Koichi Nakaoka

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Progresses in the development of the TFA-MOD process for the coated conductors in Japan are reviewed. In the fundamental approaches, some important advantages of Ba-poor starting solution were found such as for obtaining higher <i>Jc</i>, shorter reaction time and wider process temperature window. The high <i>Ic</i> value of 735 A/cm-w@77 K was attained.(More)
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/(More)
The recent progress in R&amp;D of TFA-MOD process for the coated conductors is reviewed. On the effort towards fabricating high I<sub>c</sub> tape, a new process to prevent crack formation in the thick film, which is the intermediate annealing between calcination and crystallization steps, was developed. Additionally, control of the composition from the 123(More)
Recent progress in the research and development of the TFA-MOD processing for the coated conductors in Japan was reviewed. For the higher Ic performance, the optimizations both in the calcinations and crystallization steps have taken place. Consequently, the extremely high Ic value of 413 A was achieved by the combination of the information from the above(More)
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(More)
We have investigated the influence of the H<sub>2</sub>O vapour inlet temperature in the calcination on both the microstructure and superconducting properties of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub>, (YBCO) films fabricated by the TFA-MOD method, from the viewpoint of the process control in the reel-to-reel system. Low critical current(More)
We have investigated the effects of the heating rate in the crystallization process on I<sub>c</sub> values and microstructures of YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-5</sub> (YBCO) films, which were fabricated by the advanced metalorganic deposition(MOD) method using trifluoroacetates. As a result, it was found that the slow heating rate less than(More)
The crystallization process of trifluoroacetate-metal-organic deposition derived YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-y</sub> (YBCO) crystals has been investigated to understand the influence of the starting solution composition on the crystal growth process. The starting solutions with molar ratios of Y: Ba: Cu = 1.0: 2.0: 3.0 (stoichiometry) and(More)
Influence of process conditions including water vapor partial pressure, gas flow rate and total annealing pressure on YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-y</sub> (YBCO) film growth has been investigated in order to clarify the YBCO growth mechanism and to increase the growth rate. YBCO films have been fabricated on a LaAlO<sub>3</sub> substrate by(More)
We fabricated Y<sub>0.77</sub>Gd<sub>0.23</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<italic><sub>y</sub></italic> [(Y,Gd)BCO] and BaZrO<sub>3</sub> (BZO) nanoparticle doped (Y,Gd)BCO ((Y,Gd)BCO+BZO) films on CeO<sub>2</sub> buffered metallic substrates [ = coated conductor (CC)] by using trifluoroacetate metal organic deposition (TFA-MOD). In this paper, in order(More)