Hybrid transverse thermoelectric power generation element and power generation method using same

Abstract

Provided is a transverse thermoelectric conversion element having a thermoelectric power generation performance comparable to or higher than that of the Seebeck effect. The transverse thermoelectric conversion element comprises: a first electrode and a second electrode that are disposed opposing each other; and a laminate that is sandwiched between the first and second electrodes and that is electrically connected to both the first and second electrodes. The laminate has a structure in which layers of a first thermoelectric material and layers of a second thermoelectric material are alternately laminated. The first thermoelectric material and the second thermoelectric material have different values of at least one of Seebeck coefficient, electrical conductivity, or thermal conductivity. At least one of the first and second thermoelectric materials exhibits a longitudinal magneto-thermoelectric effect or a transverse magneto-thermoelectric effect. Laminated surfaces of the first layers and the second layers are inclined with respect to a direction in which the first electrode and the second electrode oppose each other. A potential difference is generated between the first and second electrodes due to a temperature difference in a direction perpendicular to the opposing direction in the transverse thermoelectric conversion element and a magnetic field applied in a direction in which the magneto-thermoelectric effect is generated.

Description

Hybrid horizontal thermoelectric power generation element and power generation method using the same

[0001] The present invention relates to a hybrid lateral thermoelectric power generation element that combines a magneto-thermoelectric effect with lateral thermoelectric conversion derived from an anisotropic laminated structure, and a power generation method using the same.

[0002] Thermoelectric conversion is the phenomenon of direct conversion of thermal energy to electrical energy within a material. When a temperature difference is applied to a thermoelectric material, the kinetic energy of the carriers (electrons and holes) is greater at the high-temperature end, so thermal diffusion causes a bias toward the low-temperature end, generating a potential difference between both ends of the thermoelectric material. This is called the Seebeck effect, and is used in thermocouples and thermoelectric power generation. In addition, when a potential difference is applied to a thermoelectric material using an external power source, a temperature difference can be generated between both ends of the thermoelectric material. This is called the Peltier effect, and thermoelectric cooling and temperature modulation are performed.

[0003] The basic structure of a thermoelectric conversion module using the Seebeck effect is to increase voltage and power by arranging n-type and p-type thermopiles in a matrix and connecting them in series. However, because the Seebeck effect generates an electric field parallel to the temperature gradient, it has inherent problems, such as mechanical fragility due to the large number of electrical junctions, power loss due to contact resistance, a complex manufacturing process for thermoelectric conversion modules, and difficulty in achieving large surface areas. Therefore, a horizontal thermoelectric conversion element has been developed in which the output voltage and current are perpendicular to the direction of the temperature difference (see Non-Patent Document 1).

[0004] Next, as a type of lateral thermoelectric conversion element, in addition to the normal or anomalous Nernst effect, artificial multilayers (hereinafter referred to as artificially graded multilayers) in which two types of conductors are alternately and obliquely stacked are known (see Non-Patent Document 1). In artificially graded multilayers, even if each conductor exhibits isotropic conductivity, anisotropic conduction of conduction electrons and holes occurs, resulting in finite off-diagonal terms in the thermoelectric transport tensor, and they function as lateral thermoelectric conversion elements (see Non-Patent Document 2). Lateral thermoelectric conversion in such artificial composite materials has long been studied, and by selecting appropriate constituent materials and optimizing the cutting angle and element shape, it is possible to design the lateral thermoelectric power and dimensionless figure of merit ZT. Much of the research on artificially graded multilayers has been conducted on sinter-bonded bulk materials, achieving ZTs exceeding 0.2. Lateral thermoelectric conversion has been demonstrated not only in macroscale sintered bodies but also in nanometer-scale superlattices with similar graded structures, often referred to as (p×n) multilayers (see Non-Patent Document 3).

[0005] The multilayer structure for thermoelectric conversion is, for example, as disclosed in Patent Document 1, a multilayer structure of Bi and metal (Bi ２ Te ３ ) is known (see paragraph

[0081] ). Furthermore, Patent Document 2 discloses a graded superlattice structure (InAs / GaSb) that drives lateral thermoelectric power generation, and cites the Nernst-Ettingshausen effect and stacked composite devices as background art (see paragraph

[0008] ). However, Patent Documents 1 and 2 do not describe hybridization of magneto-thermoelectric effects derived from magnetism in an artificially graded multilayer stack.

[0006] WO2008 / 056466 US Patent No. 8829324

[0007] Japan Society of Applied Physics Homepage > GX: Applied Physics Challenging Green Transformation > Lateral Thermoelectric Conversion / Kenichi Uchida https: / / www.jsap.or.jp / columns / gx / e3-5H. J. Goldsmid, Introduction to Thermoelectricity (Springer-Verlag, Berlin Heidelberg, 2010). Y. Tang, B. Cui, C. Zhou, and M. Grayson, “p×n-Type Transverse Thermoelectrics: A Novel Type of Thermal Management Material,” J. Electron. Mater. 44, 2095 (2015).

[0008] Conventionally known horizontal thermoelectric conversion elements have a problem in that they are inferior in thermoelectric power generation performance compared to a Seebeck element, which is a general thermoelectric element.

[0009] The present invention can solve the above-mentioned problems of the conventional technology, and aims to provide a lateral thermoelectric conversion element having thermoelectric power generation performance comparable to or higher than that of a Seebeck element, and a power generation method using the same.

[0010] The present inventors have conceived the idea that if a material exhibiting a magneto-thermoelectric effect is incorporated into an artificially inclined multilayer laminate, hybrid thermoelectric conversion will be possible, utilizing a contribution that is independent of the magnetic field and magnetization derived from the conventional anisotropic multilayer structure and a contribution from the magneto-thermoelectric effect that is dependent on the magnetic field and magnetization, and that this may enable the provision of a horizontal thermoelectric conversion element with thermoelectric power generation performance comparable to or even higher than that of the Seebeck effect. [1] A hybrid lateral thermoelectric power generation element of the present invention is a thermoelectric power generation element including, for example, first and second electrodes arranged opposite each other, and a laminate sandwiched between the first and second electrodes and electrically connected to both the first and second electrodes, as shown in Figures 3C and 8A, in which the laminate has a structure in which layers of a first thermoelectric material and layers of a second thermoelectric material are alternately stacked, the first thermoelectric material and the second thermoelectric material have different values ​​for at least one of the Seebeck coefficient, the electrical conductivity, and the thermal conductivity, at least one of the first and second thermoelectric materials exhibits a vertical magneto-thermoelectric effect or a horizontal magneto-thermoelectric effect, the stacking surfaces of the layers of the first thermoelectric material and the layers of the second thermoelectric material are inclined with respect to the direction in which the first electrode and the second electrode face each other, and a potential difference is generated between the first and second electrodes due to a temperature difference in the thermoelectric power generation element in a direction perpendicular to the facing direction and a magnetic field applied in a direction that generates the magneto-thermoelectric effect.

[0011] [2] In the hybrid horizontal thermoelectric power generation element [1] of the present invention, preferably, the vertical magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more, more preferably 10 μV / K or more, and is a magnetic Seebeck effect derived from an external magnetic field, or an anisotropic magnetic Seebeck effect derived from spontaneous magnetization, and the horizontal magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more, more preferably 10 μV / K or more, and is a normal Nernst effect derived from an external magnetic field, or an anomalous Nernst effect derived from spontaneous magnetization. If the thermoelectric power of the vertical magneto-thermoelectric effect and the horizontal magneto-thermoelectric effect is less than 5 μV / K, there is a disadvantage that the enhancement effect on the horizontal thermoelectric effect derived from the gradient stack structure is insufficient, but the operation itself is not impaired. [3] In the hybrid horizontal thermoelectric power generation element [1] or [2] of the present invention, preferably, the first thermoelectric material layer is Bi １００－ｘ Sb ｘ layer (0≦x≦50), and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Preferably, the first thermoelectric material layer is a layer (0≦y≦2). More preferably, the first thermoelectric material layer is a layer of Bi １００－ｘ Sb ｘ layers (5≦x≦25), and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Preferably, the layer of the first thermoelectric material is a layer (1.5≦y≦1.95). If x exceeds 50, there is a disadvantage that the magneto-thermoelectric effect is reduced. Since the optimum properties of the second thermoelectric material depend on the type of the first thermoelectric material used, it is necessary to select the optimum composition of the second thermoelectric material depending on the thermoelectric properties of the first thermoelectric material. [4] In the hybrid lateral thermoelectric power generation element [1] or [2] of the present invention, preferably, the layer of the first thermoelectric material is Co ２ MnGa layer, and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Alternatively, the second thermoelectric material layer may be a Bi layer (0≦y≦2). ２ Te ３layer (y=0). Since the optimal properties of the second thermoelectric material depend on the first thermoelectric material, there is an advantage in that the optimal composition can be selected depending on the thermoelectric properties of the first thermoelectric material. [5] In the hybrid lateral thermoelectric power generation element [1] or [2] of the present invention, preferably, the external magnetic field is applied to the first thermoelectric material layer and the second thermoelectric material layer by a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet. [6] In the hybrid lateral thermoelectric power generation element [1] of the present invention, preferably, the first thermoelectric material layer is made of a material exhibiting a magneto-thermoelectric effect, and the second thermoelectric material layer is made of a permanent magnet material, so that a magnetic field can be applied to the first thermoelectric material without applying an external magnetic field by spontaneous magnetization of the permanent magnet, thereby enabling the magneto-thermoelectric effect of the first thermoelectric material to be exhibited. [7] In the hybrid lateral thermoelectric power generation element [6] of the present invention, preferably, the first thermoelectric material layer is made of Bi. １００－ｘ Sb ｘ layer (0≦x≦50), and the second thermoelectric material layer is SmCo ５ system magnet, Sm ２ Co １７ Nd-based magnets ２ Fe １４ Preferably, the first thermoelectric material layer is made of one or more permanent magnet materials selected from the group consisting of B-based magnets, alnico magnets, and ferrite magnets. More preferably, the first thermoelectric material layer is made of Bi １００－ｘ Sb ｘlayers (5≦x≦25). If x exceeds 50, the magneto-thermoelectric effect is disadvantageously reduced. [8] In the hybrid lateral thermoelectric power generation element [1] of the present invention, preferably, the inclination angle θ of the lamination plane with respect to the direction is 10° or more and 80° or less. If the inclination angle θ is less than 10° or more, or if the inclination angle θ exceeds 80°, the lateral thermoelectric effect resulting from the inclined lamination may not be fully exhibited. [9] In the hybrid lateral thermoelectric power generation element [1] of the present invention, preferably, the figure of merit of the hybrid lateral thermoelectric power generation element is 0.1 or more. If the figure of merit is less than 0.1, the hybrid thermoelectric conversion element may not fully exhibit its performance.

[10] In the hybrid lateral thermoelectric power generation element [1] of the present invention, preferably, the magnetic field applied in the direction generating the magneto-thermoelectric effect is 0.1 T or more.

[0012]

[11] The present invention provides a method for generating electricity using a horizontal thermoelectric conversion element, which involves applying a temperature difference to the horizontal thermoelectric conversion element and a magnetic field in a direction that generates a magneto-thermoelectric effect, thereby obtaining electric power from a direction perpendicular to the direction in which the temperature difference is generated in the horizontal thermoelectric conversion element, wherein the horizontal thermoelectric conversion element comprises: a first electrode and a second electrode arranged opposite to each other; and a laminate sandwiched between the first and second electrodes and electrically connected to both the first and second electrodes; The laminate has a structure in which layers of a first thermoelectric material and layers of a second thermoelectric material are alternately stacked, and the first thermoelectric material and the second thermoelectric material have different values ​​for at least one of the Seebeck coefficient, electrical conductivity, and thermal conductivity, and at least one of the first and second thermoelectric materials exhibits a vertical magneto-thermoelectric effect or a horizontal magneto-thermoelectric effect, and the stacking surfaces of the first thermoelectric material layers and the second thermoelectric material layers are inclined with respect to the direction in which the first electrode and the second electrode face each other, so that a temperature difference is generated in a direction perpendicular to the facing direction in the horizontal thermoelectric conversion element, and a magnetic field is applied in a direction in which the magneto-thermoelectric effect is generated, thereby obtaining electric power via the first and second electrodes.

[0013]

[12] In the power generation method

[11] using a horizontal thermoelectric conversion element of the present invention, preferably, the vertical magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more, more preferably 10 μV / K or more, and is a magnetic Seebeck effect derived from an external magnetic field, or an anisotropic magnetic Seebeck effect derived from spontaneous magnetization; and the horizontal magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more, more preferably 10 μV / K or more, and is a normal Nernst effect derived from an external magnetic field, or an anomalous Nernst effect derived from spontaneous magnetization. If the thermoelectric power due to the vertical magneto-thermoelectric effect and the horizontal magneto-thermoelectric effect is less than 5 μV / K, there is a disadvantage that the enhancement effect on the horizontal thermoelectric effect derived from the gradient stack structure is insufficient.

[13] In the power generation method

[11] or

[12] using a horizontal thermoelectric conversion element of the present invention, preferably, the first thermoelectric material layer is made of Bi. １００－ｘ Sb ｘ layer (0≦x≦50), and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Preferably, the first thermoelectric material layer is a layer (0≦y≦2). More preferably, the first thermoelectric material layer is a layer of Bi １００－ｘ Sb ｘ layers (5≦x≦25), and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Preferably, the layer has a value of 1.5≦y≦1.95. If x exceeds 50, the magneto-thermoelectric effect is reduced. Since the optimum properties of the second thermoelectric material depend on the type of the first thermoelectric material, it is necessary to select the optimum composition of the second thermoelectric material depending on the thermoelectric properties of the first thermoelectric material.

[14] In the power generation method for a horizontal thermoelectric conversion element according to the present invention,

[11] or

[12] , preferably, the layer of the first thermoelectric material is Co ２ MnGa, and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ Alternatively, the second thermoelectric material layer may be a Bi layer (0≦y≦2). ２ Te ３layer (y=0). Since the optimum properties of the second thermoelectric material depend on the first thermoelectric material, there is an advantage in that the optimum composition can be selected depending on the thermoelectric properties of the first thermoelectric material.

[15] In the power generation method

[12] of the horizontal thermoelectric conversion element of the present invention, preferably, the external magnetic field is applied to the first thermoelectric material layer and the second thermoelectric material layer by a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet.

[16] In the power generation method

[11] of the horizontal thermoelectric conversion element of the present invention, preferably, the first thermoelectric material layer is made of a material that exhibits a magneto-thermoelectric effect, and the second thermoelectric material layer is made of a permanent magnet material, so that a magnetic field can be applied to the first thermoelectric material without applying an external magnetic field by spontaneous magnetization of the permanent magnet, and the magneto-thermoelectric effect of the first thermoelectric material can be exhibited.

[17] In the power generation method

[16] of the horizontal thermoelectric conversion element of the present invention, preferably, the first layer is made of Bi １００－ｘ Sb ｘ layer (0≦x≦50), and the permanent magnet layer is SmCo ５ system magnet, Sm ２ Co １７ Nd-based magnets ２ Fe １４ Preferably, the first thermoelectric material layer is made of one or more permanent magnet materials selected from the group consisting of B-based magnets, alnico magnets, and ferrite magnets. More preferably, the first thermoelectric material layer is made of Bi １００－ｘ Sb ｘ layers (5≦x≦25). If x exceeds 50, there is a disadvantage that the magneto-thermoelectric effect is reduced.

[18] In the power generation method

[11] of the present invention using a horizontal thermoelectric conversion element, preferably, the figure of merit of the horizontal thermoelectric conversion element is 0.1 or more. If the figure of merit is less than 0.1, there is a possibility that the hybrid thermoelectric conversion element does not exhibit sufficient performance.

[19] In the power generation method

[11] of the present invention using a horizontal thermoelectric conversion element, preferably, the magnetic field applied in the direction that generates the magneto-thermoelectric effect is 0.1 T or more.

[0014] The hybrid lateral thermoelectric power generation element of the present invention has a structure in which layers of a first thermoelectric material exhibiting the magneto-thermoelectric effect and layers of a second thermoelectric material are alternately stacked, and the first layer is made of Bi.１００－ｘ Sb ｘ layer (0≦x≦50), and the second layer is Bi ２－ｙ Sb ｙ Te ３ Since the first thermoelectric material layer is a layer (0≦y≦2), the horizontal thermoelectric power generation characteristics can be improved as the applied magnetic field increases due to at least one of the magnetic Seebeck effect and the normal Nernst effect. Also, the hybrid horizontal thermoelectric power generation element of the present invention has a structure in which first thermoelectric material layers exhibiting the magneto-thermoelectric effect and second thermoelectric material layers having remanent magnetization and capable of driving the magneto-thermoelectric effect in the absence of a magnetic field are alternately stacked, and the first thermoelectric material layer is made of Bi. １００－ｘ Sb ｘ layer (0≦x≦50), and the second thermoelectric material layer is SmCo ５ system magnet, Sm ２ Co １７ Nd-based magnets ２ Fe １４ Since the permanent magnet is one or more types selected from the group consisting of B-based magnets, alnico magnets, and ferrite magnets, the horizontal thermoelectric power generation characteristics can be improved in the magnetized state due to the magnetic Seebeck effect and the normal and anomalous Nernst effects, compared to when the second thermoelectric material layer is not magnetized.

[0015] Figure 1 shows a systematic classification of magneto-thermoelectric effects in single materials. Figure 2A shows the configuration of a lock-in thermography measurement device suitable for measuring thermoelectric effects, focusing on cooling and heating phenomena. Figure 2B shows waveforms of input current and output temperature change signals in lock-in thermography measurements. Figure 2C shows observations of amplitude and phase measured with the lock-in thermography measurement device. Figure 3A shows an explanatory diagram of the visualization of lateral thermoelectric conversion in an artificially inclined multilayer laminate in a zero magnetic field, illustrating a perspective view of the sample configuration and a steady-state temperature image of the imaging surface. Figure 3B shows an explanatory diagram of the visualization of lateral thermoelectric conversion in an artificially inclined multilayer laminate in a zero magnetic field, illustrating an observation of amplitude and phase measured with the lock-in thermography measurement device when a net heat flow is generated in the lateral direction. Figure 3C shows an explanatory diagram of the visualization of lateral thermoelectric conversion in an artificially inclined multilayer laminate in a zero magnetic field, illustrating a perspective view of the sample configuration and a steady-state temperature image of the imaging surface. Figure 3D is an explanatory diagram of visualization of horizontal thermoelectric conversion in an artificially inclined multilayer stack in zero magnetic field. It shows the amplitude and phase observed when a net heat flow is generated from the top surface to the bottom surface, measured with a lock-in thermography measurement device. Figure 4 shows the separation of the component showing even dependence on the magnetic field (symmetric component) and the component showing odd dependence on the magnetic field (antisymmetric component). Figure 5 shows the contribution of the magnetic Peltier effect, which shows even dependence on the magnetic field. Figure 6 shows the contribution of the normal Etchingshausen effect, which shows odd dependence on the magnetic field. Figure 7 shows the magnetic field dependence of the average temperature modulation. Figure 8 shows steady-state thermoelectric cooling. Figure 9A is a perspective view of the configuration of a permanent-magnet-based artificially inclined multilayer stack for horizontal thermoelectric conversion. Figure 9B is a diagram showing the amplitude and phase of the temperature change in a permanent-magnet-based artificially inclined multilayer stack for horizontal thermoelectric conversion. Figure 9C shows the magnetic properties and horizontal thermoelectric conversion characteristics of the permanent magnet layer in a permanent-magnet-based artificially inclined multilayer stack for horizontal thermoelectric conversion. FIG. 10A shows the Bi ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３FIG. 10B shows the magnetic field dependence of the thermoelectric power output of the artificially inclined multilayer laminate, and shows the results when a temperature difference ΔT of 7.9 K is applied to sample A, which has an inclination angle θ of 45° relative to the bottom surface of the multilayer laminate. ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ 11A shows the magnetic field dependence of the thermoelectric power output of the artificially inclined multilayer laminate, and shows the results when a temperature difference ΔT of 9.8 K is applied to sample B, which has an inclination angle θ of 21° with respect to the bottom surface of the multilayer laminate. FIG. 11A is a diagram showing the configuration of a rectangular horizontal thermoelectric element, showing an example of an artificially inclined multilayer laminate. FIG. 11B shows the configuration of Bi ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ Fig. 11C is a perspective view showing a configuration for measuring the magnetic field dependence of the thermoelectric power generation output of an artificially inclined multilayer laminate. Fig. 11C is a diagram showing the dependence on the external magnetic field H in the correlation diagram between the temperature difference ΔT and the electromotive force V in the device of Fig. 11B. Fig. 11D is a diagram showing the dependence on the temperature difference ΔT in the correlation diagram between the external magnetic field H and the electromotive force V in the device of Fig. 11B. Fig. 12A is a diagram showing the dependence on the temperature difference ΔT in the correlation diagram between the external magnetic field H and the electromotive force V in the device of Fig. 11B. ２ 12B is a perspective view showing a configuration for measuring the magnetic field dependence of the thermoelectric power output of a MnGa-based artificially inclined multilayer laminate. ２ MnGa / Bi ０．２ Sb １．８ Te ３ FIG. 12C shows the results of measuring the magnetic field dependence of the transverse electromotive force when the temperature difference ΔT of the artificially tilted multilayer laminate is changed. ２ MnGa / Bi ２ Te ３ The results of measuring the magnetic field dependence of the transverse electromotive force when the temperature difference ΔT of the artificially tilted multilayer laminate is changed are shown in Fig. 12D. ２ MnGa / Bi ０．２ Sb １．８ Te ３ and Co ２ MnGa / Bi ２ Te ３ This shows the results of measuring the temperature gradient dependence of the lateral electric field of an artificially graded multilayer laminate.

[0016] (Definitions of technical terms used in thermoelectric conversion) First, the technical terms used in this specification are defined. Thermoelectric conversion is a phenomenon in which thermal energy and electrical energy are directly converted into each other within a substance. The only difference between the power generation phenomenon and the cooling / heating (temperature modulation) phenomenon is the alternation of input and output, and it can be evaluated using the dimensionless figure of merit ZT. That is, when a module using thermoelectric conversion is applied to a location where there is a temperature difference, electric power can be obtained from the electromotive force resulting from the Seebeck effect. On the other hand, when a module using thermoelectric conversion is connected to an external power source and a direct current is applied, a temperature difference occurs due to the absorption and generation of heat resulting from the Peltier effect. Here, ZT is expressed as follows using the electrical resistivity ρ, thermal conductivity κ, and Seebeck coefficient S, which are physical properties specific to the material: ZT = S ２ T / (ρκ) (1) Here, the Seebeck coefficient S represents the thermoelectric power per 1 K of temperature difference in the Seebeck effect. When materials with different Seebeck coefficients are joined and a temperature difference is created, a thermoelectric power is generated in each material, and the difference in the electromotive power between the two materials is generated as the open circuit voltage. (See Masayuki Murata, "Fundamentals of Thermoelectric Conversion," Advances in Micro-Nano Thermal Engineering, Part 2 "Micro-Nano Phenomena in Thermal Engineering," Chapter 9 "Thermoelectric Conversion," pp. 301-309 (2021))

[0017] Thermoelectric conversion elements can be broadly classified into vertical and horizontal thermoelectric conversion elements. In a longitudinal thermoelectric conversion element, the thermoelectric conversion phenomenon occurs in the same direction as the electric current and heat flow. In a transverse thermoelectric conversion element, the thermoelectric conversion phenomenon occurs in perpendicular directions as the electric current and heat flow. (Definition of technical terms related to the magneto-thermoelectric effect) Here, the magneto-thermoelectric effect is a thermoelectric effect that depends on an external magnetic field or the spontaneous magnetization of a magnetic material. Figure 1 systematically classifies the magneto-thermoelectric effect. (A) shows the electron transport phenomenon caused by an external magnetic field, and (B) shows the electron transport phenomenon caused by spontaneous magnetization, divided into longitudinal and transverse effects. The input is divided into electric current and heat flow, and the output is divided into electric current and heat flow, with the names of the phenomena listed in each column. (See Kenichi Uchida, "Conversion Phenomena of Heat Current, Electric Current, and Spin Current," in Advances in Micro-Nano Thermal Engineering, Part 1: "Basic Theory of Micro-Nano Thermal Engineering," Chapter 3: "Energy Transport Phenomena in Solids," pp. 62-71 (2021))

[0018] Among electron transport phenomena resulting from external magnetic fields, the thermoelectric conversion phenomenon in which the input is heat flow and the output is current due to the longitudinal effect is called the magnetic Seebeck effect, and the thermoelectric conversion phenomenon in which the input is current and the output is heat flow due to the longitudinal effect is called the magnetic Peltier effect. The thermoelectric conversion phenomenon in which the input is heat flow and the output is current due to the transverse effect is called the normal Nernst effect, and the thermoelectric conversion phenomenon in which the input is current and the output is heat flow due to the transverse effect is called the normal Echingshausen effect. Among electron transport phenomena resulting from spontaneous magnetization, the thermoelectric conversion phenomenon in which the input is heat flow and the output is current due to the longitudinal effect is called the anisotropic magnetic Seebeck effect, and the thermoelectric conversion phenomenon in which the input is current and the output is heat flow due to the longitudinal effect is called the anisotropic magnetic Peltier effect. The thermoelectric conversion phenomenon in which the input is heat flow and the output is current due to the transverse effect is called the anomalous Nernst effect, and the thermoelectric conversion phenomenon in which the input is current and the output is heat flow due to the transverse effect is called the anomalous Echingshausen effect.

[0019] Note that in Figure 1, the names of the phenomena are also given in each column, even for cases where the input and output are the same electric current or heat flow, rather than for thermoelectric conversion phenomena. In electron transport phenomena resulting from an external magnetic field, the phenomenon in which the input is an electric current and the output is also an electric current due to the longitudinal effect is called the magnetoresistance effect, and the phenomenon in which the input is a heat flow and the output is also a heat flow due to the longitudinal effect is called the magnetothermal resistance effect (or McGehee-Lieguier-Leduc effect). In the phenomenon in which the input is an electric current and the output is also an electric current due to the transverse effect is called the normal Hall effect, and the phenomenon in which the input is a heat flow and the output is also a heat flow due to the transverse effect is called the thermal Hall effect (or Lieguier-Leduc effect). In electron transport phenomena resulting from spontaneous magnetization, the phenomenon in which the input is an electric current and the output is also an electric current due to the longitudinal effect is called the anisotropic magnetoresistance effect, and the phenomenon in which the input is a heat flow and the output is also a heat flow due to the longitudinal effect is called the anisotropic magnetothermal resistance effect. The phenomenon in which the input becomes a current and the output also becomes a current due to the transverse effect is called the anomalous Hall effect, and the phenomenon in which the input becomes a heat flow and the output also becomes a heat flow due to the transverse effect is called the anomalous thermal Hall effect.

[0020] Next, focusing on thermoelectric generation phenomena, we explain the magneto-Seebeck effect as a longitudinal effect of electron transport due to an external magnetic field (Figure 1A), and the anisotropic magneto-Seebeck effect as a longitudinal effect of electron transport due to spontaneous magnetization (Figure 1B). We also explain the normal Nernst effect as a transverse effect of electron transport due to an external magnetic field (Figure 1A), and the anomalous Nernst effect as a transverse effect of electron transport due to spontaneous magnetization (Figure 1B). The magneto-Seebeck effect is an electron transport phenomenon due to an external magnetic field, in which the thermoelectric power generated in the same direction as the temperature gradient varies depending on the magnetic field strength. See Felix Spathelf et al., "Magneto-Seebeck effect in bismuth," Physical Review B 105, 235116 (2022). It typically exhibits an even dependence on the magnetic field direction. The anisotropic magneto-Seebeck effect is an electron transport phenomenon resulting from spontaneous magnetization. The thermoelectric power generated in the same direction as the temperature gradient varies depending on the relative angle between the temperature gradient and the magnetization. See M. Hashizume et al., "Anisotropic magneto-Seebeck effect in the antiferromagnetic semimetal FeGe2", Physical Review B 104, 115109 (2021), and K. Uchida et al., "Observation of anisotropic magneto-Peltier effect in nickel", Nature 558, 95 (2018). It typically exhibits an even dependence on the magnetization direction.

[0021] The ordinary Nernst effect (ONE) is an electron transport phenomenon caused by an external magnetic field. It is caused by the Lorentz force acting on conduction electrons and holes, generating a thermoelectric power in the direction of the cross product of the temperature gradient and the external magnetic field. While the ordinary Nernst effect in typical metals generates only a very small thermoelectric power, Bi-based semimetals are known to exhibit high thermoelectric conversion performance due to the ordinary Nernst effect (for example, BiSb alloys achieve ZT>0.3 at 100-200K when an external magnetic field of 1T is applied). However, a drawback of utilizing thermoelectric power generation via the ordinary Nernst effect is the need to apply an external magnetic field. It typically exhibits an odd-order dependence on the magnetic field direction.

[0022] The anomalous Nernst effect (ANE) is an electron transport phenomenon resulting from spontaneous magnetization, in which a thermoelectric power is generated in a magnetic material in the direction of the cross product of the temperature gradient and magnetization. If the magnetization is aligned in one direction, it will operate without applying an external magnetic field. The mechanism of the anomalous Nernst effect differs from the normal Nernst effect, and originates from a virtual magnetic field resulting from the band structure of electrons and impurity scattering dependent on spin. The transverse thermoelectric power (anomalous Nernst coefficient) due to the anomalous Nernst effect in pure metals that exhibit ferromagnetism, such as Fe, Ni, and Co, is only about 0.1 μV / K, but in Co, ２ In magnetic Heusler alloys such as MnGa, a transverse thermoelectric power exceeding 6 μV / K, which originates from the topological electronic structure, has been observed in the temperature range including room temperature. Typically, it shows an odd dependence on the magnetization direction.

[0023] Next, focusing on cooling and heating phenomena, we explain the magneto-Peltier effect as a longitudinal effect of electron transport due to an external magnetic field (Figure 1A), and the anisotropic magneto-Peltier effect as a longitudinal effect of electron transport due to spontaneous magnetization (Figure 1B). We also explain the normal Etchingshausen effect as a transverse effect of electron transport due to an external magnetic field (Figure 1A), and the anomalous Etchingshausen effect as a transverse effect of electron transport due to spontaneous magnetization (Figure 1B). The magneto-Peltier effect is an electron transport phenomenon due to an external magnetic field, in which heat flow generated in the same direction as the input current varies depending on the magnetic field strength. It usually exhibits even dependence on the magnetic field direction. The anisotropic magneto-Peltier effect is an electron transport phenomenon due to spontaneous magnetization, in which heat flow generated in the same direction as the input current varies depending on the relative angle between the current and magnetization. See K. Uchida et al., “Observation of anisotropic magneto-Peltier effect in nickel”, Nature 558, 95 (2018). It usually shows an even dependence on the magnetization direction.

[0024] The Ordinary Ettingshausen Effect (OEE) is an electron transport phenomenon resulting from an external magnetic field, in which heat flow occurs in the direction of the cross product of the input current and the external magnetic field. While the OEE in typical metals generates only a very small temperature gradient, Bi-based semimetals are known to exhibit high thermoelectric conversion performance due to the OEE (for example, BiSb alloys achieve ZT>0.3 at 100-200K when an external magnetic field of 1 T is applied). However, a drawback of the OEE is the need to apply an external magnetic field to utilize the cooling and heating phenomena. It typically exhibits an odd-order dependence on the magnetic field direction.

[0025] The anomalous Ettingshausen effect (AEE) is an electron transport phenomenon resulting from spontaneous magnetization, in which a heat flow occurs in the direction of the cross product of the input current and the magnetization in a magnetic material. If the magnetization is aligned in one direction, it will operate without applying an external magnetic field. The mechanism of the anomalous Ettingshausen effect differs from that of the normal Ettingshausen effect, and originates from a virtual magnetic field resulting from the electron band structure and impurity scattering dependent on the spin. Co ２ Magnetic Heusler alloys such as MnGa and SmCo ５ A large anomalous Etchingshausen effect has been observed in permanent magnets such as those shown in Fig. 1. It usually shows an odd dependence on the magnetization direction.

[0026] An embodiment of the present invention will be described below with reference to the drawings. FIG. 2A is a block diagram of a lock-in thermography measurement device suitable for measuring cooling and heating phenomena due to the thermoelectric effect. In the figure, the lock-in thermography measurement device includes a sample 10, the thermoelectric effect of which is to be measured, an electromagnet 20, a current source 30, an infrared camera 40, and a signal processing system 50. The sample 10, the object of thermoelectric effect measurement, has a roughly rectangular parallelepiped shape. Specifically, the sample 10 is an artificially tilted multilayer laminate with different tilt angles in a zero magnetic field, as shown in FIG. 9A. In a three-dimensional orthogonal coordinate system xyz, the x-axis is the longitudinal direction of the sample 10, the y-axis is the width direction of the sample 10, and indicates the direction in which an external magnetic field H is applied by the electromagnet 20, and the z-axis is the thickness direction of the sample 10, and indicates the direction in which an image is captured by the infrared camera 40. The electromagnet 20 applies a magnetic field H in the width direction y of the cross section of the sample 10. It has a core made of a magnetic material and a winding made of a conductive material wound around the core. A permanent magnet may be used instead of the electromagnet 20, or may be used together with the electromagnet 20. The current source 30 passes a current Jc in the longitudinal direction x of the sample 10. In lock-in thermography measurement, the current source 30 is used to apply an AC rectangular wave current. The infrared camera 40 photographs the sample 10 located between the north and south poles of the electromagnet 20 from the z-axis direction. For example, an FEI model (ELITE) or an InfraTec model (ImageIR) may be used. The signal processing system 50 performs Fourier analysis using the thermal image signal sent from the infrared camera 40 and the reference signal sent from the current source 30, and extracts the lock-in amplitude signal A and the lock-in phase signal φ. The signal processing system 50 can be implemented using a computer as hardware.

[0027] Figure 2B shows waveforms of the input current and output temperature change signal. The input signal is a periodic square-wave current with a time period (1 / f) equal to the inverse of frequency f, an amplitude Jc, and a duty ratio of 0.5. The output signal consists of a thermoelectric effect signal synchronized with the input current period and a finite Joule heat signal that does not change over time superimposed on it. Lock-in thermography allows for the extraction of only the temperature change component synchronized with the frequency of the input signal, enabling imaging and measurement of the thermoelectric effect signal alone.

[0028] 2C is an observation diagram of the amplitude and phase of the temperature change measured with a lock-in thermography measurement device. In the figure, the lock-in amplitude signal image A and the lock-in phase signal image φ are planar images of the sample 10, which is the imaging surface of the infrared camera 40. The shading of the planar image of the sample 10 represents the strength of the amplitude and the degree of phase delay. The repeated pattern in the shading of the planar image is due to the repeated appearance of the material junction interface in the artificially gradient multilayer laminate.

[0029] FIG. 3A is an explanatory diagram illustrating the visualization of horizontal thermoelectric conversion in a zero magnetic field in an artificially tilted multilayer stack, with the longitudinal cross section being rectangular. The multilayer stack is stacked at an inclination within the xy plane of the sample 10. FIG. 3A(a) is a perspective view of the sample configuration. In a three-dimensional orthogonal coordinate system xyz, the x-axis direction is the current axis direction along which an external current is supplied, the y-axis direction is the magnetic axis direction indicating the magnetic field direction of the applied external magnetic field H, and the z-axis direction is the thickness direction of the sample. In this arrangement, the net heat flow direction generated by the horizontal thermoelectric effect resulting from the tilted structure is the y-axis direction. The magnetic field direction along which the external magnetic field H is applied is not limited to the y-axis direction of the three-dimensional orthogonal coordinate system xyz. As long as the magnetic field direction is a direction in which temperature modulation occurs due to the magneto-thermoelectric effect, it does not need to strictly coincide with the y-axis direction and may be within an appropriate tolerance, for example, within ±30° of the y-axis direction.

[0030] The multilayer laminate is stacked at an inclination in the xy plane of the sample 10. In the xz plane of the sample 10, it is stacked parallel. In FIG. 3A(a), sample A is used, in which the inclination angle θ of the multilayer laminate in the xy plane is 45°. Indium electrodes are provided on both ends of the multilayer laminate in the current axis direction x. FIG. 3A(b) shows a steady-state temperature image that appears on the imaging surface (xy plane) when a driving current is passed between a first electrode and a second electrode that are provided as a pair in the x-axis direction of the sample 10. In the xy plane, Bi as the first thermoelectric material ８８ Sb １２ layer and Bi as the second thermoelectric material ０．２ Sb １．８ Te ３ When a steady current of 1 A is applied, Bi ８８ Sb １２ The temperature distribution of the layer is 293.5K to 296K, and Bi ０．２ Sb １．８ Te ３ The temperature distribution in the layer is 298K to 302K.

[0031] Figure 3B(c) shows the lock-in amplitude signal image of the sample, showing the square-wave periodic current with frequencies f of 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz, in that order. Large amplitude signal areas (dark areas) indicate large temperature changes, while small amplitude signal areas (light areas) indicate small temperature changes. It can be seen that the lower the frequency f, the larger the temperature changes within the sample.

[0032] Figure 3B(d) shows the lock-in phase signal image of the sample, showing the square-wave periodic current frequency f of 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz, in order. In the steady state, a phase difference of 0° from the reference signal indicates heat generation, and a phase difference of 180° indicates heat absorption. At high frequencies, the phase difference from the reference signal changes spatially continuously due to the effects of thermal diffusion. However, as the frequency f decreases, the steady state approaches and the spatial distribution of the phase signal image φ decreases. At 0.1 Hz, although the effects of thermal diffusion remain slight, it can be seen that cooling occurs in the upper region and heat generation occurs in the lower region. Furthermore, a thermal distribution reflecting the tilt angle of the element's tilted stack structure is formed approximately in the center of the element.

[0033] FIG. 3B(e) shows the values ​​of the grayscale signal shown in FIG. 3B(c) near the side surface of the sample, with the horizontal axis representing the position in the longitudinal direction of the sample and the vertical axis representing the amplitude value A, where the frequency f of the square wave periodic current is 10 Hz, 1 Hz, and 0.1 Hz in order. For example, Bi ８８ Sb １２ The maximum amplitude of the temperature change in the layer is 0.9 K at 10 Hz, 2.8 K at 1 Hz, and 4.0 K at 0.1 Hz. Figure 3B(f) shows the grayscale signal values ​​near the side of the sample shown in Figure 3B(d), with the horizontal axis representing the longitudinal position of the sample and the vertical axis representing the phase value φ, for square-wave periodic current frequencies f of 10 Hz, 1 Hz, and 0.1 Hz, respectively. At 10 Hz and 1 Hz, the phase difference from the reference signal changes continuously due to the influence of thermal diffusion, which has not yet reached a steady state. At 0.1 Hz, the phase difference is 180° across almost the entire region, indicating heat absorption.

[0034] FIG. 3B(g) shows the amplitude values ​​for each frequency f shown in FIG. 3B(e) averaged over the range of one pair of junctions of different materials. ａｖｅ (K) shows the average amplitude value A ａｖｅ (K) is 0.2 K at 10 Hz, 0.3 K at 5 Hz, 0.5 K at 2 Hz, 1.0 K at 1 Hz, 1.3 K at 0.5 Hz, 1.6 K at 0.2 Hz, and 1.6 K at 0.1 Hz. Figure 3B(h) shows the average value φ of the phase value for each frequency f shown in Figure 3B(f) within the range of one pair of junctions of different materials. ａｖｅ (deg). The average phase value φ ａｖｅ (deg) is 260° at 10 Hz, 260° at 5 Hz, 250° at 2 Hz, 240° at 1 Hz, 220° at 0.5 Hz, 200° at 0.2 Hz, and 190° at 0.1 Hz.

[0035] 3C and 3D are explanatory diagrams for visualizing horizontal thermoelectric conversion in a zero magnetic field in an artificially tilted multilayer stack, showing the generation of a net heat flow Jq flowing from the top surface to the bottom surface in the z-axis direction. Figure 3C(i) is a perspective view of the sample configuration. In the three-dimensional orthogonal coordinate system xyz, the x-axis direction is the current axis direction along which an external current is supplied, the y-axis direction is the magnetic axis direction indicating the magnetic field direction of the applied external magnetic field H, and the z-axis direction is the thickness direction of the sample. In this configuration, the net heat flow direction generated by the thermoelectric effect is the z-axis direction. The magnetic field direction along which the external magnetic field H is applied is not limited to the y-axis direction of the three-dimensional orthogonal coordinate system xyz. As long as the magnetic field direction is a direction in which temperature modulation occurs due to the magneto-thermoelectric effect, it does not need to strictly coincide with the y-axis direction, but may be within an appropriate tolerance, for example, within ±30° of the y-axis direction. The multilayer stack is stacked at an angle within the xz plane of the sample 10. In the xy plane of the sample 10, the stacks are stacked parallel to each other. 3C(i), Sample A is used, in which the inclination angle θ of the multilayer laminate relative to the bottom surface is 45°. Indium electrodes are provided on both ends of the multilayer laminate in the current axis direction x.

[0036] 3C(j) shows a steady-state temperature image that appears on the imaging surface (xy plane) in the direction of heat flow when a driving current is applied between a pair of first and second electrodes arranged in the x-axis direction of the sample 10. In the xy plane, Bi as the first thermoelectric material is ８８ Sb １２ layer and Bi as the second thermoelectric material ０．２ Sb １．８ Te ３ When a steady current of 1 A is applied, Bi ８８ Sb １２ The temperature distribution of the layer is 295K to 296K, and Bi ０．２ Sb １．８ Te ３ The temperature distribution in the layer is 298K to 300K.

[0037] Figure 3D(k) shows the lock-in amplitude signal image of the sample, with the square-wave periodic current frequency f set to 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz, respectively. It can be seen that the lower the frequency f, the greater the temperature change within the sample. Figure 3D(l) shows the lock-in phase signal image φ of the sample, with the square-wave periodic current frequency f set to 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz, respectively. The lower the frequency f, the smaller the change in the phase signal image φ, with the region around 180° dominating at 0.1 Hz. This indicates that the entire sample surface is cooled near steady state.

[0038] Referring to FIG. 3D(k) and FIG. 3D(l), Bi ８８ Sb １２ When examining the position where the maximum value of the temperature change amplitude appears in the layer, in the region where the phase signal image φ is around 180°, Bi ８８ Sb １２ The maximum value appears in the layer, i.e., Bi ８８ Sb １２ In the layer, the maximum value of the temperature change amplitude occurs in a region where the phase signal image φ in the current axis direction x is near 180°. For example, ８８ Sb １２ The maximum value is reached in the region of one-quarter to one-half of the width of the layer in the direction of the current axis x. On the other hand, no dependence of the temperature change distribution is observed in the direction of the magnetic axis y.

[0039] FIG. 3D(m) shows the grayscale signal shown in FIG. 3D(k), with the horizontal axis representing the position in the longitudinal direction of the sample and the vertical axis representing the amplitude value A, and shows the frequency f of the square wave periodic current as 10 Hz, 1 Hz, and 0.1 Hz in order. For example, Bi ８８ Sb １２The maximum amplitude of the temperature change in the layer is 1.0 K at 10 Hz, 3.5 K at 1 Hz, and 5.5 K at 0.1 Hz. Figure 3D(n) shows the grayscale signal shown in Figure 3D(l), with the horizontal axis representing the longitudinal direction of the sample and the vertical axis representing the phase value φ, for square-wave periodic current frequencies f of 10 Hz, 1 Hz, and 0.1 Hz, respectively. At 10 Hz and 1 Hz, the phase difference from the reference signal changes continuously due to the influence of thermal diffusion, which has not yet reached a steady state. At 0.1 Hz, the phase difference is 180° across almost the entire region, indicating heat absorption.

[0040] FIG. 3D(o) shows the average value A of the amplitude value for each frequency f of the current shown in FIG. 3D(m) within the range of one pair of junctions of different materials. ａｖｅ (K) shows the average amplitude value A ａｖｅ (K) is 0.2 K at 10 Hz, 0.4 K at 5 Hz, 0.7 K at 2 Hz, 1.2 K at 1 Hz, 1.8 K at 0.5 Hz, 2.1 K at 0.2 Hz, and 2.5 K at 0.1 Hz. Figure 3D(p) shows the average value φ of the phase value for each frequency f shown in Figure 3D(n) within the range of one pair of junctions of different materials. ａｖｅ (deg). The average phase value φ ａｖｅ (deg) is 260° at 10 Hz, 260° at 5 Hz, 250° at 2 Hz, 240° at 1 Hz, 220° at 0.5 Hz, 200° at 0.2 Hz, and 190° at 0.1 Hz.

[0041] The samples shown in Fig. 3A(a) and Fig. 3C(i) are made of alternately stacked Bi ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ The multilayer stack was fabricated by spark plasma sintering, with each material approximately 1 mm thick and an applied current amplitude of 1 A (except for Figure 8). Lock-in thermography reveals how the localized heat release and absorption at the interface between different materials functions as lateral thermoelectric conversion.

[0042] The modulation due to the magneto-thermoelectric effect is measured by performing lock-in thermography measurements under an applied magnetic field H. Figure 4 shows the results of separating the lock-in thermography image into the symmetric and antisymmetric components of the magnetic field. Figure 4(a) shows the applied magnetic flux density μ ０ The original image at H = +0.8 T, and Fig. 4(b) shows the applied magnetic flux density μ ０ The original image at H = -0.8 T, and Fig. 4(c) shows the applied magnetic flux density intensity μ ０ The symmetric component of the magnetic field when |H| is 0.8 T. Fig. 4(d) shows the applied magnetic flux density intensity μ ０ The figure shows a pair of lock-in amplitude signal image and lock-in phase signal image of the sample, where |H| indicates the antisymmetric component of the magnetic field at 0.8 T. The frequency f of the square-wave periodic current is 1.0 Hz.

[0043] The magnetic field symmetric component has an amplitude value A ｅｖｅｎ (K) and the phase value φ ｅｖｅｎ The magnetic field symmetric component is extracted by complex-summing the lock-in thermography image signal at a negative applied magnetic field with the lock-in thermography image signal at a positive applied magnetic field, and dividing the summed image signal by two.

[0044] The magnetic field antisymmetric component has an amplitude value A ｏｄｄ (K) and the phase value φ ｏｄｄ The magnetic field antisymmetric component is extracted by complex subtracting the lock-in thermography image signal at a negative applied magnetic field from the lock-in thermography image signal at a positive applied magnetic field, and dividing the subtracted image signal by two.

[0045] In FIG. 4(a), the amplitude value A(K) and phase value φ(deg) of the original image in which the magnetic field symmetric component and the magnetic field antisymmetric component are not clearly distinguished are shown. The image of the amplitude value A(K) of the original image is similar to the case of 1 Hz in FIG. 3D(k), but the Bi ８８ Sb １２ The maximum amplitude of the temperature change in the layer is 4.0 K. ８８ Sb １２ The maximum value occurs in the region of one-quarter to one-half of the width of the layer in the direction of the current axis x. ８８ Sb１２ Temperature changes occur throughout the entire layer. On the other hand, no temperature change distribution dependence is observed in the magnetic axis direction (y-axis). The phase value φ (deg) of the original image shows alternating regions of approximately 0° and approximately 180° in the phase signal image φ, as in the 1 Hz case in Figure 3D(l). Figure 4(b) shows the amplitude value A (K) and phase value φ (deg) of the original image without a clear distinction between the symmetric and antisymmetric components of the magnetic field, similar to Figure 4(a).

[0046] In FIG. 4(c), the amplitude value A ｅｖｅｎ (K) and the phase value φ ｅｖｅｎ (deg), which is the same as FIG. 4(a). In FIG. 4(d), the amplitude value A ｏｄｄ (K) and the phase value φ ｏｄｄ (deg), and Bi ８８ Sb １２ The maximum temperature change amplitude that appears in the layer is 0.3 K. ８８ Sb １２ Temperature changes occur in the entire layer, and the area where the maximum temperature change amplitude occurs is Bi ８８ Sb １２ This is about half the width of the layer in the direction of the current axis x. On the other hand, no dependence of the temperature change distribution is observed in the direction of the magnetic axis y. ８８ Sb １２ The value of the phase signal image φ appearing in the layer is close to 180°.

[0047] Figure 5 is an explanatory diagram of the contribution of the magnetic Peltier effect. The area enclosed by the white rectangle in the thermal image is Bi. ８８ Sb １２ and Bi ０．２ Sb １．８ Te ３ The magnetic field symmetric component shows the contribution of the magnetic Peltier effect in the artificially tilted multilayer stack. Figure 5(a) shows the amplitude signal image of the magnetic field symmetric component, Figure 5(b) shows the phase signal image, and Figure 5(c) shows the amplitude value A of the magnetic field symmetric component. ｅｖｅｎ This graph shows the magnetic field dependence of (K), with the horizontal axis representing the magnetic field μ ０ |H|, the vertical axis is the amplitude value A ｅｖｅｎ (K). Figure 5(d) shows the phase value φ of the symmetric component of the magnetic field. ｅｖｅｎThe graph shows the magnetic field dependence of the magnetic flux density μ ０ |H|, the vertical axis is the phase value φ ｅｖｅｎ (deg).

[0048] Figure 5(a) shows an amplitude signal image of the symmetric component of the magnetic field, which is a reprint of Figure 4(c). Figure 5(b) shows a phase signal image of the symmetric component of the magnetic field, which is a reprint of Figure 4(c). In Figure 5(c), the magnetic field μ ０ When |H| is 0.0T, 0.2T, 0.4T, 0.6T, 0.8T, and 1.0T, the corresponding amplitude values ​​A ｅｖｅｎ (K) is 3.3K, 3.4K, 3.5K, 3.7K, 3.8K, and 3.9K. In FIG. 5(d), the magnetic field μ ０ When |H| is 0.0T, 0.2T, 0.4T, 0.6T, 0.8T, and 1.0T, the corresponding phase values ​​φ ｅｖｅｎ (deg) shows the same value as 210°. ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ The temperature modulation signal near the interface increases with increasing applied magnetic field due to the magnetic Peltier effect.

[0049] FIG. 6 is an explanatory diagram of the contribution of the normal etching shausen effect. FIG. 6(a) shows the lock-in amplitude signal image A of the sample. ｏｄｄ In (K), the frequency f of the periodic square wave current is shown as 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz in order. The lower the frequency f, the higher the temperature amplitude. For example, Bi ８８ Sb １２ The maximum temperature change amplitude appearing in the layer is 0.090 K at 10 Hz, 0.13 K at 5 Hz, 0.25 K at 1 Hz, 0.3 K at 0.5 Hz, and 0.4 K at 0.1 Hz. Figure 6(b) shows the lock-in phase signal image φ of the sample. ｏｄｄ(K) shows the frequency f of the square-wave periodic current as 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz. As the frequency f decreases, the sample approaches a steady state and the spatial distribution of the phase signal image φ decreases. At 0.1 Hz, the effect of thermal diffusion remains slight, but the phase is close to 180° across the entire sample surface, indicating that the sample is being cooled.

[0050] FIG. 6(c) shows the amplitude value A of the antisymmetric magnetic field component. ｏｄｄ In this graph, the horizontal axis represents frequency f and the vertical axis represents amplitude A. ｏｄｄ (K). Amplitude value A ｏｄｄ (K) is 0.07 K at 10 Hz, 0.1 K at 5 Hz, 0.15 K at 2 Hz, 2.0 K at 1 Hz, 0.24 K at 0.5 Hz, 0.28 K at 0.2 Hz, and 0.32 K at 0.1 Hz. Figure 6(d) shows the phase value φ of the antisymmetric component of the magnetic field. ｏｄｄ In this graph, the horizontal axis represents frequency f and the vertical axis represents phase value φ. ｏｄｄ (deg). Phase value φ ｏｄｄ (deg) is 240° at 10 Hz, 240° at 5 Hz, 230° at 2 Hz, 220° at 1 Hz, 210° at 0.5 Hz, 200° at 0.2 Hz, and 190° at 0.1 Hz.

[0051] FIG. 6(e) shows the amplitude value A of the antisymmetric magnetic field component. ｏｄｄ This graph shows the magnetic field dependence of (K), with the horizontal axis representing the magnetic field μ ０ |H|, the vertical axis is the amplitude value A ｏｄｄ (K). Magnetic field μ ０ When |H| is 0.2T, 0.4T, 0.6T, 0.8T, and 1.0T, the corresponding amplitude values ​​A ｏｄｄ (K) is 0.12K, 0.17K, 0.20K, 0.21K, and 0.22K. Figure 6(f) shows the phase value φ of the antisymmetric magnetic field component. ｏｄｄ The graph shows the magnetic field dependence of the magnetic field μ ０ |H|, the vertical axis is the phase value φ ｏｄｄ (deg). Magnetic field μ ０ When |H| is 0.2T, 0.4T, 0.6T, 0.8T, and 1.0T, the corresponding phase values ​​φ ｏｄｄ(deg) shows a value that is approximately the same as 210°.

[0052] The antisymmetric component of the magnetic field indicates the contribution of the normal Etchingshausen effect in the artificially graded multilayer stack. The contribution of the normal Etchingshausen effect is mainly due to the Bi ８８ Sb １２ The magnetic field dependence of the normal etching shausen effect contribution is ８８ Sb １２ This coincides with the magnetic field dependence of the thermoelectric power due to the normal Nernst effect (see FIG. 6(e)).

[0053] 7A and 7B are diagrams illustrating the magnetic field dependence of the average temperature modulation. FIG. 7A shows the average amplitude A of sample A, in which the inclination angle θ relative to the bottom surface of the multilayer laminate is 45°, when the frequency f of the rectangular wave periodic current is 0.1 Hz. ａｖｅ (K), the horizontal axis is the magnetic field μ ０ |H|, the vertical axis is the average amplitude value A ａｖｅ (K). Magnetic field μ ０ As |H| increases from −1.0T to 1.0T, the corresponding amplitude value A ａｖｅ (K) increases from 2.2 K to 2.68 K. Fig. 7(b) is a graph showing the rate of change δ of temperature change due to the application of a magnetic field by horizontal thermoelectric conversion when the frequency f of the square wave periodic current is 0.1 Hz for sample A, in which the inclination angle θ with respect to the bottom surface of the multilayer laminate is 45°, and sample B, in which the inclination angle θ is 21°. The horizontal axis is the magnetic field μ ０ |H|. Magnetic field μ ０ As |H| increases from −1.0T to 1.0T, the corresponding change δ for sample A increases from −8% to 12%, and for sample B increases from −9% to 15%.

[0054] Here, the rate of change δ of the temperature change due to horizontal thermoelectric conversion caused by the application of a magnetic field is expressed as the amplitude value A ａｖｅ It is calculated from the ratio of the value at zero magnetic field to the value at a magnetic field of 0.8 T, and is expressed by the following formula: δ = [ A ave (0.8T) - A ave (0T) ] / A ave (0T) Bi８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ Average amplitude A of the artificially inclined multilayer laminate ａｖｅ can be enhanced by applying a magnetic field due to the superposition of the structure-induced signal, the magnetic Peltier effect, and the normal Etchingshausen effect. The rate of change δ of the current-induced temperature difference depending on the magnetic field can be adjusted by changing the tilt angle θ, and its value also depends on the magnetic field.

[0055] 8A and 8B are explanatory diagrams of thermoelectric cooling in a steady state. In Fig. 8A, the horizontal axis represents the constant current I applied to the sample in the direction of the current axis x, and the vertical axis represents the average temperature change ΔT in the steady state. ０ When |H| is -0.8 T, the maximum average temperature change ΔT is -4 K when the constant current I is 4 A. ０ When |H| is +0.8 T and the constant current I is 5 A, the maximum average temperature change ΔT is -6 K. In Figure 8(b), the horizontal axis is the constant current |I| applied in the direction of the current axis x of the sample, and the vertical axis is the temperature change ΔT due to the thermoelectric effect. ＴＥ The thermoelectric effect for sample B is ０ When |H| is +0.8T, the maximum average temperature change ΔT when the constant current I is 7A ＴＥ The magnetic field μ ０ When |H| is -0.8T, the maximum average temperature change ΔT is when the constant current I is 7A. ＴＥ In the thermoelectric effect, the temperature change ΔT is proportional to the increase in the constant current I. ＴＥ In FIG. 8(c), the horizontal axis represents the constant current |I| applied to the sample in the direction of the current axis x, and the vertical axis represents the temperature change ΔT due to Joule heat. Ｊ The Joule heat for sample B does not depend on the sign of the magnetic field, and the magnetic field μ ０ When |H| is ±0.8T, when the constant current I is 7A, the temperature change ΔT Ｊ In Joule heating, the temperature change ΔT is proportional to the square of the constant current I. Ｊ increases.

[0056] Here, the measurement points in the figure are indicated by the magnetic flux density μ ０Regarding the steady-state temperature change ΔT when H is +0.8T, the magnetic flux density μ ０ The steady-state temperature change ΔT at H = -0.8 T is indicated by △. The steady-state temperature change ΔT from room temperature due to the thermoelectric effect or Joule heat ＴＥ , ΔT Ｊ For , the following equation holds: Here, ΔT(+I) is the average temperature change ΔT when a positive current is applied, and ΔT(−I) is the average temperature change ΔT when a negative current is applied.

[0057] Bi ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ Steady-state thermoelectric cooling is possible with an artificially graded multilayer stack. Steady-state cooling can be enhanced by applying a positive magnetic field, and as a result of competition between thermoelectric cooling and Joule heating, a temperature change of up to -6 K can be achieved at Jc = +5 A. Because the magnitude relationship between thermoelectric cooling and Joule heating depends on the thermal boundary conditions of the element, optimizing the thermal design can also achieve greater thermoelectric cooling with the same element.

[0058] In the embodiment shown in FIG. ０．２ Sb １．８ Te ３ The layer is made of Nd ２ Fe １４ The first thermoelectric material was Bi. ８８ Sb １２ layer and Nd as the second thermoelectric material ２ Fe １４ The sample is an artificially inclined multilayer laminate of B-based magnet layers. Figure 9A shows a perspective view of the structure of an artificially inclined multilayer laminate based on a permanent magnet for horizontal thermoelectric conversion. The artificially inclined multilayer laminate is stacked at an inclination angle θ in the xz plane of the sample 10. The generated heat flow Jq flows in the z-axis direction, from the top surface to the bottom surface. The magnetization M is Nd ２ Fe １４ The magnetization direction of the B-based magnet layer is the normal direction to the stacking surface of the artificially tilted multilayer stack. ２ Fe １４ The magnetization M of the B-based magnet layer allows the Bi８８ Sb １２ A magnetic field H is applied to the layer.

[0059] Figure 9B shows the amplitude and phase of the current-induced temperature change in a permanent magnet-based artificially tilted multilayer stack for horizontal thermoelectric conversion. Figure 9B(c) shows the side view of Figure 9A, and Figure 9B(d) shows the top view of Figure 9A. The upper and lower left figures of Figure 9B(c) show the Bi values ​​for the side view of Figure 9A. ８８ Sb １２ The lock-in amplitude signal image of the NdFeB magnet artificially tilted multilayer laminate sample shows the results when the frequency f of the square wave periodic current is 10 Hz and 1.0 Hz, respectively. ８８ Sb １２ The maximum temperature change amplitude in the layer is 120 mK at 10 Hz and 220 mK at 1 Hz. The upper right and lower right figures in Figure 9B(c) show the Bi ８８ Sb １２ This is a lock-in phase signal image of a NdFeB-based magnet artificially tilted multilayer laminate, showing the square-wave periodic current frequency f of 10 Hz and 1.0 Hz in sequence. Due to the influence of thermal diffusion, the phase difference with the reference signal changes spatially and continuously.

[0060] Referring to FIG. 9B(c), the temperature change amplitude is Bi ８８ Sb １２ In the low frequency region, the temperature amplitude is small in the center of the inclined region in the xy plane of the sample 10, and is large near both edges of the y axis.

[0061] The upper and lower left drawings of FIG. 9B(d) are Bi ８８ Sb １２ The lock-in amplitude signal image of the NdFeB magnet artificially tilted multilayer laminate shows the frequency f of the square wave periodic current of 10 Hz and 1.0 Hz in sequence. ８８ Sb １２ The maximum temperature change amplitude in the layer is 120 mK at 10 Hz and 220 mK at 1 Hz. The upper right and lower right figures in Figure 9B(d) show the Bi ８８ Sb １２This is a lock-in phase signal image of a NdFeB-based magnet artificially tilted multilayer laminate, showing the square-wave periodic current frequency f of 10 Hz and 1.0 Hz in sequence. Due to the influence of thermal diffusion, the phase difference with the reference signal changes spatially and continuously.

[0062] Referring to FIG. 9B(d), the temperature change amplitude is Bi ８８ Sb １２ / NdFeB system magnet interface. ８８ Sb １２ The maximum temperature change is observed in the region of one-quarter to one-half of the width of the layer in the direction of the current axis x. On the other hand, no dependence of the temperature change distribution is observed in the direction of the magnetic axis y.

[0063] FIG. 9C shows a Bi- ８８ Sb １２ / Nd ２ Fe １４ The magnetic properties and lateral thermoelectric conversion properties of the B-based magnet artificially inclined multilayer laminate are shown in Fig. 9C(e). ２ Fe １４ The hysteresis curve for B-type magnets, with the horizontal axis representing the applied magnetic field μ ０ H, the vertical axis is the magnetization μ of the sample ０ M, and the applied magnetic field μ ０ The saturation magnetization curve shows a loop curve with a range of ±1.2 T within the range of ±2.5 T. ８８ Sb １２ / Nd ２ Fe １４ It can be seen that the B-based magnet artificially tilted multilayer laminate has a large coercive force and residual magnetization. ２ Fe １４ The graph shows the average amplitude of temperature change when a B-based permanent magnet is demagnetized and magnetized. As shown in Figure 9A, the magnetization direction is perpendicular to the lamination direction of the artificially inclined multilayer laminate. The temperature change in Figure 9C(f) is the result of measuring the top surface of Figure 9A, with the horizontal axis representing frequency (Hz) and the vertical axis representing the average amplitude of temperature change (mK). All of the results shown in Figure 9 are from the case where no magnetic field is applied, i.e., the applied magnetic flux density μ ０The graph shows the case where H is 0 T. When the frequency f of the square wave periodic current is 10 Hz, 5 Hz, 2 Hz, 1.0 Hz, and 0.5 Hz, the average amplitude (mK) of the temperature change in the unmagnetized state is 25, 38, 70, 105, and 130 mK, respectively. In contrast, the results for the cases are shown in order. The average amplitude (mK) of the temperature change in the magnetized state is 26, 40, 75, 110, and 145 mK, respectively. In Figure 9C (g), the horizontal axis is frequency (Hz) and the vertical axis is Nd ２ Fe １４ This shows the rate of change δ% of the average amplitude of a B-based permanent magnet when it is generated and when it is magnetized. When the frequency f of the square wave periodic current is 10 Hz, 5 Hz, 2 Hz, 1.0 Hz, and 0.5 Hz, the rate of change δ is 8, 8, 8, 8, and 9%, respectively.

[0064] 9A to 9C are Nd ２ Fe １４ B-based magnets and Bi ８８ Sb １２ and Bi ８８ Sb １２ exhibits a large magneto-thermoelectric effect, so Nd ２ Fe １４ Although measurements were taken without applying a magnetic field in either the demagnetized or magnetized state of B, the signal was clearly enhanced in the magnetized state due to the magneto-thermoelectric effect, demonstrating the realization of hybrid lateral thermoelectric conversion. Figure 9C(g) shows that magnetization increased the temperature change signal by approximately 8%. By constructing a permanent-magnet-based artificially tilted multilayer laminate for lateral thermoelectric conversion in this way, it is possible to enhance output by utilizing magneto-thermoelectric effects (such as the magnetic Seebeck effect and the normal and anomalous Nernst effects) while incorporating the benefits of permanent magnets.

[0065] Next, a method for manufacturing a hybrid magneto-thermoelectric effect element based on an artificially graded multilayer laminate will be described. ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３ Artificially graded multilayer laminate and Bi ８８ Sb １２ / Nd ２ Fe１４ All of the B-based magnet artificially inclined multilayer laminates were fabricated using spark plasma sintering. Spark plasma sintering (SPS) is a processing method that uses mechanical pressure and pulsed current heating to sinter, join, and synthesize workpieces. In addition to the thermal and mechanical energy used in general sintering, the driving force for sintering is a combination of electromagnetic energy from pulsed current, self-heating of the workpiece, and spark plasma energy generated between particles.

[0066] In the above embodiment, a temperature change signal generated by inputting a current is measured, but a hybrid horizontal thermoelectric power generation can also be performed by inputting a temperature gradient based on the same principle. ８８ Sb １２． / Bi ０．２ Sb １．８ Te ３ Thermoelectric power V in artificially graded multilayer laminates ｏｕｔ and output power P ｏｕｔ Load current I ｌｏａｄ The graph shows the results of measurements of the output power P at various magnetic field values, where (a) shows the measurement results for sample A when ΔT is 7.9 K, and (b) shows the measurement results for sample B when ΔT is 9.8 K. ｏｕｔ was estimated from the following equation: By applying a positive magnetic field, the output power P ｏｕｔ It was shown that the magneto-thermoelectric effect can also improve power generation output.

[0067] In the above example, the hybrid lateral thermoelectric power generation element structure in the artificially inclined multilayer laminate is made of Bi as the first thermoelectric material layer. １００－ｘ Sb ｘ layer (0≦x≦50), and Bi as the second thermoelectric material layer ２－ｙ Sb ｙ Te ３Although the case of layers (0≦y≦2) has been described, the present invention is not limited to the above embodiment, and other material combinations may be used. In this case, the vertical magneto-thermoelectric effect should exhibit a thermoelectric power change of 5 μV / K or more, for example, Bi and Bi-based alloys. Also, the horizontal magneto-thermoelectric effect should exhibit a thermoelectric power change of 5 μV / K or more, for example, Bi, Bi-based alloys, Co ２ MnGa, Co ２ MnAl, SmCo ５ As a result of combining the above, it is preferable that the figure of merit of the hybrid lateral thermoelectric power generation element is 0.1 or more.

[0068] Here, the individual thermoelectric power, electrical resistivity ρ, and thermal conductivity κ of the first thermoelectric material layer and the second thermoelectric material layer used in the hybrid lateral thermoelectric power generation element are measured as follows. For example, the thermoelectric power measurement method specified in JIS R 1650-1, "Measuring Methods for Fine Ceramics Thermoelectric Materials, Part 1: Thermoelectric Power," or the measurement method disclosed in Japanese Patent Publication No. 6202580 (WO 2015 / 025586 A1) may be used. For the measurement of electrical resistivity ρ, the DC four-terminal method or the AC two-terminal method may be used. For the measurement of thermal conductivity κ, for example, a steady-state method may be used, in which a steady temperature gradient is applied to a sample and the temperature at each position on the sample is measured using a thermocouple or thermography. Alternatively, a method may be used in which the thermal diffusivity, specific heat capacity, and density are measured using a laser flash method, a differential scanning calorimeter, and an Archimedes method, respectively, and then calculated by multiplying the results by one order. The thermal conductivity κ can be calculated using the following formula, which is described in the section on calculation of thermal conductivity in Part 3: Thermal diffusivity, specific heat capacity, and thermal conductivity of JIS R 1650-3, Measurement methods for fine ceramic thermoelectric materials.

[0069] The thermoelectric power and figure of merit of an artificially graded multilayer laminate can be calculated as follows, without considering the magneto-thermoelectric effect. The Seebeck tensor, when the basis vectors are taken in the layer-parallel direction ( / / ) and the layer-normal direction (⊥), which are orthogonal to each other, is expressed as follows. At this point, the off-diagonal terms of the Seebeck tensor are 0. This material is cut into a rectangle of length 1 and thickness d so that the angle between it and the layered structure is θ, as shown in Figure 11A. When each side is oriented along the x-axis and z-axis, respectively, and a temperature difference ΔT is applied across the thickness d in the z-axis direction, the electromotive force generated between both ends of the element in the x-axis direction is ΔV. ｘ When the Seebeck tensor is rewritten along the x-axis and z-axis, which are the directions of input and output, the transverse thermoelectric power S ｘｚ is expressed by the following equation and takes a finite value. Here, if we calculate the electromotive force using equation (1), we get This becomes:

[0070] The dimensionless figure of merit due to the transverse thermoelectric effect in the artificially graded multilayer stack is defined as follows: Here, the electrical resistivity ρ ｘｘ and thermal conductivity κ ｚｚ For example, H. Zhou et al., “Geometrical Optimization and Transverse Thermoelectric Performances of Fe / Bi2Te 2.7 Se 0.3 It is recommended to estimate this in accordance with equations (3) to (9) described in “Artificially Tilted Multilayer Thermoelectric Devices” Micromachines 13, 233 (2022).

[0071] <Giant anisotropy of BiSb / BiSbTe laminate> The first thermoelectric material used in this study (BiSb:Bi ８８ Sb １２ ) and a second thermoelectric material (BiSbTe:Bi ０．２ Sb １．８ Te ３ ) is a polycrystalline body, and each material itself is isotropic. However, when the equivalent circuit is calculated as a laminate as shown in Figure 11A, the macroscopic thermoelectric properties of the laminate (Seebeck coefficient S, electrical resistivity ρ, thermal conductivity κ) become anisotropic in the layer-parallel direction ( / / ) and the layer-perpendicular direction (⊥) as follows:

[0072] where t is the thickness ratio of BiSbTe.ＢｉＳｂＴｅ / (t ＢｉＳｂ +t ＢｉＳｂＴｅ The thermoelectric properties of the BiSb and BiSbTe used here are significantly different from each other, as shown in Table 1. This results in a large anisotropy in the thermoelectric properties of the laminate. where σ, κ, S Ｓ , S Ｎ , Z Ｓ T and Z Ｎ T are the electrical conductivity, the thermal conductivity, the Seebeck coefficient, the Nernst coefficient, the figure of merit due to the Seebeck effect, and the figure of merit due to the Nernst effect, respectively.

[0073] In the hybrid lateral thermoelectric power generation element of the present invention, the thermal conductivity of the entire artificially inclined multilayer laminate can be calculated from equation (16), and the electrical conductivity σ, which is the reciprocal of the electrical resistivity ρ, can be calculated from equation (15). It is only necessary to consider the magnetic field and magnetization dependence of the thermal conductivity and electrical conductivity, and the equations themselves are the same. On the other hand, the lateral thermoelectric power S ｘｚ Regarding the Seebeck-Peltier coefficient, the contribution of the magnetic Seebeck-Peltier effect can be taken into account as the magnetic field and magnetization dependence in the formula as it is, but the contribution of the Nernst-Ettingshausen effect is not included, making it difficult to calculate analytically. Therefore, in calculating the figure of merit of a hybrid horizontal thermoelectric generator, S ｘｚ Only the temperature needs to be measured directly.

[0074] FIG. 11B shows the Bi ８８ Sb １２ / Bi ０．２ Sb １．８ Te ３FIG. 11C shows a perspective view of the configuration used to measure the magnetic field dependence of the thermoelectric power generation output of an artificially inclined multilayer stack. A heater is provided on the xy plane, which is the top of the artificially inclined multilayer stack, to generate a temperature gradient in the z-axis direction. The electromotive force generated in the x-axis direction of the artificially inclined multilayer stack is measured by a voltmeter V. An external magnetic field H is applied in the y-axis direction. FIG. 11C shows the dependence of the electromotive force V on the external magnetic field H in the correlation diagram between the temperature difference ΔT and the electromotive force V in the device shown in FIG. 11B. When the temperature difference ΔT is 1.4 K, 3.6 K, 5.7 K, and 7.9 K, and the external magnetic field H is 0 T, the electromotive force V is -0.45 mV, -1.1 mV, -1.8 mV, and -2.5 mV, respectively. When the external magnetic field H is 0.8 T, the electromotive force V is -0.5 mV, -1.2 mV, -1.95 mV, and -2.7 mV, respectively. When the external magnetic field H is -0.8 T, the electromotive force V is -0.4 mV, -1.0 mV, -1.65 mV, and -2.3 mV, respectively. In this way, the electromotive force V increases or decreases depending on the applied external magnetic field H. The dependence of the electromotive force V on the temperature difference ΔT is linear, and from the slope and the sample size, the transverse thermoelectric power S ｘｚ 11D is a diagram showing the temperature difference ΔT dependency in the correlation diagram between the external magnetic field H and the electromotive force V in the device of FIG. 11B.

[0075] Co ２ The results of measurements of the lateral thermoelectric power generation output of the MnGa-based artificially inclined multilayer laminate will be described.

[0076] Co ２ MnGa / Bi ０．２ Sb １．８ Te ３ and Co ２ MnGa / Bi ２ Te ３ The artificially graded multilayer laminate was prepared by SPS. ２ The MnGa disks and Bi--Sb--Te powder or Bi--Te powder were alternately stacked and bonded by SPS.

[0077] FIG. 12A shows Co ２This is a perspective view of the configuration when measuring the magnetic field dependence of thermoelectric power generation output of an MnGa-based artificially inclined multilayer laminate. A heater is provided on the top plane of the artificially inclined multilayer laminate, generating a temperature gradient in the thickness direction. A magnetic field H is applied in the direction of the minor axis of the sample, which is perpendicular to the temperature gradient ∇T, and the electromotive force V generated in the direction of the major axis of the sample, which is perpendicular to the temperature gradient ∇T and the magnetic field H, is Ｔ was measured.

[0078] FIG. 12B shows Co ２ MnGa / Bi ０．２ Sb １．８ Te ３ Transverse electromotive force V when the temperature difference ΔT of the artificially inclined multilayer laminate is changed Ｔ When the temperature difference ΔT is 1.8K, 3.7K, 5.6K, 7.6K, and 9.5K, and the external magnetic field H is 0.8T, the electromotive force V Ｔ are -0.68 mV, -1.37 mV, -2.08 mV, -2.80 mV, and -3.55 mV, respectively. When the external magnetic field H is -0.8 T, the electromotive force V Ｔ are −0.70 mV, −1.43 mV, −2.17 mV, −2.91 mV, and −3.68 mV, respectively. Ｔ increases or decreases. Ｔ The temperature difference ΔT dependence of is linear, and from its slope and the sample size, the transverse thermoelectric power S ｘｚ can be calculated.

[0079] FIG. 12C shows Co ２ MnGa / Bi ２ Te ３ Transverse electromotive force V when the temperature difference ΔT of the artificially inclined multilayer laminate is changed Ｔ When the temperature difference ΔT is 1.7K, 3.5K, 5.2K, 7.0K, and 8.8K, and the external magnetic field H is 0.8T, the electromotive force V Ｔ are 0.22 mV, 0.44 mV, 0.67 mV, 0.90 mV, and 1.13 mV, respectively. When the external magnetic field H is -0.8 T, the electromotive force V Ｔare 0.19 mV, 0.39 mV, 0.60 mV, 0.80 mV, and 1.00 mV, respectively. Ｔ increases or decreases. Ｔ The temperature difference ΔT dependence of is linear, and from its slope and the sample size, the transverse thermoelectric power S ｘｚ can be calculated.

[0080] FIG. 12D shows Co ２ MnGa / Bi ０．２ Sb １．８ Te ３ and Co ２ MnGa / Bi ２ Te ３ Lateral electric field E of artificially inclined multilayer laminate Ｔ The temperature gradient ∇T dependence of the electromotive force V generated in the major axis direction while sweeping the magnetic field H applied in the minor axis direction of the sample perpendicular to the temperature gradient ∇T is shown. Ｔ is measured and normalized by the length l of the sample to obtain the transverse electric field E Ｔ =V Ｔ The electromotive force V when the applied magnetic field H was +0.8T and -0.8T was calculated. Ｔ The horizontal electric field E calculated from Ｔ is proportional to the temperature gradient ∇T, and its slope, i.e., the transverse thermoelectric power S Ｔ changes depending on the applied magnetic field H. The transverse thermoelectric power S obtained from actual measurements Ｔ When the dimensionless figure of merit ZT is calculated from the electrical conductivity σ and thermal conductivity κ obtained by simulation, at an absolute temperature of 300 K, ２ MnGa / Bi ０．２ Sb １．８ Te ３ In the case of the artificially tilted multilayer stack, the magnetic field H was 0.088 and 0.095 at +0.8 T and −0.8 T, respectively. ２ MnGa / Bi ２ Te ３ In the case of the artificially tilted multilayer stack, the values ​​were 0.010 and 0.008 when the magnetic field H was +0.8 T and −0.8 T, respectively. ２The modulation of the dimensionless figure of merit ZT of lateral thermoelectric conversion in the MnGa-based artificially graded multilayer laminate by applying an external magnetic field H is the highest value (~7 × 10) of the dimensionless figure of merit ZT due to the anomalous Nernst effect in a single magnetic material reported so far. -４ As described above, by incorporating the anomalous Nernst effect into an artificially tilted multilayer stack and configuring it as a hybrid lateral thermoelectric temperature modulation element, it is possible to induce modulation of performance several times greater than the thermoelectric conversion performance of the anomalous Nernst effect alone.

[0081] In the examples shown in Figures 3 to 9, the temperature modulation phenomenon (cooling and heating phenomenon) of the hybrid lateral thermoelectric temperature modulation element of the present invention is directly measured, and the magnetic Peltier effect and the normal Ettingshausen effect are measured through observation of lock-in thermography image signals.

[0082] Furthermore, the temperature modulation phenomenon of the hybrid lateral thermoelectric temperature modulation element of the present invention has been proven in the case of the magnetic Peltier effect or the normal Echingshausen effect, but the electron transport phenomenon resulting from spontaneous magnetization can be proven by measuring the temperature modulation phenomenon (cooling / heating phenomenon) of the thermoelectric conversion element by measuring the anisotropic magnetic Peltier effect or the anomalous Echingshausen effect. The hybrid lateral thermoelectric temperature modulation due to the anomalous Echingshausen effect has been proven because the contribution of the anomalous Nernst effect, which is a reciprocal phenomenon, was confirmed in the example shown in Figure 12.

[0083] The hybrid lateral thermoelectric power generation element of the present invention alternately stacks layers of a first thermoelectric material exhibiting a magneto-thermoelectric effect and a second thermoelectric material, or layers of a first thermoelectric material exhibiting a magneto-thermoelectric effect and a second thermoelectric material having remanent magnetization and capable of driving the magneto-thermoelectric effect in the absence of a magnetic field. This allows for enhanced power generation through magneto-thermoelectric effects, such as the magnetic Seebeck effect and the normal Nernst effect, when an applied magnetic field is increased or when magnetized. Therefore, the element has the following industrial applicability: (i) Since the element does not have the complex three-dimensional junction structure of conventional Seebeck elements, it is effective in improving element durability, reducing costs, and increasing power generation density. (ii) Because of the scaling law that output power is proportional to the device area, high output power can be achieved simply by synthesizing or connecting large composite materials, unlike conventional Seebeck elements.

[0084] 10 Sample 20 Electromagnet 30 Constant current source 40 Infrared camera 50 Signal processing system

Claims

1. A hybrid lateral thermoelectric generating element comprising: a first electrode and a second electrode arranged opposite to each other; and a laminate sandwiched between the first and second electrodes and electrically connected to both the first and second electrodes, wherein the laminate has a structure in which layers of a first thermoelectric material and layers of a second thermoelectric material are alternately laminated, the first thermoelectric material and the second thermoelectric material have different values ​​for at least one of the Seebeck coefficient, the electrical conductivity, and the thermal conductivity, and at least one of the first and second thermoelectric materials exhibits a vertical magneto-thermoelectric effect or a horizontal magneto-thermoelectric effect, the lamination surfaces of the layers of the first thermoelectric material and the layers of the second thermoelectric material are inclined with respect to the direction in which the first electrode and the second electrode face each other, and a potential difference is generated between the first and second electrodes due to a temperature difference in the thermoelectric generating element in a direction perpendicular to the facing direction and a magnetic field applied in a direction that generates a magneto-thermoelectric effect.

2. A hybrid horizontal thermoelectric power generation element as described in claim 1, wherein the vertical magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more and is a magnetic Seebeck effect derived from an external magnetic field or an anisotropic magnetic Seebeck effect derived from spontaneous magnetization, and the horizontal magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more and is a normal Nernst effect derived from an external magnetic field or an anomalous Nernst effect derived from spontaneous magnetization.

3. The first layer of thermoelectric material is Bi １００－ｘ Sb ｘ layer (0≦x≦50), the second layer of thermoelectric material being Bi ２－ｙ Sb ｙ Te ３ The hybrid lateral thermoelectric power generation element according to claim 1 or 2, wherein the layer (0≦y≦2) is a layer.

4. The first layer of thermoelectric material is Co ２ MnGa layer, and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ The hybrid lateral thermoelectric power generation element according to claim 1 or 2, wherein the layer (0≦y≦2) is a layer.

5. A hybrid lateral thermoelectric power generation element as described in claim 1 or 2, wherein the external magnetic field is applied to the first layer of thermoelectric material and the second layer of thermoelectric material by a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet.

6. The hybrid lateral thermoelectric power generation element according to claim 1, wherein the second thermoelectric material layer is a permanent magnet layer having residual magnetization, capable of driving the magneto-thermoelectric effect in the first thermoelectric material layer in the absence of a magnetic field, and improving lateral thermoelectric conversion characteristics by the magneto-thermoelectric effect.

7. The first thermoelectric material layer is Bi １００－ｘ Sb ｘ layer (0≦x≦50), the second layer of thermoelectric material being SmCo ５ system magnet, Sm ２ Co １７ Magnets, Nd ２ Fe １４ The hybrid lateral thermoelectric power generation element according to claim 6 , wherein the permanent magnet material is one or more types selected from the group consisting of B-based magnets, alnico magnets, and ferrite magnets.

8. A hybrid horizontal thermoelectric power generation element according to claim 1, wherein the inclination angle θ of the lamination surface with respect to the direction is 10° or more and 80° or less.

9. The hybrid horizontal thermoelectric power generation element according to claim 1, wherein the thermoelectric power generation element has a figure of merit of 0.1 or more.

10. The hybrid horizontal thermoelectric power generation element according to claim 1, wherein the magnetic field applied in the direction in which the magneto-thermoelectric effect is generated is 0.1 T or more.

11. A power generation method using a horizontal thermoelectric conversion element, which generates a temperature difference in the horizontal thermoelectric conversion element and applies a magnetic field in a direction that generates a magneto-thermoelectric effect, thereby obtaining electric power from a direction perpendicular to the temperature difference generation direction and the magnetic field application direction of the horizontal thermoelectric conversion element, wherein the horizontal thermoelectric conversion element comprises: a first electrode and a second electrode arranged opposite to each other; and a laminate sandwiched between the first and second electrodes and electrically connected to both the first and second electrodes, the laminate having a structure in which layers of a first thermoelectric material and layers of a second thermoelectric material are alternately laminated, the first thermoelectric material and the second thermoelectric material having at least one different value of the Seebeck coefficient, the electrical conductivity, or the thermal conductivity, and at least one of the first or second thermoelectric material exhibits a vertical magneto-thermoelectric effect or a horizontal magneto-thermoelectric effect, a power generation method using a horizontal thermoelectric conversion element, the method comprising: a lamination surface of the first thermoelectric material layer and the second thermoelectric material layer being inclined with respect to a direction in which the first electrode and the second electrode face each other; generating a temperature difference in a direction perpendicular to the facing direction in the horizontal thermoelectric conversion element; and applying a magnetic field in a direction in which a magneto-thermoelectric effect is generated, thereby obtaining electric power via the first and second electrodes.

12. A power generation method using a horizontal thermoelectric conversion element as described in claim 11, wherein the vertical magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more and is a magnetic Seebeck effect derived from an external magnetic field or an anisotropic magnetic Seebeck effect derived from free magnetization, and the horizontal magneto-thermoelectric effect exhibits a thermoelectric power change of 5 μV / K or more and is a normal Nernst effect derived from an external magnetic field or an anomalous Nernst effect derived from spontaneous magnetization.

13. The first thermoelectric material layer is Bi １００－ｘ Sb ｘ layer (0≦x≦50), the second layer of thermoelectric material being Bi ２－ｙ Sb ｙ Te ３ The power generating method using the horizontal thermoelectric conversion element according to claim 11 or 12, wherein the horizontal thermoelectric conversion element has a thickness of 0≦y≦2.

14. The first layer of thermoelectric material is Co ２ MnGa layer, and the second thermoelectric material layer is Bi ２－ｙ Sb ｙ Te ３ The power generating method using the horizontal thermoelectric conversion element according to claim 11 or 12, wherein the horizontal thermoelectric conversion element has a thickness of 0≦y≦2.

15. A method of generating electricity using a horizontal thermoelectric conversion element as described in claim 11 or 12, wherein the external magnetic field is applied to the first layer of thermoelectric material and the second layer of thermoelectric material by a permanent magnet, an electromagnet, or a permanent magnet and an electromagnet.

16. A method of generating electricity using a horizontal thermoelectric conversion element as described in claim 11, wherein the second layer of thermoelectric material is a permanent magnet layer that enhances the output of the horizontal thermoelectric conversion element by the magneto-thermoelectric effect in a magnetized state compared to an unmagnetized state.

17. The first thermoelectric material layer is Bi １００－ｘ Sb ｘ layer (0≦x≦50), the second layer of thermoelectric material being SmCo ５ system magnet, Sm ２ Co １７ Magnets, Nd ２ Fe １４ 17. A power generating method using the horizontal thermoelectric conversion element according to claim 16, wherein the permanent magnet material is one or more types selected from the group consisting of B-based magnets, alnico magnets, and ferrite magnets.

18. A method for generating electricity using a horizontal thermoelectric conversion element according to claim 11, wherein the figure of merit of the horizontal thermoelectric conversion element is 0.1 or more.

19. A power generation method using a horizontal thermoelectric conversion element as described in claim 11, wherein the magnetic field applied in the direction in which the magneto-thermoelectric effect is generated is 0.1 T or more.

Images