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

We have 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.

Pinning effect induced by a grainlike structure on top of a TbFeCo recording layer with an Al or Ag underlayer is investigated. We confirm that the pinning effect depends on the surface structure of the recording layer as well as the underlayer. The Al-underlayered TbFeCo medium shows higher recording density during thermally assisted magnetic recording and higher coercivity than those of the Ag-underlayered one. We can observe that only the Al-underlayered TbFeCo medium has the grainlike structure on top of the TbFeCo recording layer, which reflects well a grainlike structure on the Al underlayer's surface. It indicates that the surface profile of not only the underlayer but also the TbFeCo recording layer laminated onto the underlayer is necessary for inducing the strong pinning effect in the TbFeCo magnetic recording media.

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.

Recent progress in the research and development of the TFA-MOD processing for the coated conductors is reviewed. For the higher Ic performance, process conditions such as heating rate and water vapor inlet temperature in the calcination step and heating rate and water vapor pressure in the crystallization step have been optimized to obtain YBCO films with good crystallinity. Consequently, a high Ic value of 431A/cm-w was achieved by the combination of the above optimized conditions with the use of highly textured CeO2 cap layered substrates. Forwards the effort for long tape fabrication with high production rate, the multi-turn system for coating and calcination step was developed. Additionally, the reel-to-reel system for the crystallization step was developed for the longer tape, and a 25m long YBCO tape with a reasonable end-to-end Ic value of 100A, which corresponds to 2500Am as a product of IcxL, was obtained by the above continuous system. For the higher production rate in the crystallization step, it was confirmed that optimization of the processing parameters such as high water partial pressure, high diffusion constants due to low total pressure, and a high gas flow rate affects the YBCO growth rate.

A multi-turning Reel-to-Reel tape conveyance system of the long YBCO coated conductors using TFA-MOD process is desired to be high production rate without large degradation between tape lines. The numerical simulation, which calculated the YBCO growth kinetics, gas element diffusion and gas flow, shown a possibility that the vertical gas flow onto the tape surface realized high production rate of YBCO conductor even on the wider tape. This possibility was also proved by experimental measurements.

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.

We developed a new precursor solution that consists of copper naphthenate, and yttrium- and barium-trifluoroacetates (advanced TFA solution) that can make the heating rate during calcination increase while maintaining a high Jc. In this paper, we investigated the influence of HF gas generation on the calcination process in order to optimize an advanced TFA-MOD process. The high heating rate and/or low copper content in the starting solution lead to a low Jc. In both cases, a high generation rate of HF gas was observed. Consequently, it is clear that rapid HF gas generation leads to the formation of pores that cause a reduction in Jc values.

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.

In order to shorten the calcination time in the metal-organic deposition (MOD) process using metal trifluoroacetate (TFA), a new combination of starting materials was developed using the F-free salt of Cu and TFA salts of Y and Ba as a so-called "new solution". Moreover, a new process temperature profile for this solution was developed as an advanced TFA-MOD process in which a high heating rate was achieved. Consequently, an overall transport Ic value of 210 A and a Jc value of 1.5 MA/cm2 (77 K, Self-field), similar to Ic and Jc values using TFA for all salts, were obtained. In order to obtain higher Jc performance, the effects of process parameters such as the heating rate in the calcination process for the Jc characteristics were investigated. As a result, a YBCO film with a thickness of 1.2μm was fabricated on a CeO2/IBAD-Gd2Zr2O7 layer-buffered Hastelloy substrate with Δφ∼7°. The overall Ic value of 251 A (77 K Self-field) corresponding to the Jc value of 2.1 MA/cm2 was achieved by calcination at a heating rate of 2°C/min.

The YBCO growth rate dependence on flow-direction during the TFA-MOD process was investigated in order to apply the model to long tape processing. As a result, the YBCO growth rate strongly depended on the substrate position from the windward and decreased as distance increased from the windward position along the film-width direction. This suggests the effect of two-dimensional diffusion is not negligible. The use of two-dimensional analysis of the YBCO growth rate for the gas flow-direction during the post-annealing process has been discussed to understand substrate position influence on the growth rate by considering the gas flow rate and mass diffusion in the gas boundary layer and precursor. From the analysis, it was suggested that the YBCO growth rate decreases toward the leeward region with the distribution of both H2O and HF gases, which rise out of the YBCO growth. Consequently, the growth rate estimation from the model was in good agreement with the experimental results.

YBa2Cu3O7-δ (Y123) films were deposited under various water vapor partial pressures (P(H2O)) in the crystallization process by an 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(H2O) such as 2.1%, large pores were remarkably observed. Furthermore, there were many amorphous layers of non-superconducting phases in the film. In contrast, small pores were distributed in the films deposited under higher P(H2O) of 4.2, 6.3 and 13.5%. Considering that the critical current (Ic) values become higher as P(H2O) increases, the existence of large pores and non-superconducting phase compounds causes a reduction in Ic. By investigating the microstructures of the films quenched during the crystallization process, it was found that the pores in the films are generated by the reaction of the non-superconducting phases trapped in the growing Y123 film, which then transform to Y123 afterwards accompanied by volume reduction of about 30%. The sizes of the entrapped phase crystals in the Y123 film depend on the P(H2O), and this may determine the pore sizes in the final film.

In order to shorten the calcination time in the metal-organic deposition (MOD) process using metal trifuluoroacetete (TFA), a new combination of starting materials was developed using F-free salt of Cu and TFA salts of Y and Ba as called “New solution”. Moreover, a new process temperature profile for this solution was developed as an advanced TFA-MOD process where the high heating rate was achieved. Consequently, the overall transport Ic value of 210 A and the Jc value of 1.5 MA/cm2 (77 K, Self field) similar to Ic and Jc values using TFA for all salts were obtained. In order to obtain higher Jc performance, the effects of process parameters such as degree of in-plane alignment Δφ of the buffer layer and PH2O in the annealing process for the Jc characteristics were investigated. As a result, a YBCO film with 1.48 μm in thickness was fabricated on a CeO2/IBAD-Gd2Zr2O7 layer buffered Hastelloy substrate with Δφ=4.7°. The overall Ic value of 292 A (77 K Self-field) corresponding to the Jc value of 2.0 MA/cm2 was achieved. Moreover, the overall Jc value of 2.1 MA/cm2 (77 K Self-field) for the YBCO film with 1.2 μm thickness was achieved by annealing under the PH2O value of 13.5 vol% on a similar metal substrate even with Δφ∼7°.

The effect of thin Al underlayers for amorphous TbFeCo-based, perpendicular magnetic recording media were studied in a laser-assisted and also in a non-assisted, conventional magnetic recording method. With the insertion of only a few nanometers of Al underlayer underneath a TbFeCo layer, an increase of coercivity was observed and the linear recording density was improved. It is considered that the relatively rough, grain-like surface structure, of the Al underlayer worked as pinning sites for the TbFeCo laver.

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.

YBa2Cu3O7−y(Y123) and Nd1+xBa2−xCu3O7−y (Nd123) films were deposited by the metalorganic deposition method, and the growth mechanism of these films was investigated by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy. The Y123 and Nd123 films were prepared by spin-coating LaAlO3 (001) and SrTiO3 (STO) (001) substrates, respectively, with solutions including trifluoroacetates. Then, the samples were heat treated at 673 K in a humid O2 gas flow to form amorphous precursor films. Finally, the precursor films were heated at higher temperatures for 0–30 min in a humid Ar/O2 gas flow and cooled rapidly from those annealing temperatures. It was found that CuO crystals with a size of 10–20 nm are segregated in the Y123 and Nd123 amorphous precursor films. In the Y123 quenched film prepared by cooling the precursor film rapidly after the heat-treatment at 1048 K for 30 min, a polycrystalline film including Y2Cu2O5, BaF2, and CuO crystals was found to be generated on the c-axis-oriented Y123 film. In contrast, in the Nd123 quenched films, (NdBa)2CuO4(Nd201) phase was found to be formed first on the surface of the STO substrate. In conclusion, the c-axis-oriented Y123 film is formed by diffusion and reaction of Y2Cu2O5, BaF2, and CuO crystals, and the Nd201 phase reacts with BaF2 and CuO crystals in a humid atmosphere to form a c-axis-oriented Nd123 film.

We attempted to increase the signal intensity of small pits the sizes of which were smaller than the optical diffraction limit in read-only memory (ROM) disks. For this purpose we employed a granular film and a thermochromic film in this study. The reason for using these films was to apply the super-resolution near-field structure (super-RENS) model, which suggests that the signal intensity of very small marks is increased by metal nanoparticles or a small aperture in the disk, to super-ROM. We investigated the effect of adjoining these films to a reflective layer on readout signals. It was found that the signal intensity of very small pits was increased by both of these films, but the mechanisms of increase were different.