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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.

Compared with the undoped YBa2Cu3O7−δ (YBCO) film, 10 mol% Sn-doped YBCO film exhibited significantly enhanced critical current densities (Jc) in magnetic fields up to 5 T at 65 and 77 K for H//c, indicating that the Sn-doped YBCO film possesses more effective flux pinning centers. Both samples were grown on the SrTiO3 (STO) (1 0 0) single crystal substrates by the metal-organic deposition (MOD) process. Larger Jc (77 K, 1 T) values of Sn-doped YBCO film are observed over a wide field-orientation angle (θ) except the field-orientations close to the ab-plane of YBCO (85°

A single-coat YBa2Cu3O7- (YBCO) film of high critical currents (Ic) could be successfully fabricated by optimizing the viscosity of the coating solution in the metal-organic deposition (MOD) process. From a Ba-deficient coating solution (Y: Ba: Cu = 1: 1.5: 3) having the viscosity of 212 mPasec, 0.9 m-thick single coat YBCO film with the Ic value of 289 A/cm-width (Jc = 3.2 MA/cm2) at 77 K was achievable on the SrTiO3 (STO) substrate, which was superior to that of our previous report for 0.8 m-thick single coat YBCO film from a stoichiometric coating solution (Y: Ba: Cu = 1: 2: 3) on the LaAlO3 (LAO) substrate. This result might be attributed to denser and more homogeneous microstrcuture in the case of the YBCO film from the Ba-deficient coating solution.

We report the effects of BSO addition on the crystallinity, texture, and the field dependency of critical current density (Jc) of GdBCO coated conductors (CCs) prepared by pulsed laser deposition (PLD). Undoped and BSO-doped GdBCO films showed only c-axis oriented growth, and the incorporated BSO nanorods exhibited epitaxial relationship with the GdBCO matrix. In comparison with undoped film, BSO-doped GdBCO film exhibited greatly enhanced Jc and higher pinning force densities in the entire field region of 0–5 T (H//c) at 77 and 65 K. The BSO-doped GdBCO film showed the maximum pinning force densities (Fp) of 6.5 GN/m3 (77 K, H//c) and 32.5 GN/m3 (65 K, H//c), ∼2.8 times higher than those of the undoped sample. Cross-sectional TEM analyses exhibited nano-structured BSO nanorods roughly aligned along the c-axis of the GdBCO film, which are believed effective flux pinning centers responsible for strongly improved critical current densities in magnetic fields.

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.

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.

We report a successful fabrication of c -axis oriented GdBa 2 Cu 3 O 7− δ (GdBCO) films on the BaSnO 3 (BSO) buffer layers on ion-beam assisted deposition (IBAD)-MgO template by pulsed-laser deposition (PLD). The (0 0 l ) growth and in-plane textures of BSO buffer layers were found sensitive to the substrate temperature ( T s ). With increasing the BSO layer thickness up to ∼165 nm, in-plane texture (Δ ϕ ∼ 6.2°) of BSO layers was almost unaltered while completely c -axis oriented BSO layers were obtainable from samples with the thickness below ∼45 nm. On the BSO buffer layers showing in-plane texture of 6.2° and RMS surface roughness of ∼8.6 nm, GdBCO films were deposited at 780–800 °C. All GdBCO films exhibited Δ ϕ values of 4.6–4.7°, T c,zero of ∼91 K, and critical current density ( J c ) over 1 MA/cm 2 at 77 K in a self-field. The highest J c value of 1.82 MA/cm 2 ( I c of 51 A/cm-width) was achieved from the GdBCO film deposited at T s of 790 °C. These results support that BSO can be a promising buffer layer on the IBAD-MgO template for obtaining high- J c GdBCO coated conductors.

We report a successful fabrication of high-J c GdBa 2 Cu 3 O 7-δ (GdBCO) films by the metal-organic deposition process on the LaAlO 3 (LAO) (0 0 1 ) substrates. The coating solution was prepared by mixing Gd, Cu fluorine-free sources with Ba trifluoroacetate. Samples were dip-coated, pyrolized within 3 h at the temperature up to 400 °C in a humid oxygen atmosphere, and finally fired at various high temperatures in 100 ppm Ar/O 2 atmosphere. The GdBCO films fired at 775 and 800 °C exhibited J c values of ~2.1 MA/ cm 2 at 77 K in a self-field, which are attributable to both high T c,zero values of ~89 K and high in-plane textures of 1.3-1.4°. Above 800°C, however, the superconducting properties of GdBCO films are degraded due to the thermal decomposition of GdBCO film in 100 ppm Ar/O 2 atmosphere. .

High temperature superconducting GdBa 2 Cu 3 O 7 (GdBCO) thin films were grown by pulsed laser ablation. Textured MgO on metal substrates was used as a template for second generation wire applications. Growth conditions of GdBCO thin films were investigated for substrate temperature ( T s ) and oxygen partial pressure (PO 2 ) during deposition. Superconducting critical currents of the films were obtained in the films grown at 790–810 °C of T s and at 100–700 mTorr of PO 2 . Scanning electron micrographs of the films revealed uniform and well-connected grains with some outgrown structures. X-ray θ –2 θ scans of the films grown at 810 °C and 300–500 mTorr exhibited c -axis oriented texture. In-plane alignment and c -axis mosaic spread of the films were determined from X-ray Φ scans and rocking curves, respectively. Polarized Raman scattering spectroscopy was used to characterize optical phonon modes, oxygen content, cation disorder, and some possible second phases of the films. The Raman spectra of the films with large critical current density showed modes at 326–329 cm −1 , 444–447 cm −1 , 500–503 cm −1 related to vibration of oxygen atoms. Origin of small peaks near 600 cm −1 will be discussed as well. The information obtained from Raman scattering measurements will be useful for quality control of the conductors as well as optimization of the process conditions.

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.

Gd1+xBa2-xCu3O7 (GdBCO) coated conductors on Ion-beam assisted deposition (IBAD)-MgO templates were grown by pulsed laser deposition (PLD). Growth conditions for the PLD of high quality of GdBCO turn out to have a rather larger range than for Nd-based cuprate thin films. The structural properties and critical current of GdBCO have been measured. The GdBCO layers show ~ 100 A/cm at 0.5 micron-thick films. In our measurement of Raman scattering spectroscopy from 180 ~ 1,200 cm-1, one strong B1g mode and two strong A1g modes were observed. The high critical-current is ascribed to well-grown highly textured 123-structure without cation disorder and oxygen deficiency. It is notable that the GdBCO films do not have second phases like BaCuO2, which is a signature liquid phase-based material that occurs in other rare-earth based cuprates.

Using two different IBAD-MgO templates with the in-plane textures of ∼8.5° and ∼6.5° for MgO (2 2 0), respectively, we tried to identify the correlation between the LaMnO 3 (LMO) buffer layer and IBAD-MgO template and also to optimize the PLD processing conditions for the LMO layer. Better in-plane texture of the LMO buffer layer less than 7° was obtained from the IBAD-MgO template of ∼6.5° in-plane texture over almost all deposition temperature and time, supporting that the processing window is very wide, although the in-plane texture of LMO buffer layers was somewhat sensitive not only to deposition temperature but also to deposition time (or layer thickness). Optimally processed LMO buffer layer at deposition temperature of 775 °C in P O 2 of 100 mTorr for 10 min exhibited the Δ φ value of 5.2°.

We report a successful fabrication of high- I C YBCO films on the LaAlO 3 (1 0 0) substrate by the MOD process with the single dip-coating method. The coating solution was made by mixing the fluorine-free precursor solution containing Y and Cu with Ba–fluorine precursor solution. The total decomposition time could be reduced only to 3 h with the heat treatment up to 500 °C, and the cracking problem of thicker YBCO films prepared by the conventional TFA–MOD method could be avoided. Optimally processed YBCO film of ∼0.8 μm thickness exhibited high- I C values over 200 A/cm-width at 77.3 K in a self-field. Our results clearly show that fluorine-free precursors for Y and Cu elements are very effective for the fabrication of high- I C YBCO films.

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.

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.

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.

A cross-sectional transmission electron microscope (TEM) analysis was conducted on the GdBa 2 Cu 3 O 7− δ (GdBCO) tapes, which were synthesized by depositing Al 2 O 3 /Gd 2 O 3 /IBAD–MgO/epi-MgO buffer layers on the hastelloy substrate by the ion-beam-assisted deposition (IBAD) method and subsequently depositing LaMnO 3 and GdBCO layer by pulsed laser deposition (PLD) method. The average critical current ( I c ) value was 62.5 A and the average full width at half maximum (FWHM) values of the in-plane GdBCO(1 0 2) was 4.4°. The thickness of the each stacked layer was precisely measured with TEM micrographs and the structural features were analyzed with scanning transmission electron microscope-energy dispersive X-ray spectrometer (STEM-EDS). The diffusion of the Cr ion in the hastelloy into the Al 2 O 3 layer was detected and the thickness of the diffused layer was about 10 nm.

We investigated the effect of film thickness on the superconducting properties of GdBa2Cu3O7 (GdBCO) films on the SrTiO3 (STO)(1 0 0) substrates which were fabricated using pulsed laser deposition (PLD) with a KrF exicmer laser (248 nm) pulses of 2.5 J/cm2. With the target-to-substrate distance of 6.5 cm, GdBCO films were deposited at the substrate temperature of 810 °C in the oxygen pressure of 400 mTorr. Optimally processed GdBCO samples exhibited Tc of 91.3 K and Jc of 5.2 MA/cm2 at 77 K in self field. When the film thickness increased from 0.15 to 2.2 μm, Jc values were decreased from 5.2 to 1.3 MA/cm2. It was considered that the Jc reduction with increasing the thickness is attributed to the increase in the average size and density of particulates, leading to decrease in superconducting phase fraction, and also to the formation of cracks, reducing the supercurrent path.

We analyzed Nd1+x Ba2−x Cu3O7 (NdBCO) coated conductors grown at various substrate temperatures by using Raman spectroscopy. Epitaxial NdBCO films were deposited on ion beam assisted deposition yttrium stabilized zirconia (IBAD-YSZ) templates by pulsed laser deposition. Raman scattering spectroscopy shows that the NdBCO film grown at a relatively low substrate temperature of 750 ◦ C contains some a-axis oriented grains as well as c-axis oriented grains and an excess cation disorder between Nd 3+ ions and Ba 2+ sites, which result in degradation of superconducting properties with critical temperature (Tc )o f∼83 K and critical current density (Jc )o f less than 1 MA cm −2 at 77 K and self-field. The samples grown at higher temperatures ranging from 775 to 800 ◦ C are found to have strong c-axis orientation with little cation disorder, and subsequently excellent superconducting properties with Tc of 88–90 K and Jc of 1.2–1. 8M A cm −2 at 77 K and self-field. (Some figures in this article are in colour only in the electronic version)

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 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.

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 explore optimal growth conditions for superconducting Nd1+xBa2?xCu3O7 (NdBCO) thin films deposited under various oxygen pressures in the range of 100?800?mTorr. In this study we address spatial inhomogeneity, growth orientation, impurity phases, cation disorder, and oxygen deficiency of NdBCO thin films by using micro-Raman scattering. The films grown in the low oxygen pressure range of 100?200?mTorr show predominantly a-axis orientation and degraded superconducting properties with a critical temperature (Tc) of ~80?K. The degradation of the transition temperature of the films deposited at lower oxygen pressure is attributed to the cation disorder, on the basis of analysis of the apical oxygen Raman mode. On the other hand, the samples grown in the higher oxygen pressure range of 400?800?mTorr show strong c-axis orientation and much less cation disorder. These features correlate with their high values of Tc and Jc.

We report the upper critical field ( H c2 ), the irreversibility field ( H irr ), and the lower critical field ( H c1 ) of a dense polycrystalline MgB 2 superconductor which was prepared by the spark plasma sintering (SPS). The isothermal magnetizations M ( H ) of MgB 2 sample was measured at temperatures between 5 and 50 K in fields up to 8 T. The H c2 ( T ) data were well fitted to the BCS-type function H c2 ( T ) = H c2 (0)[1 − ( T / T c ) α ] β , with H c2 (0) = 8.5 T, α = 1.60 and β = 1.15. The H irr (melting line) could be described by the power-law relation H irr ( T ) = H irr (0)[1 − ( T / T c )] n with n = 1.10 and H irr (0) = 8.1 T. The deduced values of H c1 approximately followed a linear temperature dependence, not following a parabolic dependence of H c1 ( T ) = H c1 (0)[1 − ( T / T c ) 2 ].

NdBa 2 Cu 3 O 7-δ (NdBCO) films were grown by pulsed-laser deposition (PLD) on SrTiO 3 (STO)(1 0 0), MgO(1 0 0), and STO-buffered MgO(1 0 0) substrates for a comparative study on the effect of substrate on the textures, microstructures, and superconducting properties of NdBCO films. All NdBCO films were deposited at the same substrate temperature of 800 °C under the same total pressure of 800 mTorr with 1%O 2 /Ar gas. The transport J c value of 3.5 MA/cm 2 at 77 K in self-field was obtained from the NdBCO/STO with T c value of 91.2 K, while the NdBCO/MgO with T c of 86.8 K exhibited the low J c value of 0.25 MA/cm 2 . On the other hand, J c value of 1.55 MA/cm 2 was obtained from NdBCO film on STO-buffered MgO(1 0 0) substrate with T c of 91.5 K. The higher J c value of the NdBCO/STO than NdBCO/STO/MgO resulted from much better in-plane and out-of-plane textures of NdBCO/STO, while the low J c value of the NdBCO/MgO can be attributed to both depressed T c value and the existence of 45°-rotated grains with [001] NdBCO ∥[110] MgO .

We report a successful fabrication of high- J c NdBa 2 Cu 3 O 7− δ (NdBCO) coated conductors on CeO 2 /IBAD-YSZ/SS templates (YSZ ∼ 2 μm thick, CeO 2 ∼ 20 nm thick). The NdBCO films were prepared by pulsed laser deposition (PLD) at the substrate temperatures ( T s ) ranging from 750 to 830 °C under the same total pressure of 800 mTorr with 1%O 2 /Ar gas. Transport J c values over 1 MA/cm 2 at 77 K in self-field were achieved for NdBCO coated conductors deposited at T s of 775–800 °C. The highest J c value of 1.8 MA/cm 2 was obtained from the NdBCO coated conductor deposited at 775 °C, implying that NdBCO is comparable to YBCO for coated conductors. These samples had T c values of 88–90 K, commonly exhibited good in- and out-of-plane textures with the FWHM values of (1 0 3) ϕ -scan and the (0 0 6) ω -scan of 7–8° and 3.5–4.5°, respectively, and the densities and sizes of outgrowth particles in the films were not apparently different from each other.

We for the first time report a successful fabrication of a high-J/sub C/ SmBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//(SmBCO) thin film (/spl sim/240 nm thickness) on SrTiO/sub 3/ (100) substrate by the pulsed electron beam deposition (PED) process. For this study, we systematically investigated the effect of processing parameters, including substrate temperature (Ts), ambient oxygen pressure (PO/sub 2/), and target-to-substrate distance, on superconducting properties, including critical temperature (T/sub C/) and critical current density (J/sub C/), of PED-processed SmBCO films. The highest J/sub C/ value of 1.37 MA/cm/sup 2/ at 77 K in self field was obtained from an optimally processed sample using Ts of 900/spl deg/C (corresponding to real substrate temperature of 810/spl deg/C), PO/sub 2/ of 15 mTorr, and target-to-substrate distance of 9 cm, evidencing that this process is a potential alternative to the PLD process.

A study regarding the epitaxial growth of Y2O3 film on textured metal substrate and its use as a single buffer layer of a YBCO coated conductor is reported. Different deposition conditions were employed and compared in order to obtain good epitaxial Y2O3 film followed by deposition of YBCO superconducting films. The YBCO film deposited by PLD on top of the Y2O3 films has good microstructure and superconducting properties. The effect of the thickness of Y2O3 film on the texture of Y2O3 film and the critical current density (Jc) of YBCO film deposited on top of that were analysed. The Jc of YBCO films on Y2O3/Ni and Y2O3/NiW were 1.0 × 106 A cm−2 and 1.1 × 106 A cm−2 at 77 K and self-field respectively, which indicated that Y2O3 is a suitable candidate as a single buffer layer for the fabrication of a YBCO coated conductor.

YBCO films with various thicknesses from 100 nm to 1.6 µm were deposited on single crystal SrTiO3 substrates by pulsed laser deposition (PLD). The effects of thickness and deposition rate—by means of controlling the pulsed laser frequency—on the critical current density (Jc) were studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to examine the orientation, crystallization and surface quality. The amount of a-axis YBCO component evaluated from the ratio of XRD chi-scan intensities of the a-axis and c-axis for the YBCO (102) plane increased as the YBCO film became thicker. SEM was used to analyse the surface of YBCO film, and it was shown that the surface of YBCO film became rougher with increasing thickness. There were many large singular outgrowths and networks of outgrowths on the surface of the YBCO films with thickness greater than 0.4 µm. The increased amount of a-axis YBCO component and the coarse microstructure of the thick YBCO film caused degradation of Jc with increasing thickness.

We report positional dependence of superconducting properties in a Y–Ba–Cu–O single grain fabricated with a top seeded melt growth technique. It is found that the distributions of the second phase of Y2BaCuO5 (Y211) inclusions and the magnetic properties vary with position in a large sample. The peak effect is observed in the region where the volume fraction of the Y211 particles is low. The optimum oxygen-annealing temperature for achieving high critical current is also dependent on the position in a large bulk. The regional distributions of the microstructure and the properties are not arbitrarily scattered but reasonably depend on the spatial distributions of growth rate and growth direction in a large grain.

The magnetic properties of high Tc superconductor (HTS) YBa2Cu3O7−δ (YBCO) coated conductors (CCs) which are based on RABiTS (rolling-assisted biaxially textured substrate) and IBAD (ion-beam-assisted deposition) templates were investigated. The measurement of isothermal magnetizations M(H) for the prepared YBCO-CCs was carried out at 77 K and 100 K in magnetic fields up to 3000 G. The magnetic properties for the applied magnetic fields parallel to the ab-plane are much smaller than that perpendicular to the ab-plane. Large magnetic property in the YBCO-CC based on the RABiTS template comes from the strong ferromagnetism of the textured Ni–W alloy substrate.

We report the NdBa2Cu3Oy (Nd123)-Ba3Cu5Oz(035) pseudo-binary section in the Nd2O3-BaO-CuO system under the oxygen partial pressure pO2 = 0.01 atm. We performed thermogravitational and differential thermal analysis (TG-DTA) and powder x-ray diffraction (XRD) measurements for quenched samples. We also performed high-temperature XRD for the determination of equilibrium solid phases at elevated temperatures. In situ observation of the primary solid phases with laser scanning microscopy was also performed for an accurate determination of the liquidus line. In comparison with the Nd123-035 pseudo-binary phase diagram in air, the liquidus line under pO2 = 0.01 atm shifts to a lower temperature.

We have studied the levitation of Y-Ba-Cu-O bulk superconductors above a Bi-Sr-Ca-Cu-O superconducting pancake coil with and without the function of the inner coil. It was found that the inner coil with small diameter can enhance the levitation force through its contribution to the radial component of the magnetic field. We also successfully applied the total energy balance method for the understanding of the bulk levitation.

Large Nd1+xBa2-xCu3Oy (Nd123ss) single crystal cubes of side 3 mm were fabricated isothermally by the flux method. The crystals exhibited a Tc of 95 K with a sharp superconducting transition. One crystal was cut into small pieces, and its magnetic properties were measured to study the spatial distribution of the superconducting properties. It was found that although Tc values were almost constant, a small but significant intrinsic difference in the Jc-B properties and irreversibility field was observed depending on the sample position. This suggests that the distribution of Nd-rich Nd123ss clusters are spatially different even within the same single crystal. Such differences may be caused by the time variation of Nd concentration in the liquid during crystal growth.

It is known that the amount of Nd ions substituting for a Ba site in the Nd1+xBa2−xCu3Oy solid solution (Nd123ss) tends to decrease with either decreasing oxygen partial pressure PO2 or increasing temperature, however, the precise solubility limit of Nd123ss has not been obtained. In the present study, we carefully studied the solubility limit of Nd123ss under low PO2 and for the first time could show the presence of x

Short time relaxation effect in Nd0.5Sr0.5MnO3 manganites was observed. The effect is manifested as negative peak of imaginary component of ac magnetic susceptibility near the point of first order phase transition. The effect is explained at the frame of Landau theory of phase transition, where the coexistence of metastable and stable phases is considered.

We have successfully melt-processed La-Ba-Cu-O bulk superconductors which exhibit high T c and large J c values. The employment of a 0.1% O 2 -Ar atmosphere and a Ba-rich La 4- x Ba 2+ x Cu 2- x O 10-2 x second phase as a precursor was the key to obtaining a high T c phase. Fabricated bulk samples exhibit onset T c of 94 K and the secondary peak effect in the J c - B curve. The respective peak position and the irreversibility field were 1 T and 4.5 T at 77 K and the J c at the peak field was about 18000 A cm −2 .

The magnetic flux dynamics of Nd-Ba-Cu-O (NdBCO) bulk superconductors produced by the Oxygen-Controlled-Melt-Growth (OCMG) method has been investigated using the Magneto-Optical (M-O) technique at various low temperatures for an external magnetic field applied both parallel (H//c) and perpendicular (H⊥c) to the c -axis of the sample. While for H//c the flux motion was isotropic, for H⊥c anisotropic penetration and expulsion of the flux lines was observed directly. In the configuration H⊥c the flux lines were observed to move in and out the sample predominantly parallel to the a-b planes. The flux behaviour has also been correlated to the microstructure. Particularly, microcracks along the basal plane were found to provide a low resistance channel for flux motion.

REBaCuO (RE: rare earth element selected from Nd, Sm, Eu, Gd) superconductors exhibit high T c and J c values when they are melt processed in a reduced oxygen atmosphere (oxygen-controlled-melt-growth: OCMG process). Large J c values in these systems can be attributed to finely dispersed RE rich 123 clusters, which can act as field-induced pinning centers, and thus leading to the second peak effect in M - H loops. In this paper, we first propose the mechanism how RE rich clusters are formed during melt processing. Second we show that flux pinning depends on oxygen annealing conditions, because the optimum oxygenation conditions are different depending on the range of NdBa substitution. We also report that the addition of ND422 is effective in raising J c , although the mechanism is rather complicated owing to the fact that ND422 also has a REBa solid solution toward Ba rich direction.

We investigated the magnetic flux dynamics of NdBaCuO (NdBCO) bulk superconductors produced by the Oxygen-Controlled-Melt-Growth (OCMG) method using the Magneto-Optical (M-O) technique at various low temperatures. An external magnetic field was applied both parallel ( H t | c ) and perpendicular ( H ⊥ c ) to the c -axis of the sample. While for H t | c the flux motion was isotropic, for H ⊥ c anisotropic penetration and expulsion of the flux lines were directly visualized. In the configuration H ⊥ c the flux lines were observed to move in and out of the sample predominantly parallel to the a - b planes. The flux behavior was also correlated to the microstructure. Particularly, the microcracks along the basal plane were found to provide a channel for easy flux motion. The anisotropic behavior of the flux front reflects the anisotropy in the critical current density J c . The different components of J c were independently calculated from the M-O data directly analyzing the magnetic induction profiles. These J c values were consistent with those estimated interpreting the magnetization hysteresis measurements within the framework of the extended Bean model.

Critical current densities of Nd123 crystals flux grown by the oxygen-controlled-melt-growth (OCMG) process have been studied with DC magnetization measurements. The superconducting transition temperature ( T c ) of the Nd123 crystal flux grown in 0.1%O 2 Ar gas was 94 K with the applied field of 10 Oe parallel to the c -axis. The sample was found to be homogeneous without weakly linked regions through magneto-optical measurements. DC magnetization-hysteresis curves measured with a SQUID magnetometer exhibited a peak effect at various temperatures above 70 K. The peak effect is attributable to field-induced pinning by finely distributed low- T c phases. The sample exhibited high critical current density ( J c ) valuesof 4 × 10 4 A/cm 2 in 2 T and over 1 × 10 4 A/cm 2 in 4 T at 77 K for fields parallel to the c -axis.

An oxygen-controlled melt growth (OCMG) process has been employed for NdBa/sub 2/Cu/sub 3/O/sub y/ (Nd123) and SmBa/sub 2/Cu/sub 3/O/sub y/ (Sm123) superconductors for a comparative study. Both Nd123 and Sm123 samples melt-grown in reduced oxygen atmospheres exhibited an enhanced superconducting transition temperature (T/sub c/) with a sharp transition and large critical current density (J/sub c/) in a high field region at 77 K and for the applied field parallel to the c-axis of samples (H/c). For Nd123, a preferential formation of high T/sub c/ phase in a low oxygen partial pressure (P(O/sub 2/)) could be qualitatively described considering the thermodynamic stability boundaries of the Nd/sub 1+x/Ba/sub 2-x/Cu/sub 3/O/sub y/ solid solutions on the LOG[P(O/sub 2/)] vs. 1/T (K/sup 9/-1) phase diagram. A long-term oxygen annealing study for an OCMG-processed Nd123 sample revealed that the annealing temperature should be as low as 300/spl deg/C. >

The continuing increase in packing density of VLSI circuits requires that the inspection process be completely automated. The paper suggests a new method for automatic inspection of that part of the wire bond where the wire connects to the bond pad on the chip. A popular type of bonding (connected to bond pad) known as "ball bond" is considered. Although several approaches for ball bond inspection have been introduced, they do not reveal efficient results. The suggested method consists of five steps: (1) enhance the edges using Binomial and the modified Laplace filter; (2) binarize the image: (3) extract center point of the ball bond; (4) extract the ball bond boundary; (5) fit the ellipse using direct ellipse-specific fitting. Experimental results illustrate that the proposed method performs the inspection of ball bond more fast and accurately as compared to the conventional ball bond inspection methods. In addition, our method finds the size and orientation of the ball from the bond image containing the part of the ball.

Wire bonding in IC assembly process involves making a physical connection between the IC pad and the lead by bonding wires between the two. Inspection of wire bond quality is a highly labour intensive process and the continuing increase in packing density of VLSI circuits requires that the inspection process be completely automated. This paper suggests a new method for automated visual inspection of wire bond. A popular type of bonding (connected to bond pad) known as "ball bond" is considered here. Although several approaches for ball bond inspection have been introduced, they do not reveal the efficient results. The suggested method consists of five steps: (1) to enhance the edges using binomial and the modified Laplace filter; (2) to binarize the image; (3) to extract center of the ball bond; (4) to extract the ball bond boundary; (5) to fit the ellipse using direct ellipse-specific fitting. Experimental results illustrate that the proposed method performs the inspection of ball bond more fast and accurately as compared to the conventional ball bond inspection methods and, in addition, our method finds the size and orientation of the ball from the bond image containing the part of the ball.

Agent based information retrieval systems have gained great attention, due to the proliferation of readily available but overwhelming information on the Web. We present a neural network based multi agent, especially hierarchically organized information retrieval system. The motivation is based on our experience with an experimental system called Hierarchically Organized Multi-agent Information Retrieval System (HOMIRS) and an analysis of the tradeoff between multi-agent coordination overhead and the benefits of the hierarchical organization of agents. We first introduce our neural network based information retrieval system and then present experimental results with HOMIRS.

The authors previously suggested a graph-aided inference browser in which the knowledge engineers may easily verify the knowledge bases by consulting the sequence of inferring steps. In the suggested inference browser, however, the knowledge engineers themselves keep trying to find the error in the knowledge bases by checking if the displayed inferring sequence faces the undesirable situation. This error-detecting process may be slow and not very accurate as the size of the knowledge base becomes very large. The authors present an extended version of the graph-aided inference browser in which the error detecting process is automatically done. As compared to the previous graph-aided inference browser, the presented inference browser involves one additional module, called an automatic verification module, which detects and analyzes the erroneous situation during the inferring process and corrects the associated errors in the knowledge base.

Content-based image retrieval system retrieves an image from a database using visual information. Among approaches to expressing visual aspects in queries, "query by sketch" is most convenient and expressive. However, the query drawn by the user is typically quite different from the original image and makes it difficult to retrieve the intended image effectively. In this paper, a new method to retrieve the intended image from imperfect queries is presented. The user-drawn query image is converted to a prime edge graph that represents the topological structure of the objects in the image. The experimental results show that the system retrieves the intended image even from a partial or shifted query.

Studies a new method for integrating forward and backward chaining controls based on a Rete network. The authors introduce the concept of the hypothesis objects, and augment the production rule format by adding the hypothesis condition elements in the LHS part of a rule, which control the forward and backward chaining invocation of rules. To be applied to the backward chaining, a modified version of the Rete network has been formulated by adding the hypothesis-and-nodes and backward direction edges to the node network generated by the Rete algorithm. The authors then develop a backward chaining algorithm which takes advantage of already existing partial match results obtained by the previous forward chaining. The forward and backward chaining can be naturally integrated via the generation of hypotheses from forward chaining inference. The whole mixed inference process has the potential advantages over purely forward and backward chaining strategy.