JP7050467B2 - Thermoelectric conversion element, thermoelectric conversion module, and mobile body - Google Patents

Description

The present invention relates to a thermoelectric conversion element, a thermoelectric conversion module, and a mobile body.

For example, in Patent Document 1, a p-type thermoelectric conversion material portion 112 having a p-type thermoelectric conversion material and an n-type thermoelectric conversion material portion 111 having an n-type thermoelectric conversion material are directly joined to form a U-shaped cross section. The thermoelectric conversion element is disclosed (see FIG. 9). The p-type thermoelectric conversion material unit 112 and the n-type thermoelectric conversion material unit 111 of the U-shaped thermoelectric conversion element are both square columnar members, and one end side portions of the square columnar members in the height direction of the side surfaces facing each other are connected to each other. Is directly joined to form a joined portion 121, and the other end side portion is separated to form a slit 131.

Japanese Patent No. 3949848

Since the thermoelectric conversion element receives vibration or shock during mounting, etc., or is placed in a thermal cycle environment during use, etc. and receives thermal stress, cracks are likely to occur in the joint portion, and when the joint portion is separated, thermoelectric conversion is performed. There is a problem that the thermodynamic performance of the conversion element is lost. In particular, in the case of a usage mode in which the thermoelectric conversion element uses heat from a specific direction to generate electricity, a large temperature distribution may occur in the joint portion, and the thermal stress may cause damage to the joint portion. ..
INDUSTRIAL APPLICABILITY The present invention is a thermoelectric conversion element in which the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion is less likely to be damaged even in the case of a usage form in which heat is generated from a specific direction. , A thermoelectric conversion module, and a moving body.

The thermoelectric conversion element according to one aspect of the present invention is a thermoelectric conversion element in which a p-type thermoelectric conversion material portion having a p-type thermoelectric conversion material and an n-type thermoelectric conversion material portion having an n-type thermoelectric conversion material are joined. The p-type thermoelectric conversion material section and the n-type thermoelectric conversion material section are both rod-shaped members, and one side surface of the p-type thermoelectric conversion material section and the n-type thermoelectric conversion material section face each other and face each other on both sides. Of these, only one end side portion in the height direction of the rod-shaped member is joined, and the joint portion between the opposite side surfaces is the height direction of the rod-shaped member when one side surface of the opposite side surfaces is viewed from the front. The gist is that the length of the rod-shaped member in the direction parallel to the height direction differs between the one end side and the other end side in the direction orthogonal to the above.

The gist of the thermoelectric conversion module according to another aspect of the present invention is to include the thermoelectric conversion element according to the above one aspect.
It is a gist that the mobile body according to still another aspect of the present invention is equipped with the thermoelectric conversion module according to the other aspect.

According to the present invention, even in the case of a usage mode in which heat is generated from a specific direction, the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion of the thermoelectric conversion element is damaged. Is unlikely to occur.

It is a perspective view which shows typically the structure of one Embodiment of the thermoelectric conversion element which concerns on this invention. It is sectional drawing explaining the main part of the thermoelectric conversion element of FIG. It is a perspective view which shows typically the structure of the thermoelectric conversion element of the modification. It is sectional drawing explaining the main part of the thermoelectric conversion element of FIG. It is a figure which shows the example of the shape of the shape of the joint part of the p-type thermoelectric conversion material part and the n-type thermoelectric conversion material part. It is sectional drawing which shows typically the operation effect of the thermoelectric conversion element of FIGS. 1 to 4, while comparing with the conventional thermoelectric conversion element. It is a figure which shows typically the structure of one Embodiment of the thermoelectric conversion module which concerns on this invention. It is a perspective view which shows typically the structure of the conventional thermoelectric conversion element.

An embodiment of the present invention will be described in detail below. It should be noted that the present embodiment shows an example of the present invention, and the present invention is not limited to the present embodiment. In addition, various changes or improvements can be added to the present embodiment, and the embodiment to which such changes or improvements are added can also be included in the present invention.

In the thermoelectric conversion element of the present embodiment, as shown in FIG. 1, a p-type thermoelectric conversion material unit 12 having a p-type thermoelectric conversion material and an n-type thermoelectric conversion material unit 11 having an n-type thermoelectric conversion material are joined to each other. The p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are rod-shaped members, and one side surface of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11. They face each other, and only one end of the rod-shaped member in the height direction of the facing surfaces is joined. The joint portion 21 between the opposite side surfaces is a rod-shaped member having one end side and the other end side in a direction orthogonal to the height direction of the rod-shaped member when one side surface of the opposite side surfaces is viewed from the front. The shapes are different in length in the direction parallel to the height direction.

More specifically, the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are square columnar members having the same shape, and one side surface of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 is connected to each other. , The outer edges are aligned and facing each other. Then, of the facing side surfaces, only one end side portions of the columnar members in the height direction (in the example of FIG. 1, the upper end side portions of the columnar members) are directly joined to each other without using electrodes or the like. 21 is formed, and the other end side portion in the height direction of the columnar member (in the example of FIG. 1, the lower end side portion of the columnar member) is separated to form the slit 31. Therefore, the thermoelectric conversion element of FIG. 1 is formed in a U-shaped cross section as a whole. The method of joining the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 is not particularly limited as long as they are physically and electrically connected.

Next, the joint portion 21 of the p-type thermoelectric conversion material portion 12 and the n-type thermoelectric conversion material portion 11 will be described in detail with reference to FIGS. 1 and 2. FIG. 2 is a schematic view in which the p-type thermoelectric conversion material portion 12 and the n-type thermoelectric conversion material portion 11 are separated at the joint portion 21 and the side surface of the p-type thermoelectric conversion material portion 12 including the joint portion 21 is viewed from the front. ..

In FIG. 2, the joint portion 21 has the following shape. That is, the joint portion 21 is in the height direction of the rod-shaped member at one end side and the other end side in the direction (horizontal direction in FIG. 2) orthogonal to the height direction of the rod-shaped member (vertical direction in FIG. 2). They have different shapes in parallel directions. As can be seen from FIG. 2, the length b on the other end side (right side in FIG. 2) is larger than the length a on one end side (left side in FIG. 2) in the direction orthogonal to the height direction of the rod-shaped member. long. In other words, the front view shape of the joint portion 21 is trapezoidal, and the two bases having different lengths are the one end side side and the other end side side of the joint portion 21.

The front view shape of the joint portion 21 is not limited to the trapezoidal shape, and if the length is different between the one end side and the other end side in the direction orthogonal to the height direction of the rod-shaped member, the other shape is used. But it doesn't matter. For example, the front view shape of the joint portion 21 may be a right triangle as shown in FIGS. 3 and 4. In the case of the modified examples shown in FIGS. 3 and 4, the length a on one end side (left side in FIG. 4) in the direction orthogonal to the height direction of the rod-shaped member is zero.

Alternatively, it may be arcuate as shown in FIG. 5 (c). In the case of the modification shown in FIG. 5 (c), the length a on one end side (left side in FIG. 5) in the direction orthogonal to the height direction of the rod-shaped member is zero. The arc shape means the shape of the portion between the two points on the curve.

As described above, the front view shape of the joint portion 21 is not particularly limited as long as the length is different between the one end side and the other end side in the direction orthogonal to the height direction of the rod-shaped member. As shown collectively in FIGS. 5A, 5B, and 5C, various shapes such as a triangle such as a right triangle, a trapezoid, and an arc can be taken.

The shape of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 is not limited to a square columnar shape and may be another columnar shape, for example, a polygonal columnar shape such as a triangular columnar column or a hexagonal columnar column. It may be columnar or semi-cylindrical. Further, any columnar shape such as a polygonal columnar column, a columnar column, or a semi-cylindrical column may be used, and it may be either a right-angled columnar column or an oblique columnar column. Further, the shapes of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 may be formed as long as they can be joined to form a thermoelectric conversion element, for example, a pyramid, a frustum, a cone, or a cone. It may be trapezoidal or ellipsoidal. Further, the shapes of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 do not have to be the same.

Of both ends of the p-type thermoelectric conversion material portion 12 and the n-type thermoelectric conversion material portion 11, the end portion on the side where the joint portion 21 exists (the upper end portion in the example of FIG. 1) is used as the high temperature side end portion, and the slit is formed. The end portion on the side where 31 is present (the lower end portion in the example of FIG. 1) is defined as the low temperature side end portion. Electrodes and wiring are connected to the low temperature side end using a joining method such as solder or metal paste. Then, if a temperature difference is provided between the high temperature side end portion and the low temperature side end portion by heating the high temperature side end portion or the like, power can be generated by the thermoelectric action of the thermoelectric conversion element. The thermoelectric conversion element of this embodiment can be used, for example, for waste heat power generation. The source of waste heat is not particularly limited, but examples thereof include moving objects such as automobiles, trains, aircraft, and ships. In addition, waste heat generated in industrial and consumer processes such as factories, incinerators, and power plants can also be used.

Although the thermoelectric conversion element of the present embodiment is a U-shaped thermoelectric conversion element, as described above, it has a structure different from that of the conventional U-shaped thermoelectric conversion element. That is, in the case of the conventional U-shaped thermoelectric conversion element shown in FIG. 8, the front view shape of the joint portion 121 of the p-type thermoelectric conversion material portion 112 and the n-type thermoelectric conversion material portion 111 is shown in FIG. As shown in the above, it is rectangular, and the length on one end side and the length on the other end side in the direction orthogonal to the height direction of the rod-shaped member (vertical direction in FIG. 6) are the same. On the other hand, in the thermoelectric conversion element of the present embodiment, as described above, the front view shape of the joint portion 21 of the p-type thermoelectric conversion material portion 12 and the n-type thermoelectric conversion material portion 11 is in the height direction of the rod-shaped member. The shape is such that the length on the one end side and the length on the other end side in the direction orthogonal to the above are different.

Due to such a difference in structure, the thermoelectric conversion element of the present embodiment is a p-type thermoelectric conversion material unit 12 of the thermoelectric conversion element even in the case of a usage mode in which heat is generated from a specific direction. It has an excellent property that the joint portion 21 of the n-type thermoelectric conversion material portion 11 is less likely to be damaged. Therefore, the thermoelectric conversion element of the present embodiment is less likely to lose its thermoelectric performance than the conventional U-shaped thermoelectric conversion element shown in FIG. The mechanism by which the thermoelectric conversion element of the present embodiment has such characteristics will be described in detail later.

Further, since the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are directly bonded without using an electrode, the p-type thermoelectric conversion material unit and the electrode and between the p-type thermoelectric conversion material unit and the electrode, and n-type thermoelectric conversion. In some cases, the compound layer is not formed at the interface between the material part and the electrode, or there is no large difference in the coefficient of linear expansion between the thermoelectric conversion material part and the electrode. Therefore, even if the thermoelectric conversion element is used in such a way that a high load acts on the thermoelectric conversion element, such as heating the thermoelectric conversion element with an open flame and then cooling it with water, the thermoelectric conversion element is unlikely to be cracked or damaged. Highly durable. Further, since the resistance value at the junction interface between the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 becomes almost zero, the amount of power generation can be increased and the power generation efficiency can be improved. Moreover, since the number of parts can be reduced, the assembly cost can be reduced.

In addition, at least one of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 may be provided with a through hole or a bottomed hole that opens to a surface other than one side surface to be joined. If a through hole or a bottomed hole is provided so that the temperature difference between the high temperature side end portion and the low temperature side end portion becomes large at the time of use, the thermoelectric performance of the thermoelectric conversion element can be improved. At least one of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 may be provided with either a through hole or a bottomed hole, or both may be provided. Further, the number of through holes and bottomed holes may be one or a plurality.

Here, a mechanism in which the thermoelectric conversion element of the present embodiment has an excellent characteristic that "the joint portion 21 is less likely to be damaged" will be described in detail with reference to FIG. FIG. 3B shows a conventional U-shaped thermoelectric conversion element, but the height of the rod-shaped member when the side surface of the p-type thermoelectric conversion material section 112 facing the n-type thermoelectric conversion material section 111 is viewed from the front. When the thermoelectric conversion element is heated from one side (lower side in the example of FIG. 3) orthogonal to the direction using a heat source such as a flame 150, the temperature of the thermoelectric conversion element changes in order from the side closer to the heat source to the side farther from the heat source. As the temperature rises, a large temperature distribution is generated at the joint portion 121 of the front view rectangle.

More specifically, in the example of FIG. 3B, the temperature of the joint portion 121 is the highest in the lower corner portion heated by the flame 150, and the temperature is concentrically formed with the lower corner portion as the base point. A distribution occurs, with the upper corner at the diagonal of the lower corner being the coldest. In FIG. 3B, the temperature distribution is shown by the broken line.

On the other hand, FIG. 3A shows the thermoelectric conversion element of the present embodiment, but when the side surface of the p-type thermoelectric conversion material unit 12 facing the n-type thermoelectric conversion material unit 11 is viewed from the front, (a) of FIG. Similar to the example of b), even if the thermoelectric conversion element is heated by using a heat source such as a flame 50 from one side (lower side in the example of FIG. 3) in the direction orthogonal to the height direction of the rod-shaped member, the front view A large temperature distribution does not occur at the joint portion 21 of the right triangle.

More specifically, even in the example of FIG. 3A, the temperature of the joint portion 21 is the highest at the lower corner portion heated by the flame 50, and the temperature is concentrically circular with the lower corner portion as the base point. Distribution occurs, and the hypotenuse of the right triangle facing the lower corner is the coldest. Also in FIG. 3A, the temperature distribution is shown by the broken line. From the comparison between (a) and (b) of FIG. 3, although the temperature distribution is generated in both cases, even if the joint portion 21 and the joint portion 121 have the same area, considering the number of broken lines indicating the temperature distribution. It can be seen that the thermoelectric conversion element of the present embodiment is less likely to generate a large temperature distribution than the conventional thermoelectric conversion element.

Therefore, even in the case of the usage mode in which the thermoelectric conversion element of the present embodiment uses heat from a specific direction to generate electricity, the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are joined. Since a large temperature distribution is unlikely to occur in the portion 21, the joint portion 21 is unlikely to be damaged by the thermal stress.

However, in order to exhibit the above-mentioned excellent characteristics when the thermoelectric conversion element of the present embodiment uses heat from a specific direction to generate electricity, the heat from the specific direction is on the high temperature side of the thermoelectric conversion element. Must be received at the "specific part" of the end. That is, it is necessary to receive heat from a specific direction in a portion where a large temperature distribution is unlikely to occur in the joint portion 21. This "specific part" is as follows.

As described above, when the side surface of the p-type thermoelectric conversion material portion 12 including the joint portion 21 is viewed from the front, the joint portion 21 is formed on one end side and the other end side in the direction orthogonal to the height direction of the rod-shaped member. , The length in the direction parallel to the height direction of the rod-shaped member is different, but the length in the direction parallel to the height direction of the rod-shaped member is longer among the one end side and the other end side of the joint portion 21. In one part, it is necessary to receive heat from a specific direction. That is, in the case of FIG. 2, since the length b is longer than the length a, it is necessary to receive heat from a specific direction at the right side portion in FIG. 2 of the high temperature side end portion. Therefore, in FIG. 6A, the joint portion 21 has a shape in which the lower end side has a longer length in the direction parallel to the height direction of the rod-shaped member than the upper end side in FIG. The lower portion of the high temperature side end in FIG. 6 is heated by the flame 50.

Therefore, the thermoelectric conversion element of the present embodiment can be suitably used for a thermoelectric conversion module that generates electricity by using a heat source that generates heat in one direction such as a flame. A thermoelectric conversion module configured by using the thermoelectric conversion element of the present embodiment will be described. For example, in the thermoelectric conversion module 60 shown in FIG. 7, the thermoelectric conversion element of the present embodiment shown in FIG. 1 or 3 is electrically connected in series with the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11. It is provided with a low temperature side wiring 42, a low temperature side insulating substrate 41 for fixing the thermoelectric conversion element and the low temperature side wiring 42, and terminals 43 and 43 for taking out electric power.

In the thermoelectric conversion module 60 of the present embodiment, as shown in FIG. 7, a plurality of thermoelectric conversion elements are arranged in an annular shape, and the low temperature side end of the p-type thermoelectric conversion material portion 12 possessed by one thermoelectric conversion element. The unit and the low temperature side end portion of the n-type thermoelectric conversion material portion 11 of another thermoelectric conversion element have a configuration in which they are electrically arranged in series via the low temperature side wiring 42.

The low temperature side insulating substrate 41 has a function of fixing the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 and the low temperature side wiring 42, and further has a function of uniformly dissipating heat from the thermoelectric conversion module 60.
The material of the low temperature side wiring 42 may be any conductive metal, and Cu, Ag, Al and the like can be used. The material of the low temperature side insulating substrate 41 needs to be a material capable of insulating from the low temperature side wiring 42, and for example, alumina can be used.

In the thermoelectric conversion module 60 of the present embodiment, the portion of the joint portion 21 of the p-type thermoelectric conversion material portion 12 and the n-type thermoelectric conversion material portion 11 that has a longer length on one end side and the other end side is , Each thermoelectric conversion element is arranged so as to receive heat facing the heat source. For example, when the longer portion of the joint portion 21 on one end side and the other end side is directed upward in the vertical direction, the heat source is arranged vertically above the thermoelectric conversion module 60.

Such a thermoelectric conversion module 60 of the present embodiment may be mounted on a combustion device that utilizes a combustion flame such as a gas stove, a gas burner, and an alcohol lamp. Then, the combustion heat of the combustion device can be used to generate electricity. Further, the thermoelectric conversion module 60 of the present embodiment may be mounted on a moving body such as an automobile. In that case, it can be used for power generation using the waste heat of the moving body.

Next, the thermoelectric conversion material used for the thermoelectric conversion element of the present embodiment will be described. The types of the p-type thermoelectric conversion material and the n-type thermoelectric conversion material are not particularly limited, but if a heat source of 600 ° C. or higher is used and it is assumed that the material is used in the atmosphere (for example, direct flame heating), Si. Clathrate compounds such as clathrate compounds can be used. When a clathrate compound is used, at least one of the p-type thermoelectric conversion material and the n-type thermoelectric conversion material may be a clathrate compound.

If at least one of the p-type thermoelectric conversion material and the n-type thermoelectric conversion material is a clathrate compound, the electrical conductivity of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 becomes high, and the thermal conductivity is improved. Can be reduced. Therefore, the temperature difference between the high temperature side end portion and the low temperature side end portion is increased, and the amount of power generation can be increased. Further, if the p-type thermoelectric conversion material and the n-type thermoelectric conversion material are Si clathrate compounds having similar structures, the bonding strength of the bonding portion 21 is improved and the thermoelectric conversion element is less likely to be damaged. The p-type thermoelectric conversion material and the n-type thermoelectric conversion material may contain a small amount of additives and impurities as long as the Si clathrate compound is the main component.

Here, the Si clathrate compound will be described. The Si clathrate compound is a compound in which guest atoms are enclosed in the internal space of a crystal lattice composed of a plurality of Si atoms, and can be represented by the chemical formula A _x By S _{i z} . A in the chemical formula A _{x By Siz} may be barium (Ba). _Further , B in the chemical formula A _x By _Siz may be gallium (Ga) and aluminum (Al), or may be copper (Cu) or nickel (Ni).

Alternatively, when used as a p-type thermoelectric conversion material, B in the chemical formula A _{x By Siz} is one selected from the group consisting of Ga, Al, Cu, Ni, gold (Au) and platinum (Pt). Alternatively, it may be two or more kinds of elements. Generally, when B is Au or Pt, the Si clathrate compound tends to form a p-type thermoelectric conversion material.

When used as a p-type thermoelectric conversion material and an _n -type thermoelectric conversion material, Ba is selected as A in the chemical formula A _x By Si _z , and Ga and Al are selected as B. Ba-Ga-Al-Si. Clathrate compounds are preferred. In the Ba-Ga-Al-Si clathrate compound, the basic lattice is mainly composed of a Si clathrate lattice, Ba atoms are contained therein, and a part of the atoms constituting the clathrate lattice is Ga. , Al-substituted structure. This clathrate compound is a compound containing Ba, Ga, Si, and Al at the same time.

The composition ratios a, b, c, and _d of the chemical formula Ba _a Ga _b Al _c Sid of the Ba-Ga-Al-Si clathrate compound generally have a relationship of a + b + c + d = 54. Further, the composition ratios b, c, and d of Ga, Al, and Si have a relationship of approximately b + c + d = 46. If these relationships are satisfied, the Ba-Ga-Al-Si clathrate compound becomes mainly composed of the Si clathrate phase and can have an ideal crystal structure.

It is also possible to use a Si clathrate compound substituted with an element other than Ga and Al as a thermoelectric conversion material. For example, a Si clathrate compound represented by the chemical formula Ba _a Ga _b Al _c Cu _d Ni _e Au _f Pt _g Si _h can be mentioned. The composition ratios a, b, c, d, e, f, g, and h of each of Ba, Ga, Al, Cu, Ni, Au, Pt, and Si of this Si clathrate compound have a relationship of approximately a + b + c + d + e + f + g + h = 54. .. Further, the composition ratios b, c, d, e, f, g, and h of Ga, Al, Cu, Ni, Au, Pt, and Si have a relationship of approximately b + c + d + e + f + g + h = 46. If these relationships are satisfied, the Si clathrate compound becomes mainly composed of the Si clathrate phase and can have an ideal crystal structure.

For example, the composition in which the compound represented by the chemical formula Ba _a Ga _b Al _c Si _h is a Si clathrate compound is 7 ≦ a ≦ 9, 0 ≦ b ≦ 15, 0 ≦ c ≦ 15, 27 ≦ h ≦ 35. .. Further, for example, the composition in which the compound represented by the chemical formula Ba _a Cu _d Si _h is a Si clathrate compound is 7 ≦ a ≦ 9, 2 ≦ d ≦ 10, 36 ≦ h ≦ 44. Further, for example, the composition in which the compound represented by the chemical formula Ba _a N _e Si _h is a Si clathrate compound is 7 ≦ a ≦ 9, 1 ≦ e ≦ 7, 39 ≦ h ≦ 45. Further, for example, the composition in which the compound represented by the chemical formula Ba _a Au _f Si _h is a Si clathrate compound is 7 ≦ a ≦ 9, 2 ≦ f ≦ 10, 36 ≦ h ≦ 44. Further, for example, the composition in which the compound represented by the chemical formula Ba _a Pt _g Si _h is a Si clathrate compound is 7 ≦ a ≦ 9, 1 ≦ g ≦ 7, 39 ≦ h ≦ 45.

A compound containing a small amount of additives and impurities in the Ba-Ga-Al-Si clathrate compound may be used as the Si clathrate compound. That is, a Ba-Ga-Al-Si-X-based clathrate compound represented by the chemical formula Ba _a Ga _b Al _c Si _d X _x may be used. Here, X is boron (B) and Pd. Boron (B) and Pd may be useful in increasing the Seebeck coefficient.

Chemical formulas of Ba-Ga-Al-Si-X clathrate compounds The composition ratios a, b, c, d, and x of Ba, Ga, Al, Si, and X of Ba _a Ga _b Al _c Si _d X _x are , Approximately a + b + c + d + x = 54. A compound containing a small amount of additives and impurities in a Ba-Ga-Al-Si-X-based clathrate compound may be used as the Si clathrate compound.

Next, an example of the method for manufacturing the thermoelectric conversion element of the present embodiment will be described. First, a method for producing a Si clathrate compound will be described. An ingot of a Si clathrate compound having a predetermined atomic composition and having a uniform composition is produced. First, a predetermined amount of raw materials (Eu, Ba, Sr, Ga, Al, Si, etc.) are weighed and mixed so as to have a desired atomic composition (mixing step). The raw material may be a simple substance of an element, or may be an alloy or a compound. The shape may be powder, flaky or lumpy, but a fine powder is preferable in order to make the mixture homogeneously mixed in a short time. However, Ba is preferably in the form of a lump in order to prevent oxidation. If a mother alloy of Al—Si is used as the raw material of Si instead of Si alone, the melting point can be lowered.

Next, the mixed raw materials are heated and melted (melting step). The melting method is not particularly limited, and various methods can be used. Examples of the melting method include heating melting with a resistance heating element, high frequency induction melting, arc melting, plasma melting, electron beam melting and the like. Graphite, alumina, cold crucible, or the like is used as the material of the crucible into which the raw material is put at the time of melting, depending on the heating method. The melting is preferably carried out in an inert gas atmosphere or a vacuum atmosphere in order to prevent oxidation of the raw material.

As the heating time, a time in which all the raw materials are uniformly mixed in a liquid state is required, but the heating time may be short in consideration of the amount of energy required for producing the Si clathrate compound. For example, the heating time may be 1 minute or more and 100 minutes or less, further 1 minute or more and 10 minutes or less, or 1 minute or more and 5 minutes or less. Further, at the time of melting, stirring may be added by a mechanical or electromagnetic method.

Subsequently, an ingot is produced from the molten raw material. The method for producing the ingot is not particularly limited, and the ingot may be cast using a mold or solidified in a crucible. Then, in order to homogenize the finished ingot, the ingot may be heated and subjected to annealing treatment.

When the obtained ingot is pulverized using a ball mill or the like, a fine particle Si clathrate compound can be obtained. The obtained fine particles preferably have a fine particle size in order to improve the sinterability. For example, the particle size of the fine particles is preferably 100 μm or less, and more preferably 1 μm or more and 75 μm or less.

The particle size may be adjusted after crushing the ingot with a ball mill or the like in order to obtain fine particles having a desired particle size. Examples of the method for adjusting the particle size include sieving using a test sieve manufactured by Lecce Co., Ltd. and a sieve shaker AS200 digit manufactured by Lecce Co., Ltd. specified in ISO3310-1. Fine powder may be produced by changing the sieving to various atomization methods such as a gas atomization method, a flowing gas evaporation method, or the like.

Next, a manufacturing method of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 will be described. The obtained fine particle Si clathrate compound is sintered, and a sintered body (p-type thermoelectric conversion material unit 12 and n-type thermoelectric conversion material unit) having a predetermined shape (for example, a columnar shape such as a square columnar) having a homogeneous shape and few voids is sintered. 11) can be obtained. As the sintering method, a discharge plasma sintering method, a hot press method, a hot isotropic pressure pressure sintering method, or the like can be used.

When the discharge plasma sintering method is used, the sintering temperature, which is one of the conditions for sintering, is preferably 600 ° C. or higher and 1000 ° C. or lower, and more preferably 900 ° C. or higher and 1000 ° C. or lower. The sintering time is preferably 1 minute or more and 10 minutes or less, and more preferably 3 minutes or more and 7 minutes or less. The sintering pressure is preferably 40 MPa or more and 80 MPa or less, and more preferably 50 MPa or more and 70 MPa or less.

If the sintering temperature is less than 600 ° C, the sintering may not be completed, and if the sintering temperature exceeds 1000 ° C, the fine particle Si clathrate compound may melt. If the sintering time is less than 1 minute, the density may be low, and if the sintering time exceeds 10 minutes, the sintering is completed and saturated, and it is considered meaningless to spend more time.

In particular, in the sintering step, the fine-grained Si clathrate compound is heated to the sintering temperature and held at that temperature for the sintering time, and then the Si clathrate compound is cooled to the temperature before heating. In this case, the step of heating the fine-grained Si clathrate compound to the sintering temperature and the step of holding the compound at that temperature are in a pressurized state, and the subsequent step of cooling the Si clathrate compound is in a pressurized state. unlock. By such a pressure operation, it is possible to suppress cracking of the sintered body of the Si clathrate compound in the sintering step.

Each sintered body of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 obtained in the sintering step is joined to prepare a bonded body (bonding step). For example, when the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are square columnar members having the same shape, one side surface thereof is opposed to each other so that the outer edges coincide with each other, and both side surfaces facing each other are opposed to each other. Of these, only one end side portion of the square columnar member in the height direction is directly joined. It is desirable to use the diffusion bonding method for bonding the sintered body.

Alternatively, the above sintering step and joining step may be performed at the same time to manufacture a bonded body of the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11. That is, the p-type is formed by stacking fine particles of the p-type thermoelectric conversion material and fine particles of the n-type thermoelectric conversion material in layers in a sintered mold for forming a bonded body having the slit 31, and sintering the mixture. A bonded body having a shape as shown in FIG. 1 to which the thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 are joined can be manufactured in one step.

A thermoelectric conversion element is manufactured by shaping a bonded body in which the p-type thermoelectric conversion material unit 12 and the n-type thermoelectric conversion material unit 11 obtained in this manner are directly bonded into a desired shape (shaping process). do. Alternatively, a sintering mold having a desired shape may be prepared, and the above-mentioned sintering step, joining step, and shaping processing step may be performed in one step.
The thermoelectric conversion element of the first embodiment is easier to manufacture and lower in cost than the conventional thermoelectric conversion element as shown in FIG.

〔Example〕
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
(Manufacturing of thermoelectric conversion element)
High-purity Ba with a purity of 99% or higher and high-purity Al, Ga, Si, and Au with a purity of 99.9% or higher are mixed at the blending ratio (blending amount (unit: g)) shown below to prepare a raw material. Mixtures A and B were obtained (mixing step). The blending ratio of the raw material mixture A is Ba: 12.8 g, Al: 3.0 g, Ga: 7.7 g, and Si: 8.9 g. The blending ratio of the raw material mixture B is Ba: 14.4 g, Si: 14.4 g, Au: 14.5 g.

The obtained raw material mixtures A and B are placed on a water-cooled copper hearth, respectively, and arc-melted in an Ar (argon) atmosphere with a current of 300 A for 1 minute, and then cooled to room temperature on the water-cooled copper hearth to cool the ingot. Obtained. In order to eliminate the non-uniformity of the raw material, the ingot was inverted, arc melting was performed again, and then the ingot was cooled in the same manner as described above. Such a step was repeated 5 times to obtain an ingot having a Si clathrate compound (ingot manufacturing step).

Next, in order to improve the uniformity of the ingot, the ingot was subjected to an annealing treatment in which the ingot was heated at 900 ° C. for 6 hours in an argon atmosphere (annealing treatment step). The composition of the obtained ingot may be slightly different from the composition (blending ratio) of the raw materials due to the solid solution limit of each element and the formation of the second phase and the third phase.

The obtained ingot was pulverized using an agate planetary ball mill to obtain fine particles (crushing step). At this time, the particle size was adjusted by using an ISO3310-1 standard test sieve manufactured by Lecce and an AS200 digit sieve shaker manufactured by Lecce so that the particle size of the obtained fine particles was 75 μm or less.

In order to confirm the performance of each of the obtained fine particles, a sintered body for character evaluation was prepared. Each fine particle was filled in a sintering mold, and sintering was performed using a discharge plasma sintering method (SPS method). At the time of sintering, the pressure was increased to 50 MPa and then heated. Although the sintering was performed in a vacuum atmosphere, the sintering may be performed in an inert atmosphere such as Ar gas. By measuring the temperature of the surface of the sintered mold, it is heated to about 900 to 1050 ° C, sintered at that temperature for 5 minutes, then released from the pressurized state, cooled to room temperature, and sintered for characteristic evaluation. I got a body. When the temperature at the time of cooling is 500 ° C. or higher, it is preferable to hold the sintered body for characteristic evaluation in a vacuum atmosphere, but when it is lower than 500 ° C., it may be held in an atmospheric atmosphere.

Since each fine particle has a different atomic composition, all of them are Si clathrate compounds, but the suitable sintering temperature is different. If the sintering temperature is too low, the sintered body will have a low density and may cause cracking. Also, if the sintering temperature is too high, the sample may melt. Therefore, it is necessary to select a suitable sintering temperature while checking the temperature and the progress of sintering.
The characteristic evaluation sintered body thus obtained from the raw material mixture A exhibited n-type thermoelectric conversion characteristics, and the characteristic evaluation sintered body obtained from the raw material mixture B exhibited p-type thermoelectric conversion characteristics. ..

Since it was confirmed that each of the obtained fine particles exhibited n-type thermoelectric conversion characteristics or p-type thermoelectric conversion characteristics, a thermoelectric conversion element having the same shape as that shown in FIG. 1 was produced from these fine particles. That is, each of the obtained fine particles is filled in a sintering mold for forming a bonded body having slits and sintered, and the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion are bonded. A thermoelectric conversion element was manufactured. The sintered mold was first filled with fine particles obtained from the raw material mixture A, and then filled with the fine particles obtained from the raw material mixture B in layers. At this time, the upper surface of the layer of fine particles obtained from the raw material mixture A is formed as horizontally as possible, and the boundary between the layer of fine particles obtained from the raw material mixture A and the layer of fine particles obtained from the raw material mixture B becomes horizontal. Is desirable.

A mixture of the fine particles obtained from the raw material mixture A and the fine particles obtained from the raw material mixture B is arranged between the layer of the fine particles obtained from the raw material mixture A and the layer of the fine particles obtained from the raw material mixture B. May be sintered. Then, solid-phase diffusion can be further promoted at the boundary between the layer of fine particles obtained from the raw material mixture A and the layer of fine particles obtained from the raw material mixture B, so that the p-type thermoelectric conversion material portion and n The mold thermoelectric conversion material part is more firmly bonded.

As the sintering method, a discharge plasma sintering method (SPS method) was used. At the time of sintering, the pressure was increased to 50 MPa and then heated. Although the sintering was performed in a vacuum atmosphere, the sintering may be performed in an inert atmosphere such as Ar gas. By measuring the temperature of the surface of the sintered mold, the surface was heated to about 900 ° C., sintered at that temperature for 5 minutes, released from the pressurized state, and cooled to room temperature to obtain a bonded body.

At this time, since it is desirable that both the fine particles obtained from the raw material mixture A and the fine particles obtained from the raw material mixture B are densely sintered, the sintering temperature is higher than the sintering temperature of both. 900 ° C was selected. Further, when the cooling temperature is 500 ° C. or higher, it is preferable to hold the sintered body in a vacuum atmosphere, but when it is lower than 500 ° C., it may be held in an atmospheric atmosphere.

The joint of the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion thus obtained is shaped into external dimensions of depth 1 mm × width 5 mm × height 5 mm, and has the same shape as that shown in FIG. The thermoelectric conversion element of was obtained. When the side surface of the p-type thermoelectric conversion material portion facing the n-type thermoelectric conversion material portion is viewed from the front, the shape of the joint portion is trapezoidal, but the length of the longer base of the two bases having different lengths. The a is 3 mm, and the length b of the shorter base is 1 mm.

Here, the height corresponds to the length in the direction along the opposite side surfaces of the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion and connecting the high temperature side end portion and the low temperature side end portion, and corresponds to the width. Corresponds to the length in the direction orthogonal to the opposite side surfaces of the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion, and the depth is the mutual of the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion. It corresponds to the length along the opposite side surface and in the direction orthogonal to the direction connecting the high temperature side end portion and the low temperature side end portion.

It is sufficient that the p-type thermoelectric conversion material and the n-type thermoelectric conversion material can be directly bonded by directly diffusing the p-type thermoelectric conversion material and the n-type thermoelectric conversion material, so that a method other than the above method can be used. But it is possible to manufacture a junction.
For example, a sintered body obtained by sintering fine particles obtained from the raw material mixture A is placed in a sintering mold, and the fine particles obtained from the raw material mixture B are filled therein to form a sintered body. Fine particles obtained from the raw material mixture B are placed on top. By sintering this at a temperature lower than the sintering temperature of the fine particles obtained from the raw material mixture A, a sintered body in which the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion are directly bonded is obtained. Be done. When the sintering temperatures of the p-type thermoelectric conversion material and the n-type thermoelectric conversion material are different, such a method can also be adopted.

Alternatively, the fine particles obtained from the raw material mixture A and the fine particles obtained from the raw material mixture B may be sintered separately, and energization bonding may be performed in a state where the sintered bodies are in contact with each other. In this method, the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion are joined by solid phase diffusion.
Further, the fine particles obtained from the raw material mixture A and the fine particles obtained from the raw material mixture B are sintered separately, and an electric furnace or the like is used while maintaining the state in which the sintered bodies are in pressure contact with each other. It is also possible to adopt a method of heat-treating to a high temperature.

The high temperature side end of the thermoelectric conversion element obtained as described above was heated by a flame. More specifically, the front view shape of the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion is trapezoidal, and the rod-shaped members are rod-shaped on one end side and the other end side in the direction orthogonal to the height direction of the rod-shaped member. It has shapes with different lengths in the direction parallel to the height direction of the member. The thermoelectric conversion element is arranged so that the longer portion of the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion on one end side and the other end side receives heat from the flame. bottom.

As a result, since a large temperature distribution did not occur in the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion, it was difficult for the joint portion to be damaged by thermal stress. Therefore, the thermoelectric conversion module and the power generation device using the thermoelectric conversion element of this embodiment have very high reliability.
On the other hand, in the conventional thermoelectric conversion element in which the joint portion between the p-type thermoelectric conversion material portion and the n-type thermoelectric conversion material portion is rectangular in front view, when the high temperature side end portion is heated by a flame, the p-type thermoelectric conversion material is used. Since a large temperature distribution was generated at the joint portion between the portion and the n-type thermoelectric conversion material portion, the joint portion was damaged due to thermal stress.

11 n-type thermoelectric conversion material part 12 p-type thermoelectric conversion material part 21 Joint part 31 Slit 60 Thermoelectric conversion module

Claims (5)

A thermoelectric conversion element in which a p-type thermoelectric conversion material portion having a p-type thermoelectric conversion material and an n-type thermoelectric conversion material portion having an n-type thermoelectric conversion material are joined.
The p-type thermoelectric conversion material section and the n-type thermoelectric conversion material section are both rod-shaped members, and one side surface of the p-type thermoelectric conversion material section and the n-type thermoelectric conversion material section face each other and face each other on both sides. Of the surfaces, only one end side portions of the rod-shaped member in the height direction are joined to each other.
The joint portion between the opposite side surfaces is the one end side and the other end side in the direction orthogonal to the height direction of the rod-shaped member when one side surface of the opposite side surfaces is viewed from the front. Thermoelectric conversion elements having different shapes in the direction parallel to the height direction of the rod-shaped member. The thermoelectric conversion element according to claim 1, wherein the shape of the joint portion between the facing side surfaces is a right triangle, a trapezoid, or an arc shape when one side surface of the facing side surfaces is viewed from the front. The thermoelectric conversion element according to claim 1 or 2, wherein the p-type thermoelectric conversion material is a p-type Si clathrate compound, and the n-type thermoelectric conversion material is an n-type Si clathrate compound. A thermoelectric conversion module including the thermoelectric conversion element according to any one of claims 1 to 3. A mobile body equipped with the thermoelectric conversion module according to claim 4.

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