JPH0891917A - Ferrite material and its production - Google Patents

Abstract

PURPOSE: To obtain a ferrite material having good magnetic characteristics by adding at least one kind of additive producing a liquid phase in baking process to a ferrite-constituting oxide and a metal powder and baking the mixture. CONSTITUTION: One or more kinds of ferrites selected from Fe2 O3 , NiO, ZnO, CuO, MnO, ZnFe2 O4 , NiFe2 O4 , CuFe2 O4 and MnFe2 O4 are compounded with one or more kinds of powdery metals selected from Zn, Ni, Cu, Mn and Fe at a ratio to get a prescribed composition. The obtained mixture is further incorporated with 0.02-5.0wt.% (based on the metal powder) of one or more kinds of additives to form a liquid phase in baking and selected from Bi2 O3 , V2 O5 , PbO, B2 O3 , SiO2 , Sb2 O3 , CaCO3 , Li2 CO3 and glass powder. The compounded mixture is mixed and pulverized by a ball mill, etc., dried, calcined at a prescribed temperature, incorporated with a binder, formed to a prescribed form and baked to obtain a ferrite material having good magnetic characteristics at a low shrinkage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite material used in various electronic parts and a method for producing the same.

[0002]

2. Description of the Related Art A conventional ferrite material as a magnetic material has been manufactured as follows.

First, the ferrite raw material powder is calcined, then the calcined body is crushed, and then the powder obtained by crushing is put into a mold to be molded, and then the molding is taken out from the mold. The product was fired to obtain a ferrite material.

However, as is well known, the ferrite material produced in this way shrinks during the main firing, so in consideration of this shrinkage, the ferrite material should be baked slightly larger than the desired size. There is.

Therefore, after the main calcination, the work of cutting the ferrite material into the desired size and shape was required.

However, since the ferrite material after the main calcination is very hard, the cutting blade used for cutting is significantly worn, and the cutting blade must be frequently replaced, resulting in high cost. It was a thing.

Therefore, there has been proposed one in which the shrinkage during the main firing is substantially eliminated so that the above-mentioned cutting work is unnecessary (JP-A-1-264959).

First of all, the magnetic material is silicon, titanium,
Filling powder selected from one of aluminum is mixed, then this mixture is put into a mold to be molded, and then the molded body taken out from the mold is subjected to main firing in an oxygen atmosphere or a nitrogen atmosphere. Met.

According to this prior art, since the above-mentioned filling powder expands by oxidation or expands by nitriding, the shrinkage of the magnetic material during the main firing can be suppressed to an extremely small level.

[0010]

However, there is a problem in that the magnetic properties of the magnetic material are deteriorated as a result of mixing non-magnetic materials such as silicon, titanium, and aluminum into the magnetic material powder. It was Further, in the process of oxidizing or nitriding the metal powder, the reaction does not proceed uniformly, and only the surface of the molded body reacts, and the inside of the molded body remains as metal, resulting in a non-uniform structure and good magnetic properties. There was a problem that I could not.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a ferrite material in which the dimensional change due to the main firing is small and the magnetic characteristics are not deteriorated.

[0012]

In order to solve the above-mentioned problems, the present invention comprises adding, to a starting material composed of an oxide and a metal powder, at least one additive which produces a liquid phase at the time of baking, and baking the same. It is a ferrite material obtained by

[0013]

[Function] In the process of oxidizing the metal powder, the reaction speed is too fast, and only the metal powder on the surface of the molded product reacts, and a part of the metal powder inside the molded product does not completely react and remains as a metal component. However, a non-uniform structure is formed and good magnetic properties cannot be obtained. Therefore, by adding an additive that causes a liquid phase during firing, the metal particles are uniformly wetted by the liquid phase, and oxygen diffused in the liquid phase reacts with the metal to form a uniform composition, which has a good low shrinkage ratio. A ferrite material with magnetic properties can be obtained.

[0014]

EXAMPLES It has been proposed in the past to add various additives to ferrite in order to promote liquid phase sintering (Japanese Patent Laid-Open No. 55-62235). However, according to the present invention, since the starting material contains a metal powder and an additive that produces a liquid phase during firing is added, the liquid phase effectively works on the metal powder, so that ferrite having a low shrinkage and a uniform structure is obtained. The material is obtained. Therefore, the additive amount is effective not for the entire starting material but for the metal powder contained in the starting material. In the present invention, the lower limit of the additive is the minimum necessary for the metal powder to uniformly wet in the liquid phase. On the other hand, the reason for setting the upper limit is that if the addition amount is excessively increased, the magnetic characteristics are deteriorated due to an increase in the non-magnetic portion, abnormal grain growth and the like. The magnetic properties of these additives are improved as compared with the case where no additives are added, as long as the upper limit of addition is not exceeded even when only one kind of additive is added or when multiple additives are added. Further, additives other than those mentioned in the present invention may be added as long as the amount thereof is not particularly large.

Further, it is preferable that the liquid phase component is generated in the firing process in the temperature range where the oxidation reaction of the metal powder is not completed more than half.

Specific examples will be described below. (Example 1) Fe ₂ O ₃ , NiO, Zn as starting materials
Each of O and CuO powders was weighed so as to have the following composition ratio, mixed with a ball mill, pulverized and dried, and then 80
After calcination in air at 0 ° C. for 2 hours, it was crushed by a ball mill and dried to prepare powder A. In addition, metallic Fe and NiO, ZnFe ₂ O ₃ , and CuO powders were used as starting materials so that the composition ratios were as follows, and the additives were added in amounts of (Table 1) to (Table 3) with respect to metallic Fe. Weigh each so that
Powder B was prepared by mixing.

Powder A; Fe ₂ O ₃ 49.0 mol% NiO 10.0 mol% ZnO 31.0 mol% CuO 10.0 mol% Powder B; Fe 41.4 mol% NiO 11.5 mol% ZnFe ₂ O ₄ 35.6 mol% CuO 11.5 mol% Additives These powder A and powder B were added in an amount of 50 mol% and 5%, respectively.
After blending and mixing so as to be 0 mol%, polyvinyl alcohol was added, and the mixture was passed through a 30 # sieve to granulate. These granulated powders are molded in a mold with an outer diameter of 20 mm and an inner diameter of 14 m.
A ring-shaped sample having a thickness of m and a thickness of 3 mm was molded. After the binder was out in the air at 500 ° C. for 1 hour,
It was baked at 900 ° C. for 2 hours. The method of measuring the relative permeability is to wind an insulated wire around the ferrite core one layer,
It was measured at 100 kHz using an impedance analyzer, and the dimensional change rate was calculated from the dimension of the outer diameter of the ring core before and after firing (+ indicates expansion, − indicates contraction). The microstructure was observed by SEM, and it was represented by x for a nonuniform structure (when different grain sizes are mixed), ◯ for a uniform structure, and * for abnormal grain growth.

The relative permeability is shown in (Table 1), the dimensional change rate is shown in (Table 2), and the result of SEM observation is shown in (Table 3). The characteristics of only the powder A are the relative magnetic permeability 646 and the dimensional change rate -1.
It was 6.5%.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

As is clear from (Table 1), (Table 2) and (Table 3), the relative magnetic permeability is 500 or more when the additive amount is 0.02 wt% or more and 5.0 wt% or less with respect to the metal powder. It can be seen that the dimensional change rate is -0.5% or more and + 0.5% or less, which is very small and the structure is uniform.

(Example 2) In the same manner as in Example 1, powders of Fe ₂ O ₃ , MnO and ZnO as starting materials were weighed so as to have the following composition ratios and mixed by a ball mill. After crushing and drying, calcination was performed in air at 900 ° C. for 2 hours, and then crushing and drying with a ball mill to prepare powder C. In addition, metallic Fe and metallic Mn and Z as starting materials
The powders of nO were mixed in the following composition ratios, and the additives were mixed in amounts of (Table 4) to (Table 6) with respect to the total amount of metallic Fe and metallic Mn, and powder D was mixed. I prepared.

Powder C; Fe ₂ O ₃ 52.0 mol% MnO 24.0 mol% ZnO 24.0 mol% Powder D; Fe 68.4 mol% Mn 15.8 mol% ZnO 15.8 mol% Additive These powder C is 60 mol% and powder D is 40 mol%
The mixture was mixed and mixed so that polyvinyl alcohol was added, and the mixture was granulated by passing through a 30 # sieve. These granulated powders are molded in a mold with an outer diameter of 20 mm, an inner diameter of 14 mm, and a thickness of 3
A ring-shaped sample of mm was molded. This molded body is 500 ° C
After binder out in air for 1 hour at 1200 ° C
It was fired for 2 hours under controlled oxygen atmosphere. The method of measuring the relative magnetic permeability is as follows: An insulated conductor is wound around the ferrite core one layer, and an impedance analyzer is used to measure 100%.
The measurement was performed at kHz, and the dimensional change rate was calculated from the dimensions of the outer diameter of the ring core before and after firing (+ indicates expansion, − indicates contraction). The microstructure was observed by SEM, and the nonuniform structure (when different particle sizes are mixed) was represented by x, the uniform structure was represented by o, and the abnormal grain growth was represented by *.

The relative permeability is shown in (Table 4), the dimensional change rate is shown in (Table 5), and the result of SEM observation is shown in (Table 6). The characteristics of the powder C alone are that the relative magnetic permeability is 3870 and the dimensional change rate is -2.
It was 0.2%.

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

[Table 6]

As is clear from (Table 4), (Table 5) and (Table 6), when the additive amount is 0.02 wt% or more and 5.0 wt% or less relative to the metal powder, the relative magnetic permeability is 3000 or more. It can be seen that the dimensional change rate is -0.5% or more and + 0.5% or less, which is very small and the structure is uniform.

In the examples, the case where the additive is used alone is shown, but the total amount of addition is 0.02 wt% or more of the metal powder,
It goes without saying that if the addition amount is 5.0 wt% or less, the same effect can be obtained by the composite addition. In addition, the oxides mentioned in the examples are oxides of other forms (for example, CaCO ₃ → Ca).
It goes without saying that the same effect can be obtained with O).

[0031]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, by adding at least one kind of an additive generated in the firing process of a liquid phase to the oxide and the metal powder constituting ferrite, and firing the mixture, A ferrite material with good magnetic properties that is shrinkable is obtained.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01F 1/34 (72) Inventor Shinji Harada 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A ferrite material obtained by adding at least one kind of an additive generated in a firing process of a liquid phase to an oxide and a metal powder constituting ferrite and firing the mixture. 2. Bi ₂ O ₃ , V ₂ O ₅ , Pb as an additive
O, B ₂ O ₃ , SiO ₂ , CaCO ₃ , Sb ₂ O ₃ , LiCO
The ferrite material according to claim 1, containing at least one or more of ₃ and glass powder. 3. The ferrite material according to claim 1, wherein the amount of the additive is at least 0.02 wt% and not more than 5.0 wt% with respect to the metal powder. 4. An oxide of ZnO, NiO, CuO,
MnO ₂ , Fe ₂ O ₃ , ZnFe ₂ O ₄ , NiFe ₂ O ₄ , C
The ferrite material according to claim 1, containing at least one kind of uFe ₂ O ₄ , MnFe ₂ O ₄ , and Fe ₃ O ₄ . 5. Zn, Ni, Cu, M as metal powder
The ferrite material according to claim 1, comprising at least one kind of n and Fe. 6. A powder obtained by adding at least one kind of an additive generated in a firing process of a liquid phase to an oxide and a metal powder forming a ferrite is mixed with a binder, and molded into a predetermined shape. Then, a method for producing a ferrite material obtained by firing.