Revealing the Impact of Ga and Y Doping on Thermal and Electrical Behavior of LaMnO₃ Ceramic Materials

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I went through the paper entitled: "Revealing the impact of Ga /Y .....".

It can be published after a major revision. I left some comments on the manuscript PDF file. Please find the attachment. 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Dear reviewers,

We would like to thank you for carefully reading the paper and for your comments and suggestions which improve the overall scientific quality of our manuscript. All the corrections have been marked in blue in the revised manuscript and a point-by-point response to your comments is provided in this letter. We believe that the manuscript is now ready to be published in Applied Sciences.

 

1. It should be changed to specific and quantified results regarding findings.

• The electrical conductivity of Ga or Y doped lanthanum manganite is higher than that of pristine sample, which shows that the presence of Ga³⁺ or Y³⁺ ions in the LaMnO₃ perovskite leads to an increase in the electrical conductivity.

2. Keywords: more specifics keywords are needed.

• Additional keywords have been added: ceramics materials, thermal behaviour.

3. The introduction is short. should be compare other synthesis techniques.

below articles should be useful:

1-https://doi.org/10.1016/j.ceramint.2020.11.123

2-https://doi.org/10.1016/j.ceramint.2020.05.140

• The two bibliographic references suggested by the rviewer were added to the Introduction Part.

1. Tajik, A. Sayyadi-Shahraki, E.Taheri-Nassaj, A.Meysami, K. Xin Song, H. Barzgar Bafrooei, Effect of synthesis and sintering technique on the long-range 1:3 cation ordering and microwave dielectric loss of Li₂ZnTi₃O₈ ceramics, Ceram. Int. 46 20905 (2020).
2. Zhou, K. Wang, S. Hu, X. Luan, S. He, X. Wang, S. Zhou, X.Chen, H.Zhou, Preparation, structure and microwave dielectric properties of novel La₂MgGeO₆ ceramics with hexagonal structure and adjustment of its τf value, Ceram.Int. 47 7783 (2021).

• Many techniques could be applied to synthesize undoped and doped LaMnO₃ materials such as: sol-gel, hydrothermal, microwave, solid state reaction, the combustion method, or ultrasonically method with immersed sonotrode in the reaction medium [8-12].

 

 

4. Please clarify the novelty of work regarding literature.

• According to the literature, the novelty of this study refers to the Ga or Y dopant influence on the structural and electrical properties of the LaMnO₃ perovskite materials.

5. Please bring source and purity of reagents

• All chemicals reagents used purchased from Sigma-Aldrich, with highest purity (p.a.), and were used without any further purification.

6. Can you provide some pictures of produced gel and powder?

• Unfortunately, we cannot provide pictures of the gel formed during the synthesis. It should be mentioned that the gel had the same color as the powder (black color), as can be seen from the transmitted images.

 

               

7. This sentence is not sufficient. You need to specify the exact phase at every peak. Additionally, it is better to use ICCD cards for better clarification of XRD patterns.
8.  

 

9. Please explain how you calculate the lattice parameters.

• The crystalline structure was studied with the High Score X′Pert Plus program by Rietveld refinement, using FullProf software.

10. XRD does nor make sense. Please clarify the phases.
11.  

 

 

12. You did not explain this test in section 2.2. Please explain

• The thermal analysis is presented at 2. Materials and Methods, Section 2.2 - Characterization of materials, the lines 81-85.
• Thermal behavior was conducted under a dynamic air atmosphere (synthetic air 5.0 Linde Gas with flow 100 mL min−1) to highlight possible thermal-oxidative degradation stability of samples. The measurements were determined using a Diamond TG/DTA PerkinElmer, in the temperature range 25–900 °C, at a heating rate of 10 °C min−1, using open alumina crucibles.

13. The Y doped LaMnO₃ shows a higher mass loss than in the undoped and Ga-doped samples. Please explain why?

• The first exothermic peak on the HF curves of all samples is highlighted at approximately 400 °C and can be attributed to the loss of interstitial water or the decomposition of organic impurities. Regarding the second mass loss process that occurs above 600 ℃, it can be attributed to the OH groups attached to the surface or coordinated to the central metal ion in different forms. In general, the -OH groups are attached to the metal ion surface in two forms, either terminal La-OH or bridging La-(OH)-Mn. In both cases, the dissociation of surface OH groups contrasts with each other depending on the chemical environment and for this reason we do not have a clear peak on the HF curve. From the data of the thermogravimetric study, we can propose the hypothesis that doping with Ga and Y makes the number of OH groups linked either on the surface or in the bridge to be higher and hence the mass loss is higher in the case of doped samples. It seems that doping with Y favors OH bonding more than in the case of doping with Ga, which can be argued by the greater mass loss at temperatures above 600 ℃.

14. SEM images do not have a acceptable quality

• In accordance with the reviewer comment, the quality of the SEM image was increased.

15. Please describe VRH model

• The VRH (variable-range-hopping) theoretical model of Mott is applicable in non-crystalline materials (amorphous solids, nanopowders). It can be used to investigate electrical conduction and is based on the of the theory of hopping of charge carriers between localized states in the vicinity of the Fermi level, in an extended temperature range. Localized states are induced in non-crystalline materials by doping, impurities or defects, which leads to a high degree of disorder in the crystalline lattice of the material. The electrical conductivity, σ is due to the hopping of the charge carriers over variable distances (larger or smaller) between the localized states within the band-gap (BI), near the Fermi level. In the case of Mott's VRH model, it was shown that the temperature dependence of the electrical conductivity, σ(T) in strongly disordered systems with localized states of the charge carriers has a characteristic dependence of T^-1/4.

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors investigated Ga/Y doping effect on structural space group, thermal and electric properties in the Lanthanum manganese systematically and comprehensively. Thus this manuscript should be considered for the publication in applied sciences. I have a few questions and comments as listed below.

1. The presence of Ga/Y doping appears to influence the thermal and electrical properties of the material. Could you elaborate on how the doping levels were considered in relation to these properties?

2. The best way to make this conclusion is to show a SEM image of pristine sample (LaMnO3) in figure 4 to make this conclusion (154 line).

3. From the fitting results in Figure 6, B can be extracted as a constant. However, regarding the temperature dependence of the EA, cond (T) in function (3) from Figure 7, it is not immediately apparent why there is a linear relationship. Could the authors provide further clarification or additional data to explain the linear temperature dependence observed in this instance?

4. Please check English expressions, for example, 35, 49, 98, 244 …lines. And correct the position of citation of (a), (b) in figure

5. The significance (application) of the work is suggested to be added in the conclusion part.

Comments on the Quality of English Language

Please check English expressions, for example, 35, 49, 98, 244 …lines. And correct the position of citation of (a), (b) in figure. 

Author Response

Dear reviewers,

We would like to thank you for carefully reading the paper and for your comments and suggestions which improve the overall scientific quality of our manuscript. All the corrections have been marked in blue in the revised manuscript and a point-by-point response to your comments is provided in this letter. We believe that the manuscript is now ready to be published in Applied Sciences.

 

The authors investigated Ga/Y doping effect on structural space group, thermal and electric properties in the Lanthanum manganese systematically and comprehensively. Thus this manuscript should be considered for the publication in applied sciences. I have a few questions and comments as listed below.

1. The presence of Ga/Y doping appears to influence the thermal and electrical properties of the material. Could you elaborate on how the doping levels were considered in relation to these properties?

• The aim of the present study was the influence of the type of dopant on the structural and electrical properties. Thus, a dopant concentration of 1% was used, both for Ga and for Y.

2. The best way to make this conclusion is to show a SEM image of pristine sample (LaMnO₃) in figure 4 to make this conclusion (154 line).

• As the reviewer suggested, an SEM image of the undoped perovskite material (LaMnO₃) was presented.

3. From the fitting results in Figure 6, B can be extracted as a constant. However, regarding the temperature dependence of the EA, c_ond (T) in function (3) from Figure 7, it is not immediately apparent why there is a linear relationship. Could the authors provide further clarification or additional data to explain the linear temperature dependence observed in this instance?

By fitting the results from Fig. 6 with a straight line, it allows the determination of constant B. In accordance with Mott's VRH theoretical model [28], B is given by relation (3). If expression (3) of B is introduced in relation (2) we obtain: , which leads to the following expression for E_A,cond:. This relationship shows a linear dependence on temperature of the activation energy, as was also obtained experimentally in Figure 7.

 

4. Please check English expressions, for example, 35, 49, 98, 244 …lines. And correct the position of citation of (a), (b) in figure

• As suggested by the reviewer, the English expressions have been checked and modified accordingly:
• Mixed oxides of manganese and rare earth have been invetigated concerning interplaying among orbital, lattice, magnetism and transport properties in various R1-xAxMn1-yByO3 compounds (where R = rare earth; A = divalent cation; B = transition metal).
• For example, in the case of Ga-doped LaMnO₃ perovskite materials synthesized by conventional ceramic procedure, the increase in the Ga content determines a decrease of the transition pressure to the higher symmetry phases [13].
• The crystal structure analysis through XRD powder diffraction has been performed for all 3 compounds and as observed in Figure 1, the samples present a very good crystallinity proven by sharp and well-defined peaks. The perovskite type structure is characteristic for the undoped LaMnO₃ sample indexed in the R-3c space group (corresponding to JCPDS card file no. 01-089-0678).
• Using the values obtained for EA,cond (T) from Figure 7 and Eq. (6), we computed N(EF) in the temperature range (28-120) °C at a low frequency (f = 1 kHz). For the studied samples the following values: N(EF)S1=1.158͘˴1018 cm-3˴eV-1, N(EF)S2=1.288͘˴1018 cm-3˴eV-1 and N(EF)S3=1.231˴1018 cm-3˴eV-1 were obtained. These results show that the density of states at the Fermi level N(EF), does not depend on the temperature, remaining constant on the whole investigated domain, as shown recently in the papers [34, 35], for other oxide materials (Fe-P or Cu-Mn type).
• The position of citation (a) and (b) in the figure was corrected.

5. The significance (application) of the work is suggested to be added in the conclusion part.

• The present study evaluates for the first time the electric properties of perovskite materials and the obtained results extend the available knowledge of relevance in electrocatalytic domain.

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors addressed the comments fine.

I believe it can be published right now after a minor editing of English language.

Comments on the Quality of English Language

Minor editing of English language might be required.