WO2022153800A1 - 圧電素子 - Google Patents

圧電素子 Download PDF

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WO2022153800A1
WO2022153800A1 PCT/JP2021/047266 JP2021047266W WO2022153800A1 WO 2022153800 A1 WO2022153800 A1 WO 2022153800A1 JP 2021047266 W JP2021047266 W JP 2021047266W WO 2022153800 A1 WO2022153800 A1 WO 2022153800A1
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piezoelectric
piezoelectric element
electrode
orientation
plane
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PCT/JP2021/047266
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English (en)
French (fr)
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小木曽晃司
三輪恭也
石井秀樹
黒田大輔
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株式会社村田製作所
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Priority to JP2022575168A priority Critical patent/JPWO2022153800A1/ja
Priority to DE112021005944.0T priority patent/DE112021005944T5/de
Priority to CN202180090395.7A priority patent/CN116848967A/zh
Publication of WO2022153800A1 publication Critical patent/WO2022153800A1/ja
Priority to US18/345,332 priority patent/US20230345838A1/en

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Definitions

  • the present invention relates to a piezoelectric element.
  • Piezoelectric elements that can convert electrical energy into mechanical energy and electrically convert mechanical energy are known.
  • Patent Document 1 includes a PZT and an electrode, and the PZT is a perovskite structure having a composition ratio in which Zr and Ti contained therein become tetragonal crystals at room temperature, and the PZT is in the [100] direction, the [010] direction, or the perovskite structure.
  • the piezoelectric element whose crystal orientation is substantially perpendicular to the electrode surface in the [001] direction and the PZT have a perovskite structure having a composition ratio in which Zr and Ti contained therein are tetragonal at room temperature.
  • a piezoelectric element in which the [001] direction is crystal-oriented so as to be substantially perpendicular to the electrode surface is described.
  • the piezoelectric element As compared with the conventional piezoelectric element in which the [111] direction is oriented perpendicular to the electrode surface, the piezoelectric element has a large piezoelectric constant in the electric field direction, and the characteristics can be improved. It is described in 1.
  • the present invention solves the above problems, and an object of the present invention is to provide a piezoelectric element having a large piezoelectric constant.
  • the piezoelectric element of the present invention is A pressure electromagnetic device containing a composite oxide having a perovskite type crystal structure as a main component, A first electrode provided on the first surface of the pressure electromagnetic device, and a second electrode provided on a second surface facing the first surface.
  • the pressure electromagnetic device mainly has a rhombic crystal structure and has a crystal structure.
  • the crystal axis of the pressure electromagnetic device is ⁇ 100 ⁇ oriented.
  • the direction of the ⁇ 100 ⁇ orientation is characterized in that the direction in which the first electrode and the second electrode face each other is orthogonal to the direction in which the first electrode and the second electrode face each other.
  • the piezoelectric element in another aspect of the present invention is Piezoelectrics containing a composite oxide having a perovskite crystal structure as the main component, A first electrode provided on the first surface of the piezoelectric device, and a second electrode provided on a second surface facing the first surface.
  • the crystal axis of the piezoelectric device is ⁇ 100 ⁇ oriented.
  • the direction of the ⁇ 100 ⁇ orientation is a direction orthogonal to the direction in which the first electrode and the second electrode face each other.
  • the half width of the composite peak composed of the diffraction of the (002) plane and the (200) plane in the X-ray diffraction pattern seen from the ⁇ 100 ⁇ orientation plane of the piezoelectric device is 0.5 ° or more.
  • a piezoelectric element having a higher piezoelectric constant and a higher piezoelectric characteristic can be obtained as compared with a non-oriented piezoelectric element and a piezoelectric element in which the crystal axes are oriented in a direction in which a pair of electrodes face each other.
  • FIG. 1 is a diagram showing an X-ray diffraction pattern seen from the ⁇ 100 ⁇ orientation plane of six types of piezoelectrics having changed compositions, and (b) is a diffraction peak in which an X-ray diffraction angle is around 45 °. It is an enlarged view of. It is a figure which shows the relationship between the polarization axis and the orientation direction of a crystal axis of plate-shaped ceramics which is a piezoelectric. It is a figure which shows typically the relationship of each direction of the electric field direction, the orientation direction of plate-shaped ceramics, the polarization direction, and the vibration direction of a piezoelectric element.
  • the piezoelectric element of the present invention has a piezoelectric element containing a composite oxide having a perovskite-type crystal structure as a main component, and a second electrode provided on the first surface of the piezoelectric element and a second surface facing the first surface.
  • the piezoelectric device has a crystal structure of rhombic crystals, and the crystal axis of the piezoelectric device is ⁇ 100 ⁇ oriented and ⁇ 100 ⁇ oriented. Is a direction orthogonal to the direction in which the first electrode and the second electrode face each other.
  • the piezoelectric element of the present invention faces a pressure electromagnetic device containing a composite oxide having a perovskite type crystal structure as a main component, and a first electrode and a first surface provided on the first surface of the pressure electromagnetic device.
  • a second electrode provided on the second surface is provided, the crystal axis of the piezoelectric device is ⁇ 100 ⁇ oriented, and the direction of the ⁇ 100 ⁇ orientation is such that the first electrode and the second electrode are aligned.
  • the half-value width of the composite peak consisting of the diffraction of the (002) plane and the (200) plane in the X-ray diffraction pattern seen from the ⁇ 100 ⁇ orientation plane of the piezoelectric device, which is the direction orthogonal to the opposite direction, is 0.5 ° or more. It can also be expressed as.
  • FIG. 1 is a cross-sectional view schematically showing the configuration of the piezoelectric element 10 of the present invention.
  • the piezoelectric element 10 of the present invention is provided on the pressure electromagnetic device 1, the first electrode 2a provided on the first surface 1a of the pressure electromagnetic device 1, and the second surface 1b facing the first surface 1a. It also includes a second electrode 2b.
  • Piezoelectric device 1 contains a composite oxide having a perovskite-type crystal structure as a main component.
  • the main component means a component of 50% or more of the contained components by weight.
  • Composite oxides having a perovskite-type crystal structure include, for example, PZT (lead zirconate titanate), PNN-PZT (lead niobate nickelate (PNN) -lead zirconate (PT) -lead zirconate (PZ)), and the like.
  • PZT lead zirconate titanate
  • PNN-PZT lead niobate nickelate (PNN) -lead zirconate (PT) -lead zirconate (PZ)
  • PMN-PZT lead niobate magnesiumate (PMN) -lead titanate (PT) -lead zirconate (PZ)
  • PMN-PZT lead
  • the crystal axis of the piezoelectric device 1 is oriented in the ⁇ 100 ⁇ direction, that is, in the [100] direction, the [010] direction, or the [001] direction.
  • the direction of ⁇ 100 ⁇ orientation is the direction orthogonal to the direction in which the first electrode 2a and the second electrode 2b face each other (the direction of the arrow Y1 in FIG. 1), that is, the first surface 1a and the first surface 1a of the pressure electromagnetic device 1.
  • the direction is parallel to the second surface 1b.
  • the "direction orthogonal to the direction in which the first electrode 2a and the second electrode 2b face each other" includes a direction within a range of ⁇ 10 ° with respect to the orthogonal direction. do.
  • the crystal axis of the piezoelectric device 1 is ⁇ . It shall be 100 ⁇ oriented.
  • the piezoelectric device 1 may be configured by a laminated structure in which a plurality of layers are laminated.
  • the direction of ⁇ 100 ⁇ orientation can be determined as follows. That is, the surface or cross section of the main surface, side surface, or end surface of the element is measured by the ⁇ -2 ⁇ method with an XRD analyzer, and the surface showing the highest value by the lotgering method is the orientation direction.
  • the pressure electromagnetic device 1 mainly has a rhombohedral crystal (R phase) crystal structure, and in the X-ray diffraction pattern seen from the ⁇ 100 ⁇ oriented plane obtained by X-ray diffraction, the (002) plane and the (200) plane )
  • the half-value width of the composite peak consisting of surface diffraction is 0.5 ° or more.
  • the fact that the pressure electromagnetic device 1 mainly has a rhombohedral crystal structure means that at least 50% or more of the crystal structure of the pressure electromagnetic device 1 is a rhombohedral crystal.
  • FIG. 2A is a diagram showing an X-ray diffraction pattern seen from the ⁇ 100 ⁇ orientation plane of six types of piezoelectrics having different compositions
  • FIG. 2B is a diagram showing an X-ray diffraction angle of 45 °. It is an enlarged view of the diffraction peak in the vicinity.
  • the diffraction peak with an X-ray diffraction angle of about 45 ° shown in FIG. 2B indicates a composite peak composed of diffraction between the (002) plane and the (200) plane.
  • the samples of the six types of piezoelectrics are referred to as samples S1 to S6 in order from the top. Samples S1 to S6 are unpolarized samples. In the case of a polarized device, it is preferable to measure the X-ray diffraction pattern after depolarizing by heating above the Curie point.
  • the diffraction pattern of the sample S1 has two peaks, a diffraction peak on the (002) plane and a diffraction peak on the (200) plane.
  • the diffraction pattern of the sample S6 a composite peak in which the diffraction peak on the (002) plane and the diffraction peak on the (200) plane overlap is formed.
  • the piezoelectric device 1 has an MPB composition
  • the MPB composition is a transition region between the R phase and the T phase, and microscopically, there is a region in which the lengths of the a-axis and the c-axis of the crystal are different.
  • a diffraction peak on the (002) plane and a diffraction peak on the (200) plane are observed.
  • the half width of the composite peak composed of the diffraction of the (002) plane and the (200) plane of the sample S6 is 0.5 ° or more. Further, the half width of the composite peak composed of the diffraction of the (002) plane and the (200) plane of the samples S3 to S5 is also 0.5 ° or more.
  • the height of the diffraction peak on the (200) plane of sample S2 is higher than half the height of the diffraction peak on the (002) plane, and the half width of the composite peak consisting of the diffraction on the (002) plane and the (200) plane is , 0.5 ° or more.
  • the height of the diffraction peak on the (200) plane of the sample S1 is lower than half the height of the diffraction peak on the (002) plane. Therefore, the half width of the composite peak composed of the diffraction of the (002) plane and the (200) plane of the sample S1 is less than 0.5 °. Therefore, the pressure electromagnetic device of the sample S1 cannot be the pressure electromagnetic device 1 of the piezoelectric element 10 of the present invention.
  • the piezoelectric element 10 of the present invention has high piezoelectric characteristics due to having the above-mentioned structure.
  • the piezoelectric element 10 of the present invention can be used in various piezoelectric devices such as piezoelectric vibrators, piezoelectric filters, and piezoelectric actuators.
  • Powders of Pb 3 O 4 , TiO 2 , ZrO 2 , NiO, and Nb 2 O 5 were prepared, weighed to have a predetermined composition, and then placed in a pot mill together with water and mixed for 16 hours. Subsequently, the mixture was dried and then calcined at 900 ° C. After mixing the obtained calcined powder and an aqueous binder solution, the slurry was obtained by putting it in a pot mill and pulverizing and mixing for 16 hours.
  • a ceramic green sheet was prepared by applying the obtained slurry in the form of a sheet by the doctor blade method and then applying a magnetic field of 10 T in a direction parallel to the sheet until it was dried.
  • the produced ceramic green sheet was cut to a predetermined size, laminated while aligning the orientation directions, and pressure-bonded at a pressure of 100 MPa to obtain a molded product.
  • the obtained molded body is degreased by heating it in air at 350 ° C. for 5 hours, and then fired in air at 1050 ° C. for 2 hours to obtain plate-shaped ceramics which is a piezoelectric generator.
  • electrodes made of Ag were formed on both main surfaces of the plate-shaped ceramics, that is, on the front surface and the back surface by sputtering, and then polarization treatment was performed under the conditions of 80 ° C., 2 kV / mm, and 30 minutes. .. Finally, a diecer cut was performed so that the orientation direction was the longitudinal direction to obtain a rectangular cuboid-shaped piezoelectric element having a longitudinal direction of 13 mm, a lateral direction of 3 mm, and a thickness of 0.6 mm.
  • the obtained plate-shaped ceramic of the piezoelectric element contains a composite oxide having a perovskite-type crystal structure, specifically, PNN-PZT as a main component.
  • the crystal axis of the plate-shaped ceramics which is a pressure electromagnetic device, is oriented ⁇ 100 ⁇ , and the orientation direction is the direction orthogonal to the direction in which the pair of electrodes face each other, more specifically, the length of the piezoelectric element.
  • the plate-shaped ceramics mainly have a rhombohedral crystal structure, and is half of the composite peak composed of the diffraction of the (002) plane and the (200) plane in the X-ray diffraction pattern viewed from the ⁇ 100 ⁇ oriented plane.
  • the price range is 0.5 ° or more.
  • the X-ray diffractometer uses MiniFlex2 manufactured by Rigaku Co., Ltd., and uses a Cu tube under the conditions of a scan speed of 4 ° / min, a step of 0.02 °, and a slit width of 1.25 °. It was measured by the 2 ⁇ method. For the measured data, the K ⁇ 2 peak was removed using Jade 5.0 as analysis software.
  • FIG. 3 shows the relationship between the polarization axis of the plate-shaped ceramic and the orientation direction of the crystal axis.
  • the direction of the polarization axis which is the direction of spontaneous polarization, is the [111] direction, and the direction of the polarization treatment is the same as the direction of applying the electric field.
  • FIG. 4 schematically shows the relationship between the electric field direction, the orientation direction of the plate-shaped ceramics, the polarization direction (the direction of spontaneous polarization), and the vibration direction of the piezoelectric element when ideally 100% oriented. It is a figure.
  • FIG. 4 shows the relationship of each direction when the orientation directions are 0 °, 15 °, 55 °, 75 °, and 90 °.
  • the angle in the orientation direction is the electric field direction, that is, the angle with respect to the direction in which the pair of electrodes face each other.
  • the angle of the orientation direction of the piezoelectric element of the present invention is 90 °
  • the angle of the orientation direction of the piezoelectric element described in Patent Document 1 is 0 °.
  • FIG. 4 also shows the polarization direction when viewed in the electric field direction when the orientation direction angles are 0 °, 55 °, and 90 °.
  • the polarization direction when the angle of the orientation direction is 0 °, the polarization direction is dispersed in the range indicated by the cone, and is uniformly dispersed in the plane when viewed from above, but 90 °.
  • the cone showing the range in which the polarization direction can be distributed faces sideways, so that the cones are concentrated in the direction in which the in-plane bias occurs when viewed from above.
  • FIG. 5 is a diagram showing the relationship between the angle in the orientation direction and the piezoelectric constant.
  • FIG. 6 is a diagram showing the relationship between the angle in the orientation direction and the coupling coefficient.
  • the coupling coefficient is one of the parameters indicating the magnitude of the piezoelectric effect, and the larger the value, the higher the piezoelectric effect.
  • the data shown by the dotted line shows the values in the case of no orientation.
  • the notations of 31 mode, 32 mode, and t mode in FIGS. 5 and 6 are vibration modes in different directions in the same sample, as shown in FIG. 7, respectively.
  • the 31 mode is a vibration mode in the longitudinal direction of the first surface on which the first electrode 2a is formed and the second surface on which the second electrode 2b is formed. ..
  • the orientation direction at which the angle is 90 ° is adjusted so as to coincide with the longitudinal direction of the first surface and the second surface.
  • the piezoelectric constant in the 31 mode became the largest when the angle in the orientation direction was 90 °. That is, the crystal axis of the piezoelectric device having a crystal structure mainly of rhombohedral is ⁇ 100 ⁇ oriented, and the direction of ⁇ 100 ⁇ orientation is the direction in which the first electrode 2a and the second electrode 2b face each other.
  • the piezoelectric element 10 of the present invention having a direction orthogonal to the piezoelectric element 10 of the present invention is more piezoelectric than a non-oriented piezoelectric element or a piezoelectric element in which a pair of electrodes are oriented in opposite directions, such as the piezoelectric element described in Patent Document 1. It has a high constant and has high piezoelectric characteristics. It is considered that this is because the polarization directions of the piezoelectric device 1 are concentrated in the vibration direction.
  • the direction of ⁇ 100 ⁇ orientation is preferably the longitudinal direction of the first surface 1a and the second surface 1b of the piezoelectric device 1.
  • the piezoelectric element described in Patent Document 1 controls the crystal orientation by utilizing the crystal growth from the substrate, the crystal orientation can be made only in the direction in which the pair of electrodes face each other.
  • the piezoelectric element 10 of the present invention does not utilize crystal growth from the substrate, the orientation direction can be freely controlled. Further, unlike a single crystal, it is relatively easy to put it into practical use in industry from the viewpoint of composition control and ease of processing. Further, as in the above-described embodiment, it is also possible to obtain a piezoelectric element having a laminated structure by laminating ceramic green sheets.

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Abstract

圧電素子１０は、ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器１と、圧電磁器１の第１の面１ａに設けられた第１の電極２ａ、および、第１の面１ａと相対する第２の面１ｂに設けられた第２の電極２ｂとを備える。圧電磁器１は、主として菱面体晶の結晶構造を有している。圧電磁器１の結晶軸は、｛１００｝配向しており、｛１００｝配向の方向は、第１の電極２ａと第２の電極２ｂとが対向する方向と直交する方向である。

Description

圧電素子
　本発明は、圧電素子に関する。
　電気的エネルギーを機械的エネルギーに変換し、機械的エネルギーを電気的に変換できる圧電素子が知られている。
　特許文献１には、ＰＺＴと電極を備え、ＰＺＴは、そこに含まれるＺｒとＴｉが室温において菱面体晶となる組成比のペロブスカイト構造であって、その［１００］方向、［０１０］方向または［００１］方向が電極面にほぼ垂直となるように結晶配向している圧電素子、および、ＰＺＴは、そこに含まれるＺｒとＴｉが室温において正方晶となる組成比のペロブスカイト構造であって、その［００１］方向が電極面にほぼ垂直となるように結晶配向している圧電素子が記載されている。この圧電素子によれば、［１１１］方向を電極面と垂直に向けていた従来の圧電素子と比較して、電界方向で大きな圧電定数を持つことになり、特性を高めることができると特許文献１には記載されている。
特開平１１－２３３８４４号公報
　しかしながら、圧電素子のさらなる特性向上のため、さらに大きい圧電定数を有する圧電素子の開発が望まれている。
　本発明は、上記課題を解決するものであり、圧電定数の大きい圧電素子を提供することを目的とする。
　本発明の圧電素子は、
　ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、
　前記圧電磁器の第１の面に設けられた第１の電極、および、前記第１の面と相対する第２の面に設けられた第２の電極と、
を備え、
　前記圧電磁器は、主として菱面体晶の結晶構造を有しており、
　前記圧電磁器の結晶軸は、｛１００｝配向しており、
　前記｛１００｝配向の方向は、前記第１の電極と前記第２の電極とが対向する方向と直交する方向であることを特徴とする。
　本発明の別の態様における圧電素子は、
　ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、
　前記圧電磁器の第１の面に設けられた第１の電極、および、前記第１の面と相対する第２の面に設けられた第２の電極と、
を備え、
　前記圧電磁器の結晶軸は、｛１００｝配向しており、
　前記｛１００｝配向の方向は、前記第１の電極と前記第２の電極とが対向する方向と直交する方向であり、
　前記圧電磁器の｛１００｝配向面から見たＸ線回折パターンにおける（００２）面と（２００）面の回折から成る複合ピークの半値幅は０．５°以上であることを特徴とする。
　本発明の圧電素子によれば、無配向の圧電素子および一対の電極が対向する方向に結晶軸が配向した圧電素子と比べて、高い圧電定数を有し、高い圧電特性を得ることができる。
本発明の圧電素子の構成を模式的に示す断面図である。 （ａ）は、組成を変更した６種類の圧電磁器の｛１００｝配向面から見たＸ線回折パターンを示す図であり、（ｂ）は、Ｘ線の回折角が４５°付近の回折ピークの拡大図である。 圧電磁器である板状セラミックスの分極軸と結晶軸の配向方向との関係を示す図である。 電界方向、板状セラミックスの配向方向、分極方向、および、圧電素子の振動方向の各方向の関係を模式的に示す図である。 配向方向の角度と圧電定数との関係を示す図である。 配向方向の角度と結合係数との関係を示す図である。 ３１モード、３２モード、および、ｔモードの振動モードについて説明するための図である。
　以下に本発明の実施形態を示して、本発明の特徴を具体的に説明する。
　本発明の圧電素子は、ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、圧電磁器の第１の面に設けられた第１の電極および第１の面と相対する第２の面に設けられた第２の電極とを備え、圧電磁器は、主として菱面体晶の結晶構造を有しており、圧電磁器の結晶軸は、｛１００｝配向しており、｛１００｝配向の方向は、第１の電極と第２の電極とが対向する方向と直交する方向である。
　また、本発明の圧電素子は、ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、圧電磁器の第１の面に設けられた第１の電極および第１の面と相対する第２の面に設けられた第２の電極とを備え、圧電磁器の結晶軸は、｛１００｝配向しており、｛１００｝配向の方向は、第１の電極と第２の電極とが対向する方向と直交する方向であり、圧電磁器の｛１００｝配向面から見たＸ線回折パターンにおける（００２）面と（２００）面の回折から成る複合ピークの半値幅は０．５°以上であると表現することもできる。
　図１は、本発明の圧電素子１０の構成を模式的に示す断面図である。本発明の圧電素子１０は、圧電磁器１と、圧電磁器１の第１の面１ａに設けられた第１の電極２ａ、および、第１の面１ａと相対する第２の面１ｂに設けられた第２の電極２ｂとを備える。
　圧電磁器１は、ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む。主成分とは、重量比で、含有成分のうちの５０％以上の成分を意味する。ペロブスカイト型結晶構造を有する複合酸化物は、例えば、ＰＺＴ（チタン酸ジルコン酸鉛）、ＰＮＮ－ＰＺＴ（ニッケル酸ニオブ酸鉛（ＰＮＮ）－チタン酸鉛（ＰＴ）－ジルコン酸鉛（ＰＺ））、ＰＭＮ－ＰＺＴ（マグネシウム酸ニオブ酸鉛（ＰＭＮ）－チタン酸鉛（ＰＴ）－ジルコン酸鉛（ＰＺ））などである。
　圧電磁器１の結晶軸は、｛１００｝配向、すなわち、［１００］方向、［０１０］方向、または、［００１］方向に配向している。｛１００｝配向の方向は、第１の電極２ａと第２の電極２ｂとが対向する方向（図１の矢印Ｙ１の方向）と直交する方向、すなわち、圧電磁器１の第１の面１ａおよび第２の面１ｂと平行な方向である。ただし、本発明において、「第１の電極２ａと第２の電極２ｂとが対向する方向と直交する方向」には、直交する方向を基準として±１０°の範囲内の方向が含まれるものとする。ここでは、［１００］軸、［０１０］軸、または、［００１］軸を合わせた配向度がロットゲーリング（Lotgering Method）法で０．３０以上である場合に、圧電磁器１の結晶軸が｛１００｝配向しているものとする。圧電磁器１は、複数の層が積層された積層構造により構成されていてもよい。
　なお、｛１００｝配向の方向は、次のように決定することができる。すなわち、素子の主面、側面、端面の表面あるいは断面に対して、ＸＲＤ分析装置にてθ－２θ法で測定し、ロットゲーリング法で最も高い値を示した面が配向方向である。
　圧電磁器１は、主として菱面体晶（Ｒ相）の結晶構造を有しており、Ｘ線回折により得られる、｛１００｝配向面から見たＸ線回折パターンにおいて、（００２）面と（２００）面の回折から成る複合ピークの半値幅が０．５°以上である。なお、圧電磁器１が主として菱面体晶の結晶構造を有するとは、圧電磁器１の結晶構造の少なくとも５０％以上が菱面体晶であることを意味する。
　図２（ａ）は、組成を変更した６種類の圧電磁器の｛１００｝配向面から見たＸ線回折パターンを示す図であり、図２（ｂ）は、Ｘ線の回折角が４５°付近の回折ピークの拡大図である。図２（ｂ）に示す、Ｘ線の回折角が４５°付近の回折ピークは、（００２）面と（２００）面の回折から成る複合ピークを示す。なお、図２（ａ）および（ｂ）において、６種類の圧電磁器の試料を上から順に、試料Ｓ１～Ｓ６と呼ぶ。試料Ｓ１～Ｓ６は、未分極の試料である。なお、分極された素子の場合、キュリー点以上に加熱して脱分極してからＸ線回折パターンを測定することが好ましい。
　図２（ａ）、（ｂ）に示すように、試料Ｓ１の回折パターンには、（００２）面の回折ピークと（２００）面の回折ピークの２つのピークが存在する。一方、試料Ｓ６の回折パターンでは、（００２）面の回折ピークと（２００）面の回折ピークが重なった複合ピークが形成されている。なお、圧電磁器１はＭＰＢ組成を有するが、ＭＰＢ組成はＲ相とＴ相の遷移領域であり、微視的には、結晶のａ軸とｃ軸の長さが異なる領域が存在するため、（００２）面の回折ピークと（２００）面の回折ピークが観察される。
　試料Ｓ６の（００２）面と（２００）面の回折から成る複合ピークの半値幅は、０．５°以上である。また、試料Ｓ３～Ｓ５の（００２）面と（２００）面の回折から成る複合ピークの半値幅も０．５°以上である。試料Ｓ２の（２００）面の回折ピークの高さは、（００２）面の回折ピークの高さの半分よりも高く、（００２）面と（２００）面の回折から成る複合ピークの半値幅は、０．５°以上である。
　一方、試料Ｓ１の（２００）面の回折ピークの高さは、（００２）面の回折ピークの高さの半分よりも低い。このため、試料Ｓ１の（００２）面と（２００）面の回折から成る複合ピークの半値幅は、０．５°未満となっている。したがって、試料Ｓ１の圧電磁器は、本発明の圧電素子１０の圧電磁器１とはなり得ない。
　本発明の圧電素子１０は、上述した構造を有することにより、高い圧電特性を有する。本発明の圧電素子１０は、圧電振動子、圧電フィルター、圧電アクチュエータなどの各種圧電デバイスに用いることができる。
　（実施例）
　Ｐｂ3Ｏ4、ＴｉＯ2、ＺｒＯ2、ＮｉＯ、および、Ｎｂ2Ｏ5の各粉末を用意し、所定の組成となるように秤量した後、ポットミルに水とともに入れて１６時間混合した。続いて、混合物を乾燥させた後、９００℃で仮焼した。得られた仮焼粉体とバインダ水溶液を混合した後、ポットミルに入れて１６時間、粉砕混合することによって、スラリーを得た。
　得られたスラリーをドクターブレード法によってシート状に塗布した後、乾燥するまでの間にシートと平行な方向に１０Ｔの磁場を印加することによって、セラミックグリーンシートを作製した。作製したセラミックグリーンシートを所定の大きさにカットした後、配向方向を揃えながら積層し、１００ＭＰａの圧力で圧着することによって、成形体を得た。
　得られた成形体を空気中、３５０℃、５時間の条件で加熱することによって脱脂を行った後、空気中、１０５０℃、２時間の条件で焼成することによって、圧電磁器である板状セラミックスを得た。
　続いて、スパッタリングにより、板状セラミックスの両主面、すなわち、表面と裏面のそれぞれに、Ａｇからなる電極を成膜した後、８０℃、２ｋＶ／ｍｍ、３０分の条件で分極処理を行った。最後に、配向方向が長手方向となるようにダイサーカットして、長手方向１３ｍｍ、短手方向３ｍｍ、厚さ０．６ｍｍの直方体形状の圧電素子を得た。
　得られた圧電素子の板状セラミックスは、ペロブスカイト型結晶構造を有する複合酸化物、具体的には、ＰＮＮ－ＰＺＴを主成分として含む。
　この圧電素子において、圧電磁器である板状セラミックスの結晶軸は、｛１００｝配向しており、その配向方向は、一対の電極が対向する方向と直交する方向、より詳しくは、圧電素子の長手方向である。また、板状セラミックスは、主として菱面体晶の結晶構造を有しており、｛１００｝配向面から見たＸ線回折パターンにおける（００２）面と（２００）面の回折から成る複合ピークの半値幅は０．５°以上である。なお、Ｘ線回折装置は、株式会社リガク製のMiniFlex2を用い、Ｃｕ管球を使用して、スキャン速度４°/ｍｉｎ、ステップ０．０２°、スリット幅１．２５°の条件で、θ－２θ法で測定した。測定したデータは、解析用ソフトウェアとしてJade 5.0を用いて、Ｋα２ピークを除去した。
　板状セラミックスの分極軸と結晶軸の配向方向との関係を図３に示す。図３において、自発分極の方向である分極軸の方向は、［１１１］方向であり、分極処理の方向は、電界印加方向と同じである。
　また、磁場の印加方向を変えることによって、配向方向の角度を変えた複数の圧電素子を作製し、作製した圧電素子の圧電定数を求めた。図４は、理想的に１００％配向したときに、電界方向、板状セラミックスの配向方向、分極方向（自発分極の方向）、および、圧電素子の振動方向の各方向の関係を模式的に示す図である。図４では、配向方向が０°、１５°、５５°、７５°、９０°の場合の各方向の関係を示している。配向方向の角度は、電界方向、すなわち、一対の電極が対向する方向に対する角度である。本発明の圧電素子の配向方向の角度は９０°であり、特許文献１に記載の圧電素子の配向方向の角度は０°である。
　図４では、配向方向の角度が０°、５５°、９０°の場合に、電界方向に見たときの分極方向も合わせて示している。図４に示すように、配向方向の角度が０°の場合には、分極方向が円錐で示される範囲に分散し、上方から見た時に面内には均一に分散しているが、９０°の場合には、分極方向が分布できる範囲を示した円錐が横を向くことで、上方から見ると面内で偏りが生じある方向に集約される。
　図５は、配向方向の角度と圧電定数との関係を示す図である。また、図６は、配向方向の角度と結合係数との関係を示す図である。結合係数は、圧電効果の大きさを表すパラメータの１つであり、値が大きいほど、圧電効果が高いことを示す。図５および図６において、点線で示すデータは、無配向の場合の値を示している。
　図５および図６における３１モード、３２モード、および、ｔモードの表記はそれぞれ、図７に示す様に、同一サンプルにおける異なる方向の振動モードである。図７に示すように、３１モードは、第１の電極２ａが形成されている第１の面、および、第２の電極２ｂが形成されている第２の面の長手方向の振動モードである。なお、角度が９０°の配向方向は、第１の面および第２の面の長手方向と一致するように調整されている。
　図５に示すように、３１モードにおける圧電定数は、配向方向の角度が９０°の場合に最も大きくなった。すなわち、主として菱面体晶の結晶構造を有する圧電磁器の結晶軸が｛１００｝配向しており、かつ、｛１００｝配向の方向が第１の電極２ａと第２の電極２ｂとが対向する方向と直交する方向である本発明の圧電素子１０は、無配向の圧電素子や、特許文献１に記載の圧電素子のように、一対の電極が対向する方向に配向した圧電素子と比べて、圧電定数が高く、高い圧電特性を有する。なお、これは、圧電磁器１の分極方向が振動方向に集中することによるものと考えられる。
　また、｛１００｝配向の方向が第１の電極２ａと第２の電極２ｂとが対向する方向と直交する方向の中でも、圧電磁器１の第１の面１ａおよび第２の面１ｂの長手方向である場合に、より高い振動効果が得られる。したがって、｛１００｝配向の方向は、圧電磁器１の第１の面１ａおよび第２の面１ｂの長手方向であることが好ましい。
　なお、特許文献１に記載の圧電素子は、基板からの結晶成長を利用して、結晶配向を制御しているため、一対の電極が対向する方向にしか結晶配向させることができない。
　しかしながら、本発明の圧電素子１０は、基板からの結晶成長を利用しないため、配向方向を自由に制御することができる。また、単結晶とは異なり、組成制御や加工容易さの観点から、工業的実用化も比較的容易である。また、上述した実施例のように、セラミックグリーンシートを積層することにより、積層構造の圧電素子を得ることも可能である。
　本発明は、上記実施形態に限定されるものではなく、本発明の範囲内において、種々の応用、変形を加えることが可能である。
１　　圧電磁器
１ａ　第１の面
１ｂ　第２の面
２ａ　第１の電極
２ｂ　第２の電極
１０　圧電素子

Claims (6)

  1. 　ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、
    　前記圧電磁器の第１の面に設けられた第１の電極、および、前記第１の面と相対する第２の面に設けられた第２の電極と、
    を備え、
    　前記圧電磁器は、主として菱面体晶の結晶構造を有しており、
    　前記圧電磁器の結晶軸は、｛１００｝配向しており、
    　前記｛１００｝配向の方向は、前記第１の電極と前記第２の電極とが対向する方向と直交する方向であることを特徴とする圧電素子。
  2. 　ペロブスカイト型結晶構造を有する複合酸化物を主成分として含む圧電磁器と、
    　前記圧電磁器の第１の面に設けられた第１の電極、および、前記第１の面と相対する第２の面に設けられた第２の電極と、
    を備え、
    　前記圧電磁器の結晶軸は、｛１００｝配向しており、
    　前記｛１００｝配向の方向は、前記第１の電極と前記第２の電極とが対向する方向と直交する方向であり、
    　前記圧電磁器の｛１００｝配向面から見たＸ線回折パターンにおける（００２）面と（２００）面の回折から成る複合ピークの半値幅は０．５°以上であることを特徴とする圧電素子。
  3. 　前記｛１００｝配向の方向は、前記第１の面および前記第２の面の長手方向であることを特徴とする請求項１または２に記載の圧電素子。
  4. 　前記複合酸化物は、ＰＺＴであることを特徴とする請求項１～３のいずれか一項に記載の圧電素子。
  5. 　前記複合酸化物は、ＰＮＮ－ＰＺＴであることを特徴とする請求項１～３のいずれか一項に記載の圧電素子。
  6. 　前記複合酸化物は、ＰＭＮ－ＰＺＴであることを特徴とする請求項１～３のいずれか一項に記載の圧電素子。
PCT/JP2021/047266 2021-01-12 2021-12-21 圧電素子 WO2022153800A1 (ja)

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Citations (4)

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JPH11233844A (ja) * 1998-02-13 1999-08-27 Omron Corp 圧電素子及びその製造方法
JP2004006645A (ja) * 2002-04-19 2004-01-08 Seiko Epson Corp 圧電体素子の製造方法、圧電体素子並びに液滴吐出式記録ヘッド
JP2007243200A (ja) * 2002-11-11 2007-09-20 Seiko Epson Corp 圧電体デバイス、液体吐出ヘッド、強誘電体デバイス及び電子機器並びにこれらの製造方法
JP2008024532A (ja) * 2006-07-18 2008-02-07 Canon Inc 圧電体、圧電体素子、圧電体素子を用いた液体吐出ヘッド及び液体吐出装置

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US8667088B1 (en) 2009-11-10 2014-03-04 Amazon Technologies, Inc. Distribution network providing customized content at delivery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11233844A (ja) * 1998-02-13 1999-08-27 Omron Corp 圧電素子及びその製造方法
JP2004006645A (ja) * 2002-04-19 2004-01-08 Seiko Epson Corp 圧電体素子の製造方法、圧電体素子並びに液滴吐出式記録ヘッド
JP2007243200A (ja) * 2002-11-11 2007-09-20 Seiko Epson Corp 圧電体デバイス、液体吐出ヘッド、強誘電体デバイス及び電子機器並びにこれらの製造方法
JP2008024532A (ja) * 2006-07-18 2008-02-07 Canon Inc 圧電体、圧電体素子、圧電体素子を用いた液体吐出ヘッド及び液体吐出装置

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