JP6705114B2 - Thermoelectric conversion element, manufacturing method thereof, and thermoelectric conversion module - Google Patents

Description

The present invention relates to a thermoelectric conversion element that uses corusite as a thermoelectric conversion material, a method for manufacturing the same, and a thermoelectric conversion module including the thermoelectric conversion element.

Thermoelectric conversion is a technique of mutually converting thermal energy and electric energy using a solid thermoelectric conversion element.
The technique of converting heat energy into electric energy is called thermoelectric power generation, and is based on the Seebeck effect, which is one of the thermoelectric effects. In thermoelectric power generation, the temperature difference between both ends of the thermoelectric conversion element is directly converted into electric energy. By utilizing this thermoelectric power generation, a huge amount of unused thermal energy emitted from factories and automobiles is recovered and electric power is generated from it, greatly reducing fossil fuel consumption, that is, CO ₂ reduction and energy saving. I can contribute.

On the other hand, the conversion of electric energy into heat energy originates from the Peltier effect, which is another thermoelectric effect, and is applied to cooling and precise temperature control. Here, the conversion of electric energy derived from the Peltier effect into thermal energy is called Peltier cooling. The Peltier cooling uses a phenomenon in which one end of the thermoelectric conversion element is cooled when a current is applied to the thermoelectric conversion element. This Peltier cooling is advantageous in that it does not require a refrigerant such as CFC gas for cooling, it has no mechanical drive unit, and that it can precisely control the cooling temperature based on current control.

The thermoelectric conversion element used for both the thermoelectric power generation and the Peltier cooling is formed from a thermoelectric conversion material layer formed of a thermoelectric conversion material and an electrode layer formed of an electrode material, and the thermoelectric conversion element is used. A conversion module, ie a thermoelectric generation module/Peltier cooling module, can be constructed. Specifically, for example, a P-type thermoelectric conversion element (charge-carrying carriers are holes) and an N-type thermoelectric conversion element (charge-carrying carriers are electrons) are efficiently transmitted, for example, a metal member. A thermoelectric conversion module (thermoelectric power generation module/Peltier cooling module) can be configured by connecting the components in a thermally parallel manner and electrically in a serial manner.
The thermoelectric conversion module is usually configured by combining a plurality of pairs of the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements in order to obtain a large power generation effect or a cooling effect. The element and the N thermoelectric conversion element alone function as a thermoelectric conversion module. Here, in addition to a thermoelectric conversion module configured by a pair of the P-type thermoelectric conversion element and the N thermoelectric conversion element, a thermoelectric conversion configured by combining a plurality of pairs of the P-type thermoelectric conversion element and the N thermoelectric conversion element. Modules are also included in the concept of the thermoelectric conversion module.

The performance of the thermoelectric conversion material can be expressed as a dimensionless thermoelectric conversion performance index ZT (also referred to as thermoelectric performance index ZT), and the higher this ZT, the better the performance. The dimensionless thermoelectric conversion performance index ZT is represented by the following equation, ZT=S ² T/ρκ, S represents the Seebeck coefficient of the thermoelectric conversion material, T represents the absolute temperature, and ρ represents the thermoelectric conversion. Indicates the electrical resistivity of the material, and κ indicates the thermal conductivity of the thermoelectric conversion material.

The electrode material is required to have low electrical resistivity, high thermal conductivity, and the electrode itself being chemically stable even at high temperatures. In addition, the electrode material is required not to cause a chemical reaction with the thermoelectric conversion material layer, and is also disposed on the surface of the electrode layer opposite to the surface to be joined to the thermoelectric conversion material layer. It is required that a chemical reaction does not occur even with the junction electrode to be formed. Furthermore, a role of relieving stress between the thermoelectric conversion material layer and the bonding electrode is required.

As the thermoelectric conversion material forming the P-type thermoelectric conversion elements, the chemical composition _{Cu 26-x M x A 2} E 6 S 32 ( although, M is, Mn, Fe, Co, at least one of Ni and Zn A represents a metal material containing, A represents a metal material containing at least one of V, Nb and Ta, E represents a metal material containing at least one of Si, Ge and Sn, and x represents 0 to 5 The "corusite" represented by the formula (1) is proposed (for example, see Non-Patent Document 1 and Non-Patent Document 2).

The corusite is composed mainly of copper (Cu) and sulfur (S), which are low in toxicity and have large crustal reserves, have high environmental harmony, and have a higher dimensionless thermoelectric conversion performance index ZT. And has an excellent feature that it is relatively lightweight (about 4.7 g·cm ⁻³ ).
However, since the corusite contains sulfur (S) having high reactivity with other substances as a main component, when the thermoelectric conversion element and the thermoelectric conversion module are manufactured by using the corusite as the thermoelectric conversion material, The corusite and the electrode material react to generate a high resistance phase at the interface between the thermoelectric conversion material layer and the electrode layer, or the corusite and the electrode material react to each other during use to generate the thermoelectric conversion material. There is a possibility that defects may occur in which the layers are altered.

K. Suekuni, FS Kim, H. Nishiate, M. Ohta, HI Tanaka, and T. Takabatake, ``High-performance thermoelectric minerals: Colusites Cu26V2M6S32 (M = Ge, Sn)'', Applied Physics Letters, 105, 132107- Pages 1 to 4, October 2014. K. Suekuni, FS Kim, and T. Takabatake, ``Tunable electronic properties and low thermal conductivity in synthetic colusites Cu26-xZnxV2M6S32 (x ≤ 4, M = Ge, Sn)'', Journal of Applied Physics, 116, 063706-1. ~ Page 5, August 2014.

The present invention solves the above-mentioned problems in the prior art, enables stable bonding of the thermoelectric conversion material layer formed of the corusite and the electrode layer, and the thermoelectric conversion material when used in a high temperature environment. It is an object of the present invention to provide a thermoelectric conversion element capable of being stably manufactured by suppressing deterioration of the material, a method for manufacturing the same, and a thermoelectric conversion module using the thermoelectric conversion element.

In order to solve the above problems, the present inventor has made it possible to stably bond the thermoelectric conversion material layer formed of the corusite and the electrode layer, and to modify the thermoelectric conversion material during use in a high temperature environment. Therefore, the inventors have made earnest studies on the electrode material that can be stably manufactured as the thermoelectric conversion element having the thermoelectric conversion material layer.
As a result, the corusite has many properties that have not yet been known, and it has been difficult to select a suitable electrode material. However, as a result of trial and error, if the electrode layer is formed of several electrode materials. We have found that the above problems can be solved.

The present invention is based on the above findings, and means for solving the above problems are as follows. That is,
<1> A thermoelectric conversion material layer formed of a thermoelectric conversion material represented by the following chemical formula (1), and an electrode material that is bonded to the thermoelectric conversion material layer and contains at least one of Ti, Pt, and Au. An electrode layer, and a thermoelectric conversion element.
However, in the chemical formula (1), M represents a metal material containing at least one of Mn, Fe, Co, Ni and Zn, and A represents a metal material containing at least one of V, Nb and Ta. , E represent a metallic material containing at least one of Si, Ge and Sn, and x represents a numerical value of 0-5.
<2> The thermoelectric conversion element according to <1>, wherein x in the chemical formula (1) is 0.
<3> A compound in which A in the chemical formula (1) is Nb and E is any one of Si, Ge, and Sn in the thermoelectric conversion material, and the A in the chemical formula (1) is V and The thermoelectric conversion element according to any one of <1> to <2>, wherein the thermoelectric conversion element is one of Ta and is one of the compounds in which E is Sn.
<4> The thermoelectric conversion element according to any one of <1> to <3>, wherein the electrode material contains Au.
<5> The method for manufacturing a thermoelectric conversion element according to any one of <1> to <4>, wherein a laminated structure forming step of forming a laminated structure in which a thermoelectric conversion material layer and an electrode layer are laminated And a heating step of heating the laminated structure to sinter the thermoelectric conversion material layer and joining the thermoelectric conversion material layer and the electrode layer to each other, and a method of manufacturing a thermoelectric conversion element. ..
<6> The method for producing a thermoelectric conversion element according to <5>, wherein the heating temperature in the heating step is 400°C to 1,050°C.
<7> The method for producing a thermoelectric conversion element according to any one of <5> to <6>, wherein the heating in the heating step is performed under pressure.
<8> The method for producing a thermoelectric conversion element according to <7>, wherein the pressure applied is at least 10 MPa.
<9> A thermoelectric conversion module comprising the thermoelectric conversion element according to any one of <1> to <4> as a P-type thermoelectric conversion element.

ADVANTAGE OF THE INVENTION According to this invention, the said various problems in a prior art can be solved, the said thermoelectric conversion material layer and the said electrode layer which are formed by the said corusite can be joined stably, and it uses under high temperature environment. It is possible to provide a thermoelectric conversion element that can suppress the deterioration of the thermoelectric conversion material and can be stably manufactured, a method for manufacturing the thermoelectric conversion element, and a thermoelectric conversion module using the thermoelectric conversion element.

It is a figure for demonstrating the structure of a thermoelectric conversion element. It is a figure which shows an example of the sintering shrinkage curve of a laminated structure. It is a figure for demonstrating the structure of a thermoelectric conversion module. It is a figure which shows the electrical resistance distribution in a thermoelectric conversion element.

(Thermoelectric conversion element)
The thermoelectric conversion element of the present invention has a thermoelectric conversion material layer and an electrode layer.

<Thermoelectric conversion material layer>
The thermoelectric conversion material layer is a layer formed of a thermoelectric conversion material represented by the following chemical formula (1).

However, in the chemical formula (1), M represents a metal material containing at least one of Mn, Fe, Co, Ni and Zn, and A represents a metal material containing at least one of V, Nb and Ta. , E represent a metallic material containing at least one of Si, Ge and Sn, and x represents a numerical value of 0-5.

The thermoelectric conversion material represented by the chemical formula (1) is called "corusite" because it has the same crystal structure as corusite, which is a kind of natural copper sulfide mineral, and has low toxicity and crustal reserves. Is composed mainly of copper (Cu) and sulfur (S), has a high dimensionless thermoelectric conversion performance index ZT, and is relatively lightweight (about 4.7 g·cm ⁻³ ). Have. Regarding the dimensionless thermoelectric conversion performance index ZT, the present inventors have confirmed that the thermoelectric conversion material exhibits a high value of 0.2 to 0.7 in a wide temperature range of 75°C to 400°C.

M in the above-mentioned chemical formula (1) of corusite acts as a dopant for adjusting the amount of charge-carrying carriers in corusite. As x in the chemical formula (1) of corusite, if M is a numerical value in the range of 0 to 5, the M acts as the dopant and is not particularly limited, but a high dimensionless thermoelectric conversion performance index ZT can be obtained. Therefore, 0 is preferable.
The x, that is, the substitution amount in the chemical formula (1) is 8% with respect to the total composition even when the substitution amount is 5, and the physical and chemical ratio of the corusite to the electrode layer is high. Even if the compound having this composition does not exert a great influence on the stability, it is possible to obtain chemical stability with respect to the electrode layer, and it can be used as the thermoelectric conversion material.

Further, the thermoelectric conversion material is not particularly limited, but since the high environmental harmony and the high dimensionless thermoelectric conversion index ZT, which are characteristics of corusite, can be obtained, the A in the chemical formula (1) is A compound which is Nb and E is any one of Si, Ge and Sn, and the A in the chemical formula (1) is any one of V and Ta, and the E is Sn. It is preferably any of the compounds.
Each element of A and each element of E are elements belonging to the same group in the periodic table, have the same valence ionic state, and show the same electronegativity. Each element of A and each element of E can be chemically stable with respect to the electrode layer even when a selection different from the selection of these suitable compounds is made.

The method for forming the thermoelectric conversion material layer is not particularly limited, and it can be formed by a known forming method, for example, the forming methods described in Non-Patent Documents 1 and 2.

<Electrode layer>
The electrode layer is a layer that is bonded to the thermoelectric conversion material layer and is made of an electrode material containing at least one of Ti, Pt, and Au.

It was confirmed that Ti, Pt, and Au are stable without chemically reacting with the corusite, and have a melting point higher than the synthesis temperature of the corusite (1,050° C.) and have a high temperature. It has been confirmed that it is chemically stable against the corusite even under the conditions.
The electrode material containing these elements is a material having a low electric resistivity and a high thermal conductivity, and thus is a suitable material as a material for forming the electrode layer, but among these elements, from the viewpoint of obtaining a lower electric resistance. Au is particularly preferred.
The electrode material may be composed of at least one of Ti, Pt, and Au as a main component and may contain a small amount of an element other than these elements as long as it is chemically stable to the corusite. ..

The electrode material is not particularly limited, and those manufactured by a known manufacturing method or commercial products can be used, and in forming the electrode layer, powder, foil, plate, or the like is used. A processed product can be used.

One embodiment of the thermoelectric conversion element is shown in FIG. FIG. 1 is an explanatory diagram for explaining the configuration of the thermoelectric conversion element. The thermoelectric conversion element 10 shown in FIG. 1 has the same element configuration as a general thermoelectric conversion element.
The thermoelectric conversion element 10 has a structure in which the thermoelectric conversion material layer 1 is sandwiched between two electrode layers 2a and 2b.
The electrode layers 2a and 2b electrically and thermally connect the thermoelectric conversion material layer 1 and a bonding electrode to be described later, and conduct current and heat well, while connecting the thermoelectric conversion material layer 1 and the bonding electrode. It has a role of suppressing the reaction and a role of relieving the stress between the thermoelectric conversion material layer 1 and the bonding electrode.

(Method for manufacturing thermoelectric conversion element)
The method for producing a thermoelectric conversion element of the present invention is a method for producing the thermoelectric conversion element of the present invention, and includes a laminated structure forming step and a heating step.

<Layered structure forming step>
The laminated structure forming step is a step of forming a laminated structure in which the thermoelectric conversion material layer and the electrode layer are laminated.
The method for carrying out the laminated structure forming step is not particularly limited, and for example, a method of arranging the electrode material in the form of powder, foil, plate, etc. on the upper and lower surfaces of the thermoelectric conversion material solidified into pellets may be used. Can be mentioned.
Note that the thermoelectric conversion material may be annealed in advance at an appropriate heating temperature before the step of forming the laminated structure.

<Heating process>
The heating step is a step of heating the laminated structure to sinter the thermoelectric conversion material layer and to bond the thermoelectric conversion material layer and the electrode layer.
Further, the heating step has a role of improving the density of the thermoelectric conversion material layer that is sintered in a state of being bonded to the electrode layer. When the density of the thermoelectric conversion material layer (corusite) is improved, a low electric resistivity can be obtained, and a good electric conductor can be obtained. The density at which a low electrical resistivity is obtained is preferably 95% or more, more preferably 98% or more, with respect to the theoretical density of corusite.

FIG. 2 shows an example of the sintering shrinkage curve of the laminated structure. This sintering shrinkage curve shows the measurement result of how much the length of the laminated structure shrinks by heating in the state where the thermoelectric conversion material layer and the electrode layer are stacked and heated. is there.
As shown in FIG. 2, the corusite forming the thermoelectric conversion material layer contracts from 400° C. in the state where the electrode layer is arranged, as understood from the fact that the expansion tendency starting from around 250° C. slows down. Starts to change from a powder state to a sintered body, and densification (improvement of density) proceeds. It is also confirmed that from 550° C., the shrinkage due to the densification is completely superior to the expansion, and the shrinkage tends to occur as a whole.
Therefore, the lower limit of the heating temperature is not particularly limited, but is preferably 400° C. or higher, more preferably 550° C. or higher, because of the above-mentioned role. The upper limit of the heating temperature is lower than the melting point of the electrode material and the synthesis temperature (1,050° C.) of the thermoelectric conversion material layer.

As a method for producing a sintered body, an atmospheric pressure sintering method in which firing is performed without applying pressure from the outside is widely known and is commonly used (see Reference 1 below).
With this method, it is possible to sinter the materials and join different materials while using the temperature rise (heating) as a driving force (driving force). That is, heating is the most important driving force that promotes sintering and bonding.
The pressure sintering method in which sintering is performed while applying pressure in addition to heating is particularly effective for a difficult-to-sinter material such as tungsten carbide, but since the corusite is not a difficult-to-sinter material, the pressing The sintering method is not essential, and an atmospheric pressure sintering method can be applied as in the case of the sintered body. In the pressure sintering method, pressure acts as a driving force together with heating to accelerate sintering and bonding. When the driving force is not enough for heating, pressurization is performed.
That is, for the corusite, the sintering and the electrode layers are joined by applying a heating force at a temperature of 400° C. or higher and a melting point to a temperature below the synthesis temperature (1,050° C.) as a driving force without applying an external pressure. Is possible.
Reference 1; (Corporation) Japan Ceramics Association, "Ceramic Engineering Handbook", Basic, Volume 2, 6. "Firing and Sintering", pp202-226 (2014)

However, the pressure applied during sintering has a role of improving the density of the thermoelectric conversion material layer, and is advantageous in forming the thermoelectric conversion material layer. That is, when the density of the thermoelectric conversion material layer (corusite) is improved, a low electric resistivity can be obtained, and a good electric conductor can be obtained.
Therefore, from the viewpoint of realizing high-density sintering of the thermoelectric conversion material with few voids and firmly joining the thermoelectric conversion material layer and the electrode layer, the heating is performed in a pressurized environment. It is preferable to carry out the treatment by applying a pressure of 10 MPa or more.
Note that the higher the pressure in the pressure heating step in which the pressure sintering method is performed, the higher the density of the corusite sintered body can be expected, and further, the bonding between the thermoelectric conversion material layer and the electrode layer can be expected. Therefore, the upper limit of the applied pressure is not particularly limited, and is, for example, about 500 MPa which is the pressurizing limit of a general pressurizing and heating apparatus, and about 200 MPa in consideration of cost and the like.
By sintering the corusite within the numerical ranges of the heating temperature and the pressure, a density of 98% or more with respect to the theoretical density of the corusite can be obtained.

The method for carrying out the heating step is not particularly limited, and examples thereof include a method of arranging the laminated structure in a known heating device or a pressure heating device, and heating or pressurizing it. .

(Thermoelectric conversion module)
The thermoelectric conversion module of the present invention is configured to have the thermoelectric conversion element of the present invention as a P-type thermoelectric conversion element.
Hereinafter, the thermoelectric conversion module of the present invention will be specifically described with reference to FIG. Note that FIG. 3 is an explanatory diagram for explaining the configuration of the thermoelectric conversion module. The thermoelectric conversion module 100 shown in FIG. 3 has the same module configuration as a general thermoelectric conversion module.

The thermoelectric conversion module 100 has two thermoelectric conversion elements, that is, the P-type thermoelectric conversion element 20 and the N-type thermoelectric conversion element 30, which are composed of the thermoelectric conversion elements of the present invention, and bridges these two thermoelectric conversion elements above. As shown in FIG. 3, each of the upper joint electrodes 13 is arranged as described above, and the lower joint electrodes 14 and 14' are arranged below the P-type thermoelectric conversion element 20 and the N-type thermoelectric conversion element 30, respectively. The whole has a π-type shape. The upper bonding electrode 13 and the lower bonding electrodes 14 and 14' correspond to the bonding electrodes described above.
In addition, the P-type thermoelectric conversion element 20 has a configuration in which the thermoelectric conversion material layer 11 is sandwiched between two electrode layers 12a and 12b, like the thermoelectric conversion element 10. A known N-type conversion element can be appropriately selected as the N-type thermoelectric conversion element 30. For example, the thermoelectric conversion material layer 11′ is sandwiched between two electrode layers 12a′ and 12b′.

In the thermoelectric conversion module 100, when the upper joint electrode 13 side is heated to a high temperature and the lower joint electrodes 14 and 14′ side are cooled to a low temperature, it can be used as a thermoelectric power generation module that causes a potential difference between the lower joint electrodes 14-14′. it can.
Further, in the thermoelectric conversion module 100, a positive voltage is applied to the lower bonding electrode 14′ and a negative voltage is applied to the lower bonding electrode 14 to introduce a current from the lower bonding electrode 14′ into the module, and a current is applied from the lower bonding electrode 14 to the current. When a voltage is applied so as to send out the heat, a heat absorption phenomenon occurs on the side of the upper bonding electrode 13 and a heat radiation phenomenon occurs on the side of the lower bonding electrodes 14 and 14', so that the temperature of the object in contact with the upper bonding electrode 13 is increased. It can be used as a lowering Peltier cooling module.
Although the configuration of the thermoelectric conversion module of the present invention has been described with reference to FIG. 3, the module configuration shown in FIG. 3 shows an example of the configuration of the thermoelectric conversion module of the present invention, and other known configurations. It does not exclude the configuration of the thermoelectric conversion module.

(Example 1)
First, the raw materials Cu (1.386 g), Nb (0.156 g), Sn (0.598 g) and S (0.861 g) were vacuum sealed in a quartz tube and melted at 1,050°C. , About 3 g of a polycrystalline sample having a composition of Cu ₂₆ Nb ₂ Sn ₆ S ₃₂ was synthesized. The production phase of the synthesized polycrystalline sample was confirmed by powder X-ray diffraction.
Next, of the synthesized polycrystalline powder of Cu ₂₆ Nb ₂ Sn ₆ S ₃₂ that was crushed into powder, 2.5 g of it was used as a material for an electrode in a cylindrical mold made of graphite and having an inner diameter of 10 mm. A 0.25 mm Au foil was laminated so as to be sandwiched from both sides, and a sintering operation was performed under conditions of 750° C., 70 MPa pressure application, and 1 hour holding in Ar gas flow.
As described above, a thermoelectric conversion element according to Example 1 having a structure in which the thermoelectric conversion material layer formed of corusite was sandwiched between Au electrode layers was manufactured.
The electric resistance and the position of the probe were measured by measuring the electric resistance while moving the voltage probe from one end of the thermoelectric conversion element to the other end side with the current source connected to both ends of the thermoelectric conversion element according to the first embodiment. Was measured to obtain the electric resistance distribution in the thermoelectric conversion element. The measurement result is shown in FIG. The electric resistance value of the thermoelectric conversion element according to Example 1 was 17 mΩ, while the electric resistance value of the thermoelectric conversion element predicted from the electric resistivity of the single substance of corusite was 12 mΩ. It is confirmed that the high resistance phase is not formed in the and the good bonding is obtained.

<Evaluation of thermoelectric conversion characteristics>
Using a thermoelectric conversion efficiency measuring device (mini-PEM, manufactured by Advance Riko Co., Ltd.), in a predetermined temperature range (about 50° C. to about 400° C.), the electromotive force P _out generated in the thermoelectric conversion element and the low temperature side The amount of heat Q _out flowing _out from the end (the electrode on the low temperature side) was precisely measured, and the thermoelectric conversion efficiency η (=P _out /(P _out +Q _out )) of the thermoelectric conversion element according to Example 1 was obtained.
The measurement results of the thermoelectric conversion element according to Example 1 are shown in Tables 1-1 and 1-2 below. In Table 1-1 below, the temperature of one end (high temperature side electrode) of the thermoelectric conversion element according to Example 1 is 98° C. and the temperature of the other end (low temperature side electrode) of the thermoelectric conversion element is shown in vacuum. Shows the measurement result when the measurement was performed under the condition of 23° C., and Table 1-2 below shows the case where the temperature of the high temperature side electrode was 393° C. and the temperature of the low temperature side electrode was 26° C. The measurement result of is shown.

As described above, the thermoelectric conversion element according to Example 1 can be manufactured by bonding the thermoelectric conversion material layer and the electrode layer in a chemically stable state, and can be stably used in a high temperature environment. ..
In addition, in each thermoelectric conversion element according to Examples 2 to 7 to be described later, as in the thermoelectric conversion element according to Example 1, the thermoelectric conversion material layer and the electrode layer are electrically well joined, Generated power and conversion efficiency similar to those of the first embodiment can be obtained.
Therefore, also in each of the thermoelectric conversion elements according to Examples 2 to 7, the thermoelectric conversion material layer and the electrode layer can be bonded to each other in a chemically stable state, and can be stably used in a high temperature environment. Is.

(Example 2)
First, the raw materials Cu (1.634 g), Nb (0.184 g), Si (0.107 g) and S (1.015 g) were vacuum sealed in a quartz tube and melted at 1,050° C. , About 3 g of a polycrystalline sample having a composition of Cu ₂₆ Nb ₂ Si ₆ S ₃₂ was synthesized. The production phase of the synthesized polycrystalline sample was confirmed by powder X-ray diffraction. In addition, this corusite polycrystal sample is obtained by substituting Si for Sn in the corusite polycrystal sample in Example 1.
Then, the synthesized Cu ₂₆ Nb ₂ Si ₆ S ₃₂ polycrystalline sample was subjected to the same sintering operation as in Example 1 to manufacture a thermoelectric conversion element according to Example 2.
The electrical resistance value of the thermoelectric conversion element according to the second embodiment is 220 mΩ, whereas the electrical resistance value of the thermoelectric conversion element predicted from the electrical resistivity of the simple substance of corusite is 220 mΩ. It is confirmed that a high resistance phase was not formed between them and good bonding was obtained.

(Example 3)
First, the raw materials Cu (1.502 g), Nb (0.169 g), Ge (0.396 g) and S (0.933 g) were vacuum sealed in a quartz tube and melted at 1,050°C. , About 3 g of a polycrystalline sample having a composition of Cu ₂₆ Nb ₂ Ge ₆ S ₃₂ was synthesized. The production phase of the synthesized polycrystalline sample was confirmed by powder X-ray diffraction. Further, this corusite polycrystal sample is obtained by substituting Ge for Sn in the corusite polycrystal sample in Example 1.
Next, the same Cu ₂₆ Nb ₂ Ge ₆ S ₃₂ polycrystal sample was subjected to the same sintering operation as in Example 1 to manufacture a thermoelectric conversion element according to Example 3.
The electric resistance value of the thermoelectric conversion element according to Example 3 is 7 mΩ, while the electric resistance value of the thermoelectric conversion element predicted from the electric resistivity of the single substance of corusite is 7 mΩ. It is confirmed that a high resistance phase was not formed between them and good bonding was obtained.

(Example 4)
First, the raw materials Cu (1.419 g), V (0.088 g), Sn (0.612 g) and S (0.881 g) were vacuum sealed in a quartz tube and melted at 1,050°C. , About 3 g of a polycrystalline sample having a composition of Cu ₂₆ V ₂ Sn ₆ S ₃₂ was synthesized. The production phase of the synthesized polycrystalline sample was confirmed by powder X-ray diffraction. Further, this corusite polycrystal sample is obtained by substituting V for Nb of the corusite polycrystal sample in Example 1.
Then, the synthesized Cu ₂₆ V ₂ Sn ₆ S ₃₂ polycrystal sample was subjected to the same sintering operation as in Example 1 to manufacture a thermoelectric conversion element according to Example 4.
The electrical resistance value of the thermoelectric conversion element according to Example 4 is 27 mΩ, while the electrical resistance value of the thermoelectric conversion element predicted from the electrical resistivity of the single substance of corusite is 24 mΩ. It is confirmed that a high resistance phase is not formed between them and good bonding is obtained.

(Example 5)
First, the raw materials Cu (1.321 g), Ta (0.289 g), Sn (0.569 g) and S (0.820 g) were vacuum sealed in a quartz tube and melted at 1,050°C. , About 3 g of a polycrystalline sample having a composition of Cu ₂₆ Ta ₂ Sn ₆ S ₃₂ was synthesized. The production phase of the synthesized polycrystalline sample was confirmed by powder X-ray diffraction. In addition, this corusite polycrystal sample is obtained by substituting Ta for Nb of the corusite polycrystal sample in Example 1.
Then, the synthesized Cu ₂₆ Ta ₂ Sn ₆ S ₃₂ polycrystal sample was subjected to the same sintering operation as in Example 1 to manufacture a thermoelectric conversion element according to Example 5.
The electrical resistance value of the thermoelectric conversion element according to Example 5 is 15 mΩ, whereas the electrical resistance value of the thermoelectric conversion element predicted from the electrical resistivity of corusite alone is 15 mΩ. It is confirmed that a high resistance phase was not formed between them and good bonding was obtained.

(Example 6)
Cu ₂₆ V was used in the same manner as in Example 4 except that Ti powder was used as the electrode material instead of the Au foil, and the weight of the polycrystalline sample used in the sintering operation was changed from 2.5 g to 0.8 g. _A thermoelectric conversion element according to Example 6 having a structure in which a thermoelectric conversion material layer formed of ₂ Sn ₆ S ₃₂ was sandwiched between Ti electrodes was manufactured.
The electric resistance value of the thermoelectric conversion element according to Example 6 was 8.4Ω, while the electric resistance value of the thermoelectric conversion element predicted from the electric resistance of the single substance of corusite was 1 mΩ. Although it is a large value, it is confirmed that good bonding is obtained.

(Example 7)
Cu ₂₆ V was used in the same manner as in Example 4 except that Pt foil was used as the electrode material instead of Au foil, and the weight of the polycrystalline sample used for the sintering operation was changed from 2.5 g to 1.0 g. _A thermoelectric conversion element according to Example 7 having a structure in which a thermoelectric conversion material layer formed of ₂ Sn ₆ S ₃₂ was sandwiched between Pt electrodes was manufactured.
The electric resistance value of the thermoelectric conversion element according to Example 7 was 2.4 Ω, while the electric resistance value of the thermoelectric conversion element predicted from the electric resistivity of the corusite alone was 1 mΩ. Although it is a large value, it is confirmed that good bonding is obtained.

(Comparative Example 1)
Thermoelectric conversion according to Comparative Example 1 of a structure in which a thermoelectric conversion material layer formed of corusite was sandwiched between Fe electrodes in the same manner as in Example 4 except that Fe powder was used instead of Au foil as an electrode material. Tried to manufacture the device.
However, during the sintering operation, the product generated by the reaction between the corusite powder and the Fe powder was melted and overflowed from the sintering mold, and the thermoelectric conversion element according to Comparative Example 1 could not be manufactured. It was

(Comparative example 2)
Thermoelectric conversion according to Comparative Example 2 having a structure in which a thermoelectric conversion material layer formed of corusite was sandwiched between Ni electrodes in the same manner as in Example 4 except that Ni powder was used instead of the Au foil as the electrode material. Tried to manufacture the device.
However, during the sintering operation, the product produced by the reaction between the corusite powder and the Ni powder melts and overflows from the sintering mold, and the thermoelectric conversion element according to Comparative Example 2 cannot be manufactured. It was

(Comparative example 3)
Thermoelectric conversion according to Comparative Example 3 having a structure in which a thermoelectric conversion material layer formed of corusite was sandwiched between Mo electrodes in the same manner as in Example 4 except that Mo powder was used instead of Au foil as the electrode material. Tried to manufacture the device.
However, during the sintering operation, the product generated by the reaction between the corusite powder and the Mo powder melts and overflows from the sintering mold, and the thermoelectric conversion element according to Comparative Example 3 cannot be manufactured. It was

(Comparative example 4)
Thermoelectric conversion according to Comparative Example 4 having a structure in which a thermoelectric conversion material layer formed of corusite was sandwiched between Pd electrodes in the same manner as in Example 4 except that Pd foil was used instead of Au foil as the electrode material. Tried to manufacture the device.
However, during the sintering operation, the product generated by the reaction between the corusite powder and the Pd foil was melted and overflowed from the sintering mold, and the thermoelectric conversion element according to Comparative Example 4 could not be manufactured. It was

(Comparative example 5)
Thermoelectric conversion according to Comparative Example 5 having a structure in which a thermoelectric conversion material layer formed of corusite was sandwiched between Ag electrodes in the same manner as in Example 4 except that Ag powder was used instead of the Au foil as the electrode material. Tried to manufacture the device.
However, during the sintering operation, the product generated by the reaction between the corusite powder and the Ag powder was melted and overflowed from the sintering mold, and the thermoelectric conversion element according to Comparative Example 5 could not be manufactured. It was

The electrode layer is required to have low electric resistivity, high thermal conductivity, and be chemically stable even at high temperature. When the electric resistivity is low, the electric power can be efficiently extracted from the corusite, and when the thermal conductivity is high, the heat can be efficiently transferred to the corusite, which is chemically stable even at a high temperature. Corusite can be stably used as a thermoelectric conversion material even at high temperatures.
Therefore, in Examples 1 to 7, Au, Ti, and Pt having high melting points are selected as the electrode material among metals having low electric resistivity and high thermal conductivity. On the other hand, the electrode materials Fe, Ni, Mo, Pd, and Ag used in Comparative Examples 1 to 5 have high melting points similarly to the electrode materials Au, Ti, and Pt used in Examples 1 to 7. (See Table 2 below for melting point).
However, in Comparative Examples 1 to 5, as described above, Fe, Ni, Mo, Pd, and Ag reacted with corusite to be melted out, and the thermoelectric conversion element could not be manufactured.
Among the materials selected as the electrode materials, Mo having the highest melting point and corusite did not react, and Au having a relatively low melting point did not react with corusite. It clearly shows that the reactivity with the site cannot be predicted.

*Source: Japan Institute of Metals, Metal Data Book Revised 4th Edition, Maruzen Co., Ltd., 2004

Further, among various metals studied as the electrode material, Fe, Ni, Mo, Pd, and Ag were considered to be leached out because it reacted with S, which has the highest reactivity among the constituent elements of corusite.
Then, looking at changes in standard free energy of formation of sulfides of Fe, Ni, Mo, Pd, Ag, Ti, Pt, and Au examined as electrode materials, all values are negative (see Table 3 below, Ti , And Au are not available, but are assumed to be negative due to the high reactivity of S). The negative change in standard free energy of formation indicates that the reaction between the metal and S proceeds so as to form a sulfide.

* Source: Chemistry Handbook, 4th revised edition, Chemical Society of Japan, Maruzen Co., Ltd., 2004

Therefore, Fe, Ni, Mo, Pd, Ag, Ti, Pt, and Au examined as electrode materials were all expected to react with S of corusite. However, it was confirmed that Ti, Pt, and Au did not react with corusite and could function as an electrode layer as described in Examples 1 to 7.
Also from the viewpoint of the change in standard free energy of formation, the experimental results that Ti, Pt, and Au do not react with corusite and function as an electrode layer indicate that it cannot be inferred from generally known data. The new thermoelectric conversion material corusite (Non-patent document 1 and non-patent document 2) discovered in 2014 has thermodynamic properties that have not yet been known, and the unknown properties are found in the experimental results. It is presumed that it has an influence.

1, 11, 11' thermoelectric conversion material layer 2a, 2b, 12a, 12b, 12a', 12b' electrode layer 10 thermoelectric conversion element 20 P-type thermoelectric conversion element 30 N-type thermoelectric conversion element 13 upper junction electrode 14, 14' lower portion Bonding electrode 100 Thermoelectric conversion module

Claims (9)

A thermoelectric conversion material layer formed of a thermoelectric conversion material represented by the following chemical formula (1),
An electrode layer formed of an electrode material that is joined to the thermoelectric conversion material layer and contains at least one of Ti, Pt, and Au;
A thermoelectric conversion element comprising:
However, in the chemical formula (1), M represents a metal material containing at least one of Mn, Fe, Co, Ni and Zn, and A represents a metal material containing at least one of V, Nb and Ta. , E represent a metallic material containing at least one of Si, Ge and Sn, and x represents a numerical value of 0-5. The thermoelectric conversion element according to claim 1, wherein x in the chemical formula (1) is 0. The thermoelectric conversion material is a compound in which A in the chemical formula (1) is Nb, and E is any one of Si, Ge, and Sn, and any one of the A in the chemical formula (1) is V or Ta. The thermoelectric conversion element according to any one of claims 1 and 2, wherein the thermoelectric conversion element is one of the compounds wherein E is Sn. The thermoelectric conversion element according to claim 1, wherein the electrode material contains Au. It is a manufacturing method of the thermoelectric conversion element in any one of Claim 1 to 4, Comprising:
A laminated structure forming step of forming a laminated structure in which a thermoelectric conversion material layer and an electrode layer are laminated,
While heating the laminated structure to sinter the thermoelectric conversion material layer, a heating step of joining the thermoelectric conversion material layer and the electrode layer,
A method of manufacturing a thermoelectric conversion element, comprising: The method for producing a thermoelectric conversion element according to claim 5, wherein the heating temperature in the heating step is 400°C to 1,050°C. The method for producing a thermoelectric conversion element according to claim 5, wherein the heating in the heating step is performed under pressure. The method for manufacturing a thermoelectric conversion element according to claim 7, wherein the pressure applied is at least 10 MPa. A thermoelectric conversion module comprising the thermoelectric conversion element according to any one of claims 1 to 4 as a P-type thermoelectric conversion element.