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REBa2Cu3Ox (REBCO, RE = rare earth) coated conductors (CCs) are promising as superconducting wires for high-field magnets because of their high in-field critical current density (Jc) performance and high tensile tolerance. Fujikura, Ltd., has been developing BaHfO3 (BHO)-doped EuBa2Cu3Ox (EuBCO, Eu = Europium) CCs using a hot-wall-type pulsed-laser deposition (PLD) in order to further improve the in-field performance. Although a high deposition rate in the PLD process is necessary for mass production, it has been found that the in-field performance greatly differ depending on the deposition rate. In this study, flux pinning properties of BHO-doped EuBCO CCs fabricated with different deposition rates by the hot-wall PLD on IBAD substrates were investigated in detail. From the scaling characteristics of the flux-pinning force density (Fp) curve, the BHO precipitates in a fast deposition rate REBCO film appeared to behave like random pinning centers, which was almost consistent with a result of transmission electron microscope observation. On the other hand, from a decrease of anisotropy in the magnetic field angle dependence of Jc, it was also confirmed that BHO precipitates were not completely random pinning centers, that is, it has some kind of anisotropy. Considering the critical current value per production time, it was also found that the fast deposition rate is advantageous since the REBCO layer could be thicker.

Fujikura Ltd., Chiba, Japan, has developed stable and high-throughput production techniques for REBCO coated conductors (CC) by using large-area ion-beam-assisted-deposition (IBAD), and hot-wall type pulsed-laser-deposition (PLD). Recently, we have been attempting to dope BaMO 3 (BMO, M: Zr or Hf) to REBCO layer in order to enhance in-field critical current density (J c ). In the course of optimizing deposition conditions of PLD for BaHfO 3 doped EuBCO films on IBAD templates, “high J c condition” and “high growth rate condition” were found. For samples prepared under these conditions, the magnetic field angle dependence of I c and REBCO thickness dependence were investigated. Finally, we succeeded in fabricating a 300-m-long CC with uniform I c distribution at the high-growth-rate condition. The longitudinal I c homogeneity (defined as standard deviation divided by average) at 77 K evaluated by magnetization method was 2.6%, which is comparable to nondoped conductors. Transport in-field I c for the both end points were 1756 and 1786 A/cm at 30 K, 2 T, respectively.

BaMO 3 (BMO, M: Zr or Hf)-doped REBCO-coated conductors were prepared by Hot-Wall PLD method on IBAD template. The highest J c was obtained for BaHfO 3 -doped EuBCO. Quite strong pinning force density (F p ) of 1.6 TN/m 3 was observed at 4.2 K, 15 T, for a sample deposited with growth rate of ~5 nm/s. It had strong c-axis correlated pinning at the temperature above 20 K with the matching field of ~5 T. A 45-m-long sample was formed by productive high growth rate over 20 nm/s, being consistent with commercial nondoped conductors. It had also large I c of 1687 A/cm and F p of 0.96 7 TN/m 3 was obtained at 4.2 K, 15 T. The end-to-end longitudinal Ic homogeneity (σ) at 77 K in low field was evaluated to be 2.2% by magnetization. Transport in-fields I c were also measured for the both end points at 30 K, 2 T, resulting in 1863 and 1883A/cm, respectively.

Recent development of production technique for RE123 coated conductors was reviewed, using Hot-wall PLD/ IBAD process. Lot-to-lot distributions for both average value and longitudinal uniformity of Ic at 77 K, 0 T were summarized for 127 run of 300-500-m-long 10-mm-wide CC. By optimizing hotwall PLD process parameters we found a reproducible high Jc production condition (20% enhancement in field at 20 K), less angular dependent to applied magnetic field. Furthermore, new hermetic type Cu stabilization foil configuration was developed and general mechanical properties against tensile strain, etc. were surveyed.

We have developed an ion-beam-assisted-deposition (IBAD) and a pulsed-laser-deposition (PLD) technique to produce REBa 2 Cu 3 O x (RE123, RE: rare earth) coated conductors with high performances. Distributions of critical currents ( I c ) in the longitudinal direction were improved in most wires routinely fabricated under optimized process. A typical wire showed I c of 460 A/cm at 77 K and self-field, about 200 A/cm at 65 K and 3 T and about 300 A/cm at 50 K and 5 T. In addition, further high I c values over 800 A/cm were also obtained in thick films. Finally, we succeeded in fabricating an 816.4 m long wire with end-to-end I c of 572 A/cm, corresponding to the new world record I c × L value of 466,981 Am/cm.

We have developed a characterization method for two-dimensional imaging of critical current density in coated conductors (CCs) based on scanning Hall-probe microscopy (SHPM). The distributions of the magnetic field around a sample were measured for several different conditions of external magnetic fields, and then were converted to those of the sheet current density which flowed to shield the external magnetic field or to trap the penetrated magnetic field. As a result, it was found that the amplitude of the sheet current density corresponded to that of critical current density almost in all the area of the sample except for the region where current direction changed. This indicates that we could obtain an in-plane distribution of the critical current density with a spatial resolution of around 100 μm in non-destructive manner by this method. We believe that this measurement will be a multifunctional and comprehensive characterization method for coated conductors.

We have carried out observations of current flow in processed RE123 coated conductors using a scanning Hall-probe microscope. Using this system, the position of defects and the resulting disturbed current flow could be observed. The two-dimensional current distribution in a 10-filament formed coated conductor (400 mum width and 100 mum space) was also investigated. Current sharing and the current distribution in each filament were quantitatively estimated. Furthermore, current penetration in quasi-static AC current mode was also measured.

By an IBAD/PLD method, a 500 m-length high-performance GdBa2Cu3Ox (GdBCO) coated conductor with BaZrO3 (BZO) was fabricated. End-to-end Ic of the 503.5 m tape was 349.6 A/cm at 77 K, corresponding Ic times L value of 176,023 Am. New approaches to decrease the thickness of IBAD buffer layers were developed by combination of IBAD-MgO(111) and IBAD-Gd2Zr2O7 (GZO). The maximum Jc of the GdBCO on the buffer layer was 550 A/cm. We also started to investigate IBAD-MgO(OOl) by using a large IBAD system with a 110 cm times 15 cm ion source. A 50 m-length IBAD-MgO tape with DeltaPhi of 13deg was fabricated at a 100 m/h-1 pass. Insulated REBCO wires with Cu or Ni-Cr lamination were developed using 5 mm-wide conductors sliced from 10 mm-wide IBAD/PLD tapes. Practical long insulated wires were supplied for several prototypes of motors, transformers and fault current limiters in fiscal 2007.

Four 5 mm-wide YBCO conductors with identical critical current were assembled face to face to obtain a stacked YBCO conductor. The magnetization losses without transport current, the transport losses without external magnetic field, and the total AC losses of the stacked YBCO conductor as well as a single YBCO conductor carrying various transport currents in transverse magnetic fields with various orientations were measured. The difference between the AC loss characteristics of the stacked YBCO conductor and those of the single YBCO conductor was clarified.

Three YBCO coated conductors with various critical currents, up to 189 A, were prepared. The magnetization losses without transport current and the total AC losses of the conductors carrying various transport currents in transverse magnetic fields with various orientations were measured electromagnetically to study the AC loss characteristics systematically. The measured total AC losses were compared with the numerical values using a one-dimensional FEM model

Thick YBa2Cu3O7-x (YBCO) films with high critical current density (Jc) values were deposited by pulsed-laser deposition (PLD) on Hastelloy with a textured CeO2/Gd2Zr2O7 buffer layer. Both cross-sectional and plan-view TEM specimens of the YBCO films were prepared, and then the nanostructural characterization of the films was performed by transmission electron microscopy (TEM). The YBCO films less than 1 μm thick were predominantly composed of c-axis-oriented grains, however, many a-axis-oriented grains, which grew larger with the increase of the thickness of the YBCO film, were formed beyond about 1 μm from the CeO2 interface. We found Y2O3 and copper oxides between a- and c-axes-oriented grains. In particular, Y2O3 grains were formed between the {001} plane of an a-axis-oriented grain and the {100} or {010} plane of a c-axis-oriented grain. The orientation relationships between Y2O3 and YBCO are found to be; (001)YBCO//(001)Y2O3 and (100)YBCO//(110)Y2O3. In addition, we also found gaps between YBCO grains. Since a-axis-oriented grain growth and the formation of Y2O3, copper oxides and the gaps are considered to reduce the J c values of the YBCO film, it is important to determine the optimum process conditions to suppress the nucleation of a-axis-oriented grains, impurity oxides and gaps.

Current transport characteristics in a Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) coated conductor fabricated by a trifluoroacetates-metal organic deposition (TFA-MOD) process were investigated over a wide range of temperature and magnetic field up to 25 T. Improved TFA-MOD process was successfully introduced for the better property of critical current density, J/sub c/, at high magnetic fields. The J/sub c/ and critical current, I/sub c/, values of multi-coated film with 1.2 /spl mu/m thickness and 1 cm width were 2.1 MA/cm/sup 2/ and 251 A at 77 K in self-field. Additionally, the superior J/sub c/ properties remained even at high magnetic fields over 20 T and lower temperature, e.g. J/sub c/ value at 30 K in 25 T was 1.0 MA/cm/sup 2/. The J/sub c/ value was about 2.5 times higher than those of previous TFA-MOD process at wide range of magnetic field. Moreover, the statistical distribution of J/sub c/ in the conductor was also estimated within a framework of the percolation model. The uniformity in the YBCO coated conductor was improved by optimizing the TFA-MOD process.

Long length Y-123 superconducting tapes were produced by reel-to-reel continuous vacuum processing, by using Ion-Beam-Assisted Deposition (IBAD) and Pulsed-Laser-Deposition (PLD). Biaxially textured Gd/sub 2/Zr/sub 2/O/sub 7/ buffer layers up to 255-m long were fabricated by IBAD with production speed of 0.5-1.0 m/h. Y-123 films were formed on them by PLD with production speed of 1.0-4.0 m/h. A 105-m long Y-123 film was fabricated with uniform thickness of 1.0 /spl mu/m and /spl Delta//spl phi/ of 3-4/spl deg/. I/sub c/ of 126 A was obtained in end-to-end at 77 K, 0 T, whose I-V curve had n-value of 28.5. I/sub c/ times length reached 13,230 Am. Another 70-m long Y-123 tape with I/sub c/ over 90 A (77 K, 0 T) was wound into a Solenoid type magnet whose inner diameter was 60 mm. The central field of 0.27 T was obtained at 66 K, with operating current of 130 A.

The AC losses of YBCO coated conductors fabricated by the IBAD/PLD method were electromagnetically measured. Both the magnetization loss without transport current and the total AC loss during the simultaneous application of AC transport current and an AC external magnetic field were measured. The AC losses were numerically calculated using the one-dimensional FEM model. The magnetic field dependence and the spatial distribution of critical current density were taken into account in numerical calculations, and the calculated AC losses were compared with the measured AC losses. The critical current, the transport current, and the applied external magnetic field were varied in order to calculate the total AC loss systematically.

Spatially resolved measurements of dissipative state in YBCO coated conductors have been carried out by use of the low temperature scanning laser microscopy (LTSLM). It has been shown that the current dependent dissipation peak is well scaled by the Gaussian distribution, and its normalized distribution becomes narrower in inversely proportion to the square root of power index in the local current-voltage characteristic. From the LTSLM analysis, we can collect positional information of current limiting coordinate as well as spatial variation of local critical current. Optimizing the measurement condition, we also succeeded to visualize the dissipation even in the tape which is covered by a 10 /spl mu/m thick Ag stabilization layer.

We have developed 100-m class YBCO conductors using reel-to-reel vacuum apparatuses for ion-beam-assisted deposition (IBAD) and pulsed-laser deposition (PLD). IBAD-Gd2Zr2O7 films 100m long were obtained with Δφ of 10°on non-textured Hastelloy tapes. Second buffer layers of Y2O3 or CeO2 that were 100m long were grown by PLD on the IBAD templates with Δφ of 7°or 5°, respectively. YBCO films were formed on a Y2O3/Gd2Zr2O7/Hastelloy substrate using PLD. An end-to-end Ic of 38 A and Jc of 0.76 MA/cm2 (77 K, self-field) were obtained in a 100m-long sample.

The E – J characteristics were measured for a YBCO-coated conductor by using the four probe method and the relaxation method of DC magnetization. The result on the latter measurement at extremely low electric fields was theoretically analyzed based on the flux creep-flow model. From the result on n -value the flux lines in YBCO are considered to be in the glass state even at high fields. The apparent pinning potential U 0 ∗ estimated from the relaxation of DC magnetization is much larger than that of Bi-2223. The present theoretical analysis clarifies a much stronger flux pinning and a higher dimensionality of YBCO in comparison with Bi-2223.

Tapes of 30-m length high-J/sub c/ Y-123 were processed by using ion-beam-assisted deposition (IBAD) and pulsed-laser deposition (PLD). Biaxially textured Gd/sub 2/Zr/sub 2/O/sub 7/ buffer layers up to 60-m length were fabricated by IBAD with production speed of 0.5 - 1.0 m/h. Y-123 films were processed on them by PLD with production speed of 1.0 - 4.0 m/h. A 30-m Y-123 film was obtained with uniform thickness of 0.5 /spl mu/m and /spl Delta//spl phi/ of 8 - 11/spl deg/. I/sub c/ of 49 A (J/sub c/ = 0.99 MA/cm/sup 2/) was obtained in 10-m length part end-to-end, whose I-V curve had high n-value of 46. The 30-m length end-to-end I/sub c/ value was 40 A (J/sub c/ = 0.8 MA/cm/sup 2/), where I/sub c/ times length reached 1200 Am.

We have investigated extended electric field-vs.-current density E-J characteristics in YBCO coated IBAD tapes. The results of a Monte-Carlo study on the depinning in a random pin medium were compared with measurements. Using a low temperature scanning laser microscope, we examined the percolative behavior of the local resistive transition in the YBCO tape. It was also shown that the depinning probability, which is proportional to the dynamic resistance of the E-J curves, is scaled as a function of reduced current density with the aid of a power index. Consequently, the E-J characteristics in the tapes can be described by the combination of the two kinds of scaling laws: one is the scaling law of the depinning probability predicted in a random network and the other is the scaling law for the flux pinning force. These properties agree well with the percolation model of depinned clusters.

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.

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.

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.

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.

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.

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.