Abstract Superconductivity was discovered more than a century ago, and it has achieved full commercialization for MRI and NMR applications. Superconducting technology has got on spotlight recent years for transportation, power network, and fusion energy, due to the significant advantages offered against its counterpart technologies, including lighter weight, compacter size, lower losses, higher efficiency, and higher power density. Therefore, many superconducting applications are moving towards higher technology readiness levels, with a fast pace. The accelerated research around superconducting applications for modern transportation is due to unique features of this technology towards decarbonisation via electrified systems. Meeting the Net Zero targets to decelerate global warming issue is the main driver of implementing the superconducting technology for aerospace, marine, and railway transport. However, many challenges still remain to be addressed for superconducting devices and applications, which will in turn pave the way for the commercialization of superconducting technology. In this article, a roadmap on electrification of transportation systems for aerospace, marine, and railway application is presented, covering challenges and solutions in design analysis, modelling, monitoring, and operation. A series of short articles are presented to outline the potential applications and solutions. These potential futuristic routes and their materials/technologies are considered/suggested for a 10-20 years time-frame.

Pulsed laser deposition (PLD) of biaxially oriented cuprate superconducting films rapidly progresses from versatile research method to large scale production method. This development is likely the first example when PLD gets to industrial production tool. In this article we have thoroughly reviewed vast literature data on PLD of YBa2Cu3O7 superconductor coatings on buffered metal tapes and compared these observations with our own experimental results. This comprehensive comparison allowed us to determine for the first time practically useful limits of superconducting performance of PLD-derived YBCO tapes in dependence on underlying buffer layer misorientation and film thickness. We also demonstrate that the PLD process has remarkably low power consumption and enables high-rate production without any performance degradation. We elaborate on further development of high power excimer lasers for superconductor tape production.

REBa2Cu3O7-delta (REBCO, RE: rare earth element) coated conductors (CCs) have superior in-field performance compared to low-temperature superconductors and Bi-based superconductors, however, due to its crystal structure, REBCO CCs exhibit significant anisotropy, i.e., critical current density (J(c)) is generally high for B // a-b and low for B // c-axis. Isotropic angular dependence would be ideal for such applications as magnets and coils, because anisotropic angular dependence will hinder current carrying capability in the winding and also make it more difficult for quench protection. To realize an isotropic angular dependence, artificial pinning centers (APCs), such as BaMO3 (M: Metal), have been introduced to enhance J(c) for B // c-axis. However, it is still challenging to enhance pinning over all angles. In this study, we investigated a possible way to improve the angular dependence of REBCO CCs by applying face-to-face double-stacked (FFDS) configuration. Our previous study showed that FFDS interface resistivity is around 50 n Omega cm(2) at 77 K, enabling sufficient current sharing with small enough dissipation in cases of local J(c) degradation in one side of the REBCO CC. In addition, Based on this finding, we examined whether to compensate for the angular dependence of the REBCO CCs. We made a FFDS CC by combining two REBCO CCs with different angular dependences, i.e., YBa2Cu3O7-delta (YBCO) CC with low J(c) for B // c-axis and EuBa2Cu3O7-delta (EuBCO) with BaHfO3 (BHO) doping CC which has high J(c) for B // c-axis. Current-voltage (I-V) measurements at various angles confirmed that FFDS CCs facilitate current sharing under applied fields. As a result, we analyze the I-V characteristics by applying an equivalent circuit model and confirmed the more isotropic angle dependence of I-c properties as designed. In conclusion, the FFDS configuration provides a practical means to current-carrying performance compared to the original CC strands and presents a practical method for tailoring REBCO CCs angular dependence with flexibility.

During the fabrication of commercial REBa2Cu3O7-x (REBCO; RE: rare-earth element)-coated conductors (CCs), inhomogeneities with low critical current (I-c) are occasionally introduced, which may result in electromagnetic instability, particularly at low temperatures. To mitigate the degradation of the current carrying capabiity caused by these defects, we developed long face-to-face double-stacked (FFDS) CCs via reel-to-reel solder bonding process. Previously, we successfully fabricated 400-m-long FFDS CCs via this process and investigated their mechanical properties. However, the current transport properties are still unclear. In this study, we investigated the interfacial resistivity of the FFDS CCs made by the continuous soldering process, and it was confirmed that the joint resistivity is consistently between 40 to 50 n Omega cm(2) where the joint distances were changed to 3.5, 5.0, and 11.6 cm. In addition, the effect on the current carrying capability was also examined by using model samples in which we introduced artificial defects with almost 50% drop of local I-c. It has been demonstrated demonstrated that the transport current can be recovered at almost 85 to 90% of a defect-free CCs, with I-c nearly two times of the strand, thanks to the current sharing effect through the solder joints. Namely, the interface resistivity of 40-50 n Omega cm(2) by our process was sufficiently small to obtain a current sharing effect and suppress the influence of the local inhomogeneity effectively.

The rapid advancement of second-generation high-temperature superconductors, especially REBCO materials, underpins innovations in energy, medicine, and transport. Pulsed laser deposition (PLD) stands out as a premier method for producing high-quality REBCO thin films with controlled composition and microstructure-crucial for achieving high critical current density (Jc) and temperature (Tc). This review synthesizes recent progress in PLD-grown REBCO films, detailing how parameters such as laser energy, deposition temperature, background pressure, and substrate design influence superconducting performance. Special attention is given to nanoengineering, doping, and multilayer techniques that enhance flux pinning, as well as innovations in PLD setups-including multi-beam and high-rate processes-to enable industrial-scale production. The review also discusses the integration of artificial intelligence and machine learning for optimizing film properties and accelerating discovery. By comparing strategies and results from academia and industry, this work provides a comprehensive roadmap for advancing PLD-based REBCO superconductor technology.

This study investigates the impact of heavy ion irradiation on the superconducting performance of second-generation high-temperature superconducting (2G-HTS) wires in strong magnetic fields. We have performed irradiation experiments using 18 MeV Au, 12 MeV Ni and 15 MeV O ions accelerated by a tandem ion accelerator, targeting 2G-HTS wires composed of YBCO, EuBCO/BHO, GdBCO, or (NdEuGd) BCO. The superconducting properties of these wires were measured under various magnetic fields and temperatures. Our results indicate that oxygen ion irradiation has minimal effect on Ic(B) characteristics. In contrast, nickel ion irradiation at doses of 1.2 x 1011 ions cm-2 significantly improved Ic(B), particularly at lower temperatures (20-30 K), without rapid material degradation at higher doses. Similarly, gold ion irradiation is enhanced Ic(B) across a wide range of temperatures and fields. TRIM simulations suggest that ion penetration and energy loss vary by ion type, affecting defect formation and superconducting performance. The presence of heavy rare-earth elements in the HTS material increased susceptibility to ion irradiation, leading to more pronounced improvements in Ic. These findings demonstrate the potential of ion irradiation as a practical method for enhancing the superconducting properties of 2G-HTS wires, paving the way for their industrial application in high-field environments.

To suppress the anisotropy of the angular dependence of the critical current density Jc(theta) under high-temperature ( T similar to 77K) and low-magnetic-field ( B less than or similar to 3T) conditions, where superconducting motor and generator applications are anticipated, we fabricated a bilayer structure comprised of a YBa2Cu3O 7-delta (YBCO) thin film containing Y2O3 nano-particles ('Y-NP' layer) atop a EuBa2Cu3O 7-delta (EuBCO) thin film containing BaHfO3 nano-rods ('Eu-NR' layer) deposited on a buffered metallic substrate. By comparing vortex pinning properties of the Eu-NR/Y-NP bilayer sample with those of single-layer Eu-NR and Y-NP samples, we found that introduced BaHfO3 nano-rods (BHO NRs) in the Eu-NR layer primarily enhance Jc(theta) near the B parallel to c direction, whereas the Y2O3 nano-particles (YO NPs) improve Jc(theta) near the B parallel to ab direction, where the effect of BHO NRs is less prominent. This complementary effect of BHO NRs ( theta similar to 0deg) and YO NPs ( theta similar to 90deg) successfully reduced the Jc(theta) anisotropy at B [T]less than or similar to 8-0.375(T [K]-65). Simulations of the Jc(theta) anisotropy factor based on the measured Jc(theta) data suggest that optimizing the volume fraction of Y-NP and Eu-NR layers could further minimize the Jc(theta) anisotropy depending on (T, B) conditions.

GdBa 2 Cu 3 O 7-δ (GdBCO) coated conductors (CCs) are promising wire materials because of their high critical temperature and critical current density in magnetic fields. The CCs must contain superconducting joints to create long wires. Previously, we fabricated a GdBCO CC with a superconducting joint by face-to-face crystallization of two CC samples with a GdBCO precursor film. To obtain a high current and low resistance, the crystallinity of GdBCO and a wide joint area are key considerations. This study investigates the effect of the heat-treatment temperature and precursor film thickness on these two factors. GdBCO samples were prepared without or with a precursor film of ∼50–200 nm thickness via pulsed laser deposition. The samples were set face-to-face and crystallized at 700-820 °C under a mechanical pressure of 40 MPa in an electric furnace. X-ray diffraction (XRD) analysis and optical microscopy revealed that both the peak intensity ratio of crystallized GdBCO and the joint rate at 800 °C were respectively 1.5 and 1.6 times higher than that at 720 °C. As the precursor film thickness increased from 50– 200 nm, the joint rate increased from 15.7– 25.4%, indicating that the heat treatment at ∼800 °C with a thick precursor film, is suitable. The results of this article lead to that the proposed method used in GdBCO CCs to reduce the electrical resistance.

For the development of electric propulsion aircrafts with light weight, low emission and high efficiency, MW-class fully superconducting synchronous machines operating at liquid nitrogen temperature were conceptually designed with REBa 2 Cu 3 O 7- δ (REBCO) superconducting tapes in our previous studies. To verify the actualization of the structure and cooling method, a 1 kW-class prototype fully superconducting synchronous motor was designed and constructed in this study. The fixed armature was cooled with subcooled liquid nitrogen at 65 K. The rotor was cooled with helium gas. The pole number was two for the future high speed operation. The applicability of the complicated casing structure with three chambers into fully superconducting motor was also investigated from the viewpoint of thermal insulation. The operations as a motor up to 500 rpm and a generator demonstrated that the designed structure and cooling method were reasonable and effective for cooling the fixed armature and rotating field windings.

The fusion power density produced in a tokamak is proportional to its magnetic field strength to the fourth power. Second-generation high temperature superconductor (2G HTS) wires demonstrate remarkable engineering current density (averaged over the full wire), JE, at very high magnetic fields, driving progress in fusion and other applications. The key challenge for HTS wires has been to offer an acceptable combination of high and consistent superconducting performance in high magnetic fields, high volume supply, and low price. Here we report a very high and reproducible JE in practical HTS wires based on a simple YBa2Cu3O7 (YBCO) superconductor formulation with Y2O3 nanoparticles, which have been delivered in just nine months to a commercial fusion customer in the largest-volume order the HTS industry has seen to date. We demonstrate a novel YBCO superconductor formulation without the c-axis correlated nano-columnar defects that are widely believed to be prerequisite for high in-field performance. The simplicity of this new formulation allows robust and scalable manufacturing, providing, for the first time, large volumes of consistently high performance wire, and the economies of scale necessary to lower HTS wire prices to a level acceptable for fusion and ultimately for the widespread commercial adoption of HTS.

In this work, we present a study of the resistive transition in magnetic field of 2G high-temperature superconductor wire samples with BaSnO3 (BSO) artificial pinning centres (APCs) in a GdBa2Cu3O7-x (GdBCO) superconductor. The GdBCO layer was fabricated by pulsed laser deposition, using production equipment to obtain samples with varied concentrations of APC: 0, 6, 12 and 18mol% of BSO. Resistive transition curves were measured in the magnetic field range from 0 to 9 T, and magnetic field orientations from B parallel to c (theta =.0 degrees) to B parallel to ab (theta = 90 degrees) with an angle step of 15 degrees. We observed an irreversibility temperature peak at the B parallel to ab orientation. We determined the angular regions where correlated pinning centres dominated and found them to expand with the increase of BSO concentration. The activation energy (U-a) obtained from the lg(rho/rho(0)) against the 1/T plots was almost constant in the whole angular range, with a small peak at B parallel to ab. The activation energy as well as the irreversibility temperature decreased with the increasing doping level, but the U-a(theta) curves looked similar for all samples with APCs. The logarithmic resistivity plot of the undoped sample looked substantially different from those of the APC samples, with a kink and two different slopes corresponding to two regions with different U-a. We discuss that this difference is related to the different pinning landscapes in samples with and without APCs.

We investigate the field, angle and temperature dependence of the full-width critical current, I-c, of pulsed laser deposition-grown GdBa2Cu3O7 coated conductors with and without additional 6 mol% BaSnO3 (BSO) nanoparticles fabricated by SuperOx. The transport characteristics measured from 7 to 77 K and in applied magnetic fields of up to 6 T are complemented by scanning transmission electron microscopy. This combined approach allows for further insight into the vortex pinning mechanism and helps with understanding the enhancement in I-c. An exemplary scaling of the pinning force curves versus field at different temperatures confirms the additional contribution to pinning by the BSO nanoparticles. Through the temperature dependence of I-c, the weak and strong pinning contributions are determined: strong pinning dominates over almost the entire temperature range especially near the matching field of 1 T, where the largest enhancement in I-c is achieved.

Superconducting joints have been demanded to lengthen REBa2Cu3Oy-coated conductors for electrical power applications. In this study, we propose a new joint method for GdBa2Cu3Oy-coated conductors via crystallizing precursor films additionally deposited on the conductors. Two GdBa2Cu3Oy-coated conductors with precursor films were placed in a face-to-face manner in a furnace, then they were crystallized under mechanical pressure to joint them. A superconducting joint was achieved with a high critical temperature of 90.8 K. Microstructural observation by a transmission electron microscope revealed that there were only a few pores at the joint boundary without a secondary phase having c-axis-oriented GdBa2Cu3Oy.

There has been demand to lengthen superconducting joints of REBa2Cu3Oy coated conductors to realize magnet applications. In this work, jointed samples of GdBa2Cu3Oy coated conductors were prepared by crystallizing precursor films deposited by a pulsed laser deposition method under mechanical pressures, and influence of the pressures on superconducting and mechanical properties were investigated. While areal fraction and shearing stress of the joints were increased by increasing the pressure, superconducting properties were degraded. X-ray diffraction analysis indicated that the degradation was due to the formation of a secondary phase and decrease of oxygen contents in GdBa2Cu3Oy.

We present the preparation of a new architecture of coated conductor by Inkjet printing of low fluorine YBa 2 Cu 3 O 7-x (YBCO) on top of SuperOx tape: CGO/LMO/IBAD-MgO/Y 2 O 3 /Al 2 O 3 /Hastelloy. A five-layered multideposited, 475-nm-thick YBCO film was structurally and magnetically characterized. A good texture was achieved using this combination of buffer layers, requiring only a 30-nm-thin ion-beam-assisted deposition (IBAD)MgO layer. The LF-YBCO CC reaches self-field critical current density values of J c GB ~ 15.9 MA/cm 2 (5 K), ~1.23 MA/cm 2 (77 K) corresponding to an I c (77 K) = 58.4 A/cm-width. Inkjet printing offers a flexible and cost effective method for YBCO deposition, allowing patterning of structures.

When the critical current density J(c) for a superconductor is constant, the critical current I-c increases in proportion to the superconducting cross-sectional area. However, in the case of a superconducting coated conductor, when the thickness of the superconducting layer exceeds about 2 mu m, there is no further increase in I-c. This is because J(c) decreases due to the structural degradation of the superconducting layer. In this study, J(c) for samples with superconducting layers of different thicknesses was measured using the longitudinal magnetic field effect in order to investigate the optimum layer thickness for maximizing I-c. Differences in the J(c) characteristics due to the layer thickness appeared more clearly under a longitudinal magnetic field than a transverse magnetic field. This was particularly true at low temperatures, and the optimum layer thickness was found to be approximately 1 mu m.