JP2004238211A - Manganese-zinc ferrite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Mn-Zn ferrite having excellent initial permeability in high frequency region of MHz order. <P>SOLUTION: The Mn-Zn ferrite contains ≥43.0 mol% to <50.0 mol% Fe<SB>2</SB>O<SB>3</SB>, ≥16.5 mol% to 24.0 mol% ZnO and the balance MnO as basic components and 0.005-0.100 mass% CaO and 0.001-0.025 mass% SiO<SB>2</SB>as assistant components and P and B contained in the ferrite are suppressed to be respectively <50 ppm and <20 ppm. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２６】
同表に示したとおり、発明例はいずれも、異常粒成長の発生がなく、１ｋＨｚ での初透磁率が４０００以上，１０ ＭＨｚでの初透磁率が ２２０以上という優れた特性を有している。
これに対し、Ｆｅ_２Ｏ_３ が ５０．０ｍｏｌ％以上の比較例（試料番号１−１， １−２ ）はいずれも、比抵抗が低いため、高周波域で渦電流損失の影響を受け、１０ ＭＨｚでの初透磁率は１になっている。また、Ｆｅ_２Ｏ_３ が ４３．０ｍｏｌ％未満の比較例（試料番号１−１４）およびＺｎＯが １６．５ｍｏ１％未満の比較例（試料番号１−１１）はいずれも、１ｋＨｚ での初透磁率が目標値の４０００よりも低い値に止まっている。
さらに、副成分であるＣａＯおよびＳｉＯ_２に着目すると、両成分を含まない比較例（試料番号１−８ ）は、１０ ＭＨｚでの初透磁率の値が極めて小さく、一方両成分を上限値を超えて多量に含有する比較例（試料番号１−９ ）は、異常粒成長の発生が確認され、磁気特性、比抵抗とも著しく劣化している。
【００２７】
実施例２
ＢおよびＰの含有量が異なる種々の酸化鉄原料を使用し、試料が最終的にＰ：５０ ｐｐｍ以下， Ｂ：２０ ｐｐｍ以下の種々の値をとるように計算した上で、焼成後の比率が Ｆｅ_２Ｏ_３：４８．５ ｍｏｌ％，ＺｎＯ：２１．０ ｍｏｌ％，残部：ＭｎＯとなるように調整した原料を、秤量し、ボールミルを用いて混合した後、空気中にて ９２５℃， ３時間の仮焼を行った。次に、副成分としてＣａＯおよびＳｉＯ_２を、最終的にそれぞれ０．０５０ｍａｓｓ％，０．０１０ ｍａｓｓ％となるよう添加し、ボールミルで１２時間の粉砕を行った。この混合粉に、ポリビニルアルコールを加えて造粒し、１１８ ＭＰａ （１．２ ｔｏｎ／ｃｍ^２）の圧力を加えてトロイダルコアを成形した。その後、この成形体を焼戌炉に入れ、窒素流入により酸素濃度を制御した雰囲気中にて１３５０℃の温度で焼成した後、冷却し、外径：３０．５ｍｍ、内径：１８．５ｍｍ、高さ：６．３ ｍｍの焼結体コアを得た。
これらの各試料について、結晶粒径、比抵抗および１ｋＨｚ，１０ ＭＨｚにおける初透磁率を測定した。
得られた結果を表２に示す。
【００２８】
【表２】

【００２９】
同表から明らかなように、ＰおよびＢ成分がそれぞれ５０ ｐｐｍ未満、２０ ｐｐｍ未満を同時に満たす発明例（試料番号２−１ ，２−２ ）はいずれも、異常粒成長が見られず、比抵抗が８０Ω・ｍ 以上で、初透磁率については１ｋＨｚ で４０００以上、１０ ＭＨｚで ２２０以上という優れた特性値が得られた。
これに対し、Ｐ， Ｂ成分のどちらか一方、または両方とも上限値を超えて含有する比較例（試料番号２−３ ，２−４ ，２−５ ）はいずれも、異常粒の発生が観察され、比抵抗および初透磁率ともに大きく劣化している。
【００３０】
実施例３
実施例１の発明例について、 Ｆｅ_２Ｏ_３およびＺｎＯ量を次式（１）’
ｘ−２ｙ −−− （１）’
ただし、ｘ：Ｆｅ_２Ｏ_３ 量（ ｍｏｌ％）、
ｙ：ＺｎＯ量（ ｍｏｌ％）
に代入した時の値およびキュリー温度について調査した結果を、表３に示す。
【００３１】
【表３】

【００３２】
同表に示したとおり、上掲式（１）’で示した Ｆｅ_２Ｏ_３量とＺｎＯ量の関係式が ６．０以上を満足する場合には、キュリー温度を実用上問題を生じない目安である １２０℃以上に制御できることが分かる。従って、Ｆｅ_２Ｏ_３ とＺｎＯの成分比は、前掲式（１）の関係を満足する範囲に調整することが望ましい。
【００３３】
実施例４
実施例２と同組成の混合粉（但し、Ｐ：５ ｐｐｍ， Ｂ：５ ｐｐｍ）に、副成分であるＣａＯおよびＳｉＯ_２をそれぞれ最終成分が０．０５０ ｍａｓｓ％，０．０１０ ｍａｓｓ％となるように添加し、さらに添加物としてＺｒＯ_２， Ｔａ_２Ｏ_５， ＨｆＯ_２， Ｎｂ_２Ｏ_５（第１添加成分群）をそれぞれ最終成分が表４に示すとおりになるよう加え、ボールミルで１２時間の粉砕を行った。この混合粉に、ポリビニルアルコールを加えて造粒し、１１８ ＭＰａ （１．２ ｔｏｎ／ｃｍ^２） の圧力を加えてトロイダルコアを成形し、その後、この成形体を焼成炉に入れ、窒素流入により酸素濃度を制御した雰囲気中にて１３５０℃の温度で焼成したのち、冷却し、外径：３０．５ｍｍ、内径：１８．５ｍｍ、高さ：６．３ ｍｍの焼結体コアを得た。
これらの各試料について、結晶粒径、比抵抗および１ｋＨｚ および１０ ＭＨｚにおける初透磁率を測定した。
得られた結果を表４に示す。
【００３４】
【表４】

【００３５】
同表に示したとおり、ＺｒＯ_２， Ｔａ_２Ｏ_５， ＨｆＯ_２， Ｎｂ_２Ｏ_５をそれぞれ、最終的に成分がＺｒＯ_２：０．００５ 〜０．１００ ｍａｓｓ％、Ｔａ_２Ｏ_５ ： ０．００５ 〜０．１００ ｍａｓｓ％、ＨｆＯ_２：０．００５ 〜０．１００ ｍａｓｓ％、Ｎｂ_２Ｏ_５ ： ０．００５ 〜０．１００ ｍａｓｓ％を満足する範囲で１種または２種以上添加した発明例（試料番号３−１ 〜３−１５）はいずれも、結晶の成長が抑制され、その結果比抵抗および１０ ＭＨｚにおける初透磁率が上昇した。
しかしながら、これら４成分のうち１種類でも適正範囲を超えて多量に含有する比較例（試料番号３−１６〜３−１８）では、異常粒成長を誘発し、不純物を多く含む異常粒内での磁壁の移動がスムーズに行かないことおよび非磁性イオンの増加が原因となって、低周波および高周波領域共に初透磁率が低い値に止まっている。
【００３６】
実施例５
実施例２と同組成の混合粉（但し、Ｐ：５ ｐｐｍ， Ｂ：５ ｐｐｍ）に、副成分としてＣａＯおよびＳｉＯ_２をそれぞれ最終成分が０．０５０ ｍａｓｓ％，０．０１０ ｍａｓｓ％となるように添加し、さらに添加物としてＶ_２Ｏ_５， Ｂｉ_２Ｏ_３， Ｉｎ_２Ｏ_３， ＭｏＯ_３およびＷＯ_３（第２添加成分群）をそれぞれ、焼結体中の成分が表５に示すとおりになるよう加え、ボールミルで１２時間の粉砕を行った。この混合粉に、ポリビニルアルコールを加えて造粒し、１１８ ＭＰａ （１．２ ｔｏｎ／ｃｍ^２） の圧力を加えてトロイダルコアを成形し、その後この成形体を焼成炉に入れ、窒素流入により酸素濃度を制御した雰囲気中にて１３５０℃の温度で焼成したのち、冷却し、外径：３０．５ｍｍ、内径：１８．５ｍｍ、高さ：６．３ ｍｍの焼結体コアを得た。
これらの各試料について、結晶粒径、比抵抗および１ｋＨｚ および１０ ＭＨｚにおける初透磁率を測定した。
得られた結果を表５に示す。
【００３７】
【表５】

【００３８】
表５に示したとおり、Ｖ_２Ｏ_５， Ｂｉ_２Ｏ_３， Ｉｎ_２Ｏ_３， ＭｏＯ_３およびＷＯ_３の１種または２種以上を適量添加した発明例（試料番号４−１ 〜４−３１）はいずれも、結晶粒の成長および焼結密度の上昇が見られ、その結果無添加のものに比べて１ｋＨｚ における初透磁率が上昇した。
これに対し、５成分のうちどれか１つでも適正な値より多く含む比較例（試料番号４−３２， ４−３３）はいずれも、異常粒が発生し、粒内に多数の不純物、空孔を含むため、初透磁率、比抵抗はともに大きく劣化している。
【００３９】
実施例６
実施例２と同組成の混合粉（但し、Ｐ：５ ｐｐｍ， Ｂ：５ ｐｐｍ）に、副成分としてＣａＯおよびＳｉＯ_２をそれぞれ最終成分が０．０５０ ｍａｓｓ％，０．０１０ ｍａｓｓ％となるように添加し、さらに添加物としてＺｒＯ_２， Ｔａ_２Ｏ_５， ＨｆＯ_２， Ｎｂ_２Ｏ_５（第１添加成分群）およびＶ_２Ｏ_５， Ｂｉ_２Ｏ_３， Ｉｎ_２Ｏ_３， ＭｏＯ_３， ＷＯ_３（第２添加成分群）をそれぞれ、焼結体中の成分が表６に示すとおりになるよう組み合わせて加え、ボールミルで１２時間の粉砕を行った。この混合粉に、ポリビニルアルコールを加えて造粒し、１１８ ＭＰａ（１．２ ｔｏｎ／ｃｍ^２） の圧力を加えてトロイダルコアを成形し、その後この成形体を焼成炉に入れ、窒素流入により酸素濃度を制御した雰囲気中にて１３５０℃の温度で焼成したのち、冷却し、外径：３０．５ｍｍ、内径：１８．５ｍｍ、高さ：６．３ ｍｍの焼結体コアを得た。
これらの各試料について、結晶粒径、比抵抗および１ｋＨｚ および１０ ＭＨｚにおける初透磁率を測定した。
得られた結果を表６に示す。
【００４０】
【表６】

【００４１】
表６に示したとおり、第１添加成分群および第２添加成分群に記載の添加物を組み合わせて添加した発明例（試料番号５−１ 〜５−２７）はいずれも、これらが無添加の場合に比べて、１ｋＨｚ および１０ ＭＨｚにおける初透磁率が共に上昇した。
これに対し、これら９成分のうちどれか１つでも適正な値より多く含む比較例（試料番号５−２８〜５−３０）はいずれも、異常粒が発生し、また粒内に多数の不純物や空孔を含むために、初透磁率および比抵抗ともに大きく劣化している。
【００４２】
【発明の効果】
かくして、本発明に従い、Ｆｅ_２Ｏ_３ ： ４３．０ ｍｏｌ％以上、５０．０ ｍｏｌ％未満、ＺｎＯ：１６．５ ｍｏｌ％以上、２４．０ ｍｏｌ％以下、残部：ＭｎＯの基本組成になるＭｎ−Ｚｎフェライトに、副成分としてＣａＯおよびＳｉＯ_２の１種または２種添加し、粒界偏析および焼結促進の効果を利用することにより、比抵抗が７０Ω・ｍ 以上で、高周波領域である１０ ＭＨｚでの初透磁率が ２２０を超えるＭｎ−Ｚｎフェライトを得ることができる。
また、この組成に、ＺｒＯ_２， Ｔａ_２Ｏ_５， ＨｆＯ_２ および Ｎｂ_２Ｏ_５（第１添加成分群）を適量添加することにより高周波領域における初透磁率のさらなる上昇を、他方Ｖ_２Ｏ_５， Ｂｉ_２Ｏ_３， Ｉｎ_２Ｏ_３， ＭｏＯ_３およびＷＯ_３（第２添加成分群）を適量添加させることにより低周波領域における初透磁率を上昇させることができ、加えてこれらを組み合わせて添加することにより、高周波領域および低周波領域両方の初透磁率の上昇を達成することができる。
さらに、原料酸化鉄に含まれるＰやＢのフェライトへの混入を極力制限することにより、実用上発生する不良品を減少させることができ、製造の安定化に大きく貢献する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to Mn-Zn ferrite, and more particularly to achieve an advantageous improvement in initial magnetic permeability in a high-frequency region on the order of MHz.
[0002]
[Prior art]
A typical example of the soft magnetic oxide magnetic material is Mn-Zn ferrite. When this Mn-Zn ferrite is used as a material having a high initial permeability, the amount of Fe ²⁺ having a positive magnetic anisotropy is increased to offset the amount of Fe ³⁺ having a negative magnetic anisotropy at around room temperature. An operation of obtaining a high initial magnetic permeability is performed. In addition, since the initial magnetic permeability is proportional to the easiness of movement of the domain wall in the crystal grain, the firing conditions and additives are adjusted so that the crystal grain becomes large to assist the movement of the domain wall.
[0003]
However, when the amount of Fe ^{2+ is} increased, the transfer of electrons between Fe ³⁺ -Fe ²⁺ is likely to occur, and as a result, the specific resistance becomes a very small value, that is, to the order of 0.1 (Ω · m). There is a disadvantage that it is lowered. Therefore, as the frequency range used increases, the loss due to eddy current flowing in the ferrite increases rapidly.
Further, as the crystal grains become coarse, domain wall loss due to domain wall components in the crystal grains also increases.
Due to these effects, a problem arises that the initial permeability of the Mn-Zn ferrite is remarkably reduced in a high frequency region, and the practical useful frequency is limited to about several hundred kHz.
[0004]
For this reason, Ni-Zn ferrite is mainly used as ferrite used in a frequency range on the order of MHz. The reason is that the Ni—Zn ferrite has a very high specific resistance of about 10,000 times that of the Mn—Zn ferrite, that is, about 10 ⁵ (Ω · m). That is, the attenuation of the initial magnetic permeability is small even in the region.
However, since Ni is used instead of Mn, the saturation magnetization and the initial permeability are smaller than that of Mn-Zn ferrite, and there still remains a problem in that the raw material NiO is more expensive than MnO.
[0005]
As a solution to the above problem, there is a technique of increasing the specific resistance by reducing the amount of Fe ²⁺ contained in the Mn—Zn ferrite, reducing the eddy current loss, and coping with high frequencies.
One such method, _Fe 2 _{O 3} component reduced the amount of ^{Fe 2+} as less than 50 mol% of raising the specific resistivity, Mn-Zn ferrite having high initial permeability even in the high frequency region has been proposed (e.g. Patent Documents 1).
However, this technique adds only low-melting-point additives such as V ₂ O ₅ and Bi ₂ O _{3 as} additives to grow the crystal grain size, and to increase the initial magnetic permeability in a low-frequency region with this composition. It is the main focus, and no operation is performed on the control of grain boundaries and the optimization of the crystal grain size for the purpose of increasing the specific resistance and taking measures against high frequency. Therefore, as compared with ordinary Mn-Zn ferrite, the initial magnetic permeability at 10 MHz is 100 or more, and although the effect is somewhat improved, the initial magnetic permeability in a high frequency region is still low.
[0006]
Another problem in the production of ferrite is abnormal grain growth. This abnormal grain growth is a phenomenon that often occurs when manufacturing is performed using powder metallurgy, which occurs when the grain growth is locally unbalanced for some reason. Since a substance that greatly hinders the movement of the domain wall is mixed, the soft magnetic characteristics are significantly deteriorated. Therefore, suppression of abnormal grain growth is an important point in ferrite production.
[0007]
Furthermore, since Fe ₂ O _{3, which} is a ferrite raw material, mainly depends on the scale generated at the time of iron making, it is inevitable that P and B components contained in steel are mixed to some extent. Ferrite containing these impurities in excess of an appropriate amount induces abnormal grain growth and consequently has a serious adverse effect on various properties such as magnetic properties of the Mn-Zn ferrite.
However, in Patent Document 1 mentioned above, such an amount of impurities is not limited, and therefore, the production of Mn—Zn ferrite having desirable properties as described in the document is almost impossible only based on this document. Impossible and extremely low feasibility.
[0008]
[Problems to be solved by the invention]
The present invention advantageously solves the above-mentioned problems. The present invention suppresses the crystal grain size smaller than that of the conventional one, and sufficiently grows the grain boundaries by adding CaO and SiO ₂ , thereby achieving eddy current loss and domain wall loss. It is an object of the present invention to propose a Mn-Zn ferrite capable of effectively reducing Mn-Zn ferrite in a high frequency region.
Further, the present invention suppresses abnormal grain growth of ferrite by providing appropriate limits to the P and B components contained in ferrite, thereby achieving stable production of Mn-Zn ferrite having the above characteristics. is there.
[0009]
[Patent Document 1]
JP 2001-220222A (Claims, paragraph [0011])
[0010]
[Means for Solving the Problems]
That is, the gist configuration of the present invention is as follows.
1. Fe ₂ O ₃ : 43.0 mol% or more and less than 50.0 mol%,
ZnO: 16.5 mol% or more, 24.0 mol% or less,
MnO: balance was used as a basic component, CaO as an auxiliary component: 0.005 to 0.100 mass% and _SiO 2: 0.001 _~0.025 mass%
And the value of P contained in the ferrite is suppressed to less than 50 ppm and the value of B is suppressed to less than 20 ppm.
[0011]
2. In the above item 1, Fe ₂ O ₃ and ZnO among the basic components are
Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%,
ZnO: 17.0 mol% or more and 21.5 mol% or less, and the following formula (1)
x-2y ≧ 6.0 (1)
However, x: Fe ₂ O ₃ amount (mol%),
y: ZnO amount (mol%)
A Mn-Zn ferrite, characterized by having a Curie temperature of 120 ° C. or higher.
[0012]
3. In the above 1 or 2, the ferrite further contains ZrO ₂ : 0.005 to 0.100 mass%,
_{Ta 2 O 5: 0.005 ~0.100 mass} %,
HfO _2: 0.005 ~0.100 mass% and _{Nb 2 O 5: 0.005 ~0.100 mass} %
Mn-Zn ferrite comprising one or more selected from the group consisting of:
[0013]
4. In the 1, 2 or 3, ferrite, further _{V 2 O 5: 0.001 ~0.100 mass} %,
_{Bi 2 O 3: 0.001 ~0.050 mass} %,
In ₂ O ₃ : 0.001 to 0.050 mass%,
MoO _3: 0.001 ~0.050 mass% and _WO 3: 0.001 _~0.050 mass%
Mn-Zn ferrite comprising one or more selected from the group consisting of:
[0014]
By controlling the grain boundary and the grain size in the above-described configuration, the Curie temperature is 120 ° C. or higher, and the initial permeability at room temperature (23 ° C.) is 1 kHz. Excellent characteristics of 220 or more can be obtained.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described specifically.
First, the reason why the basic component and the subcomponent are limited to the above ranges in the present invention will be described.
Fe ₂ O ₃ : 43.0 mol% or more and less than 50.0 mol% When the amount of Fe ₂ O ₃ is excessive among the basic components, the amount of Fe ²⁺ increases, thereby increasing the specific resistance of the Mn—Zn ferrite. And adversely affect the magnetic properties in the high frequency range. In order to avoid this, the amount of Fe ₂ O ₃ needs to be suppressed to less than 50 mol%. However, if the amount is too small, the saturation magnetization, the initial magnetic permeability, and the Curie temperature will be lowered. Therefore, the content should be at least 43.0 mol%.
[0016]
ZnO: 16.5 mol% or more and 24.0 mol% or less ZnO is an effective component for increasing the sintering density because it increases the saturation magnetization of ferrite and has a relatively low saturated vapor pressure. In order to obtain these effects, it is necessary to contain at least 16.5 mol%. However, excessive addition causes a decrease in saturation magnetization, so ZnO is contained in the range of 16.5 to 24.0 mol%. Limited to.
[0017]
Further, both Fe ₂ O ₃ and ZnO described above affect the Curie temperature. In view of satisfying Tc ≧ 120 ° C., which is one measure of the Curie temperature that does not cause a practical problem, Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%, ZnO: 17.0 mol% or more and 21.5 mol% or less, and the following formula (1)
x-2y ≧ 6.0 (1)
However, x: Fe ₂ O ₃ amount (mol%),
y: ZnO amount (mol%)
Is desirably contained in a range that satisfies the relationship of
[0018]
CaO: 0.005 ~0.100 mass% and _SiO 2: 0.001 _~0.025 mass%
CaO and SiO ₂ have the effect of increasing the electrical resistance of ferrite by segregating at the crystal grain boundaries, and also have the effect of promoting sintering. However, if the added amount is too small, these effects cannot be clearly obtained. Therefore, it is necessary to add at least 0.005% by mass of CaO and 0.001% by mass of SiO ₂ . On the other hand, when added excessively, it induces abnormal grain growth in the ferrite grains, and since these additives are non-magnetic substances, they lower the initial permeability of ferrite. Therefore, these upper limits were respectively limited to 0.100 mass% of CaO and 0.025 mass% of SiO ₂ .
[0019]
In the present invention, it is also important to suppress the incorporation of P and B into the ferrite.
That is, both P and B are components contained in the raw iron oxide. If they are very small, they can promote ferrite grain growth.However, if they are contained in relatively large amounts, they induce abnormal ferrite grain growth and have a serious adverse effect on the properties of the resulting ferrite. Exert. Therefore, in the present invention, P and B are suppressed to less than 50 ppm and less than 20 ppm, respectively (preferably, both less than 10 ppm). Therefore, it is important to consider that these P and B are not mixed as much as possible in the raw material adjustment stage.
[0020]
As described above, the basic component and the sub-component have been described. However, in the present invention, the following components can be further appropriately contained.
_{ZrO 2: 0.005 ~0.100 mass%,} Ta 2 O 5: 0.005 ~0.100 mass%, HfO 2: 0.005 ~0.100 mass% and _Nb 2 _O 5: 0.005 ~ 0.100 mass% (first additive component group)
Each of these components is a compound having a high melting point, and when added to Mn-Zn ferrite, has a function of reducing crystal grains. However, if the amount is less than the lower limit described above, a sufficient effect cannot be obtained.On the other hand, if the added amount exceeds the upper limit, a decrease in initial magnetic permeability is caused. It is preferable to include them.
[0021]
_{V 2 O 5: 0.001 ~0.100 mass} %, Bi 2 O 3: 0.001 ~0.050 mass%, In 2 O 3: 0.001~0.050 mass%, MoO 3: 0. 001 to 0.050 mass% and _WO 3: 0.001 ~0.050 mass% (second additive component group)
Each of these components is a compound having a low melting point, and has a function of increasing the sintering density of Mn-Zn ferrite and increasing the initial magnetic permeability. However, if the addition amount is less than the lower limit, a sufficient effect cannot be obtained.On the other hand, if the addition amount exceeds the upper limit, the occurrence of abnormal grain growth and a decrease in the initial magnetic permeability in a high frequency region are caused. Is preferably contained in the above range.
[0022]
Next, a preferred method for producing Mn-Zn ferrite according to the present invention will be described.
In the production of Mn-Zn ferrite, first, Fe ₂ O ₃ , ZnO, and MnO powder, which are basic components, are weighed so as to have a predetermined ratio, and calcined after sufficiently mixing these. Then, the above-mentioned various additives are added to the obtained calcined powder at a predetermined ratio, and then pulverized. In this operation, it is important to sufficiently homogenize the powder so that the concentration of the added component is not biased. Thereafter, the powder having the target composition is granulated by using an organic binder such as polyvinyl alcohol, molded by applying pressure, and then fired under appropriate firing conditions.
[0023]
In the Mn-Zn ferrite thus obtained, the Fe2 ⁺ content is greatly reduced as compared with a normal Mn-Zn ferrite, so that the specific resistance is increased. In addition, since the thickness of the crystal grain boundary and the crystal grain size are controlled to appropriate values, the problem of reducing the initial magnetic permeability in a high-frequency region has been significantly improved.
Here, the thickness of the crystal grain boundary is preferably about 0.001 to 0.05 μm, and the crystal grain size is preferably about 7 to 13 μm.
[0024]
【Example】
Example 1
After firing, the raw material powders weighed so that the ratio of Fe ₂ O ₃ , ZnO and MnO become the values shown in Table 1 were mixed for 16 hours using a ball mill, and then mixed at 925 ° C. for 3 hours in the air. Calcination was performed. Then, CaO and SiO ₂ were added as accessory components so that the final composition after firing had the ratio shown in Table 1, and the mixture was ground by a ball mill for 12 hours. Polyvinyl alcohol was added to the mixed powder to granulate, and a pressure of 118 MPa (1.2 ton / cm ² ) was applied to form a toroidal core. Thereafter, the formed body is placed in a firing furnace, fired at a temperature of 1350 ° C. in an atmosphere in which the oxygen concentration is controlled by flowing nitrogen, and then cooled, and the outer diameter: 30.5 mm, the inner diameter: 18.5 mm, and the height: A 6.3 mm sintered body core was obtained.
For each of these samples, the crystal grain size, specific resistance, and initial magnetic permeability at 1 kHz and 10 MHz were measured.
Table 1 shows the obtained results.
[0025]
[Table 1]

[0026]
As shown in the table, all of the examples of the invention have excellent characteristics that no abnormal grain growth occurs and the initial permeability at 1 kHz is 4000 or more and the initial permeability at 10 MHz is 220 or more. .
On the other hand, the comparative examples (Sample Nos. 1-1 and 1-2) each containing 50.0 mol% or more of Fe ₂ O ₃ are affected by eddy current loss in a high frequency range because of low specific resistance. The initial magnetic permeability at MHz is 1. In addition, in each of Comparative Examples in which Fe ₂ O ₃ was less than 43.0 mol% (Sample No. 1-14) and Comparative Examples in which ZnO was less than 16.5 mol 1% (Sample No. 1-11), the initial permeability at 1 kHz was obtained. Is lower than the target value of 4000.
Further, paying attention to CaO and SiO ₂ as auxiliary component, Comparative Examples not containing both components (Sample No. 1-8), the very small value of initial magnetic permeability at 10 MHz, whereas the upper limit of both components In the comparative example (Sample No. 1-9) containing a large amount exceeding that, occurrence of abnormal grain growth was confirmed, and both the magnetic properties and the specific resistance were significantly deteriorated.
[0027]
Example 2
Using various iron oxide raw materials having different contents of B and P, calculation was made so that the sample finally took various values of P: 50 ppm or less, B: 20 ppm or less, and the ratio after firing. Were weighed and mixed using a ball mill, and then mixed at 925 ° C. in the air at a temperature of 925 ° C., with Fe ₂ O ₃ : 48.5 mol%, ZnO: 21.0 mol%, and the balance: MnO. Calcination was performed for 3 hours. Next, CaO and SiO ₂ were added as subcomponents so that the final amounts would be 0.050% by mass and 0.010% by mass, respectively, and pulverization was performed for 12 hours by a ball mill. Polyvinyl alcohol was added to the mixed powder to granulate, and a pressure of 118 MPa (1.2 ton / cm ² ) was applied to form a toroidal core. Thereafter, the molded body was placed in a burning furnace, fired at a temperature of 1350 ° C. in an atmosphere in which the oxygen concentration was controlled by inflow of nitrogen, cooled, and cooled to an outer diameter of 30.5 mm, an inner diameter of 18.5 mm and a height of 18.5 mm. Sa: A sintered body core of 6.3 mm was obtained.
For each of these samples, the crystal grain size, specific resistance, and initial magnetic permeability at 1 kHz and 10 MHz were measured.
Table 2 shows the obtained results.
[0028]
[Table 2]

[0029]
As is clear from the table, the invention examples (Sample Nos. 2-1 and 2-2) in which the P and B components simultaneously satisfy less than 50 ppm and less than 20 ppm respectively do not show abnormal grain growth, and When the resistance was 80 Ω · m or more, excellent characteristic values of initial magnetic permeability of 4000 or more at 1 kHz and 220 or more at 10 MHz were obtained.
On the other hand, in any of Comparative Examples (Sample Nos. 2-3, 2-4, 2-5) in which one or both of the P and B components exceeded the upper limit, generation of abnormal grains was observed. As a result, both the specific resistance and the initial magnetic permeability are greatly deteriorated.
[0030]
Example 3
Regarding the invention example of Example 1, the amounts of Fe ₂ O ₃ and ZnO were determined by the following formula (1) ′.
x-2y --- (1) '
However, x: Fe ₂ O ₃ amount (mol%),
y: ZnO amount (mol%)
Table 3 shows the results obtained by investigating the value and the Curie temperature at the time of substituting into.
[0031]
[Table 3]

[0032]
As shown in the table, when the relational expression between the amount of Fe ₂ O _{3 and the} amount of ZnO expressed by the above equation (1) ′ satisfies 6.0 or more, the Curie temperature is a measure that does not cause a practical problem. It can be seen that the temperature can be controlled to 120 ° C. or higher. Therefore, it is desirable to adjust the component ratio of Fe ₂ O ₃ and ZnO to a range that satisfies the relationship of the above-described formula (1).
[0033]
Example 4
In the mixed powder having the same composition as in Example 2 (however, P: 5 ppm, B: 5 ppm), CaO and SiO ₂ as sub-components have final components of 0.050 mass% and 0.010 mass%, respectively. And ZrO ₂ , Ta ₂ O ₅ , HfO ₂ , and Nb ₂ O ₅ (first additive component group) as additives, respectively, so that the final components are as shown in Table 4, and are added by a ball mill for 12 hours. Was crushed. Polyvinyl alcohol is added to the mixed powder to granulate, and a pressure of 118 MPa (1.2 ton / cm ² ) is applied to form a toroidal core. Thereafter, the formed body is placed in a firing furnace, and nitrogen is introduced by flowing nitrogen. After firing at a temperature of 1350 ° C. in an atmosphere with a controlled oxygen concentration, it was cooled to obtain a sintered body core having an outer diameter of 30.5 mm, an inner diameter of 18.5 mm, and a height of 6.3 mm.
For each of these samples, the crystal grain size, specific resistance, and initial permeability at 1 kHz and 10 MHz were measured.
Table 4 shows the obtained results.
[0034]
[Table 4]

[0035]
As shown in the table, ZrO ₂ , Ta ₂ O ₅ , HfO ₂ , and Nb ₂ O ₅ are each finally composed of ZrO ₂ : 0.005 to 0.100 mass%, and Ta ₂ O ₅ : 0. _{005 ~0.100 mass%, HfO 2:} 0.005 ~0.100 mass%, Nb 2 O 5: 0.005 ~0.100 invention example of adding one or more in a range satisfying mass% In all of (Sample Nos. 3-1 to 3-15), the crystal growth was suppressed, and as a result, the specific resistance and the initial permeability at 10 MHz increased.
However, in Comparative Examples (Sample Nos. 3-16 to 3-18) in which even one of these four components is contained in a large amount exceeding an appropriate range, abnormal grain growth is induced and abnormal grains containing a large amount of impurities are caused. The initial magnetic permeability remains at a low value in both the low-frequency and high-frequency regions due to the non-smooth movement of the domain wall and the increase in non-magnetic ions.
[0036]
Example 5
CaO and SiO ₂ were added as auxiliary components to the mixed powder having the same composition as in Example 2 (P: 5 ppm, B: 5 ppm) so that the final components became 0.050 mass% and 0.010 mass%, respectively. And V ₂ O ₅ , Bi ₂ O ₃ , In ₂ O ₃ , MoO ₃ and WO ₃ (second additive component group) as additives are shown in Table 5 below. And pulverized by a ball mill for 12 hours. Polyvinyl alcohol is added to the mixed powder to perform granulation, and a pressure of 118 MPa (1.2 ton / cm ² ) is applied to form a toroidal core. Thereafter, the formed body is placed in a firing furnace, and oxygen is introduced by flowing nitrogen. After firing at a temperature of 1350 ° C. in an atmosphere with a controlled concentration, the resultant was cooled to obtain a sintered body core having an outer diameter of 30.5 mm, an inner diameter of 18.5 mm, and a height of 6.3 mm.
For each of these samples, the crystal grain size, specific resistance, and initial permeability at 1 kHz and 10 MHz were measured.
Table 5 shows the obtained results.
[0037]
[Table 5]

[0038]
As shown in Table _{5, V 2 O 5, Bi} 2 O 3, In 2 O 3, invention example of an appropriate amount of one or more of MoO ₃ and WO ₃ (Sample No. 4-1 ～4-31 In each of the cases (1) and (2), the growth of crystal grains and an increase in the sintered density were observed, and as a result, the initial permeability at 1 kHz was increased as compared with the case where no additive was added.
On the other hand, in Comparative Examples (Sample Nos. 4-32 and 4-33) containing any one of the five components more than an appropriate value, abnormal grains were generated, and many impurities and vacancies were present in the grains. Because of the inclusion of the holes, both the initial permeability and the specific resistance are greatly degraded.
[0039]
Example 6
CaO and SiO ₂ were added as auxiliary components to the mixed powder having the same composition as in Example 2 (P: 5 ppm, B: 5 ppm) so that the final components became 0.050 mass% and 0.010 mass%, respectively. , And ZrO ₂ , Ta ₂ O ₅ , HfO ₂ , Nb ₂ O ₅ (first additive component group) and V ₂ O ₅ , Bi ₂ O ₃ , In ₂ O ₃ , MoO ₃ , WO as additives. ₃ (the second additive component group) was added in combination such that the components in the sintered body were as shown in Table 6, and pulverized for 12 hours by a ball mill. Polyvinyl alcohol is added to the mixed powder to perform granulation, and a pressure of 118 MPa (1.2 ton / cm ² ) is applied to form a toroidal core. Thereafter, the formed body is placed in a firing furnace, and oxygen is introduced by flowing nitrogen. After firing at a temperature of 1350 ° C. in an atmosphere with a controlled concentration, the resultant was cooled to obtain a sintered body core having an outer diameter of 30.5 mm, an inner diameter of 18.5 mm, and a height of 6.3 mm.
For each of these samples, the crystal grain size, specific resistance, and initial permeability at 1 kHz and 10 MHz were measured.
Table 6 shows the obtained results.
[0040]
[Table 6]

[0041]
As shown in Table 6, the invention examples (Sample Nos. 5-1 to 5-27) in which the additives described in the first additive component group and the second additive component group were added in combination, all of which did not contain these additives. The initial permeability at 1 kHz and 10 MHz both increased compared to the case.
On the other hand, in Comparative Examples (Sample Nos. 5-28 to 5-30) in which any one of these nine components is larger than an appropriate value, abnormal grains are generated and a large number of impurities are present in the grains. Because of the inclusion of pores and voids, both the initial magnetic permeability and the specific resistance are greatly degraded.
[0042]
【The invention's effect】
Thus, according to the present invention, Fe ₂ O ₃ : 43.0 mol% or more and less than 50.0 mol%, ZnO: 16.5 mol% or more and 24.0 mol% or less, and the balance: Mn which is a basic composition of MnO in -Zn ferrite, adding one or two CaO and SiO ₂ as an auxiliary component, by utilizing the effect of the grain boundary segregation and sintering accelerator, in specific resistance 70 ohm · m or more, a high frequency region 10 An Mn-Zn ferrite having an initial magnetic permeability in MHz exceeding 220 can be obtained.
Further, by adding an appropriate amount of ZrO ₂ , Ta ₂ O ₅ , HfO _2, and Nb ₂ O ₅ (first additive component group) to this composition, the initial magnetic permeability in the high frequency region is further increased, while V ₂ O ₅ , Bi ₂ O ₃ , In ₂ O ₃ , MoO _3, and WO ₃ (second additive component group) can be added in appropriate amounts to increase the initial magnetic permeability in the low-frequency region. By doing so, it is possible to achieve an increase in the initial permeability in both the high frequency region and the low frequency region.
Furthermore, by limiting the mixing of P and B contained in the raw iron oxide into ferrite as much as possible, it is possible to reduce defective products that occur practically, which greatly contributes to stabilization of production.

Claims (4)

Fe ₂ O ₃ : 43.0 mol% or more and less than 50.0 mol%,
ZnO: 16.5 mol% or more, 24.0 mol% or less,
MnO: balance was used as a basic component, CaO as an auxiliary component: 0.005 to 0.100 mass% and _SiO 2: 0.001 _~0.025 mass%
And the value of P contained in the ferrite is suppressed to less than 50 ppm, and the value of B is suppressed to less than 20 ppm. In claim 1, Fe ₂ O ₃ and ZnO among the basic components are
Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%,
ZnO: 17.0 mol% or more and 21.5 mol% or less, and the following formula (1)
x-2y ≧ 6.0 (1)
However, x: Fe ₂ O ₃ amount (mol%),
y: ZnO amount (mol%)
A Mn-Zn ferrite, characterized by having a Curie temperature of 120 ° C. or higher. According to claim 1 or 2, ferrite, further _ZrO 2: 0.005 _~0.100 mass%,
_{Ta 2 O 5: 0.005 ~0.100 mass} %,
HfO _2: 0.005 ~0.100 mass% and _{Nb 2 O 5: 0.005 ~0.100 mass} %
Mn-Zn ferrite comprising one or more selected from the group consisting of: According to claim 1, 2 or 3, ferrite, further _{V 2 O 5: 0.001 ~0.100 mass} %,
_{Bi 2 O 3: 0.001 ~0.050 mass} %,
In ₂ O ₃ : 0.001 to 0.050 mass%,
MoO _3: 0.001 ~0.050 mass% and _WO 3: 0.001 _~0.050 mass%
Mn-Zn ferrite comprising one or more selected from the group consisting of: