Thermoelectric device

Abstract

The present invention efficiently concentrates heat flow on a thermoelectric material, thereby realizing a highly efficient thermoelectric conversion element. A thermoelectric device according to the present invention comprises: a thermoelectric material bulk (bulk thermoelectric permanent magnet) having remanent magnetization; a contact surface for contacting an object; a heat dissipation surface on the opposite side of the contact surface with the bulk thermoelectric permanent magnet therebetween; and electrode surfaces sandwiching the bulk thermoelectric permanent magnet in a direction different from the contact surface and the heat dissipation surface. The present invention is characterized in that the heat dissipation surface has a heat dissipation structure integrated with the bulk thermoelectric permanent magnet. The "bulk thermoelectric permanent magnet" is a composite material containing a magnetic substance and is a group of materials that exhibit high thermoelectric performance by developing various horizontal and / or vertical thermoelectric conversion phenomena. The remanent magnetization of the bulk thermoelectric permanent magnet superimposes a magneto-thermoelectric effect onto the thermoelectric material.

Description

thermoelectric device

[0001] The present invention relates to thermoelectric devices.

[0002] To improve the efficiency of energy use, the practical application of thermoelectric conversion devices that can generate electricity from waste heat or the environment is desired. A thermoelectric conversion device applies a temperature gradient to the thermoelectric material inside the device by contacting the contact surface of the device with a heat source, and the electromotive force generated in the thermoelectric material is output from the device's output terminals. Conventional thermoelectric conversion devices are classified into two types: vertical thermoelectric conversion devices, in which the temperature gradient applied to the thermoelectric material and the electromotive force generated in the thermoelectric material are in the same direction (parallel), and horizontal thermoelectric conversion devices, in which the temperature gradient applied to the thermoelectric material and the electromotive force generated in the thermoelectric material are perpendicular.

[0003] Patent Document 1 discloses a thermoelectric device configured by stacking gradient stacks, in which metal layers and thermoelectric material layers are stacked at an inclination, in the thickness direction (stacking direction) of the device. The temperature gradient is perpendicular to the stacking surface, and the interface between the metal layer and the thermoelectric material layer is inclined from the stacking direction. The thermoelectric device is configured by alternately stacking gradient stacks with opposite inclination directions and electrically connecting them in series.

[0004] Patent Document 2 discloses a thermoelectric conversion element in which a magnetic field is applied to a thermoelectric conversion material with a large Nernst effect to improve the Seebeck coefficient. When the temperature gradient is in the z direction, p-type and n-type thermoelectric conversion material layers are alternately stacked in the x direction, sandwiching a permanent magnet. The permanent magnet applies a magnetic field in the x direction to each thermoelectric conversion material layer. Each thermoelectric material layer has electrodes on both sides in the x direction, separated in the z direction, i.e., on the high-temperature side and the low-temperature side. The p-type high-temperature electrode is connected to the n-type high-temperature electrode, and the p-type low-temperature electrode is connected to the n-type low-temperature electrode, respectively, to form a series circuit. If the two electrodes are located at the same temperature, only the Nernst effect is observed. However, by arranging the two electrodes separated in the z direction, i.e., on the high-temperature side and the low-temperature side, the Seebeck coefficient can also be improved by the action of the magnetic field. The thermoelectric conversion element described in Patent Document 3 is similar.

[0005] The thermoelectric conversion device of Patent Document 1 is a horizontal type that generates an electromotive force in a direction perpendicular to the temperature gradient, and in the thermoelectric conversion devices of Patent Documents 2 and 3, the electromotive force generated when the electrodes are separated in the y direction is due to the Nernst effect, and therefore can be said to be a horizontal type thermoelectric conversion, but the electromotive force generated when the electrodes are separated in the z direction is due to the Seebeck effect, albeit enhanced by the magnetic field, and therefore is a vertical type thermoelectric conversion.

[0006] JP 2012-069626 A JP 2002-064228 A JP 2001-168403 A

[0007] Conventional vertical thermoelectric converters are constructed by connecting multiple π-type structures in which p-type and n-type thermoelectric materials are connected in series. In vertical thermoelectric converters, the temperature gradient and electromotive force of the thermoelectric material are in the same direction. This inevitably requires the presence of electrodes, substrates, etc. between the heat source and the thermoelectric material. Furthermore, if a heat dissipation mechanism is provided on the low-temperature side, it will be provided on the low-temperature side of the electrodes. As such, in vertical thermoelectric converters, electrodes, substrates, etc. are interposed as thermal resistance sources between the heat source and the thermoelectric material, and between the thermoelectric material and the heat dissipation mechanism. This means that the thermal energy of the heat source cannot be sufficiently supplied to the thermoelectric material. As a result, the temperature difference applied to the thermoelectric material is small, and the material's inherent thermoelectric conversion capacity is not fully utilized.

[0008] On the other hand, in a horizontal thermoelectric conversion device, the direction of the temperature gradient and the direction of the electromotive force are perpendicular to each other, so there is no need to provide electrodes between the heat source and the thermoelectric material, or between the thermoelectric material and the heat dissipation mechanism. However, even in the case of a horizontal thermoelectric device using a material with the anomalous Nernst effect or the spin Seebeck effect, which has high thermoelectric conversion performance, the thermoelectric material is configured as a thin film or multilayer film on a substrate, and the thermoelectric material has a lower thermal resistance and is thinner than the substrate, so there is a problem that when configured as a thermoelectric device, there is almost no effective temperature difference in the thermoelectric material.

[0009] As a result of the inventor's investigation of Patent Documents 1, 2 and 3, it was found that there existed the following new problems.

[0010] As mentioned above, the thermoelectric conversion element disclosed in Patent Document 1 is horizontal, but an electrical insulating layer is formed between the gradient stacks (see FIG. 2, reference numeral 23). Furthermore, the thermoelectric device 91 is sandwiched between heat sinks 92 and 93 (see FIG. 9). In this way, the heat sink and the electrical insulating layer are interposed in the temperature gradient from high to low, thereby reducing the temperature difference applied to the thermoelectric material. Patent Document 1 prevents voltage loss by stacking the gradient stacks, in which metal and thermoelectric material are obliquely stacked, in the direction of the temperature gradient. In an example using a BiSbTe-based thermoelectric material, a power generation capacity of 25 to 50 mW was observed, which is 5.5 to 11 mW / cm per unit area. 2 This becomes:

[0011] The same is true for the thermoelectric conversion elements of Patent Documents 2 and 3. In the stacked thermoelectric conversion materials, the p-type high-temperature electrode and the n-type high-temperature electrode, and the p-type low-temperature electrode and the n-type low-temperature electrode are connected to form a series circuit, and the wiring is formed on or passes through the top and bottom surfaces of the element (Figure 1). Therefore, the thermoelectric material cannot be directly contacted with the heat source on the high-temperature and low-temperature sides. Note that Figure 2B shows a configuration in which the length of the thermoelectric material is longer than the permanent magnet in the temperature gradient direction so that it is in direct contact with the cold or hot plate. However, by configuring only n-type or p-type, no metal wire is wired between the thermoelectric material and the cold or hot source. In other words, to avoid wiring or electrodes acting as a thermal resistance source along the temperature gradient path, a configuration in which p-type and n-type are alternately connected in series is not possible. Furthermore, when the thermoelectric conversion element is viewed from above in the direction of the temperature gradient, the area is shared between the thermoelectric conversion material and the permanent magnet, which reduces the amount of power generated per unit area. If a configuration is adopted in which the thermoelectric material is in direct contact with a cooling or heating plate as shown in Figure 2B, the heat flow can be relatively concentrated in the thermoelectric conversion material, but in other configurations, the heat flow flows to the permanent magnet, which reduces the thermal energy supplied to the thermoelectric material.

[0012] As discussed above, when the temperature gradient is viewed three-dimensionally, there are serial heat flow paths from the high temperature side to the low temperature side, and parallel heat flow paths when viewed in a plane from the direction of the temperature gradient. It was found that the serial heat flow paths have thermal resistance sources such as electrodes inserted in series, while the parallel heat flow paths have materials such as permanent magnets that do not directly contribute to thermoelectric conversion inserted in parallel, which poses the issue of reducing the heat flow through the thermoelectric material.

[0013] An object of the present invention is to efficiently concentrate heat flow in a thermoelectric material, thereby realizing a highly efficient thermoelectric conversion element.

[0014] According to a first embodiment of the present invention, the following is true: the first embodiment of the present invention is a thermoelectric device comprising a bulk thermoelectric material (bulk thermoelectric permanent magnet) having remanent magnetization, a contact surface for contacting an object, a heat dissipation surface facing the contact surface across the bulk, and electrode surfaces sandwiching the bulk in a direction different from the contact surface and the heat dissipation surface, the heat dissipation surface being a heat dissipation structure integrally formed with the bulk. Here, a "bulk thermoelectric permanent magnet" refers to a composite material containing a magnetic substance, a group of materials that exhibit high thermoelectric performance by exhibiting various horizontal and / or vertical thermoelectric conversion phenomena. The remanent magnetization of the bulk thermoelectric permanent magnet superimposes a magneto-thermoelectric effect on the thermoelectric material. In this specification, a "bulk thermoelectric permanent magnet" may be simply referred to as a "bulk thermoelectric material" or even simply as "bulk." The general term "bulk," which does not refer to a bulk thermoelectric permanent magnet, refers to a mass that is not numerically defined in size but is distinct from a thin film or powder.

[0015] According to the second embodiment, the following is true: In the thermoelectric device described in the first embodiment, it is preferable that the residual magnetization has a component perpendicular to the contact surface.

[0016] According to the third embodiment, the thermoelectric device is as follows: That is, in the thermoelectric device described in the first or second embodiment, the heat dissipation structure has a surface area that is at least twice the area of ​​the heat dissipation surface in a plan view.

[0017] According to a fourth embodiment, the thermoelectric device is as follows: That is, in the thermoelectric device according to any one of the first to third embodiments, the contact surface is a surface of the bulk.

[0018] According to the fifth embodiment, the thermoelectric device is as follows: That is, in the thermoelectric device described in any one of the first to fourth embodiments, the bulk is made up of a plurality of unit structures arranged in a direction different from the contact surface, the heat dissipation surface, and the electrode surface while being electrically insulated, and the plurality of unit structures are electrically connected to each other at the electrode surface.

[0019] The sixth embodiment is as follows: That is, in the thermoelectric device described in the fifth embodiment, the heat dissipation structure is the unevenness of the unit structure.

[0020] The seventh embodiment is as follows: That is, in the thermoelectric device described in the fifth or sixth embodiment, the unit structure has a structure in which at least two types of thermoelectric materials are stacked in a direction inclined with respect to a direction perpendicular to the electrode surface, and one of the at least two types of thermoelectric materials is a magnetic material.

[0021] The effects obtained by the embodiment are briefly described below.

[0022] That is, the heat flow can be efficiently concentrated in the thermoelectric material, thereby realizing a highly efficient thermoelectric conversion element.

[0023] FIG. 1 is an explanatory diagram schematically showing the basic configuration of a thermoelectric device of the present invention. FIG. 2 is an explanatory diagram schematically showing one embodiment of a thermoelectric device of the present invention. FIG. 3 is an explanatory diagram showing an example of a thermoelectric device of the present invention. FIG. 4 is an explanatory diagram of residual magnetization. FIG. 5 is a graph showing the measurement results of the power generation performance of a bulk thermoelectric module fabricated as Example 1. FIG. 6 is a graph showing the measurement results of the power generation performance of a bulk thermoelectric module fabricated as Example 2.

[0024] 1. Overview of the Embodiments First, an overview of the representative embodiments disclosed in the present application will be described. Reference numerals in parentheses in the drawings used in the overview of the representative embodiments merely illustrate components included in the concept of the components to which they are attached.

[0025] [1] Thermoelectric Device with a Heat Dissipation Structure Integrated with a Bulk Thermoelectric Material (Figure 1). A representative embodiment disclosed herein is a thermoelectric device comprising a bulk thermoelectric material (bulk thermoelectric permanent magnet) (1) with remanent magnetization, a contact surface (3) for contacting an object, a heat dissipation surface (2) facing the contact surface across the bulk, and electrode surfaces (4) sandwiching the bulk in a direction different from the contact surface and the heat dissipation surface. The heat dissipation surface is a heat dissipation structure integrally formed with the bulk. This allows heat flow to be efficiently concentrated in the thermoelectric material, thereby achieving a highly efficient thermoelectric conversion element. Furthermore, the remanent magnetization allows the contact surface to easily adhere to an object made of a magnetic material such as iron.

[0026] [2] Residual magnetization perpendicular to the contact surface In the thermoelectric device described in [1], the remanent magnetization has a component perpendicular to the contact surface. This can strengthen the adhesion of the contact surface to a magnetic object such as iron. Even if the remanent magnetization is completely parallel to the contact surface, the bonding force is reduced but not completely eliminated, and the thermoelectric device of [1] can be attached to a magnetic object such as iron.

[0027] [3] Heat Dissipation Structure: In the thermoelectric device according to [1] or [2], the heat dissipation structure has a surface area at least twice the area of ​​the heat dissipation surface in a plan view. When the heat dissipation structure comes into contact with a fluid such as air or water, it can increase the heat transfer coefficient and dissipate heat efficiently. This allows heat to be dissipated directly from the bulk thermoelectric material without passing through an electrode, a substrate, a heat sink, or the like.

[0028] [4] The contact surface is a part of the bulk thermoelectric material. In the thermoelectric device according to any one of [1] to [3], the contact surface is a surface of the bulk. This allows heat to be dissipated directly from the bulk thermoelectric material without the intervention of an electrode, a substrate, a heat sink, etc. When the bulk thermoelectric material is brought into close contact with a planar object, the contact surface of the bulk thermoelectric material is made flat, thereby reducing thermal resistance and enabling efficient heat dissipation.

[0029] [5] Stacking of Unit Structures (Fig. 2) In the thermoelectric device according to any one of [1] to [4], the bulk is composed of a plurality of unit structures (11, 12) arranged in a direction different from the contact surface, the heat dissipation surface, and the electrode surface while being electrically insulated, and the plurality of unit structures are electrically connected to each other at the electrode surface. This allows the plurality of thermoelectric materials to be electrically connected in series, thereby increasing the output voltage.

[0030] [6] A heat dissipation structure having an uneven surface is formed by stacking the unit structures. In the thermoelectric device described in [5], the heat dissipation structure is formed by the uneven surface of the unit structures. This makes it possible to easily form the heat dissipation structure.

[0031] [7] Inclined laminate (FIG. 3): The thermoelectric device according to [5] or [6], wherein the unit structure has a structure in which at least two types of thermoelectric materials are laminated in a direction inclined with respect to a direction perpendicular to the electrode surface, and one of the at least two types of thermoelectric materials is a magnetic material. This makes it possible to integrate a heat dissipation structure even in a high-performance thermoelectric device in which inclined laminates are laminated, and to attach the device to an object by magnetic force.

[0032] 2. Details of the embodiment The embodiment will be described in further detail.

[0033] [Embodiment 1] Figure 1 is an explanatory diagram schematically showing the basic configuration of a thermoelectric device of the present invention. The thermoelectric device of the present invention includes a bulk thermoelectric permanent magnet (bulk of thermoelectric material having remanent magnetization) 1, a contact surface 3 for contacting an object (-z surface of the bulk 1; a plane perpendicular to the -z direction when the height direction of the bulk 1 is assumed to be a rectangular parallelepiped) and a heat dissipation surface 2 (+z surface of the bulk 1) facing the contact surface 3 with the bulk thermoelectric permanent magnet 1 sandwiched between them, and electrode surfaces 4 sandwiching the bulk thermoelectric permanent magnet 1 in a direction different from the contact surface 3 and the heat dissipation surface 2 (+y / -y direction). The heat dissipation surface 2 is a heat dissipation structure formed integrally with the bulk thermoelectric permanent magnet 1.

[0034] This allows the heat flow to be efficiently concentrated in the thermoelectric material (bulk thermoelectric permanent magnet 1), thereby realizing a highly efficient thermoelectric conversion element. The contact surface 3 is brought into direct contact with a high-temperature object, and heat can be dissipated directly into the atmosphere or the like from the heat dissipation structure integrally formed with the heat dissipation surface 2. Since no components other than the thermoelectric material, such as electrodes, substrates, or heat sinks, are present in the path of the temperature gradient (heat flow) from the object to the atmosphere or the like, the entire temperature gradient is applied to the thermoelectric material.

[0035] Furthermore, the area of ​​the bulk thermoelectric permanent magnet 1 when viewed in plan from the z-axis direction coincides with the path of the heat flow from the contact surface 3 to the heat dissipation surface 2, so all of the heat flow contributes to thermoelectric conversion. As mentioned above, since the entire temperature gradient is applied to the thermoelectric material, the heat flow does not include a thermal resistance source in series, and there is no path in parallel that passes through anything other than the thermoelectric material, so this can be said to be an ideal structure in which all of the supplied thermal energy is supplied to the thermoelectric material and used for thermoelectric conversion.

[0036] Furthermore, it is preferable from the viewpoint of adhesion that the remanent magnetization of the bulk thermoelectric permanent magnet 1 has a component perpendicular to the contact surface 3. On the other hand, if the remanent magnetization has a component parallel to the contact surface 3, there is an advantage that the thermoelectric power due to the anomalous Nernst effect in the bulk thermoelectric permanent magnet can be superimposed. The remanent magnetization of the bulk thermoelectric permanent magnet superimposes the magneto-thermoelectric effect on the thermoelectric material, and the same remanent magnetization can be used to magnetically attach the contact surface 3 to an object made of a magnetic metal such as iron, making the installation of the thermoelectric device extremely easy.

[0037] Furthermore, the heat dissipation structure has a surface area that is at least twice the area of ​​the heat dissipation surface 2 in a plan view (the area when viewed from the +z side in the -z direction). This allows heat to be dissipated directly from the bulk thermoelectric permanent magnet 1 without going through an electrode, substrate, heat sink, or the like. Here, the surface area refers to the area in contact with the medium that is the target of heat dissipation. When the heat dissipation structure comes into contact with a fluid such as air or water, the heat transfer coefficient is increased, allowing for efficient heat dissipation.

[0038] In addition, it is more preferable that the contact surface 3 is one surface of the bulk thermoelectric permanent magnet 1 itself. This allows the bulk thermoelectric permanent magnet 1 to be heated directly without the need for an electrode, substrate, heat sink, or the like. When the bulk thermoelectric permanent magnet 1 is brought into close contact with a flat object, the contact surface 3 of the bulk thermoelectric permanent magnet 1 is made flat, thereby reducing the interfacial thermal resistance and enabling efficient heating. Here, "heating" does not mean active heating, but rather means transferring heat from the object to the bulk thermoelectric permanent magnet 1 via the contact surface 3.

[0039] Second Embodiment FIG. 2 is an explanatory diagram that schematically shows an example of the configuration of a thermoelectric device according to a second embodiment of the present invention.

[0040] As in the first embodiment, the thermoelectric device includes a bulk thermoelectric permanent magnet 1 (bulk of thermoelectric material having remanent magnetization), a contact surface 3 (-z surface of the bulk 1) for contacting an object, a heat dissipation surface 2 (+z surface of the bulk 1) facing the contact surface 3 with the bulk thermoelectric permanent magnet 1 in between, and electrode surfaces 4 sandwiching the bulk thermoelectric permanent magnet 1 in a direction (+y / -y direction) different from that of the contact surface 3 and the heat dissipation surface 2. The heat dissipation surface 2 is a heat dissipation structure integrally formed with the bulk thermoelectric permanent magnet 1. In the second embodiment, the bulk thermoelectric permanent magnet 1 includes a plurality of unit structures 11 and 12 arranged in a direction (+ / -x direction) different from that of the contact surface 3 (-z direction), the heat dissipation surface 2 (+z direction), and the electrode surfaces 4 (+ / -y directions) while being electrically insulated from each other, and the plurality of unit structures 11 and 12 are electrically connected to each other at the electrode surfaces 4. That is, the output voltage can be increased by electrically connecting a plurality of thermoelectric material unit structures 11 and 12 in series alternately. The output voltage can be maximized by designing the thermoelectric material so that a potential difference occurs in the opposite directions between the unit structures 11 and 12 relative to the temperature gradient in the z direction, for example, so that a potential difference occurs in the +y direction in the unit structure 11 and in the −y direction in the unit structure 12.

[0041] In the second embodiment, the heat dissipation structure can be configured with irregularities due to the differences in length between unit features 11 and 12. For example, as shown in Fig. 2 , by making the height (length in the z direction) of unit feature 11 longer than the height (length in the z direction) of unit features 12, and by bringing contact surface 3 into close contact with a planar object and arranging unit features 11 and 12 in the x direction, irregularities due to the difference in height between unit features 11 and 12 are formed on heat dissipation surface 2, and this functions as a heat dissipation structure.

[0042] As a result, the heat dissipation structure can be easily formed. Since the unit structures 11 and 12 are generally sintered bodies of thermoelectric material, they are not suitable for processing into complex shapes by cutting or stamping. However, as shown in this embodiment, the heat dissipation structure can be formed simply by configuring the unit structures 11 and 12 as rectangular parallelepipeds with only the heights changed and arranging them alternately.

[0043] Like in the first embodiment, the unit structures 11 and 12 are bulk thermoelectric permanent magnets 1 having remanent magnetization, and it is preferable that the remanent magnetization has a component perpendicular to the contact surface 3. As in the first embodiment, the remanent magnetization of the bulk thermoelectric permanent magnet 1 can be used to magnetically attach the contact surface 3 to a magnetic object such as iron, thereby greatly facilitating the installation of the thermoelectric device. Furthermore, multiple unit structures 11 and 12 can be installed in an alternating arrangement, allowing a thermoelectric device of any length to be constructed depending on the number of units. This is particularly convenient because it can be adjusted during the installation process and can be tailored to the object at the installation site. Furthermore, when multiple unit structures 11 and 12 are alternately arranged, they may be installed in close contact with each other via an isolation layer having a conductive region and an insulating region, thereby forming wiring between adjacent unit structures. In this case, if the remanent magnetization has a component perpendicular to the contact surface 3 as well as a component perpendicular to the stacking plane, the magnetic force can be used to attach the units to each other.

[0044] Third Embodiment FIG. 3 is an explanatory diagram that schematically shows an example of the configuration of a thermoelectric device according to a third embodiment of the present invention.

[0045] The thermoelectric device of the third embodiment is basically the same as the thermoelectric devices of the first and second embodiments, but is particularly characterized in that the unit structures 11 and 12 have a structure in which at least two types of thermoelectric materials are stacked in a direction inclined with respect to the direction perpendicular to the electrode surface 4, and one of the at least two types of thermoelectric materials is a magnetic material. This makes it possible to configure a high-performance thermoelectric device in which an inclined laminate is stacked, and which has an integrated heat dissipation structure and can be attached to an object by magnetic force. The additional configurations and effects described for the first and second embodiments are also applicable to the third embodiment.

[0046] FIG. 4 is an explanatory diagram of remanent magnetization. The remanent magnetization 10 of unit structures 11 and 12 in the y-z plane is shown as a vector, with the remanent magnetization 10 of unit structure 11 in the right quadrant and the remanent magnetization 10 of unit structure 12 in the left quadrant, centered on the origin. However, the origin is meaningless. Unit structure 11 is a laminate of two types of thermoelectric materials, including a magnetic thermoelectric material, stacked at a predetermined angle θ from the direction perpendicular to electrode surface 4 (y-axis direction (+y direction)). It has remanent magnetization 10 in the stacking direction, and this remanent magnetization 10 has a component perpendicular to contact surface 3. Meanwhile, unit structure 12 is also preferably a laminate of two types of thermoelectric materials, including a magnetic thermoelectric material, stacked at an angle opposite to the direction perpendicular to electrode surface 4 (y-axis direction) (-y to -θ). Unit structure 12 also has remanent magnetization 10 in its stacking direction, and this remanent magnetization 10 has a component perpendicular to contact surface 3. In order to make the unit structures 11 and 12 have a predetermined angle (θ) and an opposite angle (-y to -θ) from the direction perpendicular to the electrode surface 4 (y-axis direction), it is sufficient to manufacture the same inclined laminate and arrange them upside down (rotate 180°) around the z-axis.

[0047] As an example of the present invention, in order to evaluate the thermoelectric performance, a thermoelectric element was fabricated by stacking unit structures of the gradient laminate, and its characteristics were evaluated.

[0048] [Material Preparation] A samarium-cobalt (SmCo5) magnet (diameter 20 mm x thickness 0.5 mm, YX24 manufactured by Magfine Corporation) was demagnetized by heating at 800 °C for 40 minutes in a vacuum. The demagnetized SmCo5 magnet and the p-type thermoelectric material bismuth antimony telluride Bi were then used. 0.3 Sb 1.7 1.05 g of Te3 powder (3N, 200 μm mesh pass, manufactured by Toshima Manufacturing Co., Ltd.) was layered alternately in a carbon die and pressed with a punch to obtain a multilayer green compact. The standard conditions for this multilayer green compact were 10 to 13 laminations.

[0049] This multilayer compact was sintered in an atmosphere-controlled spark plasma sintering apparatus (SPS-212HFEG manufactured by Fuji Electric Industrial Co., Ltd.) to obtain a bulk thermoelectric material. The sintering conditions were a uniaxial pressure of 30 MPa, 450 °C, and 20 minutes in a vacuum atmosphere created by an oil rotary pump.

[0050] [Module Processing] The bulk thermoelectric material obtained above was cut using a diamond wire saw (DWS100 manufactured by Sakae Research Co., Ltd.). 0.3 Sb 1.7 The surface was cut at an angle of approximately 23° relative to the surface where the film was laminated with Te3 to create a surface for contact with the heat source, and then cut into a rectangular shape using this contact surface as a reference to obtain a rectangular parallelepiped-shaped tilted laminate.

[0051] The SmCo5 magnet was magnetized in the stacking direction of this gradient laminate by applying a magnetic field of 8 T to the stacking direction using a pulse magnetic field generator (manufactured by Toei Scientific Industry Co., Ltd.) As a result, the angle between the magnetization direction and the direction perpendicular to the contact surface with the object was approximately 23°, and the bulk thermoelectric material had a remanent magnetization vector component perpendicular to the contact surface.

[0052] Next, the gradient stack was cut into a thickness of approximately 1.5 mm using the diamond wire saw to form a unit structure. Similar to Figure 3, one unit structure 11 and the other unit structure 12 rotated 180° around the z-axis were aligned in the x-direction and stacked. As shown in Figure 4, the direction of remanent magnetization is reversed in the y-axis direction and aligned in the z-axis direction, resulting in a total remanent magnetization vector component in the height direction for the entire stack.

[0053] Paper towels (manufactured by AS ONE) were sandwiched between the unit structures as insulating layers, and a total of 13 unit structures were adhered together with instant adhesive (Aron Alpha Tough Power, manufactured by Toagosei Co., Ltd.) Furthermore, similar to the example shown in Figure 3, the 13 unit structures 11 and 12 were alternately connected to form an electrical series circuit by alternately wiring and connecting them to each other using indium electrodes 5 (manufactured by Nilaco Corporation) formed on the electrode surfaces 4 of the unit structures, thereby obtaining a bulk thermoelectric module.

[0054] In this example, the heights of the unit structures 11 and 12 are the same, but for various applications, unit structures of different heights can be fabricated and stacked alternately with their contact surfaces aligned, so that the thermoelectric material of the gradient stack itself forms a heat dissipation structure on the heat dissipation surface. To fabricate unit structures of different heights, various methods can be used, such as varying the height of the rectangular parallelepiped gradient stack and cutting out unit structures 11 and 12 from each, or, as described in Example 2 below, cutting out a tall unit structure 11 from the rectangular parallelepiped gradient stack, and then shortening the height of the rectangular parallelepiped gradient stack with a diamond wire saw to cut out a shorter unit structure 12.

[0055] [Measurement of power generation performance] Copper wires (manufactured by Nilaco Corporation) were connected to both ends of the electrical circuit of the fabricated bulk thermoelectric module, and the sides excluding the contact surface and heat dissipation surface were fixed with a heat dissipation adhesive (COM-G52 manufactured by Com Lab Co., Ltd.). With a temperature difference ΔT applied between the contact surface and the heat dissipation surface, four-terminal DC electrical measurements were carried out on the two copper wires. One of the copper wires was defined as a positive voltage (V+) and a negative current (I-), and the other was defined as a negative voltage (V-) and a positive current (I+), and the load current I load The voltage V (V) was measured by sweeping the load current I load and the voltage V. With five temperature differences ΔT of 135 K, 109 K, 87 K, 61 K, and 42 K applied, the load current I load The voltage V was measured by sweeping the current in the range from 0 A to 1 A to 1.2 A, and the power generation output P was calculated.

[0056] FIG. 5 is a graph showing the measurement results of the power generation performance of the bulk thermoelectric module fabricated as an example. The horizontal axis represents the swept load current I load The vertical axis shows voltage V on the left side (left axis) and power output P on the right side (right axis). The circle plots represent the measured voltage V (left axis), and the triangle plots represent power output P (right axis). For the maximum temperature difference ΔT = 135 K, the plot is solid black, while the plots for other temperature differences are white.

[0057] As a result of the measurements, the maximum power generation was 54 mW at the maximum temperature difference ΔT = 135 K. This value corresponds to 20 mW / cm per unit contact area. 2 This power generation per unit area is approximately twice that of the inclined stacked thermoelectric module shown in Patent Document 1.

[0058] As another example of the present invention, a thermoelectric element having a concave-convex structure formed by the heights of an inclined laminate was fabricated, mainly to evaluate the heat dissipation performance, and its characteristics were evaluated.

[0059] [Material Preparation] This is the same as in Example 1, so a repeated explanation will be omitted.

[0060] [Module Processing] The bulk thermoelectric material obtained above was cut out using the same diamond wire saw (DWS100 manufactured by Sakae Research Co., Ltd.) as in Example 1. 0.3 Sb 1.7 The material was cut at an angle of approximately 27° relative to the laminated surface with Te3 to create a contact surface with the heat source, and then cut into a rectangular shape using this contact surface as a reference, resulting in a rectangular parallelepiped tilted laminate with a height of 8.4 mm and a length of 11.0 mm.

[0061] Next, the gradient stack was cut into a thin piece with a width of about 1.5 mm using the diamond wire saw to form a unit structure of the convex portion, and this unit structure of the convex portion was cut into a piece with a height of 6.3 mm using the diamond wire saw to form a unit structure of the concave portion.

[0062] Paper towels (manufactured by AS ONE) were sandwiched between the unit structures as an insulating layer, and a total of eight unit structures (four recessed and four protruding) were adhered alternately using instant adhesive (Aron Alpha Tough Power, manufactured by Toagosei Co., Ltd.). By aligning the contact surfaces, the thermoelectric material of the gradient laminate itself formed an uneven heat dissipation structure on the heat dissipation surface, measuring 2.1 mm in height, 1.5 mm in width, and spaced 1.5 mm apart. This heat dissipation structure has a surface area 2.4 times larger than when viewed in plan.

[0063] Furthermore, similar to the example shown in Fig. 3, four convex unit structures (corresponding to unit structure 11 in Fig. 3) and four concave unit structures (corresponding to unit structure 12 in Fig. 3) were alternately connected to form an electrical series circuit by alternately wiring and connecting them to each other using electrodes 5 made of indium (manufactured by Nilaco Corporation) formed on the electrode surfaces 4 of the unit structures, thereby obtaining a bulk thermoelectric module. Note that, similar to the bulk thermoelectric module of Example 1, one unit structure 11 and the other unit structure 12 rotated 180° about the z-axis were stacked in the x direction.

[0064] This inclined laminate was magnetized in the lamination direction, which is the easy axis of magnetization of the SmCo5 magnet, by applying a magnetic field of 8 T to the height direction using a pulse magnetic field generator (manufactured by Toei Scientific Industrial Co., Ltd.). As a result, the angle between the magnetization direction and the direction perpendicular to the contact surface with the object was approximately 27°, and the bulk thermoelectric material had a remanent magnetization vector component perpendicular to the contact surface. As shown in Figure 4, the direction of remanent magnetization reverses in the y-axis direction and aligns in the z-axis direction, so that the laminate as a whole generates a remanent magnetization vector component in the height direction.

[0065] [Measurement of power generation performance] Copper wires (manufactured by Nilaco Corporation) were connected to both ends of the electrical circuit of the fabricated bulk thermoelectric module and fixed with indium. The bulk thermoelectric module was magnetically attached to a stainless steel member via a highly thermally conductive heat dissipation sheet, MANION (manufactured by Sekisui Polymatec), and the stainless steel member was heated on a hot plate. The load current I load The voltage V was measured by sweeping the voltage, and the power generation output P was calculated.

[0066] FIG. 6 is a graph showing the measurement results of the power generation performance of the bulk thermoelectric module fabricated as Example 2. The horizontal axis represents the swept load current I loadThe vertical axis shows voltage V on the left side (left axis) and power output P on the right side (right axis). The circle plots represent the measured voltage V (left axis), and the triangle plots represent power output P (right axis). Plots with a fan are filled in black, and plots without a fan are open. As a result of the measurements, air-cooled heat dissipation type thermoelectric power generation of up to 1 mW was demonstrated with a fan.

[0067] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the invention is not limited thereto and can be modified in various ways without departing from the spirit of the invention.

[0068] REFERENCE SIGNS LIST 1 bulk thermoelectric permanent magnet 2 heat dissipation surface 3 contact surface 4 electrode surface 5 electrode 10 residual magnetic field 11, 12 unit structure of thermoelectric material

Claims

1. A thermoelectric device comprising: a bulk of thermoelectric material having residual magnetization; a contact surface for contacting an object; a heat dissipation surface facing the contact surface across the bulk; and electrode surfaces sandwiching the bulk in a direction different from that of the contact surface and the heat dissipation surface, wherein the heat dissipation surface is a heat dissipation structure formed integrally with the bulk.

2. A thermoelectric device according to claim 1, wherein the residual magnetization has a component perpendicular to the contact surface.

3. A thermoelectric device according to claim 1 or 2, wherein the heat dissipation structure has a surface area that is at least twice the area of ​​the heat dissipation surface in a plan view.

4. A thermoelectric device according to any one of claims 1 to 3, wherein the contact surface is a surface of the bulk.

5. A thermoelectric device according to any one of claims 1 to 4, wherein the bulk is composed of a plurality of unit structures arranged in a manner that is electrically insulated from the contact surface, the heat dissipation surface and the electrode surface in different directions, and the plurality of unit structures are electrically connected to each other at the electrode surface.

6. A thermoelectric device according to claim 5, wherein the heat dissipation structure is an uneven surface of the unit structure.

7. A thermoelectric device according to claim 5 or 6, wherein the unit structure has a structure in which at least two types of thermoelectric materials are laminated in a direction inclined with respect to a direction perpendicular to the electrode surface, and one of the at least two types of thermoelectric materials is a magnetic material.

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