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Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics
Accepted Manuscript Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics Dan Chen, Fa Luo, Wancheng Zhou, Dongmei Zhu PII: DOI: Reference:
S0167-577X(18)30498-1 https://doi.org/10.1016/j.matlet.2018.03.128 MLBLUE 24089
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
19 January 2018 28 February 2018 19 March 2018
Please cite this article as: D. Chen, F. Luo, W. Zhou, D. Zhu, Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics, Materials Letters (2018), doi: https://doi.org/10.1016/j.matlet.2018.03.128
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics Dan Chen1*, Fa Luo1, Wancheng Zhou1, Dongmei Zhu1 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, China Abstract: Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics have been rarely studied. The work attempted to develop a new kind of high temperature microwave absorption material. Na3Zr2Si2PO12 ceramics were sintered at different temperatures by a traditional solid-state reaction method for dielectric and microwave absorption properties study. Results showed that the complex permittivity increased to the maximum at 1250 °C then decreased with the elevated sintering temperature. The effective absorption bandwidth (below -5 dB) was obtained in 8.98-12.4 GHz for the ceramic in 2.3 mm thickness and the lowest reflection loss is -12.9 dB at 10.74 GHz, which indicated that Na3Zr2Si2PO12 ceramics would be potential microwave absorption materials by further improvement. Keywords: Dielectrics; Electroceramics; Na3Zr2Si2PO12; Microwave absorption 1. Introduction With the extensive application of electromagnetic (EM) wave both in civilian and military fields, radiation pollution and electromagnetic interference are becoming serious. Therefore, materials which can absorb or shield the EM wave have drawn large attentions. Traditional microwave absorption materials, such as carbon-based materials [1-4], ferrite [5-6] and conduction polymer [7-8], are usually limited to be used in the room temperature due to their poor oxidation resistance, low Curie temperature and
1
Corresponding author at: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China. Tel. /fax: +86 029 88494574. E-mail address: [email protected] (D. Chen).
1
undesirable high-temperature stability. However, microwave absorption materials are used at high temperature in some cases. Therefore, materials with high temperature stability and good dissipation of EM waves are needed. NASICON type Na3Zr2Si2PO12 ceramic has been widely used as solid electrolytes in Na-ion batteries. Many researches have been devoted to further improving its conductivity by optimizing preparation methods [9-12] and doping strategies [13-15]. However, the study of dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramic is rare. The work aims to study the dielectric properties of Na3Zr2Si2PO12 ceramics and develop a new kind of microwave absorption material by taking advantage of its high conductivity, high temperature stability and good oxidation resistance. For the above aims, Na3Zr2Si2PO12 ceramics were fabricated by the solid-state reaction method at different sintering temperatures. The phase and density were characterized. The conductivity and complex permittivity in the frequency range of 8.2-12.4 GHz (X-band) were measured. The microwave absorption properties in the X-band were evaluated. 2. Material and methods Na3Zr2Si2PO12 was obtained from the raw materials: Na3PO12·12H2O, ZrO2 and SiO2. 15 wt.% quantities of excessive Na3PO4·12H2O was added to compensate the volatilization of sodium and phosphorus at high temperature. All the compounds were ball-milled in ethanol using agate balls for 6 h with a rotary speed of 300 rpm. Then, the slurry was dried and calcined at 1100 °C for 6 h. After that the powder was ball-milled again for 6 h. Next, using polyvinyl alcohol (PVA) as the binder, the slurry was dried and pressed into disks of 13 mm and 45 mm diameter. After burning off PVA, the ceramics were sintered at 1150 °C, 1200 °C, 1250 °C and 1300 °C for 4 h with the
2
heating rate of 5 °C/min. The phase identification was carried out by x-ray diffractometry (XRD) using CuKα radiation as the x-ray source. The density was examined by the Archimedes method. The small sintered disks were used for conductivity measurement by electrochemical impedance spectroscopy and detailed measurement was narrated in our previous work [16]. The large sintered disks were cut into rectangular bars with the dimensions of 22.86l mm×10.16w mm×1.95t mm for the measurement of complex permittivity. The EM parameters were measured by a vector network analyzer (Agilent technologies E8362B: 10 MHz-20 GHz) in the X- band using waveguide method. 3. Results and discussion
Fig. 1 XRD patterns of Na3Zr 2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Fig. 2 Impedance spectra at 25 °C of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
Fig. 1 shows the XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Monoclinic ZrO2 was detected in synthesis powder and all ceramics, which was generally observed in all types of NASICON synthesis [11-15]. The powder was in relatively pure NASICON phase, no other additional phases except a trace amount of ZrO2 were detected, which illustrated that the mixtures had a sufficient reaction at 1100 °C. Since the sintering temperature 3
reached 1300 °C, the amount of ZrO2 increased sharply, which indicated faster volatilization of sodium and phosphorus at elevated temperature [11-12]. Moreover, the relative density increased from 72 % to 91 % as the sintering temperature increased from 1150 °C to 1300 °C. Fig. 2 shows the impedance spectra at 25 °C of Na3Zr2Si2PO12 ceramics sintered at different temperatures. The equivalent electrical circuit model for fitting the impedance spectra [14] is also exhibited in Fig. 2. Rg is grain resistance, Rgb is grain boundary resistance, R is total resistance, σ is calculated total conductivity, CPE is constant phase angle element. An upward trend of conductivity was obvious from 1150 °C to 1250 °C, and a gradual drop emerged at 1300 °C. The highest conductivity was 2.02×10-4 S·cm-1 at 1250 °C. Because close contact of grains favored the migration of Na+ ions, the conductivity increased with densification. The sharply decreased conductivity at 1300 °C was attributed to the large amount of ZrO2.
Fig. 3 (a) Real parts and (b) imaginary parts of the complex permittivity of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
The microwave absorption properties usually depend on the dielectric properties. Fig. 3 illustrates the complex permittivity (the real part ε’ and imaginary part ε”) of the sintered samples in the frequency range of 8.2-12.4 GHz. Arrhenius plots of total conductivities of Na3Zr2Si2PO12 ceramics as a function of the testing temperature are
4
presented in Fig. 3(a). It can be seen that the real and imaginary parts both increased first then decreased with increasing the sintering temperature. It is well known that the ε’ is determined by the polarization mechanism, i.e., electronic displacement polarization, ionic displacement polarization, dipole rotation polarization, thermal ion relaxation polarization and space charge polarization [17]. It takes only about 10-15 s~10-12 s to produce electronic displacement polarization and ionic displacement polarization, which is less than the EM field period (~10-10 s) [17-18]. The NASICON structure consists of a three-dimensional rigid framework with ZrO6 octahedral and PO4 (SiO4) tetrahedral sharing common corners, which contains interconnected channels that provide the conduction pathway for the Na+ ions. The thermal ion relaxation polarization is induced by the migration of activated Na+ ions under an EM field, which causes the unsymmetrical distribution of the charges, then forms electric moment. The change of polarization direction usually lags behind that of EM field direction and it usually takes 10-2 s~10-10 s. The activation energies of the ionic motion (ΔE) of all ceramics were calculated from the line slopes on (lnσT) axis at 1000/T. They were 0.46, 0.46, 0.40 and 0.46 eV for Na3Zr2Si2PO12 ceramics sintered from 1150 °C to 1300 °C. Due to the minimum activation energy of Na3Zr2Si2PO12 ceramic sintered at 1250 °C, it was easier for Na+ ions to pass away in compact Na3Zr2Si2PO12 ceramic, thus they were facile to be polarized. Furthermore, the porosity and the second phase also had an effect on the complex permittivity, which can be explained by Lichtenecker’s equation [19]. The sintered samples were regarded as the composition of the low-permittivity pores, low-permittivity ZrO2 and high-permittivity Na3Zr2Si2PO12 ceramic. Therefore, the low permittivity of the ceramics sintered at 1150 °C and 1200 °C was ascribed to weaker relaxation polarization and larger amounts of pores, and that of the ceramics sintered at
5
1300 °C was due to the emergence of ZrO2. According to Debye’s theory [17], ε” is proportional to polarization loss and conduction loss. For conductive material, the contribution of ε” was mainly controlled by conduction loss, which had a same trend as the range of conductivity. In order to investigate the microwave absorption properties, the reflection loss (RL) was calculated according to the transmission line theory [20]. The calculated RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness is exhibited in Fig. 4(a). The Na3Zr2Si2PO12 ceramic sintered at 1250 °C had the optimum microwave absorption property compared to the other samples. The minimum RL (RL m) was -12.9 dB at 10.74 GHz and the bandwidth (RL<-5 dB) was 3.42 GHz, ranging from 8.98 GHz to12.4 GHz, which was close to the whole frequency range of the X-band. The RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness is shown in Fig. 4(b). It was obvious that the matching frequency shifted to low frequency with increasing thickness. The absorption peaks can be tailored by altering the thickness of the absorber. In consideration of the bandwidth and RLm, the optimum thickness was 2.3 mm.
Fig.4 (a) RL of Na3Zr 2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO 12 ceramic sintered at 1250 °C in different thickness.
4. Conclusions
6
This work developed a new kind of high temperature microwave absorption material. Na3 Zr2Si2PO12 ceramic was chosen to be studied due to its good conductivity, high temperature stability and high temperature oxidation resistance. Na3Zr2Si2PO12 ceramic sintered at 1250 °C exhibited the highest conductivity and complex permittivity. It had the optimum microwave absorption property with a bandwidth of 3.42 GHz and a RLm value of -12.9 dB at 10.74 GHz in 2.3 mm thickness. The calculated RL values revealed that Na3Zr2Si2PO12 ceramics could be developed as a new kind of microwave absorption materials, and much work should be done to further adjust and optimize its dielectric properties in the future. Acknowledgements This work was financially supported by Fundamental Research Funds for the Central Universities (No.3102017ZY050), and State Key Laboratory of Solidification Process (NWPU), China (Grant No. KP201604). References: [1] Y.C. Qing, D.D. Min, Y.Y. Zhou, F. Luo, W.C. Zhou, Carbon 86(2015)98-107. [2] J.H. Sui, C. Zhang, J. Li, Z.L. Yu, W. Cai, Mater. Lett. 75(2012)158-160. [3] K. Osouli-Bostanabad, E. Hosseinzade, A. Kianvash, A. Entezami, Appl. Surf. Sci. 356(2015)1086-1095. [4] P.B. Liu, Y. Huang, X. Zhang, Compos. Sci. Technol. 107(2015)54-60. [5] A. Maqsood, K. Khan, J. Alloys Compd. 509(2011)3393-3397. [6] J. Wang, H. Zhang, S.X. Bai, K. Chen, C.R. Zhang, J. Magn. Magn. Mater. 312(2007)310-313. [7] F.F. Xu, L. Ma, M.Y. Gan, J.H. Tang, Z.T. Li, J.Y. Zheng, J. Zhang, S. Xie, H. Yin, X.Y. Shen, J.L. Hu, F. Zhang, J. Alloys Compd. 593(2014)24-29. [8] B.T. Su, X.W. Zuo, C.L. Hu, Z.Q. Lei, Acta Phys. Chim. Sin. 24(2008)1932-1936. [9] M. Kotobuki, M. Koishi, Ceram. Int. 41(2015)8562-8567. [10] M. Kotobuki, M. Koishi, Y. Kato, Ionics 19(2013)1945-1948.
7
[11] N.S. Bell, C. Edney, J.S. Wheeler, D. Ingersoll, E.D. Spoerke, J. Am. Ceram. Soc. 97(2014)3744-3748. [12] J.S. Lee, C.M. Chang, Y.I. Lee, J.H. Lee, S.H. Hong, J. Am. Ceram. Soc. 87(2010)305-307. [13] M. Samiee, B. Radhakrishnan, Z. Rice, Z. Deng, Y.S. Meng, S.P. Ong, J. Luo, J. Power Sources 347(2017)229-237. [14] Z. Khakpour, Electrochim. Acta 196(2016)337-347. [15] A.G. Jolley, G. Cohn, G.T. Hitz, E.D. Wachsman, Ionics 21(2015)3031-3038. [16] D. Chen, F. Luo, L. Gao, W.C. Zhou, D.M. Zhu, J. Electron. Mater. 46(2017)6367-6372. [17] K.C. Kao, Dielectric phenomena in solids, Elsevier Academic Press, Cambridge, 2004. [18] Q.L. Wen, W.C. Zhou, Y.D. Wang, Y.C. Qing, F. Luo, D.M. Zhu, Z.B. Huang, J. Mater. Sci. 52(2017)832-842. [19] C.M. Regalado, Geoderma 123(2004)41-50. [20] F. Qin, C. Brosseau, J. Appl. Phys. 111(2012)061301.
Figure captions: Fig.1. XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Fig.2. Impedance spectra of Na3Zr2Si2PO12 ceramics at 25 °C sintered at different temperatures Fig.3. (a) Real parts and (b) imaginary parts of the complex permittivity of Na 3Zr2Si2PO12 ceramics sintered at different temperatures. Fig.4 (a) RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness.
8
Fig.1. XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures.
Fig.2. Impedance spectra of Na3Zr2Si2PO12 ceramics at 25 °C sintered at different
9
temperatures
Fig.3. (a) Real parts and (b) imaginary parts of the complex permittivity of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
Fig.4 (a) RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness.
10
Highlights: 1. Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics have been studied. 2. Thermal ion relaxation polarization is induced by the migration of activated Na + ions under an EM field. 3. Na3Zr2Si2PO12 ceramics could be developed as a new kind of microwave absorption materials by further improvement.
11
S0167-577X(18)30498-1 https://doi.org/10.1016/j.matlet.2018.03.128 MLBLUE 24089
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
19 January 2018 28 February 2018 19 March 2018
Please cite this article as: D. Chen, F. Luo, W. Zhou, D. Zhu, Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics, Materials Letters (2018), doi: https://doi.org/10.1016/j.matlet.2018.03.128
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics Dan Chen1*, Fa Luo1, Wancheng Zhou1, Dongmei Zhu1 State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shaanxi 710072, China Abstract: Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics have been rarely studied. The work attempted to develop a new kind of high temperature microwave absorption material. Na3Zr2Si2PO12 ceramics were sintered at different temperatures by a traditional solid-state reaction method for dielectric and microwave absorption properties study. Results showed that the complex permittivity increased to the maximum at 1250 °C then decreased with the elevated sintering temperature. The effective absorption bandwidth (below -5 dB) was obtained in 8.98-12.4 GHz for the ceramic in 2.3 mm thickness and the lowest reflection loss is -12.9 dB at 10.74 GHz, which indicated that Na3Zr2Si2PO12 ceramics would be potential microwave absorption materials by further improvement. Keywords: Dielectrics; Electroceramics; Na3Zr2Si2PO12; Microwave absorption 1. Introduction With the extensive application of electromagnetic (EM) wave both in civilian and military fields, radiation pollution and electromagnetic interference are becoming serious. Therefore, materials which can absorb or shield the EM wave have drawn large attentions. Traditional microwave absorption materials, such as carbon-based materials [1-4], ferrite [5-6] and conduction polymer [7-8], are usually limited to be used in the room temperature due to their poor oxidation resistance, low Curie temperature and
1
Corresponding author at: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China. Tel. /fax: +86 029 88494574. E-mail address: [email protected] (D. Chen).
1
undesirable high-temperature stability. However, microwave absorption materials are used at high temperature in some cases. Therefore, materials with high temperature stability and good dissipation of EM waves are needed. NASICON type Na3Zr2Si2PO12 ceramic has been widely used as solid electrolytes in Na-ion batteries. Many researches have been devoted to further improving its conductivity by optimizing preparation methods [9-12] and doping strategies [13-15]. However, the study of dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramic is rare. The work aims to study the dielectric properties of Na3Zr2Si2PO12 ceramics and develop a new kind of microwave absorption material by taking advantage of its high conductivity, high temperature stability and good oxidation resistance. For the above aims, Na3Zr2Si2PO12 ceramics were fabricated by the solid-state reaction method at different sintering temperatures. The phase and density were characterized. The conductivity and complex permittivity in the frequency range of 8.2-12.4 GHz (X-band) were measured. The microwave absorption properties in the X-band were evaluated. 2. Material and methods Na3Zr2Si2PO12 was obtained from the raw materials: Na3PO12·12H2O, ZrO2 and SiO2. 15 wt.% quantities of excessive Na3PO4·12H2O was added to compensate the volatilization of sodium and phosphorus at high temperature. All the compounds were ball-milled in ethanol using agate balls for 6 h with a rotary speed of 300 rpm. Then, the slurry was dried and calcined at 1100 °C for 6 h. After that the powder was ball-milled again for 6 h. Next, using polyvinyl alcohol (PVA) as the binder, the slurry was dried and pressed into disks of 13 mm and 45 mm diameter. After burning off PVA, the ceramics were sintered at 1150 °C, 1200 °C, 1250 °C and 1300 °C for 4 h with the
2
heating rate of 5 °C/min. The phase identification was carried out by x-ray diffractometry (XRD) using CuKα radiation as the x-ray source. The density was examined by the Archimedes method. The small sintered disks were used for conductivity measurement by electrochemical impedance spectroscopy and detailed measurement was narrated in our previous work [16]. The large sintered disks were cut into rectangular bars with the dimensions of 22.86l mm×10.16w mm×1.95t mm for the measurement of complex permittivity. The EM parameters were measured by a vector network analyzer (Agilent technologies E8362B: 10 MHz-20 GHz) in the X- band using waveguide method. 3. Results and discussion
Fig. 1 XRD patterns of Na3Zr 2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Fig. 2 Impedance spectra at 25 °C of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
Fig. 1 shows the XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Monoclinic ZrO2 was detected in synthesis powder and all ceramics, which was generally observed in all types of NASICON synthesis [11-15]. The powder was in relatively pure NASICON phase, no other additional phases except a trace amount of ZrO2 were detected, which illustrated that the mixtures had a sufficient reaction at 1100 °C. Since the sintering temperature 3
reached 1300 °C, the amount of ZrO2 increased sharply, which indicated faster volatilization of sodium and phosphorus at elevated temperature [11-12]. Moreover, the relative density increased from 72 % to 91 % as the sintering temperature increased from 1150 °C to 1300 °C. Fig. 2 shows the impedance spectra at 25 °C of Na3Zr2Si2PO12 ceramics sintered at different temperatures. The equivalent electrical circuit model for fitting the impedance spectra [14] is also exhibited in Fig. 2. Rg is grain resistance, Rgb is grain boundary resistance, R is total resistance, σ is calculated total conductivity, CPE is constant phase angle element. An upward trend of conductivity was obvious from 1150 °C to 1250 °C, and a gradual drop emerged at 1300 °C. The highest conductivity was 2.02×10-4 S·cm-1 at 1250 °C. Because close contact of grains favored the migration of Na+ ions, the conductivity increased with densification. The sharply decreased conductivity at 1300 °C was attributed to the large amount of ZrO2.
Fig. 3 (a) Real parts and (b) imaginary parts of the complex permittivity of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
The microwave absorption properties usually depend on the dielectric properties. Fig. 3 illustrates the complex permittivity (the real part ε’ and imaginary part ε”) of the sintered samples in the frequency range of 8.2-12.4 GHz. Arrhenius plots of total conductivities of Na3Zr2Si2PO12 ceramics as a function of the testing temperature are
4
presented in Fig. 3(a). It can be seen that the real and imaginary parts both increased first then decreased with increasing the sintering temperature. It is well known that the ε’ is determined by the polarization mechanism, i.e., electronic displacement polarization, ionic displacement polarization, dipole rotation polarization, thermal ion relaxation polarization and space charge polarization [17]. It takes only about 10-15 s~10-12 s to produce electronic displacement polarization and ionic displacement polarization, which is less than the EM field period (~10-10 s) [17-18]. The NASICON structure consists of a three-dimensional rigid framework with ZrO6 octahedral and PO4 (SiO4) tetrahedral sharing common corners, which contains interconnected channels that provide the conduction pathway for the Na+ ions. The thermal ion relaxation polarization is induced by the migration of activated Na+ ions under an EM field, which causes the unsymmetrical distribution of the charges, then forms electric moment. The change of polarization direction usually lags behind that of EM field direction and it usually takes 10-2 s~10-10 s. The activation energies of the ionic motion (ΔE) of all ceramics were calculated from the line slopes on (lnσT) axis at 1000/T. They were 0.46, 0.46, 0.40 and 0.46 eV for Na3Zr2Si2PO12 ceramics sintered from 1150 °C to 1300 °C. Due to the minimum activation energy of Na3Zr2Si2PO12 ceramic sintered at 1250 °C, it was easier for Na+ ions to pass away in compact Na3Zr2Si2PO12 ceramic, thus they were facile to be polarized. Furthermore, the porosity and the second phase also had an effect on the complex permittivity, which can be explained by Lichtenecker’s equation [19]. The sintered samples were regarded as the composition of the low-permittivity pores, low-permittivity ZrO2 and high-permittivity Na3Zr2Si2PO12 ceramic. Therefore, the low permittivity of the ceramics sintered at 1150 °C and 1200 °C was ascribed to weaker relaxation polarization and larger amounts of pores, and that of the ceramics sintered at
5
1300 °C was due to the emergence of ZrO2. According to Debye’s theory [17], ε” is proportional to polarization loss and conduction loss. For conductive material, the contribution of ε” was mainly controlled by conduction loss, which had a same trend as the range of conductivity. In order to investigate the microwave absorption properties, the reflection loss (RL) was calculated according to the transmission line theory [20]. The calculated RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness is exhibited in Fig. 4(a). The Na3Zr2Si2PO12 ceramic sintered at 1250 °C had the optimum microwave absorption property compared to the other samples. The minimum RL (RL m) was -12.9 dB at 10.74 GHz and the bandwidth (RL<-5 dB) was 3.42 GHz, ranging from 8.98 GHz to12.4 GHz, which was close to the whole frequency range of the X-band. The RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness is shown in Fig. 4(b). It was obvious that the matching frequency shifted to low frequency with increasing thickness. The absorption peaks can be tailored by altering the thickness of the absorber. In consideration of the bandwidth and RLm, the optimum thickness was 2.3 mm.
Fig.4 (a) RL of Na3Zr 2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO 12 ceramic sintered at 1250 °C in different thickness.
4. Conclusions
6
This work developed a new kind of high temperature microwave absorption material. Na3 Zr2Si2PO12 ceramic was chosen to be studied due to its good conductivity, high temperature stability and high temperature oxidation resistance. Na3Zr2Si2PO12 ceramic sintered at 1250 °C exhibited the highest conductivity and complex permittivity. It had the optimum microwave absorption property with a bandwidth of 3.42 GHz and a RLm value of -12.9 dB at 10.74 GHz in 2.3 mm thickness. The calculated RL values revealed that Na3Zr2Si2PO12 ceramics could be developed as a new kind of microwave absorption materials, and much work should be done to further adjust and optimize its dielectric properties in the future. Acknowledgements This work was financially supported by Fundamental Research Funds for the Central Universities (No.3102017ZY050), and State Key Laboratory of Solidification Process (NWPU), China (Grant No. KP201604). References: [1] Y.C. Qing, D.D. Min, Y.Y. Zhou, F. Luo, W.C. Zhou, Carbon 86(2015)98-107. [2] J.H. Sui, C. Zhang, J. Li, Z.L. Yu, W. Cai, Mater. Lett. 75(2012)158-160. [3] K. Osouli-Bostanabad, E. Hosseinzade, A. Kianvash, A. Entezami, Appl. Surf. Sci. 356(2015)1086-1095. [4] P.B. Liu, Y. Huang, X. Zhang, Compos. Sci. Technol. 107(2015)54-60. [5] A. Maqsood, K. Khan, J. Alloys Compd. 509(2011)3393-3397. [6] J. Wang, H. Zhang, S.X. Bai, K. Chen, C.R. Zhang, J. Magn. Magn. Mater. 312(2007)310-313. [7] F.F. Xu, L. Ma, M.Y. Gan, J.H. Tang, Z.T. Li, J.Y. Zheng, J. Zhang, S. Xie, H. Yin, X.Y. Shen, J.L. Hu, F. Zhang, J. Alloys Compd. 593(2014)24-29. [8] B.T. Su, X.W. Zuo, C.L. Hu, Z.Q. Lei, Acta Phys. Chim. Sin. 24(2008)1932-1936. [9] M. Kotobuki, M. Koishi, Ceram. Int. 41(2015)8562-8567. [10] M. Kotobuki, M. Koishi, Y. Kato, Ionics 19(2013)1945-1948.
7
[11] N.S. Bell, C. Edney, J.S. Wheeler, D. Ingersoll, E.D. Spoerke, J. Am. Ceram. Soc. 97(2014)3744-3748. [12] J.S. Lee, C.M. Chang, Y.I. Lee, J.H. Lee, S.H. Hong, J. Am. Ceram. Soc. 87(2010)305-307. [13] M. Samiee, B. Radhakrishnan, Z. Rice, Z. Deng, Y.S. Meng, S.P. Ong, J. Luo, J. Power Sources 347(2017)229-237. [14] Z. Khakpour, Electrochim. Acta 196(2016)337-347. [15] A.G. Jolley, G. Cohn, G.T. Hitz, E.D. Wachsman, Ionics 21(2015)3031-3038. [16] D. Chen, F. Luo, L. Gao, W.C. Zhou, D.M. Zhu, J. Electron. Mater. 46(2017)6367-6372. [17] K.C. Kao, Dielectric phenomena in solids, Elsevier Academic Press, Cambridge, 2004. [18] Q.L. Wen, W.C. Zhou, Y.D. Wang, Y.C. Qing, F. Luo, D.M. Zhu, Z.B. Huang, J. Mater. Sci. 52(2017)832-842. [19] C.M. Regalado, Geoderma 123(2004)41-50. [20] F. Qin, C. Brosseau, J. Appl. Phys. 111(2012)061301.
Figure captions: Fig.1. XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures. Fig.2. Impedance spectra of Na3Zr2Si2PO12 ceramics at 25 °C sintered at different temperatures Fig.3. (a) Real parts and (b) imaginary parts of the complex permittivity of Na 3Zr2Si2PO12 ceramics sintered at different temperatures. Fig.4 (a) RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness.
8
Fig.1. XRD patterns of Na3Zr2Si2PO12 powder calcined at 1100 °C and the ceramics sintered at different temperatures.
Fig.2. Impedance spectra of Na3Zr2Si2PO12 ceramics at 25 °C sintered at different
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temperatures
Fig.3. (a) Real parts and (b) imaginary parts of the complex permittivity of Na3Zr2Si2PO12 ceramics sintered at different temperatures.
Fig.4 (a) RL of Na3Zr2Si2PO12 ceramics sintered at different temperatures in 2.3 mm thickness. (b) RL of Na3Zr2Si2PO12 ceramic sintered at 1250 °C in different thickness.
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Highlights: 1. Dielectric properties in the microwave range of Na3Zr2Si2PO12 ceramics have been studied. 2. Thermal ion relaxation polarization is induced by the migration of activated Na + ions under an EM field. 3. Na3Zr2Si2PO12 ceramics could be developed as a new kind of microwave absorption materials by further improvement.
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