10][11][12] . Indeed, the key to magnet applications of superconductors lies in the rare combination of low cost and a ready wire fabrication route, which produces conductors with high upper critical fields H c2 , and critical current densities J c 13 . Modern conductors are made from Nb-Ti (T c = 9 K, H c2 (4.2 K) = 10 T), Nb 3 Sn (T c = 18 K, H c2 (4.2 K) = 28 T), and the high-temperature superconductors (HTS), Bi 2 Sr 2 CaCu 2 O 8-x (T c ~ 90 K), and (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10-x (T c ~ 110 K). ...
... Here we show how H c2 (T) of MgB 2 can be radically enhanced beyond that of any Nb-based superconductor by introducing strong impurity scattering. The resulting increase of H c2 along with the significant decrease of H c2 anisotropy, from H c2 || /H c2 ⊥ ≈ 5-6 2 down to H c2 || /H c2 ⊥ < 2, can make MgB 2 well suited for high-field magnet applications at 20-30 K where HTS conductors presently are without challenge 13 . ...
... Since no viable wire route has ever been developed for PbMo 6 S 8 , the real competitors to MgB 2 are only HTS tapes of Bi 2 Sr 2 CaCu 2 O 8-x , (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10-x , YBa 2 Cu 3 O 7-δ or Nb 3 Sn or Nb-Ti 3 . As follows from Figure 6, MgB 2 is already competitive with Nb 3 Sn at low temperatures and with cuprate HTS at 20-25 K for electric utility applications for which fields up to ~ 5 T are needed 13 . Today the majority of superconducting magnet applications use Nb-Ti at 4.2 K and fields below 7 Tesla. ...
We report a significant enhancement of the upper critical field $H_{c2}$ of different $MgB_2$ samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities $\rho$, we show a clear trend of $H_{c2}$ increase as $\rho$ increases. One particular high resistivity film had zero-temperature $H_{c2}(0)$ well above the $H_{c2}$ values of competing non-cuprate superconductors such as $Nb_3Sn$ and Nb-Ti. Our high-field transport measurements give record values $H_{c2}^\perp (0) \approx 34T$ and $H_{c2}\|(0) \approx 49 T$ for high resistivity films and $H_{c2}(0)\approx 29 T$ for untextured bulk polycrystals. The highest $H_{c2}$ film also exhibits a significant upward curvature of $H_{c2}(T)$, and temperature dependence of the anisotropy parameter $\gamma(T) = H_{c2}\|/ H_{c2}^\perp$ opposite to that of single crystals: $\gamma(T)$ decreases as the temperature decreases, from $\gamma(T_c) \approx 2$ to $\gamma(0) \approx 1.5$. This remarkable $H_{c2}$ enhancement and its anomalous temperature dependence are a consequence of the two-gap superconductivity in $MgB_2$, which offers special opportunities for further $H_{c2}$ increase by tuning of the impurity scattering by selective alloying on Mg and B sites. Our experimental results can be explained by a theory of two-gap superconductivity in the dirty limit. The very high values of $H_{c2}(T)$ observed suggest that $MgB_2$ can be made into a versatile, competitive high-field superconductor. Comment: An updated version of the paper (12/12/2002)that was placed on cond-mat on May 7 2003
