Thermoelectric element

Abstract

Provided is a thermoelectric element which has high thermoelectric conversion efficiency, can obtain a high ZT value, and can be surface-mounted and reduced in size. A thermoelectric element according to the present invention is provided with: a first thermoelectric material part (1) having one end part (1a) and the other end part (1b); a second thermoelectric material part (2) that is directly bonded to the first thermoelectric material part or is bonded to the first thermoelectric material part via a conductor (2a); and a pair of electrodes (3) connected to the first thermoelectric material part, the first thermoelectric material part having an absolute value of a Seebeck coefficient higher than that of the second thermoelectric material part and a resistivity higher than that of the second thermoelectric material part, and an assembly (4) of the first thermoelectric material part and the second thermoelectric material part having end surfaces on one end side and the other end side. The pair of electrodes is in contact with the first thermoelectric material portion without being in contact with the second thermoelectric material portion, and is formed on an end surface on the one end portion side and an end surface on the other end portion side of the joined body.

Description

Technical Field

[0001] The present invention relates to a thermoelectric element capable of achieving high thermoelectric conversion efficiency. Background Art

[0002] Conventionally, a so-called segmented thermoelectric element is known, which is formed by joining a plurality of materials having different compositions.

[0003] For example, Patent Document 1 describes a thermoelectric element having a first electrode, a second electrode, a P-type semiconductor thin film made of a thermoelectric material, and an N-type semiconductor thin film made of a thermoelectric material formed on a substrate, wherein the P-type semiconductor thin film is connected to the first electrode, and the N-type semiconductor thin film is connected to the second electrode. In the above-mentioned thermoelectric element, the P-type semiconductor thin film and the N-type semiconductor thin film are overlapped and bonded, and the bonding surface exists on substantially the entire surface of the substrate.

[0004] Furthermore, Patent Documents 2 and 3 also describe thermoelectric elements in which a first thermoelectric material and a second thermoelectric material, each made of a different material, are joined together, one of a pair of electrodes is connected to the first thermoelectric material, and the other of the pair of electrodes is connected to the second thermoelectric material. Specifically, in these conventional thermoelectric elements, electrodes are provided on each of the joined first and second thermoelectric materials, and the first and second thermoelectric materials are electrically connected in series.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-303471

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2009-32960

[0007] Patent Document 3: Japanese Patent Application Publication No. 2018-152464

[0008] The above-mentioned conventional technologies still have the following problems.

[0009] That is, as the performance of thermoelectric elements required for practical use of thermoelectric power generation, a ZT value (dimensionless performance index ZT (= S 2 T / ρκ): where S, T, ρ, and κ are the Seebeck coefficient (thermoelectromotive force; the electromotive force generated per 1K temperature difference), absolute temperature, resistivity, and thermal conductivity κ, respectively. Furthermore, in order to simultaneously increase the voltage output and power generation (= voltage × current) obtained through thermoelectric conversion, the following high performance is required: P-type and N-type characteristics, an absolute value of the Seebeck coefficient of 100μV / K or higher, and an output factor (power factor, Power factor PW = S 2 / ρ)) exceeds 1×10 -3 W / mK 2 .

[0010] To date, research and development aimed at increasing the ZT value has been conducted using a single material in various material systems. However, the only practical materials with a ZT value of approximately 1 at room temperature are Bi-Te materials. Bi-Te materials have low heat resistance, limiting their use below approximately 200°C. Furthermore, their low thermoelectric conversion efficiency makes their practical application difficult.

[0011] On the other hand, using conventional segmented thermoelectric elements allows for placement of thermoelectric materials with a heat resistance of 200°C or higher on the high-temperature side. However, the ZT values of the individual thermoelectric materials that make up the segmented thermoelectric elements are low, and the multiple thermoelectric elements form a series circuit both electrically and thermally. This reduces the ZT value of the element as a whole, making it difficult to achieve an increase in thermoelectric conversion efficiency. Furthermore, thermoelectric elements that can be surface mounted and miniaturized are required. Summary of the Invention

[0012] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a thermoelectric element that has high thermoelectric conversion efficiency, can obtain a high ZT value, and can be surface mounted and miniaturized.

[0013] To solve the aforementioned problems, the present invention employs the following structure. Specifically, the thermoelectric element according to the first invention is characterized by comprising: a first thermoelectric material portion having one end and another end; a second thermoelectric material portion directly bonded to the first thermoelectric material portion or bonded via a conductor; and a pair of electrodes connected to the first thermoelectric material portion, wherein the first thermoelectric material portion has a higher absolute value of the Seebeck coefficient and a higher resistivity than the second thermoelectric material portion; a junction of the first thermoelectric material portion and the second thermoelectric material portion having end surfaces on the one end and the other end; and the pair of electrodes contacting the first thermoelectric material portion while not in contact with the second thermoelectric material portion and formed on the end surfaces on the one end and the other end of the junction.

[0014] In this thermoelectric element, a junction of a first thermoelectric material portion and a second thermoelectric material portion has end surfaces on one end side and the other end side, and a pair of electrodes are in contact with the first thermoelectric material portion without being in contact with the second thermoelectric material portion, and are formed on the end surfaces on one end side and the other end side of the junction, thereby enabling surface mounting and miniaturization, and enabling a component with higher thermoelectric conversion efficiency and ZT value.

[0015] Specifically, the thermoelectric element of the present invention is entirely chip-type, with electrodes formed on both end surfaces. This facilitates surface mounting using solder, etc., and its compact shape provides a high degree of flexibility in placement. For example, while conventional π-type thermoelectric modules have multiple thermoelectric elements with electrodes electrically connected in series on a substrate, the chip-type thermoelectric element of the present invention can be installed without changing the thermoelectric module's structure.

[0016] In addition, in this thermoelectric element, the first thermoelectric material portion has an absolute value of a Seebeck coefficient higher than that of the second thermoelectric material portion and a resistivity higher than that of the second thermoelectric material portion, and a pair of electrodes are connected to one end side and the other end side of the first thermoelectric material portion separately from each other, so that the first thermoelectric material portion and the second thermoelectric material portion constitute an electrothermal parallel circuit. If a temperature difference is generated between the one end side and the other end side (heat flow is generated), an electromotive force is generated with high thermoelectric conversion efficiency. That is, in the first thermoelectric material portion connected to the pair of electrodes and having a high Seebeck coefficient (absolute value) and a high resistance value, an electromotive voltage path that follows the Seebeck effect is mainly formed, and in the second thermoelectric material portion having a low resistance value that is bonded to and in contact with the first thermoelectric material portion, a current path is formed. The current value flowing in the second thermoelectric material portion preferably follows Ohm's law. In this way, by forming a parallel circuit of the electromotive voltage path and the current path, a current path is formed to become a current channel separated from the electromotive voltage path, thereby increasing the conductivity while maintaining the high Seebeck coefficient (absolute value) of the first thermoelectric material part, and obtaining a higher thermoelectric conversion efficiency and ZT value.

[0017] In addition, the second thermoelectric material portion is not directly bonded to the pair of electrodes, but is electrically contacted via the first thermoelectric material portion. The present invention employs a structure of a thermoelectric element formed by bonding multiple materials of different compositions, but is characterized in that a pair of electrodes (two electrodes) are connected to the first thermoelectric material portion. (Segmented thermoelectric elements also employ a structure formed by bonding multiple materials of different compositions, but a pair of electrodes are connected to different thermoelectric materials, using a different electrode connection method than the present invention.)

[0018] The thermoelectric element according to the second invention is characterized in that, in the first invention, a pair of insulating material portions are provided on the end surface on the one end side and the end surface on the other end side of the junction body so as to cover at least the second thermoelectric material portion.

[0019] That is, in this thermoelectric element, a pair of insulating material parts are provided on the end face on one end side and the end face on the other end side of the junction body, which are formed to at least cover the second thermoelectric material part, so that the insulating material part can prevent a pair of electrodes from contacting the second thermoelectric material part on the end face of the junction body.

[0020] The thermoelectric element according to the third invention is characterized in that, in the first or second invention, the first thermoelectric material portion is bonded to the upper and lower surfaces of the second thermoelectric material portion, and the pair of electrodes are connected to the upper and lower surfaces of the first thermoelectric material portion, respectively.

[0021] That is, in this thermoelectric element, the first thermoelectric material part is stacked on the upper and lower surfaces of the second thermoelectric material part, and a pair of electrodes are connected to the upper and lower first thermoelectric material parts respectively, thereby forming electromotive voltage paths on the upper and lower surfaces, respectively, and achieving higher thermoelectric conversion efficiency.

[0022] The thermoelectric element according to the fourth invention is characterized in that, in the third invention, the first thermoelectric material portion is further bonded to both side surfaces of the second thermoelectric material portion, and the pair of electrodes are further connected to the first thermoelectric material portion on both side surfaces.

[0023] That is, in this thermoelectric element, the first thermoelectric material part is also joined to the two side surfaces of the second thermoelectric material part, and a pair of electrodes are also connected to the first thermoelectric material parts on the two side surfaces, respectively. Therefore, an electromotive voltage path is formed not only on the upper and lower surfaces, but also on the two side surfaces, thereby achieving a higher thermoelectric conversion efficiency.

[0024] The thermoelectric element according to the fifth invention is characterized in that, in the first invention, the first thermoelectric material portion is further bonded to both end surfaces of the second thermoelectric material portion, and the pair of electrodes are formed on the first thermoelectric material portion on the both end surfaces.

[0025] Specifically, in this thermoelectric element, the first thermoelectric material portion is further bonded to the respective end surfaces of the second thermoelectric material portion, and a pair of electrodes are formed on the first thermoelectric material portion at these end surfaces. Thus, an electromotive voltage path is formed from the pair of electrodes through the first thermoelectric material portion at the end surfaces, at least on the outer peripheral surface of the first thermoelectric material portion, thereby achieving higher thermoelectric conversion efficiency. Furthermore, there is no need to form insulating material portions on the end surfaces of the second thermoelectric material portion, which can reduce the number of manufacturing steps.

[0026] The thermoelectric element according to the sixth invention is characterized in that, in the first or second invention, the first thermoelectric material portion has an absolute value of a Seebeck coefficient 50 μV / K or greater and a resistivity 10 times or greater than that of the second thermoelectric material portion.

[0027] That is, in this thermoelectric element, the absolute value of the Seebeck coefficient of the first thermoelectric material part is more than 50 μV / K larger than that of the second thermoelectric material part, and the resistivity is more than 10 times larger. Therefore, by forming an electromotive voltage path with a sufficiently high Seebeck effect and a current path with sufficiently high conductivity, a higher thermoelectric conversion efficiency and ZT value can be obtained.

[0028] The thermoelectric element according to the seventh invention is characterized in that, in the first invention or the second invention, the first thermoelectric material portion and the second thermoelectric material portion are both made of A 2+δ M (wherein A is at least one of Ag and Cu, and M is at least one of S, Se, and Te) is formed.

[0029] In addition, by using the first thermoelectric material portion A 2+δ M and A of the second thermoelectric material portion 2+δ A larger ZT value can be obtained by designing the material composition so that the absolute value of the Seebeck coefficient is larger than that of the material by 50 μV / K or more and the resistivity is increased by more than 10 times.

[0030] The thermoelectric element according to the eighth invention is characterized in that, in the seventh invention, the first thermoelectric material portion is formed of Ag—S, and the second thermoelectric material portion is formed of Ag—Se or Ag—S—Se.

[0031] That is, in this thermoelectric element, for example, by forming the first thermoelectric material portion from Ag 2 S and the second thermoelectric material portion from Ag 2 Se, a ZT value of 1 or more can be obtained at least at room temperature.

[0032] The thermoelectric element according to the ninth invention is characterized in that, in the seventh invention, the first thermoelectric material portion is formed of Cu—S, and the second thermoelectric material portion is formed of Cu—Se.

[0033] That is, in this thermoelectric element, for example, by forming the first thermoelectric material portion from Cu 2 S and the second thermoelectric material portion from Cu 2 Se, a ZT value of 1 or more can be obtained at least at room temperature.

[0034] The thermoelectric element according to the tenth invention is characterized in that, in any one of the first to sixth inventions, the first thermoelectric material portion is formed of a material containing at least Bi and Te.

[0035] That is, in this thermoelectric element, the first thermoelectric material portion is a material containing at least Bi and Te, such as Bi-Te or Bi-Sb-Te, and the first thermoelectric material portion is formed of Bi2Te3, and the Cu 0.55 Ni 0.45 (Constantan) forming the second thermoelectric material portion can achieve a power factor at least twice that of Bi2Te3 alone. In addition, if the first thermoelectric material portion has a higher absolute value of the Seebeck coefficient and a higher resistivity than the second thermoelectric material portion, the thermoelectric properties will be improved compared to the case of the first thermoelectric material portion alone, regardless of the composition of the second thermoelectric material portion.

[0036] According to the present invention, the following effects are achieved.

[0037] That is, according to the thermoelectric element involved in the present invention, the junction of the first thermoelectric material part and the second thermoelectric material part has end surfaces on one end side and the other end side, and a pair of electrodes are in contact with the first thermoelectric material part without contacting the second thermoelectric material part, and are formed on the end surface on one end side and the end surface on the other end side of the junction, thereby enabling surface mounting and miniaturization, and enabling an element with higher thermoelectric conversion efficiency and ZT value.

[0038] Therefore, the thermoelectric element of the present invention has a high degree of installation freedom and can be easily mounted in a circuit or module, and can achieve high thermoelectric conversion efficiency and ZT value, thereby realizing the practical application of environmental power generation that efficiently outputs electricity using temperature differences. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 1 is a cross-sectional view showing a thermoelectric element according to a first embodiment of the present invention.

[0040] Figure 2 This is a conceptual diagram for explaining the principle of the thermoelectric element in the first embodiment.

[0041] Figure 3 This is a cross-sectional view perpendicular to the axial direction (the direction from one end to the other end) of the thermoelectric element according to the second embodiment of the present invention.

[0042] Figure 4 It is a perspective view showing a thermoelectric element in the second embodiment.

[0043] Figure 5 This is a cross-sectional view showing a thermoelectric element according to a third embodiment of the present invention, taken along the axial direction (a direction from one end toward the other end).

[0044] Figure 6 This is a cross-sectional view showing an embodiment of the thermoelectric element of the present invention, which was produced to verify the principle of the thermoelectric element of the present invention.

[0045] Figure 7 This is a graph showing the results of evaluating the power generation characteristics of the thermoelectric element in Examples of the thermoelectric element according to the present invention. DETAILED DESCRIPTION

[0046] Below, reference Figure 1 and Figure 2 In the drawings used in the following description, the scales of the components are appropriately changed as needed to make the size of each component recognizable or easy to recognize.

[0047] like Figure 1 and Figure 2 As shown, the thermoelectric element 10 of this embodiment includes: a first thermoelectric material part 1 having one end 1a and the other end 1b; a second thermoelectric material part 2 directly connected to the first thermoelectric material part 1 or connected via a conductor 2a; and a pair of electrodes 3 connected to the first thermoelectric material part 1.

[0048] Furthermore, when the first thermoelectric material portion 1 and the second thermoelectric material portion 2 are bonded together via the conductor 2a, the conductor 2a also functions as an intermediate layer. The conductor 2a is, for example, a conductive bonding material such as solder or In.

[0049] The first thermoelectric material portion 1 has a higher Seebeck coefficient and a higher resistivity than the second thermoelectric material portion 2 .

[0050] Furthermore, the junction body 4 of the first thermoelectric material portion 1 and the second thermoelectric material portion 2 is formed into a chip having end surfaces on one end side and the other end side. That is, the junction body 4 is in the shape of a plate or a rectangular parallelepiped, with one end 1a and the other end 1b of the first thermoelectric material portion 1 arranged on its two end surfaces.

[0051] The thickness of the first thermoelectric material portion 1 (i.e., the thickness in the stacking direction of the first thermoelectric material portion 1 and the second thermoelectric material portion 2) is preferably 100 nm to 10 mm, and may be 1 μm to 3 mm. The thickness of the second thermoelectric material portion 2 is preferably 0.1 mm to 10 mm, and may be 0.5 mm to 3 mm.

[0052] The pair of electrodes 3 are in contact with the first thermoelectric material portion 1 while not in contact with the second thermoelectric material portion 2 .

[0053] That is, the thermoelectric element 10 of this embodiment includes a pair of insulating material portions 5 formed to cover at least the second thermoelectric material portion 2 on the end surface on the one end 1 a side and the end surface on the other end 1 b side of the junction body 4 .

[0054] Furthermore, a pair of electrodes 3 is formed on an end surface on the one end portion 1 a side and an end surface on the other end portion 1 b side of the bonded body 4 .

[0055] That is, the pair of electrodes 3 are connected separately from each other to the one end portion 1 a and the other end portion 1 b of the first thermoelectric material portion 1 .

[0056] Furthermore, the pair of electrodes 3 are not in contact with the second thermoelectric material portion 2 but are arranged away from the second thermoelectric material portion 2 .

[0057] Furthermore, the end surface of the joint body 4 on the one end portion 1a side and the end surface on the other end portion 1b side are arranged to face each other.

[0058] The first thermoelectric material portion 1 is bonded to the upper and lower surfaces of the second thermoelectric material portion 2 .

[0059] Furthermore, a pair of electrodes 3 are connected to the first thermoelectric material portions 1 on the upper and lower surfaces, respectively.

[0060] That is, the pair of electrodes 3 are connected to the surface of the first thermoelectric material portion 1 and are formed on both end surfaces of the junction body 4, covering the pair of insulating material portions 5. Furthermore, the pair of electrodes 3 extend beyond the pair of insulating material portions 5 to reach the upper and lower surfaces of the junction body 4 (the first thermoelectric material portion 1).

[0061] In this manner, the pair of electrodes 3 are in contact with and connected only to the first thermoelectric material portion 1 , and are not in contact with the second thermoelectric material portion 2 due to the pair of insulating material portions 5 .

[0062] The first thermoelectric material portion 1 preferably has an absolute value of a Seebeck coefficient that is 50 μV / K or greater and a resistivity that is 10 times or greater than that of the second thermoelectric material portion 2 .

[0063] In addition, the resistivity of the first thermoelectric material portion 1 at room temperature is preferably 10 -5 Ωcm or less.

[0064] For example, the first thermoelectric material portion 1 and the second thermoelectric material portion 2 are both made of A 2+δ M (wherein A is at least one of Ag and Cu, and M is at least one of S, Se, and Te) is formed.

[0065] Furthermore, the range of δ is preferably -0.5≤δ≤+0.5, and the range of δ is more preferably -0.05 to +0.02.

[0066] Furthermore, in the present invention, the thermoelectric material is a material having an absolute value of a Seebeck coefficient of 0.1 μV / K or more. That is, the absolute value of the Seebeck coefficient of the second thermoelectric material portion 2 is 0.1 μV / K or more.

[0067] Furthermore, the absolute value of the Seebeck coefficient of the first thermoelectric material portion 1 is preferably 10 mV / K or less.

[0068] Furthermore, when the resistivity of the first thermoelectric material portion 1 at room temperature is 10 mΩcm or less, the first thermoelectric material portion 1 is preferably thinner than the second thermoelectric material portion 2 .

[0069] Furthermore, when the resistivity of the first thermoelectric material portion 1 at room temperature is less than 10 mΩcm, and when the resistivity of the second thermoelectric material portion 2 at room temperature is less than 1 mΩcm and the thermal conductivity is greater than 10 W / mK, the thickness of the first thermoelectric material portion 1 is preferably thicker than the thickness of the second thermoelectric material portion 2.

[0070] As A 2+δ In the case of an N-type thermoelectric element, for example, the first thermoelectric material portion 1 may be formed of Ag-S and the second thermoelectric material portion 2 may be formed of Ag-Se or Ag-S-Se. In the case of a P-type thermoelectric element, for example, the first thermoelectric material portion 1 may be formed of Cu-S and the second thermoelectric material portion 2 may be formed of Cu-Se.

[0071] For example, the first thermoelectric material portion 1 can be formed of Ag2S, and the second thermoelectric material portion 2 can be formed of Ag2Se. In addition, Ag2S has an absolute value of a Seebeck coefficient that is 50 μV / K or greater and a resistivity that is 10 times greater than that of Ag2Se.

[0072] Furthermore, the first thermoelectric material portion 1 may be formed of Cu 2 S, and the second thermoelectric material portion 2 may be formed of Cu 2 Se. Cu 2 S has an absolute value of a Seebeck coefficient greater than that of Cu 2 Se by 50 μV / K or more, and a resistivity greater than 10 times.

[0073] Furthermore, the first thermoelectric material portion 1 may be formed of a material containing at least Bi and Te, such as Bi—Te or Bi—Sb—Te.

[0074] For example, the first thermoelectric material portion 1 may be made of Bi2Te3 or (Bi 0.7 Sb 0.3 )Te3, and the second thermoelectric material portion 2 can be made of Cu 0.55 Ni 0.45 (Constantan) forms. Bi2Te3 and (Bi 0.7 Sb 0.3 )Te3 and Cu 0.55 Ni 0.45 In comparison, the absolute value of the Seebeck coefficient is greater than 50 μV / K, and the resistivity is greater than 10 times.

[0075] Alternatively, the first thermoelectric material portion 1 may be formed by adding impurities such as Ru and Cu to the material containing Bi and Te.

[0076] Thus, the first thermoelectric material portion 1 is formed of a high-resistance semiconductor material or insulating material such as a low-thermal-conductivity chalcogenide material, and the second thermoelectric material portion 2 is formed of a low-resistance conductive material such as a semiconductor material or an alloy.

[0077] Furthermore, the thermal conductivity of the first thermoelectric material portion 1 and the second thermoelectric material portion 2 is preferably low to increase the temperature difference applied to the thermoelectric element 10. In particular, to obtain a high thermoelectromotive force through the Seebeck effect, the thermal conductivity of the first thermoelectric material portion 1 is preferably 10 W / mK or less.

[0078] Furthermore, the thermal conductivity of the first thermoelectric material portion is preferably 0.02 W / mK or higher.

[0079] The first thermoelectric material portion 1 may be a thin film, but the second thermoelectric material portion 2 is preferably a conductive block or the like that is thicker than the first thermoelectric material portion 1 .

[0080] The thickness of the first thermoelectric material portion 1 (i.e., the thickness in the stacking direction of the first thermoelectric material portion 1 and the second thermoelectric material portion 2) is preferably 100 nm to 10 mm, and may be 1 μm to 3 mm. The thickness of the second thermoelectric material portion 2 is preferably 0.1 mm to 10 mm, and may be 0.5 mm to 3 mm.

[0081] When the first thermoelectric material portion 1 and the second thermoelectric material portion 2 are joined via the conductor 2a, the conductor 2a can be a conductive joining material such as solder or In. The resistivity of the conductor 2a used in the joining portion is preferably about the same as that of the second thermoelectric material portion 2.

[0082] The resistivity of the alloy material and the solder material are often similar (10 -4 For example, if Cu 0.55 Ni 0.45 (Constantan) is used as an alloy material, and the resistivity of the second thermoelectric material part 2 is about the same as that of the solder. Therefore, in essence, for the first thermoelectric material part 1, from the perspective of conductivity, the solder can also be regarded as a part of the second thermoelectric material part 2, thereby increasing the design freedom of the thermoelectric element.

[0083] The pair of electrodes 3 can be formed on both end surfaces of the bonded body 4 by dipping, for example, using Ag paste or Ag solder.

[0084] In addition, the material of the pair of electrodes 3 is 10 -4 Materials below Ωm.

[0085] The insulating material portion 5 is formed of, for example, alumina or SiO 2 .

[0086] The method of manufacturing the thermoelectric element 10 of this embodiment includes a joining step of joining the second thermoelectric material portion 2 to the first thermoelectric material portion 1 , and an electrode forming step of forming a pair of electrodes 3 on the first thermoelectric material portion 1 .

[0087] For example, in the above-mentioned joining step, the second thermoelectric material portion 2 and the first thermoelectric material portion 1 are joined using a conductive joining material such as solder.

[0088] Furthermore, in the above-mentioned bonding step, various thin film growth methods (vapor phase growth methods such as PVD, sputtering, and CVD) are employed.

[0089] When a chalcogenide material is used for the first thermoelectric material portion 1 , it is preferable to form the first thermoelectric material portion 1 on the second thermoelectric material portion 2 by MBD (Molecular Beam Deposition).

[0090] Furthermore, in the above-mentioned bonding step, the first thermoelectric material portion 1 may be formed on the second thermoelectric material portion 2 by a sol-gel method.

[0091] In addition, in the above-mentioned joining process, the following hot pressing method can be used: while the powder to become the first thermoelectric material part 1 and the powder to become the second thermoelectric material part 2 are stacked, the first thermoelectric material part 1 and the second thermoelectric material part 2 are sintered and the first thermoelectric material part 1 and the second thermoelectric material part 2 are joined at the same time.

[0092] Thus, in the thermoelectric element 10 of this embodiment, the junction body 4 of the first thermoelectric material portion 1 and the second thermoelectric material portion 2 has end surfaces on one end side and the other end side. A pair of electrodes 3 are in contact with the first thermoelectric material portion 1 while not in contact with the second thermoelectric material portion 2. These electrodes are formed on the end surfaces on the one end 1a side and the other end 1b side of the junction body 4. This allows for surface mounting and miniaturization, and results in an element with high thermoelectric conversion efficiency and ZT value. Specifically, the thermoelectric element 10 of this embodiment is entirely chip-type, with electrodes 3 formed on both end surfaces. This facilitates surface mounting using solder, etc., and its compact shape provides a high degree of freedom in placement.

[0093] In addition, in the thermoelectric element 10, the first thermoelectric material portion 1 has a higher Seebeck coefficient and a higher resistivity than the second thermoelectric material portion 2, and a pair of electrodes 3 are connected separately from each other to one end 1a side and the other end 1b side of the first thermoelectric material portion 1, so that the first thermoelectric material portion 1 and the second thermoelectric material portion 2 form a parallel circuit. If a temperature difference is generated between the one end 1a side and the other end 1b side (heat flow is generated), an electromotive force is generated with high thermoelectric conversion efficiency.

[0094] That is, Figure 2As shown, in the first thermoelectric material part 1 connected to a pair of electrodes 3 and having a high Seebeck coefficient (absolute value) and a high resistance value, an electromotive voltage path R1 that mainly follows the Seebeck effect is formed, and in the second thermoelectric material part 2 having a low resistance value that is bonded and in contact with the first thermoelectric material part 1, a current path R2 is formed. The current value flowing in the second thermoelectric material part 2 preferably follows Ohm's law. In this way, by forming a parallel circuit of the electromotive voltage path R1 and the current path R2, a current path R2 that becomes a current channel is formed separately from the electromotive voltage path R1, thereby increasing the conductivity flowing between the pair of electrodes 3 while maintaining the high Seebeck coefficient (absolute value) of the first thermoelectric material part 1, and achieving a higher thermoelectric conversion efficiency and ZT value. In addition, in Figure 2 In the figure, arrow Y is the direction of heat flow (the direction in which heat flux flows, the direction in which temperature difference is generated).

[0095] In addition, a pair of insulating material parts 5 are provided on the end face on the side of one end 1a and the end face on the side of the other end 1b of the junction body 4, which are formed to at least cover the second thermoelectric material part 2. Therefore, the insulating material part 5 can prevent the pair of electrodes 3 from contacting the second thermoelectric material part 2 on the end face of the junction body 4.

[0096] Moreover, the first thermoelectric material part 1 is stacked on the upper and lower surfaces of the second thermoelectric material part 2, and a pair of electrodes 3 are connected to the upper and lower first thermoelectric material parts 1, respectively, so that an electromotive voltage path R1 is formed on the upper and lower surfaces, respectively, which can achieve higher thermoelectric conversion efficiency.

[0097] Moreover, the absolute value of the Seebeck coefficient of the first thermoelectric material part 1 is greater than that of the second thermoelectric material part 2 by more than 50 μV / K, and the resistivity is greater than 10 times. Therefore, by forming an electromotive voltage path R1 with a sufficiently high Seebeck effect and a current path R2 with a sufficiently high conductivity, a higher thermoelectric conversion efficiency and ZT value can be obtained.

[0098] Furthermore, the absolute value of the Seebeck coefficient of the first thermoelectric material portion 1 may be greater than the absolute value of the Seebeck coefficient of the second thermoelectric material portion 2 by at least 100 μV / K. A larger difference between the absolute values of the Seebeck coefficients of the first thermoelectric material portion 1 and the second thermoelectric material portion 2 is preferred, and the upper limit is not particularly limited, but may be 10,000 μV / K.

[0099] Furthermore, by forming the first thermoelectric material portion 1 from Ag2S and the second thermoelectric material portion 2 from Ag2Se, the output factor (PW=S) of the composite thermoelectric element of the present invention is improved compared to Ag2S and Ag2Se alone. 2 / ρ) becomes larger, at least an N-type thermoelectric element with a ZT value of 1 or more at room temperature can be obtained.

[0100] Furthermore, by forming the first thermoelectric material portion 1 from Cu2S and the second thermoelectric material portion 2 from Cu2Se, the output factor (PW=S) of the composite thermoelectric element of the present invention is improved compared to Cu2S and Cu2Se alone. 2 / ρ) becomes larger, at least a P-type thermoelectric element with a ZT value of 1 or more at room temperature can be obtained.

[0101] Furthermore, by forming the first thermoelectric material portion 1 from Bi2Te3 and the 0.55 Ni 0.45 By forming the second thermoelectric material portion 2 with (Constantan), an N-type thermoelectric element having a power factor at least twice that of Bi2Te3 alone can be obtained.

[0102] And, by (Bi 0.7 Sb 0.3 )2Te3 forms the first thermoelectric material portion 1, and is made of Cu 0.55 Ni 0.45 (Constantan) forms the second thermoelectric material portion 2, which can at least obtain (Bi 0.7 Sb 0.3 )P-type thermoelectric element with a power factor about twice that of 2Te3 monomer.

[0103] Next, refer to Figures 3 to 6 , the second to third embodiments of the thermoelectric element according to the present invention will be described. In the following description of each embodiment, the same components as those described in the above embodiment will be denoted by the same reference numerals, and their description will be omitted.

[0104] The difference between the second embodiment and the first embodiment is that, in the first embodiment, the first thermoelectric material portion 1 is bonded to the upper and lower surfaces of the second thermoelectric material portion 2, and a pair of electrodes 3 are connected to the upper and lower first thermoelectric material portions 1, respectively. In contrast, in the thermoelectric element 20 of the second embodiment, as shown in FIG. Figure 3 and Figure 4 As shown, the first thermoelectric material portion 1 is further bonded to both side surfaces of the second thermoelectric material portion 2 , and a pair of electrodes 3 is further connected to the first thermoelectric material portion 1 on both side surfaces.

[0105] The junction body 4 is formed in a plate-like or rectangular parallelepiped chip shape, and the upper and lower surfaces of the second thermoelectric material portion 2 are perpendicular to both side surfaces of the second thermoelectric material portion 2 .

[0106] That is, in the second embodiment, the first thermoelectric material portion 1 covers the entire outer peripheral surface of the second thermoelectric material portion 2 , and the first thermoelectric material portion 1 is bonded to all four outer peripheral surfaces of the second thermoelectric material portion 2 .

[0107] In this way, in the thermoelectric element 20 of the second embodiment, the first thermoelectric material part 1 is also respectively joined to the two side surfaces of the second thermoelectric material part 2, and a pair of electrodes 3 are also respectively connected to the first thermoelectric material part 1 on the two side surfaces. Therefore, an electromotive voltage path R1 is formed not only on the upper and lower surfaces, but also on the two side surfaces, thereby achieving a higher thermoelectric conversion efficiency.

[0108] Next, the difference between the third embodiment and the second embodiment is that, in the second embodiment, the first thermoelectric material portion 1 and the second thermoelectric material portion 2 are bonded to each other on the upper and lower surfaces and both side surfaces, whereas, in the thermoelectric element 30 of the third embodiment, Figure 5 As shown, the first thermoelectric material portion 1 is further bonded to both end surfaces of the second thermoelectric material portion 2 , and a pair of electrodes 3 are formed on the first thermoelectric material portion 1 at the both end surfaces.

[0109] That is, in the third embodiment, the entire surface of the chip-shaped second thermoelectric material portion 2 is covered with the first thermoelectric material portion 1 .

[0110] Thus, in the thermoelectric element 30 of the third embodiment, the first thermoelectric material portion 1 is further bonded to the respective end surfaces of the second thermoelectric material portion 2, and a pair of electrodes 3 are formed on the first thermoelectric material portion 1 at these end surfaces. Thus, an electromotive voltage path R1 is formed from the pair of electrodes 3 through the end surfaces in each of the first thermoelectric material portions 1 on the outer peripheral surface, thereby achieving higher thermoelectric conversion efficiency. Furthermore, there is no need to form insulating material portions on the end surfaces of the second thermoelectric material portion 2, which can reduce the number of manufacturing steps.

[0111] Example

[0112] In order to verify the principle of the thermoelectric properties of the present invention, the following Figure 6 The samples shown are used as examples, and the results of evaluation are shown in Tables 1 and 2.

[0113] In an embodiment of the present invention, the first thermoelectric material part and the second thermoelectric material part are produced by using a variety of materials and production methods described in the above-mentioned embodiments, and the thermoelectric properties (conductivity type determination (P / N type determination), Seebeck coefficient, resistivity and output factor) at room temperature (300K) are investigated.

[0114] Furthermore, as a comparative example of the present invention, a thermoelectric element produced from a single thermoelectric material was evaluated in the same manner as in the examples of the present invention.

[0115] Each example was prepared as follows.

[0116] In the examples of the present invention, for evaluation purposes, the first thermoelectric material portion 1 was bonded only to the upper surface of the second thermoelectric material portion 2. Furthermore, a pair of electrodes 3 were formed on the upper surface of the first thermoelectric material portion 1.

[0117] <Example 1, Example 2> <Example 9 to Example 12> (Solder Bonding)

[0118] First, a Bi-Te bulk sintered body (or Bi-Sb-Te bulk sintered body) to become the first thermoelectric material part and a Cu-Ni alloy plate or Cu plate to become the second thermoelectric material part are prepared, cut into specified sizes, and the joining surfaces are polished.

[0119] Then, solder foil is placed on the joint surface between the Bi-Te bulk sintered body and the Cu-Ni alloy plate or Cu plate, and the Bi-Te bulk sintered body and the Cu-Ni alloy plate or Cu plate are joined using a hot press to melt the solder. In other words, the second thermoelectric material portion is joined to the first thermoelectric material portion via an intermediate layer of solder, which serves as a conductor.

[0120] The bonding conditions were a pressure of 100 MPa, a bonding temperature of 250°C, and a holding time of approximately 5 minutes. After visual confirmation of solder melting, a cooling process and a pressure reduction process were performed.

[0121] Then, two pairs of electrodes were formed on the first thermoelectric material portion side (Bi—Te side) using Ag paste or the like, as Examples 1 and 2.

[0122] <Example 3> (MBD film formation)

[0123] First, an Ag2S thin film, which will become the first thermoelectric material, was formed on an Ag2Se bulk sintered body, which will become the second thermoelectric material, using MBD (molecular beam deposition) equipment. The Ag2Se bulk sintered body was formed using SHS (self-propagating high-temperature synthesis).

[0124] In the film formation based on the above-mentioned MBD method, the substrate temperature is set to room temperature, and the unit containing Ag and S as raw materials is heated to an appropriate temperature using a heater to form a film, thereby obtaining a single-phase thin film of Ag2S that becomes the first thermoelectric material part.

[0125] In addition, X-ray diffraction experiments confirmed that Ag2S thin films and Ag2Se bulk sintered bodies are crystalline materials. 1-x Se x In the system, in the low-temperature phase near room temperature below the phase transition temperature, when x≤0.6, it has the same crystal structure as Ag2S (monoclinic, space group P21 / c), and when x≥0.7, it has the same crystal structure as Ag2Se (orthorhombic, space group P212121) (in the composition region of 0.6<x<0.7, a mixed phase or different crystal structures are adopted depending on the film formation conditions).

[0126] The preparation of the electrodes is the same as that of Example 1 and Example 2.

[0127] <Examples 4 to 8> <Examples 13 to 17> (Hot Pressing)

[0128] First, the raw material powders of the first thermoelectric material part and the second thermoelectric material part (for example, Ag, S, Cu, etc.) are weighed and mixed in a prescribed stoichiometric ratio, formed using a punch, and then heat treated at a prescribed temperature, thereby obtaining, for example, a single-phase sintered body of Ag2S.

[0129] Furthermore, when a chalcogenide containing S, Se, and Te is used, a single-phase sintered body can be obtained even by using a self-heating reaction method.

[0130] If an unreacted phase can be confirmed by X-ray diffraction, the sintered body is pulverized into powder and the above process is repeated. Since a single-phase sintered body can be obtained by X-ray diffraction, the experiment is repeated.

[0131] After obtaining a single-phase sintered body, the sintered body is crushed using a mortar or the like to obtain Ag2S, Ag2Se, Cu 2-δ S, Cu 2-δ Se powder.

[0132] Using these powders, a hot press is used to heat and pressurize them, thereby producing a block of the first thermoelectric material portion and the second thermoelectric material portion, and also producing a joint of the first thermoelectric material portion and the second thermoelectric material portion. In addition, during hot pressing, considering the density, weigh Ag2S, Ag2Se, Cu 2-δ S, Cu 2-δ Se to achieve the specified thickness, put in the raw materials in sequence and form.

[0133] Then, the bonding conditions using the hot press were set to a pressure of 100 MPa, a predetermined holding temperature, and a holding time of 20 minutes, thereby forming a bonded body.

[0134] Then, by cutting the bonded body using a wire saw or the like, a bonded body in the form of a chip having a size of, for example, 17 mm×3 mm×2 mm in thickness can be obtained.

[0135] The preparation of the electrodes is the same as that of Example 1 and Example 2.

[0136] <Evaluation Methods for Thermoelectric Elements>

[0137] When a temperature difference ΔT is applied to a thermoelectric element, a voltage ΔV proportional to the temperature difference is generated. This phenomenon is called the Seebeck effect, the generated voltage is called the thermoelectromotive force, and the proportionality factor S = ΔV / ΔT is defined as the Seebeck coefficient S. In other words, to measure the Seebeck coefficient, it is necessary to measure both the potential difference (thermoelectromotive force) and the temperature difference between the two terminals.

[0138] The Seebeck coefficient was measured using two commercially available Peltier elements, with one element being cooled and the other heated to create a temperature difference between the two elements. A temperature difference of 0.1 to 5° C. was applied.

[0139] Furthermore, a T-type thermocouple (Cu-Constantan) was used as the thermocouple for measurement. This thermocouple was an extremely thin type, approximately 20 microns thick, and a rubber material with high electrical and thermal insulation properties was used to apply the load, achieving good thermal and electrical contact between the material and the thermocouple.

[0140] Furthermore, a two-terminal method called a thermoelectric probe method was used to measure the potential difference (thermoelectromotive force) between two terminals using Cu wires of two T-type thermocouples.

[0141] The relationship between the thermoelectromotive force ΔV and the temperature difference ΔT was plotted, and the Seebeck coefficient was evaluated based on the linear relationship near zero temperature difference (near the origin of ΔV / ΔT).

[0142] In addition, the determination of P-type and N-type (determination of conductivity type) is determined based on the sign of the measured Seebeck coefficient. Moreover, when the first thermoelectric material portion and the second thermoelectric material portion are joined, it is preferred to make the polarity of the P-type / N-type consistent, that is, it is preferred that P-types or N-types are joined together, but different polarities, that is, P-type and N-type, can also be joined together. In this case, the first thermoelectric material portion also has a higher absolute value of the Seebeck coefficient than the second thermoelectric material portion joined and a higher resistivity than the second thermoelectric material portion joined.

[0143] The resistivity (conductivity) was measured by a four-terminal method.

[0144] In this measurement, both the current measurement terminal and the voltage measurement terminal were connected to the electrode terminal.

[0145] Furthermore, when calculating resistivity from resistance values, the thickness is calculated as the sum of the thicknesses of the various materials. For example, when calculating the resistivity of a composite of 0.1 mm thick Ag2S (the first thermoelectric material) and 2 mm thick Ag2Se (the second thermoelectric material) in Example 4, the thickness is the sum of the thicknesses of the two materials, or 2.1 mm.

[0146] The output factor is represented by the product of the "square of the Seebeck coefficient" and the "inverse of the resistivity (=conductivity)", and is calculated from the measured Seebeck coefficient and resistivity.

[0147]

[0148] The above evaluation results show that the output factors of the embodiments of the present invention are significantly improved compared to the comparative examples of the first thermoelectric material portion or the second thermoelectric material portion as a single material.

[0149] The absolute value of the Seebeck coefficient of the Bi-Te-based materials in Comparative Examples 1 and 2 is greater than that of the Cu-Ni material in Comparative Example 3 by more than 50 μV / K, and the resistivity of the Bi-Te-based materials in Comparative Examples 1 and 2 is greater than that of the Cu-Ni material in Comparative Example 3 by more than 10 times. Therefore, in Examples 1 and 2, where the first thermoelectric material portion is a Bi-Te-based material and the second thermoelectric material portion is Cu-Ni, by simultaneously forming an electromotive voltage path with a sufficiently high Seebeck effect and a current path with sufficiently high conductivity, both the electromotive voltage and current values output from the pair of electrodes are increased, significantly improving the output factor. N-type characteristics are achieved in Example 1, and P-type characteristics are achieved in Example 2.

[0150] The absolute value of the Seebeck coefficient of Ag2S in Comparative Example 4 is greater than the absolute value of the Seebeck coefficient of Ag2Se in Comparative Example 5 by more than 50 μV / K, and the resistivity of Ag2S in Comparative Example 4 is greater than the resistivity of Ag2Se in Comparative Example 5 by more than 10 times. Therefore, in Examples 3 to 6, in which the first thermoelectric material portion is an Ag2S-based material and the second thermoelectric material portion is Ag2Se, by simultaneously forming an electromotive voltage path with a sufficiently high Seebeck effect and a current path with sufficiently high conductivity, both the electromotive voltage and current values output from a pair of electrodes are increased, significantly improving the output factor.

[0151] In addition, Example 5 shows N-type characteristics, while Example 4 shows P-type characteristics. However, since this material generally has N-type characteristics, it is believed that in Example 4, P-type characteristics are achieved due to impurities, crystal defects, etc.

[0152] Furthermore, the absolute value of the Seebeck coefficient of Cu2S in Comparative Example 6 is greater than that of Cu2Se in Comparative Example 7 by more than 50 μV / K, and the resistivity of Cu2S in Comparative Example 6 is greater than that of Cu2Se in Comparative Example 7 by more than 10 times. 2-δ S-based material, and the second thermoelectric material portion is Cu 2-δIn Examples 7, 8, and 13 to 17 of Se, by simultaneously forming an electromotive voltage path with a sufficiently high Seebeck effect and a current path with a sufficiently high conductivity, the electromotive voltage and current values output from between a pair of electrodes are increased, and the output factor is greatly improved.

[0153] Furthermore, the absolute values of the Seebeck coefficients of the Bi-Te-based materials of Comparative Examples 1 and 2 are greater than the absolute value of the Seebeck coefficient of Cu of Comparative Example 8 by more than 50 μV / K, and the resistivity of the Bi-Te-based materials of Comparative Examples 1 and 2 is greater than the resistivity of Cu of Comparative Example 8 by more than 10 times. Therefore, in Examples 9 to 12, in which the first thermoelectric material portion is a Bi-Te-based material and the second thermoelectric material portion is Cu, by simultaneously forming an electromotive voltage path with a sufficiently high Seebeck effect and a current path with sufficiently high conductivity, both the electromotive voltage and current values output from a pair of electrodes are increased, significantly improving the output factor.

[0154] In the embodiment in which the first thermoelectric material part is set to Ag2S and the second thermoelectric material part is set to Ag2Se, it is confirmed that the thermal conductivity of Ag2S and Ag2Se at room temperature is less than 1 W / mK. For example, in Example 4, high thermoelectric performance with a ZT value of about 3 at room temperature is obtained.

[0155] Furthermore, a four-element π-type thermoelectric conversion module was fabricated using two each of the Bi-Te / Cu-Ni elements exhibiting n-type characteristics from Example 1 and the Bi-Sb-Te / Cu-Ni elements exhibiting p-type characteristics from Example 2. The power generation performance was compared with four-element π-type thermoelectric conversion modules made solely of Bi-Te (Comparative Example 1) and Bi-Sb-Te (Comparative Example 2). The results confirmed that the thermoelectric conversion module using the elements of the examples achieved a 38.4% improvement in power generation when a temperature difference of 30K was applied (the lower temperature side was approximately 20°C, near room temperature).

[0156] <Example 21 to Example 25> (Hot Pressing)

[0157] Examples 21 to 25 of the present invention were produced by the same production method as that of Examples 4 to 6 described above, and the temperature dependence of the thermoelectric characteristics of these Examples 21 to 25 was evaluated.

[0158] In Example 22, the second thermoelectric material portion and the first thermoelectric material portion were bonded by hot pressing via an intermediate layer of Ag as a conductor, and in Example 23, via an intermediate layer of In as a conductor.

[0159] ·Evaluation of thermoelectric properties at high temperatures

[0160] In the evaluation methods of Examples 1 to 17, the thermoelectric characteristics were measured at room temperature (25°C). However, in Examples 21 to 25 of the present invention, the thermoelectric characteristics were measured at high temperatures of 88 to 95°C.

[0161] In Examples 21 to 25, the first thermoelectric material portion was made of Ag 2 S, and the second thermoelectric material portion was made of Ag 2 Se. The results are shown in Table 2.

[0162] The evaluation results of Examples 21 to 25 show that the Seebeck coefficient (absolute value) is maintained high even at a measurement temperature of 88 to 95° C., and the output factor is significantly improved.

[0163] At a measurement temperature of 88-95°C, the output factor of Ag2S monomer and Ag2Se monomer is 2×10 -3 W / mK 2 In Examples 21 to 25, significantly higher thermoelectric conversion properties were achieved compared to the single element. The thermal conductivity of the thermoelectric elements of Examples 21 to 25 was 1.2 W / mK or less. In Examples 24 and 25, a ZT value (=S 2 T / ρκ): where S, T, ρ, and κ are Seebeck coefficient, absolute temperature, resistivity, and thermal conductivity, respectively. In Example 21, a ZT value of 5 or more was measured, and very high thermoelectric conversion characteristics were obtained.

[0164]

[0165] Evaluation of power generation characteristics

[0166] Next, as Example 26, the first thermoelectric material portion was made of Ag2S and the second thermoelectric material portion was made of Ag2S. 0.5 Se 0.5 The power generation characteristics of the thermoelectric elements were evaluated.

[0167] In addition, Ag2S and Ag2S 0.5 Se 0.5 Both show N-type characteristics. In addition, Ag2S and Ag2S 0.5 Se 0.5 The bonding was performed by hot pressing at a temperature of 200° C. or lower. In Example 26, the elements were directly bonded without using an intermediate layer.

[0168] Regarding the thickness of the element, the thickness of the Ag2S in the first thermoelectric material portion was set to 10 μm, and the thickness of the Ag2S in the second thermoelectric material portion was set to 10 μm. 0.5 Se 0.5The thickness was set to 0.70 mm. The width of the element was set to 2.2 mm. The distance between the pair of electrodes was set to 2.91 mm. Furthermore, electrode needles were used as electrodes and were brought into point contact with the first thermoelectric material portion to evaluate power generation characteristics.

[0169] exist Figure 7 The Ag2S / Ag2S of Example 26 of the present invention is shown in FIG. 0.5 Se 0.5 The results of evaluating the power generation characteristics of the thermoelectric element.

[0170] To evaluate the power generation characteristics, a closed circuit consisting of a thermoelectric element, a variable resistance element (external load resistance element), and an ammeter was constructed. A temperature difference was applied across the thermoelectric element, and the voltage, current, and electric power output from the thermoelectric element were measured.

[0171] exist Figure 7 The output voltage value relative to the current (shown on the left axis) and the power generation power density (shown on the right graph) are shown in FIG.

[0172] The thermoelectric element of Example 26 exhibits N-type characteristics, so the voltage value shows a negative value, but Figure 7 The voltage value shown on the left axis of is expressed in absolute value. Furthermore, the power generation is expressed as the product of the voltage and current values. Furthermore, the power generation density is calculated by dividing the power generation by the cross-sectional area of the element (the product of the thickness and width of the element).

[0173] In addition, Figure 7 In the diagram, the measured values are shown as points, and the values calculated from the measured values are shown as lines. The voltage value when the output current is zero is called the open circuit voltage. The current value when the output voltage is 0V is called the short circuit current. Figure 7 , the results of evaluating the open circuit voltage with the low temperature side temperature of the element set to 50°C, 60°C, and 70°C and a temperature difference of 3K are shown.

[0174] The power generation characteristics of the thermoelectric element of Example 26 were evaluated. When the low temperature side temperature of the element was 60°C, the open circuit voltage was 0.59 mV, the short circuit current was 191 μA, and the power generation density was 1.7 μW / cm 2 .

[0175] The absolute value of the Seebeck coefficient calculated from the open circuit voltage is 196 μV / K.

[0176] Ag2S 0.5 Se 0.5 The absolute value of the Seebeck coefficient of the single body is 130 μV / K, and therefore it can be seen that the output voltage of Example 26 is increased.

[0177] Furthermore, Ag 2 S alone has a high resistivity, and the short-circuit current value of Example 26 is more than 1000 times greater than that of Ag 2 S alone.

[0178] Ag2S monomer, Ag2S 0.5 Se 0.5 The power density of each cell is calculated to be less than 0.1 μW / cm 2 , 1.0μW / cm 2 In contrast, it can be seen that the Ag2S / Ag2S of Example 26 0.5 Se 0.5 The power density of the thermoelectric element (=1.7μW / cm 2 ) is large, and compared with single elements, very high thermoelectric conversion characteristics are achieved.

[0179] In addition, the technical scope of the present invention is not limited to the above-described embodiment and examples, and various modifications can be made without departing from the spirit of the present invention.

[0180] For example, in the above-mentioned embodiment, the thermoelectric element of the present invention is described as being used for power generation, but the thermoelectric element of the present invention can also be applied to applications such as Peltier cooling or Peltier temperature control.

[0181] And, in Figure 3 The shape of the first thermoelectric material portion is a quadrangular prism, but it may be a cylindrical shape (a combination of a cylindrical first thermoelectric material portion and a cylindrical second thermoelectric material portion) or a polygonal column shape.

[0182] Explanation of symbols

[0183] 1-first thermoelectric material portion; 1a-one end portion; 1b-the other end portion; 2-second thermoelectric material portion; 2a-conductor; 3-electrode; 4-junction; 5-insulating material portion; 10, 20, 30-thermoelectric elements.

Claims

1. A thermoelectric element, characterized in that have: a first thermoelectric material portion having one end and another end; a second thermoelectric material portion, directly bonded to the first thermoelectric material portion or bonded via a conductor; and a pair of electrodes connected to the first thermoelectric material portion, The first thermoelectric material portion has a higher absolute value of the Seebeck coefficient and a higher resistivity than the second thermoelectric material portion. The bonded body of the first thermoelectric material portion and the second thermoelectric material portion has end surfaces on the one end side and the other end side. The pair of electrodes are in contact with the first thermoelectric material portion without being in contact with the second thermoelectric material portion, and are formed on an end surface on the one end side and an end surface on the other end side of the junction body.

2. The thermoelectric element according to claim 1, characterized in that A pair of insulating material portions that are formed to cover at least the second thermoelectric material portion are provided on the end surface on the one end side and the end surface on the other end side of the junction body.

3. The thermoelectric element according to claim 1, characterized in that The first thermoelectric material portion is bonded to the upper and lower surfaces of the second thermoelectric material portion, The pair of electrodes are connected to the first thermoelectric material portions on the upper and lower surfaces, respectively.

4. The thermoelectric element according to claim 3, characterized in that The first thermoelectric material portion is further bonded to both side surfaces of the second thermoelectric material portion. The pair of electrodes are further connected to the first thermoelectric material portions on the two side surfaces, respectively.

5. The thermoelectric element according to claim 3, characterized in that The first thermoelectric material portion is further bonded to both end surfaces of the second thermoelectric material portion. The pair of electrodes are formed on the first thermoelectric material portion at the both end surfaces.

6. The thermoelectric element according to claim 1, characterized in that The first thermoelectric material portion has an absolute value of a Seebeck coefficient greater than that of the second thermoelectric material portion by 50 μV / K or more, and a resistivity greater than that of the second thermoelectric material portion by 10 times or more.

7. The thermoelectric element according to claim 1, characterized in that The first thermoelectric material portion and the second thermoelectric material portion are both made of A 2+δ M is formed, wherein A is at least one of Ag and Cu, and M is at least one of S, Se and Te.

8. The thermoelectric element according to claim 7, characterized in that The first thermoelectric material portion is formed of Ag—S, The second thermoelectric material portion is formed of Ag—Se or Ag—S—Se.

9. The thermoelectric element according to claim 7, characterized in that The first thermoelectric material portion is formed of Cu—S, The second thermoelectric material portion is formed of Cu—Se.

10. The thermoelectric element according to claim 1, characterized in that The first thermoelectric material portion is formed of a material containing at least Bi and Te.

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