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High engineering critical current density ( J e) is demanded in high-performance large-scale applications such as power cables, high-magnetic-field magnets, accelerators, and fusion reactors. In developing high current capacity and low vulnerability under a high magnetic field, high-temperature superconducting (HTS) rare-earth barium copper oxide coated conductors (CCs) have undergone various trials, and CC tape characteristics have ultimately been greatly improved. The Korea Electrotechnology Research Institute recently developed a “multiple HTS layers on one substrate” (MHOS) conductor that can carry high critical current, I c, based on the number of superconducting layers deposited on one substrate. The superconducting layers in a MHOS conductor are much thicker than in a single-layered CC tape, possibly affecting the degradation behaviors of I c under a mechanical load. To ensure the performance and reliability of MHOS conductors, it is necessary to evaluate the strain/stress response of I c. In this study, the electromechanical properties of MHOS conductors were investigated using the uniaxial tension test method as well as the single-sided bending test at 77 K and self-field and at 0.5 T using a pair of neodymium permanent magnets.

The turn-to-turn contact resistance of second-gene-ration (2G) HTS coil with metal insulation is a very important parameter in the viewpoint of the stability and current charging speed of the HTS coil. Controllability of the contact surface resistance of the 2G HTS coil with advanced metal insulation was observed in contrast with the case of the stainless steel (SS) metal insulation (MI). Three types of model coils—a no insulation coil, a metal insulation coil cowound with SS tape, and an MI coil cowound with copper (Cu) electroplated SS tape—were prepared and evaluated. The contact surface resistances between two Cu-plated 2G HTS tapes, between a Cu-plated 2G HTS tape and an SS tape, and between a Cu-plated 2G HTS tape and a Cu-plated SS tape are 6.3, 362.4, and 7.9 μ Ω·cm2, respectively. Dramatic reduction of the turn-to-turn contact surface resistance in model coils was achieved by using MI coil cowound with the Cu-plated SS tape. Also, the possibility of changing such contact surface resistance will be useful for designing the MI magnet.

In order to increase the current capacity of a high-temperature superconducting REBCO-coated conductor, in this paper, a lighter aluminum alloy was employed for mechanical reinforcement. Two GdBCO tapes fabricated using the reactive coevaporation by deposition and reaction (RCE-DR) process were laminated with three Al alloy (AA-3104) tapes using a two-step process involving pretinning and bonding. It was confirmed that ultrasonic soldering using Sn-3 wt% Ag-0.5 wt% Cu was efficient at laminating the GdBCO and aluminum alloy tapes. The bonding strengths and critical currents of the laminated conductors were evaluated.

A dc reactor is operated under a dc current to reduce the current's ripple or harmonics in the power system. General dc reactors in high-voltage dc systems use a metal conductor. This has some disadvantages such as large reactor size, leakage flux, wide install space, heavy weight, and electrical losses due to the large operating current. This paper describes the design of the toroid-type high-temperature superconductor (HTS) dc reactor magnet. Target operating current and inductance of the HTS dc reactor are 1500 A and 400 mH, respectively. The HTS dc reactors were designed through electromagnetic analysis and a 3-D CAD program. The two-layered 12-mm-width 2G GdBCO wire was considered. In addition, we analyze the operating performance of the double pancake coil module for the 1500-A 400-mH HTS dc reactor magnet under the liquid nitrogen condition.

POSCO and the Research Institute of Industrial Science and Technology developed a 10-kW superconducting synchronous generator using high-temperature superconducting wire. The generator consists of four-pole racetrack-type superconducting coils using GdBCO wire for rotor and 24 slots copper windings for stator. The rated power of the generator was 10 kW at 600 r/min, and the operating temperature was 30 K by thermosyphon cooling method using liquid neon. The output power was measured when the generator was connected to a vector motor, and the detailed results were discussed in this paper.

We report the fabrication of Gd films with dimples on the surface by vacuum evaporation method on Hastelloy substrate. The Gd films are structurally and morphologically studied by x-ray diffraction and field emission scanning electron microscope respectively and found to be hexagonal crystal structure. The magnetocaloric properties are studied and found to be well comparable with commercial Gd sheet. The calculated magnetic entropy change in Gd films is 9.57 J/kg K at Curie temperature (TC) of 294 K with second order magnetic phase transition under applied magnetic field 5 T.

Nonuniformity of critical current, Ic is one of the most important factors to be considered for the practical applications of high-temperature superconducting (HTS) REBCO coated conductors. To investigate the variation of Ic due to mechanical strain, local critical currents were measured at various tensile strain values from 0 to 1.2% for brass-laminated GdBCO tapes at 77 K, and analyzed using the Weibull distribution function. Measured local critical currents vary and decrease significantly at strain levels above about 0.8%. The Weibull function with three parameters turned out to be applicable for describing the Ic distribution of REBCO HTS wire for the entire strain range. The statistical minimum Ic calculated from the Weibull distribution function decreased with increased tensile strain. The degree of Ic variation was observed to drastically increase when the applied tensile strain exceeded the irreversible strain of about 0.8%.

Under application of tensile stress to a SmBCO (SmBa2Cu3O7¹¤) coated conductor sample consisting of series electric circuit of local sections, the relation of voltage­current curve, critical current and n-value of the sections to those of overall sample was studied. The change in critical current and n-value with increasing applied stress was different from section to section due to the difference in damage behavior of the SmBCO layer among the sections. When the difference in extent of damage among the sections was small, the voltages developed in all sections contributed to the voltage of overall sample. In this case, the critical current and n-value of overall sample were within the range of the highest and lowest values among the sections. On the other hand, when the damage in one section was far severer than that of other sections, the voltage developed in the most severely damaged section largely contributed to the overall voltage, and hence the voltage­current curves of the most severely damaged section were almost the same as those of overall sample. In this case, critical current of the overall sample was slightly higher and n-value of the overall sample was lower than the critical current and n-value of the most severely damaged section. Accordingly, the decrease in n-value with decreasing critical current in overall sample was sharper than that in sections. This phenomenon was accounted for by the increase in shunting current at cracked part at higher voltage in the most severely damaged section. [doi:10.2320/matertrans.MBW201301]

This paper reviews recent progress in research and development (R&D) of reactive co-evaporation for high performance REBCO coated conductors in Korea. Two types of reactive co-evaporation methods were developed for the deposition of SmBCO and GdBCO superconducting layers respectively on the IBAD (Ion Beam Assisted Deposition)-MgO template in the Korean coated conductor project. Batch type reactive co-evaporation equipment and its processing were developed for SmBCO coated conductors at Korea Electrotechnology Research Institute (KERI) in conjunction with the Korea Advanced Institute of Science and Technology (KAIST), and a very high critical current exceeding 1,000 A/cm at 77 K in the self field was achieved through the optimization of deposition parameters. Reel-to-reel type reactive co-evaporation processing with a high conversion rate was also developed, while long length GdBCO coated conductors have been routinely produced by SuNAM Co. The minimum critical current of 422 A/cm-w at 77 K in self field was confirmed for 1 km-long GdBCO tape.

We have fabricated the superconducting MgB 2 /carbon fiber by physical vapor deposition method. Mg (Magnesium) and B (Boron) were simultaneously deposited on the carbon fiber using the RF-sputtering and thermal evaporation, respectively. To ensure the relatively high vapor pressure of Mg at the growth region and the subsequent phase stability of MgB 2 at the deposition temperature, inverted funnel-like guide made of Mg-foil was employed while one side of the guide were open for the sputtered B flux. Mg vapor pressure should be controlled precisely to secure the complete reaction. The MgB 2 /carbon fiber showed a uniformly deposited thin layer with dense and well-formed grains. The MgB 2 /carbon fibers in this study showed c T~37.5K, J c ~ 2×10 4 A/cm 2 in the 20K, 0T. will be in the gas phase and be easily evacuated by the 1. INTRODUCTION The discovery of superconductivity in magnesium diboride (MgB 2 ) certainly revived the interest in the field of superconductivity, especially in non -oxide material system, and initiated a search for superconductivity in the related boron compounds [1- 3]. Its high critical temperature gave a hope for obtaining even higher

Sm 1+ x Ba 2− x Cu 3+ y O 7− δ (SmBCO) films were directly deposited on the epi-MgO/IBAD-MgO/Y 2 O 3 /Al 2 O 3 /Hastelloy template by co-evaporation using the evaporation using drum in dual chambers (EDDC) system without the buffer layer in order to investigate the effect of the composition ratios on superconducting property, microstructure and texture of SmBCO film. The films with gradient composition ratios of Sm:Ba:Cu were deposited using a shield with an opening which was placed between the substrate and the boats. The highest I c of 52 A (corresponding to J c = 1.6 MA/cm 2 and a thickness of 800 nm) was observed at 77 K in self field at a composition x = 0.01–0.05 and y = −0.23 to −0.46. When the composition ratio is outside this range, the I c value rapidly decreased. The superconducting critical current was highly dependent on the composition ratio. As the composition ratio is farther away from that of the highest I c , the SmBCO (1 0 3) peak intensity increased and the amount of a -axis oriented parts increased. A dense microstructure with round-shape grains was observed in the region showing the highest I c . The optimum composition ratio can be found by analyzing films deposited with variable deposition rates of each depositing element.

The magnetic properties of high T c superconductor (HTS) SmBa 2 Cu 3 O 7− δ (SmBCO) coated conductors (CCs) which are based on IBAD (ion-beam-assisted deposition) templates were investigated. The SmBCO CCs were fabricated on LaMnO 3 (LMO)/epi-MgO/IBAD-MgO/Hastelloy substrates by Evaporation using Drum in Dual Chamber (EDDC) processing. The measurements of isothermal magnetizations M ( H ) for the prepared SmBCO-CCs were carried out at various temperatures in magnetic fields up to 8.5 T. The magnetic properties for the applied magnetic fields parallel to the ab -plane show non-conventional behaviors when compared to those parallel to both c -axis and c -axis + 45°. These normal and anomalous properties can be explained by introducing the magnetic flux pinning effects related to the direction of the applied magnetic fields.

SmBa2Cu3O7 (SmBCO)-coated conductors were grown on IBAD-MgO templates by in-situ co-evaporation using a drum-in-dual-chambers system. The conductors, which had a coating thickness of up to 3 μm, showed a critical temperature of 92 ~ 94 K and a critical current of 150 ~ 625 A/cm-w at 77 K in a self-field. The phonon modes and cation disorder of the SmBCO-coated conductors were examined by polarized Raman scattering spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy. XRD showed (00l) peaks for the SmBCO phase. The Raman spectra revealed common vibration modes, including Ba-Ba stretching, Cu2-Cu2 stretching, O(2)+/O(3)-, and apical O(4) modes. In addition, polarized-Raman spectra were obtained to examine the crystal orientation and grain growth behavior. Structural information from the Raman spectra turned out to be useful to determine the optimal thickness of SmBCO-coated conductors with high critical currents.

The magnetic properties of SmBa2Cu3O7-x (SmBCO) coated conductor (CC) that was fabricated on LaMnO3(LMO)/IBAD-MgO substrates using Evaporation using Drum in Dual Chamber (EDDC), which is a batch type co-evaporation system, was investigated. LMO buffer layer was deposited on IBAD-MgO templates by PLD method. The measurements of both the magnetization M(H) and the resistance R(T) for the SmBCO CC, were carried out at temperatures between 10 and 120 K in fields up to 8.5 T, using a PPMS-9T (with both ACMS and DCR options, Quantum Design). The SmBCO CC exhibited Tc (onset temperature) of 94.7 K with a narrow transition width of 0.6 K, which indicates a good homogeneity of the superconducting properties. The upper critical field Hc2 near Tc of the SmBCO CC has been estimated by the resistance R(T) approaches. The magnetization curves M(H) are symmetric about the line M = 0 for the SmBCO CC with the field applied parallel to both the c-axis and c-axis +45°. For the SmBCO CC with the field applied parallel to the ab-plane, they are asymmetric. These symmetric and asymmetric curves can be explained by introducing the bulk pinning of 1-D flux lines and surface barrier-dominated system of 2-D pancake vortices.

In superconducting cable applications using the HTS tapes, striation of ReBCO coated conductor (CC) is being considered to reduce ac loss. The striation of ReBCO coating film with laser patterned filaments has been tried. In practical applications, the striated ReBCO CC tapes should also exhibit acceptable tolerance to mechanical stress/strains. However, reports on the electromechanical properties of striated CC tapes in bending or torsion mode are limited. In this study, the critical current degradation behavior of the striated Cu stabilized SmBCO CC tapes in pure torsion mode was investigated using a sample holder which gives torsional deformation to CC tapes. The CC tape has been laser scribed to produce multi-filaments. The Ic/Ic0 and n-value-torsional angle (θ) behaviors in the striated SmBCO CC tapes were examined and compared with the case of non-striated ones. According to the location of the coating film strip striated within the cross-section, there existed some difference in the Icf degradation behavior indicating that a non-uniform deformation was induced on each striated strip.

Long-length (Sm1+xB2-xC3O7-y) coated conductor was fabricated using ion beam assisted deposition (IBAD)-MgO template (LaMnO3/IBAD - MgO/Y2O3/Al2O3/Hastelloy) by the reactive co-evaporation method for electric power applications. SmBCO superconducting layers with thicknesses from 1 to 3 ?m were deposited to investigate the effect of SmBCO thickness on the in-plane texture, surface morphology and superconducting properties. In this study, the optimal deposition conditions were examined to make thick SmBCO coated conductor without degradation of critical current density. The oxygen partial pressure and temperature were controlled in the range of 1~20 mTorr and 600 ~ 800°C, respectively. SmBCO/IBAD-MgO coated conductors showed high critical current densities over 2.0 MA/cm2 with small amount of degradation by increasing the thickness of superconducting layer up to 3 ?m. The critical current of 637.5 A/cm-w (JC = 2.12 MA/cm2) at 77 K in self- field was obtained in 3 ?m-thick and 1 m long coated conductor. This is the highest critical current reported so far of the coated conductor with SmBCO superconducting layer deposited by co-evaporation.

The Hall probe measurement system was used to measure the critical current distribution of superconducting coated conductor. The system consists of reel to reel moving apparatus, 7 array Hall probe, a rotary encoder and permanent magnet. The magnetic field profile across the width of superconducting coated conductor using Bean's critical state model was calculated. The effect of various parameters of the formulas on the magnetic field distribution and the effect of shape and size of artificial defects, which were formed on the surface of SmBa2Cu3O7-d(SmBCO) coated conductor using laser marking system, on the Hall probe magnetic field signal of the Hall probe measurement system was investigated.

It is environmentally important to recycle the wastewater, since paper factories use a large amount of water and equivalent amount of wastewater is generated. Conventional water treatment facilities like precipitation process need large-scale equipment and wide space to purify the wastewater of paper factory. In case of massive waste water, high gradient magnetic separation (HGMS) parts are more effective to purify it rapidly and to occupy relatively small space, since large voids at filter with HGMS are adopted. In this respect, we prepared two types of superconducting magnets in order to apply HGMS parts for wastewater purification process. We made cryo-cooled Bi-2223 (HTS) superconducting magnet parts with room temperature bore in diameter of 70 mm and 200 mm in height. Also, cryo-cooled Nb-Ti superconducting magnet with room temperature bore in diameter of 100 mm and 600 mm in height was used for magnetic separator. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The faster wastewater's flow rate was, the worse the degree of clarity in treated water was. The ability of wastewater treatment in the case of magnetic separation used with 10 of magnetite particles was better than that in the case of 5 of magnetite particles.

The influences of bending strain on the critical current, I c in stabilized YBa 2 Cu 3 O 7− δ (YBCO) and SmBCO coated conductor (CC) tapes in different modes of easy and hard bending were investigated at 77 K and self-field. Under easy bending, the influences of the compressive and tensile bending strains on the I c in REBCO (rare earth element, Barium and Copper oxide) CC tapes were investigated. Under tensile bending strain, when the I c was plotted against the strain on the YBCO film layer, the 95% I c retention strain limit under bending was comparable to the value obtained in the axial-tension test. Under the hard bending of YBCO CC tape, I c started to degrade when the bending strain exceeded 0.6% and the recovery of I c did not occur when the bending strain applied was released. This might be a result of the generation of a new type of damage such as local buckling during hard bending which is different from the damage type experienced in Bi-2223 tapes. The n -value behavior showed a good agreement with the I c degradation behavior. On the other hand, the SmBCO CC tape showed a superior strain tolerance under hard bending resulted from its flexibility to in-plane deformation due to thin geometry compared to other copper stabilized YBCO CC tapes.

The deposition conditions of LaMnO3 (LMO) buffer layer on Ion Beam Assisted Deposition (IBAD)-MgO template by reactive DC sputtering were investigated. We developed a specially designed chamber for reactive DC magnetron sputtering. The deposition chamber was composed of two sputtering guns with the mixed metallic target of La (50 at%) + Mn (50 at%), halogen lamp heater, QCM (Quartz Crystal Microbalance), RGA (Residual Gas Analyzer) and reel to reel tape moving system. We investigated the effect of oxygen flow rate on the deposition rate of LMO layer. We found that there was an optimal range of oxygen flow rate to have the desired layer. Above the range, the deposition rate decreased sharply and plasma was unstable. Below the range, the deposited layer was partially metallic. We investigated the effect of substrate temperature on the texturing of LMO layer. The texturing of LMO layer was improved by increasing the substrate temperature. We investigated the effect of deposition rate on the texturing of LMO layer. The LMO layer has a good texture in the deposition rate range of 0.07–0.21 nm/s. We confirmed that deposition rate had little effect on the texturing of LMO layer in the deposition rate range. Sm1Ba2Cu3O7−d superconducting layer was deposited on the LMO(reactive)/IBAD-MgO template. Ic and Jc were 81.6 A and 1 MA/cm2. This means that LMO layer deposited by reactive DC sputtering shows a good performance in superconductor coated conductor.

We measured the magnetic hysteresis loops (M-H loop) of SmBCO coated conductor (CC) and YBCO-CC by using SQUID-magnetometer. These samples were fabricated by RABiTS method and IBAD method. We found the peak shifts of their M-B loops were qualitatively different. To understand this, we measured the magnetic field profiles, H(x), of SmBCO-CC and YBCO-CC by using scanning Hall probe method and calculated their current profiles, J(x). We found that the contrasting difference of M-B loops of the two types of CC was partly due to the inhomogeneous distributions of field and current, which depend on the sample shapes.

The evaporation and sputtering simultaneous deposition (ESSD) system was developed for in-situ deposition of MgB2 thin films. Mg was evaporated from the nozzle of cylinder crucible which is heated by high frequency induction heating, while B was sputtered by RF-magnetron sputtering. The nozzle-substrate distance was small enough to keep high vapor pressure of Mg on the substrate. The Mg-flux coming out of the nozzle was controlled by means of regulating the temperature of Mg source, was monitored and was calculated in detail with the variation of the distance from its nozzle. The optimal deposition condition with the variations of substrate temperature, the temperature of Mg source and the power of RF-magnetron sputtering, was investigated. MgB2 films with onset Tc of 14 K was obtained. The Tc of the film is lower than the bulk value of 39 K. Further works are in progress to improve the quality of MgB2 films by further optimization of deposition parameters and improvement of the ESSD system.

In order to investigate the possibility of using mixed rare earth (Nd1/3Eu1/3Gd1/3)Ba2Cu3O7-x (NEG123) as the superconducting layer of the HTS coated conductor, the NEG123 thin film was deposited epitaxially on LAO(100) single crystal and IBAD_YSZ metal templates by pulsed laser deposition. Systematic studies were carried out to investigate the influences of deposition parameters of PLD on the microstructure, texture and superconducting properties of NEG-123 coated conductor. Deposition at oxygen partial pressure of 600 mTorr was needed to routinely obtain high quality NEG123 films with JC's (77 K) over 2 MA/cm2 and Tc's over 90 K (DeltaT ~ 2 K) . We verified from magnetization study that the NEG123 has an improved in-field Jc as the field increases at temperatures between 10 K and 77 K compared with Gd123. The JC (77 K, self field) and the value of onset TC of NEG123 thin film on LAO substrate was 4.0 MA/cm2 and 92 K, respectively. This is the first report, to the best of our knowledge, of coated conductors with NEG123 film as the superconducting layer which have Ic and Jc over 40 A/cm-width and 1.6 MA/cm2 at 77 K, self field. This study shows the possibility of using NEG123 film as the superconducting layer of the HTS coated conductor which can be used in high magnetic field power electric devices.

Influences of bending strain on the critical current, Ic, in Cu-stabilized IBAD/EDDC processed SmBCO coated conductor (CC) tapes were investigated at 77 K and self-field using a small-scale Goldacker type bending test rig. Considering the location of the superconducting layer against the neutral axis, tensile and compressive bending strains were applied to the SmBCO coating layer and the strain effect on Ic degradation was discussed. Under tensile bending strain, the Ic decreased monotonically but recovered reversibly up to the irreversible strain limit. Under compressive bending strain, however, the Ic increased but in some cases it suddenly dropped after straightening due to the delamination of the copper stabilizer. Also, repeated bending strains were applied to Cu-stabilized SmBCO CC samples in order to observe the behavior of Ic under cyclic loading. Ic Initially decreased with the application of 0.7% bending strain, but when the tape was subjected to repeated bending up to 100 cycles, no more degradation occurred. And finally, the Ic almost recovered to Ic0 when the tape was straightened.

The important merit of Bi-2212/Ag high Tc superconducting wire is to apply cable as round wire geometry. Bi-2212/Ag wires were fabricated in order to develop Rutherford cable for SMES near the future. Various Ag ratio and various numbers of filaments for PIT (Powder-In-Tube) process were applied to investigate the workability during drawing and to improve critical current property of the wires. Rutherford cabling machine for B-2212/Ag strands was designed and manufactured. We designed and manufactured Rutherford cabling machine with 32 bobbins which had 2 km length of wire. This machine was constituted with Turks head, caterpillar tread and take-up facility. In order to obtain uniform working conditions without defects, Turks head's rolling system and Ag ratio of Bi-2212/Ag strands were modified. We tried to fabricate Rutherford cables with 20 and 30 Bi-2212 strands. Proper working conditions for without breakage strand in cable were investigated. We made successfully Bi-2212 Rutherford cable. The critical current of Bi-2212 Rutherford cable with 30 strands showed 420 A at 64 K and 4008 A at 4.2 K. The critical current of Bi-2212/Ag wire with 847 filaments was 398 A at 4.2 K and self field.

To examine the effect of solvent treatments on the superconducting properties of MgB 2 , solvent-treated MgB 2 powders were prepared by mixing with water, acetone, or ethanol. No degradation of the superconductivity of MgB 2 by the acetone or ethanol treatments was observed. Appreciable change which accompanies degradation of superconducting properties was observed only when MgB 2 was mixed with water. In addition, to investigate the variation of the flux pinning effect due to the aging, the Ag 8 –MgB 2 , (SiC) 4 –MgB 2 , and sintered pure-MgB 2 pellets were kept at room temperature for two and half years in air. The aged Ag 8 –MgB 2 composite superconductor has showed degradation of flux pinning effect. The in-field superconducting properties of (SiC) 4 –MgB 2 , however, did not change after aging.

SrRuO 3 thin films have been grown in situ on single crystal LaAlO 3 substrates and textured metal templates which contain an MgO layer produced by an ion-beam growth method. Deposition was made of oxygen partial pressure in a range from 50 m Torr to 250 m Torr with laser repetition rate of 5 Hz. Substrate temperature was between 600 °C and 800 °C. Dependence of out-of-plane and in-plane orientation of SrRuO 3 thin films on pressure and growth temperature was investigated by X-ray diffraction. The surface morphology and grain growth behaviors of SrRuO 3 thin films were analyzed by atomic force microscopy and scanning electron microscopy. In addition, the transverse magnetoresistance value in a field of 4 and 8 T was measured in temperature range of 50–200 K and the ferromagnetic transition at ∼140 K of SrRuO 3 films on LaAlO 3 was detected by resistivity measurement.

Highly textured long-length MgO template was successfully deposited on a polycrystalline metal tape using ion-beam-assisted deposition (IBAD). To increase the speed of the IBAD processing, tape moving system was modified from a single-turn to multi-turn system with 14-pass and five heating zones, which leads to larger deposition area. The overall process consists of reel-to-reel electro-polishing of a Hastelloy C276 tape, deposition of Al 2 O 3 diffusion layer and Y 2 O 3 seed layer, deposition of IBAD*-MgO and homo-epi MgO layer, and deposition of LaMnO 3 (LMO) buffer layer and YBa 2 Cu 3 O 7-δ (YBCO) superconducting layer using pulsed laser deposition (PLD). Recently, 100 m long IBAD-MgO tape with in-plane texture of Δ∅ < 7° has been successfully fabricated. Critical current density (J c ) of 0.94 MA/cm 2 at 77 K in self field was obtained from the YBCO coated conductor grown on 20 cm long LMO-buffered IBAD-MgO template by the PLD process.

We have fabricated SmBCO coated conductor on IBAD-MgO substrates using unique co-evaporation method. The batch type co-deposition system was specially designed and was named EDDC (evaporation using drum in dual chamber) that is possible to deposit superconducting layer with optimum composition ratio of materials at temperature over 700 °C and several mTorr of oxygen. In this study, we have investigated the influence of SmBCO phase composition ratio on the critical current density of coated conductor. We have optimized the composition ratio by changing the deposition rates of Ba and Cu during co-evaporation for better critical current density. A higher critical current density was measured at the composition ratio of Ba deficiency (1.9–2.0) and Cu rich (3.2–3.4) compared to the Sm 1 Ba 2 Cu 3 O y stoichiometry. Especially, highest critical current density of 2.6 MA/cm 2 was measured at the composition of Sm 1 Ba 1.9 Cu 3.2 O y that has dense surface morphology.

As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost. Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of for low cost coated conductors has been tried using thermal evaporation technique. 100 nm-thick layers deposited by thermal evaporation were found to act as a diffusion layer. SmBCO superconducting layers were deposited by thermal co-evaporation on the buffered Ni-5%W substrate. Critical current of 90 A/cm was obtained for the SmBCO coated conductors.

SrRuO3 thin films have been grown in-situ on and LaAIO3 textured metal templates by pulsed laser deposition. Deposition was carried out between 3 mTorr to 300 mTorr of oxygen partial pressure with laser repetition rate of 5 Hz. Substrate temperature was between 500 and 800degC . Dependence of out-of plane orientation SrRuO3 of thin films on pressure and growth temperature is investigated by X-ray diffraction. The surface morphology and grain growth behaviors of thin films are analysed by atomic force microscopy. In addition, a ferromagnetic transition at ~150 K SrRuO3 of films on LaAIO3 is detected by resistivity and magnetization measurement.

The important merit of Bi-2212/Ag high Tc superconducting wire is to apply cable as round wire geometry. Bi-2212/Ag wires were fabricated in order to develop Rutherford cable for SMES near the future. Various Ag ratio and various numbers of filaments for PIT (powder-in-tube) process were applied to investigate the workability during drawing and to improve critical current property of the wires. In order to find proper working process, we investigated the variation of drawing stress during working. Post-annealing of Bi-2212/Ag wires at various atmospheres was carried out after main heat-treatment in order to increase critical current density. The results of post-annealing in nitrogen were better than that of post-annealing in oxygen. Jc of Bi-2212/Ag wire was increased as increased maximum temperature,Tm , for partial melting until 890degC, and highest Jc was over than 2000 A/mm2. The shape of grain was observed by SEM to investigate Bi-2212 phase formation in filaments. The critical current density increased in proportion to the increase of Bi-2212/Ag wire's filaments number.

The degree of ferromagnetism of Ni-Wy alloys decreases as W-content y increases. Both the saturation magnetization M sat and Curie temperature T c decrease linearly with W-content y, and both M sat and T c go to zero at critical concentration of yc ~9.50 at.% W. To compare with Ni-W alloys, the magnetic properties of a series of both as-rolled (non-textured) and annealed (biaxially textured) [Ni97at.%-W3at.%]100-x-Cux alloy tapes with compositions x = 0, 1, 3, 5, and 7 at.%, were studied. Characterization methods included XRD analyses to investigate the biaxial texturing of the annealed [Ni-W]-Cu alloy tapes and studies of the magnetization for both as-rolled and annealed [Ni-W]-Cu alloy tapes. Both the isothermal mass magnetizations M(H) of a series of samples at different fixed temperatures and M(T) in fixed field, were measured. The effect of Cu addition on both the saturation magnetization and Curie temperature Tc of the Ni97at.%-W3at.% alloy was investigated.

Bi-2223/Ag tapes are usually used for superconducting power cables and magnets. Bi- 2223 ceramic superconducting core can be damaged under complicated stress and strain conditions such as winding tension, bending and twisting. In this study, we have presented the effect of axial stress and bending strain on the superconducting properties of Bi-2223/Ag tapes. In order to establish the value for 95% retained Ic of the Bi-2223/Ag tapes under various stress-strain conditions, the tension apparatus with bending former was used to apply the tension and bending stress-strain. Tension and bending stress-strain simultaneously applied to the tapes could reduce the critical current even though each applied stress and strain values were not higher than that of 95% retained Ic of the tapes. Complex stress-strain conditions including the thermal stress-strain have accelerated the degradation of the Bi-223/Ag tapes. The deformation temperature was important to maintain the 95% retained Ic of the Bi-2223/Ag tapes after bending or tension deformation because mechanical strength of the tapes can be changed drastically between room temperature and 77 K.

Five kinds of double stacked 385 (55ⅹ7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of 2,218 A/mm2 at 4.2 K, 0 T.

We measured the field profiles near the surface of a coated conductor (CC) under various applied fields by using the scanning Hall probe method. The field, applied in the normal direction, was increased from zero to 171.5 Oe and then decreased to −58.8 Oe. We could not analyse our data completely by the direct use of Brandt's calculation but by a modification with unusual field dependences of the introduced parameters. Since Brandt's original calculation was based on homogeneous films, it was not suitable for CCs with coarse granular structures. The modified calculations with appropriate parameters are related to the coarse granular structures. Those parameters, D, Jc, and R, represent the three characteristics of the flux penetration network: the average distance of flux penetrations, the density of critical sheet currents, and the range of meandering of the flux penetration front, respectively. The external field dependences of these parameters were different from those of the classical critical state model.

YBCO film was fabricated by the TFA-MOD method based on the “211 process” in which precursors of Y 2 Ba 1 Cu 1 O x (Y211) and Ba 3 Cu 5 O 8 powders, instead of Y-, Ba-, and Cu-based acetates, were dissolved in trifluoroacetic acid (TFA) in order to explore its possible application in coated conductors. We evaluated the effects of the humidity and firing temperature on the phase formation, texture formability, and critical temperature ( T c ) and current ( I c ) of the YBCO film. We successively synthesized pure YBCO films of which those fired in 12.1–20.0% humidified Ar gas showed the highest critical properties, viz. a T c -zero of 88.6 K and I c of 30 A/cm width. These improvements in the critical properties were attributed to the formation of pure YBCO phase, to the improved density and the large grain size. In addition, we observed that the I c varied significantly with the firing temperature. The variation of the I c with the firing temperature was correlated with the microstructural evolution.

BaZrO3 nanopowder was added to YBCO powder to make (BaZrO3)x(YBCO)(100−x)mol.% (BZOx-YBCO) (0 ⩽ x ⩽ 10) composite targets for pulsed laser deposition of superconducting film in order to investigate the effect of the addition of BZO nanopowder in the YBCO target on the flux pinning properties of YBCO coated conductor. All the BZOx-YBCO films were grown on SrTiO3 single crystal substrate under the same conditions in the PLD chamber. The effect of adding BZO to YBCO targets on the flux pinning properties of BZOx-YBCO films has been investigated. No impurity phase was identified, and all the peaks could be indexed as YBCO, BZO, and STO. There were traces of strong pinning centers at low temperature and high magnetic field region (above ∼3 T) in BZO6-YBCO film with the addition of ∼6 mol.% BZO nanopowder. However, the Tc of the BZOx-YBCO films gradually decreased as the amount of BZO nanopowder added increased.

We evaluated the dependence of the critical current ( I c ) and index number ( n ) of Y-123 and Bi-2223 tapes on the magnetic field up to 17 T at 4.2 K, in order to explore their possible application for high field magnet. We observed that the I c and n values depended on the magnitude and direction of the magnetic field for the Y-123 tape, whereas in the case of Bi-2223 tape, the I c depended on the magnetic field but the n did not significantly depend on the magnitude of the field. It is to be noted that, for the Y-123 tape, the I c ( B ) characteristics showed highly anisotropic behavior: the I c decreased nearly linearly in an increasing parallel field and approximately 45% of the I c (1.071 A/cm-width in a self-field) was retained at 17 T, whereas it decreased exponentially and only 14% of the I c was retained in a perpendicular field at 10 T. In addition, no hysteric behavior was observed in the Y-123 tape when the fields were applied in increasing and decreasing paths, which is in remarkable contrast with the hysteretic behavior observed in the Bi-2223 tape. In the case of the Y-123 tape, the n decreased with increasing magnetic field and varied in the range of 16.8–49.7 in a parallel field ranging from 0 to 17 T and 5.2 to 45.2 in a perpendicular field ranging from 0 to 9 T. For the Bi-2223 tape, on the other hand, the n did not significantly depend on the magnitude of the field and the mean value and standard deviation were 24.5 and 5.3, respectively, in the range of 0–17 T.