JP2004043262A - Mn-Zn FERRITE AND ITS MANUFACTURING PROCESS - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide Mn-Zn ferrite of high magnetic permeability stably by excluding adverse effect due to B without especially reducing the B in iron oxide. <P>SOLUTION: The Mn-Zn ferrite is obtained by compounding and sintering iron nitride and is essentially composed of MnO of 20-30mol%, ZnO of 18-25mol% and Fe<SB>2</SB>O<SB>3</SB>being remainder. Further, in the essential component, SiO<SB>2</SB>of 0.001-0.02mass% and CaO of 0.005-0.1mass% are contained. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
【発明の効果】
この発明によれば、窒化鉄を配合し、かつ主成分と添加する微量成分の組成を適正な範囲で選択することにより、高透磁率のＭｎ−Ｚｎ系フェライトを安定して得ることができる。この発明のＭｎ−Ｚｎ系フェライトをスイッチング電源のパルストランスやノイズフィルターの磁芯に適用することによって、小型で高性能なスイッチング電源を構成することが可能となる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a Mn-Zn based ferrite having a high initial magnetic permeability, which is suitable as a coil core used for a switching power supply or the like, and a method for producing the same.
[0002]
[Prior art]
For example, a noise filter used in a switching power supply is required to have a high impedance to a noise signal in a frequency band from which noise is to be removed. Therefore, the ferrite core used in the noise filter must have high magnetic permeability. Further, a pulse transformer used for transmitting a digital signal also requires a ferrite core having high magnetic permeability.
[0003]
The initial permeability of the Mn-Zn ferrite core is determined by the composition ratio of Fe ₂ O ₃ , MnO, and ZnO and the crystal grain size, which constitute the main phase and control the magnetic anisotropy constant and magnetostriction constant. It is known that it is greatly affected by the dominant trace components and the firing conditions, and attempts have been made to achieve high magnetic permeability by various methods.
For example, in JP-B-51-49079, by adding an appropriate amount of _Bi 2 _{0 3} and CaO in Mn-Zn ferrite, to obtain a material with a high degree 8,000 to 9,000 permeability. Japanese Patent Application Laid-Open No. 2001-85217 discloses that a high magnetic permeability material of 15000 or more is realized by containing 0.0003 to 0.003% by weight of P and setting the average crystal grain size to 50 μm to 200 μm. I have.
[0004]
[Problems to be solved by the invention]
Incidentally, impurities contained in Mn—Zn-based ferrite, particularly B (boron), have a great effect on magnetic properties. That is, regarding the influence of B among the trace components in the Mn-Zn-based ferrite, for example, the document “Ferrite” (Hiraga et al., Maruzen Co., 1986), p. It must be kept at 50 ppm or less because it inhibits the development of magnetic susceptibility. " In addition, under severe manufacturing conditions such as raising the firing temperature or reducing the particle size of the pulverized powder in order to obtain a higher magnetic permeability material, the effect of B becomes apparent, Is preferably as low as possible.
[0005]
Most of the B is inevitably contained in iron oxide which accounts for about half or more of the total weight among iron oxide, manganese oxide and zinc oxide, which are main raw materials of Mn-Zn ferrite.
[0006]
Conventionally, attempts have been made to improve magnetic properties by a method of reducing B in iron oxide. However, it takes a great deal of time and cost to produce an iron oxide raw material having a significantly reduced B content. There was a problem of cost.
[0007]
Therefore, an object of the present invention is to eliminate the adverse effects of B in iron oxide without particularly reducing B, thereby stably providing a Mn-Zn-based ferrite having high magnetic permeability. .
[0008]
[Means for Solving the Problems]
The gist configuration of the present invention is as follows.
(1) mixing an iron nitride, an Mn-Zn ferrite obtained by sintering, MnO: 20~30mol%, ZnO: 18~25 mol% and _Fe 2 _{0 3:} the balance as the basic component, the during basic _components, SiO 2: 0.001 _~0.02mass% and CaO: 0.005 ~0.1 mass% Mn- Zn ferrite comprising the component composition containing.
[0009]
(2) The Mn-Zn ferrite according to (1), wherein the compounding amount of the iron nitride is 0.01 to 2.0 mass%.
[0010]
(3) above (1) or (2), further bismuth oxide _(Bi 2 _{0 3} basis), indium oxide _{(an In} 2 _{0 3} basis), tantalum oxide _(Ta 2 _{0 5} equivalent), niobium oxide _(Nb 2 0 ₅ equivalent), titanium oxide (Ti0 ₂ equivalent), is selected from tin oxide (SnO ₂ basis) and molybdenum oxide (MoO3 equivalent), either one or not more than 0.3 mass% or less of the range of two or more in total A Mn-Zn ferrite having a contained component composition.
[0011]
(4) After wet mixing and drying iron oxide, manganese oxide and zinc oxide, heat treatment is performed to obtain a calcined powder. Then, at least SiO ₂ and CaO are added to the calcined powder and iron nitride is added. A method for producing a Mn-Zn ferrite in which the powder is added, pulverized, formed into a predetermined shape, and then fired.
[0012]
(5) The method for producing a Mn-Zn-based ferrite according to the above (4), wherein the addition amount of the iron nitride is 0.01 to 2.0 mass%.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically.
Structural factors for realizing high permeability ferrite include a sintered density and a crystal grain size. As described above, B mainly contained in iron oxide induces these structural factors in a direction unfavorable for a high magnetic permeability material. However, it is apparent that the addition of iron nitride greatly reduces this adverse effect. became.
[0014]
Here, it is presumed that the iron nitride compounded into the ferrite raw material prior to the firing of the ferrite has the following effects. That is, in the firing step, nitrogen atoms destabilized with increasing temperature and dissociated from the iron nitride combine with B in the raw material to form a stable and highly electrically insulating nitride. Segregates at the grain boundaries during the sintering process. Such a phenomenon suppresses the adverse effect of B, which makes the crystal structure non-uniform, further improves the purity of individual crystal grains, facilitates magnetization, and suppresses eddy current flowing in the sintered body. Therefore, a high magnetic permeability can be obtained.
[0015]
Note that iron atoms derived from iron nitride are oxidized in a normal ferrite baking step to form a spinel phase, so that an appropriate addition amount does not adversely affect magnetic properties.
As described above, the present invention has achieved excellent magnetic properties based on a novel concept of detoxifying harmful elements.
[0016]
In accordance with this invention, the iron nitride to be incorporated in the ferrite raw material, chemical formula as long as it can be displayed in _{Fe x N (X> 0)} , no matter its physical form. For example, powders of Fe ₃ N, Fe ₄ N, and the like can be given. The iron nitride only needs to be contained in the material to be fired in the firing step, and, of course, may be blended in any step before firing.
[0017]
Here, it is preferable to mix the iron nitride in a range of 0.01 to 2.0 mass%. That is, if the content is less than 0.01 mass%, the above-described effect is not exhibited. On the other hand, if the content exceeds 2.0 mass%, the crystal structure becomes inhomogeneous, and the magnetic characteristics deteriorate.
[0018]
On the other hand, the composition of the Mn-Zn ferrite, in order to realize the desired for high permeability, firstly the basic components, ZnO: 18~25mol%, MnO: 20~30mo1% and _Fe 2 O: balance Range. This is to control factors such as the magnetic anisotropy constant and the magnetostriction constant, which are determined by the composition ratio and affect the magnetic permeability.
[0019]
Further, in the above basic _components, SiO 2: 0.001 _~0.02mass% and CaO: it is important to contain 0.005 to 0.1 mass%. That, SiO ₂ and CaO, by segregating at the grain boundaries, which contribute to reducing the magnetic loss, to suppress a decrease in permeability. For this _purpose, SiO 2: _0.001mass% or more and CaO: More than 0.005 mass% is _necessary, SiO 2: _0.02mass% and CaO: If more than 0.1 mass%, grain growth inhibiting Or, conversely, abnormal grain growth occurs and pores remain in the crystal grains, so that it becomes difficult to control the crystal structure and the magnetic permeability is reduced.
[0020]
Other additive components, while increasing the permeability, such to improve its frequency characteristics, for a variety of purposes, bismuth oxide _(Bi 2 _{0 3} basis), indium oxide _{(an In} 2 _{0 3} basis), tantalum oxide ( ta ₂ 0 ₅ equivalent), niobium oxide _(Nb 2 _{0 5} equivalent), titanium oxide (Ti0 ₂ equivalent), is selected from tin oxide (SnO ₂ basis) and molybdenum oxide (MoO3 conversion), one kind or two or Species or more can be contained in a range of 0.3 mass% or less in total.
[0021]
That is, Bi ₂ O ₃ and In ₂ O ₃ contribute to high permeability by promoting crystal growth as low melting point compounds.
Further, TiO ₂ and SnO ₂ is by a high resistance to crystallization inside, and _Ta 2 _{0 5} and _Nb 2 _{0 5} is by height Koka grain boundaries, to reduce the respective eddy current loss, high It contributes to magnetic susceptibility. Further, MoO ₃ contributes to high magnetic permeability by promoting uniform grain growth. These are all effective when added in trace amounts. On the other hand, if each of the additional components is excessive, the magnetic properties are degraded due to an increase in porosity or abnormal grain growth. Therefore, one or more of the above seven components is 0.3 mass% or less in total. It is preferable to contain in the range of.
[0022]
The above-mentioned Mn-Zn-based ferrite is wet-mixed with iron oxide, manganese oxide and zinc oxide, dried, and then subjected to a heat treatment to form a calcined powder. Then, at least SiO ₂ and CaO are added to the calcined powder. At the same time, it is obtained by adding iron nitride, pulverizing and molding into a predetermined shape, and then firing this molded body.
The firing temperature varies depending on the composition of the main component and the trace component and the target magnetic properties, but is preferably 1300 ° C. or higher.
[0023]
【Example】
Various iron oxides, manganese oxides and zinc oxides, whose B contents are known by X-ray fluorescence analysis, are wet-mixed and dried, and then calcined at 950 ° C. for 3 hours to produce calcined powder. did. Then, the calcined _{powder, SiO 2, CaO, Bi 2} 0 3, In 2 O 3, Ta 2 0 5, Nb 2 0 5, TiO 2, SnO 2, MoO 3 and, Fe ₃ N or _Fe 4 N Was added as appropriate, and after wet pulverization with a ball mill for 10 hours, the mixture was molded into a ring-shaped core. The molded body is heated in the air at a heating rate of 250 ° C./h, and at a temperature of 1100 ° C. or more, the temperature is raised to a maximum temperature of 1350 ° C. in nitrogen at a heating rate of 500 ° C./h. After holding for 3 hours, the mixture was cooled. From the maximum temperature holding region to the cooling region, the atmospheric oxygen concentration was controlled by a mixed gas of air and nitrogen so that the equilibrium oxygen partial pressure at which a spinel phase was formed was obtained. Table 1 shows the composition of the produced sintered body and the type and amount of the compounded iron nitride.
[0024]
A winding was applied to the sample thus obtained, and the relative initial magnetic permeability μ _i / μ ₀ with respect to vacuum was measured. Table 1 also shows the measurement results. The magnetic permeability was measured using an impedance analyzer under the conditions of 10 kHz and 23 ° C. In Table 1, the sample No. Sample Nos. 1 to 15 and 34 are Invention Examples and Sample Nos. 16 to 33 are comparative examples.
[0025]
[Table 1]

[0026]
【The invention's effect】
According to the present invention, a high magnetic permeability Mn-Zn ferrite can be stably obtained by blending iron nitride and selecting the composition of the main component and the added minor component within an appropriate range. By applying the Mn-Zn-based ferrite of the present invention to a pulse transformer of a switching power supply or a magnetic core of a noise filter, a small and high-performance switching power supply can be configured.

Claims (5)

Mn-Zn ferrite obtained by blending and firing iron nitride,
MnO: 20 to 30 mol%,
ZnO: 18 to 25 mol% and Fe ₂ O ₃ : The balance is a basic component.
SiO ₂ : 0.001 to 0.02 mass% and CaO: 0.005 to 0.1 mass%
Mn-Zn based ferrite having a component composition containing The Mn-Zn-based ferrite according to claim 1, wherein the compounding amount of the iron nitride is 0.01 to 2.0 mass%. According to claim 1 or 2, further bismuth oxide _(Bi 2 _{0 3} basis), indium oxide _{(an In} 2 _{0 3} basis), tantalum oxide _(Ta 2 _{0 5} equivalent), niobium oxide _(Nb 2 _{0 5} equivalent), titanium oxide (In terms of TiO ₂ ), tin oxide (in terms of SnO ₂ ), and molybdenum oxide (in terms of MoO ₃ ), which have a component composition containing at least one of them in a range of 0.3 mass% or less in total. Mn-Zn ferrite. After wet mixing and drying iron oxide, manganese oxide, and zinc oxide, heat treatment is performed to obtain a calcined powder. Then, at least SiO ₂ and CaO are added to the calcined powder, and iron nitride is added. A method for producing a Mn-Zn-based ferrite, which comprises pulverizing and molding into a predetermined shape, and then firing the compact. The method for producing a Mn-Zn-based ferrite according to claim 4, wherein the addition amount of the iron nitride is 0.01 to 2.0 mass%.