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Influence of the buffer material addition to the liquid for the YBa 2 Cu 3 O y (Y123) growth in liquid phase epitaxy (LPE) process and the suitable constructions of the LPE coated conductors were investigated for both MgO- and NiO-saturated systems. In the MgO-saturated system, influence of MgO addition to the liquid was negligible in Y-solubility in liquid and the peritectic temperature ( T p ) value. The double layered LPE films of YBa 2 Cu 3 O y layer on YBa 2 (Cu,Mg) 3 O y layer, which were grown from MgO-saturated liquid, was grown on the Hastelloy tape with an MgO buffer layer. However, the growth of the second layer was unstable. It was found that the partial melting back of the first layer during dipping of the second layer growth is the reason for the unstable growth of the second layer. The problem was solved by lowering the growth temperature for the second layer than that of first layer due to selection of RE in RE123. On the other hand, NiO-addition made T p of the Y123 phase decrease and the crystallization temperature increase. This means that the possible temperature range for stable growth of the YBa 2 (Cu,Ni) 3 O y phase becomes narrow due to NiO addition. This problem was also solved by the selection of RE element in RE123 with high T p . The double layered construction was confirmed using Y123(LPE)/Sm123-Ni(LPE)/NiO/Ni. Consequently, the suitable constructions for each system were developed.

We have investigated the influence of increasing the thickness on the alignments of Y123 films for long Y123 tapes with metallic substrates using the PLD method. As increasing the thickness of the Y123 films, the ratio of the a-direction increases in comparison with that of the c-direction for the alignment of the Y123 films to the surface of the substrates but the in-plane alignment did not change. The tendency was remarkable as increasing the frequency of the laser or decreasing the temperature of the substrates. It was found that the relationship with the alignment of the Y123 films on the substrate and those parameters could be explained by the general idea of the melt growth. In result, it was found that the Y123 films should be prepared under the low frequency and the high substrate temperature of the PLD method to hold on the alignment of the c-direction as increasing the thickness of the Y123 films.

Scale-up matters for ion-beam-assisted deposition (IBAD) method was surveyed on biaxially textured yttria-stabilized-zirconia (YSZ) buffer layer by using 66 cm ×6 cm square-shaped RF-discharged ion source. Textured YSZ films with the in-plane mosaic spread ( Δφ ) of 9–15 were obtained in the growth area of 60×8 cm 2 by optimizing the beam collimation for the assisting Ar ions. 5.5 m long YSZ textured template layers were formed with 0.1 m/h by IBAD on Ni–Cr alloy tapes with the Δφ of 12–13° in whole length. The Δφ of 10.8° was obtained in a short tape moved with 0.3 m/h. Y-123 films were deposited by PLD on the YSZ templates with tape shifting speed of 1.0 m/h. I c of 84.0 A and J c of 0.76 MA/cm 2 were obtained at 77 K, 0 T in the length of 1.0 m with Δφ for the Y-123 film was 7°.

The critical current density (Jc) distribution in YBCO coated conductors is attracting interest from the viewpoint of its influence on their AC loss characteristics as well as from material science and process engineering. A two-dimensional Jc distribution in a YBCO coated conductor made by the IBAD (ion-beam assisted deposition) and the PLD (pulse-laser deposition) method can be determined by the magnetic-knife method with spatial resolutions of 0.2 mm lateral and 10 mm longitudinal directions, respectively. In an up-to-date 80A-class YBCO coated conductor, the Jc is relatively uniform in the central part and reaches \mbox{7$×$109 A m-2, } while the Jc fluctuates spatially in the central part of a tape fabricated earlier and with less critical current. Near the edges of the tapes, the Jc is higher or lower than in the central part and the experimentally determined Jc distributions are far from uniform. This suggests that a presumption of a uniform Jc for AC loss estimations is not always reasonable and can lead to a large error in the estimated AC losses.

A liquid phase epitaxy (LPE) process on a metal substrate has been developed for the RE123 coated conductors. In order to prevent the reaction between the solvent and metal substrate, which is the first problem to be solved, for its development, an MgO buffer layer on the metal substrate was applied, since MgO is relatively stable in the liquid solvent. However, it disappeared when the substrate was dipped into the liquid. This phenomenon was clarified by a solubility measurement that was not due to melting but due to dissolution. Then, a combination of using a buffer layer and a saturated liquid by the MgO was considered to prevent the dissolution. Actually, the MgO buffer layer retained and it protects the Hastelloy substrate from the reaction. Additionally, it was clarified that there is little difference in Y 2 O 3 solubility in the liquid with and without the MgO addition in the liquid. The Mg substituted Y123 LPE layer was grown at a similar growth rate even from MgO-saturated liquid under the same temperature conditions for the growth of Y123 from the solvent without MgO. Furthermore, the Y123 layer was grown from the liquid without MgO on the Mg substituted Y123 LPE layer to obtain the high superconducting characteristics. The double layered LPE film on MgO single crystal substrates revealed a high T c value of 90 K and a high J c value of 10 5 A/cm 2 at 77 K. Then, the new construction of RE123(LPE)/RE123–Mg(LPE)/MgO/Hastelloy was proposed for applying the LPE process to the coated conductor production. The fabrication of the construction on Hastelloy substrates was achieved.

Growth of REBa2Cu3Oy (REBCO, RE=Y, Nd) crystals on the MgO substrates by the liquid phase epitaxy (LPE) process was investigated in order to clarify the growth mechanism. The in-plane alignment of crystal orientation was improved during the LPE process due to preferential dissolution and growth, even from the polycrystalline seed film. It was found that the orientation of preferential growth depended on the kind of RE for the REBCO system. The phenomenon could be explained by the coarsening mechanism, considering the interfacial energies between the REBCO and the MgO crystals. The preferential growth mechanism could be understood by considering both the lattice matching and the Coulomb force between the REBCO crystal and the substrate materials at the interface. The calculation results were in good agreement with the experimental results.

Growth of the REBa2Cu3Oy (REBCO, RE = Y, Nd) crystals on the MgO substrates by the liquid phase epitaxy (LPE) process was investigated to clarify the growth mechanism. The crystal orientation of in-plane alignment was improved during the LPE process due to the preferential dissolution and growth even from a polycrystalline seed film. The orientation of preferential growth depended on the kind of RE for the REBCO system. The phenomena could be explained by the coarsening model by introducing the difference in the interfacial energies, which were considered not only general lattice matching but the Coulomb force at the interface between the REBCO and the MgO crystals. The preferential growth model was developed, and the calculation results showed a good agreement with the experimental results.

Continuous deposition of Y-123 tapes was performed by ion-beam-assisted deposition (IBAD) and pulsed laser deposition (PLD) method. YSZ template films were deposited by IBAD on Ni-based alloy tapes with tape shifting speeds of 0.1-0.3 m/h. They were uniformly coated with an in-plane mosaic spread of 12-13 degrees in 5 m length. In order to overcome the low deposition rate of the IBAD process, large area ion sources with inductively coupled discharge plasma were applied. Y-123 films were deposited by PLD on the YSZ templates with a tape shifting speed of 1.0 m/h. The degradation of Y-123 targets for the PLD process was effectively restricted by combined motion of rapid rotation and linear shifting. I/sub c/ of 84.0 A and J/sub c/ of 0.76MA/cm/sup 2/ were obtained at 77 K, 0 T in the length of 1.0 m when the in-plane mosaic spread for the Y-123 film was 7 degrees. I/sub c/ of 35.0 A and J/sub c/ of 0.25MA/cm/sup 2/ were obtained in a 4.6 m long sample at the length of 4.0 m, when the in-plane mosaic spread for the Y-123 film was 11 degrees.

We tried to apply NiO materials as a buffer layer for LPE (Liquid Phase Epitaxy) coated conductors with Ni substrate. We confirmed that NiO could suppress the reaction between NiO/Ni substrate and solution saturated with NiO. On the other hand, NiO addition to the solution decreased the peritectic temperature of the Y123 and increased the crystallization temperature of the Ba-Cu-Ni-O compound. This makes it difficult to grow the Y123 crystal from the NiO saturated solution. Instead of Y123, we selected Sm123 which has a higher peritectic temperature than Y123, and confirmed that Sm123 could be grown stably from the NiO saturated solution not only on MgO substrate but also Ni substrate. Because of its low T/sub c/ value of Sm123 grown from the NiO saturated solution, the (Y,Yb)123 layer was epitaxially grown as the superconductive layer on it from the solution without NiO.

In Fujikura, a large-scale ion-beam-assisted deposition (IBAD) system with a large ion source has been employed to fabricate biaxially textured MgO films. The large-scale IBAD system has multiple deposition lanes where substrate tapes move, and therefore we have to optimize experimental conditions at each lane. We selected an appropriate deposition area and, finally, we successfully fabricated a 1 km-length IBAD-MgO film at a production rate of 1 km/h. We also studied pulsed-laser-deposited (PLD) CeO 2 films directly on the IBAD-MgO films in spite of a large lattice mismatch between CeO 2 and MgO. From transmission electron microscope (TEM) observations at an interface between MgO and CeO 2 films, it is revealed that there is domain-matching-epitaxy relationship between MgO and CeO 2 films. We also fabricated thin (1.0 μm) and thick (3.7 μm) PLD – GdBa 2 Cu 3 O 7− x (GdBCO) film on the long-length CeO 2 /MgO substrate (over 150 m). Critical currents ( I c ) and current density ( J c ) were over 300 A and 3 MA/cm 2 respectively for the thin GdBCO film and were about 645 A and 1.7 MA/cm 2 for the thick GdBCO film at 77 K in self-field.

The fabrication process of REBa 2 Cu 3 O y (RE123: RE=Y, Sm, Nd3·) system superconducting tapes was developed using the Hastelloy substrate by the liquid phase epitaxy (LPE) process. The reaction between Hastelloy and the BaCuO melt is prevented by an MgO buffer layer for the melt saturated with MgO. The suitable construction for tape processing by LPE was consequently found as YBa 2 Cu 3 O y (Y123) 〈by LPE〉 / YBa 2 (Cu,Mg) 3 O y (Y123(Mg)) 〈by LPE〉 / MgO / Hastelloy. The superconducting properties of the Y123 layer with this construction were confirmed on the MgO single crystal substrates. The Y123 / Y123(Mg) / MgO structure revealed a high T c value of 91 K and a J c value of 1.2×10 5 A/cm 2 (77K, 0T). For short smaples, the Y123(Mg) layer was successfully grown on Hastelloy substrate with MgO by the LPE process. For the fabrication of long LPE conductors, the ability of the long tape LPE apparatus was confirmed as a preliminary study in which the Y123 layer was grown on the MgO substrates by laterally moving the substrates on the melt surface.

The mechanism of improving the in-plane alignment of LPE-grown YBCO films on MgO substrate was investigated by the experiments and model analysis. The preferential dissolution and growth of the islands in seed film due to the difference in the in-plane alignment relationship between the island and substrate were observed even when the size of the seed islands were similar. The phenomena can be explained by the coarsening mechanism by considering the difference in the interface energies between YBCO grains and MgO substrate. The preferential growth model was developed based on the above idea. The results of the calculation by the model are in good agreement with the experimental results.

The initial stage of growth for YBa2Cu3Ox (Y123) films on (100) MgO substrates by liquid phase epitaxy (LPE) was investigated. In the initial stage, Y123 seed films partially dissolved into BaO–CuO solution, and Y123 islands were epitaxially grown from the undissolved seed grains on an MgO substrate within 1 s. It was found by XRD analysis that the LPE films with grain orientation of fourfold symmetry on the surface of MgO substrate were grown from not only a fourfold symmetrical seed film but also an eightfold symmetrical one. This phenomenon cannot be fully explained by the coarsening mechanism due to the curvature difference. The difference in the interface energies between Y123 and MgO should be considered to understand the preferential dissolution and growth.

For practical applications of high-temperature superconductor tape, the high production rate of tapes is needed to reduce its cost. Recently, the long-length coated conductor with high performance has been fabricated by an ion beam assisted deposition/pulsed laser deposition (IBAD/PLD) method in Fujikura. In IBAD process, we adopted IBAD–Gd2Zr2O7 (GZO) film. The process speed of IBAD–GZO film was increased up to 5 m/h using a polished metal substrate tape. To fabricate biaxially-textured buffer layers at a higher rate, we have started to develop another structures such as (a) IBAD–GZO/IBAD–MgO (3-fold symmetry) and (b) IBAD–MgO (4-fold symmetry). In the case (a), we fabricated GdBCO/CeO2/IBAD–GZO/IBAD–MgO tape and the critical current was Ic = 550 A/cm (2.46 MA/cm2) and throughput of IBAD processes were 20 m/h. In the case (b), IBAD–MgO short samples with ΔΦ of 9°–11° were obtained at 500 m/h. The 500 m/h (10 mm width) is extremely high rate in IBAD process in the world. As long-length IBAD layer 10 m, 50 m and 100 m IBAD–MgO films were fabricated at the speed of 100 m/h. After CeO2 deposition, in-plane textures of these samples were ΔΦ of 3.7°–3.7°, 4.1°–4.9° and 4.2°–4.8°. Using some of these buffer layers, we have obtained GdBCO film with Ic = 400 A/cm (2 MA/cm2, 10 m) and Ic = 550 A/cm (2.7 MA/cm2, short sample).

Long-length and low-cost coated conductors are necessary for practical use such as motor, generator, transformer, fault current limiter, SMES and so on. For fabricating low-cost coated conductors, production speeds at each process should be faster. The structure of coated conductor we adopted, is GdBa2Cu3Oy(GdBCO)/CeO2/Gd2Zr2O7 (GZO)/metal. To make processes faster without changing such beneficial structures, we adopted another buffer layer under GZO film. At the IBAD (ion-beam-assisted deposition) process, MgO is known as one of the suitable materials to achieve high alignment with thin film thickness. We fabricated IBAD-MgO film with changing deposition rates and ion-current densities, and got two types of IBAD-MgO film. One is the film with its crystal orientation aligned to the MgO(1 1 1) parallel to the tape surface, and the other is with MgO(1 0 0). And each film has in-plane texture such that 3-fold symmetry, and 4-fold symmetry respectively in the pole figure of MgO . We performed IBAD-GZO on the 3-fold IBAD-MgO film, and got 4-fold IBAD-GZO film. In-plane textures of GZO were not so different from the ordinary IBAD-GZO film, but the thickness of the films became from 1.2 μm to 0.3 μm (1/4). And a critical current of the GdBCO film on the buffer layer was over 210 A/cm (Jc > 1.5 MA/cm2) at 77 K.

We have obtained the good superconducting performance in Y-123 tapes made by Ion-Beam-Assisted Deposition (IBAD) and Pulsed Laser Deposition (PLD) method. In this paper, we describe recent progresses of long Y-123 conductor by IBAD/PLD process using reel to reel systems. Ic of 88 A was obtained in end to end of a 217 m long one. Furthermore, we developed the conduction cooled HTS test solenoid coil using 100 m-Y123 conductors. The results of coil operating tests are described.

Gd2Zr2O7 (GZO) layers were deposited on rolled, mirror like polished and electropolished Ni-based alloy (Inconel) tapes by the ion-beam-assisted deposition (IBAD) method and were investigated especially in terms of the effect of substrate roughness on the crystal grain alignment. Their surface roughness, Ra, was 7.6–12.3 nm, 4.3–4.7 nm and 1.4–3.4 nm, respectively. The deposition time was varied from 1 h to 6 h. Crystalline alignment of these films was observed by X-ray diffraction (XRD) and cross-sectional transmission electron microscope (TEM). The grain alignment of the IBAD–GZO was improved by using flat surfaces. GZO film on the electropolished substrate got to align from closer point near the interface than that on rolled substrates.

Two kinds of Ag-sheated YBaCuO tapes, prepared with the same starting composition but annealed under different conditions, showed prominently different superconducting properties. A scanning electron microscope equipped with an energy dispersive X-ray spectrometer, and a transmission electron microscope, were employed to observe the microstructure as well as the localized compositions of these tapes. For the specimen having a very small value of J c , many small precipitates of an impurity phase are formed in the matrix of (123) phase. The (123) phase in this tapedoes not include any stacking faults. On the other hand, for the specimen showing a rather high value of J c (∼ 700 A/cm 2 ), stacking faults due to fluctuations in the (001) lattice spacing are frequently formed. The (124) phase is found in small, local areas in this sample. The pinning sites of the magnetic flux are proposed.

IBAD-Gd 2 Zr 2 O 7 (GZO) film was fabricated on polycrystalline Ni-based alloy tape by the IBAD-system with 110 cm × 15 cm ion source. Using long-length faraday-cup-array, effects of argon gas-flows on ion-current densities were investigated. As a result, lower gas-flow leads to higher ion-current density at the substrate in the system. Under the condition of low gas-flow, 10 m (with production speed of 5 m/h), 60 m (3 m/h) and 500 m (5 m/h)-length IBAD-GZO films were fabricated and their in-plane textures were Δ ϕ = 15°, 13° and 18°, respectively. After that, PLD-CeO 2 experiments were performed on the IBAD-GZO substrates with Δ ϕ = 15° and 13°, and then CeO 2 films with Δ ϕ = 5.5° and 5.7° were achieved with the tape-speed of 5.0 m/h and 10.0 m/h, respectively.

REBa2Cu3Oy, (RE : rare earth elements, RE123) coated conductors are expected to show high performance in superconducting applications, due to their high mechanical strength and high current density in magnetic fields. Fujikura has developed ion-beam-assisted-deposition (IBAD) and pulsed-laser-deposition (PLD) technique, and today we routinely manufacture coated conductors with length over 500 m and Ic over 500 A/cm-width at 77 K, self field. We have also been able to fabricate long conductors with higher Ic by thickening RE123 layer. Although Ic performances at 77 K, self field are important, but performances in magnetic fields at lower temperatures below 77 K are more important for coil applications. In this work, we evaluated coated conductors with thick RE123 layer in magnetic fields at low temperatures. All samples are fabricated with long length. We measured samples by four-probe transport method at wide temperature range from 77 K to 10 K by using cryo-cooled cryostat. A conductor with 5.5 μm thick RE123 exhibits high Ic values of 937 A/cm-width at 77 K, self field, 637 A/cm-width at 50 K, 5T and 976 A/cm-width at 40 K, 5T.

A large-scale IBAD system with the world largest ion source was employed to fabricate ion beam-assisted deposition (IBAD) MgO films. Finally, we successfully fabricated a 1 km-length IBAD-MgO film at a production rate of 1 km/h. We also studied pulsed laser deposited (PLD) CeO 2 films directly on IBAD-MgO films. An observation at the interface between MgO and CeO 2 films by a transmission electron microscope (TEM), showed that a CeO 2 film was finely textured on an IBAD-MgO film though a lattice mismatch was large (28.5%). Then we fabricated PLD–GdBa 2 Cu 3 O 7− x (GdBCO) film on the CeO 2 /MgO substrate. Critical currents ( I c ) and critical current density ( J c ) of the films were over 300 A and 3 MA/cm 2 at 77 K, self-field.

We have investigated the influence of MgO in liquid for the LPE growth process of Y123 film. From the measurement of the Mg-solubility of solution for LPE growth, it was found that the existence of MgO in liquid scarcely influences the peritectic temperature of Y123 and the Y-solubility. The Mg-substituted Y123 LPE layer was grown on an MgO substrate from the MgO-saturated solution. Additionally, the Y123 LPE layer was grown from the solution without MgO under almost the same temperature condition as that for the Mg-substituted Y123 growth on the MgO substituted Y123 Layer. The Y123 LPE layer on Mg-substituted Y123 LPE layer revealed a Tc value of 90 K.

The fabrication process of Y-system superconducting films on Hastelloy substrates by the Liquid Phase Epitaxy (LPE) method was developed. The reaction between Hastelloy and the oxide melt was prevented by an MgO buffer layer for MgO saturated oxide melt. Consequently, the suitable construction for tape processing by LPE was found as YBa2Cu3Oy /YBa2(Cu,Mg)3Oy /MgO/ Hastelloy. The ability of this system superconducting properties were confirmed using MgO single crystal substrates. Y123 /Y123(Mg) /MgO revealed a high Tc value of 9IK and a high Jc value of 1.2 X 105 A/cm2(77K,0T). Finally, the continuous YBa2 (Cu,Mg)3Oy layer was succeeded in growing on Hastelloy substrates.

Sm1+xBa2-xCu3Oy(Sm123) films on MgO substrates with seed films were prepared by the Liquid Phase Epitaxy(LPE) process. The initial growth mechanism of Sm123 LPE films was investigated by vertical dipping. In the initial growth stage of LPE, the seed films partially dissolved into BaO-CuO melt, and then island crystals of Sm123 were grown epitaxially. The relative angle of θ=45° between the [100] direction of the Sm123 island crystal and the [100] direction of the MgO substrate was preferentially grown with dissolving of the other island crystal with θ=0°. It is found that the preferential dissolution phenomenon could be explained by the difference bonding at the interface between Sm123 and MgO. It was also found that the growth rate in the Sm system was higher than that of the Y system under the same undercooling.

We have investigated the relationship of the grain alignment between the seed films and the LPE films. It was found by XRD analysis that four fold symmetrical LPE films on the surface of MgO substrates were grown not only from a four fold symmetrical seed film but from an eight fold symmetrical one. These results could be explained by means of the coarsening mechanism using the difference in interface energies between the Y123 grains and the MgO substrate with different orientations.

The initial stage of YBa2Cu3Ox (Y123) films grown on (100) MgO substrates by liquid phase epitaxy (LPE) was investigated. Y123 films could not be grown on MgO substrates by LPE directly but it was grown successfully on the MgO substrates with Y123 thin films deposited by vapor phase growth methods. In the initial stage Y123 seed film partially dissolved into BaO-CuO solution, and Y123 islands were epitaxially formed on an MgO substrate within one second. It is found that the dissolution phenomenon could be explained by means of the Ostwald ripening mechanism.

We have designed and constructed a prototype model of superconducting power cable (77kV, 3kA) consisted of superconductor, electric insulation, thermal insulation, going and returning LN2 paths for cooling, and corrugated aluminum sheath with PVC layer. Length of the model cable was 1m. Critical Current of the model cable, in which one of ten grooves in the copper former was filled with Bi-2223 Ag sheathed tapes, was 180A at 77K. Degradation of critical current by electric insulator winding or heat cycles up to five times was not observed.

Increase of production rate and improvement of quality for RE123 coated conductors have been tried. In-plane texturing of MgO was attempted by the IBAD system with the world largest ion source. As a result of optimizing condition in large deposition area, the dramatically high throughput of 1000 m / h was realized to obtain the IBAD-MgO with Δ 600 A except some locations was obtained at the throughput of 15 m / h. In addition to the speed-up, the very high Ic of 1040 A was also achieved by the hot-wall heating PLD system.

Utiligation of MgO as a buffer layer for LPE(Liquid Phase Epitaxy) growth of YBa 2 Cu 3 O y (Y123) was investigated. In order to investigate the reaction, the tapes with MgO layers were dipped into the melt of two different compositions. The tape was completely dissolved into the melt without addition of MgO. However, the tape survived in the MgO-saturated solution. The modified LPE process was developed which is the Y123 LPE growth using the Y123 layer saturated with MgO as the second buffer layer to prevent dissolution of the first MgO buffer layer into the melt.

We have studied the ion-beam-assisted deposition (IBAD)-MgO process using a large IBAD system with a large ion source. Using the large IBAD system, we successfully fabricated a long-length IBAD-MgO tape (1 km) at a production rate of 1 km h−1. We have also studied a process to deposit CeO2 films directly on IBAD-MgO tapes. It is revealed that the CeO2 film is fully textured at about 100 nm. GdBa2Cu3O7−x (GdBCO) film was fabricated on a 180 m-long CeO2 /IBAD-MgO film. Its critical current (Ic) and current density (Jc) were over 300 A and 3 MA cm−2 at 77 K, self-field.

We have studied the use of a hot-wall heating system for producing GdBa2Cu3O7?X (Gd123) films with large critical current (Ic), stably, at high speed, by a pulsed laser deposition (PLD) method. We achieved a material yield from the PLD system with hot-wall heating of about 50% through optimization of the evaporation conditions. With the PLD system, we were able to fabricate a Gd123 film about 20?cm long with a high Ic of 997?A (77?K, self-field) at about 6??m thickness. The maximum Ic that we achieved for a Gd123 film about 2?cm long was 1040?A (77?K, self-field) at about 6? ?m thickness. Furthermore, we were able to form a Gd123 film about 1? ?m thick and 20?cm long with an Ic of 352?A (77?K, self-field) at a high speed of 60? m?h?1 using high laser power. For the production of long conductors coated with RE123 (REBa2Cu3O7?X, where RE stands for rare earth) using hot-wall heating, it was found that RE123 coated conductors over 100?m long with Ic of over 200?A had uniform Ic distributions with ? 2% variations in the direction of the length.

We fabricated a long-length GdBCO(GdBa2Cu3O7-?) coated conductor by the ion-beam assisted deposition (IBAD) and the pulsed laser deposition (PLD) methods. The GdBCO tape was over 400 m in length with 1.5-2.0 MA/cm2 of the critical density. The critical currents of the tape were over 304.8 A/cm along 368 m in length. So we have achieved Ic ? L = 112,116 Am. For the IBAD process, we have already developed 500 m-length IBAD-Gd2Zr2O7 (IBAD-GZO) tapes with highly aligned in-plane texture, and continuously fabricate 250 m-length tapes at a rate of 0.5~1 km/month. In addition, we have also developed a new type template for the IBAD-GZO, to enable the production rate fast. Structure of the template is IBAD-GZO/IBAD-MgO/Y2O3. It is note that MgO (111) is parallel to the substrate normal and three fold symmetry. For this structure, the film thickness of the IBAD-GZO could lessen from 1.2 ?m to 0.3 ?m. By the new IBAD buffer layer, a production rate is expected to be over 30 m/h.

Four 5 mm wide YBCO conductors were assembled face to face to obtain a stacked YBCO conductor (YBCO stack). The space between the conductors composing the YBCO stack was set at 1.0 mm to investigate the influence of the space on AC loss characteristics. The magnetization losses without transport current, the transport losses without external magnetic field, and total AC losses of the YBCO stack carrying various transport currents in transverse magnetic fields with various orientations were measured. The measured AC losses in the YBCO stack were compared with those in a 0.2 mm space YBCO stack composed of the same conductors used in the 1.0 mm space YBCO stack as well as a single YBCO conductor. Magnetization loss without transport current in a YBCO stack decreases with decreasing space between the conductors in low and intermediate magnetic field. Transport loss without external magnetic field in a YBCO stack increases with decreasing space between conductors. There are three characterized regions, when comparing the total AC losses in the two YBCO stacks with different space between the conductors composing the stacks: (a) in the low magnetic field region, the total AC losses in the YBCO stack with smaller space are larger than those in the YBCO stack with larger space, (b) in the intermediate magnetic field region, the total AC losses in the YBCO stack with smaller space are larger than those in the YBCO stack with larger space, (c) in the high magnetic field region, the total AC losses in both YBCO stacks agree well with those in the single YBCO conductor as well as Brandt and Indembom's analytical values.

Longitudinal homogeneity and REBa2Cu3Ox: RE123 thickness dependence of in-field superconducting properties for commercial RE123 coated conductors (C.C.) were measured at varied temperatures. Self-field Ic homogeneity for typical ∼500-m long samples were evaluated below 2% measured by continues reel-to-reel measurement. In-field Ic distributions were not changed at temperatures from 10K to 77.3K, being estimated by Ic measurements at separated points of a 1 km long sample. Linear dependences of in-field Ic on RE123 thickness up to 5 μm were observed at temperatures of 20K and 77.3K, in contrast with non-linear dependences observed for self-field Ic for RE123 films. The results indicate good longitudinal homogeneity and universal linearity of thickness dependence for in-field Ic at wide temperature range, which suggest simple scaling for in-field Ic of RE123 wires among different temperatures.

Current transport properties in YBCO coated tapes have been studied by the low temperature scanning laser microscopy (LTSLM) as well as the four‐probe method. The LTSLM measurement allows us to visualize the local resistive transition with a spatial resolution of a few μm. It has been shown that the localized resistive region percolates into the sample as the bias current density is increased. From the LTSLM measurements, we can estimate the spatial distribution of the inhomogeneous Jc. Relationship between the local Jc distribution and the global E‐J characteristics has also been investigated. The percolation probability obtained based on the LTSLM measurement agreed quantitatively with that of the four‐probe measurement. Namely, those two measurements support the percolation model.