JP2009132598A - Piezoelectric/electrostrictive body, and piezoelectric/electrostrictive element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric/electrostrictive body and piezoelectric/electrostrictive element both of which do not require a long-time treatment such as an aging treatment but in which a strain ratio is increased. <P>SOLUTION: The piezoelectric/electrostrictive body is represented by a composition formula ABO<SB>3</SB>(A includes at least one element selected from the group consisting of Li, Na and K, and B includes at least one element selected from the group consisting of Nb, Ta, Sb and Mn), and the body is formed so that a main phase is a tetragonal system, and the orientation degree of a (001) face after a polarization treatment is smaller than that of a (100) face, in a plane vertical to the applying direction of an electric field applied so as to perform the polarization treatment. The piezoelectric/electrostrictive body has a ratio between a diffraction peak intensity I<SB>001</SB>of the (001) face and a diffraction peak intensity I<SB>100</SB>of the (100) face of I<SB>001</SB>/I<SB>100</SB>≤1, in an X-ray diffraction pattern in the same plane after the polarization treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric / electrostrictive body and a piezoelectric / electrostrictive element.

  Conventionally, piezoelectric / electrostrictive elements are known as elements capable of controlling minute displacements on the order of submicrons. In particular, a piezoelectric / electrostrictive in which a piezoelectric / electrostrictive portion made of a piezoelectric / electrostrictive porcelain composition (hereinafter simply referred to as “piezoelectric ceramic”) and an electrode portion to which a voltage is applied are laminated on a ceramic substrate. In addition to being suitable for controlling minute displacement, the element has excellent characteristics such as high electromechanical conversion efficiency, high-speed response, high durability, and power saving. These piezoelectric / electrostrictive elements include a piezoelectric pressure sensor, a probe moving mechanism of a scanning tunnel microscope, a linear guide mechanism in an ultra-precision machining apparatus, a servo valve for hydraulic control, a head of a VTR device, and a flat panel type image display device. The present invention can be applied to various uses such as constituting pixels or inkjet printer heads.

Various studies have also been made on the composition of piezoelectric ceramics constituting the piezoelectric / electrostrictive portion. For example, in recent years, the influence on the global environment, such as elution of lead (Pb) due to acid rain, tends to be regarded as a problem. Therefore, it contains lead (Pb) as a piezoelectric / electrostrictive material considering the influence on the environment. Development of (LiNaK) (NbTa) O ₃ -based piezoelectric ceramics that can provide piezoelectric bodies and piezoelectric elements exhibiting at least good piezoelectric / electrostrictive characteristics has been made.

  Piezoelectric ceramics are ferroelectrics, and are generally subjected to polarization treatment in order to be incorporated in electronic equipment or the like and use their properties (piezoelectric characteristics). This polarization process refers to a process in which a high voltage is applied to align the direction of spontaneous polarization in a specific direction, and is performed by applying a voltage to the piezoelectric ceramic under an appropriate temperature condition. In other words, ferroelectrics have multiple domains (domains) due to the bias of charge due to spontaneous polarization, and piezoelectric ceramics are used after being subjected to a polarization treatment that aligns the direction of the domains of the ferroelectric material in a certain direction. The

  Incidentally, the piezoelectric material (ferroelectric material) is an aggregate of domains, and the domains are divided into 180 ° domains and non-180 ° domains. Of these, the 180 ° domain contribution to strain is small and the non-180 ° domain contribution is large. This is because the non-180 ° domain has a large volume change due to the rotation of the domain. Then, during the above-described polarization treatment, non-180 ° domain rotation occurs and a large distortion occurs.

  However, since rotation of non-180 ° domain, particularly 90 ° domain showing a large volume change, is highly irreversible, once the polarization processing is held at a high voltage, the strain becomes smaller than the strain generated during the polarization processing. . In view of this, a piezoelectric material exhibiting a giant electrostrictive effect by enhancing the reversibility of domain rotation has been disclosed (Patent Document 1).

JP 2004-363557 A

  However, according to the manufacturing method of Patent Document 1, the number of days (5 days to 3 months) is required for the aging treatment, which is inefficient and causes an increase in manufacturing cost.

  An object of the present invention is to provide a piezoelectric / electrostrictive body and a piezoelectric / electrostrictive element having an increased distortion rate without requiring a long-time treatment such as an aging treatment.

In order to solve the above problems, a composition formula ABO ₃ (A is at least one element selected from Li, Na, and K, and B is at least one element selected from Nb, Ta, and Sb) And the orientation of the (00l) plane is the orientation degree of the (100) plane after the polarization treatment in a plane perpendicular to the direction of application of the electric field applied to perform the polarization treatment. A smaller piezoelectric / electrostrictive body is preferable. Specifically, according to the present invention, the following piezoelectric / electrostrictive body and piezoelectric / electrostrictive element are provided.

[1] Composition formula ABO ₃ (A is at least one element selected from Li, Na, K, and B includes at least one element selected from Nb, Ta, Sb, Mn) The orientation of the (00l) plane after polarization is higher than the orientation of the (100) plane on a plane perpendicular to the direction of application of the electric field applied to perform polarization treatment. Small piezoelectric / electrostrictive body.

[2] after the polarization treatment, the X-ray diffraction pattern in the application direction perpendicular the plane of the electric field, the ratio of the diffraction peak intensity _{I L00} of the diffraction peak intensity _{I 00l} and (L00) plane of the (00l) face the piezoelectric / electrostrictive body according to [1] is _{I 00l} / I l00 ≦ 1.

[3] The piezoelectric / electrostrictive body represented by the composition formula ABO ₃ includes a parent phase and an additive phase having a composition different from that of the parent phase. The piezoelectric / electrostrictive body according to [1] or [2] Electrostrictive body.

[4] The parent phase is:
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, and 0.05 ≦ z ≦ 0.50)
The piezoelectric / electrostrictive body according to [3] represented by

[5] The additive material phase is:
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z-w Ta _z Mn _w ) O ₃
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and 0 ≦ w ≦ 0. 03)
The piezoelectric / electrostrictive body according to [3] or [4] represented by

[6] The mother phase is
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃ + nMn compound (provided that 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and n is 3 mol parts or less in terms of Mn atoms)
The piezoelectric / electrostrictive body according to [3] represented by

[7] The additive material phase is:
Composition formula: _{[{Li y (Na 1-x} K x) 1-y} 1-t Bi t ] _{a (Nb 1-z Ta z} ) O 3 + nMn compound (where, 0.90 ≦ a ≦ 1.20 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, 0 ≦ t ≦ 0.002, and n is 3 mol parts or less in terms of Mn atoms. )
The piezoelectric / electrostrictive body according to [3] or [6] represented by

[8] A piezoelectric / electrostrictive element including the piezoelectric / electrostrictive body according to any one of [1] to [7] and an electrode portion disposed on the piezoelectric / electrostrictive body.

Expressed by a composition formula ABO _3, there main phase tetragonal in applying direction perpendicular to the plane of the electric field applied so as to perform the polarization treatment, the degree of orientation of (00l) face after polarization treatment (L00) plane By configuring the piezoelectric / electrostrictive body so as to be smaller than the degree of orientation, it is possible to increase the distortion rate when an electric field is applied after the polarization treatment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  The term “piezoelectric / electrostrictive body” as used in this specification is a piezoelectric / electrostrictive material used to form a piezoelectric / electrostrictive portion, and exhibits a specific piezoelectric characteristic by being polarized. Say what.

The piezoelectric / electrostrictive body of the present invention has a composition formula ABO ₃ (A is one or more elements selected from at least Li, Na, and K, and B is at least selected from Nb, Ta, Sb, and Mn. In the plane perpendicular to the direction of application of the electric field applied for the polarization treatment, the degree of orientation of the (00l) plane after the polarization treatment is ( less than the orientation degree of the (100) plane. The main phase refers to a phase occupying 50 Vol% or more.

The piezoelectric / electrostrictive body of the present invention has a diffraction peak intensity I _00l on the (00l) plane and a diffraction peak on the (100) plane in the X-ray diffraction pattern on the plane perpendicular to the direction of application of the electric field after the polarization treatment. the ratio of the intensity _{I L00} is _I 00l _{/ I l00} ≦ 1.

  Specifically, a phase different from the base material is dispersed in the base material, and this is polarized to introduce stress into the crystal. That is, the piezoelectric / electrostrictive body of the present invention is preferably formed in a state where the base material and the additive are mixed. When the additive material phase is formed so that the residual strain is different from that of the parent phase, it exhibits excellent piezoelectric characteristics (large strain characteristics). Specifically, a material having a larger residual strain during polarization than the base material may be selected as the additive material. Here, the residual strain refers to the strain amount at the time of polarization. As shown in FIG. 7, when the strain amount before the polarization treatment is the origin, the strain amount values after the polarization treatment (before the polarization treatment and after the polarization treatment (electric field) The amount of change in the length of the sample before and after application) is expressed in terms of the amount of change in length per unit length.

  Since the additive material phase only needs to have a residual strain different from that of the matrix phase, the composition phase may be different from that of the matrix phase. Specifically, a material having a completely different composition from the base material may be used. For example, as in Example 1 described later, Mn is added to the base material (a part of the base material is replaced with Mn). Such a composition may be used. In any composition system, the strain rate is expected to be improved by selecting one having a larger residual strain after polarization than the base material.

  Furthermore, it is preferable that the additive material has crystal grains larger than the crystal grains of the base material in the microstructure after firing. That is, a bimodal structure in which an additive material that is large crystal particles is dispersed in a base material that is small crystal particles is preferable. This is because a large crystal grain has a smaller grain boundary than a small crystal grain when compared at the same volume, and is considered to have a large residual strain during polarization.

That is, the additive material phase exhibits a (large) residual strain different from that of the parent phase, and the composition formula ABO ₃ (A is at least one element selected from Li, Na, and K, and B is at least Nb, Ta. Including one or more elements selected from Sb, Mn), and the parent phase preferably has a different composition and may have a different particle size. In the piezoelectric / electrostrictive body of the present invention, the main phase and the main phase are tetragonal crystals in the utilization temperature range.

  The piezoelectric / electrostrictive body of the present invention is a ceramic material in which the crystal structure of the parent phase formed by the base material can reversibly phase change to cubic, tetragonal or orthorhombic at the phase transition point. . More specifically, the parent phase is cubic under high temperature conditions, and changes from cubic to tetragonal at the first phase transition point as the temperature decreases. When the temperature is lowered, the phase transition from tetragonal to orthorhombic occurs at the second phase transition point.

  In addition, the crystal structure of the additive material phase formed by the additive material is also a ceramic material that can reversibly revert to cubic, tetragonal, and orthorhombic crystals at the phase transition point as in the case of the base material described above. is there. And in the utilization temperature range utilized as a piezoelectric / electrostrictive material, both the parent phase and the additive material phase are tetragonal. For example, when the utilization temperature region is −20 ° C. or higher and 80 ° C. or lower, a base material and an additive having a crystal structure of a main phase in this range are selected. For example, when the utilization temperature region is 50 ° C. or more and 150 ° C. or less, a base material and an additive having a crystal structure of a tetragonal main phase in this range are selected.

  The piezoelectric / electrostrictive portion constituting the piezoelectric / electrostrictive element described later has a temperature lower than the first phase transition point at which the parent phase changes from cubic to tetragonal crystal structure. The region is formed by a polarization process in which an electric field (voltage) is applied. The piezoelectric / electrostrictive body and the piezoelectric / electrostrictive portion of the piezoelectric / electrostrictive element of the present invention are formed in a state in which a base material includes an additive and has a matrix phase and an additive material phase, and a voltage is applied. It exhibits excellent piezoelectric properties because it is polarized.

As described above, the piezoelectric / electrostrictive body of the present invention has a cubic crystal structure in which the parent phase is at a temperature higher than the first phase transition point, and in a use temperature range lower than the first phase transition point. A piezoelectric / electrostrictive body that has a tetragonal crystal structure and generates spontaneous polarization. Specifically, the parent phase is composed of a composition formula ABO ₃ (A is at least one element selected from Li, Na, K, and B is at least one element selected from Nb, Ta, Sb) In the piezoelectric / electrostrictive body of the present invention, the main phase is a tetragonal crystal, and a composition formula ABO ₃ (A is different from the parent phase) in the parent phase. One or more elements selected from Li, Na, K, and B is one or more elements selected from Nb, Ta, Sb, Mn), and the main phase is a tetragonal crystal A strain body is included as an additive material phase.

More specifically, the parent phase is, for example, an alkali niobate-based ferroelectric, and examples thereof include those represented by the following composition formula (1).
_{{Li y (Na 1-x} K x) 1-y} a (Nb 1-z Ta z) O 3 (1)
(However, in the composition formula (1), 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, and 0.05 ≦ z ≦ 0. 50)
The range of a in the composition formula (1) is preferably 1.00 <a ≦ 1.20, and more preferably 1.00 <a ≦ 1.10.

  In the case where the composition of the matrix is represented by the composition formula (1), the B site (site containing Nb and Ta as constituent metal elements) in the composition formula (1) includes Nb and A transition metal element other than Ta may further be contained. Examples of transition metal elements other than Nb and Ta include V, W, Cu, Ni, Co, Fe, Mn, Cr, Ti, Zr, Mo, and Zn. Further, when the composition of the matrix is represented by the composition formula (1), the A site (site containing Li, Na, and K as constituent metal elements) in the composition formula (1) Elements other than Li, Na, and K may be further included. Examples of elements other than Li, Na, and K include Ag, La, Ba, Ca, Sr, Pb, Bi, and the like. These above elements may be contained in the grains or in the grain boundaries as oxides or the like.

  Further, in the case where the composition of the matrix is represented by the composition formula (1), the inclusion of Sb in the composition formula (1) results in a larger amount of strain and further excellent piezoelectric characteristics. It is preferable in order to be able to manufacture a piezoelectric / electrostrictive element exhibiting

Examples of the additive material phase contained in the parent phase include BaTiO ₃ , PZT, PbTiO ₃ , (Bi _0.5 , Na _0.5 ) TiO ₃ , and more specifically, the following composition formula What is represented by (2) can be mentioned.
Composition formula: {Li _y (Na _1−x K _x ) _1−y } _a (Nb _1−z−w Ta _z Mn _w ) O ₃ (2)
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and 0 ≦ w ≦ 0. 03)

  When the composition of the additive material phase is expressed by the composition formula (2), the B site (site containing Nb and Ta as constituent metal elements) in the composition formula (2) Similarly to the phase, a transition metal element other than Nb and Ta may further be included. Examples of transition metal elements other than Nb and Ta include V, W, Cu, Ni, Co, Fe, Cr, Ti, Zr, Mo, Zn and the like in addition to Mn in the composition formula (2). . Further, when the composition of the additive material phase is represented by the composition formula (2), the A site (site containing Li, Na, and K as constituent metal elements) in the composition formula (2). May further contain elements other than Li, Na, and K. Examples of elements other than Li, Na, and K include Ag, La, Ba, Ca, Sr, Pb, Bi, and the like. These elements may be contained in the grains or in the grain boundaries as oxides or the like.

  Further, in the case where the composition of the additive material phase is represented by the composition formula (2), the inclusion of Sb in the composition formula (2) further increases the amount of generated strain and further improves the piezoelectricity. This is preferable in order to be able to manufacture a piezoelectric / electrostrictive element exhibiting characteristics.

Moreover, as a parent phase, what is represented by the following compositional formula (3) of a Mn addition composition can be mentioned.
Composition _{formula: {Li y (Na 1-} x K x) 1-y} a (Nb 1-z Ta z) O 3 + nMn compound (3)
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and n are in terms of Mn atoms. 3 mol parts or less)

Examples of the additive material phase contained in the matrix phase of the Mn-added composition represented by the composition formula (3) include those represented by the following composition formula (4) of the Mn-added composition and Bi-substituted composition.
Composition formula: _{[{Li y (Na 1-x} K x) 1-y} 1-t Bi t ] _{a (Nb 1-z Ta z} ) O 3 + nMn compound (4)
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, 0 ≦ t ≦ 0.002. , And n are 3 mol parts or less in terms of Mn atoms)

  In the piezoelectric / electrostrictive body in which the matrix phase of Mn addition is combined with the additive material phase of Mn addition composition and Bi substitution composition, the matrix phase has a high strain ratio composition and the residual strain difference is further increased. For one reason, the distortion improvement effect is further increased.

  A suitable addition amount of the additive is 5 Vol% or more and 45 Vol% or less, preferably 20 Vol% or more and 45 Vol% or less, more preferably 35 Vol% or more and 45 Vol% or less by volume ratio. In the present specification, the volume ratio of the additive means a ratio of the additive to the volume of the piezoelectric / electrostrictive body in which the base material and the additive are mixed (for example, if the additive is 5 Vol%, The base material is 95 Vol%).

  In order to manufacture a piezoelectric / electrostrictive body used to form a piezoelectric / electrostrictive portion of a piezoelectric / electrostrictive element, first, a base material powder and an additive material powder are individually manufactured. The compound containing each metal element is weighed so as to satisfy the ratio (molar ratio) of each metal element in the composition of the raw material powder, and mixed with a solvent such as ethanol by a mixing method such as a ball mill to obtain a mixed slurry. . The type of the compound containing each metal element is not particularly limited, but an oxide or carbonate of each metal element is preferably used. For example, lithium carbonate, potassium tartrate, sodium tartrate, niobium oxide, oxide Tantalum can be used.

  The mixed raw material can be obtained by drying the obtained mixed slurry by using a dryer or by an operation such as filtration. The obtained mixed raw material is calcined and, if necessary, pulverized. In this way, the base material powder and the additive material powder are individually manufactured.

  The average particle size of the additive material powder and the base material powder after calcining and pulverization is preferably 0.1 μm or more and 1 μm or less. Here, the average particle diameter is a 50% diameter (median diameter) in the cumulative distribution.

  The additive raw material powder after calcination and pulverization is fired at 1000 ° C. or higher to grow grains, and then pulverized, and the average particle size is adjusted to 0.5 μm or more and 10 μm or less by a classifier. When the average particle size of the additive material powder is larger than 10 μm, it is difficult to obtain a stable strain characteristic with a large variation in strain characteristics.

  When the average particle size of the additive material powder is smaller than 0.5 μm, it is difficult to obtain a great effect of increasing the distortion rate. This is presumably because if the particle size is too small, it reacts (solid solution) with the base material and becomes a uniform piezoelectric / electrostrictive body (uniform crystal phase or composition). Further, if the crystal grain size of the additive after firing is too small, it will have domain walls in only one direction, so that anisotropy will occur in the strain of the additive during the polarization treatment. As a result, it is considered that a non-uniform residual stress exists in the applied electric field direction. In other words, it is preferably a piezoelectric / electrostrictive body having a composite structure in which an additive phase different from the crystal phase of the base material exists, and the crystal grain size of the additive has a domain wall in a plurality of directions. It is preferable that When an additive material powder having domain walls in only one direction is used, it is desirable that the additive powder be oriented and added to the base material particles in order to have residual stress in the same uniform direction. The average particle diameter of the additive material powder is preferably larger than the average particle diameter of the base material powder.

  The additive material powder is added to the base material powder so as to be 5 vol% or more and 45 vol% or less, and dry-mixed using a ball mill. After molding the obtained mixed powder, the compact is fired at a temperature of 950 to 1200 ° C. to expand the average particle size of the base material (matrix) to 0.5 μm to 15 μm to obtain a piezoelectric / electrostrictive body. Can do. In addition, the calcination of the raw material powder may be performed at a temperature of about 600 to 1000 ° C. The pulverization may be performed by a method such as a ball mill. Next, the obtained piezoelectric / electrostrictive body is processed into an appropriate shape (for example, a square plate shape) as necessary, and then heat-treated at a temperature of about 400 to 900 ° C. for 1 hour or more. Thereafter, polarization treatment is performed, and the piezoelectric / electrostrictive body is used. The polarization treatment is performed by applying a voltage of about 5 kV / mm to the piezoelectric / electrostrictive body for 15 minutes or more.

  The piezoelectric / electrostrictive portion and the electrodes constituting the piezoelectric / electrostrictive element of the present embodiment can have various shapes. Specifically, a block shape (so-called bulk body), a sheet shape (film shape), and the like can be given as suitable examples.

As described above, the piezoelectric / electrostrictive body represented by the composition formula ABO ₃ is manufactured and subjected to the polarization treatment. A piezoelectric / electrostrictive body having a (00l) plane orientation degree smaller than the (100) plane orientation degree can be obtained. As described above, the strain rate of the piezoelectric / electrostrictive body can be increased by manufacturing the orientation degree of the (00l) plane to be smaller than the orientation degree of the (100) plane.

Table In Specifically, the piezoelectric / electrostrictive body represented by the composition formula ABO ₃ as described above as a base material, on the base material, the residual strain during the polarization is larger than the base material composition formula ABO ₃ By adding the piezoelectric / electrostrictive body to be added as an additive, the piezoelectric / electrostrictive body is manufactured, so that the distortion rate of the piezoelectric / electrostrictive body can be increased.

  Next, an embodiment in which the piezoelectric / electrostrictive portion is formed in a film shape is shown in FIG. As shown in FIG. 1, the piezoelectric / electrostrictive element 51 of this embodiment is electrically connected to a substrate 1 made of ceramics, a film-like piezoelectric / electrostrictive portion 2, and the piezoelectric / electrostrictive portion 2. The piezoelectric / electrostrictive portion 2 is fixed on the substrate 1 with the electrode 4 interposed therebetween. The piezoelectric / electrostrictive portion may be directly fixed on the substrate without interposing an electrode. In this specification, “adhesion” means that both the organic piezoelectric material and the inorganic adhesive material are used in a solid phase reaction between the first piezoelectric portion 2 and the substrate 1 or the electrode 4 without using any organic or inorganic adhesive. A state of tight integration.

  In the piezoelectric / electrostrictive element 51 (see FIG. 1) of the present embodiment, the thickness of the piezoelectric / electrostrictive portion 2 is preferably 0.5 to 50 μm, more preferably 0.8 to 40 μm. It is especially preferable that it is 0.0-30 micrometers. If the thickness of the piezoelectric / electrostrictive portion 2 is less than 0.5 μm, densification of the piezoelectric / electrostrictive portion may be insufficient. On the other hand, if the thickness of the piezoelectric / electrostrictive portion 2 exceeds 50 μm, the contraction stress of the piezoelectric / electrostrictive body during firing increases, and the substrate 1 needs to be thickened to prevent the substrate 1 from being destroyed. Therefore, it may be difficult to cope with the downsizing of the element. The piezoelectric / electrostrictive element 51 can also be configured as a so-called multilayer type.

  The substrate 1 constituting the piezoelectric / electrostrictive element 51 of the embodiment of the present invention is made of ceramics, but the type of the ceramics is not particularly limited. However, at least one selected from the group consisting of stabilized zirconium oxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride, silicon nitride, and glass in terms of heat resistance, chemical stability, and insulation. Ceramics containing are preferred.

  The thickness of the substrate is preferably 1 μm to 1 mm, more preferably 1.5 to 500 μm, and particularly preferably 2 to 200 μm. If the thickness of the substrate is less than 1 μm, the mechanical strength of the piezoelectric / electrostrictive element may decrease. On the other hand, when it exceeds 1 mm, when an electric field is applied to the piezoelectric / electrostrictive portion, the rigidity of the substrate with respect to the generated contraction stress increases, and the bending displacement of the piezoelectric / electrostrictive portion may decrease.

  In the piezoelectric / electrostrictive element of the present embodiment, the electrode is electrically connected to the piezoelectric / electrostrictive portion and is disposed between the piezoelectric / electrostrictive portions. Examples of the material of the electrode include at least one metal selected from the group consisting of Pt, Pd, Rh, Au, Ag, and alloys thereof. Among these, platinum or an alloy containing platinum as a main component is preferable in terms of high heat resistance when firing the piezoelectric / electrostrictive portion. In view of the fact that the piezoelectric / electrostrictive portion can be formed at a lower firing temperature, an alloy such as Ag—Pd can also be suitably used.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

Example 1
The raw material powder for the base material and additive was prepared by a general solid phase method. As starting materials, lithium carbonate (Li ₂ CO ₃ ), sodium tartrate (C ₄ H ₅ O ₆ Na.H ₂ O), potassium tartrate (C ₄ H ₅ O ₆ K), niobium oxide (Nb ₂ O ₅ ), Tantalum oxide (Ta ₂ O ₅ ) and manganese carbonate (MnCO ₃ ) were weighed so as to have respective compositions. After mixing in alcohol for 16 hours using a ball mill, the resulting mixture was dried and calcined at a temperature of 800 ° C. Next, pulverization and calcination were performed again, and after coarse pulverization, the particle size was adjusted. The average particle size of the base material powder at this time was 0.4 to 0.5 μm, and the average particle size of the additive material powder was also 0.4 to 0.5 μm. The additive material powder was grain-grown at a temperature of 1000 ° C., then coarsely pulverized, and the average particle diameter was adjusted to 1 to 2 μm using a classifier.

Thus, the base material raw material powder is an alkali niobate-based ferroelectric, and the composition formula {Li _0.060 (Na _0.55 K _0.45 ) _0.94 } _1.011 (Nb _0.918 Ta _0.082 ) It was formed as represented by O ₃ .

The additive raw material powder is composed of the composition formula {Li _0.060 (Na _0.55 K _0.45 ) _0.94 } _1.011 (Nb _0.916 Ta _0.082 Mn _0.002 ) O ₃ . (Nb of the base material is replaced with Mn).

  And after adding an additive so that it might become 10-50 Vol% with respect to a base material raw material powder and dry-mixing, it shape | molded in the disk of diameter 15mm and thickness about 10mm. The molded body was fired at a temperature of 950 to 1030 ° C. The obtained sintered body was processed into 12 mm × 3 mm × 1 mm and heat-treated at 900 ° C.

  In addition, when the residual strain was measured by preparing a sample having only the composition of the base material and the additive and measuring the strain of the unpolarized sample, the base material has a residual strain of approximately 50 to 150 ppm, The additive showed approximately 500 to 600 ppm, and the additive had a large residual strain relative to the base material.

(Evaluation)
In order to evaluate the crystal phase before the polarization treatment, the sample is set so that X-rays are irradiated onto the 12 mm × 3 mm surface of the processed sample, and the X-ray diffraction pattern of the sample is 20 ° -60 ° by the 2θ / θ method. Measured in the range of °. For X-ray diffraction, an X-ray diffractometer was used, using Cu—Kα rays as a radiation source, and a graphite monochromator was installed in front of the detector. X-ray generation conditions were measured as 35 kV-30 mA, scan width 0.02 °, scan speed 2 ° / min, diverging slit 1 °, and light receiving slit 0.3 mm, and the intensity ranged from 2θ = 44 ° to 47 °. It was confirmed that two large peaks were present. At this time, when the peak intensity on the high angle side is about twice the peak intensity on the low angle side, it is mainly tetragonal, the peak on the low angle side is the (002) plane, and the peak on the high angle side is (200). It can be determined as a surface.

  Next, Au was sputtered on a 12 mm × 3 mm surface (both sides) of the sample, and a polarization treatment was performed by applying a voltage of 5 kV / mm for 15 minutes. In the same manner as described above, the sample was set so that X-rays were irradiated onto the surface sputtered with Au, and X-rays were irradiated to obtain an X-ray diffraction pattern. The crystal orientation is preferably compared with the higher order plane index as much as possible since the X-ray penetration depth becomes shallower as the lower order plane index (l is smaller). However, since the diffraction intensity becomes weaker when it becomes larger than the second order (l = 2), the evaluation was made with the second order peak. In this case, there are three high intensity peaks in the range of 2θ = 44 ° to 47 °, but the lowest angle peak (low intensity peak existing at 2θ = 44 ° to 45 °) was sputtered. It is a peak derived from Au. The X-ray diffraction patterns of the samples containing 20, 40, and 50 Vol% of the additive are shown in FIGS.

Figure 2 As shown in Figure 4, a parent phase with tetragonal represented by the composition formula ABO _3, the composition formula ABO ₃ is the mother phase of the tetragonal including the additive material phase having different compositions piezoelectric / electrostrictive The body has a peak intensity of the (002) plane on the surface of the sample (plane perpendicular to the applied direction of the electric field applied to perform the polarization process), even after the polarization process, from the peak intensity of the (200) plane. Was also small. That is, the orientation degree of the (002) plane after the polarization treatment was smaller than the orientation degree of the (200) plane.

  Thereafter, a strain gauge was attached to one side with an adhesive, and a voltage of 4 kV / mm was applied to measure the strain rate (ppm). Residual strain was determined by measuring strain on an unpolarized sample. Table 1 and FIG. 6 show the distortion rate of the sample of Example 1 when 4 kV / mm is applied.

(Comparative Example 1)
In Comparative Example 1, a sample was prepared in the same manner as in Example 1. However, the average particle diameter of the additive material was mixed at 0.4 to 0.5 μm. FIG. 5 shows an X-ray diffraction pattern of a sample in which the additive of Comparative Example 1 is 40 Vol%. From the X-ray diffraction pattern of the base material / additive material alone shown in FIG. 5, in Comparative Example 1, the peak intensity of the (002) plane is higher than the peak intensity of the (200) plane after polarization treatment in the direction perpendicular to the surface of the sample. Was also big. That is, the peak intensity of the (002) plane increased before and after the polarization treatment, and the degree of orientation of (002) increased. In addition, although FIG. 5 is a sample whose additive is 40 Vol%, the same tendency was shown even when the addition amount was different.

  Thereafter, in the same manner as in Example 1, a strain gauge was attached to one surface with an adhesive, a voltage of 4 kV / mm was applied, and the strain rate (ppm) was measured. The distortion rate of the sample of Comparative Example 1 when 4 kV / mm is applied is shown in Table 1 and FIG.

  In Example 1, a piezoelectric / electrostrictive body including an additive having a composition different from that of the matrix (the crystal structure of the additive is the same as that of the matrix) is used. And showed a large distortion rate. Furthermore, when the mixing amount of the additive was 40 Vol%, the distortion rate increased.

(Example 2)
A sample was prepared by combining the matrix phase of the Mn addition composition with the additive material phase of the Mn addition composition and the Bi substitution composition. The same raw materials as in Example 1 were used for Li, Na, K, Nb, and Ta. Bi was bismuth oxide (Bi ₂ O ₃ ). In the case of a Mn addition system, manganese dioxide (MnO ₂ ) was used as Mn. In the same manner as in Example 1, the raw materials excluding MnO ₂ were weighed, mixed and calcined, and MnO ₂ was added and coarsely pulverized to adjust the particle size after the _second calcining. The average particle size of the base material powder at this time was 0.4 to 0.5 μm, and the average particle size of the additive material powder was also 0.4 to 0.5 μm. The additive material powder was grain-grown at a temperature of 1000 ° C., then coarsely pulverized, and the average particle diameter was adjusted to 1 to 2 μm using a classifier.

Thus, the base material powder is represented by {Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _1.01 (Nb _0.918 Ta _0.082 ) O ₃ +0.02 mol% MnO ₂ . Formed to be.

The additive raw material powder is [{Li _0.06 (Na _0.55 K _0.45 ) _0.94 } _0.9995 Bi _0.0005 ] _1.01 (Nb _0.918 Ta _0.082 ) O. ₃ + was formed as represented by 0.02 mol% MnO _2.

  Hereinafter, samples were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

  As a result of X-ray diffraction, the peak intensity of the (002) plane was smaller than the peak intensity of the (200) plane even after the polarization treatment as in Example 1. That is, the orientation degree of the (002) plane after the polarization treatment was smaller than the orientation degree of the (200) plane.

As described above, a piezoelectric / electrostrictive body represented by the composition formula ABO ₃ and having a tetragonal crystal structure is manufactured and subjected to polarization treatment, whereby X-ray diffraction in a plane perpendicular to the direction of electric field application after polarization treatment is performed. in the pattern, can be designed such that the ratio is _I 00l _{/ I l00} ≦ 1 the diffraction peak intensity _{I 00l} and (L00) plane of the diffraction peak intensity _{I L00} of (00l) plane. In other words, a piezoelectric / electrostrictive body in which the orientation degree of the (00l) plane after the polarization treatment is smaller than the orientation degree of the (100) plane on the plane perpendicular to the direction of application of the electric field applied for the polarization treatment. be able to. As described above, the strain rate of the piezoelectric / electrostrictive body can be increased by manufacturing the orientation degree of the (00l) plane to be smaller than the orientation degree of the (100) plane. More specifically, the strain rate is increased by using a piezoelectric / electrostrictive body including a parent phase and an additive material phase different from a parent phase having a large residual strain. In particular, the additive material may be configured to have a volume ratio of 5 Vol% to 45 Vol% with respect to the base material. In Comparative Example 1 in which the average particle size of the additive raw material powder was the same as that of the base material raw material powder, since the improvement in the distortion rate was smaller than that in Example 1, the reason for the improvement in the distortion rate was estimated as follows. Is done.

  When attention is paid to the non-180 ° domain of the crystal, the base material having a tetragonal composition also has other than the 90 ° domain. Polarization treatment of a uniform sintered body (sintered body that does not have a parent phase and an additive phase) formed by mixing the additive material powder with an average particle size similar to that of the base material powder. When an electric field is applied), it contracts perpendicularly to the applied electric field direction and extends horizontally. When the electric field is removed, the 90 ° domain is not reversible (strongly irreversible) and cannot be restored. On the other hand, when a sintered body including an additive material phase having a large residual strain is subjected to polarization treatment, the residual strain of the additive material is larger than that of the parent phase. A residual compressive stress remains horizontally. It is considered that this residual stress increases the amount of strain because part of the 90 ° domain existing in the parent phase returns, that is, the reversible increases.

  In order to increase the residual stress, it is preferable to select an additive material having a large residual strain (additive material having a strong 90 ° domain with strong irreversibility). When the additive amount is less than 5 Vol%, the residual stress The 90 ° domain in the base material is not reversible and the amount of strain does not change so much, but if the mixing amount is greater than 45 Vol%, the influence of the additive material having a strong 90 ° domain is large. Therefore, it is considered that the distortion rate is small (compared to a uniform sintered body).

  Further, in order to allow the additive material to exist as an additive material phase in the matrix without reacting (solid solution) with the matrix, the additive material powder is preliminarily coarsened and mixed with the matrix material powder. Good. In this case, the average particle diameter of the additive material powder is preferably 0.5 μm or more and 10 μm or less. When the base material powder and additive material powder have the same average particle size and are mixed and sintered, by using a hot press method, SPS method (discharge plasma sintering method), etc., grain growth is unlimited. By sintering while suppressing, a piezoelectric / electrostrictive body including a parent phase and an additive material phase different from the parent phase can be obtained.

  The piezoelectric / electrostrictive body and the piezoelectric / electrostrictive element of the present invention exhibit excellent piezoelectric / electrostrictive characteristics and are suitable for actuators, sensors, and the like.

It is sectional drawing which shows typically one Embodiment of the piezoelectric / electrostrictive element of this invention. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric / electrostrictive body containing 20 Vol% of additives. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric / electrostrictive body containing 40 Vol% of additives. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric / electrostrictive body containing 50 Vol% of additives. It is a figure which shows the X-ray-diffraction pattern of the piezoelectric material / electrostrictive body of a base material / additive material single-piece | unit. It is a figure which shows the relationship between the addition amount of the additive of Example 1 and Comparative Example 1, and a distortion. It is a figure which shows the distortion curve for demonstrating a residual distortion.

Explanation of symbols

1: substrate, 2: piezoelectric / electrostrictive body (piezoelectric / electrostrictive portion), 4, 5: electrode, 51: piezoelectric / electrostrictive element.

Claims (8)

Represented by the composition formula ABO ₃ (A is at least one element selected from Li, Na, K, and B includes at least one element selected from Nb, Ta, Sb, Mn). , The main phase is tetragonal,
A piezoelectric / electrostrictive body in which the orientation degree of the (00l) plane after the polarization treatment is smaller than the orientation degree of the (100) plane on a plane perpendicular to the direction of application of the electric field applied for the polarization treatment. Wherein after the polarization treatment, the X-ray diffraction pattern in the application direction perpendicular the plane of the electric field, (00l) plane ratio of the diffraction peak intensity _{I 00l} and (L00) plane of the diffraction peak intensity _{I L00} of _{I 00l} / the piezoelectric / electrostrictive body according to claim 1 which is I _L00 ≦ 1. _{3. The} piezoelectric / electrostrictive body according to claim 1, wherein the piezoelectric / electrostrictive body represented by the composition formula ABO ₃ includes a parent phase and an additive phase having a composition different from that of the parent phase. The mother phase is
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, and 0.05 ≦ z ≦ 0.50)
The piezoelectric / electrostrictive body according to claim 3 represented by: The additive material phase is
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z-w Ta _z Mn _w ) O ₃
(However, 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and 0 ≦ w ≦ 0. 03)
The piezoelectric / electrostrictive body according to claim 3 or 4, represented by: The mother phase is
Composition formula: {Li _y (Na _1-x K _x ) _1-y } _a (Nb _1-z Ta _z ) O ₃ + nMn compound (provided that 0.90 ≦ a ≦ 1.20, 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, and n is 3 mol parts or less in terms of Mn atoms)
The piezoelectric / electrostrictive body according to claim 3 represented by: The additive material phase is
Composition formula: _{[{Li y (Na 1-x} K x) 1-y} 1-t Bi t ] _{a (Nb 1-z Ta z} ) O 3 + nMn compound (where, 0.90 ≦ a ≦ 1.20 0.20 ≦ x ≦ 0.80, 0.02 ≦ y ≦ 0.20, 0.05 ≦ z ≦ 0.50, 0 ≦ t ≦ 0.002, and n is 3 mol parts or less in terms of Mn atoms. )
The piezoelectric / electrostrictive body according to claim 3 or 6, represented by: The piezoelectric / electrostrictive body according to any one of claims 1 to 7,
An electrode portion disposed on the piezoelectric / electrostrictive body;
A piezoelectric / electrostrictive element including:

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