Relation between Electronic Structure and Thermoelectric Properties of Heusler-Type Ru2VAl Compounds
, Kensuke Onishi 2, Takehiko Hihara 1,2, Masato Yoshimura 5, Hirofumi Ishii 5, Masashi Mikami 6 and Yoichi Nishino 1Round 1
Reviewer 1 Report
Dear editor,
the paer "Relation between electronic structure and thermoelectric properties of Heusler-type Ru2VAl compounds" by H Miyazaki et al reports a theoretical and experimental investigation on a material potentially relevant to thermoelectricity.
Though the authors did not find any striking results, the investigation is well conducted and presented. The theoretical approach is adequate for the systems presented here. The experimental setup is quite standard, but results are meaningful and accurate. The experimental data and the theoretical results are clearly presented, some connections between experiment and theory are explained and rationalized. The article is well written and organized, the quality of artworks is adequate. The quality of English is adequate. I believe that this paper might be an interesting reference for the community involved in electronic structure studies of solid state systems.
Overall, this is a good article, and I suggest publication in the present form but for the list of articles included in the Reference section. Indeed, the number of self-citations is exceedingly high (i.e. much larger than 10). I do not believe that such a high number of self-citations is justified.
Author Response
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Our response to the Report of Reviewer 1
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We would like to thank for reviewing our manuscript and judging it interesting and worth to be published in Crystals.
The reviewer pointed out that there are many papers from my related groups, and you are right. However, the research on Fe2VAl, an analogue of Ru2VAl reported in this paper, has been advanced by our group, and in particular, direct observation of the electronic structure has not been reported by anyone other than our group. Therefore, we have decided that it is unavoidable to cite our group's research paper in order to present the reader with the previous research reports on Fe2VAl and to provide appropriate information.
We are very grateful to the referee for his/her critical reading of our manuscript and the valuable comments, which have helped us to further improve our manuscript for resubmission to Crystals.
Yours sincerely,
Hidetoshi Miyazaki
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Our response to the Report of Reviewer 2
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We would like to thank for reviewing our manuscript. We are very grateful to the referee for his/her critical reading of our manuscript and the valuable comments, which have helped us to further improve our manuscript for resubmission to Crystals.
Reviewer #2 Comments 1
1) English should be revised.
Reviewer #2 Reply 1
Thank you for reading our paper in detail and pointing out the inadequacies. We have corrected some grammatical errors in the English language and some parts of the paper that were difficult to read. In addition, this paper has been proofread in English by Editage co., and a certificate of proof is attached. We believe that these corrections have made the paper easier for readers to understand.
Reviewer #2 Comments 2
2) The authors should revise the introduction section of the manuscript to clarify and justify the importance of the project.
Reviewer #2 Reply 2
The size of the pseudogap, which is the origin of the high thermoelectric conversion properties in Fe2VAl, differs from that expected from experimental and band calculations. Based on understanding this difference and controlling the electronic structure, the high thermoelectric conversion properties are achieved by designing the Fe2VAl material. Therefore, the purpose of this paper is to discuss the potential of Ru2VAl as a thermoelectric conversion material by experimentally and theoretically investigating its electronic structure, which is expected to have high thermoelectric conversion properties due to its lower thermal conductivity compared to Fe2VAl. Since this point was unclear in the introduction, the following sentences are included in the introduction to clarify the subject of this paper.
- 2 line 70 : The sentence of “The pseudogap width in Fe2VAl is actually much smaller than predicted by band calculations due to the strong electron correlation induced by the Fe atoms39. Based on the un-derstanding of this difference in electronic structure,” is inserted.
Reviewer #2 Comments 3
3) The authors should explore/include the previously similar published articles and compare them with their strategy on the introduction of the revised manuscript.
Reviewer #2 Reply 3
This point has to do with clarifying the subject of the paper in Comments 2. As noted in our response to Comment 2, we have added a new sentence to clarify the need to investigate the electronic structure in Ru2VAl through the study of Fe2VAl.
Reviewer #2 Comments 4
4) There are no justification for the fact that Ru2VAl is a material for next-generation thermoelectric conversion properties at higher temperatures.
Reviewer #2 Reply 4
In fact, the experimental Seebeck coefficient of Fe2VAl has a maximum value from room temperature to about 400 K. This is because the pseudogap width of Fe2VAl is smaller than the value calculated by band calculation. The pseudogap width of Ru2VAl is expected to be similar to the band calculation result due to the itinerant nature of Ru atoms. Therefore, Ru2VAl is expected to have a higher Seebeck coefficient peak at higher temperatures than Fe2VAl due to its wider pseudogap width, and is expected to be a thermoelectric conversion material with higher performance at higher temperatures than Fe2VAl. The following sentence was added to describe why Ru2VAl is expected to have higher thermoelectric performance at higher temperatures than Fe2VAl.
Page 7 line 236 : The sentence of “The pseudogap width of Ru2VAl is expected to be similar to the band calculation result due to the itinerant nature of Ru atoms. Therefore, Ru2VAl is expected to have a higher Seebeck coefficient peak at higher temperatures than Fe2VAl due to its wider pseudogap width, and is expected to be a thermoelectric conversion material with higher performance at higher temperatures than Fe2VAl.” is inserted.
Reviewer #2 Comments 5
5)It is not clear to the readers why the Fe2VAl material is not completely ordered-L21 structure, according to the SR-XRD results.
Reviewer #2 Reply 5
The heat treatment conditions used for ordering Ru2VAl in this paper are those that yield an L21-regular phase in Fe2VAl. Therefore, the heat treatment conditions used to completely regularize Ru2VAl to the L21-regular phase may be different, and it is possible that the conditions used to prepare the sample in this paper could have yielded Ru2VAl in the B2-irregular phase. As pointed out by the reviewer, we have added the following text in the text to avoid misleading the reader.
- 5 line 172 : In order to obtain the L21 ordered phase of Ru2VAl in the future, it is necessary to explore for the optimum heat treatment conditions for ordering.
Reviewer #2 Comments 6
6)Conclusions are not supported by the data
Reviewer #2 Reply 6
Your precise points have prompted me to add several new sentences for a more detailed discussion of this paper. The addition of these sentences has ensured the consistency of the conclusions and data in this paper. Your many comments are deeply appreciated.
Yours sincerely,
Hidetoshi Miyazaki
Reviewer 2 Report
After the reading of the manuscript, in my opinion, the main problem of the work is the lack of novelty and the poor justification for the obtained results.
Other revising suggestions are listed as follows.
1) English should be revised.
2) The authors should revise the introduction section of the manuscript to clarify and justify the importance of the project.
3) The authors should explore/include the previously similar published articles and compare them with their strategy on the introduction of the revised manuscript.
4) There are no justification for the fact that Ru2VAl is a material for next-generation thermoelectric conversion properties at higher temperatures
5)It is not clear to the readers why the Fe2VAl material is not completely ordered-L21 structure, according to the SR-XRD results.
6)Conclusions are not supported by the data.
Comments for author File: 
Comments.pdf
Author Response
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Our response to the Report of Reviewer 2
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We would like to thank for reviewing our manuscript. We are very grateful to the referee for his/her critical reading of our manuscript and the valuable comments, which have helped us to further improve our manuscript for resubmission to Crystals.
Reviewer #2 Comments 1
1) English should be revised.
Reviewer #2 Reply 1
Thank you for reading our paper in detail and pointing out the inadequacies. We have corrected some grammatical errors in the English language and some parts of the paper that were difficult to read. In addition, this paper has been proofread in English by Editage co., and a certificate of proof is attached. We believe that these corrections have made the paper easier for readers to understand.
Reviewer #2 Comments 2
2) The authors should revise the introduction section of the manuscript to clarify and justify the importance of the project.
Reviewer #2 Reply 2
The size of the pseudogap, which is the origin of the high thermoelectric conversion properties in Fe2VAl, differs from that expected from experimental and band calculations. Based on understanding this difference and controlling the electronic structure, the high thermoelectric conversion properties are achieved by designing the Fe2VAl material. Therefore, the purpose of this paper is to discuss the potential of Ru2VAl as a thermoelectric conversion material by experimentally and theoretically investigating its electronic structure, which is expected to have high thermoelectric conversion properties due to its lower thermal conductivity compared to Fe2VAl. Since this point was unclear in the introduction, the following sentences are included in the introduction to clarify the subject of this paper.
- 2 line 70 : The sentence of “The pseudogap width in Fe2VAl is actually much smaller than predicted by band calculations due to the strong electron correlation induced by the Fe atoms39. Based on the un-derstanding of this difference in electronic structure,” is inserted.
Reviewer #2 Comments 3
3) The authors should explore/include the previously similar published articles and compare them with their strategy on the introduction of the revised manuscript.
Reviewer #2 Reply 3
This point has to do with clarifying the subject of the paper in Comments 2. As noted in our response to Comment 2, we have added a new sentence to clarify the need to investigate the electronic structure in Ru2VAl through the study of Fe2VAl.
Reviewer #2 Comments 4
4) There are no justification for the fact that Ru2VAl is a material for next-generation thermoelectric conversion properties at higher temperatures.
Reviewer #2 Reply 4
In fact, the experimental Seebeck coefficient of Fe2VAl has a maximum value from room temperature to about 400 K. This is because the pseudogap width of Fe2VAl is smaller than the value calculated by band calculation. The pseudogap width of Ru2VAl is expected to be similar to the band calculation result due to the itinerant nature of Ru atoms. Therefore, Ru2VAl is expected to have a higher Seebeck coefficient peak at higher temperatures than Fe2VAl due to its wider pseudogap width, and is expected to be a thermoelectric conversion material with higher performance at higher temperatures than Fe2VAl. The following sentence was added to describe why Ru2VAl is expected to have higher thermoelectric performance at higher temperatures than Fe2VAl.
Page 7 line 236 : The sentence of “The pseudogap width of Ru2VAl is expected to be similar to the band calculation result due to the itinerant nature of Ru atoms. Therefore, Ru2VAl is expected to have a higher Seebeck coefficient peak at higher temperatures than Fe2VAl due to its wider pseudogap width, and is expected to be a thermoelectric conversion material with higher performance at higher temperatures than Fe2VAl.” is inserted.
Reviewer #2 Comments 5
5)It is not clear to the readers why the Fe2VAl material is not completely ordered-L21 structure, according to the SR-XRD results.
Reviewer #2 Reply 5
The heat treatment conditions used for ordering Ru2VAl in this paper are those that yield an L21-regular phase in Fe2VAl. Therefore, the heat treatment conditions used to completely regularize Ru2VAl to the L21-regular phase may be different, and it is possible that the conditions used to prepare the sample in this paper could have yielded Ru2VAl in the B2-irregular phase. As pointed out by the reviewer, we have added the following text in the text to avoid misleading the reader.
- 5 line 172 : In order to obtain the L21 ordered phase of Ru2VAl in the future, it is necessary to explore for the optimum heat treatment conditions for ordering.
Reviewer #2 Comments 6
6)Conclusions are not supported by the data
Reviewer #2 Reply 6
Your precise points have prompted me to add several new sentences for a more detailed discussion of this paper. The addition of these sentences has ensured the consistency of the conclusions and data in this paper. Your many comments are deeply appreciated.
Yours sincerely,
Hidetoshi Miyazaki
Author Response File: 
Author Response.docx
Round 2
Reviewer 2 Report
The manuscript is recommended to be accepted
