Thermoelectric conversion element

Abstract

To provide a thin thermoelectric conversion element having flexibility.SOLUTION: A thermoelectric transducer comprising: a substrate having flexibility; a base layer formed on the substrate and made of a metal-oxide material; and a magnetic layer laminated on the base layer and having conductivity and ferromagnetic or antiferromagnetic properties, wherein a thickness of the base layer is not less than 10nm and not more than 50nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion element using the anomalous Nernst effect. [Background technology]

[0002] The anomalous Nernst effect is a phenomenon in which, when a temperature gradient perpendicular to the magnetization direction of a conductive magnetic material is applied, an electromotive force is generated in the direction of the cross product of the magnetization direction and the temperature gradient, and is also called the magnetothermoelectric effect.Applications of thermoelectric conversion elements that utilize the anomalous Nernst effect include a thermoelectric power generation device that can generate electricity using a temperature difference perpendicular to the magnetization direction (Patent Document 1) and a heat flow measurement sensor that can measure the inflow and outflow of heat (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6079995 [Patent Document 2] Japanese Patent Application Publication No. 2023-141388 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a growing demand for thermal monitoring to manage the heat generated by batteries used in electric vehicles (EVs) and mobile devices, and semiconductor chips used in data processing, in order to prevent performance degradation and reduced lifespan. However, in these thermal monitoring applications, if the sensor element used for heat detection is too thick, the thermal resistance of the sensor element may affect the thermal characteristics of the object being measured, making it difficult to accurately detect the state of heat dissipation or absorption.

[0005] Generally, silicon substrates or magnesium oxide (MgO) substrates are used as substrates for thermoelectric conversion elements that utilize the anomalous Nernst effect. However, because these substrates have high rigidity, it is difficult to install thermoelectric conversion elements on curved surfaces, and there is also the possibility of them being damaged by impact.

[0006] The present invention has been made in view of the above problems, and has an object to provide a thin thermoelectric conversion element that is flexible. [Means for solving the problem]

[0007] One aspect of the present invention for solving the above problem is a thermoelectric conversion element having a flexible substrate, an underlayer formed on the substrate and made of a metal oxide material, and a magnetic layer stacked on the underlayer and having electrical conductivity and ferromagnetic or antiferromagnetic properties, wherein the thickness of the underlayer is 10 nm or more and 50 nm or less. [Effects of the Invention]

[0008] According to the present invention, a flexible thin thermoelectric conversion element can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic plan view of a thermoelectric conversion element according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA' shown in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line BB' shown in FIG. [Figure 4] FIG. 4 is a schematic plan view of a thermoelectric conversion element according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view taken along line CC' shown in FIG. [Figure 6] FIG. 5 is a cross-sectional view taken along line DD' shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment Hereinafter, an embodiment of the present invention will be described. The embodiment is an example of the present invention, and the description is not limited to the specific example. In addition, in the description of the drawings, the same parts are designated by the same reference numerals.

[0011] (composition) FIG. 1 is a schematic plan view of a thermoelectric conversion element according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line A-A' in FIG. 1, and FIG. 3 is a cross-sectional view taken along line B-B' in FIG. 1. The thermoelectric conversion element 100 includes a substrate 1, an underlayer 2 formed on the substrate 1, a magnetic layer 3 formed on the underlayer 2, a conductive layer 4, and a protective layer 5. The thermoelectric conversion element 100 is configured so that the anomalous Nernst effect occurs in the magnetic layer 3, and can be used as a heat flow sensor element or a thermoelectric power generation element. Note that in FIG. 1, the protective layer 5 is shown by a dashed line for convenience.

[0012] (substrate) The substrate 1 is a flat plate-like member made of an insulating material. The substrate 1 is preferably flexible from the viewpoint of closely contacting the thermoelectric conversion element 100 with the object to be measured. Materials that can be used for the substrate 1 include, for example, polycarbonate, polyethylene sulfide, polyethersulfone, polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, ethylene-tetrafluoroethylene copolymer resin, glass fiber reinforced acrylic resin film, polyimide, fluorine-based resin, and thin glass. The substrate 1 may be made of one of these materials, or may be made of a composite substrate 1 by laminating two or more types of materials.

[0013] When the substrate 1 is an organic film, a gas barrier layer (not shown) may be formed to improve the durability of the thermoelectric conversion element 100. Materials for the gas barrier layer include aluminum oxide (Al2O3), silicon oxide (SiO x ), silicon nitride (SiN xExamples of suitable gas barrier layers include, but are not limited to, silicon oxynitride (SiON), silicon carbide (SiC), and diamond-like carbon (DLC). Two or more of these gas barrier layers can also be stacked. The gas barrier layer can be formed on only one side of the substrate 1 using an organic film, or on both sides. The gas barrier layer can be formed using known methods such as, but not limited to, vacuum deposition, ion plating, sputtering, laser ablation, plasma CVD (Chemical Vapor Deposition), hot-wire CVD, and sol-gel methods.

[0014] (base layer) The underlayer 2 is made of an inorganic oxide material and is formed between the substrate 1 and the magnetic layer 3 as a base for the magnetic layer 3. By forming the underlayer 2 between the substrate 1 and the magnetic layer 3, the film density of the magnetic layer 3 formed on the underlayer 2 can be increased. If the underlayer 2 is not provided between the substrate 1 and the magnetic layer 3, the film density of the magnetic layer 3 cannot be sufficiently obtained, the thermoelectric properties of the thermoelectric conversion element 100 deteriorate, and it becomes difficult for the thermoelectric conversion element 100 to generate a voltage even when a temperature difference occurs. When a non-metallic substrate such as a flexible resin is used, it is difficult to obtain a magnetic layer 3 with sufficient film density if the magnetic layer 3 is formed directly on the substrate. Therefore, the underlayer 2 is particularly effective when the substrate 1 is flexible.

[0015] Furthermore, by forming the base layer 2, it is possible to improve the gas barrier property and improve the durability of the thermoelectric conversion element 100. Furthermore, by providing the protective layer 5 on the thermoelectric conversion element 100, it is possible to further improve the durability.

[0016] The thickness of the underlayer 2 is preferably 10 nm or more and 50 nm or less. A thickness exceeding 50 nm is undesirable because it impairs the flexibility of the thermoelectric conversion element 100. Furthermore, a thickness less than 10 nm impairs the functionality of the underlayer 2, resulting in insufficient film density of the magnetic layer 3 and reduced thermoelectric properties of the thermoelectric conversion element 100. When flexibility is particularly important in the thermoelectric conversion element 100, a thinner underlayer 2 is preferred. Furthermore, the thickness of the underlayer 2 is preferably, for example, 10 nm or more and 15 nm or less. When gas barrier properties are particularly important in the thermoelectric conversion element 100, such as when a plastic substrate is used for the substrate 1, it is preferable to form the underlayer 2 thicker, for example, 30 nm or more and 50 nm or less. When flexibility is not required for the thermoelectric conversion element 100, the thickness of the underlayer 2 may exceed 50 nm.

[0017] From the viewpoint of improving flexibility, it is preferable that the base layer 2 is not formed on the entire surface of the thermoelectric conversion element 100, and the area of ​​the base layer 2 in a plan view is S F , the area of ​​the magnetic layer 3 is S M , the area of ​​the conductive layer 4 is S C In this case, S F ≦(S M +S C ) is preferable.

[0018] The material of the underlayer 2 can be selected to match the constituent material of the magnetic layer 3 formed on the underlayer 2. Examples of materials that can be used for the underlayer 2 include inorganic materials such as silicon oxide, magnesium oxide, aluminum oxide, titanium oxide, tantalum oxide, hafnium oxide, yttrium oxide, and zirconium oxide. These materials may be used as a single layer or as a laminate of two or more layers. The underlayer 2 may also be a mixture or copolymer of these materials, or a thin film of an inorganic-organic resin hybrid material in which these inorganic materials are added to a resin. Furthermore, the film may be formed with a composition gradient in the growth direction during film formation.

[0019] The underlayer 2 may be an amorphous film, or a microcrystalline film or a polycrystalline film, but when the magnetic layer 3 formed on the underlayer 2 is a crystalline thin film, it is preferable to control the crystal orientation to match that of the magnetic layer 3. Therefore, it is preferable to select a material for the underlayer 2 so that the d value (lattice spacing) and lattice constant in the crystal structure of the underlayer 2 and the magnetic layer 3 are close to each other.

[0020] Generally, a thin film with a high density close to a bulk state (a dense thin film) is considered to be of high quality, and in the case of the underlayer 2 of the present invention, a higher density is preferable because it allows for the formation of a higher density magnetic layer 3. The density of the underlayer 2 is preferably 85% or more of the density of the material that constitutes the underlayer 2 in a bulk state.

[0021] The method for forming the underlayer 2 is appropriately selected from known vacuum film formation methods and wet film formation methods depending on the material used. Vacuum film formation methods that can be used include, for example, sputtering, atomic layer deposition (ALD), pulsed laser deposition (PLD), chemical vapor deposition (CVD), molecular beam deposition (MBE), and electron beam evaporation. Wet film formation methods that can be used include spin coating, slit coating, and various printing methods that use liquid raw materials in which materials such as organometallic compounds as precursors or organic materials are dissolved or dispersed.

[0022] A known dry etching method, wet etching method, etc. can be used to pattern the underlayer 2. In order to reduce the number of steps, a method of simultaneously patterning the underlayer 2 and the magnetic layer 3 after they are formed can also be suitably used.

[0023] In this embodiment, the underlayer 2 is provided only below the magnetic layer 3 as a base for the magnetic layer 3, but since it can also function as a base for the conductive layer 4, it may also be provided below the conductive layer 4. In this case, the material for the underlayer 2 can be selected from the materials for the underlayer 2 described above, depending on the constituent materials of the magnetic layer 3 and conductive layer 4 formed on the underlayer 2.

[0024] (Magnetic layer) The magnetic layers 3 are stacked on the underlayer 2 so that adjacent magnetic layers 3 are electrically connected in series by the conductive layers 4 disposed between each magnetic layer 3. Due to the anomalous Nernst effect, when a temperature gradient perpendicular to the magnetization direction is applied, the magnetic layers 3 generate an electromotive force in the direction of the cross product of the magnetization direction and the temperature gradient. In Figure 1, the direction of the electromotive force is the positive x-axis, the magnetization direction is the positive y-axis, and the temperature gradient (direction of heat flow) is the negative z-axis.

[0025] To obtain the anomalous Nernst effect, the magnetic layer 3 must be electrically conductive and either ferromagnetic or antiferromagnetic. Examples of electrically conductive ferromagnetic or antiferromagnetic materials that can be used for the magnetic layer 3 include, but are not limited to, Fe-based alloys such as FeAl alloys, FeGa alloys, and FeSi alloys, Co2MnGa and Co2MnAl known as Heusler alloys, and Mn3Sn and Mn3Ge known as topological magnets.

[0026] The method for forming the magnetic layer 3 is appropriately selected from known vacuum film formation methods and wet film formation methods depending on the material used. Vacuum film formation methods include, for example, sputtering, atomic layer deposition (ALD), pulsed laser deposition (PLD), chemical vapor deposition (CVD), molecular beam deposition (MBE), and electron beam evaporation. Wet film formation methods include spin coating, slit coating, and various printing methods using a liquid source in which the target material is dispersed as fine particles. Vacuum film formation is particularly suitable for forming high-quality thin films, and by successively depositing the underlayer 2 and magnetic layer 3 in a vacuum atmosphere, a magnetic layer 3 with good film quality can be formed.

[0027] The thin film of the magnetic layer 3 may be an amorphous film, a microcrystalline film, or a polycrystalline film as long as it exhibits the anomalous Nernst effect. However, when a magnetic material having a Heusler structure or a pseudo-Heusler structure is used as the material of the magnetic layer 3, it is preferable that the material be crystalline.

[0028] The magnetic layer 3 is also preferably a thin film (dense thin film) with high density close to a bulk state, and the density of the magnetic layer 3 is preferably 85% or more of the density of the material that makes up the magnetic layer 3 in a bulk state.

[0029] In the anomalous Nernst effect, which is a magneto-thermoelectric effect, the electromotive force (anomalous Nernst voltage V ANE ) is the anomalous Nernst coefficient S of the material constituting the magnetic layer 3 ANE It is known that the voltage is proportional to the wiring length (length of the magnetic layer 3 in the x-axis direction) L and the temperature gradient ∇T (temperature gradient of the magnetic layer 3 in the z-axis direction), and the film thickness d of the magnetic layer 3 in the z-axis direction does not contribute to the magnitude of the voltage (Equation 1). However, when a large power P ex To obtain this, a large current value I is required, and therefore a large film thickness d is preferable (Equations 2 to 4). (Formula 1) JPEG2026005607000002.jpg25103 V ANE :Abnormal Nernst voltage S ANE : Anomalous Nernst coefficient ∇T: temperature gradient in the z-axis direction of the magnetic layer 3 L: length of the magnetic layer 3 in the x-axis direction (Formula 2) JPEG2026005607000003.jpg1871 P ex : Element output (power) R ex :External resistance (Formula 3) JPEG2026005607000004.jpg2066 R int : Internal resistance (Formula 4) JPEG2026005607000005.jpg2091 ρ: conductivity S: Cross-sectional area w: line width of the magnetic layer 3 in the y-axis direction d: Film thickness

[0030] Therefore, when the thermoelectric conversion element 100 is used as a thermoelectric power generation element requiring a large amount of power, it is preferable to increase the thickness d of the magnetic layer 3. On the other hand, when the thermoelectric conversion element 100 is used as a heat flow sensor for detecting heat flow, the thickness d can be set taking into account the electrical conductivity of the magnetic layer 3 and the internal resistance of the thermoelectric conversion element 100. In this case, the thickness d of the magnetic layer 3 does not necessarily need to be set to a large thickness. However, if the magnetic layer 3 is formed as an extremely thin film, it becomes difficult to obtain good film quality and the resistance value of the thermoelectric conversion element 100 increases. Therefore, from the viewpoint of electrical conductivity, it is preferable that the magnetic layer 3 has a certain thickness. In the thermoelectric conversion element 100 of the present invention, in order to achieve both flexibility and thermoelectric properties, the thickness d of the magnetic layer 3 is preferably 30 nm to 300 nm, more preferably 50 nm to 100 nm. Regarding thermoelectric properties, it is preferable that a voltage of 0.1 mV or more can be obtained per meter of the magnetic layer.

[0031] In addition, the power P ex To increase the resistance, it is preferable that the length L of the magnetic layer 3 is long, and to increase the length L of the magnetic layer 3, the width w of the magnetic layer 3 can be narrowed within a range in which the resistance value of the magnetic layer 3 does not become excessive. By narrowing the width w of the magnetic layer 3, it is possible to increase the number of patterns in the magnetic layer 3, thereby improving the thermoelectric properties. For example, the width w of the magnetic layer 3 is preferably approximately 5 μm or more and 50 μm or less.

[0032] (Conductive layer) The conductive layer 4 is conductive and functions as wiring that electrically connects adjacent magnetic layers 3. The conductive layer 4 is provided at least between adjacent magnetic layers 3 and electrically connects one end of the magnetic layer 3 to the other end of the magnetic layer 3 adjacent to that magnetic layer 3 on one side of the magnetic layer 3 in series. In this embodiment, the conductive layer 4 includes a portion formed parallel to the magnetic layer 3 between the adjacent magnetic layers 3 and a portion formed perpendicular to the extension direction of the magnetic layers 3, connecting both ends of the parallel conductive layer 4 to the adjacent magnetic layers 3 (FIG. 1). The conductive layer 4 may also be used as a connection terminal between the thermoelectric conversion element 100 and the outside. As a component of the thermoelectric conversion element 100, the conductive layer 4 does not need to be clearly separated into a wiring portion and a connection terminal portion, and in this embodiment, both portions are collectively referred to as the conductive layer 4.

[0033] A conductive metal material can be suitably used as the material for the conductive layer 4. For example, metal materials such as silver (Ag), aluminum (Al), copper (Cu), and chromium (Cr), alloy materials containing these, conductive metal oxide materials such as indium tin oxide (ITO) and indium zinc oxide (IZO), and conductive carbon materials such as carbon nanotubes (CNT) and graphene can be used. These materials can be used in a single layer or in a laminate of two or more layers.

[0034] Furthermore, it is more preferable that the conductive layer 4 be a ferromagnetic or antiferromagnetic material that exhibits the anomalous Nernst effect and has thermoelectric power opposite to that of the magnetic layer 3. Here, having opposite thermoelectric power means that when a temperature gradient in the same direction is applied in the anomalous Nernst effect, an electromotive force in the opposite direction is generated. Therefore, the conductive layer 4 can also generate thermoelectric power similar to that of the magnetic layer 3, thereby improving the thermoelectric conversion characteristics. In this case, the conductive layer 4 may be made of a different material from that of the magnetic layer 3, or may be made of the same material but with a different magnetization direction.

[0035] Since the conductive layer 4 functions as wiring, it preferably has high conductivity to suppress delay and attenuation of the electromotive force generated in the magnetic layer 3. Therefore, the thickness of the conductive layer 4 is appropriately adjusted taking into consideration the conductivity of the material used. Furthermore, when a ferromagnetic or antiferromagnetic material exhibiting the anomalous Nernst effect is used for the conductive layer 4, the thickness can be approximately the same as that of the magnetic layer 3.

[0036] The conductive layer 4 can be formed by a vacuum deposition method such as a vacuum deposition method or a sputtering method, a sol-gel method using a precursor of a conductive material, or a wet deposition method in which nanoparticles of a conductive material are made into an ink and then coated or printed. However, the method is not limited to these, and any known method can be appropriately selected and used.

[0037] The conductive layer 4 can be patterned, for example, by using photolithography to protect the pattern formation area with resist or the like and then removing unnecessary areas by etching, or by directly patterning using a printing method or the like. However, the method is not limited to these, and any known patterning method can be appropriately selected and used.

[0038] (protective layer) The protective layer 5 is provided to protect the magnetic layer 3 and the conductive layer 4. For example, the thermoelectric conversion element 100 may be oxidized and deteriorated due to the influence of the temperature of the object on which the thermoelectric conversion element 100 is installed, the ambient temperature of the installation location, or moisture or oxygen that has penetrated the thermoelectric conversion element 100. Therefore, by protecting the magnetic layer 3 and the conductive layer 4 with the protective layer 5, it is possible to maintain the thermoelectric conversion element 100 in good condition for a long period of time. The protective layer 5 may be formed so as to cover at least the magnetic layer 3 and the conductive layer 4, but may also be formed on the entire surface of the conductive layer 4 except for the portions corresponding to the connection terminals between the thermoelectric conversion element 100 and the outside. The protective layer 5 may also be omitted.

[0039] Examples of materials that can be used for the protective layer 5 include inorganic insulating materials such as silicon oxide, aluminum oxide, tantalum oxide, hafnium oxide, yttrium oxide, zirconium oxide, and silicon nitride; insulating materials containing silicon oxynitride or organic materials; and organic insulating resin materials such as acrylic resins such as polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyvinyl phenol (PVP), epoxy resins, polyimide, and parylene. These materials may be used as a single layer or as a laminate of two or more layers. They may also be mixtures or copolymers of these materials, or thin films of inorganic-organic resin hybrid materials in which the aforementioned inorganic materials are added to the resin. Furthermore, the composition may be graded in the growth direction during film formation. In particular, when flexibility of the thermoelectric conversion element 100 is important, it is preferable to form the protective layer 5 from an organic material.

[0040] The thickness of the protective layer 5 can be appropriately selected depending on the flexibility required for the thermoelectric conversion element 100, but in consideration of flexibility and protection, when an organic material is used as the material for the protective layer 5, the thickness is preferably 0.1 μm or more and 3 μm or less. When an inorganic material is used, the thickness of the protective layer 5 is preferably 5 nm or more and 200 nm or less.

[0041] The resistivity of the protective layer 5 is 10 11 It is preferable that the resistance is 10 Ωcm or more. 14 It is more preferable that the resistivity is Ωcm or more, which makes it possible to suppress leakage current between the patterns of the magnetic layer 3 and the conductive layer 4.

[0042] Furthermore, in order to suppress the influence of parasitic capacitance and the like, it is preferable that the relative dielectric constant of the protective layer 5 is low, and for example, the relative dielectric constant of the protective layer 5 is preferably not less than 2 and not more than 5. The relative dielectric constant can be calculated by applying a voltage at a desired frequency to a measurement element using an LCR meter or the like and measuring the capacitance at that time.

[0043] The method for forming the protective layer 5 is appropriately selected depending on the material to be used from vacuum film formation methods such as sputtering, atomic layer deposition (ALD), pulsed laser deposition (PLD), and chemical vapor deposition (CVD), and wet film formation methods such as spin coating, slit coating, and various printing methods. Furthermore, the protective layer 5 can be patterned by appropriately selecting from known general patterning methods.

[0044] When using the thermoelectric conversion element 100 as a heat flow sensor element, for example, it can be installed on an object using thermally conductive grease or a thermally conductive adhesive. While there are no particular limitations on the materials used, it is preferable to place the thermoelectric conversion element in close contact with the object without leaving any gaps so as not to impede heat conduction between the object and the thermoelectric conversion element. Furthermore, when using the thermoelectric conversion element 100 as a heat flow sensor element, it is possible to detect these as heat by combining a material that generates or absorbs heat in response to specific molecules or ions as the sensor active layer. Furthermore, depending on the intended use, multiple thermoelectric conversion elements 100 may be installed connected in series or parallel.

[0045] (film thickness measurement) The film thicknesses of the substrate 1, underlayer 2, magnetic layer 3, conductive layer 4, and protective layer 5 can be measured by a known method using a stylus profilometer, a laser microscope, a white light interference microscope, a scanning probe microscope (SPM), a scanning electron microscope (SEM), or the like, but these methods can be appropriately selected depending on the size and shape of the sample and the range of film thickness.

[0046] (Film density evaluation) The density (film density) of the thin films of the underlayer 2 and the magnetic layer 3 can be evaluated by X-ray reflectometry (XRR) or the like.

[0047] (Conductivity measurement) The conductivity of the magnetic layer 3 and the conductive layer 4 can be determined from the current value when a voltage is applied to the pattern of each layer, and may be calculated from the current-voltage curve between two terminals (IV curve) or by performing four-terminal measurement such as the Van der Pauw method.

[0048] (Evaluation of the composition of the underlayer 2 and the magnetic layer 3) To evaluate the compositions of the underlayer 2 and the magnetic layer 3, it is possible to observe the film compositions of the underlayer 2 and the magnetic layer 3 by providing a measurement area separate from the thermoelectric conversion element 100 or by preparing a measurement sample. For example, if the magnetic layer 3 is made of an alloy material, the metal ratio can be evaluated using X-ray photoelectron spectroscopy (XPS), X-ray fluorescence analysis (XRF), or the like, or if the underlayer 2 is made of an oxide material, the element ratio of metal to oxygen can be evaluated.

[0049] (Measurement of crystallinity) The crystallinity of the underlayer 2 and the magnetic layer 3 can be measured by a method such as X-ray diffraction (XRD), and the crystallinity can be evaluated by a known method.

[0050] As described above, the thermoelectric conversion element 100 according to this embodiment has an underlayer 2 of 10 nm or more formed thereon. This allows the film density of the magnetic layer 3 formed on the underlayer 2 to be increased, resulting in a thermoelectric conversion element 100 with excellent thermoelectric properties.

[0051] Furthermore, since the substrate 1 is flexible and the underlayer 2 is 50 nm or less, the thermoelectric conversion element 100 is strong against bending and can be installed on a curved surface. Furthermore, the provision of the underlayer does not hinder the thinness of the thermoelectric conversion element, making it possible to provide a thin thermoelectric conversion element.

[0052] Second Embodiment The thermoelectric conversion element 200 according to the second embodiment will be described, mainly focusing on the differences from the thermoelectric conversion element 100 according to the first embodiment. Fig. 4 is a schematic plan view of the thermoelectric conversion element according to the second embodiment of the present invention, Fig. 5 is a cross-sectional view taken along line CC' in Fig. 4, and Fig. 6 is a cross-sectional view taken along line DD' in Fig. 4.

[0053] The thermoelectric conversion element 200 according to the second embodiment, like the thermoelectric conversion element 100, has a configuration in which the conductive layer 4 electrically connects one end of the magnetic layer 3 to the other end of the adjacent magnetic layer 3 on one side of the magnetic layer 3 in series, thereby generating the anomalous Nernst effect in the magnetic layer 3. However, the thermoelectric conversion element 200 differs from the thermoelectric conversion element 100 in that the conductive layer 4 is formed on the protective layer 5, except for the connection between the conductive layer 4 and the magnetic layer 3. By forming the conductive layer 4 on a different layer from the magnetic layer 3, the conductive layer 4 and the magnetic layer 3 can be formed overlapping in the parallel direction of the magnetic layer 3 in a plan view. Therefore, compared to the thermoelectric conversion element 100 according to the first embodiment, the pattern of the magnetic layer 3 can be formed more densely, enabling the thermoelectric conversion element to be miniaturized. Appropriate openings are provided in the protective layer 5 to establish electrical connection between the magnetic layer 3 and the conductive layer 4 ( FIG. 6 ).

[0054] In this embodiment, a configuration has been described in which the base layer 2 and the magnetic layer 3 are formed on the substrate 1, and the conductive layer 4 is formed on the protective layer 5. However, even in a configuration in which the conductive layer 4 is formed on the substrate 1, and the base layer 2 and the magnetic layer 3 are formed on the protective layer 5, the pattern of the magnetic layer 3 can be formed densely, which can contribute to miniaturizing the thermoelectric conversion element.

[0055] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Example]

[0056] Example 1 The thermoelectric conversion element 100 according to the first embodiment was fabricated to provide a thermoelectric conversion element according to Example 1 (FIGS. 1 to 3). The specific fabrication method is as follows.

[0057] A non-alkali glass substrate having a thickness of 0.7 mm was used as a supporting substrate, and polyimide varnish was applied thereon and then baked to form a substrate 1 made of a polyimide film having a thickness of 20 μm.

[0058] A magnesium oxide film was formed on the substrate 1 using RF magnetron sputtering to a thickness of 10 nm, followed by a MnSn alloy film formed to a thickness of 100 nm using DC magnetron sputtering. This was then patterned using photolithography to form an underlayer 2 made of magnesium oxide and a magnetic layer 3 made of an MnSn alloy. The pattern size of the underlayer 2 and magnetic layer 3 was a wiring shape with a width w of 20 μm and a length L of 15 mm, and 150 lines were formed at predetermined intervals.

[0059] An aluminum alloy film was formed to a thickness of 100 nm on the substrate 1 on which the underlayer 2 and magnetic layer 3 were formed, and then patterned using photolithography to form a conductive layer 4 between adjacent magnetic layers 3. The conductive layer 4 was formed parallel to the magnetic layers 3, with a width of 10 μm and a wiring length of 15 mm. However, both ends of the conductive layer 4 formed between the magnetic layers 3 were formed perpendicular to the extension direction of the magnetic layers 3 in order to connect to the magnetic layers 3 (Figure 1). By forming the conductive layer 4, the patterns of the magnetic layers 3 were connected in series, with a length of 2.25 m.

[0060] A photosensitive acrylic resin was applied by spin coating, exposed to light using a mask, patterned by alkaline development, and baked to form a protective layer 5. The protective layer 5 had a thickness of 1 μm and a resistivity of 1×10 15 The dielectric constant was 3.5.

[0061] The substrate 1 was peeled off from the support base material to produce a flexible thermoelectric conversion element.

[0062] Example 2 A thermoelectric conversion element was fabricated in the same manner as in Example 1, except that the thickness of the magnetic layer 3 was set to 30 nm.

[0063] Example 3 A thermoelectric conversion element was fabricated in the same manner as in Example 1, except that the thickness of the magnetic layer 3 was set to 300 nm.

[0064] Example 4 A thermoelectric conversion element was produced in the same manner as in Example 1, except that the thickness of the underlayer 2 was set to 30 nm.

[0065] Example 5 A thermoelectric conversion element was produced in the same manner as in Example 1, except that the thickness of the underlayer 2 was set to 50 nm.

[0066] Example 6 A thermoelectric conversion element was fabricated in the same manner as in Example 1, except that the thermoelectric conversion element 200 according to the second embodiment was used.

[0067] (Comparative Example 1) A thermoelectric conversion element was produced in the same manner as in Example 1, except that the underlayer 2 was not formed.

[0068] (Comparative Example 2) A thermoelectric conversion element was produced in the same manner as in Example 1, except that the thickness of the underlayer 2 was set to 70 nm.

[0069] (Comparative Example 3) A thermoelectric conversion element was fabricated in the same manner as in Example 1, except that the thickness of the underlayer 2 was set to 70 nm and the thickness of the magnetic layer 3 was set to 30 nm.

[0070] The thermoelectric properties were evaluated, a bending test was performed, and the thermoelectric properties after the bending test were evaluated for each of the thermoelectric conversion elements produced in Examples 1 to 6 and Comparative Examples 1 to 3. Specific evaluation and test methods are as follows.

[0071] (Evaluation of thermoelectric properties before bending test) The thermoelectric conversion element was sandwiched between copper plates and placed on a cooling plate, and a film heater was placed above the thermoelectric conversion element to create a temperature gradient. Then, the voltage at both ends of the conductive layer 4 (the locations corresponding to the connection terminals between the thermoelectric conversion element and the outside) was measured using a digital multimeter. A voltage of 0.1 mV or more per meter of magnetic layer was evaluated as ◯, and otherwise as ×.

[0072] (Bending test) A 5 mm diameter metal rod was placed along the y-axis direction on the element part of the thermoelectric conversion element, and the thermoelectric conversion element was bent along the x-axis direction. After bending, the element was observed under a microscope to see if cracks occurred. If cracks occurred, it was evaluated as ×, and if no cracks occurred, it was evaluated as ○.

[0073] (Evaluation of thermoelectric properties after bending test) The thermoelectric characteristics of the thermoelectric conversion element after the bending test were evaluated in the same manner as in the evaluation of the thermoelectric characteristics before the bending test.

[0074] Table 1 shows the film thicknesses of the underlayer 2 and magnetic layer 3, as well as the results of evaluation and testing, for the thermoelectric conversion elements according to Examples 1 to 6 and Comparative Examples 1 to 3.

[0075] [Table 1]

[0076] The thermoelectric conversion elements according to Examples 1 to 6 had an underlayer 2 of 10 nm or more formed thereon. As a result, a magnetic layer 3 with sufficient film density was formed, and the thermoelectric conversion elements 100 exhibited excellent thermoelectric properties. Furthermore, since the formed underlayer 2 was 50 nm or less, no cracks occurred in the bending test, and the thermoelectric conversion elements 100 exhibited excellent thermoelectric properties even after the bending test.

[0077] The thermoelectric conversion element according to Comparative Example 1 did not have the underlayer 2. Therefore, the film density of the magnetic layer 3 was not sufficient, and the thermoelectric characteristics of the thermoelectric conversion element 100 were poor both before and after the bending test.

[0078] The thermoelectric conversion elements according to Comparative Examples 2 and 3 had an underlayer 2 of 10 nm or more. Therefore, a magnetic layer 3 with sufficient film density was formed, and the thermoelectric conversion elements before the bending test exhibited excellent thermoelectric properties. However, because the thickness of the underlayer 2 exceeded 50 nm, cracks occurred along the y-axis direction during the bending test in which the elements were bent in the x-axis direction, and locations of disconnections were confirmed. Therefore, the thermoelectric properties of the thermoelectric conversion elements after the bending test were poor.

[0079] In particular, cracks occurred in the bending test in the thermoelectric conversion element according to Comparative Example 3, even though the total thickness of the underlayer 2 and the magnetic layer 3 was thinner than in Examples 1 and 3 to 5. From this and the results of the Examples, it was confirmed that if the film thickness of the underlayer 2 is in the range of 10 nm to 50 nm, the thermoelectric conversion element can achieve both thermoelectric properties and flexibility. [Industrial Applicability]

[0080] The present invention can be applied to a thermoelectric conversion element using the anomalous Nernst effect. [Explanation of symbols]

[0081] 1: Circuit board 2: Base layer 3: Magnetic layer 4: Conductive layer 5:Protective layer 100: Thermoelectric conversion element 200: Thermoelectric conversion element

Claims

1. a flexible substrate; an underlayer formed on the substrate and made of a metal oxide material; a magnetic layer laminated on the underlayer and having electrical conductivity and ferromagnetic or antiferromagnetic properties; The thermoelectric conversion element, wherein the underlayer has a thickness of 10 nm or more and 50 nm or less.

2. 2. The thermoelectric conversion element according to claim 1, wherein the density of said underlayer and the density of said magnetic layer are 85% or more of the density of the material constituting each layer in a bulk state.

3. a plurality of linear magnetic layers are formed in parallel and spaced apart from one another; a conductive layer electrically connecting adjacent magnetic layers; The area of ​​the underlayer is S Ｆ , the area of ​​the magnetic layer is S Ｍ , the area of ​​the conductive layer is S Ｃ In this case, S Ｆ ≦(S Ｍ +S Ｃ 2. The thermoelectric conversion element according to claim 1, wherein

4. 4. The thermoelectric conversion element according to claim 3, wherein the conductive layer is made of a magnetic material having ferromagnetic or antiferromagnetic properties and has a thermoelectric power opposite to that of the magnetic layer.

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