- Email: [email protected]
Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites
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ScienceDirect JOURNAL OF IRON AND STEEL RESEARCH. INTERNATIONAL. 2010, 17(2): 59-62
Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites YU Cheng-Ieng":",
LI Yu-guang",
xu Hui-yu",
GAO Jin-sheng'
(1. College of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai
200237. China; 201900, China;
2. Technology and Quanlity Management Department, Baoshan Iron and Steel Co Ltd. Shanghai 3. Shanghai Baosteel Tiantong Magneitic Materials Co Ltd. Shanghai 201900. China)
Abstract: The ferrites of PC30 (Mn-Zn ferrites) were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H 3 B0 3 was investigated on the basis of microstructure analysis. The results of the samples doped with H 3B03 less than 5XlO- 5 showed that the doping had no significant effect on power loss. initial permeability, fine grain microstructure. and density of Mn-Zn ferrites. With the further increase in H, BO" doping (up to 1 X 10-'\), the microstructure of Mn-Zn ferrites is in the critical state between fine grain and "sandwich". and the initial permeability and density of Mn-Zn ferrites begin falling quickly; the increased H,B0 3 doping also results in deteriorated power loss properties. Thus. the control of the boron content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process. Key words: iron oxide; Mn-Zn ferrite; boron content; initial permeability
Recently, electric components of soft magnetic ferrites are becoming smaller and thinner in size with the updated progress of technology to meet portable electronic equiprnent-U. The ferrites with properties on usage, such as high frequency, low power waste, and high permeability, will be the future trends. Also, nano magnetic ferrites need further investigation[2J. To get high performance with iron oxide, which is the main raw materiel of soft magnetic ferrite material accounting for about 70 % of ferrite component by mass[I,3J, some special physical and chemical properties are demanded'<":". The purity and chemical homogeneity of iron oxide which is used to manufacture high grade Mn-Zn ferrites will be higher than ever[4-5J. Presently, the iron oxide used for magnetic ferrite material is generally manufactured by purifying waste pickling acid (ferrous chloride solution) generated from steelmaking plant, and then by spray-roasting the purified ferrous chloride solutionl'", When the iron oxide is generated by steelmaking process, some residual elements, such as AI, st. S, Mn, Mg. Na, P, c-. Ni, and c«. etc. , will be mixed in. In some cases, B, Ca , Ti , Biography: YU Cheng-feng0974-). Male. Doctor Candidate. Engineer;
Nb , and V elements are also taken into the manufacture process of the iron oxide. Magnetic properties of Mn-Zn ferrites can be improved with some trace impurity elements in the raw material of iron oxide[7-9 J. However, the magnetic properties of MnZn ferrites will be deteriorated rapidly with the increase in the content and type of impurity elements in the iron oxide-". Several studies on the effects of doping with small amount of the additives to Mn-Zn ferrites have been carried out[7-IOJ. By using a citrate gel processing route to prepare the Mn-Zn Ierrites , Fan, et al[1I-12J have studied the relationship between the microstructure, magnetic properties, and impedance spectroscopy of Mn-Zn ferrites doped with B2 0 3 (up to O. 5 %). The sol-gel chemical preparation can be used for powder preparation to yield chemically homogeneous and high purity powder[IO.13-14J, but traditional dry method process (ceramic process) has the advantage of high efficiency and low cost[I5 J. However, by using traditional dry method process to manufacture the Mn-Zn Ierrites , the influence of doping boron in iron oxide on the properties of MnE-mail: [email protected];
Received Date, October 7. 2008
journal of Iron and Steel Research, International
• 60 •
Zn ferrites is unclear. To ameliorate steel product specifications. boron is often added in the steelmaking process. Thus. it is necessary to investigate the effects of boron in iron oxide on the preparation of Mn-Zn ferrites by using dry method process.
1 1. 1
der from each batch. by using a specially designed hydraulic presser. Subsequently. the ring samples were sintered at peak temperatures of 1380 C using a specially constructed programmable kiln. The spray-roasted iron oxides were analyzed by using ICP-emission spectroscopy type Varian Vista PRO. The final density of the specimens was measured by the Archimedes method using distilled water as the immersion fluid. The electric and magnetic properties of the specimens were measured by an Agilent HP4284ALCR. The power losses were measured using an IW A TSU SY8232 B- H. The microstructures of the sintered samples were examined by using optical and scanning electron microscope (SEM). and pictures were taken by using a JEOL 6460LV scanning electron microscopy.
Experimental Process route
Presently. the main methods for preparing manganese-zinc ferrite materials include traditional dry method process (ceramic process) and wet method process. The wet method process is easy to control and has high chemical homogeneity of product. But the dry method process has the advantages of high efficiency and low cost. In this study. the Mn-Zn ferrite of PC30 was synthesized and investigated by using the manufacturing procedure of dry method process which include weighing and wet mixing of Fez 0" • Mn:,OI' ZnO. and HIBO". prefiring , coarse pulverizing. fine pulverizing. spray granulation. pressing. and sintering , etc. 1. 2
2
One of the specific issues when dealing with soft magnetic ceramics such as Mn-Zn ferrites is that their properties depend strongly on parameters other than their main composition. such as density. microstruct ure , and grain boundary structure. etc. Dopants have. in genera], also influence on the microstruct ural properties and therefore may affect the magnetic performance in an indirect way[16]. Power loss. initial permeability. final density. and microstructures of Mn-Zn ferrites for different boron doping levels of all six batches are shown in Table 1. From Table 1. it can be concluded that the microstructure of the Mn-Zn ferrite specimens may be considered almost as critical state between fine grain and .. sandwich" with the addition of small amounts of H, BO, up to 1 X 10- I. Further increasing the H 3 BO"
Six experimental syntheses of Mn-Zn Ierrires were performed by using the Mn-Zn ferrite formulas of PC30. and the H, BO, (99.5 % in purity) was used as boron dopant. which also dissolved in the mixed ferrite powders to give different boron doping levels (presented in Table 1). The raw materials used were Fez()", Mn:IOI' and ZnO supplied separately by steel factory (spray-roasted iron oxides). Kingray New Materials Science and Technology Company and GMP (Analytical Grade). The ring samples of 25 mm in outer diameter. 15 mm in inner diameter. and 10 mm in height were shaped by uniaxially pressing at 500 kg/ ern" of the granulated pow-
Dopant 110 "
()
0
50
Results and Discussion
2. 1 Effect of boron doping level on power loss. 101tial permeability. final density. and microstructures of Mn-Zn ferrites
Materials and methods
Table 1
Vol. 17
Power loss, initial permeability, final density. and microstructures of Mn-Zn ferrites for different boron doping levels of all six batches
Initial permeability! (H'm- I )
Density;'
Power loss at 25kHz and 200mT/(mW· ern
")
Micros t ruct ure
(g' cm ":")
21 C
60 C
2,,80
1.77
92
56
90
Fine grain
2866
l. 811
93
58
88
Fine grain
80 C
100
18
27] 7
I. 8:,
98
61
92
150
26
2070
'I. 76
23]
200
256
Surface fine grain
200
35
] 823
I. 71
229
208
260
Inherent large grain
335
62
1514
I. 69
266
2,11
:306
Large grain
Fine grain or sandwich II
Note: 1) In some kilns, the microstructure of the MnZn [erritcs is fine grain. while in other kilns. the microstructure is surface fine grain and inherent large grain. which is called "sandwich".
Influence of Boron Content in Iron Oxide on Performance of Mn- Zn Ferrites
Issue 2
doping level (more than 1. 5 X 10- 4 ) , the microstructure of the Mn-Zn ferrite specimens shows "sandwich" and even totally large grain. Fig. 1 shows the relationship between power loss and temperature with different H:, B03 content doping levels, and Fig. 2 shows the relationship between the power loss and the H 3 B0 3 doping levels. The samples have the lowest values of power loss at 60'C in all measuring H 3 B0 3 doping levels, and the variation of power loss is very small. The power loss increases rapidly at small doping levels (more than lXl0- 1 ) . Fig. 3 shows the relationship between the initial permeability and final density with different H,BO, content doping levels. The initial permeability increases sharply with small amounts of HI B03 additions (less than 1 X 10- 1 ) , and the final density also increases with small amounts of H 3 B(\ additions (less than 5 X 10- 5 ) . The initial permeability and final density decrease rapidly at small H 3 B03 doping levels (more than 1 X 10- 4 ). 300 C'
.~
f
250 200
H,BO:, content/% ......... 0 0.015 __ O.OO!) 0.020 ~ 0.010 --- 0.0:3:1!)
150
t
~
100 50
......
'-'-------~'-------'----_
20
Fig. 1
40 60 Temperature/ 'C
80
Variation of power loss with temperature and H3803 content for Mn-Zn ferrites
250
60 'C, 25 kHz, 200 mT
f"
B 200
I
lW
~ 100
cf
50 L..-_
o Fig.2
___'~
0.005
_
___'~
0.010
_
___'_ _
0.015 H:3803 contentlYo
~
_ _.............
0.020 0.0335
Variation of power loss with H3 8 03 content for Mn-Zn ferrites
4000
c- 3500
's
• 61 •
4.85
4.80
:i: ~ 3000
~E 2500
'""' '7
B
4.75 ~
>. .~
Q.I
0-
]
:5
4.70
Q
2000 1 500 L . . - _ - - ' -_ _~_ _'___ __'__ _""4.65 o 0.005 O.OlO 0.015 0.020 0.0335 Ha80:1 contentlYo
Fig.3
Variation of initial permeability and density with H3 8 03 content for Mn-Zn ferrites
2.2 Microstructural properties of Mn-Zn ferrites doped with boron Fig. 4 shows the typical optical micrographs of the samples. The undoped sample [Fig. 4 (a), boron-free] has a uniform microstructure. These small grains are nearly pore-free, and the average grain size is between 10 J1.m and 18 J1.m. At 1. 5 X 10- 5 of boron doping level, the sample [Fig. 4 (b)] shows a duplex structure which includes fine grain and large grain. With boron doping, the SEM micrographs [Fig. 4 (c). boron doping level of 2. 5 X 10- 5] only show a part of the large grains. These large grains include also plenty of pores, and the size of these large grains can hardly be identified. The solid iron oxide (Fe2 ( 3 ) powder used for Mn-Zn ferrite preparation is prepared by pickling spray-roasting in air at temperatures of 300 - 600 'C[17J . The boron element in iron oxides is oxidized at high temperature, and the melting point of B20 3 is only 450 'C. In the process of calcination and agglomeration, the B20 1 is in liquid, which can quickly increase the reaction speed and promote the grain particles growth. The impurity ions present in small amounts in the iron oxide (e. g. Si , Ca , P, etc. ) have positive effect on its reactivity and consequently on the densification of the ferrites[17 J. Small amounts of boron in iron oxide can make calcium and silicon impurity content uniform in Mn-Zn ferrites samples; the magnetic properties are fine, and the microstructure shows fine grain. However, a microstructure showing discontinuous grain growth is observed at relative high amounts of boron in Mn-Zn ferrites samples, and plenty of pores were interfused. These
Journal of Iron and Steel Research. International
• 62 •
(a) Boron-Iree ,
Fig.4
(b) Boron doping of 1. 5X 10-";
[5J
for a Rosy Future [6J
Conclusions
[JJ.
HUA:--JG Ai-ping , HE Hua-hui , FENG Ze-kun • et al. Effects meability [j]. J Huazhong Univ of Sci and Tech: Nature Science Edition. 2006. 3H2): 39 (in Chinese).
[8J
SlJ Hua . ZHA:'J(; Huai-wu , TA:--JG Xiao-Ii. Effects of CuO, MoO" and WO" Doping on Magnetic Properties of NiZn Ferrites
[JJ.
Chinese Journal of Materials Research. 2005. 19(5):
5·19 (in Chinese). [9J
DAI Yu-hui , WEI Xu-boo SlJ Hua . et al, Effects of P,O" Addition on the Properties of High Permeability Mn Zn Ferrite
[JJ.
Journal of Magnetic Materials and Devices. 2005. 36(2): 29 (in Chinese).
[IOJ
Goldman A. Modern Ferrite Technology [M]. New York: Van Nostrand Rein- Hold. 1990.
[11 J
Fan J. Sale F R. Influence of H,O" on the Production of Pure. Gel-Processed Mn-Zn Ferrites
[12J
[JJ.
J Phys , 1997.4(7): 81.
Fan J. Sale F R. The Microstructures. Magnetic Properties and Impedance Analysis of Mn-Zn Ferrites Doped With H2 0 ,
[JJ.
Journal of the European Ceramic Society, 2000. 20( 16):
27.l3. [13J
SHI Xin-yu . WlJ Dong-hui , JI:--J Rui-di. et al. Preparation of Nano-Maghernit e by Citrate-Gel Process [JJ. Inorganic Chemical Industry. 2006. 38( 12): 16 (in Chinese). JING Mao-xiang , SHE:--J Xiang-qian , SHE:--J Yu-jun. Prepa-
Kikuchi Takahiro , Okazaki Yukiko , Ikeda Kohji. Fine Iron
ration of Nanometer Nickel Oxide by the Citrate-Gel Process
Oxide Powder as a Raw Material of Soft Ferrites [j]. J FE
[Jl. Journal of Inorganic Materials. 2004.19(2): 289
Technical Report. 200S( 6): 29. GUAN Xiao-rong , ZHA:'JG j ian-guang , ZHU Chun-cheng , et
[15J
Ni-Zn Ferrites
[JJ.
Jour-
Chinese).
Chinese) . SHAO Feng , LI Xiaoqing , QIA:--J Qiong-hui. Requirements
[JJ.
[HiJ
Zaspalis V T. Antoniadis E. Papazoglou E. et al. The Effect of Nb,O-. Dopant on the Structural and Magnetic Properties of
Journal of
[JJ.
Magnetic Materials and Devices. 2004. 35(4): 42 (in Chi-
MnZn-Ferrites
nese).
rials. 2002. 2S0(]/Z,!3): 98.
Manfred Zenger. New Developments in the Field of Soft Magnetic Ferrites [j]. Journal of Magnetism and Magnetic Materials. 1992. 112(1/2/3): :J72.
[JJ.
nal of Magnetic Materials and Devices. 2006. 37(4): 49 (in
Materials Review. 2006. 2M 12): 109 (in
for Property of Ferric Oxide for Mn Zn Ferrires
XU Hui-yu . DAI Zhi-yun. Development of Soft Ferrite Material HRLl5K With Super High Initial Permeability
al. Current Research Situation and Development of Mn-Zn and
[4J
Industrial Minerals. 1994. 4(2): 24.
of Addition on Performance of Mn Zn Ferrites With High-Per-
[I4J
[3J
[JJ.
ZHAO Guang, Ferric Oxide Used for Soft Ferrite in China (in Chinese).
[7J
References:
[2J
Tom Kendall. Inorganic Colored Pigments-Iron Oxides Looking
journal of Magnetic Materials and Devices, 2002, 33(3): 28
It is believed that the key issue of .. sandwich" and large grain in manganese zinc Ierrites is relative high boron content in the raw materials of pickling spray-roasted iron oxides. When the boron dopant is below 1. 0 X 10 - 0 • the magnetic properties and microstructure of manganese zinc ferrites is fine. But boron added in manganese zinc Ierrites in quantities up to 1. 5 X 10-' acts as .. sandwich" or large grain element. which promotes grain growth and deteriorates magnetic properties. To obtain either low magnetic power losses or high magnetic permeabilities in Mn-Zn Ierrites for low or high frequency applications. the iron oxide used for the preparation should be of low impurity. and the amount of boron in iron oxide should be no more than 1. 0 X 10-'; .
[IJ
Boron doping of 2. 5X 10-'-'.
SEM micrographs of Mn-Zn ferrites materials with different boron contents
will result in the deterioration of magnetic properties and decrease the final density rapidly.
3
(c)
Vol. 17
[17J
Journal of Magnetism and Magnetic Mate-
Vassilios Zaspalis , Marcel Kolenbrander. Design Principles for Spray' Roasted Iron Oxides for the Manufacturing of Ferriles [j]. Powder Technology. 2006. 161(3): 169.
ScienceDirect JOURNAL OF IRON AND STEEL RESEARCH. INTERNATIONAL. 2010, 17(2): 59-62
Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites YU Cheng-Ieng":",
LI Yu-guang",
xu Hui-yu",
GAO Jin-sheng'
(1. College of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai
200237. China; 201900, China;
2. Technology and Quanlity Management Department, Baoshan Iron and Steel Co Ltd. Shanghai 3. Shanghai Baosteel Tiantong Magneitic Materials Co Ltd. Shanghai 201900. China)
Abstract: The ferrites of PC30 (Mn-Zn ferrites) were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H 3 B0 3 was investigated on the basis of microstructure analysis. The results of the samples doped with H 3B03 less than 5XlO- 5 showed that the doping had no significant effect on power loss. initial permeability, fine grain microstructure. and density of Mn-Zn ferrites. With the further increase in H, BO" doping (up to 1 X 10-'\), the microstructure of Mn-Zn ferrites is in the critical state between fine grain and "sandwich". and the initial permeability and density of Mn-Zn ferrites begin falling quickly; the increased H,B0 3 doping also results in deteriorated power loss properties. Thus. the control of the boron content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process. Key words: iron oxide; Mn-Zn ferrite; boron content; initial permeability
Recently, electric components of soft magnetic ferrites are becoming smaller and thinner in size with the updated progress of technology to meet portable electronic equiprnent-U. The ferrites with properties on usage, such as high frequency, low power waste, and high permeability, will be the future trends. Also, nano magnetic ferrites need further investigation[2J. To get high performance with iron oxide, which is the main raw materiel of soft magnetic ferrite material accounting for about 70 % of ferrite component by mass[I,3J, some special physical and chemical properties are demanded'<":". The purity and chemical homogeneity of iron oxide which is used to manufacture high grade Mn-Zn ferrites will be higher than ever[4-5J. Presently, the iron oxide used for magnetic ferrite material is generally manufactured by purifying waste pickling acid (ferrous chloride solution) generated from steelmaking plant, and then by spray-roasting the purified ferrous chloride solutionl'", When the iron oxide is generated by steelmaking process, some residual elements, such as AI, st. S, Mn, Mg. Na, P, c-. Ni, and c«. etc. , will be mixed in. In some cases, B, Ca , Ti , Biography: YU Cheng-feng0974-). Male. Doctor Candidate. Engineer;
Nb , and V elements are also taken into the manufacture process of the iron oxide. Magnetic properties of Mn-Zn ferrites can be improved with some trace impurity elements in the raw material of iron oxide[7-9 J. However, the magnetic properties of MnZn ferrites will be deteriorated rapidly with the increase in the content and type of impurity elements in the iron oxide-". Several studies on the effects of doping with small amount of the additives to Mn-Zn ferrites have been carried out[7-IOJ. By using a citrate gel processing route to prepare the Mn-Zn Ierrites , Fan, et al[1I-12J have studied the relationship between the microstructure, magnetic properties, and impedance spectroscopy of Mn-Zn ferrites doped with B2 0 3 (up to O. 5 %). The sol-gel chemical preparation can be used for powder preparation to yield chemically homogeneous and high purity powder[IO.13-14J, but traditional dry method process (ceramic process) has the advantage of high efficiency and low cost[I5 J. However, by using traditional dry method process to manufacture the Mn-Zn Ierrites , the influence of doping boron in iron oxide on the properties of MnE-mail: [email protected];
Received Date, October 7. 2008
journal of Iron and Steel Research, International
• 60 •
Zn ferrites is unclear. To ameliorate steel product specifications. boron is often added in the steelmaking process. Thus. it is necessary to investigate the effects of boron in iron oxide on the preparation of Mn-Zn ferrites by using dry method process.
1 1. 1
der from each batch. by using a specially designed hydraulic presser. Subsequently. the ring samples were sintered at peak temperatures of 1380 C using a specially constructed programmable kiln. The spray-roasted iron oxides were analyzed by using ICP-emission spectroscopy type Varian Vista PRO. The final density of the specimens was measured by the Archimedes method using distilled water as the immersion fluid. The electric and magnetic properties of the specimens were measured by an Agilent HP4284ALCR. The power losses were measured using an IW A TSU SY8232 B- H. The microstructures of the sintered samples were examined by using optical and scanning electron microscope (SEM). and pictures were taken by using a JEOL 6460LV scanning electron microscopy.
Experimental Process route
Presently. the main methods for preparing manganese-zinc ferrite materials include traditional dry method process (ceramic process) and wet method process. The wet method process is easy to control and has high chemical homogeneity of product. But the dry method process has the advantages of high efficiency and low cost. In this study. the Mn-Zn ferrite of PC30 was synthesized and investigated by using the manufacturing procedure of dry method process which include weighing and wet mixing of Fez 0" • Mn:,OI' ZnO. and HIBO". prefiring , coarse pulverizing. fine pulverizing. spray granulation. pressing. and sintering , etc. 1. 2
2
One of the specific issues when dealing with soft magnetic ceramics such as Mn-Zn ferrites is that their properties depend strongly on parameters other than their main composition. such as density. microstruct ure , and grain boundary structure. etc. Dopants have. in genera], also influence on the microstruct ural properties and therefore may affect the magnetic performance in an indirect way[16]. Power loss. initial permeability. final density. and microstructures of Mn-Zn ferrites for different boron doping levels of all six batches are shown in Table 1. From Table 1. it can be concluded that the microstructure of the Mn-Zn ferrite specimens may be considered almost as critical state between fine grain and .. sandwich" with the addition of small amounts of H, BO, up to 1 X 10- I. Further increasing the H 3 BO"
Six experimental syntheses of Mn-Zn Ierrires were performed by using the Mn-Zn ferrite formulas of PC30. and the H, BO, (99.5 % in purity) was used as boron dopant. which also dissolved in the mixed ferrite powders to give different boron doping levels (presented in Table 1). The raw materials used were Fez()", Mn:IOI' and ZnO supplied separately by steel factory (spray-roasted iron oxides). Kingray New Materials Science and Technology Company and GMP (Analytical Grade). The ring samples of 25 mm in outer diameter. 15 mm in inner diameter. and 10 mm in height were shaped by uniaxially pressing at 500 kg/ ern" of the granulated pow-
Dopant 110 "
()
0
50
Results and Discussion
2. 1 Effect of boron doping level on power loss. 101tial permeability. final density. and microstructures of Mn-Zn ferrites
Materials and methods
Table 1
Vol. 17
Power loss, initial permeability, final density. and microstructures of Mn-Zn ferrites for different boron doping levels of all six batches
Initial permeability! (H'm- I )
Density;'
Power loss at 25kHz and 200mT/(mW· ern
")
Micros t ruct ure
(g' cm ":")
21 C
60 C
2,,80
1.77
92
56
90
Fine grain
2866
l. 811
93
58
88
Fine grain
80 C
100
18
27] 7
I. 8:,
98
61
92
150
26
2070
'I. 76
23]
200
256
Surface fine grain
200
35
] 823
I. 71
229
208
260
Inherent large grain
335
62
1514
I. 69
266
2,11
:306
Large grain
Fine grain or sandwich II
Note: 1) In some kilns, the microstructure of the MnZn [erritcs is fine grain. while in other kilns. the microstructure is surface fine grain and inherent large grain. which is called "sandwich".
Influence of Boron Content in Iron Oxide on Performance of Mn- Zn Ferrites
Issue 2
doping level (more than 1. 5 X 10- 4 ) , the microstructure of the Mn-Zn ferrite specimens shows "sandwich" and even totally large grain. Fig. 1 shows the relationship between power loss and temperature with different H:, B03 content doping levels, and Fig. 2 shows the relationship between the power loss and the H 3 B0 3 doping levels. The samples have the lowest values of power loss at 60'C in all measuring H 3 B0 3 doping levels, and the variation of power loss is very small. The power loss increases rapidly at small doping levels (more than lXl0- 1 ) . Fig. 3 shows the relationship between the initial permeability and final density with different H,BO, content doping levels. The initial permeability increases sharply with small amounts of HI B03 additions (less than 1 X 10- 1 ) , and the final density also increases with small amounts of H 3 B(\ additions (less than 5 X 10- 5 ) . The initial permeability and final density decrease rapidly at small H 3 B03 doping levels (more than 1 X 10- 4 ). 300 C'
.~
f
250 200
H,BO:, content/% ......... 0 0.015 __ O.OO!) 0.020 ~ 0.010 --- 0.0:3:1!)
150
t
~
100 50
......
'-'-------~'-------'----_
20
Fig. 1
40 60 Temperature/ 'C
80
Variation of power loss with temperature and H3803 content for Mn-Zn ferrites
250
60 'C, 25 kHz, 200 mT
f"
B 200
I
lW
~ 100
cf
50 L..-_
o Fig.2
___'~
0.005
_
___'~
0.010
_
___'_ _
0.015 H:3803 contentlYo
~
_ _.............
0.020 0.0335
Variation of power loss with H3 8 03 content for Mn-Zn ferrites
4000
c- 3500
's
• 61 •
4.85
4.80
:i: ~ 3000
~E 2500
'""' '7
B
4.75 ~
>. .~
Q.I
0-
]
:5
4.70
Q
2000 1 500 L . . - _ - - ' -_ _~_ _'___ __'__ _""4.65 o 0.005 O.OlO 0.015 0.020 0.0335 Ha80:1 contentlYo
Fig.3
Variation of initial permeability and density with H3 8 03 content for Mn-Zn ferrites
2.2 Microstructural properties of Mn-Zn ferrites doped with boron Fig. 4 shows the typical optical micrographs of the samples. The undoped sample [Fig. 4 (a), boron-free] has a uniform microstructure. These small grains are nearly pore-free, and the average grain size is between 10 J1.m and 18 J1.m. At 1. 5 X 10- 5 of boron doping level, the sample [Fig. 4 (b)] shows a duplex structure which includes fine grain and large grain. With boron doping, the SEM micrographs [Fig. 4 (c). boron doping level of 2. 5 X 10- 5] only show a part of the large grains. These large grains include also plenty of pores, and the size of these large grains can hardly be identified. The solid iron oxide (Fe2 ( 3 ) powder used for Mn-Zn ferrite preparation is prepared by pickling spray-roasting in air at temperatures of 300 - 600 'C[17J . The boron element in iron oxides is oxidized at high temperature, and the melting point of B20 3 is only 450 'C. In the process of calcination and agglomeration, the B20 1 is in liquid, which can quickly increase the reaction speed and promote the grain particles growth. The impurity ions present in small amounts in the iron oxide (e. g. Si , Ca , P, etc. ) have positive effect on its reactivity and consequently on the densification of the ferrites[17 J. Small amounts of boron in iron oxide can make calcium and silicon impurity content uniform in Mn-Zn ferrites samples; the magnetic properties are fine, and the microstructure shows fine grain. However, a microstructure showing discontinuous grain growth is observed at relative high amounts of boron in Mn-Zn ferrites samples, and plenty of pores were interfused. These
Journal of Iron and Steel Research. International
• 62 •
(a) Boron-Iree ,
Fig.4
(b) Boron doping of 1. 5X 10-";
[5J
for a Rosy Future [6J
Conclusions
[JJ.
HUA:--JG Ai-ping , HE Hua-hui , FENG Ze-kun • et al. Effects meability [j]. J Huazhong Univ of Sci and Tech: Nature Science Edition. 2006. 3H2): 39 (in Chinese).
[8J
SlJ Hua . ZHA:'J(; Huai-wu , TA:--JG Xiao-Ii. Effects of CuO, MoO" and WO" Doping on Magnetic Properties of NiZn Ferrites
[JJ.
Chinese Journal of Materials Research. 2005. 19(5):
5·19 (in Chinese). [9J
DAI Yu-hui , WEI Xu-boo SlJ Hua . et al, Effects of P,O" Addition on the Properties of High Permeability Mn Zn Ferrite
[JJ.
Journal of Magnetic Materials and Devices. 2005. 36(2): 29 (in Chinese).
[IOJ
Goldman A. Modern Ferrite Technology [M]. New York: Van Nostrand Rein- Hold. 1990.
[11 J
Fan J. Sale F R. Influence of H,O" on the Production of Pure. Gel-Processed Mn-Zn Ferrites
[12J
[JJ.
J Phys , 1997.4(7): 81.
Fan J. Sale F R. The Microstructures. Magnetic Properties and Impedance Analysis of Mn-Zn Ferrites Doped With H2 0 ,
[JJ.
Journal of the European Ceramic Society, 2000. 20( 16):
27.l3. [13J
SHI Xin-yu . WlJ Dong-hui , JI:--J Rui-di. et al. Preparation of Nano-Maghernit e by Citrate-Gel Process [JJ. Inorganic Chemical Industry. 2006. 38( 12): 16 (in Chinese). JING Mao-xiang , SHE:--J Xiang-qian , SHE:--J Yu-jun. Prepa-
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It is believed that the key issue of .. sandwich" and large grain in manganese zinc Ierrites is relative high boron content in the raw materials of pickling spray-roasted iron oxides. When the boron dopant is below 1. 0 X 10 - 0 • the magnetic properties and microstructure of manganese zinc ferrites is fine. But boron added in manganese zinc Ierrites in quantities up to 1. 5 X 10-' acts as .. sandwich" or large grain element. which promotes grain growth and deteriorates magnetic properties. To obtain either low magnetic power losses or high magnetic permeabilities in Mn-Zn Ierrites for low or high frequency applications. the iron oxide used for the preparation should be of low impurity. and the amount of boron in iron oxide should be no more than 1. 0 X 10-'; .
[IJ
Boron doping of 2. 5X 10-'-'.
SEM micrographs of Mn-Zn ferrites materials with different boron contents
will result in the deterioration of magnetic properties and decrease the final density rapidly.
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