JP4601907B2 - High frequency magnetic material powder, high frequency magnetic component using the same, and manufacturing method - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、１０ＭＨｚ以上で、特に１００ＭＨｚ以上でＧＨｚの範囲までの高周波域で用いる磁性部品などに有効な高周波磁性材料、および高周波磁性部品並びにその製造方法に関する。
【０００２】
【従来の技術】
近年、磁性材料部品をキー材料、部品にする用途は拡大しており、重要さは年々増してきている。用途の一例を挙げれば、インダクタンス素子、電磁波吸収体、磁性インクなどがある。
例えば、１ＭＨｚ以上の高周波域で使用するインダクタンス素子に用いられる磁性材料としては、主にフェライトやアモルファス合金が挙げられる。これら磁性材料は１ＭＨｚ〜１０ＭＨｚ域においては良好な特性を示すものの、１０ＭＨｚ以上のさらなる高周波域では必ずしも満足行く特性が得られていなかった。
【０００３】
このような不具合を改善するために、高透磁率材料をスパッタ法、めっき法などの薄膜技術を用いたインダクタンス素子の開発も盛んに行われている（特開平５−１３２３５号公報：特許文献１）。このようなインダクタンス素子は１０ＧＨｚ以上の高周波域においても優れた特性を示すことが確認されているものの、スパッタ法などの薄膜技術には大型の設備が必要であり、また、膜厚等を精密に制御しなくてはならないことからコストや歩留りの点では必ずしも十分であるとは言えなかった。
【０００４】
また、他の用途としては電磁波吸収体が挙げられる。電磁波吸収体は、電子機器の高周波化に伴い発生したノイズを吸収し、電子機器の誤動作等の不具合を低減させるものである。電子機器としては、ＩＣチップ等半導体素子や各種通信機器などが挙げられる。このような電子機器は１ＭＨｚから数ＧＨｚ、さらには数１０ＧＨｚ以上の高周波域で使用されるものなど様々なものがあり、特に近年は１ＧＨｚ以上の高周波域で使用される電子機器が増加する傾向にある。
このような高周波域で使用される電子機器の電磁波吸収体として、従来はフェライト粒子、カルボニル鉄粒子、ＦｅＡｌＳｉフレーク、ＦｅＣｒＡｌフレークなどを樹脂と混合したものが用いられていたが１ＧＨｚ以上の高周波域においては必ずしも満足行く特性は得られていなかった。
【０００５】
近年、１ＧＨｚ以上の高周波域の電磁波吸収体としては、特開２００１−３５８４９３号公報（特許文献２）に示されたような磁性金属粒子とセラミックスを一体にした複合磁性粒子を用いるものが示されている。この材料は高周波域における電磁波吸収特性は良いものの、メカニカルアロイング法により製造しなければならず磁性金属粒子とセラミックス粒子を均一に反応させるためには長時間混合しなければならなかった。特に、一度に大量（例えば１０ｋｇ以上）の材料をメカニカルアロング法で作製しようとすると、より長時間の混合が必要であり歩留りもよいとは言えなかった。
【０００６】
【特許文献１】
特開平５−１３２３５号公報
【特許文献２】
特開２００１−３５８４９３号公報
【特許文献３】
特開２００１−２７８６５６号公報
【０００７】
【発明が解決しようとする課題】
従来の高周波磁性材料であるアモルファス合金やフェライト等は急冷法や焼結法により歩留り良く製造できるものの、１０ＭＨｚ以上の高周波域においては十分な特性が得られていなかった。
一方、スパッタ法を用いた磁性薄膜やメカニカルアロイングを用いた磁性材料は、１ＧＨｚ以上の高周波域においても優れた特性が得られるものの、その製造においては、歩留りやコストに問題があった。
以上のように従来の高周波磁性材料は、１０ＭＨｚ以上の高周波特性と歩留り等の製造性の両方が優れているものは得られていなかった。
【０００８】
【課題を解決するための手段】
本発明は上記のような課題を解決するためのものであり、高周波磁性材料の第１の形態として、難還元性金属酸化物および、Ｆｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種以上からなる金属粒子を具備したことを特徴とするものである。また、高周波磁性材料の第２の形態として、難還元性金属酸化物と、ＦｅまたはＣｏの少なくとも1種以上を含む金属酸化物との複合酸化物と、Ｆｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種以上からなる金属粒子を具備したことを特徴とするものである。
【０００９】
また、該金属粒子の平均粒径が１０〜２０００ｎｍであることが好ましい。また、高周波磁性材料は多結晶体であると共に、該金属粒子が結晶の粒界または粒内の少なくとも一方に存在していることが好ましい。
また、難還元性金属酸化物は、マグネシウム酸化物、アルミニウム酸化物、カルシウム酸化物、けい素酸化物、希土類金属酸化物、チタニウム酸化物、ジルコニウム酸化物、バリウム酸化物、ストロンチウム酸化物、亜鉛酸化物から選ばれる少なくとも1種であることが好ましい。
また、該複合酸化物がＦｅ−Ｍｇ−Ｏ系、Ｆｅ−Ｃｏ−Ｍｇ−Ｏ系、Ｆｅ−Ｃｏ−Ｎｉ−Ｍｇ−Ｏ系、Ｃｏ−Ｍｇ−Ｏ系、Ｆｅ−Ａｌ−Ｏ系、Ｃｏ−Ａｌ−Ｏ系、Ｆｅ−Ｃｏ−Ａｌ−Ｏ系、Ｆｅ−Ｃｏ−Ｎｉ−Ａｌ−Ｏ系の少なくとも一種であることが好ましい。
【００１０】
このような高周波磁性材料を用いた高周波磁性部品は、高飽和磁束密度を有しており、例えば、電磁波吸収体または１０ＭＨｚ以上、好ましくは１００ＭＨｚ以上で動作させる高周波磁性部品等に好適である。
また、製造方法としては、難還元性金属酸化物粉末（Ａ）とＦｅあるいはＣｏの少なくとも１種を含む金属酸化物粉末（Ｂ）からなり、難還元性金属酸化物とＦｅあるいはＣｏの少なくとも１種を含む金属酸化物の比がモル比でＡ：Ｂ＝１０：９０から９０：１０の範囲からなる複合酸化物を作製する工程、該複合酸化物を還元して複合酸化物の粒内あるいは粒界にＦｅ、Ｃｏまたはそれらを基とする合金の少なくとも1種からなる金属粒子を析出させる工程を具備することが好ましい。
本発明は、このような構成とすることにより、磁気特性の優れた高周波磁性材料を歩留りよく製造することを可能とするものである。歩留りが向上することから、製造コストの低減に効果的である。
【００１１】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。
高周波磁性材料の第１の実施の形態として、難還元性金属酸化物および、Ｆｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種からなる金属粒子を具備したことを特徴とするものである。また、高周波磁性材料の第２の実施の形態として、難還元性金属酸化物と、ＦｅまたはＣｏの少なくとも1種を含む金属酸化物との複合酸化物と、Ｆｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種からなる金属粒子を具備したことを特徴とするものである。
ここで、難還元性金属酸化物とは、室温から１５００℃の水素雰囲気下で、金属へ還元され難い金属酸化物を示す。このような金属酸化物としては、Ｃａ、Ａｌ、Ｓｉ、Ｍｇ、Ｚｒ、Ｔｉ、Ｈｆ、希土類元素、Ｂａ、Ｓｒなどの酸化物が挙げられる。本発明では、難還元性金属酸化物としては、上記酸化物１種のみであってもよいし、これらの複数種を使用してもよいものとする。なお、上記「室温から１５００℃の水素雰囲気下で、金属へ還元され難い金属酸化物」とは、水素雰囲気下に２時間放置したとしても金属が析出しない金属酸化物を示す。
【００１２】
また、複合酸化物は組成の自由度から考慮すると固溶体が好ましく、特に全率固溶体が好ましい。また、難還元性金属酸化物を２種以上用いた場合、複合酸化物も２種以上形成されていてもよい。
本発明の第１および第２の実施の形態は、Ｆｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種からなる金属粒子を具備するものである。金属粒子はＦｅ粒子、Ｃｏ粒子、Ｆｅ−Ｃｏ合金粒子、Ｆｅ−Ｃｏ−Ｎｉ合金粒子、Ｆｅ基合金粒子、Ｃｏ基合金粒子の少なくとも一種以上であることが好ましい。Ｆｅ基合金またはＣｏ基合金としては、第２成分としてＮｉ、Ｍｎ、Ｃｕなどを含有したＦｅ−Ｎｉ合金、Ｆｅ−Ｍｎ合金、Ｆｅ−Ｃｕ合金、Ｃｏ−Ｎｉ合金、Ｃｏ−Ｍｎ合金、Ｃｏ−Ｃｕ合金、さらにはＦｅ−Ｃｏ合金にＮｉ，Ｍｎ，Ｃｕを含有させた合金などが挙げられる。これら金属粒子は高周波特性を向上させることができる。また、ＦｅやＣｏの酸化物は難還元性金属酸化物と固溶体を形成し易いので好ましい。さらに、耐酸化性の観点から、Ｆｅ基粒子は一部他の元素で置換された系が好ましく、具体的にはＦｅ−Ｃｏ系、Ｆｅ−Ｃｏ―Ｎｉ系、Ｆｅ−Ｎｉ系が好ましく、さらに第３元素（他の成分）が置換されていてもよい。
【００１３】
なお、本発明においては、金属粒子としてＦｅ粒子、Ｃｏ粒子、Ｆｅ−Ｃｏ合金粒子、Ｆｅ−Ｃｏ−Ｎｉ合金粒子、Ｆｅ基合金粒子、Ｃｏ基合金粒子の少なくとも一種が存在していればよく、これに他の非磁性金属元素が合金化していてもよいが、多すぎると飽和磁化が下がりすぎるため、高周波特性を考慮すると他の非磁性金属元素（Ｆｅ、Ｃｏ以外の還元性金属）による合金化は１０ａｔ％以下であることが好ましい。また、非磁性金属が組織中に単独で分散していてもいいが、その量は面積比で２０％以下である。析出した微細結晶の耐酸化性の観点から、Ｆｅ基粒子はＣｏあるいはＮｉが一部含まれている方が好ましく、特に飽和磁化の観点からＦｅ−Ｃｏ基粒子が好ましい。
【００１４】
金属粒子は、平均粒径１０〜２０００ｎｍが好ましい。平均粒径が１０ｎｍ未満では、超常磁性が生じたりして磁束量が足りなくなってしまう。一方、２０００ｎｍを超えると渦電流損が大きくなり、狙いとする高周波領域での磁気特性が低下してしまう。さらに、好ましくは２０〜１５００ｎｍである。また、本発明の高周波磁性材料は多結晶体であることが好ましい。多結晶体であるということは、粉末冶金法（焼結法）により作製可能なことを意味するものでありコストの低減を可能とする。なお、析出した金属粒子は単結晶であってもよい。
また、上記金属粒子は高周波磁性材料を構成する結晶粒子の結晶粒子内または結晶粒界の少なくとも一方に存在していることが好ましい。高周波磁気特性を向上させるためには、結晶粒子内および結晶粒界の両方に金属粒子を存在させることが好ましい。
【００１５】
例えば、１ＧＨｚ以上と周波数が高くなると磁性材料（磁性部品）には表皮効果（ｓｋｉｎ ｅｆｆｅｃｔ）の影響が大きくなるため、平均粒径の最大値は２μｍ（＝２０００ｎｍ）以下の金属粒子が本発明の高周波用途には好ましい。
また、高周波磁性材料を構成する結晶としては、難還元性金属酸化物結晶と金属粒子以外に、難還元性金属とＦｅまたはＣｏの酸化物からなる複合酸化物（固溶体）の結晶が含まれていても良い。該複合酸化物が残存していると第２の実施の形態となる。該複合酸化物は、単に２種類の酸化物を混合して樹脂で固めたものではなく、２種以上の金属を構成元素として含む酸化物を示すものである。「複合酸化物」と「単に２種混合して固めたもの」はＸ線回折、ＥＰＭＡ、ＥＤＸ等により判別（分析）可能である。
【００１６】
また、難還元性金属とＦｅまたはＣｏの酸化物からなる複合酸化物は、後述する還元工程の際に、結晶粒子内に金属粒子を析出させ易いため磁気特性の制御に有効である。特に、金属粒子を析出させ易い複合酸化物の一例としては全率固溶体が挙げられ、具体的にはＦｅ−Ｍｇ−Ｏ系、Ｆｅ−Ｃｏ−Ｍｇ−Ｏ系、Ｆｅ−Ｃｏ−Ｎｉ−Ｍｇ−Ｏ系、Ｃｏ−Ｍｇ−Ｏ系があり、またそれ以外にも、Ｆｅ−Ａｌ−Ｏ系、Ｃｏ−Ａｌ−Ｏ系、Ｆｅ−Ｃｏ−Ａｌ−Ｏ系、Ｆｅ−Ｃｏ−Ｎｉ−Ａｌ−Ｏの少なくとも一種が挙げられる。これら化合物は、難還元性金属酸化物としてＭｇＯまたはおよびＡｌ２Ｏ３（または、ＭｇかＡｌを構成元素として含む複合金属酸化物）を用いた場合に形成される。
【００１７】
以上のような所定の金属粒子と難還元性金属酸化物を具備した高周波磁性材料は、１００ＭＨｚから数ＧＨｚ、さらには１０ＧＨｚ以上の高周波域においても優れた特性を示すものである。そのため、該高周波磁性材料を用いた高周波磁性部品は優れた高周波特性を示すことから、例えばインダクタ、チョークコイル、フィルター、トランスや電磁波吸収体などの１００ＭＨｚ、さらには１ＧＨｚ以上の高周波域で使用される高周波磁性部品に好適である。
【００１８】
次に、製造方法について説明する。本発明の高周波磁性材料は上記のような構成を具備していればその製造方法については特に限定されるものではないが、好ましい製造方法の一例として以下の方法を示す。
工程１：難還元性金属酸化物粉末（Ａ）とＦｅあるいはＣｏの少なくとも１種を含む金属酸化物粉末（Ｂ）からなり、難還元性金属酸化物とＦｅあるいはＣｏの少なくとも１種を含む金属酸化物の比がモル比でＡ：Ｂ＝１０：９０から９０：１０の範囲からなる複合酸化物、例えば固溶体を作製する工程、
工程２：該複合酸化物を還元して複合酸化物の粒内あるいは粒界にＦｅ、Ｃｏまたはそれらを基とする合金の少なくとも1種からなる金属粒子を析出させる工程、
の２つの工程を具備する製造方法が好ましい。
【００１９】
この製造方法は、工程１で複合酸化物を作製し、工程２で還元することにより所定の金属粒子を析出させる方法である。なお、このような還元を利用した製造方法に関しては特開２００１−２７８６５６号公報（特許文献３）があるが、特許文献３は高周波磁性材料を得ることを目的としたものではない。
まず、工程１について説明する。工程１とは、難還元性金属酸化物粉末（Ａ）とＦｅ、Ｃｏの少なくとも1種を含む金属酸化物粉末（Ｂ）からなり、（Ａ）と（Ｂ）をモル比でＡ：Ｂ＝１０：９０から９０：１０の範囲からなる複合酸化物、たとえば固溶体を作製する工程のことである。
【００２０】
Ｆｅ、Ｃｏの少なくとも1種を含む金属酸化物粉末（Ｂ）としては、一酸化鉄（ＦｅＯ）、酸化コバルト（ＣｏＯ）が好ましい。例えば、酸化鉄としてはＦｅＯ、Ｆｅ２Ｏ３、Ｆｅ３Ｏ４など様々な形態（化学量論）があるが、一酸化鉄（ＦｅＯ）は、難還元性金属酸化物と広い組成範囲で複合酸化物を形成し易い。例えば、難還元性金属酸化物としてＭｇＯを用いた場合、ＦｅＯ、ＣｏＯは全率固溶体となるので特に好ましい。全率固溶体の場合は、還元工程（工程２）において結晶粒内に微細な金属粒を任意の割合で析出させることができる。なお、一部に他の価数の酸化鉄が含まれていても良く、またＦｅ−Ａｌ−Ｏ系化合物の固溶体を形成する場合はＦｅ２Ｏ３を用いることが好ましい。
【００２１】
また、ＦｅまたはＣｏを含む金属酸化物としては、Ｎｉ、Ｃｕ、Ｍｎが加わった複合金属酸化物でもよく、その量はＮｉの場合ＣｏあるいはＦｅに対して５０モル％まで、ＣｕまたはＭｎの場合は１０モル％まで含有しても良い。複合金属酸化物としては、ＣｏＦｅ２Ｏ４、ＮｉＦｅ２Ｏ４のような複合金属酸化物でもよいし、酸化ニッケル、酸化銅、酸化マンガンを別途添加したものでもよいし、不純物として含まれるものを利用しても良い。
金属酸化物（Ｂ）は、２００℃から１５００℃の水素雰囲気下で、金属へ還元されうるＦｅまたはＣｏを含む金属酸化物であるため、後述の析出工程において金属粒子を析出させることができる。このため、Ｆｅ、Ｃｏの少なくとも１種を含む金属酸化物（Ｂ）は還元性金属酸化物（Ｂ）と呼ぶこともできる。
【００２２】
Ａ：Ｂはモル比で１０：９０〜９０：１０が好ましい。該モル比において、Ａ：Ｂ＝９０：１０よりＡが多いと、金属酸化物（Ｂ）の割合が少なく、また粒子間の磁気的相互作用が小さくなり、場合によっては超常磁性が発生してしまい、特性が劣化してしまう。一方、Ａ：Ｂ＝１０：９０よりＢが多いと還元工程により析出した金属粒子の結晶粒が大きくなり、高周波での特性が低下してしまい、高周波用磁心、電磁波吸収体などに必要な磁気特性が低下してしまう。
【００２３】
工程１としては、まず、所定のモル比になるように難還元性金属酸化物（Ａ）と還元性金属酸化物（Ｂ）を計りとり、ボールミルなどで混合して原料粉末を調整する原料粉末調整工程を行う。次に、原料粉末を所定温度に加熱して反応を行わせる。反応の加熱温度など諸条件は原料粉末や目的とする性質に応じて適宜決定すればよく、例えば、原料粉末をプレス成形した後、酸化性雰囲気中、あるいは真空中、Ａｒなど不活性雰囲気中で１０００℃以上の温度で加熱して、焼結させる方法が挙げられる。酸化性雰囲気とは、大気、酸素を含有する不活性ガス雰囲気などが挙げられるが、酸素量を変動させないためには不活性雰囲気あるいは真空中で焼結することが好ましい。なお、原料粉末は化学反応による沈殿物を用いると、より細かな原料粉が得られ、種々のプロセスを経たあとの結晶粒の微細化にも反映する。
【００２４】
工程１によって得られる複合酸化物は、粉末、バルクなど形状は特に限定されない。また、粉末やバルクのいずれの形態であったとしても焼結法（粉末冶金法）により作製されたものは多結晶体となる。
【００２５】
次に、得られた複合酸化物を還元してＦｅ、Ｃｏまたはそれらを基とする合金の少なくとも１種からなる金属粒子を析出させる工程２を行う。
得られた複合酸化物に水素還元を行うことにより、金属粒子を結晶粒内または粒界の少なくとも一方に析出させることができる。本発明における水素還元は、上記粉末、バルク（たとえばペレット状、リング状、矩形）、さらにはバルク状試料を粉砕した粉砕粉の状態で水素還元してもよく、特に粉末（粉砕粉含む）の場合、反応時間が短くて済むため、微細な金属粒子が均一に分散して得られやすい。また、所定の磁性部品の形状にして還元するとその後の部品化までの処理が簡単になる。
【００２６】
水素還元の温度と時間は、水素により少なくとも酸化物の一部が還元される温度であれば良く、特に限定されるものではない。ただし、２００℃以下では還元反応の進みが遅すぎ、また１５００℃を超えると析出した金属微粒子の成長が短時間で進むため、２００〜１５００℃の範囲が好ましい。また、時間は還元温度との兼ね合いで決まるが、１０分〜１００時間の範囲でよい。また、水素雰囲気は、フローが好ましく、その値は１０ｃｃ／ｍｉｎ.以上であればよい。水素気流中（水素フロー中）で還元を行えば複合酸化物の全面に均一に金属粒子を析出させ易い。
【００２７】
また、複合酸化物中のＦｅまたはＣｏを全量析出するように還元すれば第１の実施の形態、一部複合酸化物が残るように還元すれば第２の実施の形態になる。
以上のように本発明の製造方法では、一旦、複合酸化物を作製した後、還元処理により金属粒子を析出する工程を具備するものである。複合酸化物を還元する方法を採用していることから、還元で均一分散した析出金属粒子の形成が生じ易い。
また、高周波磁性材料を高周波磁性部品に加工する場合は、焼結体の場合は研磨や切削等の機械加工、粉末の場合は樹脂とのコンパウンド化を、さらには表面処理などを必要に応じ行うものとする。また、インダクタ、チョークコイル、フィルター、トランスとして用いる場合は巻線処理を行う。
【００２８】
以上のように、本発明の高周波磁性材料はインダクタ、フィルター、トランス、チョークコイルや電磁波吸収体など様々な分野に適用可能である。また、同一材料で様々な分野に適用できるので材料としての汎用性が高く、製造性を向上させる要因にもなる。
【００２９】
（実施例）
以下に、本発明を実施例で説明する。
（実施例１〜２２、比較例１〜３）
表１に示した組成になるように、ＭｇＯ、Ａｌ２Ｏ３などの難還元性金属酸化物粉末（Ａ）とＦｅＯ、ＣｏＯ、ＮｉＯなどの還元性金属酸化物粉末（Ｂ）を秤量した後、ボールミルで混合した（０．５時間、回転数３００ｒｐｍ）。得られた混合粉を１ｔ／ｃｍ２（９８ＭＰａ）の圧力でプレス成形し、ペレット状試料を作製した。
次いで、得られた試料を大気炉内に導入して、５００℃で1時間脱脂し、さらに連続して１１００℃〜１５００℃で４〜８時間焼結することにより酸化物固溶体（ペレット状試料）を作製した。
【００３０】
焼結したペレット状試料を粉砕した後、水素炉内に入れ、純度９９．９％の水素ガスを毎分２００ｃｃ流しながら、毎分１０℃の速度で所定の各温度まで昇温し、７００〜９００℃の各温度で２０〜６０分間還元を行った後、炉冷して、本実施例の高周波磁性材料を得た。
これをエポキシ樹脂（２ｗｔ％）と混合し、幅４．４ｍｍ、長さ５ｍｍ、高さ１ｍｍの直方体に成形し、１５０℃でキュアして、評価用試料に供した。
比較例として、ＦｅＡｌＳｉ粒子をエポキシ樹脂で固めたものを比較例１、カルボニル鉄粒子をエポキシ樹脂で固めたものを比較例２、またＮｉＺｎフェライト焼結体を比較例３とした。
【００３１】
高周波の磁気特性は透磁率と電磁波吸収特性の評価を行った。透磁率の測定は１ＧＨｚで行った。また、電磁波吸収特性として２ＧＨｚでの電磁波の吸収量＝［入力―（反射量＋透過量）］の比を測定し，比較例１を１として、相対値で示した。さらに、温度６０℃、湿度９０％の高温恒湿槽内に１０００Ｈ（時間）放置した後、再度透磁率を測定し、初期値との比較をした。経時変化＝（１０００Ｈ放置後の透磁率／放置前の透磁率）で示した。
析出金属粒子の平均結晶粒径の測定方法は、ＴＥＭ観察をもとに行った。具体的にはＴＥＭ観察（写真）で示された個々の金属粒子の最も長い対角線をその粒子径とし、その平均から求めた。なお、ＴＥＭ写真は単位面積１０μｍ×１０μｍを３ヶ所以上とり平均値を求めた。
【００３２】
【表１】
表から分かる通り、本実施例にかかる高周波磁性材料は、優れた磁気特性が得られることが分かった。なお、透磁率は１ＧＨｚのみであるが、平坦な周波数特性を示しており、１００ＭＨｚでもほぼ同じ値となっている。また、実施例にかかる高周波磁性材料において析出金属粒子はいずれもＦｅ粒子、Ｃｏ粒子、Ｆｅ基合金粒子、Ｃｏ基合金粒子の少なくとも１種であった。また、析出金属粒子の最大径はいずれも２０００ｎｍ以下であった。また、いずれも結晶粒内および粒界に析出金属粒子が確認された。
また、焼結によって生成された複合酸化物の還元後の残存性をＥＰＭＡで確認したところ、実施例１〜２２は複合酸化物無し（第１の実施の形態）であった。
また、実施例２２のように析出金属粒子としてＦｅまたはＣｏが主でないものは高周波特性が低下することが確認された。
さらに、Ｃｏが少なくとも一部に含まれたＦｅ基合金微粒子は高温、高湿度における磁気特性の安定性に優れることが確認できた。
【００３４】
（実施例２３〜４４）
表１と同じ組成の複合酸化物を、ＭｇＯ、Ａｌ２Ｏ３などの難還元性金属酸化物粉末（Ａ）とＦｅＯ、ＣｏＯ、ＮｉＯなどの還元性金属酸化物粉末（Ｂ）を用いて作製した。秤量後、ボールミルで混合した（０．５時間、回転数３００ｒｐｍ）。得られた混合粉を１ｔ／ｃｍ２の圧力でプレス成形し、ペレット状試料を作製した。
次いで、得られた試料を大気炉内に導入して、５００℃で１時間脱脂し、さらに連続して１１００℃〜１５００℃で４〜８時間焼結することにより酸化物固溶体（ペレット状試料）を作製した。
焼結したペレット状試料を粉砕した後、水素炉内に入れ、純度９９．９％の水素ガスを毎分２００ｃｃ流しながら、毎分１０℃の速度で所定の各温度まで昇温し、５００〜７００℃の各温度で１０〜６０分間還元を行った後、炉冷して、本実施例の高周波磁性材料を得た。
これをエポキシ樹脂(２ｗｔ％)と混合し、幅４．４ｍｍ、長さ５ｍｍ、高さ１ｍｍの直方体に成形し、１５０℃でキュアして、評価用試料に供した。
【００３５】
【表２】
表２から分かる通り、本実施例にかかる高周波磁性材料は、優れた磁気特性が得られることが分かった。なお、透磁率は１ＧＨｚのみであるが、平坦な周波数特性を示しており、１００ＭＨｚでもほぼ同じ値となっている。また、実施例にかかる高周波磁性材料において析出金属粒子はいずれもＦｅ粒子、Ｃｏ粒子、Ｆｅ基合金粒子、Ｃｏ基合金粒子の少なくとも１種であった。また、析出金属粒子の最大径はいずれも２０００ｎｍ以下であった。また、いずれも結晶粒内および粒界に析出金属粒子が確認された。
【００３７】
また、焼結によって生成された複合酸化物の還元後の残存性をＥＰＭＡで確認したところ、実施例２３〜４４は複合酸化物あり（第２の実施の形態）であった。
また、実施例３３のように難還元性金属酸化物（Ａ）を２種用いたものは、Ｆｅ−Ｓｉ−Ｏ化合物、Ｆｅ−Ｍｇ−Ｏ化合物と言った複数の複合酸化物が確認される場合もあった。
また、実施例２２と同様に実施例４４でも析出金属粒子としてＦｅまたはＣｏが主でないものは高周波特性が低下することが確認された。
さらに、Coが少なくとも一部に含まれたFe基合金微粒子は高温、高湿度における磁気特性の安定性に優れることが確認できた。
【００３８】
（実施例４５、比較例４）
実施例１の試料を同様の方法で処理量のみ変化させて複合酸化物を作製し、１ｋｇ／バッチあるいは１０ｋｇ／バッチで還元処理し、結晶の析出を試みた。なお、均質還元を目的として試料をロータリーキルンで動かしながら、還元している。
比較例４として、平均粒径５μｍのＦｅ粒子と平均粒径２μｍのＳｉＯ2粒子を体積比で１：１として、メカニカルアロイング法にてＦｅ結晶粒含有ＳｉＯ２粒子の作製を試みた。ステンレス製ボールと上記粉末の重量比を４０：１として、ＳＵＳ製のポットに入れ、２００ｒｐｍで５０時間処理した。なお、処理量は1ｋｇ／バッチと１０ｋｇ／バッチである。
得られた試料を粉砕し、平均粒径２０μｍ以下になるように分級して実施例２１、比較例４の高周波磁性材料（粉末試料）とした。
各粉末試料を任意に抜き取り、Ｆｅ粒子の評価を行い、平均粒経２０００μｍ以下になっている粒子の数を測定し、歩留り（％）＝（平均粒経２０００ｎｍ以下のＦｅ粒子範囲／全体評価数）×１００（％）で示した。
【００３９】
【表３】
以上のようにメカニカルアロイング法では、処理量が増えると金属粒子の析出にバラツキが生じることが分かった。それに対し、本実施例は水素気流中で還元しているので、均一に金属粒子を析出できることが分かった。
【００４１】
（実施例４６〜４９、比較例５）
実施例１と同様の組成の高周波磁性材料において還元条件を変えることにより析出金属粒子のサイズを変えたものを用意した。各試料に関して実施例１と同様の測定を行った。その結果を表４に示す。
【００４２】
【表４】
以上のように析出金属粒子の平均結晶粒径は１０〜２０００ｎｍである方が優れた特性を示すことが分かった。
【００４４】
【発明の効果】
以上のように本発明の高周波磁性材料は、高周波特性がよく、歩留りも高いことが分かる。また、粉末や焼結体など様々な形状で使用できるため、インダクタンス素子や電磁波吸収体など各種高周波磁性部品に適用できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency magnetic material, a high-frequency magnetic component, and a method for manufacturing the same, which are effective for a magnetic component used in a high frequency range of 10 MHz or higher, particularly 100 MHz or higher up to GHz.
[0002]
[Prior art]
In recent years, the use of magnetic material parts as key materials and parts has been expanding, and the importance has been increasing year by year. Examples of applications include inductance elements, electromagnetic wave absorbers, and magnetic inks.
For example, as a magnetic material used for an inductance element used in a high frequency range of 1 MHz or higher, mainly ferrite and amorphous alloy can be cited. Although these magnetic materials exhibit good characteristics in the 1 MHz to 10 MHz region, satisfactory characteristics are not necessarily obtained in a further high frequency region of 10 MHz or higher.
[0003]
In order to improve such a problem, an inductance element using a thin film technology such as a sputtering method and a plating method for a high permeability material has been actively developed (JP-A-5-13235: Patent Document 1). ). Although such an inductance element has been confirmed to exhibit excellent characteristics even in a high frequency range of 10 GHz or higher, thin film technology such as sputtering requires a large facility, and the film thickness and the like are precisely determined. Since it has to be controlled, it was not necessarily sufficient in terms of cost and yield.
[0004]
Moreover, an electromagnetic wave absorber is mentioned as another use. The electromagnetic wave absorber absorbs noise generated with higher frequency of the electronic device and reduces problems such as malfunction of the electronic device. Examples of the electronic device include a semiconductor element such as an IC chip and various communication devices. There are various electronic devices such as those used in a high frequency range of 1 MHz to several GHz, and even several tens of GHz. Especially, in recent years, electronic devices used in a high frequency range of 1 GHz or more tend to increase. is there.
As electromagnetic wave absorbers for electronic devices used in such a high frequency range, conventionally, those in which ferrite particles, carbonyl iron particles, FeAlSi flakes, FeCrAl flakes and the like are mixed with a resin have been used, but in a high frequency range of 1 GHz or more. However, satisfactory characteristics were not obtained.
[0005]
In recent years, as electromagnetic wave absorbers in a high frequency region of 1 GHz or more, those using composite magnetic particles in which magnetic metal particles and ceramics are integrated as shown in JP 2001-358493 A (Patent Document 2) have been shown. ing. Although this material has good electromagnetic wave absorption characteristics in a high frequency range, it must be manufactured by a mechanical alloying method and must be mixed for a long time in order to uniformly react magnetic metal particles and ceramic particles. In particular, when a large amount (for example, 10 kg or more) of material is to be produced at a time by the mechanical alloy method, mixing for a longer time is required and it cannot be said that the yield is good.
[0006]
[Patent Document 1]
JP-A-5-13235
[Patent Document 2]
JP 2001-358493 A
[Patent Document 3]
JP 2001-278656 A
[0007]
[Problems to be solved by the invention]
Amorphous alloys, ferrites, and the like, which are conventional high-frequency magnetic materials, can be manufactured with a high yield by a rapid cooling method or a sintering method, but sufficient characteristics have not been obtained in a high-frequency region of 10 MHz or more.
On the other hand, a magnetic thin film using a sputtering method and a magnetic material using mechanical alloying have excellent characteristics even in a high frequency region of 1 GHz or more, but have problems in yield and cost in manufacturing.
As described above, no conventional high-frequency magnetic material has been obtained that has both high-frequency characteristics of 10 MHz or more and manufacturability such as yield.
[0008]
[Means for Solving the Problems]
The present invention is for solving the above-described problems, and as a first form of a high-frequency magnetic material, at least one or more of a non-reducible metal oxide and Fe, Co, or an alloy based thereon are used. It has the metal particle which consists of. It is characterized by the above-mentioned. As a second form of the high-frequency magnetic material, a complex oxide of a non-reducible metal oxide and a metal oxide containing at least one of Fe or Co, and Fe, Co or an alloy based on them It comprises the metal particle which consists of at least 1 sort (s) of these.
[0009]
Moreover, it is preferable that the average particle diameter of this metal particle is 10-2000 nm. The high-frequency magnetic material is preferably a polycrystal and the metal particles are preferably present in at least one of crystal grain boundaries or grains.
In addition, refractory metal oxides are magnesium oxide, aluminum oxide, calcium oxide, silicon oxide, rare earth metal oxide, titanium oxide, zirconium oxide, barium oxide, strontium oxide, zinc oxide. It is preferable that it is at least one selected from products.
In addition, the composite oxide is Fe-Mg-O, Fe-Co-Mg-O, Fe-Co-Ni-Mg-O, Co-Mg-O, Fe-Al-O, Co- It is preferably at least one of Al—O, Fe—Co—Al—O, and Fe—Co—Ni—Al—O.
[0010]
A high-frequency magnetic component using such a high-frequency magnetic material has a high saturation magnetic flux density, and is suitable for, for example, an electromagnetic wave absorber or a high-frequency magnetic component that operates at 10 MHz or higher, preferably 100 MHz or higher.
Further, the production method includes a hardly reducible metal oxide powder (A) and a metal oxide powder (B) containing at least one of Fe or Co, and comprises at least one of the hardly reducible metal oxide and Fe or Co. A step of producing a composite oxide having a molar ratio of the metal oxide containing seeds in the range of A: B = 10: 90 to 90:10; It is preferable to include a step of precipitating metal particles comprising at least one of Fe, Co, or an alloy based on them at the grain boundaries.
The present invention makes it possible to manufacture a high-frequency magnetic material having excellent magnetic properties with a high yield by adopting such a configuration. Since the yield is improved, it is effective in reducing the manufacturing cost.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
The first embodiment of the high-frequency magnetic material is characterized by comprising a metal particle composed of at least one of a non-reducible metal oxide and Fe, Co, or an alloy based on them. Further, as a second embodiment of the high-frequency magnetic material, a complex oxide of a hardly-reducible metal oxide and a metal oxide containing at least one of Fe or Co, and Fe, Co, or a base thereof. It is characterized by comprising metal particles comprising at least one kind of alloy.
Here, the hardly reducible metal oxide refers to a metal oxide that is difficult to be reduced to a metal in a hydrogen atmosphere at room temperature to 1500 ° C. Examples of such metal oxides include oxides such as Ca, Al, Si, Mg, Zr, Ti, Hf, rare earth elements, Ba, and Sr. In the present invention, as the hardly-reducible metal oxide, only one kind of the oxide may be used, or a plurality of these kinds may be used. Note that the above-mentioned “metal oxide that is difficult to be reduced to metal in a hydrogen atmosphere at room temperature to 1500 ° C.” refers to a metal oxide in which no metal precipitates even when left in a hydrogen atmosphere for 2 hours.
[0012]
The complex oxide is preferably a solid solution in view of the degree of freedom of composition, and a solid solution is particularly preferable. In addition, when two or more kinds of hardly-reducible metal oxides are used, two or more kinds of composite oxides may be formed.
The first and second embodiments of the present invention comprise metal particles made of at least one of Fe, Co or alloys based on them. The metal particles are preferably at least one of Fe particles, Co particles, Fe—Co alloy particles, Fe—Co—Ni alloy particles, Fe-based alloy particles, and Co-based alloy particles. As the Fe-based alloy or Co-based alloy, Fe—Ni alloy, Fe—Mn alloy, Fe—Cu alloy, Co—Ni alloy, Co—Mn alloy, Co—Mn containing Ni, Mn, Cu or the like as the second component are used. Examples thereof include Cu alloys, and alloys obtained by adding Ni, Mn, and Cu to Fe—Co alloys. These metal particles can improve high frequency characteristics. Fe and Co oxides are preferable because they easily form a solid solution with a hardly-reducible metal oxide. Furthermore, from the viewpoint of oxidation resistance, a system in which the Fe-based particles are partially substituted with other elements is preferable, and specifically, Fe-Co-based, Fe-Co-Ni-based, and Fe-Ni-based are preferable. The third element (other components) may be substituted.
[0013]
In the present invention, it is sufficient that at least one of Fe particles, Co particles, Fe—Co alloy particles, Fe—Co—Ni alloy particles, Fe-based alloy particles, and Co-based alloy particles exists as metal particles, Other non-magnetic metal elements may be alloyed with this, but if it is too much, the saturation magnetization will be too low, so considering high-frequency characteristics, alloys with other non-magnetic metal elements (reducing metals other than Fe and Co) The conversion is preferably 10 at% or less. The nonmagnetic metal may be dispersed alone in the structure, but the amount is 20% or less in terms of area ratio. From the viewpoint of oxidation resistance of the precipitated fine crystals, the Fe-based particles preferably contain part of Co or Ni, and particularly Fe-Co-based particles are preferable from the viewpoint of saturation magnetization.
[0014]
The metal particles preferably have an average particle size of 10 to 2000 nm. If the average particle size is less than 10 nm, superparamagnetism may occur and the amount of magnetic flux will be insufficient. On the other hand, if it exceeds 2000 nm, eddy current loss increases, and the magnetic characteristics in the intended high-frequency region are degraded. Furthermore, it is preferably 20 to 1500 nm. The high-frequency magnetic material of the present invention is preferably a polycrystalline body. The fact that it is a polycrystal means that it can be produced by a powder metallurgy method (sintering method), which enables cost reduction. The deposited metal particles may be single crystals.
The metal particles are preferably present in at least one of the crystal grains of the crystal grains constituting the high-frequency magnetic material or in the crystal grain boundaries. In order to improve the high-frequency magnetic characteristics, it is preferable that metal particles exist both in the crystal grains and in the crystal grain boundaries.
[0015]
For example, when the frequency is increased to 1 GHz or higher, the magnetic material (magnetic component) is more affected by the skin effect, so the maximum value of the average particle diameter is 2 μm (= 2000 nm) or less. Preferred for high frequency applications.
Further, the crystals constituting the high-frequency magnetic material include crystals of complex oxides (solid solution) made of an oxide of Fe or Co and a non-reducing metal oxide crystal and metal particles. May be. If the composite oxide remains, the second embodiment is obtained. The composite oxide is not simply a mixture of two kinds of oxides and hardened with a resin, but an oxide containing two or more kinds of metals as constituent elements. “Composite oxide” and “simply mixed and hardened” can be discriminated (analyzed) by X-ray diffraction, EPMA, EDX, or the like.
[0016]
In addition, a composite oxide composed of a hardly-reducible metal and an oxide of Fe or Co is effective in controlling magnetic properties because it easily deposits metal particles in crystal particles during the reduction step described later. In particular, an example of a complex oxide that easily deposits metal particles is a solid solution, specifically, Fe-Mg-O-based, Fe-Co-Mg-O-based, Fe-Co-Ni-Mg--. There are O-based, Co-Mg-O-based, and other than these, Fe-Al-O-based, Co-Al-O-based, Fe-Co-Al-O-based, Fe-Co-Ni-Al-O At least one of them. These compounds are MgO or Al as refractory metal oxides 2 O 3 It is formed when (or a composite metal oxide containing Mg or Al as a constituent element) is used.
[0017]
The high-frequency magnetic material including the predetermined metal particles and the hardly-reducible metal oxide as described above exhibits excellent characteristics even in a high-frequency region of 100 MHz to several GHz, and further 10 GHz or more. For this reason, high-frequency magnetic parts using the high-frequency magnetic material exhibit excellent high-frequency characteristics, and are therefore used in high-frequency regions of 100 MHz, such as inductors, choke coils, filters, transformers and electromagnetic wave absorbers, and further 1 GHz or higher. Suitable for high frequency magnetic parts.
[0018]
Next, a manufacturing method will be described. The production method of the high-frequency magnetic material of the present invention is not particularly limited as long as it has the above-described configuration, but the following method is shown as an example of a preferred production method.
Step 1: A metal comprising a hardly reducible metal oxide powder (A) and a metal oxide powder (B) containing at least one of Fe or Co, and comprising a hardly reducible metal oxide and at least one of Fe or Co. A step of producing a complex oxide, for example, a solid solution, in which the oxide ratio is in a molar ratio of A: B = 10: 90 to 90:10;
Step 2: reducing the composite oxide to deposit metal particles composed of at least one of Fe, Co, or an alloy based on them in the grains or grain boundaries of the composite oxide,
A production method comprising the two steps is preferable.
[0019]
This manufacturing method is a method in which a composite oxide is produced in step 1 and predetermined metal particles are precipitated by reduction in step 2. In addition, although there exists Unexamined-Japanese-Patent No. 2001-278656 (patent document 3) regarding the manufacturing method using such reduction | restoration, patent document 3 is not aimed at obtaining a high frequency magnetic material.
First, step 1 will be described. Step 1 consists of a hardly-reducible metal oxide powder (A) and a metal oxide powder (B) containing at least one of Fe and Co. A: B = (A) and (B) at a molar ratio of A: B = This is a step of producing a complex oxide having a range of 10:90 to 90:10, for example, a solid solution.
[0020]
As the metal oxide powder (B) containing at least one of Fe and Co, iron monoxide (FeO) and cobalt oxide (CoO) are preferable. For example, as iron oxide, FeO, Fe 2 O 3 , Fe 3 O 4 There are various forms (stoichiometry) and the like, but iron monoxide (FeO) is easy to form a complex oxide with a hardly reducible metal oxide in a wide composition range. For example, when MgO is used as the hard-to-reduced metal oxide, FeO and CoO are particularly preferable because they are all solid solutions. In the case of a full solid solution, fine metal grains can be precipitated in the crystal grains at an arbitrary ratio in the reduction step (step 2). In addition, iron oxides of other valences may be included in part, and in the case of forming a solid solution of Fe-Al-O compound, Fe 2 O 3 Is preferably used.
[0021]
Further, the metal oxide containing Fe or Co may be a composite metal oxide to which Ni, Cu, or Mn is added. The amount is up to 50 mol% with respect to Co or Fe in the case of Ni, and in the case of Cu or Mn. May be contained up to 10 mol%. As the composite metal oxide, CoFe 2 O 4 NiFe 2 O 4 Such composite metal oxides may be used, nickel oxide, copper oxide, manganese oxide may be added separately, or those contained as impurities may be used.
Since the metal oxide (B) is a metal oxide containing Fe or Co that can be reduced to a metal in a hydrogen atmosphere at 200 ° C. to 1500 ° C., the metal particles can be precipitated in the precipitation step described later. For this reason, the metal oxide (B) containing at least one of Fe and Co can also be called a reducible metal oxide (B).
[0022]
A: B is preferably 10:90 to 90:10 in molar ratio. In the molar ratio, when A is larger than A: B = 90: 10, the ratio of the metal oxide (B) is small, the magnetic interaction between the particles is small, and superparamagnetism is generated in some cases. As a result, the characteristics deteriorate. On the other hand, if B is more than A: B = 10: 90, the crystal grains of the metal particles precipitated by the reduction process become large, and the characteristics at high frequency are deteriorated. The characteristics will deteriorate.
[0023]
In step 1, first, a raw material powder is prepared by measuring a hardly reducible metal oxide (A) and a reducible metal oxide (B) so as to have a predetermined molar ratio and mixing them with a ball mill or the like to prepare a raw material powder. An adjustment process is performed. Next, the raw material powder is heated to a predetermined temperature to cause the reaction. Various conditions such as the heating temperature of the reaction may be appropriately determined according to the raw material powder and the desired properties. For example, after the raw material powder is press-molded, in an oxidizing atmosphere or in vacuum, in an inert atmosphere such as Ar There is a method of heating and sintering at a temperature of 1000 ° C. or higher. Examples of the oxidizing atmosphere include air, an inert gas atmosphere containing oxygen, and the like. In order not to fluctuate the amount of oxygen, it is preferable to sinter in an inert atmosphere or vacuum. In addition, if the raw material powder uses the precipitate by a chemical reaction, finer raw material powder will be obtained and it will reflect also in refinement | miniaturization of the crystal grain after passing through various processes.
[0024]
The shape of the composite oxide obtained by step 1 is not particularly limited, such as powder and bulk. Moreover, even if it is any form of a powder and a bulk, what was produced by the sintering method (powder metallurgy method) turns into a polycrystal.
[0025]
Next, Step 2 is performed in which the obtained composite oxide is reduced to deposit metal particles made of at least one of Fe, Co, or an alloy based on them.
By performing hydrogen reduction on the obtained composite oxide, metal particles can be precipitated in at least one of crystal grains or grain boundaries. The hydrogen reduction in the present invention may be performed by hydrogen reduction in the state of the above powder, bulk (for example, pellet, ring, rectangular), or pulverized powder obtained by pulverizing a bulk sample, and particularly powder (including pulverized powder). In this case, since the reaction time is short, it is easy to obtain fine metal particles uniformly dispersed. Further, if the shape is reduced to a predetermined magnetic part shape, the subsequent process up to the partization is simplified.
[0026]
The temperature and time for hydrogen reduction are not particularly limited as long as at least a part of the oxide is reduced by hydrogen. However, since the progress of the reduction reaction is too slow at 200 ° C. or less, and the growth of the deposited metal fine particles proceeds in a short time when it exceeds 1500 ° C., the range of 200 to 1500 ° C. is preferable. Moreover, although time is decided by balance with reduction temperature, the range of 10 minutes-100 hours may be sufficient. The hydrogen atmosphere is preferably flow, and the value may be 10 cc / min. Or more. If the reduction is performed in a hydrogen stream (in a hydrogen flow), the metal particles are easily deposited uniformly on the entire surface of the composite oxide.
[0027]
Further, the first embodiment is obtained by reducing the total amount of Fe or Co in the composite oxide so as to precipitate, and the second embodiment is obtained by reducing the composite oxide so that a part of the composite oxide remains.
As described above, the production method of the present invention includes a step of once producing a composite oxide and then depositing metal particles by reduction treatment. Since the method of reducing the composite oxide is employed, the formation of precipitated metal particles uniformly dispersed by reduction is likely to occur.
Also, when processing high-frequency magnetic materials into high-frequency magnetic parts, mechanical processing such as polishing or cutting is performed for sintered bodies, compounding with resin is performed for powders, and surface treatment is performed as necessary. Shall. When used as an inductor, choke coil, filter, or transformer, winding processing is performed.
[0028]
As described above, the high-frequency magnetic material of the present invention can be applied to various fields such as inductors, filters, transformers, choke coils, and electromagnetic wave absorbers. In addition, since the same material can be applied to various fields, the versatility of the material is high, and it becomes a factor that improves manufacturability.
[0029]
(Example)
Hereinafter, the present invention will be described with reference to examples.
(Examples 1-22, Comparative Examples 1-3)
MgO, Al so as to have the composition shown in Table 1. 2 O 3 After weighing the reducible metal oxide powder (A) such as FeO, CoO, NiO, etc. and the reducible metal oxide powder (B), they were mixed by a ball mill (0.5 hours, rotation speed 300 rpm). 1 t / cm of the obtained mixed powder 2 The sample was press-molded at a pressure of (98 MPa) to prepare a pellet sample.
Next, the obtained sample is introduced into an atmospheric furnace, degreased at 500 ° C. for 1 hour, and further continuously sintered at 1100 ° C. to 1500 ° C. for 4 to 8 hours to form an oxide solid solution (pellet-like sample). Was made.
[0030]
After the sintered pellet sample is pulverized, it is placed in a hydrogen furnace and heated to a predetermined temperature at a rate of 10 ° C. per minute while flowing 200 cc of hydrogen gas with a purity of 99.9% per minute. After performing reduction at each temperature of 900 ° C. for 20 to 60 minutes, the furnace was cooled to obtain the high-frequency magnetic material of this example.
This was mixed with an epoxy resin (2 wt%), formed into a rectangular parallelepiped having a width of 4.4 mm, a length of 5 mm, and a height of 1 mm, cured at 150 ° C., and used as an evaluation sample.
As comparative examples, FeAlSi particles hardened with an epoxy resin were used as Comparative Example 1, carbonyl iron particles hardened with an epoxy resin were used as Comparative Example 2, and NiZn ferrite sintered bodies were used as Comparative Example 3.
[0031]
High-frequency magnetic characteristics were evaluated for permeability and electromagnetic wave absorption characteristics. The permeability was measured at 1 GHz. Further, as an electromagnetic wave absorption characteristic, a ratio of electromagnetic wave absorption amount at 2 GHz = [input− (reflection amount + transmission amount)] was measured. Furthermore, after leaving in a high temperature and humidity chamber of 60 ° C. and 90% humidity for 1000 H (hours), the magnetic permeability was measured again and compared with the initial value. Change with time = (permeability after leaving 1000H / permeability before leaving).
The average crystal grain size of the deposited metal particles was measured based on TEM observation. Specifically, the longest diagonal line of each metal particle shown by TEM observation (photograph) was used as the particle diameter, and the average was obtained from the average. In addition, the average value was calculated | required for the TEM photograph, taking a unit area 10 micrometers x 10 micrometers in three or more places.
[0032]
[Table 1]
As can be seen from the table, it was found that the high-frequency magnetic material according to this example can obtain excellent magnetic properties. Although the magnetic permeability is only 1 GHz, it shows a flat frequency characteristic and is almost the same value even at 100 MHz. In the high-frequency magnetic material according to the example, the precipitated metal particles were all at least one of Fe particles, Co particles, Fe-based alloy particles, and Co-based alloy particles. Further, the maximum diameter of the deposited metal particles was 2000 nm or less. In both cases, precipitated metal particles were confirmed in the crystal grains and in the grain boundaries.
Moreover, when the residual property after reduction | restoration of the composite oxide produced | generated by sintering was confirmed by EPMA, Examples 1-22 was no composite oxide (1st Embodiment).
In addition, it was confirmed that the high frequency characteristics of the precipitated metal particles that were not mainly Fe or Co as in Example 22 were deteriorated.
Furthermore, it was confirmed that Fe-based alloy fine particles containing at least a part of Co are excellent in stability of magnetic properties at high temperature and high humidity.
[0034]
(Examples 23 to 44)
A composite oxide having the same composition as in Table 1 is made of MgO, Al. 2 O 3 It produced using reducible metal oxide powder (A), such as, and reducible metal oxide powders (B), such as FeO, CoO, and NiO. After weighing, they were mixed with a ball mill (0.5 hours, rotation speed: 300 rpm). 1 t / cm of the obtained mixed powder 2 The sample was press-molded at a pressure of 1 to produce a pellet sample.
Next, the obtained sample is introduced into an atmospheric furnace, degreased at 500 ° C. for 1 hour, and further continuously sintered at 1100 ° C. to 1500 ° C. for 4 to 8 hours to obtain an oxide solid solution (pellet-like sample). Was made.
After the sintered pellet sample is pulverized, it is placed in a hydrogen furnace and heated to a predetermined temperature at a rate of 10 ° C. per minute while flowing 200 cc of hydrogen gas with a purity of 99.9% per minute. After performing reduction at each temperature of 700 ° C. for 10 to 60 minutes, the furnace was cooled to obtain the high-frequency magnetic material of this example.
This was mixed with an epoxy resin (2 wt%), formed into a rectangular parallelepiped having a width of 4.4 mm, a length of 5 mm, and a height of 1 mm, cured at 150 ° C., and used as an evaluation sample.
[0035]
[Table 2]
As can be seen from Table 2, the high-frequency magnetic material according to this example was found to have excellent magnetic properties. Although the magnetic permeability is only 1 GHz, it shows a flat frequency characteristic and is almost the same value even at 100 MHz. In the high-frequency magnetic material according to the example, the precipitated metal particles were all at least one of Fe particles, Co particles, Fe-based alloy particles, and Co-based alloy particles. Further, the maximum diameter of the deposited metal particles was 2000 nm or less. In both cases, precipitated metal particles were confirmed in the crystal grains and in the grain boundaries.
[0037]
Moreover, when the persistence after reduction | restoration of the complex oxide produced | generated by sintering was confirmed by EPMA, Example 23-44 had complex oxide (2nd Embodiment).
In addition, in the case of using two kinds of hardly-reducible metal oxides (A) as in Example 33, a plurality of composite oxides such as Fe—Si—O compound and Fe—Mg—O compound are confirmed. There was a case.
In addition, as in Example 22, in Example 44, it was confirmed that the high frequency characteristics of the precipitated metal particles that were not mainly Fe or Co were lowered.
Furthermore, it was confirmed that the Fe-based alloy fine particles containing Co at least partially have excellent magnetic property stability at high temperature and high humidity.
[0038]
(Example 45, Comparative Example 4)
A composite oxide was produced by changing only the treatment amount of the sample of Example 1 in the same manner, reduction treatment was performed at 1 kg / batch or 10 kg / batch, and crystal precipitation was attempted. For the purpose of homogeneous reduction, the sample is reduced while moving with a rotary kiln.
As Comparative Example 4, Fe particles having an average particle diameter of 5 μm and SiO particles having an average particle diameter of 2 μm 2 Fe particles containing SiO grains by mechanical alloying method with 1: 1 volume ratio 2 Attempts were made to produce particles. The weight ratio of the stainless steel balls to the powder was 40: 1, and the mixture was placed in a SUS pot and treated at 200 rpm for 50 hours. The throughput is 1 kg / batch and 10 kg / batch.
The obtained sample was pulverized and classified so as to have an average particle size of 20 μm or less to obtain high-frequency magnetic materials (powder samples) of Example 21 and Comparative Example 4.
Each powder sample is arbitrarily extracted, the Fe particles are evaluated, the number of particles having an average particle size of 2000 μm or less is measured, and the yield (%) = (Fe particle range having an average particle size of 2000 nm or less / total evaluation number) ) × 100 (%).
[0039]
[Table 3]
As described above, in the mechanical alloying method, it was found that when the amount of treatment increases, the precipitation of metal particles varies. On the other hand, since the present Example reduced in the hydrogen stream, it turned out that a metal particle can be deposited uniformly.
[0041]
(Examples 46 to 49, Comparative Example 5)
A high-frequency magnetic material having the same composition as in Example 1 was prepared by changing the reducing conditions to change the size of the deposited metal particles. The same measurement as in Example 1 was performed on each sample. The results are shown in Table 4.
[0042]
[Table 4]
As described above, it has been found that the average crystal grain size of the deposited metal particles is more excellent when it is 10 to 2000 nm.
[0044]
【The invention's effect】
As described above, the high-frequency magnetic material of the present invention has good high-frequency characteristics and a high yield. Further, since it can be used in various shapes such as powder and sintered body, it can be applied to various high-frequency magnetic parts such as inductance elements and electromagnetic wave absorbers.
Claims (9)
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| JP4664649B2 (en) * | 2004-10-27 | 2011-04-06 | 株式会社東芝 | High frequency magnetic material and high frequency magnetic component using the same |
| JP2008041771A (en) | 2006-08-02 | 2008-02-21 | Toshiba Corp | Method of manufacturing high frequency magnetic material |
| JP4585493B2 (en) | 2006-08-07 | 2010-11-24 | 株式会社東芝 | Method for producing insulating magnetic material |
| JP4686494B2 (en) | 2007-03-12 | 2011-05-25 | 株式会社東芝 | High frequency magnetic material and manufacturing method thereof |
| JP5065960B2 (en) * | 2008-03-28 | 2012-11-07 | 株式会社東芝 | High-frequency magnetic material and method for producing the same. |
| JP5472694B2 (en) * | 2009-07-09 | 2014-04-16 | 日立金属株式会社 | Composite sintered body of aluminum oxide and iron, and method for producing the same |
| US8840800B2 (en) * | 2011-08-31 | 2014-09-23 | Kabushiki Kaisha Toshiba | Magnetic material, method for producing magnetic material, and inductor element |
| JP2015007272A (en) * | 2013-06-25 | 2015-01-15 | 株式会社東芝 | Magnetic material and device |
| JP2015190017A (en) * | 2014-03-28 | 2015-11-02 | 三菱マテリアル株式会社 | Softly magnetic thin film forming sputtering target |
| JP6280157B2 (en) * | 2016-05-17 | 2018-02-14 | 株式会社リケン | Near-field noise suppression sheet |
| TWI678144B (en) * | 2017-07-24 | 2019-11-21 | 理研股份有限公司 | Noise suppression film for near field |
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