- Email: [email protected]
A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics
Journal Pre-proof A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics Zhuozhuang Xie, Hongbo Liu PII:
S0272-8842(19)33259-6
DOI:
https://doi.org/10.1016/j.ceramint.2019.11.070
Reference:
CERI 23439
To appear in:
Ceramics International
Received Date: 4 October 2019 Revised Date:
6 November 2019
Accepted Date: 8 November 2019
Please cite this article as: Z. Xie, H. Liu, A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics, Ceramics International (2019), doi: https://doi.org/10.1016/j.ceramint.2019.11.070. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics Zhuozhuang XIE, Hongbo LIU*
School of Materials Engineering, Shanghai University of Engineering Science, Shanghai, 201620, China
Abstract: Lead-free antiferroelectric silver niobate AgNbO3 ceramics have attracted growing interest for their superior energy storage density. The ceramics are commonly prepared by the conventional solid-state reaction method using Ag2O and Nb2O5 as the raw materials. An O2 atmosphere is maintained to prevent the possible decomposition of Ag2O during sintering, which increases the complexity of the process. In this work, we prepared successfully the pure phase AgNbO3 ceramics in air with the hydrothermally synthesized AgNbO3 powders. In comparison with the ceramics prepared by the conventional solid-state reaction method, the ceramics prepared by the hydrothermally synthesized powders have a broader antiferroelectric phase region and show pinched polarization-electric field hysteresis loops at moderate electric fields. Keywords: AgNbO3; Antiferroelectricity
∗
Corresponding author. Email address: [email protected] (H. LIU)
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1. Introduction Electrical energy storage plays a key role in mobile electronic devices and hybrid electric vehicles[1]. Among various electrical energy storage devices such as batteries, fuel cells, capacitors, and supercapacitors, dielectric capacitors are promising candidates for their high power density but suffered from their low energy storage density [2,3]. The materials used in dielectric capacitors include ferroelectrics, antiferroelectrics, relaxors, and linear dielectrics. Among them, antiferroelectrics with an electric field-induced phase transition enables a large amount of energy to be stored and released [4,5]. However, the materials with antiferroelectricity are very few and may contain harmful element Pb[6], which is one of the substances restricted by ROHS. Recently, the double polarization-electric field hysteresis loop has been observed in lead-free AgNbO3 [7]. A high energy storage density of ~2 J/cm3 has been obtained in it [8,9]. The energy storage density is further enhanced by doping with Ba2+, Bi3+, and La3+[10–12]. The main method of preparing AgNbO3 ceramics is the conventional solid-state reaction. To avoid the decomposition of Ag2O at 100-300 , the sintering has to be finished in an oxygen atmosphere with the excess of Ag2O [13]. To avoid this complexity, we first prepared the pure AgNbO3 powders by a hydrothermal reaction method. Then, the synthesized powders were sintered at high temperature to prepare AgNbO3 ceramics. In other words, the work provides an alternative route to prepare the important antiferroelectric ceramics. 2. Experiment Ag2O powders were prepared by combing aqueous solutions of AgNO3 (0.5mol/L) and NaOH (0.3mol/L). Then, Ag2O and Nb2O5 powders were weighted and dissolved in aqueous NH4HF2 solution
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(1.6mole/L) with an Ag2O: Nb2O5: NH4HF2 mole ratio of 1:1:3. The mixture was sealed in a 100 mL Teflon-lined stainless-steel autoclave, and heated at 200
for 24h-48h. The synthesized powders were
washed with distilled water and dried at 70 . The crystal structure of the powders was examined by an X-ray diffraction Diffractometer (PANalytical X'Pert PRO) with Cu Kα radiation (λ=1.5406Å). The powders were then shaped into pellets and sintered at 1050
for 6h. After painted with silver electrodes,
the dielectric properties of the ceramics were measured by an impedance analyzer (Keysight E4990A) with temperature varying from room temperature to 450 . The polarization-electric field hysteresis loops were measured by a commercial ferroelectric tester (Radiant Technology Precision LC Ferroelectric Tester). 3. Results and Discussion Figure 1 depicts the X-ray diffraction patterns of hydrothermally synthesized AgNbO3 powders. The reaction time is crucial for synthesizing pure phase AgNbO3. Neither 24h nor 36h produces pure phase AgNbO3. After 48h reaction, the pure orthorhombic phase AgNbO3 is produced.
Fig. 1 X-ray diffraction patterns of hydrothermally synthesized AgNbO3 powders with different reaction times (24h, 36h, 44h, and 48h respectively).
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AgNbO3 undergoes several phase transitions on heating: M1 to M2 at 67oC, M2 to M3 at 267oC, M3 to O1 at 353oC, O1 to O2 at 361 oC, O2 to T at 387oC, and T to C at 579oC [14]. Here M1, M2, and M3 denote the phases with orthorhombic symmetry in the rhombic orientation while O1 and O2 are the phases with orthorhombic symmetry in the parallel orientation, T is the tetragonal phase, and C represents the cubic phase. These phase transitions can be reflected by the anomalies of the temperature-dependent dielectric permittivity. As shown in figure 2, we notice the dielectric anomalies at ~78 , 310 , and 410 . According to previous studies on the structural phase transitions and dielectric responses [15,16], the sharp dielectric peak at 410
is the phase transition from the paraelectric orthorhombic phase O1 to the
antiferroelectric phase M3, the diffused dielectric peak at 310
arises in between the antiferroelectric
phases M3 and M2 with different degrees of ordering, and the dielectric anomaly at ~78
is the phase
transition from the antiferroelectric phase M2 to the ferrielectric phase M1. For the ceramics prepared by the solid-reaction method, the phase transition temperatures for M1-M2, M2-M3, and M3-O1 from dielectric anomalies are 70 , 260 , and 350 and 353
[8] respectively, or 70 , 260 ,
respectively [9]. In Bi3+, La3+, or Ta5+ doped AgNbO3, the phase transition temperatures
decrease or remain the same as that of pure AgNbO3[10,12,17]. In comparison with the ceramics prepared by the solid-reaction method, the ceramics prepared by the hydrothermally synthesized powders can stabilize the antiferroelectric M2 or M3 phase in a more broad temperature range. For instance, the temperature range which stabilizes M2 phase varies from 190K to 232K, and the temperature range stabilizing M3 phase varies from 90K to 100K. The whole temperature range for the antiferroelectric phases is from 78
to 410 , which is the widest one. It should be also noted that the room temperature
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dielectric permittivity of AgNbO3 prepared by the hydrothermal powders is also higher than that of the solid-reaction sintered ceramics [8,9].
Fig. 2 The temperature dependence of dielectric permittivity of AgNbO3
The polarization-electric field hysteresis loops are shown in figure 3. With the increase of the applied electric field, the linear curves change to the pinched loop at 60kV/cm, indicating the coexistence of a weak ferroelectric component and the antiferroelectric order. The maximum polarization is 9.6 µC/cm2, which is superior to that of ceramics prepared by the solid reaction method at the same electric field [8,9].
Fig. 3 The polarization-electric field hysteresis loops of AgNbO3 under different electric fields
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4. Conclusions Using a hydrothermal reaction method, we successfully synthesized AgNbO3 powders. The key parameter to prepare pure phase AgNbO3 powders by the hydrothermal reaction method is the reaction time, which needs at least 44h. The AgNbO3 ceramics were then successfully prepared by the hydrothermal powders without flowing O2 during sintering. In comparison with the ceramics prepared by the solid-reaction method, the ceramics prepared by the hydrothermal powders have enhanced dielectric and polar performance. The antiferroelectric phases are stabilized in a wider temperature range.
Acknowledgment The work was supported by the National Natural Science Foundation of China (Grant No. 11704242) and Natural Science Foundation of Shanghai, China (Grant No. 17ZR1447200). References [1]
H. Liu, B. Dkhil, Effect of resistivity ratio on energy storage and dielectric relaxation properties of 0–3 dielectric composites, J. Mater. Sci. 52 (2017) 6074-6080.
[2]
Z. Yao, Z. Song, H. Hao, Z. Yu, M. Cao, S. Zhang, M.T. Lanagan, H. Liu, Homogeneous/inhomogeneous-structured dielectrics and their energy-storage performances, Adv. Mate. 29 (2017) 1601727.
[3]
L. Yang, X. Kong, F. Li, H. Hao, Z. Cheng, H. Liu, J.-F. Li, S. Zhang, Perovskite lead-free
[4]
H. Liu, B. Dkhil, A brief review on the model antiferroelectric PbZrO3 perovskite-like material, Z.
dielectrics for energy storage applications, Prog. Mater Sci. 102 (2019) 72-108. Kristallogr. 226 (2011) 163-170. [5]
Z. Liu, T. Lu, J. Ye, G. Wang, X. Dong, R. Withers, Y. Liu, Antiferroelectrics for energy storage applications: a review, Adv. Mater. Technol-US. 3 (2018) 1800111.
[6]
H. Liu, Universal dielectric relaxation induced giant dielectric permittivity in Mn-doped PbZrO3 ceramics, Ceram. Int. 45 (2019) 10380–10384.
[7]
D. Fu, M. Endo, H. Taniguchi, T. Taniyama, M. Itoh, AgNbO3: a lead-free material with large polarization and electromechanical response, Appl. Phys. Lett. 90 (2007) 252907.
[8]
Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, E.D. Politova, S.Yu. Stefanovich, N.V. Tarakina, I. Abrahams, H. Yan, High energy density in silver niobate ceramics, J. Mater. Chem. A. 4 (2016) 17279-17287.
[9]
J. Gao, L. Zhao, Q. Liu, X. Wang, S. Zhang, J.-F. Li, Antiferroelectric-ferroelectric phase transition
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in lead-free AgNbO3 ceramics for energy storage applications, J. Amer. Ceram. Soc. 101 (2018) 5443-5450. [10] Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, G. Viola, I. Abrahams, H. Yan, Phase transitions in bismuth-modified silver niobate ceramics for high power energy storage, J. Mater. Chem. A. 5 (2017) 17525-17531. [11] K. Han, N. Luo, Y. Jing, X. Wang, B. Peng, L. Liu, C. Hu, H. Zhou, Y. Wei, X. Chen, Q. Feng, Structure and energy storage performance of Ba-modified AgNbO3 lead-free antiferroelectric ceramics, Ceram. Int. 45 (2019) 5559-5565. [12] J. Gao, Y. Zhang, L. Zhao, K.-Y. Lee, Q. Liu, A. Studer, M. Hinterstein, S. Zhang, J.-F. Li, Enhanced antiferroelectric phase stability in La-doped AgNbO3: perspectives from the microstructure to energy storage properties, J. Mater. Chem. A. 7 (2019) 2225-2232. [13] A. Kania, A. Niewiadomski, S. Miga, I. Jankowska-Sumara, M. Pawlik, Z. Ujma, J. Koperski, J. Suchanicz, Silver deficiency and excess effects on quality, dielectric properties and phase transitions of AgNbO3 ceramics, J. Eur. Ceram Soc. 34 (2014) 1761-1770. [14] P. Sciau, A. Kania, B. Dkhil, E. Suard, A. Ratuszna, Structural investigation of AgNbO3 phases using x-ray and neutron diffraction, J. Phys.: Condens. Matter. 16 (2004) 2795-2810. [15] A. Kania, Dielectric properties of Ag1-xAxNbO3(A: K, Na and Li) and AgNb1-xTaxO3 solid solutions in the vicinity of diffuse phase transitions, J. Phys. D: Appl. Phys. 34 (2001) 1447-1455. [16] I. Levin, V. Krayzman, J.C. Woicik, J. Karapetrova, T. Proffen, M.G. Tucker, I.M. Reaney, Structural changes underlying the diffuse dielectric response in AgNbO3, Phys. Rev. B. 79 (2009) 104113. [17] Y. Tian, L. Jin, Q. Hu, K. Yu, Y. Zhuang, G. Viola, I. Abrahams, Z. Xu, X. Wei, H. Yan, Phase transitions in tantalum-modified silver niobate ceramics for high power energy storage, J. Mater. Chem. A. 7 (2019) 834-842.
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
S0272-8842(19)33259-6
DOI:
https://doi.org/10.1016/j.ceramint.2019.11.070
Reference:
CERI 23439
To appear in:
Ceramics International
Received Date: 4 October 2019 Revised Date:
6 November 2019
Accepted Date: 8 November 2019
Please cite this article as: Z. Xie, H. Liu, A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics, Ceramics International (2019), doi: https://doi.org/10.1016/j.ceramint.2019.11.070. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
A novel method of preparing antiferroelectric silver niobate AgNbO3 ceramics Zhuozhuang XIE, Hongbo LIU*
School of Materials Engineering, Shanghai University of Engineering Science, Shanghai, 201620, China
Abstract: Lead-free antiferroelectric silver niobate AgNbO3 ceramics have attracted growing interest for their superior energy storage density. The ceramics are commonly prepared by the conventional solid-state reaction method using Ag2O and Nb2O5 as the raw materials. An O2 atmosphere is maintained to prevent the possible decomposition of Ag2O during sintering, which increases the complexity of the process. In this work, we prepared successfully the pure phase AgNbO3 ceramics in air with the hydrothermally synthesized AgNbO3 powders. In comparison with the ceramics prepared by the conventional solid-state reaction method, the ceramics prepared by the hydrothermally synthesized powders have a broader antiferroelectric phase region and show pinched polarization-electric field hysteresis loops at moderate electric fields. Keywords: AgNbO3; Antiferroelectricity
∗
Corresponding author. Email address: [email protected] (H. LIU)
1/7
1. Introduction Electrical energy storage plays a key role in mobile electronic devices and hybrid electric vehicles[1]. Among various electrical energy storage devices such as batteries, fuel cells, capacitors, and supercapacitors, dielectric capacitors are promising candidates for their high power density but suffered from their low energy storage density [2,3]. The materials used in dielectric capacitors include ferroelectrics, antiferroelectrics, relaxors, and linear dielectrics. Among them, antiferroelectrics with an electric field-induced phase transition enables a large amount of energy to be stored and released [4,5]. However, the materials with antiferroelectricity are very few and may contain harmful element Pb[6], which is one of the substances restricted by ROHS. Recently, the double polarization-electric field hysteresis loop has been observed in lead-free AgNbO3 [7]. A high energy storage density of ~2 J/cm3 has been obtained in it [8,9]. The energy storage density is further enhanced by doping with Ba2+, Bi3+, and La3+[10–12]. The main method of preparing AgNbO3 ceramics is the conventional solid-state reaction. To avoid the decomposition of Ag2O at 100-300 , the sintering has to be finished in an oxygen atmosphere with the excess of Ag2O [13]. To avoid this complexity, we first prepared the pure AgNbO3 powders by a hydrothermal reaction method. Then, the synthesized powders were sintered at high temperature to prepare AgNbO3 ceramics. In other words, the work provides an alternative route to prepare the important antiferroelectric ceramics. 2. Experiment Ag2O powders were prepared by combing aqueous solutions of AgNO3 (0.5mol/L) and NaOH (0.3mol/L). Then, Ag2O and Nb2O5 powders were weighted and dissolved in aqueous NH4HF2 solution
2/7
(1.6mole/L) with an Ag2O: Nb2O5: NH4HF2 mole ratio of 1:1:3. The mixture was sealed in a 100 mL Teflon-lined stainless-steel autoclave, and heated at 200
for 24h-48h. The synthesized powders were
washed with distilled water and dried at 70 . The crystal structure of the powders was examined by an X-ray diffraction Diffractometer (PANalytical X'Pert PRO) with Cu Kα radiation (λ=1.5406Å). The powders were then shaped into pellets and sintered at 1050
for 6h. After painted with silver electrodes,
the dielectric properties of the ceramics were measured by an impedance analyzer (Keysight E4990A) with temperature varying from room temperature to 450 . The polarization-electric field hysteresis loops were measured by a commercial ferroelectric tester (Radiant Technology Precision LC Ferroelectric Tester). 3. Results and Discussion Figure 1 depicts the X-ray diffraction patterns of hydrothermally synthesized AgNbO3 powders. The reaction time is crucial for synthesizing pure phase AgNbO3. Neither 24h nor 36h produces pure phase AgNbO3. After 48h reaction, the pure orthorhombic phase AgNbO3 is produced.
Fig. 1 X-ray diffraction patterns of hydrothermally synthesized AgNbO3 powders with different reaction times (24h, 36h, 44h, and 48h respectively).
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AgNbO3 undergoes several phase transitions on heating: M1 to M2 at 67oC, M2 to M3 at 267oC, M3 to O1 at 353oC, O1 to O2 at 361 oC, O2 to T at 387oC, and T to C at 579oC [14]. Here M1, M2, and M3 denote the phases with orthorhombic symmetry in the rhombic orientation while O1 and O2 are the phases with orthorhombic symmetry in the parallel orientation, T is the tetragonal phase, and C represents the cubic phase. These phase transitions can be reflected by the anomalies of the temperature-dependent dielectric permittivity. As shown in figure 2, we notice the dielectric anomalies at ~78 , 310 , and 410 . According to previous studies on the structural phase transitions and dielectric responses [15,16], the sharp dielectric peak at 410
is the phase transition from the paraelectric orthorhombic phase O1 to the
antiferroelectric phase M3, the diffused dielectric peak at 310
arises in between the antiferroelectric
phases M3 and M2 with different degrees of ordering, and the dielectric anomaly at ~78
is the phase
transition from the antiferroelectric phase M2 to the ferrielectric phase M1. For the ceramics prepared by the solid-reaction method, the phase transition temperatures for M1-M2, M2-M3, and M3-O1 from dielectric anomalies are 70 , 260 , and 350 and 353
[8] respectively, or 70 , 260 ,
respectively [9]. In Bi3+, La3+, or Ta5+ doped AgNbO3, the phase transition temperatures
decrease or remain the same as that of pure AgNbO3[10,12,17]. In comparison with the ceramics prepared by the solid-reaction method, the ceramics prepared by the hydrothermally synthesized powders can stabilize the antiferroelectric M2 or M3 phase in a more broad temperature range. For instance, the temperature range which stabilizes M2 phase varies from 190K to 232K, and the temperature range stabilizing M3 phase varies from 90K to 100K. The whole temperature range for the antiferroelectric phases is from 78
to 410 , which is the widest one. It should be also noted that the room temperature
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dielectric permittivity of AgNbO3 prepared by the hydrothermal powders is also higher than that of the solid-reaction sintered ceramics [8,9].
Fig. 2 The temperature dependence of dielectric permittivity of AgNbO3
The polarization-electric field hysteresis loops are shown in figure 3. With the increase of the applied electric field, the linear curves change to the pinched loop at 60kV/cm, indicating the coexistence of a weak ferroelectric component and the antiferroelectric order. The maximum polarization is 9.6 µC/cm2, which is superior to that of ceramics prepared by the solid reaction method at the same electric field [8,9].
Fig. 3 The polarization-electric field hysteresis loops of AgNbO3 under different electric fields
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4. Conclusions Using a hydrothermal reaction method, we successfully synthesized AgNbO3 powders. The key parameter to prepare pure phase AgNbO3 powders by the hydrothermal reaction method is the reaction time, which needs at least 44h. The AgNbO3 ceramics were then successfully prepared by the hydrothermal powders without flowing O2 during sintering. In comparison with the ceramics prepared by the solid-reaction method, the ceramics prepared by the hydrothermal powders have enhanced dielectric and polar performance. The antiferroelectric phases are stabilized in a wider temperature range.
Acknowledgment The work was supported by the National Natural Science Foundation of China (Grant No. 11704242) and Natural Science Foundation of Shanghai, China (Grant No. 17ZR1447200). References [1]
H. Liu, B. Dkhil, Effect of resistivity ratio on energy storage and dielectric relaxation properties of 0–3 dielectric composites, J. Mater. Sci. 52 (2017) 6074-6080.
[2]
Z. Yao, Z. Song, H. Hao, Z. Yu, M. Cao, S. Zhang, M.T. Lanagan, H. Liu, Homogeneous/inhomogeneous-structured dielectrics and their energy-storage performances, Adv. Mate. 29 (2017) 1601727.
[3]
L. Yang, X. Kong, F. Li, H. Hao, Z. Cheng, H. Liu, J.-F. Li, S. Zhang, Perovskite lead-free
[4]
H. Liu, B. Dkhil, A brief review on the model antiferroelectric PbZrO3 perovskite-like material, Z.
dielectrics for energy storage applications, Prog. Mater Sci. 102 (2019) 72-108. Kristallogr. 226 (2011) 163-170. [5]
Z. Liu, T. Lu, J. Ye, G. Wang, X. Dong, R. Withers, Y. Liu, Antiferroelectrics for energy storage applications: a review, Adv. Mater. Technol-US. 3 (2018) 1800111.
[6]
H. Liu, Universal dielectric relaxation induced giant dielectric permittivity in Mn-doped PbZrO3 ceramics, Ceram. Int. 45 (2019) 10380–10384.
[7]
D. Fu, M. Endo, H. Taniguchi, T. Taniyama, M. Itoh, AgNbO3: a lead-free material with large polarization and electromechanical response, Appl. Phys. Lett. 90 (2007) 252907.
[8]
Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, E.D. Politova, S.Yu. Stefanovich, N.V. Tarakina, I. Abrahams, H. Yan, High energy density in silver niobate ceramics, J. Mater. Chem. A. 4 (2016) 17279-17287.
[9]
J. Gao, L. Zhao, Q. Liu, X. Wang, S. Zhang, J.-F. Li, Antiferroelectric-ferroelectric phase transition
6/7
in lead-free AgNbO3 ceramics for energy storage applications, J. Amer. Ceram. Soc. 101 (2018) 5443-5450. [10] Y. Tian, L. Jin, H. Zhang, Z. Xu, X. Wei, G. Viola, I. Abrahams, H. Yan, Phase transitions in bismuth-modified silver niobate ceramics for high power energy storage, J. Mater. Chem. A. 5 (2017) 17525-17531. [11] K. Han, N. Luo, Y. Jing, X. Wang, B. Peng, L. Liu, C. Hu, H. Zhou, Y. Wei, X. Chen, Q. Feng, Structure and energy storage performance of Ba-modified AgNbO3 lead-free antiferroelectric ceramics, Ceram. Int. 45 (2019) 5559-5565. [12] J. Gao, Y. Zhang, L. Zhao, K.-Y. Lee, Q. Liu, A. Studer, M. Hinterstein, S. Zhang, J.-F. Li, Enhanced antiferroelectric phase stability in La-doped AgNbO3: perspectives from the microstructure to energy storage properties, J. Mater. Chem. A. 7 (2019) 2225-2232. [13] A. Kania, A. Niewiadomski, S. Miga, I. Jankowska-Sumara, M. Pawlik, Z. Ujma, J. Koperski, J. Suchanicz, Silver deficiency and excess effects on quality, dielectric properties and phase transitions of AgNbO3 ceramics, J. Eur. Ceram Soc. 34 (2014) 1761-1770. [14] P. Sciau, A. Kania, B. Dkhil, E. Suard, A. Ratuszna, Structural investigation of AgNbO3 phases using x-ray and neutron diffraction, J. Phys.: Condens. Matter. 16 (2004) 2795-2810. [15] A. Kania, Dielectric properties of Ag1-xAxNbO3(A: K, Na and Li) and AgNb1-xTaxO3 solid solutions in the vicinity of diffuse phase transitions, J. Phys. D: Appl. Phys. 34 (2001) 1447-1455. [16] I. Levin, V. Krayzman, J.C. Woicik, J. Karapetrova, T. Proffen, M.G. Tucker, I.M. Reaney, Structural changes underlying the diffuse dielectric response in AgNbO3, Phys. Rev. B. 79 (2009) 104113. [17] Y. Tian, L. Jin, Q. Hu, K. Yu, Y. Zhuang, G. Viola, I. Abrahams, Z. Xu, X. Wei, H. Yan, Phase transitions in tantalum-modified silver niobate ceramics for high power energy storage, J. Mater. Chem. A. 7 (2019) 834-842.
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Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: