JP2000302447A - High-purity iron oxide powder for ferrite and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-purity iron oxide powder for ferrite used for electronic parts for telecommunication equipment, computers, televisions, VTR, etc., especially chip parts and provide a method for producing the iron oxide powder. SOLUTION: This high-purity iron oxide powder for ferrite has <=10 ppm P content and <=0.01 wt.% SO42- content and further has <=0.3 μm particle diameter or the iron oxide powder is obtained by wet method by using a ferric salt as a starting raw material and has <=10 ppm P content and <=0.01 wt.% SO42- content or the iron oxide powder feathers comprising <=0.06 wt.% MnO content and >=99.8 wt.% Fe2O3 content and optionally <=0.006 SiO2 content in addition to the P content and the SO42- content of the above iron oxide powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-purity iron oxide powder for ferrite used in electronic parts such as communication equipment, computers, televisions and VTRs, particularly chip parts, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, ferric oxide production methods include:
Generally, a dry method and a wet method are known. As the dry method, for example, a method of heating and dehydrating fine hydrous iron oxide and a method of heating and oxidizing fine magnetite are known. On the other hand, as a wet method, an alkali is added to a ferric salt,
After producing ferric hydroxide, which is filtered and washed,
A method of drying is described in, for example, Japanese Patent No. 26000562. Further, a method is disclosed in which a seed crystal of iron oxide is added to an alkaline suspension of metallic iron and then oxidized. Thus, a basic processing method as a wet method is already known.

[0003]

However, the above-mentioned one disclosed in, for example, Japanese Patent Publication No. 26000562 is not disclosed for ferrite, and cannot be applied to ferrite in terms of purity. The reality is that high purity iron oxide powder for ferrite, which is optimal for new electronic components, has not yet been obtained. In a laminated ferrite or the like which is a main use of the iron oxide of the present invention, a ferrite and a circuit such as Ag are sintered integrally. At this time, it is necessary to use a raw material iron oxide having excellent reactivity at a low temperature so as not to cause an adverse effect such as diffusion and movement of a metal constituting a circuit such as Ag. At present, for this purpose, raw materials that easily form ferrite at a low temperature, such as CuO, are mixed and used. However, in order to improve magnetic properties, it is desired to reduce the amount of CuO used as much as possible. .

[0004]

As a result of intensive development to solve the above-mentioned problems, the present invention has revealed that low-temperature sintering, which is a characteristic required for a chip component such as a multilayer chip inductor, is particularly required. It is an object of the present invention to provide a high-purity iron oxide powder for ferrite composed of high-purity fine particles having high electromagnetic properties and good electromagnetic properties, and a method for producing the same. The gist of the invention is (1) an iron oxide powder having P ≦ 10 ppm and SO ₄ ²⁻ ≦ 0.01% by weight, and further having a particle size ≦ 0.3 μm. High purity iron oxide powder. (2) High-purity iron oxide powder for ferrite, wherein P ≦ 10 ppm and SO ₄ ²⁻ ≦ 0.01% by weight, obtained by a wet method using a ferric salt as a starting material. .

(3) The iron oxide powder according to the above (1) or (2) further comprises MnO ≦ 0.06% by weight,
A high-purity iron oxide powder for ferrite, comprising iron oxide powder having e ₂ O ₃ ≧ 99.8%. (4) A high-purity iron oxide powder for ferrite, wherein the iron oxide powder according to (1) to (3) is further set to SiO ₂ ≦ 0.006% by weight.

(5) Ferric oxide obtained by roasting an iron chloride solution obtained by purifying a steel pickling waste liquid or the like, or ferric oxalate obtained by using oxalate dissolved in HCl. Ferric chloride, or purified ferric nitrate, or purified ferrous salt as a ferric compound using an oxidizing agent such as O ₂ , Cl ₂ , or HNO ₃ as a starting material And using the ferric salt in an alkaline aqueous solution as a starting material,
The ferric salt is adjusted to pH 2.5 to
After adjusting to the range of 6.0, by holding for 12 hours or more in the temperature range of 65 to 99 ° C., p at the end of holding is maintained.
A method for producing high-purity iron oxide powder for ferrite, wherein H is 1.5 or less, impurities in a precipitate formed after the holding are washed and removed, and the precipitate is dehydrated and dried. .

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the relationship between the P content and the sintered density. When the P content increases, abnormal grain growth increases in the ferrite sintered body (polycrystalline body), the sintered density decreases, and as a result, required electromagnetic characteristics cannot be secured. In order to obtain polycrystalline ferrite with less abnormal grain growth, the P content needs to be 10 ppm or less. Therefore, in the present invention, the P content is set to 10 ppm or less. Regarding the sintered density in this case, as shown in FIG.
m ³ or more can be obtained. When the P content is set to 10 ppm or less, the sintered density becomes 5.0 g / cm ^3.
It turns out that it can obtain above.

FIG. 2 is a diagram showing the relationship between the sintering temperature and the sintering density. As shown in this figure, it can be seen that the sintered density of the present invention is higher than that of the conventional example. In addition, according to the present invention, the sintering density is 5.0 at a sintering temperature of 800 ° C. or more.
g / cm ³ or more can be obtained. It can be seen that in order to obtain a sintered density of 5.0 g / cm ³ or more as described above, it is possible to achieve a lower sintering temperature than in the conventional example. That is, the present invention has extremely low temperature sinterability as compared with the comparative example. As described above, in the present invention, the sintering density was increased by reducing the P content to 10 ppm or less, and as a result, high-temperature sintering from low-temperature sintering, which adversely affects magnetic properties, became possible.

FIG. 3 is a diagram showing the relationship between the sintering temperature and the heat shrinkage of iron oxide depending on the content of SO ₄ ^2- at a particle size of 0.1 μm. FIG. 4 shows that the heat shrinkage curve shown in FIG.
The ratio of the shrinkage at 00 ° C. to 1200 ° C. (hereinafter, 8
FIG. 3 is a diagram in which the percentage of shrinkage at 00 ° C. is calculated and plotted against the SO ₄ ²⁻ content. As shown in FIG.
_The lower the ^42- content, the higher the percentage shrinkage at 800 ° C, indicating that the resulting iron oxide is likely to thermally shrink (highly reactive).

That is, the lower the SO ₄ ^2- content, the better the sinterability and the lower the sinterability. For iron oxide with an SO ₄ ^2- content of about 1 ppm,
This shows that the shrinkage ratio at 800 ° C. reaches as much as 90%. SO
₄ ^2- because the content is increased rapidly reactive below 100ppm (0.01%), as a means of controlling the calcined powder characteristics is a ferrite of the intermediate material, SO in the iron oxide ₄ ^2-
Controlling the content can also be employed. Therefore, in the present invention, the SO ₄ ^2- content is set to 0.01% or less. Thereby, low-temperature sinterability was obtained, and excellent magnetic properties were obtained.

FIG. 5 is a diagram showing the relationship between pH and MnO when NaOH is added to FeCl ₃ . As shown in this figure, it can be seen that at pH 6.0 or less, MnO shows a value of 0.06% or less. Raw materials containing NiO as a main component are used in ferrites for laminated parts, which are the main application range of the present invention. The presence of MnO as an impurity is one of the factors that hinder achievement of target values such as magnetic properties. One.

FIG. 6 shows FeCl_ThreeAfter adding NaOH to
PH and Fe at the end of the reaction_TwoO_ThreeFIG.
You. When the pH at the end of the reaction is 1.5 or less, at least
Fe _TwoO_ThreeCan be 99.8% or more. sand
That is, impurities (Ca, Cr, Ni, Cu, Zn, Al
And so on) by adjusting the pH to 1.5 or less,
Is discharged (dissolved). Thus, Fe_TwoO_ThreeMinute
By making the purity as high as 99.8% or more,
A product with excellent characteristics was obtained.

FIG. 7 is a diagram showing the relationship between the sintering temperature and the heat shrinkage at each particle size. As shown in FIG.
50 μm, 0.30 μm, 0.15 μm and 0.06
When the firing temperature at each particle size of μm is, for example, 800 ° C., the heat shrinkage rate is 0.3 compared to 0.50 μm.
It can be seen that the heat shrinkage is extremely increased when the thickness is 0 μm or less. That is, when the particle size is 0.30 μm or less, the heat shrinkage rate sharply increases, indicating that the low-temperature sinterability is good. Therefore, in the present invention, the particle size of the high-purity iron oxide powder is set to 0.30 μm or less.

Next, regarding SiO ₂ , SiO ₂ is a representative impurity, and a sintered body containing a large amount of SiO ₂ has a large crystal grain size and a considerable power loss. In contrast, it becomes uniform small grain size of SiO ₂ content is less sintered body, since the power loss is also small, in the present invention, the SiO ₂ content 0.00
6% or less.

Next, a manufacturing method according to the present invention will be described. In the present invention, SO ₄ ^2- : 0.01% or less,
SiO ₂ : As a raw material for reducing the content to 0.006% or less,
In particular, steel pickling waste liquid is desirable. This iron and steel pickling waste liquid is roasted with an iron chloride solution according to a usual purification method to obtain ferric oxide. The ferric oxide is subjected to steam heating to obtain an aqueous ferric chloride solution according to the following formula (1). Fe ₂ O ₃ + 6HCl → 2FeCl ₃ + 3H ₂ (1) The obtained ferric chloride aqueous solution was adjusted to pH 2.5 to NaOH with NaOH.
After adjusting to the range of 6.0, 1
By holding for 2 hours or more, the pH at the end of holding is adjusted to 1.5 or less. The reaction is represented by the following equation (2):
(3) and (4).

2FeCl ₃ + 3NaOH → Fe (OH) ₃ + 3NaCl + FeCl ₃ (2) At this time, a polymer is formed and the pH is shifted to the acidic side, and Fe (OH) ₃ + FeCl ₃ → Fe ₂ (OH) ₂ OCl ₂ + HCl ( 3) Next, β-FeOOH is generated and dehydrated, and Fe ₂ O ₃
Generate 3 / 2Fe ₂ (OH) ₂ OCl ₂ + HCl → 2βFeOOH + FeCl ₃ + 1 / 2H ₂ O + HCl → Fe ₂ O ₃ + FeCl ₃ + 3 / 2H ₂ O + HCl (4)

Thereafter, by washing, Fe ₂ O _{3 is} converted to FeC.
l ₃ , HCl, NaCl and removal of discharged metal, Si
O ₂ : 0.006% by weight or less, conductivity 30 μs / cm or less. Next, it is dried at 120 to 130 ° C. to obtain a product. In such a manufacturing process, the particle size is suppressed to 0.3 μm or less by the Fe ³⁺ concentration during neutralization and the reaction pH.

FIG. 8 shows that the Fe ³⁺ concentration is 1.8 mol and 0.1 mol.
It is a figure which shows the relationship between reaction pH and particle size in the case of 5 mol / l. As shown in this figure, it means that the particle size can be controlled by the reaction pH in order to reduce the particle size to a certain value or less. In other words, it indicates that the reaction pH needs to be 3.0 to 6.0 in order to make the particle diameter 0.3 μm or less.

FIG. 9 is a diagram showing the relationship between the Fe ³⁺ concentration and the end point pH. As shown in this figure, the lower the Fe ³⁺ concentration, the higher the end point pH and the more residual other metals. In this case, add HCl at the end point to pH
By setting it to 1.5 or less, as described above,
A purity of 99.8% or more of ₂ O ₃ can be achieved.

[0020]

The present invention will be specifically described below with reference to examples. As shown in Table 1, Nos. 1 to 13 are examples of the present invention, and Nos. 14 to 23 are comparative examples. No1 ~ 1
The starting materials No. 1 and Nos. 14 to 19 were a ferric chloride solution obtained by purifying a steel pickling waste liquid and the like, No. 12 was a ferric chloride solution recovered and purified as ferric oxalate using oxalic acid, and No. 13 was purified nitric acid nitrate. It is an iron solution, and P and Si
A raw material in which impurities such as O ₂ were reduced was used. On the other hand, No. 23 which is a comparative example has Fe ₂ (SO ₄ ) ₃ and No.
Nos. 20 to 22 are p-type with NaOH using commercially available FeCl _3.
H was adjusted. These were heated and held until the drop in pH was constant. After completion of the reaction, the precipitate is purified water and NH ₄ OH.
The mixture was washed by adding water, filtered and dried. The composition of the dried product was Fe ₂ O ₃ iron oxide. Fe of the purity of the final product
Shows ₂ O ₃ and impurity content. The particle size was obtained from an electron micrograph. FIG. 10 shows an example of an electron micrograph of the particles of the present invention. The particles have an extremely sharp particle size distribution and are free from agglomeration, and can be accurately measured from the electron micrograph.

As shown in Table 1, according to the present invention, Nos.
13 are both Fe ₂ O ₃ powder product purity is high, a comparative example with respect to this No14~21 Both Fe ₂
O ₃ purity is as low as 99.75 or less, and particularly, M which is an impurity
It can be seen that nO, CaO, SO ₄ ²⁻ , Cr, Zn, Ni and the like are high.

[0022]

[Table 1]

[0023]

As described above, according to the present invention, low-temperature sintering, which is a characteristic required for electronic components such as communication equipment, personal computers, and video cameras, and particularly for chip components such as multilayer chip inductors, is possible. High purity and fine particles having good characteristics can be obtained, and an excellent effect of providing a material which is extremely industrially advantageous can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a P content and a sintered density.

FIG. 2 is a diagram showing a relationship between a sintering temperature and a sintering density.

FIG. 3 is a graph showing the relationship between the sintering temperature and the heat shrinkage of iron oxide depending on the SO ₄ ^2- content at a particle size of 0.1 μm.

4 is a diagram in which a ratio of a shrinkage ratio at 800 ° C. to 1200 ° C. is calculated from the heat shrinkage curve shown in FIG. 3 and plotted against SO ₄ ²⁻ content.

FIG. 5 is a diagram showing the relationship between pH and MnO when NaOH is added to FeCl ₃ .

FIG. 6 shows p at the end of the reaction after adding NaOH to FeCl ₃ .
It is a diagram showing the relationship between the purity of H and Fe ₂ O _3.

FIG. 7 is a diagram showing a relationship between a sintering temperature and a heat shrinkage rate at each particle size.

FIG. 8 is a graph showing the relationship between the reaction pH and the particle size when the Fe ³⁺ concentration is 0.5 and 1.8 mol / l.

FIG. 9 is a graph showing the relationship between Fe ³⁺ concentration and end point pH.

FIG. 10 is a transmission electron micrograph of particles according to the present invention.

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[Procedure amendment]

[Submission date] April 27, 1999 (1999.4.2
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

(5) Ferric oxide obtained by roasting an iron chloride solution obtained by purifying a steel pickling waste liquid or the like, or ferric oxalate obtained by using oxalate dissolved in HCl. Ferric chloride, or purified ferric nitrate, or purified ferrous salt as a ferric compound using an oxidizing agent such as O ₂ , Cl ₂ , or HNO ₃ as a starting material The ferric salt was prepared by using an alkaline aqueous solution to have a pH of 2.5 to 6.
After being adjusted to a range of 0, a temperature range of 65 to 99 ° C.
By maintaining for 2 hours or more, the pH at the end of holding is reduced to 1.5 or less, impurities in the precipitate formed after the holding are washed and removed, and the precipitate is dehydrated and dried. A method for producing high-purity iron oxide powder for ferrite.

Continued on the front page (72) Inventor Junji Omori 7-12-14 Ginza, Chuo-ku, Tokyo Chemilite Industry Co., Ltd. (72) Inventor Yoshio Kitazawa 7-12-14 Ginza, Chuo-ku, Tokyo Chemilight Industry (72) Inventor Toru Murase 7-12-14 Ginza, Chuo-ku, Tokyo F-term (reference) 4K002 AA03 AB04 AC02 AD03 AE02 5E041 AB16 AB19 CA01 HB15 NN02 NN06 NN17 NN18

Claims (5)

[Claims] 1. A high-purity iron oxide powder for ferrite, wherein P ≦ 10 ppm and SO ₄ ²⁻ ≦ 0.01% by weight, and further, the particle size is ≦ 0.3 μm. 2. An iron oxide powder obtained by a wet method using a ferric salt as a starting material, wherein P ≦ 10 ppm, SO ₄ ²⁻ ≦
High-purity iron oxide powder for ferrite, which is 0.01% by weight. 3. The iron oxide powder according to claim 1, further comprising: MnO ≦ 0.06% by weight and Fe ₂ O ₃ ≧
A high-purity iron oxide powder for ferrite, comprising 99.8% iron oxide powder. 4. A high-purity iron oxide powder for ferrite, wherein the iron oxide powder according to claim 1 is further provided with SiO ₂ ≦ 0.006% by weight. 5. A ferric oxide obtained by roasting an iron chloride solution obtained by purifying a steel pickling waste liquid or the like, or a ferric oxalate obtained by using an oxalate dissolved in HCl. Using ferric chloride or purified ferric nitrate as a starting material, the ferric salt is adjusted to pH 2.5 to
After adjusting to the range of 6.0, by holding for 12 hours or more in the temperature range of 65 to 99 ° C., p at the end of holding is maintained.
A method for producing high-purity iron oxide powder for ferrite, wherein H is set to 1.5 or less, impurities in a precipitate formed after the holding are washed and removed, and the precipitate is dehydrated and dried.