JP4009417B2 - Piezoelectric and piezoelectric devices - Google Patents

Description

式中、ＡはＣａ，ＳｒおよびＢａからなる群のうちの少なくとも１種であり、ＢはＴａである。また、ａ，ｓ，ｗ，ｘ，ｙおよびｚは、それぞれ０≦ａ≦０．１、０．９≦ｓ＜１．０、０．２≦ｗ／ｘ≦３．０、０．１≦ｙ≦０．５、０．２≦ｚ≦０．６、ｗ＋ｘ＋ｙ＋ｚ＝１の範囲内の値である。なお、化５に示した酸素の組成は化学量論的に求めたものであり、化学量論組成でなくてもよい。
【００１４】
すなわち、この酸化物は、亜鉛ニオブ酸チタン酸ジルコン酸鉛にマンガンタンタル酸鉛を固溶させたものであり、鉛の一部をカルシウム，ストロンチウムあるいはバリウムなどのアルカリ土類金属元素で置換してもよい。本実施の形態の圧電磁器では、これにより、高い機械的強度および優れた圧電特性が得られるようになっている。
【００１５】
化５における「ａ」の値、すなわち鉛の一部を置換したカルシウムなどのアルカリ土類金属元素の組成比をモル比で０．１以下とするのは、０．１を超えると圧電特性および機械的強度が共に低下してしまうからである。特に、圧電特性を重視する場合には、「ａ」の値は０≦ａ≦０．０５の範囲内が好ましく、０≦ａ≦０．０２の範囲内であれば更に好ましい。このようにすれば、圧電トランスまたは超音波モータについてより良好な特性が得られる。
【００１６】
化５における「ｓ」の値、すなわち第１の元素の組成比をモル比で０．９≦ｓ＜１．０とするのは、１．０以上では焼結性が悪く圧電特性および機械的強度が著しく低下してしまうからであり、０．９よりも小さいと圧電特性が低下してしまうからである。特に、圧電特性および機械的強度をより高めるには、「ｓ」の値は０．９０≦ｓ≦０．９９の範囲内が好ましく、０．９３≦ｓ≦０．９７の範囲内であれば更に好ましい。なお、化５における「ｓ」の値は、第２の元素の組成比を１とした場合の第１の元素の組成比なので、第２の元素に対する第１の元素のモル比による組成比（第１の元素／第２の元素）を意味している。
【００１７】
化５における「ｗ／ｘ」の値、すなわち（Ｍｎ_1/3 Ｂ_2/3 ）に対する（Ｚｎ_1/3 Ｎｂ_2/3 ）の組成比をモル比で０．２≦ｗ／ｘ≦３．０とするのは、０．２よりも小さいと最適焼成温度が高くなり、圧電特性および強度特性が低下してしまうからであり、３．０を超えると機械的強度が低下してしまうからである。特に、ｗ／ｘの値が小さくなるほど最適焼成温度が高くなるので、積層型の圧電デバイスにおける内部電極の融点あるいは製造コストを考えると、「ｗ／ｘ」の値は０．３３３≦ｗ／ｘ≦３．０の範囲内が好ましく、０．５≦ｗ／ｘ≦３．０の範囲内であれば更に好ましい。このようにすれば、積層型の圧電デバイスであっても焼成温度を高くすることなく低コストで良好な特性が得られる。
【００１８】
化５における「ｙ」の値、すなわちチタンの組成比をモル比で０．１≦ｙ≦０．５とし、「ｚ」の値、すなわちジルコニウムの組成比をモル比で０．２≦ｚ≦０．６とするのは、これらの範囲内において良好な圧電特性を得ることができるからである。
【００１９】
化５におけるＡに２種以上の元素を配合する場合には、それらの組成比は任意である。なお、化５に示した組成は、例えば、原料配合時の金属量から化学量論的に求められる。
【００２０】
また、この圧電磁器は複数の粒子により構成されており、その平均粒径は例えば０．２μｍ〜１０μｍ程度である。
【００２１】
このような構成を有する圧電磁器は、例えば、次のようにして製造することができる。
【００２２】
まず、出発原料として第１の元素および第２の元素を含む酸化物を用意し、それらを目的の組成に応じて混合する。なお、その際、アルカリ土類金属元素またはマンガンの原料には、酸化物でなく、炭酸塩あるいはシュウ酸塩のように焼成により酸化物となるものを用いてもよい。また、その他の元素においても焼成により酸化物となる原料を用いてもよい。次いで、この混合物を例えば８００℃〜９００℃の温度で２時間程度仮焼したのち、その仮焼物を粉砕する。続いて、この仮焼粉末に結合剤を添加し、例えば約５×１０⁸ Ｐａの圧力で圧縮成形する。そののち、この成形体を例えば約１０００℃〜１２００℃の温度で大気中において２時間程度焼成する。これにより、本実施の形態に係る圧電磁器が得られる。
【００２３】
この圧電磁器は、例えば、圧電トランスあるいは超音波モータなどのように大きく振動し高い機械的強度が要求される圧電デバイスの材料として好ましく用いられる。ここでは、圧電トランスを例に挙げて具体的に説明する。
【００２４】
図１は本実施の形態に係る圧電磁器を用いた圧電トランスの構造を表すものである。この圧電トランスは、いわゆる「ローゼン型」と言われるものであり、例えば長方形の単板構造よりなるデバイス本体１０を有している。このデバイス本体１０は、本実施の形態に係る圧電磁器により構成されている。デバイス本体１０の大きさは、例えば、長手方向の長さＬが１５ｍｍ〜４０ｍｍ程度、幅Ｗが３ｍｍ〜７ｍｍ程度、厚さＴが０．７ｍｍ〜１．５ｍｍ程度とされている。なお、この圧電トランスでは、本実施の形態に係る圧電磁器を用いているので、デバイス本体１０の厚さＴが２ｍｍ以下と薄くても十分な機械的強度を得ることができ、特に厚さＴが０．０５ｍｍ〜１ｍｍの場合に顕著な効果が得られるようになっている。
【００２５】
デバイス本体１０は、また、長さ方向における一方に設けられた一次部１１と、長さ方向における他方に設けられた二次部１２とを有している。一次部１１は厚さ方向に分極されており、二次部１２は長さ方向に分極されている。一次部１１の長さＬ１は、例えば、約７ｍｍ〜２０ｍｍ程度とされている。一次部１１の厚さ方向において対向する両面には一対の入力電極２１，２２がそれぞれ設けられ、二次部１２の長さ方向の端面には出力電極２３が設けられている。入力電極２１，２２および出力電極２３は、例えば銀（Ａｇ）などの導体によりそれぞれ構成されており、厚さはそれぞれ１μｍ〜２０μｍ程度とされている。
【００２６】
このような構成を有する圧電トランスでは、入力電極２１，２２を介して一次部１１に１波長または１／２波長共振の交流電圧を印加すると、低インピーダンス特性を有する一次部１１において電気エネルギーが振動エネルギーに変換され、この振動エネルギーが高インピーダンス特性を有する二次部１２に伝搬されると、二次部１２においてこの振動エネルギーが電気エネルギーに変換されて、入力電圧の５〜１５倍程度の高電圧が得られる。ここでは、本実施の形態に係る圧電磁器によりデバイス本体１０を構成しているので、デバイス本体１０は十分な機械的強度を有している。よって、大振幅での振動が可能であり、入力電圧を高くできるので、高電圧が得られる。
【００２７】
このような圧電トランスは常法により作製することができる。例えば、まず、上述したようにして圧電磁器を作製したのち、それを所定の大きさに加工してデバイス本体１０を形成する。次いで、例えば、デバイス本体１０に入力電極２１，２２および出力電極２３をそれぞれ形成し、一次部１１、続いて二次部１２の順に分極処理を行う。これにより、図１に示した圧電トランスが得られる。
【００２８】
なお、上述した圧電トランスでは、デバイス本体１０を圧電磁器の単板構造とするようにしたが、例えば、図２に示したように、デバイス本体１０の一次部１１を積層構造とするようにしてもよい。なお、ここでは、図１に示した圧電トランスに対応する構成要素には同一の符号を付して説明する。
【００２９】
このデバイス本体１０の一次部１１は、圧電磁器層１１ａと、内部電極２４とを交互に積層した構造となっている。内部電極２４は、交互に対向する方向に延長されており、幅方向において対向する側面に設けられた一対の入力電極２１，２２にそれぞれ接続されている。その他の構成は、図１に示した圧電トランスと同様である。この圧電トランスは、このような積層構造とされることにより、図１に示した単板構造に比べて電圧の変換倍率を高くできるようになっている。
【００３０】
なお、この圧電トランスは、次のようにして作製することができる。例えば、まず、圧電磁器の原料粉末を混合し仮焼して粉砕したのち、結合剤を加えシート状に成形して内部電極２４を印刷する。次いで、これを複数積層して焼成しデバイス本体１０を形成する。続いて、上述したように、入力電極２１，２２および出力電極２３をそれぞれ形成し、分極処理を行う。これにより、図２に示した圧電トランスが得られる。
【００３１】
このように本実施の形態によれば、第１の元素と、第２の元素と、酸素とからなる酸化物を含有し、第１の元素は鉛，カルシウム，ストロンチウムおよびバリウムからなる群のうちの少なくとも鉛を含み、第２の元素は亜鉛，マンガン，チタン，ジルコニウム，ニオブおよびタンタルを含み、酸化物の組成は例えば上記化５で表されるようにしたので、原料粉末の微粉化あるいはホットプレスなどを行うことなく、簡単かつ安価に機械的強度を向上させることができると共に、優れた圧電特性も得ることができる。
【００３２】
よって、この圧電磁器を用いて圧電デバイスを構成すれば、例えば大振幅で振動させたり、外部から衝撃が加えられても、破壊を防止防止することができ、デバイスの品質および信頼性を向上させることができる。特に、圧電トランスあるいは超音波モータのように大きな動作負荷をともなう圧電デバイスの性能を向上させることができる。
【００３３】
【実施例】
更に、本発明の具体的な実施例について説明する。
【００３４】
（実施例１〜６）
まず、出発原料として酸化鉛（ＰｂＯ）粉末、酸化亜鉛（ＺｎＯ）粉末、酸化ニオブ（Ｎｂ₂ Ｏ₅ ）粉末、炭酸マンガン（ＭｎＣＯ₃ ）粉末、酸化チタン（ＴｉＯ₂ ）粉末、酸化ジルコニウム（ＺｒＯ₂ ）粉末、酸化アンチモン（Ｓｂ₂ Ｏ₃ ）粉末および酸化タンタル（Ｔａ₂ Ｏ₅ ）粉末をそれぞれ用意した。次いで、これらの原料粉末を金属元素の割合が下記の化６に示した組成になるように配合し、ボールミルにより湿式混合した。すなわち、上記化５におけるａの値が零、ｓの値が０．９６、ｙの値が０．４２およびｚの値が０．４となるようにし、Ｂの元素，ｗの値およびｘの値を実施例１〜６および参考例１〜１２で表１に示したようにそれぞれ変化させた。
【００３５】
【化６】

【００３６】
【表１】

【００３７】
続いて、この混合物を約８５０℃で２時間程度仮焼したのち、この仮焼物をボールミルで湿式粉砕した。そののち、この仮焼粉末に結合剤として水を添加し、約５×１０⁸ Ｐａの圧力で縦横５０ｍｍの板状に圧縮成形した。成形ののち、この成形体を約１１００℃で大気中において２時間程度焼成し、実施例１〜６および参考例１〜１２の圧電磁器をそれぞれ得た。なお、実施例１〜６および参考例１〜１２は、原料粉末を配合する際の上記化６におけるＢの元素，ｗの値またはｘの値が異なることを除き、他の条件は同一である。
【００３８】
また、実施例１〜６に対する比較例１〜７として、原料粉末を配合する際の上記化６におけるＢの元素，ｗの値またはｘの値を表２に示したように変化させたことを除き、実施例１〜６と同様にして圧電磁器をそれぞれ作製した。
【００３９】
【表２】

【００４０】
このようにして得られた実施例１〜６、参考例１〜１２および比較例１〜７の圧電磁器について、密度の測定をそれぞれ行った。その結果、それぞれ理論密度に対して９５％以上の値が得られていることが確認された。
【００４１】
また、実施例１〜６、参考例１〜１２および比較例１〜７の圧電磁器について、３点曲げ強度による強度試験をそれぞれ行った。その際、試験試料の大きさはそれぞれ縦２ｍｍ，横４ｍｍ，厚さ０．９ｍｍとし、ＪＩＳ（Ｒ１６０１）に従って抗折強度を測定した。それらの結果を表１および表２に合わせてそれぞれ示す。
【００４２】
更に、実施例１〜６、参考例１〜１２および比較例１〜７の圧電磁器を用いて図１に示したような圧電トランスをそれぞれ作製した。具体的には、得られた圧電磁器を長さＬ３２ｍｍ，幅Ｗ４．５ｍｍ，厚さＴ１ｍｍの大きさに加工したのち、入力電極２１，２２および出力電極２３をそれぞれ形成し、一次部１１、次いで二次部１２の順に１２０℃のシリコンオイル中において２ｋＶ／ｍｍの電界で３０分間分極処理を行い、圧電トランスを作製した。その際、一次部の長さＬ１は１６ｍｍとした。
【００４３】
作製した実施例１〜６、参考例１〜１２および比較例１〜７の圧電トランスについて、図３に示したように、ノード点と呼ばれる振動しない点と出力電極２３とをそれぞれコンタクトプローブ３０により保持して入出力を行い、圧電特性の１つであるエネルギー変換効率をそれぞれ測定した。それらの結果も表１および表２に合わせてそれぞれ示す。
【００４４】
なお、表２には、参考例１３として、特許第２９５７５３７号公報に記載されている圧電磁器の一実施例に関する抗折強度およびそれを用いて作製した圧電トランスのエネルギー変換効率もそれぞれ示した。表２に示した参考例１３の圧電磁器は、下記の化７に示した組成を有する亜鉛ニオブ酸チタン酸ジルコン酸鉛に、酸化マンガンを１．０質量％、酸化ニオブを０．５質量％それぞれ添加したものである。
【００４５】
【化７】
Ｐｂ［（Ｚｎ_1/3 Ｎｂ_2/3 ）_0.20Ｔｉ_0.4 Ｚｒ_0.4 ］Ｏ₃
【００４６】
表１および表２から分かるように、実施例１〜６によれば、比較例１〜７および参考例１３に比べて、抗折強度およびエネルギー変換効率について共に高い値がそれぞれ得られた。すなわち、（Ｍｎ_1/3 Ｂ_2/3 ）に対する（Ｚｎ_1/3 Ｎｂ_2/3 ）の組成比ｗ／ｘをモル比で０．２≦ｗ／ｘ≦３．０の範囲内とすれば、機械的強度を向上させることができると共に、優れた圧電特性を得られることが分かった。
【００４７】
（実施例１９〜２５）
原料粉末を金属元素の割合が下記の化８に示した組成になるように配合すると共に、化８におけるｓの値を実施例１９〜２５で表３に示したようにそれぞれ変化させたことを除き、実施例１〜６および参考例１〜１２と同様にして圧電磁器をそれぞれ作製した。すなわち、実施例１９〜２５では、上記化５におけるａの値が零、Ｂの元素がタンタル、ｗおよびｘの値がそれぞれ０．０９、ｗ／ｘの値が１、ｙの値が０．４２およびｚの値が０．４となるようにし、ｓの値をそれぞれ変化させた。
【００４８】
【化８】

【００４９】
【表３】

【００５０】
また、実施例１９〜２５に対する比較例８〜１０として、原料粉末を配合する際の上記化８におけるｓの値を表３に示したように変化させたことを除き、実施例１９〜２５と同様にして圧電磁器をそれぞれ作製した。
【００５１】
得られた実施例１９〜２５および比較例８〜１０の圧電磁器について、実施例１〜６および参考例１〜１２と同様に、密度の測定および強度試験をそれぞれ行うと共に、圧電トランスを作製してエネルギー変換効率をそれぞれ測定した。密度については、それぞれ理論密度に対して９５％以上の値が得られていることが確認された。強度試験およびエネルギー変換効率の結果については、表３にそれぞれ示す。
【００５２】
表３から分かるように、実施例１９〜２５によれば、比較例８〜１０および表２に示した参考例１３に比べても、抗折強度およびエネルギー変換効率について共に高い値がそれぞれ得られた。すなわち、第２の元素に対する第１の元素の組成比ｓをモル比で０．９≦ｓ＜１．０の範囲内とすれば、機械的強度を向上させることができると共に、優れた圧電特性を得られることが分かった。また、０．９０≦ｓ≦０．９９の範囲内とすれば、より高い機械的強度を得ることができ、０．９３≦ｓ≦０．９７の範囲内とすれば、更に高い機械的強度を得られることも分かった。
【００５３】
（実施例２６〜３７）
出発原料として炭酸カルシウム（ＣａＣＯ₃ ）粉末、炭酸ストロンチウム（ＳｒＣＯ₃ ）粉末および炭酸バリウム（ＢａＣＯ₃ ）粉末を更に用意し、原料粉末を金属元素の割合が下記の化９に示した組成になるように配合すると共に、化９におけるＡの元素およびａの値を実施例２６〜３７で表４に示したようにそれぞれ変化させたことを除き、実施例１〜６および参考例１〜１２と同様にして圧電磁器をそれぞれ作製した。すなわち、実施例２６〜３７では、上記化５におけるｓの値が０．９６、Ｂの元素がタンタル、ｗおよびｘの値がそれぞれ０．０９、ｗ／ｘの値が１、ｙの値が０．４２およびｚの値が０．４となるようにし、Ａの元素およびａの値をそれぞれ変化させた。
【００５４】
【化９】

【００５５】
【表４】

【００５６】
また、実施例２６〜３７に対する比較例１１〜１３として、原料粉末を配合する際の上記化９におけるＡの元素およびａの値を表４に示したように変化させたことを除き、実施例２６〜３７と同様にして圧電磁器をそれぞれ作製した。
【００５７】
得られた実施例２６〜３７および比較例１１〜１３の圧電磁器について、実施例１〜６および参考例１〜１２と同様に、密度の測定および強度試験をそれぞれ行うと共に、圧電トランスを作製してエネルギー変換効率をそれぞれ測定した。密度については、それぞれ理論密度に対して９５％以上の値が得られていることが確認された。強度試験およびエネルギー変換効率の結果については、表４にそれぞれ示す。なお、表４には、上記化９におけるａの値を零にした場合に該当する実施例３の抗折強度およびエネルギー変換効率についても合わせてそれぞれ示した。
【００５８】
表４から分かるように、実施例２６〜３７によれば、比較例１１〜１３および表２に示した参考例１３に比べても、抗折強度およびエネルギー変換効率について共に高い値がそれぞれ得られた。すなわち、鉛の一部を置換するアルカリ土類金属の組成比ａをモル比で０≦ａ≦０．１の範囲内とすれば、機械的強度を向上させることができると共に、優れた圧電特性を得られることが分かった。また、０≦ａ≦０．０５の範囲内とすれば、機械的強度および圧電特性をより高めることができ、０≦ａ≦０．０２の範囲内とすれば、圧電特性を更に高められることも分かった。
【００５９】
なお、上記実施例ではいくつかの例を具体的に挙げて説明したが、上記実施の形態において説明した酸化物を含むように構成すれば、他の圧電磁器であっても、上記実施例と同様の結果を得ることができる。
【００６０】
以上、実施の形態および実施例を挙げて本発明を説明したが、本発明は上記実施の形態および実施例に限定されるものではなく、種々変形可能である。
【００６２】
例えば、上記実施の形態および実施例では圧電磁器を圧電トランスに用いる場合について説明したが、超音波振動子あるいはフィルタなどの他の圧電デバイスにも広く用いることができる。中でも、大きな動作負荷をともなう圧電デバイスに用いれば特に高い効果を得ることができるので好ましいが、高い機械的強度をそれほど必要としない圧電デバイスについても当然用いることができる。
【００６３】
【発明の効果】
以上説明したように請求項１記載の圧電磁器によれば、第１の元素と、第２の元素と、酸素とからなる酸化物を含有し、第１の元素は鉛，カルシウム，ストロンチウムおよびバリウムからなる群のうちの少なくとも鉛を含み、その組成は上記化１で表され、第２の元素は亜鉛，マンガン，チタン，ジルコニウム，ニオブおよびタンタルを含み、その組成は上記化２で表され、第２の元素に対する第１の元素の組成比はモル比で０．９以上１．０よりも小さくなるようにしたので、原料粉末の微粉化あるいはホットプレスなどを行うことなく、簡単かつ安価に機械的強度を向上させることができ、優れた圧電特性も得ることができるという効果を奏する。
【００６４】
また、請求項２記載の圧電デバイスによれば、本発明の圧電磁器を用いるようにしたので、例えば大振幅で振動させたり、外部から衝撃が加えられても、破壊を防止することができ、デバイスの品質および信頼性を向上させることができる。特に、圧電トランスあるいは超音波モータのように大きな動作負荷をともなう圧電デバイスの性能を向上させることができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の一実施の形態に係る圧電トランスの構造を表す斜視図である。
【図２】本発明の他の圧電トランスの構造を表す斜視図である。
【図３】本発明の実施例に係る圧電トランスのエネルギー変換効率を測定する方法を説明するための図である。
【符号の説明】
１０…デバイス本体、１１…一次部、１１ａ…圧電磁器層、１２…二次部、２１，２２…入力電極、２３…出力電極、２４…内部電極、３０…コンタクトプローブ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxidation comprising a first element containing lead (Pb), a second element containing zinc (Zn), niobium (Nb), titanium (Ti) and zirconium (Zr), and oxygen (O). The present invention relates to a piezoelectric ceramic containing an object and a piezoelectric device using the same.
[0002]
[Prior art]
Currently, piezoelectric devices using piezoelectric ceramics are widely used in various technical fields. Piezoelectric devices include ultrasonic vibrators, filters, piezoelectric transformers, and the like, and in particular, piezoelectric transformers have recently attracted attention. Piezoelectric transformers are characterized in that they can be made smaller, thinner and lighter than conventional electromagnetic transformers, have higher energy conversion efficiency, and have less noise.
[0003]
A typical piezoelectric transformer is known which uses a rectangular piezoelectric ceramic plate and has a primary (input) part polarized in the thickness direction and a secondary (output) part polarized in the length direction. Yes. In this piezoelectric transformer, when an alternating voltage of 1-wavelength or 1 / 2-wavelength resonance is applied, electric energy is converted into vibration energy in the primary part of low impedance, and this vibration energy is propagated to the secondary part of high impedance. Thus, a high voltage is generated by being converted into electric energy. Such a piezoelectric transformer is required to have a strength that does not break due to an impact, and even when the input voltage is increased and excited with a large amplitude, no breakage occurs at a stress concentration point called a node point. A sufficient degree of strength is required. That is, the piezoelectric ceramic used for the piezoelectric transformer is particularly required to have high mechanical strength.
[0004]
The mechanical strength of a piezoelectric ceramic has a large correlation with defects such as holes, and various studies have been conducted so far to improve the mechanical strength. For example, by reducing the particle diameter of the raw material powder and setting the specific surface area to 10 m ² / g or more and calcining at 650 ° C. or less, the crystal grain diameter of the porcelain is set to 1 μm or less to improve the mechanical strength (Japanese Patent Laid-Open No. 6). -11542)), or a method of improving the mechanical strength by using a hot press has been reported.
[0005]
Piezoelectric ceramics that contain lead titanate or lead zirconate titanate as the main component are known, but the second component, the third component, or various additives can be added to the piezoelectric ceramic. Improvements are also being made. For example, manganese oxide and cobalt oxide are added to lead zirconate zinc niobate titanate (Japanese Patent Publication No. 54-18400), or a part of lead is replaced with strontium or barium (Japanese Patent Laid-Open No. 62-154682). No. Gazette) has been reported. Furthermore, there is a report that the mechanical strength is improved by adding niobium oxide, antimony oxide and tantalum oxide to the composition described in Japanese Patent Publication No. 54-18400 (Japanese Patent No. 2957537).
[0006]
[Problems to be solved by the invention]
However, in the method of improving the mechanical strength by pulverizing the raw material powder, it becomes difficult to handle the raw material powder when producing the piezoelectric ceramic, and a new pulverizing step of the raw material powder is newly added. Therefore, there was a problem that the production efficiency was lowered. Also, the method using a hot press has a problem that the manufacturing time is longer than that of a normal manufacturing process not using a hot press and the equipment cost is high, resulting in an increase in product price. Therefore, as a simple and inexpensive method, it is desired to further improve the mechanical strength by adjusting the composition of the piezoelectric ceramic.
[0007]
The present invention has been made in view of such problems, and an object thereof is to provide a piezoelectric ceramic that can improve mechanical strength easily and inexpensively and a piezoelectric device using the same.
[0008]
[Means for Solving the Problems]
Piezoelectric ceramic according to the present invention, Ri Contact contains an oxide including the first element and the second element and oxygen, the first element, lead, calcium (Ca), strontium (Sr) and barium ( Ba), which contains at least lead in the group consisting of the following compounds represented by the following chemical formula 3, and the second element is zinc (Zn), manganese (Mn), titanium (Ti), zirconium (Zr), Niobium (Nb) and tantalum (Ta) are included, and the composition thereof is represented by the following chemical formula 4. The composition ratio of the first element to the second element (first element / second element) is a molar ratio. It is 0.9 or more and smaller than 1.0.
[Chemical 3]
Pb _1-a A _a
(In the formula, A is at least one member selected from the group consisting of Ca, Sr and Ba, and a is a value within the range of 0 ≦ a ≦ 0.1.)
[Formula 4]
(Zn _1/3 Nb _2/3 ) _w (Mn _1/3 Ta _2/3 ) _x Ti _y Zr _z
(Where w, x, y and z are 0.2 ≦ w / x ≦ 3.0, 0.1 ≦ y ≦ 0.5, 0.2 ≦ z ≦ 0.6, and w + x + y + z = 1, respectively. (The value is within the range.)
[0009]
In this piezoelectric ceramic, than contains an oxide of the above composition, the resulting high mechanical strength and excellent piezoelectric properties.
[0010]
The piezoelectric device according to the present invention uses the piezoelectric ceramic according to the present invention.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0012]
A piezoelectric ceramic according to an embodiment of the present invention contains an oxide composed of a first element, a second element, and oxygen. The first element includes at least lead in the group consisting of lead, calcium, strontium, and barium, and the second element includes zinc, manganese, titanium , zirconium, niobium, and tantalum . This oxide has a perovskite structure, and the composition thereof is represented by the following chemical formula 5, for example.
[0013]
[Chemical formula 5]

In the formula, A is at least one selected from the group consisting of Ca, Sr and Ba, and B is Ta . A, s, w, x, y, and z are 0 ≦ a ≦ 0.1, 0.9 ≦ s <1.0, 0.2 ≦ w / x ≦ 3.0, and 0.1 ≦, respectively. The values are within the ranges of y ≦ 0.5, 0.2 ≦ z ≦ 0.6, and w + x + y + z = 1. Note that the oxygen composition shown in Chemical Formula 5 is determined stoichiometrically and does not have to be a stoichiometric composition.
[0014]
That is, the oxide, which has a solid solution between Ngantantaru lead zinc niobate lead zirconate titanate, by substituting a part of the lead calcium, an alkaline earth metal elements such as strontium or barium May be. In the piezoelectric ceramic according to the present embodiment, high mechanical strength and excellent piezoelectric characteristics are thereby obtained.
[0015]
The value of “a” in Chemical Formula 5, that is, the composition ratio of an alkaline earth metal element such as calcium in which a part of lead is substituted is 0.1 or less in terms of molar ratio. This is because the mechanical strength is lowered. In particular, when emphasizing piezoelectric characteristics, the value of “a” is preferably in the range of 0 ≦ a ≦ 0.05, and more preferably in the range of 0 ≦ a ≦ 0.02. In this way, better characteristics can be obtained for the piezoelectric transformer or the ultrasonic motor.
[0016]
The value of “s” in Chemical Formula 5, that is, the composition ratio of the first element is set to 0.9 ≦ s <1.0 in terms of molar ratio. This is because the strength is significantly reduced, and when it is less than 0.9, the piezoelectric characteristics are deteriorated. In particular, in order to further enhance the piezoelectric characteristics and mechanical strength, the value of “s” is preferably in the range of 0.90 ≦ s ≦ 0.99, and within the range of 0.93 ≦ s ≦ 0.97. Further preferred. Note that the value of “s” in Chemical Formula 5 is the composition ratio of the first element when the composition ratio of the second element is 1. Therefore, the composition ratio (the molar ratio of the first element to the second element) ( First element / second element).
[0017]
The value of “w / x” in Chemical Formula 5, that is, the composition ratio of (Zn _1/3 Nb _2/3 ) to (Mn _1/3 B _2/3 ) is 0.2 ≦ w / x ≦ 3. The reason for setting it to 0 is that if it is less than 0.2, the optimum firing temperature becomes high, and the piezoelectric characteristics and strength characteristics deteriorate, and if it exceeds 3.0, the mechanical strength decreases. is there. In particular, since the optimum firing temperature increases as the value of w / x decreases, the value of “w / x” is 0.333 ≦ w / x in view of the melting point or manufacturing cost of the internal electrode in the multilayer piezoelectric device. ≦ 3.0 is preferable, and 0.5 ≦ w / x ≦ 3.0 is more preferable. In this way, even with a laminated piezoelectric device, good characteristics can be obtained at low cost without increasing the firing temperature.
[0018]
The value of “y” in Chemical Formula 5, that is, the composition ratio of titanium is 0.1 ≦ y ≦ 0.5 in terms of molar ratio, and the value of “z”, that is, the composition ratio of zirconium is 0.2 ≦ z ≦ in terms of molar ratio. The reason of 0.6 is that good piezoelectric characteristics can be obtained within these ranges.
[0019]
In the case where two or more elements are added to A in Chemical Formula 5, the composition ratio thereof is arbitrary. In addition, the composition shown in Chemical formula 5 is obtained stoichiometrically from, for example, the amount of metal at the time of blending the raw materials.
[0020]
Moreover, this piezoelectric ceramic is comprised by several particle | grains, The average particle diameter is about 0.2 micrometer-10 micrometers, for example.
[0021]
A piezoelectric ceramic having such a configuration can be manufactured, for example, as follows.
[0022]
First, an oxide containing a first element and a second element is prepared as a starting material, and these are mixed according to the target composition. At that time, the raw material of the alkaline earth metal element or manganese may be an oxide that becomes an oxide by firing, such as carbonate or oxalate, instead of an oxide. Moreover, you may use the raw material which becomes an oxide by baking also in another element. Next, the mixture is calcined at a temperature of 800 ° C. to 900 ° C. for about 2 hours, and then the calcined product is pulverized. Subsequently, a binder is added to the calcined powder, and compression molding is performed at a pressure of about 5 × 10 ⁸ Pa, for example. After that, the compact is fired in the atmosphere at a temperature of about 1000 ° C. to 1200 ° C. for about 2 hours. Thereby, the piezoelectric ceramic according to the present embodiment is obtained.
[0023]
This piezoelectric ceramic is preferably used as a material for a piezoelectric device that vibrates greatly and requires high mechanical strength, such as a piezoelectric transformer or an ultrasonic motor. Here, a piezoelectric transformer will be specifically described as an example.
[0024]
FIG. 1 shows a structure of a piezoelectric transformer using a piezoelectric ceramic according to the present embodiment. This piezoelectric transformer is a so-called “Rosen type”, and has a device body 10 having, for example, a rectangular single plate structure. This device body 10 is constituted by a piezoelectric ceramic according to the present embodiment. The size of the device body 10 is, for example, a length L in the longitudinal direction of about 15 mm to 40 mm, a width W of about 3 mm to 7 mm, and a thickness T of about 0.7 mm to 1.5 mm. In this piezoelectric transformer, since the piezoelectric ceramic according to the present embodiment is used, sufficient mechanical strength can be obtained even if the thickness T of the device body 10 is as thin as 2 mm or less. A remarkable effect is obtained when the thickness is 0.05 mm to 1 mm.
[0025]
The device main body 10 also has a primary part 11 provided on one side in the length direction and a secondary part 12 provided on the other side in the length direction. The primary part 11 is polarized in the thickness direction, and the secondary part 12 is polarized in the length direction. The length L1 of the primary part 11 is about 7 mm to 20 mm, for example. A pair of input electrodes 21 and 22 are provided on both surfaces facing each other in the thickness direction of the primary portion 11, and an output electrode 23 is provided on the end surface in the length direction of the secondary portion 12. The input electrodes 21 and 22 and the output electrode 23 are each made of a conductor such as silver (Ag), for example, and have a thickness of about 1 μm to 20 μm.
[0026]
In the piezoelectric transformer having such a configuration, when an AC voltage having a 1-wavelength or 1 / 2-wavelength resonance is applied to the primary part 11 through the input electrodes 21 and 22, electric energy vibrates in the primary part 11 having low impedance characteristics. When converted into energy and this vibrational energy is propagated to the secondary part 12 having high impedance characteristics, the vibrational energy is converted into electric energy in the secondary part 12 and is about 5 to 15 times the input voltage. A voltage is obtained. Here, since the device main body 10 is composed of the piezoelectric ceramic according to the present embodiment, the device main body 10 has sufficient mechanical strength. Therefore, vibration with a large amplitude is possible and the input voltage can be increased, so that a high voltage can be obtained.
[0027]
Such a piezoelectric transformer can be manufactured by a conventional method. For example, first, a piezoelectric ceramic is manufactured as described above, and then processed into a predetermined size to form the device body 10. Next, for example, the input electrodes 21 and 22 and the output electrode 23 are respectively formed on the device body 10, and the polarization process is performed in the order of the primary part 11 and then the secondary part 12. Thereby, the piezoelectric transformer shown in FIG. 1 is obtained.
[0028]
In the above-described piezoelectric transformer, the device body 10 has a piezoelectric ceramic single plate structure. For example, as shown in FIG. 2, the primary portion 11 of the device body 10 has a laminated structure. Also good. Here, the same reference numerals are assigned to the components corresponding to the piezoelectric transformer shown in FIG.
[0029]
The primary part 11 of the device main body 10 has a structure in which piezoelectric ceramic layers 11a and internal electrodes 24 are alternately stacked. The internal electrodes 24 extend alternately in opposite directions and are connected to a pair of input electrodes 21 and 22 provided on side surfaces facing in the width direction. Other configurations are the same as those of the piezoelectric transformer shown in FIG. Since this piezoelectric transformer has such a laminated structure, the voltage conversion magnification can be increased as compared with the single plate structure shown in FIG.
[0030]
This piezoelectric transformer can be manufactured as follows. For example, first, the raw material powder of the piezoelectric ceramic is mixed, calcined and pulverized, and then the binder is added to form a sheet and the internal electrode 24 is printed. Next, a plurality of these are stacked and fired to form the device body 10. Subsequently, as described above, the input electrodes 21 and 22 and the output electrode 23 are formed, and polarization processing is performed. Thereby, the piezoelectric transformer shown in FIG. 2 is obtained.
[0031]
As described above, according to the present embodiment, the first element, the second element, and the oxide composed of oxygen are contained, and the first element is selected from the group consisting of lead, calcium, strontium, and barium. Since at least lead is contained, the second element contains zinc, manganese, titanium , zirconium, niobium and tantalum , and the composition of the oxide is represented by, for example, the above chemical formula 5, the raw material powder is pulverized or hot. The mechanical strength can be improved easily and inexpensively without performing pressing or the like, and excellent piezoelectric characteristics can also be obtained.
[0032]
Therefore, if a piezoelectric device is configured using this piezoelectric ceramic, for example, even if it is vibrated with a large amplitude or an impact is applied from the outside, destruction can be prevented and the quality and reliability of the device can be improved. be able to. In particular, the performance of a piezoelectric device with a large operation load such as a piezoelectric transformer or an ultrasonic motor can be improved.
[0033]
【Example】
Furthermore, specific examples of the present invention will be described.
[0034]
(Examples 1-6 )
First, as a starting material, lead oxide (PbO) powder, zinc oxide (ZnO) powder, niobium oxide (Nb ₂ O ₅ ) powder, manganese carbonate (MnCO ₃ ) powder, titanium oxide (TiO ₂ ) powder, zirconium oxide (ZrO ₂₎ ) Powder, antimony oxide (Sb ₂ O ₃ ) powder, and tantalum oxide (Ta ₂ O ₅ ) powder were prepared. Next, these raw material powders were blended so that the ratio of the metal element was as shown in the following chemical formula 6, and wet mixed by a ball mill. That is, the value of a in the above chemical formula 5 is zero, the value of s is 0.96, the value of y is 0.42 and the value of z is 0.4, and the element of B, the value of w, and the value of x The values were changed as shown in Table 1 in Examples 1 to 6 and Reference Examples 1 to 12 , respectively.
[0035]
[Chemical 6]

[0036]
[Table 1]

[0037]
Subsequently, the mixture was calcined at about 850 ° C. for about 2 hours, and then the calcined product was wet pulverized with a ball mill. After that, water was added as a binder to the calcined powder and compression molded into a plate shape of 50 mm in length and width at a pressure of about 5 × 10 ⁸ Pa. After molding, this compact was fired at about 1100 ° C. in the atmosphere for about 2 hours to obtain the piezoelectric ceramics of Examples 1 to 6 and Reference Examples 1 to 12 , respectively. In Examples 1 to 6 and Reference Examples 1 to 12 , the other conditions are the same except that the B element, the value of w or the value of x in the above chemical formula 6 when blending the raw material powder are different. .
[0038]
Moreover, as Comparative Examples 1 to 7 with respect to Examples 1 to 6 , the element of B, the value of w or the value of x in the above chemical formula 6 when blending the raw material powder was changed as shown in Table 2. Except for the above, piezoelectric ceramics were produced in the same manner as in Examples 1 to 6 , respectively.
[0039]
[Table 2]

[0040]
For the piezoelectric ceramics of Examples 1 to 6, Reference Examples 1 to 12, and Comparative Examples 1 to 7 thus obtained, the density was measured. As a result, it was confirmed that a value of 95% or more was obtained for each theoretical density.
[0041]
Moreover, about the piezoelectric ceramic of Examples 1-6, Reference Examples 1-12, and Comparative Examples 1-7, the strength test by 3-point bending strength was each performed. At that time, the size of the test sample was 2 mm in length, 4 mm in width, and 0.9 mm in thickness, respectively, and the bending strength was measured according to JIS (R1601). The results are shown in Table 1 and Table 2, respectively.
[0042]
Furthermore, using the piezoelectric ceramics of Examples 1 to 6, Reference Examples 1 to 12, and Comparative Examples 1 to 7, piezoelectric transformers as shown in FIG. Specifically, after processing the obtained piezoelectric ceramic into a size of length L32 mm, width W 4.5 mm, and thickness T1 mm, the input electrodes 21 and 22 and the output electrode 23 are formed, respectively, and the primary portion 11, then In the order of the secondary part 12, in a 120 degreeC silicon oil, the polarization process was performed for 30 minutes by the electric field of 2 kV / mm, and the piezoelectric transformer was produced. At that time, the length L1 of the primary part was 16 mm.
[0043]
For the fabricated piezoelectric transformers of Examples 1 to 6, Reference Examples 1 to 12, and Comparative Examples 1 to 7, as shown in FIG. It was held and input / output was performed, and energy conversion efficiency which is one of the piezoelectric characteristics was measured. The results are also shown in Table 1 and Table 2, respectively.
[0044]
Table 2 also shows the bending strength and the energy conversion efficiency of a piezoelectric transformer manufactured using the piezoelectric ceramic according to an example of the piezoelectric ceramic described in Japanese Patent No. 2957537 as Reference Example 13 . The piezoelectric ceramic of Reference Example 13 shown in Table 2 is composed of 1.0% by mass of manganese oxide and 0.5% by mass of niobium oxide in lead zirconate zinc niobate having the composition shown in Chemical Formula 7 below. Each is added.
[0045]
[Chemical 7]
Pb [(Zn _1/3 Nb _2/3 ) _0.20 Ti _0.4 Zr _0.4 ] O ₃
[0046]
As can be seen from Tables 1 and 2, according to Examples 1 to 6 , higher values were obtained for bending strength and energy conversion efficiency than Comparative Examples 1 to 7 and Reference Example 13 , respectively. That is, if the range of 0.2 ≦ w / x ≦ 3.0 in a molar ratio of the composition ratio w / x of (Zn _1/3 Nb _2/3) for (Mn _1/3 B _2/3) It was found that the mechanical strength can be improved and excellent piezoelectric properties can be obtained.
[0047]
(Examples 19 to 25)
The raw material powder was blended so that the ratio of the metal element was the composition shown in the following chemical formula 8, and the value of s in chemical formula 8 was changed as shown in Table 3 in Examples 19 to 25, respectively. Except for the above, piezoelectric ceramics were produced in the same manner as in Examples 1 to 6 and Reference Examples 1 to 12 , respectively. That is, in Examples 19 to 25, the value of a in Chemical Formula 5 is zero, the element of B is tantalum, the values of w and x are 0.09, the value of w / x is 1, and the value of y is 0. The values of 42 and z were set to 0.4, and the value of s was changed.
[0048]
[Chemical 8]

[0049]
[Table 3]

[0050]
Further, as Comparative Examples 8 to 10 with respect to Examples 19 to 25, Examples 19 to 25 except that the value of s in the above chemical formula 8 when blending the raw material powder was changed as shown in Table 3 Similarly, piezoelectric ceramics were produced.
[0051]
For the obtained piezoelectric ceramics of Examples 19 to 25 and Comparative Examples 8 to 10, as in Examples 1 to 6 and Reference Examples 1 to 12 , density measurements and strength tests were performed, and piezoelectric transformers were manufactured. The energy conversion efficiency was measured respectively. As for the density, it was confirmed that a value of 95% or more of the theoretical density was obtained. The results of the strength test and energy conversion efficiency are shown in Table 3, respectively.
[0052]
As can be seen from Table 3, according to Examples 19 to 25, even when compared with Comparative Examples 8 to 10 and Reference Example 13 shown in Table 2, high values were obtained for both bending strength and energy conversion efficiency. It was. That is, if the composition ratio s of the first element to the second element is within a range of 0.9 ≦ s <1.0 in terms of molar ratio, the mechanical strength can be improved and excellent piezoelectric characteristics can be obtained. I found out that Further, if it is in the range of 0.90 ≦ s ≦ 0.99, higher mechanical strength can be obtained, and if it is in the range of 0.93 ≦ s ≦ 0.97, higher mechanical strength can be obtained. I also found out that
[0053]
(Examples 26 to 37)
Calcium carbonate (CaCO ₃ ) powder, strontium carbonate (SrCO ₃ ) powder and barium carbonate (BaCO ₃ ) powder are further prepared as starting materials, and the raw material powder has a composition represented by the chemical formula 9 below. In the same manner as in Examples 1 to 6 and Reference Examples 1 to 12 , except that the element of A and the value of a in Chemical Formula 9 were changed as shown in Table 4 in Examples 26 to 37, respectively. Thus, each of the piezoelectric ceramics was produced. That is, in Examples 26 to 37, the value of s in Chemical Formula 5 is 0.96, the element of B is tantalum, the values of w and x are 0.09, the value of w / x is 1, and the value of y is The values of 0.42 and z were set to 0.4, and the element of A and the value of a were changed.
[0054]
[Chemical 9]

[0055]
[Table 4]

[0056]
Further, as Comparative Examples 11 to 13 with respect to Examples 26 to 37, except that the element of A and the value of a in the above chemical formula 9 when blending the raw material powder were changed as shown in Table 4, the examples Piezoelectric ceramics were respectively produced in the same manner as 26-37.
[0057]
For the obtained piezoelectric ceramics of Examples 26 to 37 and Comparative Examples 11 to 13, as in Examples 1 to 6 and Reference Examples 1 to 12 , a density measurement and a strength test were performed, respectively, and a piezoelectric transformer was manufactured. The energy conversion efficiency was measured respectively. As for the density, it was confirmed that a value of 95% or more of the theoretical density was obtained. The results of the strength test and energy conversion efficiency are shown in Table 4, respectively. Table 4 also shows the bending strength and energy conversion efficiency of Example 3 corresponding to the case where the value of a in Chemical Formula 9 is zero.
[0058]
As can be seen from Table 4, according to Examples 26 to 37, even when compared with Comparative Examples 11 to 13 and Reference Example 13 shown in Table 2, high values are obtained for both bending strength and energy conversion efficiency. It was. That is, if the composition ratio a of the alkaline earth metal that replaces a part of lead is within the range of 0 ≦ a ≦ 0.1 in terms of molar ratio, the mechanical strength can be improved and excellent piezoelectric characteristics can be obtained. I found out that Further, 0 if the range of ≦ a ≦ 0.05, it is possible to enhance the mechanical strength and the piezoelectric properties, if the range of 0 ≦ a ≦ 0.02, further high Mera piezoelectric properties I also found out.
[0059]
In the above-described examples, some examples have been specifically described. However, even if other piezoelectric ceramics are configured to include the oxide described in the above-described embodiment, Similar results can be obtained.
[0060]
Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made .
[0062]
For example , in the above-described embodiments and examples, the case where the piezoelectric ceramic is used for the piezoelectric transformer has been described. However, the piezoelectric ceramic can be widely used for other piezoelectric devices such as an ultrasonic vibrator or a filter. Among them, it is preferable to use a piezoelectric device with a large operating load because a particularly high effect can be obtained. However, a piezoelectric device that does not require high mechanical strength can be used as a matter of course.
[0063]
【The invention's effect】
As described above, according to the piezoelectric ceramic according to claim 1, the oxide containing the first element, the second element, and oxygen is contained , and the first element is lead, calcium, strontium, and barium. And containing at least lead in the group consisting of the following: Since the composition ratio of the first element to the second element is set to 0.9 to 1.0 in terms of molar ratio, it is simple and inexpensive without pulverizing the raw material powder or hot pressing. The mechanical strength can be improved, and excellent piezoelectric characteristics can be obtained.
[0064]
Further, according to the piezoelectric device according to claim 2, since the piezoelectric ceramic of the present invention is used, for example, even if it is vibrated with a large amplitude or an impact is applied from the outside, it can be prevented from being broken. Device quality and reliability can be improved. In particular, there is an effect that the performance of a piezoelectric device with a large operation load such as a piezoelectric transformer or an ultrasonic motor can be improved.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the structure of a piezoelectric transformer according to an embodiment of the present invention.
FIG. 2 is a perspective view showing the structure of another piezoelectric transformer of the present invention.
FIG. 3 is a diagram for explaining a method of measuring energy conversion efficiency of a piezoelectric transformer according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Device main body, 11 ... Primary part, 11a ... Piezoelectric ceramic layer, 12 ... Secondary part, 21, 22 ... Input electrode, 23 ... Output electrode, 24 ... Internal electrode, 30 ... Contact probe.

Claims (2)

And SQLDESC_BASE_TABLE_NAME This contains an oxide consisting the first element and the second element and oxygen (O), in
The first element includes at least lead in the group consisting of lead (Pb), calcium (Ca), strontium (Sr), and barium (Ba), the composition of which is represented by the following chemical formula 1,
The second element includes zinc (Zn), manganese (Mn), titanium (Ti), zirconium (Zr), niobium (Nb) and tantalum (Ta), the composition of which is represented by the following chemical formula 2,
The piezoelectric ceramic according to claim 1, wherein a composition ratio of the first element to the second element (first element / second element) is 0.9 or more and smaller than 1.0.

(In the formula, A is at least one member selected from the group consisting of Ca, Sr and Ba, and a is a value within the range of 0 ≦ a ≦ 0.1.)

(Where w, x, y and z are 0.2 ≦ w / x ≦ 3.0, 0.1 ≦ y ≦ 0.5, 0.2 ≦ z ≦ 0.6, and w + x + y + z = 1, respectively. (The value is within the range.)   A piezoelectric device using the piezoelectric ceramic according to claim 1.

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