JP4254310B2 - Piezoelectric material and method for manufacturing multilayer piezoelectric element - Google Patents
Piezoelectric material and method for manufacturing multilayer piezoelectric element Download PDFInfo
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Abstract
Description
【０００１】
【技術分野】
本発明は，Ｍｎを含むチタン酸ジルコン酸鉛系圧電材料及びこの圧電材料を用いた積層型圧電体素子の製造方法に関する。
【０００２】
【従来技術】
従来，アクチュエータ用積層型圧電体素子に使用する圧電材料として，ＰｂＺｒＯ3−ＰｂＴｉＯ3−Ｐｂ（Ｙ1/2Ｎｂ1/2）Ｏ3系圧電材料において，Ｐｂの一部をＳｒで置換し，かつＳｂ，Ｎｂ，Ｗ，Ｌａ，Ｔａ，Ｂｉ，Ｎｄ，Ｐｒから選ばれた少なくとも一つの元素とＭｎを置換した組成の化合物からなるものが知られている。
【０００３】
【特許文献１】
特開昭６２−４６９６１号公報
【０００４】
【解決しようとする課題】
しかしながら，上記圧電材料を用いて作製した積層型圧電体素子の変位量は，アクチュエータの用途によっては必ずしも十分でない場合があった。
また，上記圧電材料は，ドナー元素であるＳｂ，Ｎｂ，Ｗ等と共にアクセプタ元素であるＭｎを添加しているが，必ずしもドナー元素とアクセプタ元素の比率が適正とならない場合がある。このため，上記圧電材料から作製した積層型圧電体素子は，誘電特性の経時変化が大きく，特性が安定しないという問題があった。
【０００５】
上記問題点において，チタン酸ジルコン酸鉛系圧電材料にＭｎを添加することは，誘電損失を低下させ，機械的品質係数を向上させるため，エネルギーの損失に伴う発熱の抑制につながることが知られている。
このため，チタン酸ジルコン酸鉛系圧電材料にＭｎを無添加とすることによって誘電特性の経時変化を抑制することが可能であると思われるが，Ｍｎによる発熱抑制効果を犠牲にしなければならず，現実的ではない。
従って，Ｍｎを含有するチタン酸ジルコン酸鉛系圧電材料において，何らかの誘電特性安定対策を講じる必要があった。
【０００６】
本発明は，かかる従来の問題点に鑑みてなされたもので，変位量が大で，誘電特性が安定した積層型圧電体素子に適用可能な圧電材料とこの圧電材料を用いた積層型圧電体素子の製造方法を提供するものである。
【０００７】
【課題の解決手段】
第１の発明は，化学式（Ｐｂ1-xＭａx）1+d（Ｚｒ1-yＴｉy）1-p-q（Ｙ1/2Ｎｂ1/2）p（Ｍｎ1-z1-z2Ｍｂz1Ｍｃz2）qＯ3+dで表される圧電材料（ただしＭａは，Ｂａ，Ｃａ，Ｓｒから選択する少なくとも１種以上の元素であって，ＢａまたはＣａのいずれかを含む。ＭｂはＮｂ，Ｓｂ，Ｔａから選択する少なくとも１種以上の元素。ＭｃはＷ，Ｍｏから選択する少なくとも１種以上の元素。）であって，
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ１−ｚ２）≦０．０２，
０．７≦（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）≦１．５（ただしｚ１，ｚ２は０または正の数で，少なくとも一方は０でない。）
であることを特徴とする圧電材料にある（請求項１）。
【０００８】
第２の発明は，化学式（Ｐｂ1-xＭａx）1+d（Ｚｒ1-yＴｉy）1-p-q（Ｙ1/2Ｎｂ1/2）p（Ｍｎ1-z2Ｗz2）qＯ3+dで表される圧電材料（ただしＭａは，Ｂａ，Ｃａ，Ｓｒから選択する少なくとも１種以上の元素であって，Ｂａを含む。）であって，
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．２５≦ｚ２≦０．４０，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ２）≦０．０２であることを特徴とする圧電材料にある（請求項２）。
【０００９】
第１，第２の発明の作用効果につき説明する。
従来技術にかかる材料では，圧電材料中のＰｂの一部を置換する元素がＰｂとほぼ同じイオン半径のＳｒのみであり，ペロブスカイト結晶格子に与える歪みが十分でなかったのではないかという点に着目し，本発明にかかる圧電材料では，Ｐｂの一部を置換する元素として，少なくともイオン半径がＰｂより大きいＢａまたはＰｂよりイオン半径が小さいＣａを選択した。すなわち，Ｐｂの１２配位イオン半径は１．４９Åで，Ｂａ，Ｃａ，Ｓｒの１２配位イオン半径はそれぞれ１．６１Å，１．３４Å，１．４４Åである
【００１０】
従って，第１，第２の発明にかかる圧電材料は，ペロブスカイト結晶格子内に従来より大きな歪みが導入されるため，より大きな圧電効果を発揮する。
そのため，第１，第２の発明にかかる材料から積層型圧電体素子を作製した場合は，大きな変位量を発揮することができる。
【００１１】
また，従来技術にかかる材料では，ドナー元素とアクセプタ元素の比率が必ずしも適正でなく，これらの原子価の補償が不十分なため生成する酸素欠陥が，誘電特性の経時変化に悪影響を及ぼしているのではないかという点に着目し，本発明にかかる圧電材料では，ドナー元素であるＳｂ，Ｎｂ，Ｗ，Ｍｏとアクセプタ元素であるＭｎの比率を適正範囲に設定した。これにより，圧電材料中の結晶格子における酸素欠陥の生成量を低減させて，誘電特性の経時変化を抑制することができる。
【００１２】
また，第３の発明は，圧電層と内部電極層とを交互に積層してなる積層型圧電体素子を製造するに当たり，
請求項１または２にかかる圧電材料のＢＥＴ比表面積が１．６〜８ｍ2／ｇとなるよう調整すると共に化学式（１−β−γ）ＰｂＯ・βＷＯ3・γＭｏＯ3（０．００５≦β＋γ≦０．２７，ただしβ≧０，γ≧０。）で表される助剤酸化物を添加して混合物を作製し，
上記混合物を成形して未焼シートを作製し，該未焼シートに内部電極層用の電極材料を含有するペーストからなる印刷層を設け，
その後上記印刷層を設けた未焼シートを複数枚積層して未焼積層体となし，該未焼積層体を焼成することを特徴とする積層型圧電体素子の製造方法にある（請求項４）。
【００１３】
第３の発明にかかる製造方法にて作製した積層型圧電体素子は，第１や第２の発明にかかる圧電材料からなる圧電層を有するため，変位量が大きく，誘電特性の経時変化が抑制された圧電層を有する。
また，圧電層は上述した助剤酸化物を含んでおり，助剤酸化物の存在が圧電層における母材となる第１や第２の発明にかかる圧電材料の焼結状態に影響を与えて，未焼積層体の低温焼結が可能となる。
【００１４】
更に，第３の発明では，圧電材料の比表面積を上述した範囲内に制御する。これにより，圧電材料の周囲に助剤酸化物を均一に存在させて，圧電層における液相焼結を可能とする。従って，第１や第２の発明にかかる圧電材料の性能を生かした状態でより低温の焼結を実現することができる。
低温焼結が可能となれば，内部電極層としてより安価な電極材料（Ｃｕ，Ａｇ，Ｐｄ含有量が１０％以下のＡｇ−Ｐｄ合金等）を用いることができ，材料コストの低減を図ることができる。
【００１５】
以上，本発明によれば，変位量が大で，誘電特性が安定した積層型圧電体素子に適用可能な圧電材料とこの圧電材料を用いた積層型圧電体素子の製造方法を提供することができる。
【００１６】
【発明の実施の形態】
第１の発明において，ｄ＜−０．０２である場合は焼結温度が高くなるおそれがある。ｄ＞０．０４である場合は変位性能が低下するおそれがある。
ｘ＜０．０１である場合は変位性能が低下するおそれがある。ｘ＞０．２０である場合は圧電材料のキュリー温度が低下し（概ね２００℃以下），使用可能な温度範囲が狭く，実用性に欠ける圧電材料となってしまうおそれがある。
ｙ＜０．４０，ｙ＞０．５５である場合は変位性能が低下するおそれがある。
ｐ＜０．００５，ｐ＞０．０５である場合は変位性能が低下するおそれがある。更にｐ＞０．０５である場合は焼結温度が高くなるおそれがある。
【００１７】
ｑ・（１−ｚ１−ｚ２）＜０．００１である場合はＭｎ添加による性能向上効果（誘電損失を低下させ，機械的品質係数の向上）が得難くなるおそれがある。また，ｑ・（１−ｚ１−ｚ２）＞０．０２である場合は変位性能が低下するおそれがある。
（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）＜０．７である場合は変位性能が低下するおそれがある。（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）＞１．５である場合は誘電特性の経時変化が大きくなるおそれがある。
【００１８】
また，第１の発明にかかる圧電材料の化学式の「Ｐｂ1-xＭａx」にかかる項は圧電材料の結晶格子（ペロブスカイト構造である）でＰｂがＭａという元素で置換されていることを意味するが，Ｍａとして複数の元素を選択した場合，複数の元素を合わせた合計のモル分率がｘとなる。
すなわち，ＭａがＢａ，Ｓｒ，Ｃａからなる場合は，「Ｐｂ1-xＢａlＳｒmＣａn」でｌ＋ｍ＋ｎ＝ｘとなる。化学式の他の項で複数の元素を選択する場合についても同様である。
【００１９】
また，Ｍａは，Ｂａ，Ｃａ，Ｓｒから選択する少なくとも１種以上の元素であって，ＢａまたはＣａのいずれかを含むため，Ｍａとして選択可能な元素の組み合わせは，Ｂａのみ，Ｃａのみ，Ｂａ及びＣａ，Ｂａ及びＳｒ，Ｃａ及びＳｒ，ＢａとＣａとＳｒである。Ｓｒ単独をＭａの元素としても本発明にかかる効果は得られない。
【００２０】
第２の発明において，ｚ２＜０．２５である場合は誘電特性の経時変化が大きくなるおそれがある。ｚ２＞０．４である場合は変位性能が低下するおそれがある。
ｑ・（１−ｚ２）＜０．００１である場合はＭｎ添加による性能向上効果（誘電損失を低下させ，機械的品質係数の向上）が得難くなるおそれがある。また，ｑ・（１−ｚ２）＞０．０２である場合は変位性能が低下するおそれがある。
その他のパラメータについては第１の発明と同様である。
【００２１】
また，第１の発明又は第２の発明の圧電材料に，化学式（１−β−γ）ＰｂＯ・βＷＯ3・γＭｏＯ3（０．００５≦β＋γ≦０．２７，ただしβ≧０，γ≧０。）で表される助剤酸化物を添加してなる圧電材料であって，上記助剤酸化物の圧電材料１００重量％に対する添加量αは，０．０５〜５重量％（外％）であることが好ましい（請求項３）。
【００２２】
ここで，助剤酸化物は，上記化学式となるように配合したＰｂ酸化物とＷ酸化物および／またはMｏ酸化物を固溶させた複合酸化物のほか，上記化学式となるように配合したＰｂ酸化物とＷ酸化物および／またはMｏ酸化物の混合物や該混合物を部分的に固溶させたものであっても差し支えない。助剤酸化物中にＰｂ酸化物とＷ酸化物および／またはMｏ酸化物が残っていたとしても，これらは焼結の過程で固溶が進行し，助剤酸化物として機能するからである。
【００２３】
請求項３にかかる助剤酸化物を用いることで，第１，第２の発明にかかる圧電材料の焼成温度を下げて，より安価な電極材料（Ｃｕ，Ａｇ，Ｐｄ含有量が１０％以下のＡｇ−Ｐｄ合金等）を用いて積層型圧電体素子を作製することができる。よってコスト安な積層型圧電体素子の製造に向く圧電材料を得ることができる。
β＋γ＜０．００５，β＋γ＞０．２７である場合は，焼成温度低下の効果が得難くなるおそれがある。
α＜０．０５重量％である場合は，焼結温度低下効果が得難くなるおそれがある。α＞５重量％は変位性能が低下するおそれがある。変位に寄与しない助剤酸化物が圧電材料中に増えるためである。
【００２４】
また，第３の発明は，第１または第２の発明にかかる圧電材料を用い，請求項３にかかる助剤酸化物を混ぜて作製した圧電層を有する積層型圧電体素子を作製する方法である。
更に，第３の発明では圧電材料が所定の表面積となるよう調整するが，仮にＢＥＴ比表面積が１．６ｍ2／ｇ未満である場合は圧電材料の焼結温度が高くなるおそれがある。８ｍ2／ｇより大きい場合は，助剤酸化物の圧電材料への固溶が進行しすぎるために変位性能が低下するおそれがある。
その他圧電材料や助剤酸化物については上述した第１，第２の発明にかかる記載と同様である。
【００２５】
上記ＢＥＴ比表面積とはＢＥＴ法で測定した比表面積である。
比表面積の測定法に材料の表面に吸着占有面積の判った分子を液体窒素の温度で吸着させ，その量から試料の比表面積を求める方法があり，特に不活性気体の低温低湿物理吸着による測定をＢＥＴ法という。
【００２６】
第３の発明にかかる製造方法では，予め請求項１や２にかかる組成からなる圧電材料を作製して，そこに別途上述した組成の助剤酸化物を混ぜている。
圧電材料のＢＥＴ比表面積を上述した範囲とするための処理は，圧電材料単独の状態で行ってもよいし，助剤酸化物と混合した後に行ってもよい。
【００２７】
すなわち，まず所定の組成比となるように出発原料を秤量し，該出発原料を仮焼した後，所定のＢＥＴ比表面積となるまで粉砕する。その後，助剤酸化物を加えて混合物となす。
または，出発原料を仮焼し，その後助剤酸化物を加えて粉砕する。
【００２８】
また，出発原料を仮焼，粉砕して得られた圧電材料の微粉は，助剤酸化物との反応性が高いため，助剤酸化物の圧電材料への固溶を極力抑えるために，圧電材料を粉砕した後，４００〜７００℃で予焼して得られた粉に，助剤酸化物，溶剤，バインダー，可塑剤，分散剤を添加して成形することもできる。
【００２９】
また，本発明における積層型圧電体素子の製造方法において，圧電材料が所定のＢＥＴ比表面積となるように調整する際は，ボールミルや媒体攪拌ミル等を用いて粉砕し，粒径を微粒化することによって行うことが好ましい。
【００３０】
また，圧電材料と助剤酸化物からなる混合物を成形する際は，該混合物にバインダー等を加えたスラリーを調製し，通常知られたドクターブレード法によって未焼シートを作製することができる。その後，未焼シートに電極材料を含有するペーストを印刷して印刷層を設ける。
上記印刷層を設けた未焼シートを所望の枚数積層して，圧着し，未焼積層体を作製する。この未焼積層体を脱脂，焼成し，その後内部電極層と電気的に導通させる側面電極等を設けた後，分極処理などを施すことで，積層型圧電体素子を得ることができる。
【００３１】
また，ここで記載した手順は積層型圧電体素子でよく知られた製造方法であり，これ以外の方法で圧電体素子を作製する場合に関して第３の発明を適用することもできる。
なお，内部電極層は，後述する実施例１で示した部分電極構成（積層方向に直交する断面での面積が圧電層よりも小さい。）の他，全面電極構成（圧電層と略等しい面積を備える。）として作製することもできる。
【００３２】
また，上記積層型圧電体素子は，誘電特性が安定した圧電材料からなる圧電層を持つ。誘電特性が安定することで，変位の過渡特性のばらつきが小さくなる。そのため，電圧を印加した際の圧電層の伸び速度，すなわち圧電アクチュエータとして用いた場合，アクチュエータの伸び速度が略一定となる。
【００３３】
このような圧電アクチュエータを自動車エンジン等の内燃機関における燃料噴射用のインジェクタの駆動源として使用することで，燃料の噴射量のばらつきを減らして，燃焼状態制御をより精密に行うことができる。この点で，第１，第２の発明にかかる圧電材料は，燃料噴射インジェクタの駆動源の圧電アクチュエータの圧電層の構成材料として好適である。第３の発明で製造した積層型圧電体素子も燃料噴射インジェクタの駆動源として好適である。
【００３４】
【実施例】
以下に図面を用いて本発明の実施例について説明する。
（実施例１）
本例では，本発明にかかる圧電材料から積層型圧電体素子を作製し，その性能を評価する。
本例にかかる圧電材料は，化学式（Ｐｂ1-xＭａx）1+d（Ｚｒ1-yＴｉy）1-p-q（Ｙ1/2Ｎｂ1/2）p（Ｍｎ1-z1-z2Ｍｂz1Ｍｃz2）qＯ3+dで表される圧電材料（ただしＭａは，Ｂａ，Ｃａ，Ｓｒから選択する少なくとも１種以上の元素であって，ＢａまたはＣａのいずれかを含む。ＭｂはＮｂ，Ｓｂ，Ｔａから選択する少なくとも１種以上の元素。ＭｃはＷ，Ｍｏから選択する少なくとも１種以上の元素。）であって，
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ１−ｚ２）≦０．０２，
０．７≦（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）≦１．５
（ただしｚ１，ｚ２は０または正の数で，少なくとも一方は０でない）である。
【００３５】
または，本例にかかる圧電材料は，化学式（Ｐｂ1-xＭａx）1+d（Ｚｒ1-yＴｉy）1-p-q（Ｙ1/2Ｎｂ1/2）p（Ｍｎ1-z2Ｗz2）qＯ3+dで表される圧電材料（ただしＭａは，Ｂａ，Ｃａ，Ｓｒから選択する少なくとも１種以上の元素であって，Ｂａを含む。）であって，
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．２５≦ｚ２≦０．４０，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ２）≦０．０２である。
【００３６】
以下，詳細に説明する。
本例は，本発明にかかる試料１〜１４と比較試料Ｃ１〜Ｃ３とを用いて本発明にかかる圧電材料や本発明にかかる製造方法から得た積層型圧電体素子の性能について評価する。
すなわち，試料１〜１４は，化学式（Ｐｂ1-xＭａx）1+d（Ｚｒ1-yＴｉy）1-p-q（Ｙ1/2Ｎｂ1/2）p（Ｍｎ1-z1-z2Ｍｂz1Ｍｃz2）qＯ3+dの置換元素であるＭａ，Ｍｂ，Ｍｃの種類と組成比（ｘ，ｙ，ｚ１，ｚ２，ｐ，ｑ，ｄ）を表１のとおりに変更して得た圧電材料である。
【００３７】
比較試料Ｃ１は，（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）が０．５４であり本発明外の組成である。比較試料Ｃ２はＭｂ，Ｍｃにかかる元素を含んでおらず，本発明外の組成である。比較試料Ｃ３は（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）が２であり本発明外の組成である。
これらの圧電材料から図１〜図３に示すごとき積層型圧電体素子１を作製し，圧電特性を調べた。
【００３８】
ここで作製した積層型圧電体素子１は，図１〜図３に示すごとく，圧電層１１の層間に内部電極層２１，２２を交互に正負となるように作製してなる。図２（ａ）に示すごとく，一方の内部電極層２１は圧電層１１に対し控え部１１９を残して，図１に示すごとく，一方の側面１０１に露出するように配設され，他方の内部電極層２２は他方の側面１０２に露出するように配設されている。
そして，圧電体素子１の側面１０１，１０２には，露出した内部電極層２１，２２の端部を導通させるように側面電極３１が設けてなる。
また，圧電体素子１の積層方向の中央部分は内部電極層２１，２２に通電することで伸張する駆動部１１１であり，該駆動部１１１を挟持するセラミック層１２は，少なくとも一方の面は，図２（ｂ）に示すごとく，内部電極層２１，２２と接していなくて，よって内部電極層２１，２２に通電しても伸張しないダミー部１１２となる。
【００３９】
次に，圧電材料と積層型圧電体素子の具体的な製造方法について説明する。
圧電材料の各構成原子を含む出発原料としてＰｂＯ，ＳｒＣＯ3，ＢａＣＯ3，ＣａＣＯ3，ＺｒＯ2，ＴｉＯ2，Ｙ2Ｏ3，Ｎｂ2Ｏ5，Ｓｂ2Ｏ3，ＷＯ3，ＭｏＯ3を使用し，表１に示す所望の組成となるよう，すなわち，目的組成における各構成原子の比と出発原料における各構成原子の比が同じになるように秤量した。
【００４０】
秤量した原料を湿式混合し，乾燥後８００℃で５時間仮焼し，これを媒体攪拌ミルにより湿式粉砕し，ＢＥＴ比表面積が２．５〜３ｍ2／ｇの粉砕物を得た。これに溶剤，バインダー，可塑剤，分散剤を加えてボールミルにより混合してスラリーを得た。
ドクターブレード装置を用いて，上記スラリーから厚み１００μｍの未焼シートを成形した。この未焼シートに銀／パラジウム＝７／３（重量比）からなる電極材料を含んだ導電ペーストを印刷して内部電極層用の印刷層を設けた。
【００４１】
上記印刷層を設けた未焼シートを図３に示すように２１枚積層し，更に，上下端に内部電極層用の印刷層がない単なる未焼シートを載置し，熱圧着を行なって未焼積層体を作製した。
次いで，未焼積層体を電気炉において脱脂し，その後８５０℃〜１１００℃で焼成し，全面研磨して７×７×１．８ｍｍの積層焼結体を得た。
更に，上記積層焼結体の側面に内部電極層を一層おきに導通させるため一対の側面電極を焼き付けた後，１３０℃，２ｋＶ／ｍｍの印加電界で３０分間分極し，４８時間室温にて放置した。
以上により，積層型圧電体素子を得た。
【００４２】
積層型圧電体素子の性能測定について説明する。
得られた積層型圧電体素子のインピーダンス−周波数特性をインピーダンスアナライザーにより測定し，基本振動における共振周波数ｆｒと反共振周波数ｆａとの差を求め，これが飽和し始める焼成温度を表２に示した。
【００４３】
そして，上記温度において焼成した各積層型圧電体素子の変位量と静電容量の経時変化をそれぞれ調べた。
変位量の測定法については，まず，積層型圧電体素子に５００Ｎの荷重をかけながら１５０Ｖの電圧を印加し，その時の積層型圧電体素子の変位をレーザー変位計により測定した。測定点は２点で，２点の平均値をその素子の変位量とした。また，上記変位量の測定は室温で行うが，予め積層型圧電体素子を駆動している状態で２０分程度エージングした後に測定を行った。
【００４４】
また，静電容量の経時変化については，積層型圧電体素子を分極後，４８時間室温にて放置した後にＬＣＲメータで１ｋＨｚでの静電容量Ｑ１を測定し，更に１週間経過後に静電容量Ｑ２を測定し，Ｑ１とＱ２の変化率を計算により求めた。
上記測定結果を記載した表２から明らかなように，試料１〜１４にかかる本発明の圧電材料を用いて作製した積層型圧電体素子では，比較試料Ｃ１〜Ｃ３に比べて，変位量が大きくなっていると共に，静電容量の経時変化が小さくなって改善された。すなわち誘電特性が安定したことがわかった。
【００４５】
本例にかかる圧電材料（試料１〜１４）は，圧電材料を構成するペロブスカイト結晶格子のＰｂの一部を置換する元素として，少なくともイオン半径がＰｂより大きいＢａ，またはＰｂよりイオン半径が小さいＣａを選択している（表１参照）。圧電材料を構成するペロブスカイト結晶格子内に大きな歪みが導入され，より大きな圧電効果を発揮する。そのため，本例にかかる試料１〜１４にかかる圧電材料から図１〜図３に示すごとき積層型圧電体素子を作製した場合は，大きな変位量を得ることができる（表２参照）。
【００４６】
また，試料１〜１４にかかる圧電材料では，ドナー元素であるＳｂ，Ｎｂ，Ｗ，Ｍｏとアクセプタ元素であるＭｎの比率を適正範囲に設定した。これにより，圧電材料中のペロブスカイト結晶格子における酸素欠陥の生成量を低減して，誘電特性の経時変化を抑制することができる。
【００４７】
以上，本例によれば，変位量が大で，誘電特性が安定した積層圧電体素子に適用可能な圧電材料とこの圧電材料を用いた積層型圧電体素子の製造方法を提供することができる。
【００４８】
【表１】
【表２】
（実施例２）
本例は，圧電材料に助剤酸化物を添加して圧電層とした積層型圧電体素子の性能について，比較例と共に評価する。
まず，助剤酸化物の原料としてＰｂＯ，ＷＯ3，ＭｏＯ3を使用し，表３に示す所望の組成となるよう，すなわち，目的組成における各構成原子の比と出発原料における各構成原子の比が同じになるように秤量した。
【００５１】
これらを乾式混合した後，大気中５００℃で２時間仮焼成し，ＰｂＯとＷＯ3及び／又はＭｏＯ3の一部を反応させて助剤酸化物の仮焼粉を得た。この仮焼粉を湿式粉砕後乾燥して，ＢＥＴ比表面積が１．５〜２ｍ2／ｇの試料１５〜１９となる助剤酸化物を得た。
なお，比較試料Ｃ４の助剤酸化物は，ＭｏＯ3を含んでおらず，ＷＯ3の量が多く，請求項３，４の発明にかかる助剤酸化物ではない。
【００５２】
圧電材料は表１にかかる試料１を用いた。試料１にかかる組成が得られるように原料を調合し，８００℃で５時間仮焼し，媒体攪拌ミルにより湿式粉砕し，ＢＥＴ比表面積が２．７ｍ2／ｇの粉砕物からなる圧電材料を得た。
上記圧電材料に，表３に示す配合比率となるよう上記助剤酸化物を添加し，更に溶剤，バインダー，可塑剤，分散剤を加えてボールミルにより混合し，得られたスラリーからドクターブレード装置を用いて厚み１００μｍの未焼シートを成形した。以降は先の実施例１と同様の要領で，積層型圧電体素子の作製ならびに評価を行って，結果を表３に記載した。
【００５３】
表３から明らかなように，助剤酸化物の圧電材料１００重量％に対する添加量αを０．０５〜５重量％（外％）とすることで，焼成温度を２５〜１００℃低下させることができた。また，比較試料Ｃ４にかかる材料は焼成温度の低下効果を持たなかった。
【００５４】
以上の評価から，化学式（１−β−γ）ＰｂＯ・βＷＯ3・γＭｏＯ3（０．００５≦β＋γ≦０．２７，ただしβ≧０，γ≧０。）で表される助剤酸化物を圧電材料１００重量％に対して０．０５〜５重量％（外％）加えることで焼成温度低下効果が得られることが分かった。
【００５５】
【表３】
（実施例３）
本例は，圧電材料のＢＥＴ比表面積の違いと積層型圧電体素子の性能について評価する。
圧電材料は表１の試料１を使用する。表１に記載した組成となるように原料を調合し，８００℃で５時間仮焼して仮焼粉を得た。この仮焼粉を湿式粉砕する際に，粉砕装置，粉砕メディア径，粉砕時間等の粉砕条件を変えることにより，ＢＥＴ比表面積が１．５〜１２ｍ2／ｇの粉砕物からなる試料２０〜２３の圧電材料を作製した。
また，比較試料Ｃ５，Ｃ６として，組成の同じ圧電材料であるが，ＢＥＴ比表面積が低いもの，高いものをそれぞれ準備した。
【００５７】
各試料や比較試料にそれぞれ助剤酸化物として表３の試料１５を０．５重量％加え，更に溶剤，バインダー，可塑剤，分散剤を加えてボールミルにより混合し，得られたスラリーからドクターブレード装置を用いて厚み１００μｍの未焼シートを成形した。以降は先の実施例１と同様の要領で積層型圧電体素子の作製ならびに評価を行って，表４に記載した。
【００５８】
表４から明らかなように，圧電材料の比表面積を１．６〜８ｍ2／ｇとすることで，圧電材料の特性をほぼ維持した状態で，低温焼結化が可能となることがわかった。
【００５９】
なお，本実施例では，圧電材料の粉砕物に助剤酸化物を加えているが，出発原料を仮焼して得られた圧電材料に助剤酸化物を加えて，圧電材料と共に粉砕しても差し支えない。
また，圧電材料の粉砕によって得られる微粉は，助剤酸化物との反応性が高いため，助剤酸化物の圧電材料への固溶を極力抑えるために，圧電材料を粉砕した後，４００〜７００℃で予焼して得られた粉に助剤酸化物，溶剤，バインダー，可塑剤，分散剤を添加して成形することもできる。
【００６０】
【表４】
【図面の簡単な説明】
【図１】実施例１における，積層型圧電体素子の斜視図。
【図２】実施例１における，積層型圧電体素子の圧電層の平面図。
【図３】実施例１における，圧電層の積層状態を示す斜視展開図。
【符号の説明】
１．．．積層型圧電体素子，
１１．．．圧電層，
２１，２２．．．内部電極層，[0001]
【Technical field】
The present invention relates to a lead zirconate titanate piezoelectric material containing Mn and a method for manufacturing a multilayer piezoelectric element using this piezoelectric material.
[0002]
[Prior art]
Conventionally, PbZrO 3 —PbTiO 3 —Pb (Y 1/2 Nb 1/2 ) O 3 based piezoelectric material is used as the piezoelectric material used for the multilayer piezoelectric element for actuator, and a part of Pb is replaced with Sr. Also known is a compound comprising a compound in which Mn is substituted with at least one element selected from Sb, Nb, W, La, Ta, Bi, Nd, and Pr.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. Sho 62-46961
[Problems to be solved]
However, the displacement amount of the laminated piezoelectric element manufactured using the piezoelectric material is not always sufficient depending on the application of the actuator.
Further, although the piezoelectric material includes Mn as an acceptor element together with donor elements such as Sb, Nb, and W, the ratio of the donor element to the acceptor element may not always be appropriate. For this reason, the multilayer piezoelectric element manufactured from the above-described piezoelectric material has a problem that the change in dielectric characteristics with time is large and the characteristics are not stable.
[0005]
In the above problems, it is known that adding Mn to lead zirconate titanate-based piezoelectric materials leads to suppression of heat generation due to energy loss because it lowers dielectric loss and improves mechanical quality factor. ing.
For this reason, it seems that it is possible to suppress the time-dependent change of dielectric characteristics by adding no Mn to the lead zirconate titanate piezoelectric material, but the heat generation suppression effect by Mn must be sacrificed. , Not realistic.
Therefore, it is necessary to take some measures for stabilizing the dielectric characteristics of the lead zirconate titanate piezoelectric material containing Mn.
[0006]
The present invention has been made in view of such conventional problems. A piezoelectric material applicable to a laminated piezoelectric element having a large amount of displacement and stable dielectric characteristics, and a laminated piezoelectric body using this piezoelectric material. An element manufacturing method is provided.
[0007]
[Means for solving problems]
A first aspect of the present invention is the chemical formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z1-z2 Mb z1 Mc z2) q O piezoelectric material (except Ma represented by 3 + d is, Ba, Ca, and at least one element selected from Sr, .mb containing either Ba or Ca is Nb, Sb , At least one element selected from Ta. Mc is at least one element selected from W and Mo.)
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.005 ≦ p ≦ 0.05,
0.001 ≦ q · (1-z1-z2) ≦ 0.02,
0.7 ≦ (1-z1-z2) / (z1 + 2 · z2) ≦ 1.5 (where z1 and z2 are 0 or a positive number, at least one is not 0)
The piezoelectric material is characterized in that (Claim 1).
[0008]
The second invention has the formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z2 W z2) q O A piezoelectric material represented by 3 + d (where Ma is at least one element selected from Ba, Ca, and Sr, and includes Ba).
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.25 ≦ z2 ≦ 0.40,
0.005 ≦ p ≦ 0.05,
The piezoelectric material is characterized in that 0.001 ≦ q · (1−z2) ≦ 0.02.
[0009]
The operational effects of the first and second inventions will be described.
In the material according to the prior art, the element that replaces a part of Pb in the piezoelectric material is only Sr having the same ionic radius as Pb, and the strain applied to the perovskite crystal lattice may not be sufficient. Paying attention, in the piezoelectric material according to the present invention, at least Ba having an ion radius larger than Pb or Ca having an ion radius smaller than Pb was selected as an element for substituting a part of Pb. That is, the 12-coordinate ion radius of Pb is 1.49Å, and the 12-coordinate ion radii of Ba, Ca, and Sr are 1.61Å, 1.34Å, and 1.44Å, respectively.
Accordingly, the piezoelectric materials according to the first and second inventions exhibit a greater piezoelectric effect because a larger strain is introduced into the perovskite crystal lattice than before.
Therefore, when a laminated piezoelectric element is manufactured from the materials according to the first and second inventions, a large amount of displacement can be exhibited.
[0011]
Moreover, in the materials according to the prior art, the ratio of the donor element to the acceptor element is not always appropriate, and the oxygen vacancies generated due to insufficient compensation of these valences adversely affect the time-dependent change in dielectric properties. In the piezoelectric material according to the present invention, the ratio of donor elements Sb, Nb, W, Mo and acceptor element Mn was set within an appropriate range. As a result, the amount of oxygen defects generated in the crystal lattice in the piezoelectric material can be reduced, and the change in dielectric characteristics over time can be suppressed.
[0012]
In addition, when the third invention manufactures a laminated piezoelectric element in which piezoelectric layers and internal electrode layers are alternately laminated,
The BET specific surface area of the piezoelectric material according to claim 1 or 2 is adjusted to be 1.6 to 8 m 2 / g, and the chemical formula (1-β-γ) PbO · βWO 3 · γMoO 3 (0.005 ≦ β + γ ≦ 0.27, where β ≧ 0 and γ ≧ 0)) to add an auxiliary oxide represented by
Forming the above mixture to produce a green sheet, and providing the green sheet with a printed layer made of a paste containing an electrode material for the internal electrode layer,
Thereafter, a plurality of unfired sheets provided with the printed layer are laminated to form an unfired laminated body, and the unfired laminated body is fired. ).
[0013]
The multilayer piezoelectric element manufactured by the manufacturing method according to the third invention has a piezoelectric layer made of the piezoelectric material according to the first and second inventions, and therefore has a large displacement and suppresses changes in dielectric characteristics over time. A piezoelectric layer.
In addition, the piezoelectric layer contains the above-described auxiliary oxide, and the presence of the auxiliary oxide affects the sintered state of the piezoelectric material according to the first and second inventions which becomes the base material in the piezoelectric layer. Thus, low-temperature sintering of the green laminate is possible.
[0014]
Furthermore, in the third invention, the specific surface area of the piezoelectric material is controlled within the above-described range. This allows the auxiliary oxide to be uniformly present around the piezoelectric material and enables liquid phase sintering in the piezoelectric layer. Therefore, lower temperature sintering can be realized in a state where the performance of the piezoelectric material according to the first and second inventions is utilized.
If low-temperature sintering is possible, a cheaper electrode material (such as an Ag—Pd alloy having a Cu, Ag, Pd content of 10% or less) can be used as the internal electrode layer, and the material cost can be reduced. Can do.
[0015]
As described above, according to the present invention, it is possible to provide a piezoelectric material applicable to a laminated piezoelectric element having a large amount of displacement and stable dielectric characteristics, and a method for manufacturing a laminated piezoelectric element using this piezoelectric material. it can.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the first invention, if d <−0.02, the sintering temperature may increase. If d> 0.04, the displacement performance may be reduced.
If x <0.01, the displacement performance may be reduced. When x> 0.20, the Curie temperature of the piezoelectric material is lowered (approximately 200 ° C. or lower), the usable temperature range is narrow, and there is a possibility that the piezoelectric material lacks practicality.
If y <0.40, y> 0.55, the displacement performance may be reduced.
If p <0.005, p> 0.05, the displacement performance may be reduced. Further, when p> 0.05, the sintering temperature may be increased.
[0017]
When q · (1−z1−z2) <0.001, it is difficult to obtain a performance improvement effect (decrease in dielectric loss and improvement in mechanical quality factor) by addition of Mn. Further, when q · (1−z1−z2)> 0.02, the displacement performance may be deteriorated.
When (1−z1−z2) / (z1 + 2 · z2) <0.7, the displacement performance may be deteriorated. When (1−z1−z2) / (z1 + 2 · z2)> 1.5, the change in dielectric characteristics with time may increase.
[0018]
Further, terms relating to "Pb 1-x Ma x" in the formula piezoelectric material according to the first invention means that Pb is substituted with an element of Ma in the crystal lattice of the piezoelectric material (a perovskite structure) However, when a plurality of elements are selected as Ma, the total molar fraction including the plurality of elements is x.
That is, when Ma is Ba, Sr, consisting of Ca, the "Pb 1-x Ba l Sr m Ca n " in l + m + n = x. The same applies to the case of selecting a plurality of elements in other terms of the chemical formula.
[0019]
In addition, Ma is at least one element selected from Ba, Ca, and Sr, and includes either Ba or Ca. Therefore, combinations of elements that can be selected as Ma are Ba only, Ca only, and Ba. And Ca, Ba and Sr, Ca and Sr, Ba, Ca and Sr. Even if Sr alone is used as the element of Ma, the effect according to the present invention cannot be obtained.
[0020]
In the second invention, when z2 <0.25, there is a possibility that the change with time in the dielectric characteristics becomes large. When z2> 0.4, the displacement performance may be reduced.
When q · (1−z2) <0.001, it is difficult to obtain the performance improvement effect (reduction of dielectric loss and improvement of mechanical quality factor) by addition of Mn. Further, when q · (1−z2)> 0.02, the displacement performance may be deteriorated.
Other parameters are the same as in the first invention.
[0021]
In addition, the piezoelectric material of the first invention or the second invention has the chemical formula (1-β-γ) PbO · βWO 3 · γMoO 3 (0.005 ≦ β + γ ≦ 0.27, where β ≧ 0, γ ≧ 0). )), And an additive amount α of the auxiliary oxide with respect to 100 wt% of the piezoelectric material is 0.05 to 5 wt% (outside%). It is preferable that it is present (claim 3).
[0022]
Here, the auxiliary oxide includes Pb oxide blended to have the above chemical formula and Pb blended to have the above chemical formula in addition to a composite oxide in which W oxide and / or Mo oxide are solid-dissolved. A mixture of an oxide and a W oxide and / or Mo oxide or a solution obtained by partially dissolving the mixture may be used. This is because even if Pb oxide and W oxide and / or Mo oxide remain in the auxiliary oxide, they proceed as a solid solution during the sintering process and function as auxiliary oxide.
[0023]
By using the auxiliary oxide according to claim 3, the firing temperature of the piezoelectric material according to the first and second inventions is lowered, and a more inexpensive electrode material (Cu, Ag, Pd content is 10% or less) A laminated piezoelectric element can be manufactured using an Ag—Pd alloy or the like. Therefore, it is possible to obtain a piezoelectric material suitable for manufacturing a low-cost laminated piezoelectric element.
When β + γ <0.005, β + γ> 0.27, there is a possibility that it is difficult to obtain the effect of lowering the firing temperature.
If α <0.05% by weight, the sintering temperature lowering effect may be difficult to obtain. If α> 5% by weight, the displacement performance may be reduced. This is because auxiliary oxides that do not contribute to displacement increase in the piezoelectric material.
[0024]
According to a third aspect of the present invention, there is provided a method for producing a multilayer piezoelectric element having a piezoelectric layer produced by mixing the auxiliary oxide according to the third aspect using the piezoelectric material according to the first or second aspect. is there.
Further, in the third invention, the piezoelectric material is adjusted to have a predetermined surface area. However, if the BET specific surface area is less than 1.6 m 2 / g, the sintering temperature of the piezoelectric material may be increased. If it is larger than 8 m 2 / g, the displacement performance may be deteriorated because the auxiliary oxide is excessively dissolved in the piezoelectric material.
Other piezoelectric materials and auxiliary oxides are the same as those described in the first and second inventions.
[0025]
The BET specific surface area is a specific surface area measured by the BET method.
There is a method for measuring the specific surface area by adsorbing molecules with a known adsorption area on the surface of the material at the temperature of liquid nitrogen and determining the specific surface area of the sample from the amount, especially measurement by low-temperature and low-humidity physical adsorption of an inert gas. Is called the BET method.
[0026]
In the manufacturing method according to the third aspect of the present invention, a piezoelectric material having the composition according to claims 1 and 2 is prepared in advance, and the auxiliary oxide having the composition described above is separately mixed therewith.
The treatment for setting the BET specific surface area of the piezoelectric material in the above-described range may be performed in the state of the piezoelectric material alone or after mixing with the auxiliary oxide.
[0027]
That is, first, the starting material is weighed so as to have a predetermined composition ratio, the starting material is calcined, and then pulverized until a predetermined BET specific surface area is obtained. Thereafter, the auxiliary oxide is added to form a mixture.
Alternatively, the starting material is calcined, and then an auxiliary oxide is added and pulverized.
[0028]
In addition, since the fine powder of the piezoelectric material obtained by calcining and pulverizing the starting material is highly reactive with the auxiliary oxide, the piezoelectric oxide is used in order to minimize the solid solution of the auxiliary oxide in the piezoelectric material. After pulverizing the material, auxiliary oxides, solvents, binders, plasticizers, and dispersants may be added to the powder obtained by pre-baking at 400 to 700 ° C. to form the material.
[0029]
Further, in the method for manufacturing a laminated piezoelectric element according to the present invention, when the piezoelectric material is adjusted to have a predetermined BET specific surface area, it is pulverized using a ball mill, a medium stirring mill, or the like to reduce the particle size. Is preferably performed.
[0030]
Further, when a mixture comprising a piezoelectric material and an auxiliary oxide is formed, a slurry obtained by adding a binder or the like to the mixture can be prepared, and an unfired sheet can be produced by a generally known doctor blade method. Thereafter, a paste containing an electrode material is printed on the green sheet to provide a printed layer.
A desired number of unfired sheets provided with the printed layer are laminated and pressure-bonded to produce an unfired laminate. A laminated piezoelectric element can be obtained by degreasing and firing the unfired laminated body, and then providing a side electrode or the like that is electrically connected to the internal electrode layer, followed by polarization treatment.
[0031]
The procedure described here is a manufacturing method well known for multilayer piezoelectric elements, and the third invention can also be applied to the case of manufacturing piezoelectric elements by other methods.
In addition to the partial electrode configuration (the area in the cross section orthogonal to the stacking direction is smaller than that of the piezoelectric layer) shown in Example 1 described later, the internal electrode layer has an entire surface electrode configuration (area substantially equal to the piezoelectric layer). Can also be prepared.
[0032]
The multilayer piezoelectric element has a piezoelectric layer made of a piezoelectric material having stable dielectric characteristics. By stabilizing the dielectric characteristics, variation in the transient characteristics of the displacement is reduced. Therefore, when the piezoelectric layer is used as a piezoelectric actuator when a voltage is applied, that is, when used as a piezoelectric actuator, the elongation rate of the actuator is substantially constant.
[0033]
By using such a piezoelectric actuator as a drive source for an injector for fuel injection in an internal combustion engine such as an automobile engine, variation in the fuel injection amount can be reduced and combustion state control can be performed more precisely. In this respect, the piezoelectric material according to the first and second inventions is suitable as a constituent material of the piezoelectric layer of the piezoelectric actuator of the drive source of the fuel injection injector. The laminated piezoelectric element manufactured in the third aspect of the invention is also suitable as a drive source for the fuel injection injector.
[0034]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
Example 1
In this example, a laminated piezoelectric element is manufactured from the piezoelectric material according to the present invention, and its performance is evaluated.
The piezoelectric material according to this embodiment has the formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z1-z2 Mb z1 Mc z2 ) q O 3 + d piezoelectric material (where Ma is at least one element selected from Ba, Ca and Sr and contains either Ba or Ca. Mb is Nb) , Sb, Ta, at least one element selected from the group consisting of W and Mo.
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.005 ≦ p ≦ 0.05,
0.001 ≦ q · (1-z1-z2) ≦ 0.02,
0.7 ≦ (1-z1-z2) / (z1 + 2 · z2) ≦ 1.5
(Where z1 and z2 are 0 or a positive number, at least one is not 0).
[0035]
Or, a piezoelectric material according to this embodiment has the formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z2 W z2) q O piezoelectric material (except Ma represented by 3 + d is, Ba, Ca, and at least one element selected from Sr, a containing Ba.),
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.25 ≦ z2 ≦ 0.40,
0.005 ≦ p ≦ 0.05,
0.001 ≦ q · (1-z2) ≦ 0.02.
[0036]
This will be described in detail below.
In this example, the performance of the multilayer piezoelectric element obtained from the piezoelectric material according to the present invention or the manufacturing method according to the present invention is evaluated using the samples 1 to 14 according to the present invention and the comparative samples C1 to C3.
That is, samples 1 to 14, the chemical formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z1-z2 Mb z1 Mc z2) q O 3 + d Ma substituted element, Mb, the type and composition ratio of Mc (x, y, z1, z2, p, q, d) were obtained by changing as shown in Table 1 Piezoelectric material.
[0037]
The comparative sample C1 has a composition (1−z1−z2) / (z1 + 2 · z2) of 0.54 and is outside the scope of the present invention. Comparative sample C2 does not contain elements related to Mb and Mc and has a composition outside the present invention. In Comparative Sample C3, (1-z1-z2) / (z1 + 2 · z2) is 2, which is a composition outside the present invention.
A laminated piezoelectric element 1 as shown in FIGS. 1 to 3 was fabricated from these piezoelectric materials, and the piezoelectric characteristics were examined.
[0038]
As shown in FIGS. 1 to 3, the multilayer piezoelectric element 1 manufactured here is manufactured so that the internal electrode layers 21 and 22 are alternately positive and negative between the layers of the
Then,
The central portion of the piezoelectric element 1 in the stacking direction is a
[0039]
Next, a specific method for manufacturing the piezoelectric material and the multilayer piezoelectric element will be described.
PbO, SrCO 3 , BaCO 3 , CaCO 3 , ZrO 2 , TiO 2 , Y 2 O 3 , Nb 2 O 5 , Sb 2 O 3 , WO 3 and MoO 3 are used as starting materials containing each constituent atom of the piezoelectric material. The composition was weighed so that the desired composition shown in Table 1 was obtained, that is, the ratio of each constituent atom in the target composition was the same as that in each starting material.
[0040]
The weighed raw materials were wet-mixed, dried and calcined at 800 ° C. for 5 hours, and wet-pulverized with a medium stirring mill to obtain a pulverized product having a BET specific surface area of 2.5 to 3 m 2 / g. A solvent, a binder, a plasticizer, and a dispersant were added to this and mixed by a ball mill to obtain a slurry.
Using a doctor blade device, a green sheet having a thickness of 100 μm was formed from the slurry. A conductive layer containing an electrode material made of silver / palladium = 7/3 (weight ratio) was printed on the green sheet to provide a printed layer for an internal electrode layer.
[0041]
As shown in FIG. 3, 21 unfired sheets provided with the above printed layers were stacked, and a simple unfired sheet having no printed layers for the internal electrode layers was placed on the upper and lower ends, and thermocompression bonding was performed. A fired laminate was produced.
Next, the unfired laminated body was degreased in an electric furnace, then fired at 850 ° C. to 1100 ° C., and polished on the entire surface to obtain a 7 × 7 × 1.8 mm laminated sintered body.
Further, a pair of side electrodes were baked in order to make the internal electrode layer conductive every other side of the laminated sintered body, then polarized for 30 minutes at an applied electric field of 130 ° C. and 2 kV / mm, and left at room temperature for 48 hours. did.
Thus, a multilayer piezoelectric element was obtained.
[0042]
The performance measurement of the multilayer piezoelectric element will be described.
The impedance-frequency characteristics of the obtained multilayer piezoelectric element were measured with an impedance analyzer, the difference between the resonance frequency fr and the anti-resonance frequency fa in the fundamental vibration was determined, and the firing temperature at which this began to saturate is shown in Table 2.
[0043]
Then, the amount of displacement and capacitance change with time of each laminated piezoelectric element fired at the above temperature were examined.
Regarding the method of measuring the displacement, first, a voltage of 150 V was applied to the multilayer piezoelectric element while applying a load of 500 N, and the displacement of the multilayer piezoelectric element at that time was measured with a laser displacement meter. There were two measurement points, and the average value of the two points was used as the displacement of the element. The displacement was measured at room temperature, but was measured after aging for about 20 minutes in a state where the laminated piezoelectric element was driven in advance.
[0044]
As for the change in capacitance with time, the polarization of the laminated piezoelectric element was allowed to stand at room temperature for 48 hours, and then the capacitance Q1 at 1 kHz was measured with an LCR meter. Q2 was measured and the rate of change between Q1 and Q2 was obtained by calculation.
As can be seen from Table 2 describing the measurement results, the stacked piezoelectric element manufactured using the piezoelectric material of the present invention according to Samples 1 to 14 has a larger displacement than Comparative Samples C1 to C3. In addition, the change in capacitance with time was reduced and improved. That is, it was found that the dielectric characteristics were stable.
[0045]
The piezoelectric material according to the present example (samples 1 to 14) is an element that replaces a part of Pb of the perovskite crystal lattice constituting the piezoelectric material. At least Ba having an ionic radius larger than Pb, or Ca having an ionic radius smaller than Pb. (See Table 1). A large strain is introduced into the perovskite crystal lattice constituting the piezoelectric material, and a greater piezoelectric effect is exhibited. Therefore, when the laminated piezoelectric element as shown in FIGS. 1 to 3 is manufactured from the piezoelectric materials according to the samples 1 to 14 according to this example, a large displacement can be obtained (see Table 2).
[0046]
In the piezoelectric materials according to Samples 1 to 14, the ratio of donor elements Sb, Nb, W, Mo and acceptor element Mn was set within an appropriate range. As a result, the amount of oxygen defects generated in the perovskite crystal lattice in the piezoelectric material can be reduced, and the change in dielectric characteristics over time can be suppressed.
[0047]
As described above, according to this example, it is possible to provide a piezoelectric material applicable to a laminated piezoelectric element having a large amount of displacement and stable dielectric characteristics, and a method for manufacturing a laminated piezoelectric element using this piezoelectric material. .
[0048]
[Table 1]
[Table 2]
(Example 2)
In this example, the performance of a laminated piezoelectric element having a piezoelectric layer obtained by adding an auxiliary oxide to a piezoelectric material is evaluated together with a comparative example.
First, PbO, WO 3 , and MoO 3 are used as raw materials for the auxiliary oxide, so that the desired composition shown in Table 3 is obtained, that is, the ratio of each constituent atom in the target composition to the ratio of each constituent atom in the starting material. Were weighed to be the same.
[0051]
After these were dry-mixed, they were calcined at 500 ° C. for 2 hours in the atmosphere, and PbO was reacted with a part of WO 3 and / or MoO 3 to obtain a calcined powder of auxiliary oxide. This calcined powder was wet pulverized and dried to obtain auxiliary oxides to be samples 15 to 19 having a BET specific surface area of 1.5 to 2 m 2 / g.
Note that the auxiliary oxide of the comparative sample C4 does not contain MoO 3 , has a large amount of WO 3 , and is not an auxiliary oxide according to the third and fourth aspects of the invention.
[0052]
Sample 1 according to Table 1 was used as the piezoelectric material. A raw material was prepared so that the composition according to Sample 1 was obtained, calcined at 800 ° C. for 5 hours, wet pulverized with a medium stirring mill, and a piezoelectric material composed of a pulverized product having a BET specific surface area of 2.7 m 2 / g. Obtained.
Add the above-mentioned auxiliary oxide to the piezoelectric material so as to have the blending ratio shown in Table 3, and then add a solvent, binder, plasticizer, and dispersing agent and mix them by a ball mill. An unsintered sheet having a thickness of 100 μm was formed. Thereafter, the laminated piezoelectric element was manufactured and evaluated in the same manner as in Example 1, and the results are shown in Table 3.
[0053]
As is apparent from Table 3, the firing temperature can be lowered by 25 to 100 ° C. by setting the additive amount α of the auxiliary oxide to 100 wt% of the piezoelectric material to 0.05 to 5 wt% (outside%). did it. Moreover, the material concerning the comparative sample C4 did not have the effect of lowering the firing temperature.
[0054]
From the above evaluation, the auxiliary oxide represented by the chemical formula (1-β-γ) PbO · βWO 3 · γMoO 3 (0.005 ≦ β + γ ≦ 0.27, where β ≧ 0, γ ≧ 0) is obtained. It was found that the firing temperature lowering effect can be obtained by adding 0.05 to 5% by weight (outside%) with respect to 100% by weight of the piezoelectric material.
[0055]
[Table 3]
(Example 3)
In this example, the difference in the BET specific surface area of the piezoelectric material and the performance of the multilayer piezoelectric element are evaluated.
Sample 1 in Table 1 is used as the piezoelectric material. The raw materials were prepared so as to have the composition shown in Table 1, and calcined at 800 ° C. for 5 hours to obtain calcined powder. When the calcined powder is wet pulverized, samples 20 to 23 made of a pulverized product having a BET specific surface area of 1.5 to 12 m 2 / g are obtained by changing the pulverizing conditions such as the pulverizing apparatus, the pulverizing media diameter, and the pulverizing time. The piezoelectric material was manufactured.
Further, as comparative samples C5 and C6, piezoelectric materials having the same composition but having a low BET specific surface area and a high one were prepared.
[0057]
Add 0.5% by weight of sample 15 in Table 3 as an auxiliary oxide to each sample and comparative sample, add solvent, binder, plasticizer and dispersant and mix by ball mill. Doctor blade from the resulting slurry An unbaked sheet having a thickness of 100 μm was formed using the apparatus. Thereafter, the production and evaluation of the laminated piezoelectric element were performed in the same manner as in Example 1, and are shown in Table 4.
[0058]
As is apparent from Table 4, it was found that by setting the specific surface area of the piezoelectric material to 1.6 to 8 m 2 / g, low-temperature sintering can be performed while maintaining the characteristics of the piezoelectric material. .
[0059]
In this embodiment, the auxiliary oxide is added to the pulverized material of the piezoelectric material. However, the auxiliary oxide is added to the piezoelectric material obtained by calcining the starting material and pulverized together with the piezoelectric material. There is no problem.
In addition, since the fine powder obtained by pulverizing the piezoelectric material has high reactivity with the auxiliary oxide, after the piezoelectric material is pulverized in order to suppress the dissolution of the auxiliary oxide in the piezoelectric material as much as possible, 400 to An auxiliary oxide, a solvent, a binder, a plasticizer, and a dispersant may be added to the powder obtained by pre-baking at 700 ° C. to mold the powder.
[0060]
[Table 4]
[Brief description of the drawings]
FIG. 1 is a perspective view of a multilayer piezoelectric element in Example 1. FIG.
2 is a plan view of a piezoelectric layer of a multilayer piezoelectric element in Example 1. FIG.
3 is a perspective development view showing a stacked state of piezoelectric layers in Example 1. FIG.
[Explanation of symbols]
1. . . Laminated piezoelectric element,
11. . . Piezoelectric layer,
21,22. . . Internal electrode layer,
Claims (4)
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ１−ｚ２）≦０．０２，
０．７≦（１−ｚ１−ｚ２）／（ｚ１＋２・ｚ２）≦１．５（ただしｚ１，ｚ２は０または正の数で，少なくとも一方は０でない。）
であることを特徴とする圧電材料。Formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z1-z2 Mb z1 Mc z2) q O 3+ Piezoelectric material represented by d (where Ma is at least one element selected from Ba, Ca and Sr and contains either Ba or Ca. Mb is at least selected from Nb, Sb and Ta) One or more elements, Mc is at least one element selected from W and Mo.)
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.005 ≦ p ≦ 0.05,
0.001 ≦ q · (1-z1-z2) ≦ 0.02,
0.7 ≦ (1-z1-z2) / (z1 + 2 · z2) ≦ 1.5 (where z1 and z2 are 0 or a positive number, at least one is not 0)
A piezoelectric material characterized by
−０．０２≦ｄ≦０．０４，
０．０１≦ｘ≦０．２０，
０．４０≦ｙ≦０．５５，
０．２５≦ｚ２≦０．４０，
０．００５≦ｐ≦０．０５，
０．００１≦ｑ・（１−ｚ２）≦０．０２であることを特徴とする圧電材料。Represented by the chemical formula (Pb 1-x Ma x) 1 + d (Zr 1-y Ti y) 1-pq (Y 1/2 Nb 1/2) p (Mn 1-z2 W z2) q O 3 + d A piezoelectric material (where Ma is at least one element selected from Ba, Ca, and Sr and includes Ba),
−0.02 ≦ d ≦ 0.04
0.01 ≦ x ≦ 0.20,
0.40 ≦ y ≦ 0.55
0.25 ≦ z2 ≦ 0.40,
0.005 ≦ p ≦ 0.05,
A piezoelectric material, wherein 0.001 ≦ q · (1−z2) ≦ 0.02.
請求項１または２にかかる圧電材料のＢＥＴ比表面積が１．６〜８ｍ2／ｇとなるよう調整すると共に化学式（１−β−γ）ＰｂＯ・βＷＯ3・γＭｏＯ3（０．００５≦β＋γ≦０．２７，ただしβ≧０，γ≧０。）で表される助剤酸化物を添加して混合物を作製し，
上記混合物を成形して未焼シートを作製し，該未焼シートに内部電極層用の電極材料を含有するペーストからなる印刷層を設け，
その後上記印刷層を設けた未焼シートを複数枚積層して未焼積層体となし，該未焼積層体を焼成することを特徴とする積層型圧電体素子の製造方法。In manufacturing a laminated piezoelectric element in which piezoelectric layers and internal electrode layers are alternately laminated,
The BET specific surface area of the piezoelectric material according to claim 1 or 2 is adjusted to be 1.6 to 8 m 2 / g, and the chemical formula (1-β-γ) PbO · βWO 3 · γMoO 3 (0.005 ≦ β + γ ≦ 0.27, where β ≧ 0 and γ ≧ 0)) to add an auxiliary oxide represented by
Forming the above mixture to produce a green sheet, and providing the green sheet with a printed layer made of a paste containing an electrode material for the internal electrode layer,
Thereafter, a plurality of unfired sheets provided with the printed layer are laminated to form an unfired laminate, and the unfired laminate is fired.
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| DE200410015853 DE102004015853A1 (en) | 2003-04-01 | 2004-03-31 | Piezoelectric material for producing stacked piezoelectric components e.g. for fuel injectors in vehicles, comprises a mixed oxide of lead, zirconium, titanium, yttrium, niobium, manganese and other metals |
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