JP3751146B2 - Method for producing composition comprising BaTiO3 as main component and method for producing multilayer ceramic capacitor - Google Patents

Description

【０００９】
請求項３に記載の発明は、ＢａＴｉＯ₃を主成分に副成分を添加して湿式混合し、乾燥後、仮焼、粉砕し仮焼粉末を得る第１工程と、次にこの仮焼粉末を用いてグリーンシートを作製し、内部電極と交互に積層して積層体を作製する第２工程と、次いでこの積層体を前記内部電極の融点よりも低温かつ還元雰囲気中で焼成する第３工程と、その後前記積層体の端面に外部電極を形成する第４工程とを備え、前記副成分は、その比表面積がＢａＴｉＯ₃の比表面積よりも大きいものを用いることを特徴とする積層セラミックコンデンサの製造方法であり、高温中での電圧負荷試験による絶縁抵抗の劣化が小さく、高信頼性を有する積層セラミックコンデンサを得ることができる。
【００１０】
請求項４に記載の発明は、第２の工程後、（化４）に示す組成となるグリーンシートを用いる請求項３に記載の積層セラミックコンデンサの製造方法であり、ＢａＴｉＯ₃よりも比表面積の大きいＭｎ₃Ｏ₄とＤｙ₂Ｏ₃を副成分として添加することにより、誘電体層の局所的な半導体化部分を激減させることができる。特に誘電体層の厚みが焼結後６μｍ以下の積層セラミックコンデンサについては、有効層間に誘電体セラミック粒子が１〜３個となる。本発明の場合大多数の誘電体セラミック粒子に絶縁性が付与されるために有効層厚みが６μｍ以下でも十分な絶縁性を有するので、誘電体層を薄層化し、小型大容量かつ、高温中での電圧負荷試験による絶縁抵抗の劣化の小さい、高信頼性を有する積層セラミックコンデンサを得ることができる。
【００１１】
【化４】

【００１２】
以下本発明の一実施の形態について説明する。
出発原料には化学的に高純度のＢａＴｉＯ₃，ＢａＺｒＯ₃，ＳｒＯ，Ｍｎ₃Ｏ₄，Ｄｙ₂Ｏ₃を用い、（化５）に示すような本発明範囲内の一組成比になるように秤量した。
【００１３】
【化５】

【００１４】
ここで主成分となるＢａＴｉＯ₃は共沈法で作製されたもので、比表面積は５ｍ²／ｇであった。また副成分となる他の添加物については種々の比表面積を有する市販のＢａＺｒＯ₃，ＳｒＯ，Ｍｎ₃Ｏ₄，Ｄｙ₂Ｏ₃を用いて行った。
【００１５】
秤量後、まず出発原料をジルコニアボールを備えたボールミルに純水とともに入れ、湿式混合後、脱水乾燥し、混合粉末を得た後、高純度のアルミナルツボに入れ、９００〜１２００℃の範囲で、２時間仮焼した。
【００１６】
その後この仮焼粉末をジルコニアボールを備えたボールミルに純水とともに入れ、湿式粉砕後、脱水乾燥した。この時粉砕粉の平均粒径が１．５μｍ以下になるようにした。次に混合粉末および粉砕粉末のそれぞれに有機バインダとしてポリビニルブチラール樹脂、可塑剤としてＢＢＰ（ベンジルブチルフタレート）、溶剤としてｎ−酢酸ブチルを加えて、ジルコニアを備えたボールミルにて混合し、スラリーを調整した。次にこのスラリーを真空脱泡の後、ドクターブレード法により、フィルム状に造膜し、グリーンシートを作製した。この時、乾燥後のグリーンシートの厚みが約１０μｍとなるようにした。次に、このグリーンシート上に平均粒径約１．０μｍのニッケル粉末を含有した電極ペーストを用い、所望の内部電極パターンとなるようにスクリーン印刷を行った。次いで内部電極パターン形成済みのグリーンシートを内部電極パターンがグリーンシートを介して対向するように１００枚重ね合わせ、加熱、加圧して一体化した後、横３．８ｍｍ、縦１．８ｍｍの寸法に切断して、未焼結積層体を準備した。次にこの未焼結積層体をジルコニア粉末を敷いたジルコニア質サヤに入れ、ニッケルが過度に酸化しないように最高温度４００℃で空気中で加熱し、未焼結積層体中の有機バインダを燃焼させて除去した。
【００１７】
次いで図１を用いて焼成工程について説明する。温度については、まず昇温速度２００℃／時間で最高温度（Ｔ１）が１２５０℃になるまで昇温し、最高温度で２時間保持した後、８５０℃（Ｔ３）まで降温速度２００℃／時間で降温し、８５０℃で２時間保持し、誘電体層の再酸化を行った後、降温速度２００℃／時間で降温する温度管理を行った。雰囲気については、昇温からＴ２まではＮ₂＋Ｈ₂ガスに対してＣＯ₂ガス、Ｈ₂Ｏガスなどを用いて、本実施の形態においては、ＰＯ₂＝１０^-7ａｔｍ以下を保持し、Ｔ２以降はＨ₂ガスの送り込みを止めて、Ｔ２までよりも酸素分圧を高くして、ＰＯ₂＝１０^-5ａｔｍで誘電体層の再酸化を行った。ここでＴ２以降、再酸化を行うのは絶縁抵抗が劣化するのを防止するためである。
【００１８】
その後得られた焼結体の内部電極の露出した端面に外部電極として市販の９００℃窒素雰囲気焼成用Ｃｕペーストを塗布し、メッシュ型の連続ベルトによって焼付け、積層セラミックコンデンサを得た。
【００１９】
なお、焼成後の誘電体層の厚みは約６μｍ、内部電極層の厚みは約２〜２．５μｍであった。
【００２０】
次に得られた積層セラミックコンデンサの静電容量を２０℃の恒温槽中で周波数１ｋＨｚ、入力信号レベル１．０Ｖｒｍｓにて測定し、（数１）を用いて比誘電率を算出した。
【００２１】
【数１】

【００２２】
その後、直流１６Ｖを１分間印加し、その時の絶縁抵抗を測定した。一方で、任意に５０個の積層セラミックコンデンサを抽出し、８５℃の高温中で各々に対して３２Ｖを負荷し、１０００時間後の絶縁抵抗の劣化数を評価した。以上の測定結果を（表１）に合わせて示した。
【００２３】
【表１】

【００２４】
（表１）から明らかなように、副成分ＢａＺｒＯ₃，Ｍｎ₃Ｏ₄，Ｄｙ₂Ｏ₃およびＳｒＯの比表面積がＢａＴｉＯ₃よりも大きい場合（サンプルＮｏ．００１〜Ｎｏ．０１０）には、高温負荷試験での絶縁抵抗の劣化が見られないのに対して、ＢａＴｉＯ₃の比表面積よりも小さい場合（サンプルＮｏ．０１１〜Ｎｏ．０１５）には、絶縁抵抗の劣化が見られる。特にＭｎ₃Ｏ₄とＤｙ₂Ｏ₃の両方がＢａＴｉＯ₃の比表面積よりも小さい場合には劣化が激しいことが分かる。これらの劣化箇所を観察した結果、ボイドなどの構造欠陥ではなく、セラミック粒子自身の劣化であった。
【００２５】
つまり還元雰囲気中で焼成すると容易に還元され、半導体化してしまうＢａＴｉＯ₃に、予め各種副成分を添加することによって還元雰囲気中で焼成しても、絶縁性を確保できる。しかしながら、各種副成分粉末の比表面積がＢａＴｉＯ₃の比表面積より小さい場合には、副成分が均一にＢａＴｉＯ₃に固溶せず、副成分が固溶した箇所は絶縁性が確保できるが、副成分が添加物が十分に固溶しなかった部分は、半導体化してしまうからである。
【００２６】
以上のことから、ＢａＴｉＯ₃粉末よりも比表面積が大きい副成分粉末を添加することで、副成分粒子が均一にＢａＴｉＯ₃粒子と反応し、局所的な半導体化を抑制することができ、誘電体層の絶縁性が向上し、高信頼性を有する磁器誘電体組成物および積層セラミックコンデンサを得ることができる。
【００２７】
以下、本発明において重要なことを記載する。
（１）上記実施の形態では、（化５）に示される本発明範囲内の一組成比についてのみ示したが、（化４）に示す組成範囲内の誘電体磁器組成物はもちろんのこと、ＢａＴｉＯ₃を主成分とし、各種副成分を添加して形成する組成物においても、本発明の方法により主成分ＢａＴｉＯ₃に対して副成分を均一に固溶させることができ、電気特性の優れた組成物を得ることができる。
【００２８】
（２）内部電極としてＮｉを用いたが、Ｃｕ，Ｎｉ−Ｃｕなどの酸化されやすい卑金属だけでなく貴金属を主成分とする場合においても同様の効果が得られる。
【００２９】
（３）脱バインダ工程は、使用する有機バインダが除去できるように、その燃焼温度に応じて熱処理温度を最適に選択すればよい。
【００３０】
（４）焼成工程は、昇温速度１００〜４００℃／時間で昇温し、最高温度（Ｔ１）１２２５〜１３２５℃で２〜４時間保持し、誘電体層の再酸化を行うために降温過程において、７００〜１１５０℃（Ｔ３）で２〜６時間保持することが望ましい。また降温速度は５０〜４００℃／時間とすることが望ましい。
【００３１】
（５）昇温過程と最高温度保持過程まで（Ｔ１まで）の焼成雰囲気は、焼成の最初から内部電極となる金属の平衡酸素分圧より低い酸素分圧とするか、あるいは最初内部電極となる金属の平衡酸素分圧以上で焼成し誘電体層中に残留しているカーボンを除去した後、この雰囲気で焼成することにより金属酸化物となった内部電極が誘電体層中に拡散してしまう前に金属酸化物を金属に還元するために酸素分圧を内部電極となる金属の平衡酸素分圧より低い酸素分圧にする。
【００３２】
また降温過程以降（Ｔ２以降）は、誘電体層の再酸化を行うために、Ｔ１までよりも酸素分圧を高くすることが望ましい。しかしながら降温過程において、誘電体層の再酸化を行う際、焼成後内部電極としての機能を果たせるように内部電極が過度に酸化されない雰囲気でなければならない。
【００３３】
Ｔ２の温度は、Ｔ１以降Ｔ３までの温度範囲内にあればよい。
また酸素分圧が上述したように制御できれば、Ｎ₂＋Ｈ₂ガスだけに限らず他の方法で酸素分圧を制御しても構わない。
【００３４】
（６）外部電極は、内部電極と同じ金属かまた内部電極となる金属と合金を形成する金属を用いて形成すれば電気的接続が十分に確保でき、インピーダンスが小さく、安定した静電容量を有する積層セラミックコンデンサとなる。
【００３５】
（７）出発原料として用いるＢａＴｉＯ₃粉末は、固相法で作製されたものより、アルコキシド法やシュウ酸塩法などの共沈法で作製されたものの方が低温で副成分との反応は進行しやすい。
【００３６】
（８）（化４）の誘電体磁器組成物においては、ＢａをＳｒで置換することにより比誘電率を高め、誘電損失を小さくすることができる。またＤｙは耐還元性を向上させることができるとともに他の希土類元素と比較すると比誘電率を向上させることができる。さらにＭｎは、耐還元性を向上させることができる。そしてＭｎ₃Ｏ₄は他のＭｎ化合物と比較すると、原料混合時の分散性に優れているので、他のＭｎ化合物を用いるよりも少量の添加で絶縁抵抗の低下を抑制することができる。またＭｎ成分を添加することにより比誘電率が低下する傾向にあるが、Ｍｎ₃Ｏ₄は他のＭｎ化合物を用いた場合と比較すると、その傾向が小さい。従ってＭｎ成分の添加は、Ｍｎ₃Ｏ₄を用いて行うことが好ましい。
【００３７】
また副成分の中でも特にＭｎ₃Ｏ₄，Ｄｙ₂Ｏ₃は、ＢａＴｉＯ₃より比表面積の大きいものを用いることが重要である。Ｍｎ₃Ｏ₄やＤｙ₂Ｏ₃はＢａＴｉＯ₃に固溶し、還元雰囲気中でのＢａＴｉＯ₃の半導体化を抑制する成分である。ＢａＴｉＯ₃の比表面積が２〜６ｍ²／ｇに対して、それ以上の比表面積を有するＭｎ₃Ｏ₄やＤｙ₂Ｏ₃を添加することによって誘電体層の絶縁性が向上する。Ｍｎ₃Ｏ₄は他のＭｎ化合物と比較して比表面積が６〜８ｍ²／ｇと大きく、混合時の分散性についても優れている。一方Ｄｙ₂Ｏ₃は６〜１２ｍ²／ｇのものを用いることにより、絶縁性が向上する。また他の希土類と比較すると比誘電率を高める役割を果たす。Ｓｒ成分やＺｒ成分についても、ＢａＴｉＯ₃よりも比表面積の大きな粉体を用いることによって絶縁性を向上させる効果を有しているが、Ｍｎ成分やＤｙ成分と比較すると顕著ではない。
【００３８】
ＢａＴｉＯ₃は５．５〜１４ｍ²／ｇ、ＳｒＯは６〜８ｍ²／ｇの比表面積のものを用いることが好ましい。
【００３９】
ＢａＴｉＯ₃に対して、添加量の少ない副成分ほど比表面積の大きな原料を用いて反応性を向上させることが望ましい。
【００４０】
（９）誘電体層の副成分の出発原料として炭酸塩を用いた場合、湿式混合時に水酸化物となるためにスラリーの粘度が上昇し、各添加物の分散状態が悪くなる。
【００４１】
（化４）の組成物においては、比誘電率が低くなる。またＭｎ成分やＤｙ成分の極度に分散状態が悪い場合には、絶縁抵抗の劣化を招くこともある。
【００４２】
従って、出発原料はできるだけ炭酸塩を用いないことが好ましい。
（１０）上記実施の形態においては、積層セラミックコンデンサを作製し、誘電体磁器組成物の特性を評価したが、本発明の誘電体磁器組成物は、単板型のセラミックコンデンサにも使用できることは言うまでもない。
【００４３】
【発明の効果】
以上本発明によると、ＢａＴｉＯ ₃ 粒子の周囲に副成分を均一に固溶させることができるので、例えば誘電体磁器組成物の場合、絶縁性に優れたものとなる。
【図面の簡単な説明】
【図１】本発明の一実施形態の焼成工程を説明する図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a composition mainly composed of BaTiO ₃ and a method for producing a multilayer ceramic capacitor.
[0002]
[Prior art]
For example, a dielectric ceramic composition mainly composed of BaTiO _3, the addition of various auxiliary components BaTiO _3, after mixing, were those fired.
[0003]
[Problems to be solved by the invention]
At present, a multilayer ceramic capacitor having a dielectric layer mainly composed of BaTiO ₃ is under investigation to make the dielectric layer thinner and to reduce the size and increase the capacity. For example, the capacitance is doubled by halving the dielectric layer from the conventional 10 μm to 5 μm, but there is a problem that the insulation resistance is likely to deteriorate during the high temperature load test.
[0004]
Accordingly, an object of the present invention is to provide a method for producing a composition composed mainly of BaTiO ₃ and a method for producing a monolithic ceramic capacitor, which can obtain a monolithic ceramic capacitor in which, for example, the insulation resistance in a high-temperature medium load test does not deteriorate. It is what.
[0005]
[Means for Solving the Problems]
In order to achieve this object, the present invention includes a first step of adding a minor component to the main component BaTiO ₃ and wet mixing, drying, calcining and pulverizing to obtain a calcined powder, and then the calcining. A second step of producing a molded body using the powder, and then a third step of firing the molded body in a reducing atmosphere, the subcomponent having a specific surface area larger than that of the main component BaTiO ₃ a method for producing a composition based on BaTiO _3, which comprises using, it is possible to uniformly dissolved subcomponent around the main component BaTiO ₃ particles, for example in the case of the dielectric magnetic composition The insulation can be improved and the above object can be achieved.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 of the present invention includes a first step of adding a subcomponent to the main component BaTiO ₃ , wet mixing, drying, calcining and pulverizing to obtain a calcined powder, and then the calcining A second step of producing a molded body using the powder, and then a third step of firing the molded body in a reducing atmosphere, the subcomponent having a specific surface area larger than that of the main component BaTiO ₃ a method for producing a composition based on BaTiO _3, which comprises using, it is possible to uniformly dissolved subcomponent around the main component BaTiO ₃ particles, for example in the case of the dielectric magnetic composition In addition, a composition having excellent electrical characteristics such as improved insulation can be obtained.
[0007]
Invention of claim 2, composition based on BaTiO ₃ is a process for the manufacture of compositions based on BaTiO ₃ as set forth in claim 1, (Formula 3), especially Mn ₃ By making the specific surface area of O ₄ and Dy ₂ O ₃ larger than BaTiO ₃ , when Mn ₃ O ₄ and Dy ₂ O ₃ are uniformly dissolved in BaTiO ₃ and baked in a reducing atmosphere, BaTiO ₃ It is possible to obtain a dielectric ceramic composition that suppresses semiconductorization and has excellent insulating properties.
[0008]
[Chemical 3]

[0009]
The invention according to claim 3 includes a first step of adding BaTiO ₃ as a main component and adding a minor component, wet mixing, drying, calcining and pulverizing to obtain a calcined powder, and then the calcined powder. A second step of producing a green sheet using the internal electrode and alternately laminating the internal electrode to produce a laminate, and then a third step of firing the laminate in a reducing atmosphere at a temperature lower than the melting point of the internal electrode; And a fourth step of forming an external electrode on the end face of the laminated body, and the subcomponent having a specific surface area larger than that of BaTiO ₃ is used. It is a method, and the degradation of the insulation resistance by the voltage load test in high temperature is small, and the multilayer ceramic capacitor which has high reliability can be obtained.
[0010]
Invention according to claim 4, after the second step, a method of manufacturing a multilayer ceramic capacitor according to claim 3 using a green sheet having a composition shown in (Formula 4), the specific surface area than BaTiO ₃ By adding large Mn ₃ O ₄ and Dy ₂ O ₃ as subcomponents, the local semiconducting portion of the dielectric layer can be drastically reduced. In particular, for a multilayer ceramic capacitor having a dielectric layer thickness of 6 μm or less after sintering, there are 1 to 3 dielectric ceramic particles between the effective layers. In the case of the present invention, since the insulation is imparted to the majority of dielectric ceramic particles, it has sufficient insulation even if the effective layer thickness is 6 μm or less. It is possible to obtain a highly reliable monolithic ceramic capacitor with little deterioration of insulation resistance due to a voltage load test at 1.
[0011]
[Formula 4]

[0012]
An embodiment of the present invention will be described below.
As the starting material, chemically high-purity BaTiO ₃ , BaZrO ₃ , SrO, Mn ₃ O ₄ , and Dy ₂ O ₃ are used so that the composition ratio is within the range of the present invention as shown in (Chemical Formula 5). Weighed.
[0013]
[Chemical formula 5]

[0014]
Here, BaTiO _{3 as a} main component was prepared by a coprecipitation method, and the specific surface area was 5 m ² / g. Further, other additives serving as subcomponents were obtained using commercially available BaZrO ₃ , SrO, Mn ₃ O ₄ , and Dy ₂ O ₃ having various specific surface areas.
[0015]
After weighing, the starting material is first put into a ball mill equipped with zirconia balls together with pure water, wet mixed, dehydrated and dried to obtain a mixed powder, and then put into a high-purity alumina crucible in the range of 900 to 1200 ° C. Calcinated for 2 hours.
[0016]
Thereafter, the calcined powder was placed in a ball mill equipped with zirconia balls together with pure water, wet-ground and then dehydrated and dried. At this time, the average particle size of the pulverized powder was adjusted to 1.5 μm or less. Next, polyvinyl butyral resin as an organic binder, BBP (benzyl butyl phthalate) as a plasticizer, and n-butyl acetate as a solvent are added to each of the mixed powder and the pulverized powder and mixed in a ball mill equipped with zirconia to prepare a slurry. did. Next, this slurry was vacuum degassed and then formed into a film by a doctor blade method to produce a green sheet. At this time, the thickness of the green sheet after drying was set to about 10 μm. Next, screen printing was performed using an electrode paste containing nickel powder having an average particle size of about 1.0 μm on the green sheet so as to obtain a desired internal electrode pattern. Next, 100 green sheets on which internal electrode patterns have been formed are overlapped and integrated by heating and pressurizing so that the internal electrode patterns face each other through the green sheets, and then the dimensions are 3.8 mm wide and 1.8 mm long. It cut | disconnected and prepared the unsintered laminated body. Next, this unsintered laminate is placed in a zirconia sheath coated with zirconia powder and heated in air at a maximum temperature of 400 ° C. so that nickel is not excessively oxidized, and the organic binder in the unsintered laminate is burned. Removed.
[0017]
Next, the firing process will be described with reference to FIG. Regarding the temperature, first, the temperature was raised until the maximum temperature (T1) reached 1250 ° C. at a rate of temperature increase of 200 ° C./hour, held at the maximum temperature for 2 hours, and then decreased to 850 ° C. (T3) at a rate of temperature decrease of 200 ° C./hour. The temperature was lowered, held at 850 ° C. for 2 hours, and after the dielectric layer was re-oxidized, the temperature was controlled at a temperature drop rate of 200 ° C./hour. As for the atmosphere, from the temperature rise to T2, using CO ₂ gas, H ₂ O gas, etc. with respect to N ₂ + H ₂ gas, in this embodiment, PO ₂ = 10 ⁻⁷ atm or less is maintained, After T2, the H ₂ gas feed was stopped, the oxygen partial pressure was made higher than before T2, and the dielectric layer was reoxidized at PO ₂ = 10 ⁻⁵ atm. Here, after T2, re-oxidation is performed to prevent the insulation resistance from deteriorating.
[0018]
Thereafter, a commercially available 900 ° C. nitrogen atmosphere firing Cu paste was applied as an external electrode to the exposed end surface of the internal electrode of the obtained sintered body, and baked with a mesh type continuous belt to obtain a multilayer ceramic capacitor.
[0019]
The thickness of the dielectric layer after firing was about 6 μm, and the thickness of the internal electrode layer was about 2 to 2.5 μm.
[0020]
Next, the capacitance of the obtained multilayer ceramic capacitor was measured at a frequency of 1 kHz and an input signal level of 1.0 Vrms in a constant temperature bath at 20 ° C., and a relative dielectric constant was calculated using (Equation 1).
[0021]
[Expression 1]

[0022]
Then, DC 16V was applied for 1 minute, and the insulation resistance at that time was measured. On the other hand, 50 monolithic ceramic capacitors were arbitrarily extracted, 32V was loaded on each of them at a high temperature of 85 ° C., and the number of deterioration of the insulation resistance after 1000 hours was evaluated. The above measurement results are shown together with (Table 1).
[0023]
[Table 1]

[0024]
As apparent from (Table 1), when the specific surface areas of the subcomponents BaZrO ₃ , Mn ₃ O ₄ , Dy ₂ O ₃ and SrO are larger than BaTiO ₃ (sample No. 001 to No. 010), the temperature is high. In contrast to the deterioration of the insulation resistance in the load test, when the specific surface area of BaTiO ₃ is smaller (sample No. 011 to No. 015), the insulation resistance is deteriorated. In particular, it can be seen that when both Mn ₃ O ₄ and Dy ₂ O ₃ are smaller than the specific surface area of BaTiO ₃ , the deterioration is severe. As a result of observing these deteriorated portions, it was not structural defects such as voids, but deterioration of the ceramic particles themselves.
[0025]
In other words, insulating properties can be ensured even by firing in a reducing atmosphere by adding various subcomponents in advance to BaTiO ₃ which is easily reduced and becomes a semiconductor when fired in a reducing atmosphere. However, when the specific surface area of the various subcomponent powders is smaller than the specific surface area of BaTiO ₃ , the subcomponents are not uniformly dissolved in BaTiO ₃ , and it is possible to ensure insulation at the locations where the subcomponents are dissolved. This is because the portion where the additive does not sufficiently dissolve in the component becomes a semiconductor.
[0026]
From the above, by adding the subcomponent powder having a specific surface area larger than that of the BaTiO ₃ powder, the subcomponent particles can uniformly react with the BaTiO ₃ particles, and local semiconductorization can be suppressed. The insulating property of the layer is improved, and a highly reliable porcelain dielectric composition and multilayer ceramic capacitor can be obtained.
[0027]
Hereafter, what is important in the present invention will be described.
(1) In the above embodiment, only one composition ratio within the range of the present invention shown in (Chemical Formula 5) is shown, but of course the dielectric ceramic composition within the composition range shown in (Chemical Formula 4), Even in a composition formed by adding BaTiO ₃ as a main component and adding various subcomponents, the subcomponent can be uniformly dissolved in the main component BaTiO ₃ by the method of the present invention, and the electrical characteristics are excellent. A composition can be obtained.
[0028]
(2) Although Ni is used as the internal electrode, the same effect can be obtained when not only a base metal that is easily oxidized, such as Cu or Ni—Cu, but also a precious metal as a main component.
[0029]
(3) In the binder removal step, the heat treatment temperature may be optimally selected according to the combustion temperature so that the organic binder to be used can be removed.
[0030]
(4) In the firing step, the temperature is raised at a rate of temperature rise of 100 to 400 ° C./hour, held at the maximum temperature (T1) 1225 to 1325 ° C. for 2 to 4 hours, and the temperature is lowered to reoxidize the dielectric layer. It is desirable to hold | maintain at 700-1150 degreeC (T3) for 2 to 6 hours. Further, the temperature lowering rate is desirably 50 to 400 ° C./hour.
[0031]
(5) The firing atmosphere from the temperature raising process to the maximum temperature holding process (until T1) is set to an oxygen partial pressure lower than the equilibrium oxygen partial pressure of the metal that becomes the internal electrode from the beginning of the firing, or becomes the first internal electrode. After firing at or above the equilibrium oxygen partial pressure of the metal to remove carbon remaining in the dielectric layer, firing in this atmosphere causes the metal oxide internal electrode to diffuse into the dielectric layer. In order to reduce the metal oxide to the metal, the oxygen partial pressure is set to an oxygen partial pressure lower than the equilibrium oxygen partial pressure of the metal serving as the internal electrode.
[0032]
Further, after the temperature lowering process (after T2), it is desirable to make the oxygen partial pressure higher than that up to T1 in order to reoxidize the dielectric layer. However, when the dielectric layer is re-oxidized in the temperature lowering process, the atmosphere must not be excessively oxidized so that the function as the internal electrode can be performed after firing.
[0033]
The temperature of T2 should just be in the temperature range from T1 to T3.
Further, as long as the oxygen partial pressure can be controlled as described above, the oxygen partial pressure may be controlled not only by N ₂ + H ₂ gas but also by other methods.
[0034]
(6) If the external electrode is formed using the same metal as the internal electrode or a metal that forms an alloy with the metal serving as the internal electrode, sufficient electrical connection can be ensured, impedance is small, and stable capacitance can be obtained. The multilayer ceramic capacitor is provided.
[0035]
(7) BaTiO ₃ powder used as a starting material is more reactive at low temperatures when produced by a coprecipitation method such as an alkoxide method or an oxalate method than by a solid phase method. It's easy to do.
[0036]
In the dielectric ceramic composition of (8) (Chemical Formula 4), the dielectric constant can be increased and the dielectric loss can be reduced by replacing Ba with Sr. Dy can improve reduction resistance and can improve the relative dielectric constant as compared with other rare earth elements. Furthermore, Mn can improve reduction resistance. The Mn ₃ O ₄ is compared to other Mn compounds, since excellent dispersibility at the time of raw material mixture, it is possible to suppress the reduction of the insulation resistance with a small amount of additives than with other Mn compound. Moreover, although the relative dielectric constant tends to decrease by adding the Mn component, the tendency of Mn ₃ O ₄ is small compared to the case where other Mn compounds are used. Therefore, it is preferable to add the Mn component using Mn ₃ O ₄ .
[0037]
Among the subcomponents, it is important to use Mn ₃ O ₄ and Dy ₂ O ₃ having a specific surface area larger than that of BaTiO ₃ . Mn ₃ O ₄ and Dy ₂ O ₃ is dissolved in BaTiO _3, a component to suppress semiconductor of BaTiO ₃ in a reducing atmosphere. By adding Mn ₃ O ₄ or Dy ₂ O ₃ having a specific surface area higher than that of BaTiO _{3 having} a specific surface area of ² to 6 m ² / g, the insulating properties of the dielectric layer are improved. Mn ₃ O ₄ has a large specific surface area of 6 to 8 m ² / g as compared with other Mn compounds, and is excellent in dispersibility during mixing. On the other hand, when Dy ₂ O ₃ is 6 to 12 m ² / g, the insulating property is improved. Also, it plays a role in increasing the relative dielectric constant compared with other rare earths. The Sr component and the Zr component also have an effect of improving the insulation properties by using a powder having a specific surface area larger than that of BaTiO ₃ .
[0038]
BaTiO ₃ preferably has a specific surface area of 5.5 to 14 m ² / g, and SrO preferably has a specific surface area of 6 to 8 m ² / g.
[0039]
For BaTiO ₃ , it is desirable to improve the reactivity by using a raw material having a larger specific surface area for a subcomponent with a smaller addition amount.
[0040]
(9) When carbonate is used as a starting material for the subcomponent of the dielectric layer, it becomes a hydroxide during wet mixing, so that the viscosity of the slurry rises and the dispersion state of each additive becomes poor.
[0041]
In the composition of (Chemical Formula 4), the relative dielectric constant is low. In addition, when the dispersion state of the Mn component and the Dy component is extremely bad, the insulation resistance may be deteriorated.
[0042]
Therefore, it is preferable to use as little carbonate as the starting material.
(10) In the above embodiment, a multilayer ceramic capacitor was produced and the characteristics of the dielectric ceramic composition were evaluated. However, the dielectric ceramic composition of the present invention can also be used for a single plate type ceramic capacitor. Needless to say.
[0043]
【The invention's effect】
As described above, according to the present invention, subcomponents can be uniformly dissolved around the BaTiO ₃ particles, so that, for example, a dielectric ceramic composition is excellent in insulation.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a firing process according to an embodiment of the present invention.

Claims (4)

A first step of adding subcomponents to the main component BaTiO ₃ , wet mixing, drying, calcining and pulverizing to obtain a calcined powder, and then a second step of producing a molded body using the calcined powder When, then a third step of firing the shaped body in a reducing atmosphere, the subcomponent main component a BaTiO ₃ to which the specific surface area is characterized by using a larger than the main component BaTiO ₃ A method for producing a composition. The method for producing a composition containing BaTiO ₃ as a main component according to claim 1, wherein the composition containing BaTiO ₃ as a main component is (Chemical Formula 1).

A first step of adding BaTiO ₃ as a main component and adding a minor component, wet mixing, drying , calcining and pulverizing to obtain a calcined powder, and then producing a green sheet using this calcined powder, A second step of alternately laminating electrodes and producing a laminated body; a third step of firing the laminated body in a reducing atmosphere at a temperature lower than the melting point of the internal electrode; and then externally connecting to the end face of the laminated body And a fourth step of forming an electrode, wherein the subcomponent has a specific surface area larger than that of BaTiO ₃ . The method for producing a multilayer ceramic capacitor according to claim 3, wherein the green sheet has a composition shown after firing (Chemical Formula 2).

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