- Email: [email protected]
Influence of Sm3+ Substitution on Microwave Magnetic Performance of Barium Hexaferrites
JOURNAL OF RARE EARTHS
Vol. 25, Suppl. , Jun . 2007, p .216
Influence of Sm3 Substitution on Microwave Magnetic Performance of Barium Hexaferrites +
a),
Wang Lixi ( 33 $5 ) , Huang Qiang ( 9 $3) , Mu Lei (;* Zhang Qitu ( $k% k)* ( College of Materials Science and Engineering , Nanjing University of Technology, Nanjing 210009, China )
Abstract: Barium hexaferrites doped with Sm3+, Bal - ZSmZFe12019,x = 0.0, 0.1, were prepared by the conventional ceramic technology. The structure and electromagnetic properties of the calcined samples were studied using powder X-ray diffraction (XRD) and network analyzer ( Agilent 8722ET) . All the XRD patterns showed the single phase of the magnetoplumbite barium ferrite without other intermediate phase. The lattice parameters of ferrites doped with Sm3 decreased, indicating that the substitution of Sm3 occurred on Ba2+ basis site and resulted in a contract of the crystal cell. The microwave electromagnetic properties of the samples were studied at the frequency range from 2 to 18 GHz . It was shown that E ’ increased slightly, and the maximum of E “ appeared at higher frequency position with Sm3 doping. p” and tanp were improved significantly, and the maxima were 2 . 3 , 2 . 0 , respectively. All the reasons were discussed using electromagnetic theory. +
+
+
Key words : barium hexaferrites ; microwave electromagnetic properties ; Sm3 substitution ; rare earths Document code: A Article ID: 1002 - 0721 (2007) - 0216 - 04 CLC number: TQ174.75 +
Hexagonal ferrites such as BaFe12019 are currently used as microwave absorbing materials with great scientific and technological interest, for their low cost, low density, high stability, large electrical resistivity, and high microwave magnetic loss. Barium hexafenite is a ferromagnetic material, which has a collinear fivesublattice magnetic structure and magnetocrystalline anisotropy with easy axis parallel to the c axis of the hexagonal unit cell. Its crystal structure is comprised of two structure units: R block ( (BaFe6011)’- ) and s block ( ( Fe60s)’+ ) . The R block contains three oxygen layers, and the middle layer can be regarded as a specular layer, containing a barium ion. Besides octahedral sites and tetrahedral sites, there is still a particular trigonal bipyramidal site in the R block. S block has the same stacking form as the spinel ferrite. The magnetic properties, microstructures and absorbing performance of pure and substituted Ba-ferrites have been reported in many literatures“-61. The substitutions aim at the development of new materials with improved properties and characteristics. The main issue concerns the substitution of mixtures of paramagnetic and diamagnetic ions for the Ba2’ and Fe3+ ions in the magnetocrystalline anisotropy of the materialr7]. In the present study, an attempt has been made
to study the Sm3+ substitution position in the femte system. Furthermore, the effect of small amounts of Sm3+ substitution on the microwave electromagnetic properties of barium ferrite was also been investigated.
1 Experimental 1.1 Material preparation Samples of Bal-, Sm,Fela OI9( x = 0 . 0 , 0. 1 ) hexaferrites were prepared by the conventional ceramic method. The starting materials, BaC03, Fe203, and Sm203were stoichiometrically weighed and ball milled in water for 10 h . The mixed powders were calcined at 1250 “c for 5 h in air, and the calcined powders were ball milled in water at a rotation speed of 300 r0min-l for 6 h again.
1.2 Measurement The X-ray diffraction was carried out with an ARL X-ray powder diffractometer using Cu Ka radiation. A network analyzer ( Agilent 8722ET) was employed to determine the values of E’ , E”, p’, and 11’’ at the frequency range of 2 18 GHz using a reflection/ transmission technique. The ferrite-paraffin wax compositions with 7 0 % of ferrite by volume were prepared
-
Received date: 2006 - 1 1 - 15; revised date: 2007 - 04 - 15 Foundation item: Project supported by the National Defence Fundamental Research Project and the Doctor Discipline Fund of NJUT ( BSCX200603) Biography: Wang Lixi (1983 - ) , Female, Doctor; Research field: functional materials * Corresponding author (E-mail: zhqt @njut .edu. cn; wanglixi - njut @ 163. corn)
Wang L X et a1 . Influence of Sm”
The microwave magnetic properties of the resulting powders were measured by an analyzer (Agilent 8722ET), and the complex permittivity and complex permeability computed from S-parameter values are clarified in Figs. 3 and 4. As shown in Fig. 3 ( a ) , E’ of the Ba hexafenite doped with 10% mol Sm3+ exhibits a higher value than that of pure Ba ferrite. The substitution of Sm3+ leads to a change in Fe3+ ions to Fe2+in order to balance the electrical valence, and this replacement affects directly on the hopping process ( F e z + < = > Fe3++ e ) . The increase of the content of Fez+ ions, which are easily polarized, results in the increase of E’ . From Fig. 3( b ) , it is found that the values of E” do not have much difference. However, the maximum of E” shifts to high frequency position when the Sm3+was doped.
by homogeneously mixing the ferrite powder and toroidal-shaped samples of 3.04 mm inner diameter, 7 . 0 mm outer diameter and 4 5 mm length (Fig. 1) . The measured values of reflected and transmitted scattering parameters ( S l l , S21) were used to determine E ’ , E”, p ’ , and p’”81.
-
2
217
on Microwave Magnetic P e ~ o n n a n c eof Barium Hexafemtes
Results and Discussion
The X-ray diffraction ( XRD ) patterns of Ba, - I Sm,FeI2Ol9(x = 0 . 0 , 0.1) powders calcined at 1250 “c for 5 h in air are shown in Fig. 2. It can be seen that the calcined powders are the pure magnetoplumbite phase and no other phases are observed. It is indicated that the Sm3+ ions can be completely solved into the hexaferrite crystal lattice. Lattice parameters ( a and c ) were calculated using Jada 5 software. The refined lattice parameters are listed in Table 1. The crystal cell volume of the pure Ba hexaferrite is larger than that of the Ba hexaferrite doped with little amounts of Sm3+ due to smaller ionic radii of Sm3+( 0. 104 nm) compared with that of Ba2+(0.149 nm) . Therefore, when Ba2+was replaced by 10% mol Sm3+ions, the lattice parameters decreased, as reported by Sharma P in the system of strontium ferrite[g1. It is shown that the crystal cell of Ba ferrite contracted after being doped with little amounts of Sm3+ ions.
I
11
P O .I
BaFe,,O,, I.
Table 1
Fig. 1
Simple coaxial transmission lines hold the samples of material under test
.
i
I
Refined lattice parameters of Ba,-, Sm,Fel2Ol9 hexaferrites clnm
X
Structure
alnm
0.0
Hexagonal
0.58989
2.30655
0.6950609
0.1
Hexagonal
0.58946
2.29971
0.6919897
75 70
(a)
-1-
-.- FO.0
FO.0
PO.1
25
I
354 3 2CG
Volume/nm3
4ffi
6CG
8CG
1OOG 0
1205
Frequency/Hz Fig. 3
14CG
16OG
18CG 0
0 205
4oG
6%
80s
5 IOffi
12OG
Frequency/& Complex permittivity of Bal zSm,Fe12019hexaferrites
14oG
16CG
0 18CG
JOURNAL OF RARE EARTHS, VoE. 25, Suppl. , Jun . 2007
218
Fig .4
Complex permeability of Bal _,Sm,Fe,20,9 hexaferrites
As can be observed from Fig. 4( a ) , the substitutions of 10% mol Smz03do not have much effect on the real part of complex permeability. All the p' values fluctuate between 1 .0 and 1 . 4 . The microwave absorbing property of hexaferrrites is closely related to the imaginary part of complex permeability p", which is connected with M , and HAaccording to the equation of p" = Ms/( 2 H ~ ( )r , where M , , HA and (x are magnetization, anisotropy field and extinction coefficient, respectively. Electromagnetic properties of ferrites depend on the distribution of basic metal ions. Not having unpaired electrons in d orbit, the spin magnetic moment of Ba2' ion is 0, while that of Fe3+ ion (3d5) is 5 p e , whereas the M , is mainly attributed to the distribution of iron ions. The Fe3+ ions distribute on five lattice locations: one tetrahedral site ( 4f1) , three octahedral sites ( 1% 7 2a 3 and 4fz) 3 and one trigonal bipyramida1 site ( 2 b ) . In the magnetically ordered state in BaFel2OI9, the 12k, 2a and 2b sites have their spins aligned parallel to each other and to the crystallographic c-axis , while those of 4f2 point in the opposite direction. Replacement of divalent Ba by trivalent Sm is associated with a valence change of Fe3+ to Fe2+ . The magnetic moment of Sm3+ion consists of two parts, orbital magnetic moment and spin magnetic moment. Orbital magnetic moment of Sm3+ ion exists, because Sm3+ion does not have much stricture of crystalline field for its large ion radius. Whereas, the association of orbital magnetic moment and spin magnetic moment ( 5 pB) is greater than 5 pB. The substitution of Sm3+( > 5 pB) for Ba2+( 0 pB) causes the increase of the M , of the hexaferrite, and the increase of Fe2+ions at 4fz sites also strength the M , of the hexaferrite""' . From the equation of p" = M s / ( 2 H A a ) , the increase of p" can be obtained, which has been verified by experiments, and the results are showed in
Fig.4( b ) . It is exhibited that the maximum of p" is almost up to 2 . 3 . 2.5
20
-.-x=O.O
-0 5
2ffi
400
600
800
1000
1200
14OG
1600
18ffi
FrcqucncyiH~
Fig.5
Magnetic loss of Bal _,Sm,Fe120,phexaferrites
The tanp,, which is the ratio of p" to p ' , can represent magnetic loss of the ferrites . Fig. 5 shows the dependence of tanpr on frequency. The values exhibit an excellent frequency property, which is favorable for expanding absorbing frequency range. In addition, the values increase significantly with small amounts of Sm203 doped, and the maximum almost reaches 2.0, the minimum is still more than 0.5. It can be concluded that the substitution of 10% mol Sm3+ ions is favorable for increasing microwave absorbing performance.
3 Conclusion The barium hexaferrites doped with Sm3+, Ba, Srn,Fel2Ol9(x = 0.0, 0. 1 ) , which were calcined at 1250 T for 5 h , were pure phase of the magnetoplumbite barium ferrite without other intermediate phase. The magnetic loss properties of the prepared barium hexaferrites could be enhanced significantly by partial substitution of Sm3+ions for Ba2+sites. Substitution of Sm ions into the barium hexaferrite system can be uti-
Wang L X et a1 . Influence of Sm3+ on Microwave Magnetic Performance of Barium Hexaferrites
lized for the improvement of M , in order to improve both permeability p” and magnetic loss tanp r , thus, to improve the microwave absorbing performance. The partial substitution of Sm3’ ions the for Ba” sites resulted in the change of Fe3+ to Fez+ in order to balance the valency, which led to the slight increase of the E’ .
[5]
[6]
References : Meshram M R , Agrawal Nawal K , et a1 . Characterization of M-type barium hexagonal ferrite-based wide band microwave absorber [ J 1. Journal of Magnetism and Magnetic Materials, 2004, 271: 207. Kagotani T , Fujiwara D , et al. Enhancement of GHz electromagnetic wave absorption characteristics in aligned M-type barium ferrite Bal _ I La,Zn,Fe12..,_, ( Meo.s Mno 5 ) , 0 1 9 ( x= 0.0 0.5; y = 1 .O 3 . 0 , Me: Zr, Sn) by metal substitution [.I]. Journal of Magnetism and Magnetic Materials , 2004, 272 - 276 : e 1813 . Mendoza-Su6rez G , Rivas-V6zquez L P, et a1 . Preparation and magnetic of Zn-Ti substituted Ba-ferrite powders [ J ] . Materials Letters, 2002, 57 : 868. Zhang Haijun, Liu Zhichao, et a1 . Complex permittivity, permeability, and microwave absorpuion of Zn- and Ti-substituted barium ferrite by citrate sol-gel process
-
-
[71
[8]
[9]
[ 101
219
[ J ] . Materials Science and Engineering B , 2002, 96: 289. Ugur Topal, Husnu Ozkan, Lev Dorosinskii. Finding optimal Fe/Ba ratio to obtain single phase BaFelzOl9 prepared by ammonium nitrate melt technique [ J ] . Journal of Alloys and Compounds, 2007, 428: 17. Mallick Kajal K , Philip Shepherd, Green Roger J . Dielectric properties of M-type barium hexaferrite prepared by co-precipitation [ J ] . Journal of European Ceramic Society, 2007, 27: 2045. Ong C K , Fang H C , et a1 . Magnetic relaxation in ZnSn-doped barium ferrite nanoparticles for recording [ J 1 . Journal of Magnetism and Magnetic Materials, 2000, 213: 413. Vanzura E J , Baker-Jarvis J R , Grosvenor J H . The measurement of electromagnetic wave absorption characteristics [ J ] . ZEEE Trans. Microwave Theory Tech. , 1994, 42: 2063. Puneet Sharma, Amitabh Verma, Sidhu R K , et al. Influence of Nd3’ and Sm3+substitution on the magnetic properties of strontium ferrite sintered magnets [ J 1. Jounal of Alloys and Compounds, 2003, 361 : 257. Niem Pham Quang, Chau Nguyen, Luong Nguyen Hoang. Influence of La doping on the properties of Sr Ba hexagonal ferrites [ J] . Physica B , 2003, 327 : 266.
Vol. 25, Suppl. , Jun . 2007, p .216
Influence of Sm3 Substitution on Microwave Magnetic Performance of Barium Hexaferrites +
a),
Wang Lixi ( 33 $5 ) , Huang Qiang ( 9 $3) , Mu Lei (;* Zhang Qitu ( $k% k)* ( College of Materials Science and Engineering , Nanjing University of Technology, Nanjing 210009, China )
Abstract: Barium hexaferrites doped with Sm3+, Bal - ZSmZFe12019,x = 0.0, 0.1, were prepared by the conventional ceramic technology. The structure and electromagnetic properties of the calcined samples were studied using powder X-ray diffraction (XRD) and network analyzer ( Agilent 8722ET) . All the XRD patterns showed the single phase of the magnetoplumbite barium ferrite without other intermediate phase. The lattice parameters of ferrites doped with Sm3 decreased, indicating that the substitution of Sm3 occurred on Ba2+ basis site and resulted in a contract of the crystal cell. The microwave electromagnetic properties of the samples were studied at the frequency range from 2 to 18 GHz . It was shown that E ’ increased slightly, and the maximum of E “ appeared at higher frequency position with Sm3 doping. p” and tanp were improved significantly, and the maxima were 2 . 3 , 2 . 0 , respectively. All the reasons were discussed using electromagnetic theory. +
+
+
Key words : barium hexaferrites ; microwave electromagnetic properties ; Sm3 substitution ; rare earths Document code: A Article ID: 1002 - 0721 (2007) - 0216 - 04 CLC number: TQ174.75 +
Hexagonal ferrites such as BaFe12019 are currently used as microwave absorbing materials with great scientific and technological interest, for their low cost, low density, high stability, large electrical resistivity, and high microwave magnetic loss. Barium hexafenite is a ferromagnetic material, which has a collinear fivesublattice magnetic structure and magnetocrystalline anisotropy with easy axis parallel to the c axis of the hexagonal unit cell. Its crystal structure is comprised of two structure units: R block ( (BaFe6011)’- ) and s block ( ( Fe60s)’+ ) . The R block contains three oxygen layers, and the middle layer can be regarded as a specular layer, containing a barium ion. Besides octahedral sites and tetrahedral sites, there is still a particular trigonal bipyramidal site in the R block. S block has the same stacking form as the spinel ferrite. The magnetic properties, microstructures and absorbing performance of pure and substituted Ba-ferrites have been reported in many literatures“-61. The substitutions aim at the development of new materials with improved properties and characteristics. The main issue concerns the substitution of mixtures of paramagnetic and diamagnetic ions for the Ba2’ and Fe3+ ions in the magnetocrystalline anisotropy of the materialr7]. In the present study, an attempt has been made
to study the Sm3+ substitution position in the femte system. Furthermore, the effect of small amounts of Sm3+ substitution on the microwave electromagnetic properties of barium ferrite was also been investigated.
1 Experimental 1.1 Material preparation Samples of Bal-, Sm,Fela OI9( x = 0 . 0 , 0. 1 ) hexaferrites were prepared by the conventional ceramic method. The starting materials, BaC03, Fe203, and Sm203were stoichiometrically weighed and ball milled in water for 10 h . The mixed powders were calcined at 1250 “c for 5 h in air, and the calcined powders were ball milled in water at a rotation speed of 300 r0min-l for 6 h again.
1.2 Measurement The X-ray diffraction was carried out with an ARL X-ray powder diffractometer using Cu Ka radiation. A network analyzer ( Agilent 8722ET) was employed to determine the values of E’ , E”, p’, and 11’’ at the frequency range of 2 18 GHz using a reflection/ transmission technique. The ferrite-paraffin wax compositions with 7 0 % of ferrite by volume were prepared
-
Received date: 2006 - 1 1 - 15; revised date: 2007 - 04 - 15 Foundation item: Project supported by the National Defence Fundamental Research Project and the Doctor Discipline Fund of NJUT ( BSCX200603) Biography: Wang Lixi (1983 - ) , Female, Doctor; Research field: functional materials * Corresponding author (E-mail: zhqt @njut .edu. cn; wanglixi - njut @ 163. corn)
Wang L X et a1 . Influence of Sm”
The microwave magnetic properties of the resulting powders were measured by an analyzer (Agilent 8722ET), and the complex permittivity and complex permeability computed from S-parameter values are clarified in Figs. 3 and 4. As shown in Fig. 3 ( a ) , E’ of the Ba hexafenite doped with 10% mol Sm3+ exhibits a higher value than that of pure Ba ferrite. The substitution of Sm3+ leads to a change in Fe3+ ions to Fe2+in order to balance the electrical valence, and this replacement affects directly on the hopping process ( F e z + < = > Fe3++ e ) . The increase of the content of Fez+ ions, which are easily polarized, results in the increase of E’ . From Fig. 3( b ) , it is found that the values of E” do not have much difference. However, the maximum of E” shifts to high frequency position when the Sm3+was doped.
by homogeneously mixing the ferrite powder and toroidal-shaped samples of 3.04 mm inner diameter, 7 . 0 mm outer diameter and 4 5 mm length (Fig. 1) . The measured values of reflected and transmitted scattering parameters ( S l l , S21) were used to determine E ’ , E”, p ’ , and p’”81.
-
2
217
on Microwave Magnetic P e ~ o n n a n c eof Barium Hexafemtes
Results and Discussion
The X-ray diffraction ( XRD ) patterns of Ba, - I Sm,FeI2Ol9(x = 0 . 0 , 0.1) powders calcined at 1250 “c for 5 h in air are shown in Fig. 2. It can be seen that the calcined powders are the pure magnetoplumbite phase and no other phases are observed. It is indicated that the Sm3+ ions can be completely solved into the hexaferrite crystal lattice. Lattice parameters ( a and c ) were calculated using Jada 5 software. The refined lattice parameters are listed in Table 1. The crystal cell volume of the pure Ba hexaferrite is larger than that of the Ba hexaferrite doped with little amounts of Sm3+ due to smaller ionic radii of Sm3+( 0. 104 nm) compared with that of Ba2+(0.149 nm) . Therefore, when Ba2+was replaced by 10% mol Sm3+ions, the lattice parameters decreased, as reported by Sharma P in the system of strontium ferrite[g1. It is shown that the crystal cell of Ba ferrite contracted after being doped with little amounts of Sm3+ ions.
I
11
P O .I
BaFe,,O,, I.
Table 1
Fig. 1
Simple coaxial transmission lines hold the samples of material under test
.
i
I
Refined lattice parameters of Ba,-, Sm,Fel2Ol9 hexaferrites clnm
X
Structure
alnm
0.0
Hexagonal
0.58989
2.30655
0.6950609
0.1
Hexagonal
0.58946
2.29971
0.6919897
75 70
(a)
-1-
-.- FO.0
FO.0
PO.1
25
I
354 3 2CG
Volume/nm3
4ffi
6CG
8CG
1OOG 0
1205
Frequency/Hz Fig. 3
14CG
16OG
18CG 0
0 205
4oG
6%
80s
5 IOffi
12OG
Frequency/& Complex permittivity of Bal zSm,Fe12019hexaferrites
14oG
16CG
0 18CG
JOURNAL OF RARE EARTHS, VoE. 25, Suppl. , Jun . 2007
218
Fig .4
Complex permeability of Bal _,Sm,Fe,20,9 hexaferrites
As can be observed from Fig. 4( a ) , the substitutions of 10% mol Smz03do not have much effect on the real part of complex permeability. All the p' values fluctuate between 1 .0 and 1 . 4 . The microwave absorbing property of hexaferrrites is closely related to the imaginary part of complex permeability p", which is connected with M , and HAaccording to the equation of p" = Ms/( 2 H ~ ( )r , where M , , HA and (x are magnetization, anisotropy field and extinction coefficient, respectively. Electromagnetic properties of ferrites depend on the distribution of basic metal ions. Not having unpaired electrons in d orbit, the spin magnetic moment of Ba2' ion is 0, while that of Fe3+ ion (3d5) is 5 p e , whereas the M , is mainly attributed to the distribution of iron ions. The Fe3+ ions distribute on five lattice locations: one tetrahedral site ( 4f1) , three octahedral sites ( 1% 7 2a 3 and 4fz) 3 and one trigonal bipyramida1 site ( 2 b ) . In the magnetically ordered state in BaFel2OI9, the 12k, 2a and 2b sites have their spins aligned parallel to each other and to the crystallographic c-axis , while those of 4f2 point in the opposite direction. Replacement of divalent Ba by trivalent Sm is associated with a valence change of Fe3+ to Fe2+ . The magnetic moment of Sm3+ion consists of two parts, orbital magnetic moment and spin magnetic moment. Orbital magnetic moment of Sm3+ ion exists, because Sm3+ion does not have much stricture of crystalline field for its large ion radius. Whereas, the association of orbital magnetic moment and spin magnetic moment ( 5 pB) is greater than 5 pB. The substitution of Sm3+( > 5 pB) for Ba2+( 0 pB) causes the increase of the M , of the hexaferrite, and the increase of Fe2+ions at 4fz sites also strength the M , of the hexaferrite""' . From the equation of p" = M s / ( 2 H A a ) , the increase of p" can be obtained, which has been verified by experiments, and the results are showed in
Fig.4( b ) . It is exhibited that the maximum of p" is almost up to 2 . 3 . 2.5
20
-.-x=O.O
-0 5
2ffi
400
600
800
1000
1200
14OG
1600
18ffi
FrcqucncyiH~
Fig.5
Magnetic loss of Bal _,Sm,Fe120,phexaferrites
The tanp,, which is the ratio of p" to p ' , can represent magnetic loss of the ferrites . Fig. 5 shows the dependence of tanpr on frequency. The values exhibit an excellent frequency property, which is favorable for expanding absorbing frequency range. In addition, the values increase significantly with small amounts of Sm203 doped, and the maximum almost reaches 2.0, the minimum is still more than 0.5. It can be concluded that the substitution of 10% mol Sm3+ ions is favorable for increasing microwave absorbing performance.
3 Conclusion The barium hexaferrites doped with Sm3+, Ba, Srn,Fel2Ol9(x = 0.0, 0. 1 ) , which were calcined at 1250 T for 5 h , were pure phase of the magnetoplumbite barium ferrite without other intermediate phase. The magnetic loss properties of the prepared barium hexaferrites could be enhanced significantly by partial substitution of Sm3+ions for Ba2+sites. Substitution of Sm ions into the barium hexaferrite system can be uti-
Wang L X et a1 . Influence of Sm3+ on Microwave Magnetic Performance of Barium Hexaferrites
lized for the improvement of M , in order to improve both permeability p” and magnetic loss tanp r , thus, to improve the microwave absorbing performance. The partial substitution of Sm3’ ions the for Ba” sites resulted in the change of Fe3+ to Fez+ in order to balance the valency, which led to the slight increase of the E’ .
[5]
[6]
References : Meshram M R , Agrawal Nawal K , et a1 . Characterization of M-type barium hexagonal ferrite-based wide band microwave absorber [ J 1. Journal of Magnetism and Magnetic Materials, 2004, 271: 207. Kagotani T , Fujiwara D , et al. Enhancement of GHz electromagnetic wave absorption characteristics in aligned M-type barium ferrite Bal _ I La,Zn,Fe12..,_, ( Meo.s Mno 5 ) , 0 1 9 ( x= 0.0 0.5; y = 1 .O 3 . 0 , Me: Zr, Sn) by metal substitution [.I]. Journal of Magnetism and Magnetic Materials , 2004, 272 - 276 : e 1813 . Mendoza-Su6rez G , Rivas-V6zquez L P, et a1 . Preparation and magnetic of Zn-Ti substituted Ba-ferrite powders [ J ] . Materials Letters, 2002, 57 : 868. Zhang Haijun, Liu Zhichao, et a1 . Complex permittivity, permeability, and microwave absorpuion of Zn- and Ti-substituted barium ferrite by citrate sol-gel process
-
-
[71
[8]
[9]
[ 101
219
[ J ] . Materials Science and Engineering B , 2002, 96: 289. Ugur Topal, Husnu Ozkan, Lev Dorosinskii. Finding optimal Fe/Ba ratio to obtain single phase BaFelzOl9 prepared by ammonium nitrate melt technique [ J ] . Journal of Alloys and Compounds, 2007, 428: 17. Mallick Kajal K , Philip Shepherd, Green Roger J . Dielectric properties of M-type barium hexaferrite prepared by co-precipitation [ J ] . Journal of European Ceramic Society, 2007, 27: 2045. Ong C K , Fang H C , et a1 . Magnetic relaxation in ZnSn-doped barium ferrite nanoparticles for recording [ J 1 . Journal of Magnetism and Magnetic Materials, 2000, 213: 413. Vanzura E J , Baker-Jarvis J R , Grosvenor J H . The measurement of electromagnetic wave absorption characteristics [ J ] . ZEEE Trans. Microwave Theory Tech. , 1994, 42: 2063. Puneet Sharma, Amitabh Verma, Sidhu R K , et al. Influence of Nd3’ and Sm3+substitution on the magnetic properties of strontium ferrite sintered magnets [ J 1. Jounal of Alloys and Compounds, 2003, 361 : 257. Niem Pham Quang, Chau Nguyen, Luong Nguyen Hoang. Influence of La doping on the properties of Sr Ba hexagonal ferrites [ J] . Physica B , 2003, 327 : 266.