JP4752156B2 - Piezoelectric ceramic composition for laminated piezoelectric element, laminated piezoelectric element, method for producing laminated piezoelectric element, and laminated piezoelectric device - Google Patents

Description

【００１０】
そして、得られた混合物を乾燥し、８００〜１０００℃の温度で仮焼して、仮焼粉を得た。この仮焼粉に水と分散剤を加えて湿式粉砕した後、有機バインダーおよび添加剤を加え湿式混合し、シート成形を行った。これを所望のサイズに打抜いた後、Ａｇ／Ｐｄ＝７／３のＡｇ・Ｐｄ電極ペーストを塗布し、２０層積み重ねた後、圧着して積層体を得た。
この積層体を１０００〜１１００℃の温度で焼成し、１層のセラミックの厚みが２０〜４０μｍである積層圧電素子を得た。この積層圧電素子の内部電極を導体で接続し、絶縁オイル中にて１．５〜３．５ｋＶ／ｍｍの電界で分極処理を行った。
【００１１】
次に、この積層圧電素子の比誘電率（ε₃₃ ^T ／ε₀ ）、共振−反共振法より算出した電気機械結合係数（ｋ₃₁）および圧電ｄ₃₁定数（「｜ｄ₃₁｜⁽¹⁾ 」と記述）、１．５ｋＶ／ｍｍ印加電界下の歪みより算出した圧電ｄ₃₁定数（「｜ｄ₃₁｜⁽²⁾ 」と記述）、電気抵抗率（ρ）、キュリー温度（Ｔｃ）、リフロー炉（ピーク温度：２６０℃）２回通過による｜ｄ₃₁｜⁽¹⁾ の低下率、｜ｄ₃₁｜⁽²⁾ ／（ε₃₃ ^T ／ε₀ ）、および｜ｄ₃₁｜⁽¹⁾ の−２０℃〜８０℃における温度変化率を測定した。その結果を表２および表３に示す。なお、電気抵抗率が１．０×１０¹¹Ω・ｃｍ未満の試料については、絶縁不良の割合が高いため不良と判断し、その一部について｜ｄ₃₁｜⁽¹⁾ の温度変化率および｜ｄ₃₁｜⁽²⁾ を測定していない。また、電気抵抗率は１．０×１０¹¹Ω・ｃｍ以上であれば良品とみなせるが、好ましくは２．０×１０¹¹Ω・ｃｍ以上、さらに好ましくは３．０×１０¹¹Ω・ｃｍ以上であることが望ましい。
【００１２】
【表２】

【００１３】
【表３】

【００１４】
また、比較例として３成分系ＰＺＴについて示す。３成分系ＰＺＴ磁器の製造方法、評価方法、評価基準は、実施例に準ずるものである。比較例の組成を表４に示し、比較例の結果を表３に実施例の結果と併せて示す。
【００１５】
【表４】

【００１６】
なお、表１〜表４において、試料番号に＊印を付してあるものは、本願発明の範囲外のものである。
【００１７】
試料番号１のようにｚが０．９９８を超えるもの、および試料番号３４のような３成分系ＰＺＴでは、電気抵抗率ρが１．０×１０¹¹Ω・ｃｍ未満となり、好ましくない。
【００１８】
試料番号９のようにｚが０．９５未満のもの、試料番号１５のようにＴｉ、ＺｒサイトのＭ（ＭはＮｂ、Ｓｂ、Ｗのうち少なくとも１種）による置換量ｙが０．０３を超えるもの、試料番号２０のようにＰｂの置換量がＰｂ含有量に対して５．５ｍｏｌ％を超えるもの、および試料番号３７のような３成分系ＰＺＴでは、１１００℃以下では十分に焼結しないため、電気抵抗率ρが１．０×１０¹¹Ω・ｃｍ未満となり、好ましくない。
【００１９】
試料番号１０のようにＴｉ、Ｚｒサイトの置換量ｙが０．００５未満のもの、試料番号２３、３０のようにＴｉ／Ｚｒ比を表すｘが０．４５≦ｘ≦０．５２の範囲外にあるもの、および試料番号３６のような３成分系ＰＺＴでは、｜ｄ₃₁｜⁽¹⁾ が１００ｐＣ／Ｎ未満となり、好ましくない。
【００２０】
試料番号３５のような３成分系ＰＺＴでは、キュリー温度が３００℃未満であり、耐熱性が悪く好ましくない。
【００２１】
以上より実施例において、本願発明の範囲内における積層圧電素子用圧電磁器組成物を用いて作製した積層圧電素子は、電気抵抗率ρが１．０×１０¹¹Ω・ｃｍ以上と高く、｜ｄ₃₁｜⁽¹⁾ が１００ｐＣ／Ｎ以上と大きく、かつキュリー温度Ｔｃが３００℃以上と高く、かつリフローによる｜ｄ₃₁｜⁽¹⁾ の低下率が２０％以下と小さい。すなわち、高い圧電特性と高いキュリー温度（高耐熱性）とを両立し、かつ電気抵抗率の高い積層圧電素子を得ることができた。
【００２２】
好ましくは、試料番号２４、２５、２６を除く実施例の試料のように、Ｔｉ／Ｚｒ比を表すｘが０．４７５≦ｘ≦０．５２の範囲内にあるものは、｜ｄ₃₁｜⁽¹⁾ 温度変化率が８００ｐｐｍ／℃以下と小さく、圧電センサの感度温度特性を良くすることが可能であり、非常に有効である。
【００２３】
さらに好ましくは、試料番号２４、２５，２６、２７の試料のように、Ｔｉ／Ｚｒ比を表すｘが０．４５≦ｘ≦０．４７５の範囲内にあるものは、高い｜ｄ₃₁｜⁽²⁾ と比較的低いε₃₃ ^T ／ε₀ を両立しており、変位性能に優れかつ低消費電力のアクチュエータが得られ、非常に有効である。実施例では高い｜ｄ₃₁｜⁽²⁾ かつ低いε₃₃ ^T ／ε₀ の指標として｜ｄ₃₁｜⁽²⁾ ／（ε₃₃ ^T ／ε₀ ）を用いており、試料番号２４、２５、２６、２７の｜ｄ₃₁｜⁽²⁾ ／（ε₃₃ ^T ／ε₀ ）は０．１５×１０^-12 以上と大きい。
【００２４】
なお、この発明にかかる積層圧電素子用圧電磁器組成物は上記の実施例の組成に限定されるものではなく、発明の要旨の範囲内であれば有効である。
【００２５】
図１はこの発明にかかるショックセンサの一例を示す分解斜視図であり、図２はそのショックセンサに用いられる積層圧電素子を示す図解図である。図１に示すショックセンサ１０は、積層圧電素子１２を含む。
【００２６】
積層圧電素子１２は、２層の圧電磁器層１４ａおよび１４ｂを含む。これらの圧電磁器層１４ａおよび１４ｂは、上述のこの発明にかかる積層圧電素子用圧電磁器組成物からなり、積層されかつ一体的に形成される。また、これらの圧電磁器層１４ａおよび１４ｂは、図２の矢印で示すように、中央部分が互いに内側に向かって厚み方向に分極され、両側の外側部分が互いに外側に向かって厚み方向に分極されている。
【００２７】
２層の圧電磁器層１４ａおよび１４ｂの間には、その中央部を含む中間部に、内部電極１６が形成される。また、圧電磁器層１４ａの表面には、その中央部を含む中間部から一端部にわたって、一方の外部電極１８ａが形成される。さらに、圧電磁器層１４ｂの表面には、その中央部を含む中間部から他端部にわたって、他方の外部電極１８ｂが形成される。
【００２８】
積層圧電素子１２は、ケース２０で保持される。ケース２０は、コ字状の２つの中ケース２２ａおよび２２ｂを含む。積層圧電素子１２の両端部は、２つの中ケース２２ａおよび２２ｂの両端部で挟まれ保持される。積層圧電素子１２および中ケース２２ａ、２２ｂの上下には、上ケース２４および下ケース２６が設けられる。上ケース２４および下ケース２６には、積層圧電素子１２の中間部に対応する部分に、積層圧電素子１２の振動空間となるへこみ部が形成されている。
【００２９】
中ケース２２ａおよび２２ｂの表面には、端子電極２８ａおよび２８ｂがそれぞれ形成される。一方の端子電極２８ａは一方の外部電極１８ａに接続され、他方の端子電極２８ｂは他方の外部電極１８ｂに接続される。
【００３０】
図３はこの発明にかかる積層圧電ブザーの一例を示す分解斜視図であり、図４はその積層圧電ブザーに用いられる積層圧電素子を示す図解図である。図３に示す積層圧電ブザー３０は、積層圧電素子３２を含む。
【００３１】
積層圧電素子３２は、２層の圧電磁器層３４ａおよび３４ｂを含む。これらの圧電磁器層３４ａおよび３４ｂは、上述のこの発明にかかる積層圧電素子用圧電磁器組成物からなり、積層されかつ一体的に形成される。また、これらの圧電磁器層３４ａおよび３４ｂは、図４の矢印で示すように、厚み方向にかつ同じ方向に分極されている。
【００３２】
２層の圧電磁器層３４ａおよび３４ｂの間には、その中央部を含む中間部から一端部に、内部電極３６が形成される。また、２層の圧電磁器層３４ａおよび３４ｂの一端部には、一方の外部電極３８ａが形成される。この外部電極３８ａは、内部電極３６に接続される。また、圧電磁器層３４ａおよび３４ｂの表面の他の部分には、他方の外部電極３８ｂが形成される。
【００３３】
積層圧電素子３２は、ケース４０で保持される。ケース４０は、箱型のケース本体４２を含む。積層圧電素子３２は、ケース本体４２内に入れられ保持される。また、ケース本体４２には、板状の蓋４４が設けられる。
【００３４】
蓋４４の表面には、端子電極４６ａおよび４６ｂがそれぞれ形成される。一方の端子電極４６ａは一方の外部電極３８ａに接続され、他方の端子電極４６ｂは他方の外部電極３８ｂに接続される。
【００３５】
図５はこの発明にかかる積層圧電アクチュエータの一例を示す図解図である。図５に示す積層圧電アクチュエータ５０は、積層圧電素子５２を含む。
【００３６】
積層圧電素子５２は、多数の圧電磁器層５４を含む。これらの圧電磁器層５４は、上述のこの発明にかかる積層圧電素子用圧電磁器組成物からなり、積層されかつ一体的に形成される。また、これらの圧電磁器層５４は、厚み方向にかつ１層おきに逆の方向に分極されている。
【００３７】
これらの圧電磁器層５４の間には、内部電極５６がそれぞれ形成される。この場合、１層おきの内部電極５６が積層圧電素子５２の一端面から引き出され、他の内部電極５６が積層圧電素子５２の他端面から引き出される。
【００３８】
積層圧電素子５２の一端面および他端面には、外部電極５８ａおよび５８ｂがそれぞれ形成される。一方の外部電極５８ａは１層おきの内部電極５６に接続され、他方の外部電極５８ｂは他の内部電極５６に接続される。
【００３９】
なお、この発明は、上述のショックセンサ１０、積層圧電ブザー３０および積層圧電アクチュエータ５０以外のショックセンサ、積層圧電ブザーおよび積層圧電アクチュエータなど他の積層圧電装置にも適用される。
【００４０】
【発明の効果】
この発明によれば、ＰＺＴのＴｉ、ＺｒサイトにＮｂ、Ｓｂ、Ｗのうち少なくとも１種を置換した２成分ＰＺＴ圧電磁器において、Ａｇ／Ｐｄ比が７／３以上の内部電極を用いた積層圧電素子の作製に適した積層圧電素子用圧電磁器組成物、その積層圧電素子用圧電磁器組成物を用いた積層圧電素子、積層圧電素子の製造方法および積層圧電素子を用いた積層圧電装置が得られる。
この発明にかかる積層圧電素子用圧電磁器組成物は、１１００℃以下で焼成可能であるため、安価なＡｇ／Ｐｄ比が７／３以上の内部電極と共焼結可能であり、積層圧電素子の低コスト化が可能となる。
また、この発明にかかる積層圧電素子用圧電磁器組成物を、たとえば積層圧電アクチュエータに用いることにより、変位性能、耐熱性に優れかつ低消費電力のアクチュエータが得られる。
また、この発明にかかる積層圧電素子用圧電磁器組成物を、たとえば積層圧電センサに用いることにより、感度が高くかつ耐熱性、感度温度特性の良好な圧電センサが得られる。
【図面の簡単な説明】
【図１】この発明にかかるショックセンサの一例を示す分解斜視図である。
【図２】図２に示すショックセンサに用いられる積層圧電素子を示す図解図である。
【図３】この発明にかかる積層圧電ブザーの一例を示す分解斜視図である。
【図４】図３に示す積層圧電ブザーに用いられる積層圧電素子を示す図解図である。
【図５】この発明にかかる積層圧電アクチュエータの一例を示す図解図である。
【符号の説明】
１０ ショックセンサ
１２、３２、５２ 積層圧電素子
１４ａ、１４ｂ、３４ａ、３４ｂ、５４ 圧電磁器層
１６、３６、５６ 内部電極
１８ａ、１８ｂ、３８ａ、３８ｂ、５８ａ、５８ｂ 外部電極
２０、４０ ケース
２２ａ、２２ｂ 中ケース
２４ 上ケース
２６ 下ケース
２８ａ、２８ｂ、４６ａ、４６ｂ 端子電極
３０ 積層圧電ブザー
４２ ケース本体
４４ 蓋
５０ 積層圧電アクチュエータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric ceramic composition for a laminated piezoelectric element, a laminated piezoelectric element, a method for producing a laminated piezoelectric element, and a laminated piezoelectric device, and more particularly to a laminated piezoelectric device such as a laminated piezoelectric actuator, a laminated piezoelectric buzzer, and a laminated piezoelectric sensor. The present invention relates to a piezoelectric ceramic composition for piezoelectric elements.
[0002]
[Prior art]
Conventionally, there are a wide variety of piezoelectric devices using a piezoelectric ceramic composition, such as piezoelectric actuators, piezoelectric buzzers, and piezoelectric sensors. A piezoelectric ceramic composition used in such a piezoelectric device is required to have a high piezoelectric d constant. Such a piezoelectric ceramic composition is also required to have a high Curie temperature. When the Curie temperature is high, the heat resistance of the piezoelectric element becomes high. For example, even when the piezoelectric element is exposed to a high temperature of about 200 ° C., for example, when passing through a solder reflow furnace during mounting, deterioration of piezoelectric characteristics due to heat is relatively suppressed. can do. In particular, in a piezoelectric actuator, when the Curie temperature is high, a relatively low dielectric constant can be obtained, which is effective for reducing power consumption during driving. In the case of a piezoelectric sensor, particularly in an acceleration sensor such as a shock sensor, if the Curie temperature is high, the temperature change rate of the piezoelectric d constant is reduced, and the sensitivity temperature characteristic is improved.
Conventionally, as a piezoelectric material that achieves both a high piezoelectric d constant and a high Curie temperature, Nb, Sb, W at the Ti and Zr sites of a lead zirconate titanate (hereinafter referred to as “PZT”) piezoelectric ceramic composition. A method of substituting at least one of them has been used. In addition to this, a method of substituting at least one of Ca, Sr, and Ba into the Pb site has also been used. As an example of such a two-component PZT piezoelectric ceramic composition, JP-A-5-319925 discloses PZT in which Sr is substituted at the Pb site and Nb is substituted at the Ti and Zr sites. On the other hand, a ternary PZT containing elements such as Cr, Mn, Mg, Ni and Fe in addition to Nb, Sb and W has a lower electrical resistivity than a two-component PZT. Problems are likely to occur and are not preferred.
[0003]
[Problems to be solved by the invention]
In recent years, piezoelectric devices such as piezoelectric actuators, piezoelectric buzzers, piezoelectric sensors, and the like have become more demanding for miniaturization and higher performance, and piezoelectric elements have been stacked. There is a method for producing a laminated piezoelectric element, in which electrodes are formed on both main surfaces of a piezoelectric ceramic, the piezoelectric ceramics are stacked and bonded, and these electrodes are connected alternately, but this method is limited to miniaturization of the element. Is not preferable. Therefore, in such a case, the piezoelectric material powder is formed into green sheets, electrode paste is applied to the green sheets, the green sheets are stacked and pressure-bonded, and the piezoelectric ceramic and the internal electrode are co-fired. The production method is desirable. A relatively inexpensive Ag / Pd electrode is generally used as the internal electrode in this manufacturing method, and the Ag / Pd ratio of the Ag / Pd electrode is preferably 7/3 or more from the viewpoint of electrode cost. However, in this case, it is necessary to set the firing temperature of the laminated piezoelectric element to 1100 ° C. or lower in consideration of the melting point of the internal electrode.
However, a conventional piezoelectric ceramic as disclosed in Japanese Patent Laid-Open No. 5-319925 has a sintering temperature as high as about 1250 ° C., and a multilayer piezoelectric element using an internal electrode having an Ag / Pd ratio of 7/3 or more is prepared. There was a problem of difficulty.
[0004]
Therefore, a main object of the present invention is to provide an internal electrode having an Ag / Pd ratio of 7/3 or more in a two-component PZT piezoelectric ceramic in which at least one of Nb, Sb, and W is substituted on the Ti and Zr sites of PZT. Piezoelectric ceramic composition for laminated piezoelectric element suitable for production of the laminated piezoelectric element used, laminated piezoelectric element using the piezoelectric ceramic composition for laminated piezoelectric element, method for producing laminated piezoelectric element, and laminated piezoelectric using laminated piezoelectric element Is to provide a device.
[0005]
[Means for Solving the Problems]
The piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention has a composition formula Pb _z [(Ti _x Zr _1-x ) _{1- y My} ] O ₃ (where M is at least one of Nb, Sb, and W). ), And x and y in the composition formula are 0.45 ≦ x ≦ 0.52 and 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.95. A piezoelectric ceramic composition for laminated piezoelectric elements in which Pb is reduced from the stoichiometric composition so that ≦ z ≦ 0.998.
The piezoelectric ceramic composition for such laminated piezoelectric element in this invention, a composition formula Pb _{z [(Ti x Zr 1-x)} 1-y M y ] O ₃ (however, M is Nb, Sb, at least one of W X and y in the composition formula are 0.45 ≦ x ≦ 0.52 and 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0. A piezoelectric ceramic composition for laminated piezoelectric elements, in which Pb is subtracted from the stoichiometric composition so that .98−y ≦ z ≦ 0.998−y.
In the piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention, 5.5 mol% or less of the Pb content may be substituted with at least one of Ca, Sr, and Ba.
The multilayer piezoelectric element according to the present invention is a multilayer piezoelectric element including a piezoelectric ceramic made of the piezoelectric ceramic composition for multilayer piezoelectric element according to the present invention and an internal electrode formed on the piezoelectric ceramic.
Method of manufacturing a multilayer piezoelectric element according to the present invention, the composition formula Pb _{z [(Ti x Zr 1- x) 1} -y M y ] O ₃ (however, M is Nb, Sb, at least one of W) X and y in the composition formula are 0.45 ≦ x ≦ 0.52, 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.95 ≦ z. A method for producing a laminated piezoelectric element comprising a piezoelectric ceramic made of a piezoelectric ceramic composition for a laminated piezoelectric element obtained by reducing Pb from the stoichiometric composition so that ≦ 0.998 and an internal electrode formed in the piezoelectric ceramic. A method for manufacturing a laminated piezoelectric element, in which a piezoelectric ceramic and an internal electrode are co-sintered at 1100 ° C. or lower.
A method for manufacturing a laminated piezoelectric element according to the present invention, the compositional formula Pb _{z [(Ti x Zr 1-x)} 1-y M y ] O ₃ (however, M is Nb, Sb, at least one of W ), And x and y in the composition formula are 0.45 ≦ x ≦ 0.52 and 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.98. A laminated piezoelectric element comprising a piezoelectric ceramic composed of a piezoelectric ceramic composition for laminated piezoelectric elements in which Pb is reduced from the stoichiometric composition so that -y≤z≤0.998-y, and an internal electrode formed in the piezoelectric ceramic A method for manufacturing a multilayer piezoelectric element, wherein the piezoelectric ceramic and the internal electrode are co-sintered at 1100 ° C. or lower.
In the method for manufacturing a laminated piezoelectric element according to the present invention, 5.5 mol% or less of the Pb content in the piezoelectric ceramic composition for a laminated piezoelectric element may be substituted with at least one of Ca, Sr, and Ba.
The multilayer piezoelectric device according to the present invention is a multilayer piezoelectric device including the multilayer piezoelectric element according to the present invention and a terminal electrode connected to the internal electrode.
[0006]
The piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention is a two-component PZT piezoelectric ceramic in which at least one of Nb, Sb, and W is substituted on the Ti and Zr sites of PZT, and the Pb content is reduced to 1100 ° C. A multilayer piezoelectric element using an internal electrode having an Ag / Pd ratio of 7/3 or more can be obtained by enabling the following firing.
The laminated piezoelectric element produced by using the piezoelectric ceramic composition for laminated piezoelectric elements according to the present invention has both a high piezoelectric d constant and a high Curie temperature, and is a laminated piezoelectric actuator, laminated piezoelectric buzzer, laminated piezoelectric sensor, etc. Suitable for piezoelectric devices.
In the piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention, the reason why it is possible to sinter at 1100 ° C. or less by reducing the Pb amount from the stoichiometric composition is that the Pb site amount <Ti Pb by making the amount + Zr amount + M amount (M is at least one of Nb, Sb, W), and more preferably by setting Pb site amount <Ti amount + Zr amount as described in claim 2. This is thought to be due to the suppression of the generation of the heterophasic compound. For example, if a certain amount of a pyrochlore phase composed of Pb and M is present, the progress of reaction and sintering is inhibited, and the improvement of the piezoelectric d constant and the electromechanical coupling coefficient is also inhibited.
Further, as a characteristic effect of the multilayer piezoelectric element according to the present invention, there is an effect that the electrical resistivity can be increased by reducing the Pb amount from the stoichiometric composition. This is presumably because the diffusion of the internal electrode into the ceramic due to the interaction between the liquid phase of Pb and the internal electrode is suppressed. For example, some laminated actuators used in ink jet printer heads have a ceramic thickness of 30 μm or less between internal electrodes, and a drive electric field of 1.0 to 1.5 kV / mm is continuously applied between the internal electrodes. May be. In this case, a high electrical resistivity between the internal electrodes is very effective in terms of large displacement and high reliability.
[0007]
The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the embodiments of the present invention with reference to the drawings.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
(Example)
First, Pb ₃ O ₄ , TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Sb ₂ O ₃ , WO ₃ , CaCO ₃ , SrCO ₃ and BaCO ₃ were prepared as raw material powders.
Then, weighed these powders to obtain the compositions shown in represented Tables 1 with the composition of the composition formula Pb _{z [(Ti x Zr 1-x)} 1-y M y ] O _3, water was added to this Then, wet mixing was performed using a ball mill to obtain a mixture. In Table 1, each value of x, y, z in the composition formula Pb _z [(Ti _x Zr _1-x ) _{1- y My} ] O ₃ , elements of M, elements substituted for the Pb element, and The amount substituted for Pb is shown.
[0009]
[Table 1]

[0010]
And the obtained mixture was dried and calcined at a temperature of 800 to 1000 ° C. to obtain calcined powder. Water and a dispersant were added to this calcined powder and wet pulverized, then an organic binder and additives were added and wet mixed to perform sheet molding. This was punched out to a desired size, then an Ag / Pd electrode paste of Ag / Pd = 7/3 was applied, 20 layers were stacked, and then pressed to obtain a laminate.
This multilayer body was fired at a temperature of 1000 to 1100 ° C. to obtain a multilayer piezoelectric element in which the thickness of one ceramic layer was 20 to 40 μm. The internal electrodes of this laminated piezoelectric element were connected by a conductor and subjected to polarization treatment in an insulating oil with an electric field of 1.5 to 3.5 kV / mm.
[0011]
Next, the relative dielectric constant (ε ₃₃ ^T / ε ₀ ), the electromechanical coupling coefficient (k ₃₁ ) calculated by the resonance-antiresonance method, and the piezoelectric d ₃₁ constant (“| d ₃₁ | ⁽¹⁾⁾ ”, Piezoelectric d ₃₁ constant calculated from strain under an applied electric field of 1.5 kV / mm (described as“ | d ₃₁ | ⁽²⁾ ”), electrical resistivity (ρ), Curie temperature (Tc), reflow Reduction rate of | d ₃₁ | ⁽¹⁾ , | d ₃₁ | ⁽²⁾ / (ε ₃₃ ^T / ε ₀ ), and −d ₃₁ | ⁽¹⁾ − due to two passes of furnace (peak temperature: 260 ° C.) The temperature change rate in 20 to 80 degreeC was measured. The results are shown in Tables 2 and 3. Note that a sample with an electrical resistivity of less than 1.0 × 10 ¹¹ Ω · cm is judged to be defective because of a high proportion of insulation failure, and a part of the temperature change rate of | d ₃₁ | ⁽¹⁾ and | d ₃₁ | ⁽²⁾ is not measured. Further, if the electric resistivity is 1.0 × 10 ¹¹ Ω · cm or more, it can be regarded as a non-defective product, but preferably 2.0 × 10 ¹¹ Ω · cm or more, more preferably 3.0 × 10 ¹¹ Ω · cm or more. It is desirable that
[0012]
[Table 2]

[0013]
[Table 3]

[0014]
As a comparative example, a three-component PZT is shown. The manufacturing method, evaluation method, and evaluation criteria for the three-component PZT porcelain are the same as those in the examples. The composition of the comparative example is shown in Table 4, and the result of the comparative example is shown in Table 3 together with the result of the example.
[0015]
[Table 4]

[0016]
In Tables 1 to 4, sample numbers marked with * are outside the scope of the present invention.
[0017]
In the case where z exceeds 0.998 as in sample number 1 and the three-component PZT as in sample number 34, the electrical resistivity ρ is less than 1.0 × 10 ¹¹ Ω · cm, which is not preferable.
[0018]
As in sample number 9, z is less than 0.95, and as in sample number 15, the substitution amount y by M (M is at least one of Nb, Sb, W) of Ti and Zr sites is 0.03. Exceeding, Pb substitution amount of more than 5.5 mol% with respect to Pb content like sample number 20, and ternary PZT like sample number 37 do not sinter sufficiently at 1100 ° C or lower Therefore, the electrical resistivity ρ is less than 1.0 × 10 ¹¹ Ω · cm, which is not preferable.
[0019]
The Ti and Zr site substitution amount y is less than 0.005 as in sample number 10, and x representing the Ti / Zr ratio is out of the range of 0.45 ≦ x ≦ 0.52 as in sample numbers 23 and 30. And a three-component PZT such as sample number 36 are not preferable because | d ₃₁ | ⁽¹⁾ is less than 100 pC / N.
[0020]
In a three-component PZT such as sample number 35, the Curie temperature is less than 300 ° C., and the heat resistance is poor, which is not preferable.
[0021]
As described above, in the examples, the laminated piezoelectric element produced using the piezoelectric ceramic composition for laminated piezoelectric elements within the scope of the present invention has a high electric resistivity ρ of 1.0 × 10 ¹¹ Ω · cm or more, and | d ₃₁ | ⁽¹⁾ is as large as 100 pC / N or more, the Curie temperature Tc is as high as 300 ° C. or more, and the decrease rate of | d ₃₁ | ⁽¹⁾ due to reflow is as small as 20% or less. That is, a multilayer piezoelectric element having both high piezoelectric characteristics and high Curie temperature (high heat resistance) and high electrical resistivity could be obtained.
[0022]
Preferably, as in the samples of Examples other than Sample Nos. 24, 25, and 26, when x representing the Ti / Zr ratio is in the range of 0.475 ≦ x ≦ 0.52, | d ₃₁ | ^{( 1) The} temperature change rate is as small as 800 ppm / ° C. or less, and the sensitivity temperature characteristic of the piezoelectric sensor can be improved, which is very effective.
[0023]
More preferably, as in the sample of the sample No. 24, 25, 26, 27, which x representing the Ti / Zr ratio is in the range of 0.45 ≦ x ≦ 0.475 is higher | d ₃₁ | ^{( Both 2)} and relatively low ε ₃₃ ^T / ε ₀ are compatible, and an actuator with excellent displacement performance and low power consumption is obtained, which is very effective. In the embodiment, | d ₃₁ | ⁽²⁾ / (ε ₃₃ ^T / ε ₀ ) is used as an index of high | d ₃₁ | ⁽²⁾ and low ε ₃₃ ^T / ε ₀ , and sample numbers 24, 25, and 26 are used. 27, | d ₃₁ | ⁽²⁾ / (ε ₃₃ ^T / ε ₀ ) is as large as 0.15 × 10 ⁻¹² or more.
[0024]
The piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention is not limited to the compositions of the above-described examples, and is effective as long as it is within the scope of the gist of the invention.
[0025]
FIG. 1 is an exploded perspective view showing an example of a shock sensor according to the present invention, and FIG. 2 is an illustrative view showing a laminated piezoelectric element used in the shock sensor. A shock sensor 10 shown in FIG. 1 includes a laminated piezoelectric element 12.
[0026]
The laminated piezoelectric element 12 includes two piezoelectric ceramic layers 14a and 14b. These piezoelectric ceramic layers 14a and 14b are composed of the piezoelectric ceramic composition for laminated piezoelectric element according to the present invention described above, and are laminated and integrally formed. Further, as shown by the arrows in FIG. 2, these piezoelectric ceramic layers 14a and 14b are polarized in the thickness direction toward the inside with respect to each other in the center portion, and are polarized in the thickness direction toward the outside with respect to both sides. ing.
[0027]
Between the two piezoelectric ceramic layers 14a and 14b, an internal electrode 16 is formed in an intermediate portion including the central portion thereof. Further, one external electrode 18a is formed on the surface of the piezoelectric ceramic layer 14a from the intermediate portion including the central portion to one end portion. Further, the other external electrode 18b is formed on the surface of the piezoelectric ceramic layer 14b from the intermediate part including the central part to the other end part.
[0028]
The laminated piezoelectric element 12 is held by the case 20. The case 20 includes two U-shaped middle cases 22a and 22b. Both end portions of the laminated piezoelectric element 12 are sandwiched and held by both end portions of the two middle cases 22a and 22b. An upper case 24 and a lower case 26 are provided above and below the laminated piezoelectric element 12 and the middle cases 22a and 22b. In the upper case 24 and the lower case 26, a dent portion serving as a vibration space of the multilayer piezoelectric element 12 is formed in a portion corresponding to the intermediate portion of the multilayer piezoelectric element 12.
[0029]
Terminal electrodes 28a and 28b are formed on the surfaces of the middle cases 22a and 22b, respectively. One terminal electrode 28a is connected to one external electrode 18a, and the other terminal electrode 28b is connected to the other external electrode 18b.
[0030]
FIG. 3 is an exploded perspective view showing an example of the laminated piezoelectric buzzer according to the present invention, and FIG. 4 is an illustrative view showing a laminated piezoelectric element used in the laminated piezoelectric buzzer. A laminated piezoelectric buzzer 30 shown in FIG. 3 includes a laminated piezoelectric element 32.
[0031]
The laminated piezoelectric element 32 includes two piezoelectric ceramic layers 34a and 34b. These piezoelectric ceramic layers 34a and 34b are composed of the piezoelectric ceramic composition for laminated piezoelectric element according to the present invention described above, and are laminated and integrally formed. These piezoelectric ceramic layers 34a and 34b are polarized in the thickness direction and in the same direction as indicated by arrows in FIG.
[0032]
Between the two piezoelectric ceramic layers 34a and 34b, an internal electrode 36 is formed from an intermediate portion including the central portion to one end portion. Also, one external electrode 38a is formed at one end of the two piezoelectric ceramic layers 34a and 34b. The external electrode 38a is connected to the internal electrode 36. Further, the other external electrode 38b is formed on the other portions of the surface of the piezoelectric ceramic layers 34a and 34b.
[0033]
The laminated piezoelectric element 32 is held by the case 40. The case 40 includes a box-shaped case main body 42. The laminated piezoelectric element 32 is placed and held in the case body 42. The case body 42 is provided with a plate-like lid 44.
[0034]
Terminal electrodes 46 a and 46 b are respectively formed on the surface of the lid 44. One terminal electrode 46a is connected to one external electrode 38a, and the other terminal electrode 46b is connected to the other external electrode 38b.
[0035]
FIG. 5 is an illustrative view showing one example of a laminated piezoelectric actuator according to the present invention. A laminated piezoelectric actuator 50 shown in FIG. 5 includes a laminated piezoelectric element 52.
[0036]
The laminated piezoelectric element 52 includes a large number of piezoelectric ceramic layers 54. These piezoelectric ceramic layers 54 are made of the above-described piezoelectric ceramic composition for laminated piezoelectric elements according to the present invention, and are laminated and integrally formed. These piezoelectric ceramic layers 54 are polarized in the thickness direction and in the opposite direction every other layer.
[0037]
Between these piezoelectric ceramic layers 54, internal electrodes 56 are respectively formed. In this case, every other internal electrode 56 is drawn from one end face of the laminated piezoelectric element 52, and the other internal electrode 56 is drawn from the other end face of the laminated piezoelectric element 52.
[0038]
External electrodes 58 a and 58 b are formed on one end surface and the other end surface of the laminated piezoelectric element 52, respectively. One external electrode 58 a is connected to every other internal electrode 56, and the other external electrode 58 b is connected to the other internal electrode 56.
[0039]
The present invention is also applicable to other multilayer piezoelectric devices such as shock sensors, multilayer piezoelectric buzzers, and multilayer piezoelectric actuators other than the above-described shock sensor 10, multilayer piezoelectric buzzer 30, and multilayer piezoelectric actuator 50.
[0040]
【The invention's effect】
According to the present invention, in a two-component PZT piezoelectric ceramic in which at least one of Nb, Sb, and W is substituted at the Ti and Zr sites of PZT, a laminated piezoelectric element using an internal electrode having an Ag / Pd ratio of 7/3 or more. Piezoelectric ceramic composition for laminated piezoelectric element suitable for element fabrication, laminated piezoelectric element using the piezoelectric ceramic composition for laminated piezoelectric element, manufacturing method of laminated piezoelectric element, and laminated piezoelectric device using laminated piezoelectric element are obtained .
Since the piezoelectric ceramic composition for laminated piezoelectric elements according to the present invention can be fired at 1100 ° C. or less, it can be co-sintered with an inexpensive internal electrode having an Ag / Pd ratio of 7/3 or more. Cost reduction is possible.
Further, by using the piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention for, for example, a laminated piezoelectric actuator, an actuator having excellent displacement performance and heat resistance and low power consumption can be obtained.
In addition, by using the piezoelectric ceramic composition for a laminated piezoelectric element according to the present invention in, for example, a laminated piezoelectric sensor, a piezoelectric sensor having high sensitivity, excellent heat resistance, and sensitive temperature characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an example of a shock sensor according to the present invention.
2 is an illustrative view showing a laminated piezoelectric element used in the shock sensor shown in FIG. 2. FIG.
FIG. 3 is an exploded perspective view showing an example of a laminated piezoelectric buzzer according to the present invention.
4 is an illustrative view showing a laminated piezoelectric element used in the laminated piezoelectric buzzer shown in FIG. 3. FIG.
FIG. 5 is an illustrative view showing one example of a laminated piezoelectric actuator according to the present invention.
[Explanation of symbols]
10 Shock sensor 12, 32, 52 Multilayer piezoelectric elements 14a, 14b, 34a, 34b, 54 Piezoelectric ceramic layers 16, 36, 56 Internal electrodes 18a, 18b, 38a, 38b, 58a, 58b External electrodes 20, 40 Cases 22a, 22b Middle case 24 Upper case 26 Lower case 28a, 28b, 46a, 46b Terminal electrode 30 Multilayer piezoelectric buzzer 42 Case body 44 Lid 50 Multilayer piezoelectric actuator

Claims (8)

Represented by the composition of the composition formula Pb _z [(Ti _x Zr _1-x ) _{1- y My} ] O ₃ (wherein M is at least one of Nb, Sb, and W),
X and y in the composition formula are 0.45 ≦ x ≦ 0.52 and 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.95 ≦ z ≦ 0.998. A piezoelectric ceramic composition for laminated piezoelectric elements, in which Pb is reduced from the stoichiometric composition. Represented by the composition of the composition formula Pb _z [(Ti _x Zr _1-x ) _{1- y My} ] O ₃ (wherein M is at least one of Nb, Sb, and W),
X and y in the composition formula are 0.45 ≦ x ≦ 0.52 and 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.98−y ≦ z ≦ 0.998. A piezoelectric ceramic composition for laminated piezoelectric elements, in which Pb is reduced from the stoichiometric composition so as to be −y. The piezoelectric ceramic composition for a laminated piezoelectric element according to claim 1 or 2, wherein 5.5 mol% or less of the Pb content is substituted with at least one of Ca, Sr, and Ba. A laminated piezoelectric element comprising: a piezoelectric ceramic comprising the piezoelectric ceramic composition for a laminated piezoelectric element according to any one of claims 1 to 3; and an internal electrode formed in the piezoelectric ceramic. Composition formula Pb _{z [(Ti x Zr 1-x)} 1-y M y ] O ₃ (however, M is Nb, Sb, at least one of W) expressed by a composition of, x in the composition formula, y is 0.45 ≦ x ≦ 0.52, 0.005 ≦ y ≦ 0.03, and Pb is stoichiometrically such that z in the composition formula is 0.95 ≦ z ≦ 0.998. A method of manufacturing a laminated piezoelectric element comprising a piezoelectric ceramic made of a piezoelectric ceramic composition for a laminated piezoelectric element reduced from the theoretical composition and an internal electrode formed on the piezoelectric ceramic, wherein the piezoelectric ceramic and the internal electrode are heated to 1100 ° C. A method for producing a laminated piezoelectric element, which is co-sintered below. Composition formula Pb _{z [(Ti x Zr 1-x)} 1-y M y ] O ₃ (however, M is Nb, Sb, at least one of W) expressed by a composition of, x in the composition formula, y is 0.45 ≦ x ≦ 0.52, 0.005 ≦ y ≦ 0.03, and z in the composition formula is 0.98−y ≦ z ≦ 0.998−y. A method of manufacturing a laminated piezoelectric element comprising a piezoelectric ceramic made of a piezoelectric ceramic composition for laminated piezoelectric elements obtained by subtracting Pb from a stoichiometric composition, and an internal electrode formed on the piezoelectric ceramic, wherein the piezoelectric ceramic and the internal A method for producing a laminated piezoelectric element, wherein electrodes are co-sintered at 1100 ° C. or lower. The method for producing a laminated piezoelectric element according to claim 5 or 6, wherein 5.5 mol% or less of the Pb content in the piezoelectric ceramic composition for a laminated piezoelectric element is substituted with at least one of Ca, Sr, and Ba. . A multilayer piezoelectric device comprising the multilayer piezoelectric element according to claim 4 and a terminal electrode connected to the internal electrode.

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