JP4863597B2 - Dielectric ceramic, manufacturing method thereof, and multilayer ceramic electronic component - Google Patents

Description

【００８０】
表１において、各成分の係数はモル比を示している。
【００８１】
（実施例１）
第１反応物を一般式ＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ を用意し、希土類元素を含む化合物として、Ｄｙ₂ Ｏ₃ を用意した。また、第１添加成分として、Ｄｙ₂ Ｏ₃ を用意し、第２添加成分として、ＮｉＯ、ＳｉＯ₂ およびＭｎＯを用意した。
【００８２】
次に、ＢａＣＯ₃ 、ＴｉＯ₂ およびＤｙ₂ Ｏ₃ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【００８３】
次に、第１添加成分としてのＤｙ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。
【００８４】
次に、第２添加成分としてのＮｉＯ、ＳｉＯ₂ およびＭｎＯの各粉末を、表１に示す組成比となるように秤量し、これらを第２反応物粉末に配合して、実施例１に係る誘電体セラミックの原料粉末を得た。
【００８５】
（実施例２）
第１反応物をＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ 、ＳｒＣＯ₃ およびＣａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ を用意し、希土類元素として、Ｇｄ₂ Ｏ₃ を用意した。また、第１添加成分として、Ｈｏ₂ Ｏ₃ を用意し、第２添加成分として、ＳｉＯ₂ を用意した。
【００８６】
次に、ＢａＣＯ₃ 、ＳｒＣＯ₃ 、ＣａＣＯ₃ 、ＴｉＯ₂ およびＧｄ₂ Ｏ₃ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【００８７】
次に、第１添加成分としてのＨｏ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。
【００８８】
次に、第２添加成分としてのＳｉＯ₂ の粉末を、表１に示す組成比となるように秤量し、これを第２反応物粉末に配合して、実施例２に係る誘電体セラミックの原料粉末を得た。
【００８９】
（実施例３）
第１反応物を一般式ＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ およびＣａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ およびＺｒＯ₂ を用意し、希土類元素を含む化合物として、Ｄｙ₂ Ｏ₃ を用意した。また、第１添加成分として、Ｈｏ₂ Ｏ₃ を用意し、第２添加成分として、ＣｏＯ、ＭｇＯ、ＳｉＯ₂ およびＭｎＯを用意した。
【００９０】
次に、ＢａＣＯ₃ 、ＣａＣＯ₃ 、ＴｉＯ₂ 、ＺｒＯ₂ およびＤｙ₂ Ｏ₃ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【００９１】
次に、第１添加成分としてのＨｏ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。
【００９２】
次に、第２添加成分としてのＣｏＯ、ＭｇＯ、ＳｉＯ₂ およびＭｎＯの各粉末を、表１に示す組成比となるように秤量し、これを第２反応物粉末に配合して、実施例３に係る誘電体セラミックの原料粉末を得た。
【００９３】
（実施例４）
第１反応物を一般式ＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ およびＣａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ 、ＺｒＯ₂ およびＨｆＯ₂ を用意し、希土類元素として、Ｎｄ₂ Ｏ₃ を用意した。また、第１添加成分として、Ｙ₂ Ｏ₃ を用意し、第２添加成分として、Ｃｒ₂ Ｏ₃ 、Ｂ₂ Ｏ₃ 、ＭｎＯ、ＳｉＯ₂ およびＣａＣＯ₃ を用意した。
【００９４】
次に、ＢａＣＯ₃ 、ＣａＣＯ₃ 、ＴｉＯ₂ 、ＺｒＯ₂ 、ＨｆＯ₂ およびＮｄ₂ Ｏ₃ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【００９５】
次に、第１添加成分としてのＹ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。
【００９６】
次に、第２添加成分としてのＣｒ₂ Ｏ₃ 、Ｂ₂ Ｏ₃ 、ＭｎＯ、ＳｉＯ₂ およびＣａＣＯ₃ の各粉末を、表１に示す組成比となるように秤量し、これらを第２反応物粉末に配合して、実施例４に係る誘電体セラミックの原料粉末を得た。
【００９７】
（実施例５）
第１反応物を一般式ＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ を用意し、希土類元素を含む化合物として、Ｈｏ₂ Ｏ₃ およびＮｄ₂ Ｏ₃ を用意した。また、第１添加成分として、Ｙｂ₂ Ｏ₃ を用意し、第２添加成分として、ＳｉＯ₂ およびＭｎＯを用意した。
【００９８】
次に、ＢａＣＯ₃ 、ＴｉＯ₂ 、Ｈｏ₂ Ｏ₃ およびＮｄ₂ Ｏ₃ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【００９９】
次に、第１添加成分としてのＹｂ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。
【０１００】
次に、第２添加成分としてのＳｉＯ₂ およびＭｎＯの各粉末を、表１に示す組成比となるように秤量し、これらを第２反応物粉末に配合して、実施例５に係る誘電体セラミックの原料粉末を得た。
【０１０１】
（実施例６）
第１反応物を一般式ＡＢＯ₃ で表わしたときのＡを含む化合物として、ＢａＣＯ₃ およびＣａＣＯ₃ を用意し、Ｂを含む化合物として、ＴｉＯ₂ およびＺｒＯ₂ を用意し、希土類元素を含む化合物として、ＣｅＯ₂ を用意した。また、第１添加成分として、Ｄｙ₂ Ｏ₃ を用意した。
【０１０２】
次に、ＢａＣＯ₃ 、ＣａＣＯ₃ 、ＴｉＯ₂ 、ＺｒＯ₂ およびＣｅＯ₂ を、表１の「第１反応物」の欄に示した組成比となるように秤量し、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第１反応物粉末を得た。
【０１０３】
次に、第１添加成分としてのＤｙ₂ Ｏ₃ を、表１に示す組成比となるように秤量し、これを第１反応物粉末に加え、これらをボールミルにより湿式混合した後、１０００℃の温度で２時間仮焼し、粉砕することによって、第２反応物粉末を得た。そして、この第２反応物粉末を、実施例６に係る誘電体セラミック原料粉末とした。
【０１０４】
（比較例１）
実施例１と同じ組成になるように、ＢａＣＯ₃ 、ＴｉＯ₂ 、Ｄｙ₂ Ｏ₃ 、ＮｉＯ、ＳｉＯ₂ およびＭｎＯを、表１に示す組成比をもって一度に混合し、１０００℃の温度で２時間仮焼し、粉砕することによって、比較例１に係る誘電体セラミックの原料粉末を得た。
【０１０５】
（比較例２）
ＢａＴｉＯ₃ 、ＳｒＣＯ₃ 、ＣａＣＯ₃ 、ＴｉＯ₂ 、Ｈｏ₂ Ｏ₃ 、Ｇｄ₂ Ｏ₃ およびＳｉＯ₂ を、表１に示す組成比をもって一度に混合し、１０００℃の温度で２時間仮焼し、粉砕することによって、比較例２に係る誘電体セラミックの原料粉末を得た。
【０１０６】
（比較例３）
ＡＢＯ₃ として予め合成した（Ｂａ_0.95Ｃａ_0.04）（Ｔｉ_0.70Ｚｒ_0.30Ｍｎ_0.002 ）Ｏ₃ （仮焼物Ａ）に、添加成分として、Ｈｏ₂ Ｏ₃ 、Ｄｙ₂ Ｏ₃ 、ＣｏＯ、ＭｇＯおよびＳｉＯ₂ を、表１に示す組成比をもって加えて混合し、１０００℃の温度で２時間仮焼し（仮焼物Ｂ）、粉砕することによって、比較例３に係る誘電体セラミックの原料粉末を得た。
【０１０７】
（比較例４）
ＡＢＯ₃ として予め合成した（Ｂａ_0.90Ｃａ_0.10）（Ｔｉ_0.91Ｚｒ_0.08Ｈｆ_0.01）Ｏ₃ （仮焼物Ｃ）を用意した。また、ＣａＣＯ₃ 、Ｙ₂ Ｏ₃ 、ＳｉＯ₂ およびＮｄ₂ Ｏ₃ を、表１に示す組成比をもって混合し、１０００℃の温度で２時間仮焼し、粉砕することによって、仮焼物Ｄの粉末を得た。次に、表１に示す組成比をもって、仮焼物Ｄの粉末に、仮焼物Ｃの粉末を混合し、さらに、添加成分としてのＣｒ₂ Ｏ₃ 、Ｂ₂ Ｏ₃ およびＭｎＯを混合し、比較例４に係る誘電体セラミックの原料粉末を得た。
【０１０８】
２．積層セラミックコンデンサの作製
次に、上述の実施例１〜６および比較例１〜４の各々に係る原料粉末に、ポリビニルブチラール系バインダおよびエタノール等の有機溶剤を加え、ボールミルを用いた湿式混合を実施することによって、セラミックスラリーを作製した。
【０１０９】
次に、セラミックスラリーを、ドクターブレード法によって、焼成後の誘電体セラミック層の厚みが２．５μｍになるような厚みをもってシート状に成形し、矩形のセラミックグリーンシートを得た。
【０１１０】
次に、セラミックグリーンシート上に、ニッケルを主体とする導電性ペーストをスクリーン印刷し、内部電極となるべき導電性ペースト膜を形成した。
【０１１１】
次いで、導電性ペースト膜が引き出されている側が互い違いとなるように、導電性ペースト膜が形成されたセラミックグリーンシートを含む複数のセラミックグリーンシートを積層し、生の積層体を得た。
【０１１２】
次に、生の積層体を、窒素雰囲気中において３５０℃の温度に加熱し、バインダを燃焼させた後、酸素分圧１０^-9〜１０^-12 ＭＰａのＨ₂ −Ｎ₂ −Ｈ₂ Ｏガスからなる還元性雰囲気中において、後掲の表２に示す焼成温度にて２時間焼成し、焼結した積層体を得た。
【０１１３】
次いで、積層体の両端面上に、Ｂ₂ Ｏ₃ −Ｌｉ₂ Ｏ−ＳｉＯ₂ −ＢａＯ系のガラスフリットを含有するとともに銀を導電成分とする導電性ペーストを塗布し、窒素雰囲気中において６００℃の温度で焼き付け、内部電極と電気的に接続された外部電極を形成した。
【０１１４】
このようにして得られた積層セラミックコンデンサの外形寸法は、幅１．６ｍｍ、長さ３．２ｍｍおよび厚さ１．２ｍｍであり、内部電極間に介在する誘電体セラミック層の厚みは、２．５μｍであった。また、有効誘電体セラミック層の層数は１００であり、１層あたりの対向電極面積は２．１ｍｍ² であった。
【０１１５】
３．電気的特性の測定
このようにして得られた実施例１〜４および比較例１〜５に係る積層セラミックコンデンサの各種電気的特性を測定した。
【０１１６】
まず、各積層セラミックコンデンサの室温での誘電率εおよび絶縁抵抗を測定した。この場合、誘電率εは、温度２５℃、１ｋＨｚ、および１Ｖ_rms の条件下で測定した。また、６ｋＶ／ｍｍの電界強度の下で絶縁抵抗を測定するため、１５Ｖの直流電圧を２分間印加して、＋２５℃において絶縁抵抗を測定し、静電容量（Ｃ）と絶縁抵抗（Ｒ）との積、すなわちＣＲ積を求めた。
【０１１７】
また、高温負荷寿命試験を実施した。高温負荷寿命試験は、３６個の試料について、温度１７５℃において、電界強度が１６ｋＶ／ｍｍになるように４０Ｖの電圧を印加して、その絶縁抵抗の経時変化を求めようとしたものである。なお、高温負荷寿命として、各試料の絶縁抵抗値が２００ｋΩ以下になったときの時間を寿命時間として、その平均寿命時間を求めた。
【０１１８】
また、直流電圧印加下での静電容量の経時変化を求めた。静電容量の経時変化は、温度１２５℃、１ｋＨｚ、１Ｖ_rms 、および直流電圧４Ｖ印加の条件下で、６０時間後の容量変化を測定し、直流電圧印加直後の１２５℃での静電容量を基準として容量変化率すなわちＤＣ負荷経時変化率を求めた。
【０１１９】
以上の誘電率ε、ＣＲ積、高温負荷寿命およびＤＣ負荷経時変化率が、表２に示されている。
【０１２０】
【表２】

【０１２１】
４．希土類元素の濃度分布の調査
実施例１〜６および比較例１〜４の各々に係る積層セラミックコンデンサを薄片状に研磨し、透過型電子顕微鏡に付属のエネルギー分散型Ｘ線分光法（ＥＤＸ）により、誘電体セラミック層を構成する誘電体セラミックの結晶粒子の内部の希土類元素の濃度を分析した。具体的な測定は、任意の広さの視野に観察された主成分の結晶粒子について、次のように実施した。
【０１２２】
図２は、この分析方法を説明するためのものである。図２には、ある結晶粒子１５が図示されている。
【０１２３】
結晶粒子１５の表面近傍の希土類元素の濃度を分析する場合は、結晶粒子１５の外周を略８等分した任意の点と結晶粒子１５の中心とを結んだ８本の半直線の各々上であって、結晶粒子１５の表面近傍の領域内に位置する点を、分析点Ａとした。このとき、結晶粒子１５の外周を略８等分した任意の点を求めるため、必要であれば、結晶粒子１５の外周長を適用な近似を用いて計算し、これを略８等分するようにしてもよい。
【０１２４】
結晶粒子１５内の任意の点における希土類元素の濃度および結晶粒子１５の中心部の任意の点における希土類元素の濃度を分析する場合は、結晶粒子１５の外周を略４等分した任意の点をまず決め、これを分析点Ｂ１、Ｂ２、Ｂ３およびＢ４とした。この場合においても、必要であれば、結晶粒子１５の外周長を適当な近似を用いて計算し、これを略４等分することによって、分析点Ｂ１〜Ｂ４を決めるようにしてもよい。また、分析点Ｂ１〜Ｂ４と結晶粒子１５の中心とを結んだ４本の線分を決め、各線分の中点を求め、これら中点を、分析点Ｂ５、Ｂ６、Ｂ７およびＢ８とした。さらに、分析点Ｂ５〜Ｂ８と結晶粒子１５の中心との中点を求め、これら中点を分析点Ｂ９、Ｂ１０、Ｂ１１およびＢ１２とした。さらに、結晶粒子１５の中心を分析点Ｂ１３とした。
【０１２５】
結晶粒子１５内の任意の点における希土類元素の濃度を分析するため、上述のように決定された分析点Ｂ１〜Ｂ１３を用い、結晶粒子１５の中心部の任意の点における希土類元素の濃度を分析するため、分析点Ｂ５〜Ｂ１３を用いた。
【０１２６】
なお、上述したいずれの濃度分析においても、２０個以上の結晶粒子１５について実施した。また、分析での電子線として、２ｎｍのプローブを用いた。
【０１２７】
表３には、上述した濃度分析によって得られた結果の一部が示されている。すなわち、表３には、実施例１における３個の結晶粒子（パターンＡ、ＢおよびＣ）ならびに比較例１における１つの結晶粒子（パターンＤ）および比較例３における１つの結晶粒子（パターンＥ）の各々についての分析点Ａでの平均濃度ならびに分析点Ｂ１〜Ｂ１３の各々での濃度が示されている。これら濃度は、ＡＢＯ₃ におけるＢサイト成分１００モルに対する希土類元素のモル数を単位として示されている。
【０１２８】
【表３】

【０１２９】
表３に示すように、実施例１では、パターンＡ、ＢおよびＣのいずれにおいても、分析点Ａでの平均濃度すなわちＣｓ_AVE と、分析点Ｂ１〜Ｂ１３での濃度すなわちＣｉ_(n) と、分析点Ｂ５〜Ｂ１３での濃度すなわちＣｃ_(n) との間で、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０、およびＣｃ_(n) ／Ｃｓ_AVE ＜１の条件を満足している。
【０１３０】
他方、比較例１のパターンＤでは、Ｃｉ_(n) ／Ｃｓ_AVE ＞１／５０の条件を満足するが、Ｃｃ_(n) ／Ｃｓ_AVE ＜１の条件は満足していない。
【０１３１】
また、比較例３のパターンＥでは、Ｃｃ_(n) ／Ｃｓ_AVE ＜１の条件を満足するが、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０の条件を満足していない。
【０１３２】
表４には、表３に一例を示すような分析結果を得た後、実施例１〜６および比較例１〜４の各々について、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０の条件を満足する結晶粒子数の全結晶粒子数に対する割合［％］およびＣｃ_(n) ／Ｃｓ_AVE ＜１の条件を満足する結晶粒子数の全結晶粒子数に対する割合［％］を求めた結果が示されている。
【０１３３】
【表４】

【０１３４】
表４からわかるように、実施例１〜６によれば、いずれも、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０である結晶粒子の割合が７０％を超え、また、Ｃｃ_(n) ／Ｃｓ_AVE ＜１である結晶粒子の割合も７０％を超えている。
【０１３５】
これらに対して、比較例１および２では、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０である結晶粒子の割合は７０％を超えているが、Ｃｃ_(n) ／Ｃｓ_AVE ＜１である結晶粒子の割合は７０％以下となっている。
【０１３６】
また、比較例３および４では、Ｃｃ_(n) ／Ｃｓ_AVE ＜１である結晶粒子の割合は７０％を超えているが、Ｃｉ_(n) ／Ｃｓ_AVE ≧１／５０である結晶粒子の割合は７０％以下である。
【０１３７】
５．総合評価
前掲の表２において、誘電体セラミックの組成が互いに同じである実施例１と比較例１とを比較すると、誘電率、ＣＲ積および高温負荷寿命については、実質的に有意の差を示さないが、ＤＣ負荷経時変化率については、実施例１では−１．２％となり、比較例１の−１０．２％に比べて、大幅に改善された特性が得られている。
【０１３８】
また、実施例２〜６については、比較例２に対して、ＤＣ負荷経時変化率が大幅に改善され、比較例３および４に比較して、高温負荷寿命およびＤＣ負荷経時変化率が大幅に改善されていることがわかる。
【０１３９】
以上の表２に示した結果と表４に示した結果とを併せて考察すれば、Ｃｉ_(n)／Ｃｓ_AVE≧１／５０の条件を満足する結晶粒子数が、全結晶粒子数の７０％を超え、かつＣｃ_(n)／Ｃｓ_AVE＜１の条件を満足する結晶粒子数が、全結晶粒子数の７０％を超える、実施例１〜６によれば、ＤＣ負荷経時変化率が小さく、ＣＲ積が高く、高温負荷寿命が長く、それゆえ、誘電体セラミック層の薄層化が進んでも、信頼性に優れた積層セラミックコンデンサが得られることがわかる。
【０１４０】
【発明の効果】
以上のように、この発明に係る誘電体セラミックによれば、一般式ＡＢＯ₃（Ａは、Ｂａ、ＣａおよびＳｒのうちのＢａを含む少なくとも１種であり、Ｂは、Ｔｉ、ＺｒおよびＨｆのうちのＴｉを含む少なくとも１種である。）で表わされる主成分と、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、ＬｕおよびＹのうちの少なくとも１種の希土類元素を含む添加成分とを含む組成を有するものにおいて、結晶粒子の表面近傍での希土類元素の平均濃度をＣｓ_AVEとし、結晶粒子内の任意の点における希土類元素の濃度をＣｉ_(n)とし、結晶粒子の中心部の任意の点における希土類元素の濃度をＣｃ_(n)としたとき、希土類元素の濃度分布に関して、Ｃｉ_(n)／Ｃｓ_AVE≧１／５０の条件を満足する結晶粒子数が、全結晶粒子数の７０％を超え、かつＣｃ_(n)／Ｃｓ_AVE＜１の条件を満足する結晶粒子数が、全結晶粒子数の７０％を超えるので、これを用いて積層セラミックコンデンサのような積層セラミック電子部品を構成したとき、直流電圧印加下での静電容量の経時変化が小さく、絶縁抵抗と静電容量との積（ＣＲ積）が高く、高温かつ高電圧下における絶縁抵抗の加速寿命を長くすることができる。
【０１４１】
そのため、この誘電体セラミックをもって積層セラミック電子部品の誘電体セラミック層を構成すれば、誘電体セラミック層の薄層化に対しても、優れた信頼性を維持し得る積層セラミック電子部品を得ることができる。
【０１４２】
したがって、積層セラミックコンデンサに適用すれば、誘電体セラミック層の薄層化によって、積層セラミックコンデンサの小型化かつ大容量化が可能となり、また、誘電体セラミック層を薄層化しても、積層セラミックコンデンサの定格電圧を下げる必要がない。その結果、たとえば、誘電体セラミック層の厚みを１μｍ程度にまで薄層化することが問題なく行なうことができる。
【０１４３】
この発明に係る誘電体セラミックの製造方法によれば、一般式ＡＢＯ₃ で表わされる主成分を構成するＡを含む化合物とＢを含む化合物と、希土類元素を含む化合物の一部とを混合し、反応させ、粉砕することによって、第１の反応物粉末を得る工程と、第１の反応物粉末と希土類元素を含む化合物の残部とを混合し、反応させ、粉砕することによって、第２の反応物粉末を得る工程と、第２の反応物粉末を焼成する工程とを備えているので、これら構成元素をすべて混合して一度に反応させる方法を採用する場合に比べて、前述したような希土類元素の濃度分布をより容易に得ることが可能になる。
【図面の簡単な説明】
【図１】この発明の一実施形態による積層セラミックコンデンサ２１を図解的に示す断面図である。
【図２】ある結晶粒子１５における希土類元素の濃度分布の分析において採用される分析点の例を図解的に示す、結晶粒子１５の拡大図である。
【符号の説明】
Ａ，Ｂ１〜Ｂ１３ 分析点
１５ 結晶粒子
２１ 積層セラミックコンデンサ
２２ 積層体
２３ 誘電体セラミック層
２４，２５ 内部電極
２８，２９ 外部電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric ceramic, a method of manufacturing the same, and a multilayer ceramic electronic component, and more particularly, to make it possible to advantageously reduce the thickness of a dielectric ceramic layer in a multilayer ceramic electronic component such as a multilayer ceramic capacitor. It is about improvement.
[0002]
[Prior art]
A multilayer ceramic capacitor as an example of a multilayer ceramic electronic component of interest to the present invention is generally manufactured as follows.
[0003]
First, a ceramic green sheet containing a dielectric ceramic raw material, which is provided with a conductive material serving as an internal electrode with a desired pattern on its surface, is prepared. Examples of the dielectric ceramic include BaTiO._ThreeIs used as a main component.
[0004]
Next, a plurality of ceramic green sheets including the ceramic green sheet provided with the conductive material described above are laminated and thermocompression bonded, thereby producing an integrated raw laminate.
[0005]
The raw laminate is then fired, thereby obtaining a sintered laminate. An internal electrode made of the above-described conductive material is formed inside the laminate.
[0006]
Next, external electrodes are formed on the outer surface of the laminate so as to be electrically connected to specific ones of the internal electrodes. The external electrode is formed, for example, by applying and baking a conductive paste containing conductive metal powder and glass frit on the outer surface of the laminate.
[0007]
In this way, the multilayer capacitor is completed.
[0008]
In recent years, a relatively inexpensive base metal such as nickel or copper has been increasingly used as the conductive material for the internal electrode described above in order to reduce the manufacturing cost of the multilayer ceramic capacitor as much as possible. However, when trying to manufacture a multilayer ceramic capacitor in which an internal electrode is formed with a base metal, firing in a neutral or reducing atmosphere must be applied to prevent oxidation of the base metal during firing. The dielectric ceramic used in the multilayer ceramic capacitor must have resistance to reduction.
[0009]
As the dielectric ceramic having reduction resistance as described above, for example, in Japanese Patent Laid-Open No. 5-9066, Japanese Patent Laid-Open No. 5-9067 or Japanese Patent Laid-Open No. 5-9068, BaTiO_Three-Rare earth oxide-Co₂O_ThreeSystem compositions have been proposed.
[0010]
JP-A-9-270366 proposes a dielectric ceramic having a long high-temperature load life. JP-A-6-5460 or JP-A-10-330160 proposes a dielectric ceramic having a high withstand voltage.
[0011]
[Problems to be solved by the invention]
With the recent development of electronics technology, electronic components have rapidly been downsized, and the trend toward miniaturization and increase in capacity of multilayer ceramic capacitors has become prominent.
[0012]
Therefore, even in a firing atmosphere in which the base metal used for the internal electrode is not oxidized, the dielectric constant is high, the change of the dielectric constant under DC voltage is small, and even if the dielectric ceramic layer is thinned, the electric insulation is There is an increasing demand for high and therefore reliable dielectric ceramics. However, the conventional dielectric ceramic as described above cannot always satisfy this requirement sufficiently.
[0013]
For example, the dielectric ceramic described in Japanese Patent Laid-Open No. 5-9066, Japanese Patent Laid-Open No. 5-9067 or Japanese Patent Laid-Open No. 5-9068 shows high electrical insulation, but the dielectric ceramic layer is made thin. Then, specifically, regarding the reliability when the layer thickness is reduced to 5 μm or less, particularly 3 μm or less, it is not always possible to sufficiently satisfy the market requirements.
[0014]
In addition, the dielectric ceramic described in JP-A-6-5460 has a reliability as the dielectric ceramic layer is thinned because the rare earth element is not dissolved in the entire region inside the crystal grains. There is a problem of lowering.
[0015]
Similarly, the dielectric ceramic described in JP-A-9-270366 also has a problem that reliability decreases as the dielectric ceramic layer is thinned because most rare earth elements are present at grain boundaries. There is.
[0016]
In addition, the dielectric ceramic described in Japanese Patent Laid-Open No. 10-330160 is previously ABO._ThreeSince the acceptor components such as Mn, Co, Cr, Ni, and Fe are contained in the particles, the reduction resistance is sufficiently improved, the insulation resistance is increased, and the dielectric breakdown voltage is increased. There is a problem that the change in capacitance with time is large.
[0017]
As described above, when the dielectric ceramic layer is thinned in order to cope with the downsizing and large capacity of the multilayer ceramic capacitor, if the rated voltage is the same as that before thinning the dielectric ceramic layer, Since the electric field strength applied per layer of the ceramic layer is increased, the reliability is remarkably lowered in that the insulation resistance is lowered. Therefore, when a conventional dielectric ceramic is used, it is necessary to lower the rated voltage when the dielectric ceramic layer is thinned.
[0018]
Therefore, it is not necessary to lower the rated voltage while thinning the dielectric ceramic layer, and it is desirable to realize a multilayer ceramic capacitor that has high insulation resistance under high electric field strength and excellent reliability. .
[0019]
In addition, since the multilayer ceramic capacitor is usually used in a state where a DC voltage is applied, it is known that the capacitance changes with time. However, as a result of thinning of the dielectric ceramic layer accompanying the downsizing and increase in capacity of the multilayer ceramic capacitor, the DC electric field strength per layer of the dielectric ceramic layer is increased, and the change in capacitance with time is greater. There is a problem of becoming.
[0020]
In view of this, a multilayer ceramic capacitor is desired in which the change with time in the capacitance with a DC voltage applied is small.
[0021]
Although the multilayer ceramic capacitor has been described above, the same problem or demand applies to other multilayer ceramic electronic components using dielectric ceramics.
[0022]
Therefore, the object of the present invention is that when a multilayer ceramic capacitor or the like is configured using this, the change with time of the capacitance under the application of a DC voltage is small, and the product of the insulation resistance and the capacitance (CR product) is small. An object of the present invention is to provide a dielectric ceramic and a method for producing the same, which are high, have a long accelerated lifetime of insulation resistance under high temperature and high voltage, and thus are excellent in reliability even if the layer is thinned.
[0023]
Another object of the present invention is to provide a multilayer ceramic electronic component such as a multilayer ceramic capacitor constituted by using the dielectric ceramic as described above.
[0024]
[Means for Solving the Problems]
This invention relates to the general formula ABO_Three(A is at least one containing Ba of Ba, Ca and Sr, and B is at least one containing Ti of Ti, Zr and Hf), and La Di, having a composition comprising an additive component containing at least one rare earth element of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y It is first directed to ceramics, and is characterized by having the following configuration in order to solve the technical problems described above.
[0025]
  That is,Using the energy dispersive X-ray spectroscopy attached to the transmission electron microscope, the diameter of the probe of the electron beam was set to 2 nm, and the rare earth element concentration on the cross-sectional polished surface of the dielectric ceramic crystal particles was analyzed. The following conditions are satisfied with respect to the concentration distribution of the rare earth element.
  First, 8 points on each of eight half lines connecting an arbitrary point obtained by dividing the outer periphery of the crystal grain into approximately eight parts and the center of the crystal grain, and in a region near the surface of the crystal grain.The average concentration of rare earth elements at Cs_AVEWhenTo do.
  In addition, an arbitrary point obtained by dividing the outer periphery of the crystal grain into approximately four equal parts is first determined, and these are set as analysis points B1, B2, B3, and B4. The line segment of the book is determined, the midpoint of each line segment is obtained, these midpoints are set as analysis points B5, B6, B7 and B8, and then the midpoint between the analysis points B5 to B8 and the center of the crystal grain is obtained In the case where these midpoints are analysis points B9, B10, B11 and B12, and the center of the crystal particles is the analysis point B13,In crystal grains13 points from the above analysis points B1 to B13Of rare earth elements ineachConcentration is Ci_(n)And the center of the crystal grain9 of the above analysis points B5 to B13Of rare earth elements in terms ofeachConcentration to Cc_(n)WhenTo do.
  AndRegarding the concentration distribution of rare earth elements,
  Ci_(n)/ Cs_AVEThe number of crystal grains satisfying the condition of ≧ 1/50 exceeds 70% of the total number of crystal grains, and
  Cc_(n)/ Cs_AVEThe number of crystal grains satisfying the condition <1 exceeds 70% of the total number of crystal grains.
[0026]
The dielectric ceramic according to the present invention may further contain at least one element selected from Ni, Co, Fe, Cr, Mn, Si, Mg, V, B (boron), Ca, and Al.
[0027]
The invention is also directed to a method for producing a dielectric ceramic as described above.
[0028]
The method for manufacturing a dielectric ceramic according to the present invention has a general formula ABO._ThreeA step of obtaining a first reactant powder by mixing, reacting and pulverizing a compound containing A and a compound containing B constituting a main component represented by the formula B and a part of a compound containing a rare earth element; Mixing the first reactant powder and the remainder of the compound containing the rare earth element, reacting, and pulverizing to obtain a second reactant powder, and firing the second reactant powder; It is characterized by having.
[0029]
As described above, the dielectric ceramic according to the present invention further contains at least one element of Ni, Co, Fe, Cr, Mn, Si, Mg, V, B (boron), Ca, and Al. The general formula ABO_ThreeA step of obtaining a first reactant powder by mixing, reacting and pulverizing a compound containing A and a compound containing B constituting a main component represented by the formula B and a part of a compound containing a rare earth element; , Mixing the first reactant powder and the rest of the compound containing the rare earth element, reacting, and pulverizing to obtain the second reactant powder, the second reactant powder and Ni, Co, And a step of firing a mixed powder containing a compound powder containing at least one element of Fe, Cr, Mn, Si, Mg, V, B (boron), Ca, and Al.
[0030]
The present invention also relates to a multilayer ceramic electronic component comprising a multilayer body including a plurality of multilayer dielectric ceramic layers and internal electrodes formed along a specific interface between the dielectric ceramic layers. Directed. The multilayer ceramic electronic component according to the present invention is characterized in that the dielectric ceramic layer is made of the dielectric ceramic according to the present invention as described above.
[0031]
The present invention is particularly advantageously applied to a multilayer ceramic capacitor. In this case, the multilayer ceramic electronic component according to the present invention further includes first and second external electrodes formed on the outer surface of the multilayer body, and a plurality of internal electrodes are stacked in the stacking direction of the multilayer body. An electrode is formed, and the plurality of internal electrodes are alternately connected in the stacking direction to those electrically connected to the first external electrode and those electrically connected to the second external electrode.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 21 according to an embodiment of the present invention.
[0033]
The multilayer ceramic capacitor 21 includes a multilayer body 22. The multilayer body 22 includes a plurality of dielectric ceramic layers 23 to be laminated, and a plurality of internal electrodes 24 and 25 formed along a plurality of specific interfaces between the plurality of dielectric ceramic layers 23, respectively. The The internal electrodes 24 and 25 are formed so as to reach the outer surface of the multilayer body 22, but the internal electrode 24 is extended to one end face 26 of the multilayer body 22 and the internal electrode is extended to the other end face 27. 25 are alternately arranged in the laminated body 22.
[0034]
External electrodes 28 and 29 are formed on the outer surface of the laminate 22 and on the end faces 26 and 27, respectively. Further, first plating layers 30 and 31 made of nickel, copper or the like are formed on the external electrodes 28 and 29, respectively, and further, second plating layers 32 and 33 made of solder, tin or the like are further formed thereon. Are formed respectively.
[0035]
In this way, in the multilayer ceramic capacitor 21, the plurality of internal electrodes 24 and 25 are formed so as to overlap each other in the stacking direction of the multilayer body 22, and thereby the capacitance between the adjacent internal electrodes 24 and 25. Form. In addition, the internal electrode 24 and the external electrode 28 are electrically connected, and the internal electrode 25 and the external electrode 29 are electrically connected, whereby the above-described static electrode 28 and 29 are connected. The electric capacity is taken out.
[0036]
In such a multilayer ceramic capacitor 21, the dielectric ceramic layer 23 has a general formula ABO._Three(A is at least one containing Ba of Ba, Ca and Sr, and B is at least one containing Ti of Ti, Zr and Hf), and La Di, having a composition comprising an additive component containing at least one rare earth element of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y Composed of ceramic.
[0037]
  This dielectric ceramic also determines the average concentration of rare earth elements near the surface of the crystal grains as Cs._AVEAnd the concentration of the rare earth element at an arbitrary point in the crystal grain is Ci_(n)And the concentration of the rare earth element at an arbitrary point in the center of the crystal grain is Cc._(n)In terms of the concentration distribution of rare earth elements, Ci_(n)/ Cs_AVEThe number of crystal grains satisfying the condition of ≧ 1/50 exceeds 70% of the total number of crystal grains, and Cc_(n)/ Cs_AVEThe number of crystal grains satisfying the condition <1 exceeds 70% of the total number of crystal grains.
  Rare earth element average concentration Cs in the vicinity of the surface of the crystal grains described above _AVE , The concentration Ci of the rare earth element at an arbitrary point in the crystal grain _(n) , And the concentration Cc of the rare earth element at an arbitrary point in the center of the crystal grain _(n) More specifically, it is obtained as follows.
  First, as a premise, the energy dispersive X-ray spectroscopy attached to the transmission electron microscope is used, the probe diameter of the electron beam is set to 2 nm, and the concentration of the rare earth element on the cross-sectional polished surface of the dielectric ceramic crystal particles Is analyzed.
  Cs above _AVE Are 8 points on each of the eight half-lines connecting an arbitrary point obtained by dividing the outer periphery of the crystal grain into approximately eight parts and the center of the crystal grain, and located in a region near the surface of the crystal grain. The average concentration of rare earth elements.
  In addition, Ci _(n) First, an arbitrary point obtained by dividing the outer periphery of the crystal grain into approximately four equal parts is determined, and these are set as analysis points B1, B2, B3, and B4, and then the analysis points B1 to B4 are connected to the center of the crystal grain 4. The line segment of the book is determined, the midpoint of each line segment is obtained, these midpoints are set as analysis points B5, B6, B7 and B8, and then the midpoint between the analysis points B5 to B8 and the center of the crystal grain is obtained. In the case where these midpoints are analysis points B9, B10, B11 and B12, and the center of the crystal particles is analysis point B13, each concentration of the rare earth elements at the 13 analysis points B1 to B13 in the crystal particles It is.
  Cc _(n) Is the concentration of each rare earth element at 9 points of the analysis points B5 to B13 in the center of the crystal grain.
[0038]
Of the above-mentioned conditions regarding the rare earth element concentration distribution, Ci_(n)/ Cs_AVEThe condition of ≧ 1/50 simply means that the rare earth element is sufficiently distributed over the entire area up to the inside of the crystal grains. On the other hand, when the rare earth element is not distributed throughout the crystal grains, the accelerated lifetime of the insulation resistance at high temperature and high voltage is shortened, and the reliability when the dielectric ceramic layer 23 is thinned. Sex is reduced.
[0039]
Cc_(n)/ Cs_AVEThe condition <1 simply means that the concentration of the rare earth element in the vicinity of the surface of the crystal grain is higher than the concentration of the rare earth element in the center of the crystal grain. On the other hand, when the concentration of the rare earth element near the surface of the crystal grain is lower than the concentration of the rare earth element at the center of the crystal grain, the change with time in the capacitance under the application of a DC voltage is large. turn into.
[0040]
  Ci_(n)/ Cs_AVE≧ 1/50The number of crystal grains satisfying the above condition exceeds 70% of the total number of crystal grains, andCc_(n)/ Cs_AVE<The number of crystal grains satisfying the condition of 1 exceeds 70% of the total number of crystal grains, in order to exhibit the above-described effect. In order to reduce the change with time under a direct current voltage, It is desirable that the number of crystal grains satisfying the above conditions is 90% or more of the total number of crystal grains. When this condition is satisfied, it has been confirmed that the thickness of the dielectric ceramic layer 23 can be reduced to about 1 μm.
[0041]
In this specification, “near the surface of a crystal grain” means that when a clear layer is observed between crystal grains crystallographically in a cross section of a dielectric ceramic, It refers to the region in the crystal grain that is 2 nm inside from the interface with the grain toward the center of the crystal grain. In addition, in the cross section of the dielectric ceramic, no crystal grain boundary phase or secondary phase is observed crystallographically, and when the crystal particles are bonded to each other, It refers to the region within the crystal grain that is 2 nm inside in the central direction.
[0042]
Further, in this specification, the “center portion of the crystal grain” refers to a region surrounded by a set of midpoints of line segments connecting the crystal grain center to the outer periphery of the crystal grain in the dielectric ceramic cross section.
[0043]
In this invention, the average concentration Cs of rare earth elements in the vicinity of the surface of the crystal grains_AVE, The concentration Ci of the rare earth element at an arbitrary point in the crystal grain_(n)And the concentration Cc of the rare earth element at an arbitrary point in the center of the crystal grain_(n)Is obtained, for example, as follows.
[0044]
That is, in a certain crystal particle, the concentration of rare earth elements at various analysis points in the crystal particle is determined by energy dispersive X-ray spectroscopy (EDX) attached to a transmission electron microscope, and a 2 nm probe is used as an electron beam. Measure while.
[0045]
In this case, the concentration of rare earth elements at each analysis point was measured using any 8 or more points near the surface of the crystal grain as analysis points, and the average value was obtained as Cs._AVEIt is.
[0046]
Further, the measurement of the concentration of the rare earth element at each analysis point using any nine or more points inside the crystal particle including the center of the crystal particle as the analysis point is Ci._(n)(N is 9 or more).
[0047]
In addition, the measurement of the concentration of rare earth elements at each analysis point with any nine or more points at the center of the crystal grain as the analysis point is Cc._(n)(N is 9 or more).
[0048]
In addition to the rare earth element described above, M (M is at least one of Ni, Co, Fe, Cr, and Mn), Si, and A (which is a constituent element of the main component) are present near the surface of the crystal grains. Is at least one of Ba, Ca and Sr containing Ba) or B (B is at least one of Ti, Zr and Hf containing Ti), or Mg, V, B (this “B "" May be boron), Ca, Al, etc., and the presence of elements other than these rare earth elements does not substantially degrade the properties of the dielectric ceramic.
[0049]
ABO, the main component used to obtain dielectric ceramics_ThreeThe average particle diameter of the powder is not particularly limited, but is preferably 2 μm or less and preferably 0.05 to 0.7 μm in order to cope with the thinning of the dielectric ceramic layer 23. More desirable. ABO with such particle size_ThreeWhen the powder is used as the raw material powder, the dielectric ceramic layer 23 can be thinned to a thickness of about 1 μm without any problem.
[0050]
Next, a method for manufacturing the multilayer ceramic capacitor 21 will be described.
[0051]
First, a raw material powder for a dielectric ceramic constituting the dielectric ceramic layer 23 is prepared. This raw material powder is preferably produced as follows.
[0052]
First, a compound containing A such as carbonate (A is at least one of Ba containing Ba, Ca and Sr) and a compound containing B such as an oxide (B is Ti, Zr and Hf At least one of Ti and at least one of rare earth elements such as oxide (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) And a compound containing
[0053]
Next, the compound containing A, the compound containing B, and a part of the compound containing the rare earth element are mixed in a desired amount, reacted by calcination in the air, etc., and pulverized. A reactant powder is obtained.
[0054]
Next, the first reactant powder and the remainder of the compound containing the rare earth element are mixed together in desired amounts, reacted by calcination in the atmosphere, etc., and pulverized, whereby the second reactant powder is obtained. obtain. This second reactant powder is used as a raw material powder for the dielectric ceramic.
[0055]
As described above, when at least one of Ni, Co, Fe, Cr, Mn, Si, Mg, V, B (where “B” is boron), Ca, Al, etc. is added, these are added. A compound powder such as an oxide containing these elements is mixed with the second reactant powder, and this mixed powder is used as a raw material powder for the dielectric ceramic.
[0056]
When the raw material powder is produced as described above, the rare earth element is solidified over the entire inside of the crystal particles included in the dielectric ceramic layer 23 as a sintered body obtained by firing the compact including the raw material powder. It is easy to dissolve, and it is easy to increase the concentration of the rare earth element near the surface of the crystal grain as compared with the center part of the crystal grain. Therefore, the concentration distribution of the rare earth element as described above Is easy to get.
[0057]
In addition, the method for obtaining the first reactant and the second reactant uses a wet method such as a hydrothermal synthesis method, a coprecipitation method, or an alkali hydrolysis method in addition to the method of calcining the mixed powder described above. be able to.
[0058]
In addition to the oxides and carbonates described above, the starting material for obtaining the dielectric ceramic raw material powder includes nitrate, hydroxide, organic acid salt, alkoxide, chelate compound, etc. Can be used as appropriate.
[0059]
On the other hand, instead of the above-described method for producing a dielectric ceramic raw material powder, a general formula ABO, which is a conventional general raw material powder manufacturing method,_ThreeA compound containing A and a compound containing B, a rare earth element oxide, MO (M is at least one of Ni, Co and Mn), and SiO₂When the method of mixing all of the above and reacting at once is used, the concentration of the rare earth element in the vicinity of the surface of the crystal grain of the obtained dielectric ceramic is determined by the concentration of the rare earth element at the center of the crystal grain. It has been confirmed that it is difficult to increase the concentration compared to the concentration.
[0060]
Also, pre-synthesized ABO_ThreeIn addition, rare earth element oxide, MO (M is at least one of Ni, Co and Mn), SiO₂It is difficult to obtain a state in which a rare earth element is in solid solution throughout the entire interior of crystal grains of the obtained dielectric ceramic. Has been confirmed.
[0061]
Also, pre-synthesized ABO_ThreeMO (M is at least one of Mg, Ca, Sr and Zn) and R₂O_Three(R is at least one rare earth element of Sc, Y, Gd, Dy, Ho, Er, Yb, Tb, Tm, and Lu), and BaCO_ThreeAnd / or TiO₂It is difficult to obtain a state in which a rare earth element is dissolved in the entire region of the obtained dielectric ceramic crystal particles even when using a method in which all of the above are mixed and heat-treated at once. Has been confirmed.
[0062]
Also, a compound containing Ba, a compound containing Ti, and a compound containing M (M is at least one of Mn, V, Cr, Co, Ni, Fe, Nb, Mo, Ta, and W). Ba (Ti_1-xM_x) O_Three(However, with respect to the main component that can be represented by x <1), a compound containing Mg, MnO, Dy₂O_Three, Li₂O, SiO₂, BaO and B₂O_ThreeEven when a method of mixing an additive component containing at least one selected from the above is used, a state in which Dy as a rare earth element is dissolved in the entire region of the obtained dielectric ceramic crystal particles is obtained. Has been confirmed to be difficult.
[0063]
Also, each powder containing Si, rare earth elements and alkaline earth elements is mixed, calcined and pulverized, and ABO_ThreePowder, MnO, Li₂O and SiO₂It is difficult to obtain a state in which a rare earth element is in solid solution throughout the entire interior of crystal grains of the obtained dielectric ceramic even when using a method of mixing an additive component containing at least one selected from It has been confirmed that.
[0064]
Next, an organic binder and a solvent are added to and mixed with the raw material powder for the dielectric ceramic obtained as described above, and a slurry is produced. Using this slurry, the dielectric ceramic layer 23 is prepared. A ceramic green sheet is formed.
[0065]
Next, a conductive paste film to be the internal electrode 24 or 25 is formed on the specific ceramic green sheet by, for example, screen printing. This conductive paste film contains a base metal such as nickel, nickel alloy, copper or copper alloy as a conductive component. The internal electrodes 24 and 25 may be formed by, for example, a vapor deposition method, a plating method, or the like, in addition to a printing method such as a screen printing method.
[0066]
Next, a plurality of ceramic green sheets on which the conductive paste film was formed as described above were laminated, and a ceramic green sheet on which no conductive paste film was formed was laminated so as to sandwich these ceramic green sheets, and then pressed. Then, the raw laminated body which should become the laminated body 22 is obtained by cutting as needed. In this raw laminate, the conductive paste film has its edge exposed at any end face.
[0067]
The raw laminate is then fired in a reducing atmosphere. As a result, a sintered laminate 22 as shown in FIG. 1 is obtained. In the laminate 22, the ceramic green sheet described above forms the dielectric ceramic layer 23, and the conductive paste film is the internal electrode 24 or 25. Configure.
[0068]
Next, external electrodes 28 and 29 are formed on the end faces 26 and 27 of the multilayer body 22 so as to be electrically connected to the exposed edges of the internal electrodes 24 and 25, respectively.
[0069]
As the material of the external electrodes 28 and 29, the same material as that of the internal electrodes 24 and 25 can be used, but silver, palladium, a silver-palladium alloy, etc. can also be used.₂O_Three-SiO₂-BaO glass, B₂O_Three-Li₂O-SiO₂What added glass frit which consists of -BaO type | system | group glass etc. can also be used. An appropriate material is selected in consideration of the use and place of use of the multilayer ceramic capacitor 21.
[0070]
The external electrodes 28 and 29 are usually formed by applying and baking a paste containing conductive metal powder as described above on the outer surface of the fired laminate 22. You may form by apply | coating on the outer surface of a raw laminated body, and baking simultaneously with the baking for obtaining the laminated body 22. FIG.
[0071]
Thereafter, nickel, copper, or the like is plated on the external electrodes 28 and 29 to form first plating layers 30 and 31. Then, the second plating layers 32 and 33 are formed on the first plating layers 30 and 31 by plating with solder, tin or the like. It should be noted that the formation of conductor layers such as plating layers 30 to 33 on the external electrodes 28 and 29 may be omitted depending on the use of the multilayer ceramic capacitor 21.
[0072]
As described above, the multilayer ceramic capacitor 21 is completed.
[0073]
It should be noted that Al, Zr, Fe, Hf, Na, N, or the like may be mixed as impurities in any stage of the production of the dielectric ceramic raw material powder or the other manufacturing process of the multilayer ceramic capacitor 21. The mixing of these impurities does not cause a problem in the electrical characteristics of the multilayer ceramic capacitor 21.
[0074]
Further, there is a possibility that Fe or the like may be mixed as impurities into the internal electrodes 24 and 25 at any stage of the manufacturing process of the multilayer ceramic capacitor 21, but this mixing of impurities also becomes a problem in terms of electrical characteristics. There is nothing.
[0075]
In the dielectric ceramic constituting the dielectric ceramic layer 23 provided in the multilayer ceramic capacitor 21 obtained in this way, as described above, with respect to the concentration distribution of the rare earth element, Ci_(n)/ Cs_AVE≧ 1/50, and Cc_(n)/ Cs_AVEThe number of crystal grains satisfying the condition <1 exceeds 70% of the total number of crystal grains. Therefore, the change in capacitance with time under application of DC voltage is small, the product of insulation resistance and capacitance (CR product) is high, and the accelerated life of insulation resistance at high temperature and high voltage is long. Even if the dielectric ceramic layer 23 is thinned, the reliability of the multilayer ceramic capacitor 21 can be improved.
[0076]
From the above, it can be seen that the concentration distribution of rare earth elements contained in the dielectric ceramic greatly affects the electrical characteristics of the dielectric ceramic. Therefore, from another viewpoint, the present invention can provide a dielectric ceramic evaluation method based on the rare earth element concentration distribution. This evaluation method makes it possible to easily and efficiently identify a dielectric ceramic that can provide the above-described characteristics when designing a dielectric ceramic used in a multilayer ceramic electronic component such as a multilayer ceramic capacitor. To do.
[0077]
Next, experimental examples carried out to confirm the effects of the present invention will be described.
[0078]
[Experimental example]
1. Production of raw material powder for dielectric ceramic
Table 1 shows the composition of the dielectric ceramic raw material powder according to each of the produced samples.
[0079]
[Table 1]

[0080]
In Table 1, the coefficient of each component indicates a molar ratio.
[0081]
Example 1
The first reactant is represented by the general formula ABO_ThreeAs a compound containing A when represented by_ThreeAs a compound containing B, TiO₂As a compound containing rare earth elements, Dy₂O_ThreePrepared. As the first additive component, Dy₂O_ThreeAs the second additive component, NiO, SiO₂And MnO were prepared.
[0082]
Next, BaCO_ThreeTiO₂And Dy₂O_ThreeAre weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0083]
Next, Dy as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained.
[0084]
Next, NiO, SiO as the second additive component₂And each powder of MnO was weighed so as to have the composition ratio shown in Table 1, and these were blended with the second reactant powder to obtain a dielectric ceramic raw material powder according to Example 1.
[0085]
(Example 2)
First reactant is ABO_ThreeAs a compound containing A when represented by_Three, SrCO_ThreeAnd CaCO_ThreeAs a compound containing B, TiO₂As a rare earth element, Gd₂O_ThreePrepared. As the first additive component, Ho₂O_ThreeAs a second additive component, SiO₂Prepared.
[0086]
Next, BaCO_Three, SrCO_Three, CaCO_ThreeTiO₂And Gd₂O_ThreeAre weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0087]
Next, Ho as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained.
[0088]
Next, SiO as the second additive component₂The powder was weighed so as to have the composition ratio shown in Table 1, and blended with the second reactant powder to obtain a dielectric ceramic raw material powder according to Example 2.
[0089]
(Example 3)
The first reactant is represented by the general formula ABO_ThreeAs a compound containing A when represented by_ThreeAnd CaCO_ThreeAs a compound containing B, TiO₂And ZrO₂As a compound containing rare earth elements, Dy₂O_ThreePrepared. As the first additive component, Ho₂O_ThreeAs the second additive component, CoO, MgO, SiO₂And MnO were prepared.
[0090]
Next, BaCO_Three, CaCO_ThreeTiO₂, ZrO₂And Dy₂O_ThreeAre weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0091]
Next, Ho as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained.
[0092]
Next, CoO, MgO, SiO as the second additive component₂And each powder of MnO was weighed so that it might become the composition ratio shown in Table 1, this was mix | blended with the 2nd reactant powder, and the raw material powder of the dielectric ceramic which concerns on Example 3 was obtained.
[0093]
Example 4
The first reactant is represented by the general formula ABO_ThreeAs a compound containing A when represented by_ThreeAnd CaCO_ThreeAs a compound containing B, TiO₂, ZrO₂And HfO₂Nd as a rare earth element₂O_ThreePrepared. As the first additive component, Y₂O_ThreeAs a second additive component, Cr₂O_Three, B₂O_Three, MnO, SiO₂And CaCO_ThreePrepared.
[0094]
Next, BaCO_Three, CaCO_ThreeTiO₂, ZrO₂, HfO₂And Nd₂O_ThreeAre weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0095]
Next, Y as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained.
[0096]
Next, Cr as the second additive component₂O_Three, B₂O_Three, MnO, SiO₂And CaCO_ThreeEach of these powders was weighed so as to have the composition ratio shown in Table 1, and these were blended with the second reactant powder to obtain a dielectric ceramic raw material powder according to Example 4.
[0097]
(Example 5)
The first reactant is represented by the general formula ABO_ThreeAs a compound containing A when represented by_ThreeAs a compound containing B, TiO₂As a compound containing rare earth elements, Ho₂O_ThreeAnd Nd₂O_ThreePrepared. As the first additive component, Yb₂O_ThreeAs a second additive component, SiO₂And MnO were prepared.
[0098]
Next, BaCO_ThreeTiO₂, Ho₂O_ThreeAnd Nd₂O_ThreeAre weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0099]
Next, Yb as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained.
[0100]
Next, SiO as the second additive component₂And each powder of MnO was weighed so as to have the composition ratio shown in Table 1, and these were blended with the second reactant powder to obtain a dielectric ceramic raw material powder according to Example 5.
[0101]
(Example 6)
The first reactant is represented by the general formula ABO_ThreeAs a compound containing A when represented by_ThreeAnd CaCO_ThreeAs a compound containing B, TiO₂And ZrO₂As a compound containing a rare earth element, CeO₂Prepared. As the first additive component, Dy₂O_ThreePrepared.
[0102]
Next, BaCO_Three, CaCO_ThreeTiO₂, ZrO₂And CeO₂Are weighed so as to have the composition ratio shown in the column of “first reactant” in Table 1, these are wet mixed by a ball mill, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized. A first reactant powder was obtained.
[0103]
Next, Dy as the first additive component₂O_ThreeAre weighed to the composition ratio shown in Table 1, added to the first reactant powder, wet-mixed with a ball mill, calcined at 1000 ° C. for 2 hours, and pulverized. A second reactant powder was obtained. The second reactant powder was used as a dielectric ceramic raw material powder according to Example 6.
[0104]
(Comparative Example 1)
To obtain the same composition as in Example 1, BaCO_ThreeTiO₂, Dy₂O_Three, NiO, SiO₂And the raw material powder of the dielectric ceramic which concerns on the comparative example 1 was obtained by mixing MnO with the composition ratio shown in Table 1 at once, calcining for 2 hours at the temperature of 1000 degreeC, and grind | pulverizing.
[0105]
(Comparative Example 2)
BaTiO_Three, SrCO_Three, CaCO_ThreeTiO₂, Ho₂O_Three, Gd₂O_ThreeAnd SiO₂Were mixed at once with the composition ratio shown in Table 1, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized to obtain a dielectric ceramic raw material powder according to Comparative Example 2.
[0106]
(Comparative Example 3)
ABO_ThreeAs previously synthesized (Ba_0.95Ca_0.04) (Ti_0.70Zr_0.30Mn_0.002) O_Three(Calcined product A), Ho as an additive component₂O_Three, Dy₂O_Three, CoO, MgO and SiO₂Were added at a composition ratio shown in Table 1, mixed, calcined at a temperature of 1000 ° C. for 2 hours (calcined product B), and pulverized to obtain a dielectric ceramic raw material powder according to Comparative Example 3.
[0107]
(Comparative Example 4)
ABO_ThreeAs previously synthesized (Ba_0.90Ca_0.10) (Ti_0.91Zr_0.08Hf_0.01) O_Three(Calcined product C) was prepared. CaCO_Three, Y₂O_Three, SiO₂And Nd₂O_ThreeWere mixed at a composition ratio shown in Table 1, calcined at a temperature of 1000 ° C. for 2 hours, and pulverized to obtain a calcined product D powder. Next, with the composition ratio shown in Table 1, the powder of the calcined product C is mixed with the powder of the calcined product D, and Cr is added as an additional component.₂O_Three, B₂O_ThreeAnd the raw material powder of the dielectric ceramic which concerns on the comparative example 4 was obtained by mixing MnO.
[0108]
2. Fabrication of multilayer ceramic capacitors
Next, by adding an organic solvent such as a polyvinyl butyral binder and ethanol to the raw material powders according to each of the above-described Examples 1 to 6 and Comparative Examples 1 to 4, and performing wet mixing using a ball mill, ceramics A rally was made.
[0109]
Next, the ceramic slurry was formed into a sheet shape with a thickness such that the thickness of the dielectric ceramic layer after firing was 2.5 μm by a doctor blade method to obtain a rectangular ceramic green sheet.
[0110]
Next, a conductive paste mainly composed of nickel was screen-printed on the ceramic green sheet to form a conductive paste film to be an internal electrode.
[0111]
Next, a plurality of ceramic green sheets including the ceramic green sheet on which the conductive paste film was formed were laminated so that the side from which the conductive paste film was drawn was staggered to obtain a raw laminate.
[0112]
Next, the raw laminate is heated to a temperature of 350 ° C. in a nitrogen atmosphere to burn the binder, and then an oxygen partial pressure of 10^-9-10^-12MPa H₂-N₂-H₂In a reducing atmosphere composed of O gas, firing was performed for 2 hours at a firing temperature shown in Table 2 to obtain a sintered laminate.
[0113]
Next, on both end faces of the laminate, B₂O_Three-Li₂O-SiO₂A conductive paste containing a BaO glass frit and silver as a conductive component was applied and baked at a temperature of 600 ° C. in a nitrogen atmosphere to form an external electrode electrically connected to the internal electrode.
[0114]
The outer dimensions of the multilayer ceramic capacitor thus obtained are 1.6 mm in width, 3.2 mm in length and 1.2 mm in thickness, and the thickness of the dielectric ceramic layer interposed between the internal electrodes is 2. It was 5 μm. The number of effective dielectric ceramic layers is 100, and the counter electrode area per layer is 2.1 mm.²Met.
[0115]
3. Measurement of electrical characteristics
Various electrical characteristics of the multilayer ceramic capacitors according to Examples 1 to 4 and Comparative Examples 1 to 5 thus obtained were measured.
[0116]
First, the dielectric constant ε and insulation resistance of each multilayer ceramic capacitor at room temperature were measured. In this case, the dielectric constant ε is a temperature of 25 ° C., 1 kHz, and 1 V._rmsThe measurement was performed under the following conditions. In addition, in order to measure the insulation resistance under an electric field strength of 6 kV / mm, a DC voltage of 15 V was applied for 2 minutes, the insulation resistance was measured at + 25 ° C., and capacitance (C) and insulation resistance (R) Product, that is, the CR product.
[0117]
In addition, a high temperature load life test was conducted. In the high temperature load life test, a voltage of 40 V was applied to 36 samples so that the electric field strength was 16 kV / mm at a temperature of 175 ° C., and the change over time of the insulation resistance was obtained. In addition, as the high temperature load life, the average life time was obtained by taking the time when the insulation resistance value of each sample was 200 kΩ or less as the life time.
[0118]
Moreover, the time-dependent change of the electrostatic capacitance under DC voltage application was calculated | required. Capacitance change with time is 125 ℃, 1kHz, 1V_rmsThe capacity change after 60 hours was measured under the condition of applying a DC voltage of 4 V, and the capacity change rate, that is, the DC load change rate with time, was determined based on the electrostatic capacity at 125 ° C. immediately after the DC voltage application.
[0119]
Table 2 shows the dielectric constant ε, CR product, high temperature load life, and DC load change rate with time.
[0120]
[Table 2]

[0121]
4). Investigation of rare earth element concentration distribution
A multilayer ceramic capacitor according to each of Examples 1 to 6 and Comparative Examples 1 to 4 is polished into a thin piece, and a dielectric ceramic layer is formed by energy dispersive X-ray spectroscopy (EDX) attached to a transmission electron microscope The concentration of rare earth elements inside the dielectric ceramic crystal grains was analyzed. The specific measurement was performed as follows for the main component crystal particles observed in a field of view of an arbitrary width.
[0122]
FIG. 2 is for explaining this analysis method. FIG. 2 shows a certain crystal particle 15.
[0123]
When analyzing the concentration of the rare earth element in the vicinity of the surface of the crystal particle 15, on each of the eight half lines connecting an arbitrary point obtained by dividing the outer periphery of the crystal particle 15 into approximately eight equal parts and the center of the crystal particle 15. A point located in the region near the surface of the crystal particle 15 was designated as an analysis point A. At this time, in order to obtain an arbitrary point obtained by dividing the outer periphery of the crystal particle 15 into approximately eight equal parts, if necessary, the outer periphery length of the crystal particle 15 is calculated using an appropriate approximation, and is divided into approximately eight equal parts. It may be.
[0124]
When analyzing the concentration of the rare earth element at an arbitrary point in the crystal particle 15 and the concentration of the rare earth element at an arbitrary point in the central portion of the crystal particle 15, an arbitrary point obtained by dividing the outer periphery of the crystal particle 15 into approximately four equal parts is calculated. First, the analysis points B1, B2, B3 and B4 were determined. Also in this case, if necessary, the analysis points B1 to B4 may be determined by calculating the outer peripheral length of the crystal particle 15 using an appropriate approximation and dividing it into approximately four equal parts. In addition, four line segments connecting the analysis points B1 to B4 and the center of the crystal particle 15 were determined, the midpoints of the respective line segments were obtained, and these midpoints were set as analysis points B5, B6, B7, and B8. Further, midpoints between the analysis points B5 to B8 and the center of the crystal particle 15 were obtained, and these midpoints were set as analysis points B9, B10, B11, and B12. Furthermore, the center of the crystal particle 15 was set as the analysis point B13.
[0125]
In order to analyze the concentration of the rare earth element at an arbitrary point in the crystal particle 15, the analysis points B1 to B13 determined as described above are used to analyze the concentration of the rare earth element at an arbitrary point in the center of the crystal particle 15. Therefore, analysis points B5 to B13 were used.
[0126]
In any concentration analysis described above, 20 or more crystal particles 15 were performed. A 2 nm probe was used as an electron beam in the analysis.
[0127]
Table 3 shows a part of the results obtained by the concentration analysis described above. That is, Table 3 shows three crystal particles in Example 1 (patterns A, B and C), one crystal particle in Comparative Example 1 (pattern D), and one crystal particle in Comparative Example 3 (pattern E). The average concentration at analysis point A and the concentration at each of analysis points B1 to B13 are shown. These concentrations are ABO_ThreeThe number of moles of rare earth elements relative to 100 moles of the B site component is shown as a unit.
[0128]
[Table 3]

[0129]
As shown in Table 3, in Example 1, in any of the patterns A, B, and C, the average concentration at the analysis point A, that is, Cs_AVEAnd concentrations at analysis points B1 to B13, that is, Ci_(n)And the concentration at analysis points B5 to B13, that is, Cc_(n)Ci_(n)/ Cs_AVE≧ 1/50, and Cc_(n)/ Cs_AVEThe condition <1 is satisfied.
[0130]
On the other hand, in the pattern D of Comparative Example 1, Ci_(n)/ Cs_AVESatisfies the condition> 1/50, but Cc_(n)/ Cs_AVEThe condition <1 is not satisfied.
[0131]
In the pattern E of Comparative Example 3, Cc_(n)/ Cs_AVE<1 is satisfied, but Ci_(n)/ Cs_AVEThe condition of ≧ 1/50 is not satisfied.
[0132]
In Table 4, after obtaining the analysis results as shown in Table 3, for each of Examples 1 to 6 and Comparative Examples 1 to 4, Ci_(n)/ Cs_AVEThe ratio [%] of the number of crystal grains satisfying the condition of ≧ 1/50 to the total number of crystal grains [%] and Cc_(n)/ Cs_AVEThe result of calculating the ratio [%] of the number of crystal grains satisfying the condition <1 to the total number of crystal grains is shown.
[0133]
[Table 4]

[0134]
As can be seen from Table 4, according to Examples 1 to 6, all were Ci._(n)/ Cs_AVEThe proportion of crystal grains with ≧ 1/50 exceeds 70%, and Cc_(n)/ Cs_AVEThe ratio of <1 crystal grains is also over 70%.
[0135]
On the other hand, in Comparative Examples 1 and 2, Ci_(n)/ Cs_AVEThe proportion of crystal grains with ≧ 1/50 exceeds 70%, but Cc_(n)/ Cs_AVEThe ratio of the crystal grains <1 is 70% or less.
[0136]
In Comparative Examples 3 and 4, Cc_(n)/ Cs_AVEThe proportion of crystal grains <1 exceeds 70%, but Ci_(n)/ Cs_AVEThe ratio of crystal grains satisfying ≧ 1/50 is 70% or less.
[0137]
5. Comprehensive evaluation
In Table 2 above, when Example 1 and Comparative Example 1 in which the compositions of the dielectric ceramics are the same are compared, the dielectric constant, the CR product and the high temperature load life are not substantially different. The rate of change with time of DC load was −1.2% in Example 1, which was significantly improved compared to −10.2% in Comparative Example 1.
[0138]
Moreover, about Examples 2-6, DC load time-dependent change rate was significantly improved with respect to Comparative Example 2, and compared with Comparative Examples 3 and 4, high temperature load life and DC load time-dependent change rate were greatly improved. You can see that it has improved.
[0139]
  When considering the results shown in Table 2 and the results shown in Table 4 together, Ci_(n)/ Cs_AVE≧ 1/50The number of crystal grains satisfying the above condition exceeds 70% of the total number of crystal grains, andCc_(n)/ Cs_AVEAccording to Examples 1 to 6, the number of crystal grains satisfying the condition of <1 exceeds 70% of the total number of crystal grains, the rate of change with time of DC load is small, the CR product is high, the high temperature load life is long, Therefore, it can be seen that a multilayer ceramic capacitor having excellent reliability can be obtained even if the dielectric ceramic layer is made thinner.
[0140]
【The invention's effect】
  As described above, according to the dielectric ceramic according to the present invention, the general formula ABO_Three(A is at least one containing Ba of Ba, Ca and Sr, and B is at least one containing Ti of Ti, Zr and Hf), and La , Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and an additive component containing at least one rare earth element of Y, The average concentration of rare earth elements in the vicinity of the surface of the crystal grains is expressed as Cs_AVEAnd the concentration of the rare earth element at an arbitrary point in the crystal grain is Ci_(n)And the concentration of the rare earth element at an arbitrary point in the center of the crystal grain is Cc._(n)In terms of the concentration distribution of rare earth elements, Ci_(n)/ Cs_AVE≧ 1/50The number of crystal grains satisfying the above condition exceeds 70% of the total number of crystal grains, andCc_(n)/ Cs_AVE<The number of crystal grains satisfying the condition of 1 exceeds 70% of the total number of crystal grains. When a multilayer ceramic electronic component such as a multilayer ceramic capacitor is configured using this, electrostatic capacitance under a DC voltage is applied. The change with time of capacitance is small, the product of insulation resistance and capacitance (CR product) is high, and the accelerated life of insulation resistance at high temperature and high voltage can be extended.
[0141]
Therefore, if the dielectric ceramic layer of the multilayer ceramic electronic component is configured with this dielectric ceramic, it is possible to obtain a multilayer ceramic electronic component that can maintain excellent reliability even when the dielectric ceramic layer is thinned. it can.
[0142]
Therefore, when applied to a multilayer ceramic capacitor, it is possible to reduce the size and increase the capacity of the multilayer ceramic capacitor by thinning the dielectric ceramic layer, and even if the dielectric ceramic layer is thinned, the multilayer ceramic capacitor There is no need to reduce the rated voltage. As a result, for example, the thickness of the dielectric ceramic layer can be reduced to about 1 μm without any problem.
[0143]
According to the dielectric ceramic manufacturing method of the present invention, the general formula ABO_ThreeA step of obtaining a first reactant powder by mixing, reacting and pulverizing a compound containing A and a compound containing B constituting the main component represented by Mixing the first reactant powder and the remainder of the compound containing the rare earth element, reacting, and pulverizing to obtain a second reactant powder, and firing the second reactant powder; Therefore, it is possible to obtain the concentration distribution of the rare earth element as described above more easily than in the case of employing a method in which all of these constituent elements are mixed and reacted at once.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 21 according to an embodiment of the present invention.
FIG. 2 is an enlarged view of the crystal particle 15 schematically showing an example of analysis points employed in the analysis of the concentration distribution of the rare earth element in a certain crystal particle 15;
[Explanation of symbols]
A, B1-B13 Analysis point
15 crystal grains
21 Multilayer ceramic capacitors
22 Laminate
23 Dielectric ceramic layer
24, 25 Internal electrode
28, 29 External electrode

Claims (6)

It is represented mainly by the general formula ABO ₃ (A is at least one containing Ba of Ba, Ca and Sr, and B is at least one containing Ti of Ti, Zr and Hf). Ingredients,
La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and an additive component containing at least one rare earth element selected from Y, And
Using the energy dispersive X-ray spectroscopy attached to the transmission electron microscope, the diameter of the probe of the electron beam was set to 2 nm, and the rare earth element concentration on the cross-sectional polished surface of the dielectric ceramic crystal particles was analyzed.
Rare earths at eight points on each of eight half lines connecting an arbitrary point obtained by dividing the outer periphery of the crystal particle into approximately eight equal parts and the center of the crystal particle, and in a region near the surface of the crystal particle Let Cs _{AVE be} the average concentration of elements,
First, an arbitrary point obtained by dividing the outer periphery of the crystal grain into approximately four equal parts is determined, and this is set as analysis points B1, B2, B3, and B4. Next, four points connecting the analysis points B1 to B4 and the center of the crystal grain are connected. Decide the line segment, find the midpoint of each line segment, set these midpoints as analysis points B5, B6, B7 and B8, then find the midpoint between the analysis points B5 to B8 and the center of the crystal grain, In the case where the midpoint is the analysis points B9, B10, B11 and B12, and the center of the crystal particle is the analysis point B13,
Each concentration of the rare earth element at 13 points of the analysis points B1 to B13 in the crystal particle is Ci _(n) ,
When each concentration of the rare earth element at 9 points of the analysis points B5 to B13 at the center of the crystal grain is Cc _(n) ,
Regarding the concentration distribution of rare earth elements,
The number of crystal grains satisfying the condition of Ci _(n) / Cs _AVE ≧ 1/50 exceeds 70% of the total number of crystal grains, and the number of crystal grains satisfying the condition of Cc _(n) / Cs _AVE <1 More than 70% of the total number of crystal grains,
Dielectric ceramic. The dielectric ceramic according to claim 1, further comprising at least one element selected from Ni, Co, Fe, Cr, Mn, Si, Mg, V, B (boron), Ca, and Al. A method for producing a dielectric ceramic according to claim 1, comprising:
The first reactant powder is obtained by mixing, reacting and pulverizing the compound containing A and the compound containing B constituting the main component represented by the general formula ABO ₃ and a part of the compound containing the rare earth element. Obtaining
Mixing the first reactant powder and the remainder of the compound containing the rare earth element, reacting, and grinding to obtain a second reactant powder;
And a step of firing the second reactant powder. A method for manufacturing a dielectric ceramic according to claim 2, comprising:
The first reactant powder is obtained by mixing, reacting and pulverizing the compound containing A and the compound containing B constituting the main component represented by the general formula ABO ₃ and a part of the compound containing the rare earth element. Obtaining
Mixing the first reactant powder and the remainder of the compound containing the rare earth element, reacting, and grinding to obtain a second reactant powder;
A mixed powder comprising the second reactant powder and a compound powder containing at least one element selected from Ni, Co, Fe, Cr, Mn, Si, Mg, V, B (boron), Ca and Al. A method for producing a dielectric ceramic, comprising the step of firing. A multilayer ceramic electronic component comprising a laminate, comprising a plurality of laminated dielectric ceramic layers and an internal electrode formed along a specific interface between the plurality of dielectric ceramic layers,
A multilayer ceramic electronic component, wherein the dielectric ceramic layer is made of the dielectric ceramic according to claim 1. The apparatus further includes first and second external electrodes formed on an outer surface of the multilayer body, and the plurality of internal electrodes are formed in a state of overlapping each other in the stacking direction of the multilayer body. The one electrically connected to the first external electrode and the one electrically connected to the second external electrode are alternately arranged in the stacking direction, thereby forming a multilayer ceramic capacitor. The multilayer ceramic electronic component according to claim 5.

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