bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructure of coated conductors with La- or Nb-doped SrTiO3 conductive buffer
Authors: Ichinose A. , Ota K. , Hamada T. , Inoue S. , Horii S. , Doi T. 
Published: June 2020

Abstract
A novel configuration for coated conductors (CCs) was proposed to reduce material cost and consisted of YBa2Cu3Oy (YBCO) / conductive buffer(s) / Ni-electroplated {100} <001> textured Cu, and SUS316 lamination tape. Conductive buffers are a key subject to reduce material cost of CCs. In the CC using the conductive buffer of Nb-doped SrTiO3 (Nb-STO), a high-J
C YBCO (2.5 MA/cm2 at 77 K and self-field) was successfully obtained. Moreover, a clean interface between the buffer and the metal tape without oxides was confirmed using TEM analysis. However, the resistivity of the Nb-STO buffer increased to be several Ω·cm after the YBCO deposition, which was beyond expectations. Therefore, the La-doped STO (La-STO) conductive buffer was incorporated into CCs as a novel conductive buffer. Two CCs with the different conductive buffers were compared in terms of microstructure analysis using transmission electron microscopy.
Towards a reliable bridge joint between REBCO coated conductors
Authors: Kirchner A. , Nielsch K. , Hühne R. 
Published: June 2020

Abstract
REBa2Cu3O7-x
(REBCO; RE = Y, Gd) coated conductor wires are commercially available up to a length of about 1 km. However, for large-scale devices like superconducting coils for high-field magnets several kilometres of a coated conductors are required. Therefore, it is desirable to use joints, which exhibit similar superconducting properties as the coated conductor itself. In this study, we jointed commercial REBCO coated conductors by a two-step procedure. At first, a superconducting soldering solution was developed and deposited on unstabilized coated conductors via chemical solution deposition. The soldering precursor is based on a Cu-rich solution with a metal cation ratio Y:Ba:Cu of 1:2:4. Secondly, a piece of the coated conductor was delaminated between the superconducting and the buffer layer and used as bridge between two other conductors covered with the soldering layer. Annealing the resulting bridge joint under pressure results in a mechanical stable configuration.
In-depth resistance analysis of REBCO tape joints with indium insert and solders
Authors: Hayasaka R , Ito S , Kato T , Yokoe D , Hashizume H 
Published: June 2020

Abstract
Joints between REBCO (rare-earth barium copper oxide) tapes with low joint resistance are crucial for many superconducting applications. Joining REBCO tapes with indium insert (In-joint) is a promising joining method to fabricate low resistive joints at low temperatures (20–120°C). This study investigated the joining conditions of In-joints such as pickling, surface roughness, joining time, and temperature. The joint resistivity (product of joint resistance and joint area) was successfully reduced to 22–30 nΩcm2 at 77 K in self-field. The constitutive factors of the joint resistivity were analysed separately along with the crosssectional observations. In this study, the interface resistivity of the REBCO tape was measured as 8.5 nΩcm2 for one REBCO tape by the previously proposed method. The resistivity of the joining interface Cu/In was calculated as <3 nΩcm2 by subtracting the other resistivities from the entire joint resistivity. This result reveals the lower limit of the joint resistivity: the sum of the resistivity (nΩcm2) of indium (measurable by thickness), the resistivity of Cu/In (<3nΩcm2), and the interface resistivity of the REBCO tape (measurable beforehand). Furthermore, we demonstrated a lower and less varied joint resistivity of In-joints than those of the soldered joints.
Parameter boundaries for the heteroepitaxial growth of REBCO films by e-beam quantitative evaporation on inclined substrate deposited MgO buffered Hastelloy tapes
Authors: Troshyn Oleksiy , Hoffmann Christian , Große Veit , Hänisch Jens , Holzapfel Bernhard 
Published: June 2020

Abstract
The technology of electron beam (e-beam) quantitative evaporation of oxide powders at THEVA is quite unique among the many standard in-situ growth methods of high-temperature superconducting (HTS) films. As well known for YBa2Cu3O7-x (YBCO) film growth the temperature and oxygen pressure should be in proximity of the YBCO stability line in the Bormann diagram. In case of e-beam quantitative evaporation, we observe a shift in the DyBa2Cu3O7-x (DyBCO) stability line towards lower pressures and higher temperatures compared to YBCO. We investigated the temperature and oxygen partial pressure boundaries of epitaxial DyBCO growth on inclined substrate deposited MgO (ISD-MgO) buffered Hastelloy tapes. For completeness, the influence of powder stoichiometry and evaporation rate on HTS epitaxial growth is shown. For the first time high-quality HTS films have been grown by e-beam quantitative evaporation without employing an oxygen shuttle and with oxygen in the chamber background instead.
Angular J
c measurements at 77 K in-field, on an ISD REBCO coated conductor using a straightforward mechanical scribing technique to reduce tape width
Authors: Gurnham C W A , Große V , Hampshire D P 
Published: June 2020

Abstract

E-J traces have been measured on an inclined substrate deposition coated conductor up to 0.7 T as a function of angle at 77K. A large change in J
c is seen on reversal of the direction of the magnetic field, associated with different surface barriers to flux nucleation. The effect of angular hysteresis and field hysteresis on J
c has been found to be much smaller. Narrow bridges have been successfully fabricated by a simple scribing technique using a diamond-tipped scribe and a template. These bridges have been made from 1.4 mm to 4 mm width on the 12 mm width tape, which decrease I
c linearly with width. Measurements before and after the heat treatment for strain gauge glue curing at 170 °C for 120 min have been made and confirm there is no systematic decrease in J
c.
Effect of oxygenation process on flux pinning in pristine and BaHfO3 nanocomposite GdBa2Cu3O7 superconducting thin films
Authors: Popov Ruslan , Ackermann Kai , Rijckaert H. , Hänisch Jens , Van Driessche I. , Holzapfel Bernhard 
Published: June 2020

Abstract
Pristine and BaHfO3 (BHO) nanocomposite GdBa2Cu3O7 (GdBCO) superconducting thin films were deposited at 800 °C, 0.4 mbar O2 partial pressure using a Nd:YAG laser (λ=355 nm) with 10 Hz frequency on MgO substrate. The influence of the oxygenation process on flux pinning and electrical transport properties was investigated by changing the annealing temperature (T
ann) between 450 °C and 780 °C and the holding time (t
hold) between 10 and 30 min. The irreversibility field shows the largest shift toward higher fields for T
ann = 450 °C and thus the largest in-field J
c. Angular dependence of J
c for most of the pristine GdBCO films exhibits a large peak for B‖c, however the sample with T
ann = 550 °C has a large peak in the 90°-120° region, i.e. near B ‖ ab. For BHO nanocomposites, a decrease in T
ann increases in-field J
c by a factor of 2.
Scaling analyses on the critical current density in MgB2/NbN/Si thin film
Authors: Nishida Akihiko , Taka Chihiro , Chromik Stefan 
Published: June 2020

Abstract
Scaling analyses are performed on the critical current density J
c in MgB2/NbN/Si thin film. In our previous work on MgB2/SiC/Si film [Mat. Sci. Eng. 502 (2019) 012184], we have shown that J
c data well scale on a single line with the reduced scaling formula more than 10 orders of magnitude. We extend these studies onto MgB2 film with NbN buffer layer in comparison with SiC buffer. Experimental J
c data under perpendicular magnetic field to the film are reduced against transition temperature and critical field, and applicability of the comprehensive scaling formula is examined over 16 orders of magnitude. Our scaling formula is revealed to be well applicable to the NbN-buffered film as well.
Critical current anisotropy in Fe(Se,Te) films irradiated by 3.5 MeV protons
Authors: Leo A , Grimaldi G , Nigro A , Ghigo G , Gozzelino L , Torsello D , Braccini V , Sylva G , Ferdeghini C , Putti M 
Published: June 2020

Abstract
Irradiation effects are often used to improve the effective pinning in superconductors, but sometimes they can reveal detrimental for superconducting properties. Fe(Se,Te) has been proven to be a very robust material against irradiation, in particular proton irradiation, thus configuring as an ideal material to work in harsh environments such as particle accelerators or fusion reactors. Anyway, the study of the pinning activation energy in Fe(Se,Te) thin film irradiated by 3.5 MeV protons suggests that this treatment can modify the anisotropy of the films pinning. Thus here we present the result of further investigation analyzing the effect of proton irradiation on the critical current and the pinning force both for the magnetic field applied parallel and perpendicular to the sample surface. We find that, although a slight effect on the critical current anisotropy is observed, the pinning landscape is not affected by the irradiation process. This confirms that Fe(Se,Te) can be considered for devices working in harsh environments.
High frequency vortex dynamics in YBa2Cu3O7−x
with Ba2YTaO6-Ba2YNbO6 nanodefects
Authors: Torokhtii K. , Alimenti A. , Rizzo F. , Augieri A. , Celentano G. , Frolova A. , Silva E. , Pompeo N. 
Published: June 2020

Abstract
We studied pinning characteristics of YBa2Cu3O7−x
(YBCO) with 5 mol.% Ba2YTaO6/Ba2YNbO6 (BYNTO). In contrast to widely used d.c methods, at microwaves very short oscillations of the fluxons are involved giving the information on both the pinning strength, through the pinning constant and on dissipation, related to the vortex core physics, through the viscosity η. We estimate the pinning constant kp
, the vortex viscosity η and also the maximum creep factor χmax. The results were compared not only with the pristine YBCO sample but also with the effect of another type of columnar defects (BZO) in YBCO. All film samples were grown by Pulsed Laser Deposition (PLD) technique at nearly the same conditions to ensure the uniform. We detect an improvement of all pinning characteristics of YBCO-BYNTO sample in the temperature range 62 - 90 K and for field up to 0.75 T. While the average diameter of the defects is similar for YBCO-BYNTO and YBCO-BZO the key of the superior characteristics in YBCO-BYNTO could be both the concentration of columns and an addition of another phase of point-like defects.
Effects of Zn doping on the pinning potential and the glass-liquid transition temperature of YBa2Cu3O6+δ
films
Authors: Ackermann Kai , Mai Vadim , Hänisch Jens , Holzapfel Bernhard 
Published: June 2020

Abstract
A pristine YBa2Cu3O6+δ
film as well as two Zn-doped YBa2(Cu1−x
Zn
x
)3O6+δ
films with doping levels x of 0.2 % and 0.4 %, respectively, grown epitaxially on SrTiO3 single crystalline substrates by pulsed laser deposition, were investigated regarding the effect of the doping on the glass-liquid transition line and the pinning potential distribution. Zn doping did not show any effect on the shape of the transition line but caused a suppression of the transition temperature T
GL of about 16 K%−1. Although the doping did not lead to an additional pinning effect, the increase of the critical current density j
c towards lower temperatures is mainly driven by the variation of the threshold critical current density, j
cm. The width of the critical current density distribution j
0 saturates at low temperatures and only drops above ~ 0.9T
GL.
Strictly application-oriented REBCO bulk fabrication
Authors: Floegel - Delor U. , Riedel T. , Schirrmeister P. , Koenig R. , Kantarbar V. , Liebmann M. , Werfel F. N. 
Published: June 2020

Abstract
The ability to produce large-grain REBCO (RE=Y, Rare Earth) bulk superconductors by melt texturing growth has been improved and refined significantly over the last 20 years. Magnetic bearings, transportation systems, and scientific instrumentation are becoming major innovations of HTS bulk materials. Large grain production is dominated by cold top-seeding melt growth (TSMG). For material optimizing we demonstrate strictly application-oriented fabrication close to the final geometry and thus reducing mechanical machining and assembling work. YBCO hollow cylinder design for journal bearings with radial c axes orientation are obtained by radial-seeding geometry (RSMG). YBCO ring tiles up 120 mm show a perfect cylinder geometry with in-wall a, b orientation and radial c axes. We report improved electric and mechanical bulk properties and demonstrate great production effectiveness. For achieving high field permanent magnets up to 10 T we compare YBCO bulk and ring geometry. Top/bottom double seeded melt growth (DSMG) grain samples provide better magnetic flux trapping capability and show more homogenous properties.
Magnetizing characteristic evaluation of REBCO bulk in PFM using different yokes
Authors: Yokoyama K , Oka T 
Published: June 2020

Abstract
A REBCO bulk magnet is able to generate a several-tesla-class magnetic field by a compact system with low power consumption. Pulsed field magnetization (PFM), which is one of major magnetization method, has the advantage that the bulk is activated using a conventional equipment in a few seconds, and, therefore, it is suitable for practical use. However, a trapped field is lower than the maximum performance of material. To increase the field, improvement of magnetization method and modification of exciting equipment are considered. We aim to improve the trapped field by changing the exciting system simply and inexpensively. In the bulk magnet system, soft-iron yokes are generally used to extend the pulse width. This paper evaluated magnetizing characteristic quantitatively. A single pulsed field was applied to a new GdBCO bulk using ϕ64-mm and ϕ80-mm soft-iron yokes. The pulse width of ϕ80-mm yoke was about 35% longer than that of ϕ64-mm yoke. When comparing the trapped flux density and total magnetic flux, these values of ϕ80-mm yoke were higher than those of ϕ64-mm yoke. Also, the temperature rise of ϕ80-mm yoke was decreased by approximately 5% as compared with ϕ64-mm yoke, implying that the same effect as the long-pulse method was achieved.
Comparison of properties of a bulk HTS and a stack of HTS tapes after FC and ZFC
Authors: Kurbatova E , Kurbatov P , Kuschenko E , Sysoev M , Kulaev Y 
Published: June 2020

Abstract
This paper presents the results of the analysis of properties of a high-temperature superconducting (HTS) material in two forms - HTS bulks and a stack made of a number of HTS tape layers. Stack of HTS tape is a new type of application of superconductors, which can be used instead of a convention bulk material. In this work, we study the levitation properties of HTS stack and compare it with the same characteristics of HTS bulks to find the effective way of modelling such type of HTS. Experimental measurements of the force interaction between a permanent magnet and HTS material, as well as a "trapped" magnetic field, are performed for both types of a superconductor. The HTS samples are analysed in the case of Field Cooling (FC) and Zero Field Cooling (ZFC). The aim of the research is to analyse experimental results to compose and justify mathematical models for calculation magnetic system with such types of superconductor.
Effect of oxygen contamination on densification of Fe(Se,Te)
Authors: Masi A. , Alvani C. , Angrisani Armenio A. , Bellusci M. , Celentano G. , Fiamozzi Zignani C. , Fabbri F. , La Barbera A. , Padella F. , Pentimalli M. , Silva E. , Vannozzi A. , Varsano F. 
Published: June 2020

Abstract
The optimization of sintering behaviour of iron chalcogenides superconducting materials is mandatory to enhance their critical current density, in order to pursuit their application in the production of superconducting wires. In this context it has been investigated here the effect of oxygen contamination on the material densification, considering the issues related to industrial oxygen-free isolated production lines. Our results show that the densification process is negatively affected by oxygen contamination. However, despite the difference in density, all sintered samples are characterized by similar structural and morphological features, and show comparable electrical and magnetic properties, with low critical current densities (Jc<103 A/cm2). These results suggest that densification is not the key limiting factor in these conditions, and that grain boundary or misorientation factors may play a greater role in limiting the performance of sintered iron chalcogenides superconductors.
Pulsed Laser Deposition of quasi-multilayer superconducting Ba(Fe0.92Co0.08)2As2-BaHfO3 nanocomposite films
Authors: Meyer Sven , Langer Marco , Grünewald Lukas , Hänisch Jens , Gerthsen Dagmar , Holzapfel Bernhard 
Published: June 2020

Abstract
Quasi-multilayer films with perovskite nano-particles have already been investigated and reported in YBCO compounds. Here, we introduce this technique to iron based superconductors by preparing quasi-multilayer nanocomposite films of Co-doped BaFe2As2 with BaZrO3 and BaHfO3 perovskite nanoparticles by a pulsed laser deposition technique using a frequency-tripled Nd:YAG laser (λ = 355 nm) with separate targets of the constituents. We investigated the enhancement of pinning force density and critical current density in relation to critical temperature reduction. Application-relevant properties are discussed in relation to the deposition conditions and the microstructural properties of the films to better understand growth and behavior of strong pinning centers in these materials.
Effect of annealing on structure and superconducting properties in Fe(Se,Te)
Authors: Masi A. , Alvani C. , Angrisani Armenio A. , Augieri A. , Celentano G. , De Marzi G. , Fiamozzi Zignani C. , Fabbri F. , La Barbera A. , Padella F. , Rizzo F. , Silva E. , Vannozzi A. 
Published: June 2020

Abstract
In this paper, the effect of post synthesis annealing treatments on a Fe(Se,Te) polycrystalline material is evaluated and discussed. The samples have been obtained via melting route. The material has been subjected to a high-temperature annealing treatment, carried out for 45 h at 680 °C. The role of the cooling step was investigated comparing samples obtained after a controlled cooling or after quenching in liquid nitrogen. From a morpho-structural point of view, the annealing treatment improves homogeneity, with respect to pristine samples, and influences secondary phase precipitate morphology. Regarding superconducting properties, a key role of the cooling procedure is assessed: controlled cooling leads in fact to a significant improvement of high field behaviour with respect to the melted material, while quenched samples are characterized by a worsening of the superconducting properties. Despite the overall worsening, however, the quenched samples show evidence of the presence of superconducting phases characterized by a remarkably high critical temperature (Tc
> 18 K), observed for these materials only in films or under pressure.
Microwave impedance study of superconducting (Li1-xFex)OHFeSe single crystal
Authors: Barannik A. A. , Cherpak N. T. , Wu Y. , Zhang X. Q. , Wang J. , Dong X. L. , Sun L. , He Y. S. 
Published: June 2020

Abstract
Microwave (MW) surface impedance Zs
=Rs
+iXs
of the recently discovered high-Tc iron-based superconductor (Li0.84Fe0.16)OHFe0.98Se single crystal was measured for the first time. The special X-band “hot finger" resonator allowed carrying out measurements when temperature of the sample under test can be varied from 2K to 90K and in the same time temperature of the resonator remained constant (4.2K). The unusual and important inequality Rs<Xs
at T≥Tc
=42K was found. The possible reason of the observed feature is considered. The temperature dependence of the quasiparticle σ1
and superfluid σ2
conductivities and structure of energy gap are analyzed. Experiments show the temperature dependence of the field penetration depth as Tn
with n=2.8 at T<Tc
/3. The temperature dependence of the superfluid density confirms fully gapped behavior of a superconductor with a complex gap.
Microwave properties of Fe(Se,Te) thin films in a magnetic field: pinning and flux flow
Authors: Pompeo Nicola , Alimenti Andrea , Torokhtii Kostiantyn , Sylva Giulia , Braccini Valeria , Silva Enrico 
Published: June 2020

Abstract
We present here a microwave (16 GHz) investigation of the complex surface impedance in a dc magnetic field (up to 1 T) of Fe(Se,Te) thin ( 300 nm) films. We derive the vortex parameters: the flux-flow resistivity yields information on the dynamics of the quasiparticles, the Labusch parameter yields a measure of the steepness of the pinning potential wells, and the depinning frequency assesses the frequency range where the material is suitable for high-frequency applications in a dc magnetic field. We compare the results to the data obtained in YBCO, Nb and Nb3Sn.
Nb sheathed MgB2 superconducting tape with addition of VB2
Authors: Da Silva L B S , Andreotti L A , Rodrigues D 
Published: June 2020

Abstract
MgB2 superconductor is a strategic material for practical applications, due to its superconducting properties as well as the low cost of the raw materials. For many technological applications cable, wire or tape format are required. The addition of VB2 in the MgB2 superconducting bulk had already been used in previous works as an efficient method to enhance the critical current density of the MgB2. In the present work, MgB2 superconducting tapes were developed and characterized using different amount of VB2 addition. Niobium was used as sheath material. The goal of this work is to create an efficient method to improve the transport properties of MgB2 superconducting tapes to be useful for practical application. The results include microstructural, crystallographic, magnetic and transport characterizations. All analyzes were performed together to study the influence of the VB2 addition on the superconducting behavior of MgB2 tapes.
Heat treatment influence on microstructure and properties of MgB2 superconductor
Authors: Abdyukhanov I , Tsapleva A , Lukyanov P , Konovalov P , Kotova E 
Published: June 2020

Abstract
Study results of 1 mm diameter MgB2 superconductors fabricated by “powder in tube” method are presented. Ti and Nb were used as diffuse barriers materials. The mixture of magnesium and boron, powder of MgB2, and also mixture of magnesium, boron and MgB2 were used to form superconducting compound. Heat treatments in temperature range of 650-700 °C and 750-900 °C for 1h were conducted. It is established that 1 h heat treatment at 700 °C or 1 h at 900 °C heat treatment are sufficient for formation of MgB2 superconducting phase (Tc=38 K) in superconductors with titanium barrier and powder mixture of magnesium and boron or magnesium, boron and magnesium diboride. The Tc of in-situ process Nb - sheated superconductors was 37.6 K, the same Tc were measured for ex-situ superconductors heat treated at 900 °C for 1 h. The critical current measurement results of fabricated superconductors were presented, optimal heat treatment modes were determined for fabricated superconductors.