Influence of Ultrahigh Dilution Treatment of the Charge on the Growth and Spectroscopic Properties of Nd:MgMoO₄ Potential Laser Crystal

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Upon reviewing the document "Influence of Ultrahigh Dilution Treatment of the Charge onto the Growth and Spectroscopic Properties of Nd:MgMoO4 Potential Laser Crystal," I can conclude that the results about single crystals are novel and would be of interest to the readers of Crystals, however several areas with potential for improvement were identified:

1.     I do not understand line 145: “Figure 4. wt.% (for cerium ion in MgO).”  - there are no weight% shown in figure 4 and the sentence seems incomplete.

2.     Line 275 “conglomerats’”

3.     I would suggest to try to make the XRD (Figure 6) clearer with different arrangement, as now it is unintelligible.

4.     The linear approximation in Figure 12 seems fully inappropriate.

5.     For Figure 16., why do you use luminescence intensity in 10-4 if you anyway have arbitrary units? I suggest to multiply by a factor to make it easier to read!

6.     Given the variability in pre-melting behavior observed, how do you ensure consistency across different batches, and how might these variations affect the reproducibility of your results?

7.     How does UHD treatment of Nd:MgMoO4 crystals compare with other enhancement techniques or materials in terms of efficiency, cost, and scalability?

Comments on the Quality of English Language

English is ok. 

Author Response

Thank you so much for spent your time for revision of our manuscript and for the valuable recommendations. We have done our best to improve the text in accordance with your recommendations. All the additions into the text are marked by blue font.

4. The linear approximation in Figure 12 seems fully inappropriate. - OK, in accordance with the recommendations of both reviewers, we have calculated the simple average value of the absorption cross-section, see the modified text, although we continue to believe that the graph was more correct approach.
5. done

6. Given the variability in pre-melting behavior observed, how do you ensure consistency across different batches, and how might these variations affect the reproducibility of your results?

Thank you very much for your question. All the batches of the charge have been prepared from ONE initial basic mixture B_o. The stoichiometric mixture MgO+MoO₃ was well stirred, and only after that it was divided into several parts, which were passed through different kinds of treatment. Thus, before the treatments, the batches were absolutely equivalent. It is written in the text and shown in the scheme, fig. 3. Well, we have slightly modified the text, and hopefully, now it became more clear from the text.

If the sense of the question was: if we will repeatedly prepare additionally 3*10 batches of the charges, according to the scheme given at fig. 3, and will repeatedly grow 3*10 crystals from these charges, will we get the same results? It is very good question! We think, there is only one way to get a certain answer for this question – to prepare these charges, to grow the crystals from them, and to investigate these crystals repeatedly. But, I am afraid, it will be very time-consuming work. However, there are several indirect signs of reproducibility of the obtained results:

1. The specific pre-melting behavior was demonstrated ONLY by the charges 5 and 6. Both these charges were calcined before the UHD treatment. No any other charges, fabricated by other ways, demonstrate such behavior. On the other hand, no any additional charges, which would be calcined before the UHD treatment like the charges 5 and 6, but unlike them, demonstrate the usual pre-melting behavior. I have slightly modified the corresponding fragment of the text for stronger highlighting this fact. We believe, the specific pre-melting behavior is caused by rather strong enrichment of the charges in MgO, and by precipitation of the excess MgO as the refractory crust.
2. The crystals grown ONLY from these two charges (5 and 6) also demonstrate some special features:

- only for these two cases the “mush” in the melt started to form immediately from the start of the crystal growth, and disappeared itself after some period of growth. All the other samples demonstrate other “mush” behavior.

- only for these two cases we have observed considerably increased Nd segregation coefficient in the crystal in comparison with all other samples;

7. How does UHD treatment of Nd:MgMoO4 crystals compare with other enhancement techniques or materials in terms of efficiency, cost, and scalability? –

Thank you very much for your question. It is written in the ‘INTRODUCTION’ chapter, that UHD-treatment is tested for many various kinds of objects including drugs and other organics, ceramics (including superconducting and piezoelectric ones), porcelain, etc. However, there is no any information about the application of such UHD-treatment for any single crystals. We have added the clarifying sentence into the ‘INTRODUCTION’ chapter. So, the main aim at this stage was the first attempt to use the UHD for any single crystal. Nd:MgMoO4 was chosen only as the MODEL crystal for this research. We cannot say at this stage, how efficient is UHD-treatment as the tool for enhancement of Nd:MgMoO₄ crystal in comparison with other Nd:MgMoO₄ enhancement techniques. We didn't set ourselves a goal to find the best technique for enhancement particularly Nd:MgMoO4 crystal. Moreover, now we even cannot certainly say, whether UHD will IMPROVE the quality of Nd:MgMoO₄ crystal, or it will, on the contrary, WORSEN the crystal quality. Now we only try to answer the question, does UHD-treatment effect on growth or properties of inorganic single crystals at all, or no?

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this work, Kirill Subbotin et al. reported the “Influence of ultrahigh dilution treatment of the charge onto the growth and spectroscopic properties of Nd:MgMoO4 potential laser crystal”.  This study explored the impact of ultrahigh dilution (UHD) technology on MgMoO4 crystals doped with 1% Nd3+ ions grown using the Czochralski method. Ten Nd:MgMoO4 crystals were grown from UHD-treated, control-treated, or untreated charges. The key findings include: wetting before calcining affects MoO3 and wetting after calcining affects MgO levels. MgMoO4's congruent melting composition has excess MoO3. MoO3 solubility is temperature-independent, while MgO solubility depends on temperature. Crystals within this range exhibit enhanced Nd3+ segregation. Unit cell parameters vary with MoO3 excess. Optical properties are unaffected by treatment. Luminescence kinetics differ among crystals, and UHD-treated crystals show significantly reduced luminescence intensity. Based on these findings, the manuscript should be considered for publication in “Crystals” upon addressing the following issues.

1. In Fig. 3, there is some repetitive content that makes it appear less concise.

2. In Fig. 4, even though graph paper with gridlines was used, please provide a scale.

3. In Fig. 6, most of the data points are overlapping; please improve the clarity.

4. In Fig. 12, can data like this still be referred to as linear?

5. I suggest using EDS to examine the samples and provide element distribution.

6. Since this work involves elemental content, I hope the authors can employ multiple methods for clarification.

The data in this work doesn't align well with the author's explanations; it can only be said to exhibit similar trends. Therefore, I recommend the authors to conduct experiments and characterizations with greater attention to detail.

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Thank you so much for spent your time for revision of our manuscript and for the valuable recommendations. We have done our best to improve the text in accordance with your recommendations. All the additions into the text are marked by blue font.

1. In Fig. 3, there is some repetitive content that makes it appear less concise. – Thank you for your recommendation. We have slightly simplified the scheme. In particular, we have united two blocks concerning B_u charge. Besides that, we have deleted the information about weights of the batches. Unfortunately, I have no any additional ideas about further simplification the scheme without loss of important information. For example, there are three identical phrases “then calcining 700 ^oC, 5h” under the arrows directed towards the green blocks. However, if we will instead draw the additional united block with this phrase (with three input and three output arrows), a reader can misunderstand that we had united (mixed) the charges after the UHD-treatments, then calcined the mixture, and then divided the obtained batch into three sub-batches, which then were used for the growth of crystals 2, 3 and 4. Meanwhile, this is completely untrue: the batches were calcined separately after three different kinds of the treatment (although, of course, in the same furnace).
2. In Fig. 4, even though graph paper with gridlines was used, please provide a scale. – done
3. In Fig. 6, most of the data points are overlapping; please improve the clarity. – done
4. In Fig. 12, can data like this still be referred to as linear? - OK, in accordance with the recommendations of both reviewers, we have calculated the simple average value of the absorption cross-section, see the modified text, although we continue to believe that the graph was more correct approach.
5. I suggest using EDS to examine the samples and provide element distribution.
6. Since this work involves elemental content, I hope the authors can employ multiple methods for clarification.

The data in this work doesn't align well with the author's explanations; it can only be said to exhibit similar trends. Therefore, I recommend the authors to conduct experiments and characterizations with greater attention to detail.

Thank you for your comments. Yes, we absolutely agree that there are a lot of measurements to be done for the final understanding about the MgMoO₄ crystallization thermodynamic and kinetics features. Well, we have added the corresponding words into the chapter ‘CONCLUSIONS’. HOWEVER: this is not the main goal of the research at the present stage. The main goal was to reveal, whether the UHD treatment of the charge does affect to the crystal growth and/or properties (this is written in the INTRODUCTION). And we have really found some influence. Besides that, we have found that some effects of UHD-treatment can be blurred by the interaction of the charge with water-alcohol solution itself (3-rd type treatment). So, the next step should be the applying of some another (non-aqueous) solution for UHD-treatment. OK, we have added the corresponding clarifying words into the ‘CONCLUSIONS’ chapter.

Besides that, during the studies some non-trivial crystallization features of MgMoO4 were observed. These observations, of course, require the additional clarifying studies, whereas the conclusions, made at this stage, are, of course, the preliminary, tentative ones (this is also written in the text, and we have written some additional words into ‘CONCLUSIONS’ chapter). And we plan to perform the additional clarifying investigations. HOWEVER: it will be the subject of the NEXT paper. Certainly, these investigations cannot be done within one or two weeks, which are allocated by the editors to take into account the recommendations of reviewers. Please, understand us correctly!

As regards to EDS: we believe, it is not the best choice for these studies, because: (1) the actual neodymium concentration in our samples is much lower than the sensitivity limit of this method; (2) the typical level of measurements statistical error of EDS measurements is about ±1 relative % for the main components of molybdate crystals, as our previous experience shows. Besides that, the results of EDS measurements are very sensitive for the correct choice of etalons, that is the additional task.

Comments on the Quality of English Language:

Moderate editing of English language required

Well, English is not the native language for the main authors of the manuscript. So, the English quality was, maybe, not very good in the very first version of the manuscript. However, thanks to our funding partner, ‘Materia Medica Holding’ we had the opportunity to enhance the English of our manuscript with help of one scientist, who is living in the U.S. for many years, and knows the American English very well. And we have performed four (!) thorough iterations of editing the text of the manuscript with this person, before submission the manuscript to the journal. This editing was mostly concerned the English style and grammar. These four iterations were performed during 3 months! And we believe, now the English style and grammar of the manuscript is close to the ideal, except a couple of annoying misprints, which were appeared already at the stage of submission process of the manuscript. These misprints have been found by the Reviewer #1 (thank him very much for that), and corrected. Thus, it is very difficult for us to search for the additional English imperfections in the text, without specifying the particular fragments of the text requiring the corrections, to your opinion. Please, specify these fragments, and we will do our best to improve them.

Thank you very much for the reviewing again,

Sincerely,

Authors of the manuscript

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

My questions and concerns have been addressed.

Reviewer 2 Report

Comments and Suggestions for Authors

The author has solved the issues raised relatively well. I think it's acceptable to publish based on the current version.