Thermoelectric conversion element

Abstract

A thermoelectric conversion element 1a is provided with a base material 10 and a magnetic body 21. The magnetic body 21 is disposed on the base material 10 and has ferromagnetic or antiferromagnetic properties. The magnetic body 21 has internal stress of 900 MPa or less.

Description

thermoelectric conversion element

[0001] The present invention relates to a thermoelectric conversion element.

[0002] 2. Description of the Related Art Conventionally, thermoelectric conversion elements that utilize the magneto-thermoelectric effect have been known.

[0003] For example, Patent Document 1 describes a thermoelectric power generation device that utilizes the anomalous Nernst effect. The anomalous Nernst effect is a phenomenon in which, when a heat flow is passed through a magnetic material, a voltage is generated in a direction perpendicular to both the magnetization direction and the temperature gradient when a temperature difference occurs. The thermoelectric power generation device includes a substrate, a power generation body, and a connector. At least the surface layer of the substrate is made of MgO. The power generation body is made of multiple thin wires arranged parallel to each other along the surface of the substrate. Each thin wire is made of a ferromagnetic material and magnetized in the same direction. The connector is made of multiple thin wires arranged parallel to and between the thin wires of the power generation body. Each thin wire of the connector electrically connects one end of each thin wire of the power generation body to the other end of the adjacent thin wire on one side of each thin wire.

[0004] Japanese Patent Application Laid-Open No. 2014-072256

[0005] In Patent Document 1, the thin wires of the power generating element made of a ferromagnetic material are connected in series by connectors. This is thought to generate a high electromotive force in the thermoelectric power generating device. However, if a break occurs in any of the thin wires of the heating element or connectors due to a crack or the like, it is thought that the overall function of the thermoelectric power generating device will be impaired.

[0006] It is believed that if a thermoelectric conversion element utilizing the magneto-thermoelectric effect can be used in various environments, the value of the thermoelectric conversion element can be further increased. However, according to Patent Document 1, the durability of the thermoelectric power generation device in a specific environment is not considered at all.

[0007] In view of the above circumstances, the present invention provides a thermoelectric conversion element that utilizes the magneto-thermoelectric effect and is advantageous in that it exhibits high durability in high-temperature and high-humidity environments.

[0008] The present invention provides a thermoelectric conversion element comprising: a substrate; and a magnetic body disposed on the substrate and having ferromagnetic or antiferromagnetic properties, wherein the magnetic body has an internal stress of 900 MPa or less.

[0009] The thermoelectric conversion element described above is advantageous in that it utilizes the magneto-thermoelectric effect and exhibits high durability in high-temperature and high-humidity environments.

[0010] Fig. 1 is a perspective view showing an example of a thermoelectric conversion element according to the present invention. Fig. 2 is a cross-sectional view of the thermoelectric conversion element cut along plane II shown in Fig. 1. Fig. 3 is a schematic diagram showing a method for measuring internal stress in a magnetic body.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0012] As shown in FIG. 1 , the thermoelectric conversion element 1a includes a substrate 10 and a magnetic body 21. The magnetic body 21 is disposed on the substrate 10 and has ferromagnetic or antiferromagnetic properties. The magnetic body 21 has an internal stress of 900 MPa or less. In this specification, when the internal stress value is positive, the internal stress is tensile stress, and when the internal stress value is negative, the internal stress is compressive stress. By adjusting the internal stress in the magnetic body 21 to fall within this range, defects and cracks are less likely to occur in the magnetic body 21, even when the thermoelectric conversion element 1a is placed in a high-temperature, high-humidity environment. As a result, the thermoelectric conversion element 1a is likely to exhibit high durability in a high-temperature, high-humidity environment. In addition, even when bending stress is applied to the thermoelectric conversion element 1a, defects and cracks are less likely to occur in the magnetic body 21. Therefore, the thermoelectric conversion element 1a is likely to exhibit high durability even when bending stress is applied to the thermoelectric conversion element 1a. The internal stress of the magnetic body 21 can be measured, for example, according to the method described in the Examples. 1 and 2, the X-axis, Y-axis, and Z-axis are perpendicular to one another, and the Z-axis direction is the thickness direction of the substrate 10.

[0013] In this specification, the high-temperature, high-humidity environment is not limited to a specific environment. For example, the high-temperature, high-humidity environment is an environment having a temperature of 60°C to 120°C and a relative humidity of 60% or more. An example of a high-temperature, high-humidity environment is an environment having a temperature of 85°C and a relative humidity of 85%.

[0014] The internal stress in the magnetic body 21 may be 800 MPa or less, 700 MPa or less, or 600 MPa or less. The internal stress in the magnetic body 21 is preferably 500 MPa or less. In this case, the thermoelectric conversion element 1a is more likely to exhibit high durability in a high-temperature, high-humidity environment. In addition, the thermoelectric conversion element 1a is more likely to exhibit high durability even when bending stress is applied to the thermoelectric conversion element 1a. The internal stress in the magnetic body 21 may be 400 MPa or less, 300 MPa or less, or 200 MPa or less.

[0015] The internal stress in the magnetic body 21 is more preferably 100 MPa or less. In this case, the thermoelectric conversion element 1a is likely to exhibit higher durability in a high-temperature, high-humidity environment. In addition, the thermoelectric conversion element 1a is likely to exhibit higher durability even when a bending stress is applied to the thermoelectric conversion element 1a. The internal stress in the magnetic body 21 may be 0 MPa or less, -100 MPa or less, or -200 MPa or less.

[0016] The internal stress in the magnetic body 21 is more preferably -300 MPa or less. In this case, the thermoelectric conversion element 1a is likely to exhibit higher durability even when a bending stress is applied to the thermoelectric conversion element 1a. The internal stress in the magnetic body 21 is, for example, -2000 MPa or more. The internal stress in the magnetic body 21 may be -1500 MPa or more, -1000 MPa or more, or -500 MPa or more.

[0017] The magnetic body 21 is not limited to a specific material as long as it has an internal stress of 900 MPa or less. For example, the magnetic body 21 generates an electromotive force in a direction perpendicular to the thickness direction of the substrate 10 when a temperature gradient ∇T occurs in the thickness direction (Z-axis direction) of the substrate 10. This eliminates the need to significantly adjust the thickness of the thermoelectric conversion element 1a to increase the power generated by the temperature gradient in the thermoelectric conversion element 1a, as in thermoelectric conversion elements that utilize the Seebeck effect. For example, by increasing the dimension of the magnetic body 21 in a specific direction along the main surface of the substrate 10, the power generated by the temperature gradient ∇T in the thermoelectric conversion element 1a can be increased. This makes it easier to reduce the thickness of the thermoelectric conversion element 1a.

[0018] The magnetic body 21 generates an electromotive force by, for example, the magneto-thermoelectric effect. The magneto-thermoelectric effect is, for example, the anomalous Nernst effect or the spin Seebeck effect. This makes it easy for the thermoelectric conversion element 1 a to generate a large amount of electric power due to a temperature gradient even if the thermoelectric conversion element 1 a is thin.

[0019] The magnetic body 21 includes, for example, a material that exhibits the anomalous Nernst effect. The material that exhibits the anomalous Nernst effect is not limited to a specific material. The material that exhibits the anomalous Nernst effect may be, for example, 5×10 -3 The magnetic material 21 is a magnetic material having a saturation magnetic susceptibility of 1000 kJ or more, or a material having a band structure with a Weyl point near the Fermi energy. The magnetic material 21 contains, as a material exhibiting the anomalous Nernst effect, at least one material selected from the group consisting of the following (i), (ii), (iii), (iv), and (v): (i) a stoichiometric material having a composition represented by Fe3X; (ii) an off-stoichiometric material in which the composition ratio of Fe to X deviates from that of the material (i) above; (iii) a material in which part of the Fe sites of the material (i) above or part of the Fe sites of the material (ii) above are substituted with a main group metal element or transition element other than X; (iv) Fe3M1 1-x M2 x(v) A substance having a composition expressed by (0<x<1), in which M1 and M2 are different typical group elements. (i) A substance in which a part of the Fe site of the substance (i) is substituted with a transition element other than X, and a part of the X site of the substance (i) is substituted with a typical metal element other than X.

[0020] In the above substances (i) to (v), X is a typical element or a transition element. X is, for example, Al, Ga, Ge, Sn, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Sc, Ni, Mn, or Co. In the above substance (iv), the combination of M1 and M2 is not limited to a specific combination as long as M1 and M2 are different typical elements. In the above substance (iv), the combination of M1 and M2 is, for example, Ga and Al, Si and Al, or Ga and B.

[0021] The magnetic body 21 may contain Co2MnGa or Mn3Sn as a material that exhibits the anomalous Nernst effect.

[0022] As shown in Figures 1 and 2, the magnetic body 21 is formed, for example, in the shape of a rectangular parallelepiped elongated in a specific direction (Y-axis direction) extending along the main surface of the substrate 10. The magnetic body 21 is magnetized, for example, in the negative direction of the X-axis. When a temperature gradient occurs in the thickness direction of the substrate 10 and a heat flow occurs in the positive direction of the Z-axis, the magneto-thermoelectric effect generates an electromotive force in the positive direction of the Y-axis, which is perpendicular to the Z-axis and X-axis. As described above, the dimension of the magnetic body 21 in the Y-axis direction is larger than the dimensions of the magnetic body 21 in the Z-axis and X-axis, and the electromotive force generated by the magneto-thermoelectric effect is likely to be large. Therefore, even if the magnetic body 21 does not have a large thickness, the electromotive force generated in the thermoelectric conversion element 1a is likely to be large.

[0023] As shown in FIG. 1 , the thermoelectric conversion element 1a includes, for example, a conductive path 25. The conductive path 25 includes a magnetic material 21 and has a meander pattern. This makes it easy to increase the length of the conductive path 25, which increases the electromotive force generated in the thermoelectric conversion element 1a. For example, by connecting wiring to one end 25p and the other end 25q of the conductive path 25, the electromotive force generated in the thermoelectric conversion element 1a can be extracted to the outside. Alternatively, by applying a voltage between the one end 25p and the other end 25q, a heat flow can be generated in the thickness direction of the substrate 10.

[0024] As shown in FIG. 1 , the conductive path 25 includes a plurality of magnetic bodies 21. The magnetic bodies 21 are, for example, spaced apart at a predetermined interval in the X-axis direction and arranged parallel to one another. For example, the magnetic bodies 21 are arranged at equal intervals in the X-axis direction. The conductive path 25 further includes, for example, a plurality of connectors 22. The connectors 22 electrically connect adjacent magnetic bodies 21 in the X-axis direction. The connectors 22 electrically connect, for example, one end of a magnetic body 21 in the Y-axis direction to the other end of another magnetic body 21 adjacent to that magnetic body 21 in the Y-axis direction. With this configuration, the magnetic bodies 21 are electrically connected in series, which tends to increase the electromotive force generated in the thermoelectric conversion element 1a. One end of each of the magnetic bodies 21 in the Y-axis direction is located on the same side of the magnetic body 21 in the Y-axis direction, and the other end of each of the magnetic bodies 21 in the Y-axis direction is located on the opposite side of the one end of the magnetic body 21 in the Y-axis direction.

[0025] As shown in FIG. 1 , the connectors 22 are formed, for example, in the shape of a rectangular parallelepiped elongated in the Y-axis direction. As long as the connectors 22 can electrically connect adjacent magnetic bodies 21, the material of the connectors 22 is not limited to a specific material. The connectors 22 may contain a substance that generates an electromotive force due to the magneto-thermoelectric effect, and may have, for example, ferromagnetic or antiferromagnetic properties. In this case, the connectors 22 are magnetized, for example, in the positive direction of the X-axis. As a result, when a temperature gradient occurs in the thickness direction of the substrate 10 and a heat flow occurs in the positive direction of the Z-axis, an electromotive force is generated in the negative direction of the Y-axis, which is perpendicular to the Z-axis and the X-axis. This makes it easier for the electromotive force generated in the thermoelectric conversion element 1a to be large. The connectors 22 may also contain a non-magnetic material. In this case, the material of the connectors 22 is, for example, a paramagnetic transition element. The non-magnetic material contained in the connectors 22 is, for example, gold, copper, a copper alloy, aluminum, or an aluminum alloy. The connectors 22 may also be a hardened conductive paste.

[0026] The substrate 10 is not limited to a specific substrate as long as the magnetic body 21 has an internal stress of 900 MPa or less. The substrate 10 may be flexible, for example. This allows the thermoelectric conversion element 1a to be arranged along a curved surface. The substrate 10 has elasticity that allows elastic deformation of a strip-shaped test specimen made from the substrate 10 when the test specimen is wound around a cylindrical mandrel with a diameter of 10 cm so that both ends of the strip-shaped test specimen face in the same direction. The substrate 10 may also be a non-flexible substrate, such as a glass substrate.

[0027] When the substrate 10 is flexible, the substrate 10 contains at least an organic polymer, for example. This facilitates reducing the manufacturing cost of the thermoelectric conversion element 1 a. Examples of the organic polymer include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), polycarbonate (PC), polyimide (PI), or cycloolefin polymer (COP).

[0028] As long as the magnetic body 21 has an internal stress of 900 MPa or less, the linear expansion coefficient of the substrate 10 is not limited to a specific value. -5 / °C or more. This makes it easy to apply compressive stress to the magnetic body 21 as the substrate 10 thermally shrinks when the magnetic body 21 is formed. As a result, the internal stress of the magnetic body 21 can be easily adjusted to a desired range. In this specification, the linear expansion coefficient means the average value in the temperature range of 25°C to 150°C.

[0029] The linear expansion coefficient of the substrate 10 is 1.5×10 -5 / °C or more, and may be 2.0 x 10 -5 / °C or more, and may be 2.5 x 10 -5 / °C or more, and may be 3.0 x 10 -5 / °C or more, and may be 4.0 x 10 -5 / °C or more, and may be 5.0 x 10 -5 / °C or more, and may be 6.0 x 10 -5 / °C or more, and -5 / °C or more, and may be 8.0 x 10 -5 The linear expansion coefficient of the substrate 10 may be, for example, 15×10 -5 / ° C. or less. This makes it easy to apply tensile stress to the magnetic body 21, and makes it easy to adjust the internal stress of the magnetic body 21 to a desired range.

[0030] The thickness of the substrate 10 is not limited to a specific value as long as the magnetic body 21 has an internal stress of 900 MPa or less. The thickness of the substrate 10 is, for example, 200 μm or less. This makes it easy to deform and arrange the thermoelectric conversion elements 1 a along the curved surface.

[0031] The thickness of the substrate 10 may be 190 μm or less, 180 μm or less, 170 μm or less, or 160 μm or less. The thickness of the substrate 10 may be 150 μm or less, 140 μm or less, 130 μm or less, 120 μm or less, or 110 μm or less. The thickness of the substrate 10 may be 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less. The thickness of the substrate 10 is, for example, 10 μm or more. This makes the substrate 10 easy to transport and provides the desired handleability. The thickness of the substrate 10 may be 20 μm or more, or 30 μm or more.

[0032] The thickness of the magnetic body 21 is not limited to a specific value as long as the magnetic body 21 has an internal stress of 900 MPa or less. The magnetic body 21 has a thickness of, for example, 1000 nm or less. This reduces the amount of material used to form the magnetic body 21 in the thermoelectric conversion element 1a, making it easier to reduce the manufacturing cost of the thermoelectric conversion element 1a. In addition, breaks in the conductive paths 25 in the thermoelectric conversion element 1a are less likely to occur.

[0033] The thickness of the magnetic body 21 may be 750 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. The thickness of the magnetic body 21 is, for example, 5 nm or more. This makes it easier for the thermoelectric conversion element 1a to exhibit high durability. The thickness of the magnetic body 21 may be 10 nm or more, 20 nm or more, 30 nm or more, or 50 nm or more.

[0034] As long as the magnetic body 21 has an internal stress of 900 MPa or less, the width of each magnetic body 21 in the X-axis direction is not limited to a specific value. The width of each magnetic body 21 is, for example, 500 μm or less. This reduces the amount of material used to form the magnetic body 21 in the thermoelectric conversion element 1a, thereby facilitating a reduction in the manufacturing cost of the thermoelectric conversion element 1a. Additionally, it is easy to arrange a large number of magnetic bodies 21 in the X-axis direction, which increases the electromotive force generated in the thermoelectric conversion element 1a. It is believed that a small width of the magnetic body makes it more likely to crack in a high-temperature, high-humidity environment. Furthermore, it is believed that a small width of the magnetic body makes it more likely to develop defects and cracks when bending stress is applied to a thermoelectric conversion element including such a magnetic body. However, by having an internal stress of 900 MPa or less, even when the magnetic body has a width of 500 μm or less, cracks are less likely to develop in the magnetic body in a high-temperature, high-humidity environment. In addition, even if bending stress is applied to the thermoelectric conversion element 1a, defects and cracks are unlikely to occur in the magnetic body 21.

[0035] As described above, the thermoelectric conversion element 1a includes, for example, the conductive path 25, which forms a meander pattern including the magnetic body 21. In this case, the magnetic body 21 has a line width of 500 μm or less in the meander pattern. Even in such a case, since the magnetic body 21 has an internal stress of 900 MPa or less, cracks are unlikely to occur in the magnetic body in a high-temperature, high-humidity environment. In addition, even if bending stress is applied to the thermoelectric conversion element 1a, defects and cracks are unlikely to occur in the magnetic body 21.

[0036] The width of each magnetic body 21 may be 400 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, or 50 μm or less. The width of each magnetic body 21 is, for example, 0.1 μm or more. This makes it less likely that the conductive path 25 in the thermoelectric conversion element 1a will break, and the thermoelectric conversion element 1a is more likely to exhibit high durability. The width of each magnetic body 21 may be 0.5 μm or more, 1 μm or more, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more.

[0037] As long as the connector 22 can electrically connect adjacent magnetic bodies 21, the thickness of the connector 22 is not limited to a specific value. The thickness of the connector 22 is, for example, 1000 nm or less. This reduces the amount of material used to form the connector 22, making it easier to reduce the manufacturing cost of the thermoelectric conversion element 1a. In addition, breaks in the conductive path 25 in the thermoelectric conversion element 1a are less likely to occur. The thickness of the connector 22 may be 750 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, or 100 nm or less.

[0038] The thickness of the connector 22 is, for example, 5 nm or more. This makes it easier for the thermoelectric conversion element 1 a to exhibit high durability. The thickness of the connector 22 may be 10 nm or more, 20 nm or more, 30 nm or more, or 50 nm or more.

[0039] As long as the connecting bodies 22 can electrically connect adjacent magnetic bodies 21 to each other, the width, which is the minimum dimension in the X-axis direction, of each connecting body 22 is not limited to a specific value. The width of each connecting body 22 is, for example, 500 μm or less. This reduces the amount of material used to form the connecting bodies 22 in the thermoelectric conversion element 1a, making it easier to reduce the manufacturing cost of the thermoelectric conversion element 1a. In addition, it is easy to arrange a large number of magnetic bodies 21 in the X-axis direction, making it easier to increase the electromotive force generated in the thermoelectric conversion element 1a.

[0040] The width of each connector 22 may be 400 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, or 50 μm or less. The width of each connector 22 is, for example, 0.1 μm or more. This makes it less likely that the conductive path 25 in the thermoelectric conversion element 1a will break, and the thermoelectric conversion element 1a is more likely to exhibit high durability. The width of each connector 22 may be 0.5 μm or more, 1 μm or more, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 30 μm or more.

[0041] An example of a manufacturing method of the thermoelectric conversion element 1a will be described. First, a thin film of precursors of the magnetic material 21 is formed on one main surface of the substrate 10 by a method such as sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), ion plating, or plating. Next, a photoresist is applied to the thin film, a photomask is placed on the thin film, and exposure is performed, followed by wet etching. This forms a linear pattern of precursors of multiple magnetic materials 21 arranged at predetermined intervals. Next, a thin film of precursors of the connectors 22 is formed on one main surface of the substrate 10 by a method such as sputtering, CVD, PLD, ion plating, or plating. Next, a photoresist is applied to the thin film of precursors of the connectors 22, a photomask is placed on the thin film of precursors of the connectors 22, and exposure is performed, followed by wet etching. This results in the connectors 22, and the linear patterns of precursors of the magnetic material 21 are electrically connected to each other. Next, the precursors of the magnetic material 21 are magnetized to form the magnetic materials 21. In this way, the thermoelectric conversion element 1a is obtained. If necessary, the precursor of the connector 22 may be magnetized to form the connector 22.

[0042] The internal stress in the magnetic body 21 can be adjusted to a desired range by adjusting the conditions for forming the precursor thin film of the magnetic body 21. For example, when forming the precursor thin film of the magnetic body 21 by sputtering, the internal stress in the magnetic body 21 can be adjusted to a desired range by adjusting the pressure of the atmosphere around the substrate 10 where sputtering is performed, the temperature of the substrate 10, the distance between the target and the substrate, and the magnetic flux density.

[0043] When forming a thin film of the precursor of the magnetic material 21 by sputtering, the pressure of the atmosphere around the substrate 10 where sputtering is performed (process pressure) is not limited to a specific value as long as the internal stress of the magnetic material 21 is 900 MPa or less. The process pressure is, for example, 1.0 Pa. This makes it easy to adjust the internal stress of the magnetic material 21 to 900 MPa or less even when the substrate 10 contains an organic material. The process pressure is preferably 0.5 Pa or less, and more preferably 0.3 Pa or less. The process pressure is, for example, 0.05 Pa or more. This makes it easy for discharge to occur even when the target in sputtering is a magnetic material, and allows for stable formation of a thin film of the precursor of the magnetic material 21.

[0044] When forming a thin film of the precursor of the magnetic material 21 by sputtering, the TS distance, which is the distance between the target and the substrate, is not limited to a specific value as long as the internal stress of the magnetic material 21 is 900 MPa or less. The TS distance is, for example, 120 mm or less. This makes it easy to adjust the internal stress of the magnetic material 21 to 900 MPa or less even when the substrate 10 contains an organic material. The TS distance is preferably 100 mm or less, and may be 80 mm or less, or 60 mm or less. The TS distance is, for example, 40 mm or more. This makes it easy for discharge to occur even when the target in sputtering is a magnetic material, and allows for stable formation of a thin film of the precursor of the magnetic material 21.

[0045] When forming a thin film of the precursor of the magnetic material 21 by sputtering, the magnetic field conditions are not limited to specific conditions as long as the internal stress of the magnetic material 21 is 900 MPa or less. For example, the magnetic flux density in sputtering is 150 mT or less. This makes it easy to adjust the internal stress of the magnetic material 21 to 900 MPa or less even when the substrate 10 contains an organic material. The magnetic flux density may be 120 mT or less. The magnetic flux density is, for example, 30 mT or more. This makes it easy to generate discharge even when the target in sputtering is a magnetic material, and allows for stable formation of a thin film of the precursor of the magnetic material 21. The magnetic flux density may be 50 mT or more, or 70 mT or more.

[0046] The thermoelectric conversion element 1 a may be provided together with, for example, an adhesive layer. In this case, the substrate 10 is disposed between the magnetic material 21 and the adhesive layer in the thickness direction of the substrate 10. This allows the thermoelectric conversion element 1 a to be attached to an article by pressing the adhesive layer against the article.

[0047] The adhesive layer contains, for example, a rubber-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, or a urethane-based adhesive. The thermoelectric conversion element 1a may be provided together with an adhesive layer and a separator. In this case, the separator covers the adhesive layer. The separator is typically a film that can maintain the adhesive force of the adhesive layer while covering the adhesive layer and can be easily peeled off from the adhesive layer. The separator is, for example, a film made of a polyester resin such as PET. By peeling off the separator, the adhesive layer is exposed, allowing the thermoelectric conversion element 1a to be attached to an article.

[0048] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. First, evaluation methods for the examples and comparative examples will be described.

[0049] [Measurement of Internal Stress] Using an X-ray diffraction apparatus RINT2200 manufactured by Rigaku Corporation, Cu-Kα rays from a light source of 40 kV and 40 mA were irradiated onto the sample through a parallel beam optical system, and sin 2 The internal stress of the magnetic material in each example and comparative example was evaluated using the principle of the Ψ method. The wavelength λ of the Cu-Kα ray was 0.1541 nm. 2The Ψ method is a technique for determining the internal stress of a polycrystalline thin film from the dependence of the crystal lattice distortion of the thin film on the angle (Ψ). Using the X-ray diffraction device described above, the diffraction intensity was measured at 0.02° intervals in the 2θ range of 40° to 50° by θ / 2θ scan measurement. The integration time at each measurement point was set to 100 seconds. The crystal lattice spacing d of the magnetic material at each measurement angle (Ψ) was calculated from the peak angle 2θ of the obtained X-ray diffraction and the wavelength λ of the X-rays emitted from the light source. The crystal lattice distortion ε was calculated from the crystal lattice spacing d using the relationships in the following formulas (1) and (2). λ is the wavelength of the X-rays (Cu-Kα rays) emitted from the light source, and λ = 0.1541 nm. d0 is the lattice spacing of the magnetic material in a stress-free state, and d0 = 0.0206 nm. 2d sin θ = λ Equation (1) ε = (d - d0) / d0 Equation (2)

[0050] As shown in Figure 3, the angle (Ψ) between the normal to the main surface of the magnetic sample Sa and the normal to the crystal plane of the magnetic material Mb was 45°, 52°, 60°, 70°, and 90°, and the above-mentioned X-ray diffraction measurement was performed to calculate the crystal lattice strain ε at each angle (Ψ). Then, the residual stress (internal stress) σ in the in-plane direction of the magnetic material was calculated using sin 2 The relationship between Ψ and crystal lattice distortion ε was plotted and the slope of the line was calculated using the following formula (3). The results are shown in Table 1. Note that in Table 1, positive values ​​for the internal stress indicate tensile stress, and negative values ​​indicate compressive stress. ε = {(1 + ν) / E}σ sin 2 Ψ-(2ν / E)σ Equation (3)

[0051] In the above formula (3), E is the Young's modulus of the magnetic material (210 GPa), and v is the Poisson's ratio of the magnetic material (0.3). In the above diagram, the detector 100 detects X-ray diffraction.

[0052] [High-Temperature, High-Humidity Environmental Test] The thermoelectric conversion elements according to each example and comparative example were subjected to a durability test at a temperature of 85°C and a relative humidity of 85% for 24 hours. The electrical resistance value R of the meander pattern in the thermoelectric conversion element before the durability test and the electrical resistance value R of the meander pattern in the thermoelectric conversion element after the durability test were measured. t Measured and 100 × (R tThe value of (−R0) / R0 was calculated as the resistance change rate. The results are shown in Table 1.

[0053] [Flexibility Evaluation] Strip-shaped test specimens were prepared from the thermoelectric conversion elements according to each Example and Comparative Example. The test specimens were wound around horizontally fixed cylindrical mandrels having the following diameters, and 100 g weights were attached to both ends of the test specimens to apply a load. The test specimens were then checked for the presence or absence of breakage in the meander pattern. Breakage in the meander pattern was determined when the electrical resistance of the meander pattern reached 1.5 times or more the initial value. In each Example and Comparative Example, mandrels were selected in descending order of mandrel diameter, and the maximum mandrel diameter at which breakage in the meander pattern occurred was determined. The results are shown in Table 1. (Mandrel diameters) 21.5 mm, 20 mm, 18.5 mm, 17 mm, 15.5 mm, 14 mm, 12.5 mm, 11 mm, 9.5 mm, 8 mm, 6.5 mm, 5 mm

[0054] A sample for evaluating thermoelectric properties was prepared by fixing the thermoelectric conversion element according to each example and comparative example between a pair of Cu plates measuring 30 mm, 30 mm, and 5 mm using silicone grease KS609 manufactured by Shin-Etsu Chemical Co., Ltd. This sample was placed on a cooling plate SCP-125 manufactured by AS ONE Corporation. A film heater manufactured by Shinwa Measuring Co., Ltd. was fixed on top of the upper Cu plate using double-sided tape No. 5000NS manufactured by Nitto Denko Corporation. This heater had dimensions of 30 mm square and an electrical resistance of 20 Ω. With the temperature of the cooling plate maintained at 25°C, the film heater was heated under constant voltage control of 10 V, and the heat output from the film heater was 0.52 W / cm. 2 At this time, the electromotive force generated in the thermoelectric conversion element was measured using a data logger, and the value of the electromotive force per unit area in a steady state was read by dividing it by the area of ​​the thermoelectric conversion element. The results are shown in Table 1.

[0055] Example 1 A thin film having a thickness of 96 nm was formed on a polyethylene terephthalate (PET) film having a thickness of 50 μm by DC magnetron sputtering using a target material containing Fe and Ga. In this target material, the atomic ratio of Fe content to Ga content was 3:1. In the DC magnetron sputtering, the distance between the target material and the PET film was adjusted to 75 mm. In addition, in the DC magnetron sputtering, a magnet having a magnetic flux density of 100 mT was used, and argon gas was supplied as the process gas at a pressure of 0.1 Pa. In addition, the temperature of the PET film was adjusted to 130° C. The linear expansion coefficient of the PET film was 7.0×10 -5 / °C. Photoresist was applied to the thin film, and a photomask was placed on the thin film to perform exposure, followed by wet etching. This resulted in the formation of 98 FeGa-containing linear patterns arranged at predetermined intervals. Each FeGa-containing linear pattern had a width of 100 μm, a length of 15 mm, and a total length of the FeGa linear patterns of 147 cm. A Cu-containing target material was then used to form a Cu thin film having a thickness of 100 nm by DC magnetron sputtering. Photoresist was applied to the Cu thin film, and a photomask was placed on the Cu thin film to perform exposure, followed by wet etching. This resulted in the formation of Cu-containing linear patterns having a width of 40 μm. Pairs of adjacent FeGa-containing linear patterns were electrically connected by the Cu-containing linear patterns, forming conductive paths forming a meander pattern. Using an electromagnet with a central magnetic flux density of 0.5 T, the FeGa-containing linear pattern was magnetized in a direction parallel to the plane of the PET film and perpendicular to the longitudinal direction of the FeGa-containing linear pattern to form a magnetic body. The thickness of the magnetic body was 96 nm. In this way, a thermoelectric conversion element according to Example 1 was obtained. This thermoelectric conversion element generated an electromotive force based on the anomalous Nernst effect.

[0056] Example 2 A thermoelectric conversion element according to Example 2 was obtained in the same manner as Example 1, except that argon gas was supplied as the process gas at a pressure of 0.2 Pa. The thickness of the magnetic body in the thermoelectric conversion element according to Example 2 was 96 nm.

[0057] Example 3 A thermoelectric conversion element according to Example 3 was obtained in the same manner as Example 1, except that argon gas was supplied as the process gas at a pressure of 0.9 Pa. The thickness of the magnetic body in the thermoelectric conversion element according to Example 3 was 89 nm.

[0058] Example 4 A thermoelectric conversion element according to Example 4 was obtained in the same manner as in Example 1, except that a polyimide (PI) film having a thickness of 50 μm was used instead of the PET film and the temperature of the PI film was adjusted to 25° C. in DC magnetron sputtering. The thickness of the magnetic body in the thermoelectric conversion element according to Example 4 was 100 nm.

[0059] Example 5 A thermoelectric conversion element according to Example 5 was obtained in the same manner as in Example 1, except that in DC magnetron sputtering, the temperature of the PET film was adjusted to 100°C and argon gas was supplied as the process gas at a pressure of 0.2 Pa. The thickness of the magnetic body in the thermoelectric conversion element according to Example 5 was 96 nm.

[0060] Example 6 A thermoelectric conversion element according to Example 6 was obtained in the same manner as in Example 1, except that in DC magnetron sputtering, the temperature of the PET film was adjusted to 50°C and argon gas was supplied as the process gas at a pressure of 0.2 Pa. The thickness of the magnetic body in the thermoelectric conversion element according to Example 6 was 96 nm.

[0061] Example 7 A thermoelectric conversion element according to Example 7 was obtained in the same manner as in Example 1, except that in DC magnetron sputtering, the temperature of the PET film was adjusted to 25° C. The thickness of the magnetic body in the thermoelectric conversion element according to Example 7 was 96 nm.

[0062] Example 8 A thermoelectric conversion element according to Example 8 was obtained in the same manner as in Example 1, except that the wet etching conditions were adjusted so that the width of each FeGa-containing linear pattern was 50 μm. The thickness of the magnetic body in the thermoelectric conversion element according to Example 8 was 96 nm.

[0063] Example 9 A thermoelectric conversion element according to Example 9 was obtained in the same manner as in Example 1, except that the wet etching conditions were adjusted so that the width of each FeGa-containing linear pattern was 200 μm. The thickness of the magnetic body in the thermoelectric conversion element according to Example 9 was 96 nm.

[0064] Example 10 A thermoelectric conversion element according to Example 10 was obtained in the same manner as in Example 1, except that the wet etching conditions were adjusted so that the width of each FeGa-containing linear pattern was 300 μm. The thickness of the magnetic body in the thermoelectric conversion element according to Example 10 was 96 nm.

[0065] Example 11 A thermoelectric conversion element according to Example 11 was obtained in the same manner as in Example 1, except that the wet etching conditions were adjusted so that the width of each FeGa-containing linear pattern was 400 μm. The thickness of the magnetic body in the thermoelectric conversion element according to Example 11 was 96 nm.

[0066] <Comparative Example 1> A thermoelectric conversion element according to Comparative Example 1 was obtained in the same manner as in Example 1, except that argon gas was supplied as the process gas at a pressure of 1.6 Pa. The thickness of the magnetic body in the thermoelectric conversion element according to Comparative Example 1 was 85 nm.

[0067] Comparative Example 2 A thermoelectric conversion element according to Comparative Example 2 was obtained in the same manner as in Example 1, except that in DC magnetron sputtering, argon gas was supplied as the process gas at a pressure of 1.6 Pa and the wet etching conditions were adjusted so that the width of each FeGa-containing linear pattern was 1000 μm. The thickness of the magnetic body in the thermoelectric conversion element according to Comparative Example 2 was 85 nm. This thermoelectric conversion element did not exhibit an electromotive force based on the anomalous Nernst effect.

[0068] As shown in Table 1, the internal stress of the magnetic body of the thermoelectric conversion element according to each example was 900 MPa or less, and the internal stress of the magnetic body of the thermoelectric conversion element according to the comparative example exceeded 900 MPa. The resistance change rate in the durability test of the thermoelectric conversion element according to each example was significantly lower than the resistance change rate in the durability test of the thermoelectric conversion element according to the comparative example, suggesting that by adjusting the internal stress of the magnetic body to 900 MPa or less, the thermoelectric conversion element can exhibit high durability in a high-temperature, high-humidity environment.

[0069] As shown in Table 1, the maximum mandrel diameter at which wire breakage occurred in the bending test of the thermoelectric conversion elements according to each example was smaller than the maximum mandrel diameter at which wire breakage occurred in the bending test of the thermoelectric conversion elements according to the comparative example. This suggests that by adjusting the internal stress of the magnetic body to 900 MPa or less, the thermoelectric conversion elements can exhibit good durability when bent.

[0070] As shown in Table 1, the measurement results of the thermoelectric power of each thermoelectric conversion element showed that the thermoelectric power of the thermoelectric conversion element according to the example was greater than that of the thermoelectric conversion element according to Comparative Example 2. It was shown that by adjusting the internal stress of the magnetic body to 900 MPa or less and the line width of the magnetic body to 500 μm or less, it is possible to exhibit good durability when bent while generating an electromotive force based on the anomalous Nernst effect.

[0071]

[0072] A first aspect of the present invention provides a thermoelectric conversion element comprising: a substrate; and a magnetic body disposed on the substrate and having ferromagnetic or antiferromagnetic properties, wherein the magnetic body has an internal stress of 900 MPa or less.

[0073] A second aspect of the present invention provides the thermoelectric conversion element according to the first aspect, wherein the substrate is flexible.

[0074] A third aspect of the present invention provides the thermoelectric conversion element according to the second aspect, wherein the substrate contains at least an organic polymer.

[0075] A fourth aspect of the present invention is a thermoelectric conversion element according to any one of the first to third aspects, wherein the substrate has a surface roughness of 1.0×10 -5 The present invention provides a thermoelectric conversion element having a linear expansion coefficient of 1 / °C or more.

[0076] A fifth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to fourth aspects, wherein the substrate has a thickness of 200 μm or less.

[0077] A sixth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to fifth aspects, wherein the magnetic body has a thickness of 1000 nm or less.

[0078] A seventh aspect of the present invention provides the thermoelectric conversion element according to any one of the first to sixth aspects, wherein the magnetic body has a width of 500 μm or less.

[0079] An eighth aspect of the present invention provides a thermoelectric conversion element according to any one of the first to seventh aspects, wherein the magnetic body generates an electromotive force in a direction perpendicular to the thickness direction of the base material when a temperature gradient occurs in the thickness direction of the base material.

[0080] A ninth aspect of the present invention provides the thermoelectric conversion element according to any one of the first to eighth aspects, wherein the magnetic body generates an electromotive force by a magneto-thermoelectric effect.

[0081] A tenth aspect of the present invention provides a thermoelectric conversion element according to any one of the first to ninth aspects, the thermoelectric conversion element including the magnetic material and having a conductive path forming a meander pattern.

[0082] An eleventh aspect of the present invention provides the thermoelectric conversion element according to the tenth aspect, wherein the magnetic body has a line width of 500 μm or less in the meander pattern.

Claims

1. A thermoelectric conversion element comprising a base material and a magnetic body disposed on the base material and having ferromagnetic or antiferromagnetic properties, wherein the magnetic body has an internal stress of 900 MPa or less.

2. The thermoelectric conversion element according to claim 1, wherein the base material has flexibility.

3. The thermoelectric conversion element according to claim 2, wherein the base material contains at least an organic polymer.

4. The thermoelectric conversion element according to claim 1, wherein the base material has a linear expansion coefficient of 1.0×10 -5 / °C or more.

5. The thermoelectric conversion element according to claim 1, wherein the base material has a thickness of 200 μm or less.

6. The thermoelectric conversion element according to claim 1, wherein the magnetic body has a thickness of 1000 nm or less.

7. The thermoelectric conversion element according to claim 1, wherein the magnetic body has a width of 500 μm or less.

8. The thermoelectric conversion element according to claim 1, wherein the magnetic body generates an electromotive force in a direction orthogonal to the thickness direction of the base material when a temperature gradient occurs in the thickness direction of the base material.

9. The thermoelectric conversion element according to claim 1, wherein the magnetic body generates an electromotive force by the magnetothermoelectric effect.

10. The thermoelectric conversion element according to claim 1, further comprising a conductive path including the magnetic body and forming a meander pattern.

11. The thermoelectric conversion element according to claim 10, wherein the magnetic body has a line width of 500 μm or less in the meander pattern.