JP3620314B2

JP3620314B2 - Dielectric ceramic composition and multilayer ceramic capacitor using the same

Info

Publication number: JP3620314B2
Application number: JP31739198A
Authority: JP
Inventors: 雅文中山; 和博小松
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1998-11-09
Filing date: 1998-11-09
Publication date: 2005-02-16
Anticipated expiration: 2018-11-09
Also published as: JP2000143344A

Description

【０００１】
【発明の属する技術分野】
本発明はニッケルなどの卑金属で内部電極を形成する温度補償用の積層セラミックコンデンサに用いる誘電体磁器組成物およびこれを用いた積層セラミックコンデンサに関するものである。
【０００２】
【従来の技術】
従来の積層セラミックコンデンサは、公知の積層セラミックコンデンサの製造方法にしたがって、誘電体磁器組成物を主成分とするセラミック層グリーンシートと内部電極層を交互に複数層積層したグリーン積層体を、所定のグリーンチップ形状に切断した後、所定温度で焼成を行い、得られた焼結体の端面に露出した内部電極と電気的に接続するように、焼結体の端面部に外部電極を形成する方法が一般的に行われている。
【０００３】
しかしながら近年、積層セラミックコンデンサの大容量、高積層化に伴い内部電極にニッケル等の卑金属を用いたグリーンチップを非酸化性雰囲気中で焼結を行う方法が主流となって来ている。
【０００４】
【発明が解決しようとする課題】
従来の積層セラミックコンデンサを非酸化性雰囲気で焼成を行うのは、ニッケル等の卑金属内部電極の酸化を防ぐためである。しかしながら、積層セラミックコンデンサの内、温度補償用の積層セラミックコンデンサに用いる誘電体磁器組成物は、一般的に主成分のＭｇＴｉＯ_３、ＣａＴｉＯ_３に希土類酸化物を添加した組成が多く、この材料は非酸化性雰囲気で焼成すると主成分中の酸化チタンが還元され易く、半導体化して絶縁抵抗が低くなると共に、所望の誘電体特性が得られないという課題を有していた。
【０００５】
本発明は非酸化性雰囲気中の焼成においても、安定した電気特性の得られる誘電体磁器組成物およびこれを用いた積層セラミックコンデンサを提供することを目的とするものである。
【０００６】
【課題を解決するための手段】
前記目的を達成するため本発明は、一般式として、ｘ（Ｍｇ_ｍＣａ_１−ｍ）Ｏ−ｙ（Ｔｉ_ｎＺｒ_１−ｎ）Ｏ_２−ｚＮｄ_２Ｏ_３（但しｘ＋ｙ＋ｚ＝１）で表される三成分系組成において、ａ（ｘ＝０．４９、ｙ＝０．５０、ｚ＝０．０１）、ｂ（ｘ＝０．２５、ｙ＝０．５０、ｚ＝０．２５）、ｃ（ｘ＝０．９７、ｙ＝０．０２、ｚ＝０．０１）で囲まれた組成（但し、ｍは０．３０≦ｍ≦０．７０、ｎは０．７０≦ｎ≦０．９０の範囲）１００ｗｔ％に対し、添加物としてＢａＳｉＯ_３、ＭｇＳｉＯ_３、ＣａＳｉＯ_３の群より選ばれた一つを０．０５〜３．００ｗｔ％、更にＶ_２Ｏ_５を０．０５〜０．３０ｗｔ％添加した組成としたものである。
【０００７】
この構成により、非酸化性雰囲気中の焼成においても電気特性の安定したものが得られることになる。
【０００８】
【発明の実施の形態】
本発明の請求項１に記載の発明は、一般式として、ｘ（Ｍｇ_ｍＣａ_１−ｍ）Ｏ−ｙ（Ｔｉ_ｎＺｒ_１−ｎ）Ｏ_２−ｚＮｄ_２Ｏ_３（但しｘ＋ｙ＋ｚ＝１）で表される三成分系組成において、ａ（ｘ＝０．４９、ｙ＝０．５０、ｚ＝０．０１）、ｂ（ｘ＝０．２５、ｙ＝０．５０、ｚ＝０．２５）、ｃ（ｘ＝０．９７、ｙ＝０．０２、ｚ＝０．０１）で囲まれた組成（但し、ｍは０．３０≦ｍ≦０．７０、ｎは０．７０≦ｎ≦０．９０の範囲）１００ｗｔ％に対し、添加物としてＢａＳｉＯ_３、ＭｇＳｉＯ_３、ＣａＳｉＯ_３の群より選ばれた一つを０．０５〜３．００ｗｔ％、更にＶ_２Ｏ_５を０．０５〜０．３０ｗｔ％添加した誘電体磁器組成物である。一般式が、ｘ（Ｍｇ_ｍＣａ_１−ｍ）Ｏ−ｙ（Ｔｉ_ｎＺｒ_１−ｎ）Ｏ_２−ｚＮｄ_２Ｏ_３で表され、しかもａ（ｘ＝０．４９、ｙ＝０．５０、ｚ＝０．０１）、ｂ（ｘ＝０．２５、ｙ＝０．５０、ｚ＝０．２５）、ｃ（ｘ＝０．９７、ｙ＝０．０２、ｚ＝０．０１）で囲まれた本発明の三成分系材料組成は、ＭｇＯ、ＣａＯ、Ｎｄ_２Ｏ_３のモル比の和（ｘ＋ｚ）が、常にＴｉＯ_２、ＺｒＯ_２のモル比の和（ｙ）と等しいか、又は大きくなるように組成範囲を規定したものである。この組成にＶ_２Ｏ_５を０．０５〜０．３０ｗｔ％添加することにより、非酸化性雰囲気中で焼成を行ってもＶ_２Ｏ_５がＴｉＯ_２の還元を防止し、絶縁抵抗が大きく、しかも設計値通りの容量温度係数の小さい焼結体が得られる。従ってニッケル等の卑金属を内部電極に用いる温度補償用の積層セラミックコンデンサの誘電体磁器組成物として好適なものである。また更に、還元されやすいＴｉＯ_２の一部をＺｒＯ_２で置換することで、更に耐還元性を向上させることができる。一方ＢａＳｉＯ_３、ＭｇＳｉＯ_３、ＣａＳｉＯ_３の群より選ばれた一つを０．０５〜３．００ｗｔ％添加することにより、これらが焼結助材として焼結性を促進しＱ_Ｅ、絶縁抵抗の高い優れた焼結体を得ることができるものである。
【０００９】
本発明の請求項２に記載の発明は、請求項１に記載の誘電体磁器組成物の主成分ｘ（Ｍｇ_ｍＣａ_１−ｍ）Ｏ−ｙ（Ｔｉ_ｎＺｒ_１−ｎ）Ｏ_２−ｚＮｄ_２Ｏ_３（但しｘ＋ｙ＋ｚ＝１）で表される三成分系組成において、ａ（ｘ＝０．４９、ｙ＝０．５０、ｚ＝０．０１）、ｂ（ｘ＝０．２５、ｙ＝０．５０、ｚ＝０．２５）、ｃ（ｘ＝０．９７、ｙ＝０．０２、ｚ＝０．０１）で囲まれた組成（但し、ｍは０．３０≦ｍ≦０．７０、ｎは０．７０≦ｎ≦０．９０の範囲）１００ｗｔ％に対し、更にＡｌ_２Ｏ_３を２．０ｗｔ％以下、ＭｎＯ_２を０．５ｗｔ％以下（但し、両方とも同時に０は除く）を添加したことを特徴とする請求項１に記載の誘電体磁器組成物である（尚ｘ、ｙ、ｍ、ｎはモル比を表す）。前記組成に対しＡｌ_２Ｏ_３及びＭｎＯ_２を添加することにより焼結性を更に向上させる。特にＭｎＯ_２はＴｉＯ_２の還元を防ぎ、絶縁抵抗をより高いものとする効果がある。
【００１０】
本発明の請求項３に記載の発明は、請求項１及び請求項２に記載の誘電体磁器組成物からなるセラミック層と、ニッケル等の卑金属の内部電極で構成した積層セラミックコンデンサである。請求項１及び請求項２に記載の耐還元性誘電体磁器組成物でセラミック層を構成することによって、ニッケル等の卑金属を内部電極に用いた積層セラミックコンデンサが非酸化性雰囲気中での焼成が可能となり、Ｑ_Ｅ、絶縁抵抗が共に高く、しかも静電容量温度係数の小さい優れた温度補償用の積層セラミックコンデンサを得ることができるものである。
【００１１】
（実施の形態１）
先ず、出発原料として高純度のＭｇＯ、ＣａＯ、ＴｉＯ_２、ＺｒＯ_２、Ｎｄ_２Ｏ_３、Ｖ_２Ｏ_５、ＢａＳｉＯ_３粉末を（表１）〜（表５）に示す組成比になるように秤量し、湿式混合後、脱水乾燥を行い、得られた混合材料を高純度アルミナ質の坩堝に入れ、空気中１１５０℃の温度で２時間仮焼を行う。
【００１２】
【表１】

【００１３】
【表２】

【００１４】
【表３】

【００１５】
【表４】

【００１６】
【表５】

【００１７】
次に、仮焼材料をゴム内張りのボールミルの中に純水とジルコニアボールと共に入れ、湿式粉砕後、脱水乾燥を行い温度補償用の誘電体磁器組成物を作製した。得られた温度補償用の誘電体磁器組成物に、有機バインダーを加え造粒後、油圧プレスを用い、成形圧力１ｔｏｎ／ｃｍ^２で直径１５ｍｍ、厚み０．４ｍｍの円板を成形した。
【００１８】
次いで、成形した円板をアルミナ質のサヤに入れ、空気中にて７００℃で２時間脱脂した後、非酸化性雰囲気中にて（表６）〜（表１０）に示す温度で２時間焼成し、焼結体を得た。
【００１９】
得られた焼結体の両面に銅電極ペーストを塗布した後、非酸化性雰囲気において９００℃の温度で焼付けた後、誘電率、Ｑ_Ｅ、絶縁抵抗、静電容量温度係数の測定を行い、その結果を（表６）〜（表１０）に示した。尚、誘電率、Ｑ_Ｅの測定は温度２０℃、測定電圧１．０Ｖ_ｒｍｓ、測定周波数１ＭＨｚで行い、絶縁抵抗は電極間にＤＣ５０Ｖを１分間印加した後の抵抗値より、また静電容量温度係数は２０℃と１２５℃における静電容量を測定し（数１）より求めた。
【００２０】
【表６】

【００２１】
【表７】

【００２２】
【表８】

【００２３】
【表９】

【００２４】
【表１０】

【００２５】
【数１】

【００２６】
（表６）〜（表１０）に示すように、試料２、４、１８、２２、２３、２６はＴｉＯ_２が一部還元され絶縁抵抗が極端に低下し、試料８、１０、１４、１９は１３５０℃の温度で焼結不十分なためＱ_Ｅ、絶縁抵抗が共に低下し、試料５、７は１３５０℃の温度で焼結しない。さらに、試料１５は、静電容量温度係数がプラス２８１ｐｐｍ／℃と大きい。これに対し、試料１、３、６、９、１１、１２、１３、１６、１７、２０、２１、２４、２５の本発明の組成範囲内のものは、Ｑ_Ｅが大きく、絶縁抵抗も高く、さらに静電容量温度係数が小さい優れた誘電体特性が得られることが明らかとなる。
【００２７】
以下、それぞれの組成範囲を限定した理由について述べる。
はじめに、主成分のｘ、ｙ、ｚの範囲を限定した理由について述べる。（表１）の試料２、４のように、ＭｇＯとＣａＯ及びＮｄ_２Ｏ_３のモル比の和（ｘ＋ｚ）よりも、ＴｉＯ_２とＺｒＯ_２のモル比の和（ｙ）が大きい範囲、即ちｙ＞０．５０の組成は、非還元雰囲気で焼成すると、主成分のＴｉＯ_２が還元され絶縁抵抗が低く、安定した誘電体特性が得られず実用的でなくなる。
【００２８】
また、試料８のように、ＴｉＯ_２とＺｒＯ_２のモル比の和（ｙ）が０．０１の組成は１３５０℃の焼成では焼結が不十分でＱ_Ｅ、絶縁抵抗共が低くなる。従って、ｙの範囲は０．０２≦ｙ≦０．５０とする必要がある。また、試料５、７、８のように、ｚのモル数の２倍の値がｙのモル数と等しいか又は大きくなると、焼結不十分か焼結が困難となり、Ｑ_Ｅ、絶縁抵抗が低下することがわかる。即ち、ｙ（Ｔｉ、Ｚｒ）Ｏ_２とｚＮｄ_２Ｏ_３との関係において、Ｎｄ_２Ｏ_３のモル数ｚの２倍が、（Ｔｉ、Ｚｒ）Ｏ_２のモル数ｙより大きくなると、焼結が困難になることから、ｙ≧２ｚとする必要がある。但し、ｙの範囲は０．０２≦ｙ≦０．５０とする。従って、ｙの値が０．０２から０．５０の範囲で変化すると、ｚの値は常にｙ≧２ｚを満たし０．０１〜０．２５の範囲で変化することになる。
【００２９】
また、ｘ＋ｙ＋ｚ＝１の関係からｘの範囲はｙ、ｚの値より必然的に決定され、本発明の主成分のｘ、ｙ、ｚの範囲は図１に示す点ａ、ｂ、ｃを直線で囲まれたモル比の範囲に限定される。次にＭｇのモル比ｍの範囲を限定した理由は、（表２）、（表７）に示すようにｍの値が０．３０より小さいか、または０．７０より大きい組成の試料１０、１４は１３５０℃の焼成でも焼結不十分なために、Ｑ_Ｅ、絶縁抵抗が共に低下し実用的でなくなる。従って、ｍの範囲は０．３０≦ｍ≦０．７０に限定する必要がある。
【００３０】
また、Ｔｉのモル比ｎの範囲を限定した理由は、（表３）、（表８）に示す試料１５のように、ｎの値が０．６０の場合は静電容量温度係数がプラス方向に極めて大きくなり、温度補償用誘電体磁器組成物として実用的でなく、試料１８のようにｎの値が１．００、即ちＴｉＯ_２１００％の場合は、非酸化性雰囲気中の焼成でＴｉＯ_２が還元され、絶縁抵抗が低くなると共に、安定した誘電特性が得られなくなる。従って、ｎの値は０．７０≦ｎ≦０．９０の範囲に限定する必要がある。
【００３１】
一方、添加物のＢａＳｉＯ_３の添加量を限定した理由は（表４）、（表９）に示す試料１９のように添加量が零の組成は、１３５０℃の焼成においても焼結不十分なためにＱ_Ｅ、絶縁抵抗が共に低下し、また、試料２２のように添加量が３．０を超えると焼成温度を低下する効果があるが、添加したＢａＳｉＯ_３のＳｉ成分の一部がＴｉ位置に入り込み、置換されたＴｉが還元されてＱ_Ｅと絶縁抵抗を低下させる。従って、ＢａＳｉＯ_３の添加範囲は、０．２〜３．０ｗｔ％の範囲に限定する必要がある。
【００３２】
更に、Ｖ_２Ｏ_５の添加量を限定した理由は、（表５）、（表１０）に示す試料２３のように添加量が零の組成は、主成分のＴｉＯ_２の還元を防御することができず、非酸化性雰囲気中の焼成でＴｉＯ_２が還元され、絶縁抵抗が低下すると共に、安定した誘電特性が得られなくなる。また試料２６のように添加量が０．３ｗｔ％を超えると逆にＴｉＯ_２を還元させ、Ｑ_Ｅと絶縁抵抗を低下させるため、好ましくない。この原因は定かではないが、Ｖ_２Ｏ_５がＴｉＯ_２を原子価制御し、半導体化するためと思われる。従って、Ｖ_２Ｏ_５の添加量は、０．０５〜０．３ｗｔ％の範囲に限定する必要がある。
【００３３】
（実施の形態２）
実施の形態１の試料１２の組成のＢａＳｉＯ_３に替えてＭｇＳｉＯ_３またはＣａＳｉＯ_３を（表１１）の示す組成比になるように秤量した後、以降の工程を実施の形態１と同条件で処理し、作製した試料について実施の形態１と同様に評価し、その結果を（表１２）に示した。
【００３４】
【表１１】

【００３５】
【表１２】

【００３６】
（表１２）に示すように、ＢａＳｉＯ_３に替えてＭｇＳｉＯ_３を添加した試料２７〜２９、またはＣａＳｉＯ_３を添加した試料３１〜３３は、ＢａＳｉＯ_３添加の場合と同様にＱ_Ｅ、絶縁抵抗共に高く、しかも静電容量温度係数が小さい優れた誘電体特性が得られることが分かる。また、ＭｇＳｉＯ_３を添加した場合、ＢａＳｉＯ_３の添加に比べ、より絶縁抵抗が高く、ＣａＳｉＯ_３の添加はＢａＳｉＯ_３の添加に比べ、よりＱ_Ｅの大きい誘電体磁器組成物が得られることが分かる。しかしながら何れの場合とも添加量が３ｗｔ％を超えると、焼成温度を低下させる効果があるもののＢａＳｉＯ_３と同様に絶縁抵抗を低下させるために好ましくない。
【００３７】
（実施の形態３）
実施の形態１の試料１２の組成に、更にＡｌ_２Ｏ_３、及びＭｎＯ_２を（表１３）に示す組成となるように秤量し、以降の工程条件を実施の形態１と同条件で処理し、作製した試料について実施の形態１と同様に評価しその結果を（表１４）に示した。
【００３８】
【表１３】

【００３９】
【表１４】

【００４０】
（表１４）に示すように、本発明のＡｌ_２Ｏ_３、及びＭｎＯ_２を添加した試料３５〜３８と４０、４１、４３は、Ｑ_Ｅ、絶縁抵抗共に更に高くなり、しかも静電容量温度係数が小さい優れた誘電体特性が得られることが分かる。これに対しＡｌ_２Ｏ_３の添加量が２．０ｗｔ％を超える試料３９は焼結温度を低下させる効果はあるものの、Ｑ_Ｅが低下し、またＭｎＯ_２の添加量が０．５ｗｔ％を超える試料４２の焼結体は８μｍ以上の異常成長粒子が認められ実用上好ましくない。従ってＡｌ_２Ｏ_３、及びＭｎＯ_２の添加は夫々２．０ｗｔ％、０．５ｗｔ％以下（但し、両方とも同時に０は除く）に限定する必要があることが分かる。
【００４１】
（実施の形態４）
実施の形態１から実施の形態３で作製した、本発明の誘電体磁器組成物の試料１２、１９、２８、３２、４２、４３の各誘電体磁器組成物に酢酸ブチル、ポリビニルブチラール、可塑剤からなるビヒクルを加えて、公知のドクターブレード法により厚さ３０μｍのセラミックグリーンシートを作製した。
【００４２】
次に、得られたそれぞれの組成のセラミックグリーンシートを用い、公知の積層セラミックコンデンサの製造方法に従い、内部電極とセラミックグリーンシートを交互に１５層積層したグリーン積層体を６００ｋｇ／ｃｍ^２の圧力で加圧圧着した後、１６０８タイプの積層セラミックコンデンサのグリーンチップ形状に切断を行った。尚、内部電極にはニッケル電極ペーストを用いた。
【００４３】
次いで、グリーンチップを空気中にて３５０℃の温度で２時間脱脂した後、非酸化性雰囲気中の１３５０℃で２時間焼成を行った。
【００４４】
その後、得られた焼結体の内部電極が露出した端面に外部電極を設けてそれぞれ積層セラミックコンデンサを完成させた。
【００４５】
得られた各積層セラミックコンデンサについて静電容量、Ｑ_Ｅ、静電容量温度係数、絶縁抵抗を、実施の形態１と同様の方法で測定を行った。また寿命試験として１２５℃の恒温槽中で５０Ｖの直流電圧を積層セラミックコンデンサの外部電極間に１０００時間連続印加を行い、その結果を（表１５）に示した。
【００４６】
【表１５】

【００４７】
（表１５）から明らかなように、本発明の範囲内の誘電体磁器組成物１２、２８、３２、４３を用い作製した積層セラミックコンデンサは、Ｑ_Ｅ、絶縁抵抗が共に高く、寿命試験においても特性劣化が認められないのに対し、本発明の範囲外の誘電体磁器組成物の試料１９、４２で作製した積層セラミックコンデンサは絶縁抵抗が低下し、しかも寿命試験においても特性劣化が認められた。尚、特性劣化は寿命試験後の絶縁抵抗値が１×１０^１０（Ω）以下に低下したものを不良としてカウントした。
【００４８】
以上本発明の誘電体磁器組成物は、内部電極にニッケル等の卑金属を用い積層セラミックコンデンサ用グリーンチップを作製し、これを非酸化性雰囲気中で焼成を行っても、Ｑ_Ｅ、絶縁抵抗が共に高く、また静電容量温度変化率の小さい、しかも寿命試験においても特性劣化が発生しない優れた積層セラミックコンデンサが得られることが明らかである。
【００４９】
また、実施の形態１から３で誘電体磁器組成物の作製にＭｇＯ、ＣａＯ、ＴｉＯ_２、ＺｒＯ_２、Ｎｄ_２Ｏ_３、ＢａＳｉＯ_３、ＭｇＳｉＯ_３、ＣａＳｉＯ_３、Ｖ_２Ｏ_５の粉末を使用したが、Ｍｇ−Ｃａ−Ｔｉ−Ｚｒ−Ｏの化合物、あるいはＭｇ、Ｃａ、Ｔｉ、Ｚｒ、Ｎｄの炭酸塩、水酸化物等を本発明の組成となるように用いても、また、主成分をあらかじめ仮焼した後、添加物を添加しても実施の形態と同程度の特性を得ることができる。
【００５０】
【発明の効果】
以上の結果に示すように、本発明の誘電体磁器組成物は非酸化性雰囲気中で焼成してもＱ_Ｅ及び絶縁抵抗が共に高く、しかも静電容量温度係数の小さい優れた誘電体特性を有する焼結体が得られ、ニッケル等の卑金属を内部電極に用いる積層セラミックコンデンサ用の誘電体磁器組成物として使用が可能である。特に、Ｑ_Ｅ特性が優れ、静電容量温度係数が小さいため高周波回路などで使用する温度補償用の積層セラミックコンデンサの誘電体磁器組成物として実用性が高いものである。
【図面の簡単な説明】
【図１】本発明の誘電体磁器組成物の範囲を示す三成分系図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric ceramic composition used for a temperature-compensating multilayer ceramic capacitor in which an internal electrode is formed of a base metal such as nickel, and a multilayer ceramic capacitor using the dielectric ceramic composition.
[0002]
[Prior art]
In the conventional multilayer ceramic capacitor, a green multilayer body in which a plurality of ceramic layer green sheets mainly composed of a dielectric ceramic composition and internal electrode layers are alternately laminated according to a known multilayer ceramic capacitor manufacturing method, A method of forming an external electrode on the end face of the sintered body so as to be electrically connected to the internal electrode exposed on the end face of the obtained sintered body after being cut into a green chip shape and fired at a predetermined temperature Is generally done.
[0003]
However, in recent years, a method of sintering a green chip using a base metal such as nickel as an internal electrode in a non-oxidizing atmosphere has become a mainstream as the multilayer ceramic capacitor has a large capacity and a high multilayer.
[0004]
[Problems to be solved by the invention]
The reason why conventional multilayer ceramic capacitors are fired in a non-oxidizing atmosphere is to prevent oxidation of base metal internal electrodes such as nickel. However, among the multilayer ceramic capacitors, the dielectric ceramic composition used for the temperature-compensated multilayer ceramic capacitor generally has a composition in which rare earth oxides are added to the main components MgTiO ₃ and CaTiO _3. When fired in an oxidizing atmosphere, titanium oxide in the main component is easily reduced, resulting in a semiconductor that has a low insulation resistance and a desired dielectric property cannot be obtained.
[0005]
An object of the present invention is to provide a dielectric ceramic composition capable of obtaining stable electrical characteristics even in firing in a non-oxidizing atmosphere and a multilayer ceramic capacitor using the same.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is represented by a general formula: x (Mg _m Ca _1-m ) Oy (Ti _n Zr _1-n ) O ₂ -zNd ₂ O ₃ (where x + y + z = 1). A (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25), c (X = 0.97, y = 0.02, z = 0.01) (where m is 0.30 ≦ m ≦ 0.70, n is 0.70 ≦ n ≦ 0.90) Range) 100 wt%, 0.05 to 3.00 wt% of one selected from the group of BaSiO ₃ , MgSiO ₃ and CaSiO ₃ as an additive, and 0.05 to 0.30 wt V ₂ O ₅ % Added composition.
[0007]
With this configuration, a product having stable electrical characteristics can be obtained even in firing in a non-oxidizing atmosphere.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 of the present invention is represented by the general formula: x (Mg _m Ca _1-m ) O-y (Ti _n Zr _1-n ) O ₂ -zNd ₂ O ₃ (where x + y + z = 1). In the ternary composition represented, a (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25) , C (x = 0.97, y = 0.02, z = 0.01) (where m is 0.30 ≦ m ≦ 0.70, n is 0.70 ≦ n ≦ 0) .90 range) with respect to 100 wt%, 0.05 to 3.00 wt% of one selected from the group of BaSiO ₃ , MgSiO ₃ and CaSiO ₃ as an additive, and 0.05 to 0 V ₂ O ₅ A dielectric ceramic composition containing 30 wt%. General _{_{_{formula, x (Mg m Ca 1-}}} m) is represented by _{_{O-y (Ti n Zr 1}} -n) O 2 -zNd 2 O 3, yet a (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25), c (x = 0.97, y = 0.02, z = 0.01) In the three-component material composition of the present invention, the sum (x + z) of the molar ratios of MgO, CaO, and Nd ₂ O ₃ is always equal to or larger than the sum (y) of the molar ratios of TiO ₂ and ZrO _2. The composition range is defined as follows. By the _V 2 _{O 5} added 0.05～0.30Wt% in this composition, a non-oxidizing atmosphere _V 2 _{O 5} even if fired in is prevented the reduction of TiO _2, a large insulation resistance, Moreover, a sintered body having a small capacity temperature coefficient as designed can be obtained. Therefore, it is suitable as a dielectric ceramic composition for a temperature-compensated multilayer ceramic capacitor using a base metal such as nickel for the internal electrode. Furthermore, the reduction resistance can be further improved by substituting a part of TiO ₂ that is easily reduced with ZrO ₂ . On the other hand, by adding 0.05 to 3.00 wt% of one selected from the group of BaSiO ₃ , MgSiO ₃ , and CaSiO ₃ , these promote sinterability as a sintering aid, thereby improving Q _E and insulation resistance. A high and excellent sintered body can be obtained.
[0009]
The invention according to claim 2 of the present invention is the main component x (Mg _m Ca _1-m ) Oy (Ti _n Zr _1-n ) O ₂ -zNd of the dielectric ceramic composition according to claim 1. _{In the} ternary composition represented by ₂ O ₃ (where x + y + z = 1), a (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25), c (x = 0.97, y = 0.02, z = 0.01) (where m is 0.30 ≦ m ≦ 0.70) , N is in the range of 0.70 ≦ n ≦ 0.90) 100 wt%, Al ₂ O ₃ is further 2.0 wt% or less, and MnO ₂ is 0.5 wt% or less (however, both are excluded at the same time) The dielectric ceramic composition according to claim 1, wherein x, y, m, and n represent molar ratios. Sinterability is further improved by adding Al ₂ O ₃ and MnO ₂ to the composition. In particular, MnO ₂ has an effect of preventing the reduction of TiO ₂ and increasing the insulation resistance.
[0010]
A third aspect of the present invention is a multilayer ceramic capacitor comprising a ceramic layer made of the dielectric ceramic composition according to the first and second aspects and an internal electrode of a base metal such as nickel. By forming a ceramic layer with the reduction-resistant dielectric ceramic composition according to claim 1 and claim 2, a multilayer ceramic capacitor using a base metal such as nickel as an internal electrode can be fired in a non-oxidizing atmosphere. Thus, it is possible to obtain an excellent temperature compensating multilayer ceramic capacitor having both a high Q _E and an insulation resistance and a small capacitance temperature coefficient.
[0011]
(Embodiment 1)
First, high-purity MgO, CaO, TiO ₂ , ZrO ₂ , Nd ₂ O ₃ , V ₂ O ₅ , and BaSiO ₃ powders as starting materials are weighed so as to have the composition ratios shown in (Table 1) to (Table 5). Then, after wet mixing, dehydration drying is performed, and the obtained mixed material is put into a high-purity alumina crucible and calcined in air at a temperature of 1150 ° C. for 2 hours.
[0012]
[Table 1]

[0013]
[Table 2]

[0014]
[Table 3]

[0015]
[Table 4]

[0016]
[Table 5]

[0017]
Next, the calcined material was placed in a rubber-lined ball mill together with pure water and zirconia balls, wet-pulverized, dehydrated and dried to produce a temperature-compensating dielectric ceramic composition. An organic binder was added to the obtained temperature-compensating dielectric ceramic composition, and after granulation, a disk having a diameter of 15 mm and a thickness of 0.4 mm was molded at a molding pressure of 1 ton / cm ² using a hydraulic press.
[0018]
Next, the molded disc is put into an alumina-based sheath, degreased in air at 700 ° C. for 2 hours, and then fired at a temperature shown in (Table 6) to (Table 10) for 2 hours in a non-oxidizing atmosphere. As a result, a sintered body was obtained.
[0019]
After applying the copper electrode paste on both sides of the obtained sintered body, after baking at 900 ° C. in a non-oxidizing atmosphere, the dielectric constant, Q _E , insulation resistance, capacitance temperature coefficient are measured, The results are shown in (Table 6) to (Table 10). Incidentally, the dielectric constant, measurement of the _{Q E} is the temperature 20 ° C., measured voltage _{1.0 V rms,} measured performed at a frequency 1 MHz, than the resistance value after application of 1 minute DC50V between the insulation resistance of the electrode, also capacitance Temperature The coefficient was obtained from (Equation 1) by measuring the capacitance at 20 ° C. and 125 ° C.
[0020]
[Table 6]

[0021]
[Table 7]

[0022]
[Table 8]

[0023]
[Table 9]

[0024]
[Table 10]

[0025]
[Expression 1]

[0026]
As shown in (Table 6) to (Table 10), in Samples 2, 4, 18, 22, 23, and 26, TiO ₂ is partially reduced and the insulation resistance is extremely reduced. Is insufficiently sintered at a temperature of 1350 ° C., so that both Q _E and insulation resistance decrease, and Samples 5 and 7 do not sinter at a temperature of 1350 ° C. Furthermore, the sample 15 has a large capacitance temperature coefficient of plus 281 ppm / ° C. In contrast, those in the composition range of the present invention the sample 1,3,6,9,11,12,13,16,17,20,21,24,25, large _{Q E,} higher insulation resistance Further, it becomes clear that excellent dielectric properties having a smaller capacitance temperature coefficient can be obtained.
[0027]
Hereinafter, the reason for limiting each composition range will be described.
First, the reason why the ranges of x, y, and z of the main component are limited will be described. As in Samples 2 and 4 of Table 1, a range in which the sum (y) of the molar ratios of TiO ₂ and ZrO ₂ is larger than the sum (x + z) of the molar ratios of MgO, CaO and Nd ₂ O ₃ , that is, When the composition of y> 0.50 is fired in a non-reducing atmosphere, TiO _{2 as} a main component is reduced, insulation resistance is low, and stable dielectric characteristics cannot be obtained, making it impractical.
[0028]
In addition, as in Sample 8, a composition having a sum (y) of molar ratios of TiO ₂ and ZrO ₂ of 0.01 is not sufficiently sintered when fired at 1350 ° C., and both Q _E and insulation resistance are low. Therefore, the range of y needs to be 0.02 ≦ y ≦ 0.50. Also, as in Samples 5, 7, and 8, when the value twice the number of moles of z is equal to or larger than the number of moles of y, sintering becomes insufficient or difficult, and Q _E and insulation resistance are reduced. It turns out that it falls. That is, in the relationship between y (Ti, Zr) O ₂ and zNd ₂ O ₃ , if the number of moles z of Nd ₂ O ₃ is larger than the number of moles y of (Ti, Zr) O ₂ , sintering Therefore, it is necessary to satisfy y ≧ 2z. However, the range of y is 0.02 ≦ y ≦ 0.50. Therefore, if the value of y changes in the range of 0.02 to 0.50, the value of z always satisfies y ≧ 2z and changes in the range of 0.01 to 0.25.
[0029]
Further, from the relationship of x + y + z = 1, the range of x is inevitably determined from the values of y and z, and the range of x, y and z of the main component of the present invention is obtained by straightening points a, b and c shown in FIG. It is limited to the range of the molar ratio surrounded by. Next, the reason why the range of the molar ratio m of Mg is limited is that, as shown in (Table 2) and (Table 7), the value of m is less than 0.30 or a sample 10 having a composition greater than 0.70, No. 14 is not practical because sintering is insufficient even when fired at 1350 ° C., so that both Q _E and insulation resistance decrease. Therefore, the range of m needs to be limited to 0.30 ≦ m ≦ 0.70.
[0030]
Further, the reason for limiting the range of the molar ratio n of Ti is that the capacitance temperature coefficient is positive when the value of n is 0.60 as in Sample 15 shown in (Table 3) and (Table 8). When the value of n is 1.00, that is, 100% TiO ₂ as in the sample 18, the TiO ₂ is fired in a non-oxidizing atmosphere. ₂ is reduced, the insulation resistance is lowered, and stable dielectric properties cannot be obtained. Therefore, the value of n needs to be limited to a range of 0.70 ≦ n ≦ 0.90.
[0031]
On the other hand, the reason why the additive amount of BaSiO ₃ is limited is that the composition with the additive amount of zero as in Sample 19 shown in (Table 4) and (Table 9) is insufficiently sintered even at 1350 ° C. firing. Therefore, both Q _E and insulation resistance are reduced, and when the amount of addition exceeds 3.0 as in sample 22, there is an effect of lowering the firing temperature, but a part of the Si component of the added BaSiO ₃ is Ti. It enters the position and the substituted Ti is reduced to lower the _QE and insulation resistance. Therefore, it is necessary to limit the addition range of BaSiO _{3 to} a range of 0.2 to 3.0 wt%.
[0032]
Furthermore, the reason for limiting the amount of V ₂ O ₅ added is that the composition with a zero added amount as in Sample 23 shown in (Table 5) and (Table 10) prevents reduction of the main component TiO _2. However, TiO ₂ is reduced by firing in a non-oxidizing atmosphere, the insulation resistance is lowered, and stable dielectric properties cannot be obtained. Since the addition amount as in Sample 26 was reduced to TiO ₂ in the reverse exceeds 0.3 wt%, to lower the insulation resistance and _{Q E,} undesirable. Although this cause is not certain, it seems that V ₂ O ₅ controls the valence of TiO ₂ to make it a semiconductor. _Therefore, the addition amount of V 2 _{O 5,} it is necessary to limit the range of 0.05~0.3wt%.
[0033]
(Embodiment 2)
In place of BaSiO ₃ having the composition of sample 12 of the first embodiment, MgSiO ₃ or CaSiO ₃ is weighed so as to have the composition ratio shown in (Table 11), and the subsequent steps are processed under the same conditions as in the first embodiment. The produced samples were evaluated in the same manner as in Embodiment 1, and the results are shown in Table 12.
[0034]
[Table 11]

[0035]
[Table 12]

[0036]
As shown in Table 12, samples 27 to 29 to which MgSiO ₃ was added instead of BaSiO ₃ or samples 31 to 33 to which CaSiO ₃ was added had both Q _E and insulation resistance as in the case of BaSiO ₃ addition. It can be seen that excellent dielectric properties with high capacitance temperature coefficient are obtained. Also, in the case of adding MgSiO _3, compared with the addition of BaSiO _3, higher insulation resistance, the addition of CaSiO ₃ compared to the addition of BaSiO _3, it can be seen that a large dielectric ceramic composition of more _{Q E} is obtained . However, in any case, if the addition amount exceeds 3 wt%, although there is an effect of lowering the firing temperature, it is not preferable because the insulation resistance is lowered similarly to BaSiO ₃ .
[0037]
(Embodiment 3)
The composition of the sample 12 of the first embodiment is further weighed so that Al ₂ O ₃ and MnO ₂ have the composition shown in (Table 13), and the subsequent process conditions are processed under the same conditions as in the first embodiment. The prepared samples were evaluated in the same manner as in Embodiment 1, and the results are shown in Table 14.
[0038]
[Table 13]

[0039]
[Table 14]

[0040]
As shown in (Table 14), samples 35-38 and 40, 41, 43 to which Al ₂ O ₃ and MnO ₂ of the present invention were added had both higher Q _E and insulation resistance, and the capacitance temperature It can be seen that excellent dielectric properties with a small coefficient can be obtained. Although this to the sample 39 amount of _Al 2 _{O 3} exceeds 2.0 wt% is effective to lower the sintering temperature is, reduces the _{Q E,} also the addition amount of MnO ₂ exceeds 0.5 wt% The sintered body of the sample 42 is not practically preferable because abnormally grown particles of 8 μm or more are observed. Therefore, it can be seen that the addition of Al ₂ O ₃ and MnO ₂ needs to be limited to 2.0 wt% and 0.5 wt% or less (however, both are excluded at the same time).
[0041]
(Embodiment 4)
Dielectric porcelain compositions 12, 19, 28, 32, 42, and 43 of the dielectric porcelain composition of the present invention produced in Embodiments 1 to 3 were each added with butyl acetate, polyvinyl butyral, plasticizer A ceramic green sheet having a thickness of 30 μm was prepared by a known doctor blade method.
[0042]
Next, using the obtained ceramic green sheets of the respective compositions, according to a known method for producing a multilayer ceramic capacitor, a green laminated body in which 15 layers of internal electrodes and ceramic green sheets are alternately laminated is formed at a pressure of 600 kg / cm ² . After pressure bonding, the green chip shape of a 1608 type multilayer ceramic capacitor was cut. A nickel electrode paste was used as the internal electrode.
[0043]
Next, the green chip was degreased in air at a temperature of 350 ° C. for 2 hours, and then fired at 1350 ° C. in a non-oxidizing atmosphere for 2 hours.
[0044]
Thereafter, an external electrode was provided on the end face where the internal electrode of the obtained sintered body was exposed to complete each multilayer ceramic capacitor.
[0045]
For each of the obtained multilayer ceramic capacitors, the capacitance, Q _E , capacitance temperature coefficient, and insulation resistance were measured in the same manner as in the first embodiment. As a life test, a DC voltage of 50 V was continuously applied between the external electrodes of the multilayer ceramic capacitor in a constant temperature bath at 125 ° C. for 1000 hours, and the results are shown in Table 15.
[0046]
[Table 15]

[0047]
As is clear from Table 15, the multilayer ceramic capacitors produced using the dielectric ceramic compositions 12, 28, 32, and 43 within the scope of the present invention have both high Q _E and insulation resistance. In contrast to the fact that no deterioration of properties was observed, the multilayer ceramic capacitors produced in samples 19 and 42 of the dielectric ceramic composition outside the scope of the present invention showed a decrease in insulation resistance, and the deterioration of properties was also observed in the life test. . Incidentally, the characteristic deterioration was counted as a failure when the insulation resistance value after the life test decreased to 1 × 10 ¹⁰ (Ω) or less.
[0048]
As described above, even when the dielectric ceramic composition of the present invention produces a green chip for a multilayer ceramic capacitor using a base metal such as nickel as an internal electrode, and fires it in a non-oxidizing atmosphere, the Q _E and the insulation resistance are high. It is clear that an excellent multilayer ceramic capacitor can be obtained which is both high, has a low rate of change in capacitance temperature, and does not cause characteristic deterioration even in a life test.
[0049]
In addition, the powders of MgO, CaO, TiO ₂ , ZrO ₂ , Nd ₂ O ₃ , BaSiO ₃ , MgSiO ₃ , CaSiO ₃ , and V ₂ O ₅ were used for the production of the dielectric ceramic composition in the first to third embodiments. However, Mg—Ca—Ti—Zr—O compound, Mg, Ca, Ti, Zr, Nd carbonate, hydroxide, etc. may be used so as to have the composition of the present invention. Even if an additive is added after calcining in advance, the same characteristics as in the embodiment can be obtained.
[0050]
【The invention's effect】
As shown in the above results, the dielectric ceramic composition of the present invention has excellent dielectric properties with high _QE and insulation resistance and low capacitance temperature coefficient even when fired in a non-oxidizing atmosphere. And can be used as a dielectric ceramic composition for a multilayer ceramic capacitor using a base metal such as nickel as an internal electrode. In particular, since it has excellent _QE characteristics and a small capacitance temperature coefficient, it is highly practical as a dielectric ceramic composition for multilayer ceramic capacitors for temperature compensation used in high frequency circuits and the like.
[Brief description of the drawings]
FIG. 1 is a ternary diagram showing the range of the dielectric ceramic composition of the present invention.

Claims

As a general _formula, the ternary composition represented by _{_{x (Mg m Ca 1-m}} ) O-y (Ti n Zr 1-n) O 2 -zNd 2 O 3 ( where x + y + z = 1) , a (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25), c (x = 0.97, y = 0) 0.02 and z = 0.01) (where m is in the range of 0.30 ≦ m ≦ 0.70 and n is in the range of 0.70 ≦ n ≦ 0.90) with respect to 100 wt%. As a dielectric ceramic composition in which 0.05 to 3.00 wt% of one selected from the group of BaSiO ₃ , MgSiO ₃ , and CaSiO ₃ and 0.05 to 0.30 wt% of V ₂ O ₅ are added. x, y, m, and n represent a molar ratio).

Represented by principal component _x of the dielectric ceramic composition according to claim _{_{1 (Mg m Ca 1-m}} ) O-y (Ti n Zr 1-n) O 2 -zNd 2 O 3 ( where x + y + z = 1) A (x = 0.49, y = 0.50, z = 0.01), b (x = 0.25, y = 0.50, z = 0.25), c (X = 0.97, y = 0.02, z = 0.01) (where m is 0.30 ≦ m ≦ 0.70, n is 0.70 ≦ n ≦ 0.90) The dielectric according to claim 1, wherein Al ₂ O ₃ is added in an amount of 2.0 wt% or less and MnO ₂ is added in an amount of 0.5 wt% or less (except when both are 0 at the same time) to 100 wt%. A body porcelain composition (where x, y, m, and n represent molar ratios).

A multilayer ceramic capacitor comprising a ceramic layer comprising the dielectric ceramic composition according to claim 1 and a base metal internal electrode such as nickel.