JP2016122725A - Piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element capable of exhibiting excellent piezoelectric characteristics and improving the displacement magnitude.SOLUTION: A piezoelectric element 1 includes: a piezoelectric substrate 2 which has a pair of main surfaces 2a, 2b opposite to each other and is made of piezoelectric ceramics; and a pair of electrodes 3, 4 which is arranged on the pair of the main surfaces 2a, 2b. At least one surface 2a of the pair of main surfaces is a rough surface, and a rough curve element average length (RSm) in a first direction of the rough surface is different from the rough curve element average length (RSm) in a second direction intersecting with the first direction. The electrode 3 arranged in the rough surface out of the pair of electrodes is formed on the main surface 2a along the main surface 3a which is the rough surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric element.

    2. Description of the Related Art A piezoelectric element is known that includes a piezoelectric substrate having a pair of main surfaces facing each other and made of piezoelectric ceramic, and a pair of electrodes disposed on the pair of main surfaces (for example, , See Patent Document 1). Piezoelectric elements (piezoelectric substrates) exhibit piezoelectric characteristics when each crystal grain of piezoelectric ceramic is polarized.

JP 2001-57449 A

  An object of the present invention is to provide a piezoelectric element that exhibits excellent piezoelectric characteristics, and that can improve the amount of displacement and reduce variation in the amount of displacement.

  The present inventors have conducted research on piezoelectric elements that exhibit excellent piezoelectric characteristics and can improve the amount of displacement. As a result, the present inventors have found the following facts.

  Each crystal grain of the piezoelectric ceramic is polarized with a change in shape. Electrodes are arranged on the piezoelectric substrate. For this reason, the crystal grains located in the vicinity of the interface with the electrode in the piezoelectric substrate and in the vicinity of the interface (hereinafter simply referred to as “crystal grains located in the vicinity of the interface”) are prevented from changing in shape by the electrode. There is a fear that the polarization is inhibited. If there are crystal grains whose polarization is hindered, the piezoelectric element (piezoelectric substrate) will inevitably deteriorate in the piezoelectric characteristics, and the polarization in the piezoelectric substrate will not be uniform, resulting in variations in the displacement of the piezoelectric element. End up. That is, if the inhibition of the polarization of the crystal grains located in the vicinity of the interface is reduced, the piezoelectric element will exhibit excellent piezoelectric characteristics.

  When an electric field is applied to the piezoelectric substrate by a pair of electrodes to drive the piezoelectric element, the piezoelectric substrate attempts to displace, but the electrode itself does not attempt to displace. For this reason, the electrode acts so as to inhibit the displacement of the piezoelectric substrate, and the polarization is not uniform within the piezoelectric substrate, so that the displacement amount of the piezoelectric element may be reduced and variations may occur. That is, if the inhibition of displacement of the piezoelectric substrate is reduced, the piezoelectric element can be improved in displacement and variation.

  And the present inventors conducted further research and research, found the following facts, and came to conceive the present invention.

  At least one of the main surfaces of the piezoelectric substrate is a rough surface, and the electrode formed on the rough surface along the rough surface is a deformed crystal grain located near the interface when the crystal grain is polarized. Reduce inhibition. When the piezoelectric element is driven, the electrode formed on the rough surface reduces the inhibition of displacement of the piezoelectric substrate.

  Therefore, a piezoelectric element according to the present invention includes a piezoelectric substrate having a pair of main surfaces facing each other and made of piezoelectric ceramic, and a pair of electrodes disposed on the pair of main surfaces. At least one of the surfaces is a rough surface, and an average length (RSm) of the roughness curve element on the main surface on which the rough surface is formed is a second direction intersecting the first direction and the first direction. The electrodes arranged on the rough surface of the pair of electrodes are formed on the main surface along the rough main surface.

  In the piezoelectric element according to the present invention, the electrode disposed on the rough surface is a rough surface, and is formed on the main surface along the main surface which is the rough surface. Therefore, the electrode itself is along the rough surface. It has a shape with a mountain valley. For this reason, the electrode arranged on the rough surface easily allows the deformation of the electrode itself in a direction parallel to the main surface, and the electrode arranged on the rough surface inhibits the deformation of the crystal grains located near the interface. In addition to reducing, the inhibition of displacement of the piezoelectric substrate is reduced.

Further, when the rough surface is formed so that the average length (RSm) of the roughness curve elements is different in the first direction and the second direction intersecting the first direction, the degree of deformation of the crystal grains is determined in the direction. The amount of displacement can be controlled by changing.

The pair of main surfaces may be rectangular, and the direction parallel to the long side of the rectangle may be the first direction. Further, the average length (RSm) of the roughness curve element in the first direction may be smaller than the average length (RSm) of the roughness curve element in the second direction. In this case, the amount of displacement can be made different between the direction parallel to the long side and the direction parallel to the short side depending on the application.

The pair of main surfaces may be rough on both surfaces. In this case, the inhibition of displacement of the piezoelectric substrate can be further reduced as compared with the case where at least one of the main surfaces is roughened.

  The main surface may be a surface that is not subjected to surface treatment after firing. In this case, the detachment of the piezoelectric substrate is unlikely to occur and the generation of particles can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, while exhibiting the outstanding piezoelectric characteristic, the piezoelectric element which can aim at the improvement of a displacement amount can be provided.

It is the perspective view which shows typically the piezoelectric element which concerns on this embodiment, and its partially enlarged view. It is a figure which shows typically the AA cross section of the piezoelectric element which concerns on a natural surface, and this embodiment, and a BB cross section. It is a photograph figure of the natural surface and the rough surface of this embodiment. It is a schematic diagram explaining the deformation | transformation before and behind polarization of a piezoelectric element. It is a graph which shows the measurement result of the average length (RSm) of the roughness curve element of the 1st direction in an Example, and a 2nd direction. It is a graph which shows the measurement result of the piezoelectric-strain constant and standard deviation in the piezoelectric element which concerns on a present Example and a comparative example. It is the perspective view which shows the modification of the piezoelectric element which concerns on this embodiment, and its partially expanded view

  First, the configuration of the piezoelectric element 1 according to this embodiment will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing a piezoelectric element according to this embodiment and a partially enlarged view thereof. 2A is a natural surface, FIG. 2B is an AA cross section of the piezoelectric element according to the present embodiment, and FIG. 2C is a BB cross section of the piezoelectric element according to the present embodiment. It is a figure which shows typically a rough surface. 3A is a photograph of the natural surface, and FIG. 3B is a photograph of the rough surface of the present embodiment.

  As illustrated in FIG. 1, the piezoelectric element 1 includes a piezoelectric substrate 2 and a pair of electrodes 3 and 4. The piezoelectric element 1 is applied to, for example, a disk device provided with a magnetic disk. That is, in the dual actuator type disk device, the piezoelectric element 1 is used as the second actuator other than the voice coil motor. The piezoelectric element 1 has a rectangular plate shape. The thickness of the piezoelectric element 1 is set to 30 μm to 200 μm, for example.

  The piezoelectric substrate 2 has a pair of main surfaces 2a and 2b facing each other and a side surface 2c extending in the facing direction of the pair of main surfaces 2a and 2b so as to connect the pair of main surfaces 2a and 2b. The pair of main surfaces 2a and 2b are rough surfaces in which peaks and valleys have anisotropy as shown in FIG. In the present embodiment, the piezoelectric substrate 2 has a rectangular plate shape. Therefore, the pair of main surfaces 2a and 2b are rectangular. The second direction T intersects the first direction S with respect to the arbitrary first direction S. The average length (RSm) of the roughness curve elements in the first direction S is smaller than the average length (RSm) of the roughness curve elements in the second direction T. In the present embodiment, the first direction S is a long side direction, and the second direction T is a short side direction. The first direction S is orthogonal to the second direction T. The thickness of the piezoelectric substrate 2 is set to 30 μm to 200 μm, for example.

The piezoelectric substrate 2 is made of a piezoelectric ceramic. Examples of the piezoelectric ceramic include PZT [Pb (Zr, Ti) O ₃ ], PT (PbTiO ₃ ), PLZT [(Pb, La) (Zr, Ti) O ₃ ], or barium titanate (BaTiO ₃ ). It is done.

  The pair of electrodes 3 and 4 are disposed on the pair of main surfaces 2a and 2b. Since the pair of electrodes 3 and 4 is formed on the pair of main surfaces 2a and 2b along the pair of main surfaces 2a and 2b which are rough surfaces, the pair of electrodes 3 and 4 has a shape having a mountain and valley along the rough surface. The pair of electrodes 3 and 4 are formed on the pair of main surfaces 2a and 2b by, for example, a sputtering method or a vapor deposition method. The pair of electrodes 3 and 4 covers the entire pair of main surfaces 2a and 2b. The side surface 2 c is not covered with the pair of electrodes 3 and 4. The pair of electrodes 3 and 4 function as electrodes for applying an electric field to the piezoelectric substrate 2. The pair of electrodes 3 and 4 is made of, for example, Au, Ni, Cr, Cu, or Pt. The thickness of the pair of electrodes 3 and 4 is set to 20 nm to 1 μm, for example.

  The arithmetic average roughness (Ra) in the first direction S of the rough surfaces formed on the pair of main surfaces 2a and 2b is, for example, 0.5 μm to 1.5 μm, and the average length (RSm) of the roughness curve elements. ) Is, for example, 20 μm to 50 μm. The arithmetic average roughness (Ra) in the second direction T of the rough surfaces formed on the pair of main surfaces 2a and 2b is, for example, 0.3 μm to 1.0 μm, and the average length of the roughness curve elements (RSm) is, for example, 50 μm to 80 μm.

  The side surface 2c of the piezoelectric substrate 2 may be covered with a resin (not shown). In this case, the resin may be arranged so as to cover the entire side surface 2c. An epoxy resin or the like is used as the resin material.

  Next, the manufacturing process of the piezoelectric element 1 described above will be described.

  First, components such as a binder and an organic solvent are added to the piezoelectric ceramic powder (raw material particles) constituting the piezoelectric substrate 2 to obtain a paste of the piezoelectric ceramic powder. Next, a green sheet having a predetermined thickness is created from the paste. The green sheet is produced by, for example, a doctor blade method. The predetermined thickness is set to 50 μm to 500 μm, for example.

  Next, the produced green sheets are overlapped to form a laminated body. Thereafter, the laminate is pressed in the lamination direction to obtain piezoelectric green. The press treatment is performed, for example, using a uniaxial press machine or the like and maintaining the mold at a temperature of about 50 ° C. to 100 ° C. and a pressure of about 100 MPa.

  Next, each main surface of the obtained piezoelectric green is polished along the second direction T. The abrasive used for the polishing treatment is, for example, alumina, silicon carbide, diamond or the like. The center diameter of the abrasive is, for example, 5 μm to 50 μm, and it is more preferable that the abrasive is sufficiently washed after the polishing treatment to wash away the residual of the abrasive. By performing the polishing treatment, the main surface of the piezoelectric green becomes a rough surface.

  Next, a binder removal process is performed on the piezoelectric green subjected to the polishing process. The binder removal treatment is performed, for example, in a state where the piezoelectric green is placed on a setter made of stabilized zirconia. Subsequently, the piezoelectric body green is fired to obtain a piezoelectric body. Firing is performed at 1100 ° C., for example, by placing the setter in a magnesia mortar with the piezoelectric green placed thereon.

  In the partial cross-sectional view shown in FIG. 2, (a) is a natural surface, (b) is a rough surface of the AA cross section of the piezoelectric element according to the present embodiment, and (c) is a piezoelectric element according to the present embodiment. It corresponds to the rough surface of the BB cross section. The natural surface is a surface that has not been subjected to surface treatment such as polishing before and after firing. As shown in FIG. 2A, the natural surface has a smooth surface state. As shown in FIG. 2B, the rough surface of the AA cross section has a rougher shape than the natural surface. As shown in FIG. 2C, the rough surface of the BB cross section has a shape that is rougher than the natural surface and has a wider interval between the peaks and valleys than the AA cross section.

  In the photograph shown in FIG. 3, (a) corresponds to the natural surface, and (b) corresponds to the rough surface in the present embodiment. FIG. 3B is a rough surface, which is a main surface obtained by performing polishing using alumina as an abrasive. As shown in FIG. 3, the rough surface in the present embodiment is different from the natural surface, and the surface valleys are emphasized.

  After the polishing process, an electrode film is formed on each main surface of the piezoelectric body. Each electrode film is made of, for example, Au, Ni, Cr, Cu, or Pt. Each electrode film is formed by sputtering or vapor deposition. Each electrode film is formed on each main surface along each main surface, which is a rough surface of the piezoelectric body, and has a shape having peaks and valleys along the rough surface. The piezoelectric body is in a state in which a plurality of piezoelectric substrates 2 in an individualized state are connected, and each electrode film is in a state in which a plurality of electrodes 3 and 4 in an individualized state are connected.

  Through the above process, a piezoelectric element substrate having a piezoelectric body and an electrode film is obtained. Next, polarization processing is performed on the piezoelectric element substrate. In the polarization treatment, for example, a voltage with an electric field strength of 3 kV / mm is applied at a temperature of 100 ° C. for 3 minutes. Subsequently, the piezoelectric element substrate after the polarization treatment is processed into a product shape by a cutting machine such as a dicer. Thereby, the piezoelectric element 1 provided with the piezoelectric substrate 2 and the electrodes 3 and 4 which are separated into pieces is obtained.

  Next, the operation and effect of the piezoelectric element 1 configured as described above will be described. Here, referring to FIG. 4, while comparing the piezoelectric element 1 and the conventional piezoelectric element 11, the electrodes 3 and 4 of the piezoelectric element 1 are arranged along the main surfaces 2 a and 2 b which are rough surfaces. The operation and effect of being formed on the main surfaces 2a and 2b will be described.

FIG. 4 is a diagram for explaining the polarization state of the piezoelectric element 1 according to the present embodiment in comparison with the piezoelectric element 1 before the polarization treatment and the conventional piezoelectric element 11, and specifically, FIG. FIG. 4 is a diagram for explaining a state of spontaneous polarization before the polarization process of the piezoelectric element of FIG. 1, and FIG. 4B is a diagram for explaining a polarization state after a polarization process of a conventional piezoelectric element. FIG. 2C is a diagram illustrating a polarization state after the polarization process of the piezoelectric element in FIG. 1.

As shown in FIG. 4A, the piezoelectric substrate 2 is a piezoelectric ceramic polycrystal and includes a plurality of crystal grains 8. In the piezoelectric element 1 before the polarization treatment, the direction of spontaneous polarization of each crystal grain 8 is random. That is, since the direction of spontaneous polarization is not aligned in every direction spontaneously for each crystal grain 8, even if a voltage is applied in this state, each crystal grain 8 is displaced in the direction of its own spontaneous polarization. Attempts to cancel each other cancel each other out, and it is difficult for the displacement to occur as a whole. The piezoelectric element 1 before polarization treatment has a thickness D ₀ and a long side length L ₀ .

  As shown in FIG. 4B, the conventional piezoelectric element 11 includes a piezoelectric substrate 12 having a pair of main surfaces 12a and 12b and four side surfaces 12c facing each other and made of piezoelectric ceramic, and each main surface. And a pair of electrodes 13 and 14 disposed on 12a and 12b. Each main surface 12a, 12b is a natural surface. The pair of electrodes 13 and 14 are formed on the main surfaces 12a and 12b along the main surfaces 12a and 12b which are natural surfaces. The piezoelectric substrate 12 is a piezoelectric ceramic polycrystal and includes a plurality of crystal grains 18. The piezoelectric element 11 is mainly different from the piezoelectric element 1 of the present embodiment in that each main surface 12a, 12b of the piezoelectric substrate 12 is not a rough surface but a natural surface, and is common in other points.

In the piezoelectric element 11, although not shown, like the piezoelectric element 1, the direction of the spontaneous polarization of each crystal grain 18 of the piezoelectric ceramic is random and is not easily displaced as a whole before the polarization process. The piezoelectric element 11 before the polarization treatment has a thickness D ₀ and a long side length L ₀ . The polarization process is performed by applying a voltage between the pair of electrodes 13 and 14 and applying an electric field to the piezoelectric substrate 12. As a result, a polarization state as shown in FIG. 4B is obtained with deformation of each crystal grain 18. The piezoelectric element 11 after the polarization treatment has a thickness D ₁ (> D ₀ ) and a long side length L ₁ (<L ₀ ).

  In the piezoelectric element 11 after the polarization treatment, the direction of spontaneous polarization of each crystal grain 18 is generally aligned in a direction parallel to the opposing direction of the main surfaces 12a and 12b. However, the crystal grains 18 located in the vicinity of the interface are prevented from being deformed by the electrodes 13 and 14, and the polarization is inhibited. Therefore, in the crystal grains 18 located in the vicinity of the interface, the direction of spontaneous polarization is difficult to be aligned as compared with the other crystal grains 18. Thus, if the crystal grains 18 in which the polarization is inhibited and the direction of spontaneous polarization is not uniform, the piezoelectric element 11 (piezoelectric substrate 13) cannot deny the deterioration of the piezoelectric characteristics.

  By driving the piezoelectric element 11 by applying a voltage between the pair of electrodes 13 and 14 and applying an electric field to the piezoelectric substrate 12, the piezoelectric substrate 12 tends to be displaced, but the electrodes 13 and 14 themselves are displaced. I will not try. For this reason, the electrodes 13 and 14 act so as to inhibit the displacement of the piezoelectric substrate 12, and the displacement amount of the piezoelectric element 1 may be reduced.

On the other hand, as shown in FIG. 4C, in the piezoelectric element 1 after the polarization treatment, the direction of the spontaneous polarization of each crystal grain 8 includes each crystal grain 8 located in the vicinity of the interface. They are generally aligned in a direction parallel to the opposing direction of the surfaces 2a, 2b. This is because the electrodes 3 and 4 are formed on the main surfaces 2a and 2b along the main surfaces 2a and 2b which are rough surfaces. Each electrode 3, 4 is easy to allow deformation of each electrode 3, 4 itself in a direction parallel to each main surface 2 a, 2 b, and in the piezoelectric element 1, the deformation of the crystal grains 8 located in the vicinity of the interface is inhibited. It is reduced. Therefore, even in the crystal grains 8 located in the vicinity of the interface, the direction of spontaneous polarization is easily aligned. The piezoelectric element 1 after the polarization treatment has a thickness D ₂ (> D ₁ > D ₀ ) and a long side length L ₂ (<L ₁ <L ₀ ).

  Thus, in the piezoelectric element 1 according to this embodiment, the electrodes 3 and 4 are formed on the main surfaces 2a and 2b along the main surfaces 2a and 2b which are rough surfaces. The piezoelectric characteristics superior to those of the piezoelectric element 11 can be exhibited, and the amount of displacement can be improved.

Further, the rough surfaces formed on the main surfaces 2a and 2b of the piezoelectric element 1 according to the present embodiment have different average lengths (RSm) of the roughness curve elements in the first direction S and the second direction T. The average length (RSm) of the roughness curve elements in the first direction S is smaller than the average length (RSm) of the roughness curve elements in the second direction T. Therefore, each electrode 3, 4 formed along each main surface 2 a, 2 b allows deformation of each electrode 3, 4 itself in a direction parallel to the first direction S of each main surface 2 a, 2 b. It is easy to deform the electrodes 3 and 4 themselves in a direction parallel to the second direction T, and it is difficult to tolerate as compared to the first direction S. In the piezoelectric element 1, the inhibition of deformation of the crystal grains 8 located near the interface in the first direction S is reduced, and the inhibition of deformation of the crystal grains 8 located near the interface in the second direction T is reduced in the first direction. Less likely to be reduced than S

That is, the smaller the average length (RSm) of the roughness curve element, the smaller the inhibition of deformation of the crystal grains 8 located near the interface by the electrodes 3 and 4 during polarization. For this reason, the piezoelectric substrate can control the amount of displacement by designating one of the directions, so that the polarization can be made more constant than in the conventional configuration as shown in FIG. Therefore, the polarization is more stable than that of the piezoelectric substrate 12 shown in FIG.

  Here, according to the present embodiment, it is specifically shown by an example and a comparative example that excellent piezoelectric characteristics can be exhibited and an improvement in displacement and variation can be achieved.

  In the embodiment, a piezoelectric element corresponding to FIG. 1 was used. In the piezoelectric element according to the example, the sample size was 1.5 mm × 1 mm and the thickness was 0.10 mm. The piezoelectric substrate was made of piezoelectric ceramic powder (Pb [Zr0.53Ti0.47] O3 + 0.5 wt% WO3) mainly composed of PZT and had a thickness of 100 μm. Each electrode film has a Cr / Ni—Cu / Au laminated structure (a structure in which a Cr layer, a Ni—Cu alloy layer, and an Au layer are laminated in this order from the piezoelectric substrate side) and is formed with a thickness of 500 nm by a sputtering method. Each main surface of the piezoelectric substrate is a rectangle, and when the long side direction of the rectangle is the first direction, the average length (RSm) of the roughness curve elements in the first direction is the first direction. The surface was roughened by polishing so as to be smaller than the average length (RSm) of the roughness curve elements in the second direction intersecting and orthogonal to each other. Note that the polishing process was performed by dry polishing at the time of the piezoelectric green, and the polishing was performed along the second direction to obtain a rough surface. A polishing paper of # 1000 was used as an abrasive, and the polishing process was performed while paying attention to the polishing direction.

The arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) are measured using a three-dimensional measuring machine (SURECOM 1500SD2 manufactured by Tokyo Seimitsu Co., Ltd.) according to JIS-B0601 (2001). did. The measurement conditions were a cut-off wavelength of 0.8 mm, a measurement length of 2 mm, a measurement range of ± 32 μm, and a rough surface formed with a pair of main surface peaks and valleys under the conditions of a measurement speed of 0.15 mm / s. Measured along 2 directions.

FIG. 5 is a graph showing the measurement results of the average length (RSm) of the roughness curve elements in the first direction and the second direction in the example. Specifically, FIG. 5A shows the present example. FIG. 5B is a graph showing the measurement result of the average length (RSm) of the roughness curve elements in the first direction in FIG. 5, and FIG. 5B shows the average length of the roughness curve elements in the second direction in this example ( It is a graph which shows the measurement result of RSm). The average length (RSm) of the roughness curve element is a value obtained by averaging the lengths in which the irregularities for one cycle included in the roughness curve at a certain reference length are generated. As shown in FIG. 5, the average length (RSm) of the roughness curve element in the direction along the first direction S was about 37 μm, but along the second direction T. The average length (RSm) of the directional roughness curve element was about 79 μm.

In the comparative example, a piezoelectric element corresponding to the above-described conventional piezoelectric element 11 was used. In the piezoelectric element according to the comparative example, the main surface of the piezoelectric substrate was set to the same conditions as in the example except that the surface was a natural surface that was not subjected to surface treatment such as polishing treatment. In the example and the comparative example, the piezoelectric strain constant d ₃₁ of the long side direction extension vibration was measured.

FIG. 6 is a graph showing the measurement results of the piezoelectric strain constant in the piezoelectric elements according to the example and the comparative example. The piezoelectric strain constant is a constant indicating the piezoelectric characteristics of the piezoelectric body. That is, the piezoelectric strain constant is a constant representing how much the piezoelectric body is displaced when an electric field is applied to the piezoelectric body. As shown in FIG. 6, the average value of the piezoelectric strain constant d ₃₁ in the piezoelectric element according to the comparative example was about 294 (10 ⁻¹² mV) and the standard deviation δ was 4 (10 ⁻¹² mV). The average value of the piezoelectric strain constant d ₃₁ in the piezoelectric element according to the example was about 299 (10 ⁻¹² mV) and the standard deviation δ was 2 (10 ⁻¹² mV).

  Therefore, it was confirmed that the piezoelectric element according to the example was superior in piezoelectric characteristics to the piezoelectric element according to the comparative example, and the variation in displacement was reduced.

    The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  The rough surfaces of the main surfaces 2a and 2b are formed by the polishing process, but may be formed by a method other than the polishing process. For example, when a press treatment is performed on a laminated body in which green sheets are stacked, a press die having a rough surface such that a tin-like impression remains may be used.

  Each main surface 2a, 2b is formed with a rough surface, but may be formed on either one of the main surfaces 2a, 2b as shown in FIG. In this case, the same effect can be expected compared to the conventional case.

  The electrodes 3 and 4 are formed by sputtering or vapor deposition, but are not limited thereto. Even when each electrode 3, 4 is formed by a film forming method that increases the internal stress of the film, such as a sputtering method, each main surface 2 a, 4 b is formed along each main surface 2 a, 2 b that is a rough surface. By being formed on 2b, it is easy to allow the deformation of the electrode itself in a direction parallel to the main surfaces 2a and 2b. Therefore, inhibition of deformation of crystal grains located in the vicinity of the interface is reduced, and inhibition of displacement of the piezoelectric substrate 2 is reduced. As a result, the piezoelectric element 1 can exhibit excellent piezoelectric characteristics and can improve the amount of displacement.

The piezoelectric element 1 (piezoelectric substrate 2) has a rectangular plate shape, but is not limited thereto. It may be a disk shape, a columnar shape, or a rectangular parallelepiped shape. The thickness of the piezoelectric substrate 2 is not particularly limited, but the thinner the thickness, the higher the proportion of crystal grains located in the vicinity of the interface in the piezoelectric substrate 2. Therefore, the piezoelectric element 1 exhibits excellent piezoelectric characteristics. At the same time, the effect that the amount of displacement can be improved tends to be remarkable. A is is 0.5mm or less in thickness of the piezoelectric elements 1, this effect becomes more remarkable when the thickness of the piezoelectric substrate 2 is 0.2mm or less.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, 2 ... Piezoelectric substrate, 2a, 2b ... Main surface, 3, 4 ... Electrode, S ... 1st direction, T ... 2nd direction.

Claims (6)

A piezoelectric substrate having a pair of main surfaces facing each other and made of piezoelectric ceramic;
A pair of electrodes disposed on the pair of main surfaces,
At least one of the pair of main surfaces is a rough surface,
The average length (RSm) of the roughness curve elements on the main surface on which the rough surface is formed is
Different in a first direction and a second direction intersecting the first direction,
The electrode arranged on the rough surface of the pair of electrodes is formed on the main surface along the main surface which is the rough surface. The pair of main surfaces are rectangular,
The piezoelectric element according to claim 1, wherein a direction parallel to the long side of the rectangle is a first direction. 3. The piezoelectric element according to claim 2, wherein an average length (RSm) of the roughness curve element in the first direction is smaller than an average length (RSm) of the roughness curve element in the second direction. The piezoelectric element according to claim 1, wherein both of the pair of main surfaces are rough surfaces. The piezoelectric element according to claim 1, wherein the pair of main surfaces are surfaces that are not subjected to surface treatment after firing. The piezoelectric element according to claim 1, wherein the pair of electrodes are disposed on the entire main surface.

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