Effect of Precursor Prehistory on the Efficiency of Radiation-Assisted Synthesis and Luminescence of YAG:Ce Ceramics

Round 1

Reviewer 1 Report

The authors have synthesized a series of YAG:Ce ceramics by radiation-assisted methods and investigated the relationship between their luminescence properties and morphological as well as raw material characteristics. This study provides some insight into the subsequent synthesis of high-quality ceramics. This manuscript can be accepted after addressing the following issues. Some comments are as follows:

1. The authors used different particle sizes for the starting materials, did they come from the same company? Different batches of raw materials often also have an impact on the properties of the ceramics.

2. The authors have prepared a large number of YAG:Ce ceramics but have not characterized the phase structure of these ceramics. Can the authors add XRD data for the corresponding samples?

3. What is the object referred to by each curve in Figure 3?

4. The authors crushed the ceramics to test the radiation flux of the samples, but the size of the crushed sample particles can have an effect on the test results, how can the authors avoid this effect?

Author Response

Dear reviewer! Authors' responses are listed in numerical order to your comment:

1.Absolutely right. The results of ceramics synthesis, their properties, depend on the quality of initial materials, on the producer of initial materials. Therefore, we are forced to perform numerous studies in order to identify the most significant factors that cause changes in their properties. As shown in this work, the quality of ceramics produced by the radiation method from nanosized oxide powders is worse than that from larger ones, while the opposite is true for thermal synthesis

2. Yes we control the phase structure of the resulting samples - the XRDs are not presented in this paper because they were published recently in [Victor Lisitsyn, Aida Tulegenova, Ekaterina Kaneva, Dosimkhan Mussakhanov and Boris Gritsenko. Express Synthesis of YAG:Ce Ceramics in the High-Energy Electrons Flow Field Materials 2023, 16, 1057. https://doi.org/10.3390/ma16031057]

3. Figures 3 show groups of spectra of one series samples, the number of which is indicated. The fact is that in one crucible during synthesis a series of 1-15 samples can be formed. The figures show the spectra of the samples of the corresponding series in order to show the values of possible differences in the spectra of the samples of one series

4. Qualitative characteristics (luminescence and excitation spectra) do not depend on the size of fragmented particles. Quantitative characteristics (conversion efficiency) do. Perhaps this explains the scatter of conversion efficiencies of excitation energy in luminescence. We did not control the size of the fragmented particles, because there are difficulties in milling ceramics of small volume

Reviewer 2 Report

Referee report on “Effect of Precursor Prehistory on the Efficiency of Radiation- 2 Assisted Synthesis and Luminescence of YAG:Ce Ceramics”

This is a rather interesting and good paper that certainly can be recommended for publication, but clarifying and detailing some parts of the text.

1.     Line 38.  What is the difference between activators and modifiers?

2.     Line 44.  Among the new recently developed methods, one can also mention the so-called the extraction-pyrolytic method: Serga, Vera, et al. "Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method." Journal of materials research and technology 13 (2021): 2350-2360.

3.     Line 51. If the following article below also belongs to this study, then it should also be mentioned:   Karipbayev, Zh T., et al. "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 (2020): 222-228.

4.     What is the fundamental difference between the obtained samples, the method described in this article and for example, by the solid-state reaction method (Polisadova, E., et al. "Time-resolved cathodoluminescence spectroscopy of YAG and YAG: Ce3+ phosphors." Optical Materials 96 (2019): 109289.)

5.     Figure 3. Can it be clearly stated whether there are any new features in the luminescence spectra?

6.     What other materials have already been synthesized using this method? It would be helpful to add this information with corresponding references at the end of the manuscript.

In general, the manuscript is interesting and can be recommended for publication after constructive reflection on the above comments.

Author Response

Dear reviewer! Authors' responses are listed in numerical order to your comment:

1. By activators, we mean elements that defects cause the conversion of absorbed quanta into luminescence. By modifiers we mean elements introduced into the crystal during synthesis that distort the crystal lattice in the activator region, which leads to a shift in the luminescence band. This effect is often used to correct spectra
2. A link to an interesting article has been added.
3. Yes, this is our article. The link to the article has been added. Thanks
4. YAG:Ce phosphors are synthesized by different methods (thermal, sol-gel, SPP, combustion.... All methods of synthesis are complicated, the synthesis process takes a long time. Therefore, new methods are being developed and existing ones are being improved. Radiation synthesis is promising: the synthesis is realized in 1 second, without the use of any substances facilitating synthesis, only from materials with the desired elemental composition. The method is under development. Studies of the resulting samples, comparison with already existing samples are needed. Therefore, cathodoluminescence of samples obtained by radiation method was compared in [Karipbayev, Zh T., et al. "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 (2020): 222-228.] and thermally [E. Polisadova, D. Valiev, V. Vaganov, V. Oleshko, Tao Han, C. Zhang, A. Burachenko, A.I. Popovet. "Time-resolved cathodoluminescence spectroscopy of YAG and YAG: Ce3+ phosphors." Optical Materials 96 (2019): 109289]. The cathodoluminescence measurements were performed on a single setup
5. The type of luminescence spectra of the obtained ceramic samples does not depend on the purity degree of the initial material within the purity degree above 99% used by us. The type of spectra does not depend on the morphology of powders used for synthesis, on the concentration of introduced cerium impurity in the range of 0.2 - 1.0%. Consequently, radiation synthesis forms ceramics with a structure around the activator similar to that created by thermal synthesis
6. It can be argued that the promising method of radiation synthesis produces samples with completely similar properties in comparison with the thermally synthesized. Radiation synthesis time is less than 1 s, thermal synthesis - a week. Radiation synthesis is more efficient, the productivity is higher, and no additives other than the activator are introduced. More than ten types of ceramics have already been synthesized by the radiation method: MgF2. BaF2, tungstones, Al, Y, Ga oxides. Work on expanding the range of materials continues.
   References to works on the synthesis of other materials are added.

Reviewer 3 Report

The paper under review deals with the new method of synthesis of YAG:Ce ceramics. The method is based on the application of powerful high-energy electron beam. It allows to accelerate synthesis rate and to get the high uniformity of the luminescence spectra shape. The paper can be published in the International Journal.

I have one question which the authors must be clarify.

The formation of ceramics by the proposed method occurs in highly ionized medium which can cause the processes of radiation damage and the creation of radiation defects. It is not clear how these processes affect on the luminescence spectra of synthesized ceramics.  Please explain. If this effect is insignificant the authors must propose the adequate explanation.

Author Response

Dear reviewer!
Thank you for your careful analysis and commentary to our work.

Synthesis of YAG ceramics is carried out from a mixture of powders Y and Al. The Y₃Al₅O₁₂

 structure is created by the exchange of elements between the particles of a mixture of powders of stoichiometric composition. The exchange processes are usual diffusive ones in solid phase and between the mixture particles. To stimulate diffusion, the mixture particles are heated. It is impossible to melt the oxides at the same time: the melting points are 2040 and 2400 С. The way out is to turn the solid-phase reactions into liquid-phase reactions. To do this, materials that melt at temperatures of 1200-1500 C are added to the mixture. The oxide particles in the molten flux (e.g. BaF2) stick together, the exchange of elements between the sticking particles begins. After a long soaking the obtained product is heated to higher temperatures, the flux evaporates, the process of exchange of elements between the stuck particles continues, the formation of the IAG phase as the most corresponding to the stoichiometric composition. This is followed by multiple annealing: heating - cooling of the resulting mass. The YAG phase is formed. The duration of the synthesis procedure is about 1 week. In the structure there always remains a part of flux and other substances, the presence of which affects the result.
Radiation synthesis is realized by direct exposure to a mixture of Y and Al oxide powders of stoichiometric composition. The synthesis is performed without any additives facilitating the synthesis in a time less than 1 s. In a short time of exposure to the beam Y₃Al₅O₁₂ is formed, the phase is heated to a temperature of about 1500 C. The structure defectiveness is determined by the processes during phase formation. After synthesis, the ceramic sample is cooled down to room temperature already without radiation exposure. The special experiments of annealing to 1200 C for 8 hours and then slow cooling showed that the annealing does not change the structure and luminescent properties of ceramics. Thus, in ceramics the main defectiveness is formed not by radiation, but in the process of creation of new structural phases from the initial

Round 2

Reviewer 1 Report

The authors have revised the manuscript on the basis of the referees' comments. It can be accepted.

Reviewer 2 Report

After successful revision, this manuscript can be recommended for publication.