CN114133231A

CN114133231A - Nickel-zinc ferrite material and method for producing same

Info

Publication number: CN114133231A
Application number: CN202111305139.3A
Authority: CN
Inventors: 郭海; 聂敏; 朱晏军
Original assignee: Shenzhen Sunlord Electronics Co Ltd
Current assignee: Shenzhen Sunlord Electronics Co Ltd
Priority date: 2021-11-05
Filing date: 2021-11-05
Publication date: 2022-03-04

Abstract

The application discloses a nickel-zinc ferrite material and a manufacturing method thereof. The nickel-zinc ferrite material comprises a main component, an additive and a glass frit, wherein the main component comprises the following components in percentage by weight: 65 wt% -66.5 wt% of Fe₂O₃9.5 to 11.0 weight percent of NiO, 19.5 to 21.5 weight percent of ZnO and 3.4 to 4.6 weight percent of CuO; the additive comprises: 0.2 wt% -0.4 wt% of Co₂O₃0.2 to 0.8 weight percent of glass material; the glass frit comprises the following components in percentage by weight: 60 to 70 weight percent of Bi₂O₃8 to 15 weight percent of ZnO and 5 to 15 weight percent of B₂O₃1 to 5 weight percent of SiO₂And 1-2 wt% of CuO. The method can improve the phenomenon of creeping plating, and the prepared crystal grains are fine and uniform.

Description

Nickel-zinc ferrite material and method for producing same

Technical Field

The application relates to the field of ferrite materials, in particular to a nickel zinc (NiZn) ferrite material and a manufacturing method thereof.

Background

At present, a sheet type ferrite material is generally formed by sintering, a small amount of metal ions which do not enter crystal lattices can remain in a magnet after sintering, a small amount of metal ions can exist on the surface of the magnet, and in the electroplating process of the magnet, a terminal electrode of a product is used as a cathode, and the metal ions on the surface of the magnet are subjected to a reduction reaction and are converted into metal atoms for deposition. These reduced metal atoms also serve as plating cathodes during plating, which are called plating-over substrates, and cause nickel metal atoms and tin metal atoms to be continuously deposited, thereby generating a plating-over phenomenon. The creeping plating phenomenon can greatly influence the quality and the performance of the plating layer of the product.

Disclosure of Invention

The embodiment of the application provides a nickel-zinc ferrite material and a manufacturing method thereof, which are used for improving the creeping plating phenomenon.

In a first aspect, an embodiment of the present application provides a nickel-zinc ferrite material, including a main component, an additive, and a glass frit, where the main component includes, by weight: 65 wt% -66.5 wt% of Fe₂O₃9.5 to 11.0 weight percent of NiO, 19.5 to 21.5 weight percent of ZnO and 3.4 to 4.6 weight percent of CuO; the additive comprises: 0.2 wt% -0.4 wt% of Co₂O₃0.2 to 0.8 weight percent of glass material; the glass frit comprises the following components in percentage by weight: 60 to 70 weight percent of Bi₂O₃8 to 15 weight percent of ZnO and 5 to 15 weight percent of B₂O₃1 to 5 weight percent of SiO₂And 1-2 wt% of CuO.

In some embodiments, the principal component, the additive, and the glass frit satisfy at least one of: fe₂O₃Has a purity of greater than or equal to 99.5 wt%; the purity of NiO is more than or equal to 99.5 wt%; the purity of ZnO is more than or equal to 99.5 wt%; the purity of CuO is greater than or equal to 99.5 wt%; co₂O₃Has a purity of greater than or equal to 99.5 wt%; bi₂O₃Has a purity of greater than or equal to 99.5 wt%; b is₂O₃Has a purity of greater than or equal to 99.5 wt%; SiO 2₂Has a purity of greater than or equal to 99.5 wt%.

In some embodiments, the nickel zinc ferrite material is pressed into a sheet or ring shape.

In a second aspect, an embodiment of the present application provides a method for manufacturing a nickel zinc ferrite material, including: s1: preparing the glass material of the material, and performing ball milling, melting, vitrification and sand milling on the glass material in sequence; s2: preparing the main component of the material, and performing sanding, pulping, presintering and cooling on the main component; s3: mixing the glass material, the main component and the additive according to the weight percentage, and performing ball milling, pulping and drying in sequence; s4: adding adhesive into the dried glass material and the main component, and pressing, molding and sintering.

In some embodiments, in step S1, the glass frit and the spheres are mixed in a weight ratio of 1: 4, mixing and ball milling, melting at 1300-1500 ℃ for 2-4 hours, and the grain diameter D50 of the glass material after sand milling is 1.0 mu m +/-0.5 mu m.

In some embodiments, in the step S2, the ratio of the main component, the ball and the water is 1: 4: 1.5, sanding and pulping, drying at the temperature of 100-200 ℃ for 10-24 hours, and presintering at the temperature of 830-880 ℃, the temperature rise curve of 1-4 ℃/min and the temperature preservation of 2-4 hours.

In some embodiments, in the step S3, the ball milling time is 4 hours to 10 hours, the ball milled particle size D50 is 0.5 μm ± 0.2 μm, and the drying is performed at a temperature of 100 ℃ to 200 ℃ for 10 hours to 24 hours.

In some embodiments, in step S4, 10 wt% to 20 wt% of the binder is added.

In some embodiments, in the S4 step, the press-formed mix is in a sheet or ring shape in the S4 step.

In some embodiments, in step S4, sintering is performed at a temperature of 850 ℃ to 950 ℃.

As described above, according to the nickel-zinc ferrite material and the method for manufacturing the same of the embodiment of the present application, a proper amount of glass frit is added to the main component, the glass frit is deposited at the grain boundary of the main component material during sintering, so that the grain boundary layer becomes thick and wraps the metal ions dissociated at the surface of the main component material in the mesh structure, and meanwhile, since the glass frit is a non-magnetic substance, the resistivity of the grain boundary can be increased, the metal ions wrapped in the mesh structure are difficult to be reduced into metal atoms during electroplating and deposited at the surface of the magnet, which is beneficial to eliminating the base of the creeping plating, so that the creeping plating phenomenon can be improved; in addition, the network structure formed by the glass frit can block the growth of crystal grains, plays a role in refining the crystal grains, and can be more suitable for producing products such as laminated small-sized inductors, magnetic beads and the like.

Drawings

FIG. 1 is a microstructure of a prior art nickel zinc ferrite material;

FIG. 2 is a microstructure of a nickel zinc ferrite material according to an embodiment of the present application;

fig. 3 is a schematic flow chart of an embodiment of a method for manufacturing a nickel-zinc-ferrite material according to the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described below in detail with reference to specific embodiments and accompanying drawings. It should be apparent that the embodiments described below are only some embodiments of the present application, and not all embodiments. In the following embodiments and technical features thereof, all of which are described below may be combined with each other without conflict, and also belong to the technical solutions of the present application.

It should be understood that in the description of the embodiments of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing technical solutions and simplifying the description of the respective embodiments of the present application, and do not indicate or imply that a device or an element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present application.

The existing nickel-zinc ferrite material is generally prepared by simply mixing several metal oxides such as Fe, Ni, Cu, Zn and the like, and then adding some sintering aids for sintering, as shown in figure 1, the grains of the sintered material are relatively coarse, and the residual metal ions which do not enter into crystal lattices can be subjected to reduction reaction in the electroplating process of a magnet to be converted into metal atoms for deposition, so that an overplating substrate is formed, and the overplating phenomenon is generated.

In order to solve the problem, an embodiment of the present application provides a nickel-zinc ferrite material, which includes a main component, an additive, and a glass frit, where the main component includes, by weight: 65 wt% -66.5 wt% of Fe₂O₃9.5 to 11.0 weight percent of NiO, 19.5 to 21.5 weight percent of ZnO and 3.4 to 4.6 weight percent of CuO; the additive comprises: 0.2 wt% -0.4 wt% of Co₂O₃0.2 to 0.8 weight percent of glass material; the glass frit comprises the following components in percentage by weight: 60 to 70 weight percent of Bi₂O₃8 to 15 weight percent of ZnO and 5 to 15 weight percent of B₂O₃1 to 5 weight percent of SiO₂And 1-2 wt% of CuO.

The proper amount of the glass frit is added into the main component, the glass frit is deposited in the grain boundary of the main component material during sintering so as to form a net structure, so that a grain boundary layer becomes thicker and metal ions dissociating on the surface of the main component material are wrapped in the net structure, meanwhile, the glass frit is a non-magnetic substance, so that the resistivity of the grain boundary can be improved, the metal ions wrapped in the net structure are difficult to be reduced into metal atoms during electroplating and are deposited on the surface of a magnet, the elimination of a climbing plating substrate is facilitated, and the climbing plating phenomenon can be improved; in addition, the network structure formed by the glass frit can hinder the growth of crystal grains and play a role in refining the crystal grains, as shown in fig. 2, so that the grain size of the crystal grains is smaller, and the method can be more suitable for producing products such as stacked small-sized inductors, magnetic beads and the like.

In some embodiments, the principal component, the additive, and the glass frit satisfy at least one of: fe₂O₃Has a purity of greater than or equal to 99.5 wt%; the purity of NiO is more than or equal to 99.5 wt%; the purity of ZnO is more than or equal to 99.5 wt%; the purity of CuO is greater than or equal to 99.5 wt%; co₂O₃Has a purity of greater than or equal to 99.5 wt%; bi₂O₃Has a purity of greater than or equal to 99.5 wt%; b is₂O₃Has a purity of greater than or equal to 99.5 wt%; SiO 2₂Has a purity of greater than or equal to 99.5 wt%. The purity of each material is controlled within the corresponding threshold range, so that the purity of each material is higher, the quality and the function of each material in the process of preparing the nickel-zinc ferrite material can be guaranteed, and the creeping plating phenomenon can be further improved.

In some embodiments, the nickel zinc ferrite material may be pressed into a sheet or a ring, and it should be understood that the pressed shape of the nickel zinc ferrite material may be set according to the actual required adaptability, and the embodiments of the present application are not limited thereto. For example, in the preparation of a laminated inductor, it may be pressed into a sheet shape.

Fig. 3 is a schematic flow chart of an embodiment of a method for manufacturing a nickel-zinc-ferrite material according to the present application. Referring to fig. 3, the method for manufacturing a nickel-zinc-ferrite material includes the following steps S1 to S4.

S1: preparing a glass frit comprising Bi₂O₃、ZnO、B₂O₃、SiO₂CuO, and performing ball milling, melting, vitrification and sand milling on the glass frit in sequence.

S2: to obtain a main component containing Fe₂O₃NiO, ZnO and CuO, and performing sand grinding, pulping, presintering and cooling on the main components.

S3: mixing the glass frit, the main component and the additive according to the weight percentage, wherein the main component comprises the following components in percentage by weight: 65 wt% -66.5 wt% of Fe₂O₃9.5 to 11.0 weight percent of NiO, 19.5 to 21.5 weight percent of ZnO and 3.4 to 4.6 weight percent of CuO; the additive comprises: 0.2 wt% -0.4 wt% of Co₂O₃0.2 to 0.8 weight percent of glass material; the glass frit comprises: 60 to 70 weight percent of Bi₂O₃8 to 15 weight percent of ZnO and 5 to 15 weight percent of B₂O₃1 to 5 weight percent of SiO₂1 to 2 weight percent of CuO, and ball milling, pulping and drying are carried out in sequence.

S4: adding adhesive into the dried glass material and the main component, and pressing, molding and sintering.

In step S1, in some scenarios, the frit material (i.e., Bi) as described above₂O₃、ZnO、B₂O₃、SiO₂CuO) and grinding balls in a weight ratio of 1: 4, mixing and ball milling, pouring the glass material raw material into a crucible after ball milling for 6 hours, putting the crucible into a melting furnace, melting at 1300-1500 ℃ for 2-4 hours, pouring the molten glass material raw material into a water tank for quenching to vitrify, putting the vitrified glass material raw material into a sand mill for sand milling, wherein the particle size D50 of the vitrified glass material raw material after sand milling is 1.0-0.5 mu m, and obtaining the required glass material.

In step S2, in some scenarios, the raw material (i.e., Fe) is based on the principal component₂O₃NiO, ZnO and CuO), grinding balls and water in a weight ratio of 1: 4: 1.5, mixing and pouring into a sand mill, adding zirconia balls with the diameter of 1-5 mm and deionized water, setting the rotation speed of the sand mill to be 200-500 rpm, sanding for 4-10 hours, controlling the particle size of the main component raw materials to be 1.0 micron +/-0.2 micron after D50 is 1.0 micron to prepare slurry, then putting the slurry into a drying oven, drying at the temperature of 100-200 ℃ for 10-24 hours, then pre-sintering at the temperature of 830-880 ℃ and the temperature rise curve of 1-4 ℃/min, and naturally cooling after 2-4 hours of heat preservation to prepare the required main component.

In the step S3, in some scenarios, the glass frit prepared in the steps S1 and S2 and the main component are mixed according to the above weight percentages, and are placed in a ball mill for ball milling, wherein the ball milling time is 4 hours to 10 hours, the particle size D50 after ball milling is 0.5 μm ± 0.2 μm, and the mixture is dried at the temperature of 100 ℃ to 200 ℃ and the heat preservation time is 10 hours to 24 hours.

In the step of S4, in some scenes, 10 wt% -20 wt% of adhesive is added; sintering at 850-950 ℃; the mixture formed by pressing is in a sheet shape or a ring shape.

In the preparation process, zirconia balls and a ball mill with a zirconia lining are preferably adopted for ball milling in the embodiment of the application, so that other metal impurities (Fe metal impurities) are not easy to be mixed, the purity of various materials is high, and the quality and the function of the various materials in the preparation process are guaranteed.

The technical solution of the present application is exemplarily described below by specific embodiments:

example 1

The nickel-zinc ferrite material comprises a main component, an additive and glass frit,

the main components comprise the following components in percentage by weight: 65 wt% Fe₂O₃10.1 wt% of NiO, 20.8 wt% of ZnO and 4.1 wt% of CuO; the additive comprises: 0.25 wt% Co₂O₃0.5 wt% of glass frit;

the glass frit comprises the following components in percentage by weight: 68 wt% of Bi₂O₃13 wt% of ZnO, 14 wt% of B₂O₃4% by weight of SiO₂1 wt% of CuO.

According to the purity calculation, the main components, the additives and the glass frit meet the following requirements: fe₂O₃Has a purity of greater than or equal to 99.5 wt%; the purity of NiO is more than or equal to 99.5 wt%; the purity of ZnO is more than or equal to 99.5 wt%; the purity of CuO is greater than or equal to 99.5 wt%; co₂O₃Has a purity of greater than or equal to 99 wt%; bi₂O₃Has a purity of greater than or equal to 98 wt%; b is₂O₃Has a purity of greater than or equal to 99 wt%; SiO 2₂Has a purity of greater than or equal to 99 wt%.

The steps of preparing the required glass material are as follows: as above-mentioned glass frit raw material (i.e., Bi)₂O₃、ZnO、B₂O₃、SiO₂CuO) and grinding balls in a weight ratio of 1: 4, mixing and ball milling, pouring the glass material raw material into a crucible after ball milling for 6 hours, putting the crucible into a melting furnace, melting at 1350 ℃ for 3 hours under heat preservation, pouring the molten glass material raw material into a water tank for quenching to vitrify, putting the vitrified glass material raw material into a sand mill for sand milling, wherein the grain diameter D50 of the vitrified glass material raw material is 1.0 after sand millingμm～0.5μm。

The steps of preparing the required main components are as follows: according to the principal component of the raw material (i.e. Fe)₂O₃NiO, ZnO and CuO), grinding balls and water in a weight ratio of 1: 4: 1.5, mixing and pouring into a sand mill, adding zirconia balls with the diameter of 1-5 mm and deionized water, setting the rotation speed of the sand mill to be 250rpm, controlling the particle size of the main component raw materials to be 1.0 +/-0.2 mu m of D50 after 5 hours of sand milling to prepare slurry, then putting the slurry into an oven, drying at the temperature of 120 ℃ for 12 hours, pre-burning at the temperature of 850 ℃ and the temperature rise curve of 1.5 ℃/min, and naturally cooling after 3 hours of heat preservation.

Mixing the prepared glass material and the main component according to the weight percentage, placing the mixture into a ball mill for ball milling for 5 hours, keeping the grain diameter D50 after ball milling to be 0.5 mu m +/-0.2 mu m, and drying the mixture at the temperature of 100-200 ℃ for 10-24 hours.

Performing performance evaluation on the obtained mixed powder, adding a binder into the prepared mixed powder, uniformly mixing, granulating, and performing compression molding on the granulated powder; for example, 15 wt% of a binder with a solid content of 10% is added, the mixture is uniformly mixed and granulated, and the granulated powder is pressed into a ring shape with the thickness of 3.5mm, the inner diameter of 8.8mm and the outer diameter of 14.6mm, the forming pressure is 3.5T, and the pressure maintaining time is 4 s; and (3) placing the pressed magnetic ring sample in a sintering furnace for sintering, wherein the sintering temperature is 900 ℃.

Example 2

Example 2 differs from example 1 in that: the main component and the additive are different in weight percentage.

The main components comprise the following components in percentage by weight: 65.2 wt% Fe₂O₃10.1 wt% of NiO, 20.7 wt% of ZnO and 4.0 wt% of CuO; the additive comprises: 0.2 wt% of Co₂O₃0.55 wt% of glass frit.

Example 2 the process for preparing a nickel zinc ferrite material was substantially the same as example 1, except that: and (3) placing the pressed magnetic ring sample in a sintering furnace for sintering, wherein the sintering temperature is 920 ℃.

Example 3

Example 3 differs from examples 1 and 2 in that: the main component and the additive are different in weight percentage.

The main components comprise the following components in percentage by weight: 65.4 wt% Fe₂O₃10.1 wt% of NiO, 20.5 wt% of ZnO and 4.0 wt% of CuO; the additive comprises: 0.25 wt% Co₂O₃0.5 wt% of glass frit.

Example 3 the same procedure as in example 1 for preparing a nickel zinc ferrite material is not repeated here.

Example 4

Example 4 differs from examples 1-3 in that: the main component and the additive are different in weight percentage.

The main components comprise the following components in percentage by weight: 65.6 wt% Fe₂O₃10.1 wt% of NiO, 20.3 wt% of ZnO and 4.0 wt% of CuO; the additive comprises: 0.3 wt% of Co₂O₃0.5 wt% of glass frit.

Example 4 the procedure for preparing nickel zinc ferrite materials was substantially the same as in examples 1-3, except that: and (3) placing the pressed magnetic ring sample in a sintering furnace for sintering, wherein the sintering temperature is 910 ℃.

Example 5

Example 5 differs from examples 1 to 4 in that: the main component and the additive are different in weight percentage.

The main components comprise the following components in percentage by weight: 65.8 wt% Fe₂O₃10.3 wt% of NiO, 19.9 wt% of ZnO and 4.0 wt% of CuO; the additive comprises: 0.25 wt% Co₂O₃0.5 wt% of glass frit.

Example 5 the same procedure as in example 1 for preparing a nickel zinc ferrite material is not repeated here.

The comparison of relevant parameters of the nickel-zinc ferrite materials prepared in the embodiments 1-5 of the present application and the ferrite materials prepared by adopting the traditional materials in the prior art is shown in the following table:

test method

The magnetic ring inductance L and the electric quantity Q which are prepared by testing an E4991A +16454A radio frequency impedance analyzer, an oven and the like are adopted to calculate the magnetic conductivity mu and the Curie temperature Tc of the ferrite material; testing the saturation magnetic induction intensity Bs of the ferrite material by using a SY-8218 type hysteresis loop instrument; observing the microstructure of the ferrite material by adopting a VEGA 3EPH scanning electron microscope; the appearance of the produced product was checked with a microscope.

According to results, the inductance product prepared from the nickel-zinc ferrite material provided by the embodiment of the application has the advantages that in the frequency range of 10 KHz-1 MHz, the magnetic permeability mu is 300 +/-25%, the saturation magnetic induction Bs (4000A/m) is 370 +/-5% mT, the Curie temperature Tc is more than or equal to 170 ℃, the creeping plating phenomenon is not generated, the microstructure of the section of the material is compact, the crystal grains are fine and uniform, and the material is suitable for producing small-size inductors, magnetic beads and other products.

The embodiment of the application also provides electronic equipment, and the electronic equipment comprises the nickel-zinc ferrite material and an inductance product made of the nickel-zinc ferrite material.

Electronic devices may be implemented in various specific forms, for example, electronic products such as smart phones, wearable devices, unmanned planes, electric vehicles, electric cleaning tools, energy storage products, electric vehicles, electric bicycles, electric navigation tools, and the like. It will be understood by those skilled in the art that the configuration according to the embodiments of the present application can be applied to electronic devices of a stationary type, in addition to elements particularly for moving purposes.

Since the electronic device has the nickel zinc ferrite material of any one of the foregoing embodiments, the electronic device can produce the beneficial effects of the nickel zinc ferrite material of the corresponding embodiment.

Although step numbers such as S1 and S2 are used herein, the purpose is to briefly describe the corresponding content more clearly, and not to constitute a substantial limitation on the sequence, and in the specific implementation, S2 may be performed first, and then S1 may be performed, which are all within the protection scope of the present application.

It should be understood that the above-mentioned embodiments are only some examples of the present application, and not intended to limit the scope of the present application, and all structural equivalents made by those skilled in the art using the contents of the present specification and the accompanying drawings are also included in the scope of the present application.

Claims

1. A nickel-zinc ferrite material is characterized by comprising a main component, an additive and a glass frit which are calculated by weight percentage,

the main components comprise: 65 wt% -66.5 wt% of Fe₂O₃9.5 to 11.0 weight percent of NiO, 19.5 to 21.5 weight percent of ZnO and 3.4 to 4.6 weight percent of CuO;

the additive comprises: 0.2 wt% -0.4 wt% of Co₂O₃0.2 to 0.8 weight percent of glass material;

the glass frit comprises: 60 to 70 weight percent of Bi₂O₃8 to 15 weight percent of ZnO and 5 to 15 weight percent of B₂O₃1 to 5 weight percent of SiO₂And 1-2 wt% of CuO.

2. The nickel zinc ferrite material of claim 1, wherein the main component, the additive, and the glass frit satisfy at least one of:

said Fe₂O₃Has a purity of greater than or equal to 99.5 wt%;

the purity of the NiO is more than or equal to 99.5 wt%;

the purity of the ZnO is greater than or equal to 99.5 wt%;

the purity of the CuO is more than or equal to 99.5 wt%;

the Co₂O₃Has a purity of greater than or equal to 99.5 wt%;

the Bi₂O₃Has a purity of greater than or equal to 99.5 wt%;

b is₂O₃Has a purity of greater than or equal to 99.5 wt%;

the SiO₂Has a purity of greater than or equal to 99.5 wt%.

3. The nickel zinc ferrite material of claim 1 or 2, wherein the nickel zinc ferrite material is pressed in a sheet or ring shape.

4. A method for manufacturing a nickel-zinc ferrite material, comprising:

s1: preparing a glass frit of the material of claim 1 or 2, and ball-milling, melting, vitrifying and sand-milling the glass frit in sequence;

s2: preparing a main component of the material according to claim 1 or 2, and sanding, pulping, pre-burning and cooling the main component;

s3: mixing the glass frit, the main component and the additive according to the weight percentage as claimed in claim 1 or 2, and performing ball milling, pulping and drying in sequence;

5. The method as claimed in claim 4, wherein in the step of S1, the ratio of glass frit to ball is 1: 4, mixing and ball milling, melting at 1300-1500 ℃ for 2-4 hours under heat preservation, and grinding to obtain the glass frit with the particle size D50 of 1.0 +/-0.5 mu m.

6. The method as claimed in claim 4, wherein in the step of S2, the ratio of the main component, the balls and the water is 1: 4: 1.5, sanding and pulping, drying at the temperature of 100-200 ℃ for 10-24 hours, and presintering at the temperature of 830-880 ℃, the temperature rise curve of 1-4 ℃/min and the temperature preservation of 2-4 hours.

7. The method as claimed in any one of claims 4 to 6, wherein, in the step S3, the ball milling time is 4 to 10 hours, the ball milled particle size D50 is 0.5 μm ± 0.2 μm, and the drying is performed at a temperature of 100 to 200 ℃ for 10 to 24 hours.

8. The method as claimed in claim 7, wherein in the step of S4, the adhesive is added in an amount of 10 wt% to 20 wt%.

9. The method as claimed in claim 7, wherein in the step of S4, the press-formed mix is in a sheet or ring shape.

10. The method according to claim 9, wherein in the step of S4, sintering is performed at a temperature of 850 ℃ to 950 ℃.