Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat Treatment II: CaOx-ZrO2(1 − x) (x = 5–10 mol%)
Round 1
Reviewer 1 Report
This is the comments on the Manuscript submitted to Metals (ISSN 2075-4701)
Manuscript ID: metals-2623814
Type of manuscript: Article
Title: Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat treatment II: CaOx-ZrO2(1-x) (x =5–10 mol%)
Hyunjo Yoo , Juyoung Kim , Hwanseok Lee , Ilguk Jo * , Heesoo Lee *Rate the Manuscript:
1. Significance to field and specialization of “Metals (ISSN 2075-4701)” journal: good.
The article presents the results of studies of the effects of CaO content and post-heat treatment on the phase stability and mechanical and thermal properties of Ca-PSZ. ZrO2 specimens with 5–10 mol% CaO were sintered, and post-heat treatment was done at 1200 °C for 100 h.
2. Scientific content: good.
3. Originality: good.
4. Clarity and presentation: acceptable.
5. Appropriateness for Journal: appropriate subject matter for the “Metals (ISSN 2075-4701)”. Need for rapid publication: no.
7. Recommendations: to send after minor revision to “Metals (ISSN 2075-4701)”.
Remarks:
No any additional comments on the tables and figures.
- What is the main question addressed by the research?
The test and evaluate the crystal structure, microstructure, and mechanical and thermal properties on the specimens which were partially stabilized by 5–10 mol% CaO (5CSZ–10CSZ) in a mixed monoclinic and tetragonal phase; however, a secondary phase of CaZrO3 peaks was observed in 10CSZ.
2. Do consider the topic original or relevant in the field? Does it
address a specific gap in the field?
Yes. The mechanically and thermally stable tetragonal phase increased, and the monoclinic phase decreased as the doped Ca replaced the Zr sites, as confirmed through X-ray diffraction (XRD) analysis. Post-heat treatment and an increase in Ca addition further facilitated the replacement of Zr sites by Ca. However, at high Ca concentrations of 10CSZ, an equilibrium phase of CaZrO3 was formed as a secondary phase at the post-heat treatment temperature, resulting in low performance. And the hardness of each sample was measured after dilatometer experiments..
- What does it add to the subject area compared with other published
material?
3. Post-heat treatment resulted in further increases in these values as the CaO content increased from 5CSZ to 9CSZ; however, the Vickers hardness and flexural strength of 10CSZ decreased by approximately 8% and 9%, respectively.
4. What specific improvements should the authors consider regarding the
methodology? What further controls should be considered?
The thermal expansion coefficient exhibited the same tendency as the mechanical properties. This coefficient increased from 8.229 × 10-6 to 9.448 × 10-6 K-1 with increasing CaO content and the coefficient were enhanced after post-heat treatment in 5CSZ to 9CSZ; however, the thermal expansion coefficient of 10CSZ decreased by approximately 4% after post-heat treatment.
5. Are the conclusions consistent with the evidence and arguments presented
and do they address the main question posed?
The ratio of the monoclinic phase decreased from 62.50% (5CSZ) to 21.02% (10CSZ) as the CaO content increased. Additionally, the monoclinic phase ratio decreased from 59.38% (5CSZ) to 19.57% (9CSZ) after post-heat treatment; an increase to 24.84% was observed for 10CSZ. An increase in Vickers hardness from 676.02 to 1256.25 HV and flexural strength from 437.7 to 842.7 MPa were observed with increasing CaO content.
Comments for author File: 
Comments.pdf
This is the comments on the Manuscript submitted to Metals (ISSN 2075-4701)
Manuscript ID: metals-2623814
Type of manuscript: Article
Title: Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat treatment II: CaOx-ZrO2(1-x) (x =5–10 mol%)
Hyunjo Yoo , Juyoung Kim , Hwanseok Lee , Ilguk Jo * , Heesoo Lee *Rate the Manuscript:
1. Significance to field and specialization of “Metals (ISSN 2075-4701)” journal: good.
The article presents the results of studies of the effects of CaO content and post-heat treatment on the phase stability and mechanical and thermal properties of Ca-PSZ. ZrO2 specimens with 5–10 mol% CaO were sintered, and post-heat treatment was done at 1200 °C for 100 h.
2. Scientific content: good.
3. Originality: good.
4. Clarity and presentation: acceptable.
5. Appropriateness for Journal: appropriate subject matter for the “Metals (ISSN 2075-4701)”. Need for rapid publication: no.
7. Recommendations: to send after minor revision to “Metals (ISSN 2075-4701)”.
Remarks:
No any additional comments on the tables and figures.
- What is the main question addressed by the research?
The test and evaluate the crystal structure, microstructure, and mechanical and thermal properties on the specimens which were partially stabilized by 5–10 mol% CaO (5CSZ–10CSZ) in a mixed monoclinic and tetragonal phase; however, a secondary phase of CaZrO3 peaks was observed in 10CSZ.
2. Do consider the topic original or relevant in the field? Does it
address a specific gap in the field?
Yes. The mechanically and thermally stable tetragonal phase increased, and the monoclinic phase decreased as the doped Ca replaced the Zr sites, as confirmed through X-ray diffraction (XRD) analysis. Post-heat treatment and an increase in Ca addition further facilitated the replacement of Zr sites by Ca. However, at high Ca concentrations of 10CSZ, an equilibrium phase of CaZrO3 was formed as a secondary phase at the post-heat treatment temperature, resulting in low performance. And the hardness of each sample was measured after dilatometer experiments..
- What does it add to the subject area compared with other published
material?
3. Post-heat treatment resulted in further increases in these values as the CaO content increased from 5CSZ to 9CSZ; however, the Vickers hardness and flexural strength of 10CSZ decreased by approximately 8% and 9%, respectively.
4. What specific improvements should the authors consider regarding the
methodology? What further controls should be considered?
The thermal expansion coefficient exhibited the same tendency as the mechanical properties. This coefficient increased from 8.229 × 10-6 to 9.448 × 10-6 K-1 with increasing CaO content and the coefficient were enhanced after post-heat treatment in 5CSZ to 9CSZ; however, the thermal expansion coefficient of 10CSZ decreased by approximately 4% after post-heat treatment.
5. Are the conclusions consistent with the evidence and arguments presented
and do they address the main question posed?
The ratio of the monoclinic phase decreased from 62.50% (5CSZ) to 21.02% (10CSZ) as the CaO content increased. Additionally, the monoclinic phase ratio decreased from 59.38% (5CSZ) to 19.57% (9CSZ) after post-heat treatment; an increase to 24.84% was observed for 10CSZ. An increase in Vickers hardness from 676.02 to 1256.25 HV and flexural strength from 437.7 to 842.7 MPa were observed with increasing CaO content.
Author Response
The authors would like to express our wholehearted thanks to both the Editor and Reviewer for giving the valuable suggestions & comments regarding our paper. These reviews have been very helpful in enhancing our paper. Based on the comments and suggestions, the revised manuscript was prepared. These changes have clearly improved our manuscript.
Please find attached a point-by-point response to reviewer’s concerns. Changes to the text and figure in the manuscript are marked in blue color. We hope that you find our responses satisfactory and consider this paper as suitable for publication in Metals. I am looking forward to hearing of you. Thank you in advance.
Author Response File: Author Response.pdf
Reviewer 2 Report
Manuscript "Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat treatment II: CaOx-ZrO2(1-x) (x =5–10 mol%)" has deal with the effects of CaO content on the phase stability and physico-mechanical propertie of Ca-PSZ. As a main result of this manuscript can be marked the conclusion that the mechanical and the thermal properties were improved due to post-heat treatment with a decrease in the ratio of the monoclinic phase.
The main lack of the present study is the neglect of texture and its influence on the directional dependence of properties. The effect of texture is expect to be quite significant due to the low symmetry of the material under study. To clarify this issue, the XRD study using pole figures or inverse pole figures, as well as the measurement properties in different directions may be useful. In addition, the paragraph "Conclusions" should be reduced.
I recommend to reconsider the manuscript "Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat treatment II: CaOx-ZrO2(1-x) (x =5–10 mol%)" after major revisions.
Author Response
Q 1) You will see that a number of general and specific points are mentioned which necessitate extensive rewriting of the paper. You will see that a number of general and specific points are mentioned which necessitate extensive rewriting of the paper. The main lack of the present study is the neglect of texture and its influence on the directional dependence of properties. The effect of texture is expect to be quite significant due to the low symmetry of the material under study. To clarify this issue, the XRD study using pole figures or inverse pole figures, as well as the measurement properties in different directions may be useful.
Answer)
Thank you for your kind comment. As you said, we think it is one of the good ways to consider the texture and directional dependence of grain when analyzing the properties of materials.
Because the materials covered in this paper are synthesized from the powder stage and manufactured without any special alignment process or treatment, it is assumed that texture and direction are random.
And although it is also important to analyze textures and directions for each grain (especially in electronic and energy materials), but the bulk ceramic, which will be used in structural materials such as refractories, phase analysis is considered to be the most important characteristic, so we focused on this. In the future, we also have applications as electronic materials in mind, thus we will conduct the analysis you mentioned so that it can be reflected in the future study.
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Q 2) In addition, the paragraph "Conclusions" should be reduced.
Answer)
Thank you for your kind comment. We revised conclusion shorter and polished English.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
This manuscript may be accepted in present form.
