JP4930753B2 - Piezoelectric ceramic and piezoelectric parts - Google Patents
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Description
本発明は圧電磁器、及び圧電部品に関し、より詳しくはＰｂを含有した圧電セラミックを主成分とする圧電磁器、及び狭帯域のフィルタ用に使用される圧電セラミック発振子等の圧電部品に関する。 The present invention relates to a piezoelectric ceramic and a piezoelectric component, and more particularly to a piezoelectric ceramic mainly composed of a piezoelectric ceramic containing Pb, and a piezoelectric component such as a piezoelectric ceramic oscillator used for a narrow band filter.
圧電セラミック発振子では、温度変化やリフロー処理などの熱衝撃等、外部環境の変化に対して発振周波数の変動を小さくし、高精度化することが求められている。 Piezoelectric ceramic oscillators are required to be highly accurate by reducing fluctuations in oscillation frequency against changes in the external environment, such as thermal shocks such as temperature changes and reflow treatment.
そして、例えば、特許文献１には、Ｐｂα{（Ｍｎ1/3Ｎｂ2/3）ｘＺｒｙＴｉｚ}Ｏ３（ただし、１．００≦α≦１．０５、０．０７≦ｘ≦０．２８、０．４２≦ｙ≦０．６２、０．１８≦ｚ≦０．４５、ｘ＋ｙ＋ｚ＝１）で表される主成分１００重量部にＭｎ３Ｏ４を０．３〜０．８重量部添加した圧電磁器組成物が提案されている。 Then, for example, Patent Document 1, Pb α {(Mn 1/3 Nb 2/3) x Zr y Ti z} O 3 ( however, 1.00 ≦ α ≦ 1.05,0.07 ≦ x ≦ 0.28, 0.42 ≦ y ≦ 0.62, 0.18 ≦ z ≦ 0.45, x + y + z = 1) 100 parts by weight of the main component represents 0.3 to 0.8 Mn 3 O 4 Piezoelectric ceramic compositions with parts by weight added have been proposed.
特許文献１は、上記組成を具備することにより、厚みすべりモード共振を利用したフィルタ、発振子に適した、耐熱性に優れ、熱衝撃負荷後の共振周波数変化が極めて小さく、温度サイクルによる共振周波数変化が小さい圧電磁器組成物を得ることができる。 Patent Document 1 is excellent in heat resistance, suitable for filters and oscillators using thickness-slip mode resonance, and has a very small resonance frequency change after a thermal shock load. A piezoelectric ceramic composition having a small change can be obtained.
また、特許文献２には、少なくともＰｂ、Ｓｒ、Ｚｒ、Ｔｉ、Ｍｎ、Ｎｂ、Ｓｉ及びＡｌを含み、一般式：（Ｐｂａ Ｓｒｂ ）（ＺｒｃＴｉｄ Ｍｎｅ Ｎｂｆ ）Ｏ３（０．９３≦ａ≦１．０１、０．０１≦ｂ≦０．０４、０．３７≦ｃ≦０．４７、０．４８≦ｄ≦０．５８、０．０１０５≦ｅ≦０．０６、０．０２≦ｆ≦０．０６、及び１．０５≦２ｅ／ｆ≦２の各条件を満たす組成を有する主成分を含むと共に、副成分として、前記主成分に対して０．００３重量％以上０．１重量％以下のＳｉＯ2 および０．００３重量％以上０．１重量％以下のＡｌ2 Ｏ3 を含む圧電磁器材料が提案されている。 Further, Patent Document 2, includes at least Pb, Sr, Zr, Ti, Mn, Nb, Si and Al, the general formula: (Pb a Sr b) ( Zr c Ti d Mn e Nb f) O 3 (0 .93 ≦ a ≦ 1.01, 0.01 ≦ b ≦ 0.04, 0.37 ≦ c ≦ 0.47, 0.48 ≦ d ≦ 0.58, 0.0105 ≦ e ≦ 0.06, 0 0.02 ≦ f ≦ 0.06 and 1.05 ≦ 2e / f ≦ 2 are included, and as a subcomponent, 0.003% by weight or more with respect to the main component is included. Piezoelectric ceramic materials containing less than 1% by weight of SiO 2 and 0.003% by weight to 0.1% by weight of Al 2 O 3 have been proposed.
特許文献２は、上記組成を具備することにより、電気機械結合係数ｋが小さく、共振抵抗Ｚｒが小さく、かつ共振周波数の温度依存性の小さい圧電磁器材料を得ることができる。 Patent Document 2 can provide a piezoelectric ceramic material having a small electromechanical coupling coefficient k, a small resonance resistance Zr, and a small temperature dependence of the resonance frequency by having the above composition.
さらに、特許文献３には、Ｐｂ（Ｍｇ1/3Ｎｂ2/3)ＡＴｉＢＺｒＣＯ３（Ａ＋Ｂ＋Ｃ＝１モル）とＭｎＯ２から成る基本組成にＡｌ２Ｏ３を含有させ、仮焼後本焼成前の粉砕された平均粒子径を１μｍ以下とする圧電磁器材料の製造方法が提案されている。 Furthermore, Patent Document 3 includes Al 2 O 3 in a basic composition composed of Pb (Mg 1/3 Nb 2/3 ) A Ti B Zr C O 3 (A + B + C = 1 mol) and MnO 2 and calcining it. There has been proposed a method for manufacturing a piezoelectric ceramic material in which the pulverized average particle diameter before post-firing is 1 μm or less.
特許文献３は、上記基本組成にＡｌ２Ｏ３を含有させることにより、Ａｌ２Ｏ３が基本組成の結晶粒界に析出して結晶の粒成長が抑制され、これにより結晶粒度が揃い、機械的強度の向上を図ることができると共に、電気的特性のバラツキを抑制することが可能となる。 Patent Document 3 discloses that Al 2 O 3 is precipitated in crystal grain boundaries of the basic composition by containing Al 2 O 3 in the basic composition, thereby suppressing crystal grain growth. It is possible to improve the mechanical strength and suppress variations in electrical characteristics.
しかしながら、特許文献１は、温度変化や熱衝撃に対しては発振周波数の変動を或る程度抑制できるものの、共振子としての帯域が広いため、基板実装後に回路からの影響を受けやすく、発振周波数の変動を十分に抑制することができないという問題点があった。 However, although Patent Document 1 can suppress fluctuations in the oscillation frequency to some extent with respect to temperature changes and thermal shocks, it has a wide band as a resonator and is therefore easily affected by the circuit after mounting on the substrate. There was a problem that the fluctuation of the above could not be sufficiently suppressed.
また、特許文献２には、圧電磁器材料（圧電セラミック）中にＳｉＯ２やＡｌ２Ｏ３を所定量含有させることにより電気機械結合係数ｋを小さくできることについての示唆があり、これにより共振器の帯域を狭くして基板実装後の回路の影響を受け難くすることを可能としている。 Patent Document 2 also suggests that the electromechanical coupling coefficient k can be reduced by containing a predetermined amount of SiO 2 or Al 2 O 3 in the piezoelectric ceramic material (piezoelectric ceramic). By narrowing the band, it is possible to make it less susceptible to the influence of the circuit after mounting on the board.
しかしながら、特許文献２では、電気機械結合係数ｋの低下が不十分であった。 However, in Patent Document 2, the decrease in the electromechanical coupling coefficient k is insufficient.
一般に、チタン酸ジルコン酸鉛（以下、「ＰＺＴ」という。）を主成分とするＰＺＴ系圧電磁器材料は正方晶の比率が高いため、電気機械結合係数ｋが小さくなると、共振点―反共振点間における位相角の最大値（以下、「最大位相」という。）θmaxが低下して発振特性が悪化し、さらには共振周波数の温度変化率も悪化すると考えられている。また、共振抵抗Ｚｒも高いという問題があった。 In general, a PZT piezoelectric ceramic material mainly composed of lead zirconate titanate (hereinafter referred to as “PZT”) has a high ratio of tetragonal crystals. Therefore, when the electromechanical coupling coefficient k decreases, the resonance point-antiresonance point It is considered that the maximum value of the phase angle between them (hereinafter referred to as “maximum phase”) θmax decreases, the oscillation characteristics deteriorate, and the temperature change rate of the resonance frequency also deteriorates. There is also a problem that the resonance resistance Zr is high.
すなわち、特許文献２は、電気機械結合係数ｋを小さくすることを意図しているものの十分に小さくすることができず、しかも共振抵抗Ｚｒが高いことから、最大位相θmaxが低下して発振特性の悪化を招くおそれがあると考えられる。 That is, although Patent Document 2 intends to reduce the electromechanical coupling coefficient k, it cannot be sufficiently reduced, and since the resonance resistance Zr is high, the maximum phase θmax is lowered and the oscillation characteristic is reduced. There is a possibility of deteriorating.
しかも、特許文献２では、共振周波数の温度変化率ｆｒ−Ｔｃが大きく、このため高精度で信頼性の優れた圧電セラミック発振子を得ることができないという問題もあった。 In addition, Patent Document 2 has a problem that the temperature change rate fr-Tc of the resonance frequency is large, so that a piezoelectric ceramic oscillator having high accuracy and excellent reliability cannot be obtained.
また、特許文献３は、基本組成にＡｌ２Ｏ３を含有させることにより、電気的特性のバラツキを抑制することができ、また、Ａｌ２Ｏ３の含有量を増量することによって電気機械結合係数ｋが小さくなっているが、Ａｌ２Ｏ３の含有量が２．５重量％を超えると抗折強度が低下して機械的強度の劣化を招くとされている。また、発振特性の指標となる最大位相θmax及び共振周波数の温度変化率ｆｒ−Ｔｃについては何ら触れられておらず、したがって特許文献３の圧電磁器材料を使用しても高精度で信頼性の優れた圧電セラミック発振子を得ることは困難であると考えられる。 Further, Patent Document 3 can suppress variation in electrical characteristics by including Al 2 O 3 in the basic composition, and increase the content of Al 2 O 3 to increase the electromechanical coupling coefficient. Although k is small, when the content of Al 2 O 3 exceeds 2.5% by weight, the bending strength is lowered and the mechanical strength is deteriorated. Further, nothing is mentioned about the maximum phase θmax and the temperature change rate fr-Tc of the resonance frequency which are indices of oscillation characteristics. Therefore, even if the piezoelectric ceramic material of Patent Document 3 is used, it is highly accurate and excellent in reliability. It is considered difficult to obtain a piezoelectric ceramic resonator.
本発明はこのような事情に鑑みなされたものであって、基板実装後の回路からの影響を受けにくく、外部環境の変化に対しても発振周波数の変動を抑制することができ、かつ良好な発振特性を有し、しかも共振周波数の温度特性や耐熱性が良好で共振抵抗も小さく機械的強度にも優れた圧電磁器、及び該圧電磁器を使用して製造することにより高精度で信頼性の優れた圧電セラミック発振子等の圧電部品を提供することを目的とする。 The present invention has been made in view of such circumstances, is less susceptible to the influence of a circuit after being mounted on a substrate, can suppress fluctuations in oscillation frequency even when the external environment changes, and is excellent. A piezoelectric ceramic that has oscillation characteristics, good resonance frequency temperature characteristics and heat resistance, low resonance resistance, and excellent mechanical strength, and is manufactured using the piezoelectric ceramic. An object is to provide a piezoelectric component such as an excellent piezoelectric ceramic oscillator.
上述したように圧電セラミック発振子では、外部環境の変化や基板実装後の回路からの影響に対し発振周波数の変動を抑制するのが望まれており、そのためには電気機械結合係数を小さくする必要がある。また、良好な発振特性を得るためには最大位相θmaxの大きいことが要求される。 As described above, in the piezoelectric ceramic oscillator, it is desired to suppress fluctuations in the oscillation frequency against changes in the external environment and influences from the circuit after mounting on the board. To that end, it is necessary to reduce the electromechanical coupling coefficient. There is. In order to obtain good oscillation characteristics, the maximum phase θmax is required to be large.
しかしながら、〔発明が解決しようとする課題〕の項でも述べた理由から、ＰＺＴ系圧電セラミックでは、一般に電気機械結合係数が小さくなると最大位相θmaxも低下すると考えられており、また、特許文献３にも記載されているように、Ａｌ２Ｏ３を添加した場合であっても、単に増量しただけでは抗折強度τが低下し、機械的強度の劣化を招く。 However, for the reason described in the section of [Problems to be Solved by the Invention], in PZT piezoelectric ceramics, it is generally considered that the maximum phase θmax decreases as the electromechanical coupling coefficient decreases. As is also described, even when Al 2 O 3 is added, the bending strength τ is lowered by simply increasing the amount, leading to deterioration of mechanical strength.
しかるに、本発明者らが鋭意研究を行ったところ、ＰＺＴ系圧電セラミックを主成分とする場合であっても、大量のＡｌ２Ｏ３を前記主成分に添加することによってＡｌ２Ｏ３粒子の凝集体を生成し、該凝集体を主成分粒子の結晶粒内、結晶粒界又は三重点に析出させてＡｌ偏析部を形成し、かつ該Ａｌ偏析部を圧電磁器中に分散させることにより、最大位相θmaxの低下を招くことなく、電気機械結合係数ｋを小さくすることができるという知見を得た。 However, as a result of intensive research conducted by the present inventors, even when a PZT-based piezoelectric ceramic is a main component, a large amount of Al 2 O 3 is added to the main component to form Al 2 O 3 particles. By forming an aggregate, precipitating the aggregate in the crystal grains of the main component particles, a crystal grain boundary or a triple point to form an Al segregation part, and dispersing the Al segregation part in a piezoelectric ceramic, It was found that the electromechanical coupling coefficient k can be reduced without causing a decrease in the maximum phase θmax.
また、圧電磁器をこのような形態とすることにより、共振周波数の温度変化率を小さくすることができ、しかも耐熱性にも優れ、共振抵抗Ｚｒも小さくすることができ、さらに抗折強度τも大きく周波数定数も高い圧電磁器を得ることができるという知見も得た。 Further, by adopting such a form of the piezoelectric ceramic, the temperature change rate of the resonance frequency can be reduced, the heat resistance is excellent, the resonance resistance Zr can be reduced, and the bending strength τ is also increased. The knowledge that a piezoelectric ceramic having a large and high frequency constant can be obtained was also obtained.
具体的には、Ｐｂ系圧電セラミックからなる主成分１００容量部に対し、ＡｌをＡｌ２Ｏ３換算で１０〜４０容量部となるように配合し、十分に長時間湿式で粉砕処理等を行い、その後焼成処理を行うことにより、Ａｌ凝集体の存在比率（以下、「Ａｌ存在比」という。）が２５μｍ□の領域内で５０％以上を占める複数のＡｌ偏析部を形成することができ、しかもＡｌ偏析部同士の平均離間距離が、中心間距離で１００μｍ以上となるように、Ａｌ偏析部を圧電磁器中に分散させることができる。そして、このようにすることにより最大位相θmaxの低下を招くことなく、電気機械結合係数ｋを小さくすることができ、共振抵抗Ｚｒも小さく、共振周波数の温度変化率も小さく、耐熱性にも優れ、しかも機械的強度の優れた圧電磁器を得ることができるという知見を得た。 Specifically, for 100 parts by volume of the main component made of Pb-based piezoelectric ceramic, Al is blended so as to be 10 to 40 parts by volume in terms of Al 2 O 3 , and sufficiently pulverized and wetted for a long time. Then, by performing a baking treatment, a plurality of Al segregation parts occupying 50% or more in a region where the abundance ratio of Al aggregates (hereinafter referred to as “Al abundance ratio”) is 25 μm □ can be formed. Moreover, the Al segregation parts can be dispersed in the piezoelectric ceramic so that the average separation distance between the Al segregation parts is 100 μm or more in the center-to-center distance. In this way, the electromechanical coupling coefficient k can be reduced without reducing the maximum phase θmax, the resonance resistance Zr is also small, the temperature change rate of the resonance frequency is small, and the heat resistance is also excellent. And the knowledge that a piezoelectric ceramic excellent in mechanical strength can be obtained was obtained.
また、大量のＡｌAlso, a large amount of Al ２2 ＯO ３3 を含有させた場合に焼結性の低下を招くおそれがある。そしてこのような焼結不足を招くのを回避する観点からは、主成分として、Ｐｂ（Ｚｒ，Ｔｉ）OWhen it contains, there exists a possibility of causing a sinterability fall. From the viewpoint of avoiding such a lack of sintering, the main component is Pb (Zr, Ti) O2. ３3 系化合物と、Ｐｂ（Ｍｎ，Ｎｂ）ＯCompounds and Pb (Mn, Nb) O ３3 系化合物及びＰｂ（Ｎｉ，Ｎｂ）ＯCompounds and Pb (Ni, Nb) O ３3 系化合物のうちの少なくともいずれか一方とを含む必要があることが分かった。It has been found that it is necessary to contain at least one of the system compounds.
本発明はこのような知見に基づきなされたものであって、本発明に係る圧電磁器は、主成分が、Ｚｒ及びＴｉを含有したＰｂ（Ｚｒ，Ｔｉ）ＯThe present invention has been made based on such knowledge, and the piezoelectric ceramic according to the present invention is composed of Pb (Zr, Ti) O containing Zr and Ti as main components. ３3 系化合物と、Ｐｂ（Ｍｎ，Ｎｂ）ＯCompounds and Pb (Mn, Nb) O ３3 系化合物及びＰｂ（Ｎｉ，Ｎｂ）ＯCompounds and Pb (Ni, Nb) O ３3 系化合物のうちの少なくともいずれか一方とを含むと共に、 前記主成分１００容量部に対しＡｌがＡｌAnd at least one of the series compounds, and Al is Al relative to 100 parts by volume of the main component. ２2 ＯO ３3 換算で１０〜４０容量部含有され、Ａｌ凝集体の存在比率であるＡｌ存在比が、２５μｍ□の領域内で５０％以上の面積比率を有する複数のＡｌ偏析部が形成され、かつ前記Ａｌ偏析部同士の平均離間距離が、中心間距離で１００μｍ以上であることを特徴としている。A plurality of Al segregation parts are formed which have an area ratio of 50% or more in a region of 10 to 40 parts by volume in terms of Al and an Al abundance ratio of 25 μm □, and the Al segregation. The average separation distance between the parts is 100 μm or more in terms of the center-to-center distance.
また、このような圧電磁器の断面を観察したところ、Ａｌ偏析部は面積比で０．３〜１．０％の割合で圧電磁器中に分散していることが分かった。Moreover, when the cross section of such a piezoelectric ceramic was observed, it was found that the Al segregated portion was dispersed in the piezoelectric ceramic at an area ratio of 0.3 to 1.0%.
すなわち、本発明の圧電磁器は、前記Ａｌ偏析部の存在比率が、断面における面積比で０．３〜１．０％であるのが好ましい。That is, in the piezoelectric ceramic according to the present invention, it is preferable that the Al segregation portion is present in an area ratio of 0.3 to 1.0% in the cross section.
また、本発明に係る圧電部品は、圧電磁器の両主面に電極が形成された圧電部品において、前記圧電磁器が、上記記載の圧電磁器で形成されていることを特徴としている。 Moreover, the piezoelectric component according to the present invention is characterized in that in the piezoelectric component in which electrodes are formed on both main surfaces of the piezoelectric ceramic, the piezoelectric ceramic is formed of the piezoelectric ceramic described above.
本発明の圧電磁器によれば、主成分が、Ｚｒ及びＴｉを含有したＰｂ（Ｚｒ，Ｔｉ）Ｏ ３ 系化合物と、Ｐｂ（Ｍｎ，Ｎｂ）Ｏ ３ 系化合物及びＰｂ（Ｎｉ，Ｎｂ）Ｏ ３ 系化合物のうちの少なくともいずれか一方とを含むと共に、前記主成分１００容量部に対しＡｌがＡｌ２Ｏ３換算で１０〜４０容量部含有され、Ａｌ凝集体の存在比率であるＡｌ存在比が、２５μｍ□の領域内で５０％以上の面積比率を有する複数のＡｌ偏析部が形成され、かつ前記Ａｌ偏析部同士の平均離間距離が、中心間距離で１００μｍ以上であるので、電気機械結合係数ｋを小さくすることができ、したがって温度変化や熱衝撃のみならず、基板実装後の回路からの影響も受け難く、これら外部環境に起因した発振周波数の変動を抑制することができる。そして、大量のＡｌ ２ Ｏ ３ を含有させても焼結不足を招くこともなく良好な機械的強度を有する圧電磁器を得ることができる。 According to the piezoelectric ceramic of the present invention, the main components are Pb (Zr, Ti) O 3 based compound containing Zr and Ti , Pb (Mn, Nb) O 3 based compound and Pb (Ni, Nb) O 3. And at least one of the system compounds, Al is contained in an amount of 10 to 40 parts by volume in terms of Al 2 O 3 with respect to 100 parts by volume of the main component, and the Al abundance ratio is an abundance ratio of Al aggregates. A plurality of Al segregation portions having an area ratio of 50% or more in a region of 25 μm □ are formed, and the average separation distance between the Al segregation portions is 100 μm or more at the center-to-center distance. k can be reduced, and therefore, it is difficult to be affected not only by temperature change and thermal shock but also by the circuit after mounting on the substrate, and fluctuations in oscillation frequency due to these external environments can be suppressed. Then, it is possible to obtain a piezoelectric ceramic having good mechanical strength without causing an insufficient sintering may contain a large amount of Al 2 O 3.
また、本発明のような構造を有することで、たとえ電気機械結合係数ｋが急激に小さくなっても、最大位相θmaxの低下を極力防ぐことができることを見出した。これにより、発振特性の悪化を招くこともなく、低電圧でも安定した発振が可能となる。さらに、共振周波数の温度変化率ｆｒ−Ｔｃが小さいことから安定した共振周波数を確保することができ、耐熱性にも優れていることからリフロー処理で加熱されても素子が損傷するのを回避することができる。また、機械的強度の指標となる抗折強度τも大きいことから機械的強度にも優れ、素子の薄型化や高周波化が可能な圧電磁器を実現することができる。 Further, it has been found that the structure as in the present invention can prevent the maximum phase θmax from being lowered as much as possible even if the electromechanical coupling coefficient k rapidly decreases. Thus, stable oscillation can be achieved even at a low voltage without causing deterioration of oscillation characteristics. Furthermore, since the temperature change rate fr-Tc of the resonance frequency is small, a stable resonance frequency can be secured, and since the heat resistance is excellent, the element is prevented from being damaged even when heated by the reflow process. be able to. In addition, since the bending strength τ, which is an index of mechanical strength, is large, it is possible to realize a piezoelectric ceramic that is excellent in mechanical strength and capable of reducing the thickness and frequency of the element.
具体的には、電気機械結合係数ｋ15が４０％以下であっても、最大位相θmaxが余り低下せずに８７．９°以上を確保することができ、共振周波数ｆｒの温度変化率が−３０〜＋３０ppm／℃、耐熱性の指標となる反共振周波数ｆａの変化率が−０．１０〜＋０．１０％、機械的強度の指標となる抗折強度τが１８０ＭＰａ以上であって共振抵抗Ｚｒが３．９Ω以下の圧電磁器を得ることができる。 Specifically, even if the electromechanical coupling coefficient k 15 is 40% or less, the maximum phase θmax can be secured at 87.9 ° or more without much decrease, and the temperature change rate of the resonance frequency fr is − 30 to +30 ppm / ° C., change rate of anti-resonance frequency fa as an index of heat resistance is −0.10 to + 0.10%, bending strength τ as an index of mechanical strength is 180 MPa or more, and resonance resistance Zr Can obtain a piezoelectric ceramic of 3.9Ω or less.
また、前記Ａｌ偏析部の存在比率を、圧電磁器焼結体の断面における面積比で０．３〜１．０％の割合でＡｌ偏析部を分散せることにより、上述した作用効果を奏することができる。 In addition, the Al segregation part is dispersed at a ratio of 0.3 to 1.0% in terms of the area ratio in the cross section of the piezoelectric ceramic sintered body, so that the above-described effects can be obtained. it can.
また、本発明に係る圧電部品は、圧電磁器の両主面に電極が形成された圧電部品において、前記圧電磁器が、上記記載の圧電磁器で形成されているので、外部環境の変化や基板実装後の回路からの影響を受けることなく発振周波数の変動を抑制することができ、良好な発振特性を有し、しかも共振周波数の温度特性や耐熱性も良好であり、機械的強度にも優れた高精度かつ信頼性の優れた圧電発振子等の圧電部品を得ることができる。 Further, the piezoelectric component according to the present invention is a piezoelectric component in which electrodes are formed on both main surfaces of the piezoelectric ceramic. Since the piezoelectric ceramic is formed of the piezoelectric ceramic described above, changes in the external environment and board mounting The fluctuation of the oscillation frequency can be suppressed without being affected by the circuit later, the oscillation characteristics are good, the temperature characteristics and heat resistance of the resonance frequency are good, and the mechanical strength is also excellent. A piezoelectric component such as a piezoelectric oscillator having high accuracy and high reliability can be obtained.
次に、本発明の実施の形態を詳説する。 Next, an embodiment of the present invention will be described in detail.
図１は本発明に係る圧電磁器の一実施の形態を模式的に示した断面図である。 FIG. 1 is a sectional view schematically showing an embodiment of a piezoelectric ceramic according to the present invention.
本発明の圧電磁器は、主成分１がＰＺＴ等のＰｂ系圧電セラミックからなり、前記主成分１００容量部に対し、Ａｌ２Ｏ３が１０〜４０容量部含有されており、大部分のＡｌ２Ｏ３は主成分１と固溶せず、Ａｌ２Ｏ３粒子同士が主成分１の結晶粒内、結晶粒界又は三重点に析出し、凝集体を生成してＡｌ偏析部２を形成している。 The piezoelectric ceramic according to the present invention, the main component 1 is made of Pb-based piezoelectric ceramics such as PZT, with respect to the main component as 100 parts by volume, Al 2 O 3 are contained 10 to 40 parts by volume, most of the Al 2 O 3 does not form a solid solution with the main component 1, and Al 2 O 3 particles are precipitated in the crystal grains, grain boundaries, or triple points of the main component 1, forming aggregates to form the Al segregation part 2. ing.
ここで、本発明で定義するＡｌ偏析部２とは、所定領域３（例えば、一辺がＸの正方形領域）においてＡｌ２Ｏ３粒子の凝集体の存在比率、すなわちＡｌ存在比が面積比率で５０％以上を占める領域をいう。具体的には、本実施の形態では、一辺Ｘが２５μｍである２５μｍ□を所定領域３とし、斯かる所定領域３内でＡｌ存在比が面積比率で５０％以上の領域をＡｌ偏析部２としている。 Here, the Al segregation part 2 defined in the present invention is an abundance ratio of aggregates of Al 2 O 3 particles in a predetermined region 3 (for example, a square region with one side X), that is, an Al abundance ratio is 50 in area ratio. An area that occupies more than%. Specifically, in the present embodiment, 25 μm □ whose one side X is 25 μm is defined as the predetermined region 3, and a region in which Al abundance ratio is 50% or more in the predetermined region 3 is defined as the Al segregation portion 2. Yes.
したがって、Ａｌ２Ｏ３粒子の凝集体が主成分１の結晶粒内、結晶粒界や三重点に析出していても、所定領域３内でのＡｌ２Ｏ３粒子の凝集体が面積比率で５０％未満の場合は、本発明で定義するＡｌ偏析部２を形成しないこととなる。 Therefore, even if the aggregate of Al 2 O 3 particles is precipitated in the crystal grains of the main component 1, the crystal grain boundaries, or triple points, the aggregate of Al 2 O 3 particles in the predetermined region 3 is in an area ratio. When it is less than 50%, the Al segregation part 2 defined in the present invention is not formed.
そして、前記Ａｌ偏析部２は、その存在比率が、圧電磁器の断面における面積比で０．３〜１．０％となるように圧電磁器中に分散されており、Ａｌ偏析部２同士の平均離間距離Ｌは、Ａｌ偏析部２の最長辺を直径とした時の中心間距離（重心）で、１００μｍ以上となるように形成されている。すなわち、Ａｌ偏析部２同士は互いに過度に近接しないように適度な平均離間距離Ｌを有して圧電磁器上に略均一に分散されている。 And the said Al segregation part 2 is disperse | distributed in a piezoelectric ceramic so that the abundance ratio may be 0.3 to 1.0% by the area ratio in the cross section of a piezoelectric ceramic, The average of Al segregation parts 2 mutually The separation distance L is a center-to-center distance (center of gravity) when the longest side of the Al segregation part 2 is the diameter, and is formed to be 100 μm or more. That is, the Al segregation portions 2 are distributed substantially uniformly on the piezoelectric ceramic with an appropriate average separation distance L so as not to be too close to each other.
尚、凝集体としてのＡｌ偏析物２の平均離間距離Ｌの上限は約２５０μｍが好ましい。 The upper limit of the average separation distance L of the Al segregated material 2 as an aggregate is preferably about 250 μm.
ここで、Ａｌの含有量を上述のように限定したのは以下の理由による。 Here, the reason why the content of Al is limited as described above is as follows.
Ａｌの含有量が主成分１００容量部に対し１０容量部未満の場合は、Ａｌの含有量が少なく、上述した形態のＡｌ偏析部２を形成することができず、このため電気機械結合係数ｋも小さくできず、また、抗折強度τの低下を招く。 When the content of Al is less than 10 parts by volume with respect to 100 parts by volume of the main component, the Al content is small and the Al segregation part 2 having the above-described form cannot be formed. Cannot be reduced, and the bending strength τ is reduced.
一方、Ａｌの含有量が主成分１００容量部に対し４０容量部を超えると、Ａｌ偏析部２の圧電磁器に占める比率が多くなり過ぎて最大位相θmaxの低下を招く。 On the other hand, when the content of Al exceeds 40 parts by volume with respect to 100 parts by volume of the main component, the ratio of the Al segregation part 2 to the piezoelectric ceramic increases so much that the maximum phase θmax is lowered.
このような理由から本圧電磁器では、主成分１００容量部に対し、Ａｌ２Ｏ３を１０〜４０容量部含有させている。そして好ましくは主成分１００容量部に対しＡｌ２Ｏ３を２０〜４０容量部とするのが望ましく、これにより電気機械結合係数ｋが３５％以下であり、共振周波数の温度変化率ｆｒ−Ｔｃが２０ｐｐｍ／℃以下と小さいながらも、最大位相θmaxがほとんど低下しない圧電磁器を得ることができる。 For this reason, the present piezoelectric ceramic contains 10 to 40 parts by volume of Al 2 O 3 with respect to 100 parts by volume of the main component. Preferably, Al 2 O 3 is 20 to 40 parts by volume with respect to 100 parts by volume of the main component, so that the electromechanical coupling coefficient k is 35% or less, and the temperature change rate fr-Tc of the resonance frequency is A piezoelectric ceramic can be obtained in which the maximum phase θmax hardly decreases although it is as small as 20 ppm / ° C. or less.
このように本実施の形態では、Ｐｂ系圧電セラミックからなる主成分１００容量部に対し、Ａｌ２Ｏ３を１０〜４０容量部含有させ、Ａｌ存在比が２５μｍ□の領域内で５０％以上の面積比率を有する複数のＡｌ偏析部を形成し、かつ、Ａｌ偏析部２同士の平均離間距離Ｌは１００μｍ以上となるように分散させることにより、最大位相θmaxの低下を招くことなく電気機械結合係数ｋを小さくすることができ、したがって基板実装後にも回路からの影響を受けることがなく発振周波数の変動を抑制することができ、また良好な発振特性を有することとなって圧電部品の高精度化を実現することが可能となる。 As described above, in this embodiment, 10 to 40 parts by volume of Al 2 O 3 is contained in 100 parts by volume of the main component made of Pb-based piezoelectric ceramic, and the Al abundance ratio is 50% or more in the region of 25 μm □. By forming a plurality of Al segregation portions having an area ratio and dispersing the average separation distance L between the Al segregation portions 2 so as to be 100 μm or more, the electromechanical coupling coefficient does not cause a decrease in the maximum phase θmax. k can be reduced, and therefore fluctuations in the oscillation frequency can be suppressed without being affected by the circuit even after mounting on the board, and it has good oscillation characteristics, resulting in higher accuracy of the piezoelectric component. Can be realized.
また、上述のように電気機械結合係数ｋを小さくすることができるにも拘わらず、最大位相θmaxの低下を抑制することができるのは、大量のＡｌ２Ｏ３粒子の凝集体であるＡｌ偏析部２が近接しないように均一に分散させることによって誘電損失tanδを小さくすることができるためと考えられる。 In addition, although the electromechanical coupling coefficient k can be reduced as described above, the decrease in the maximum phase θmax can be suppressed by the segregation of Al that is an aggregate of a large amount of Al 2 O 3 particles. It is considered that the dielectric loss tan δ can be reduced by uniformly dispersing the portions 2 so as not to be close to each other.
すなわち、誘電損失tanδが小さいとＱmax値（＝１／tanδ）が大きくなるが、Ｑmax値が大きくなると発振性が安定し、低電圧で安定した駆動が可能となる。 That is, when the dielectric loss tan δ is small, the Qmax value (= 1 / tan δ) is large. However, when the Qmax value is large, the oscillation property is stabilized and stable driving can be performed at a low voltage.
したがって、Ａｌ偏析部２同士が過度に近接しないように均一に分散させることによって、誘電損失tanδを小さくすることができ、これにより最大位相θmaxが低下するのを回避できるものと思われる。 Accordingly, it is considered that the dielectric loss tan δ can be reduced by uniformly dispersing the Al segregating portions 2 so as not to be too close to each other, and thereby the maximum phase θmax can be prevented from being lowered.
さらに、本発明では、上述したように均一分散されたＡｌ偏析部２を形成することにより、良好な共振周波数の温度変化率ｆｒ−Ｔｃを得ることができ、しかも耐熱性の劣化をも防ぐことができる。これは、Ａｌ２Ｏ３粒子の凝集体が、主成分である圧電セラミックと殆ど固溶せずに大部分が結晶粒内、結晶粒界、或いは三重点に析出するため、主成分粒子の結晶構造に影響を与えないためと考えられる。 Furthermore, in the present invention, by forming the Al segregation part 2 that is uniformly dispersed as described above, it is possible to obtain a favorable temperature change rate fr-Tc of the resonance frequency, and also prevent deterioration of heat resistance. Can do. This is because the agglomerates of Al 2 O 3 particles are hardly dissolved in the main component of the piezoelectric ceramic and are mostly precipitated in the crystal grains, at the crystal grain boundaries, or at the triple points. This is probably because it does not affect the structure.
また、本発明では、上述したように主成分１００容量部に対し１０〜４０容量部という大量のＡｌ２Ｏ３を含有させながらもＡｌ偏析部２を圧電磁器中に分散させた構成とすることにより、クラック等も生じず、大きな抗折強度τを有し、しかも周波数定数も高く、機械的強度が良好で薄型化を図ることができ、素子の高周波化が可能な圧電磁器を得ることができる。 In the present invention, be configured by dispersing Al segregation area 2 also while containing a large amount of Al 2 O 3 of 10 to 40 parts by volume with respect to the main component of 100 parts by volume, as described above in the piezoelectric porcelain Therefore, it is possible to obtain a piezoelectric ceramic that does not cause cracks, has a large bending strength τ, has a high frequency constant, has a good mechanical strength, can be thinned, and can increase the frequency of the element. it can.
尚、大量のＡｌ２Ｏ３を圧電磁器に含有させると焼結性の低下を招くおそれがあることから、主成分となる圧電セラミック中には、Ｍｎ、Ｎｉ、Ｃｒ、Ｎｂ、Ｗ等を含有させるのも好ましく、例えば、第３成分として、Ｐｂ（Ｍｎ，Ｎｂ）Ｏ３やＰｂ（Ｎｉ，Ｎｂ）Ｏ３をＰＺＴ（ＰｂＺｒＯ３−ＰｂＴｉＯ３）に固溶させるのも好ましい。 In addition, if a large amount of Al 2 O 3 is contained in the piezoelectric ceramic, the sinterability may be lowered. Therefore, the piezoelectric ceramic as the main component contains Mn, Ni, Cr, Nb, W, or the like. For example, Pb (Mn, Nb) O 3 or Pb (Ni, Nb) O 3 is preferably dissolved as a third component in PZT (PbZrO 3 —PbTiO 3 ).
図２は上記圧電磁器を使用して製造された圧電部品としての圧電セラミック発振子の一実施の形態を示す断面図である。 FIG. 2 is a cross-sectional view showing an embodiment of a piezoelectric ceramic oscillator as a piezoelectric component manufactured using the piezoelectric ceramic.
該圧電セラミック発振子は、上記圧電磁器と、該圧電磁器の一方の端部が表面露出する形態で前記圧電磁器の両主面に形成された対向電極５ａ、５ｂとからなり、矢印Ａ方向に分極処理がなされ、厚みすべりモードで駆動するように構成されている。 The piezoelectric ceramic oscillator includes the piezoelectric ceramic, and opposing electrodes 5a and 5b formed on both main surfaces of the piezoelectric ceramic in such a manner that one end of the piezoelectric ceramic is exposed on the surface, and in the direction of arrow A Polarization processing is performed, and it is configured to be driven in a thickness-slip mode.
次に、上記圧電セラミック発振子の製造方法を説明する。 Next, a method for manufacturing the piezoelectric ceramic oscillator will be described.
まず、圧電セラミック素原料としてＰｂＯ等の鉛化合物、ＺｒＯ２等のジルコニウム化合物、ＴｉＯ２等のチタン化合物、及び必要に応じてＭｎＯ、Ｎｂ２Ｏ５、ＮｉＯ、ＳｉＯ２等の遷移金属系化合物を用意する。 First, a lead compound such as PbO, a zirconium compound such as ZrO 2 , a titanium compound such as TiO 2 , and a transition metal compound such as MnO, Nb 2 O 5, NiO, and SiO 2 as necessary as a piezoelectric ceramic raw material. prepare.
そして、主成分となる圧電セラミックが、所定組成となるように前記圧電セラミック素原料を秤量する。 Then, the piezoelectric ceramic raw material is weighed so that the piezoelectric ceramic as the main component has a predetermined composition.
次いで、非圧電セラミック素原料であるＡｌ２Ｏ３を用意し、前記圧電セラミック１００容量部に対しＡｌ２Ｏ３が１０〜４０容量部となるようにＡｌ２Ｏ３を秤量する。 Next, Al 2 O 3 which is a non-piezoelectric ceramic raw material is prepared, and Al 2 O 3 is weighed so that Al 2 O 3 is 10 to 40 parts by volume with respect to 100 parts by volume of the piezoelectric ceramic.
次に、これら秤量物を、例えば、直径１〜３ｍｍのＰＳＺボール（Partially Stabilized Zirconia；部分安定化ジルコニア）等の小径の粉砕媒体及び純水と共にボールミルに投入して十分に長時間（例えば２４〜７２時間）湿式で混合粉砕し、この混合物に（例えば８００〜９５０℃）の仮焼処理を施して仮焼粉末を作製する。 Next, these weighed materials are put into a ball mill together with a small-diameter grinding medium such as PSZ balls (Partially Stabilized Zirconia) having a diameter of 1 to 3 mm and pure water, for example, for a sufficiently long time (for example, 24 to 72 hours) mixed and pulverized in a wet manner, and this mixture is subjected to a calcining treatment (for example, 800 to 950 ° C.) to prepare a calcined powder.
次いで、この仮焼粉末に分散剤や粉砕媒体及び純水と共にボールミルに投入し、長時間（例えば、６〜２０時間）湿式で十分に混合、粉砕し、セラミック原料を作製する。 Next, the calcined powder is put into a ball mill together with a dispersant, a pulverizing medium and pure water, and sufficiently mixed and pulverized for a long time (for example, 6 to 20 hours) to prepare a ceramic raw material.
このように本発明ではＰｂ系圧電セラミックである主成分１００容量部に対してＡｌ２Ｏ３を１０〜４０容量部添加し、小径の粉砕媒体と共に長時間粉砕することにより、上述したような中心間距離で１００μｍ以上の平均離間距離Ｌを有するＡｌ偏析部２を形成することが可能となる。 As described above, in the present invention, 10 to 40 parts by volume of Al 2 O 3 is added to 100 parts by volume of the main component, which is a Pb-based piezoelectric ceramic, and the mixture is pulverized for a long time with a small-diameter pulverization medium. It is possible to form the Al segregation part 2 having an average separation distance L of 100 μm or more in the distance.
そしてこの後、このセラミック原料を乾燥させた後、造粒処理を施して粉末状とし、その後プレス加工を施して所定寸法のセラミック成形体を作製し、その後、焼成温度１１００〜１２００℃で所定時間焼成処理を行い、これにより所望の圧電磁器が作製される。 Then, after drying this ceramic raw material, it is granulated to form a powder, and then pressed to produce a ceramic molded body of a predetermined size, and then fired at 1100 to 1200 ° C. for a predetermined time. A firing process is performed, and thereby a desired piezoelectric ceramic is produced.
尚、前記焼成処理は、焼成して得られる焼結体の密度が収束する温度を１１００〜１２００℃の間で適切に選定し、これを最適焼成温度として焼成するのが好ましい。 In the firing process, it is preferable to appropriately select a temperature at which the density of the sintered body obtained by firing converges between 1100 to 1200 ° C. and to fire this as the optimum firing temperature.
次に、この圧電磁器の主面及び側面を研磨した後、スパッタリング法等を使用して両主面に対向電極を形成し、その後所定温度に調整されたシリコンオイル中で所定の電界を所定時間負荷して分極し、次いで所定温度（例えば、１５０〜２８０℃）で熱エージング処理を施し、これにより圧電発振子が製造される。 Next, after polishing the main surface and side surfaces of this piezoelectric ceramic, a counter electrode is formed on both main surfaces using a sputtering method or the like, and then a predetermined electric field is applied in silicon oil adjusted to a predetermined temperature for a predetermined time. The electrode is loaded and polarized, and then subjected to a heat aging treatment at a predetermined temperature (for example, 150 to 280 ° C.), whereby a piezoelectric oscillator is manufactured.
このように本実施の形態では、圧電セラミック１００容量部に対しＡｌ２Ｏ３を１０〜４０容量部添加し、小径の粉砕媒体と共に十分に長時間湿式で混合・粉砕した後、焼成処理を行うことにより、平均離間距離Ｌが１００μｍ以上のＡｌ偏析部２を形成しているので、上述したように発振周波数の変動が小さく、発振特性に優れ、共振周波数の温度変化率も小さく、耐熱性が良好で機械的強度の優れた圧電発振子を容易に得ることができる。 As described above, in this embodiment, 10 to 40 parts by volume of Al 2 O 3 is added to 100 parts by volume of the piezoelectric ceramic, mixed and pulverized sufficiently with a small-diameter pulverizing medium for a long time, and then fired. Thus, since the Al segregation part 2 having an average separation distance L of 100 μm or more is formed, the oscillation frequency variation is small as described above, the oscillation characteristics are excellent, the temperature change rate of the resonance frequency is small, and the heat resistance is low. A piezoelectric resonator having good mechanical strength is easily obtained.
尚、本発明は上記実施の形態に限定されるものではない。上記実施の形態では、Ａｌ２Ｏ３を圧電セラミック素原料と共に、湿式で混合粉砕した後、仮焼処理を行っているが、仮焼後にＡｌ２Ｏ３を主成分である圧電セラミックに添加し、混合粉砕処理してもよい。 The present invention is not limited to the above embodiment. In the above embodiment, Al 2 O 3 is pulverized by wet mixing and pulverization together with the piezoelectric ceramic raw material, and after calcination, Al 2 O 3 is added to the piezoelectric ceramic as a main component. , Mixed and pulverized.
次に、本発明の実施例及び比較例を具体的に説明する。 Next, examples and comparative examples of the present invention will be specifically described.
まず、セラミック素原料としてＰｂＯ、ＭｎＯ、Ｎｂ２Ｏ５、ＺｒＯ２、ＴｉＯ２、ＳｉＯ２、及びＡｌ２Ｏ３を用意した。 First, PbO, MnO, Nb 2 O 5 , ZrO 2 , TiO 2 , SiO 2 , and Al 2 O 3 were prepared as ceramic raw materials.
そして、主成分となる圧電セラミックの基本組成が、Ｐｂ0.99{（Ｍｎ1/3Ｎｂ2/3）0.07Ｚｒ0.42Ｔｉ0.51}Ｏ３となるようにＰｂＯ、ＭｎＯ、Ｎｂ２Ｏ５、ＺｒＯ２、及びＴｉＯ２を秤量し、さらに、前記基本組成１００重量部に対しＭｎＯが０．１重量部、及びＳｉＯ２が０．０４５重量部含有するようにＭｎＯ及びＳｉＯ２を秤量した。次いで、圧電セラミック（主成分）１００容量部に対し０〜４２容量部となるようにＡｌ２Ｏ３を秤量した。 PbO, MnO, Nb 2 O 5 , ZrO 2 , PbO, MnO, Nb 2 O 5 , ZrO 2 , Pb 0.99 {(Mn 1/3 Nb 2/3 ) 0.07 Zr 0.42 Ti 0.51 } O 3 And TiO 2 were weighed, and MnO and SiO 2 were weighed so that 0.1 part by weight of MnO and 0.045 part by weight of SiO 2 were contained with respect to 100 parts by weight of the basic composition. Next, Al 2 O 3 was weighed so that it would be 0 to 42 parts by volume with respect to 100 parts by volume of the piezoelectric ceramic (main component).
次に、これら秤量物を粉砕媒体としての直径３ｍｍのＰＳＺボール及び純水と共にボールミルに投入して４８時間湿式で混合粉砕し、この混合物を温度８５０℃で４時間仮焼し、仮焼粉末を得た。 Next, these weighed materials are put into a ball mill together with PSZ balls having a diameter of 3 mm as a grinding medium and pure water and mixed and pulverized for 48 hours by wet mixing. Obtained.
次いで、この仮焼粉末に分散剤としてのポリビニルアルコール、ＰＳＺボール及び純水と共にボールミルに投入し、１５時間湿式で混合、粉砕し、セラミック原料を得た。 Next, the calcined powder was put into a ball mill together with polyvinyl alcohol, PSZ balls and pure water as a dispersant, and mixed and pulverized for 15 hours to obtain a ceramic raw material.
次に、このセラミック原料を乾燥させ後、造粒処理を施して粉末状とし、その後プレス加工を施して所定寸法のセラミック成形体を作製し、その後、温度１１００〜１２００℃の間での最適焼成温度で３時間焼成処理を行い、縦２０ｍｍ、横３０ｍｍ、厚み７ｍｍからなる試料番号１〜８の圧電磁器を得た。 Next, after drying this ceramic raw material, it is granulated to form a powder, and then pressed to produce a ceramic molded body of a predetermined size, and then optimally fired at a temperature between 1100 and 1200 ° C. A firing process was performed at temperature for 3 hours to obtain piezoelectric ceramics having sample numbers 1 to 8 each having a length of 20 mm, a width of 30 mm, and a thickness of 7 mm.
また、原料粉末の粉砕媒体として直径５ｍｍのＰＳＺボールを用い、２４時間湿式混合粉砕を行った以外は試料５と同一の製造方法で試料番号９の圧電磁器を作製した。 A piezoelectric ceramic of sample number 9 was produced by the same manufacturing method as sample 5 except that PSZ balls having a diameter of 5 mm were used as a grinding medium for raw material powder and wet mixed grinding was performed for 24 hours.
次に、試料番号１〜９の各々について、日本電子社製：ＪＸＡ８８００Ｒを使用し、ＷＤＸ（Wavelength Dispersive X-ray Spectroscopy；波長分散型Ｘ線分光法）により、以下の分析条件で各試料を分析し、２５μｍ□の領域内でのＡｌ２Ｏ３粒子の凝集体の存在比（Ａｌ存在比）を算出した。 Next, for each of sample numbers 1 to 9, using JXA8800R manufactured by JEOL Ltd., each sample was analyzed under the following analysis conditions by WDX (Wavelength Dispersive X-ray Spectroscopy). Then, the abundance ratio (Al abundance ratio) of the aggregates of Al 2 O 3 particles in the region of 25 μm □ was calculated.
〔分析条件〕
加速電圧：１５ｋＶ
照射電流：１００ｎＡ
ピクセル数（画素数）：２５６×２５６
ピクセルサイズ（１画素の大きさ）：０．１μｍ
１つの画素での取り込み時間：５０ｍｓ
深さ方向の分析領域：約１〜２μｍ
また、上記のようにして規定したＡｌ存在比が５０％を越えたものをＡｌ偏析物と定義し、ＳＥＭ（Scanning Electron Microscope;走査型電子顕微鏡）を使用し、２０ｋＶの加速電圧を試料に印加した状態で写真撮影を行い、画像解析し、圧電磁器中のＡｌ偏析物の存在比（Ａｌ偏析物存在比）を求めた。
〔Analysis conditions〕
Acceleration voltage: 15 kV
Irradiation current: 100 nA
Number of pixels (number of pixels): 256 × 256
Pixel size (size of one pixel): 0.1 μm
Capture time for one pixel: 50 ms
Analysis area in the depth direction: about 1 to 2 μm
In addition, the Al abundance ratio specified as described above exceeds 50% is defined as Al segregated material, and an accelerating voltage of 20 kV is applied to the sample using a SEM (Scanning Electron Microscope). In this state, a photograph was taken, the image was analyzed, and the abundance ratio of Al segregated matter in the piezoelectric ceramic (Al segregated matter abundance ratio) was determined.
同様にＳＥＭを使用して２０ｋＶの加速電圧を試料に印加した状態で写真撮影を行い、画像解析し、Ａｌ偏析部の中心間距離（重心）を測定し、Ａｌ偏析部同士の離間距離の平均値、すなわち平均離間距離を求めた。 Similarly, using a SEM, take a photograph with an acceleration voltage of 20 kV applied to the sample, analyze the image, measure the center-to-center distance (center of gravity) of the Al segregation parts, and average the separation distance between the Al segregation parts. The value, ie the average separation distance, was determined.
表１は試料番号１〜９のＡｌ２Ｏ３含有量、２５μｍ□の領域内でのＡｌ存在比、Ａｌ偏析部存在比、及び前記平均離間距離を示している。 Table 1 shows the Al 2 O 3 content of Sample Nos. 1 to 9, the Al abundance ratio in the region of 25 μm □, the Al segregation portion abundance ratio, and the average separation distance.
試料番号１は、圧電磁器中にＡｌ２Ｏ３が全く含まれていない試料であり、特性については後述する。 Sample No. 1 is a sample in which no Al 2 O 3 is contained in the piezoelectric ceramic, and the characteristics will be described later.
試料番号２は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し２容量部と少なく、Ａｌ２Ｏ３粒子同士の凝集は少なく、Ａｌ存在比が１．９％と低く、本発明で定義するＡｌ偏析部を形成することができなかった。 Sample No. 2 has an Al 2 O 3 content of 2 parts by volume with respect to 100 parts by volume of the main component, little aggregation of Al 2 O 3 particles, and an Al abundance ratio as low as 1.9%. The Al segregation part to be defined could not be formed.
試料番号３も、Ａｌ２Ｏ３含有量が主成分１００容量部に対し６容量部と少なく、Ａｌ２Ｏ３粒子同士の凝集は少なく、Ａｌ存在比も８．３％と低く、Ａｌ偏析部を形成することができなかった。 Sample No. 3 also has an Al 2 O 3 content of 6 parts by volume with respect to 100 parts by volume of the main component, little aggregation of Al 2 O 3 particles, and an Al abundance ratio as low as 8.3%. Could not be formed.
試料番号８は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し４２容量部と多すぎるため、Ａｌ偏析物存在比が１．２１％となって１．０％を超えており、Ａｌ偏析部同士の平均離間距離が８１μｍと小さく、１００μｍ未満になることが分かった。 Sample No. 8 has an Al 2 O 3 content of 42 parts by volume with respect to 100 parts by volume of the main component, so the Al segregated substance abundance ratio is 1.21% and exceeds 1.0%. It was found that the average separation distance between the segregated portions was as small as 81 μm and less than 100 μm.
試料番号９は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し２０容量部ではあるが、原料粉末の粉砕媒体として直径が５ｍｍの大きなＰＳＺボールを使用しており、しかも湿式粉砕時間も２４時間と短いため、Ａｌ存在比が９．３％と低く、本発明でいうＡｌ偏析部を形成することがなかった。 Sample No. 9 has an Al 2 O 3 content of 20 parts by volume with respect to 100 parts by volume of the main component, but a large PSZ ball having a diameter of 5 mm is used as a grinding medium for the raw material powder, and the wet grinding time is also long. Since it was as short as 24 hours, the Al abundance ratio was as low as 9.3%, and the Al segregation part referred to in the present invention was not formed.
これに対し試料番号４〜７は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し１０〜４０容量部であり、Ａｌ存在比は５０％以上、Ａｌ偏析部存在比は０．３２〜０．９１％、Ａｌ偏析部同士の平均離間距離は１０６〜２０８μｍとなって１００μｍ以上となることが確認された。 In contrast, Sample Nos. 4 to 7 have an Al 2 O 3 content of 10 to 40 parts by volume with respect to 100 parts by volume of the main component, an Al abundance ratio of 50% or more, and an Al segregation part abundance ratio of 0.32 to 2. It was confirmed that the average separation distance between Al segregation parts was 0.91%, and was 106 to 208 μm, which was 100 μm or more.
図３は、Ａｌ２Ｏ３の含有量（容量部）とＡｌ存在比との関係をプロットした図である。 FIG. 3 is a graph plotting the relationship between the content of Al 2 O 3 (capacity part) and the Al abundance ratio.
この図３から明らかなように同じ製造条件であればＡｌ２Ｏ３の含有量が主成分である圧電セラミック１００容量部に対し１０容量部以上になると、Ａｌ存在比が５０％以上になることが分かる。 As is apparent from FIG. 3, under the same manufacturing conditions, when the content of Al 2 O 3 is 10 capacity parts or more with respect to 100 capacity parts of the piezoelectric ceramic as the main component, the Al abundance ratio is 50% or more. I understand.
図４は試料番号３のＳＥＭ写真であり、図４（ａ）は倍率１０００倍で撮影した図であり、図４（ｂ）は要部を倍率１００００倍に拡大して撮影した図である。 FIG. 4 is an SEM photograph of Sample No. 3, FIG. 4 (a) is a photograph taken at a magnification of 1000 times, and FIG. 4 (b) is a photograph taken at a magnification of 10,000 times at a main part.
試料番号３は、Ａｌ含有量が主成分１００容量部に対し６容量部と少ないため、図４（ｂ）に示すようにＡｌ２Ｏ３は凝集せずに粒子の状態で結晶粒界に析出し、しかも図４（ａ）に示すように粒子の状態で点在している。 In sample No. 3, since the Al content is as small as 6 parts by volume with respect to 100 parts by volume of the main component, as shown in FIG. 4 (b), Al 2 O 3 does not agglomerate and precipitates at the grain boundaries in the form of particles. Moreover, as shown in FIG. 4A, the particles are scattered in a state of particles.
一方、図５は試料番号６のＳＥＭ写真であり、図５（ａ）は倍率１０００倍で撮影した図であり、図５（ｂ）は要部を倍率１００００倍に拡大して撮影した図である。 On the other hand, FIG. 5 is an SEM photograph of Sample No. 6, FIG. 5 (a) is a view taken at a magnification of 1000 times, and FIG. 5 (b) is a view taken at a magnification of 10,000 times for the main part. is there.
試料番号６は、Ａｌ含有量が主成分１００容量部に対し３０容量部と多いため、図５（ｂ）に示すように、多量の微粉状のＡｌ２Ｏ３粒子が互いに凝集してＡｌ偏析部を形成し、該Ａｌ偏析部が結晶粒界に析出し、しかも、Ａｌ偏析部の状態で均一に分散していることが分かる。 In Sample No. 6, since the Al content is as large as 30 parts by volume with respect to 100 parts by volume of the main component, as shown in FIG. 5 (b), a large amount of finely powdered Al 2 O 3 particles aggregate to each other to cause Al segregation. It can be seen that the Al segregation part is precipitated at the grain boundary and is uniformly dispersed in the state of the Al segregation part.
次に、上記試料番号１〜９の圧電磁器の各側面を研磨した後、スパッタリング法を使用して両主面に対向電極を形成し、その後シリコンオイル中で電界：３．０ｋＶ／ｍｍ、処理温度：１００℃、処理時間：３０分の条件で分極処理を施し、次いで温度２７０℃に調整されたオーブンに６０分間収容し、熱エージング処理を施した。 Next, after polishing each side surface of the piezoelectric ceramics of sample numbers 1 to 9, a counter electrode is formed on both main surfaces using a sputtering method, and then an electric field: 3.0 kV / mm in silicon oil, treatment Polarization treatment was performed under the conditions of temperature: 100 ° C., treatment time: 30 minutes, and then housed in an oven adjusted to a temperature of 270 ° C. for 60 minutes, followed by heat aging treatment.
次いで、この熱エージング処理された圧電磁器を切断し、縦７ｍｍ、横２ｍｍ、厚み０．２ｍｍからなる試料番号１〜９の厚みすべり振動モードの圧電素子を作製した。 Next, the piezoelectric ceramic subjected to the heat aging treatment was cut to produce a thickness-shear vibration mode piezoelectric element of sample numbers 1 to 9 having a length of 7 mm, a width of 2 mm, and a thickness of 0.2 mm.
次に、各試料番号１〜９の圧電素子について、インピーダンスアナライザ（アジレント・テクノロジー社製ＨＰ４１９４Ａ）を使用し、電気機械結合係数ｋ15、最大位相θmax、比誘電率εr、周波数定数、共振周波数の温度変化率ｆｒ−Ｔｃ及び共振抵抗Ｚｒを測定した。 Next, for each of the piezoelectric elements of sample numbers 1 to 9, an impedance analyzer (HP4194A manufactured by Agilent Technologies) is used, and the electromechanical coupling coefficient k 15 , the maximum phase θmax, the relative dielectric constant εr, the frequency constant, and the resonance frequency The temperature change rate fr-Tc and the resonance resistance Zr were measured.
電気機械結合係数ｋ15は、０．５Ｖの電圧を試料に印加したときの共振周波数ｆｒ及び反共振周波数ｆａを測定し、数式（１）に基づいて算出した。尚、電気機械結合係数ｋ15は、４０％以下のものを「良」とした。 Electromechanical coupling coefficient k 15 is, the voltage of 0.5V was measured resonant frequency fr and anti-resonant frequency fa of the time of applying to the sample was calculated based on Equation (1). In addition, the electromechanical coupling coefficient k 15 is 40% or less as “good”.
ここで、Δｆは共振周波数ｆｒと反共振周波数ｆａとの差である。 Here, Δf is the difference between the resonance frequency fr and the antiresonance frequency fa.
また、最大位相θmaxは、０．５Ｖの電圧を試料に印加したときのインピーダンス特性を測定し、その測定結果から共振点と反共振点との間の位相角が最大となる角度を算出した。尚、最大位相θmaxは、８７．９°以上のものを「良」とした。 For the maximum phase θmax, the impedance characteristic when a voltage of 0.5 V was applied to the sample was measured, and the angle at which the phase angle between the resonance point and the antiresonance point was maximum was calculated from the measurement result. A maximum phase θmax of “87.9 °” or more was determined as “good”.
また 比誘電率εrは、静電容量を測定し、該静電容量と試料寸法とから求めた。 Further, the relative dielectric constant εr was obtained from the capacitance and the sample size by measuring the capacitance.
また、周波数定数は反共振周波数ｆａと圧電素子の厚みｔを乗算して求めた。 The frequency constant was determined by multiplying the antiresonance frequency fa and the thickness t of the piezoelectric element.
さらに、共振周波数の温度変化率ｆｒ−Ｔｃは、０．５Ｖの電圧を試料に印加して−４０℃〜＋１２５℃における共振周波数を測定し、数式（２）に基づいて求めた。尚、共振周波数の温度変化率ｆｒ−Ｔｃは、−３０〜＋３０ppm／℃の範囲内のものを「良」とし、共振周波数の温度特性を評価した。 Further, the temperature change rate fr-Tc of the resonance frequency was obtained based on the mathematical formula (2) by applying a voltage of 0.5 V to the sample, measuring the resonance frequency at −40 ° C. to + 125 ° C. The temperature change rate fr-Tc of the resonance frequency was evaluated as “good” when the temperature was within the range of −30 to +30 ppm / ° C.
ｆｒ−Ｔｃ＝[（ｆｒmax−ｆｒmin）×{１２５−（−４０）}／ｆｒ20）]
×１０６ …（２）
ここで、ｆｒmaxは−４０〜＋１２５℃における共振周波数ｆｒの最大値、ｆｒminは−４０〜＋１２５℃における共振周波数ｆｒの最小値、ｆｒ20は温度２０℃における共振周波数である。
fr−Tc = [(frmax−frmin) × {125 − (− 40)} / fr 20 )]
× 10 6 (2)
Here, frmax is the maximum value of the resonance frequency fr at −40 to + 125 ° C., frmin is the minimum value of the resonance frequency fr at −40 to + 125 ° C., and fr 20 is the resonance frequency at a temperature of 20 ° C.
また、各試料を温度２６０℃に調整されたリフロー炉に１回通過させて１時間放置し、リフロー通過前の反共振周波数ｆａ１とリフロー炉通過後１時間経過したときの反共振周波数ｆａ２とを測定し、数式（３）に基づいて反共振周波数の変化率Δｆａを算出し、耐熱性を評価した。尚、耐熱性評価は反共振周波数の変化率Δｆａが−０．１０〜＋０．１０％の範囲内のものを「良」とした。 In addition, each sample is passed once through a reflow furnace adjusted to a temperature of 260 ° C. and left for 1 hour. The anti-resonance frequency fa 1 before passing through the reflow furnace and the anti-resonance frequency fa 2 when passing through the reflow furnace after 1 hour have passed. And the change rate Δfa of the antiresonance frequency was calculated based on the formula (3), and the heat resistance was evaluated. In the heat resistance evaluation, “good” was evaluated when the anti-resonance frequency change rate Δfa was in the range of −0.10 to + 0.10%.
Δｆａ＝（ｆａ２−ｆａ１）／ｆａ１×１００ …（３）
また、３点曲げ試験を行って抗折強度τを測定し、機械的強度を評価した。
Δfa = (fa 2 −fa 1 ) / fa 1 × 100 (3)
Further, the bending strength τ was measured by performing a three-point bending test, and the mechanical strength was evaluated.
すなわち、各試料の両端を支持し、その中央に荷重を負荷し、各試料が破壊した時の荷重を測定して抗折強度τを算出し、機械的強度を評価した。尚、機械的強度は、抗折強度τが１８０ＭＰａ以上のものを「良」とした。 That is, both ends of each sample were supported, a load was applied to the center thereof, the bending strength τ was calculated by measuring the load when each sample was broken, and the mechanical strength was evaluated. As the mechanical strength, those having a bending strength τ of 180 MPa or more were evaluated as “good”.
また、共振抵抗Ｚｒは、０．５Ｖの電圧を印加してインピーダンスアナライザを用いて測定した。 The resonance resistance Zr was measured using an impedance analyzer with a voltage of 0.5 V applied.
表２は各測定結果を示している。 Table 2 shows the measurement results.
試料番号１は、Ａｌ２Ｏ３が全く含まれていないため（表１参照）、電気機械結合係数ｋ15が４４．３％となって４０％を超えており、したがって外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Sample No. 1 does not contain Al 2 O 3 at all (see Table 1), so the electromechanical coupling coefficient k 15 is 44.3%, which exceeds 40%. It was found that fluctuations in the oscillation frequency could not be sufficiently suppressed against the influence from the circuit after mounting.
試料番号２は、Ａｌ２Ｏ３を含有しているものの、その含有量は主成分１００容量部に対し２容量部と少なく、Ａｌ存在比が１．９％であり、Ａｌ偏析物が測定できないことから（表１参照）、電気機械結合係数ｋ15が４３．２％となって４０％を超えており、したがって試料番号１と同様、外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Sample No. 2 contains Al 2 O 3 , but its content is as small as 2 parts by volume with respect to 100 parts by volume of the main component, the Al abundance ratio is 1.9%, and Al segregated matter cannot be measured. Therefore (see Table 1), the electromechanical coupling coefficient k 15 is 43.2%, which exceeds 40%. Therefore, as with sample number 1, it is affected by changes in the external environment and effects from the circuit after mounting on the board. On the other hand, it was found that fluctuations in the oscillation frequency could not be sufficiently suppressed.
試料番号３も、Ａｌ２Ｏ３を含有しているものの、その含有量は主成分１００容量部に対し６容量部と少なく、Ａｌ存在比が８．３％であり、Ａｌ偏析物が測定できないことから（表１参照）、電気機械結合係数ｋ15が４１．３％となって４０％を超えており、したがって試料番号１と同様、外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Sample No. 3 also contains Al 2 O 3 , but its content is as small as 6 parts by volume with respect to 100 parts by volume of the main component, the Al abundance ratio is 8.3%, and Al segregated matter cannot be measured. since (see Table 1), the electromechanical coupling coefficient k 15 is above 40% becomes 41.3%, thus the same manner as sample No. 1, the influence from the circuit after the change and the substrate mounting the external environment On the other hand, it was found that fluctuations in the oscillation frequency could not be sufficiently suppressed.
試料番号８は、Ａｌ２Ｏ３の含有量が主成分１００容量部に対し４２容量部と過剰であるため（表１参照）、共振抵抗Ｚｒが４．５Ωと高く、また最大位相θmaxが８７．５°と低く、発振特性の悪化を招くおそれがある。 In Sample No. 8, the content of Al 2 O 3 is as large as 42 parts by volume with respect to 100 parts by volume of the main component (see Table 1), so that the resonance resistance Zr is as high as 4.5Ω and the maximum phase θmax is 87. As low as .5 °, the oscillation characteristics may be deteriorated.
試料番号９は、Ａｌ存在比が９．３％であり、５０％未満のため、電気機械結合係数ｋ１５は低くなるものの、最大位相θmaxが４５．０°と極端に低くなり、共振周波数の温度変化率ｆｒ−Ｔｃ、抗折強度τ、及び共振抵抗Ｚｒも悪化することが分かった。 Sample No. 9 is Al abundance ratio 9.3% for less than 50%, although made electromechanical coupling coefficient k 15 is low, the maximum phase θmax is 45.0 ° and the extremely low, the resonant frequency It was found that the temperature change rate fr-Tc, the bending strength τ, and the resonance resistance Zr were also deteriorated.
これに対し試料番号４〜７は、Ａｌ２Ｏ３の含有量が主成分１００容量部に対し１０〜４０容量部と本発明範囲内であり（表１参照）、したがって電気機械結合係数ｋ15は４０．０%以下と小さくできるにも拘わらず、最大位相θmaxは８７．９°以上を確保することができ、周波数定数も高く、共振周波数の温度変化率ｆｒ−Ｔｃも−３０〜＋３０ppm／℃の範囲内にあり、反共振周波数の変化率も−０．１０〜＋０．１０％以内となって耐熱性も良好であり、さらに抗折強度τも１８０ＭＰａ以上となって機械的強度にも優れ、かつ共振抵抗Ｚｒも４．０Ω以下の圧電素子を得ることができることが分かった。 On the other hand, Sample Nos. 4 to 7 have an Al 2 O 3 content of 10 to 40 parts by volume with respect to 100 parts by volume of the main component (see Table 1), and therefore the electromechanical coupling coefficient k 15. Can be as small as 40.0% or less, the maximum phase θmax is 87.9 ° or more, the frequency constant is high, and the temperature change rate fr-Tc of the resonance frequency is also −30 to +30 ppm / Within the range of ° C., the rate of change of the anti-resonance frequency is also within −0.10 to + 0.10%, the heat resistance is good, and the bending strength τ is 180 MPa or more, so that the mechanical strength is also improved. It was found that a piezoelectric element having excellent resonance resistance Zr of 4.0Ω or less can be obtained.
また、試料番号５〜７から明らかなように、Ａｌ２Ｏ３の含有量を主成分１００容量部に対し２０〜４０容量部とすることにより、電気機械結合係数ｋ15は３５%以下と小さいにも拘わらず、最大位相θmaxを８７．９°以上と大きくすることができる他、しかも温度変化率ｆｒ−Ｔｃが±２０ppm／℃の範囲内と小さくすることができ、抗折強度τも１９０ＭＰａ以上となって良好な機械的強度の得られることが分かった。 Further, as apparent from the sample numbers 5 to 7, the electromechanical coupling coefficient k 15 is as small as 35% or less by setting the content of Al 2 O 3 to 20 to 40 parts by volume with respect to 100 parts by volume of the main component. Nevertheless, the maximum phase θmax can be increased to 87.9 ° or more, and the temperature change rate fr-Tc can be decreased within a range of ± 20 ppm / ° C, and the bending strength τ is also 190 MPa. Thus, it was found that good mechanical strength can be obtained.
図６はＡｌ２Ｏ３含有量と電気機械結合係数ｋ15（（ａ））、最大位相θmax（（ｂ））、及び抗折強度τ（（ｃ））との関係をそれぞれプロットした図である。 FIG. 6 is a graph plotting the relationship between the Al 2 O 3 content, the electromechanical coupling coefficient k 15 ((a)), the maximum phase θmax ((b)), and the bending strength τ ((c)). is there.
すなわち、Ａｌ２Ｏ３の含有量を主成分１００容量部に対し１０容量部〜４０重量部とし、本発明のＡｌ存在比及びＡｌ偏析物の構造を有することにより、図６（ａ）に示すように電気機械結合係数ｋ15を４０％以下にすることができ、図６（ｃ）に示すように抗折強度τを１９０ＭＰａ以上にすることができ、また、図６（ｂ）に示すように最大位相θmaxを８７．９°以上とすることができる。 That is, the content of Al 2 O 3 is 10 to 40 parts by weight with respect to 100 parts by volume of the main component, and the Al abundance ratio and the structure of the Al segregated material of the present invention are shown in FIG. Thus, the electromechanical coupling coefficient k 15 can be made 40% or less, the bending strength τ can be made 190 MPa or more as shown in FIG. 6 (c), and as shown in FIG. 6 (b). In addition, the maximum phase θmax can be 87.9 ° or more.
以上より、電気機械結合係数ｋ15が低下すると最大位相θmaxも低下すると推測されていたが、本発明のようにＡｌ２Ｏ３を多く添加し、本発明の構造を有することによって、最大位相θmaxが余り低下しないことが分かった。 From the above, it has been estimated that when the electromechanical coupling coefficient k 15 decreases, the maximum phase θmax also decreases. However, by adding a large amount of Al 2 O 3 as in the present invention and having the structure of the present invention, the maximum phase θmax is reduced. Was found not to decrease much.
セラミック素原料としてＰｂＯ、ＮｉＯ、Ｎｂ２Ｏ５、ＺｒＯ２、ＴｉＯ２、ＭｎＯ、及びＡｌ２Ｏ３を用意した。 PbO, NiO, Nb 2 O 5 , ZrO 2 , TiO 2 , MnO, and Al 2 O 3 were prepared as ceramic raw materials.
そして、主成分となる圧電セラミックの基本組成が、Ｐｂ0.99{（Ｎｉ1/3Ｎｂ2/3）0.07Ｚｒ0.42Ｔｉ0.51}Ｏ３となるようにＰｂＯ、ＮｉＯ、Ｎｂ２Ｏ５、ＺｒＯ２、及びＴｉＯ２を秤量し、さらに、前記基本組成１００重量部に対しＭｎＯが０．６重量部含有するようにＭｎＯを秤量した。次いで、圧電セラミック（主成分）１００容量部に対し０〜４２容量部となるようにＡｌ２Ｏ３を秤量した。 PbO, NiO, Nb 2 O 5 , ZrO 2 , PbO, NiO, Nb 2 O 5 , ZrO 2 , and Pb 0.99 {(Ni 1/3 Nb 2/3 ) 0.07 Zr 0.42 Ti 0.51 } O 3 And TiO 2 were weighed, and MnO was weighed so that MnO contained 0.6 parts by weight with respect to 100 parts by weight of the basic composition. Next, Al 2 O 3 was weighed so that it would be 0 to 42 parts by volume with respect to 100 parts by volume of the piezoelectric ceramic (main component).
この後は〔実施例１〕の試料番号１〜９のそれぞれの製造方法と同様の方法・手順を使用し、試料番号１１〜１９の圧電磁器を作製した。 Thereafter, the same methods and procedures as the respective manufacturing methods of Sample Nos. 1 to 9 in [Example 1] were used, and piezoelectric ceramics Nos. 11 to 19 were produced.
次に、試料番号１１〜１９の各々について、〔実施例１〕と同様の方法・手順でＡｌ存在比、Ａｌ偏析物存在比、平均離間距離を各々測定した。 Next, for each of sample numbers 11 to 19, the Al abundance ratio, the Al segregated substance abundance ratio, and the average separation distance were measured by the same method and procedure as in [Example 1].
表３は試料番号１１〜１９のＡｌ２Ｏ３含有量、Ａｌ存在比、Ａｌ偏析物存在比、及び平均離間距離を示している。 Table 3 shows the Al 2 O 3 content, Al abundance ratio, Al segregated substance abundance ratio, and average separation distance of sample numbers 11 to 19.
試料番号１１は、圧電磁器中にＡｌ２Ｏ３が全く含まれていない試料であり、特性については後述する。 Sample No. 11 is a sample in which Al 2 O 3 is not contained in the piezoelectric ceramic, and the characteristics will be described later.
試料番号１２は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し２容量部と少なく、Ａｌ２Ｏ３粒子同士の凝集は少なく、Ａｌ存在比が１．４％と低く、本発明で定義するＡｌ偏析部を形成することができなかった。 Sample No. 12 has an Al 2 O 3 content of 2 parts by volume with respect to 100 parts by volume of the main component, little aggregation of Al 2 O 3 particles, and an Al abundance ratio as low as 1.4%. The Al segregation part to be defined could not be formed.
試料番号１３も、Ａｌ２Ｏ３含有量が主成分１００容量部に対し６容量部と少なく、Ａｌ２Ｏ３粒子同士の凝集は少なく、Ａｌ存在比も９．０％と低く、Ａｌ偏析部を形成することができなかった。 Sample No. 13 also has an Al 2 O 3 content of 6 parts by volume with respect to 100 parts by volume of the main component, little aggregation of Al 2 O 3 particles, and an Al abundance ratio as low as 9.0%. Could not be formed.
試料番号１８は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し４２容量部と多く、Ａｌ偏析物存在比が１．１９％と１．０％を超えており、Ａｌ偏析部同士の離間距離が８３μｍと小さく、１００μｍ未満になることが分かった。 Sample No. 18 has an Al 2 O 3 content as high as 42 parts by volume with respect to 100 parts by volume of the main component, and the Al segregated substance abundance ratio exceeds 1.19% and 1.0%. It was found that the separation distance was as small as 83 μm and less than 100 μm.
試料番号１９は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し２０容量部ではあるが、原料粉末の粉砕媒体として直径が５ｍｍの大きなＰＳＺボールを使用しており、しかも湿式粉砕時間も２４時間と短いため、Ａｌ存在比が９．５％と低く、本発明でいうＡｌ偏析部を形成することがなかった。 Sample No. 19 has an Al 2 O 3 content of 20 parts by volume with respect to 100 parts by volume of the main component, but uses a large PSZ ball having a diameter of 5 mm as a grinding medium for the raw material powder, and also has a wet grinding time. Since it was as short as 24 hours, the Al abundance ratio was as low as 9.5%, and the Al segregation part referred to in the present invention was not formed.
これに対し試料番号１４〜１７は、Ａｌ２Ｏ３含有量が主成分１００容量部に対し１０〜４０容量部でありＡｌ存在比は５０％以上、Ａｌ偏析部の存在比率は０．３１〜０．９５％、Ａｌ偏析部同士の離間距離が１０４〜２３０μｍとなって１００μｍ以上となることが確認された。 In contrast, Sample Nos. 14 to 17 have an Al 2 O 3 content of 10 to 40 parts by volume with respect to 100 parts by volume of the main component, an Al abundance ratio of 50% or more, and an abundance ratio of Al segregation parts of 0.31 to 1. It was confirmed that the separation distance between Al segregation parts was 0.95%, which was 104 to 230 μm and 100 μm or more.
次に、上記各試料について、〔実施例１〕と同様の方法・手順で試料番号１１〜１９の圧電素子を作製した。 Next, with respect to each of the above samples, piezoelectric elements of sample numbers 11 to 19 were produced by the same method and procedure as in [Example 1].
次に、各試料番号１１〜１９の圧電素子について、〔実施例１〕と同様の方法・手順で電気機械結合係数ｋ15、最大位相θmax、比誘電率εr、周波数定数、共振周波数の温度変化率ｆｒ−Ｔｃ、反共振周波数の変化率、抗折強度τ及び共振抵抗Ｚｒを測定した。 Next, with respect to the piezoelectric elements of Sample Nos. 11 to 19, the electromechanical coupling coefficient k 15 , the maximum phase θmax, the relative permittivity εr, the frequency constant, and the temperature change of the resonance frequency are performed in the same manner and procedure as in Example 1. The rate fr-Tc, the anti-resonance frequency change rate, the bending strength τ, and the resonance resistance Zr were measured.
表４はその測定結果を示している。 Table 4 shows the measurement results.
試料番号１１は、Ａｌ２Ｏ３が全く含まれていないため、電気機械結合係数ｋ15が４４．４％となって４０％を超えており、したがって外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Since sample number 11 does not contain Al 2 O 3 at all, the electromechanical coupling coefficient k 15 is 44.4%, which exceeds 40%. Therefore, from the change in the external environment and the circuit after mounting on the board It was found that the fluctuation of the oscillation frequency could not be sufficiently suppressed against the influence of
試料番号１２は、Ａｌ２Ｏ３を含有しているものの、その含有量は主成分１００容量部に対し２容量部と少なく、Ａｌ存在比が１．４％であり、Ａｌ偏析物が測定できないことから（表３参照）、電気機械結合係数ｋ15が４３．２％となって４０％を超えており、したがって試料番号１１と同様、外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Sample No. 12 contains Al 2 O 3 , but its content is as small as 2 parts by volume with respect to 100 parts by volume of the main component, the Al abundance ratio is 1.4%, and Al segregated matter cannot be measured. (see Table 3) since the electromechanical coupling factor k 15 is above 40% becomes 43.2%, thus the same manner as sample No. 11, the influence from the circuit after the change and the substrate mounting the external environment On the other hand, it was found that fluctuations in the oscillation frequency could not be sufficiently suppressed.
試料番号１３も、Ａｌ２Ｏ３を含有しているものの、その含有量は主成分１００容量部に対し６容量部と少なく、Ａｌ存在比が９．０％であり、Ａｌ偏析物が測定できないことから（表３参照）、電気機械結合係数ｋ15が４１．３％となって４０％を超えており、したがって試料番号１１と同様、外部環境の変化や基板実装後の回路からの影響に対し、発振周波数の変動を十分に抑制することができないことが分かった。 Sample No. 13 also contains Al 2 O 3 , but its content is as small as 6 parts by volume with respect to 100 parts by volume of the main component, Al abundance is 9.0%, and Al segregated matter cannot be measured. Therefore (see Table 3), the electromechanical coupling coefficient k 15 is 41.3%, which exceeds 40%. Therefore, like the sample No. 11, it is affected by the change of the external environment and the influence from the circuit after mounting on the board. On the other hand, it was found that fluctuations in the oscillation frequency could not be sufficiently suppressed.
試料番号１８は、Ａｌ２Ｏ３の含有量が主成分１００容量部に対し４２容量部と過剰であるため（表３参照）、共振抵抗Ｚｒが４．４Ω、最大位相θmaxが８７．６°と低下し、発振特性の悪化を招くおそれがある。 In Sample No. 18, the content of Al 2 O 3 is an excess of 42 parts by volume with respect to 100 parts by volume of the main component (see Table 3), so that the resonance resistance Zr is 4.4Ω and the maximum phase θmax is 87.6 °. There is a risk that the oscillation characteristics will deteriorate.
試料番号１９は、Ａｌ存在比が９．５％であり、電気機械結合係数ｋ15が低くなるものの、最大位相θmaxが３９．６°と極端に低くなり、共振周波数の温度変化率ｆｒ−Ｔｃ、抗折強度τ、及び共振抵抗Ｚｒも悪化することが分かった。 Sample No. 19 has an Al abundance ratio of 9.5%, and the electromechanical coupling coefficient k 15 is low, but the maximum phase θmax is extremely low, 39.6 °, and the temperature change rate fr-Tc of the resonance frequency. It was also found that the bending strength τ and the resonance resistance Zr were also deteriorated.
これに対し試料番号１４〜１７は、Ａｌ２Ｏ３の含有量が主成分１００容量部に対し１０〜４０容量部と本発明範囲内であり（表３参照）、したがって電気機械結合係数ｋ15は４０．０%以下と小さくできるにも拘わらず、最大位相θmaxは８８．０°以上を確保することができ、周波数定数も高く、共振周波数の温度変化率ｆｒ−Ｔｃも−３０〜＋３０ppm／℃の範囲内にあり、反共振周波数の変化率も−０．１０〜＋０．１０％以内となって耐熱性も良好であり、さらに抗折強度τも１８０ＭＰａ以上となって機械的強度の優れた圧電素子を得ることができる。 In contrast, Sample Nos. 14 to 17 have an Al 2 O 3 content of 10 to 40 parts by volume with respect to 100 parts by volume of the main component (see Table 3), and therefore the electromechanical coupling coefficient k 15. Can be as small as 40.0% or less, the maximum phase θmax can be ensured to be 88.0 ° or more, the frequency constant is high, and the temperature change rate fr-Tc of the resonance frequency is also −30 to +30 ppm / Within the range of ℃, the rate of change of anti-resonance frequency is within -0.10 to + 0.10%, heat resistance is good, and bending strength τ is 180 MPa or more, and mechanical strength is excellent A piezoelectric element can be obtained.
また、試料番号１５〜１７から明らかなように、Ａｌ２Ｏ３の含有量を主成分１００容量部に対し２０〜４０容量部とすることにより、電気機械結合係数ｋ15が３５%以下と小さいにも拘わらず、最大位相θmaxは８８．０°以上を確保することができる他、温度変化率ｆｒ−Ｔｃも±２０ppm／℃の範囲内と小さくすることができ、抗折強度τも良好な結果が得られた。 Further, as apparent from the sample numbers 15 to 17, the electromechanical coupling coefficient k 15 is as small as 35% or less by setting the content of Al 2 O 3 to 20 to 40 parts by volume with respect to 100 parts by volume of the main component. Nevertheless, the maximum phase θmax can be ensured to be 88.0 ° or more, the temperature change rate fr-Tc can be reduced within the range of ± 20 ppm / ° C, and the bending strength τ is also good. Results were obtained.
図７はＡｌ２Ｏ３含有量と電気機械結合係数ｋ15（（ａ））、最大位相θmax（（ｂ））、及び抗折強度τ（（ｃ））との関係をそれぞれプロットした図である。 FIG. 7 is a graph plotting the relationship between the Al 2 O 3 content and the electromechanical coupling coefficient k 15 ((a)), the maximum phase θmax ((b)), and the bending strength τ ((c)). is there.
すなわち、Ａｌ２Ｏ３の含有量を主成分１００容量部に対し１０容量部以上とし、本発明のＡｌ存在比、Ａｌ偏析物の構造を有することにより、図７（ａ）に示すように電気機械結合係数ｋ15を４０％以下にすることができ、図７（ｃ）に示すように抗折強度τを１８０ＭＰａ以上にすることができる。また、図７（ｂ）に示すように最大位相θmaxを８８．０°以上にすることができる。 That is, by making the content of Al 2 O 3 10 parts by volume or more with respect to 100 parts by volume of the main component, and having the Al abundance ratio of the present invention and the structure of the Al segregated material, as shown in FIG. The mechanical coupling coefficient k 15 can be made 40% or less, and the bending strength τ can be made 180 MPa or more as shown in FIG. Further, as shown in FIG. 7B, the maximum phase θmax can be set to 88.0 ° or more.
以上より、電気機械結合係数ｋ15が低下すると最大位相θmaxも低下すると推測されていたが、本発明のようにＡｌ２Ｏ３を多く添加し、本発明の構造を有することによって、最大位相θmaxが余り低下しないことが分かった。 From the above, it has been estimated that when the electromechanical coupling coefficient k 15 decreases, the maximum phase θmax also decreases. However, by adding a large amount of Al 2 O 3 as in the present invention and having the structure of the present invention, the maximum phase θmax is reduced. Was found not to decrease much.
〔実施例１〕でＡｌ２Ｏ３に代えて、Ａｌ２Ｏ３と同様、結晶粒界に析出するＳｉＯ２を使用し、本発明実施例１と比較した。 In place of Al 2 O 3 in [Example 1], SiO 2 precipitated at the grain boundaries was used in the same manner as Al 2 O 3 and compared with Example 1 of the present invention.
すなわち、〔実施例１〕と同一組成からなる主成分１００容量部に対しＳｉＯ２が０〜８容量部となるようにＳｉＯ２を秤量し、それ以外は〔実施例１〕と同様の方法・手順で圧電磁器を作製した。 That is, SiO 2 is weighed so that SiO 2 is 0 to 8 parts by volume with respect to 100 parts by volume of the main component having the same composition as [Example 1]. Otherwise, the same method as in [Example 1] A piezoelectric ceramic was produced according to the procedure.
尚、ＳｉＯ２の含有量が主成分１００容量部に対し４容量部を超えると正常な焼結体を作製することができず、このためＳｉＯ２の含有量が主成分１００容量部に対し０、２、４容量部の３種類の試料について、〔実施例１〕と同様の方法・手順で圧電素子を作製し、電気機械結合係数ｋ15、最大位相θmax、及び共振周波数の温度変化率ｆｒ−Ｔｃを測定した。 When the content of SiO 2 exceeds 4 parts by volume with respect to 100 parts by volume of the main component, a normal sintered body cannot be produced. For this reason, the content of SiO 2 is 0 for 100 parts by volume of the main component. Piezoelectric elements were prepared for the three types of samples of 2, 2 and 4 capacity parts by the same method and procedure as in Example 1, and the electromechanical coupling coefficient k 15 , the maximum phase θmax, and the temperature change rate fr of the resonance frequency. -Tc was measured.
図８はＡｌ２Ｏ３又はＳｉＯ２の含有量と電気機械結合係数ｋ15（（ａ））、最大位相θmax（（ｂ））、及び共振周波数の温度変化率ｆｒ−Ｔｃ（（ｃ））との関係を実施例１との比較においてそれぞれプロットした図である。 FIG. 8 shows the content of Al 2 O 3 or SiO 2 and the electromechanical coupling coefficient k 15 ((a)), the maximum phase θmax ((b)), and the temperature change rate fr-Tc ((c)) of the resonance frequency. FIG. 3 is a diagram in which the relationship with the above is plotted in comparison with Example 1.
圧電セラミック（主成分）にＳｉＯ２を添加した場合、図８（ａ）に示すように電気機械結合係数ｋ15は急激かつ大幅に低下するが、図８（ｂ）及び図８（ｃ）に示すように、最大位相θmax、及び共振周波数の温度変化率ｆｒ−Ｔｃも急激かつ大幅に低下し、実用性に欠けることが分かった。 When SiO 2 is added to the piezoelectric ceramic (main component), as shown in FIG. 8A, the electromechanical coupling coefficient k 15 decreases sharply and greatly, but in FIG. 8B and FIG. 8C. As shown, the maximum phase θmax and the temperature change rate fr-Tc of the resonance frequency also suddenly and drastically decreased, indicating that the practicality is lacking.
これに対し実施例１では、Ａｌ２Ｏ３含有量を主成分１００容量部に対し１０容量部以上とすることにより、電気機械結合係数ｋ15を４０％以下に大幅に低下させることができ、一方、Ａｌ２Ｏ３含有量を主成分１００容量部に対し４０容量部以下とすることにより、最大位相θmaxを余り低下させないで８７．９°以上を確保することができ、さらにＡｌ２Ｏ３含有量を主成分１００容量部に対し１０〜４０容量部とすることにより、共振周波数の温度変化率ｆｒ−Ｔｃも−３０〜＋３０℃の範囲内とすることができる。 On the other hand, in Example 1, by making the Al 2 O 3 content 10 parts by volume or more with respect to 100 parts by volume of the main component, the electromechanical coupling coefficient k 15 can be greatly reduced to 40% or less, On the other hand, by setting the Al 2 O 3 content to 40 parts by volume or less with respect to 100 parts by volume of the main component, 87.9 ° or more can be secured without significantly decreasing the maximum phase θmax, and further Al 2 O 3 By setting the content to 10 to 40 parts by volume with respect to 100 parts by volume of the main component, the temperature change rate fr-Tc of the resonance frequency can also be set within the range of -30 to + 30 ° C.
すなわち、単に、結晶粒界に析出する物質を圧電セラミック（主成分）に大量に添加しても、最大位相θmaxの低下や共振周波数の温度変化率ｆｒ−Ｔｃの悪化を招くことなく電気機械結合係数ｋ15を小さくすることはできず、本発明のように、圧電セラミック（主成分）１００容量部に対しＡｌをＡｌ２Ｏ３換算で１０〜４０容量部含有させ、分散したＡｌ偏析部を主成分の結晶粒界に析出させることにより上述した所期の作用効果が得られ、本発明の目的を達成できることが確認された。 That is, simply by adding a large amount of a substance that precipitates at the grain boundaries to the piezoelectric ceramic (main component), the electromechanical coupling does not cause a decrease in the maximum phase θmax and a deterioration in the temperature change rate fr-Tc of the resonance frequency. can not be reduced coefficients k 15, as in the present invention, the Al to the piezoelectric ceramic (main component) 100 parts by volume is contained 10 to 40 parts by volume in terms of Al 2 O 3 dispersed therein Al segregation It was confirmed that the intended effects described above can be obtained by precipitating the crystal grain boundaries of the main component, and the object of the present invention can be achieved.
１ 圧電セラミック（主成分）
２ Ａｌ偏析部
３ 所定領域
４ 圧電セラミック素体
５ａ、５ｂ対向電極（電極）
1 Piezoelectric ceramic (main component)
2 Al segregation part 3 Predetermined area 4 Piezoelectric ceramic body 5a, 5b Counter electrode (electrode)
Claims (3)
前記主成分１００容量部に対しＡｌがＡｌ２Ｏ３換算で１０〜４０容量部含有され、
Ａｌ凝集体の存在比率であるＡｌ存在比が、２５μｍ□の領域内で５０％以上の面積比率を有する複数のＡｌ偏析部が形成され、かつ前記Ａｌ偏析部同士の平均離間距離が、中心間距離で１００μｍ以上であることを特徴とする圧電磁器。 The main component is at least one of a Pb (Zr, Ti) O 3 based compound containing Zr and Ti , a Pb (Mn, Nb) O 3 based compound and a Pb (Ni, Nb) O 3 based compound And including
Al is contained in an amount of 10 to 40 parts by volume in terms of Al 2 O 3 with respect to 100 parts by volume of the main component,
A plurality of Al segregation portions having an area ratio of 50% or more in a region where the Al abundance ratio of Al aggregates is 25 μm □ are formed, and the average separation distance between the Al segregation portions is between the centers. A piezoelectric ceramic having a distance of 100 μm or more.
前記圧電磁器が、請求項１又は請求項２記載の圧電磁器で形成されていることを特徴とする圧電部品。 A piezoelectric component, wherein the piezoelectric ceramic is formed of the piezoelectric ceramic according to claim 1 or 2.
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