JP2005268240A - Thermoelectric module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric module which has a high reliability, the high heat recovery efficiency, and a wide choice for thermoelectric materials; generates little thermal stress; and causes a large temperature difference between a hot junction and a cold junction. <P>SOLUTION: The thermoelectric module 50 includes a thermoelectric element 40a comprising at least one single joint element 16 which is such that at least one p-type element 12 made of a p-type thermoelectric material and at least one n-type element 14 made of an n-type thermoelectric material are joined by the end faces in the longitudinal direction, a first electrode 30 connected to one end of the single joint element 16, and a second electrode 30 connected to the other end of the single joint element 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoelectric module, and more particularly to a thermoelectric module used for thermoelectric power generation, thermoelectric cooling, thermoelectric heating, and the like.

  Thermoelectric conversion refers to the direct conversion of electrical energy into thermal energy for cooling and heating, and conversely, thermal energy into electrical energy using the Seebeck effect and Peltier effect. Thermoelectric conversion (1) No excess waste is discharged during energy conversion, (2) Effective use of exhaust heat is possible, (3) Power can be generated continuously until the material deteriorates (4) Since a movable device such as a motor or a turbine is unnecessary and maintenance is not required, it has been attracting attention as a high-efficiency energy utilization technology.

As an index for evaluating the characteristics of a material capable of mutually converting thermal energy and electrical energy, that is, thermoelectric material characteristics, generally, the figure of merit Z (= S ² σ / κ, where S: Seebeck coefficient, σ: electrical conduction Degree, κ: thermal conductivity), or a dimensionless figure of merit ZT expressed as a product of the figure of merit Z and the absolute temperature T indicating the value. The Seebeck coefficient represents the magnitude of electromotive force generated by a temperature difference of 1K. Thermoelectric materials each have their own Seebeck coefficient, and are broadly classified into those having a positive Seebeck coefficient (p-type) and those having a negative Seebeck coefficient (n-type).

  The thermoelectric material is usually used in a state where a p-type thermoelectric material and an n-type thermoelectric material are joined. Such a junction pair is generally called a thermoelectric element. There are two known thermoelectric elements, “U-type” and “π-type”, which have different types of bonding. The “U-type” thermoelectric element is obtained by directly joining a p-type thermoelectric material and an n-type thermoelectric material so as to be U-shaped. In addition, the “π-type” thermoelectric element is an element in which an end surface of a columnar p-type thermoelectric material and an end surface of a columnar n-type thermoelectric material are joined via a metal electrode so as to be π-shaped.

However, the p-type thermoelectric material and the n-type thermoelectric material constituting the thermoelectric element are generally made of different materials. In addition, a metal electrode for extracting an output from the thermoelectric element or supplying a current to the thermoelectric element is usually joined to the open end of the thermoelectric element. That is, the dissimilar materials are joined at the joint and the open end. Further, when the thermoelectric element is used for thermoelectric power generation, the joint is usually heated and the open end is cooled. Moreover, when using a thermoelectric element for thermoelectric heating and cooling, either a junction part or an open end will generate | occur | produce heat according to the direction of an electric current. Furthermore, the thermoelectric material has a lower mechanical strength than a general structural material.
For this reason, in the conventional thermoelectric element, the joint portion and / or the thermoelectric material itself may be damaged by a thermal load and / or an external force generated during use.

  In order to solve this problem, various proposals have heretofore been made. For example, in Patent Document 1, a planar power extraction terminal is surface-bonded to a side surface on the open end side of a U-type thermoelectric element made of a prismatic p-type thermoelectric material and a prismatic n-type thermoelectric material, A thermoelectric element in which a fixed portion of a power extraction terminal is covered with a reinforcing mold is disclosed. This document describes that by adopting such a configuration, the fixing area of the power extraction terminal is increased, so that the durability and heat resistance of the power extraction terminal are improved.

  Patent Document 2 discloses a π-type thermoelectric element in which a metal electrode for joining a p-type thermoelectric material and an n-type thermoelectric material has a layered structure of a metal plate and a metal foil. This document describes that when a metal electrode having a layered structure of a metal plate and a metal foil made of a noble metal is used, the heat resistance of the electrode portion is improved.

  Further, in Patent Document 3, the hot junction of the π-type thermoelectric element is fixed to the back cover of the watch, the elastic conductor that can be elastically deformed is fixed to the cold junction of the π-type thermoelectric element, and the end of the thermal conductor is attached. A thermoelectric power generation timepiece fixed to the upper body of the timepiece is disclosed. In this document, the impact force applied to the π-type thermoelectric element is mitigated by connecting the two via a heat conductor that can be elastically deformed without directly fixing the cold junction and the upper body, and π-type due to external force The point that damage of the thermoelectric element can be avoided is described.

JP 2002-232023 A JP 2002-368294 A JP 2002-257916 A

  However, the U-type thermoelectric element basically has a structure in which an elongated p-type thermoelectric material and an n-type thermoelectric material are joined on the side surface on the tip side. Therefore, when the thermal expansion coefficients of the p-type thermoelectric material and the n-type thermoelectric material are greatly different, a large thermal shear stress is applied to the joint surface due to the thermal load generated during use. Further, when an external force is applied to the open end of the U-type thermoelectric element, a large bending moment is generated at the joint. As a result, when heating and cooling are repeated and / or when an external force is applied, there is a problem that the joint is damaged and reliability is low.

  In order to obtain a large output, the π-type thermoelectric element is generally used as a module in which a large number of π-type thermoelectric elements having the same height are connected in series and sandwiched between a pair of flat plates. Therefore, the π-type module has a problem that the efficiency of recovering heat from a heat source having a small cross-sectional area of the high temperature portion is low. For example, when a high-temperature thermal fluid flows inside a circular pipe and is cooled on the side wall surface of the pipe, when recovering heat from the side wall surface of the pipe, the π-type module can efficiently recover the heat. Can not.

  In addition, since the π-type module has a large number of π-type thermoelectric elements sandwiched between a pair of parallel flat plates, the generation of thermal stress due to the difference in thermal expansion coefficient between the p-type thermoelectric material and the n-type thermoelectric material is structurally There is a problem that cannot be avoided. In particular, when the thermal expansion coefficients of the p-type thermoelectric material and the n-type thermoelectric material are greatly different, the element may be damaged, or connection failure or bonding failure may occur. On the other hand, in order to avoid this, it is necessary to use a p-type thermoelectric material and an n-type thermoelectric material having similar coefficients of thermal expansion, and there are restrictions on the selection of the thermoelectric material.

  Furthermore, when thermoelectric power generation is performed using a conventional U-type thermoelectric element or π-type thermoelectric element, the open end is heated by heat conduction when the junction is brought close to the heat source. Therefore, in order to generate a large temperature difference between the joint portion and the open end, it is necessary to provide a heat dissipation fin having excellent heat dissipation capability on the open end side. However, the heat radiating fins having a high heat radiating capacity are generally expensive and cause the thermoelectric module to be enlarged.

  The problem to be solved by the present invention is to provide a highly reliable thermoelectric module that does not break even when thermal stress and / or external force is applied. Another problem to be solved by the present invention is to provide a thermoelectric module with high efficiency in recovering heat from a heat source having a small cross-sectional area. Another problem to be solved by the present invention is to provide a thermoelectric module that generates less thermal stress and has a high degree of freedom in selecting a thermoelectric conversion material. Furthermore, another problem to be solved by the present invention is to provide a thermoelectric module that can easily generate a large temperature difference between a hot junction and a cold junction.

  In order to solve the above problems, a thermoelectric module according to the present invention includes at least one p-type element made of a p-type thermoelectric material and at least one n-type element made of an n-type thermoelectric material at a longitudinal end face, and At least one single-junction element joined alternately, a first electrode connected to one end of the single-junction element, and a second electrode connected to the other end of the single-junction element The gist is that a thermoelectric element is provided.

A single-junction element obtained by joining a p-type element and an n-type element at the end face in the longitudinal direction has a simple structure, and therefore is less likely to be damaged even when thermal stress and / or external force is applied. Therefore, a thermoelectric module having excellent durability and reliability can be obtained.
In addition, such a single-junction element can easily bring the joint or end close to a heat source having a small cross-sectional area. Therefore, a thermoelectric module with excellent heat recovery efficiency can be obtained.

  Moreover, even when there is a large difference in thermal expansion coefficient between the p-type thermoelectric material and the n-type thermoelectric material, the individual single-junction elements obtained by joining these seem to have the same thermal expansion characteristics. Indicates. For this reason, even if a plurality of single-junction elements are joined in series via electrodes, damage to the elements and poor connection due to thermal stress are unlikely to occur. In addition, in order to avoid thermal stress, there is no need to consider the difference in thermal expansion coefficient between the p-type thermoelectric material and the n-type thermoelectric material constituting the single junction element, so there is no restriction on the selection of the material.

  Furthermore, such a single-junction element tends to generate a larger temperature difference between the hot junction and the cold junction as compared to the U-type thermoelectric element and the π-type thermoelectric element. Therefore, a thermoelectric module with excellent thermal efficiency can be obtained.

  Hereinafter, an embodiment of the present invention will be described in detail. First, a thermoelectric element provided in the thermoelectric module according to the present invention will be described.

  FIG. 1A shows a first specific example of a thermoelectric element. In FIG. 1A, the thermoelectric element 10 is connected to a single junction element 16, a first electrode 18 connected to one end of the single junction element 16, and the other end of the single junction element 16. The second electrode 20 is provided. The first electrode 18 and the second electrode 20 are connected to terminals 22 and 24 for extracting an output from the single junction element 16 or supplying a current to the single junction element 16, respectively.

  The single junction element 16 is formed by joining a p-type element 12 made of a p-type thermoelectric material and an n-type element 14 made of an n-type thermoelectric material at the end face in the longitudinal direction. In the present invention, the p-type thermoelectric material constituting the p-type element 12 and the n-type thermoelectric material constituting the n-type element 14 are not particularly limited, and various materials can be used. Even when there is a large difference in thermal expansion coefficient between the p-type thermoelectric material and the n-type thermoelectric material, they can be used as the p-type element 12 and the n-type element 14, respectively. This is different from conventional U-type elements and π-type elements.

The shape and dimensions of the p-type element 12 and the n-type element 14 are not particularly limited, and various shapes and dimensions can be used depending on the purpose, such as a columnar shape or a prismatic shape. In addition, the p-type element 12 and the π-type element 14 may have the same shape and the same dimensions, or may have different shapes and / or different dimensions. Generally, as the length of the n-type element 12 and / or the n-type element 14 increases, a larger temperature difference can be generated between the hot junction and the cold junction. Further, the generated current can be increased as the cross-sectional area of the p-type element 12 and / or the n-type element 14 increases.
A specific example of the p-type thermoelectric material constituting the p-type element 12 and the n-type thermoelectric material constituting the n-type element 14 and a method for manufacturing the single junction element 16 will be described later.

  The first electrode 18 and the second electrode 20 are connected to the end of the single junction element 16. In FIG. 1A, the first electrode 18 and the second electrode 20 are both connected to both end faces of the single junction element 16, but this is merely an example, and the first electrode 18 and the second electrode 20 may be connected to the side surface of the end portion of the single junction element 16.

  The material of the first electrode 18 and the second electrode 20 only needs to have at least higher electrical conductivity than the p-type element 12 and the n-type element 14, and various materials can be used depending on the purpose. In addition, when the electrode portion is at a high temperature, the first electrode 18 and the second electrode 20 have heat resistance and oxidation resistance and have low reactivity with the p-type element 12 or the n-type element 14. Is preferably used. Furthermore, since heat generation or heat absorption occurs in the electrode portion, it is preferable to use a material having high thermal conductivity for the first electrode 18 and the second electrode 20.

  Specifically, the materials of the first electrode 18 and the second electrode 20 are Fe-based superalloy (for example, SUH660), Ni-based superalloy (for example, Inconel X-750, Inconel 718), Co-based superalloy. Examples include alloys (for example, Phynox), various stainless steels, NiCr alloys, noble metals such as Pt, Pd, Au, Ag, Cu, and Rh, and alloys thereof, In, Al, Mo, W, Ti, and the like.

  The first electrode 18 and the second electrode 20 may be integrally joined to the single junction element 16, respectively. When the first electrode 18 and / or the second electrode 20 are bonded to the single junction element 16, the bonding method and bonding conditions are the materials of the p-type element 12, the n-type element 14, the first electrode 18, and the second electrode 20. In addition, an optimum method is selected according to the operating temperature of the thermoelectric element 10. As the bonding method, specifically, soldering, brazing, baking using a noble metal paste, diffusion bonding, or the like can be used. In addition, when the material of the element and the electrode permits, a mechanical joining method such as bolting or mating can be used.

  Further, the first electrode 18 and / or the second electrode 20 and the single junction element 16 may be in physical contact only via the biasing means. FIG. 1B shows an example of an electrode provided with biasing means (hereinafter referred to as “spring electrode”). 1B, the spring electrode 30 includes a hollow holder 30a, a probe 30b that is slidably inserted into the tip of the holder 30a, and biases the probe 30b toward the end of the single junction element 16. And a lead wire 30d fixed to the rear end of the holder 30a.

  For example, when the end portion of the single junction element 16 is supported by the frame portion 32, the spring electrode 30 is fixed to the frame portion 32, and the end portions (particularly, both end surfaces) of the single junction element 16 are pressed by the distal end surface of the probe 30b. It is preferable to do. When such a spring electrode 30 is used as the first electrode 18 and / or the second electrode 20, the electrical connection can be reliably maintained even if the single junction element 16 expands or contracts during use.

  Further, when the spring electrode 30 is used as the first electrode 18 and / or the second electrode, in order to prevent an increase in contact resistance, the end of the single junction element 16 with which the tip surface of the probe 30b contacts (in FIG. 1B) The conductive layer 34 is preferably formed on the end surface of the single junction element 16.

  The conductive layer 34 may be at least a good electrical conductor. Further, when the electrode portion becomes high temperature, it is preferable to use a material having heat resistance and oxidation resistance and low reactivity with the p-type element 12 or the n-type element 14 for the conductive layer 34. Furthermore, it is preferable to use a good heat conductor as the conductive layer 34 so that the conductive layer 34 does not become the rate of heat conduction.

  Specifically, as the material of the conductive layer 34, Pt, Pd, Au, Ag, Rh, In, Cu, Al, Mo, W, Ti, and various alloys containing these are suitable. These materials and the formation method thereof are selected optimally according to the operating temperature of the single junction element 16. For example, when the temperature of the electrode portion is relatively low, a melt of indium solder (mp: 200 to 300 ° C.) is attached and solidified on the end face of the single junction element 16 in the form of a film. Is preferable.

  On the other hand, when the temperature of the electrode portion is relatively high, a glass paste containing noble metal (for example, Ag paste, Au paste, etc.) is applied and baked on the end face of the single junction element 16 to form the conductive layer 34. preferable. Alternatively, a metal foil may be bonded to the end face of the single junction element 16, or a metal thin film may be formed using a method such as sputtering, ion plating, or vacuum deposition, and this may be used as the conductive layer 34.

  Further, when any part of the single junction element 16 is supported by the frame portion 32 or brought into contact with the heat exchange means described later, electrical insulation between the single junction element 16 and the frame portion 32 or the heat exchange means is performed. It is preferable to provide an insulating layer 36 at the contact portion between the single junction element 16 and the frame portion 32 when it is necessary to ensure the above. In this case, the insulating layer 36 is preferably thin as long as electrical insulation can be ensured. In particular, when the insulating layer 36 is provided at the junction or end of the single junction element 16, the insulating layer 36 is preferably a good heat conductor.

Specifically, the material of the insulating layer 36 is preferably polyimide, epoxy, PTFE, polyester, acetate cloth, glass cloth, or the like. These materials and forming methods are selected optimally according to the operating temperature of the single junction element 16. For example, when the temperature of the electrode portion is relatively low, it is preferable to apply polyimide dissolved in an organic solvent to a predetermined portion of the single junction element 16, remove the solvent, and use this as the insulating layer 36. Moreover, you may use the adhesive tape which consists of these insulating materials.
On the other hand, when the temperature of the electrode portion is relatively high, a thin film made of Al ₂ O ₃ , AlN or the like is formed on the predetermined portion of the single junction element 16 by using, for example, a sputtering method, and this is used as the insulating layer 36. Is preferred.

  When a thermoelectric module including such a thermoelectric element 10 is used for thermoelectric power generation, either one of the junction or the end of the single junction element 16 is heated and the other is cooled. Further, when such a thermoelectric module is used for thermoelectric heating / cooling, heat is generated at one of the joining portion and the end portion, and heat is absorbed at the other end. In this case, heat exchange may be performed directly between the junction or end of the single junction element 16 and a heat source (for example, a thermal fluid such as flame or exhaust gas) or a cold source (for example, air), or A heat exchange means (for example, a radiation fin) that promotes heat absorption or dissipation is connected to the joint or end of the single-junction element 16 so that heat is indirectly exchanged through the heat exchange means. Also good.

  Also, for example, when one of the junctions or ends of the single junction element 16 is heated and the other is cooled using heat exchange means, the cold junction is heated by heat convection or radiation in addition to heat conduction. There is. In such a case, a separator for cutting off heat may be provided in the intermediate part of the p-type element 12 and / or the intermediate part of the n-type element 14 (that is, between the hot junction and the cold junction).

  FIG. 1A shows a single junction element 16 composed of one p-type element 12 and one n-type element 14, but the number of p-type elements 12 and n-type elements 14 is as follows. , Each is not limited to one. That is, the single junction element may be one in which three or more p-type elements and n-type elements are joined alternately at the end face in the longitudinal direction. In this case, a predetermined output can be taken out by alternately heating and cooling the end portion and the junction portion of the single junction element. Further, if a power source is connected to both ends of the single junction element, the end portion and the junction portion of the single junction element can be alternately heated and cooled.

  FIG. 1C shows a second specific example of the thermoelectric element. In FIG.1 (c), the thermoelectric element 40 is in the one end part of the several single junction elements 16a-16d which consist of p-type elements 12a-12d and n-type elements 14a-14d, and the single junction elements 16a-16d. 1st electrode 18a-18c connected, and 2nd electrode 20a, 20b connected to the other edge part are provided.

  The single junction elements 16a to 16d are connected in series via the first electrodes 18a to 18c and the second electrodes 20a and 20b so that the p-type elements 12a to 12d and the n-type elements 14a to 14d are alternately connected. It is connected to the. The first electrode 18b and the second electrodes 20a and 20b are used to connect adjacent single junction elements 16a to 16d. The first electrodes 18a and 18c are connected to terminals 22 and 24, respectively, for taking out outputs or supplying current.

  In the example shown in FIG. 1C, a total of four single junction elements 16a to 16d are used, but this is merely an example, and the number of single junction elements 16 is limited to this. is not. In general, the larger the total number of single junction elements 16 connected in series, the greater the electromotive force. Alternatively, a plurality of thermoelectric elements 40 in which a plurality of single junction elements 16 are connected in series may be prepared, and these may be further connected in series or connected in parallel.

As shown in FIG. 1C, when a plurality of single junction elements 16a to 16d are joined in series, the single junction elements 16a to 16d are integrated with the first electrodes 18a to 18c and the second electrodes 20a and 20b. When they are joined together, it is preferable that the single junction elements 16a to 16d have the same length.
Further, it is preferable to use the same material or a material having substantially the same thermal expansion coefficient for each of the p-type elements 12a to 12d constituting the single junction elements 16a to 16d. The same applies to each of the n-type elements 14a to 14d.
Furthermore, it is preferable that the ratio (ΣLp / L) of the total length (ΣLp) of the p-type elements included in the single junction element to the total length (L) of the single junction element is equal for each single junction element 16a to 16d. .
When the length of each single-junction element 16a-16d and the length and material of p-type elements 12a-12d and n-type elements 14a-14d are selected in this way, the apparent thermal expansion of each single-junction element 16a-16d. The characteristics can be equal to each other.

  On the other hand, when spring electrodes are used as the first electrodes 18a to 80c and / or the second electrodes 20a and 20b, the single junction elements 16a to 16d, the p-type elements 12a to 12d, and the n-type elements 14a to 14d The lengths may be different from each other. The p-type elements 12a to 12d and the n-type elements 14a to 14d may be made of different materials. In particular, in the case where a thermoelectric module including such a thermoelectric element 40 is used for thermoelectric power generation, when the temperatures of the single junction elements 16a to 16d are greatly different from each other, if a material exhibiting the maximum performance index in the temperature range is properly used, High thermoelectric conversion efficiency can be obtained.

  Other points regarding the p-type element 12, the n-type element 14, the first electrodes 18a to 18c, the second electrodes 20a and 20c, and the single junction elements 16a to 16d as necessary may include a conductive layer and / or an insulating layer. The point that it is preferable to provide is the same as that in the first specific example described above, and thus the description thereof is omitted.

  Further, in the thermoelectric module provided with the thermoelectric element 40, a heat exchange means for promoting absorption or dissipation of heat may be connected to the junction or end of the single junction element 16, and the middle of the p-type element 12 The point which may provide the separator for interrupting | blocking heat in the intermediate part of a part and / or the n-type element 14 is the same as that of the 1st example.

  Next, the p-type thermoelectric material used for the p-type element 12 and the n-type thermoelectric material used for the n-type element 14 will be described. In the present invention, the thermoelectric material constituting the p-type element and the n-type element is not particularly limited, and the present invention can be applied to any thermoelectric material. Further, even materials having greatly different thermal expansion coefficient differences can be used.

Specific examples of thermoelectric materials made of non-oxides (metals, metalloids, intermetallic compounds, carbides, nitrides, etc.)
(1) V-VI group thermoelectric semiconductor (for example, Bi ₂ Te ₃ , Sb ₂ Te ₃ , Bi ₂ Se ₃ , (Bi, Sb) ₂ Te ₃ , (Bi, Sb) ₂ (Te, Se) _3, etc.) ,
(2) IV-VI group thermoelectric semiconductor (for example, PbTe),
(3) II-V group thermoelectric semiconductor (for example, Zn ₄ Sb ₃ etc.),
(4) silicon compounds (eg, SiGe, FeSi ₂ , MnSi _1.73, etc.),
(5) skutterudite compounds (for example, CeFe ₄ Sb ₁₂ , Co ₄ Sb _{12 and the} like),
(6) clathrate compounds (for example, Ba ₆ Ga ₂₅ , Eu ₈ Ga ₁₆ Ge ₃₀ etc.),
(7) Carbide (for example, B ₄ C, SiC, etc.),
(8) Nitride (for example, GaN, AlN, etc.),
(9) borides (eg, MgB ₂ etc.),
(10) Heusler alloy (for example, ZrNiSn, Fe ₂ VAl, etc.),
Etc.

Specific examples of the thermoelectric material made of oxide include the following.
The first specific example is a composite oxide having a YbFe ₂ O ₄ -related layered structure represented by the general formula shown in the following formula (1).
ABO _y (CO) _m (1)
(However, 2 <y <4, m is an integer.
The A site element is at least one element selected from group IIIb elements and Sc, Y and lanthanoid elements.
The B site element is at least one element selected from group IIIb elements and Fe and Cr.
The C site element is at least one element selected from Zn and Group IIa elements, divalent 3d transition metal elements, 4d transition metal elements, and 5d transition metal elements. )

YbFe ₂ O ₄ has a layered structure in which a YbO ₂ layer and an Fe ₂ O ₂ layer are stacked in a predetermined cycle in the c-axis direction. In the composite oxide represented by the formula (1), it is considered that the YbO ₂ layer of YbFe ₂ O ₄ is replaced with an AO ₂ layer, and the Fe ₂ O ₂ layer is replaced with a BC _m O _{m + 1} layer.

  Among these, the composite oxide containing Zn as the C site element and / or In as the A site element and / or the B site element is an n-type thermoelectric oxide having high thermoelectric characteristics, and is an n-type element. 14 is particularly suitable as an n-type thermoelectric material constituting 14. In this case, specifically, the proportion of Zn in the C site is preferably 10 at% or more, and more preferably 20 at% or more. Moreover, specifically, the ratio of In in the A site and the B site is preferably 10 at% or more, and more preferably 20 at% or more.

Among complex oxides containing Zn, in particular, (ZnO) _m In ₂ O ₃ , (ZnO) _m InGaO ₃ , (ZnO) _m InAlO ₃ , and (ZnO) _m InFeO ₃ have high thermoelectric characteristics and large characteristics. Since it has anisotropy in electrical characteristics, it is suitable as an n-type thermoelectric material.

Note that various composite oxides represented by the formula (1) have a part of the A site element and / or the B site element having a tetravalent metal element (for example, a group IVa element (Ti, Zr, Hf), a group IVb element ( C, Si, Ge, Sn, Pb) and the like may be further substituted.
Alternatively, in addition to or instead of this, the C site element is a trivalent metal element (for example, a group IIIa element (Sc, Y, a lanthanoid element ( ₅₇ La to ₇₁ Lu), an actinoid element ( ₈₉ Ac to ₁₀₃ Lr) )) And IIIb group elements (B, Al, Ga, In, Tl, etc.)).
Furthermore, in addition to or instead of these, the A site element and / or the B site element may be further substituted with at least one element selected from Group IIa elements (particularly, Ca).

A second specific example of the oxide thermoelectric material is made of an oxide containing Co. Some oxides containing Co have various compositions. Among them, the cobalt layered oxide is a p-type thermoelectric oxide exhibiting high thermoelectric characteristics. Here, the “cobalt layered oxide” means a CoO ₂ layer composed of CoO ₆ octahedrons with shared edges and a layer having a rock salt structure or a distorted rock salt structure (hereinafter collectively referred to as “pseudo-rock salt structure layer”). And a block layer composed of a layer made of Na ions or the like is a layered oxide laminated at a predetermined cycle.

In the first specific example of the cobalt layered oxide, the block layer is composed of a three-layered rock salt structure layer containing at least Ca and Co, and is represented by the following general formula (2).
_{{(Ca 1-x A x} ) 2 CoO 3 + α} (CoO 2 + β) y ··· (2)
(However, A is one or more elements selected from alkali metals, alkaline earth metals and Bi.
0.0 ≦ x ≦ 0.3.
0.5 ≦ y ≦ 2.0.
0.85 ≦ {3 + α + (2 + β) y} / (3 + 2y) ≦ 1.15. )

In the formula (2), “0.85 ≦ {3 + α + (2 + β) y} / (3 + 2y) ≦ 1.15” indicates the basic composition ({(Ca _1−x A _x ) ₂ CoO ₃ } (CoO ₂ ) Oxygen may be excessive or oxygen deficiency may occur in the range of ± 15 atm% at the maximum with respect to the stoichiometric amount (3 + 2y) of oxygen contained in the cobalt layered oxide having _y ) Indicates. In this case, the increasing / decreasing oxygen may be either oxygen (β) contained in the CoO ₂ layer or oxygen (α) contained in the block layer, or both oxygens.

Further, in the cobalt layered oxide represented by the formula (2), one or two selected from Cu, Sn, Mn, Ni, Fe, Zr, and Cr as a part of Co contained in the CoO ₂ layer and / or the block layer You may substitute with the element more than a seed | species (henceforth "the element C"). Substituting a part of Co with the element C has an effect of improving the Seebeck coefficient S of the cobalt layered oxide. In this case, the substitution amount of Co by the element C is preferably 25 atm% or less.

Specific examples of the cobalt layered oxide represented by the formula (2) include (Ca ₂ CoO ₃ ) _0.62 (CoO ₂ ).

In the second specific example of the cobalt layered oxide, the block layer is composed of a Na ion layer, and is represented by the general formula shown in the following formula (3).
Na _x CoO ₂ (0.3 ≦ x ≦ 0.8) (3)

  Further, in the cobalt layered oxide represented by the formula (3), a part of Na and / or Co may be substituted with another element. Specifically, Li, K, Mg, Ca, Sr and the like are preferable as the element for substituting Na. Further, specifically, the element that substitutes Co is preferably Cr, Mn, Ni, Cu, Zn, or the like.

In the third specific example of the cobalt layered oxide, the block layer is composed of a four-layer pseudo-rock salt structure layer containing at least Ca, Co, and Cu, and is represented by the following general formula (4). The
_{[(Ca 1-x A x} ) 2 (Co 1-y Cu y) 2 O 4 + α] z CoO 2 + β ··· (4)
(However, A is one or more elements selected from alkali metals, alkaline earth metals and Bi.
0.0 ≦ x ≦ 0.3.
0.1 ≦ y ≦ 0.4.
0.5 ≦ z ≦ 0.7.
0.85 ≦ {(4 + α) z + 2 + β} / (4z + 2) ≦ 1.15. )

In the formula (4), “0.85 ≦ {(4 + α) z + 2 + β} / (4z + 2) ≦ 1.15” indicates the basic composition ([(Ca _1−x A _x ) ₂ (Co _1−y Cu _y ) ₂ O ₄ ] _z CoO ₂ ) with respect to the stoichiometric amount of oxygen (4z + 2) contained in the cobalt layered oxide (4z + 2). Indicates that a defect may occur. In this case, the increasing / decreasing oxygen may be either oxygen (β) contained in the CoO ₂ layer or oxygen (α) contained in the block layer, or both oxygens.

In the formula (4), the ratio z of the block layer to the CoO ₂ layer is preferably 0.5 or more and 0.7 or less. If the ratio z exceeds this range, the structure becomes unstable, which is not preferable. The ratio z is more preferably 0.6 or more and 0.7 or less.

Further, in the formula (4), a part of Co contained in the CoO ₂ layer and / or the block layer is further replaced with one or more elements selected from Sn, Mn, Ni, Fe, Zr and Cr (hereinafter referred to as “following”). This may be replaced with “element D”). Substituting a part of Co with the element D has the effect of improving the Seebeck coefficient and / or electrical conductivity. In this case, the substitution amount of Co by the element D is preferably 15 atm% or less of the Co site not occupied by Cu in the CoO ₂ layer and / or the block layer.

Specific examples of the cobalt layered oxide represented by the formula (4) include [Ca ₂ (Co _0.65 Cu _0.35 ) ₂ O ₄ ] _0.624 (CoO ₂ ).

In the fourth specific example of the cobalt layered oxide, the block layer is composed of four pseudo rock salt structure layers containing at least Bi, “element B”, and Co. The general formula shown in the following formula (5) It is represented by
(Bi _1-xy B _x Co _y O _{1 + α} ) (CoO _{2 + β} ) _z (5)
(B is one or more elements selected from alkali metals and alkaline earth metals.
0.2 ≦ x ≦ 0.8.
0.0 ≦ y <0.5.
0.2 ≦ x + y ≦ 1.0.
0.25 ≦ z ≦ 0.5.
0.85 ≦ {1 + α + (2 + β) z} / (1 + 2z) ≦ 1.15. )

In the formula (5), “0.85 ≦ {1 + α + (2 + β) z} / (1 + 2z) ≦ 1.15” indicates the basic composition ((Bi _1−xy− B _x Co _y O) (CoO ₂ ) Oxygen may be excessive or oxygen deficiency may occur in the range of ± 15 atm% at the maximum with respect to the stoichiometric amount (1 + 2z) of oxygen contained in the cobalt layered oxide having _z ) Indicates. In this case, the increasing / decreasing oxygen may be either oxygen (β) contained in the CoO ₂ layer or oxygen (α) contained in the block layer, or both oxygens.

In the cobalt layered oxide represented by the formula (5), a part of Co contained in the CoO ₂ layer and / or the block layer may be replaced with “element C”. Substituting a part of Co with the element C has an effect of improving the Seebeck coefficient and / or electric conductivity of the layered oxide. In this case, the substitution amount of Co by the element C is preferably 25 atm% or less.

  A third specific example of the oxide thermoelectric material is made of NiO doped with a predetermined metal element (hereinafter referred to as “doped NiO”). Doped NiO is a p-type thermoelectric oxide and exhibits high thermoelectric characteristics by adjusting the carrier concentration. Specifically, as the metal element doped into NiO, Li, Na, Cu, Ag, and the like are preferable.

A fourth specific example of the oxide thermoelectric material is made of ZnO or a material doped with a predetermined metal element (hereinafter referred to as “doped ZnO”). ZnO and doped ZnO are n-type thermoelectric oxides and exhibit high thermoelectric characteristics by adjusting the carrier concentration. Specifically, Al, Bi ₂ O _{3 and the} like are preferable as the metal element doped into ZnO.

A fifth specific example of the oxide thermoelectric material is made of a perovskite type compound such as SrTiO ₃ , BaPbO ₃ , CaMnO ₃ , LaNiO ₃ , LiTi ₂ O ₄ , BaBiO ₃ , LaCuO ₃ . Perovskite compounds exhibit thermoelectric properties by adjusting the carrier concentration.

  Among the various thermoelectric materials described above, the oxide thermoelectric material is excellent in heat resistance and oxidation resistance. Therefore, the p-type element 12 constituting the single junction element 16 used in a high temperature range (several hundred degrees C. or more) and It is suitable as a thermoelectric material for the n-type element 14.

  The thermoelectric material constituting the p-type element 12 and / or the n-type element 14 may be single crystal or polycrystalline. When the thermoelectric material is polycrystalline, each crystal grain may be non-oriented, or a specific crystal plane of each crystal grain may be oriented in one direction. However, in the case where the thermoelectric material is polycrystalline and the thermoelectric characteristics have anisotropy according to the crystal orientation, in order to obtain high thermoelectric characteristics, an orientation in which a specific crystal plane is oriented in one direction Polycrystal is preferred.

  In the present invention, “the specific crystal plane is oriented in one direction” means that the specific crystal planes of each crystal grain are oriented in parallel to each other (hereinafter referred to as “plane orientation”), and This means both that a specific crystal plane of each crystal grain is oriented parallel to one axis penetrating the polycrystal (hereinafter referred to as “axial orientation”). In order to obtain a thermoelectric material having high thermoelectric properties, it is desirable that a specific crystal plane is plane-oriented.

  The degree of plane orientation of a specific crystal plane can be expressed by an average degree of orientation Q (HKL) by the Lotgering method shown in the following equation (1).

In Equation 1, ΣI (hkl) is the sum of X-ray diffraction intensities of all crystal planes (hkl) measured for the oriented polycrystal, and ΣI ₀ (hkl) is the same as that of the oriented polycrystal. It is the sum total of the X-ray diffraction intensities of all crystal planes (hkl) measured for a non-oriented polycrystal having a composition. Σ'I (HKL) is the sum of X-ray diffraction intensities of crystallographically equivalent specific crystal planes (HKL) measured for oriented polycrystals, and Σ'I ₀ (HKL) is the orientation It is the sum total of the X-ray diffraction intensities of specific crystal planes (HKL) that are crystallographically equivalent and measured for an unoriented polycrystal having the same composition as the polycrystal.

  Therefore, when the crystal grains constituting the polycrystal are non-oriented, the average degree of orientation Q (HKL) is 0%. Further, when the (HKL) planes of all the crystal grains constituting the polycrystal are oriented parallel to the measurement plane, the average degree of orientation Q (HKL) is 100%.

  In a thermoelectric material having anisotropy corresponding to crystal orientation in thermoelectric properties, the higher the degree of orientation of a specific crystal plane is, the better, in order to obtain a high performance index. Specifically, the plane orientation degree of the specific crystal plane is preferably 50% or more, and more preferably 80% or more.

  When a specific crystal plane is axially oriented, the degree of orientation cannot be defined by the equation (1). However, the average orientation degree (hereinafter referred to as “axial orientation degree”) by the Rotgering method for (HKL) diffraction when X-ray diffraction is performed on a plane perpendicular to the orientation axis is used to determine the axial orientation. The degree can be expressed. In the case of a polycrystal having a specific crystal plane axially oriented, the degree of axial orientation is a negative value. In addition, the degree of axial orientation of a polycrystal whose specific crystal plane is almost completely axially oriented is the same as the degree of axial orientation measured for a polycrystal whose specific crystal plane is almost perfectly plane oriented. .

The specific crystal plane to be oriented is selected optimally according to the type of thermoelectric material. For example, in the case of the complex oxide represented by the formula (1), it is preferable to orient the ab plane (a plane parallel to the AO ₂ layer). For example, in the case of a cobalt layered oxide represented by the formulas (2) to (5), it is preferable to orient the ab plane (a plane parallel to the CoO ₂ layer). Furthermore, it is preferable that the p-type element 12 and the n-type element 14 have their crystal planes oriented in the longitudinal direction. The ab surface of the complex oxide represented by the formula (1) and the ab surface of the cobalt layered oxide represented by the formulas (2) to (5) both have high in-plane electrical conductivity. Therefore, when this is oriented in the longitudinal direction of the p-type element 12 and / or the n-type element 14, the electrical conductivity in the longitudinal direction is increased, and high thermoelectric characteristics are obtained.

Next, a method for manufacturing the single junction element 16 will be described. As a method for manufacturing the single junction element 16 made of various thermoelectric materials, specifically,
(1) A first method of joining a p-type element 12 made of single crystal or polycrystal and an n-type element 14 made of single crystal or polycrystal,
(2) a second method in which a molded body containing a powder of a p-type thermoelectric material and a molded body containing a powder of an n-type thermoelectric material are closely adhered and sintered simultaneously under no pressure or under pressure;
(3) a third method in which a p-type thermoelectric material powder and an n-type thermoelectric material powder are filled in layers in a mold and molded, sintered, or directly sintered;
(4) A combination of the first to third methods described above,
Etc.

  When manufacturing the single junction element 16 using the first method, the p-type element 12 and the n-type element 14 may be directly abutted and joined as they are. Or you may join via a suitable intermediate | middle layer. Further, when the intermediate layer is interposed, the intermediate layer can suppress the diffusion of elements having low reactivity with the p-type element 12 and the n-type element 14 or between the p-type element 12 and the n-type element 14. It is preferable to use one. This point is the same when the second method or the third method is used, and it is preferable to interpose an intermediate layer as necessary.

  When an intermediate layer is interposed between the p-type element 12 and the n-type element 14, an optimal material is selected according to the type of thermoelectric material. For example, when joining oxide thermoelectric materials, the intermediate layer specifically includes a noble metal paste containing a glass component (Ag paste, Au paste), noble metal foil, noble metal paste + noble metal foil, and a small amount of thermoelectric material. It is preferable to use a noble metal paste or the like.

  When oriented polycrystal is used as the p-type element 12 and / or the n-type element 14, the oriented polycrystal can be produced by various methods. For example, in the case of a Bi—Te-based thermoelectric material, an axially oriented polycrystal can be produced by hot extruding non-oriented polycrystal. Alternatively, a plane-oriented polycrystal can be produced by dropping a droplet of Bi—Te-based thermoelectric material on the cooled mold surface.

  In addition, for example, an oriented polycrystal made of an oxide thermoelectric material has an anisotropic shaped powder having a lattice matching with a crystal face having high thermoelectric properties of the oxide thermoelectric material. Then, the second powder that becomes the target oxide thermoelectric material reacts with or without reacting with this anisotropically shaped powder, and this is shaped so that the anisotropically shaped powder is oriented in one direction. It is obtained by sintering the body. Here, the “anisotropic shape” means that the ratio (aspect ratio) of the maximum length of the development surface to the width or thickness of the powder is large, and corresponds to plate shape, needle shape, scale shape and the like.

The anisotropically shaped powder is selected in accordance with the type of oxide thermoelectric material to be produced. For example, when the thermoelectric material is a composite oxide represented by the formula (1) or a material doped with various elements, the anisotropically shaped powder is specifically
(A) A composite oxide represented by the formula (1) or a compound doped with various elements, having the same or different composition as the thermoelectric material to be produced, and having the ab plane as a development plane Plate powder,
(B) A plate-like powder having a structure similar to that of the AO ₂ layer, including an A-site element-containing oxide, hydroxide, etc., and having a specific crystal plane as a development plane (for example, a (001) plane Hexagonal In ₂ O ₃ plate powder having a development plane, In (OH) ₃ plate powder having a (100) plane development),
(C) A plate-like powder having a structure similar to that of the CO layer and made of an oxide or hydroxide containing a C-site element and having a specific crystal plane as a development plane (for example, a (001) plane is developed. ZnO plate-like powder with a surface, basic zinc sulfate plate-like powder with a (001) surface as a development surface),
Etc. are suitable.

Further, for example, when the thermoelectric material is a cobalt layered oxide represented by the formulas (2) to (5) or a material doped with various elements, the anisotropically shaped powder is specifically,
(D) The cobalt layered oxide represented by the formulas (2) to (5) or those doped with various elements, having the same or different composition as the thermoelectric material to be produced, and ab A plate-like powder whose surface is developed,
(E) Co (OH) ₂ plate powder having a {001} plane as a development plane, CoO plate powder having a {111} plane as a development plane, and Co ₃ O ₄ plate having a {111} plane as a development plane Powder, CoO (OH) plate-like powder with {00l} plane as the development plane,
Etc. are suitable.

On the other hand, the composition of the second powder added to the anisotropically shaped powder is determined according to the composition of the thermoelectric material to be produced and the composition of the anisotropically shaped powder. For example, in the case of producing an oriented polycrystal composed of a cobalt layered oxide represented by the formula (1), when using a Co (OH) ₂ plate-like powder having a developed plane of the {001} plane as the anisotropically shaped powder, As the two powders, Ca, alkali metal, alkaline earth metal, Bi and / or an oxide containing C and double oxides, salts, and the like may be used, and these may be blended so as to have a stoichiometric ratio. The same applies to the production of other thermoelectric materials.

  In addition, it is preferable to use a method in which a shearing force acts on the anisotropically shaped powder. For example, when the anisotropically shaped powder is oriented in a plane, specifically, a doctor blade method, a press molding method, a rolling method, an extrusion method (sheet shape) and the like are preferable. For example, when the anisotropically shaped powder is axially oriented, the extrusion method (non-sheet shape) is specifically preferred as the forming method.

  In addition, in order to increase the orientation of the development surface when the anisotropically shaped powder is surface-oriented, a molded body is prepared using a doctor blade (tape casting) method, extrusion method, press molding, etc., and then obtained. The formed body is preferably rolled (roll pressed). Or you may repeat lamination | stacking crimping | compression-bonding and rolling of a sheet-like molded object in multiple times. Furthermore, when the molded body is degreased, the density or the degree of orientation may decrease. In such a case, in order to increase the density or the degree of orientation, a hydrostatic pressure (CIP) treatment may be performed on the molded body after degreasing.

  When such an oriented molded body is sintered, an oriented polycrystal having a crystal face with high thermoelectric properties is obtained. The sintering method is not particularly limited, and various methods such as atmospheric pressure sintering, hot pressing, hot forging, HIP, and plasma sintering (SPS) can be used. Moreover, what is necessary is just to select optimal conditions for sintering conditions according to the kind of thermoelectric material.

  When the single junction element 16 is manufactured, first, the p-type element 12 and the n-type element 14 each made of oriented polycrystal may be produced using the above-described method, and then the produced oriented polycrystal may be joined. . Alternatively, an alignment molded body to be a p-type element and an alignment molded body to be an n-type element may be produced, and these may be brought into close contact and sintered simultaneously. In this case, if the sintering is performed while constraining the periphery of the oriented molded body that is in close contact, and the sintering conditions are optimized, a decrease in the degree of orientation during sintering can be suppressed.

  When thermoelectric power generation is performed by directly contacting a thermal fluid to the single junction element 16 thus obtained, when it is necessary to suppress the reaction between the single junction element 16 and the thermal fluid, the single junction element 16 is used. A protective film is preferably formed on the surface 16.

For example, in the case where a Bi-Te compound is used as the thermoelectric material, when thermoelectric power generation is performed by bringing hot water into direct contact with the junction or end of the single junction element 16, an epoxy resin or the like is used as a protective film. Is preferred.
For example, when a silicon compound is used as the thermoelectric material, when the single junction element 16 is used in a high-temperature oxidizing atmosphere, it is preferable to use silicon oxide, silicon nitride, or the like as the protective film. These protective films can be formed using a known method such as a PVD method, a CVD method, or a sputtering method.

  Next, the operation of the thermoelectric module including the thermoelectric element described above will be described. The p-type element and the n-type element constituting the thermoelectric element are generally made of different thermoelectric materials. Therefore, when thermoelectric power generation is performed with a temperature difference using a U-type thermoelectric element, the p-type element and the n-type element have different coefficients of thermal expansion, so that stress is applied to the joint portions between the materials and the electrodes. Further, when an external force acts on the open end of the U-type thermoelectric element, a large bending moment is generated at the joint.

  The π-type thermoelectric element has a structure in which each element is sandwiched between parallel plates. Therefore, the π-type thermoelectric element not only cannot structurally avoid thermal stress due to the difference in thermal expansion coefficient between the p-type element and the n-type element, but also due to slight variations in processing accuracy between elements, There is a problem that a large thermal stress is generated, the element is damaged, or the contact resistance and the bonding strength of the bonded portion vary.

  On the other hand, in the case of the single-junction element 16 in which the p-type element 12 and the n-type element 14 are joined at the end face in the longitudinal direction, even if an external force acts on this, the bending moment generated at the joint is U-type thermoelectric element. It is much smaller than Further, even when a thermal load is applied to such a single junction element 16, the single junction element 16 only expands and contracts in the longitudinal direction, and thermal shear stress does not act on the joint surface. Therefore, durability and reliability of the thermoelectric module are improved.

  Further, when the length of each single junction element 16 and the length of the p-type element 12 and the n-type element 14 are optimized, the individual single-junction elements are independent of the material of the p-type element 12 and the n-type element 14. The apparent thermal expansion characteristics of 16 can be made substantially equal. Therefore, even when such single-junction elements 16 are arranged in a horizontal row, the upper and lower parts thereof are joined by electrodes, and the upper and lower parts are sandwiched between parallel plates, the individual single-junction elements 16 are uniformly expanded and contracted. However, thermal stress due to the difference in thermal expansion coefficient between the p-type element 12 and the n-type element 14 does not occur. Further, there is no possibility that the element will be damaged or the contact resistance and bonding strength of the bonded portion will not vary due to slight variations in processing accuracy between the elements.

  In addition, when the heat source is a thermal fluid having a small cross-sectional area of the high temperature part (for example, when exposed to a flame or when a high temperature thermal fluid is flowing inside the pipe whose side wall is cooled), the π-type thermoelectric element When thermoelectric power generation is performed using, it is difficult to bring the hot junction close to the heat source or to uniformly heat the hot junction. Therefore, there is a large loss in transferring heat from the heat source to the thermoelectric material installed on the planar electrode, and it is difficult to make a large temperature difference between the hot junction and the cold junction.

  On the other hand, in the single junction element, even when the cross-sectional area of the high temperature portion of the heat source is small, it is easy to install the junction portion or the electrode portion in the high temperature portion. Therefore, a large temperature difference can be provided between the hot junction and the cold junction. Further, if the arrangement of the single junction elements is optimized, the junctions or electrode portions of the single junction elements can be heated evenly.

Furthermore, if spring electrodes are used as the electrodes connected to both ends of the single junction element 16, even if variations in processing accuracy between elements and / or temperature differences occur between the single junction elements 16, Stress can be relaxed.
In addition, when heat exchange means for promoting heat absorption or dissipation is provided at the junction and / or end of the single junction element 16, a thermoelectric module with high thermoelectric conversion efficiency can be obtained. In addition, if a separator that blocks heat is provided in the middle of the p-type element and / or the n-type element, the temperature rise of the cold junction due to convection or radiation is suppressed, and a large temperature is generated between the hot junction and the cold junction. Differences can be generated.

  Further, when an oxide thermoelectric material is used for one of the p-type element 12 and the n-type element 14, the characteristic deterioration of the single junction element 16 due to oxidation is small. In particular, when an oxide thermoelectric material is used for both the p-type element 12 and the n-type element 14, it is not necessary to cover the surface even when used in a high-temperature atmosphere, and it has excellent heat resistance and oxidation resistance. A single junction element 16 is obtained. Therefore, when such a single junction element is used, a low-cost and highly reliable thermoelectric module can be obtained.

  Furthermore, when oriented polycrystal is used as the p-type element 12 and / or the n-type element 14, the thermoelectric performance is improved as compared with the case where non-oriented polycrystal is used. In particular, when each of the p-type element 12 and the n-type element 14 is an oriented polycrystal having crystal faces with high thermoelectric properties oriented in the longitudinal direction, high thermoelectric performance can be obtained.

  Next, a specific example of a thermoelectric module using the above-described thermoelectric element will be described. FIG. 2 shows a schematic configuration diagram of the thermoelectric module according to the first embodiment. In FIG. 2, the thermoelectric module 50 includes a thermoelectric element 40 a, a support frame 52, a heat radiating plate 54, and a separator 56.

  The thermoelectric element 40a includes a plurality of single-junction elements 16, 16... In which the p-type element 12 and the n-type element 14 are joined at the end faces in the longitudinal direction. The single junction elements 16, 16... Are connected in series by spring electrodes 30, 30 so that the p-type elements 12 and the n-type elements 14 are alternately connected. Further, both ends of the single junction elements 16, 16... Connected in series are connected to the terminals 22 and 24 via the spring electrodes 30, respectively.

  The support frame 52 includes a U-shaped base 52a and heat dissipation blocks (copper blocks) 52b and 52b provided on the left and right lower surfaces of the base 52a. Both ends of each single-junction element 16, 16... Are fitted in a concave groove provided on the lower surface of the base 52a, and are sandwiched between heat radiation blocks 52b and 52b. Further, the spring electrodes 30, 30... Are fixed to both side surfaces of the base 52a, and the both end surfaces of the single junction elements 16, 16.

  On the left and right upper surfaces of the support frame 52, heat radiating plates 54, 54 are provided for cooling the electrode portions of the single junction elements 16, 16,. The heat radiating plates 54 and 54 are provided with a large number of heat radiating fins 54a and 54a, respectively, to promote heat radiation from the electrode portions.

  The separator 56 is formed of a hollow rectangular tube that is open at the top and bottom, and is inserted from above the U-shaped support frame 52 toward the opening. The separator 56 is used to block heat convection and / or radiation between the junctions of the single junction elements 16, 16... And the electrode portions at both ends. The height of the separator 56 is higher than the height of the heat sink 54. Therefore, the separator 56 suppresses that the heat sink 54 is heated by the thermal fluid when the thermal fluid is introduced into the junction of the single junction elements 16, 16... Along the arrow direction of FIG. It also has a function to do.

  Next, the operation of the thermoelectric module 50 shown in FIG. 2 will be described. When the thermoelectric module 50 is used for thermoelectric power generation, a load is connected to the terminals 22 and 24. Next, the junction of the single junction elements 16, 16... Is exposed to a flame, or hot air is introduced in the direction of the arrow in FIG. When the junction is heated, a temperature difference is generated between the junction and the electrode, and an electromotive force is obtained. At this time, the current flows in the direction from the p-type element 12 to the n-type element 14.

  When the thermoelectric module 50 is used for thermoelectric heating / cooling, a DC power source is connected to the terminals 22 and 24. When the terminal 22 is connected positively, current flows in the direction of the n-type element 14 → p-type element 12 at the junction of each single junction element 16, 16,... On the contrary, when the terminal 22 is connected to minus, current flows in the direction from the p-type element 12 to the n-type element 14 at the junction, so that the junction is heated. Therefore, if a heat exchange medium (for example, air) is passed in the direction of the arrow in FIG. 1A, the heat exchange medium can be heated or cooled.

  The thermoelectric module 50 according to the present embodiment uses spring electrodes 30, 30... To electrically connect the single junction elements 16, 16. Therefore, even if the bonding portion or the electrode portion is heated and the single bonding elements 16, 16... Expand, the thermal stress is relieved by the spring electrodes 30, 30. Further, thermal shear stress is not generated at the joint portion of the single junction elements 16 and 16, and even when an external force is applied, a large bending moment is not generated at the joint portion. Furthermore, since the separator 56 that thermally blocks between the joint portion and the electrode portion is provided, a larger temperature difference can be generated between the joint portion and the electrode portion.

  Next, a thermoelectric module according to the second embodiment will be described. In FIG. 3, the schematic block diagram of the thermoelectric module which concerns on this Embodiment is shown. In FIG. 3, the thermoelectric module 60 includes a thermoelectric element 40, a medium introduction path 62, and a heat radiating plate 64.

  As shown in FIG. 3B, the thermoelectric element 40 includes a plurality of single-junction elements 16, 16... In which the p-type element 12 and the n-type element 14 are joined at the end faces in the longitudinal direction. Each single junction element 16, 16... Is connected to electrodes 18 and 20 so that p-type element 12 and n-type element 14 are alternately connected. It should be noted that the electrodes 18 and 20 may be integrally joined to the single junction elements 16, 16... Or may be spring electrodes. Further, both ends of the single junction elements 16, 16... Connected in series are connected to terminals 22 and 24, respectively.

  Both ends of each single-junction element 16, 16 ... are supported on the inner surface of the upper wall and the inner surface of the lower wall of the tubular medium introduction path 62, respectively. Further, it is the upper wall outer surface of the medium introduction path 62 and above the portion where the upper ends of the single junction elements 16, 16... Are supported, and the lower wall outer surface of the medium introduction path 62. Radiating plates 64, 64 are provided below the portions where the lower ends of the elements 16, 16 ... are supported, respectively.

  Further, the heat dissipation plates 64, 64 provided in the vicinity of the thermoelectric elements 40, 40... And their electrode portions are respectively along the longitudinal direction of the medium introduction path 62, as shown in FIG. A plurality are provided. In this case, the plurality of thermoelectric elements 40, 40... May be connected via the terminals 22, 24 so as to be connected in series with each other, or may be connected in parallel with each other. The terminals 22 and 24 may be connected.

  Next, the operation of the thermoelectric module 60 shown in FIG. 3 will be described. When the thermoelectric module 60 is used for thermoelectric power generation, a load is connected to the terminal of the thermoelectric element 40. Next, along the direction of the arrow in FIG. 3A, the thermal fluid is introduced into the medium introduction path 62, and the refrigerant is allowed to flow outside the medium introduction path 62. Alternatively, the refrigerant is caused to flow inside the medium introduction path 62 and the thermal fluid is caused to flow outside the medium introduction path 62. When the joining portion or the electrode portion is heated by the thermal fluid, a temperature difference is generated between the joining portion and the electrode portion, and an electromotive force is obtained. For example, when a thermal fluid is introduced into the medium introduction path 62, the current flows in the direction of the p-type element 12 → n-type element 14.

  When the thermoelectric module 60 is used for thermoelectric heating / cooling, a DC power supply is connected to the terminal. In this case, when a current is passed in the direction of n-type element 14 → p-type element 12, the junction is cooled, and when a current is passed in the direction of p-type element 12 → n-type element 12, the junction is heated. Therefore, if a heat exchange medium (for example, air) is introduced into the medium introduction path 62 in the direction of the arrow in FIG. 3A, the heat exchange medium can be heated or cooled.

  Each single-junction element 16, 16... Appears to have substantially the same thermal expansion characteristics by optimizing its length and the lengths of the p-type element 12 and the n-type element 14. Therefore, as shown in FIG. 3B, even if both ends of the single junction elements 16, 16... Are constrained, a large thermal stress is generated only in some of the single junction elements 16 during use. There is nothing to do. In addition, there is no possibility that only a part of the elements will be damaged or the contact resistance and bonding strength of the bonding part will vary.

  Further, generally, when a thermal fluid is caused to flow inside the tubular medium introduction path 62, the thermal fluid is cooled from the wall surface. As a result, a temperature gradient is generated inside the medium introduction path 62, and the high temperature portion is concentrated at the center of the tube. On the other hand, since the thermoelectric module 60 according to the present embodiment uses the rod-like single junction elements 16, 16,..., The junction can be easily arranged at the center of the tube. Therefore, even when such a heat source having a small cross-sectional area of the high temperature part is used, a large temperature difference can be generated between the joint part and the electrode part, and high efficiency can be obtained.

  Next, a thermoelectric module according to the third embodiment will be described. In FIG. 4, the schematic block diagram of the thermoelectric module which concerns on this Embodiment is shown. In FIG. 4, the thermoelectric module 70 includes a thermoelectric element 40 and a heat exchanger 72.

  The heat exchanger 72 includes a base portion 72a and heat radiation fins 72b, 72b,... Provided on the base portion 72a at equal intervals. The base 72a serves as a heat source or a cooling source, and its structure is not particularly limited. That is, the base 72a may be a solid body made of a material having high thermal conductivity, or may be a hollow body into which a heat exchange medium can be introduced.

  The thermoelectric element 40 includes a plurality of single-junction elements 16, 16... In which the p-type element 12 and the n-type element 14 are joined at the end faces in the longitudinal direction. The single junction elements 16, 16... Are connected in series by electrodes 18, 20 so that the p-type elements 12 and the n-type elements 14 are alternately connected. It should be noted that the electrodes 18 and 20 may be integrally joined to the single junction elements 16, 16... Or may be spring electrodes.

  Further, in the present embodiment, the thermoelectric elements 40, 40... Are inserted between the radiation fins 72b, 72b, and supported by the radiation fins 72b, 72b. Further, the thermoelectric elements 40, 40,... Supported by the radiation fins 72b, 72b are connected in series via terminal electrodes so that the p-type element 12 and the n-type element 14 are alternately connected. Has been. Further, both ends of the thermoelectric elements 40, 40... Connected in series are connected to terminals 22 and 24, respectively.

Next, the operation of the thermoelectric module 70 shown in FIG. 4 will be described. When the thermoelectric module 70 is used for thermoelectric power generation, a load is connected to the terminals 22 and 24. Next, the base 72a is brought into contact with a high-temperature heat source, or a thermal fluid is introduced into the base 72a. When the base portion 72a is heated, the heat radiation fins 72b, 72b... Are heated by heat conduction, and the electrode portions of the thermoelectric elements 40, 40. As a result, a temperature difference is generated between the joining portion and the electrode portion, and an electromotive force is obtained. In this case, the current flows in the direction from the n-type element 14 to the p-type element 12.
On the contrary, if the radiation fins 72b and 72b are exposed to a high temperature atmosphere and the base 72b is cooled, an electromotive force is generated, and a current flows in the opposite direction to the above.

  When the thermoelectric module 70 is used for thermoelectric heating / cooling, a DC power source is connected to the terminals 22 and 24. In this case, when a current is passed in the direction from the n-type element 14 to the p-type element 12, the junction is cooled and the electrode is heated. On the other hand, when a current is passed in the direction from the p-type element 12 to the n-type element 12, the junction is heated and the electrode is cooled. Therefore, an object such as a heat exchange medium can be heated or cooled via the base 72a or the joint.

  Since the thermoelectric module 70 shown in FIG. 4 uses the single junction elements 16, 16..., The thermal expansion coefficient difference between the p-type element 12 and the n-type element 14 is different even when both ends thereof are constrained. The resulting thermal stress can be reduced. Moreover, since it is excellent in impact resistance against external force and no thermal shear stress is generated in the joint, it is excellent in durability and reliability. Furthermore, since the joint can be directly exposed to a flame, or a thermal fluid can be brought into direct contact with the joint, higher efficiency can be obtained as compared with a thermoelectric module using a conventional thermoelectric element.

(Example 1)
(1) Production of Ca ₃ Co ₄ O ₉ (CCO) Oriented Polycrystal Co (OH) ₂ plate powder was synthesized according to the following procedure. First, a 0.1 mol / l CoCl ₂ aqueous solution and a 0.4 mol / l NaOH aqueous solution were prepared. Subsequently, 300 ml of NaOH aqueous solution was dripped at a rate of 100 ml / h with respect to 600 ml of CoCl ₂ aqueous solution. This produced a blue precipitate (Co (OH) ₂ ) in the solution.

After the dropwise addition of the NaOH aqueous solution, the solution was stirred while bubbling with N ₂ and aged for 24 hours at room temperature to obtain pink crystals (Co (OH) ₂ ). The crystals were filtered with suction and dried at room temperature with N ₂ gas for 24 hours. The Co (OH) ₂ powder obtained in this example was a plate-like powder having a hexagonal shape. The average particle size of the plate-like powder was 0.5 μm, and the average aspect ratio was about 5.

Next, toluene and absolute ethanol were added to the synthesized Co (OH) ₂ plate-like powder and CaCO ₃ powder (average particle size 0.2 μm), and wet-mixed for 24 hours. After mixing, a binder (polyvinyl butyral) and a plasticizer (butyl phthalate) were added to the slurry, and further wet-mixed for 3 hours with a ball mill.

Next, the slurry was taken out of the pot and formed into a sheet having a thickness of about 100 μm by tape casting. Furthermore, the obtained sheet | seat was piled up and it pressure-bonded on the conditions of temperature: 80 degreeC and pressure: 100kg / cm < ² > (9.8MPa). Furthermore, the laminate was subjected to a rolling process. The rolling temperature was room temperature and the rolling reduction was 30%.

Next, the molded body was degreased in the atmosphere under the conditions of temperature: 700 ° C. and heating time: 2 hours. Next, the compact after degreasing was pressure-molded (hydrostatic pressure treatment) under the condition of pressure: 3 ton / cm ² (294 MPa). Further, this compact was hot-pressed in oxygen under the conditions of temperature: 920 ° C., heating time: 48 hr, applied pressure: 100 kg / cm ² (9.8 MPa), and an oriented polycrystal composed of CCO was obtained. .

(2) Preparation of In ₂ O ₃ (ZnO) ₃ (Z ₃ IO) Oriented Polycrystalline Plate-like powder of basic zinc sulfate (ZnSO ₄ .3Zn (OH) ₂ .nH ₂ O) (average particle size: 2 to 2) Toluene and ethanol were added to 10 μm, aspect ratio: 8 to 15), and In ₂ O ₃ powder (average particle size: 1.0 μm), and mixed by a ball mill for 5 hours. After the mixing was completed, a binder (polyvinyl butyllar) and a plasticizer (di-n-butyl phthalate) were further added to the slurry, and further mixed for 1 hour.

The obtained slurry was formed into a tape shape having a thickness of about 200 μm using a doctor blade method. About 80 sheets of this tape were stacked to a thickness of about 16 mm, and this was pressure-bonded at a temperature of 80 ° C. to obtain a plate-shaped molded body. Subsequently, the molded body was heated to 800 ° C. at a heating rate of 30 ° C./h, and heat treatment was performed at 800 ° C. for 30 minutes. Next, the molded body after the heat treatment was subjected to cold isostatic pressing (CIP) treatment to increase the material density, and then calcined in the atmosphere at 1150 ° C. for 12 hours. Further, this was sintered in the atmosphere at 1300 ° C. for 24 hours to obtain oriented polycrystals composed of Z ₃ IO.

(3) Production of CCO-Z ₃ IO Single Junction Element A prismatic CCO element (2 mm × 3.5 mm × 2) having a longitudinal direction parallel to the tape surface is obtained from the CCO oriented polycrystal and the Z ₃ IO oriented polycrystal. 18 mm) and Z ₃ IO elements (2 mm × 3.5 mm × 18 mm) were cut out. Ag paste was applied to one end face of the prism, and the CCO element and the Z ₃ IO element were butted at the end face to perform bonding. The joining conditions were temperature: 900 ° C. and heating atmosphere: in air. A conductive film made of indium solder is formed on the entire surface of both end faces of the obtained joined body, and further an insulating film made of polyimide having a thickness of about 50 μm is formed on the side face in the vicinity of the both ends, to obtain a CCO-Z ₃ IO single junction element Got.

(4) Production of thermoelectric module The thermoelectric module shown in FIG. 2 was produced using a total of seven CCO-Z ₃ IO single junction elements.

(Comparative Example 1)
According to the same procedure as in Example 1, prismatic CCO elements (2 mm × 3.5 mm × 18 mm) and Z ₃ IO elements (2 mm × 3.5 mm × 18 mm) were produced. Next, a metal electrode made of Pt with a thickness of 0.1 mm was joined to the upper end surfaces of the CCO element and the Z ₃ IO element to produce a π-type element. Next, a total of seven π-type elements are connected in series with a metal electrode made of Pt and having a thickness of 0.1 mm so that the CCO elements and the Z ₃ IO elements are alternately joined, and the upper and lower ends thereof are connected to each other. It was sandwiched between a pair of parallel flat plates made of AlN. Furthermore, a heat sink was connected to the flat plate on the upper end side to obtain a π-type module.

Thermoelectric power generation was performed using the thermoelectric module obtained in Example 1 and the π-type module obtained in Comparative Example 1. In the case of Example 1, with an alcohol lamp with a Atsumarien nozzle was heated junction of CCO-Z 3 _IO single junction devices. On the other hand, in the case of Comparative Example 1, the flat plate on the lower end side of the π-type module was heated using an alcohol lamp without a flame collecting nozzle.

In the case of the π-type module obtained in Comparative Example 1, the high temperature part temperature: Th = 320 ° C., the low temperature part temperature: Tc = 120 ° C., and the temperature difference ΔT between the high temperature part and the low temperature part was about 200 ° C. . The electromotive force was 0.3 V, the maximum current value was 250 mA, and the maximum output density was 20 mW / cm ² .

On the other hand, in the case of the thermoelectric module obtained in Example 1, the high temperature part temperature: Th = 630 ° C., the low temperature part temperature: Tc = 30 ° C., and the temperature difference ΔT between the high temperature part and the low temperature part is about 600 ° C. Met. The electromotive force was 1.06 V, the maximum current value was 900 mA, and the maximum output density was 240 mW / cm ² . The high power density was obtained by the thermoelectric module according to the present invention. (1) By using the CCO-Z ₃ IO single junction element, it was possible to efficiently recover heat from a heat source having a small cross section of the high temperature part. (2) By using the separator, it is considered that overheating of the cold junction and the heat sink of the CCO-Z ₃ IO single junction element due to heat convection and radiation was suppressed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  The thermoelectric module according to the present invention includes a solar thermoelectric generator, a seawater temperature difference thermoelectric generator, a fossil fuel thermoelectric generator, various thermoelectric generators such as a regenerative generator for factory exhaust heat and automobile exhaust heat, a light detection element, and a laser diode. , Field effect transistors, photomultiplier tubes, spectrophotometer cells, chromatographic columns and other precision temperature control devices, thermostats, air conditioners, refrigerators, watch power supplies, and the like.

  In addition, the thermoelectric module according to the present invention is a thermoelectric generator that uses a thermal fluid discharged from an exhaust system such as an engine, a water heater, an air conditioner, or an industrial furnace as a heat source, and a temperature difference between hot water and cold water in a hot spring. It can be used as a utilized thermoelectric generator.

FIG. 1A is a schematic configuration diagram illustrating a first specific example of a thermoelectric element provided in a thermoelectric module according to the present invention, FIG. 1B is a schematic cross-sectional view of a spring electrode, and FIG. FIG. 3 is a schematic configuration diagram illustrating a second specific example of a thermoelectric element. 2A is a front view of the thermoelectric module according to the first embodiment of the present invention, FIG. 2B is a bottom view thereof, FIG. 2C is a right side view thereof, FIG. d) is a plan view thereof. FIG. 3A is a perspective view of a thermoelectric module according to the second embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along line A-A ′. It is a schematic block diagram of the thermoelectric module which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

10, 40, 40a Thermoelectric element 12 P-type element 14 N-type element 16 Single junction element 18 First electrode 20 Second electrode 30 Spring electrodes 50, 60, 70 Thermoelectric module

Claims (7)

at least one single-junction element in which at least one p-type element made of a p-type thermoelectric material and at least one n-type element made of an n-type thermoelectric material are joined alternately at a longitudinal end face;
A first electrode connected to one end of the single junction element;
A thermoelectric module comprising a thermoelectric element including a second electrode connected to the other end of the single junction element. At least one of the first electrode and the second electrode is
A probe for bringing its tip into contact with the end of the single junction element;
2. The thermoelectric module according to claim 1, further comprising an urging unit for urging the probe toward an end of the single junction element.   The thermoelectric module according to claim 1, further comprising heat exchange means for promoting absorption or dissipation of heat at a junction and / or an end of the single junction element. The thermoelectric element comprises two or more single junction elements,
The single junction element is connected in series via the first electrode and / or the second electrode so that the p-type element and the n-type element are alternately connected. The thermoelectric module according to any one of the above.   The thermoelectric module according to any one of claims 1 to 4, further comprising a separator for interrupting heat provided in the middle of the p-type element and / or in the middle of the n-type element.   The thermoelectric module according to claim 1, wherein at least one of the p-type thermoelectric material and the n-type thermoelectric material is an oxide thermoelectric material. 7. At least one of the p-type element and the n-type element is made of oriented polycrystal having a crystal face with high thermoelectric characteristics oriented in one direction, and the longitudinal direction thereof is a direction with high thermoelectric characteristics. The thermoelectric module as described in any of the above.

Images