Ataru Ichinose

Central Research Institute of Electric Power Industry | CRIEPI · Grid Innovation Research Laboratory, Electric Facility Technology Division

Magnesium diboride (MgB 2 ) thin films were fabricated on Fe tapes by an electron-beam evaporation method and post-annealed at 650 °C for 1–5 h. Appropriate post annealing (1 h) resulted in a critical temperature ( T c ) of 34.4 K and infield critical current density ( J c ) of 0.20 MA/cm ² at 20 K under 6 T. Characterization suggests that annealin...

Anomalous changes in irreversibility lines ͑ILs͒ and critical current properties depending on growth conditions were demonstrated in ErBa 2 Cu 3 O y films with Ba-͑Nb,Er͒-O nanorods. Despite the formation of nanorods in the matrix at all growth temperatures ͑T s ͒, Bose-glass-like vortex pinning was strengthened with decreasing T s. In particular,...

Effects of columnar defects created by 320MeV Au irradiation on 2H-NbSe2 single crystals with a dose equivalent matching field (BΦ) up to 16 T were studied. Critical temperature (Tc) is found to be suppressed almost linearly at a rate of 0.07K/T. At the same time, the lattice parameters a and c are found to be expanded at rates of 0.016%/T and 0.03...

Effects of columnar defects created by 320 MeV Au irradiation on 2H-NbSe2 single crystals with a dose equivalent matching field up to 16 T were studied. Critical temperature is found to be suppressed almost linearly at a rate of 0.07 K/T. At the same time, the lattice parameters a and c are found to be expanded at rates of 0.016%/T and 0.030%/T, re...

Incorporation of a dopant, an impurity, and a non-superconducting second phase in superconducting films is an important approach to control the superconducting property. In spite of extensive studies on the oxide superconducting nanocomposite films, the influence of additive materials on the phase formation and nanostructure is unclear in the iron...

Preferred orientation and optical responses were studied for BaBiO3 films grown by pulsed laser deposition. BaBiO3 films have a monoclinic symmetry I2/m, with the (110) preferred orientation on SrTiO3 (001) substrates. From the transmittance spectra of BaBiO3 films, optical bandgaps were estimated to be around 2.3 eV for direct transition and 2.1 e...

Despite the formation of twinned microstructures in grains of REBa2Cu3Oy with y ~ 7, their grains can be biaxial aligned under modulated rotating magnetic fields (MRFs). In the present study, direct observation of twinned microstructures by transmission electron microscopy (TEM) was examined for a magnetically biaxial aligned grain of DyBa2Cu3Oy wi...

The effect of SnO2 addition (0, 1, 2, 4 w%) on thermoelectric properties of c-axis oriented Al-doped ZnO thin films (AZO) fabricated by pulsed laser deposition on silica and Al2O3 substrates have been investigated. The best thermoelectric performance has been obtained on the AZO + 2% SnO2 thin film grown on silica, with a power factor (PF) of 211.8...

We report the critical current density (Jc) and vortex pinning properties in single crystals of a novel iron-based superconductor (IBS) KCa2Fe4As4F2 with large Jc in the pristine state, before and after introduction of artificial defects by swift-particle irradiation. The effects of 2.6 GeV U and 3 MeV proton irradiations in KCa2Fe4As4F2 single cry...

Over the last 20 years, technologies for manufacturing rare-earth barium copper oxide (REBCO)-coated conductors have undergone a steady development. Currently, the properties of these conductors are reasonably stable owing to the intensive efforts of the manufacturers. However, for high-field magnet applications, such as the magnets used in nuclear...

Nanocomposite films are thin films with the addition of nano-sized second phases, and they are very promising for improving properties of chalcogenide films, such as superconducting vortex pinning. However, there are very few reports on the chalcogenide nanocomposite films, although many researchers are studying the oxide nanocomposite films. Since...

Muon spin rotation/relaxation measurements were performed to investigate magnetic properties of FeSe1−xSx thin films on LaAlO3. A drastic decrease of the initial asymmetry was observed together with the peak structure in the temperature dependence of the relaxation rate of muon spins almost at the same temperature where kink anomalies were observed...

Muon spin rotation/relaxation measurements were performed to investigate magnetic properties of FeSe$_{1-x}$S$_x$ thin films on LaAlO$_3$. A drastic decrease of the initial asymmetry was observed together with the peak structure in the temperature dependence of the relaxation rate of muon spins almost at the same temperature where kink anomalies we...

Jelly-roll (JR) processed wires using metal thin foils as starting materials have excellent cold workability and drawability. We have successfully fabricated Nb/Al composite mono-core wires having 50 m in outer diameter and over 400 meters in length. Furthermore, some of the wires were additionally drawn to 30 m in outer diameter. It is known that...

CaKFe4As4 is a new member of the 1144-type iron-based superconductors (IBSs) which is expected to show remarkable superconducting properties because its crystal structure is similar to that of 122-type IBSs. Recently, substantial anisotropy between the in-plane and out-of-plane critical current densities (Jc), with peculiar temperature dependence o...

We propose a novel fabrication technique based on the formation of a Nb protective layer on a MgB2 thin film and high-temperature post-annealing to increase the critical current density (Jc) of MgB2 films under an external magnetic field. Analyses of the crystal structure and the composition of the processed MgB2 films confirmed the suppression of...

We present a systematic study of electrical resistivity, Hall coefficient, magneto-optical imaging, magnetization, and scanning transmission electron microscopy (STEM) analyses of KCa2Fe4As4F2 single crystals. Sharp diamagnetic transition and magneto-optical imaging reveal homogeneity of single crystal and prominent Bean-like penetrations of vortic...

ARTICLE scitation.org/journal/adv Microstructure of YBa 2 Cu 3 O y coated conductor using {100} ⟨001⟩ textured Cu tape with dual functions of metal substrate and electric stabilizing layer in order to develop low-cost high-T C superconducting wires ABSTRACT A new configuration of coated conductors (CCs), REBa 2 Cu 3 Oy (RE: rare earth elements such...

To optimize the production cost of REBCO-coated conductors, the deposition rate needs to be increased. The vapour-liquid-solid (VLS) growth technique is a suitable method for fabricating a film with a high deposition rate and good crystal orientation. This technique enables growth through a liquid phase. There have been studies conducted on the fab...

Introduction of columnar defects to superconductors through particle irradiation enhances their critical current density ( J c ) . Further enhancement of J c by dispersing the direction of columnar defects has been confirmed. Moreover, in such systems with splayed columnar defects, an anomalous peak effect in J c at a certain magnetic field determi...

Jelly-rolled Nb/Al composite monofilamentary wires having an outer diameter of 50 microns and more than 100 meters in length were successfully fabricated. Moreover, some of these thin wires were additional drawn to 30 microns in outer diameter in this study. We recognized again that jelly-rolled Nb/Al composite monofilamentary wires have excellent...

We present a systematic study of electrical resistivity, Hall coefficient, magneto-optical imaging, magnetization, and STEM analyses of KCa${_2}$Fe${_4}$As${_4}$F${_2}$ single crystals. Sharp diamagnetic transition and magneto-optical imaging reveal homogeneity of single crystal and prominent Bean-like penetrations of vortices. Large anisotropy of...

A novel configuration for coated conductors (CCs) was proposed to reduce material cost and consisted of YBa 2 Cu 3 O y (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 SrTiO 3 (N...

High-temperature superconducting REBa2Cu3Oy (RE: Rare earth elements, REBCO) films need both a high-speed film fabrication with a well-oriented crystalline texture and an introduction of artificial pinning centers (APCs) to improve critical current densities Jcs in magnetic fields．A vapor-liquid-solid (VLS) growth method enables the REBCO films to...

To develop a low-cost coated conductor, a new wire architecture using conductive buffer layers and a metal tape with high conductivity has been proposed. Nb-doped SrTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (Nb–STO) was chosen as the conductive buffer layer. A high J <sub xmlns:mml=...

The potential of thermoelectric thin films lies in wide range of applications from micro-energy harvesting to the sensors. For this, it is essential to have high power factor and ultra-low thermal conductivity which have been reported in thin films produced by expensive vacuum techniques. However, for practical applications, it is essential to use...

To adopt coated conductors to various superconducting devices, characteristics such as microstructure and critical current of commercially available coated conductors were investigated. The microstructure was analyzed using a transmission microscope with an energy dispersion spectroscopy. The critical current (IC) were measured at 4.2 K and magneti...

formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> $\rm BaTbO_3$ (BTbO) is one of artificial pinning center ma-terials and forms thick rectangular nanorods with diameters of ∼20 nm when it is doped high. We expected that the rectangular na-norods would produce in-plane anisotropy of flux pinning. In...

Three independent components of critical current density, one for the H//c axis and the other two for the H//ab plane, have been studied in CaKFe4As4 single crystals. When the magnetic field is applied along the c axis, we observed fish-tail-like peaks in the M−H hysteresis loop, and the magnetization at higher temperatures exceeds that at lower te...

Three independent components of critical current density, one for the H//c axis and the other two for the H//ab plane, have been studied in CaKFe4As4 single crystals. When the magnetic field is applied along the c axis, we observed fish-tail-like peaks in the M-H hysteresis loop, and the magnetization at higher temperatures exceeds that at lower te...

In the longitudinal magnetic field state, critical current density (Jc) of a superconductor enhances compared with the Jc in self-field and it is called as Jc gain. We have reported Jc gain in BaHfO3-doped-multilayered (ML) SmBa2Cu3Oy(Sm123) films on oxide single crystalline substrates. In this study, we aim for the Jc gain appearance in ML-Sm123 f...

Columnar defects (CDs) along a-axis were installed into an in-plane aligned a-axis-oriented $\rm YBa_{2}Cu_{3}O_{y}$ film by using heavy-ion irradiation, in order to clarify the influence of CDs on flux pinning properties around B || ab. The critical current density $J_{c }$ at B || c significantly decreases after the irradiation, since the CDs...

For development of a low-cost superconducting wire operating at high-temperature, we propose a new approach using conductive rather than insulating buffer layers, combined with {100}001 textured pure Cu tape to form YBa 2 Cu 3 O 7 (YBCO)/Nb-doped SrTiO 3 /Ni/Cu/stainless steel. The critical current density of the YBCO layer was 2.5 MA cm ⁻² at 77 K...

The longitudinal magnetic field (LMF) state, in which the magnetic field is applied parallel to the applied current direction and ab-plane of SmBa 2 Cu 3 O y (Sm123) films with shaped artificial pinning centers (APCs) of various shapes is investigated. The in-field critical current density (J c ) of pure Sm123 films in the LMF state and films with...

Superconducting FeSe0.8Te0.2 thin films on SrTiO3, LaAlO3 and CaF2 substrates were electrochemically etched in an ionic liquid, DEME-TFSI, electrolyte with a gate bias of 5 V. Superconductivity at 38 K was observed on all substrates after the etching of films with a thickness greater than 30 nm, despite the different Tc values of 8 K, 12 K and 19 K...

We systematically investigated the influence of columnar defects (CDs) on the flux dynamics around B || ab in YBa2Cu3O7-δ (YBCO) films, where two types of the crossed CD configurations with the crossing angle relative to the c-axis, θ i = ±30° and ±60°, were prepared by using 200 MeV Xe ion irradiation. The crossed CDs with θ i = ±30° induce a peak...

Critical temperatures (Tc) comparable to those of bulk materials were achieved by post-annealing MgB2 thin films grown at a low temperature of 280 °C. The Tc was improved to 36.7 K under annealing conditions of 550 °C for 50 h or more. Under these annealing conditions, a critical current density several tens of times higher at than that of MgB2 wir...

Effects of 3 MeV H+ (proton) irradiation on superconductivity in BaFe2(As0.67P0.33)2 was investigated through in situ resistivity measurements and magnetotransport measurements. The suppression of Tc by H+ irradiation is more moderate in comparison with electron irradiation, yet more effective than that of irradiation of heavier He+ ions. Surprisin...

Effects of bimodal splayed columnar defects in Ba1−x K xFe2As2 and Ba(Fe1−x Co x)2As2 single crystals through 2.6 GeV U irradiation and 220 MeV Au irradiation are investigated. Magnetic field profiles measured by magneto-optical imaging clarified the presence of in-plane anisotropy of the critical current density (J c) in 2.6 GeV U irradiated cryst...

Superconducting FeSe0.8Te0.2 thin films on SrTiO3, LaAlO3 and CaF2 substrates were electrochemically etched in an ionic liquid DEME-TFSI electrolyte with a gate bias of 5 V. Superconductivity at 38 K was commonly observed on all substrates after etching the films with a thickness above 30 nm, in spite of different Tc of 8 K, 12 K and 19 K before th...

Through 2.6 GeV U irradiations, we have induced bimodal splayed columnar defects in Ba1−xKxFe2As2 single crystals with splay angles, ±5∘, ±10∘, ±15∘, and ±20∘. Critical current densities through magnetization measurements were carefully evaluated, where a splay angle of ±5∘ brought about the highest Jc. Magneto-optical images close to Tc indicate h...

Recently, we observed that Ba2SmNbO6 (BSNO), which has a double perovskite structure, forms wide nanorods in a SmBa2Cu3Oy (SmBCO) film when compared with BaHfO3 (BHO) nanorods. These wide nanorods can trap flux quanta effectively in low magnetic fields; on the other hand, narrow nanorods can trap flux quanta in high magnetic fields. In this paper,...

Two approaches to reducing the material cost of second-generation superconducting wires are proposed in this paper: (1) instead of the electrical stabilizing layers of silver and copper presently used on the superconducting layer, a Nb-doped SrTiO3 conductive buffer layer and cube-textured Cu are proposed as an advanced architecture, and (2) the us...

A high flux pinning performance was obtained for a 3.8 vol % BaHfO3-doped SmBa2Cu3O y superconducting film on a metallic substrate. At a temperature of 77.3 K, an irreversibility field of 16.8 T and the maximum flux pinning force density of 32.5 GN/m³ in fields applied parallel to the c-axis of the film were achieved, which are the highest values r...

Long-length coated conductors (CCs) have recently become commercially available, serving as a promising candidate for use in electric power applications. However, the material and manufacturing costs are high, which discourages their use in a wide range of commercially feasible products. REBa2Cu3O7 (REBCO; RE: Y or rare-earth elements) superconduct...

The effect of incorporation of nanoscale Y2BaCuO5 (Y211) inclusions on the vortex pinning properties of YBa2Cu3O7-δ (YBCO or Y123) superconducting thin films is investigated in detail on the basis of variation of critical current density (JC) with applied magnetic field and also with the orientation of the applied magnetic field at two different te...

Conventionally, δT c type (order parameter modulation) and δl type (mean free path modulation) pinning mechanisms have been proposed to explain the temperature dependence of the flux pinning of superconducting materials. According to previous studies, it is assumed that the temperature dependence of J c of REBa2Cu3O7 (REBCO, RE =Y, Gd, Sm, etc) fil...

This paper reviews the progress of studies to determine optimum shapes of the artificial pinning center (APC) of REBa2Cu3Oy thin films and coated conductors towards superconducting magnets operating at temperatures of 77 K or less. Superconducting properties vary depending on the kind and quantity of BaMO3 materials. Therefore, we study changes in...

We prepared SmBa2Cu3O y (SmBCO) films including Ba2SmNbO6 (BSNO) by Nd:YAG pulsed laser deposition (PLD) on LaAlO3 single-crystalline substrates. The BSNO formed many nanorods with a large diameter of 35 nm, which is the largest nanorod diameter in REBa2Cu3O y films, and their in-plane distribution was random. The matching field estimated from the...

The nanoengineering approach by PLD method can produce a variety of complex nanocomposite oxide thin films with unique properties for sustainable applications. We report on the epitaxial growth and superconducting properties of YBa2Cu3O7-x (YBCO) multilayers incorporating BaSnO3 (BSO) nanorods and Y2O3 nanoparticles at the same time in order to com...

We report the effects of heavy-ion irradiation on FeSe single crystals by irradiating uranium up to a dose-equivalent matching field of Bϕ=16 T. Almost continuous columnar defects along the c axis with a diameter of ∼10 nm are confirmed by high-resolution transmission electron microscopy. Tc is found to be suppressed by introducing columnar defects...

The influence of Y2O3 nanolayers on thermoelectric performance and structure of 2% Al-doped ZnO (AZO) thin films has been studied. Multilayers based on five 50 nm thick AZO layers alternated with few nanometers thick Y2O3 layers were prepared by pulsed laser deposition on Al2O3 single crystals by alternate ablation of AZO target and Y2O3 target. Th...

Superlattice thin films composed of iron chalcogenides, FeSe and FeTe, were grown via pulsed laser deposition. The X-ray diffraction patterns show clear satellite peaks demonstrating periodic stacking structures of FeSe and FeTe. The FeTe layers have the a-axis lengths identical to those of the FeSe layers, indicating that the FeTe layers are coher...

CoFe2O4(CFO)-doped BaTiO3(BTO) film is one of composite multiferroic materials. In the materials, magnetoelectric effect occurs from the stress of the interface between ferroelectric and ferromagnetic. Therefore, Interfacial stress between BTO and CFO is important for magnetoelectric effect. However, it has not been clearly yet. It is considered th...

REBa2Cu3Oy (REBCO; RE: rare-earth elements)-coated conductors (CCs) have high potential for use in superconducting devices. In particular, REBCO CCs are useful for superconducting devices working at relatively high temperatures near 77K. The important issues in their applications are high performance, reliability and low cost. To date, sufficient p...

We investigated the effect of the BaHfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BHO) nanorods' configuration on transport properties at artificial grain boundaries (GBs) in SmBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <s...

To control the anisotropy of critical current density (J c), hybrid artificial pinning centers (APCs) of elongated-nanorods and segmented-nanorods were incorporated into YBa2Cu3O7 films. The elongated-nanorods and segmented-nanorods were formed by fabricating multilayer films using YBa2Cu3O7+BaSnO3 targets with a different BaSnO3 content. According...

Microstructure of FeSe1-xTex thin films near the interface to CaF2 is investigated by means of transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). TEM observation at the initial crystal-growth stage reveals that marked lattice compression occurs along the in-plane direction in the films with Se-rich composition, while...

Multilayers (MLs) comprising of YBa2Cu3O7(YBCO)+BaSnO3(BSO) layers with different BSO content were fabricated, and their critical current density (J c) was measured to understand influence of ML structure on vortex pinning. Elongated and segmented nanorods were observed in the MLs, and ab-plane aligned nanoparticles appeared depending on BSO conten...

In accordance with the results of our previous research, a low-temperature growth (LTG) technique is effective for expanding the lower growth temperature region of c-axis-orientated SmBa2Cu3O y (SmBCO) thin films. However, BaHfO3 (BHO)-doped LTG films show a marked decrease in J c at low magnetic fields compared with conventional PLD films. In this...

In order to improve critical current density (Jc) of REBa2Cu3Oy (RE: Rare Earth elements) films, it is effective to dope BMO3 (BMO, M=Zr, Sn, Hf, Sn, Nb) nanorods into the REBCO films. The shape of the BMO nanorods depends on the kind of materials. In this study, we doped Ba2SmNbO6 (BSNO) nanorods which has large lattice constant of 0.8518 nm into...

The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by $R_H^{-1} = -en$, where $e$ is the charge of the carrier, and $n$ is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was d...

Columnar defects (CDs) were installed into YBa2Cu3Oy thin films at the crossing angle ±θ i relative to the c-axis using 200 MeV Xe ions, in order to clarify the influence of ±θ i on the angular behaviours of critical current density J c. The width of a J c peak occuring at B || c linearly increases with broadening CD-crossing angle, where its shape...

BaMO3 (M=Hf, Sn)-doped Sm1+xBa2−xCu3Oy (x=0, 0.04) superconducting films were fabricated by pulsed-laser deposition (PLD). It is known that BaMO3 nanorods are formed in superconducting films and that the morphology of nanorods affects the superconducting properties, particularly the critical current density (JC) properties. In this study, supercond...

Long length coated conductors (CCs) have recently become commercially available, serving as a promising candidate for use in electric power applications. However, the cost of materials and manufacturing is high, which discourages their use in widespread commercially feasible products. REBa2Cu3O7 (REBCO; RE: Y or rare-earth elements) superconducting...

BaSnO3 (BSO) nanocolumns and Y2BaCuO5 (Y211) nanoparticles have been successfully incorporated into YBCO thin films by premixed and surface-modified target approach. The effect of these artificially incorporated nanostructures on the vortex pinning properties of YBCO films is investigated based on the variation of critical current density (J(C)) wi...

YbBa2Cu4O8 (Yb124) films were fabricated using metal-organic deposition method, and crystal growth of c-axis oriented films was discussed based on transmission electron microscopy (TEM) and X-ray diffraction. The c-axis oriented YbBa2Cu3O7-x (Yb123) and Yb124 films were formed depending on annealing time and temperature. Yb123 grew in high temperat...