Thermoelectric conversion material, thermoelectric conversion module, and heat flow sensor

Abstract

To provide a thermoelectric conversion material that can reduce the cost of a thermoelectric conversion module.SOLUTION: A thermoelectric conversion material according to an embodiment is represented by a composition formula RCo5-xMx, in which R is at least one rare earth element, M is at least one element selected from the group consisting of Zn, Al, and fourth period transition elements excluding Co, and x is greater than 0 and less than or equal to 3.0, and has an anomalous Nernst effect.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thermoelectric conversion material, a thermoelectric conversion module, and a heat flow sensor. [Background technology]

[0002] Thermoelectric conversion modules are being actively developed to utilize unused thermal energy. A well-known example of such a module is the Seebeck effect, which generates voltage using a temperature gradient.

[0003] The Seebeck effect generates a voltage in the same direction as the temperature gradient, so thermoelectric conversion modules that utilize the Seebeck effect have a complex three-dimensional structure with π-type structures as their building blocks. This makes it difficult to make thermoelectric conversion modules that utilize the Seebeck effect large-area or film-like. Furthermore, thermoelectric conversion modules that utilize the Seebeck effect use rare materials, which poses the issue of high manufacturing costs. There are also issues with regard to toxicity.

[0004] In addition to thermoelectric conversion modules that utilize the Seebeck effect, thermoelectric conversion modules using thermoelectric conversion materials with the anomalous Nernst effect, which generates electromotive force due to the anomalous Nernst effect, have been proposed in recent years. 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.

[0005] The anomalous Nernst effect generates a voltage in a direction perpendicular to the temperature gradient. Therefore, a thermoelectric conversion module utilizing the anomalous Nernst effect can be deployed along the heat source, which has the advantage of making it easy to create a large surface area and a film.

[0006] For example, Patent Document 1 discloses a thermoelectric conversion element having the anomalous Nernst effect, which is made of an alloy containing a transition metal, the alloy being a compound having a crystal structure with Kagome lattice planes of the transition metal, and which exhibits the anomalous Nernst effect. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2021 / 215529 Summary of the Invention [Problem to be solved by the invention]

[0008] The thermoelectric conversion material disclosed in Patent Document 1 exhibits relatively high power generation performance at room temperature, but thermoelectric conversion modules using this thermoelectric conversion material are expensive, so a method for manufacturing thermoelectric conversion modules more inexpensively is needed. If a thermoelectric conversion material with a larger anomalous Nernst coefficient than the thermoelectric conversion material disclosed in Patent Document 1 could be created, the amount of thermoelectric conversion material used in the thermoelectric conversion module could be reduced, thereby reducing the cost of the thermoelectric conversion module. Alternatively, if a thermoelectric conversion material with remanent magnetization could be created, it would be possible to omit means for applying a magnetic field from an external source, such as a permanent magnet or electromagnet, which would similarly reduce the cost and space required for the thermoelectric conversion module.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a thermoelectric conversion material that can reduce the cost of thermoelectric conversion modules, and a thermoelectric conversion module and a heat flow sensor that use the thermoelectric conversion material. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention proposes the following means. <1> The thermoelectric conversion material of the first aspect of the present invention has the composition formula RCo 5-x M x is expressed as In the composition formula, R is at least one rare earth element, In the composition formula, M is at least one element selected from the group consisting of Zn, Al, and a fourth period transition element other than Co; In the composition formula, x is greater than 0 and less than or equal to 3.0, It has an anomalous Nernst effect. <2> A second aspect of the present invention is the thermoelectric conversion material of the first aspect, It may have a CaCu5 type crystal structure. <3> A third aspect of the present invention is a thermoelectric conversion material according to the first or second aspect, wherein The M may be at least one selected from the group consisting of Fe, Ni, Cu, Zn, and Al. <4> A fourth aspect of the present invention may be the thermoelectric conversion material of any one of the first to third aspects, wherein the R is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm. <5> A thermoelectric conversion module according to a fifth aspect of the present invention includes the thermoelectric conversion material according to any one of the first to fourth aspects. <6> A heat flow sensor according to a sixth aspect of the present invention includes the thermoelectric conversion module according to the fifth aspect. [Effects of the Invention]

[0011] According to the above aspects of the present invention, it is possible to provide a thermoelectric conversion material that can reduce the cost of a thermoelectric conversion module, and a thermoelectric conversion module and a heat flow sensor that use the thermoelectric conversion material. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram illustrating a thermoelectric mechanism using the thermoelectric conversion element of the first embodiment. [Figure 2] 1 is a schematic diagram showing a CaCu5-type crystal structure. [Figure 3] FIG. 2 is a perspective view showing the configuration of a thermoelectric conversion module 10 according to a second embodiment. [Figure 4]FIG. 10 is a plan view showing the configuration of a thermoelectric conversion module 20 according to a third embodiment. [Figure 5] 1 is an external view showing the configuration of a thermoelectric conversion module 40 of the present embodiment. [Figure 6] 1 shows the results of XRD measurement in Example 1. [Figure 7] 1 shows the results of XRD measurement in Example 2. [Figure 8] 1 shows the results of XRD measurement in Example 3. [Figure 9] 1 shows the results of XRD measurement in Example 4. [Figure 10] 1 shows the results of XRD measurement in Example 5. [Figure 11] 1 shows the results of XRD measurement of Comparative Example 1. [Figure 12] 1 shows the measurement results of the anomalous Nernst coefficient of the thermoelectric conversion material of Example 1. [Figure 13] 1 shows the measurement results of the anomalous Nernst coefficient of the thermoelectric conversion material of Example 2. [Figure 14] 1 shows the measurement results of the anomalous Nernst coefficient of the thermoelectric conversion material of Example 3. [Figure 15] 1 shows the measurement results of the anomalous Nernst coefficient of the thermoelectric conversion material of Example 4. [Figure 16] 10 shows the measurement results of the anomalous Nernst coefficient of the thermoelectric conversion material of Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) The thermoelectric conversion material, thermoelectric conversion module, and heat flow sensor according to the present embodiment will be described in detail below with reference to the drawings. The drawings used in the following description may, for convenience, show characteristic parts in a schematic manner to make the features easier to understand, and the dimensional ratios of the components may not necessarily be the same as those in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate modifications can be made within the scope of the present invention.

[0014] (Thermoelectric materials 1) First, a thermoelectric conversion material 1 according to an embodiment of the present invention and its thermoelectric mechanism will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the configuration of a thermoelectric conversion material 1 according to a first embodiment.

[0015] The shape of the thermoelectric conversion material 1 according to this embodiment is not particularly limited. For example, as shown in FIG. 1 , the shape of the thermoelectric conversion material 1 is a rectangular parallelepiped having a predetermined thickness (length in the Z direction) and extending in one direction (the Y direction). Here, for example, it is assumed that magnetization or a magnetic field is applied in the +Z direction. When a heat flow Q (∝ -∇T) flows in the +X direction through the thermoelectric conversion material 1, a temperature difference occurs in the +X direction. As a result, an electromotive force V (∝ M × (-∇T)) is generated in the thermoelectric conversion material 1 due to the anomalous Nernst effect in the cross product direction (the Y direction) perpendicular to both the direction of the heat flow Q (the +X direction) and the direction of the magnetization M or the applied magnetic field (the +Z direction).

[0016] The thermoelectric conversion material 1 preferably has a CaCu5-type crystal structure. By having a CaCu5-type crystal structure, it is possible to have a high anomalous Nernst coefficient. The thermoelectric conversion material 1 may be polycrystalline or single crystalline.

[0017] The crystal structure of CaCu5 type is shown in Figure 2, and is D2 in the notation of Strukturbericht (hereafter abbreviated as SB). d , the crystal structure of space group P6 / mmm.

[0018] The above-mentioned crystal structure can be identified by X-ray diffraction (XRD) analysis. For example, a sample is collected, and XRD measurement is performed to obtain a diffraction pattern. The obtained diffraction pattern can be compared with diffraction patterns in a known database for identification. For example, the Powder Diffraction File (PDF) provided by the International Centre for Diffraction Data (ICDD) can be used as a known database.

[0019] The thermoelectric conversion material 1 has the anomalous Nernst effect. Here, the anomalous Nernst effect is a phenomenon in which, when a heat flow is passed through a magnetic material and a temperature difference is generated, a voltage is generated in a direction perpendicular to both the magnetization (magnetic field) direction and the temperature gradient. The predetermined temperature range is, for example, 20°C to 100°C.

[0020] Thermoelectric material 1 exhibits the anomalous Nernst coefficient S ANE It is preferable that the anomalous Nernst coefficient maintains a finite value even when the magnetic field is returned to zero. If the anomalous Nernst coefficient generated by applying a magnetic field once maintains a finite value even when the magnetic field is returned to zero, the thermoelectric conversion module can generate power without applying an external magnetic field. Here, it is preferable that the anomalous Nernst coefficient maintains approximately the same value as when the magnetic field was applied, even when the magnetic field is returned to zero. Furthermore, the sign of the anomalous Nernst coefficient changes when a magnetic field is applied in the opposite direction to the magnetic field initially applied, and it is preferable that the magnetic field in the opposite direction at which the sign changes is strong. The stronger the magnetic field in the opposite direction at which the sign of the anomalous Nernst coefficient changes, the more stable the thermoelectric conversion module can generate power without being affected by an external magnetic field.

[0021] "Anomalous Nernst coefficient S ANE " Anomalous Nernst coefficient S ANE is expressed by the following formula (1). yy means the longitudinal resistance. α in Equation (1) yx means the transverse thermoelectric coefficient. σ in Eq. (1) yx means the Hall conductivity. S in equation (1) SE means the Seebeck coefficient.

[0022] Transverse thermoelectric coefficient α yx is expressed by the following equation (2). Here, ∂σ in the following equation (2) yx / ∂ε is the value at the Fermi level. k in the following equation (2) B is the Boltzmann constant. In the following formula (2), ε means energy, and e means elementary charge. In the following formula (2), T means the absolute temperature (K) of the measurement sample.

[0023] S ANE =ρ yy α yx -σ yx ρ yy S SE ···(1) α yx =-(π 2 / 3)·{(k B 2 T) / e}(∂σ yx / ∂ε) (2)

[0024] "Anomalous Nernst coefficient S ANE Measurement method The anomalous Nernst coefficient S of the above-mentioned thermoelectric conversion material 1 ANE is measured, for example, as follows: A sample is cut into a flat plate (length L: 8 mm, width W: 2 mm, thickness t: 1 mm). One longitudinal end of the cut sample is heated with a heater, and the other longitudinal end is brought into contact with a heat sink, creating a temperature difference along the side L of the sample. A uniform temperature gradient is applied to the rectangular sample, and the temperature difference ΔT (K) is measured at two points spaced apart by L_temp (mm). A magnetic field is applied in a direction perpendicular to this temperature difference, and the voltage (V) generated at two points spaced apart by a distance W (mm) in a direction perpendicular to both the temperature difference and the magnetic field is measured. The anomalous Nernst coefficient S ANE is calculated from the obtained voltage (V) and other information using the following equation (3). Here, the anomalous Nernst coefficient S ANE is calculated from the voltage when a magnetic flux density of 2 T is applied based on the following formula (3).

[0025] S ANE =(V / ΔT)×(L_temp / W)···(3)

[0026] Thermoelectric conversion material 1 is RCo 5-x M x It is expressed by the formula: 5-x M x In the formula, R is at least one rare earth element. 5-x M xIn the formula, M is at least one element selected from the group consisting of Zn, Al, and the fourth period transition elements (first transition elements) excluding Co. Here, the fourth period transition elements are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. By doing so, the anomalous Nernst coefficient S of the thermoelectric conversion material 1 can be increased. ANE The absolute value of becomes larger, and the anomalous Nernst coefficient tends to become a finite value even when the magnetic field is returned to zero.

[0027] Composition formula RCo 5-x M x where x is greater than 0 and less than or equal to 3.0. 5-x M x In the formula, x is greater than 0 and less than or equal to 3.0, whereby the anomalous Nernst coefficient S of thermoelectric conversion material 1 is ANE becomes larger, and the anomalous Nernst coefficient tends to become a finite value even when the magnetic field is returned to zero.

[0028] In addition, the anomalous Nernst coefficient S of thermoelectric conversion material 1 ANE The absolute value of tends to be large, so the composition formula RCo 5-x M x In this case, x is preferably greater than 0 and less than 1. From this viewpoint, x is preferably 0.01 or greater, more preferably 0.05 or greater, even more preferably 0.08 or greater, and is preferably 0.9 or less, more preferably 0.7 or less, even more preferably 0.5 or less, particularly preferably 0.3 or less, and most preferably 0.2 or less.

[0029] On the other hand, the anomalous Nernst coefficient S of thermoelectric conversion material 1 ANE tends to have a finite value even when the magnetic field is returned to zero, so the composition formula RCo 5-x M x In this formula, x is preferably 1 or more and 3.0 or less. From this viewpoint, x is preferably 1.01 or more, more preferably 1.05 or more, and even more preferably 1.08 or more, and is preferably 2.9 or less, more preferably 2.7 or less, and even more preferably 2.5 or less.

[0030] Composition formula RCo 5-x M xR in the formula RCo is at least one rare earth element, and among these, Y and / or lanthanides are preferred, and at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm is more preferred. 5-x M x R in the formula (I) is at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm, and the anomalous Nernst coefficient S ANE From this viewpoint, the absolute value of the composition formula RCo can be increased. 5-x M x In the formula, R is preferably at least one selected from the group consisting of Y, Dy, Ho, Tb, Er, Gd, and Sm, more preferably Y, Dy, Ho, and / or Gd, and even more preferably Gd.

[0031] Composition formula RCo 5-x M x In the formula, M is at least one element selected from the group consisting of the fourth period transition elements excluding Co, Zn, and Al, and is preferably at least one element selected from the group consisting of Fe, Ni, Cu, Zn, and Al. When M is at least one element selected from the group consisting of Fe, Ni, Cu, Zn, and Al, the anomalous Nernst coefficient S ANE This is preferable because it is possible to increase the absolute value of the anomalous Nernst coefficient, and the anomalous Nernst coefficient tends to become a finite value even when the magnetic field is returned to zero. Among these, the anomalous Nernst coefficient tends to remain a finite value even when the magnetic field is returned to zero, so the composition formula RCo 5-x M x In the formula, M is preferably Al and / or Cu, and more preferably Cu.

[0032] The thickness of the thermoelectric conversion material 1 is preferably 1.0 mm or more. By making the thickness 1.0 mm or more, the amount of current generated can be increased within a predetermined temperature range.

[0033] Thermoelectric conversion material 1 exhibiting the anomalous Nernst effect can be produced by known methods such as arc melting. Alternatively, thin films can be produced using methods such as sputtering, vacuum deposition, or chemical vapor deposition (CVD). It may be either a single crystal or a polycrystal. Furthermore, since it is a very stable substance, the crystals can be crushed into powder and used to produce ink. The raw material is a material having the composition formula RCo 5-x M x By blending so as to satisfy the above condition, it becomes easier to obtain a CaCu5 type crystal structure.

[0034] The thermoelectric conversion material 1 according to the first embodiment has been described above. The thermoelectric conversion material 1 is a material having a composition formula RCo 5-x M x R in the composition formula is at least one rare earth element, M in the composition formula is at least one element selected from the group consisting of Zn, Al, and fourth period transition elements excluding Co, and x in the composition formula is greater than 0 and less than or equal to 3.0. Since the anomalous Nernst effect is present, thermoelectric conversion modules can be produced inexpensively.

[0035] The magnetic field can be applied using, for example, a magnetic field application means (not shown). The magnetic field application means is, for example, an electromagnet. If the thermoelectric conversion material 1 has residual magnetization, the magnetic field application means may not be necessary.

[0036] (Second embodiment) Next, a thermoelectric conversion module including the thermoelectric conversion material of this embodiment will be described. Fig. 3 shows the external configuration of a thermoelectric conversion module 10 according to this embodiment. The thermoelectric conversion module 10 includes a substrate 12 and a power generation body 13 placed on the substrate 12. In the thermoelectric conversion module 10, when a heat flow Q flows from the substrate 12 toward the power generation body 13, a temperature difference occurs in the power generation body 13 in the direction of the heat flow, and a voltage V is generated in the power generation body 13 due to the anomalous Nernst effect.

[0037] The substrate 12 has a first surface 12a on which the power generating body 13 is placed and a second surface 12b opposite to the first surface 12a. Heat from a heat source is applied to the second surface 12b. The material of the substrate 12 is not particularly limited as long as it can transfer heat. Examples of materials for the substrate 12 include MgO, Si, and Al2O3.

[0038] The power generating body 13 has a plurality of thermoelectric conversion elements 14 and a plurality of thermoelectric conversion elements 15, each of which has an L-shaped three-dimensional shape and is made of the above-described thermoelectric conversion material 1. As shown in Fig. 3, the plurality of thermoelectric conversion elements 14 and the plurality of thermoelectric conversion elements 15 are arranged alternately in parallel on the substrate 12 in a direction (Y direction) perpendicular to the longitudinal direction (X direction) of each of the elements. Note that the number of thermoelectric conversion elements 14 and thermoelectric conversion elements 15 constituting the power generating body 13 is not limited.

[0039] The thermoelectric conversion elements 14 and the thermoelectric conversion elements 15 are arranged such that the direction of magnetization M1 of the thermoelectric conversion elements 14 is opposite to the direction of magnetization M2 of the thermoelectric conversion elements 15. The thermoelectric conversion elements 14 and the thermoelectric conversion elements 15 have anomalous Nernst coefficients S ANE The thermoelectric conversion elements 14 and 15 can be made of the same material as the thermoelectric conversion material 1 of the present disclosure.

[0040] One end (-Y side) of one side surface (-X side) in the longitudinal direction (Y direction) of thermoelectric conversion element 14 is defined as first end surface 14a, and the other end (+Y side) of the other side surface (+X side) is defined as second end surface 14b. The other end (+Y side) of one side surface (-X side) in the longitudinal direction (Y direction) of thermoelectric conversion element 15 is defined as first end surface 15a, and one end (-Y side) of the other side surface (+X side) is defined as second end surface 15b.

[0041] The first end surface 15a of the thermoelectric conversion element 15 is connected to the second end surface 14b of the thermoelectric conversion element 14 adjacent on the -Y side, and the second end surface 15b of the thermoelectric conversion element 15 is connected to the first end surface 14a of the thermoelectric conversion element 14 adjacent on the opposite side (+Y side). This electrically connects the multiple thermoelectric conversion elements 14 and the multiple thermoelectric conversion elements 15 in series. That is, the power generation body 13 is provided in a serpentine shape on the first surface 12a of the substrate 12. The thermoelectric conversion elements 14 and the thermoelectric conversion elements 15 are insulated from each other except for the connection points.

[0042] When heat is applied from a heat source to second surface 12b of substrate 12, heat flow Q flows in the +Z direction toward power generator 13. When a temperature difference occurs due to heat flow Q, an electromotive force E1 is generated in thermoelectric conversion element 14 in a direction (+Y direction) perpendicular to both the direction of magnetization M1 (-X direction) and the direction of heat flow Q (+Z direction) due to the anomalous Nernst effect. In thermoelectric conversion element 15, an electromotive force E2 is generated in a direction (-Y direction) perpendicular to both the direction of magnetization M2 (+X direction) and the direction of heat flow Q (+Z direction) due to the anomalous Nernst effect.

[0043] As described above, the thermoelectric conversion elements 14 and 15 arranged in parallel are electrically connected in series, so that the electromotive force E1 generated in one thermoelectric conversion element 14 can be applied to the adjacent thermoelectric conversion element 15. Furthermore, since the electromotive force E1 generated in one thermoelectric conversion element 14 and the electromotive force E2 generated in the adjacent thermoelectric conversion element 15 are in opposite directions, the electromotive forces of the adjacent thermoelectric conversion elements 14 and 15 are added together, and the output voltage V can be increased.

[0044] As a modification of the thermoelectric conversion module 10 shown in FIG. 3, the adjacent thermoelectric conversion elements 14 and 15 have anomalous Nernst coefficients S ANE and a configuration in which the plurality of thermoelectric conversion elements 14 and the plurality of thermoelectric conversion elements 15 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).

[0045] (Third embodiment) Next, a thermoelectric conversion module 20 according to a third embodiment will be described. Fig. 4 shows a plan view of the thermoelectric conversion module 20 according to this embodiment. The thermoelectric conversion module 20 has a power generating body 23, and the anomalous Nernst coefficient S ANE The thermoelectric conversion element 24 has a plurality of rectangular parallelepiped thermoelectric conversion elements 24. Each thermoelectric conversion element 24 is made of the thermoelectric conversion material 1 described above.

[0046] The thermoelectric conversion elements 24 are arranged in parallel on the substrate 22 so that the direction of magnetization M is the same (y direction) in a direction (y direction) perpendicular to the longitudinal direction (x direction). One end (+x side) of a thermoelectric conversion element 24 is connected to the other end (-x side) of an adjacent thermoelectric conversion element 24 on the -y side by copper wiring 26, so that the thermoelectric conversion elements 24 are electrically connected in series. Examples of materials for the substrate 22 include MgO, Si, and Al2O3, but are not particularly limited.

[0047] The heat flow is from the substrate 22 side toward the power generation body 23 (in the +z direction). The thermoelectric conversion module 20 has a configuration in which adjacent thermoelectric conversion elements 24 are connected via copper wiring 26, and therefore can be manufactured more easily than the thermoelectric conversion module 10 shown in FIG.

[0048] (Fourth embodiment) 5 shows the external configuration of a thermoelectric conversion module 40 according to this embodiment. The thermoelectric conversion module 40 includes a hollow member 42 and a long sheet-like (tape-like) thermoelectric conversion element 44 that is wrapped around and covers the outer surface of the hollow member 42. The thermoelectric conversion element 44 is made of the thermoelectric conversion material 1 described above.

[0049] 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.

[0050] In the thermoelectric conversion module 40 of FIG. 5, 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.

[0051] 3 to 5, if the longitudinal length of the thermoelectric conversion element is L and the thickness (height) is H, 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 using 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.

[0052] The thermoelectric conversion modules shown in Figures 3 to 5 can be used in a variety of applications, particularly in the temperature range from room temperature to several hundred degrees Celsius, as a standalone power source or heat flow sensor for Internet of Things (IoT) sensors.

[0053] For example, by applying the thermoelectric conversion module 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 module 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 module 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.

[0054] 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.

[0055] The thermoelectric conversion module of this embodiment can also be given a function of temperature modulation (particularly cooling) by supplying power, like a Peltier element.

[0056] The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, and the above-described modifications can be combined as appropriate, without departing from the spirit of the present invention. [Example]

[0057] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0058] Example 1 Gd (purity 99.9%), Co (purity 99.97%), and Ni (purity 99.99%) were weighed in a molar ratio of 1:4:1 and melted in an arc furnace to obtain a polycrystalline ingot of GdCo4Ni. The resulting polycrystalline ingot was melted again in the arc furnace, and a tungsten rod was brought into contact with the molten liquid to grow a single crystal by the pulling method. The XRD analysis results shown in Figure 6 confirmed that the product had a CaCu5-type crystal structure.

[0059] Example 2 Gd (purity 99.9%), Co (purity 99.97%), and Ni (purity 99.99%) were weighed in a molar ratio of 1:2.5:2.5 and melted in an arc furnace to produce GdCo 2.5 Ni 2.5A polycrystalline ingot of CaCu5 type was obtained. The obtained polycrystalline ingot was melted again in an arc furnace, and a tungsten rod was brought into contact with the molten liquid to grow a single crystal by the pulling method. The XRD analysis results shown in Figure 7 confirmed that the crystal had a CaCu5 type crystal structure.

[0060] Example 3 Gd (purity 99.9%), Co (purity 99.97%), and Cu (purity 99.99%) were weighed in a molar ratio of 1:3.5:1.5 and melted in an arc furnace to obtain GdCo. 3.5 Cu 1.5 A polycrystalline ingot of CaCu5 type was obtained. The obtained polycrystalline ingot was melted again in an arc furnace, and a tungsten rod was brought into contact with the molten liquid to grow a single crystal by the pulling method. The XRD analysis results shown in Figure 8 confirmed that the crystal had a CaCu5 type crystal structure.

[0061] Example 4 Gd (purity 99.9%), Co (purity 99.97%), and Al (purity 99.999%) were weighed in a molar ratio of 1:4:1 and melted in an arc furnace to obtain a polycrystalline ingot of GdCo4Al. The resulting polycrystalline ingot was melted again in the arc furnace, and a tungsten rod was brought into contact with the molten liquid to grow a single crystal by the pulling method. The XRD analysis results shown in Figure 9 confirmed that the product had a CaCu5-type crystal structure.

[0062] Example 5 Gd (purity 99.9%), Co (purity 99.97%), and Ni (purity 99.99%) were weighed in a molar ratio of 1:4.9:0.1 and melted in an arc furnace to produce GdCo 4.9 Ni 0.1 A polycrystalline ingot of CaCu5 type was obtained. The obtained polycrystalline ingot was melted again in an arc furnace, and a tungsten rod was brought into contact with the molten liquid to grow a single crystal by the pulling method. The XRD analysis results shown in Figure 10 confirmed that the crystal had a CaCu5 type crystal structure.

[0063] (Comparative Example 1) Gd (purity 99.9%) and Co (purity 99.97%) were weighed in a molar ratio of 1:5 and melted using an arc furnace to obtain a polycrystalline ingot of GdCo5. The obtained polycrystalline ingot was melted again in an arc furnace, and a tungsten rod was brought into contact with the melt to grow a single crystal by the pulling method. From the XRD analysis results shown in Fig. 11, it was confirmed that it had a CaCu5-type crystal structure.

[0064] <XRD measurement> For each of Examples 1 to 5 and Comparative Example 1, XRD measurements were performed at an interval of 0.01°, and the above results were obtained. The apparatus and conditions used were as follows. Apparatus: Rigaku SmartLab-LP X-ray source: CuKα Accelerating voltage: 40 kV Current: 100 mA Kβ cut-off method: Ni filter

[0065] <Anomalous Nernst coefficient S ANE evaluation> A flat plate-shaped (length L = 8 mm, width W = 2 mm, thickness t = 1 mm) sample was cut out from the ingot obtained in the arc furnace and used as an evaluation sample. Using the Thermal Transport Option of the Physical Property Measurement System manufactured by Quantum Design, heat was injected pulsewise from one end in the length direction of the sample at a temperature of 300 K, and a heat sink was brought into contact with the other end to apply a temperature difference along the length direction of the sample. The temperature difference was set to about 2 - 3% of the evaluation temperature (6 - 9 K in the case of 300 K). Also, a magnetic field of 2 T was applied in a direction orthogonal to the direction of this temperature difference and in the plane direction of the sample, and the voltage V generated at two points separated by a distance W in a direction orthogonal to both the temperature difference and the magnetic field was measured, and the anomalous Nernst coefficient S ANE value was calculated using the above formula (3).

[0066] Anomalous Nernst coefficient S ANE was calculated based on the above formula (3) from the voltage when a magnetic flux density of 2 T was applied. The anomalous Nernst coefficients S of Examples 1 to 5 and Comparative Example 1ANE The anomalous Nernst coefficients S of Examples 1 to 5 are shown in Table 1. ANE The absolute value of was 0.9μV / K or more.

[0067] 12 to 16 show the anomalous Nernst coefficients S of the thermoelectric conversion materials of Examples 1 to 5. ANE The measurement results are shown in the figures. The horizontal axis of each graph represents the magnetic flux density, and the vertical axis of each graph represents the anomalous Nernst coefficient. As shown in Figures 12 to 15, the thermoelectric conversion materials of Examples 1 to 4 had almost constant anomalous Nernst coefficients even when the magnetic flux density was reduced to zero after a magnetic flux density of 2 T was applied. On the other hand, as shown in Figure 16, in the case of Example 5, when the magnetic flux density was set to zero, the anomalous Nernst coefficient was 0. The results are shown in Table 1. As shown in Table 1, the composition formula RCo 5-x M x In all of Examples 1 to 4, in which the value of x was 1 or more and 3.0 or less, the magnetic flux density at which the sign of the Nernst coefficient changed exceeded 0 T.

[0068] Composition formula RCo 5-x M x In Example 5, where the value of x was less than 1, the magnetic flux density at which the sign of the Nernst coefficient changed was 0 T, but the anomalous Nernst coefficient S ANE The absolute value of was 5.3, which was high. Regarding M in the composition formula, the effect on the anomalous Nernst coefficient when Ni is substituted with Al can be estimated as a simple ratio of 1.95 / 2.5 by comparing Ni in Example 1 (x=1) with Al in Example 4. Therefore, when Ni in Example 5 is substituted with Al, the absolute value of the anomalous Nernst coefficient at x=0.1 can be estimated as (1.95 / 2.5)×5.3=4. Furthermore, assuming that the anomalous Nernst coefficient changes linearly when x is 1 or greater, the anomalous Nernst coefficient of Ni (x = 1.5) can be estimated to be -2 from the anomalous Nernst coefficients for x = 1 and 2.5 (Examples 1 and 2, respectively). When Ni is replaced with Cu, the anomalous Nernst coefficient can be estimated in the same manner as for Al by comparing the estimated value for Ni at x = 1.5 with the value in Example 3. The absolute value of the anomalous Nernst coefficient for x = 0.1 is (1.9 / 2) × 5.3 = 5. From the above, it is expected that even when Ni is replaced with Al or Cu in Example 5, a high anomalous Nernst coefficient will be exhibited when x is less than 1. On the other hand, the composition formula RCo 5-x M x The thermoelectric conversion material of Comparative Example 1, which did not satisfy the anomalous Nernst coefficient S ANE The value was lower than that of the thermoelectric conversion material of Example 5. From the above, according to the thermoelectric conversion materials of Examples 1 to 5, the anomalous Nernst coefficient S ANE It was found that the cost of thermoelectric conversion modules can be reduced because the absolute value of is higher than that of conventional thermoelectric conversion materials, or the magnetic flux density at which the sign of the anomalous Nernst coefficient changes is greater than 0 T.

[0069] [Table 1] [Explanation of symbols]

[0070] 1 thermoelectric conversion material, 10 thermoelectric conversion module, 12 substrate, 13 power generation body, 14 thermoelectric conversion element, 15 thermoelectric conversion element, 20 thermoelectric conversion module, 22 substrate, 23 power generation body, 24 thermoelectric conversion element, 40 thermoelectric conversion module, 42 hollow member, 44 thermoelectric conversion element

Claims

1. Composition formula RCo ５－ｘ M ｘ is expressed as In the composition formula, R is at least one rare earth element, In the composition formula, M is at least one element selected from the group consisting of Zn, Al, and the fourth period transition elements excluding Co, In the composition formula, x is greater than 0 and less than or equal to 3.0, A thermoelectric material with anomalous Nernst effect.

2. CaCu ５ The thermoelectric conversion material according to claim 1 , having a crystal structure of the type:

3. 3. The thermoelectric conversion material according to claim 1, wherein M is at least one element selected from the group consisting of Fe, Ni, Cu, Zn, and Al.

4. 3. The thermoelectric conversion material according to claim 1, wherein R is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm.

5. A thermoelectric conversion module comprising the thermoelectric conversion material according to claim 1 or 2.

6. A heat flow sensor comprising the thermoelectric conversion module according to claim 5 .

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