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Ce-doped yttrium aluminum garnet (YAG:Ce) has been used as a phosphor emitting white light using a blue-light-emitting diode as a light source. Recently, studies on laser lighting as next-generation lighting have been carried out. However, because a high-power blue laser diode is used as the light source, the decrease in phosphor emission due to temperature increase (thermal quenching) has become a serious issue. Therefore, it is desirable to develop a method to suppress the temperature increase of the YAG:Ce phosphor. To increase the thermal conductivity of the YAG:Ce phosphor and suppress the temperature increase, we fabricated a composite ceramic of AlN (nonoxide), which has a high thermal conductivity, and YAG:Ce (oxide) using a modified vapor transport equilibration technique. The oxynitride was not completely removed, but we succeeded in adding up to 80 wt% AlN to YAG:Ce. The ceramic with 50% added AlN had a thermal conductivity up to 19.2 W m−1K−1 and emitted almost the same intensity as that of the nondoped YAG:Ce. This thermal conductivity exceeds the reported values of 12–13 W m−1K−1 for Al2O3–YAG:Ce composite ceramics. Moreover, the luminous efficacy exhibited by the ceramic with a 20 wt% AlN addition was 266.0 lmW−1, which is larger than the reported values obtained from composite ceramics.

We have studied two types of heating systems to produce thick GdBa2Cu3O7−X (Gd123) films with high critical current (Ic) stably at a high speed by the PLD method. Material yields of both PLD systems reached about 50–60% by optimization of evaporation condition. Hot-wall heating type (type 2) could fabricate the thicker Gd123 film with the higher Ic compared to contact heating type (type 1) and maximum Ic reached 1040 A at about 6 μm thick. Furthermore, it was estimated that type 2 could fabricate Gd123 film with an Ic of about 700 A at about twice speed compared to type 1. Finally, it was considered that the hot-wall heating type was very advantageous to prepare thick Gd123 film with high Ic at a high speed from the system structure.

This paper describes a process for the fabrication of coated conductor (CC) wires, which is developed by Fujikura, and discusses their properties. These wires are composed of a buffer layer, which is formed by the ion beam assisted deposition (IBAD) technique, and a superconducting layer, which is formed by the pulsed laser deposition (PLD) process. In order to increase the I c × L which means the product of critical current ( I c ) and the length ( L ) of the CC wires the I c value and I c distribution along the length of CC wires have been improved by using a new PLD pilot plant. The I c value increases approximately linearly with the thickness of the superconducting layer, and it continues to increase up to a thickness of approximately 4 μm or 5 μm. The I c × L value of our fabricated CC wire is 176,023 Am. The I c value of a short sample is 972 A/cm. The process rate of IBAD is enhanced up to 100 m/h and that of PLD is enhanced up to 20 m/h. A 40-m long CC tape, which has an average I c of 300 A, is fabricated by the improved IBAD and PLD techniques.

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.

We have developed long Gd-123 coated conductors by ion-beam-assisted deposition (IBAD) and pulsed-laser-deposition (PLD) method. Recently, large-scale reel-to-reel apparatus with the 110 cm × 15 cm assisting ion source was introduced to IBAD system. It was enable to produce 500 m-class IBAD–Gd 2 Zr 2 O 7 (GZO) tapes with Δ ϕ of below 15° and high throughputs of 3 m/h. Furthermore, apparatus with multi-lane and laser scanning was introduced to PLD system. As a result, end to end I c of 318 A were obtained for a 201.5 m long tape, and I c × L values were 64,077 Am. Furthermore, 500 m-class deposition was carried out by improving PLD conditions. As a result, I c × L values of 112,166 Am was obtained and it’s a world record on August 2007. In the short samples, I c of over 500 A was obtained with Gd-123 thickness of 2.0 μm and over 100 A was obtained in magnetic field of 3 T, perpendicular to c -axis.

We have developed a long Y-123 coated conductors by ion-beam-assisted deposition (IBAD) and pulsed-laser-deposition (PLD) method. Now, we can routinely obtained 100 m class Y-123 tapes with over 100 A at 77 K. For power applications using Y-123 conductors, coiling and cooling techniques are important elements. From 2004, we have developed and demonstrated a solenoid type coil that is the most suitable for practical application because it has advantage such as (1) uniformity of magnetic field (2) no joint. In this paper, we describe the development of conduction-cooled HTS test coil that has 14 turn × 22 layers using 100 m Y-123 conductors. In order to use the conduction cooling system, the Y-123 conductors were stabilized for 0.1 mm thick Cu tapes and spacers between the layers consisted of aluminum nitride in the coils. In the demonstration of this coil at 30 K, 40 K, 50 K, 60 K and 77 K by cryo-cooling system, the good cooling and superconducting performances were observed. The central magnetic fields of over 1 T were successfully obtained with operating currents of over 400 A and under 40 K. Furthermore, this coil was operated on additional magnetic fields of 3 T by combination of LTS magnets. The central magnetic fields of 0.5 T were generated from the cooled HTS coils with operating current of 190 A on additional magnetic fields of 3 T by LTS magnets at 30 K. Total magnetic fields were exceeded 3.5 T at 30 K.

We have developed long tape processing for coated conductors by the advanced TFA-MOF method. In order to obtain uniform and high superconducting performance, a 25-m long tape with dummy tapes, which were connected at the both end of the 25-m long tape, was fabricated by the reel-to-reel (RTR) system with a relatively high gas flow rate. As a result, a uniform I c value over 100 A and a high end-to-end I c value of 100 A were obtained in the tape. It revealed the I c · L product of 2500 A m. For higher I c · L products in long tapes, the key process factors were investigated.

We have investigated the effects of a heating rate in the calcination process on microstructures of YBa 2 Cu 3 O 7− y (YBCO) precursor and final films. As a result, it was found CuO segregation in the YBCO precursor film, when the precursor was prepared at a rapid heating rate in the calcination. In the case of heating this precursor film in the crystallization process, many large pores and misoriented YBCO crystals tend to remain in the YBCO final film and its I C value deteriorates compared with the case of crystallizing the precursor, which is prepared at the slow heating rate in the calcination. It is important to control the heating rate in the calcination, in order to attain higher J C of the YBCO final films.

Recent progress in the research and development of the TFA-MOD processing for the coated conductors was reviewed. For the higher I c performance, crack generation in the thick films was a problem, which limits increasing I c values. It was found that both lower heating rate and low P H 2 O in the crystallization step are effective to improve the critical thickness for obtaining crack-free films. However, the high P H 2 O is preferable for a high production rate and high J c performance. Then, the new heat treatment profile, which could suppress crack formation even in thick films under the high P H 2 O , was developed. Consequently, the high I c value of 470 A at 77 K was realized in the film with 3 μm in thick. Concerning the long-tape processing, the key factors for high I c performance by TFA-MOD process were investigated. The highly textured substrate for high crystallinity of the YBCO layer, the thick film with maintaining reasonable high J c and full conversion reaction to form the YBCO layer are important to obtain high superconducting performance in long tapes. At present, a 25 m long tape with a reasonable high I c value of 100 A, and a high I c value of 250 A in a 4 m long tape were achieved. In order to realize a high production rate, the processes for both calcination and crystallization steps have to be developed. In the calcination step, the multi-turning continuous system was developed to maintain an effective travelling rate even in the multi-coating method. On the other hand, in the crystallization step, it was confirmed that optimization of the processing parameters such as a high water vapour partial pressure, a low total pressure, and a high gas flow rate could make the YBCO growth rate increase. The combination effect of these parameters is experimentally confirmed and the 5 times higher production rate was achieved in the crystallization step. Additionally, the equipment design of the multi-turning system with a new gas flow concept, which is a vertical gas flow system, was investigated by means of both numerically and experimentally, and the concept was confirmed at least. Consequently, a high production rate over 5 m/h could be expected by combining the above mentioned effects.

High quality YBa 2 Cu 3 O 7− δ coated conductors with a length of several hundred meters are available now. For practical applications of long tapes, non-destructive and efficient techniques for characterization are necessary. For that purpose, we installed a commercial machine. The measuring principle is that a tape is introduced into a space of an applied magnetic field and the induced current within the superconducting tape is evaluated by measuring the magnetic field distribution just above the tape surface using a Hall sensor array. The advantages of the technique are that the measurement speed is rather high, 15 mm/s at maximum, and tapes are absolutely safe from damages by excessive heating. On the other hand, the estimation of the critical current is not straightforward because the issue of the calibration is not trivial. A 2D computer simulation code was developed to calculate the distribution of the induced current within the tape. In the simulation, it was assumed that the current–voltage relation of the superconductor obeys a power law. It is shown that the critical current deduced from the measurement is strongly dependent on the n -value.

We have investigated influences of the H2O gas inlet temperature in the calcination process on both microstructures and superconducting properties of YBCO films fabricated by the advanced TFA-MOD process, from the viewpoint of the process control in the reel-to-reel system. Low Ic values were recognized in the films which were prepared by introducing the H2O gas from the lower temperature than 200 °C. XRD measurements and cross-sectional TEM observations suggest that the YBCO films calcined with the H2O inlet temperature below 200 °C revealed a random orientation without epitaxial growth. Consequently, it has been understood that control to keep low partial pressure of the H2O gas in a lower temperature region is important for fabrication of long-length YBCO tapes with high performance by the reel-to-reel system.

We fabricated Y 1− x Sm x Ba 2 Cu 3 O y and YSm x Ba 2 Cu 3 O y (YSmBCO) films on SrTiO 3 (STO) single crystalline substrates and IBAD buffered metallic tapes (PLD-CeO 2 /IBAD-GZO/Hastelloy) by the advanced TFA-MOD process by mixing TFA salts of Y, Sm, Ba and Cu naphthenate, and tried to improve the superconductivity properties compared with those of the pure YBa 2 Cu 3 O 7− δ (YBCO). As a result, J c values of Y 1− x Sm x Ba 2 Cu 3 O y films with x = 0.05 or 0.3, which were fabricated on STO substrates, were improved under the high magnetic fields compared with those of the YBCO without substitution. However, Sm segregation was detected near the STO substrate which was obtained by the TEM–EDS (transmission electron microscopy–energy-dispersive X-ray spectroscopy) analysis. On the other hand, Y 1− x Sm x Ba 2 Cu 3 O y films with x = 0.05 and YSm x Ba 2 Cu 3 O y films with x = 0.3, which were fabricated on IBAD buffered metallic substrates, also improved I c value under the high magnetic fields compared with those of the YBCO without substitution. Moreover, from the TEM-EDS analysis, Y or Sm segregation was not found. The difference in the Sm segregation behavior between the film on STO and CeO 2 buffered substrates could be explained by the difference in the ratios of the misfit parameters between YBCO/substrate and SmBCO/substrate. Additionally, it was considered that the above phenomenon might be unique in the MOD system and could not be observed in the PLD system, because of the difference in the crystal growth mechanism. In the film of YSm 0.3 Ba 2 Cu 3 O y , we observed the grains of (Y, Sm) 2 O 3 and (Y, Sm) 2 Cu 2 O 5 by TEM observation. We will further investigate the origin of pinning centers.

To realize a higher production rate is one of the important issues in the development of the long-tape processing for the YBCO coated conductors by the TFA-MOD process using the reel-to-reel system. Not only scale-up of the furnace and decrease of YBCO thickness with the higher Jc value, but higher YBCO growth rates could be effective to achieve a higher traveling rate in this system. It was confirmed that optimization of the process parameters such as high water vapor partial pressure, high diffusion constants due to a low applied total pressure, and a high gas flow rate affect the YBCO growth rate. Consequently, these higher growth rate conditions were simultaneously applied to the reel-to-reel system. As a result, the traveling rate of 1.2 m/h was achieved for fabricating YBCO films in the reel-to-reel system, which is about five times as fast as the previous traveling rate with maintaining high Ic value of higher than 200 A/cm-width by controlling above conditions.

We have investigated the influence of the heating rate in the calcination process on the superconducting properties in order to optimize an advanced TFA-MOD process. The increase of the heating rate makes J c values lower, and the maximum values of HF gas generation rate higher. From TEM observation of the precursor film, the large pores and segregation of Cu elements were observed in the films at high heating rates. Consequently, it is clear that the increase of the heating rate during calcination process caused abrupt HF gas generation leading to degradation of the surface morphologies, formation of large pores and segregation of Cu elements. These morphological and microstructual differences could be one of the reasons for a reduction in J c values of the YBCO films.

We have prepared Y123 quenched and fully crystallized films by the conventional and the advanced TFA-MOD processes. Then, we have investigated microstructures of the films by means of transmission electron microscopy, in order to understand the initial stage of the Y123 growth. As a result, it is found that Y–Ba–O–F grains firstly nucleate on LaAlO 3 single crystals as well as on CeO 2 buffered metal substrates both in the TFA-MOD processes. The Y–Ba–O–F is grown with epitaxially orientated relationship to the substrate. A BaCeO 3 reaction product layer is formed due to Ba diffusion from Y123 to CeO 2 mainly through the grain boundaries. At the crystallization temperature of 760 °C, the diffusion rate of Ba is slow. Therefore, it was found that the thickness of the BaCeO 3 layer does not increase much further with increasing the holding time until about 1000 min.

We have developed a reel-to-reel reaction furnace equipped with seven transverse flow modules, for the continuous TFA-MOD process. Experimental results have revealed that as the wire length increases, the processing parameters need to be adjusted in order to obtain YBCO films with high critical current density ( J c ) than 1 MA/cm 2 at 77 K and self-field. As a result of fabrication under the appropriate process conditions, we have successfully produced uniform tapes with a high performance in a short sample. In the recent progress, heat-treatment conditions have been optimized and the higher gas flow rate was applied to the long tape fabrication, and the I c value of higher than 100 A as the end-to-end one of a 8.5 m long tape was attained.

The recent progress in coated conductor development by the TFA-MOD process was reviewed. Much progress was recognized in the R&D on TFA-MOD processing for satisfying several requirements, such as high superconducting performance, long tape production, high production rate, etc., considering the real application. For high superconducting performance, the high I c value of 413 A was achieved in a short sample with an architecture of MOD-YBCO/IBAD-GZO/IBAD-GZO/Hastelloy. It was realized by improving the in-plane crystal grain alignment of the CeO 2 buffer layer and optimizing conditions of the heat treatments in the calcination and crystallization processes. In the calcination process, it was found that lower heating rate was effective to improve the morphology of the multi-layered precursor by preventing from pore generation and segregation of Cu elements. In the crystallization process, it was found that high humid gas partial pressure was effective to improve the J c values by reducing the amounts and size of pores in the YBCO layers. Furthermore, in the case of thicker firm, it was found that the low heating rate in the crystallization process was effective to prevent from the crack formation. On the other hand, in order to obtain the long tape with uniform I c values, in the crystallization process, the gas flow condition in a large scale equipment for the continuous long tape process was investigated using a computer simulation technique. Consequently, the 8.6 m YBCO on PLD-CeO 2 /IBAD-Gd 2 Zr 2 O 7 /Hastelloy tape which shows high I c performance of 119 A as an end-to-end value at 77.3 K in self fields, was successfully obtained. As a result, I c × L (length) value of 1024 A m was achieved.

YBCO films were fabricated on PLD-CeO 2 /IBAD-Gd 2 Zr 2 O 7 /Hastelloy substrates using the TFA-MOD process. In order to obtain higher I c performance, the thicker films maintaining high- J c values are required. J c depended strongly on the P H 2 O during the crystallization in the process. The pore size was smaller in the high- J c films crystallized under the medium P H 2 O condition and became larger in the low- J c films under both lower and higher P H 2 O for the YBCO films with a constant thickness. Furthermore, crack generation was observed in thick films crystallized at the high P H 2 O condition. Consequently, both pore and crack formations limit the J c properties since large pore causes local reduction of current paths and additionally results in local concentration of electric fields. J c also depended strongly on the YBCO crystal grain alignment which is affected by in-plane grain alignment of the buffered substrate. Then, the effect of in-plane grain alignment of the CeO 2 cap layer on J c was investigated for thicker YBCO films. As a result, the J c value increased with improvement of the crystal alignment of the CeO 2 cap layers. Finally, a YBCO film with a high- I c value of 413 A at 77 K in self-field was achieved in a film fabricated on Δ ϕ = 4° of the CeO 2 layer using the appropriate crystallization conditions for crack-free film.

We proposed a multi-dimensional numerical model of the YBCO growth in the TFA-MOD process, which was established in consideration of the basic concept of the one-dimensional analytical growth model, multi-component diffusion and convective gas flow. It was confirmed that the calculated growth rate values were in good agreement with experimental ones. Furthermore, this numerical method revealed an effective tool to determine a suitable configuration of the gas flow in the reaction tube for a high production rate in long YBCO coated conductors.

The TFA-MOD process was applied to fabricate YBCO films on PLD-CeO/sub 2//IBAD-Gd/sub 2/Zr/sub 2/O/sub 7//Hastelloy substrates. In order to obtain higher Ic performance, thicker films maintaining high J/sub c/ values are required. J/sub c/ depends strongly on the YBCO crystal alignment. Dependences of J/sub c/ on /spl Delta//spl phi/ of the CeO/sub 2/ substrates has been investigated. It was found that the J/sub c/ value increased with improvement of the crystal alignment of the CeO/sub 2/ buffer layers. Also, the J/sub c/ value depended strongly on the P/sub H2O/ during the crystallization. The pore size in the film was smaller in the high J/sub c/ films fabricated under medium P/sub H2O/ and becomes larger in the low-J/sub c/ films under low and high P/sub H2O/. Furthermore, crack formation was observed in thick films crystallized at high P/sub H2O/. The large pore causes local reduction of current paths and additionally introduces the concentration of electric fields. It was found that both the porosity and crack formations limit the J/sub c/ properties. Finally, a YBCO film with 2.05 /spl mu/m in thickness was fabricated on a CeO/sub 2//Gd/sub 2/Zr/sub 2/O/sub 7/ layer buffered Hastelloy substrate with /spl Delta//spl phi//spl sim/4/spl deg/. A J/sub c/ value of 2.02 MA/cm/sup 2/ and transport I/sub c/ value of 413 A at 77 K, self-field were obtained.

We have investigated the effects of heating rates in the calcination process on microstructures of Y123 precursor and final films. As a result, it was found that there is CuO segregation in the vicinity of the Y123 precursor film surface, when the precursor is prepared at a rapid heating rate in the calcination. In the case of heat-treating this precursor film in the crystallization process, many large pores and misoriented Y123 crystals tend to remain in the Y123 final film. It is important to control the heating rate in the calcination, in order to attain higher J/sub C/ of the Y123 final films.

As a method of the fabrication process of YBa 2 Cu 3 O 7− x (YBCO) coated conductors, the metalorganic deposition (MOD) process using metal trifluoroacetates (TFA) has been considered to be a strong candidate as a low cost fabrication process for coated conductors with high J c . In the case of the MOD process using the TFA salts for the all three elements, it requires several tens hours in the calcination process for each single coated film to minimize the generation of pores in the film. In order to shorten the calcination time, a new combination of starting materials was developed. In this study, the new heating process for these new materials has been investigated. Consequently, the calcination time was shortened to be about 17%. Also, the overall transport I c of 292 A and the J c value of 2.0 MA/cm 2 were achieved with 1.48 μm in thickness at 77 K in self-field.

Influence of the process conditions, including the water partial pressure and the total annealing pressure, on YBa 2 Cu 3 O 7− y (YBCO) film growth has been investigated in order to increase the growth rate. YBCO films have been fabricated on SrTiO 3 substrate by metal-organic deposition using trifluoroacetates (TFA) as a solute source under the low-pressure atmosphere. It was observed that the growth rate of the YBCO film was in proportion to the square root of the water partial pressure and was in inverse proportion to the total pressure. A higher YBCO growth rate was achieved about 3 times as fast as that under the atmospheric fabrication conditions with maintaining the high J c performance. On the other hand, the volume fraction of a -axis oriented grains in the YBCO film was strongly dependent on the growth rate, a -axis oriented YBCO grains were clearly recognized in the films grown with either very low or very high growth rate. As a result, it was found that the growth region should be controlled to prevent from the growth of the a -axis oriented grains.

The recent progress in R&D of coated conductors by TFA–MOD process was reviewed. For the several targets, such as high superconducting performance, high production rate, long tape etc., the steady progresses could be recognized. The high J c and I c values of 3.6 MA/cm 2 and 291 A were achieved by using a highly aligned CeO 2 cap on an IBAD–GZO layer and optimizing the conditions in the multi-coating process, respectively. For improving the production rate, the calcination time was extremely reduced by the development of the new combination of the starting materials. As the improvement of the production rate, the process for achieving high growth rate was investigated by controlling the atmosphere conditions in the high temperature heat treatment. It was found that both high humid partial pressure and low total pressure conditions were both effective to improve the growth rate and the three times higher growth rate with maintaining high J c than that in the conventional conditions was confirmed. Additionally, a 0.25 m long tape with uniform I c values over 200 A and the end-to-end I c value of 210 A was successfully fabricated with traveling in the furnace of the Reel-to-Reel system.

YBa 2 Cu 3 O 7− δ (Y123) films were deposited under various water partial pressures ( P H 2 O ) in the crystallization process by the advanced metalorganic deposition (MOD) method using trifluoroacetates. Microstructures of the films were evaluated by means of transmission electron microscopy. As a result, in the Y123 film crystallized under lower P H 2 O such as 2.1%, large pores were remarkably observed. Furthermore, there were many amorphous layers of a non-superconducting phase in this film. In contrast, small pores were distributed in the films deposited under higher P H 2 O . Considering that the critical current ( I C ) values become higher as P H 2 O increases, existence of large pores and non-superconducting phase crystals causes to reduce I C . Through the investigation of the microstructure of the films quenched during the crystallization process, it was found that the pores in the film are generated by reaction of the non-superconducting phases, which are trapped in the growing Y123 film afterwards, to transform to Y123 with accompanied by the volume reduction of about 30%. The sizes of the entrapped phase crystals in Y123 film depend on the P H 2 O and it may determine the pore sizes in the final film.

The long tape process was developed using the advanced TFA precursor solution. In a long tape production, the advanced TFA precursor solution was coated by a die-coater using the reel-to-reel system, and the multi-coating method was applied for thicker film fabrication. We successfully fabricated long uniform precursor films. In the high temperature treatment, a large scale equipment for the continuous long tape process was developed. This equipment had a perpendicular gas flow system to the tape length which is effective to fabricate the uniform films. I c values and its distribution in the YBCO tape fabricated by this method on CeO 2 /IBAD-Gd 2 Zr 2 O 7 /Hastelloy were measured. And the uniform and high performance was confirmed. A 0.25 m long YBCO film with 1.38 μm in thickness on the metal substrate shows the high I c performance of 210 A with end to end at 77.3 K in self-fields.

Y123 precursor and final films were deposited at various heating rates in the calcination process of metal organic deposition method using trifluoroacetates. The superconducting characteristics were evaluated in the final films. The microstructures and the distributions of chemical compositions of these films were also investigated using transmission electron microscopy and energy dispersive X-ray spectroscopy. In the Y123 precursor film prepared by heating at the rate of 0.2 °C/min in the temperature range from 200 to 250 °C, Cu was distributed uniformly. On the other hand, in the precursor film prepared by heat-treating at the rate of 5 °C/min from 200 to 250 °C, Cu was found to be segregated in the vicinity of the surface of the film. This Cu segregation in the precursor film might cause the differences of crystallinity and superconducting properties of the final film. The former precursor film was grown into a c-axis oriented Y123 film with good crystallinity, and exhibited the high JC value of 2 × 106 A/cm2. However, the final film prepared by heat-treating the latter precursor film had many stacking faults of CuO planes, and showed the lower JC value of 0.3 × 106 A/cm2.

In the development for the coated conductors, the trifluoroacetates-metal organic deposition (TFA-MOD) process using the multi-coating method was applied to form thicker YBa2Cu3Oy (YBCO) films on the CeO2 buffered IBAD(Zr2Gd2O7)/Hastelloy tape. As a result, in the 5 times coated film with 1.38 μm in thickness, the Jc and Ic values achieved to be 1.5 MA/cm2 and 210 A, respectively. Then, we fabricated a 1 m long YBCO tape by the continuous reel-to-reel system. As a result, we confirmed the tape to be homogeneous by XRD analysis. Additionally, we report the theoretical analysis of YBCO growth during post-annealing in the TFA-MOD process considering both the diffusion in the gas boundary layer and the growth kinetics at the precursor/YBCO interface. This model reveals a basic idea of the growth mechanism to define the steady state growth rate, and could explain the experimental results. In addition, it predicts that the growth rate could be estimated from the partial pressure of the water vapor of the inlet gas.

As a method of the fabrication processes of YBa 2 Cu 3 O 7− x (YBCO), the metalorganic deposition (MOD) process using metal trifluoroacetete (TFA) is considered to be a strong candidate due to its low cost fabrication process for coated conductors with high J c . In our previous work, a triple coated film with 1 μm in thickness was fabricated on a CeO 2 /IBAD–YSZ layer buffered Hastelloy substrate by optimizing the condition of heat treatments such as P H 2 O in the multi-coating method [Physica C 378–381 (2002) 1013]. The J c value of 1.6 MA/cm 2 (77 K in self-field) in this film patterned 100 μm width and the I c * value of 153 A/cm-width at 77 K in self-field were achieved. In order to obtain a thicker film with high overall I c * for 1 cm width, the influence of the heat treatment conditions of P H 2 O , P O 2 , and the temperature in the MOD process was investigated. Subsequently, a 5 times coated film was obtained on a CeO 2 /IBAD–Zr 2 Gd 2 O 7 layer buffered Hastelloy substrate by optimizing the conditions of heating and dip coating. As a result, the overall transport I c value was improved to 210 A and J c value of 1.53 MA/cm 2 was obtained (77 K in self-field).

The growth rate expression in the TFA-MOD process for fabrication of coated conductors was revised according to the measurement of the growth rate using a long tape. The P (H 2 O) distribution along the gas flow-direction was calculated by the advection diffusion model. The above two outputs were combined to predict the minimum annealing time for complete reaction in the sample tape with a finite width. The prediction from the model was in good agreement with the experimental results.

The metal organic deposition (MOD) process of YBa 2 Cu 3 O 7 - x (YBCO) using metal trifluoroacetate (TFA) precursors is considered to be a strong candidate as a low cost fabrication process in coated conductors since the TFA-MOD process is a non vacuum process and can provide high J c films. In order to develop long tape conductors using this process, the influence of the gas flow direction in the heat treatment was investigated. The J c value decreases toward to leeward side in the case of the parallel gas flow condition. On the other hand, in the case of the perpendicular gas flow condition. The J c value reveals uniformity in all over the tape and the high J c level is maintained. In the case of long tape production, it was found that the perpendicular gas flow to the tape length is effective to fabricate the uniform films. It could minimize the influence of consumption of H 2 O and generation of HF gas in the up-stream area to the leeward region. The J c and I c properties and these distribution of the YBCO tape fabricated by this method on CeO 2 /IBAD-Gd 2 Zr 2 O 7 /Hastelloy is presented. Furthermore, a large scale equipment for the continues long tape process was developed based on the above findings. Consequently we have fabricated a 1 m long Y123 tape conductor by a reel to reel system. Even in the first trial, the uniform reaction for the entire length was recognized.

For the development of the YBa/sub 2/Cu/sub 3/O/sub y/ (YBCO) coated conductors, processing of the thicker film and long tape have been investigated using the metal organic deposition (MOD) method with the trifluoroacetates solution. About 1 micro-meter thick MOD film was realized by the control of the P/sub H2O/ condition during annealing for the formation of the YBCO layer. The improvement was explained by the competition between the nucleation of the undesirable grains and the epitaxial growth up to the surface. By applying the suitable condition to the metallic substrate system, high critical current density (Jc) and critical current corresponding to 1 cm wide tape (Ic/sup */) were realized as to be 1.6 MA/cm/sup 2/ and 153 A/cm-w in the film with 1 micrometer thickness, respectively. For the fundamental investigation of long tape processing, influence of the gas flow direction during annealing for the YBCO formation was investigated. Although nonuniformities in the X-ray diffraction (XRD) intensities and Jc values were recognized in the film grown under the gas flow parallel to the long direction of the tape, both of them was improved by changing the gas flow direction to the transverse one.

We report the theoretical analysis of YBCO growth during post annealing in the TFA-MOD process considering both the diffusion in the boundary layer and the growth kinetics at the precursor/YBCO interface. As a result, we could obtain the analytical solution of the growth rate of YBCO. Subsequently, the unknown parameters in this solution were evaluated by the experimental measurements of the growth rate. The experimental results of the growth rate showed that it was independent of the film thickness and proportional to the square root of the water vapor pressure. These results suggested that the mass transfer in the gas boundary layer limited the growth rate. This model reveals a basic idea of the mechanism to determine the steady state growth rate, and could explain the experimental results. In addition, it predicts that the growth rate can be estimated from the water vapor pressure of the inlet gas. Consequently, it was confirmed that this growth model is effective for understanding of the growth kinetics in the TFA-MOD process.

YBa 2 Cu 3 O 7− y (Y123) and Nd 1+ x Ba 2− x Cu 3 O 7− y (Nd123) films were deposited by metalorganic deposition (MOD) method, and investigated by transmission electron microscopy and energy dispersive X-ray spectroscopy in order to elucidate the growth mechanism of the films in the MOD process. Y123 and Nd123 films were prepared by cooling rapidly during the final heat-treatment. In the case of the Y123 quenched film, it was found that a polycrystalline film is formed over a c -axis oriented Y123 film, and that there are Y 2 Cu 2 O 5 , BaF 2 and CuO particles in the polycrystalline film. In contrast, in the Nd123 quenched film, (Nd,Ba) 2 CuO 4 phase was found to be generated on the surface of the substrate. In conclusion, we suggest that the Nd123 film is formed by a reaction of (Nd,Ba) 2 CuO 4 , BaF 2 and CuO, although the Y123 film is grown by diffusion and reaction of Y 2 Cu 2 O 5 , BaF 2 and CuO crystals.

We have succeeded in patterning narrow lines and dots with 100 nm dimensions in a photoresist film by a ‘thermal lithography’ technique using a semiconductor laser with 635 nm wavelength. The demonstrated resolution of the patterns produced is far beyond the diffraction limit of 530 nm given by our optical set-up. We utilized a focused laser spot, which approximately has a Gaussian profile in its light intensity distribution, to produce a spatially confined hot area in a phase change recording layer on a conventional polycarbonate optical disk. This hot area induced a thermal cross-linking reaction in an adjacent photoresist film. By optimizing the sample rotation speed and the laser power, we were able to confine the area where the thermal cross-linking reaction in the photoresist occurred and patterned extremely fine structures.

The metal organic deposition process of YBa 2 Cu 3 O 7− X (Y123) using metal trifluoroacetate precursors is considered to be a strong candidate not only for high J c but also for low cost processing due to its a non-vacuum process. In this work, in order to obtain high I c films, thicker Y123 film processing on LaAlO 3 was investigated using the multi-coating method. In the case of thicker films, it was found that the low partial pressure of H 2 O, P (H 2 O) for the second heat treatment is effective to maintain the entire epitaxial growth for the thick films. Consequently, increasing of I c was realized from single to triple coating films. Further, in order to apply the technique to fabrication of coated conductors on metal, the bi-axially textured buffer layers is necessary to achieve a high in-plane alignment of the superconducting layer. Subsequently, the thicker film processing was applied to the CeO 2 /IBAD-YSZ/Hastelloy substrates using the multi-coating method. The triple coating Y123 film with 1 μm in thickness on the metal substrate shows the J c value of 1.6 MA/cm 2 at 77.3 K in self-fields and the I c performance of 153 A/cm-width.

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

Metal organic deposition (MOD) process using metal trifluoroacetate (TFA) precursors was applied to the NdBa 2 Cu 3 O 6+ y (Nd123) and the T c dependence of experimental conditions such as oxygen partial pressure ( P O 2 ) and substrate temperature ( T s ) for annealing was investigated. Thin films grown on single crystal SrTiO 3 at T s =800°C under P O 2 =3×10 −4 atm showed a T c0 of 89 K. However, from the results of TEM-EDS measurements, the substitution value of x in Nd 1+ x Ba 2− x Cu 3 O 6+ y increased from the substrate toward the surface in the film. These experimental results could be explained thermodynamically by the following model. The basic idea of our model is that the Ba potential is changed by coarsening of BaF 2 during the annealing for the growth. This model predicts that the small substitution value can be obtained with a higher growth rate of the Nd123 phase under low P O 2 .

Trifluoroacetate metalorganic deposition (TFA-MOD) process is expected as a low cost process for mass production of coated conductors because it is a non-vacuum process. In order to apply the technique to fabrication of coated conductors, suitable buffer layers have to be considered to achieve a high orientation of superconducting layer and prevention of the reaction with metal substrate. The combination of CeO 2 on IBAD-YSZ is considered as an effective buffer for TFA-MOD process expecting to satisfy a high acid resistivity and high crystal grain alignment. The CeO 2 buffer layer was deposited on IBAD-YSZ/Hastelloy substrates by RF magnetron sputtering. From XRD analysis, the CeO 2 buffer layer showed very good in-plane alignment on YSZ-IBAD buffer layer. In a holding time of 1 h, the suitable maximum heat treatment temperature was found to be from 750°C to 775°C for TFA-Y123 on metal substrate. The J c – B property of Y123 on CeO 2 /YSZ/Hastelloy shows the J c values of 1.4 MA/cm 2 at 77.3 K, 0 T and more than 10 5 A/cm 2 at 77.3 K, 2 T. The high performance under high magnetic field was confirmed.

We tried to apply NiO as a buffer layer to liquid phase epitaxy coated conductors on the Ni substrate. The 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 single phase from the NiO-saturated solution. Instead of Y123, we selected Sm123 or Nd123 that has a higher peritectic temperature than Y123, and confirmed that Sm123 or Nd123 could be grown stably from the NiO-saturated solution. Because of its low T c value of Sm123 or Nd123 grown from the NiO-saturated solution, the (Y,Yb)123 layer should be epitaxially grown as the superconductive layer on it. Finally we succeeded in growing a Sm123 layer on a Ni substrate from the NiO-saturated solution, and confirmed the structure of NiO buffered system.

Super-resolution readout was established by using a non-magnetic readout layer on a magneto-optical disk. The readout layer was composed of AgOx and separated from a recording layer at a near-field coupling distance as well as a super-resolution near-field structure (Super-RENS) disk. A laser-generated Ag cluster works as a scattering center in the readout layer to reproduce a Kerr rotation angle of a recorded mark. As a result, by using the AgOx readout layer, marks of about 200-nm size could be read out beyond the diffraction limit

As a result of applying super-resolution near-field structure to a magneto-optical disk with a non-magnetic mask layer such as a silver oxide light scattering center type mask layer, we could retrieve the signals of below 200-nm mark length. With the improved antimony transparent aperture type mask layer, in this work, we could get the polarized magneto-optical signals as well that we had not been able to obtain by using the previous antimony mask layer. This was well agreed with computer simulation result. Another optimization, such as magnetic layer thickness, dielectric materials and so on, was also investigated for a better magneto-optical disk of super-resolution near-field structure with a silver oxide light scattering center type mask layer.

A technique for reducing cross-recording on data storage media with high track density is described. In order to detect cross-recording sensitively, an inverted mark pattern was first recorded on adjacent tracks and then synchronized with a normal recorded mark pattern on the central track. These patterns were repeatedly recorded as the recording power was increased. Readout signals of the recorded mark pattern were evaluated on the central track in each condition, and an optimum recording power was precisely determined from the maximum amplitude of the signals. When this new technique was applied to a magneto-optical disk, the bit error rate was reduced to less than 10/sup -4/. This is the first technique to reduce cross-recording by laser power only.

Acoustic emission (AE) signals induced from an alternating current (ac) NbTi superconducting coil were studied to observe the relationship between AE signals and the superconducting states of the winding of the ac coil, around the time of quenching initiation during operation at a commercial frequency of 50 Hz. The envelopes of the AE signals induced at quenching initiation were analyzed using information from operating currents and voltages in the coil. The AE signals rose and increased in accordance with the appearance and enhancement of the normal components for most cases in a series of quenching tests, where the quenching was initiated at the coil ends. In the case that the quenching was initiated by a different cause, the AE waveform had a different pattern, in which the AE signals started like a impulsive signal having slow decay, and normal zone propagation was not initiated at the moment when the AE signal started. Those differences are compared and discussed.

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

In order to develop AC superconducting apparatus for power use, 10 kA/sub r.m.s./-class AC superconducting coils should be developed. From such a viewpoint, the authors have been investigating AC superconducting coils having a large AC transport current capacity. In this paper, the specification and experimental results of an 1 T/sub r.m.s.//1 kA/sub r.m.s./-class AC superconducting coil are shown. Two experimental AC coils using the sub-cable and single strand of this AC superconducting coil are also fabricated and tested to investigate the stability of AC coils. The quench current of each AC coil is measured and is compared to the DC critical current characteristics of the strand. From the result of the comparison, it is confirmed that the AC quench current of each superconducting coil is close to the DC quench current, and is close to the current which is determined by the critical current characteristics defined by 0.1 /spl mu/V/cm criterion. It is also confirmed that the quench point of the developed AC coil reaches to 1.396 T/sub peak//1288 A/sub peak/.

Acoustic emission (AE) induced from an alternating current (ac) superconducting coil was studied during operation in liquid helium. The operating current of the coil was increased from zero with a constant ramp rate at a commercial frequency of 50 Hz until quenching in the coil. The AE signals induced from the coil around the time of the quenching initiation were compared with the operating current, the coil voltage, and the phase difference between the current and the voltage in order to estimate the changes in those signals which resulted from the quenching process. The AE signals continued almost at very low levels before the quenching, At the moment of the quenching initiation, the AE signals clearly and drastically rose approximately 10-15 ms earlier than the decrease in the operating current or the phase difference. The AE signals induced by the wire motion during 50-Hz ac operation were also compared with the operating current.