Vol.7 No.4 2015

Research paper : Preparation of superconducting films by metal organic deposition (T. MANABE et al.)−250−Synthesiology - English edition Vol.7 No.4 (2015) Award of the Ichimura Prize in Technology and others. Engaged in the inorganic materials science research mainly for energy related applications. Succeeded for the first time in the world to synthesize the YBCO superconducting film using this method in 1987, and led the R&D for its synthesis and application. In this paper, was mainly in charge of Scenario I.Discussions with Reviewers1 OverallComment (Hiroshi Akoh, Thermal Management Materials and Technology Research Association)This paper focuses on the target of electrical application of a high-temperature oxide superconductor to the fault current limiter, and builds the scenario for its development and shows the selection and combination of the elemental technologies. I think it is valuable as a Synthesiology paper.Comment (Tetsuhiko Kobayashi, AIST)This paper is about the creation of a large-area superconducting film for application to FCL, and I recommend its publication in the journal.2 Explanation of FCLQuestion and Comment (Hiroshi Akoh)In this paper, the development of FCL is given as the electric power application of high-temperature oxide superconductors. Therefore, I think it is important to show a diagram that allows the readers outside the field to grasp the image of FCL. In the paper, the structure and operational principle of FCL are shown in diagrams, and it is described in the text in chapter 2, however I think readers can more easily understand if you present a figure that shows the role and importance of FCL in the power grid system. Also, I think you can clarify the correspondence to the photograph of the device which includes the prototype FCL shown in Fig. 8.Moreover, there is a description of “development of many types of FCLs” in chapter 1, however I think you should clarify by giving specific examples of other types of FCLs.Answer (Toshiya Kumagai)I added a figure that shows the role of FCL in the power grid system as Fig. 1, and inserted in the upper part of Fig. 2 a figure that shows the “FCL cooled in the cryostat” that shows correspondence to the photo of the device in Fig. 8.I added a few examples of active and passive FCLs in chapter 2.3 Relationship of Scenarios I and IIQuestion and Comment (Hiroshi Akoh)I understand that Scenarios I and II are continuously related toward the development of FCL, however the relationship of Scenarios I and II seems to become unclear since you explain them separately in Figs. 4 and 5. I think the main point of this paper is that you succeeded in achieving high Tc and high Jc by the MOD method, and using that as core technology and advancing the R&D to achieve a large-area film and multilayer, there was considerable progress in the FCL development. I think the scenario continues to mention that the application can extend to microwave devices by achieving low surface resistance and patterning, and in the future it can be applied to superconducting wires by achieving the long length and thick thickness. What do you think of the scenario where you discuss mainly the development of FCL and then spreading out to microwave devices and superconducting wire applications?Answer (Toshiya Kumagai and Takaaki Manabe)The scenario of the whole paper and its main point are as you indicated. However, describing the research in chronological order, it was still unclear that FCL was the outlet when we were setting Scenario I (at the time of discovery of the high-temperature superconductor). The application to various electric power devices was a “dream,” and in reality, we conducted R&D for “high Jc” as the essential goal to realize that dream. Later, when we achieved high Jc, we could regard various devices including FCL as specific targets, and only then did we set the goal to fulfill the product requirements, build the scenario to achieve them, and then engaged in the R&D. In this paper, we focus on the application to FCL, but we have concurrently worked on the application to microwave devices to some extent. Considering these points, we shall describe Scenarios I and II separately in the figures. In Fig. 5, we specify that the “success of epitaxial deposition and achievement of high Jc” in I-2 are the core technologies in Scenario II.4 Characteristic of the MOD methodQuestion and Comment (Tetsuhiko Kobayashi)You describe in subchapter 1.2 as one of the characteristics of MOD that “(4) it has low environmental load since it emits only steam and carbon dioxide during firing,” but aren’t VOC and incomplete combustion gas produced depending on the condition?Answer (Takaaki Manabe)As you indicated gases such as VOC may be produced in incomplete combustion. Also, this item is not a characteristic of the MOD method compared with the gas phase method, but is the characteristic of the FF-MOD method using fluorine-free materials that was employed in this paper, in contrast to the TFA-MOD method that uses trifluoroacetate as the raw material. I added and revised item 4 to make this clear to the readers.5 Infrared rapid heating processQuestion and Comment (Hiroshi Akoh)This is a technical question. As you describe in chapter 5, you developed the rapid heating process by infrared heating to inhibit the a-axis oriented growth and to obtain the c-axis oriented film. Were there any cracks in the film due to the difference in thermal expansion coefficients of the substrate and the film? Please explain if there were no cracks.Answer (Takaaki Manabe)No cracks occurred by rapid heating for the YBCO film with thickness of 700 nm on LAO. I explained that it is because they are lattice matched and their thermal expansion coefficients are close.Also, the film on sapphire that has large thermal expansion difference tends to get micro-cracks during cooling after deposition, and the thickness of the YBCO film is limited to 300 nm or less. I added this in chapter 2.6 Achievement of a large-area thin films and a low-temperature processQuestion and Comment (Tetsuhiko Kobayashi)To achieve a large-area thin films, you say, “a low-temperature process was developed to increase the Jc by decreasing the interface reaction between the film and the substrate and by improving the orientation.” For readers outside the field, the meaning of “decreasing the interface reaction between the film and the substrate” is difficult to understand, and I think you need some supplementary explanation.Answer (Takaaki Manabe)Including the point that you indicated, the description of the draft was not well organized, so I changed the description to the following: the chemical reaction occurs at the interface between the YBCO film and the substrate when the firing temperature is high → a low-temperature process was developed to inhibit the interface reaction → this low temperature allowed use of lattice-matched substrates → orientation of the YBCO film was improved using the lattice-matched substrate.


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