Thermoelectric conversion element and thermoelectric conversion device

Abstract

To provide a thermoelectric conversion element and a thermoelectric conversion device which are made of an inexpensive and low-toxicity material and exhibit an anomalous Nernst effect.SOLUTION: A thermoelectric conversion device (20) includes a substrate (22) and a plurality of thermoelectric conversion elements (24, 25) provided on the substrate (22). Each of the plurality of thermoelectric transducers (24, 25) is made of iron nitride (e.g., Fe16N2) exhibiting the anomalous Nernst effect, and has a rectangular parallelepiped shape. The plurality of thermoelectric transducers (24, 25) are arranged in parallel in a meandering manner in a direction (y direction) perpendicular to the longitudinal direction (x direction), and are electrically connected in series.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion element and a thermoelectric conversion device including the thermoelectric conversion element. [Background technology]

[0002] The Seebeck effect is known as a thermoelectric mechanism that generates a voltage when a temperature gradient is applied to a material (see, for example, Patent Document 1). However, in thermoelectric mechanisms using the Seebeck effect, materials that can be used above room temperature are primarily made from bismuth, tellurium, lead, or the like, which are highly toxic and therefore unsuitable for practical use. They are also mechanically fragile, susceptible to vibration, and lack durability. Furthermore, because the Seebeck effect generates a voltage in the same direction as the temperature gradient, it is necessary to fabricate a complex, three-dimensional structure in which p-type and n-type modules are alternately arranged in a direction perpendicular to the heat source surface, resulting in high manufacturing costs. Furthermore, it is difficult to deploy such three-dimensional elements over a large area.

[0003] Another thermoelectric mechanism that generates voltage due to a temperature gradient is the anomalous Nernst effect. The anomalous Nernst effect is a phenomenon in which, when a heat flow is passed through a magnetic material and a temperature difference is created, a voltage is generated in a direction perpendicular to both the magnetization direction and the temperature gradient. In recent years, it has been discovered that by utilizing the topology of the electronic structure, the Nernst coefficient can be increased much more than the previously known value (0.1 μV / K). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 181777 Summary of the Invention [Problem to be solved by the invention]

[0005] Although various magnetic materials that exhibit the anomalous Nernst effect have been developed, they have involved the problem of high costs because they use relatively expensive metals.

[0006] The present invention has been made in view of the above problems, and has as its object to provide a thermoelectric conversion element and a thermoelectric conversion device that are made of inexpensive, low-toxicity materials and that exhibit the anomalous Nernst effect. [Means for solving the problem]

[0007] A thermoelectric conversion element according to one embodiment of the present invention is made of iron nitride and exhibits the anomalous Nernst effect.

[0008] A thermoelectric conversion device according to one embodiment of the present invention includes a substrate and a plurality of thermoelectric conversion elements provided on the substrate, each of which is a thermoelectric conversion element that exhibits the above-described anomalous Nernst effect and has a shape extending in one direction, and the plurality of thermoelectric conversion elements are arranged in parallel in a direction perpendicular to the one direction and electrically connected in series.

[0009] A thermoelectric conversion device according to another embodiment of the present invention comprises a hollow member and a thermoelectric conversion element exhibiting the above-described anomalous Nernst effect, the thermoelectric conversion element being a sheet or wire arranged to cover the outer surface of the hollow member. [Effects of the Invention]

[0010] According to the present invention, the anomalous Nernst effect can be achieved by using a thermoelectric conversion element made of inexpensive and low-toxicity materials. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram for explaining a thermoelectric mechanism of a thermoelectric conversion element according to an embodiment of the present invention. [Figure 2A] 1 is a schematic diagram showing the crystal structure of Fe3Sn2. [Figure 2B] 1 is a schematic diagram showing the crystal structure of the ab plane of Fe3Sn2. [Figure 3A] 1 is a graph showing the temperature dependence of magnetization of Fe3Sn2 upon cooling in zero magnetic field and cooling in a magnetic field when the applied magnetic field is parallel to the ab plane. [Figure 3B] 3B is a graph showing the temperature derivative of the magnetization shown in FIG. 3A. [Figure 3C] 1 is a graph showing the magnetic field dependence of the magnetization of Fe3Sn2 at 5 K, 200 K, and 300 K when a magnetic field parallel to the ab plane is applied. [Figure 4A] 1 is a graph showing the temperature dependence of magnetization of Fe3Sn2 upon zero-field cooling and magnetic field cooling when the applied magnetic field is parallel to the c-axis. [Figure 4B] 1 is a graph showing the magnetic field dependence of the magnetization of Fe3Sn2 at 5 K, 200 K, and 300 K when a magnetic field parallel to the c-axis is applied. [Figure 5A] 1 is a graph showing the magnetic field dependence of the Nernst coefficient of Fe3Sn2 at 200K, 300K, and 390K. [Figure 5B] 1 is a graph showing the magnetic field dependence of the Hall resistivity of Fe3Sn2 at 200K and 300K. [Figure 5C] 1 is a graph showing the temperature dependence of the Nernst coefficient of Fe3Sn2. [Figure 6] Schematic diagram showing the crystal structure of Fe16N2. [Figure 7A] 10 is a graph showing the magnetic field dependence of the Nernst coefficient of the first sample made of Fe16N2. [Figure 7B] 10 is a graph showing the magnetic field dependence of the Nernst coefficient of a second sample made of Fe16N2. [Figure 8] Schematic diagram showing the crystal structure of RCo5 (R is a rare earth element). [Figure 9A] 1 is a graph showing an X-ray diffraction pattern of YCo5 polycrystal. [Figure 9B] 1 is a graph showing the magnetic field dependence of the magnetization of YCo5 polycrystal at 10K and 300K. [Figure 9C] 1 is a graph showing the temperature dependence of magnetization of YCo5 polycrystal. [Figure 9D]1 is a graph showing the magnetic field dependence of the Nernst coefficient of YCo5 polycrystal at 100K, 200K, and 300K. [Figure 10] FIG. 1 is a schematic diagram showing the crystal structure of RCo4M (R is a rare earth element; M is B or Ga). [Figure 11] 1 is a graph showing the magnetic field dependence of the Nernst coefficient of DyCo4Ga at 300K and 350K. [Figure 12] 1 is a perspective view showing the configuration of a thermoelectric conversion device according to Example 1 that includes a thermoelectric conversion element of the present embodiment. [Figure 13] FIG. 10 is a plan view showing the configuration of a thermoelectric conversion device according to Example 2 that includes the thermoelectric conversion element of the present embodiment. [Figure 14] FIG. 10 is an external view showing the configuration of a thermoelectric conversion device according to Example 3 that includes the thermoelectric conversion element of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. The drawings are schematic, and the relationship between planar dimensions and thicknesses, and the thickness ratios of each member may differ from those in reality.

[0013] First, with reference to FIG. 1, a thermoelectric conversion element and its thermoelectric mechanism according to an embodiment of the present invention will be described.

[0014] As shown in Fig. 1, the thermoelectric conversion element 1 according to this embodiment has a rectangular parallelepiped shape extending in one direction (y direction), a predetermined thickness (length in the z direction), and is magnetized in the +z direction. When a heat flow Q (∝-∇T) flows in the +x direction through the thermoelectric conversion element 1, a temperature difference occurs in the +x direction. As a result, an electromotive force V (∝M × (-∇T)) is generated in the thermoelectric conversion element 1 in the cross product direction (y direction) perpendicular to both the direction of the heat flow Q (+x direction) and the direction of the magnetization M (+z direction) due to the anomalous Nernst effect.

[0015] Among materials that exhibit the anomalous Nernst effect, the highest Nernst coefficient to date is Co2MnGa, which was achieved by the present inventors. The Nernst coefficient of Co2MnGa reaches approximately 6 μV / K at room temperature and approximately 8 μV / K at 400 K (see Nature Physics 14, 1119-1124 (2018) and WO 2019 / 009308).

[0016] <fe3sn2> The inventors of the present invention have succeeded in achieving a Nernst coefficient approaching the highest value ever achieved using an alloy of inexpensive, low-toxicity iron (Fe) and tin (Sn).

[0017] Figures 2A and 2B show the crystal structure of Fe3Sn2, which can exhibit the anomalous Nernst effect. Fe3Sn2 has a crystal structure in which Fe-Sn kagome bilayers, in which Fe atoms form a kagome lattice, and honeycomb-structured Sn layers are alternately stacked in the c-axis direction. As shown in Figure 2A, two Fe-Sn kagome bilayers are separated by a Sn layer. As shown in Figure 2B, each Fe-Sn kagome bilayer is composed of equilateral triangles (solid lines, dashed lines) with different Fe-Fe distances, and Sn is located at the center of each hexagon in the kagome lattice.

[0018] Such Fe3Sn2 ferromagnetic materials can be produced by known methods such as the self-flux method. Alternatively, thin films of Fe3Sn2 can be produced using methods such as sputtering, molecular beam epitaxy (MBE), or chemical vapor deposition (CVD). Fe3Sn2 can be either single crystal or polycrystalline. Because Fe3Sn2 is a very stable substance, the crystals can be crushed into powder and used to produce ink.

[0019] Figure 3A shows the temperature dependence of the magnetization M of Fe3Sn2 during zero-field cooling (ZFC) and field cooling (FC) when the applied magnetic field B is 100 Oe parallel to the ab plane, and Figure 3B shows the temperature derivative (dM / dT) of the magnetization in Figure 3A. Figure 3C shows the magnetic field dependence of the magnetization M of Fe3Sn2 at T = 5 K, 200 K, and 300 K when a magnetic field B parallel to the ab plane is applied.

[0020] Figure 3A shows that at low temperatures, the domains of FC are aligned, while those of ZFC are not, resulting in a slightly larger magnetization of FC than ZFC. Figures 3A and 3B also show that the transition temperature (Curie temperature) Tc of Fe3Sn2 is 656 K. Figure 3C shows that at T = 5 K, the saturation magnetization of Fe3Sn2 reaches 6.03 μB / FU, with a saturation magnetization per Fe atom of 2.01 μB.

[0021] Figure 4A shows the temperature dependence of the magnetization M of Fe3Sn2 in ZFC and FC when the applied magnetic field B is 100 Oe parallel to the c-axis, and Figure 4B shows the magnetic field dependence of the magnetization M of Fe3Sn2 at T = 5K, 200K, and 300K when a magnetic field B parallel to the c-axis is applied. Figure 4A shows that FC and ZFC show almost the same magnetization even at low temperatures. Figure 4B shows that they show almost the same saturation magnetization as Figure 3C.

[0022] 5A to 5C show the observation results of the anomalous Nernst effect and the anomalous Hall effect of Fe3Sn2. Specifically, Fig. 5A shows the Nernst coefficient S of Fe3Sn2 at T = 200K, 300K, and 390K when a magnetic field B parallel to the

[0001] direction is applied and a heat flow Q parallel to the [2-1-10] direction is passed. yx Figure 5B shows the magnetic field dependence of the Hall resistivity ρ of Fe3Sn2 at T = 200 K and 300 K when a magnetic field B parallel to the

[0001] direction is applied and a current I parallel to the [2-1-10] direction is passed. yx Figure 5C shows the magnetic field dependence of the Nernst coefficient S of Fe3Sn2 when a magnetic field B = 2 T parallel to the

[0001] direction is applied and a heat flow Q parallel to the [2-1-10] direction is applied. yx where the four integers in square brackets represent the Miller indices.

[0023] From Figures 5A and 5C, the Nernst coefficient S of Fe3Sn2 yx is highly temperature dependent, and its absolute value |S yx | is approximately 2.4 μV / K at T=300 K and reaches approximately 5.1 μV / K at T=390 K. In addition, |S yx is almost zero, but above T=150K, |S yx It can be seen that | increases rapidly with increasing temperature. Furthermore, Fig. 5B shows that Fe3Sn2 exhibits a large anomalous Hall effect at room temperature.

[0024] As described above, Fe3Sn2 can exhibit a large anomalous Nernst effect.

[0025] <Iron nitride> The inventor of the present application further found that an anomalous Nernst effect also appears in iron nitride.

[0026] Fig. 6 shows the crystal structure of Fe 16 N2 in which the anomalous Nernst effect can occur. Fe 16 The unit cell of N2 has a body-centered cubic (bcc) structure for N (nitrogen) atoms, and Fe atoms occupy three crystallographically different sites (4e, 4d, and 8h). Fe 16 N2 can be produced by a known method. For example, Fe 16 N2 can be produced by sputtering iron in a nitrogen atmosphere.

[0027] Fig. 7A shows the magnetic field dependence of the Nernst coefficient S 16 at T = 300 K for the first sample composed of Fe yx N2, and Fig. 7B shows the magnetic field dependence of the Nernst coefficient S 16 at T = 300 K for the second sample composed of Fe yx N2. The first sample and the second sample are both fabricated on a substrate made of MgO, but the contact state between the sample and the terminal is different. As shown in Fig. 7A and Fig. 7B, the |S 16 | of Fe yx N2 shows about 0.6 μV / K and about 0.8 μV / K, indicating that the anomalous Nernst effect is occurring.

[0028] Note that an anomalous Nernst effect can also be expected in iron nitrides other than Fe 16 N2. For example, Fe4N has a crystal structure belonging to the space group Pm-3m and a high Curie temperature Tc of 760 K. In high-throughput calculations, the maximum value of the transverse thermal conductivity α [A / Km] of Fe4N estimated at the Fermi energy at T = 500 K or lower is 2.4 A / Km.

[0029] <R-Co-based alloy> The present inventors have further discovered that the anomalous Nernst effect also occurs in R-Co alloys, such as RCo5, where R is a rare earth element, such as Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Sm (samarium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), and Er (erbium).

[0030] Figure 8 shows the crystal structure of RCo5. RCo5 has a hexagonal structure in the space group P6 / mmm, with the a-axis and b-axis being equal in length, the angle α between the b-axis and c-axis, and the angle β between the c-axis and a-axis, are α = β = 90°, and the angle γ between the a-axis and b-axis is γ = 120°. In RCo5, R atoms occupy the 1a site, and Co atoms occupy the 2c site and the 3g site that forms the kagome lattice plane. RCo5 analogs include R2Co7 and R2Co 17 There is.

[0031] Figure 9A shows the X-ray diffraction pattern of the YCo5 polycrystal prepared by arc melting. For comparison, the X-ray diffraction pattern obtained from the simulation is also shown. These X-ray diffraction patterns confirm that the YCo5 polycrystal sample is a single phase.

[0032] Figure 9B shows the magnetic field dependence of the magnetization M of YCo5 polycrystal at 10 K and 300 K, and Figure 9C shows the temperature dependence of the magnetization M of YCo5 polycrystal when a magnetic field B = 1 T is applied. Figures 9B and 9C confirm that a ferromagnetic state has been achieved.

[0033] Figure 9D shows the Nernst coefficient S of YCo5 polycrystal at 100K, 200K, and 300K. yx From Figure 9D, |S yx It can be seen that | is a relatively large value of 1.7 μV / K at 300 K (room temperature).

[0034] A larger Nernst coefficient can be obtained with RCo5 single crystal. Table 1 shows the composition formula, space group, Curie temperature Tc, transverse thermoelectric conductivity α, and Nernst coefficient S of RCo5 single crystal. yx The transverse thermoelectric conductivity α and the Nernst coefficient S yx is the value at room temperature. Here, R = Y, Dy, Ho, Tb, Er, Gd, Sm. From Table 1, S of YCo5 single crystal at room temperature yx shows an even larger value of 4.33 μV / K. [Table 1]

[0035] RCo5 has a high Curie temperature of over 900 K and strong uniaxial magnetic anisotropy. For example, when R is La, Ce, Pr, Sm, or Y, the c-axis is the easy axis at room temperature. Furthermore, by miniaturizing RCo5 particles to a single-domain size, permanent magnets with high coercivity can be produced, and the Nernst effect can be exhibited in zero magnetic field.

[0036] The anomalous Nernst effect can also be exhibited in a compound whose composition formula is RCo4M, where M is B (boron) or Ga (gallium).

[0037] The crystal structure of RCo4M is shown in Figure 10. In RCo4M, R atoms occupy the 1a and 1b sites, and Co atoms occupy the 2c site and the 6i site that forms the kagome lattice plane.

[0038] Figure 11 shows the Nernst coefficient S of DyCo4Ga at 300K and 350K. yx From Figure 11, |S yx It can be seen that | is a relatively large value of 1.5 μV / K at 350 K.

[0039] In addition to the above-mentioned RCo5 and RCo4M, R2Co7 and R2Co 17 , RCo3, RCo 4―x B x , RCo 4―x Ga x Similarly, a large value of the Nernst coefficient is obtained.

[0040] Next, a thermoelectric conversion device in which the thermoelectric conversion elements of this embodiment are modularized will be described. [Example]

[0041] 12 shows the external configuration of a thermoelectric converter 20 according to Example 1 of this embodiment. The thermoelectric converter 20 includes a substrate 22 and a power generator 23 placed on the substrate 22. In the thermoelectric converter 20, when a heat flow Q flows from the substrate 22 side toward the power generator 23, a temperature difference occurs in the power generator 23 in the direction of the heat flow, and a voltage V is generated in the power generator 23 due to the anomalous Nernst effect.

[0042] The substrate 22 has a first surface 22a on which the power generating body 23 is placed and a second surface 22b opposite to the first surface 22a. Heat from a heat source (not shown) is applied to the second surface 22b. Materials for the substrate 22 include, but are not limited to, MgO, Si, and Al2O3.

[0043] The power generating body 23 has a plurality of thermoelectric conversion elements 24 and a plurality of thermoelectric conversion elements 25, each of which has an L-shaped three-dimensional shape and is made of the above-mentioned Fe3Sn2, iron nitride (Fe 16 12, a plurality of thermoelectric conversion elements 24 and a plurality of thermoelectric conversion elements 25 are arranged alternately in parallel on a substrate 22 in a direction perpendicular to the longitudinal direction (x direction) of each element. The number of thermoelectric conversion elements 24 and thermoelectric conversion elements 25 constituting the power generation body 23 is not limited.

[0044] The plurality of thermoelectric conversion elements 24 and the plurality of thermoelectric conversion elements 25 are arranged so that the direction of magnetization M1 of the thermoelectric conversion elements 24 is opposite to the direction of magnetization M2 of the thermoelectric conversion elements 25. The plurality of thermoelectric conversion elements 24 and the plurality of thermoelectric conversion elements 25 have Nernst coefficients of the same sign.

[0045] One end (+x side) of one side surface (+y side) in the longitudinal direction (x direction) of thermoelectric conversion element 24 is defined as first end surface 24a, and the other end (-x side) of the other side surface (-y side) is defined as second end surface 24b. The other end (-x side) of one side surface (+y side) in the longitudinal direction (x direction) of thermoelectric conversion element 25 is defined as first end surface 25a, and one end (+x side) of the other side surface (-y side) is defined as second end surface 25b.

[0046] The first end surface 25a of the thermoelectric conversion element 25 is connected to the second end surface 24b of the thermoelectric conversion element 24 adjacent on the +y side, and the second end surface 25b of the thermoelectric conversion element 25 is connected to the first end surface 24a of the thermoelectric conversion element 24 adjacent on the opposite side (-y side). This electrically connects the plurality of thermoelectric conversion elements 24 and the plurality of thermoelectric conversion elements 25 in series. That is, the power generation body 23 is provided in a serpentine shape on the first surface 22a of the substrate 22. The thermoelectric conversion elements 24 and the thermoelectric conversion elements 25 are insulated from each other except for the connection points.

[0047] When heat is applied from a heat source to second surface 22b of substrate 22, heat flow Q flows in the +z direction toward power generator 23. When a temperature difference occurs due to heat flow Q, an electromotive force E1 is generated in thermoelectric conversion element 24 in a direction (-x direction) perpendicular to both the direction of magnetization M1 (-y direction) and the direction of heat flow Q (+z direction) due to the anomalous Nernst effect. In thermoelectric conversion element 25, an electromotive force E2 is generated in a direction (+x direction) perpendicular to both the direction of magnetization M2 (+y direction) and the direction of heat flow Q (+z direction) due to the anomalous Nernst effect.

[0048] As described above, the thermoelectric conversion elements 24 and 25 arranged in parallel are electrically connected in series, so that the electromotive force E1 generated in one thermoelectric conversion element 24 can be applied to the adjacent thermoelectric conversion element 25. Furthermore, since the electromotive force E1 generated in one thermoelectric conversion element 24 and the electromotive force E2 generated in the adjacent thermoelectric conversion element 25 are in opposite directions, the electromotive forces of the adjacent thermoelectric conversion elements 24 and 25 are added together, and the output voltage V can be increased.

[0049] As a modified example of the thermoelectric conversion device 20 of FIG. 12, a configuration may be adopted in which adjacent thermoelectric conversion elements 24 and 25 have Nernst coefficients of opposite signs, and the plurality of thermoelectric conversion elements 24 and the plurality of thermoelectric conversion elements 25 are arranged so that their magnetization directions are the same (i.e., so that the direction of magnetization M1 and the direction of magnetization M2 are the same). [Example]

[0050] 13 shows a plan view of a thermoelectric converter 30 according to Example 2 of this embodiment. The thermoelectric converter 30 has a plurality of rectangular parallelepiped thermoelectric conversion elements 1A having the same Nernst coefficient as a power generating body 34. Each thermoelectric conversion element 1A is made of the above-mentioned Fe3Sn2, iron nitride, or R-Co alloy.

[0051] The thermoelectric conversion elements 1A are arranged in parallel on the substrate 32 in a direction (y direction) perpendicular to the longitudinal direction (x direction) so that the directions of the magnetization M are the same (y direction). One end (+x side) of the thermoelectric conversion element 1A is connected to the other end (-x side) of the adjacent thermoelectric conversion element 1A on the -y side by copper wiring 36, so that the thermoelectric conversion elements 1A are electrically connected in series. Examples of materials for the substrate 32 include MgO, Si, and Al2O3, but are not particularly limited.

[0052] The heat flow is made to flow from the substrate 32 side toward the power generation body 34 (in the +z direction). The thermoelectric conversion device 30 has a configuration in which adjacent thermoelectric conversion elements 1A are connected via copper wiring 36, and therefore can be manufactured more easily than the thermoelectric conversion device 20 of Example 1 shown in FIG. [Example]

[0053] In the thermoelectric mechanism based on the anomalous Nernst effect, the temperature gradient, the magnetization direction, and the voltage direction are perpendicular to each other, making it possible to fabricate a thin sheet-like thermoelectric conversion element.

[0054] 14 shows the external configuration of a thermoelectric converter 40 according to Example 3, which includes a sheet-like thermoelectric conversion element 44. Specifically, the thermoelectric converter 40 includes a hollow member 42 and a long sheet-like (tape-like) thermoelectric conversion element 44 wound around the outer surface of the hollow member 42 to cover it. The thermoelectric conversion element 44 is made of the above-mentioned Fe3Sn2, iron nitride, or R-Co alloy.

[0055] The magnetization of the thermoelectric conversion element 44 is parallel to the longitudinal direction (x direction) of the hollow member 42. When a heat flow occurs from the inside to the outside of the hollow member 42 and a temperature gradient occurs due to the heat flow, a voltage V is generated along the longitudinal direction of the long thermoelectric conversion element 44 (a direction perpendicular to the direction of magnetization and the direction of heat flow) due to the anomalous Nernst effect.

[0056] In the thermoelectric converter 40 of FIG. 14, instead of the long sheet-like thermoelectric conversion element 44, a configuration in which a wire thermoelectric conversion element is wound around the hollow member 42 may be employed.

[0057] 12 to 14, where L is the longitudinal length of the thermoelectric conversion element and H is the thickness (height), the voltage generated by the anomalous Nernst effect is proportional to L / H. In other words, the longer and thinner the thermoelectric conversion element, the greater the generated voltage. Therefore, by employing a power generator in which multiple thermoelectric conversion elements are electrically connected in series, or a wire or long sheet-shaped thermoelectric conversion element, it is possible to expect an improvement in the anomalous Nernst effect.

[0058] The thermoelectric converters shown in Examples 1 to 3 can be used in a variety of applications. In particular, they are expected to be used as a standalone power source or heat flow sensor for Internet of Things (IoT) sensors in the temperature range from room temperature to several hundred degrees Celsius.

[0059] For example, by applying the thermoelectric conversion device of this embodiment to a heat flow sensor, it is possible to determine the quality of the thermal insulation performance of a building. Furthermore, by installing a thermoelectric conversion device in the exhaust system of an automobile or the like, it is possible to generate electricity using the heat (waste heat) of the exhaust gas, and the thermoelectric conversion device can be effectively used as an auxiliary power source. Furthermore, by arranging heat flow sensors in a mesh pattern on the wall surface of a space, it is possible to spatially recognize heat flows and heat sources. This is expected to be applied, for example, to high-precision temperature control for high-density crop cultivation and livestock breeding, and as a driver detection system for autonomous driving. Furthermore, heat flow sensors can also be used in indoor air conditioning management and deep body temperature management in medicine. Furthermore, by making the thermoelectric conversion element of this embodiment into a powder or paste, it is expected to be applicable to a wide range of fields.

[0060] In this embodiment, attention is focused on the voltage generated by the anomalous Nernst effect, but it is possible to increase the output voltage through the synergistic effect of the voltage generated by the Seebeck effect due to the temperature gradient, the Hall effect generated based on the voltage created by the Seebeck effect, and the voltage generated by the anomalous Nernst effect. [Explanation of symbols]

[0061] 1, 1A, 24, 25, 44 Thermoelectric conversion element 20, 30, 40 Thermoelectric conversion device 22, 32 board 23, 34 Power generating body 42 Hollow members

Claims

1. A thermoelectric conversion element made of iron nitride that exhibits the anomalous Nernst effect.

2. The iron nitride is Fe １６ N ２ The thermoelectric conversion element according to claim 1 ,

3. A substrate; a plurality of thermoelectric conversion elements provided on the substrate, 3. The thermoelectric conversion element according to claim 1, wherein each of the plurality of thermoelectric conversion elements has a shape extending in one direction, The thermoelectric conversion device, wherein the plurality of thermoelectric conversion elements are arranged in parallel in a direction perpendicular to the one direction and are electrically connected in series.

4. The thermoelectric conversion device according to claim 3 , wherein the plurality of thermoelectric conversion elements are arranged in a serpentine pattern.

5. A hollow member; The thermoelectric conversion element according to claim 1 or 2, The thermoelectric conversion device, wherein the thermoelectric conversion element is a sheet or wire provided so as to cover the outer surface of the hollow member.

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