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  • Jianshe Yue 1,
  • Zhen Li 1 and
  • Huimin Cai 2,*

Reviewer 1: Anonymous Reviewer 2: Anonymous Reviewer 3: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article addresses an interesting and important technological issue related to the fabrication of single-layer Y₂O₃ buffer films on Ni-W tapes using a photochemical sol-gel method for YBCO superconducting tapes. The presented results, including the achievement of a dense microstructure and a critical current density Jc of 2.65 MA/cm² at 77 K, are coherent and well-documented. However, the manuscript requires several significant editorial and formal revisions.

In the section dedicated to photochemical equations on page 7, there is a numbering error, as all three consecutive equations describing the formation of ozone and oxygen radicals have been mistakenly labeled with the same number (1).

Additionally, typos appear in the main subsection headings on pages 4 and 6 in the word "Analysis", which was incorrectly spelled as "Anlysis" (in sections 3.2 and 3.3, respectively).

A minor editorial flaw also concerns the axis label in Figure 11, where the vertical axis of the resistance versus temperature (R-T) plot uses the incorrect term "Resistance(Omhic)" instead of the standard form (or Ohmic word).

The manuscript lacks information on the thickness of the YBCO superconducting layer, which prevents the evaluation of the total critical current (Ic) of the superconducting tape, despite providing the critical current density Jc. The authors should supplement the data with the YBCO thickness (measured, for example, by cross-sectional SEM) and provide the Ic value.

Furthermore, in the section concerning the Y2O3 buffer layer, the authors should provide a broader discussion on the choice of repeating the coating procedure three times (which yields a final thickness of approx. 0.488 µm) and address how the buffer thickness affects the effectiveness of blocking diffusion from the Ni-W substrate. 

The authors rightly emphasize that employing a single-layer Y2O3 buffer simplifies the superconductor architecture and reduces manufacturing costs compared to traditional multi-layered structures. However, the manuscript lacks any information or discussion regarding the mechanical bending performance of the tape. Since HTS tapes are intended for practical applications requiring flexibility, the authors should be encouraged to add a brief discussion (or outline it in the conclusions as a future perspective) on how the reduction of buffer layers impacts the mechanical integrity and strain tolerance of the Ni-W/Y₂O₃/YBCO tapes. 

Considering the high substantive value of the work and the correctness of the experimental analyses performed, the manuscript is suitable for publication after revision.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper is focused on the development of a synthesis method for effective ittria buffer layers. The results are interesting, but some aspects should be addressed before publication.

  • Regarding XRD measurements. In the 800°C sample in figure 1, also some other peaks are evident. To better show this, I suggest to put a logarithmic scale on the intensity axis (you should also remove the scale if arbitrary units are used, or else put (counts)).
  • Again regarding XRD, the grain size analysis on the 004 direction would lead to its estimate along the c axis, and in the case of an epitaxial growth is not directly related to the other dimensions. I think that a microscopic evaluation of the other samples (at least 800°C) would be needed to assess the difference.
  • Regarding the superconducting chartacterization, a higher level of details would be useful. I imagine the authors performed VSM hysteresis loops at different temperatures and up to higher fields, maybe this part could be expanded
  • Resistance of the sample should be given as resistivity or normalized to room temperature (the absolute value may not be useful for the reader). The figure should also focus on the transition, either with an inset or the opposite (normal state in the inset). The value of the zero-resistance critical temperature should be given.
  • Regarding critical temperature, and the superconducting transition – no value has been given – it should be stated how the transition width is calculated. Moreover, 5.6 K is far from being a narrow transition. Good YBCO films usually have zero resistance towards the high 90.X kelvin, with onset around 94.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript entitled “Epitaxial growth of Y2O3 buffer films on biaxially textured Ni-W tapes via a photochemical method” presents a sol-gel approach for the fabrication of superconducting tapes. The tapes are based on a YBa2Cu3O7-δ (YBCO) layer applied onto Ni-W tapes coated by a Y2O3 buffer layer. UV-irradiation of gel of the buffer layer gel is employed in the manuscript. In fact, the sol-gel preparation of such superconducting structures has already been investigated. However, thermal treatment of gels has been used in such papers. Nevertheless, UV- assisted low temperature treatment of gels has also been applied for Y2O3 -based gels for phosphors and memories (e.g. in Nanomaterials 2024, 14, 791) and YBCO ones (e.g. in MRS Communications 2018, 8, 1037). Thus, the manuscript novelty can be found in the application of UV-assisted sol-gel approach for the fabrication of a good quality of Y2O3 buffer layers and obtaining superconducting YBCO tapes with a self-field critical current density of 2.65 MA/cm² at 77K. The sol composition seems to be novel, as well, because usually 2-methoxymethanol has been used as the solvent. Thus, such a manuscript could be suitable for Materials. However, the current manuscript requires some additional details. They are,

  1. In Introduction I can recommend adding some papers dealing with the application UV-assisted sol-gel techniques for Y2O3
  2. Explain please, what was the reason for using lactic acid for the sol preparation (Line 115).
  3. What was the sol stability, and did you apply it immediately after the mixing?
  4. Did you apply the sol on both sides of the Ni-W tape (Line 122 and 123). Specify it, please.
  5. The temperature of 50°C is lower than the boiling point of methanol. Explain please the reason for it.
  6. It is necessary to specify the instrumentation for the UV radiation in Line 124 (source and its producer, supplier).
  7. What were dimensions (thickness length, width) of the applied films?
  8. I would expect a reference for the YBCO film preparation (Lines 129-139).
  9. You dried the film at 50°C not at room temperature (Line 154). Correct it, please.
  10. In Lines 213 and 214 you mentioned acetic acid. Why do not mention lactic acid used in sol preparation, too?
  11. What about the C-C bond energy (Line 235). I think that it is also relevant.
  12. 5 implies two UV sources. I think that you used a UV lamp with two main wavelengths.
  13. It is necessary to specify how the deconvolution of the peaks in Fig. 6 was made (software).  A reader can hardly find a clear decrease of the Y-OC peak in Fig. 6b. I think that a table with peak heights and widths would be useful.
  14. The reference [22] does not deal with UV treatment of gels but with photocatalysis. I recommend its replacement.
  15. A reader can hardly understand that YBCO films were prepared by sol-gel method from Abstract. Modify it, please.
  16. In Keywords, I would expect words such as sol-gel, UV irradiation, YBCO superconductor, Ni-W tape
  17. Have you tried to prepare YBCO layers by the UV-assisted sol-gel method, too? It would be interesting.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After improvements, the paper is ready to be published

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

I accept some modifications made in the previous manuscript by considering my comments on it. However, some of your responses have not been implemented into the current manuscript and I do not understand reasons for it. Thus, your responses #2,3,4,5,7 should be implemented into this manuscript before its publication. After that, in my view, such a manuscript will be fully suitable for Materials.

Author Response

Please see the attachment

Author Response File: Author Response.pdf