Low-Temperature Co-Precipitation Synthesis of HoFeO₃ Nanoparticles

Round 1

Reviewer 1 Report

The submitted paper describes the synthesis of ultrafine HoFeO₃ nanocrystals by heat treatment of corresponding hydroxides, co-precipitated at low temperatures. The detailed research of the synthesized HoFeO₃ nanocrystals was carried out to define their structural, electrooptical and magnetic features. Superparamagnetic HoFeO₃ NPs were successfully obtained with unusually low band gap energy that which allows considering them as the basis of materials for modern electronics and photocatalysis. Thus, the scientific novelty, significance and subject matter of the work is fully consistent with the concept and profile of the Journal. Some minor comments raised after paper reading are presented below:

1. The pyrolysis (64th row) seems to be a not appropriate term for HoO(OH)·yH₂O decomposition process since it assumes primarily a chemical transformation of organic compounds in an inert atmosphere;
2. The “raman spectrum” (80th row) must be capitalized;
3. Some other typos and grammatical errors need to be carefully corrected in the manuscript;
4. The quality (dpi) of Figs should be improved if possible;
5. The Introduction section should be supplemented with the following works:

- the temperature effect on the formation of RFeO₃ nanocrystals - 10.1134/S0020168509110211, 10.1134/S1070427209110020

- the morphology and size effect on the magnetic behavior of RFeO₃ nanocrystals - 10.1007/s10854-017-6676-1

- on the solution combustion synthesis of HoFeO₃ nanocrystals and their functional properties

I believe that the paper can be recommended for publication in the Crystals after minor corrections of the article following the remarks above.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript reports the synthesis and characteristics of HoFeO₃ nanoparticles (NP) obtained by the co-precipitation.  Thermal analysis (TG-DSC), XRD, SEM, TEM, Raman and UV-Vis spectroscopy, magnetic measurements were utilized to characterize the process of NP formation and the properties of final product.

The content of the paper satisfies the Aims and Scopes of Crystals.

The manuscript is written clearly and in general makes a positive impression. Unfortunately, there is a few comments concerning manuscript content, data presentation and discussion:

• The text of the manuscript is mostly descriptive – there is almost no discussion. The paper could be more attractive and useful if the authors explain/propose/discuss reasons of the difference between the obtained experimental results and published one.
• Part “Conclusions” includes statements which are written in broad terms. The novelty of the results obtained should be clearly emphasized and deductions relevant to the results of the work should be added.
• The paper - Tien A.Nguyen, et al. Optical and magnetic properties of HoFeO3 nanocrystals prepared by a simple co-precipitation method using ethanol. Journal of Alloys and Compounds, 834(2020) 155098 – should be considered in “Introduction” and “Discussion” sections.
• Description of methods used (Page 2, lines 52-56) needs to be substantially improved, reasonable details concerning the devices, methods and operation conditions are necessary.
• It is not clear why co-precipitation temperature was chosen to be 4° С. The explanation of the choice looks logical.
• Fig.2 (page 3) is vacuous. It seems to be better to redraw the Fig.2 (similar Fig.2 of the paper mentioned above using I^0.5 as y-axis).
• Page 4, Line 103:  wrong or unclear ref. to Fig. 2.
• Abstract claims “annealing of the precipitates at 750, 850, and 950 °C”, but manuscript contains no data for 950 °C except undecipherable XRD-pixture.

Author Response

Please see the attachment

Author Response File: Author Response.docx