JP2003212547A - Iron oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide iron oxide powder as a raw material of NiCuZn ferrite powder which is used for a chip inductor, does not contain coarse particles, particularly iron oxide powder which can be calcined and pulverized in a short time to manufacture the NiCuZn ferrite powder having 6 to 10 m<SP>2</SP>/g specific surface area. <P>SOLUTION: The iron oxide powder used as the raw material of the NiCuZn ferrite powder for the chip inductor has a B<SB>2</SB>O<SB>3</SB>content of ≤8 ppm by mass expressed in terms of B, a MnO content of 600 to 5,000 ppm by mass and a specific surface area of 6 to 60 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material of a NiCuZn ferrite powder for forming a ferrite layer of a chip inductor used as an electronic component of a mobile phone, a personal computer, a video camera, and the like. Iron oxide powder. 2. Description of the Related Art A chip inductor is manufactured by laminating a ferrite layer, which is a magnetic material, and a silver pattern, which is a conductor, and then sintering. As the ferrite powder forming the ferrite layer of the chip inductor, the melting point of silver (ie,
A NiCuZn ferrite powder that can be sintered at 900 ° C or lower, which is lower than 961 ° C, is used. Particularly, in order to promote sintering at a low temperature of 900 ° C. or less, fine NiCuZn-based ferrite powder having a specific surface area of about 6 to 10 m ² / g (particle diameter of about 0.1 to 0.4 μm) is widely used. [0003] NiCuZn-based ferrite powder includes iron oxide powder, NiO
Powder mixed with powder, ZnO powder and CuO powder 700-900
The powder is calcined at ℃, and the obtained coarse powder of NiCuZn ferrite (hereinafter, referred to as calcined powder) is further pulverized to produce. If the calcined powder is pulverized for a long period of time (for example, ten and several hours), the particles of the calcined powder are destroyed to form NiCuZn-based ferrite powder having irregularities on the surface. When a solvent is added to a ferrite powder having irregularities on the surface to form a paste, the fluidity is reduced, so that it is difficult to form a ferrite layer of the chip inductor. Therefore, in order to prevent the particles of the calcined powder from being broken, the pulverization is performed in a short time (for example, several hours). When the pulverization is completed in a short time, an effect of preventing contamination of impurities can be obtained. [0004] Iron oxide powder, NiO mixed with raw material mixed powder
Among the powder, ZnO powder, and CuO powder, the mixing ratio of iron oxide powder is the largest, and accounts for about 70% by mass of the raw material mixed powder. Therefore, the purity and the particle size of the iron oxide greatly affect the particle size distribution and the particle shape of the NiCuZn-based ferrite powder. For example, when low-melting impurities are mixed into iron oxide powder, a liquid phase is formed in the process of calcining the raw material mixed powder, and coarse calcined powder (for example, having a particle size of 1 μm
Degree). Since the calcined powder is pulverized in a short time as described above, the coarse calcined powder is not pulverized but remains as a coarse NiCuZn-based ferrite powder (for example, a particle size of about 1 μm). [0005] When iron oxide powder mixed with coarse particles is used, coarse powder remains after calcining the raw material mixed powder. This is because, in the calcination, the other components dissolve into the iron oxide powder and the ferrite formation reaction proceeds, so that the shape of the iron oxide powder hardly changes. Since the calcined powder is pulverized in a short time, the coarse calcined powder (for example, having a particle size of about 1 μm) is not pulverized, but remains as a coarse NiCuZn-based ferrite powder (for example, having a particle size of about 1 μm). [0006] These coarse NiCuZn ferrite powders
The promotion of sintering (that is, low-temperature sintering) of the chip inductor is hindered, and the density of the obtained sintered body is reduced. For this reason,
The specific resistance and initial permeability decrease, and the characteristics of the chip inductor are impaired. NiCu used in chip inductors
In the production of Zn-based ferrite powder, it is extremely important to select the purity and particle size of the iron oxide powder as a raw material. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an iron oxide powder optimal as a raw material for obtaining a NiCuZn ferrite powder containing no coarse particles. More specifically, even if the calcined powder is pulverized in a short time, it does not contain coarse particles, and has a specific surface area of 6 to 10 m ² / g.
It is an object of the present invention to provide an iron oxide powder capable of producing a NiCuZn-based ferrite powder. [0008] Usually, iron oxide powder, which is a raw material of NiCuZn-based ferrite powder, is produced from waste acid generated in steel pickling equipment.
Contains Mn. On the other hand, MnO is added to NiCuZn ferrite powder.
It is known that the addition of about 0.3% by mass has the effect of increasing electric resistance. Therefore, MnO inevitably mixed into iron oxide powder
And maintain a high content of fine Ni
The conditions for obtaining CuZn-based ferrite powder (specific surface area of about 6 to 10 m ² / g) were studied. As a result, the iron oxide powder MnO
When the content is within the range of 600 to 5000 ppm by mass and B ₂ O ₃
It was found that when the content was 8 ppm by mass or less in terms of B, fine NiCuZn-based ferrite powder was obtained without containing coarse particles. [0010] That is, the present invention relates to Ni for chip inductors.
An iron oxide powder used as a raw material of a CuZn-based ferrite powder, wherein the content of B ₂ O ₃ is 8 mass ppm or less in terms of B,
Is an iron oxide powder having a content of 600 to 5000 ppm by mass and a specific surface area of 6 to 60 m ² / g. In the present invention, the method for producing iron oxide powder is not limited to a specific technique. For example, a ferrous chloride solution and an alkaline solution are mixed, and after adding ferric chloride, the mixture is adjusted to a predetermined temperature and pH (ie, neutralized) to obtain Fe ₃ O ₄ powder. This is desalted, dried and crushed to obtain Fe ₃ O ₄ powder, which is further oxidized by heating at 150 to 600 ° C. to obtain a γ-Fe ₂ O ₃ single phase, α-Fe ₂ O ₃ single phase or γ-Fe ₂ An iron oxide powder consisting of a mixed phase of O ₃ and α-Fe ₂ O ₃ can be obtained. As another method for obtaining iron oxide powder, α
A conventionally known technique such as a method of synthesizing -FeOOH and further oxidizing by heating, a method of synthesizing α-Fe ₂ O ₃ by a wet method, or a spray roasting method can be used. The iron oxide powder thus obtained is classified as necessary, and the iron oxide powder having a specific surface area of 6 to 60 m ² / g is selected.
If the specific surface area of the iron oxide powder is less than 6 m ² / g, the NiCuZn-based ferrite powder also generates a large amount of particles less than 6 m ² / g.
In addition, grain growth occurs locally at the heating stage of calcining the raw material mixed powder, and coarse calcined powder and NiCuZn-based ferrite powder are generated. As a result, it becomes difficult to produce NiCuZn-based ferrite powder having a specific surface area of 6 to 10 m ² / g. On the other hand, if the specific surface area of the iron oxide powder exceeds 60 m ² / g, it tends to agglomerate and coarse calcined powder is generated.
As a result, the characteristics of a chip inductor manufactured using the NiCuZn-based ferrite powder may be impaired. Therefore, in order to obtain fine NiCuZn-based ferrite powder (specific surface area: 6 to 10 m ² / g) which does not contain coarse particles, the specific surface area of iron oxide powder must satisfy the range of 6 to 60 m ² / g. There is a need to. The specific surface area of the iron oxide powder is preferably 10
4040 m ² / g. Further, the MnO content of the iron oxide powder is 600 mass pp
If it is less than m 2, the effect of increasing the electric resistance of the ferrite layer of the chip inductor manufactured using the NiCuZn-based ferrite powder obtained from the raw material mixed powder containing the iron oxide cannot be expected. On the other hand, when the MnO content exceeds 5000 mass ppm,
Mn oxide precipitates at the grain boundary of the ferrite layer of the chip inductor manufactured using the NiCuZn-based ferrite powder obtained from the raw material mixed powder into which the iron oxide is mixed, and the magnetic characteristics are impaired. Therefore, the MnO content of the iron oxide powder is 600 to 500
It is necessary to satisfy the range of 0 mass ppm. The content is preferably from 1,000 to 3,500 ppm by mass. If the B ₂ O ₃ content of the iron oxide powder exceeds 8 ppm by mass in terms of B, the particle size of the NiCuZn-based ferrite powder obtained from the raw material mixture powder containing the iron oxide becomes non-uniform, and the chip The magnetic properties of the ferrite layer of the inductor are impaired. Therefore, the B ₂ O ₃ content of the iron oxide powder is set to 8 ppm by mass or less in terms of B. Preferably, the content is 1 to 5 ppm by mass. [0016] By calcining the raw material mixed powder using the iron oxide powder of the present invention at a low temperature, coarse particles are not contained.
The reason why the NiCuZn-based ferrite powder is obtained is not yet clear, but it is considered to be due to the following mechanism. That is, since B ₂ O ₃ has a melting point in the temperature range of about 450 to 600 ° C., when calcination is performed at a normal calcination temperature (about 700 to 900 ° C.), a liquid phase is formed during the heating process. In addition, grain growth occurs locally during the progress of calcination, and as a result, coarse NiCuZn-based ferrite powder is generated. However, when MnO and B ₂ O ₃ coexist, a liquid phase is generated from about 750 ° C (Phase Diagrams
for Ceramists (1964), Fig. 276). As a result, in the calcining process at a low temperature, local grain growth is suppressed, and coarse Ni
The generation of CuZn-based ferrite powder can be prevented. Some studies have been made on the effects of B in the raw material on the microstructure and magnetic properties of MnZn ferrite, but the composition and calcination temperature are different from those of the present invention. For example, on page 47 of the document “Ferrite” (Hiraga et al., Maruzen, 1986), “B ₂ O ₃ promotes grain growth remarkably with a trace amount”, and on page 92, “B has a uniform crystal structure and high magnetic permeability. To inhibit the expression of
It states that it must be done below. As described above, it is shown that good microstructure and magnetic properties can be obtained by reducing the B content of MnZn ferrite. However, as described in the literature, these are effective methods when firing MnZn ferrite at a high temperature range of 1200 to 1400 ° C, calcining at a low temperature of 750 ° C or less, and a low temperature of 900 ° C or less. This is different from the manufacturing conditions for the NiCuZn-based ferrite powder for chip inductors, which is supposed to be fired at a temperature. Japanese Patent Application Laid-Open No. 3-163802 discloses Mn-Zn
There is disclosed a technique for reducing iron loss by adding a small amount of B to a system ferrite. However, JP-A-3-163802
Discloses that a predetermined amount of B and MnO is contained in iron oxide powder as a raw material.
Is not described. Japanese Patent Application Laid-Open No. 2000-277318 discloses a technique for improving initial magnetic permeability by adding a small amount of B to MnZn-based ferrite. However, Japanese Patent Application Laid-Open No. 2000-277318 does not disclose that predetermined amounts of B and MnO are contained in iron oxide powder as a raw material in order to prevent the formation of coarse NiCuZn-based ferrite powder. As described above, when the iron oxide powder of the present invention is used, the raw material mixed powder mixed with other raw materials (namely, NiO powder, ZnO powder, CuO powder) is calcined at 750 ° C. or less, and then calcined powder. By milling, a fine and uniform NiCuZn-based ferrite powder having a ferrite conversion ratio of 90% or more can be obtained. In addition, this pulverization can be performed in a short time to obtain a NiCuZn ferrite powder having a specific surface area of 6 to 10 m ² / g suitable for use in a chip inductor. A ferrite layer of a chip inductor manufactured using this NiCuZn-based ferrite powder has a sintered density of 5.1 g / cm ³ or more (95% or more of the true density) at a sintering temperature of about 900 ° C. [0020] The iron oxide powder of the present invention is composed of SiO ₂ , Ca, Al, Cr, Ni, M which is inevitably contained in the pickling waste acid of ordinary steel materials.
It may contain impurities derived from metal components such as g, Cu, Ti and the like, and 0.15% by mass or less of Cl remaining in a small amount even after generation of iron oxide. EXAMPLES Example 1 A steel sheet having a high B content was dissolved in hydrochloric acid to prepare a ferrous chloride solution containing B. Next, a mixed solution of the reagents ferrous chloride solution, ferric chloride solution and the above-mentioned ferrous chloride solution containing B is neutralized with caustic soda, and the temperature is maintained at 85 ° C. and pH 8.5 ± 0.2. Oxidation was performed by passing air through to synthesize Fe ₃ O ₄ particles. After the reaction was completed, desalting, filtration, drying and crushing were performed to obtain a dry powder of Fe ₃ O ₄ . Subsequently, it was heated and oxidized at 480 ° C. to obtain B-containing α-Fe ₂ O ₃ particles. By changing the ratio of the ferrous chloride solution containing B to the ferrous chloride solution of the reagent, α-Fe ₂ O ₃ particles having different B contents shown in Table 1 were obtained. The MnO content of each sample was 1000 mass ppm and the specific surface area was 15
m ² / g. [Table 1] Inventive Examples 1 to 3 are examples in which the B content satisfies the range of the present invention, and Comparative Example 1 is an example in which the B content is out of the range of the present invention. Each iron oxide powder and NiO shown in Table 1
Powder, ZnO powder, and CuO powder in a mixing ratio of Fe ₂ O ₃ : NiO: Zn
It was weighed so that O: CuO = 49: 9: 30: 12 (mol%), and the obtained raw material mixed powder was calcined at a predetermined temperature for 2 hours. After the calcination was completed, the phase composition of the calcined powder was measured by X-ray analysis, and the peak intensity ratio of the spinel phase was determined. Next, the calcination temperature was changed, and calcination was performed for 2 hours, the peak intensity ratio of the spinel phase was determined, and the relationship between the calcination temperature and the peak intensity ratio of the spinel phase was determined. From this relationship, the peak intensity ratio of the spinel phase is 90%.
Is the ferrite temperature. After calcining the raw material mixed powder at this ferrite-forming temperature for 2 hours, the calcined powder was pulverized by a wet ball mill for 2 hours, dried and sized to obtain a NiCuZn-based ferrite powder. Next, PVA was added to the NiCuZn ferrite powder.
Is added and granulated, and a ring is formed.
Sintered for hours. Measure the size and weight of the obtained sintered body,
The sintering density was calculated. The results are as shown in Table 1. In Table 1, the B content of the iron oxide powder,
The MnO content and specific surface area are ICP and fluorescent X, respectively.
Line, measured by the BET method. Note that coarse particles of the NiCuZn-based ferrite powder obtained by calcining the raw material mixed powder and pulverizing the obtained calcined powder can be confirmed by SEM (so-called scanning electron microscope) observation. In other words, when observed at a magnification of about 10,000 times, in the NiCuZn-based ferrite powder containing coarse particles, particles (particle diameter: about 1 μm) that are clearly coarser than surrounding particles (particle diameter: about 0.05 to 0.4 μm) appear in one to three fields. About a few are observed. Observation by SEM at 10 visual fields at random was evaluated as ○ when there were no coarse particles, Δ when about 1 in 1 to 3 visual fields, and × when there was one or more in 1 visual field. As is clear from Table 1, in Invention Examples 1 to 3, the calcined powder did not contain coarse particles and the specific surface area was 6 to 10 m ^2.
/ G of NiCuZn-based ferrite powder having a uniform particle size distribution. Further, when the NiCuZn-based ferrite powders of Inventive Examples 1 to 3 were sintered at 900 ° C., a sintered density of 5.1 g / cm ³ or more was obtained. In the case of a high B content (Comparative Example 1), coarse particles are present in the calcined powder and the NiCuZn-based ferrite powder.
For this reason, the density of the sintered body is low and the characteristics are poor. Example 2 A steel sheet having a high B content was dissolved in hydrochloric acid to prepare a ferrous chloride solution containing B. Next, a mixed solution of the reagents ferrous chloride solution, ferric chloride solution, ferrous chloride solution containing B, and manganese chloride is neutralized with caustic soda, and the temperature is maintained at 75 ° C. and pH 9.8 ± 0.2. Then, air was passed to oxidize to synthesize Fe ₃ O ₄ particles. After the reaction was completed, desalting, filtration, drying and crushing were performed to obtain a dry powder of Fe ₃ O ₄ . Subsequently, it was heated and oxidized at 500 ° C. to obtain α-Fe ₂ O ₃ particles containing B and MnO. By changing the ratio of the ferrous chloride solution containing B to the ferrous chloride solution of the reagent, α-Fe ₂ O ₃ particles having different B contents and MnO contents shown in Table 2 were obtained. Inventive Examples 4 to 7 are examples in which the MnO content satisfies the range of the present invention, and Comparative Examples 2 to 4 are examples in which the MnO content is out of the range of the present invention. [Table 2] The step of calcining the raw material mixed powder to obtain the NiCuZn-based ferrite powder is the same as that of the first embodiment, and therefore the description is omitted. As is evident from Table 2, in Examples 4 to 7, the calcined powder did not contain coarse particles, and NiCuZn-based ferrite powder having a specific surface area of 6 to 10 m ² / g and a uniform particle size distribution was obtained. further,
When the NiCuZn-based ferrite powders of Inventive Examples 4 to 7 were sintered at 900 ° C., a sintered density of 5.1 g / cm ³ or more was obtained. [0030] In the case of a small amount of MnO (Comparative Example 2), coarse particles do not exist but the specific resistance is low. An example with a large amount of MnO (Comparative Example 3) and an example with a large amount of both MnO and O (Comparative Example 4) have coarse particles, low sintering density, and poor characteristics. (Example 3) F obtained under the same conditions as Inventive Example 5 shown in Table 2
and the e ₃ O ₄ dry powder was heated oxidized at one hundred eighty to six hundred ° C. with a specific surface area shown in Table ₃ α- Fe ₂ O 3 particles, and γ- Fe ₂ O ₃ particles or alpha-Fe ₂ O ₃ particles .gamma. An iron oxide powder consisting of a mixture with Fe ₂ O ₃ particles was obtained. B content and MnO content are
B: 5 mass ppm and MnO content: 1490 mass ppm equivalent to Inventive Example 5. The steps from mixing this iron oxide powder with NiO powder, ZnO powder and CuO powder and calcining the obtained raw material mixed powder to obtaining NiCuZn ferrite powder are the same as those in Example 1. Therefore, the description is omitted. Inventive Examples 8 to 12 are examples in which the specific surface area satisfies the range of the present invention, and Comparative Examples 5 and 6 are examples in which the specific surface area is out of the range of the present invention. [Table 3] As is apparent from Table 3, in Invention Examples 8 to 12, the calcined powder after calcination does not contain coarse particles, and has a specific surface area of 6 to 10 m ² / g and a uniform particle size distribution of NiCuZn-based ferrite. A powder was obtained. Further, when the NiCuZn-based ferrite powders of Inventive Examples 8 to 12 were sintered at 900 ° C., a sintered density of 5.1 g / cm ³ or more was obtained. When the specific surface area of the iron oxide powder is out of the range of the present invention, coarse particles are present. According to the present invention, when manufacturing a chip injector using NiCuZn-based ferrite powder obtained from the raw material mixed powder mixed with the iron oxide powder of the present invention, the raw material mixed powder is calcined at a low temperature of 750 ° C. or less. As a result, calcined powder containing no coarse particles is obtained, and the calcined powder is pulverized in a short time to obtain a rounded Ni having a specific surface area of 6 to 10 m ² / g.
A CuZn-based ferrite powder is obtained, and a chip injector made using this NiCuZn-based ferrite powder is sintered at 900 ° C or lower at a low temperature to obtain a sintered density of 5.1 g /
A ferrite layer having a high magnetic property of at least ³ cm ³ can be obtained.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Satoshi Goto             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba             Iron Research Institute F term (reference) 4G002 AA06 AA12 AC02                 5E041 AB01 AB03 CA01 NN02

Claims (1)

Claims 1. An iron oxide powder used as a raw material of a NiCuZn-based ferrite powder for a chip inductor, wherein the content of B ₂ O ₃ is 8 mass ppm or less in terms of B, and the content of MnO is 600 ~
An iron oxide powder having a 5,000 mass ppm and a specific surface area of 6 to 60 m ² / g.