Fine-Grained Tb3Al5O12 Transparent Ceramics Prepared by Co-Precipitation Synthesis and Two-Step Sintering
Round 1
Reviewer 1 Report
Referee Report on “Fine-grained Tb3Al5O12 transparent ceramics prepared by co-precipitation synthesis and two-step sintering”
This is, of course, a work that could be recommended for publication, but only after some of the improvements formulated below.
1. Line 44-48. These sentences need supporting references. Furthermore, concerning similar garnet transparent ceramics, recently several new production methods (electron beam assisted synthesis and etc), were demonstrated:
Karipbayev, Z. T., et al (2020). Time-resolved luminescence of YAG: Ce and YAGG: Ce ceramics prepared by electron beam assisted synthesis. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 479, 222-228.
Chaika, M. A., Tomala, R., & Strek, W. (2021). Infrared laser stimulated broadband white emission of transparent Cr: YAG ceramics obtained by solid state reaction sintering. Optical Materials, 111, 110673.
2. For these claimed applications, the properties of point defects, including oxygen vacancies, their formation, stability and photostimulated transformations are clearly important. This is left out of the introduction, which unnecessarily narrows the interest of the work. It would be important to add 4-5 sentences about the importance of the defect.
3. It was also important to indicate the most important parameters and characteristics, such as at least band gap energy Eg. This would be interesting to see for many potential readers.
4. How important is the influence of oxygen, OH and hydrogen and the formation of the corresponding point defects, both in bulk and on the surface. Especially realizing that many other factors act simultaneously?
5. Much more information could have been obtained if the authors had used Raman spectra measurements. Was it real? It is well known that in the case of YAG ceramics, two other modifications, such as YAP and YAM, can also be seen. How can this be in the case of this work?
6. About porosity. Actually, pore evolution is a difficult problem with its dynamics and unique transformation mechanisms and it is clear that it should be treated with great attention. This is where positron annihilation spectroscopy helps a lot. See recent report in MDPI: Klym, H.; Karbovnyk, I.; Piskunov, S.; Popov, A.I. Positron Annihilation Lifetime Spectroscopy Insight on Free Volume Conversion of Nanostructured MgAl2O4 Ceramics. Nanomaterials 2021, 11, 3373. https://doi.org/10.3390/nano11123373
7. In the conclusions, please clearly state what new data on studied materials were obtained in this work.
In principle, the article is interesting and can be recommended for publication after due consideration of the above comments.
Author Response
1. Line 44-48. These sentences need supporting references. Furthermore, concerning similar garnet transparent ceramics, recently several new production methods (electron beam assisted synthesis and etc), were demonstrated: Karipbayev, Z. T., et al (2020). Time-resolved luminescence of YAG: Ce and YAGG: Ce ceramics prepared by electron beam assisted synthesis. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 479, 222-228. Chaika, M. A., Tomala, R., & Strek, W. (2021). Infrared laser stimulated broadband white emission of transparent Cr: YAG ceramics obtained by solid state reaction sintering. Optical Materials, 111, 110673. Response: Thank you for your valuable comments and suggestions. The supporting references have been added in the re-submitted manuscript. We have noticed that there emerged various new production methods for garnet ceramics, however, few of them have been conducted for TAG ceramics yet. Supplements have been made in the re-submitted manuscript. 2. For these claimed applications, the properties of point defects, including oxygen vacancies, their formation, stability and photo stimulated transformations are clearly important. This is left out of the introduction, which unnecessarily narrows the interest of the work. It would be important to add 4-5 sentences about the importance of the defect. Response: Thank you for your valuable suggestions. Supplements about the point defects have been added in the re-submitted manuscript. 3. It was also important to indicate the most important parameters and characteristics, such as at least band gap energy Eg. This would be interesting to see for many potential readers. Response: Thank you for your valuable suggestions. In our opinion, the band gap energy has weak relevance to the theme of this article, which is about magneto-optical ceramics and Faraday isolators. Besides, the band gap energy Eg of TAG material has been reported, so we think it is unnecessary to report this parameter again: Y. Zorenko et al. Energy transfer to Ce3+ ions in Tb3Al5O12:Ce single crystalline films. Radiation Measurements. 2007, 42, 648-651, doi: 10.1016/j.radmeas.2007.01.059. 4. How important is the influence of oxygen, OH and hydrogen and the formation of the corresponding point defects, both in bulk and on the surface. Especially realizing that many other factors act simultaneously? Response: Thank you for your questions. The residual impurity ions, radicals, and molecules in the calcined TAG powder have similar effects on the formation of the corresponding defects. These defects reduce the optical quality of TAG ceramics, so all these residual impurities need to be eliminated as much as possible. That is why we chose 1100°C as the optimum calcination temperature and the precursor was calcined for 4 hours. 5. Much more information could have been obtained if the authors had used Raman spectra measurements. Was it real? It is well known that in the case of YAG ceramics, two other modifications, such as YAP and YAM, can also be seen. How can this be in the case of this work? Response: Thank you for your questions. The precursor and calcined powders were investigated by FT-IR method in our previous works for many times. The radicals like CO32-, -OH, SO42-, and so on can be investigated by FT-IR, however, XPS gives the relative contents of each element, which is much more concerned by us. Considering the Raman spectra measurements are similar to FT-IR in many ways, XPS method is adequate for the investigation of precursor and powders in our opinion. There are also TAP and TAM phase in Tb2O3-Al2O3 phase diagram, which is similar to the case in YAG ceramics. TAG, TAP, TAM, Tb2O3, and Al2O3 phases can be detected when Tb2O3 and Al2O3 diffused incompletely. As the co-precipitation method is used in this work, Tb3+ and Al3+ have quite short diffusion distance in the obtained uniform powders, so TAP and TAM can be hardly detected after calcination. Similar phenomenon is common in the fabrication of garnet ceramics when powders are prepared by the wet chemistry method. Related supplements have been made in the re-submitted manuscript. 6. About porosity. Actually, pore evolution is a difficult problem with its dynamics and unique transformation mechanisms and it is clear that it should be treated with great attention. This is where positron annihilation spectroscopy helps a lot. See recent report in MDPI: Klym, H.; Karbovnyk, I.; Piskunov, S.; Popov, A.I. Positron Annihilation Lifetime Spectroscopy Insight on Free Volume Conversion of Nanostructured MgAl2O4 Ceramics. Nanomaterials 2021, 11,3373.https://doi.org/10.3390/nano11123373 Response: Thank you for your valuable suggestions. It is true that pore evolution is a difficult problem, and we are looking for more research methods. We will lean more about positron annihilation spectroscopy and we believe this can be a powerful research tool. 7. In the conclusions, please clearly state what new data on studied materials were obtained in this work. In principle, the article is interesting and can be recommended for publication after due consideration of the above comments. Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.Reviewer 2 Report
This article investigates the synthesis of terbium aluminum garnet by the co-precipitation method. The topic under discussion is important from a scientific and practical point of view. Overall, it is very well written. However, there are a few minor errors that need to be fixed before I can recommend it for publishing.
1. Line 59, what do you mean by “poor sintering activity”? do you mean poor sinterability?
2. Line 62, please add some sentences about the “co-precipitation method”.
3. Lines 67 and 68, please write “dwelling time” instead of “duration time”.
4. Lines 78-83, please add the particle size of the raw powders that you used.
5. Line 86, please explain the preparation method in brief here as well, other than referring to another source.
6. Line 87, please state the name of the model, manufacturer, city, and country from where the ball milling equipment was sourced.
7. What was the relative density of the pallets after cold isostatic pressing?
8. Line 91, please put a space between numbers and physical units, e.g., 1475 °C. Check this in the whole text.
9. Line 91, please state the name of the model, manufacturer, city, and country from where the conventional sintering and HIP devices were sourced.
10. Lines 106-107, please explain the characterization methods of XRD, FESEM, Verdet constant, and optical transmittance measurement without referring to other articles.
11. Lines 114 and 134, please DO NOT use the condensed form of the expressions, i.e., Don't.
12. Lines 194-208, this information is not the results of your work and should not be included in the results section. Move them to the introduction section.
13. figure 6, please put the standard deviation for relative densities and average grain sizes.
Author Response
- Line 59, what do you mean by “poor sintering activity”? do you mean poor sinterability?
Response: Thank you for your question and valuable suggestions. “Sinterability” is more appropriate. Changes have been made in the re-submitted manuscript.
- Line 62, please add some sentences about the “co-precipitation method”.
Response: Thank you for your valuable suggestions. Supplements have been made in the re-submitted manuscript.
- Lines 67 and 68, please write “dwelling time” instead of “duration time”.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Lines 78-83, please add the particle size of the raw powders that you used.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Line 86, please explain the preparation method in brief here as well, other than referring to another source.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Line 87, please state the name of the model, manufacturer, city, and country from where the ball milling equipment was sourced.
Response: Thank you for your valuable suggestions. Statement has been made in the re-submitted manuscript.
- What was the relative density of the pallets after cold isostatic pressing?
Response: Thank you for your question. The relative density was about 50%. Supplement has been made in the re-submitted manuscript.
- Line 91, please put a space between numbers and physical units, e.g., 1475 °C. Check this in the whole text.
Response: Thank you for your valuable suggestions. Changes has been made in the re-submitted manuscript.
- Line 91, please state the name of the model, manufacturer, city, and country from where the conventional sintering and HIP devices were sourced.
Response: Thank you for your suggestions. Statement has been made in the re-submitted manuscript.
- Lines 106-107, please explain the characterization methods of XRD, FESEM, Verdet constant, and optical transmittance measurement without referring to other articles.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Lines 114 and 134, please DO NOT use the condensed form of the expressions, i.e., Don't.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Lines 194-208, this information is not the results of your work and should not be included in the results section. Move them to the introduction section.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
- Figure 6, please put the standard deviation for relative densities and average grain sizes.
Response: Thank you for your valuable suggestions. Changes have been made in the re-submitted manuscript.
Round 2
Reviewer 1 Report
The authors have successfully improved their original manuscript, which now can be recommended for publication,
