WO2013149574A1

WO2013149574A1 - Nickel-zinc soft ferrite and method of producing the same

Info

Publication number: WO2013149574A1
Application number: PCT/CN2013/073582
Authority: WO
Inventors: Bin Xu; Qijun XIANG
Original assignee: Shenzhen Byd Auto R&D Company Limited; Byd Company Limited
Priority date: 2012-04-01
Filing date: 2013-04-01
Publication date: 2013-10-10
Also published as: CN103360042A

Abstract

A nickel-zinc soft ferrite is provided. The nickel-zinc soft ferrite comprises: a main component comprising 51-52 mol% of Fe₂O_3, 14.5-16 mol% of NiO, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and an auxiliary component comprising A1₂O₃, V₂O₅ and CaO. A method of producing the nickel-zinc soft ferrite is also provided.

Description

NICKEL-ZINC SOFT FERRITE AND METHOD OF PRODUCING THE SAME

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and benefits of Chinese Patent Application No. 201210094838.2, filed with the State Intellectual Property Office of P. R. C. on April 1, 2012, the entire contents of which are hereby incorporated by reference.

FIELD

The present disclosure relates to a field of soft magnetic material, and more particularly to a nickel-zinc soft ferrite.

BACKGROUND

In order to increase the communication distance of an antenna module, a magnetic core component is added between the antenna module and a metal module, and a magnetic powder with a high magnetoconductivity is used as the material of the magnetic core component. A magnetic sheet obtained by mixing a ferrum-silicon-aluminum alloy with an organic system is widely applicable. A material obtained by sintering a ferritic powder is used as the material of the magnetic core, the magnetoconductivity of which is higher than that of the ferrum-silicon-aluminum alloy. Ferritic materials with different components have different magnetic performances. Although a magnetic sheet made of a conventional soft ferrite has a relatively high magnetoconductivity when having a relatively large thickness, for example, larger than 0.5 mm to meet the requirement of the communication distance, the magnetic sheet may not have a relatively high magnetoconductivity when having a relatively small thickness. Thus, the trend of miniaturization of a portable information terminal may not be coped with.

SUMMARY

The present disclosure is directed to solve at least one of problems in the prior art such as a fact that the magnetic sheet may not have a relatively high magnetoconductivity when having a relatively small thickness.

According to embodiments of the present disclosure, a nickel-zinc soft ferrite is provided, comprising: a main component comprising 51-52 mol% of Fe20₃, 14.5-16 mol% of NiO, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and an auxiliary component comprising AI2O₃, V2O5 and CaO.

According to embodiments of the present disclosure, the nickel-zinc soft ferrite has a relatively high Fe203 content, and Fe²⁺ ions produced during the sintering process make up the magnetocrystalline anisotropic constant of the ferrite by its own positive magnetocrystalline anisotropic constant, so as to improve the magnetoconductivity. However, it has been found by the inventors that the magnetoresistance of the magnetic sheet may increase with an increase of the content of Fe²⁺, so that the magnetic loss may increase. Thus, according to embodiments of the present disclosure, the content of CuO also increases, so as to reduce the magnetoresistance of the magnetic sheet and thus reduce the magnetic loss. Since sintered crystalline grains grow anomaly with an increase of the content of CuO to affect the magnetic performance and mechanical property of the ferrite, a trace amount of AI2O₃ is added to control the growth of the crystalline grains effectively. In the present disclosure, the content of ZnO is reduced to increase the Curie temperature of the ferrite and improve the performance of the ferrite. According to embodiments of the present disclosure, the content of O is optimized to ensure a relatively high magnetic performance of the ferrite. An auxiliary component comprising AI2O₃ and CaO may enter into a grain boundary of the ferritic material, so that the grain boundary resistivity of the ferritic material will be significantly increased and the quality factor of the ferritic material may be increased. With the nickel-zinc soft ferrite according to embodiments of the present disclosure, a magnetic sheet with a thickness smaller than 0.2 mm may be produced by casting, and the antenna module comprising the magnetic sheet may have a large communication distance. For example, in one embodiment, a magnetic sheet with a thickness of 0.10± 0.01 mm may be produced, and the communication distance of an antenna module comprising the magnetic sheet may reach 67 mm.

In one embodiment, the auxiliary component comprises 0.1-1 mol% of AI2O₃, 0.1-1 mol% of V2O5, and 0.1-1 mol% of CaO. The content of the auxiliary component may not be too high, otherwise, blowholes will be formed in the magnetic sheet after sintering, so that the magnetic performance and mechanical property of the magnetic sheet may be affected adversely.

In one embodiment, the auxiliary component further includes 0.1-1 mol% of Mn0₂ and 0.1-1 mol% of B12O₃. Mn0₂ and B12O₃ enter into a liquid phase at a relatively low sintering temperature, so as to improve the density and mechanical strength of the magnetic sheet and enhance the initial magnetoconductivity. In one embodiment, a total content of the auxiliary component in the nickel-zinc soft ferrite is 0.1-1 mol%. The content of the auxiliary component should be controlled in a certain range. If the content of the auxiliary component is too high, the magnetic performance and mechanical property of the magnetic sheet may be affected adversely.

According to embodiments of the present disclosure, a method of producing a nickel-zinc soft ferrite is provided, steps of:

weighing metal oxides according to a content of each metal oxide, and wet ball-milling the metal oxides to obtain a first powder;

drying the first powder;

pre-sintering the dried powder;

ball-milling the pre-sintered powder to obtain a second powder having a predetermined particle size;

mixing the second powder with an organic system and casting to obtain ferritic slabs;

laminating the ferritic slabs; and

sintering the laminated ferritic slabs to form the nickel-zinc soft ferrite.

According to embodiments of the present disclosure, since the ferritic slabs are obtained by casting, a magnetic sheet with a thickness smaller than 0.1 mm may be produced, and the ferrite powder grains are distributed in the slurry uniformly, so as to ensure a relatively high uniformity and a relatively high magnetoconductivity of the magnetic sheet.

In one embodiment, the nickel-zinc soft ferrite comprises a main component comprising

51-52 mol% of Fe₂0₃, 14.5-16 mol% of NiO, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and an auxiliary component comprising AI2O₃, V2O5 and CaO.

With the method of producing the nickel-zinc soft ferrite according to embodiments of the present disclosure, by optimizing the content of metal oxides in the nickel-zinc soft ferrite, a long communication distance of the antenna module may be ensured when the magnetic sheet has a relatively small thickness. The nickel-zinc soft ferrite has a relatively high Fe₂0₃ content, and Fe²⁺ ions produced during the sintering process make up the magnetocrystalline anisotropic constant of the ferrite by its own positive magnetocrystalline anisotropic constant, so as to improve the magnetoconductivity. However, it has been found by the inventors that the magnetoresistance of the magnetic sheet may increase with an increase of the content of Fe²⁺, so that the magnetic loss may increase. Thus, according to embodiments of the present disclosure, the content of CuO also increases, so as to reduce the magnetoresistance of the magnetic sheet and thus reduce the magnetic loss. Since sintered crystalline grains grow anomaly with an increase of the content of CuO to affect the magnetic performance and mechanical property of the ferrite, a trace amount of AI2O3 is added to control the growth of the crystalline grains effectively. In the present disclosure, the content of ZnO is reduced to increase the Curie temperature of the ferrite and improve the performance of the ferrite. According to embodiments of the present disclosure, the content of NiO is optimized to ensure a relatively high magnetic performance of the ferrite. An auxiliary component comprising AI2O₃ and CaO may enter into a grain boundary of the ferritic material, so that the grain boundary resistivity of the ferritic material will be significantly increased and the quality factor of the ferritic material may be increased. With the nickel-zinc soft ferrite according to embodiments of the present disclosure, a magnetic sheet with a thickness smaller than 0.2 mm may be produced by casting, and the antenna module comprising the magnetic sheet may have a large communication distance.

In one embodiment, the auxiliary component further includes 0.1-1 mol% of Mn0₂ and 0.1-1 mol% of B12O₃. Mn0₂ and B12O₃ enter into a liquid phase at a relatively low sintering temperature, so as to improve the density and mechanical strength of the magnetic sheet and enhance the initial magnetoconductivity.

In one embodiment, a total content of the auxiliary component in the nickel-zinc soft ferrite is 0.1-1 mol%. The content of the auxiliary component should be controlled in a certain range. If the content of the auxiliary component is too high, the magnetic performance and mechanical property of the magnetic sheet may be affected adversely. If the content of the auxiliary component is too low, the corresponding function of the auxiliary component may not be achieved.

In one embodiment, the method further comprises a step of dicing the laminated ferritic slabs, so as to avoid the warping of ferritic slabs during the sintering process and facilitate the subsequent assembly of the products. Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flow chart of a method of producing a nickel-zinc soft ferrite according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The aforementioned features and advantages of the present disclosure as well as the additional features and advantages thereof will be further clearly understood hereafter as a result of a detailed description of the following embodiments when taken in conjunction with the drawings.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. In case of conflict, the specification, including definitions, will control.

According to embodiments of the present disclosure, a nickel-zinc soft ferrite is provided, comprising: a main component comprising 51-52 mol% of Fe₂0₃, 14.5-16 mol% of O, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and an auxiliary component comprising 0.1-1 mol% of A1₂0₃, 0.1-1 mol% of V2O5, 0.1-1 mol% of CaO, 0.1-1 mol% of Mn0₂ and 0.1-1 mol% of Bi₂0₃. The total content of the auxiliary component in the nickel-zinc soft ferrite is 0.1-1 mol%.

As shown in Fig. 1, according to embodiments of the present disclosure, a method of producing a nickel-zinc soft ferrite is provided, comprising steps of:

weighing oxides according to a content of each oxide, and wet ball-milling the oxides at a rotational speed ranging from 200 r/min to 400 r/min for 4 hours to 12 hours to obtain a first powder;

drying the first powder at a temperature ranging from 40°C to 120°C for 2 hours to 8 hours; pre-sintering the dried powder by increasing the temperature at a heating rate of l-5°C/min to 1000-1100°C, keeping the temperature at 1000-1100°C for 1 hour to 4 hours, and then cooling the heated powder;

ball-milling the pre-sintered powder at a rotational speed of 300-500 r/min for 8 hours to 14 hours to obtain a second powder having a predetermined particle size ranging from 2 μιη to 5 μιη; mixing the second powder with an organic system to obtain a slurry, ball-milling and defoaming the slurry, and then casting to obtain ferritic slabs with a thickness ranging from 0.05 mm to 0.08 mm;

drying and cutting the ferritic slabs, and then laminating two ferritic slabs under a pressure of 5-50 MPa for 0.5 minutes to 5 minutes; and

sintering the laminated ferritic slabs by increasing the temperature at a heating rate of 0.5-3°C/min to 250°C, keeping the temperature at 250°C for 20 minutes to 100 minutes, increasing the temperature at a heating rate of 0.5-3°C/min to 600°C, keeping the temperature at 600°C for 20 minutes to 100 minutes, increasing the temperature at a heating rate of 0.5-3°C/min to 900°C, keeping the temperature at 900°C for 20 minutes to 100 minutes, increasing the temperature at a heating rate of 0.5-3°C/min to a highest temperature ranging from 1050°C to 1150°C, keeping the temperature at 1050-1150°C for 60 minutes to 180 minutes, and then cooling the heated ferritic slabs to form a nickel-zinc soft ferrite (i.e., a magnetic sheet).

In some embodiments, the organic system contains a solvent, a binding agent, and a plasticizing agent. The solvent is a mixture of ethanol and methylbenzene, the binding agent is polyvinylbutyral, and the plasticizing agent is dibutyl-o-phthalate.

In one embodiment, preferably, the method further comprises a step of dicing the laminated ferritic slabs to form a quadrate lattice of (0.5-3 mm) x (0.5-3 mm), with a cutting depth being one-third to a half as large as the thickness of each slab.

According to embodiments of the present disclosure, the nickel-zinc soft ferrite has a relatively high Fe2C>3 content, and Fe²⁺ ions produced during the sintering process make up the magnetocrystalline anisotropic constant of the ferrite by its own positive magnetocrystalline anisotropic constant, so as to improve the magnetoconductivity. However, it has been found by the inventors that the magnetoresistance of the magnetic sheet may increase with an increase of the content of Fe²⁺, so that the magnetic loss may increase. Thus, according to embodiments of the present disclosure, the content of CuO also increases, so as to reduce the magnetoresistance of the magnetic sheet and thus reduce the magnetic loss. Since sintered crystalline grains grow anomaly with an increase of the content of CuO to affect the magnetic performance and mechanical property of the ferrite, a trace amount of AI2O₃ is added to control the growth of the crystalline grains effectively. In the present disclosure, the content of ZnO is reduced to increase the Curie temperature of the ferrite and improve the performance of the ferrite. According to embodiments of the present disclosure, the content of O is optimized to ensure a relatively high magnetic performance of the ferrite. An auxiliary component comprising AI2O₃ and CaO may enter into a grain boundary of the ferritic material, so that the grain boundary resistivity of the ferritic material will be significantly increased and the quality factor of the ferritic material may be increased. With the nickel-zinc soft ferrite according to embodiments of the present disclosure, a magnetic sheet with a thickness smaller than 0.1 mm may be produced by casting, and the antenna module comprising the magnetic sheet may have a large communication distance.

The present disclosure will be described in further detail below by making reference to the following Examples.

Example 1

A nickel-zinc soft ferrite comprises a main component comprising 51.5 mol% of Fe2C>3, 14.5 mol% of O, 16 mol% of ZnO, and 17 mol% of CuO; and an auxiliary component comprising 0.4 mol% of AI2O₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of A method of producing the nickel-zinc soft ferrite comprises steps of:

weighing metal oxides according to the above content of each metal oxide, and wet ball-milling the metal oxides at a rotational speed of 200 r/min for 12 hours to obtain a first powder;

drying the first powder at a temperature of 120°C for 4 hours;

pre-sintering the dried powder by increasing the temperature at a heating rate of 2°C/min to

1050°C, and then keeping the temperature at 1050°C for 2 hours, and then cooling the heated powder;

ball-milling the pre-sintered powder at a rotational speed of 400 r/min for 10 hours to obtain a second powder;

mixing the second powder with an organic system, and then casting to obtain ferritic slabs with a thickness of 0.08 mm, in which the organic system contains a solvent being a mixture of ethanol and methylbenzene, a binding agent being polyvinylbutyral, and a plasticizing agent being dibutyl-o-phthalate;

laminating two ferritic slabs under a pressure of 30 MPa for 5 minutes; dicing the laminated ferritic slabs with a hot cutting machine to form a quadrate lattice of 2 mmx 2 mm on a surface of the slab, with a cutting depth being one -third as large as the thickness of each slab; and

sintering the laminated ferritic slabs by increasing the temperature at a heating rate of l°C/min to 250°C, keeping the temperature at 250°C for 60 minutes, increasing the temperature at a heating rate of l°C/min to 600°C, keeping the temperature at 600°C for 60 minutes, increasing the temperature at a heating rate of l°C/min to 900°C, keeping the temperature at 900°C for 30 minutes, increasing the temperature at a heating rate of l°C/min to a highest temperature of 1050°C, keeping the temperature at 1050°C for 120 minutes, and then cooling the heated ferritic slabs to form the nickel-zinc soft ferrite (i.e., a magnetic sheet) with a thickness of 0.10± 0.01 mm.

Example 2

A nickel-zinc soft ferrite comprises a main component comprising 52 mol% of Fe₂03, 14.5 mol% of NiO, 15 mol% of ZnO, and 17.5 mol% of CuO; and an auxiliary component comprising 0.4 mol% of A1₂0₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of

The nickel-zinc soft ferrite is produced by a method substantially similar to that in Example

1.

Example 3

A nickel-zinc soft ferrite comprises a main component comprising 51 mol% of Fe₂03, 14.5 mol% of NiO, 17 mol% of ZnO, and 16.5 mol% of CuO; and an auxiliary component comprising 0.4 mol% of A1₂0₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of Bi₂0₃.

1.

Example 4

A nickel-zinc soft ferrite comprises a main component comprising 51.5 mol% of Fe₂0₃, 15.5 mol% of NiO, 18 mol% of ZnO, and 14 mol% of CuO; and an auxiliary component comprising 0.4 mol% of A1₂0₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of Bi₂0₃.

1. Example 5

A nickel-zinc soft ferrite comprises a main component comprising 51.5 mol% of Fe₂0₃, 14.5 mol% of NiO, 16 mol% of ZnO, and 17 mol% of CuO; and an auxiliary component comprising 0.4 mol% of A1₂0₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of Bi₂0₃.

Ferritic slabs formed by casting have a thickness of 0.05 mm, the magnetic sheet (i.e., the nickel-zinc soft ferrite) has a thickness of 0.065± 0.01 mm, and other steps in the method of forming the nickel-zinc soft ferrite are substantially similar to those in Example 1.

Comparative Example 1

A Fe-Si-Al magnetic alloy comprises 85 wt% of Fe, 9.5 wt% of Si and 5.5 wt% of Al.

A method of producing the Fe-Si-Al magnetic alloy comprises steps of:

weighing oxides according to the content of each oxide, and wet ball-milling the oxides at a rotational speed of 500 r/min for 12 hours to obtain a first powder, with a ratio of a ball to oxides being 5:1;

drying the first powder at a temperature of 80°C for 2 hours to obtain a second powder;

mixing the second powder with an organic system, and then casting to obtain slabs with a thickness of 0.1 mm;

laminating four ferritic slabs under a pressure of 20 MPa at a temperature of 120°C for 4 minutes to form a Fe-Si-Al magnetic alloy (i.e., a magnetic sheet) with a thickness of 0.20± 0.01 mm.

Comparative Example 2

A nickel-zinc soft ferrite comprises a main component comprising 49.3 mol% of Fe₂0 , 28.9 mol% of NiO, 12.6 mol% of ZnO, and 9.2 mol% of CuO; and an auxiliary component comprising 0.4 mol% of A1₂0₃, 0.2 mol% of V₂0₅, 0.15 mol% of CaO, 0.1 mol% of Mn0₂ and 0.15 mol% of Bi₂0₃.

The nickel-zinc soft ferrite is formed by a method substantially similar to that in Example 1. Performance Test

The magnetic sheets and the antenna modules comprising the magnetic sheets in Examples 1-5 and Comparative Examples 1-2 were tested as follows.

1. Complex permeability test was carried out by using E4991 impedance analyzer commercially available from American Aglient and magnetic permeability measurement special fixture 16454A. Each material to be tested was made into a three-dimensional circular ring as a single-turn coil. The inductance of the coil was obtained by testing its impedance, and then the magnetoconductivity of the tested material was calculated and the variation trend of the complex permeability at a frequency ranging from 1 M to 1 G was given. Since the experiment was applied to a frequency of 13.56 MHz, the complex permeability at a frequency of 13.56 MHz was taken.

2. Test of the characteristics of the antenna modules was carried out by using E4991 impedance analyzer commercially available from American Aglient to obtain the values of L, R and Q of the antenna modules at a frequency of 13.56 MHz.

3. Test of the communication distance of the antenna modules was carried out by using a self-made communication distance tester comprising a fixture movable up and down, a phone having a near field communication function, and a standard card. The phone was fixed on the fixture, the fixture was close to the standard card, and the communication was realized and a prompt signal was generated when the phone was at a certain distance from the standard card. This distance was the communication distance of each antenna module.

Results were shown in Table 1.

Table 1

It may be seen from Table 1 that, with the nickel-zinc soft ferrite according to embodiment of the present disclosure, when the auxiliary components of the nickel-zinc soft ferrites are identical, the performances of the magnetic cores vary depending on different main components of the nickel-zinc soft ferrites. In Example 1, the magnetic core material has a relatively high quality factor, i.e., a relatively high magnetoconductivity and a relatively low magnetic loss, and the communication distance of the antenna module may reach 67 mm when the magnetic sheet has a thickness of 0.10± 0.01 mm.

The content of the components of the nickel-zinc soft ferrite in Example 5 is substantially similar to that of the components of the nickel-zinc soft ferrite in Example 1, but the magnetic sheet obtained in Example 5 is thinner than that obtained in Example 1 , so that the communication distance of the antenna module in Example 5 is shorter than that of the antenna module in Example 1.

The performance of the magnetic sheets and the antenna modules comprising the magnetic sheets in Examples 1-5 are better than that of the magnetic sheets and the antenna modules comprising the magnetic sheets in Comparative Examples 1-2. The components of the nickel-zinc soft ferrite in Comparative Example 2 are identical with the components of the nickel-zinc soft ferrites in Examples 1-5, but the content of the components of the nickel-zinc soft ferrite in Comparative Example 2 is different from that of the components of the nickel-zinc soft ferrites in Examples 1-5, so that the quality factor of the magnetic core in Comparative Example 2 is smaller than that of the magnetic cores in Examples 1-5 and the communication distance of the antenna module in Comparative Example 2 is shorter than that of the antenna modules in Examples 1 -5.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments can not be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.

Claims

WHAT IS CLAIMED IS:

1. A nickel-zinc soft ferrite, comprising:

a main component comprising 51-52 mol% of Fe2C>3, 14.5-16 mol% of NiO, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and

an auxiliary component comprising AI2O₃, V2O5 and CaO.

2. The nickel-zinc soft ferrite according to claim 1, wherein the auxiliary component comprises 0.1-1 mol% of A1₂0₃, 0.1-1 mol% of V₂0₅, and 0.1-1 mol% of CaO.

3. The nickel-zinc soft ferrite according to claim 1, wherein the auxiliary component further includes 0.1-1 mol% of Mn0₂ and 0.1-1 mol% of Bi₂0 .

4. The nickel-zinc soft ferrite according to any one of claims 1-3, wherein a total content of the auxiliary component in the nickel-zinc soft ferrite is 0.1-1 mol%.

5. A method of producing a nickel-zinc soft ferrite, comprising steps of:

drying the first powder;

pre-sintering the dried powder;

laminating the ferritic slabs; and

sintering the laminated ferritic slabs to form the nickel-zinc soft ferrite.

6. The method according to claim 5, wherein the nickel-zinc soft ferrite comprises a main component comprising 51-52 mol% of Fe₂0₃, 14.5-16 mol% of NiO, 15-18 mol% of ZnO, and 14-18 mol% of CuO; and an auxiliary component comprising Al₂03, V₂Os and CaO.

7. The method according to claim 6, wherein the auxiliary component comprises 0.1-1 mol% of A1₂0₃, 0.1-1 mol% of V₂0₅, and 0.1-1 mol% of CaO.

8. The method according to claim 6, wherein the auxiliary component further includes 0.1-1 mol% of Mn0₂ and 0.1-1 mol% of Bi₂0₃.

9. The method according to any one of claims 6-8, wherein a total content of the auxiliary component in the nickel-zinc soft ferrite is 0.1-1 mol%.

10. The method according to claim 5, further comprising a step of dicing the laminated ferritic slabs.