JP7200796B2 - Piezoelectric element - Google Patents

Description

The present disclosure relates to piezoelectric elements.

Patent Literature 1 describes a piezoelectric element that includes an element body and a pair of external electrodes provided on a pair of main surfaces of the element body. This piezoelectric element is fixed to the actuator base of the magnetic head, and drives the actuator base by transmitting the vibration of the piezoelectric element to the actuator base.

Japanese Patent Application Laid-Open No. 2002-184140

An object of the present disclosure is to provide a piezoelectric element with excellent efficiency in transmitting vibration (hereinafter referred to as "vibration transmission efficiency").

As a result of investigation and research by the present inventors, it was found that when a piezoelectric element having a main surface that is a natural surface is fixed to a vibrating body and used, it is easier to deform if the two main surfaces have different smoothness. .

Therefore, the piezoelectric element of the present disclosure includes a body having a first principal surface and a second principal surface facing each other, the first principal surface and the second principal surface being natural surfaces, and the second principal surface being: It is fixed to the vibrating body and transmits vibration to the vibrating body, and the smoothness of the first main surface is lower than that of the second main surface.

In this piezoelectric element, since the smoothness of the first main surface is lower than the smoothness of the second main surface, deformation of the first main surface is easier than deformation of the second main surface. In this manner, the piezoelectric element can be efficiently deformed by fixing the easily deformable first principal surface side to the vibrating body and fixing the less deformable second principal surface side to the vibrating body. Therefore, this piezoelectric element has excellent vibration transmission efficiency.

The piezoelectric element may further comprise a first external electrode arranged on the first principal surface and a second external electrode arranged on the second principal surface.

The piezoelectric element may further comprise a first external electrode and a second external electrode arranged on the first main surface.

According to the present disclosure, a piezoelectric element with excellent vibration transmission efficiency is provided.

1 is a cross-sectional view of a piezoelectric element according to a first embodiment; FIG. FIG. 2 is a partially enlarged view of the piezoelectric element of FIG. 1; 2 is a cross-sectional view of a vibrating device comprising the piezoelectric element of FIG. 1; FIG. FIG. 4 is a cross-sectional view of a piezoelectric element according to a second embodiment; FIG. 5 is a cross-sectional view along line VV of FIG. 4; FIG. 5 is an exploded perspective view of the piezoelectric element of FIG. 4;

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and overlapping descriptions are omitted.

[First embodiment]
FIG. 1 is a cross-sectional view of a piezoelectric element according to the first embodiment. As shown in FIG. 1, a piezoelectric element 10 according to the first embodiment includes an element body 11 and a plurality of external electrodes 13 and 15. As shown in FIG. In this embodiment, the piezoelectric element 10 has a pair of external electrodes 13 and 15 . The piezoelectric element 10 is of a single plate type and does not have an electrode layer inside.

The element body 11 has a rectangular parallelepiped shape. The element body 11 has a pair of main surfaces 11a and 11b facing each other. The rectangular parallelepiped shape includes, for example, a rectangular parallelepiped shape with chamfered corners and edges, and a rectangular parallelepiped shape with rounded corners and edges. Each main surface 11a, 11b has, for example, a rectangular shape. Each principal surface 11a, 11b has a rectangular shape with a pair of long sides and a pair of short sides. That is, the piezoelectric element 10 (element body 11) has a rectangular shape having a pair of long sides and a pair of short sides in plan view. Rectangular shapes include, for example, shapes with chamfered corners and shapes with rounded corners.

The direction in which the pair of main surfaces 11a and 11b face each other is the first direction D1. The first direction D1 is also a direction perpendicular to the main surfaces 11a and 11b. An external electrode 13 is arranged on the main surface 11a. An external electrode 15 is arranged on the main surface 11b. The length of the long side of each main surface 11a, 11b is, for example, 20 mm. The length of the short side of each main surface 11a, 11b is, for example, 10 mm. The length (thickness) of the element body 11 in the first direction D1 is, for example, 500 μm.

2 is a partially enlarged view of the piezoelectric element of FIG. 1. FIG. In FIG. 2A, the shapes of the main surface 11a and the external electrodes 13 are schematically shown. FIG. 2B schematically shows the shapes of the main surface 11b and the external electrodes 15. As shown in FIG. 2(a) and 2(b) are created by tracing the shapes of the main surfaces 11a and 11b and the external electrodes 13 and 15 from a cross-sectional photograph of the actual piezoelectric element 10. FIG.

Principal surfaces 11a and 11b shown in FIGS. 2(a) and 2(b) are natural surfaces. Here, the natural surface is a surface formed by the surfaces of crystal grains grown by firing, and exhibits a shape having peaks and valleys due to the crystal grains. The main surface 11a has lower smoothness than the main surface 11b. The main surface 11a has a larger surface area than the main surface 11b. The main surface 11b is a vibration transmission surface that is fixed to the vibrating body 2 (see FIG. 3) and transmits vibration to the vibrating body 2. As shown in FIG.

The undulations of the main surface 11a are larger than the undulations of the main surface 11b. Here, the waviness is, for example, the average length (RSm) of the roughness curve elements in the long side direction of the main surface 11a. The main surface 11a is a surface in which ridges and valleys are formed along the long side direction of the main surface 11a. On the main surface 11a, peaks and valleys are alternately arranged along the long side direction of the main surface 11a. The main surface 11a is arranged so that the average length (RSm) of the roughness curvilinear elements in the long side direction of the main surface 11a is larger than the average length (RSm) of the roughness curvilinear elements in the short side direction of the main surface 11a. is formed in That is, the main surface 11a is formed so that the peaks and valleys have anisotropy. On the other hand, the main surface 11b is substantially flat, and the average length (RSm) of the roughness curvilinear elements in the long side direction of the main surface 11b is the average length of the roughness curvilinear elements in the short side direction of the main surface 11b. It is formed to be equal to the height (RSm). The average length (RSm) of the roughness curvilinear elements in the long side direction of the main surface 11a is, for example, 50 μm or more and 90 μm or less, and the average length (RSm) of the roughness curvilinear elements in the short side direction of the main surface 11a is For example, it is 20 μm or more and 50 μm or less. The average length (RSm) of the roughness curve elements in the long side direction and the short side direction of the main surface 11b is, for example, 10 μm or more and 50 μm or less.

The element body 11 is made of a piezoelectric ceramic material. As the piezoelectric ceramic material, for example, a material containing zirconate titanate as a main component to which an element such as Nb, Zn, Ni or Sr is added is used. Examples of piezoelectric ceramic materials include PZT[Pb(Zr,Ti)O3], PT( _PbTiO3 ) _, PLZT[(Pb,La)(Zr,Ti)O3] _, PZN[Pb(Zn,Nb) O ₃ ], or barium titanate (BaTiO ₃ ) is used. The element body 11 is composed of, for example, a sintered ceramic green sheet containing the piezoelectric ceramic material described above.

The external electrodes 13 are arranged along the main surface 11a. Therefore, the external electrode 13 exhibits a shape having peaks and valleys along the main surface 11a. That is, the surface 13a of the external electrode 13 reflects the shape of the main surface 11a. The external electrodes 15 are arranged along the main surface 11b. Therefore, the external electrode 15 exhibits a shape having peaks and valleys along the main surface 11b. That is, the surface 15a of the external electrode 15 reflects the shape of the main surface 11b. Therefore, surface 13a is less smooth than surface 15a.

The thickness (the length in the first direction D1) of the external electrodes 13 and 15 is, for example, 0.5 μm or more and 3.0 μm or less. The external electrodes 13, 15 are made of a conductive material. Ag, Pd, or Ag--Pd alloy is used for the conductive material, for example. Au, Pt, Ni, or the like, for example, may be used as the conductive material. The external electrodes 13 and 15 are configured, for example, as sintered bodies of conductive paste containing the conductive material. External electrodes 13 and 15 may be formed by, for example, baking, sputtering, electroless plating, or the like.

3 is a cross-sectional view of a vibrating device comprising the piezoelectric element of FIG. 1. FIG. As shown in FIG. 3, the vibrating device 1 includes a piezoelectric element 10 and a vibrating body 2. As shown in FIG. The vibrating body 2 is, for example, a plate-like member (diaphragm). The vibrating body 2 may be an electronic device on which the piezoelectric element 10 is mounted. The vibrating body 2 has a main surface 2a on which the piezoelectric element 10 is arranged.

The piezoelectric element 10 is arranged on the main surface 2 a of the vibrating body 2 . The piezoelectric element 10 is bonded to the principal surface 2a by, for example, a bonding member (not shown). The main surface 11b faces the main surface 2a via the external electrode 15 and the joining member. The entire external electrode 15 is bonded to the main surface 2a. As the joining member, for example, a resin layer made of epoxy resin or acrylic resin is used. The joint member may include, for example, a plurality of conductive particles (not shown), and may be configured such that a voltage is applied to the external electrode 15 via the joint member.

[Second embodiment]
FIG. 4 is a cross-sectional view of the piezoelectric element according to the second embodiment. 5 is a cross-sectional view along line VV of FIG. 4. FIG. 6 is an exploded perspective view of the piezoelectric element of FIG. 4. FIG. As shown in FIGS. 4 to 6, a piezoelectric element 10A according to the second embodiment has a base body 11 and a pair of external electrodes 13A and 15A. The piezoelectric element 10A is mainly different from the piezoelectric element 10 (see FIG. 1) in that it is a so-called laminated piezoelectric element. The pair of external electrodes 13A, 15A mainly differs from the pair of external electrodes 13, 15 (see FIG. 1) in terms of arrangement and shape.

In addition to the pair of main surfaces 11a and 11b, the element body 11 has a pair of side surfaces 11c facing each other and a pair of side surfaces 11e facing each other. The direction in which the pair of side surfaces 11c face each other is the second direction D2. The second direction D2 is also a direction orthogonal to each side surface 11c. The direction in which the pair of side surfaces 11e face each other is the third direction D3. The third direction D3 is also a direction orthogonal to each side surface 11e. In this embodiment, the long-side direction of the main surfaces 11a and 11b coincides with the third direction D3. The short side directions of the main surfaces 11a and 11b match the second direction D2.

The pair of side surfaces 11c extend in the first direction D1 so as to connect the pair of main surfaces 11a and 11b. The pair of side surfaces 11c also extend in the third direction D3. The pair of side surfaces 11e extend in the first direction D1 so as to connect the pair of main surfaces 11a and 11b. The pair of side surfaces 11e also extend in the second direction D2. Although enlarged views are omitted, in the piezoelectric element 10A as well, the main surfaces 11a and 11b are natural surfaces as in the piezoelectric element 10, and the main surface 11a has lower smoothness than the main surface 11b. The main surface 11b is a vibration transmission surface that is fixed to the vibrating body 2 (see FIG. 3) by, for example, a bonding member and transmits vibration to the vibrating body 2. As shown in FIG. In this embodiment, the joining member does not contain conductive particles and has electrical insulation.

The element body 11 is configured by stacking a plurality of piezoelectric layers 17a, 17b, 17c, 17d, and 17e in the first direction D1. The element body 11 has a plurality of laminated piezoelectric layers 17a, 17b, 17c, 17d, and 17e. In this embodiment, the element body 11 has five piezoelectric layers 17a, 17b, 17c, 17d and 17e. In the element body 11, the direction in which the plurality of piezoelectric layers 17a, 17b, 17c, 17d, and 17e are laminated coincides with the first direction D1. The piezoelectric layer 17a has a main surface 11a. The piezoelectric layer 17e has a main surface 11b. The piezoelectric layers 17b, 17c and 17d are located between the piezoelectric layers 17a and 17e.

Each piezoelectric layer 17a, 17b, 17c, 17d, 17e is made of, for example, the piezoelectric ceramic material described above. Each of the piezoelectric layers 17a, 17b, 17c, 17d, and 17e is composed of, for example, a sintered ceramic green sheet containing the piezoelectric ceramic material described above. In the actual element body 11, the piezoelectric layers 17a, 17b, 17c, 17d, and 17e are integrated to such an extent that the boundaries between the piezoelectric layers 17a, 17b, 17c, 17d, and 17e cannot be recognized.

The length (thickness) of each piezoelectric layer 17a, 17b, 17c, 17d, 17e in the first direction D1 is, for example, 40 μm. The piezoelectric layer 17a has such transparency that an electrode layer 21, which will be described later, can be visually recognized through the piezoelectric layer 17a from the main surface 11a side. The other piezoelectric layers 17b, 17c, 17d and 17e also have the same transparency as the piezoelectric layer 17a.

The piezoelectric element 10A includes a plurality of electrode layers 21, 22, 23, 24 arranged inside the element body 11. As shown in FIG. In this embodiment, the piezoelectric element 10A has four electrode layers 21, 22, 23, and 24. As shown in FIG. Each electrode layer 21, 22, 23, 24 is an internal electrode. Each electrode layer 21, 22, 23, 24 is made of a conductive material. Ag, Pd, Pt, Cu, or Ag--Pd alloys, for example, are used for the conductive material. Each of the electrode layers 21, 22, 23, 24 is configured as, for example, a sintered body of a conductive paste containing the conductive material.

Each of the electrode layers 21, 22, 23, 24 is arranged at different positions (layers) in the first direction D1. The main surface 11a and the electrode layer 21 face each other with a gap in the first direction D1. The electrode layer 21 and the electrode layer 22 face each other with a gap in the first direction D1. The electrode layer 22 and the electrode layer 23 face each other with a gap in the first direction D1. The electrode layer 23 and the electrode layer 24 face each other with a gap in the first direction D1. The electrode layer 24 and the main surface 11b face each other with a gap in the first direction D1.

The electrode layer 21 is located between the piezoelectric layer 17a and the piezoelectric layer 17b. The electrode layer 22 is positioned between the piezoelectric layer 17b and the piezoelectric layer 17c. The electrode layer 23 is positioned between the piezoelectric layer 17c and the piezoelectric layer 17d. The electrode layer 24 is positioned between the piezoelectric layer 17d and the piezoelectric layer 17e. Each electrode layer 21 , 22 , 23 , 24 is not exposed on the surface of the element body 11 . That is, the electrode layers 21, 22, 23, and 24 are spaced apart from the side surfaces 11c and 11e and are not exposed to the side surfaces 11c and 11e. Each of the electrode layers 21, 22, 23, 24 is separated from all edges (four sides) of the main surfaces 11a, 11b when viewed from the first direction D1.

Each of the electrode layers 21, 22, 23, 24 has a rectangular shape when viewed from the first direction D1. Each of the electrode layers 21, 22, 23, and 24 has a rectangular shape having a pair of long sides and a pair of short sides when viewed in the first direction D1 (in plan view). In this embodiment, the long-side direction of each electrode layer 21, 22, 23, 24 matches the third direction D3. The short side direction of each electrode layer 21, 22, 23, 24 matches the second direction D2. When viewed from the first direction D1, the outer edges of the electrode layers 21, 22, 23, 24 have the same shape and match each other.

The external electrodes 13A, 15A are arranged on the main surface 11a. The external electrodes 13A and 15A are arranged in the third direction D3. The external electrode 13A and the external electrode 15A are adjacent to each other in the third direction D3. The external electrodes 13A and 15A are separated from all edges (four sides) of the main surface 11a when viewed from the first direction D1. The external electrodes 13A and 15A have a rectangular shape when viewed from the first direction D1. The rectangular shape includes, for example, a shape with chamfered corners and a shape with rounded corners.

The external electrodes 13A and 15A have the same shape when viewed from the first direction D1. When viewed from the first direction D1, the short-side direction of the external electrodes 13A, 15A matches the second direction D2, and the long-side direction of the external electrodes 13A, 15A matches the third direction D3. The length of the external electrodes 13A, 15A in the second direction D2 is, for example, 3 mm. The length of the external electrodes 13A, 15A in the third direction D3 is, for example, 3.6 mm. The distance between the external electrodes 13A and 15A in the third direction D3 is, for example, 3.4 mm.

Since the external electrodes 13A and 15A are formed on the main surface 11a having the shape as described above, they exhibit a shape along the shape of the main surface 11a. That is, the peaks and valleys of the main surface 11a are reflected on the outer surfaces of the external electrodes 13A and 15A. Also in this embodiment, the thickness (the length in the first direction D1) of the external electrodes 13A and 15A is, for example, 0.5 μm or more and 3.0 μm or less. Also, the external electrodes 13A and 15A are made of the same conductive material as the external electrodes 13 and 15. As shown in FIG.

A wiring member (not shown) such as a flexible printed circuit board (FPC) or a flexible flat cable (FFC) is electrically connected to the external electrodes 13A and 15A. The wiring member is bonded to surfaces 13a and 15a by, for example, a resin layer (not shown) containing a plurality of conductive particles. Conductive particles are, for example, metal particles and gold-plated particles. The resin layer contains, for example, a thermosetting elastomer. The resin layer is formed, for example, by curing an anisotropic conductive paste or an anisotropic conductive film. Since the smoothness of the surfaces 13a, 15a is low, the bonding strength between the external electrodes 13A, 15A and the wiring member is improved as compared with the case where the smoothness of the surfaces 13a, 15a is high.

The external electrodes 13A are electrically connected to the connection conductors 25 through the via conductors 31 . The connection conductor 25 is located in the same layer as the electrode layer 21 . The connection conductor 25 is positioned inside the electrode layer 21 . Openings are formed in the electrode layer 21 at positions corresponding to the external electrodes 13A when viewed from the first direction D1. The connection conductor 25 is positioned within an opening formed in the electrode layer 21 . The entire edge of the connection conductor 25 is surrounded by the electrode layer 21 when viewed from the first direction D1.

The connection conductor 25 is positioned between the piezoelectric layers 17a and 17b. The electrode layer 21 and the connection conductor 25 are separated from each other. The connection conductor 25 faces the external electrode 13A in the first direction D1. The via conductors 31 are connected to the connection conductors 25 as well as to the external electrodes 13A. The connection conductor 25 is electrically connected to the electrode layer 22 through the via conductor 32 . The connection conductor 25 faces the electrode layer 22 in the first direction D1. The via conductors 32 are connected to the connection conductors 25 and the electrode layers 22 .

The electrode layer 22 is electrically connected to the connection conductor 26 through the via conductor 32 . The connection conductor 26 is located in the same layer as the electrode layer 23 . The connection conductor 26 is positioned inside the electrode layer 23 . Openings are formed in the electrode layer 23 at positions corresponding to the external electrodes 13A (connection conductors 25) when viewed from the first direction D1. The connection conductor 26 is positioned within an opening formed in the electrode layer 23 . The entire edge of the connection conductor 26 is surrounded by the electrode layer 23 when viewed from the first direction D1.

The connection conductor 26 is positioned between the piezoelectric layer 17c and the piezoelectric layer 17d. The electrode layer 23 and the connection conductor 26 are separated from each other. The connection conductor 26 faces the electrode layer 22 in the first direction D1. The via conductors 33 are connected to the electrode layers 22 as well as to the connection conductors 26 . The connection conductors 26 are electrically connected to the electrode layers 24 through via conductors 34 . The connection conductor 26 faces the electrode layer 24 in the first direction D1. The via conductors 34 are connected to the connection conductors 26 and the electrode layers 24 .

External electrode 15A is electrically connected to electrode layer 21 through via conductor 35 . The electrode layer 21 faces the external electrode 15A in the first direction D1. The via conductors 35 are connected to the electrode layers 21 as well as to the external electrodes 15A.

Electrode layer 21 is electrically connected to connection conductor 27 through via conductor 36 . The connection conductor 27 is located in the same layer as the electrode layer 22 . The connection conductor 27 is positioned inside the electrode layer 22 . Openings are formed in the electrode layer 22 at positions corresponding to the external electrodes 15A when viewed from the first direction D1. The connection conductor 27 is positioned within an opening formed in the electrode layer 22 . The entire edge of the connection conductor 27 is surrounded by the electrode layer 22 when viewed from the first direction D1.

The connection conductor 27 is located between the piezoelectric layer 17b and the piezoelectric layer 17c. The electrode layer 22 and the connection conductor 27 are separated from each other. The connection conductor 27 faces the electrode layer 21 in the first direction D1. The via conductors 36 are connected to the electrode layers 21 as well as to the connection conductors 27 . The connection conductor 27 is electrically connected to the electrode layer 23 through the via conductor 37 . The connection conductor 27 faces the electrode layer 23 in the first direction D1. The via conductors 37 are connected to the connection conductors 27 and the electrode layers 23 .

The electrode layer 23 is electrically connected to the connection conductor 28 through the via conductor 38 . The connection conductor 28 is located in the same layer as the electrode layer 24 . The connection conductor 28 is located inside the electrode layer 24 . Openings are formed in the electrode layer 24 at positions corresponding to the external electrodes 15A when viewed from the first direction D1. The connection conductors 28 are positioned within openings formed in the electrode layer 24 . The entire edge of the connection conductor 28 is surrounded by the electrode layer 24 when viewed in the first direction D1.

The connection conductor 28 is positioned between the piezoelectric layer 17d and the piezoelectric layer 17e. The electrode layer 24 and the connection conductor 28 are separated from each other. The connection conductor 28 faces the electrode layer 23 in the first direction D1. The via conductors 38 are connected to the electrode layers 23 as well as to the connection conductors 28 .

The external electrodes 13</b>A are electrically connected to the via conductors 31 , connection conductors 25 , via conductors 32 , electrode layers 22 , via conductors 33 , connection conductors 26 , via conductors 34 and electrode layers 24 . The external electrodes 15A are electrically connected to the via conductors 35 , the electrode layers 21 , the via conductors 36 , the connection conductors 27 , the via conductors 37 , the electrode layers 23 , the via conductors 38 and the connection conductors 28 .

The connection conductors 25, 26, 27, 28 and via conductors 31, 32, 33, 34, 35, 36, 37, 38 are made of a conductive material. Ag, Pd, or Ag--Pd alloy is used for the conductive material, for example. The connection conductors 25, 26, 27, 28 and the via conductors 31, 32, 33, 34, 35, 36, 37, 38 are formed, for example, as sintered bodies of conductive paste containing the conductive material. The connection conductors 25, 26, 27, and 28 have a rectangular shape when viewed from the first direction D1. Via conductors 31, 32, 33, 34, 35, 36, 37, 38 are conductive conductors filled in through holes formed in ceramic green sheets for forming corresponding piezoelectric layers 17a, 17b, 17c, 17d. It is formed by sintering a viscous paste.

Conductors electrically connected to the electrode layers 21 and 23 and conductors electrically connected to the electrode layers 22 and 24 are not arranged on the main surface 11b of the element body 11 . In this embodiment, the main surface 11b is entirely exposed when viewed from the first direction D1. Neither the conductors electrically connected to the electrode layers 21, 23 nor the conductors electrically connected to the electrode layers 22, 24 are disposed on the respective side surfaces 11c, 11e of the element body 11, respectively. In this embodiment, when each side surface 11c is viewed from the second direction D2, each side surface 11c is entirely exposed. When each side surface 11e is viewed from the third direction D3, each side surface 11e is entirely exposed.

A region sandwiched between the electrode layer 21 and the electrode layer 22 in the piezoelectric layer 17b, a region sandwiched between the electrode layer 22 and the electrode layer 23 in the piezoelectric layer 17c, and an electrode layer 23 and the electrode in the piezoelectric layer 17d. The region sandwiched by layer 24 constitutes the piezoelectrically active active region. When viewed from the first direction D1, the element body 11 includes an active region in a region located between the external electrodes 13A and 15A. When viewed from the first direction D1, the element body 11 also includes an active region outside the regions where the external electrodes 13A and 15A are located.

As described above, in the piezoelectric elements 10 and 10A, since the smoothness of the main surface 11a is lower than that of the main surface 11b, deformation of the main surface 11a is easier than deformation of the main surface 11b. be. In this manner, the piezoelectric elements 10 and 10A can be efficiently deformed by fixing the less deformable main surface 11b side to the vibrating body 2 without fixing the easily deformable main surface 11a side to the vibrating body 2. can. Therefore, the piezoelectric elements 10 and 10A are excellent in vibration transmission efficiency.

In the piezoelectric element 10, the external electrode 13 is provided on the main surface 11a, and the shape of the main surface 11a is reflected on the surface 13a. The external electrode 15 is provided on the main surface 11b, and the shape of the main surface 11b is reflected on the surface 15a. Therefore, since the surface 13a is less smooth than the surface 15a, the bonding strength between the external electrode 13 and the wiring member is improved.

In the piezoelectric element 10A, the external electrodes 13A and 15A are provided on the principal surface 11a, and the surfaces 13a and 15a reflect the shape of the principal surface 11a. Therefore, since the surfaces 13a and 15a are less smooth than when the external electrodes 13A and 15A are provided on the main surface 11b, the bonding strength between the external electrodes 13A and 15A and the wiring member is improved.

The present invention is not necessarily limited to the above-described embodiments, and various modifications are possible without departing from the scope of the invention.

Reference Signs List 10, 10A Piezoelectric element 11 Base body 11a Principal surface (first principal surface) 11b Principal surface (second principal surface) 13, 13A External electrode (first external electrode) 15, 15A ...external electrode (second external electrode).

Claims (3)

A body having a first principal surface and a second principal surface facing each other,
The first main surface and the second main surface are natural surfaces each having a shape having peaks and valleys ,
The second main surface is fixed to a vibrating body and transmits vibration to the vibrating body,
The piezoelectric element, wherein the first principal surface is less smooth than the second principal surface. a first external electrode disposed on the first main surface;
2. The piezoelectric element according to claim 1, further comprising a second external electrode arranged on said second main surface. 2. The piezoelectric element according to claim 1, further comprising a first external electrode and a second external electrode arranged on said first main surface.

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