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Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2
Journal Pre-proofs Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2 Mohammad Maleki Shahraki, Pezhman Mahmoudi, Asadollah Karimi PII: DOI: Reference:
S0167-577X(20)30218-4 https://doi.org/10.1016/j.matlet.2020.127513 MLBLUE 127513
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 January 2020 4 February 2020 16 February 2020
Please cite this article as: M. Maleki Shahraki, P. Mahmoudi, A. Karimi, Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2, Materials Letters (2020), doi: https:// doi.org/10.1016/j.matlet.2020.127513
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.
© 2020 Published by Elsevier B.V.
Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2 Mohammad Maleki Shahraki1*, Pezhman Mahmoudi2, Asadollah Karimi3 1. Department of Materials Engineering, Faculty of Engineering, University of Maragheh, Maragheh, 55181-83111, Iran 2. Department of Materials Science and Engineering, Sharif University of Technology, Tehran, 11365-9466, Iran 3. 5.
Department of Chemical Engineering, Faculty of Engineering, University of Maragheh, Maragheh, 5518183111, Iran *: Corresponding author email: [email protected]
Abstract In this research, for the first time, the effect of air quenching on the microstructural and electrical properties of (In, Nb) co-doped TiO2 was investigated. The FE-SEM images showed that the air quenching has no effect on microstructure of co-doped TiO2. However, air quenching affected the electrical properties so that the dielectric constant in the frequency of 1 kHz at room temperature sharply enhanced from 21*103 to 26*104 and the dielectric loss surprisingly decreased from 0.6 to 0.1. This incredible improvement in the dielectric properties is attributed to the electron-pined defect dipoles which has been activated through air quenching. Keywords: Ceramics; (In, Nb) co-doped TiO2; Air quenching; Dielectrics 1. Introduction With progressive development in the electric and microelectronic area, new materials with colossal dielectric constant (εr ˃ 103) are needed for miniaturization of electronic devices and also for high energy storage applications [1]. As a novel dielectric material, TiO2 doped with an accepter additive (In2O3) and a donor additive (Nb2O5) introduced by Hu et al., exhibited a giant
1
dielectric constant with low dielectric loss [2]. There is a significant controversy concerning the origin of colossal dielectric constant in these ceramics between researchers, however it was proposed that the electron-pined defect dipoles (EPDD) is responsible for observed unique dielectric properties [3,4]. According to our literature survey, it can be observed that dielectric properties of these materials are very sensitive to the processing conditions and the measurement techniques [4-8]. Already, the effect of conventional solid-state ceramic processing variables, such as sintering temperature, soaking time, sintering atmosphere, and post-annealing have been studied on dielectric properties of co-doped TiO2 ceramics [3, 4, 9-15]. Recently, the effect of cooling rate on dielectric properties of other colossal dielectric such as CaCu3Ti4O12 (CCTO) ceramics has been observed [16-18]. By air quenching from sintering temperature to room temperature, the dielectric loss of the sample is reduced from 0.074 to 0.030, while its dielectric constant remains stable without any considerable change. Therefore, the aim of this work is to study the effect of air quenching from sintering temperature on microstructure and dielectric properties of (Nb, In)-doped TiO2 ceramics. 2. Experimental procedure The co-doped TiO2 ceramic with molar composition of (Nb0.5, In0.5)0.05Ti0.95 was prepared through the conventional processing of ceramics. The raw materials used in this work were TiO2 with rutile structure (Aldrich, 99.9%, ˂ 5µm), In2O3 (US-nano, 99.99%, 70nm), and Nb2O5 (Merck, 99%). To obtain fine powder, Nb2O5 power were separately milled by high energy ball milling of SPEX for 1 h. The weighted powder of Nb2O5 and In2O3 was added to distilled water and then sonicated by high power ultra-sonication for 5 min. Then, TiO2 powder was added to obtained the slurry and was again sonicated for 10 min. After drying slurry, the resultant was sieved and granulated by the 2 wt.% of PVA binder solution. About 0.5 g of the powder was 2
pressed using a uniaxial hydraulic press at the pressure of 200 MPa to form a green pellet. The green samples were sintered at temperature of 1450 ºC for 5 h at the heating rate of 5 ºC/min in electric muffle furnace and then samples were naturally cooled in furnace (FC) or were quenched in air (AQ) to room temperature. A field emission scanning electron microscope (FESEMTESCAN) was used to study the microstructures of the sintered samples. After applying the silver contacts, the dielectric properties and impedance analysis of sintered samples were performed by the HP4192A impedance analyzer. The non-Ohmic properties were evaluated by a source meter (Keithely 2430-C). 3. Results and discussion Fig. 1 shows FE-SEM, and elemental mapping analysis of furnace cooled and those of quenched in air from sintering temperature. As can be observed in FE-SEM images, there is no any trace of secondary phases in samples. The elemental mapping analyses show good distribution of indium and niobium elements in TiO2 structure, where no segregation of Nb and In ions was seen at the grain boundaries. Furthermore, there is no significant difference between grain size of both samples. According to these data, one can be concluded that cooling rate have no obvious effect on microstructure of sintered samples. Fig. 2 illustrates the variation of dielectric constant and dielectric loss of both samples versus frequency in room temperature. Clearly, the dielectric properties of FC sample are strongly dependent on frequency. A sharp reduction of both εr and tanδ is observed in frequencies lower than 105 Hz for this sample and the value of both parameters at 1 kHz are 21000 and 0.6, respectively (Table 1). Although this sample exhibits colossal εr, but its tanδ is extremely higher than the value reported by Hu et al. Some researchers reported dielectric properties in co-doped TiO2 almost similar to those observed in our sample. [9, 19]. It must be mentioned that we applied various reported techniques [9, 10, 12, and 19] such 3
as pre-calcination at different temperature, annealing, and changing composition in order to reduce tanδ, although the final samples cooled in furnace still showed a high value of dielectric loss. In FC sample, the electrode polarization is responsible for the higher εr and also tanδ in low frequency region. Considering a low value of εr with a high value of tanδ, it seems that EPDD mechanism is not activated in FC sample. According to the semi-circle arc of complex impedance in Fig. 3a, internal barrier layer capacitor (IBLC) is the mechanism which justify the observed dielectric properties in FC sample in frequencies higher than 104 Hz. The air-quenched sample shows the excellent dielectric properties over the frequency in the range of 102-106 Hz. It is obvious the dielectric constant curve of AQ sample versus frequency shifted to much higher value than FC sample, meanwhile dielectric loss of this sample drifted to much lower values compared to FC sample. The εr and tanδ values for air-quenched sample in frequency of 1 kHz at room temperature are 2.6*106 and 0.1, respectively. Surprisingly, sharp reduction in tanδ from 0.6 to 0.1 occurs simultaneously with the increase in εr by one order of magnitude in AQ sample compared to the FC sample. Furthermore, changes in εr of AQ sample is nearly constant in the frequency range of 103 up to 106 Hz. There is a weakened electrode polarization in AQ sample in frequencies lower than 1 kHz, as well. Due to this phenomenon, changes in tanδ is sharper in frequencies lower than 1 kHz compared to the higher frequencies. It seems that the unique improvement of dielectric properties induced by air quenching cannot be explained by IBLC model because of two reasons: similar microstructure and lower tanδ in AQ sample compared to the FC sample. It is seen in Fig. 3a that impedance curve of samples has semi-circle shape and the impedance is decreased by air quenching. According to this figure, the electric resistance of grain boundaries (Rgb) and that of grains (Rg) in samples were extracted and are presented in Table 1. Rgb of samples is decreased by air quenching and consequently it is expected that the
4
dielectric loss increased according to the IBLC model, however this is not happened and tanδ decreases by air quenching. The E-J curve of both samples are plotted in Fig. 3b. Both samples present non-Ohmic characteristics. The electric breakdown field (Eb), and nonlinear coefficient (α) are listed in Table 1. The Eb decreased from 5.6 V/mm in furnace cooling condition to 2.1 V/mm in quenched-sample, meanwhile the change in α is negligible. The mechanism of the reduction in Eb by air quenching is not clear.It was reported the air quenching has considerable effect on microstructure of CCTO, whereby the grain morphology and grain size were changed [15, 16]. According to the results obtained in the above-mentioned ceramics, the colossal εr with low tanδ can be attained by air or water quenching of sintered samples and this behavior is justified by IBLC model and attributed to increase of electric resistance of grain boundaries which its effect is appeared in higher electric breakdown of air quenched samples. It is interesting to note that the reduction in Eb without any changes in grain size in our air-quenched sample is another evidence which rejects the IBLC model to play role in the improving observed dielectric properties. Here, it is proposed that new mechanism of EPDD introduced by Hu et al. [2] can be activated by air quenching and is contributed to other mechanisms of EP and IBLC to present excellent dielectric properties. 4. Conclusions The air quenching had no effect on the microstructure of (Nb, In)-doped TiO2. By air quenching, εr sharply increased from 21*103 to 26*104 while surprisingly tanδ decreased from 0.6 to 0.1. Air quenched sample had a lower breakdown electric field than the furnace cooled sample. The mechanism of EPDD was activated by air quenching and was contributed to EP and IBLC mechanisms. References: 5
1. Y. Wang, W. Jie, C. Yang, X. Wei, J. Hao, Adv. Funct. Mater. (2019)1808118 2. W. Hu, Y. Liu, R. L. Withers, T. J. Frankcombe, L. Norén, A. Snashall, M. Kitchin, P. Smith, B. Gong, H. Chen, J. Schiemer, F.Brink, J. Wong-Leung, Nat. Mater., 12 (2013) 821–826 3. D. A. Crandles, S. M. M. Yee, M. Savinov, D. Nuzhnyy, J. Petzelt, S. Kamba, J. Proke, J. Appl. Phys. 119 (2016)154105 4. J. Li, F. Li, Y. Zhuang, L. Jin, L. Wang, X. Wei, Z. Xu, S. Zhang, J. Appl. Phys. 116 (2014)074105 5. T. Nachaithong, P. Kidkhunthod, P. Thongbai, S. Maensiri, J. Am. Cerm.Soc., 100(2017) 1452–1459 6. P. Siriya, W. Tuichai, S. Danwittayakul, N. Chanlek, P. Thongbai, Ceram. Int., 44 (2018) 7234–7239 7. X. Zhu, L. Yang, J. Li, L. Jin, L.Wang, X. Wei, Z. Xu, F. Li, Ceram. Int., 43 (2017) 6403– 6409 8. J. Li, F.Li, C. Li, G. Yang, Z. Xu , S. Zhang, Sci Rep, 5 (2015) 8295 9. Y. Q. Wu, X. Zhao, J. L. Zhang, W. B. Su, J. Liu, Appl. Phys. Lett., 107 (2015) 242904 10. X. Cheng, Z. Li, J. Wu, J. Mater. Chem. A, 3 (2015) 5805–5810 11. W. Tuichai, S. Danwittayakul, N. Chanlek, P. Thongbai, J. Alloys. Compd., 725 (2017) 310317 12. Y. Song, P. Liu, X. Zhao, B. Guo, X. Cui, J. Alloys. Compd., 722(2107) 676-682
6
13. P. Siriya, W. Tuichai, S. Danwittayakul, N. Chanlek., P.Thongbai, Ceram. Int., 44 (2018) 7234–7239 14. C. Yang, B. Zhong, Z. Long, X. Wei, Ceram. Int., 46(2020) 3420-3425 15. C. Yang, X. Wei, J. Hao, Ceram. Int., 44 (2018) 12395-12400 16. W. Li, L. Tang, F. Xue, Z.Xin, Z. Luo, G. Du, Ceram. Int., 43 (2017) 6618–6621 17. L. Liu, D. Shi, S. Zheng, Y. Huang, S. S. Wu, Y. Li, L. Fang, C. Hu, Mater. Chem. Phys., 139 (2013) 844-850 18. J. Zhang, J. Zheng, Y. Liu, C. Zhang, W. Hao, Z. Lei, M. Tian, Materials Research Bulletin 115 (2019) 49–54 19. L. Zhao, J. Wang, Z. Gai, J. Li, J. Liu, J. Wang, C. Wang, X. Wang, RSC Adv., 9 (2019) 8364–8368 Figure captions: Fig. 1. FE-SEM and elemental mapping analysis of a) FC and b) AQ samples Fig. 2. Dielectric constant and dielectric loss versus frequency for FC and AQ samples. Fig. 3. a) complex impedance curve, b) E-J curve of FC and AQ samples.
Fig.1 7
Fig. 2
a
b
Fig. 3 Table 1. Electrical properties of furnace-cooled and air-quenched samples εr @
tanδ @
εr @
1kHz
1kHz
10kHz
FC
21400
0.6
9300
0.34
5.6
AQ
263000
0.1
209000
0.04
2.1
Sample
tanδ @
Eb
α
Rgb
Rg
(Ω)
(Ω)
5
190000
30
6
23500
3
10kHz (V/mm)
Conflict of Interest 8
The authors declared that they have no conflicts of interest to this work.
Credit authorship contribution statement: Mohammad Maleki Shahraki: Investigation, writing - original draft, review & editing, supervision. Pezhman Mahmoudi: Investigation, review & editing. Asadollah Karimi: Investigation, review & editing.
Declaration of Competing Interest 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.
Highlights: The unique electrical properties were obtained in air quenched co-doped TiO2 By quenching, εr enhanced from 21*103 to 26*104 and tanδ decreased from 0.6 to 0.1 Air quenched sample had a lower Eb than the furnace cooled sample The mechanism of EPDD was activated by air quenching and contributed to EP and IBLC
9
S0167-577X(20)30218-4 https://doi.org/10.1016/j.matlet.2020.127513 MLBLUE 127513
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
1 January 2020 4 February 2020 16 February 2020
Please cite this article as: M. Maleki Shahraki, P. Mahmoudi, A. Karimi, Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2, Materials Letters (2020), doi: https:// doi.org/10.1016/j.matlet.2020.127513
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.
© 2020 Published by Elsevier B.V.
Air quenching as a reliable technique to obtain colossal dielectric constant with low loss in (In, Nb)-co doped TiO2 Mohammad Maleki Shahraki1*, Pezhman Mahmoudi2, Asadollah Karimi3 1. Department of Materials Engineering, Faculty of Engineering, University of Maragheh, Maragheh, 55181-83111, Iran 2. Department of Materials Science and Engineering, Sharif University of Technology, Tehran, 11365-9466, Iran 3. 5.
Department of Chemical Engineering, Faculty of Engineering, University of Maragheh, Maragheh, 5518183111, Iran *: Corresponding author email: [email protected]
Abstract In this research, for the first time, the effect of air quenching on the microstructural and electrical properties of (In, Nb) co-doped TiO2 was investigated. The FE-SEM images showed that the air quenching has no effect on microstructure of co-doped TiO2. However, air quenching affected the electrical properties so that the dielectric constant in the frequency of 1 kHz at room temperature sharply enhanced from 21*103 to 26*104 and the dielectric loss surprisingly decreased from 0.6 to 0.1. This incredible improvement in the dielectric properties is attributed to the electron-pined defect dipoles which has been activated through air quenching. Keywords: Ceramics; (In, Nb) co-doped TiO2; Air quenching; Dielectrics 1. Introduction With progressive development in the electric and microelectronic area, new materials with colossal dielectric constant (εr ˃ 103) are needed for miniaturization of electronic devices and also for high energy storage applications [1]. As a novel dielectric material, TiO2 doped with an accepter additive (In2O3) and a donor additive (Nb2O5) introduced by Hu et al., exhibited a giant
1
dielectric constant with low dielectric loss [2]. There is a significant controversy concerning the origin of colossal dielectric constant in these ceramics between researchers, however it was proposed that the electron-pined defect dipoles (EPDD) is responsible for observed unique dielectric properties [3,4]. According to our literature survey, it can be observed that dielectric properties of these materials are very sensitive to the processing conditions and the measurement techniques [4-8]. Already, the effect of conventional solid-state ceramic processing variables, such as sintering temperature, soaking time, sintering atmosphere, and post-annealing have been studied on dielectric properties of co-doped TiO2 ceramics [3, 4, 9-15]. Recently, the effect of cooling rate on dielectric properties of other colossal dielectric such as CaCu3Ti4O12 (CCTO) ceramics has been observed [16-18]. By air quenching from sintering temperature to room temperature, the dielectric loss of the sample is reduced from 0.074 to 0.030, while its dielectric constant remains stable without any considerable change. Therefore, the aim of this work is to study the effect of air quenching from sintering temperature on microstructure and dielectric properties of (Nb, In)-doped TiO2 ceramics. 2. Experimental procedure The co-doped TiO2 ceramic with molar composition of (Nb0.5, In0.5)0.05Ti0.95 was prepared through the conventional processing of ceramics. The raw materials used in this work were TiO2 with rutile structure (Aldrich, 99.9%, ˂ 5µm), In2O3 (US-nano, 99.99%, 70nm), and Nb2O5 (Merck, 99%). To obtain fine powder, Nb2O5 power were separately milled by high energy ball milling of SPEX for 1 h. The weighted powder of Nb2O5 and In2O3 was added to distilled water and then sonicated by high power ultra-sonication for 5 min. Then, TiO2 powder was added to obtained the slurry and was again sonicated for 10 min. After drying slurry, the resultant was sieved and granulated by the 2 wt.% of PVA binder solution. About 0.5 g of the powder was 2
pressed using a uniaxial hydraulic press at the pressure of 200 MPa to form a green pellet. The green samples were sintered at temperature of 1450 ºC for 5 h at the heating rate of 5 ºC/min in electric muffle furnace and then samples were naturally cooled in furnace (FC) or were quenched in air (AQ) to room temperature. A field emission scanning electron microscope (FESEMTESCAN) was used to study the microstructures of the sintered samples. After applying the silver contacts, the dielectric properties and impedance analysis of sintered samples were performed by the HP4192A impedance analyzer. The non-Ohmic properties were evaluated by a source meter (Keithely 2430-C). 3. Results and discussion Fig. 1 shows FE-SEM, and elemental mapping analysis of furnace cooled and those of quenched in air from sintering temperature. As can be observed in FE-SEM images, there is no any trace of secondary phases in samples. The elemental mapping analyses show good distribution of indium and niobium elements in TiO2 structure, where no segregation of Nb and In ions was seen at the grain boundaries. Furthermore, there is no significant difference between grain size of both samples. According to these data, one can be concluded that cooling rate have no obvious effect on microstructure of sintered samples. Fig. 2 illustrates the variation of dielectric constant and dielectric loss of both samples versus frequency in room temperature. Clearly, the dielectric properties of FC sample are strongly dependent on frequency. A sharp reduction of both εr and tanδ is observed in frequencies lower than 105 Hz for this sample and the value of both parameters at 1 kHz are 21000 and 0.6, respectively (Table 1). Although this sample exhibits colossal εr, but its tanδ is extremely higher than the value reported by Hu et al. Some researchers reported dielectric properties in co-doped TiO2 almost similar to those observed in our sample. [9, 19]. It must be mentioned that we applied various reported techniques [9, 10, 12, and 19] such 3
as pre-calcination at different temperature, annealing, and changing composition in order to reduce tanδ, although the final samples cooled in furnace still showed a high value of dielectric loss. In FC sample, the electrode polarization is responsible for the higher εr and also tanδ in low frequency region. Considering a low value of εr with a high value of tanδ, it seems that EPDD mechanism is not activated in FC sample. According to the semi-circle arc of complex impedance in Fig. 3a, internal barrier layer capacitor (IBLC) is the mechanism which justify the observed dielectric properties in FC sample in frequencies higher than 104 Hz. The air-quenched sample shows the excellent dielectric properties over the frequency in the range of 102-106 Hz. It is obvious the dielectric constant curve of AQ sample versus frequency shifted to much higher value than FC sample, meanwhile dielectric loss of this sample drifted to much lower values compared to FC sample. The εr and tanδ values for air-quenched sample in frequency of 1 kHz at room temperature are 2.6*106 and 0.1, respectively. Surprisingly, sharp reduction in tanδ from 0.6 to 0.1 occurs simultaneously with the increase in εr by one order of magnitude in AQ sample compared to the FC sample. Furthermore, changes in εr of AQ sample is nearly constant in the frequency range of 103 up to 106 Hz. There is a weakened electrode polarization in AQ sample in frequencies lower than 1 kHz, as well. Due to this phenomenon, changes in tanδ is sharper in frequencies lower than 1 kHz compared to the higher frequencies. It seems that the unique improvement of dielectric properties induced by air quenching cannot be explained by IBLC model because of two reasons: similar microstructure and lower tanδ in AQ sample compared to the FC sample. It is seen in Fig. 3a that impedance curve of samples has semi-circle shape and the impedance is decreased by air quenching. According to this figure, the electric resistance of grain boundaries (Rgb) and that of grains (Rg) in samples were extracted and are presented in Table 1. Rgb of samples is decreased by air quenching and consequently it is expected that the
4
dielectric loss increased according to the IBLC model, however this is not happened and tanδ decreases by air quenching. The E-J curve of both samples are plotted in Fig. 3b. Both samples present non-Ohmic characteristics. The electric breakdown field (Eb), and nonlinear coefficient (α) are listed in Table 1. The Eb decreased from 5.6 V/mm in furnace cooling condition to 2.1 V/mm in quenched-sample, meanwhile the change in α is negligible. The mechanism of the reduction in Eb by air quenching is not clear.It was reported the air quenching has considerable effect on microstructure of CCTO, whereby the grain morphology and grain size were changed [15, 16]. According to the results obtained in the above-mentioned ceramics, the colossal εr with low tanδ can be attained by air or water quenching of sintered samples and this behavior is justified by IBLC model and attributed to increase of electric resistance of grain boundaries which its effect is appeared in higher electric breakdown of air quenched samples. It is interesting to note that the reduction in Eb without any changes in grain size in our air-quenched sample is another evidence which rejects the IBLC model to play role in the improving observed dielectric properties. Here, it is proposed that new mechanism of EPDD introduced by Hu et al. [2] can be activated by air quenching and is contributed to other mechanisms of EP and IBLC to present excellent dielectric properties. 4. Conclusions The air quenching had no effect on the microstructure of (Nb, In)-doped TiO2. By air quenching, εr sharply increased from 21*103 to 26*104 while surprisingly tanδ decreased from 0.6 to 0.1. Air quenched sample had a lower breakdown electric field than the furnace cooled sample. The mechanism of EPDD was activated by air quenching and was contributed to EP and IBLC mechanisms. References: 5
1. Y. Wang, W. Jie, C. Yang, X. Wei, J. Hao, Adv. Funct. Mater. (2019)1808118 2. W. Hu, Y. Liu, R. L. Withers, T. J. Frankcombe, L. Norén, A. Snashall, M. Kitchin, P. Smith, B. Gong, H. Chen, J. Schiemer, F.Brink, J. Wong-Leung, Nat. Mater., 12 (2013) 821–826 3. D. A. Crandles, S. M. M. Yee, M. Savinov, D. Nuzhnyy, J. Petzelt, S. Kamba, J. Proke, J. Appl. Phys. 119 (2016)154105 4. J. Li, F. Li, Y. Zhuang, L. Jin, L. Wang, X. Wei, Z. Xu, S. Zhang, J. Appl. Phys. 116 (2014)074105 5. T. Nachaithong, P. Kidkhunthod, P. Thongbai, S. Maensiri, J. Am. Cerm.Soc., 100(2017) 1452–1459 6. P. Siriya, W. Tuichai, S. Danwittayakul, N. Chanlek, P. Thongbai, Ceram. Int., 44 (2018) 7234–7239 7. X. Zhu, L. Yang, J. Li, L. Jin, L.Wang, X. Wei, Z. Xu, F. Li, Ceram. Int., 43 (2017) 6403– 6409 8. J. Li, F.Li, C. Li, G. Yang, Z. Xu , S. Zhang, Sci Rep, 5 (2015) 8295 9. Y. Q. Wu, X. Zhao, J. L. Zhang, W. B. Su, J. Liu, Appl. Phys. Lett., 107 (2015) 242904 10. X. Cheng, Z. Li, J. Wu, J. Mater. Chem. A, 3 (2015) 5805–5810 11. W. Tuichai, S. Danwittayakul, N. Chanlek, P. Thongbai, J. Alloys. Compd., 725 (2017) 310317 12. Y. Song, P. Liu, X. Zhao, B. Guo, X. Cui, J. Alloys. Compd., 722(2107) 676-682
6
13. P. Siriya, W. Tuichai, S. Danwittayakul, N. Chanlek., P.Thongbai, Ceram. Int., 44 (2018) 7234–7239 14. C. Yang, B. Zhong, Z. Long, X. Wei, Ceram. Int., 46(2020) 3420-3425 15. C. Yang, X. Wei, J. Hao, Ceram. Int., 44 (2018) 12395-12400 16. W. Li, L. Tang, F. Xue, Z.Xin, Z. Luo, G. Du, Ceram. Int., 43 (2017) 6618–6621 17. L. Liu, D. Shi, S. Zheng, Y. Huang, S. S. Wu, Y. Li, L. Fang, C. Hu, Mater. Chem. Phys., 139 (2013) 844-850 18. J. Zhang, J. Zheng, Y. Liu, C. Zhang, W. Hao, Z. Lei, M. Tian, Materials Research Bulletin 115 (2019) 49–54 19. L. Zhao, J. Wang, Z. Gai, J. Li, J. Liu, J. Wang, C. Wang, X. Wang, RSC Adv., 9 (2019) 8364–8368 Figure captions: Fig. 1. FE-SEM and elemental mapping analysis of a) FC and b) AQ samples Fig. 2. Dielectric constant and dielectric loss versus frequency for FC and AQ samples. Fig. 3. a) complex impedance curve, b) E-J curve of FC and AQ samples.
Fig.1 7
Fig. 2
a
b
Fig. 3 Table 1. Electrical properties of furnace-cooled and air-quenched samples εr @
tanδ @
εr @
1kHz
1kHz
10kHz
FC
21400
0.6
9300
0.34
5.6
AQ
263000
0.1
209000
0.04
2.1
Sample
tanδ @
Eb
α
Rgb
Rg
(Ω)
(Ω)
5
190000
30
6
23500
3
10kHz (V/mm)
Conflict of Interest 8
The authors declared that they have no conflicts of interest to this work.
Credit authorship contribution statement: Mohammad Maleki Shahraki: Investigation, writing - original draft, review & editing, supervision. Pezhman Mahmoudi: Investigation, review & editing. Asadollah Karimi: Investigation, review & editing.
Declaration of Competing Interest 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.
Highlights: The unique electrical properties were obtained in air quenched co-doped TiO2 By quenching, εr enhanced from 21*103 to 26*104 and tanδ decreased from 0.6 to 0.1 Air quenched sample had a lower Eb than the furnace cooled sample The mechanism of EPDD was activated by air quenching and contributed to EP and IBLC
9