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Magnetic Properties of Gd and Tb Doped Co2Z Type Hexagonal Soft Magnetic Ferrites
JOURNAL OF RARE EARTHS Vol.25, Suppl., Jun. 2007, p.220
Magnetic Properties of Gd and Tb Doped Co2Z Type Hexagonal Soft Magnetic Ferrites Guo Shihai ($-EA$)’*2*, Zhang Yanghuan (%~.#&)’,Feng Zekun (;-%JllIq)’, Wang Xinlin (3-%Jf$+)2, He Huahui (jTq%f)’ ( 1 . Department of Electronics Science and Technology, Huathong University of Science and Technology, Wuhan
430074, China ; 2 . Functional Materials Research Institute , Central Iron and Steel Research Institute , Beijing 100081 , China ) Abstract : The Gd and Tb doped CozZ type hexagonal ferrite materials were prepared by the conventional ceramic method. The results showed that the CozZ ferrite materials doped with a small amount of Gd and Tb presented still the single phase of CozZ planar hexagonal structure. The real part p’ of the samples increased significantly, but cut-off frequency of the ferrites went down. T h e Tb doped CozZ ferrites sintered at 1150 ‘T exhibited excellent high frequency properties such as high initial permeability up to 8 and high cut-off frequency more than 1 .8 GHz . Apparently, it was of benefit to the application of the materials. With the increasing of sintering temperature, the real part p‘ of complex permeability increased and cut-off frequency want down.
Key words : hexafenites ; CozZ; magnetic properties ; rare earths Article ID : 1002 - 0721 (2007) - 0220 - 03 CLC number : TM277 Document code : A
The electronic devices are attempting to high frequency tendency with the development of electronic technology. The operating frequency of the electric devices like notebook PC and cellular phone has been in the GHz region. The Electromagnetic Interference (EMI) has become more and more serious. Therefore, high initial permeability and high cut-off frequency are required for anti-EM1 magnetic material. NiZn spinel ferrites are only used at lower frequencies ( < 300 MHz) due to the Snoek’s limit. Ba3C02Fe24041 hexaferrites (Co2Z) with planar hexagonal structure can be applied in GHz region because of its strong magnetocrystalline anisotropy field and high cut-off frequency . Recently, more and more attention has been paid to improve the magnetic properties of Co2Z fenites in higher frequency Although there are some reports about the effects of doped elements on the magnetic properties of Co2Z f e r r i t e ~ [ ~, -systematic ~] study on the effects of rare-earth ions on the microstructure and magnetic properties of Co2Z fenites has been scarcely reported. The main objective of this study was to investigate the microstructure and magnetic properties of Co2Z with the addition of Gd and Tb rare-earth ions. The magnetic properties of CozZ femtes with different sintering temperatures were presented.
*
1 Experimental A series of specimens with various compositions, 3(Ba,5Sro.50)*2CoO* 10.8Fe203, 3(B%. 5Sro. 5 0 )* 2CoO * 0.05Gd203 * 10. 8Fe203and 3 ( Ba,,5 Sr0.50 ) 2CoO 0. 05Tb4O7* 10. 8Fe203were prepared by the conventional ceramic method. This study adopted an iron deficient and barium ions partially replaced by strontium ions compositions in order to obtain the permeability as high as possible, which based on the results already reportedr8’. The raw materials, BaO , SrC 0 3 , COO, Gd203, Tb407 and Fe203, of analytic reagent-grade were mixed in a deionized water by ballmilling for 20 h , and dried. The mixed powers were calcined at 1150 “c for 3 h and then mixed with 8% of polyvinyl alcohol ( PVA ) for granulation. The obtained powers were dry-pressed at 360 MPa into toroidal (@ 18 mm x @ I 1 mm x 4 mm) and pellet (@ 18 mm x 4 mm ) specimens. These specimens were sintered in air for 3.5 h at 1150, 1175, 1200 and 1225 ‘t, respectively. The phase structures of the samples were determined by Philips X’Pert MPD Pro X-ray diffractometer using Cu K a . Microstructures for the fracture surface of the sintered ferrites were observed by scanning elec-
Received date: 2006 - 1 1 - 15; revised date: ZOO7 - 04 - 14 Biography: Guo Shihai (1975 - ), Male, Postdoctor; Research field: magnetic materials Corresponding author (E-mail: guoshihai21@ 163. com)
Guo S H et a1 . Magnetic Properties of Gd and Tb Doped CoJ Type Hexagonal Ferrites
10
20
30
40
50
80
70
80
90
20/(”)
Fig. 1 X-ray diffraction patterns of samples sintered at lux) “c
tron microscopy (SEM) JSM-6400. For measurements of the complex permeability in the range from 1 MHz to 1 . 8 GHz the impedance analyzer Agilent-4396B was used.
2
Results and Discussion
Fig. 1 shows the X-ray diffraction patterns of the RE undoped and doped samples sintered at 1200 “c . Compared with the standard XRD pattern of Ba3 C02 Fe2404,ferrite , the RE undoped sample is the
!Au -
221
single phase of Co2Z structure. The Gd and Tb doped samples still show the single phase of Co2Z structure without the second phase such as Cozy. Therefore, we consider that the rare earth ions with small amount form solid solution in Z type ferrite. Fig.2 shows the SEM images of the RE undoped and doped samples sintered at 1200 “c. It is seen from Fig. 2 that all samples are single phases without the second phase, which agreed with the results of Xray diffraction patterns. However, the grain size of RE doped samples, especially Tb doped sample, is larger than that of RE undoped Co2Z samples. Fig. 3 shows the X-ray diffraction patterns of 3(Ba,,5Sro.50) .2CoO*O. 05Tb40,* 10. 8Fe203 samples sintered at different temperatures. It is seen from Fig.2 that the Tb doped samples sintered at higher than 1150 “c show the single phase of Co2Z structure without the second phase. Fig. 4 shows the frequency dependence of the complex permeability for different RE doped samples sintered at 1200 “c . It is seen from Fig. 4 that the addition of Gd and Tb has a remarkable effect on the complex permeability ,u of Co2Z ferrites. The real part p’ of the sample increased significantly form 2 for un-
1200 ‘c b .
1150 ‘c
I
I
0 10
20
30
40
50
80
70
80
500OM
90
Fig.3 X-ray diffraction patterns of 3(Bao,sSro.s0).2Co0.0.~~07. 1O.8Fr4O3samples sintered at different temperatures
1.OG Frequency/Hz
204”)
Fig .4
Frequency dependence of complex permeability of different RE doped samples sintered at 1200 “c:
222
I
1.oG
5oo.m
1%
References :
FrequencyIHz Fig. 5
Frequency dependence of the complex permeability of 3(Ba, sSro,,O)* 2CoO 0.05Tb40, 10. 8FeZ03ferrite samples sintered at different temperatures
-
hexagonal structure. The real part p’ of the samples increased significantly, but cut-off frequency of the ferrites went down. The Tb doped Co2Z ferrites could be obtained after sintering at 1150 “c , exhibiting excellent high frequency properties such as high initial permeability up to 8 and high cut-off frequency above 1.8 GHz. Apparently, it is of benefit to the application of the materials. With the increasing of sintering temperature, the real part p’ of complex permeability increases and cut-off frequency goes down.
-
doped CozZ samples to 15 for Tb doped samples, but cut-off frequency of the ferrites went down. It is known that the grain size affects the initial permeability of a ferrite. The ferrite with a larger grain size can obtain the bigger initial permeability. It explains why there is a higher initial permeability in Tb doped sample form Fig.2. The grain size of RE doped samples is larger than that of RE undoped CozZ samples. Fig. 5 shows the frequency dependence of the complex permeability for Tb doped samples sintered at the different temperatures. It is seen from Fig. 5 that the real part p‘ of complex permeability increased and cut-off frequency went down with the increasing of sintering temperature. The reason for this can be explained by the increasing of the grain size of the samples with the increasing of sintering temperature. It is worth noting that p’ of Tb doped samples sintered at 1150 “c is four times that of undoped Co2Z sample and its cut-off frequency is above 1. 8 GHz. The results show that this material will become a promising soft magnetic ferrite for anti-EM1 magnetic material application in high frequency region.
3 Conclusion The Gd and Tb with small amount doped CozZ ferrite materials show the single phase of CozZ planar
[ 1] Wang Changsheng, Li Longtu , Zhou Ji , et al.
[2]
[3]
[4]
[5]
[ 61
[ 71
[8]
Microstructures and high-frequency magnetic properties of lowtemperature sintered Co-Ti substituted barium femtes [ J ] . J . Magn. Magn. Mater., 2003, 257: 100. Zhang Hongguo, Li Longtu, Wu Pinggui , Zhou Ji , Ma Zhenwei, Gui Zhilun. Investigation on structure and properties of low-temperature sintered composite ferrites [J ] . Materials Research Bulletin , 2000, 35 : 2207. Osamu Kimura, Kazuo Shoji, Hiroshi Maiw . Low temperature sintering of iron deficient Z type hexagonal femtes [J ] . Journal of the European Ceramic Society, 2006, 26 ( 1 3 ) : 2845. Zhang Hongguo, Zhou Ji , Yue Zhengxing , Gui Zhilun . Investigation of low-temperature sintering of Pb-modified CozZ hexafenite [ J ] . Material Science and Engineering B , 1999, 65: 184. Hsiang Hsing-I, Hsi Chi-Shiung, Lee Tin-Chin, et al. Effects of glass additions on 3Ba,.,Sr0,,O 2CoO 12Fe,O3 for high-frequency applications [ J 1 . J . Magn . Magn . Mat e r . , 2004, 268: 186. Wang Xiaohui , Li Longtu, Su Shuiyuan , et a1 . Electromagnetic properties of low-temperature-sintered Ba3C02Zn,FeaO,, ferrites prepared by solid state reaction method [ J ] . J . Magn. Magn. Mater., 2004, 280: 10. Takeshi Tachibana, Takashi Nakagawab, Yukio Takadab, et al. Yamamoto Influence of ion substitution on the magnetic structure and Permeability of Z-type hexagonal Ba-ferrites: Ba3Coz_, Fea+,_, CrYO4,[ J ] . J . Magn. Magn . Mater . , 2004, 284: 369. Kimura 0, Matsumto M , Sakakura M. Enhanced dispersion frequency of hot-pressed Z-type magnetoplumbite ferrite with the corn position 2C00.3Ba&3r,,~O. 10.8Fe,03[J]. J . A m . Ceram . Soc . , 1995, 78: 2857.
Magnetic Properties of Gd and Tb Doped Co2Z Type Hexagonal Soft Magnetic Ferrites Guo Shihai ($-EA$)’*2*, Zhang Yanghuan (%~.#&)’,Feng Zekun (;-%JllIq)’, Wang Xinlin (3-%Jf$+)2, He Huahui (jTq%f)’ ( 1 . Department of Electronics Science and Technology, Huathong University of Science and Technology, Wuhan
430074, China ; 2 . Functional Materials Research Institute , Central Iron and Steel Research Institute , Beijing 100081 , China ) Abstract : The Gd and Tb doped CozZ type hexagonal ferrite materials were prepared by the conventional ceramic method. The results showed that the CozZ ferrite materials doped with a small amount of Gd and Tb presented still the single phase of CozZ planar hexagonal structure. The real part p’ of the samples increased significantly, but cut-off frequency of the ferrites went down. T h e Tb doped CozZ ferrites sintered at 1150 ‘T exhibited excellent high frequency properties such as high initial permeability up to 8 and high cut-off frequency more than 1 .8 GHz . Apparently, it was of benefit to the application of the materials. With the increasing of sintering temperature, the real part p‘ of complex permeability increased and cut-off frequency want down.
Key words : hexafenites ; CozZ; magnetic properties ; rare earths Article ID : 1002 - 0721 (2007) - 0220 - 03 CLC number : TM277 Document code : A
The electronic devices are attempting to high frequency tendency with the development of electronic technology. The operating frequency of the electric devices like notebook PC and cellular phone has been in the GHz region. The Electromagnetic Interference (EMI) has become more and more serious. Therefore, high initial permeability and high cut-off frequency are required for anti-EM1 magnetic material. NiZn spinel ferrites are only used at lower frequencies ( < 300 MHz) due to the Snoek’s limit. Ba3C02Fe24041 hexaferrites (Co2Z) with planar hexagonal structure can be applied in GHz region because of its strong magnetocrystalline anisotropy field and high cut-off frequency . Recently, more and more attention has been paid to improve the magnetic properties of Co2Z fenites in higher frequency Although there are some reports about the effects of doped elements on the magnetic properties of Co2Z f e r r i t e ~ [ ~, -systematic ~] study on the effects of rare-earth ions on the microstructure and magnetic properties of Co2Z fenites has been scarcely reported. The main objective of this study was to investigate the microstructure and magnetic properties of Co2Z with the addition of Gd and Tb rare-earth ions. The magnetic properties of CozZ femtes with different sintering temperatures were presented.
*
1 Experimental A series of specimens with various compositions, 3(Ba,5Sro.50)*2CoO* 10.8Fe203, 3(B%. 5Sro. 5 0 )* 2CoO * 0.05Gd203 * 10. 8Fe203and 3 ( Ba,,5 Sr0.50 ) 2CoO 0. 05Tb4O7* 10. 8Fe203were prepared by the conventional ceramic method. This study adopted an iron deficient and barium ions partially replaced by strontium ions compositions in order to obtain the permeability as high as possible, which based on the results already reportedr8’. The raw materials, BaO , SrC 0 3 , COO, Gd203, Tb407 and Fe203, of analytic reagent-grade were mixed in a deionized water by ballmilling for 20 h , and dried. The mixed powers were calcined at 1150 “c for 3 h and then mixed with 8% of polyvinyl alcohol ( PVA ) for granulation. The obtained powers were dry-pressed at 360 MPa into toroidal (@ 18 mm x @ I 1 mm x 4 mm) and pellet (@ 18 mm x 4 mm ) specimens. These specimens were sintered in air for 3.5 h at 1150, 1175, 1200 and 1225 ‘t, respectively. The phase structures of the samples were determined by Philips X’Pert MPD Pro X-ray diffractometer using Cu K a . Microstructures for the fracture surface of the sintered ferrites were observed by scanning elec-
Received date: 2006 - 1 1 - 15; revised date: ZOO7 - 04 - 14 Biography: Guo Shihai (1975 - ), Male, Postdoctor; Research field: magnetic materials Corresponding author (E-mail: guoshihai21@ 163. com)
Guo S H et a1 . Magnetic Properties of Gd and Tb Doped CoJ Type Hexagonal Ferrites
10
20
30
40
50
80
70
80
90
20/(”)
Fig. 1 X-ray diffraction patterns of samples sintered at lux) “c
tron microscopy (SEM) JSM-6400. For measurements of the complex permeability in the range from 1 MHz to 1 . 8 GHz the impedance analyzer Agilent-4396B was used.
2
Results and Discussion
Fig. 1 shows the X-ray diffraction patterns of the RE undoped and doped samples sintered at 1200 “c . Compared with the standard XRD pattern of Ba3 C02 Fe2404,ferrite , the RE undoped sample is the
!Au -
221
single phase of Co2Z structure. The Gd and Tb doped samples still show the single phase of Co2Z structure without the second phase such as Cozy. Therefore, we consider that the rare earth ions with small amount form solid solution in Z type ferrite. Fig.2 shows the SEM images of the RE undoped and doped samples sintered at 1200 “c. It is seen from Fig. 2 that all samples are single phases without the second phase, which agreed with the results of Xray diffraction patterns. However, the grain size of RE doped samples, especially Tb doped sample, is larger than that of RE undoped Co2Z samples. Fig. 3 shows the X-ray diffraction patterns of 3(Ba,,5Sro.50) .2CoO*O. 05Tb40,* 10. 8Fe203 samples sintered at different temperatures. It is seen from Fig.2 that the Tb doped samples sintered at higher than 1150 “c show the single phase of Co2Z structure without the second phase. Fig. 4 shows the frequency dependence of the complex permeability for different RE doped samples sintered at 1200 “c . It is seen from Fig. 4 that the addition of Gd and Tb has a remarkable effect on the complex permeability ,u of Co2Z ferrites. The real part p’ of the sample increased significantly form 2 for un-
1200 ‘c b .
1150 ‘c
I
I
0 10
20
30
40
50
80
70
80
500OM
90
Fig.3 X-ray diffraction patterns of 3(Bao,sSro.s0).2Co0.0.~~07. 1O.8Fr4O3samples sintered at different temperatures
1.OG Frequency/Hz
204”)
Fig .4
Frequency dependence of complex permeability of different RE doped samples sintered at 1200 “c:
222
I
1.oG
5oo.m
1%
References :
FrequencyIHz Fig. 5
Frequency dependence of the complex permeability of 3(Ba, sSro,,O)* 2CoO 0.05Tb40, 10. 8FeZ03ferrite samples sintered at different temperatures
-
hexagonal structure. The real part p’ of the samples increased significantly, but cut-off frequency of the ferrites went down. The Tb doped Co2Z ferrites could be obtained after sintering at 1150 “c , exhibiting excellent high frequency properties such as high initial permeability up to 8 and high cut-off frequency above 1.8 GHz. Apparently, it is of benefit to the application of the materials. With the increasing of sintering temperature, the real part p’ of complex permeability increases and cut-off frequency goes down.
-
doped CozZ samples to 15 for Tb doped samples, but cut-off frequency of the ferrites went down. It is known that the grain size affects the initial permeability of a ferrite. The ferrite with a larger grain size can obtain the bigger initial permeability. It explains why there is a higher initial permeability in Tb doped sample form Fig.2. The grain size of RE doped samples is larger than that of RE undoped CozZ samples. Fig. 5 shows the frequency dependence of the complex permeability for Tb doped samples sintered at the different temperatures. It is seen from Fig. 5 that the real part p‘ of complex permeability increased and cut-off frequency went down with the increasing of sintering temperature. The reason for this can be explained by the increasing of the grain size of the samples with the increasing of sintering temperature. It is worth noting that p’ of Tb doped samples sintered at 1150 “c is four times that of undoped Co2Z sample and its cut-off frequency is above 1. 8 GHz. The results show that this material will become a promising soft magnetic ferrite for anti-EM1 magnetic material application in high frequency region.
3 Conclusion The Gd and Tb with small amount doped CozZ ferrite materials show the single phase of CozZ planar
[ 1] Wang Changsheng, Li Longtu , Zhou Ji , et al.
[2]
[3]
[4]
[5]
[ 61
[ 71
[8]
Microstructures and high-frequency magnetic properties of lowtemperature sintered Co-Ti substituted barium femtes [ J ] . J . Magn. Magn. Mater., 2003, 257: 100. Zhang Hongguo, Li Longtu, Wu Pinggui , Zhou Ji , Ma Zhenwei, Gui Zhilun. Investigation on structure and properties of low-temperature sintered composite ferrites [J ] . Materials Research Bulletin , 2000, 35 : 2207. Osamu Kimura, Kazuo Shoji, Hiroshi Maiw . Low temperature sintering of iron deficient Z type hexagonal femtes [J ] . Journal of the European Ceramic Society, 2006, 26 ( 1 3 ) : 2845. Zhang Hongguo, Zhou Ji , Yue Zhengxing , Gui Zhilun . Investigation of low-temperature sintering of Pb-modified CozZ hexafenite [ J ] . Material Science and Engineering B , 1999, 65: 184. Hsiang Hsing-I, Hsi Chi-Shiung, Lee Tin-Chin, et al. Effects of glass additions on 3Ba,.,Sr0,,O 2CoO 12Fe,O3 for high-frequency applications [ J 1 . J . Magn . Magn . Mat e r . , 2004, 268: 186. Wang Xiaohui , Li Longtu, Su Shuiyuan , et a1 . Electromagnetic properties of low-temperature-sintered Ba3C02Zn,FeaO,, ferrites prepared by solid state reaction method [ J ] . J . Magn. Magn. Mater., 2004, 280: 10. Takeshi Tachibana, Takashi Nakagawab, Yukio Takadab, et al. Yamamoto Influence of ion substitution on the magnetic structure and Permeability of Z-type hexagonal Ba-ferrites: Ba3Coz_, Fea+,_, CrYO4,[ J ] . J . Magn. Magn . Mater . , 2004, 284: 369. Kimura 0, Matsumto M , Sakakura M. Enhanced dispersion frequency of hot-pressed Z-type magnetoplumbite ferrite with the corn position 2C00.3Ba&3r,,~O. 10.8Fe,03[J]. J . A m . Ceram . Soc . , 1995, 78: 2857.