JP7267597B2 - Piezomagnetostrictive composites and power generation elements - Google Patents

Description

The present invention relates to piezoelectric magnetostrictive composites and power generation elements.

Attention is focused on power generation elements that convert mechanical energy such as vibration into electrical energy. For example, piezoelectric materials and magnetostrictive materials are known as materials capable of converting mechanical energy into electrical energy. Piezoelectric materials produce an electric charge or electric field due to the piezoelectric effect when stressed. When the magnetostrictive material is distorted, the surrounding magnetic field changes due to the inverse magnetostrictive effect, and an induced electromotive force is generated.

For example, Patent Literature 1 describes a composite piezoelectric-electrostrictive magnetic sensor in which a magnetostrictive film is formed on one surface of a piezoelectric substrate. Further, Patent Document 2 describes a magnetostrictive material with excellent characteristics.

WO2010/110423 Japanese Patent No. 6112582

Mechanical energy such as vibration has not been sufficiently utilized. There is a demand for a power generation element that can more efficiently convert mechanical energy into electrical energy.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-output power generating element and a piezoelectric magnetostrictive composite used therein.

The inventors of the present invention laminated a magnetostrictive film and a piezoelectric film, and formed microscopic unevenness at the interface between the two materials, thereby increasing the frequency of contact between the two materials at the microscopic interface. It was found that an electromagnetic physical interaction occurs and the output characteristics of the power generating element are improved.
That is, the present invention provides the following means in order to solve the above problems.

(1) A piezoelectric-magnetostrictive composite according to a first aspect includes a piezoelectric film containing a polarized piezoelectric body and a magnetostrictive film laminated on at least one surface of the piezoelectric film, and the magnetostrictive film on the piezoelectric film side of the magnetostrictive film The first surface has unevenness with an arithmetic mean roughness of 50 μm or less, and the second surface of the piezoelectric film on the magnetostrictive film side follows the unevenness of the first surface.

(2) In the piezoelectric-magnetostrictive composite according to the aspect described above, the magnetostrictive films may be laminated on both sides of the piezoelectric film.

(3) In the piezoelectric magnetostrictive composite according to the aspect described above, the piezoelectric film may include a resin and a piezoelectric material dispersed in the resin.

(4) A power generation element according to a second aspect includes the piezoelectric-magnetostrictive composite according to the aspect described above and a coil wound around the piezoelectric-magnetostrictive composite.

It is possible to provide a high-output power generating element and a piezoelectric magnetostrictive composite used therefor.

1 is a perspective view of a power generation element according to a first embodiment; FIG. FIG. 4 is a cross-sectional view of the vicinity of the interface between the magnetostrictive film and the piezoelectric film of the power generation element according to the first embodiment, taken with a scanning electron microscope; 3 is an enlarged cross-sectional view of the vicinity of the interface between the magnetostrictive film and the piezoelectric film of the power generating element according to the first embodiment; FIG. 3 is a diagram showing power generation characteristics of the power generation elements of Example 1, Comparative Examples 1 and 2. FIG.

Hereinafter, this embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the gist of the invention.

"First Embodiment"
(power generation element)
FIG. 1 is a perspective view of a power generating element 100 according to this embodiment. The power generation element 100 includes a piezoelectric magnetostrictive composite 10 and a coil 20 . The power generation element 100 outputs an induced electromotive force generated in the coil 20 . The induced electromotive force is caused by the changing magnetic field around the piezo-magnetostrictive composite 10 according to the law of electromagnetic induction.

<Piezoelectric strain composite>
A piezoelectric magnetostrictive composite 10 comprises a magnetostrictive film 1 and a piezoelectric film 2 . A piezoelectric magnetostrictive composite 10 shown in FIG. 1 has magnetostrictive films 1 laminated on both sides of a piezoelectric film 2 . The magnetostrictive film 1 may be laminated only on one surface of the piezoelectric film 2 .

FIG. 2 is a scanning electron microscope (SEM) image of the vicinity of the interface between the magnetostrictive film 1 and the piezoelectric film 2 of the power generation element 100 according to the first embodiment. In FIG. 2, a boundary B between the magnetostrictive film 1 and the piezoelectric film 2 is illustrated to aid understanding. FIG. 3 is a cross-sectional view schematically showing the vicinity of the interface between the magnetostrictive film 1 and the piezoelectric film 2 of the power generation element 100 according to the first embodiment. The magnetostrictive film 1 has a plurality of magnetic domains M (partially schematically shown in FIG. 3) inside, and the piezoelectric film 2 has a plurality of polarization domains P (partially shown schematically in FIG. 3) inside. ).

The magnetostrictive film 1 has unevenness on the first surface 1a on the piezoelectric film 2 side. The piezoelectric film 2 has a second surface 2a on the magnetostrictive film 1 side that follows the first surface 1a. Here, "the second surface 2a follows the first surface 1a" means that, as shown in FIG. It is not limited to the case where they are fitted and the first surface 1a and the second surface 2a match. If the second surface 2a is a convex portion at a position where the first surface 1a is a concave portion with respect to a specific reference plane perpendicular to the lamination direction of the piezoelectric-magnetostrictive composite 10, "the second surface 2a is the first It satisfies the relation "follows surface 1a". That is, if a part of the piezoelectric film 2 enters into the concave portion of the first surface 1a of the magnetostrictive film 1, the relationship "the second surface 2a follows the first surface 1a" is satisfied. For example, when an adhesive layer or the like is provided between the magnetostrictive film 1 and the piezoelectric film 2, the unevenness of the first surface 1a and the unevenness of the second surface 2a may not fit.

The unevenness of the first surface 1a has an average arithmetic roughness of 50 μm or less. The unevenness of the first surface 1a preferably has an average arithmetic roughness of 1 μm or more and 30 μm or less, more preferably 5 μm or more and 10 μm or less. The maximum height of the unevenness of the first surface 1a is preferably 100 μm or less, more preferably 2 μm or more and 80 μm or less, and preferably 10 μm or more and 60 μm or less. The ten-point average roughness Rzjs of the first surface 1a is preferably 100 μm or less, more preferably 2 μm or more and 80 μm or less, and preferably 10 μm or more and 50 μm or less.

The unevenness of the first surface 1a can be determined using, for example, a scanning probe microscope, a non-contact interference microscope, a laser microscope, a contact needle method, or the like.

The magnetostrictive film 1 contains a magnetic material. The magnetostrictive film 1 is preferably made of Co, Pd, Ga, or an Fe-based alloy containing rare earth elements. The magnetostrictive film 1 contains, for example, Tb--Dy--Fe alloy, FeGa alloy, FeCo alloy, or the like. It is particularly preferable that the magnetostrictive film 1 is a Co-excess FeCo alloy containing 67% by mass or more and 87% by mass or less of Co. An FeCo alloy with excessive Co has excellent machinability and excellent magnetostrictive properties.

When the magnetostrictive film 1 contains the FeCo alloy of the bcc structure, the (200) peak and the (211) peak are confirmed by X-ray diffraction (XRD). The peak intensity of the (200) peak in XRD is preferably 5 times or more, more preferably 8 times or more, that of the (211) peak. The magnetic properties of the magnetostrictive film 1 (eg, saturation magnetization, residual magnetization, coercive force) change depending on the crystal orientation of the magnetostrictive film 1 . When the above range is satisfied, the magnetostrictive properties are improved.

The thickness of the magnetostrictive film 1 is preferably 30 μm or more and 1 mm or less, more preferably 50 μm or more and 300 μm or less, and more preferably 80 μm or more and 200 μm or less. If the magnetostrictive film 1 is too thin, it becomes difficult to transport the magnetostrictive film 1 alone. The single magnetostrictive film 1 is easy to handle during manufacturing and is excellent in mass productivity of the piezoelectric-magnetostrictive composite 10 . On the other hand, if the thickness of the magnetostrictive film 1 is too thick, the displacement of the magnetostrictive film 1 against stress becomes small.

The unevenness of the first surface 1a of the magnetostrictive film 1 is formed by surface processing. For surface processing, for example, polishing, sandblasting, or the like can be used. For example, when the first surface 1a of the magnetostrictive film 1 is polished with a #2000 mesh, minute unevenness can be formed on the first surface 1a.

The piezoelectric film 2 contains a polarized piezoelectric material. A piezoelectric body is polarized when a predetermined voltage is applied to the piezoelectric body.

The piezoelectric material is, for example, barium titanate (BaTiO ₃ ), lead zirconate titanate (Pb(Zr,Ti)O ₃ : hereinafter referred to as PZT), potassium niobate (KNbO ₃ ), or the like. Preferably, the piezoelectric material is PZT. PZT has a Curie temperature of 300° C. or higher and exhibits a large piezoelectric effect.

The piezoelectric film 2 preferably includes a resin and a piezoelectric material dispersed in the resin. That is, it is preferable that the piezoelectric body exist in a form dispersed in the resin. The piezoelectric material is dispersed in the resin as particles, fillers, or the like. The piezoelectric body is ceramic and hard. If the piezoelectric material is dispersed in the resin, the piezoelectric material is likely to enter the irregularities of the magnetostrictive film 1 when the piezoelectric film 2 is adhered to the magnetostrictive film 1 .

A resin that can disperse the piezoelectric material and is softer than ceramic is used. For example, an epoxy resin or the like can be used as the resin. For example, Araldite (manufactured by Huntsman Japan), which is an epoxy resin adhesive, can be used.

The thickness of the piezoelectric film 2 is preferably 30 μm or more and 1 mm or less, more preferably 100 μm or more and 700 μm or less, and more preferably 150 μm or more and 500 μm or less. If the piezoelectric film 2 is too thin, it becomes difficult to transport the piezoelectric film 2 alone. The single piezoelectric film 2 is easy to handle during manufacturing, and is excellent in mass productivity of the piezoelectric-magnetostrictive composite 10 . On the other hand, if the thickness of the piezoelectric film 2 is too thick, the piezoelectric magnetostrictive composite 10 becomes large.

The second surface 2a of the piezoelectric film 2 is, for example, laminated with the magnetostrictive film 1 to form unevenness. The unevenness of the second surface 2 a of the piezoelectric film 2 is preferably within the same range as the unevenness of the first surface 1 a of the magnetostrictive film 1 .

The unevenness of the second surface 2a of the piezoelectric film 2 may be formed by surface processing. For surface processing, for example, polishing, sandblasting, or the like can be used. Further, when the piezoelectric film 2 has dispersed piezoelectric bodies, unevenness is formed on the second surface 2a by the dispersed piezoelectric bodies.

An adhesive layer may be provided between the magnetostrictive film 1 and the piezoelectric film 2 . The adhesive layer is preferably thin enough not to fill the unevenness of the first surface 1 a of the magnetostrictive film 1 and the second surface 2 a of the piezoelectric film 2 .

<Coil>
A coil 20 is wound around the piezo-magnetostrictive composite 10 . Coil 20 outputs an induced electromotive force when the magnetic field around piezo-electrostrictive composite 10 changes. The piezoelectric-magnetostrictive composite 10 has excellent magnetostrictive properties, and when the piezoelectric-magnetostrictive composite 10 receives stress, the magnetic field around the piezoelectric-magnetostrictive composite 10 changes greatly. Therefore, the coil 20 can output a large induced electromotive force even with a small number of turns. When the number of turns of the coil 20 is small, the size of the power generation element 100 is reduced.

The power generation element 100 according to this embodiment outputs a large output voltage due to the interaction between the magnetostrictive film 1 and the piezoelectric film 2 on the first surface 1a and the second surface 2a. Microscopic unevenness is formed on the first surface 1a and the second surface 2a to increase the physical contact surface area, thereby promoting electromagnetic interaction between the magnetostrictive film 1 and the piezoelectric film 2. FIG.

When the piezoelectric magnetostrictive composite 10 receives stress, a plurality of polarization domains P are formed near the second surface 2a of the piezoelectric film 2, as shown in FIG. When the polarization domains P are formed, charges are generated on the second surface 2 a of the piezoelectric film 2 . The generated electric charge acts on the vicinity of the first surface 1a of the magnetostrictive film 1 and promotes the generation of magnetic domains M. As shown in FIG. As a result, the magnetic field around the piezo-electrostrictive composite 10 changes significantly, and a large induced electromotive force is generated in the coil 20 . Since the power generation element 100 outputs this induced electromotive force, the output characteristics of the power generation element 100 are improved. Since the first surface 1a and the second surface 2a have unevenness, the magnetic charges (spins) accumulated on the first surface 1a of the magnetostrictive film 1 and the charges (electrons) accumulated on the second surface 2a of the piezoelectric film 2 ) is promoted, and the output characteristics of the power generation element 100 are improved.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments, and various can be transformed or changed.

(Example 1)
<Production of magnetostrictive film>
A 1 mm thick Fe ₃₀ Co ₇₀ alloy was prepared. The prepared Fe ₃₀ Co ₇₀ alloy was cold rolled to produce a magnetostrictive film having a thickness of 0.1 mm, a width of 2.0 mm and a length of 20.0 mm. The surface of the magnetostrictive film was polished with #2000 mesh. After polishing, unevenness was formed on the surface of the magnetostrictive film, and the unevenness had an arithmetic average roughness Ra of 6.85 μm, a maximum height Rz of 50.5 μm, and a ten-point average roughness Rzjs of 43.8 μm. . The produced magnetostrictive film was heated at 580° C. for 1 hour and slowly cooled at room temperature. When the heat-treated magnetostrictive film was measured by XRD, the peak intensity of the (200) peak was seven times the peak intensity of the (211) peak.

<Fabrication of piezoelectric film>
The piezoelectric film was produced by dispersing a piezoelectric material in a resin. PZT powder (C-2 material, Fuji Ceramics) was used as the piezoelectric body. Araldite (manufactured by Huntsman Japan), which is an epoxy resin adhesive, was used as the resin. Araldite and PTZ powder were mixed and stirred at a weight ratio of 1:1. The mixture was poured into molds and left at room temperature for 12 hours to cure. The piezoelectric film had a thickness of 0.3 mm, a width of 2.0 mm, and a length of 20.0 mm. The thickness of the piezoelectric film was adjusted by polishing.

Next, a conductive tape was attached to both surfaces of the produced piezoelectric film, and a polarization treatment was performed using this as an electrode. The polarization treatment was performed by applying a voltage of 1000 V for 30 minutes using a direct current source. The polarization treatment was performed in silicon oil at 100°C.

<Production of power generation element>
A magnetostrictive film was adhered to both surfaces of the produced piezoelectric film to produce a piezoelectric magnetostrictive composite. Concavities and convexities reflecting the concavity and convexity of the surface of the magnetostrictive film were formed on the surface of the piezoelectric film. Adhesion was performed using strain gauge cement CC-33A (manufactured by Kyowa). A coil having 4100 turns, a resistance value of 784Ω, and a wire diameter of 0.03 mm was placed around the manufactured piezoelectric-magnetostrictive composite to form a power generating element.

<Measurement of power generation characteristics>
For power generation characteristics, a power generation element was installed at the base of the cantilever with double-sided tape, and the output voltage output from the power generation element was measured when the cantilever was vibrated using a vibrator. The measurement was performed under the conditions that the cantilever length was 100 mm, the resonance frequency was approximately 40 Hz, and the maximum amplitude at the tip of the cantilever was 15 mm. A bias magnet was installed at the end of the cantilever beam. The measurement results are shown in FIG.

(Comparative example 1)
Comparative Example 1 differs from Example 1 in that the piezoelectric film was not subjected to polarization treatment. Other fabrication and measurement conditions were the same as in Example 1. FIG. 4 shows the measurement results of the power generation element of Comparative Example 1. As shown in FIG.

(Comparative example 2)
Comparative Example 2 is different in that wiring is connected to the magnetostrictive film without winding a coil around the piezoelectric-magnetostrictive composite. That is, in Comparative Example 2, the power generation element was a piezoelectric magnetostrictive composite body connected to a wiring. Other fabrication and measurement conditions were the same as in Example 1. FIG. 4 shows the measurement results of the power generation element of Comparative Example 1. As shown in FIG.

The output voltage of the power generating element according to Example 1 subjected to polarization treatment was higher than the output voltage of the power generating element according to Comparative Example 1 not subjected to polarization treatment. In the power generation element according to Example 1, interaction occurred at the interface between the polarized piezoelectric film and the magnetostrictive film, whereas in the power generation element according to Comparative Example 1, the piezoelectric film was not polarized, so no interaction occurred. It is thought that this is because That is, Example 1 is the output voltage generated by the interaction between the piezoelectric film and the magnetostrictive film, and Comparative Example 1 is the output voltage generated by the magnetostrictive film alone.

Also, the power generating element according to Comparative Example 2 had a lower output voltage than the power generating element according to Example 1. In the power generation element according to Comparative Example 2, the magnetostrictive film merely exists as an electrode. In other words, Comparative Example 2 is the output voltage produced by the piezoelectric film alone.

Therefore, it was confirmed that the power generating element according to Example 1 exhibits a high output voltage due to the interaction between the piezoelectric film and the magnetostrictive film.

1 Magnetostrictive Film 2 Piezoelectric Film 10 Piezoelectric Electrostrictive Composite 20 Coil 100 Power Generation Element

Claims (4)

a piezoelectric film including a polarized piezoelectric body;
a magnetostrictive film laminated on at least one surface of the piezoelectric film;
a first surface of the magnetostrictive film on the piezoelectric film side has irregularities with an arithmetic mean roughness Ra of 50 μm or less,
A piezoelectric magnetostrictive composite, wherein a second surface of the piezoelectric film on the magnetostrictive film side follows the irregularities of the first surface. 2. The piezoelectric magnetostrictive composite according to claim 1, wherein said magnetostrictive film is laminated on both sides of said piezoelectric film. 3. The piezoelectric magnetostrictive composite according to claim 1, wherein said piezoelectric film comprises a resin and a piezoelectric material dispersed in said resin. A piezoelectric magnetostrictive composite according to any one of claims 1 to 3;
and a coil wound around the piezoelectric-magnetostrictive composite.

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