Thermoelectric conversion element and sensor

Abstract

A thermoelectric conversion element (1a) is provided with a base material (20) and a thermoelectric conversion body (11). The thermoelectric conversion body (11) is disposed on the first surface (S1) of the substrate (20). The thermoelectric conversion body (11) has a second surface (S2) that intersects a perpendicular line (P) of the first surface (S1). At least one selected from the group consisting of the first surface S1 and the second surface S2 has a maximum height roughness Rz of 30 nm or less.

Description

Technical Field

[0001] This invention relates to thermoelectric conversion elements and sensors. Background Technology

[0002] Previously, thermoelectric conversion elements were known to have a structure in which a material exhibiting thermoelectric conversion properties is disposed on a substrate.

[0003] For example, Patent Document 1 describes a thermoelectric conversion element having a laminate comprising a substrate, a buffer layer, and two hybrid layers. The substrate can be a flexible substrate. The buffer layer, having a defined crystal structure of AlN, is disposed on the substrate. Two hybrid layers are disposed on the buffer layer. The hybrid layers have an alloy layer and a capping layer from the side closest to the buffer layer. The alloy layer has a defined magnetic material. This magnetic material is a polycrystalline Co-based Heusler alloy. The Co-based Heusler alloy exhibits a large anomalous Nernst effect. The capping layer has AlN. This laminate, by sandwiching the alloy layer with the AlN layer, exhibits a large anomalous Nernst effect or anomalous Hall effect, and has high thermoelectric conversion efficiency.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-129848 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In the Internet of Things (IoT) society, the demand for heat-related monitoring is constantly increasing in areas such as health monitoring, thermal management of electric vehicle (EV) batteries, and high-speed data processing chips. To address this demand, the use of thermoelectric conversion elements with thermoelectric converters on a substrate for thermal sensing is being considered. High durability of such thermoelectric conversion elements in the operating environment is considered important.

[0009] Regarding the durability of the thermoelectric conversion element described in Patent Document 1 under various operating environments, no specific study was conducted. The thermoelectric conversion element described in Patent Document 1 has a laminated structure comprising a substrate, a buffer layer, and two hybrid layers. In this laminated structure, cracks may occur in certain layers depending on the operating environment. For example, if cracks occur in the alloy layer of the thermoelectric conversion element described in Patent Document 1, the desired thermoelectric conversion performance may be compromised. Patent Document 1 did not conduct research from this perspective, and from the viewpoint of durability under various operating environments, the thermoelectric conversion element described in Patent Document 1 warrants further investigation.

[0010] In view of this situation, the present invention provides a thermoelectric conversion element that is advantageous from the viewpoint of durability in the operating environment.

[0011] Methods for solving problems

[0012] This invention provides a thermoelectric conversion element comprising:

[0013] Substrate; and

[0014] A thermoelectric converter, disposed on a first surface of the aforementioned substrate, and having a second surface intersecting a line perpendicular to the aforementioned first surface.

[0015] At least one of the aforementioned first surface and the aforementioned second surface is selected to have a maximum height roughness Rz of less than 30 nm.

[0016] In addition, the present invention provides a sensor,

[0017] It possesses the aforementioned thermoelectric conversion elements.

[0018] Effects of the Invention

[0019] The aforementioned thermoelectric conversion element is advantageous from the viewpoint of durability in the operating environment. Attached Figure Description

[0020] [ Figure 1 ] Figure 1 This is a perspective view showing an example of an embodiment of the thermoelectric conversion element.

[0021] [ Figure 2 ] Figure 2 It will Figure 1 The diagram shows a cross-sectional view of the thermoelectric conversion element with plane II as the cutting section.

[0022] [ Figure 3 ] Figure 3 This is a diagram showing the relationship between the magnetization of the thermoelectric converter involved in the embodiment and the external magnetic field.

[0023] [ Figure 4 ] Figure 4 This is a side view showing an example of a thermoelectric conversion element constituting a wound structure.

[0024] [ Figure 5 ] Figure 5 This is a diagram illustrating one example of how the sensor can be implemented.

[0025] [ Figure 6 ] Figure 6 This is a perspective view showing another example of an embodiment of the thermoelectric conversion element.

[0026] [ Figure 7 ] Figure 7This is a diagram schematically illustrating a method for measuring the internal stress of a thermoelectric converter. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the following description is illustrative of the present invention, and the present invention is not limited to the following embodiments.

[0028] like Figure 1 and Figure 2 As shown, the thermoelectric conversion element 1a includes a substrate 20 and a thermoelectric converter 11. The thermoelectric converter 11 is disposed on a first surface S1 of the substrate 20. The thermoelectric converter 11 has a second surface S2 that intersects a perpendicular line P with the first surface S1. In the thermoelectric conversion element 1a, at least one of the first surface S1 and the second surface S2 has a maximum height roughness Rz of 30 nm or less. The maximum height roughness Rz is determined, for example, according to Japanese Industrial Standard (JIS) B 0601:2013. The first surface S1 and the second surface S2 are, for example, surfaces parallel to the XY plane. In the figures, the X-axis, Y-axis, and Z-axis are orthogonal to each other, and the Z-axis is perpendicular to the first surface S1.

[0029] According to the inventors' research, it is advantageous to maintain a predetermined internal stress within the thermoelectric converter to improve the thermoelectric conversion performance of a thermoelectric conversion element having a thermoelectric converter disposed on a substrate. However, it has been newly discovered that if the internal stress within the thermoelectric converter is adjusted to a predetermined state, cracks may occur in the thermoelectric converter due to this internal stress, depending on the usage environment, thus reducing the thermoelectric conversion performance of the thermoelectric conversion element. In particular, it is known that if the thermoelectric conversion element is exposed to a high-temperature and high-humidity environment for a prolonged period, cracks may occur in the thermoelectric converter. It is known that the formation of such cracks is related not only to the state of the internal stress within the thermoelectric converter but also to the state of the surface of the substrate in contact with the thermoelectric converter.

[0030] In the manufacture of a thermoelectric conversion element having a thermoelectric converter disposed on a substrate, it is considered to form a film of the precursor of the thermoelectric converter on the surface of the substrate while transporting the substrate. For example, when transporting the substrate from a state where the substrates are overlapping each other, a substrate with an uneven surface is used to prevent adhesion caused by the overlapping of the substrates. According to the research of the inventors of this application, the unevenness of the substrate surface is related to the generation of cracks in the thermoelectric converter when the thermoelectric conversion element is exposed to a high temperature and high humidity environment for a long time.

[0031] Therefore, the inventors of this application have repeatedly conducted a large number of trials and errors, and as a result, they have made a new discovery: by adjusting the maximum height roughness Rz of at least one of the surfaces of the substrate in contact with the thermoelectric converter and the surface of the thermoelectric converter to a specified range, cracks are less likely to occur in the thermoelectric converter.

[0032] As described above, at least one of the selected surfaces S1 and S2 has a maximum height roughness Rz of 30 nm or less. Therefore, even if the thermoelectric conversion element is exposed to a high-temperature and high-humidity environment for a long period, cracks are less likely to form in the thermoelectric converter. Thus, the thermoelectric conversion element 1a easily exhibits high durability in the operating environment. The maximum height roughness Rz can be 25 nm or less, 20 nm or less, or 15 nm or less, for example, it can be 1 nm or more.

[0033] like Figure 2 As shown, the substrate 20 has, for example, a third surface S3. The third surface S3 is separate from the thermoelectric converter 11 and extends parallel to the first surface S1. The surface state of the third surface S3 is not limited to a specific state. The third surface S3 has, for example, an arithmetic mean roughness Ra of 8 nm or more. With this configuration, when transporting the substrate 20 during the manufacture of the thermoelectric conversion element 1a, adhesion due to overlap of the substrates 20 is less likely to occur, and the substrate 20 is easily transported. The arithmetic mean roughness Ra is determined, for example, according to JIS B 0601:2013.

[0034] The arithmetic mean roughness Ra of the third surface S3 can be 9 nm or more, or 10 nm or more. The arithmetic mean roughness Ra of the third surface S3 can be, for example, 20 nm or less, 15 nm or less, or 12 nm or less. The arithmetic mean roughness Ra of the third surface S3 can be any one of the ranges defined by any combination of any lower limit value among 8 nm, 9 nm, and 10 nm and any upper limit value among 20 nm, 15 nm, and 12 nm.

[0035] Minimum internal stress σ in thermoelectric converter 11 min Not limited to a specific value. Minimum internal stress σ min It is the minimum internal stress of the thermoelectric converter 11 in the plane parallel to the first surface S1. Minimum internal stress σ min For example, below -300 MPa. Under this condition, the thermoelectric conversion performance of thermoelectric conversion element 1a tends to be higher. It should be noted that in this specification, positive internal stress represents tensile stress, and negative internal stress represents compressive stress. Minimum internal stress σ minA value below -300 MPa indicates that a relatively large compressive stress exists as internal stress in the thermoelectric converter 11. With such compressive stress, under conditions of long-term exposure to high temperature and humidity, the thermoelectric converter element interacts with the surface irregularities of the substrate, making it prone to cracking. However, if the maximum height roughness Rz of at least one of the selected surfaces S1 and S2 is below 30 nm, then even the minimum internal stress σ... min With a pressure below -300 MPa, cracks are not easily generated in the thermoelectric converter 11. Therefore, the thermoelectric conversion element 1a tends to have high durability in the operating environment.

[0036] Minimum internal stress σ min For example, above -900 MPa. Minimum internal stress σ min It can be any of the ranges defined by any one of the upper limits from -300MPa, -350MPa, -400MPa, -450MPa, -500MPa, -550MPa and -600MPa and any one of the lower limits from -900MPa, -850MPa, -800MPa, -750MPa and -700MPa.

[0037] The thermoelectric converter 11 may be formed, for example, into fine wires 11a containing magnetic material. With such a configuration, the thermoelectric conversion element 1a can easily achieve the desired thermoelectric conversion performance due to the thermoelectric conversion characteristics of the magnetic material. The thermoelectric converter 11 may contain, for example, multiple fine wires 11a.

[0038] like Figure 1 As shown, the thin wire 11a extends, for example, along the Y-axis direction. The dimension, i.e., the thickness, of the thin wire 11a in the Z-axis direction is not limited to a specific value. This thickness is, for example, 1000 nm or less. Therefore, the amount of material used in the thin wire 11a can be reduced, easily lowering the manufacturing cost of the thermoelectric conversion element 1a. Furthermore, wire breakage is less likely to occur in the thermoelectric converter 11. The thickness of the thin wire 11a is, for example, 5 nm or more. Therefore, the thermoelectric conversion element 1a easily exhibits high durability.

[0039] The thickness of the fine line 11a can be any of the ranges defined by any combination of any one of the lower limits of 5nm, 10nm, 20nm, 30nm and 50nm and any one of the upper limits of 1000nm, 750nm, 500nm, 400nm, 300nm and 200nm.

[0040] The dimension, i.e., the width, in the X-axis direction of the fine wire 11a is not limited to a specific value. For example, the width of the fine wire 11a is 500 μm or less. This reduces the amount of material used in the fine wire 11a, easily lowering the manufacturing cost of the thermoelectric conversion element 1a. Furthermore, multiple fine wires 11a can be easily arranged in the X-axis direction, allowing the thermoelectric conversion element 1a to easily achieve the desired thermoelectric conversion performance. For example, the width of the fine wire 11a is 1 μm or more. This reduces the likelihood of wire breakage in the fine wire 11a, making the thermoelectric conversion element 1a more durable.

[0041] The width of the thin line 11a can be any of the ranges defined by any combination of any one of the lower limits of 1μm, 2μm, 5μm, 10μm, 20μm and 30μm and any one of the upper limits of 500μm, 400μm, 300μm, 200μm, 100μm and 50μm.

[0042] The first internal stress σ of thermoelectric converter 11 Y With the second internal stress σ X The difference |σ X -σ Y |Not limited to a specific value. First internal stress σ Y This refers to the internal stress of the thermoelectric converter 11 along the length direction (Y-axis direction) of the thin wire 11a. The second internal stress σ X This refers to the internal stress of the thermoelectric converter 11 along the width direction (X-axis direction) of the thin wire 11a. The difference |σ X -σ Y For example, the pressure is 50 MPa or higher. In this case, the magnetic properties of the magnetic material contained in the thin wire 11a tend to have large anisotropy in both the length and width directions, and the thermoelectric converter 11 tends to have the desired thermoelectric conversion characteristics. Therefore, the thermoelectric conversion element 1a can easily achieve the desired thermoelectric conversion performance.

[0043] As described above, the thin wire 11a extends linearly in the Y-axis direction. Therefore, considering shape magnetic anisotropy, it is also assumed that in the thermoelectric converter 11, an easily magnetized axis is generated in the length direction of the thin wire 11a, and a difficult-to-magnetize axis is generated in the width direction of the thin wire 11a. However, in the thermoelectric converter 11, if the difference |σ X -σ Y If the magnetic strength is above 50 MPa, the magnetic properties of the magnetic material contained in the thin wire 11a tend to exhibit large anisotropy in both the length and width directions. For example, the magnetic anisotropy energy E of the magnetic material... u With E u = (3 / 2)λσ. In this relationship, λ is the magnetostriction constant of the magnetic material, and σ represents the internal stress of the magnetic material. Therefore, it can be understood that, for example, when the magnetostriction constant λ is positive, if the difference σX -σ Y The larger the positive value, or the greater the difference σ when the magnetostriction constant λ is negative. X -σ Y The smaller the negative value, the greater the anisotropy of the magnetic properties of the magnetic material in the length and width directions of the thin wire 11a.

[0044] Figure 3 This is a diagram showing the relationship between the magnetization of the thermoelectric converter 11 and the external magnetic field. Figure 3 In the diagram, the solid line shows the relationship between the magnetization of the thermoelectric converter 11 and the external magnetic field along the width direction (X-axis) of the thin line 11a. The dashed line shows the relationship between the magnetization of the thermoelectric converter 11 and the external magnetic field along the length direction (Y-axis) of the thin line 11a. Figure 3 As shown, in the thermoelectric converter 11, by making the difference |σ X -σ Y The magnetic strength is 50 MPa or higher, resulting in significant anisotropy in the magnetic properties of the thermoelectric converter 11 along both the length and width directions of the thin wire 11a. Due to this significant anisotropy, a difficult-to-magnetize axis is easily generated along the length of the thin wire 11a, while an easy-to-magnetize axis is easily generated along the width direction of the thin wire 11a. Consequently, the thermoelectric converter 11 readily exhibits stable behavior relative to an external magnetic field, and the thermoelectric conversion element 1a readily achieves the desired thermoelectric conversion performance. Preferably, the magnetic material contained in the thin wire 11a has an easy-to-magnetize axis along the width direction of the thin wire 11a.

[0045] In thermoelectric converter 11, the difference |σ X -σ Y |It can be above 100MPa, above 150MPa, or above 200MPa. Difference |σ X -σ Y The upper limit of | is not limited to a specific value. Difference |σ X -σ Y For example, below 900 MPa. In this case, even if a bending load is applied across the width to both ends of the thin wire 11a, cracks are not easily generated in the thermoelectric converter 11.

[0046] First internal stress σ Y It can be either tensile stress or compressive stress. The first internal stress σ Y It can be any of the ranges defined by any combination of a lower limit value among -900MPa, -700MPa, -500MPa and -300MPa and an upper limit value among 900MPa, 700MPa, 500MPa and 300MPa.

[0047] Second internal stress σ X It can be either tensile stress or compressive stress. The second internal stress σ X It can be any of the ranges defined by any combination of a lower limit value among -900MPa, -700MPa, -500MPa and -300MPa and an upper limit value among 900MPa, 700MPa, 500MPa and 300MPa.

[0048] The magnetostriction constant of the magnetic material contained in the thin wire 11a can be positive or negative. For example, if the magnetostriction constant of the magnetic material is positive, then σ can be satisfied. X -σ Y The condition ≥50MPa can be satisfied when the magnetostriction constant of the magnetic material is negative, σ Y -σ X The condition is ≥50MPa. In the former case, the first internal stress σ Y It can be the minimum internal stress σ min In the latter case, the second internal stress σ X It can be the minimum internal stress σ min .

[0049] The rectangle ratio, determined by the MH curve along the width direction of the thin wire 11a of the thermoelectric converter 11, is not limited to a specific value. The rectangle ratio is the ratio of remanent magnetization Mr to saturation magnetization Ms in the MH curve, Mr / Ms. For example, the rectangle ratio is 80% or higher. Therefore, the thermoelectric conversion element 1a more easily achieves the desired thermoelectric conversion performance. The rectangle ratio can be 85% or higher, or even 90% or higher.

[0050] Thermoelectric converter 11 utilizes, for example, a temperature gradient in a direction perpendicular to the first surface S1 (Z-axis direction). An electromotive force is generated along the length direction (Y-axis direction) of the thin wire 11a. Based on this configuration, by adjusting the length of the thin wire 11a, the electromotive force generated by thermoelectric conversion can be adjusted, and the thermoelectric conversion element 1a can be used in various applications.

[0051] Thermoelectric converter 11, for example, utilizes the magnetothermal-electric effect to generate electromotive force. The magnetothermal-electric effect is, for example, the anomalous Nernst effect.

[0052] Thermoelectric converter 11 may contain, for example, a material exhibiting an anomalous Nernst effect. The material exhibiting an anomalous Nernst effect is not limited to a specific substance. For example, a material exhibiting an anomalous Nernst effect has a density of 5 × 10⁻⁶. -3A magnetic material with a saturation magnetization above T or a material with a band structure having Weyl points near the Fermi level. The magnetic material can be a ferrimagnetic material. The thermoelectric converter 11 contains, for example, at least one substance selected from the group consisting of the following (i), (ii), (iii), (iv), and (v) as a substance showing an anomalous Nernst effect.

[0053] (i) A stoichiometric substance having a composition represented by Fe3X

[0054] (ii) A non-stoichiometric substance in which the composition ratio of Fe to X deviates from that of the substance in (i)

[0055] (iii) A substance obtained by replacing a part of the Fe sites in the substance in (i) or a part of the Fe sites in the substance in (ii) with a typical metal element or a transition element other than X

[0056] (iv) A substance having a composition represented by Fe3M1 1-x M2 x (0 < x < 1), and M1 and M2 are typical elements different from each other

[0057] (v) A substance obtained by replacing a part of the Fe sites in the substance in (i) with a transition element other than X and replacing a part of the X sites in the substance in (i) with a typical metal element other than X

[0058] Among the substances in (i) to (v) above, 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 (iv) above, for the combination of M1 and M2, as long as M1 and M2 are typical elements different from each other, it is not limited to a specific combination. In (iv) above, the combination of M1 and M2 is, for example, Ga and Al, Si and Al, or Ga and B.

[0059] The thermoelectric converter 11 may contain Co2MnGa or Mn3Sn as a substance showing an anomalous Nernst effect.

[0060] The magnetostriction constant λ of the magnetic material contained in the thin wire 11a is not limited to a specific value. The absolute value of the magnetostriction constant λ is, for example, 5 × 10 -6 or more. As described above, the magneto - anisotropic energy E u has a relationship of E u = (3 / 2)λσ. Therefore, when the absolute value of the magnetostriction constant λ is 5 × 10 -6 or more, the anisotropy of the magnetic properties in the length direction and the width direction of the thin wire 11a tends to become large.

[0061] The absolute value of the magnetostrictive constant λ can be 10 × 10⁻⁶. -6 The above can be 20×10 -6 above.

[0062] like Figure 1 As shown, the thermoelectric conversion element 1a has a zigzag pattern including the thermoelectric converter 11. With this configuration, the total length of the fine wires 11a included in the thermoelectric conversion element 1a tends to increase. The greater the total length of the fine wires 11a, the more effective the temperature gradient can be in the direction perpendicular to the first surface S1. The electromotive force generated along the length of the thin wire 11a is more likely to increase. Therefore, by making the thermoelectric conversion element 1a have a zigzag pattern that includes the thermoelectric conversion body 11, the electromotive force generated in the thermoelectric conversion element 1a is more likely to increase.

[0063] like Figure 1 and Figure 2 As shown, the thermoelectric conversion element 1a also includes wiring 12, for example. Wiring 12 electrically connects the thin wires 11a to each other. For example, multiple thin wires 11a in the thermoelectric conversion element 11 are connected in series via wiring 12. Wiring 12, for example, has multiple wirings 12a. The multiple thin wires 11a and the multiple wirings 12a are connected in series. With this configuration, even if the area of ​​the surface where multiple thin wires 11a and multiple wirings 12a are arranged is small, a large electromotive force can be easily generated in the thermoelectric conversion element 1a.

[0064] Wiring 12 can be formed from a metallic element or an alloy.

[0065] Multiple fine lines 11a and multiple wirings 12a are arranged, for example, in the manner described above in a zigzag pattern. This forms a conductive path 15. For example, by connecting one end 15p and the other end 15q of the conductive path 15 to external wiring, the electromotive force generated by the thermoelectric conversion element 1a can be output to the outside. Alternatively, by applying a voltage between one end 15p and the other end 15q, heat flow can be generated in the thickness direction of the substrate 20.

[0066] Multiple thin lines 11a are separated at predetermined intervals in the X-axis direction and arranged parallel to each other. Multiple thin lines 11a are arranged at equal intervals in the X-axis direction. Multiple wirings 12a electrically connect adjacent thin lines 11a in the X-axis direction. Wirings 12a electrically connect one end of a thin line 11a in the Y-axis direction to another end of another thin line 11a adjacent to that thin line 11a in the Y-axis direction. One end of the multiple thin lines 11a in the Y-axis direction is located on the same side of the thin line 11a in the Y-axis direction, and another end of the multiple thin lines 11a in the Y-axis direction is located on the opposite side of the first end of the thin line 11a in the Y-axis direction.

[0067] The dimension, i.e. the thickness, in the Z-axis direction of wiring 12a is not limited to a specific value. The thickness can be any of the ranges defined by any combination of any one of the lower limits of 5nm, 10nm, 20nm, 30nm and 50nm and any one of the upper limits of 1000nm, 750nm, 500nm, 400nm, 300nm and 200nm.

[0068] The width of wiring 12a is not limited to a specific value. The width can be any of the ranges defined by any one of the lower limits of 0.1μm, 0.5μm, 1μm, 2μm, 5μm, 10μm, 20μm and 30μm and any one of the upper limits of 500μm, 400μm, 300μm, 200μm, 100μm and 50μm.

[0069] As for the substrate 20, it is not limited to a specific substrate as long as at least one of the groups consisting of the first surface S1 and the second surface S2 has a maximum height roughness Rz of less than 30 nm.

[0070] The substrate 20 may contain, for example, an organic material. With this configuration, from the viewpoint of thermoelectric conversion performance, it is easy to adjust the internal stress in the thermoelectric converter 11 to the desired state. Furthermore, it is easy to reduce the manufacturing cost of the thermoelectric conversion element 1a.

[0071] The substrate 20 may contain an organic polymer as an organic material. Examples of organic polymers are polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), polycarbonate (PC), polyimide (PI), or cyclic olefin polymer (COP).

[0072] The thickness of the substrate 20 is not limited to a specific value. For example, the thickness is 10 to 250 μm.

[0073] The substrate 20 is flexible, for example. The substrate 20 has elasticity such that when the test piece, which is a strip made of the substrate 20, is wound around a cylindrical mandrel with both ends pointing in the same direction along its length, the test piece can elastically deform.

[0074] The second dimensional change rate C of substrate 20 X With the first size change rate C Y The difference | C X -C Y |Not limited to a specific value. First dimensional change rate C Y The value is obtained by dividing the dimension at 25°C after the test (Y-axis direction) along the length direction of the fine line 11a of the first surface S1 during the test of heating the substrate 20 at 150°C for 30 minutes by the dimension at 25°C before the test. Second dimensional change rate C X This value is obtained by dividing the dimension of the thin line 11a in the width direction (X-axis direction) at 25°C after the above test by the dimension at 25°C before the test. Difference |C X -C Y For example, it is 0.10% or more. In this case, for example, by performing a prescribed heat treatment while the precursor of the thermoelectric converter 11 is formed on the first surface S1 of the substrate 20, the shrinkage of the substrate 20 after heat treatment is different in the length direction and width direction of the fine wire 11a. As a result, from the viewpoint of thermoelectric conversion performance, it is easy to adjust the internal stress in the thermoelectric converter 11 to the desired state.

[0075] Difference | C X -C Y | It can be above 0.2%, above 0.3%, above 0.4%, or above 0.5%, for example, below 10%.

[0076] The first surface S1 of the substrate 20 may be formed, for example, by a surface layer such as a hard coating.

[0077] An example of a method for manufacturing a thermoelectric conversion element 1a is shown. The thermoelectric conversion element 1a is manufactured, for example, by a method including the following (I) and (II).

[0078] (I) A precursor of thermoelectric converter 11 is formed on the first surface S1 of substrate 20.

[0079] (II) The precursors of the substrate 20 and the thermoelectric converter 11 are heated at a specified temperature.

[0080] In step (I), a film of the precursor of the thermoelectric converter 11 is formed on the first surface S1 of the substrate 20 using methods such as sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), ion plating, and coating. Next, a photoresist is coated onto this film, a photomask is placed on the film, exposure is performed, and then wet etching is performed. This forms multiple fine lines of the precursor of the thermoelectric converter 11 arranged at predetermined intervals. Next, a film of the precursor of the wiring 12 is formed on the first surface S1 of the substrate 20 using methods such as sputtering, CVD, PLD, ion plating, and coating. Next, a photoresist is coated onto the film of the precursor of the wiring 12, a photomask is placed on the film of the precursor of the wiring 12, exposure is performed, and then wet etching is performed. This results in the wiring 12, where the fine lines of the precursor of the thermoelectric converter 11 are electrically connected to each other.

[0081] In (II), the temperature of the heat treatment is not limited to a specific temperature. The ambient temperature of the substrate 20 and the precursor of the thermoelectric converter 11 during the heat treatment is, for example, 50°C or higher. Therefore, from the viewpoint of thermoelectric conversion performance, it is easy to adjust the internal stress of the thermoelectric converter 11 to the desired state. The ambient temperature of the substrate 20 and the precursor of the thermoelectric converter 11 during the heat treatment can be 100°C or higher, 150°C or higher, or 200°C or higher. For example, the ambient temperature is 300°C or lower.

[0082] During heat treatment, the time during which the ambient temperature of the substrate 20 is maintained above 50°C is not limited to a specific value. This time is, for example, more than 10 minutes and less than 3 hours.

[0083] After heat treatment, the precursor of thermoelectric converter 11 is magnetized to obtain thermoelectric converter 11. The thermoelectric conversion element 1a is manufactured, for example, in this way.

[0084] The thermoelectric conversion element 1a can be provided together with an adhesive layer, for example. In this case, the substrate 20 is disposed between the thermoelectric conversion element 11 and the adhesive layer in the thickness direction of the substrate 20. As a result, the adhesive layer can be pressed against the article, thereby mounting the thermoelectric conversion element 1a to the article.

[0085] The adhesive layer may include, for example, rubber-based adhesives, acrylic adhesives, silicone adhesives, or urethane adhesives. The thermoelectric conversion element 1a may also be provided together with the adhesive layer and a release liner. In this case, the release liner covers the adhesive layer. Typically, the release liner is a film that maintains the adhesive strength of the adhesive layer when it is covered and can be easily peeled off from the adhesive layer. The release liner is, for example, a film made of polyester resin such as PET. The adhesive layer can be exposed by peeling off the release liner, and the thermoelectric conversion element 100 can be attached to the article.

[0086] like Figure 4 As shown, the thermoelectric conversion element 1a can be provided, for example, in the form of a wound structure 5. For example, the wound structure 5 is obtained by winding a film-shaped or sheet-shaped thermoelectric conversion element 1a around the side of a cylindrical or cylindrical core 4.

[0087] like Figure 5 As shown, for example, a sensor 3 equipped with a thermoelectric conversion element 1a can be provided. In this sensor 3, for example, a temperature gradient is generated in the thickness direction of the substrate 20. At that time, an electromotive force is generated along the length of the thin wire 11a. The sensor 3 can sense heat by processing the electrical signal output to the outside of the thermoelectric conversion element 1a based on this electromotive force. The sensor 3 also includes, for example, a signal processing device 2. The signal processing device 2 processes the electrical signal output to the outside of the thermoelectric conversion element 1a.

[0088] The thermoelectric conversion element 1a can be modified from various perspectives. For example, the thermoelectric conversion element 1a can be modified to... Figure 6 The thermoelectric conversion element 1b is shown. Except where specifically stated, thermoelectric conversion element 1b is constructed in the same manner as thermoelectric conversion element 1a. For components of thermoelectric conversion element 1b that are identical or corresponding to those of thermoelectric conversion element 1a, the same reference numerals are used, and detailed descriptions are omitted. The description of thermoelectric conversion element 1a also applies to thermoelectric conversion element 1b, provided it is not technically contradictory.

[0089] like Figure 6 As shown, in the thermoelectric conversion element 1b, the thermoelectric conversion body 11 extends continuously, for example, on the first surface S1. Wiring 12 is disposed on a portion of the thermoelectric conversion body 11. For example, multiple wirings 12a included in the wiring 12 are disposed separately from each other on the thermoelectric conversion body 11 at predetermined intervals.

[0090] In the thermoelectric conversion element 1b, the thermoelectric converter 11 is formed, for example, a zigzag pattern. In top view, the thermoelectric conversion element 1b is configured as a single layer of thermoelectric converter 11 and a laminate containing thermoelectric converter 11 and wiring 12a, which alternate in the X-axis direction.

[0091] Example

[0092] The present invention will now be described in more detail using examples. However, the present invention is not limited to the following examples.

[0093] <Example 1>

[0094] A thin film with a thickness of 96 nm was formed on a polyethylene terephthalate (PET) film A with a hard coating layer of 4 μm as the surface layer and a total thickness of 54 μm using DC magnetron sputtering with a target containing Fe and Ga. Argon gas was supplied as the process gas at a pressure of 0.1 Pa during DC magnetron sputtering. The Fe content to Ga content ratio in the target was 3:1 (atomic ratio). The temperature around the PET film A was adjusted to 100 °C. The PET film A with the formed film was then heat-treated at 150 °C for 30 minutes. Next, a photoresist was coated onto the film, a photomask was placed on top of the film, exposure was performed, and then wet etching was carried out. This resulted in 115 FeGa-containing fine lines arranged at specified intervals. Each FeGa-containing fine line had a width of 40 μm and a length of 1.5 cm. Then, using a Cu-containing target, a Cu thin film with a thickness of 100 nm was formed on the hard coating of PET film A by DC magnetron sputtering. A photoresist was coated onto the Cu thin film, a photomask was placed on top of the Cu thin film, exposure was performed, and then wet etching was carried out. This resulted in the formation of Cu-containing fine lines with a width of 40 μm. Adjacent pairs of FeGa-containing linear patterns were electrically connected to each other through the Cu-containing fine lines, forming conductive paths that constitute a zigzag pattern.

[0095] Using an electromagnet with a central magnetic flux density of 0.5T, the FeGa-containing wire is magnetized in a width direction that is parallel to the main surface of the PET film A and perpendicular to the length direction of the FeGa-containing wire. The thermoelectric conversion element according to Example 1 is fabricated in this way. In this thermoelectric conversion element, the vertical direction (TD) of the PET film A is aligned with the width direction of the FeGa-containing wire.

[0096] <Comparative Example 1>

[0097] The thermoelectric conversion element involved in Comparative Example 1 was fabricated in the same manner as in Example 1, except that a PET film B with a total thickness of 50 μm without a hard coating was used instead of PET film A.

[0098] <Comparative Example 2>

[0099] Except as described below, the thermoelectric conversion element involved in Comparative Example 1 was fabricated in the same manner as in Example 1. PET film B, used in Comparative Example 1, was used instead of PET film A. In DC magnetron sputtering, the pressure of the argon gas supplied as the process gas was adjusted to 1.6 Pa.

[0100] <Comparative Example 3>

[0101] The thermoelectric conversion element involved in Comparative Example 3 was fabricated using a PET film C different from the PET film used in Example 1 and Comparative Example 1, except that it was fabricated in the same manner as in Example 1.

[0102] [Magnetic properties]

[0103] The magnetic properties of the FeGa-containing fine wires in the thermoelectric conversion elements of each embodiment and comparative example were measured using the PPMS-versalab miniature refrigerant-free physical property measurement system from Qantum Design. For this measurement, a 2mm square portion of the module involved in each embodiment and comparative example, containing a conductive path, was used as the measurement sample. Furthermore, a Vibration Sample Magnetrometer (VSM) was used to scan a magnetic field of ±800 kA / m in a direction parallel to the magnetization direction of the magnetized FeGa-containing fine wire. Under a temperature of 300 K, considering the thickness of the FeGa-containing fine wire and the area of ​​the FeGa-containing fine wire in the measurement sample, the MH curve was obtained. The ratio Mr / Ms, where ±800 kA / m is the magnetization Ms and Mr is the magnetization Mr at 0 kA / m during the magnetic field scan, was determined as the rectangle ratio. The results are shown in Table 1.

[0104] [Determination of internal stress]

[0105] Using the Smartlab X-ray diffraction apparatus manufactured by Rigaku Corporation, Cu-Kα lines were directed from a 40 kV and 50 mA light source through a parallel beam optical system and irradiated onto the sample, based on sin 2 The principle of the Ψ method's tilting method is used to determine the first internal stress σ of the FeGa-containing fine wires in each embodiment and comparative example. Y and the second internal stress σ X First internal stress σ Y It is the internal stress along the length of the thin wire containing FeGa, the second internal stress σ X It is the internal stress in the width direction, parallel to the main surface of the PET film and perpendicular to the length direction of the FeGa-containing fine wire. The wavelength λ of the Cu-Kα wire is 0.1541 nm. 2The Ψ method is a method for determining the internal stress of a polycrystalline thin film by observing the dependence of its lattice strain on the angle (Ψ). Using the X-ray diffraction apparatus described above, the diffraction intensity was measured at 0.01° intervals within the range of 2θ = 75° to 85° by Θ / 2Θ scanning. The cumulative time at each measurement point was set to 100 seconds. The interplanar spacing d of the magnetic material at each measurement angle (Ψ) was calculated from the obtained peak angle 2θ of the X-ray diffraction and the wavelength λ of the X-rays irradiated from the light source. Based on the relationship between the following equations (1) and (2), the lattice strain ε was calculated from the interplanar spacing d. λ is the wavelength of the X-rays (Cu-Kα line) irradiated from the light source, λ = 0.1541 nm. d0 is the interplanar spacing in the stress-free state, d0 = 0.0206 nm.

[0106] 2dsinθ=λ Equation (1)

[0107] ε=(d-d0) / d0 Equation (2)

[0108] like Figure 7 As shown, X-ray diffraction measurements were performed at angles (Ψ) between the normal to the principal plane of sample Sa and the normal to the crystal plane of crystal Mb, which were 0°, 17°, 24°, 30°, 35°, 40°, and 45°, respectively, and the lattice strain ε at each angle (Ψ) was calculated. Then, according to the following equation (3), based on the plotted sin 2 The slope of the straight line relating Ψ and lattice strain ε is used to determine the first internal stress σ. Y and the second internal stress σ X The results are shown in Table 1. It should be noted that in the internal stresses of Table 1, positive values ​​represent tensile stress, and negative values ​​represent compressive stress. Since the stress is measured in the tilt method at a direction 90° relative to the beam direction, the first internal stress σ is calculated... Y and the second internal stress σ X The sample was set up with the direction to be measured perpendicular to the direction of the beam, and the measurement was performed. The results are shown in Table 1.

[0109] ε={(1+ν) / E}σsin 2 Ψ-(2ν / E)σ Equation (3)

[0110] In the above formula (3), E is the Young's modulus of the magnetic material (130 GPa), and ν is the Poisson's ratio of the magnetic material (0.3). Figure 7 The detector D in the detector detects X-ray diffraction.

[0111] [Surface Roughness Measurement]

[0112] Using a Zygo NewView 7300 three-dimensional non-contact surface roughness meter, with a 10x objective lens and a measurement area of ​​0.70 mm × 0.52 mm, the roughness curves of various PET films containing FeGa fine lines and the surfaces with FeGa fine lines were measured, obtaining the roughness curves for each surface. According to JIS B0601:2013, the arithmetic mean roughness R and the maximum height roughness Rz were calculated from the obtained roughness curves. The results are shown in Table 1.

[0113] [Substrate Dimensional Change Rate]

[0114] Test pieces made from the substrates used in the various embodiments and comparative examples were subjected to a heating test at 150°C for 30 minutes. The dimension of the FeGa-containing fine wire at 25°C after the heating test along its length was divided by the dimension at 25°C before the heating test, and the resulting value was determined as the first dimensional change rate C. Y The dimension of the FeGa-containing fine wire at 25°C after the heating test in the width direction is divided by the dimension at 25°C before the heating test, and the resulting value is determined as the second dimensional change rate C. X Furthermore, the rate of change of the second dimension, C, is calculated. X With the first size change rate C Y The difference | C X -C Y The results are shown in Table 1.

[0115] [High Temperature and High Humidity Environment Test]

[0116] The thermoelectric conversion elements involved in each embodiment and comparative example were subjected to a high-temperature and high-humidity environment test for 120 hours at a temperature of 85°C and a relative humidity of 85%. The resistance R0 of the conductive path before the high-temperature and high-humidity environment test and the resistance R of the conductive path 24 hours after the start of the test were recorded. 24 The resistance R of the conductive path after the high temperature and high humidity environment test 120 The measurement was performed. At the resistance R... 24 or resistor R 120 When the resistance becomes more than 1.5 times that of R0, it is determined that a break in the conductive path has occurred. The results are shown in Table 1.

[0117] As shown in Table 1, in Example 1, no wire breakage was detected in the conductive path even after a 120-hour high-temperature and high-humidity environmental test. On the other hand, in each comparative example, wire breakage was detected in the conductive path after a 120-hour high-temperature and high-humidity environmental test. Based on the comparison between Example 1 and the comparative examples, the maximum height roughness Rz of the surface of each PET film containing FeGa fine lines or the surface of FeGa fine lines is less than 30 nm, indicating that it can maintain high durability for a long time in high-temperature and high-humidity environmental tests.

[0118] Based on the comparison between Example 1 and Comparative Example 2, it can be understood that in the difference |σ X -σ Y When the size is large, the rectangularity ratio tends to be high, and from the perspective of thermoelectric conversion performance, FeGa fine wires tend to have the desired magnetic properties.

[0119] In Comparative Example 1, no breakage of the conductive path was detected after 24 hours from the start of the high temperature and humidity environment test. However, in Comparative Example 2, a breakage of the conductive path was detected after 24 hours from the start of the high temperature and humidity environment test. In Comparative Example 2, a large internal stress as tensile stress was generated in the FeGa-containing wire, which interacted with the tensile stress generated by the expansion of the PET film accompanying exposure to the high temperature and humidity environment, resulting in cracks in the FeGa-containing wire. In Comparative Example 1, internal stress as compressive stress was generated in the FeGa-containing wire, which withstood the tensile stress generated by the expansion of the PET film accompanying exposure to the high temperature and humidity environment, thus preventing cracks from forming in the FeGa-containing wire. On the other hand, it is believed that when the PET film is exposed to a high temperature and humidity environment for 120 hours, the interface between the FeGa-containing wire and the PET film deteriorates, their adhesion decreases, and buckling occurs due to the compressive stress in the FeGa-containing wire, resulting in cracks in the FeGa-containing wire. The crack propagation direction of the FeGa-containing fine wire in the high-temperature and high-humidity environment test of Comparative Example 1 is different from that of the crack propagation direction of the FeGa-containing fine wire in the high-temperature and high-humidity environment test of Comparative Example 2. Therefore, as described above, it shows that the crack initiation mechanisms in Comparative Examples 1 and 2 are different.

[0120] In Comparative Example 3, a break in the conductive path was confirmed after 24 hours from the start of the high temperature and high humidity environment test. Based on the comparison between Example 1 and Comparative Example 3, it can be understood that in order to maintain high durability over a long period during the high temperature and high humidity environment test, the difference in the PET film used as the substrate |C X -C Y | Preferably, it is 0.1% or higher.

[0121] [Table 1]

[0122]

[0123] The first side of the present invention provides a thermoelectric conversion element, which includes:

[0124] Substrate; and

[0125] A thermoelectric converter, disposed on a first surface of the aforementioned substrate, and having a second surface intersecting a line perpendicular to the aforementioned first surface.

[0126] At least one of the aforementioned first surface and the aforementioned second surface is selected to have a maximum height roughness Rz of less than 30 nm.

[0127] The second side of the present invention provides the thermoelectric conversion element involved in the first side, wherein,

[0128] The aforementioned substrate has a third surface that is separate from the aforementioned thermoelectric converter and extends parallel to the aforementioned first surface.

[0129] The aforementioned third surface has an arithmetic mean roughness Ra of more than 8 nm.

[0130] The third side of the present invention provides the thermoelectric conversion element involved in the first or second side, wherein,

[0131] The aforementioned thermoelectric converter has a minimum internal stress of -300 MPa.

[0132] The aforementioned minimum internal stress is the minimum value of the internal stress of the aforementioned thermoelectric converter in a plane parallel to the aforementioned first surface.

[0133] The fourth side of the present invention provides a thermoelectric conversion element relating to any one of the first to third sides, wherein,

[0134] The aforementioned thermoelectric converter forms a fine wire containing magnetic material.

[0135] The fifth side of the present invention provides the thermoelectric conversion element involved in the fourth side, wherein,

[0136] The difference between the first internal stress of the aforementioned thermoelectric converter in the length direction of the aforementioned thin wire and the second internal stress of the aforementioned thermoelectric converter in the width direction perpendicular to the aforementioned length direction and parallel to the aforementioned first surface is 50 MPa or more.

[0137] The sixth side of the present invention provides the thermoelectric conversion element involved in the fourth or fifth side, wherein,

[0138] The aforementioned thermoelectric converter utilizes the temperature gradient in a direction perpendicular to the aforementioned first surface to generate an electromotive force along the length of the aforementioned thin wire.

[0139] The seventh side of the present invention provides a thermoelectric conversion element relating to any one of the first to sixth sides, wherein,

[0140] The aforementioned substrate contains organic materials.

[0141] The eighth side of the present invention provides a thermoelectric conversion element relating to any one of the first to seventh sides, wherein,

[0142] The aforementioned thermoelectric conversion element has a zigzag pattern including the aforementioned thermoelectric conversion body.

[0143] The ninth side of the present invention provides a thermoelectric conversion element relating to any one of the first to eighth sides, wherein,

[0144] The aforementioned thermoelectric conversion element forms a wound structure.

[0145] The tenth side of the present invention provides a sensor having a thermoelectric conversion element involved in any of the first to ninth sides.

Claims

1. A thermoelectric conversion element, which comprises: Substrate; and A thermoelectric converter, disposed on a first surface of the substrate and having a second surface intersecting a line perpendicular to the first surface, At least one of the surfaces selected from the group consisting of the first surface and the second surface has a maximum height roughness Rz of less than 30 nm.

2. The thermoelectric conversion element as claimed in claim 1, wherein, The substrate has a third surface that is separate from the thermoelectric converter and extends parallel to the first surface. The third surface has an arithmetic mean roughness Ra of more than 8 nm.

3. The thermoelectric conversion element as described in claim 1, wherein, The thermoelectric converter has a minimum internal stress of less than -300 MPa. The minimum internal stress is the minimum value of the internal stress of the thermoelectric converter in a plane parallel to the first surface.

4. The thermoelectric conversion element as claimed in claim 1, wherein, The thermoelectric converter is formed into a fine wire containing magnetic material.

5. The thermoelectric conversion element as described in claim 4, wherein, The difference between the first internal stress of the thermoelectric converter in the length direction of the thin wire and the second internal stress of the thermoelectric converter in the width direction, which is perpendicular to the length direction and parallel to the first surface, is more than 50 MPa.

6. The thermoelectric conversion element as claimed in claim 4, wherein, The thermoelectric converter generates an electromotive force along the length of the wire by utilizing a temperature gradient in a direction perpendicular to the first surface.

7. The thermoelectric conversion element as claimed in claim 1, wherein, The substrate contains organic materials.

8. The thermoelectric conversion element as claimed in claim 1, wherein, The thermoelectric conversion element has a zigzag pattern that includes the thermoelectric converter.

9. The thermoelectric conversion element as claimed in claim 1, wherein, The thermoelectric conversion element forms a wound structure.

10. A sensor comprising the thermoelectric conversion element according to any one of claims 1 to 9.

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