Dielectric Properties of Mg₂TiO₄-Doped Ca_0.65Sr_0.35Zr_0.65Ti_0.35O₃ with High Withstand Voltage and Low Loss

Round 1

Reviewer 1 Report

Hello. Overall, nice work. I have some minor changes and questions to share before I think your work is ready for publication.

1. In your XRD figure, you label two minor peaks as being Mg2TiO4 at ~ 43 and 75 2-theta. However, neither line up with the highest intensity peak given in the PDF card. That peak (at 35 2-theta) does not appear in your XRD spectra. Can you explain why you think these minor peaks belong to Mg2TiO4 and why they are not impurities or perhaps k-beta peaks (you do not state whether a Ni filter or monochromator in XRD was used?
2. For table 1, I think you can remove the first column on deposition time since it is the same for all samples.

Good work and good luck.

Author Response

Please see the attached file.

Thanks

Author Response File: Author Response.pdf

Reviewer 2 Report

In the article “Dielectric Properties of Mg2TiO4-Doped Ca0.65Sr0.35Zr0.65Ti0.35O3 2

With High Withstand Voltage and Low Loss” Liu et al investigated the dielectric response of dielectric response of the x mol% Mg2TiO4–CSZT thin films prepared using magnetron sputtering. Though the authors have done good work of in section of the research problem I have following concerns:

 

1. Authors have used x = 2, 4,6 ,8 mol%. Why were these values chosen?
2. How was “x” determined experimentally. Elemental analysis of the films is missing.
3. Line 66 “All the prepared thin films were conventional thermal 65 annealed (CTA) in air at 700 °C for 180 minutes to obtain well-crystallized grains”. Where does this information comes from?
4. Line 100 “It is obvious that the growth rate of the films increases significantly with the increase of 100 the doping amount”. Is it a common behavior or something authors have seen for the first time? Authors should check previous work.
5. Why was temperature dependence done? What was the motivation?
6. In conclusion authors have reported the recorded parameters. But a comparison with previous work is missing. Authors need to investigate related literature to make the observations more concrete.

Author Response

Please see the attached file

Thanks

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript reports on the room-temperature (RT) structural, microstructural and leakage current characterisation as well as temperature-variable dielectric spectroscopy analysis of x mol% Mg2TiO4 – Ca0.65Sr0.35Zr0.65Ti0.65O3 (CSZT) thin films. 6% Mg2TiO4–CSZT thin film was found to be the most promising for capacitor applications due to its high temperature stability (TCC ~ −67.85 ppm/℃, from −55 ℃ to 205 ℃) combined with low loss (tanδ ~0.008 at 1 MHz) and leakage current. However, before considering the manuscript for publication the data presentation, description, analysis and discussion have to be improved.

Right in the abstract, the authors provide a value of 2.61×10-6 A/cm as a leakage current value for 6% sample. However, neither the value corresponds to Figure 5, showing higher leakage current density, nor the units correspond to the leakage current or current density. This comment is also valid for corrections to be done in Conclusions section. Moreover, the authors are advised to avoid words like “excellent” and “improve(d)” in the scientific texts substituting them by less ambiguous words or just by values.

In addition, the use of term “dielectric permittivity” across the text instead of “dielectric constant” would make the manuscript sounding also more scientifically correct.

In the introduction section, besides substitution of “et al” by “etc.” at line 28 and reduction of 3 times repetition of phrase “thin film” at a single line 36, the authors have to correct their statement at lines 51-52 that they deposited thin films on p-type silicon substrate. According to further reading, instead they deposited the films on LaNiO3 (LNO) covered silicon and that fact is very important, requiring an overview in the Introduction section of some literature like Refs. 20,21 as well as Appl. Phys. Lett. 92 (2008) 092902 and Materials and Design 160 (2018) 1322. Mentioning of this cover layer in the abstract is also requested.

Accordingly, the Experimental section has also to provide the parameters (particularly deposition time) for deposition of LNO layer with further indication of its thickness. Besides that, writing about the powders for targets the authors have to inform the reader how and/or where from they did got the powders. Such magnetron sputtering conditions as used gas or gas mixture and target – substrate distance are also missing. Measurement conditions, which have to be provided in the Experimental section, are not shown there at all. Thus, XRD range, rate, step, SEM acceleration voltage, dielectric spectroscopy oscillation voltage, frequency, voltage and temperature ranges as well as temperature rate have to be indicated there. In addition, it is unclear what the authors meant by P-E loops and C-tanδ curves and where are these data in the manuscript. Furthermore, in contrast to sentence “The P-E loops and current-voltage curve (I-V curve) measured using a Radiant Precision Workstation (United Kingdom) under different temperatures.” no current-voltage curve at a temperature different from RT is shown in this manuscript.

Results and discussion part has to be reconstructed showing the figures after their mentioning in the text but not before that. Figure captions have to make figures self-explaining that is not the case, particularly for Figure 1, which caption neither report the presented compositions nor introduce the bottom pattern. Moreover, peaks in the top graph marked with • do not look to correspond the reflection lines shown at the bottom of Fig. 1 in contrast to the authors statement. Furthermore, stating that “The shift of diffraction peaks was observed”, the authors have to show it clearly in the Figure and indicate the shift direction. Otherwise, their explanation that “It was caused by Mg2+ ions entering into the B site of the perovskite structure” looks baseless that does not correspond to the level of a journal like Crystals.

Figure 2 does not show photographs but micrographs. Moreover, related Table 1 should better show the thickness error and LNO thickness values instead of numerous repetition that CSZT films were deposited during 600 min. This fact as well as the film compositions should be better reflected in the Table 1 head.

Figure 3 has to be plotted with frequency in the log scale and switched positions of Fig. 3b and Fig 3c so that dielectric permittivity is shown on top of the figure while dielectric loss on its bottom. Then corresponding sentence at lines 108-109 has to be revised, while sentence at lines 112-113 has to cite works like J. Eur. Ceram. Soc. 19 (1999) 1987 and Appl. Phys. A 79 (2004) 2013, since Ref. 22 reported on Ba0.55Sr0.45TiO3 but not SrTiO3 in contrast to the authors statement. Moreover, according to Acta Crystallogr. A 32 (1976) 751, ionic radii of 6-coordinated Mg2+ and Ti4+ are 0.72 Å and 0.605 Å, respectively, but not 0.65 Å and 0.68 Å as stated by the authors.

Sentence at lines 135-136 states that “Figure 4 shows the variation of dielectric constant (εr) and dielectric loss (tanδ) of x% Mg2TiO4–CSZT thin films with temperature at 100 kHz”, but no tanδ is shown in Figure 4, although its temperature dependence would be interesting to see. Moreover, error associated with the determination of TCC from Fig. 4 has to be also indicated, while either Tcc or TCC has to be used across all the manuscript by the authors for consistency.

Finally, current density dimensions has to be revised at line 150, while phrase “film has a thinner thickness” has to be revised at line 153. General English revision of the manuscript is also necessary.

 

As a result, current manuscript can be considered for publication only when it is revised according to the comments above.

Author Response

Please see the attached file

Thanks

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Manuscript can be accepted in present form.

Reviewer 3 Report

The manuscript is revised addressing the previous review comments.

Just in Figure 3, x axis label should be “Frequency” but not “Frequence”. Frequency range is also still missing in the Experimental section.

Author Response

Thanks a lot for the suggestions. The errors have been corrected, and frequency range has been supplemented in the Experimental section part in the revised manuscript.