JP4129917B2 - Ferrite material and manufacturing method thereof - Google Patents

Description

【００２７】
表１に示すように、焼成雰囲気の酸素分圧が低くなるとコア損失の変化率は小さくなるが、逆にコア損失および渦電流損失の値は大きくなりコア損失自体が劣化することがわかる。また、コア損失の変化率とδ値は関連しており、コア損失の変化率を１０％以下にするためには、δ値が０．００３４でコア損失の変化率が１５％程度であるから、δ値を０．００３３以下に規制すべきであることがわかる。
本発明は低酸素分圧下での焼成によるコア損失の劣化を抑制するために降温過程に除冷帯域を設ける点に特徴がある。そこで、除冷帯域について図１（ａ）〜（ｃ）を参照しつつ説明する。
図１（ａ）において、保持過程IIに続く降温過程IIIが、IIIａ、IIIｂおよびIIIｃから構成される。このIIIｂの部分が除冷帯域である。この除冷帯域IIIｂは、他の領域IIIａおよびIIIｃよりも冷却速度が遅い。具体的には、この除冷帯域IIIｂは、１００℃／ｈｒ以下、望ましくは５０℃／ｈｒ以下、さらに望ましくは３０℃／ｈｒ以下の冷却速度とする。
【００２８】
除冷帯域IIIｂは図１（ａ）に示したように連続して設ける場合に限らず、図１（ｂ）に示すように断続的に設けても良い。さらに、本発明における除冷帯域IIIｂは、降温する場合に限らず図１（ｃ）に示すように所定温度に所定時間保持する形態をも包含する概念である。前述したように、除冷帯域IIIｂを設けるのは、結晶粒内に固溶しているＣａＯ等の副成分を結晶粒界中に偏析させることを目的としており、この目的は所定温度に所定時間保持する形態であっても達成されると解されるからである。
【００２９】
本発明において除冷帯域IIIｂを設ける温度範囲を限定するものではないが、後述するように１０００〜９００℃の温度範囲で除冷することによる効果が大きい。したがって、除冷帯域IIIｂは、降温過程IIIの１０００〜９００℃の温度範囲に設けることが望ましい。この根拠となる実験結果を表２に示す。
【００３０】
【表２】

【００３１】
測定用のサンプルの組成は上記と同様で、焼成温度１３５０℃、焼成時の酸素分圧を０．０２％とした。表２に示すように、除冷帯域IIIｂの温度が１０００〜９００℃の場合に体積抵抗率（ρ）が最も高く、かつコア損失（Ｐｃｖ）および渦電流損失（Ｐｅｖ）が最も低減されていることがわかる。１０００〜９００℃の温度域を除冷することにより、除冷帯域IIIｂを設けない場合に比べてコア損失は１／２以下に低減できる。
なお、以上の説明では、低酸素分圧下で行われる保持過程IIの直後に降温過程IIIを行う例を示したが、保持過程IIと降温過程IIIとの間に低酸素分圧下で焼成温度から降温させる過程を設けることもできる。
【００３２】
以下、本発明を実施例に基づいて説明する。
（実施例１）
主成分の原料として、Ｆｅ₂Ｏ₃粉末：６４．０ｍｏｌ％、ＭｎＯ粉末：１７．５ｍｏｌ％、ＺｎＯ粉末：１６．５ｍｏｌ％およびＮｉＯ粉末：２．０ｍｏｌ％を用意し、湿式混合した後、８５０℃で３時間仮焼した。
次いで、主成分の原料の仮焼物と副成分の原料とを混合した。副成分の原料には、ＳｉＯ₂粉末、ＣａＣＯ₃粉末、Ｎｂ₂Ｏ₅粉末を用いた。主成分原料の仮焼物に副成分の原料を添加して、粉砕しながら混合した。粉砕は、仮焼物の平均粒径が約１．５μｍとなるまで行った。得られた混合物にバインダを加え、顆粒化した後、成形してトロイダル形状の成形体を得た。
なお、主成分および副成分のうちＮｂ₂Ｏ₅粉末の配合比率は下記のとおりである。
Ｆｅ₂Ｏ₃：６４．０ｍｏｌ％、ＭｎＯ：１７．５ｍｏｌ％
ＺｎＯ：１６．５ｍｏｌ％、ＮｉＯ：２．０ｍｏｌ％
Ｎｂ₂Ｏ₅：２００ｐｐｍ
また、副成分のうちでＳｉＯ₂粉末およびＣａＣＯ₃粉末の配合比率を、表３に示すように種々変えた。
【００３３】
得られた成形体を酸素分圧制御下において、温度１３５０℃（保持過程５時間、保持過程酸素分圧（ＰＯ₂）：０．０２％，１％）で焼成することにより、フェライトコアを得た。
また、このフェライトコアを用いて、１００℃、測定磁界：１１９４Ａ／ｍにおける飽和磁束密度（以下、Ｂｓと表記することがある）、コア損失（測定条件：１００ｋＨｚ、２００ｍＴ）、体積抵抗率、コア損失の変化率を測定した。その結果を表３に併せて示す。なお、コア損失の変化率は以下により求めた。
コア損失の変化率＝（Ｐｃｖ１−Ｐｃｖ２）／Ｐｃｖ１×１００、
Ｐｃｖ１：高温貯蔵前のコア損失、Ｐｃｖ２：高温貯蔵後のコア損失、高温貯蔵：１５０℃×２０００時間保持
【００３４】
【表３】

【００３５】
本発明は、前述したように高飽和磁束密度を前提とし、低コア損失かつコア損失の信頼性の高いフェライト材料を提供することを目的としている。表３において、Ｎｏ．１〜１１の何れの材料も４５０ｍＴ以上、あるいは４７０ｍＴ以上、さらには５００ｍＴ以上の高い飽和磁束密度を有している。ところが、コア損失およびコア損失の変化率については、両者ともに優れた特性を有している例は限られている。例えば、Ｎｏ．１−１（保持過程の酸素分圧が０．０２％）と１−２（保持過程の酸素分圧が１．０％）とを比較すると、前者はコア損失の変化率が２．７％と低い値を示し、コア損失は３５００ｋＷ／ｍ³を超えているのに対し、後者はコア損失が１５００ｋＷ／ｍ³以下という値を示し、コア損失の変化率は１５．４％と悪い。こうした傾向は、Ｎｏ．２−１と２−２等についても同様である。以上の相違は、前述したように、焼成時の保持過程における酸素分圧に起因している。
【００３６】
一方で、Ｎｏ．４−１あるいはＮｏ．７〜９、１１は、低コア損失でかつコア損失の変化率も低い。これらの材料と、その他の材料を比較すると、副成分であるＳｉＯ₂とＣａＣＯ₃の総量およびその比（ＳｉＯ₂／ＣａＣＯ₃、表中ではＳｉ／Ｃａと表記）の値が相違している。つまり、低コア損失でかつコア損失の変化率も低い材料は、ＳｉＯ₂とＣａＣＯ₃の総量が多いかまたはその比が高い。例えば、Ｎｏ．１−１とＮｏ．８とを比較すると、ＳｉＯ₂とＣａＣＯ₃の総量は１００ｐｐｍしか差異がないが、ＳｉＯ₂とＣａＣＯ₃の比は、Ｎｏ．１−１が０．０５０であるのに対してＮｏ．８は０．１００と高い。また、Ｎｏ．３−１とＮｏ．４−１とを比較すると、ＳｉＯ₂とＣａＣＯ₃の比はＮｏ．３−１の方が高いが、ＳｉＯ₂とＣａＣＯ₃の総量は２６５０ｐｐｍとＮｏ．４−１の方が高い。
【００３７】
以上より、高飽和磁束密度を前提とする低酸素分圧で焼成したＦｅリッチなフェライト材料において、低コア損失とコア損失の安定性を確保する要素として、副成分であるＳｉＯ₂とＣａＣＯ₃の総量および／またはその比を制御することが掲げられる。具体的には、ＳｉＯ₂とＣａＣＯ₃の比は０．０５５を超えることが望ましい。また、ＳｉＯ₂とＣａＣＯ₃の総量は１７００ｐｐｍ以上とすることが望ましい。この範囲内において、ＳｉＯ₂とＣａＣＯ₃の比が低い場合にはＳｉＯ₂とＣａＣＯ₃の総量を多くすることが望ましく、ＳｉＯ₂とＣａＣＯ₃の比が高い場合にはＳｉＯ₂とＣａＣＯ₃の総量を低くすることができる。
【００３８】
以上のように副成分であるＳｉＯ₂とＣａＣＯ₃の総量およびその比を制御することにより低コア損失とコア損失の安定性を確保することができるが、この効果は焼成工程における降温過程において除冷帯域を設けることにより顕著となる。以下、表４に基づいて除冷帯域を設けることによる効果について説明する。
【００３９】
【表４】

【００４０】
表４は、表３に示した材料と同様の組成、製造方法により得られた材料の飽和磁束密度等の特性を示している。ただし、表４に示した材料は、降温過程において、１０００〜９００℃の温度域を３０℃／ｈｒで冷却する除冷帯域を設けて製造した点で表３とは相違する。なお、除冷帯域以外の冷却速度は、３００℃／ｈｒである。参考のために表４の「対応」の欄には表３において同一組成の材料のＮｏ．を記載している。
表３のＮｏ．３−１および６は、１５００ｋＷ／ｍ³あるいは２０００ｋＷ／ｍ³を超えるコア損失を示していたが、除冷帯域を設けることによりコア損失は１５００ｋＷ／ｍ³以下となった。体積抵抗率についてみても、０．１Ω・ｍ以下であったものが、０．２Ω・ｍあるいは０．４Ω・ｃｍを超える値となっている。
【００４１】
以上説明したように、副成分であるＳｉＯ₂とＣａＣＯ₃の総量およびその比を制御することにより低コア損失とコア損失の安定性に有効であり、さらにこの効果は焼成工程の降温過程に除冷帯域を設けることにより顕著となる。降温過程に除冷帯域を設けることにより、ＳｉＯ₂とＣａＣＯ₃の総量が９００ｐｐｍ程度であっても低コア損失とコア損失の安定性を確保することができる。
このような効果が得られる原因を確認したところ、副成分であるＳｉＯ₂とＣａＣＯ₃の総量およびその比が大きい材料は、結晶粒界にＳｉＯ₂とＣａＣＯ₃の偏析が確認されたとともに、除冷帯域を設けることにより偏析の程度が顕著となることが確認された。これに対して副成分であるＳｉＯ₂とＣａＣＯ₃の総量が少ないかまたはその比が小さい材料は、ＳｉＯ₂とＣａＣＯ₃の結晶粒界への偏析を確認することができなかった。
【００４２】
（実施例２）
表５に示す組成を有するフェライトコアを実施例１と同様にして作製した。なお、焼成工程（酸素分圧：０．０２％）の降温過程において、１０００〜９００℃の温度域を３０℃／ｈｒで冷却する除冷帯域を設けた。このフェライトコアを用いて飽和磁束密度等の特性を実施例１と同様に測定した。その結果を表５に併せて示す。
【００４３】
【表５】

【００４４】
Ｎｏ．２６、２７、２８、２９および３０は、この順にＦｅ₂Ｏ₃が増加している。その中で、Ｆｅ₂Ｏ₃が６０．０ｍｏｌ％と本発明の範囲より少ない場合、および７０．０ｍｏｌ％と本発明の範囲より多い場合に飽和磁束密度が低くかつコア損失が大きいことがわかる。
次に、Ｎｏ．３１、３２、３３および３４は、この順にＺｎＯが増加している。その中で、ＺｎＯが１０．０ｍｏｌ％と本発明の範囲より少ない場合、および２１．０ｍｏｌ％と本発明の範囲より多い場合に飽和磁束密度が低くコア損失が大きいことがわかる。
以上の結果より、高飽和磁束密度、かつ低コア損失を確保するために、Ｆｅ₂Ｏ₃を６２〜６８ｍｏｌ％の範囲、ＺｎＯを１２〜２０ｍｏｌ％の範囲に設定することが重要であることがわかる。
Ｎｏ．３５、３６、３７および３８は、この順にＮｉＯが増加している。表５を見ると、ＮｉＯの添加によりコア損失や飽和磁束密度が変動していることがわかる。
ＮｉＯの添加により飽和磁束密度が向上すること、６．０ｍｏｌ％添加した例のコア損失が１４００ｋＷ／ｍ³を超えることを考慮してＮｉＯの添加量を設定する必要がある。ＮｉＯの添加量は０．５〜４．０ｍｏｌ％の範囲とすることが望ましい。
【００４５】
（実施例３）
表６に示す組成を有するフェライトコアを実施例１と同様にして作製した。なお、副成分としてはＳｉＯ₂、ＣａＣＯ₃およびＮｂ₂Ｏ₅の他に、表６中に記載の副成分を各々添加している。また、焼成工程（酸素分圧：０．０２％）の降温過程において、１０００〜９００℃の温度域を３０℃／ｈｒで冷却する除冷帯域を設けた。このフェライトコアを用いて飽和磁束密度等の特性を実施例１と同様に測定した。その結果を表６に併せて示す。
【００４６】
【表６】

【００４７】
表６に示すように、副成分としてＭｏＯ₃、Ｖ₂Ｏ₅およびＧｅＯ₂を添加することにより、飽和磁束密度（Ｂｓ）が５００ｍＴを超えており、これら副成分が飽和磁束密度向上に効果があることがわかる。また、この効果は焼成工程の降温過程において除冷帯域を設けた場合にも有効であることがわかる。
【００４８】
【発明の効果】
以上説明したように、本発明によれば、高温域における飽和磁束密度が高いとともに、低コア損失であってかつコア損失の信頼性が高いフェライト材料が提供される。
【図面の簡単な説明】
【図１】 本発明の除冷帯域を説明するための図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ferrite material having a high saturation magnetic flux density in a temperature range near 100 ° C., low loss, and small loss deterioration.
[0002]
[Prior art]
In recent years, downsizing and higher output of electronic devices are progressing. Along with this, various components have been highly integrated and high-speed processing has progressed, and there has been a demand for increasing the current of the power supply line for supplying power. Further, there is a demand for a power supply line that maintains a predetermined performance even in a high temperature range, such as heat generated from components such as a CPU, or a high operating environment temperature such as an electronic circuit for an automobile. Therefore, transformers and reactors used for power lines are also required to be used with a large current at high temperatures.
Materials used for these transformers and reactors include soft magnetic metal materials and ferrite materials. Ferrite materials are classified into MnZn ferrite and Ni ferrite.
Since the soft magnetic metal material has a higher saturation magnetic flux density than ferrite, magnetic saturation does not occur even when a larger current is passed. However, soft magnetic metal materials generally have problems such as high loss, high price, high specific gravity, and poor rust prevention.
On the other hand, ferrite is excellent in cost performance and has an advantage that loss is low in a frequency band of several tens of kHz to several hundreds of kHz. In addition, MnZn ferrite having a higher saturation magnetic flux density than Ni ferrite is generally used for transformers and choke coils for large currents. However, for the recent advancement of specification requirements, even with MnZn-based ferrite, the saturation magnetic flux density was insufficient in the temperature range near 100 ° C. (hereinafter simply referred to as the high temperature range).
[0003]
Therefore, various studies for improving the saturation magnetic flux density in the high temperature range have been made. Among them, for example, JP 2000-159523 A contains a large amount of iron oxide as 60 to 75 mol%, a zinc oxide content of 0 to 20 mol% (however, not including 0) and the balance. Made of manganese oxide, the saturation magnetic flux density at 100 ° C. is 450 mT or more, and the minimum core loss at 50 kHz and 150 mT is 1500 kW / m.^ThreeThe following ferrite sintered body is disclosed.
On the other hand, various proposals have been made for reducing the loss of MnZn-based ferrite. For example, JP-B-63-59241, JP-A-6-310321, and JP-A-11-3813.
[0004]
[Patent Document 1]
JP 2000-159523 A (Claims)
[Patent Document 2]
Japanese Patent Publication No. 63-59241 (Claims)
[Patent Document 3]
JP-A-6-310321 (Claims)
[Patent Document 4]
JP-A-11-3813 (Claims)
[Patent Document 5]
JP 2002-255559 A (page 3)
[0005]
[Problems to be solved by the invention]
As described above, high saturation magnetic flux density and low loss of MnZn-based ferrite have been studied. On the other hand, the core loss is less deteriorated by use in the high temperature range, that is, reliability is required. Yes. One method for ensuring the reliability of core loss is disclosed in Japanese Patent Laid-Open No. 2002-255559. In JP-A-2002-255559, Fe₂O_Three: 55.0 to 59.0 mol%, ZnO: 0 to 15.0 mol%, NiO: 2.0 to 10.0 mol%, the balance being sintered in a Mn-Ni-Zn-based ferrite substantially containing MnO as a main component The atmosphere is low oxygen partial pressure. Furthermore, in the temperature lowering process after holding at a predetermined temperature, it is proposed to switch to a nitrogen atmosphere below the predetermined temperature and to increase the cooling rate than before.
[0006]
However, the proposal of Japanese Patent Application Laid-Open No. 2002-255559 is effective for ensuring the reliability of the core loss. However, since the iron oxide content is as low as 55.0 to 59.0 mol%, The saturation magnetic flux density in the high temperature region does not reach the value of 470 mT or more at 100 ° C. disclosed in JP-A No. 2000-159523.
The present invention has been made based on such a technical problem, and provides a ferrite material having a high saturation magnetic flux density in a high temperature region, a low core loss and a high core loss reliability, and a method for manufacturing the same. Is an issue.
[0007]
[Means for Solving the Problems]
Under such an object, the present inventor conducted an investigation to solve the above-described problems with respect to Fe-rich Mn—Zn-based ferrite in which the amount of iron oxide capable of obtaining a high saturation magnetic flux density exceeds 60 mol%. The following knowledge was obtained.
Fe-rich Mn—Zn ferrite is advantageous for obtaining a high saturation magnetic flux density, but on the other hand, reliability deterioration of core loss cannot be overlooked due to the easy generation of cation defects.
In order to suppress the generation of cation defects, the atmosphere during firing may be controlled to a low oxygen partial pressure (for example, less than 1% oxygen partial pressure). Firing with a low oxygen partial pressure is effective in suppressing the generation of cation defects and reducing the core loss, but the core loss itself is deteriorated.
[0008]
Based on the above background, the present inventor examined the relationship between core loss and eddy current loss and volume resistivity of Fe-rich Mn—Zn ferrite sintered at a low oxygen partial pressure. As a result, it was confirmed that the Fe-rich Mn—Zn-based ferrite showing high values of core loss and eddy current loss showed a low volume resistivity. It is understood that this volume resistivity depends on the existence form of CaO or the like added as an auxiliary component to the Mn—Zn ferrite. That is, a predetermined volume resistivity can be obtained when an appropriate amount of subcomponents such as CaO is segregated at the crystal grain boundaries of Mn—Zn ferrite.
[0009]
The present inventors presumed that the Fe-rich Mn—Zn-based ferrite fired at a low oxygen partial pressure has a low volume resistivity due to the presence of many subcomponents such as CaO in the crystal grains. An attempt was made to segregate an appropriate amount of subcomponents such as CaO present in the grains to the grain boundaries.
Here, subcomponents such as CaO are present in the crystal grains in the high temperature region of the firing step, but the form existing in the crystal grains is unstable, and thus segregates at the grain boundaries during the temperature lowering process after maintaining a predetermined temperature. . However, it is understood that in a low oxygen partial pressure atmosphere, subcomponents such as CaO tend to stay in the crystal grains, so that segregation to the crystal grain boundaries is suppressed and the volume resistivity is lowered. Therefore, in order to segregate an appropriate amount of subcomponents such as CaO to the grain boundaries, subcomponents such as CaO were added more than before, or the cooling rate in the temperature lowering process of the firing step was slowed. The Fe-rich Mn—Zn ferrite thus obtained was confirmed to have an improved volume resistivity.
[0010]
  The present invention is based on the above technical idea, and Fe₂O₃: 62-68 mol%, ZnO: 12-20 mol%, NiO:1.5˜5 mol%, the balance being substantially composed of a sintered body mainly composed of MnO, a saturation magnetic flux density at 100 ° C. of 470 mT or more (measuring magnetic field: 1194 A / m), and a volume resistivity at room temperature of 0.13 Ω · m or more It is a ferrite material characterized by being.
  The ferrite material of the present invention has a core loss of 1400 kW / m³Below (measurement conditions: 100 kHz, 200 mT) and change rate of core loss is 10% or less (change rate of core loss = (Pcv1-Pcv2) / Pcv1 × 100, Pcv1: core loss before high-temperature storage, Pcv2: high-temperature storage The following characteristics can be obtained: core loss, high-temperature storage: 150 ° C. × 2000 hours holding. In the definition of the present invention, when simply referred to as core loss, it means the minimum value of core loss.
[0011]
The ferrite material of the present invention uses Si and Ca as SiO as the first subcomponent.₂And CaCO_ThreeIn terms of SiO₂/ CaCO_ThreeIt is desirable to contain 900 to 3000 ppm under the condition of 0.055 to 0.30. In the ferrite material of the present invention, it is desirable that the δ value (cation defect amount) in the following composition formula (1) of ferrite is 0.0033 or less. Furthermore, in the present invention, it is effective to include a second subcomponent and a third subcomponent which will be described later.
(Zn_a ²⁺, Ni_b ²⁺, Mn_c ²⁺, Mn_d ³⁺, Fe_e ²⁺, Fe_f ³⁺) O₄₊δ (1)
However, a + b + c + d + e + f = 3, δ = a + b + c + (3/2) d + e + (3/2) f-4
[0012]
As described above, when a predetermined amount of the first subcomponent is included, it is possible to obtain a ferrite material having a high saturation magnetic flux density in a high temperature region, a low core loss, and a high core loss reliability. Specifically, Si and Ca as SiO are added as subcomponents.₂And CaCO_ThreeIn terms of SiO₂/ CaCO_ThreeIt is important to contain 1700 to 3000 ppm under the condition of 0.055 to 0.19. In order to have a high saturation magnetic flux density, Fe₂O_Three: 62-68 mol%, ZnO: 12-20 mol%, NiO: 5 mol% or less (however, including 0%), the balance is required to be substantially composed mainly of MnO.
[0013]
  As described above, SiO as an auxiliary component₂And CaCO₃Is added under predetermined conditions, or a subcooling zone is provided in the temperature lowering process of firing, so that these subcomponents are segregated in an appropriate amount at the grain boundaries. Accordingly, the present invention provides Fe₂O₃: 62-68 mol%, ZnO: 12-20 mol%, NiO:1.5˜5 mol%, the balance being substantially composed of a sintered body mainly composed of MnO, with SiO 2 as a minor component₂And CaCO₃And a ferrite material in which the subcomponent is segregated in an appropriate amount in the grain boundary of the sintered body.
[0014]
  The ferrite material according to the present invention described above is Fe₂O₃: 62-68 mol%, ZnO: 12-20 mol%, NiO:1.5A method for producing a ferrite material mainly comprising MnO as a main component, with the remainder being substantially 5% by mol, a molding step using a powder containing the main component, and a molding obtained in the molding step A firing step for firing the substrate, and the firing step includes a holding process for holding in a predetermined temperature range, and a temperature lowering process performed in a nitrogen atmosphere after the holding process. It can be obtained by a method for producing a ferrite material characterized by providing a cooling zone of not more than ° C./hr. The cooling zone desirably includes a range of 1000 to 900 ° C.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First, the reasons for limiting the components in the present invention will be described.
Fe₂O_ThreeIncreasing the amount tends to improve the saturation magnetic flux density in the high temperature region, while decreasing the core loss. Fe₂O_ThreeIf it is less than 62 mol%, the saturation magnetic flux density in the high temperature range decreases. On the other hand, Fe₂O_ThreeWhen it exceeds 68 mol%, the increase in core loss becomes remarkable. Therefore, in the present invention, Fe₂O_ThreeIs 62 to 68 mol%. Desirable Fe₂O_ThreeThe amount of Fe is 63 to 67 mol%, more desirable Fe₂O_ThreeIs 63-66 mol%.
[0016]
The amount of ZnO also affects the saturation magnetic flux density and core loss. When ZnO is less than 12 mol%, the saturation magnetic flux density is lowered and the loss is increased. Moreover, even if ZnO exceeds 20 mol%, the saturation magnetic flux density is lowered and the loss is increased. Therefore, in this invention, ZnO shall be 12-20 mol%. In this range, the bottom temperature (the temperature at which the core loss shows the minimum value) shifts to the high temperature side as the ZnO amount increases. A desirable amount of ZnO is 13 to 19 mol%, and a more desirable amount of ZnO is 14 to 18 mol%.
[0017]
  Furthermore, the present invention provides1.5~ 5 mol%ofContains NiOTheNiO is effective in improving the saturation magnetic flux density as the Curie temperature increases. In order to fully enjoy the effect,1.5Contains at least mol%. However, if the content exceeds 5 mol%, the loss increases. Therefore, in the present invention, the amount of NiO is reduced.1.5~ 5mol%, the desired amount of NiO is1.5~ 4mol%, more desirable amount of NiO1.5˜3 mol%.
  In addition to the above, the ferrite material of the present invention contains MnO as a substantial remainder.
[0018]
Next, the reasons for limiting the subcomponents will be described.
The ferrite material of the present invention uses Si and Ca as SiO as the first subcomponent.₂, CaCO_ThreeConverted (hereinafter simply referred to as SiO₂, CaCO_ThreeMay be included). SiO₂And CaCO_ThreeHas the effect of improving the sintering density as a sintering aid while segregating at the grain boundaries to form a high resistance layer and contributing to low loss. Here, the ferrite material of the present invention includes both a case where a cooling zone is provided and a case where a cooling zone is not provided in the temperature lowering process of firing. In the case where no cooling zone is provided, the subcomponent is SiO.₂And CaCO_ThreeIncluding 1700 to 3000 ppm in total and SiO₂/ CaCO_ThreeIs desired to be 0.055 or more. Also, when providing a cooling zone, less SiO₂And CaCO_ThreeThe amount is enough. Specifically, SiO₂/ CaCO_ThreeIt is desirable to contain 900 to 3000 ppm under the condition of = 0.055 to 0.30.
As a premise of the above conditions, SiO₂And CaCO_ThreeAre respectively SiO₂: 300 ppm or less (excluding 0) and CaCO_Three: 2700 ppm or less (however, not including 0) can be included. SiO₂Exceeds 300 ppm, or CaCO_ThreeIf it exceeds 2700 ppm, the deterioration of loss due to discontinuous abnormal grain growth is large. Therefore, in the present invention, SiO₂: 300 ppm or less, CaCO_Three: Should be 2700 ppm or less. Desirable SiO₂And CaCO_ThreeThe amount of SiO₂: 100-250 ppm, CaCO_Three: 1300-2500 ppm, more desirable SiO₂And CaCO_ThreeThe amount of SiO₂: 150-200 ppm, CaCO_Three: 1500-2500 ppm.
[0019]
The present invention uses Nb as the second subcomponent.₂O_Five: 400 ppm or less (excluding 0), ZrO₂: 1000 ppm or less (excluding 0), Ta₂O_Five: 1000 ppm or less (excluding 0), V₂O_Five: 1000 ppm or less (excluding 0), GeO₂: 1000 ppm or less (excluding 0), In₂O_Five: 1000 ppm or less (excluding 0), Ga₂O_Five: 1000 ppm or less (excluding 0), MoO_Three: 1000 ppm or less (however, 0 is not included) can be included. In order to fully enjoy the effect, Nb₂O_Five, MoO_ThreeIs more than 50ppm, ZrO₂, Ta₂O_Five, V₂O_Five, GeO₂, In₂O_Five, Ga₂O_FiveIt is desirable to add 100 ppm or more. A more desirable range is Nb₂O_Five: 80-300 ppm, ZrO₂, Ta₂O_Five, V₂O_Five, GeO₂, In₂O_Five, Ga₂O_Five: 200 to 800 ppm, MoO_Three: 50 to 800 ppm. In addition, when adding a 2nd subcomponent in combination, it is desirable for the sum total of addition amount to be 1000 ppm or less.
[0020]
The present invention provides SnO as the third subcomponent.₂: 10000 ppm or less (excluding 0) and TiO₂: 10000 ppm or less (however, not including 0) can be included. SnO₂And TiO₂Exists in the crystal grains and at the crystal grain boundaries, and has an effect of reducing loss. If it exceeds 10,000 ppm, the loss due to the discontinuous abnormal grain growth and the saturation magnetic flux density are reduced. Therefore, in the present invention, SnO₂And TiO₂Each upper limit value is 10000 ppm. On the other hand, in order to fully enjoy the above effects, it is desirable to add 500 ppm or more of the third subcomponent. More desirable SnO₂And TiO₂The amount of SnO is 1000-8000 ppm, more desirable SnO₂And TiO₂The range is 1000 to 7000 ppm. In addition, when adding a 3rd subcomponent combining, it is desirable for the sum total of addition amount to be 10000 ppm or less.
[0021]
Next, a manufacturing method suitable for the ferrite material according to the present invention will be described.
As a raw material for the main component, an oxide or a powder of a compound that becomes an oxide by heating is used. Specifically, Fe₂O_ThreePowder, Mn_ThreeO_FourPowder, ZnO powder, NiO powder and the like can be used. What is necessary is just to select suitably the average particle diameter of each raw material powder to prepare in the range of 0.1-3.0 micrometers.
The raw material powder of the main component is wet mixed and then calcined. The calcining temperature is a predetermined temperature in the range of 800 to 1000 ° C., and the atmosphere is N₂~ What to do between the air. After the calcination, the calcined body is pulverized, for example, to an average particle size of about 0.5 to 2.0 μm. What is necessary is just to select the stable time of calcination suitably in the range of 0.5 to 5.0 hours. In the present invention, not only the above-mentioned main component materials, but also a composite oxide powder containing two or more metals may be used as the main component materials. For example, a complex oxide powder containing Fe and Mn can be obtained by oxidizing and baking an aqueous solution containing iron chloride and manganese chloride. This powder and ZnO powder may be mixed and used as a main component material. In such a case, calcining is unnecessary.
[0022]
Similarly, an oxide or a powder of a compound that becomes an oxide by heating can also be used as a raw material for the accessory component. Specifically, SiO₂, CaCO_Three, Nb₂O_Five, ZrO₂, Ta₂O_Five, V₂O_Five, GeO₂, In₂O_Five, Ga₂O_Five, SnO₂TiO₂Etc. can be used. The raw material powders of these subcomponents are mixed with the main component powder pulverized after calcining. However, after mixing with the raw material powder of the main component, it can be subjected to calcining together with the main component.
[0023]
The mixed powder composed of the main component and the subcomponent is granulated into a granule in order to smoothly execute the subsequent molding process. Granulation can be performed using, for example, a spray dryer. A small amount of a suitable binder such as polyvinyl alcohol (PVA) is added to the mixed powder, and this is sprayed and dried with a spray dryer. The particle size of the resulting granule is desirably about 80 to 200 μm.
[0024]
The obtained granule is formed into a desired shape using, for example, a press having a mold having a predetermined shape, and this formed body is subjected to a firing step.
As shown in FIG. 1 (d), the firing process is performed after a temperature raising process I for raising the temperature to a predetermined temperature, a holding process II for holding a predetermined temperature following the temperature raising process, and a holding process II. It includes the cooling process III. The holding temperature in the holding process II will be referred to as a firing temperature in the present specification.
The firing temperature can be appropriately selected from the range of 1250 to 1450 ° C., but it is desirable to fire in the range of 1300 to 1400 ° C. in order to sufficiently bring out the effect of the ferrite material of the present invention. In the present invention, the oxygen partial pressure of the atmosphere (firing atmosphere) at this time is less than 1%, desirably 0.2% or less, and more desirably 0.05% or less. The reason why the firing atmosphere is set to such a low oxygen partial pressure is to suppress cation defects that tend to occur with the Fe-rich composition targeted by the present invention.
[0025]
Oxygen partial pressure (PO₂) Volume resistivity at room temperature (hereinafter simply referred to as volume resistivity, sometimes referred to as ρ), minimum value of core loss at 100 kHz and 200 mT (hereinafter simply referred to as core loss, Pcv) ), Minimum value of eddy current loss (hereinafter simply referred to as eddy current loss, sometimes referred to as Pev), rate of change in core loss (hereinafter also referred to as Pcv rate of change), and the aforementioned The variation of the δ value was measured. The results are shown in Table 1. The composition of the sample for measurement was as follows, and the firing temperature was 1350 ° C. In addition, the specific manufacturing method of a sample is based on the Example mentioned later.
Main component: Fe₂O_Three64.0 mol%, MnO; 17.5 mol%, ZnO; 16.5 mol%, NiO; 2.0 mol%
Subcomponent: SiO₂; 100 ppm, CaCO_Three1500 ppm, Nb₂O_Five200 ppm
[0026]
[Table 1]

[0027]
As shown in Table 1, when the oxygen partial pressure in the firing atmosphere is lowered, the change rate of the core loss is reduced, but conversely, the values of the core loss and the eddy current loss are increased and the core loss itself is deteriorated. Also, the change rate of the core loss and the δ value are related, and in order to make the change rate of the core loss 10% or less, the δ value is 0.0034 and the change rate of the core loss is about 15%. Δ value should be regulated to 0.0033 or less.
The present invention is characterized in that a cooling zone is provided in the temperature lowering process in order to suppress deterioration of the core loss due to firing under a low oxygen partial pressure. Therefore, the cooling zone will be described with reference to FIGS.
In FIG. 1A, the temperature lowering process III subsequent to the holding process II is composed of IIIa, IIIb and IIIc. This portion IIIb is a cooling zone. The cooling zone IIIb has a slower cooling rate than the other regions IIIa and IIIc. Specifically, the cooling zone IIIb has a cooling rate of 100 ° C./hr or less, desirably 50 ° C./hr or less, and more desirably 30 ° C./hr or less.
[0028]
The cooling zone IIIb is not limited to being continuously provided as shown in FIG. 1A, but may be provided intermittently as shown in FIG. Furthermore, the cooling zone IIIb in the present invention is not limited to the case where the temperature is lowered, but is a concept including a form in which the temperature is kept at a predetermined temperature for a predetermined time as shown in FIG. As described above, the provision of the cooling zone IIIb is intended to segregate subcomponents such as CaO dissolved in the crystal grains in the crystal grain boundaries, and this purpose is performed at a predetermined temperature for a predetermined time. It is because it is understood that even if it is the form to hold | maintain, it will be achieved.
[0029]
Although the temperature range in which the cooling zone IIIb is provided in the present invention is not limited, the effect obtained by cooling in the temperature range of 1000 to 900 ° C. is great as will be described later. Therefore, it is desirable to provide the cooling zone IIIb in the temperature range of 1000 to 900 ° C. in the temperature lowering process III. The experimental results that serve as the basis for this are shown in Table 2.
[0030]
[Table 2]

[0031]
The composition of the measurement sample was the same as above, the firing temperature was 1350 ° C., and the oxygen partial pressure during firing was 0.02%. As shown in Table 2, when the temperature of the cooling zone IIIb is 1000 to 900 ° C., the volume resistivity (ρ) is the highest, and the core loss (Pcv) and eddy current loss (Pev) are reduced most. I understand that. By removing the temperature range of 1000 to 900 ° C., the core loss can be reduced to ½ or less compared to the case where the removal zone IIIb is not provided.
In the above description, an example in which the temperature lowering process III is performed immediately after the holding process II performed under a low oxygen partial pressure is shown, but from the firing temperature under a low oxygen partial pressure between the holding process II and the temperature lowering process III. A process of lowering the temperature can also be provided.
[0032]
Hereinafter, the present invention will be described based on examples.
Example 1
As raw material of main component, Fe₂O_ThreePowder: 64.0 mol%, MnO powder: 17.5 mol%, ZnO powder: 16.5 mol%, and NiO powder: 2.0 mol% were prepared, wet mixed, and then calcined at 850 ° C for 3 hours.
Next, the calcined product of the main component material and the subcomponent material were mixed. The raw material of the accessory component is SiO₂Powder, CaCO_ThreePowder, Nb₂O_FivePowder was used. The auxiliary component raw material was added to the calcined material of the main component raw material and mixed while being pulverized. The pulverization was performed until the average particle size of the calcined product was about 1.5 μm. A binder was added to the resulting mixture, granulated, and then molded to obtain a toroidal shaped molded body.
Of the main components and subcomponents, Nb₂O_FiveThe blending ratio of the powder is as follows.
Fe₂O_Three: 64.0 mol%, MnO: 17.5 mol%
ZnO: 16.5 mol%, NiO: 2.0 mol%
Nb₂O_Five: 200ppm
Of the subcomponents, SiO₂Powder and CaCO_ThreeThe blending ratio of the powder was variously changed as shown in Table 3.
[0033]
The obtained compact was subjected to a temperature of 1350 ° C. (holding process 5 hours, holding process oxygen partial pressure (PO) under oxygen partial pressure control.₂): 0.02%, 1%) to obtain a ferrite core.
Also, using this ferrite core, saturation magnetic flux density (hereinafter sometimes referred to as Bs) at 100 ° C., measurement magnetic field: 1194 A / m, core loss (measurement conditions: 100 kHz, 200 mT), volume resistivity, core The rate of change of loss was measured. The results are also shown in Table 3. The rate of change in core loss was determined as follows.
Change rate of core loss = (Pcv1-Pcv2) / Pcv1 × 100,
Pcv1: Core loss before high-temperature storage, Pcv2: Core loss after high-temperature storage, high-temperature storage: 150 ° C x 2000 hours hold
[0034]
[Table 3]

[0035]
An object of the present invention is to provide a ferrite material having a low core loss and high core loss reliability on the premise of a high saturation magnetic flux density as described above. In Table 3, no. Any of the materials 1 to 11 has a high saturation magnetic flux density of 450 mT or more, 470 mT or more, and further 500 mT or more. However, with respect to the core loss and the rate of change of the core loss, there are limited examples in which both have excellent characteristics. For example, no. Comparing 1-1 (oxygen partial pressure in the holding process is 0.02%) and 1-2 (oxygen partial pressure in the holding process is 1.0%), the former has a core loss change rate of 2.7%. The core loss is 3500 kW / m^ThreeWhile the latter has a core loss of 1500 kW / m^ThreeThe following values are shown, and the rate of change of core loss is as bad as 15.4%. Such a tendency is The same applies to 2-1 and 2-2. As described above, the above difference is caused by the oxygen partial pressure in the holding process during firing.
[0036]
On the other hand, no. 4-1 or No. 7 to 9 and 11 have a low core loss and a low change rate of the core loss. When these materials are compared with other materials, the subcomponent SiO₂And CaCO_ThreeAnd its ratio (SiO₂/ CaCO_ThreeIn the table, the value of Si / Ca is different. That is, a material having a low core loss and a low change rate of the core loss is SiO 2₂And CaCO_ThreeThe total amount is high or the ratio is high. For example, no. 1-1 and No.1. Compared with 8₂And CaCO_ThreeThe total amount of Si is only 100 ppm, but SiO₂And CaCO_ThreeThe ratio of No. 1-1 is 0.050, whereas No. 1-1. 8 is as high as 0.100. No. 3-1. 4-1 and SiO₂And CaCO_ThreeThe ratio of No. 3-1 is higher, but SiO₂And CaCO_ThreeNo. 2 was 2650 ppm in total. 4-1 is higher.
[0037]
As described above, in the Fe-rich ferrite material fired at a low oxygen partial pressure on the premise of a high saturation magnetic flux density, as an element for ensuring low core loss and stability of the core loss, the subsidiary component SiO₂And CaCO_ThreeTo control the total amount and / or ratio thereof. Specifically, SiO₂And CaCO_ThreeThe ratio is preferably more than 0.055. In addition, SiO₂And CaCO_ThreeThe total amount of is desirably 1700 ppm or more. Within this range, SiO₂And CaCO_ThreeWhen the ratio is low, SiO₂And CaCO_ThreeIt is desirable to increase the total amount of SiO,₂And CaCO_ThreeWhen the ratio is high, SiO₂And CaCO_ThreeThe total amount of can be reduced.
[0038]
As described above, the subsidiary component SiO₂And CaCO_ThreeBy controlling the total amount and the ratio thereof, low core loss and stability of the core loss can be secured, but this effect becomes remarkable by providing a cooling zone in the temperature lowering process in the firing process. Hereinafter, the effect by providing a cooling zone based on Table 4 is demonstrated.
[0039]
[Table 4]

[0040]
Table 4 shows characteristics such as the saturation magnetic flux density of the material obtained by the same composition and manufacturing method as the material shown in Table 3. However, the material shown in Table 4 is different from Table 3 in that it is manufactured by providing a cooling zone in which the temperature range of 1000 to 900 ° C. is cooled at 30 ° C./hr in the temperature lowering process. The cooling rate other than the cooling zone is 300 ° C./hr. For reference, in the column “Correspondence” in Table 4, the material Nos. Is described.
No. in Table 3 3-1 and 6 are 1500 kW / m^ThreeOr 2000kW / m^ThreeThe core loss exceeded 1500 kW / m by providing a cooling zone.^ThreeIt became the following. The volume resistivity is 0.1Ω · m or less, but is more than 0.2Ω · m or 0.4Ω · cm.
[0041]
As described above, the subsidiary component SiO₂And CaCO_ThreeBy controlling the total amount and the ratio thereof, it is effective for the stability of the low core loss and the core loss, and this effect becomes remarkable by providing a cooling zone in the temperature lowering process of the firing process. By providing a cooling zone in the cooling process, SiO₂And CaCO_ThreeEven if the total amount is about 900 ppm, low core loss and stability of core loss can be secured.
As a result of confirming the cause of such an effect, it is SiO that is a subsidiary component.₂And CaCO_ThreeA material having a large total amount and a ratio thereof is SiO at the grain boundary.₂And CaCO_ThreeIn addition, it was confirmed that the degree of segregation becomes significant by providing a cooling zone. In contrast, SiO, which is a subsidiary component₂And CaCO_ThreeA material with a small total amount or a small ratio is SiO 2₂And CaCO_ThreeSegregation to the crystal grain boundary could not be confirmed.
[0042]
(Example 2)
Ferrite cores having the compositions shown in Table 5 were produced in the same manner as in Example 1. In the temperature lowering process of the firing step (oxygen partial pressure: 0.02%), a cooling zone for cooling the temperature range of 1000 to 900 ° C. at 30 ° C./hr was provided. Using this ferrite core, characteristics such as saturation magnetic flux density were measured in the same manner as in Example 1. The results are also shown in Table 5.
[0043]
[Table 5]

[0044]
No. 26, 27, 28, 29 and 30 are Fe in this order.₂O_ThreeHas increased. Among them, Fe₂O_ThreeIs 60.0 mol%, less than the range of the present invention, and 70.0 mol%, more than the range of the present invention, it is understood that the saturation magnetic flux density is low and the core loss is large.
Next, no. In 31, 32, 33 and 34, ZnO increases in this order. Among them, it can be seen that the saturation magnetic flux density is low and the core loss is large when ZnO is 10.0 mol%, which is less than the range of the present invention, and when 2O mol% is more than the range of the present invention.
From the above results, in order to ensure high saturation magnetic flux density and low core loss, Fe₂O_ThreeIt is understood that it is important to set the range of 62 to 68 mol% and the range of ZnO to 12 to 20 mol%.
No. In 35, 36, 37 and 38, NiO increases in this order. When Table 5 is seen, it turns out that core loss and saturation magnetic flux density are fluctuate | varied by addition of NiO.
The saturation magnetic flux density is improved by the addition of NiO, and the core loss of the example in which 6.0 mol% is added is 1400 kW / m.^ThreeIt is necessary to set the addition amount of NiO in consideration of exceeding. The amount of NiO added is desirably in the range of 0.5 to 4.0 mol%.
[0045]
(Example 3)
Ferrite cores having the compositions shown in Table 6 were produced in the same manner as in Example 1. As a secondary component, SiO₂, CaCO_ThreeAnd Nb₂O_FiveIn addition, the subcomponents listed in Table 6 are added. Further, in the temperature lowering process of the firing step (oxygen partial pressure: 0.02%), a cooling zone for cooling the temperature range of 1000 to 900 ° C. at 30 ° C./hr was provided. Using this ferrite core, characteristics such as saturation magnetic flux density were measured in the same manner as in Example 1. The results are also shown in Table 6.
[0046]
[Table 6]

[0047]
As shown in Table 6, MoO is used as a secondary component._Three, V₂O_FiveAnd GeO₂Is added, the saturation magnetic flux density (Bs) exceeds 500 mT, and it can be seen that these subcomponents are effective in improving the saturation magnetic flux density. It can also be seen that this effect is also effective when a cooling zone is provided in the temperature lowering process of the firing process.
[0048]
【The invention's effect】
As described above, according to the present invention, a ferrite material having a high saturation magnetic flux density in a high temperature region, a low core loss, and a high core loss reliability is provided.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a cooling zone according to the present invention.

Claims (8)

Fe ₂ O ₃ : 62 to 68 mol%, ZnO: 12 to 20 mol%, NiO: 1.5 to 5 mol%, and the balance substantially consists of a sintered body mainly containing MnO,
A ferrite material having a saturation magnetic flux density at 100 ° C. of 470 mT or more (measured magnetic field: 1194 A / m) and a volume resistivity at room temperature of 0.13 Ω · m or more. Core loss is 1400 kW / m ³ or less (measurement conditions: 100 kHz, 200 mT) and core loss change rate is 10% or less (core loss change rate = (Pcv1-Pcv2) / Pcv1 × 100, Pcv1: before high-temperature storage) 2. The ferrite material according to claim 1, wherein: core loss, Pcv2: core loss after high-temperature storage, high-temperature storage: 150 ° C. × 2000 hours holding. The first subcomponent contains Si and Ca in an amount of 900 to 3000 ppm in terms of SiO ₂ and CaCO ₃ under the condition of SiO ₂ / CaCO ₃ = 0.055 to 0.30. Or the ferrite material of 2. The ferrite material according to any one of claims 1 to 3, wherein a δ value (amount of cation defects) in the composition formula (1) of the following ferrite is 0.0033 or less.
^{_{(Zn a 2+, Ni b 2+}} , Mn c 2+, Mn d 3+, Fe e 2+, Fe f 3+) O 4+ δ ... (1)
However, a + b + c + d + e + f = 3, δ = a + b + c + (3/2) d + e + (3/2) f-4 As the second subcomponent, Nb ₂ O ₅ : 400 ppm or less (excluding 0), ZrO ₂ : 1000 ppm or less (excluding 0), Ta ₂ O ₅ : 1000 ppm or less (excluding 0) ), V ₂ O ₅ : 1000 ppm or less (excluding 0), GeO ₂ : 1000 ppm or less (excluding 0), In ₂ O ₅ : 1000 ppm or less (excluding 0), Ga ₂ One or more of O ₅ : 1000 ppm or less (however, not including 0) and MoO ₃ : 1000 ppm or less (however, not including 0) are contained. The ferrite material described. Fe ₂ O ₃ : 62 to 68 mol%, ZnO: 12 to 20 mol%, NiO: 1.5 to 5 mol%, and the balance substantially consists of a sintered body mainly containing MnO,
As an auxiliary component, Si, Ca in the _SiO 2, CaCO _{3 conversion,} ferrite material, characterized in that it comprises 1700~3000ppm under conditions of SiO ₂ / CaCO 3 = 0.055~0.19. Fe ₂ O ₃ : 62 to 68 mol%, ZnO: 12 to 20 mol%, NiO: 1.5 to 5 mol%, the balance is a method for producing a ferrite material mainly comprising MnO,
A molding step of obtaining a molded body using the powder containing the main component;
A firing step of firing the molded body obtained in the molding step,
The firing step includes
A holding process for holding in a predetermined temperature range and a temperature lowering process performed in a nitrogen atmosphere after the holding process,
A method for producing a ferrite material, wherein a cooling zone having a cooling rate of 100 ° C./hr or less is provided in the temperature lowering process.   The method for producing a ferrite material according to claim 7, wherein the cooling zone includes a range of 1000 to 900 ° C.

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