Impact of Particle and Crystallite Size of Ba0.6Sr0.4TiO3 on the Dielectric Properties of BST/P(VDF-TrFE) Composites in Fully Printed Varactors
Round 1
Reviewer 1 Report
The “Impact of particle and crystallite size of Ba0.6Sr0.4TiO3 on the dielectric properties of BST/P(VDF-TrFE) composites in fully printed varactors” manuscript reports the fabrication and characterization of 3D printed ferroelectric varactors. This work reports a technological development and the results are well organized and presented in a good manner. The paper is interesting and may deserve publication in Polymers journal even though some point should be addressed:
1. Introduction, from line 57 to line 60
The “For (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ), Wang et al. observed an initial increase for the relative permittivity to a maximum, followed by a decrease with increasing sintering temperature and grain size. On the other hand, the dielectric loss increases with higher sintering temperature [18]” sentences should be revised or deleted. I suggest the authors to underline the effect of the sintering temperature on the dielectric function of Ba0.6Sr0.4TiO3 and to replace reference 18 with a more appropriate one.
2. BST synthesis, line 94
Was the value of the density measured or is it the theoretical one?
3. BST synthesis, line 95
I suggest the authors to revise the “crystallite sizes of the BST were investigated by XRD” expression. Moreover, they should provide more detail concerning the method used to determine the mean crystallite size from X-ray diffraction patterns.
4. Ink preparation, line 103
To be more clear for readers, the authors should mention which suspensions were evaporated at room temperature.
5. Dielectric properties, from line 356 to line 358
The “higher temperature” and “over a temperature range” expression are confusing. Probably will be better if authors will write “were measured at room temperature” instead of “were measured” (line 340).
6. Dielectric properties
More discussion concerning the contribution of the P(VDF-TrFE) on the dielectric properties, especially on the tunability should be done. For comparison, will be great to have the dielectric properties of a ferroelectric varactor printed only with P(VDF-TrFE).
7. In what specific applications can these varactors be used? The authors should better explain that the goal of the manuscript. If RF and microwave frequencies are targeted, are the reported data (at 200 kHz) appropriate to prove the potential for applications?
Author Response
- Introduction, from line 57 to line 60
The “For (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ), Wang et al. observed an initial increase for the relative permittivity to a maximum, followed by a decrease with increasing sintering temperature and grain size. On the other hand, the dielectric loss increases with higher sintering temperature [18]” sentences should be revised or deleted. I suggest the authors to underline the effect of the sintering temperature on the dielectric function of Ba0.6Sr0.4TiO3 and to replace reference 18 with a more appropriate one.
Response 1: The sentence has been deleted and replaced with a more appropriate one.
- BST synthesis, line 94
Was the value of the density measured or is it the theoretical one?
Response 2: The theoretical density has been added from the PDF Card No. 00-034-0411.
- BST synthesis, line 95
I suggest the authors to revise the “crystallite sizes of the BST were investigated by XRD” expression. Moreover, they should provide more detail concerning the method used to determine the mean crystallite size from X-ray diffraction patterns.
Response 3: The expression has been changed to "X-ray diffraction (XRD) measurements of the BST powders were performed at a D8 advance A25 diffractometer (Bruker, 40 kV, 40 mA) in an angle range of 2θ = 15 – 90° using Cu Kα (1.5406 Å) with a step size of 0.02° The measurement time was 1 h and Rietveld refinement was performed using TOPAS."
- Ink preparation, line 103
To be more clear for readers, the authors should mention which suspensions were evaporated at room temperature.
Response 4: All suspensions were evaporated at room temperature. One fraction was taken out (RT-samples) and the remaining powders were subsequently thermally treated at different temperatures (@700, 900, 1100 °C). This passage has been changed in the manuscript.
- Dielectric properties, from line 356 to line 358
The “higher temperature” and “over a temperature range” expression are confusing. Probably will be better if authors will write “were measured at room temperature” instead of “were measured” (line 340).
Response 5: The expressions have been modified.
- Dielectric properties
More discussion concerning the contribution of the P(VDF-TrFE) on the dielectric properties, especially on the tunability should be done. For comparison, will be great to have the dielectric properties of a ferroelectric varactor printed only with P(VDF-TrFE).
Response 6: The goal of the paper is to discuss about composite systems and not about polymer based varactor systems. In the literature, a pure P(VDF-TrFE) system has been reported. However, the tunability is very low with around 2.5 %. This part has been included in the introduction.
- In what specific applications can these varactors be used? The authors should better explain that the goal of the manuscript. If RF and microwave frequencies are targeted, are the reported data (at 200 kHz) appropriate to prove the potential for applications?
Response 7: The results presented in the paper are fundamentally comparing the influences of the particle and crystallite sizes on the dielectric properties. For the application, the varactors have to be tested in the GHz-range in the next step. The conclusion has been updated accordingly.
Reviewer 2 Report
Journal: Polymers (ISSN 2073-4360)
Manuscript ID: polymers- 1981373
Type: Article
Title: Impact of particle and crystallite size of Ba0.6Sr0.4TiO3 on the dielectric properties of BST/P(VDF-TrFE) composites in fully printed varactors.
Authors: Tim P. Mach * , Yingfang Ding , Joachim R. Binder.
a) Introduction: In the literature, add more than three to the number of authors who have worked on their subject and achieved results.
b) Write the objective of the present work clearly.
c) Why the authors didn’t measure the thermal conductivity of the sampls?.
d) Table 5 how the author measure the standard deviation of the samples? And what is the benefit?
e) Why the authors didn’t measure the grain size using XRD for the samples?
f) Why the author didn’t measure the EDX for the samples?
g) For references, choose recent refs. Please, refer to these refs for dielectric properties.
DOI: https://doi.org/10.1016/j.mseb.2021.115191
DOI: https://doi.org/10.1016/j.jallcom.2017.02.117
Best Regards
Author Response
a) Introduction: In the literature, add more than three to the number of authors who have worked on their subject and achieved results.
Response a: The literature has been updated and more research works have been added.
b) Write the objective of the present work clearly.
Response b: The objective of the presented work has been updated in the introduction.
c) Why the authors didn’t measure the thermal conductivity of the sampls?.
Response c: In our opinion, the thermal conductivity plays a minor role for layers in the µm-range. Therefore, the measurement was not performed.
d) Table 5 how the author measure the standard deviation of the samples? And what is the benefit?
Response d: The coherent domain sizes (crystallite sizes) were determined via XRD, using a Rietveld refinement. The crystallite sizes were calculated through the peak broadening of the reflexes and the standard deviation was measured through the Rietveld refinement using the least square method. However, the values should be more taken as a estimation.
e) Why the authors didn’t measure the grain size using XRD for the samples?
Response e: With the XRD, the crystallite size can be measured. For the determination of the grain size, SEM should be employed. However, since we are working with composite materials and not with purely sintered ceramic materials, the grain size cannot be determined.
f) Why the author didn’t measure the EDX for the samples?
Response f: The method used to synthesize BST is an established synthesis route that has been used in our group. In previous works, X-ray fluorescence (XRF) was already conducted to analyze the synthesized BST on their composition.
http://dx.doi.org/10.1016/j.jeurceramsoc.2014.04.007
10.1007/s10832-009-9580-0
https://doi.org/10.1016/j.ceramint.2008.01.014
However, in the manuscript, we added an ICP-OES analysis, where small amounts of Zr (0.926 wt%) could be found from the milling process due to abrasion of ZrO2 grinding media.
g) For references, choose recent refs. Please, refer to these refs for dielectric properties.
DOI: https://doi.org/10.1016/j.mseb.2021.115191
DOI: https://doi.org/10.1016/j.jallcom.2017.02.117
Response g: We do not understand this comment, as the refs mentioned are not comparable to our material in regard to material synthesis, measurement technology or tunabilty. However, in the introduction, more recent literature has been cited.
Round 2
Reviewer 1 Report
The revised version of the Polymers-1981373 manuscript entitled “Impact of particle and crystallite size of Ba0.6Sr0.4TiO3 on the dielectric properties of BST/P(VDF-TrFE) composites in fully printed varactors” have been significantly improved. Only 2 minor corrections are necessary before publication in Polymers journal.
1. Introduction, line 82
Instead of “29 kV per micrometer” should be written “29 kV per millimetre” or “29 V per micrometer”.
2. Results and discussion, from line 395 to line 396
The sentence should be revised. The parallel plate capacitor formula (equation 1) is valid also for thicker layers.
Author Response
- Introduction, line 82
Instead of “29 kV per micrometer” should be written “29 kV per millimetre” or “29 V per micrometer”.
This part has been adjusted to 29 kV per mm.
- Results and discussion, from line 395 to line 396
The sentence should be revised. The parallel plate capacitor formula (equation 1) is valid also for thicker layers.
This part has been adjusted to : "Since the applied external electric field is dependent on the thickness, the maximum tunability increases even further the thinner the layers are."
