JP2017168609A - Thermoelectric conversion element, thermoelectric conversion module, and thermoelectric conversion system - Google Patents

Abstract

Matching with a Sb-containing thermoelectric conversion material having a filled skutterudite structure, it is possible to prevent diffusion of constituent components at the joint surface between the thermoelectric conversion material and an electrode member even if the temperature changes greatly due to operation or the like. A thermoelectric conversion element capable of maintaining good power generation characteristics is provided.
A thermoelectric conversion member having a filled skutterudite structure and made of a thermoelectric conversion material containing Sb; and provided in contact with the thermoelectric conversion member; at least one element selected from Cr, Mo, and W And a plated layer having a thickness of 0.1 μm or more and 500 μm or less.
[Selection] Figure 1

Description

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

  In recent years, there has been a tendency to reduce environmental impact on a global scale. As part of promoting the efficient use of energy, thermoelectric conversion modules have been actively researched and developed as a technology for recovering waste heat generated from heat engines and converting it into electricity. A thermoelectric conversion module is a device that can directly convert thermal energy into electrical energy or electrical energy into thermal energy. The thermoelectric conversion module includes a p-type thermoelectric conversion member and an n-type thermoelectric conversion member. In general, a plurality of p-type thermoelectric conversion members and n-type thermoelectric conversion members are alternately electrically connected in series. Provide structure. In particular, thermoelectric conversion modules for power generation use the Seebeck effect in which an electromotive force is generated due to a temperature difference between one end and the other end where different kinds of conductors are joined. In such a thermoelectric conversion module, one end where the p-type thermoelectric conversion member and the n-type thermoelectric conversion member are connected is a high temperature portion and the other end is a low temperature portion, and a temperature difference is given to both ends.

The property of the thermoelectric conversion material is evaluated by the figure of merit Z. The figure of merit Z is represented by the following formula (1) using the Seebeck coefficient S, the thermal conductivity κ, and the electrical resistivity ρ.
Z = S ² / (κρ) (1)
Moreover, the property of the thermoelectric conversion material may be evaluated by the product of the figure of merit Z and the temperature T. In this case, the following equation (2) is obtained by multiplying both sides of the equation (1) by a temperature T (where T is an absolute temperature).
ZT = S ² T / (κρ) (2)
ZT shown in Formula (2) is called a dimensionless figure of merit and serves as an index indicating the performance of the thermoelectric conversion material. The thermoelectric conversion material has higher thermoelectric performance at the temperature T as the ZT value is larger. From the formulas (1) and (2), an excellent thermoelectric conversion material is a material that can increase the value of the figure of merit Z, that is, a material that has a large Seebeck coefficient S and a small thermal conductivity κ and electrical resistivity ρ. .

Moreover, when evaluating the performance of the thermoelectric conversion material from an electrical viewpoint, the output factor P represented by following Formula (3) may be used.
P = S ² / ρ Formula (3)

The maximum conversion efficiency η _max of the thermoelectric conversion material is represented by the following formula (4).
η _max = {(T _h −T _c ) / T _h } {(M−1) / (M + (T _c / T _h ))} Equation (4)
M in the equation (4) is represented by the following equation (5). Here, _Th is the temperature at the high temperature end of the thermoelectric conversion material, and T _c is the temperature at the low temperature end.
M = {1 + Z (T _h + T _c ) / 2} ^−0.5 (5)
From the above formulas (1) to (5), it can be seen that the thermoelectric conversion efficiency of the thermoelectric conversion material improves as the performance index and the temperature difference between the high temperature end and the low temperature end increase.

Typical examples of thermoelectric conversion materials that have been studied so far include Bi ₂ Te ₃ , PbTe, AgSbTe ₂ -GeTe, SiGe, skutterudites represented by (Ti, Zr, Hf) NiSn, CoSb ₃ and Examples include filled skutterudite compounds, Zn ₄ Sb ₃ , FeSi ₂ , NaCo ₂ O ₄ oxide, and Ca ₃ Co ₄ O ₉ oxide.

Among them, an Sb-containing alloy having a filled skutterudite structure that can be used in an intermediate temperature range of 300 ° C. to 600 ° C. has attracted attention because of its high thermoelectric conversion performance in this temperature range. If a thermoelectric conversion module can be manufactured using a filled skutterudite-type thermoelectric conversion material, the conversion efficiency in a higher temperature range than a thermoelectric conversion module using a conventional thermoelectric conversion material such as Bi ₂ Te ₃ is used. High module can be used.

  On the other hand, when producing a thermoelectric conversion module using a thermoelectric conversion member, it is necessary to join each p-type and n-type thermoelectric conversion member and an electrode member at a high temperature part and a low temperature part. In order to manufacture a thermoelectric conversion module that can be used in the intermediate temperature region of 300 ° C. to 600 ° C., selection of the material of the electrode member that connects the p-type thermoelectric conversion member and the n-type thermoelectric conversion member and the joining method are important. It was a challenge. This is because the element contained in the electrode member diffuses into the thermoelectric conversion member on the surface where the thermoelectric conversion member and the electrode member are in contact with each other, or the thermoelectric conversion performance of the thermoelectric conversion member deteriorates or is included in the thermoelectric conversion member. This is because the mechanical characteristics or electrical characteristics of the electrode member may deteriorate due to the diffusion of the element to be diffused into the electrode member, and the power generation performance of the thermoelectric conversion module may be reduced.

  In order to prevent such diffusion of elements on the contact surface between the thermoelectric conversion member and the electrode member, there has been proposed a thermoelectric conversion device in which a diffusion prevention layer is provided between the thermoelectric conversion member and the electrode member (Patent Literature). 1, Patent Document 2, Patent Document 3, Patent Document 4).

  The thermoelectric conversion device described in Patent Document 1 and Cited Document 2 is a diffusion prevention device for a thermoelectric conversion element containing at least two elements of bismuth (Bi), tellurium (Te), antimony (Sb), and selenium (Se). A layer is provided. This diffusion prevention layer is formed by an ion plating method.

  In the thermoelectric conversion device described in the cited document 3, an alloy layer of Cu—Te, Cu—Bi, Ni—Te, Ni—Bi, or the like is formed on a thermoelectric conversion element containing Bi—Sb—Te by a plating method. .

  In the thermoelectric conversion device described in Patent Document 4, a diffusion prevention layer is provided by plating or sputtering on the surface of a thermoelectric conversion member having a skutterudite structure, a filled skutterudite structure, a Heusler structure, a half-Heusler structure, or a crestrate structure. ing. Copper oxide, aluminum nitride, cobalt antiantimonide compounds having a skutterudite type crystal structure, and the like are used as a material for forming the diffusion prevention layer.

Japanese Patent Laying-Open No. 2015-50272 Japanese Patent Laying-Open No. 2015-50273 JP 2014-197660 A Patent No. 4686171

  The Sb-containing thermoelectric conversion member having a filled skutterudite structure exhibits high thermoelectric conversion performance in an intermediate temperature region of 300 ° C. to 600 ° C., but antimony (Sb), which is a component of the thermoelectric conversion member, and a component of the electrode member, Or the component of the brazing material or the paste material used for joining the electrodes may react to deteriorate the thermoelectric conversion performance. In addition, the Sb-containing thermoelectric conversion member having a filled skutterudite structure has a relatively large coefficient of thermal expansion compared to other alloys such as a skutterudite structure, and thus the adhesion of the diffusion preventing layer may be insufficient. .

  The present invention has been made in view of the problems as described above, and is consistent with the Sb-containing thermoelectric conversion member having a filled skutterudite structure, and the thermoelectric conversion member and the electrode member It is possible to provide a thermoelectric conversion element capable of preventing the diffusion of constituent components on the bonding surface of the glass and maintaining good power generation characteristics.

  According to the present invention, a thermoelectric conversion member having a filled skutterudite structure and made of a thermoelectric conversion material containing Sb, and provided in contact with the thermoelectric conversion member, at least one of Cr, Mo, and W is provided. And a plated layer having a thickness of 0.1 μm or more and 500 μm or less.

According to the present invention, there is provided a thermoelectric conversion module including a thermoelectric conversion member, an electrode member, and a diffusion prevention layer provided between the thermoelectric conversion member and the electrode member,
The thermoelectric conversion member has a filled skutterudite structure and is made of a thermoelectric conversion material containing Sb,
The diffusion prevention layer is a plating layer that is provided in contact with the thermoelectric conversion member and includes at least one element of Cr, Mo, and W, and has a thickness of 0.1 μm or more and 500 μm or less. A module is provided.

Moreover, according to the present invention, there is provided a thermoelectric conversion system including a thermoelectric conversion member, an electrode member, a diffusion prevention layer provided between the thermoelectric conversion member and the electrode member, and a current extraction unit. ,
The thermoelectric conversion member has a filled skutterudite structure and is made of a thermoelectric conversion material containing Sb,
The diffusion prevention layer is a plating layer that is provided in contact with the thermoelectric conversion member and includes at least one element of Cr, Mo, and W, and has a thickness of 0.1 μm or more and 500 μm or less. A system is provided.

  ADVANTAGE OF THE INVENTION According to this invention, while being excellent in a thermoelectric conversion characteristic, the thermoelectric conversion element which can maintain a favorable thermoelectric conversion characteristic, and the thermoelectric conversion module and thermoelectric conversion system which can maintain a favorable thermoelectric conversion characteristic and electric power generation characteristic are provided.

It is a schematic diagram which shows an example of the thermoelectric conversion module concerning this embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all drawings, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted suitably.

  FIG. 1 is a schematic diagram illustrating an example of a thermoelectric conversion module in which the thermoelectric conversion element according to the present embodiment is used. 1, the thermoelectric conversion module includes a p-type thermoelectric conversion member 1 and an n-type thermoelectric conversion member 2, which are thermoelectric conversion members, a high-temperature side plating layer 5 and a low-temperature side plating layer 6, and a high-temperature side electrode 3 and a low-temperature side electrode 4. Is provided. These plated layers 5 and 6 function as a diffusion preventing layer.

  In the present specification, the thermoelectric conversion element indicates a configuration including the thermoelectric conversion member 1 or 2 and the plating layer 5 or 6. In addition, the thermoelectric conversion system indicates a configuration in which the thermoelectric conversion module shown in FIG. 1 is further provided with a current extraction means (not shown). Here, the current extraction means is electrically connected to the two low temperature side electrodes 4 shown in FIG.

  The thermoelectric conversion element according to this embodiment has a filled skutterudite structure, and includes a thermoelectric conversion member made of a thermoelectric conversion material containing Sb, and a plating layer provided in contact with the thermoelectric conversion member. This plating layer contains at least one element of Cr, Mo, and W, and has a thickness of 0.1 μm or more and 500 μm or less.

In one embodiment, the Sb-containing thermoelectric conversion material having a filled skutterudite structure is preferably represented by R _r T _t X _x (0 <r ≦ 1, 3 ≦ t ≦ 5, 0 <x ≦ 15). Material,
R is a rare earth element, an alkali metal element, an alkaline earth metal element, and a Group 13 element;
T is a transition metal element,
X is Sb.

Here, examples of the rare earth element include Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
Examples of the alkali metal element include Li, Na, K, Rb, Cs, and Fr.
Examples of the alkaline earth metal element include Ca, Sr, and Ba.
Examples of Group 13 elements include B, Al, Ga, In, and Tl.
As a transition metal element, Preferably, Fe, Co, and Ni are mentioned.

  The thermoelectric conversion material used in the present invention contains Sb. When the Sb-containing thermoelectric conversion material is combined with a plating layer containing Cr, Mo, or W, Sb cannot pass through the plating layer, so that Sb diffusion to other members is prevented.

  Thermoelectric conversion materials having such a structure include dissolution methods, rapid solidification methods (gas atomization, water atomization, centrifugal atomization, single roll method, twin roll method), mechanical alloying method (ball mill method), or single crystal growth method, etc. And a hot press method, a heat sintering method, a discharge plasma molding method, a heat treatment method, or the like. However, as long as a filled skutterudite structure is obtained, the production method is not particularly limited to the above.

  Examples of specific methods for synthesizing the thermoelectric conversion material according to the present embodiment include the following (i) to (iii).

(I) An example in which a dissolution method and a heat treatment method are combined.
Pure metal raw material is put in a carbon crucible at a predetermined ratio, and heated and melted to 1200 ° C. by heating in an electric furnace in an inert gas atmosphere. After holding for 5 hours, hold at 900 ° C. for 6 hours, subsequently at 800 ° C. for 12 hours, at 700 ° C. for 24 hours, and further at 600 ° C. for 12 hours. Then, the target thermoelectric conversion material can be obtained by cooling to room temperature.

(Ii) An example in which a melting method and a discharge plasma molding method are combined.
Pure metal raw material is put in a carbon crucible at a predetermined ratio, heated to 1200 ° C. in an inert gas atmosphere, held for 5 hours, and then rapidly cooled with water. The water-quenched material is heated to 700 ° C. and held for 24 hours, and then cooled to room temperature to obtain the desired ingot. This ingot raw material is pulverized, and the powder is put into a carbon die and heated to a temperature of 500 to 750 ° C. while applying a pulse current under a pressure of 60 MPa in a vacuum or an inert gas atmosphere. After holding for 10 minutes, the target thermoelectric conversion material can be obtained by cooling to room temperature.

(Iii) An example in which a mechanical alloying method and a discharge plasma molding method are combined.
First, pure metal powder is put into an alumina container at a predetermined ratio in an inert gas atmosphere and mixed with alumina balls. Next, mechanical alloying is performed for 24 hours to obtain a raw material powder. This powder is put into a carbon die, heated to a temperature of 500 to 750 ° C. while applying a pulse current under a pressure of 60 MPa in a vacuum or an inert gas atmosphere, and held for 10 minutes. Then, the target thermoelectric conversion material can be obtained by cooling to room temperature.

    Even when any of the synthesis methods (i) to (iii) was used, it was confirmed by powder X-ray diffraction that the obtained thermoelectric conversion material had a filled skutterudite structure. Then, the relationship between the Seebeck coefficient S, electrical resistivity ρ, thermal conductivity κ, and temperature T was measured, and the temperature dependence of the dimensionless figure of merit ZT was examined. As a result, ZT increases with increasing temperature, and ZT reaches 1.0 to 1.3 in the temperature range of room temperature to 600 ° C.

As a p-type thermoelectric conversion material, (La, Ce, Pr) _{0.5 to 0.9} Ba _{0.01 to 0.1} Ga _{0.05 to} 0.20 Ti _{0.05 to 0.2} Fe _2.5 Compounds having a composition of _˜4.0 Co _0-1.5 Sb _11-13 are preferred.

The n-type thermoelectric conversion _{material, (Yb, La, Ce)} 0.05~0.3 Ca 0.01~0.2 Al 0~0.2 Ga 0~0.2 In 0~0.3 Fe 0 Compounds having a composition of _˜0.5 Co _3.5-4 Sb _11-13 are preferred.

The plating layer is formed by plating on at least a part of the surface of the thermoelectric conversion material. The plating layer is at least one selected from the group consisting of Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, W—Co, and W—Ni. It is preferably made of an alloy.
When a plated layer made of these alloys is used as a diffusion preventing layer, Sb contained in the thermoelectric conversion material cannot pass through the plated layer, and Sb diffusion to members such as electrode members is prevented. A particularly preferred alloy for use as the plating layer is an alloy having a composition of Cr, Mo, or W greater than 0 wt% and not greater than 80 wt%.

  The plating layer may include two or more plating layers made of different alloys. Examples of the metal or alloy constituting each plating layer include Cr, Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, W—Co, and W—Ni. The selected metal or alloy can be used.

  Or a plating layer may be comprised from the ternary alloy which consists of 3 types of elements selected from the group which consists of Cr, Mo, W, Fe, Co, and Ni. Or the plating layer may be comprised from 3 or more types of elements selected from these metals.

  As a plating method for producing the plating layer, a technique usually used in this field can be used. In this embodiment, the thickness of the plating layer is 0.1 μm or more and 500 μm or less. The thickness of the plating layer is more preferably 10 μm or more and 300 μm or less, and further preferably 50 μm or more and 200 μm or less. By setting it as the plating layer of such thickness, the thickness of a plating layer can be suitably adjusted within the said range by adjusting the implementation time of a plating method. In addition, by using a plating method, it is easy to adjust the composition and thickness of the resulting plating layer. Furthermore, it is also possible to use an inclined material in which the composition, thickness, etc. change gently. Moreover, the layer which consists of an alloy can be produced at low cost by a plating method compared with a rolled sheet.

  The plating method used to form the plating layer is preferably an electrolytic plating method. By using the electrolytic plating method, the composition and thickness can be easily adjusted, and a plating layer can be produced at low cost.

  In one embodiment, the plating layer can be a graded material with a gently changing linear expansion coefficient. The inclined material can be produced by a known method using a plating method.

  In the present embodiment, the thermoelectric conversion module is manufactured by joining the thermoelectric conversion element and the electrode member via a plating layer. The plating layer prevents diffusion of constituent components between the thermoelectric conversion material and the electrode member. Specifically, the constituent components of the thermoelectric conversion material are prevented from diffusing into the electrode member, the thermoelectric conversion characteristics of the thermoelectric conversion material are maintained, and the power generation performance of the electrode member can be maintained. Moreover, when the thickness of the plating layer is within the above range, the diffusion preventing ability of the plating layer is maintained.

  In this embodiment, a thermoelectric conversion system is produced by electrically connecting the thermoelectric conversion module and the current extraction means. In the case of the thermoelectric conversion module shown in FIG. 1, a thermoelectric conversion system can be produced by electrically connecting two low-temperature side electrode members 4 via current extraction means. As current extraction means, means known in the art can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

  In each Example, the electroplating method was implemented on the conditions shown below using the thermoelectric conversion material, and the thermoelectric conversion material which has a plating layer was produced.

In the following examples, a thermoelectric conversion material was used as a cathode, and a plating layer was formed on the thermoelectric conversion material by performing plating treatment with the following composition and conditions. Thereafter, the composition and thickness of the obtained plating layer were measured. Since the composition of the plating layer varies depending on the measurement location, the range is described. Moreover, the average value of the composition of the plating layer is measured and described.
The thickness of the plating layer was measured by a scanning electron microscope (SEM) observation photograph of the cross section of the plating layer. Moreover, the composition of the plating layer was measured by SEM-EDX.

Example 1
<Plating conditions>
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
Cathode (p-type thermoelectric conversion material): La _1.0 Fe ₄ Sb ₁₂
Composition of the obtained plating layer (wt%): Fe (30 to 90 wt%) Mo (10 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Fe (70 wt%) Mo (30 wt%)
Plating layer thickness: 20 μm

(Example 2)
<Plating conditions>
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
Cathode (p-type thermoelectric conversion material): Ce _0.9 Fe _3.5 Co _0.5 Sb ₁₂
Composition of the obtained plating layer (wt%): Fe (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Fe (75 wt%) W (25 wt%)
Plating layer thickness: 20 μm

(Example 3)
And composition nickel sulfate plating bath _{(NiSO 4 · 6H 2 O)} : 0.2M
Sodium molybdate (Na ₂ MoO ₄ .2H ₂ O): 0.05 to 0.5M
Sodium gluconate _{(C 6 H 11 O 7 Na} ): 0.3M
・ Plating bath pH: 9-11
・ Plating bath temperature: 25-80 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Ni
Cathode (p-type thermoelectric conversion material): Pr _0.7 Ba _0.1 Ga _0.1 Ti _0.1 Fe ₄ Sb ₁₂
Composition of the obtained plating layer (wt%): Ni (30 to 98 wt%) Mo (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Ni (70 wt%) Mo (30 wt%)
Plating layer thickness: 25 μm

Example 4
-Composition of plating bath Nickel sulfate (NiSO ₄ .6H ₂ O): 0.08M
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 0.32M
Sodium citrate (Na ₃ C ₆ H ₅ O ₇ ): 0.3M
Ammonium sulfate ((NH ₄ ) 2 SO ₄ ): 0.5M
Sodium lauryl sulfate _{(NaC 12 H 25 SO 4)} : 0.5M
・ Plating bath pH: 2-12
・ Plating bath temperature: 25-80 ° C
Current density: 2-100 A / dm ²
・ Anode: C / Ni
Cathode (p-type thermoelectric conversion material): La _0.4 Ce _0.4 Ga _0.1 Ti _0.1 Fe ₃ Co ₁ Sb ₁₂
Composition of the obtained plating layer (wt%): Ni (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Ni (75 wt%) W (25 wt%)
Plating layer thickness: 25 μm

(Example 5)
And composition cobalt sulfate plating bath _{(CoSO 4 · 6H 2 O)} : 82g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 48 g / L
Sodium citrate (Na ₃ C ₆ H ₅ O ₇ ): 88 g / L
Boric acid (H ₃ BO ₃ ): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 40 ℃
Current density: 5-20 A / dm ²
・ Anode: C / Co
Cathode (p-type thermoelectric conversion material): La _0.4 Pr _0.4 Ga _0.1 Ti _0.1 Fe ₃ Co ₁ Sb ₁₂
Composition of the obtained plating layer (wt%): Co (30 to 98 wt%) Mo (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Co (80 wt%) Mo (20 wt%)
Plating layer thickness: 22 μm

(Example 6)
-Composition of plating bath Cobalt sulfate (CoSO ₄ · (6H ₂ O)): 200 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10g / L
Ammonium chloride (NH ₄ Cl): 60 g / L
Boric acid (H ₃ BO ₃ ): 30 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 40 ℃
Current density: 1-10 A / dm ²
・ Anode: C / Co
Cathode (p-type thermoelectric conversion material): Ce _0.4 Pr _0.4 Ga _0.1 Ti _0.1 Fe ₃ Co ₁ Sb ₁₂
Composition of the obtained plating layer (wt%): Co (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Co (85 wt%) W (15 wt%)
Plating layer thickness: 18 μm

(Example 7)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 7, La _0.8 Fe ₃ Co ₁ Sb ₁₂ was used as the p-type thermoelectric conversion material (cathode).
(First plating layer (Fe-Mo))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 106g / L
Potassium formate (HCOONa): 80 g / L
Ammonium chloride (NH ₄ Cl): 54 g / L
Boric acid (H ₃ BO ₃ ): 40 g / L
Potassium bromide (KBr): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 30 ℃
・ Current density: 5 A / dm ²
・ Anode: C
The obtained plating layer was heated at 600 ° C. The plated layer after heating was present as an alloy of Fe, Mo and Cr. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (65 wt%) Cr (20 wt%) Mo (15 wt%)
Plating layer thickness: 120 μm

(Example 8)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 8, Ce _0.8 Fe ₃ Co ₁ Sb ₁₂ was used as the p-type thermoelectric conversion material (cathode).
(First plating layer (Fe-W))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 106g / L
Potassium formate (HCOONa): 80 g / L
Ammonium chloride (NH ₄ Cl): 54 g / L
Boric acid (H ₃ BO ₃ ): 40 g / L
Potassium bromide (KBr): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 30 ℃
・ Current density: 5 A / dm ²
・ Anode: C
The obtained plating layer was heated at 600 ° C. The plated layer after heating existed as an alloy of Fe, Cr and W. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (65 wt%) Cr (20 wt%) W (15 wt%)
Plating layer thickness: 100 μm

Example 9
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 9, a p-type thermoelectric conversion material (cathode) _was used _{La 0.7 Ba 0.1 Ga 0.1 Ti 0.1} Fe 3 Co 1 Sb 12.
(First plating layer (Fe-Mo))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Fe-Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 80g / L
Iron chloride tetrahydrate (FeCl ₂ .4H ₂ O): 60 g / L
Ammonium chloride (NH ₄ Cl): 48 g / L
Boric acid (H ₃ BO ₃ ): 15 g / L
Glycine (C ₂ H ₅ NO ₂ ): 75 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 30 ℃
・ Current density: 10 A / dm ²
・ Anode: C / Fe
The obtained plating layer was heated at 600 ° C. The plated layer after heating was present as an alloy of Fe, Cr and Mo. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (80 wt%) Cr (13 wt%) Mo (7 wt%)
Plating layer thickness: 150 μm

(Example 10)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 10, Ce _0.7 Ba _0.1 Ga _0.1 Ti _0.1 Fe _3.5 Co _0.5 Sb ₁₂ was used as the p-type thermoelectric conversion material (cathode).
(First plating layer (Fe-W))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Fe-Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 80g / L
Iron chloride tetrahydrate (FeCl ₂ .4H ₂ O): 60 g / L
Ammonium chloride (NH ₄ Cl): 48 g / L
Boric acid (H ₃ BO ₃ ): 15 g / L
Glycine (C ₂ H ₅ NO ₂ ): 75 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 30 ℃
・ Current density: 10 A / dm ²
・ Anode: C / Fe
The obtained plating layer was heated at 600 ° C. The plated layer after heating existed as an alloy of Fe, Cr and W. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (77 wt%) Cr (15 wt%) W (8 wt%)
Plated layer thickness: 200 μm

(Example 11)
<Plating conditions>
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
Cathode (n-type thermoelectric conversion material): Yb _0.3 Ca _0.1 Ga _0.1 Fe _0.25 Co _3.75 Sb ₁₂
Composition of the obtained plating layer (wt%): Fe (30 to 90 wt%) Mo (10 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Fe (65 wt%) Mo (35 wt%)
Plating layer thickness: 23 μm

Example 12
<Plating conditions>
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
Cathode (n-type thermoelectric conversion material): Yb _0.3 Ca _0.1 In _0.1 Fe _0.25 Co _3.75 Sb ₁₂
Composition of the obtained plating layer (wt%): Fe (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Fe (70 wt%) W (30 wt%)
Plating layer thickness: 19 μm

(Example 13)
And composition nickel sulfate plating bath _{(NiSO 4 · 6H 2 O)} : 0.2M
Sodium molybdate (Na ₂ MoO ₄ .2H ₂ O): 0.05 to 0.5M
Sodium gluconate _{(C 6 H 11 O 7 Na} ): 0.3M
・ Plating bath pH: 9-11
・ Plating bath temperature: 25-80 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Ni
Cathode (n-type thermoelectric conversion material): Yb _0.2 Co ₄ Sb ₁₂
Composition of the obtained plating layer (wt%): Ni (30 to 98 wt%) Mo (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Ni (70 wt%) Mo (30 wt%)
Plating layer thickness: 22 μm

(Example 14)
-Composition of plating bath Nickel sulfate (NiSO ₄ .6H ₂ O): 0.08M
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 0.32M
Sodium citrate (Na ₃ C ₆ H ₅ O ₇ ): 0.3M
Ammonium sulfate ((NH ₄ ) 2 SO ₄ ): 0.5M
Sodium lauryl sulfate _{(NaC 12 H 25 SO 4)} : 0.5M
・ Plating bath pH: 2-12
・ Plating bath temperature: 25-80 ° C
Current density: 2-100 A / dm ²
・ Anode: C / Ni
Cathode (n-type thermoelectric conversion material): Yb _0.2 Ca _0.1 Fe _0.25 Co _3.75 Sb ₁₂
Composition of the obtained plating layer (wt%): Ni (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Ni (65 wt%) W (35 wt%)
Plating layer thickness: 20 μm

(Example 15)
And composition cobalt sulfate plating bath _{(CoSO 4 · 6H 2 O)} : 82g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 48 g / L
Sodium citrate (Na ₃ C ₆ H ₅ O ₇ ): 88 g / L
Boric acid (H ₃ BO ₃ ): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 40 ℃
Current density: 5-20 A / dm ²
・ Anode: C / Co
Cathode (n-type thermoelectric conversion material): Yb _0.3 Ca _0.1 Ga _0.1 In _0.1 Fe _0.25 Co _3.75 Sb ₁₂
Composition of the obtained plating layer (wt%): Co (30 to 98 wt%) Mo (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Co (80 wt%) Mo (20 wt%)
Plating layer thickness: 21 μm

(Example 16)
And composition cobalt sulfate plating bath _{(CoSO 4 · 6H 2 O)} : 200g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10g / L
Ammonium chloride (NH ₄ Cl): 60 g / L
Boric acid (H ₃ BO ₃ ): 30 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 40 ℃
Current density: 1-10 A / dm ²
・ Anode: C / Co
Cathode (n-type thermoelectric conversion material): La _0.3 Ca _0.1 Ga _0.1 In _0.1 Fe _0.25 Co _3.75 Sb ₁₂
Composition of the obtained plating layer (wt%): Co (30 to 98 wt%) W (2 to 70 wt%)
Composition of the obtained plating layer (average, wt%): Co (85 wt%) W (15 wt%)
Plating layer thickness: 20 μm

(Example 17)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 17, Ce _0.3 Ca _0.1 Ga _0.1 In _0.1 Fe _0.25 Co _3.75 Sb ₁₂ was used as the n-type thermoelectric conversion material (cathode).
(First plating layer (Fe-Mo))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 106g / L
Potassium formate (HCOONa): 80 g / L
Ammonium chloride (NH ₄ Cl): 54 g / L
Boric acid (H ₃ BO ₃ ): 40 g / L
Potassium bromide (KBr): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 30 ℃
・ Current density: 5 A / dm ²
・ Anode: C
The obtained plating layer was heated at 600 ° C. The plated layer after heating was present as an alloy of Fe, Cr and Mo. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (70 wt%) Cr (15 wt%) Mo (15 wt%)
Plating layer thickness: 300 μm

(Example 18)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 18, Yb _0.3 Ca _0.1 Al _0.1 Ga _0.1 In _0.1 Fe _0.25 Co _3.75 Sb ₁₂ was used as the n-type thermoelectric conversion material (cathode).
(First plating layer (Fe-W))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 106g / L
Potassium formate (HCOONa): 80 g / L
Ammonium chloride (NH ₄ Cl): 54 g / L
Boric acid (H ₃ BO ₃ ): 40 g / L
Potassium bromide (KBr): 10 g / L
・ Plating bath pH: 3
・ Plating bath temperature: 30 ℃
・ Current density: 5 A / dm ²
・ Anode: C
The obtained plating layer was heated at 600 ° C. The plated layer after heating existed as an alloy of Fe, Cr and W. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (80 wt%) Cr (15 wt%) W (10 wt%)
Plating layer thickness: 350 μm

(Example 19)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 19, the n-type thermoelectric conversion material (cathode) _was used _{La 0.3 Ca 0.1 Al 0.1 Ga 0.1} In 0.2 Fe 0.25 Co 3.75 Sb 12.
(First plating layer (Fe-Mo))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O): 30 to 80 g / L
Sodium citrate _{(Na 3 C 6 H 5 O} 7): 70~120g / L
・ Plating bath pH: 3-6
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Fe-Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 80g / L
Iron chloride tetrahydrate (FeCl ₂ .4H ₂ O): 60 g / L
Ammonium chloride (NH ₄ Cl): 48 g / L
Boric acid (H ₃ BO ₃ ): 15 g / L
Glycine (C ₂ H ₅ NO ₂ ): 75 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 30 ℃
・ Current density: 10 A / dm ²
・ Anode: C / Fe
The obtained plating layer was heated at 600 ° C. The plated layer after heating was present as an alloy of Fe, Cr and Mo. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (82 wt%) Cr (13 wt%) Mo (5 wt%)
Plating layer thickness: 400 μm

(Example 20)
After the first plating layer was produced under the first plating conditions, the second plating layer was produced under the second plating conditions. In Example 20, the n-type thermoelectric conversion material (cathode) _was used _{Ce 0.3 Ca 0.1 Al 0.1 Ga 0.1} In 0.1 Fe 0.25 Co 3.75 Sb 12.
(First plating layer (Fe-W))
-Composition of plating bath Iron sulfate (FeSO ₄ · 7H ₂ O): 20 to 100 g / L
Sodium tungstate _{(Na 2 WO 4 · 2H 2} O): 10~100g / L
Ammonium citrate tribasic _{(H 4 NOCOCH 2 C (OH} ) (COONH 4) CH 2 COONH 4): 50~120g / L
・ Plating bath pH: 2-7
・ Plating bath temperature: 25-50 ° C
Current density: 2-50 A / dm ²
・ Anode: C / Fe
(Second plating layer (Fe-Cr))
And composition of chromium chloride hexahydrate plating bath _{(CrCl 3 · 6H 2 O)} : 80g / L
Iron chloride tetrahydrate (FeCl ₂ .4H ₂ O): 60 g / L
Ammonium chloride (NH ₄ Cl): 48 g / L
Boric acid (H ₃ BO ₃ ): 15 g / L
Glycine (C ₂ H ₅ NO ₂ ): 75 g / L
・ Plating bath pH: 6
・ Plating bath temperature: 30 ℃
・ Current density: 10 A / dm ²
・ Anode: C / Fe
The obtained plating layer was heated at 600 ° C. The plated layer after heating existed as an alloy of Fe, Cr and W. The composition of the plating layer is shown as an average value.
Composition of plating layer (average, wt%): Fe (78 wt%) Cr (15 wt%) W (7 wt%)
Plating layer thickness: 450 μm

(Production and evaluation of thermoelectric conversion module)
The p / n type thermoelectric material with a plating layer produced in Example 1 to Example 20 was processed into a thermoelectric conversion element having a size of 5 mm × 5 mm × 7 mm (height), and p / n type thermoelectric using a Cu electrode and Ag brazing. The elements were connected alternately to produce a thermoelectric conversion module having a size of 50 mm × 50 mm × 7.6 mm (height). About the produced thermoelectric conversion module, the heat cycle test was done. Specifically, a heat cycle test was performed in a vacuum using a block heater on the high temperature side and holding the low temperature side at 50 ° C. or lower by water cooling.
The temperature of the electrode member on the high temperature side is increased from 200 ° C. over 60 minutes, held at 600 ° C. for 30 minutes, and then controlled to decrease to 200 ° C. or lower over 30 minutes, and this cycle is performed for 200 hours. went. After this cycle, neither the power generation performance of the thermoelectric conversion module changed nor the internal resistance increased. Furthermore, when the joining state of the thermoelectric conversion member and the electrode member was observed, they were joined in a good state. When elemental analysis of the thermoelectric conversion member and electrode member after the heat cycle was performed, interdiffusion of elements between them was not recognized.

(Comparative Example 1)
The p-type thermoelectric conversion material of Example 9 and the n-type thermoelectric conversion material of Example 18 without a plating layer were processed into thermoelectric conversion elements having a size of 5 mm × 5 mm × 7 mm (height), and Cu electrodes and Ag brazing were used. A p / n type thermoelectric element was alternately connected to produce a thermoelectric conversion module having a size of 50 mm × 50 mm × 7.6 mm (height). About the produced thermoelectric conversion module, it carried out similarly to the said Example, and performed the heat cycle test. As a result, the power generation output of the thermoelectric conversion module decreased with the passage of time, and when 6 hours passed, the thermoelectric conversion module collapsed and power generation was not possible. As a result of analyzing the thermoelectric conversion module, it was recognized that the Cu electrode reacted with the thermoelectric element to become a compound having a melting point of 600 ° C. or lower.

  As can be seen from the above results, the thermoelectric conversion module of the present invention can continuously generate power even at a high temperature of 600 ° C., and the high temperature stability of the electrode / thermoelectric conversion element was maintained.

1 p-type thermoelectric conversion member 2 n-type thermoelectric conversion member 3 high temperature side electrode 4 low temperature side electrode 5 high temperature side plating layer (diffusion prevention layer)
6 Low temperature side plating layer (diffusion prevention layer)

Claims (21)

A thermoelectric conversion member having a filled skutterudite structure and made of a thermoelectric conversion material containing Sb;
A plating layer provided in contact with the thermoelectric conversion member, containing at least one element of Cr, Mo, and W, and having a thickness of 0.1 μm or more and 500 μm or less;
A thermoelectric conversion element including: The thermoelectric conversion material is represented by R _r T _t X _x (0 <r ≦ 1, 3 ≦ t ≦ 5, 0 <x ≦ 15),
R is a rare earth element, an alkali metal element, an alkaline earth metal element, and a Group 13 element;
T is a transition metal element,
The thermoelectric conversion element according to claim 1, wherein X is Sb.   The plating layer is at least one selected from the group consisting of Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, W—Co, and W—Ni. The thermoelectric conversion element of Claim 1 or 2 which consists of an alloy of these.   The plating layer includes at least two plating layers, and each plating layer includes Cr, Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, and W. The thermoelectric conversion element of any one of Claims 1-3 which consists of a metal selected from the group which consists of -Co and W-Ni.   The thermoelectric conversion element according to claim 1, wherein the plating layer includes a ternary alloy composed of three elements selected from the group consisting of Cr, Mo, W, Fe, Co, and Ni.   The thermoelectric conversion element according to claim 1, wherein the plating layer has an average crystal grain size of 0.1 μm or more and 500 μm or less.   The thermoelectric conversion element according to claim 1, wherein at least a part of the plating layer is an inclined material in which a linear expansion coefficient changes gently. A thermoelectric conversion module comprising a thermoelectric conversion member, an electrode member, and a diffusion prevention layer provided between the thermoelectric conversion member and the electrode member,
The thermoelectric conversion member has a filled skutterudite structure and is made of a thermoelectric conversion material containing Sb,
The diffusion prevention layer is a plating layer that is provided in contact with the thermoelectric conversion member and includes at least one element of Cr, Mo, and W, and has a thickness of 0.1 μm or more and 500 μm or less. module. The thermoelectric conversion material is represented by R _r T _t X _x (0 <r ≦ 1, 3 ≦ t ≦ 5, 0 <x ≦ 15),
R is a rare earth element, an alkali metal element, an alkaline earth metal element, and a Group 13 element;
T is a transition metal element,
The thermoelectric conversion module according to claim 8, wherein X is Sb.   The plating layer is at least one selected from the group consisting of Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, W—Co, and W—Ni. The thermoelectric conversion module according to claim 8, comprising the alloy of:   The plating layer includes at least two plating layers, and each plating layer includes Cr, Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, and W. The thermoelectric conversion module according to claim 8, comprising a metal selected from the group consisting of —Co and W—Ni.   The thermoelectric conversion module according to claim 8, wherein the plating layer includes a ternary alloy composed of three elements selected from the group consisting of Cr, Mo, W, Fe, Co, and Ni.   The thermoelectric conversion module according to any one of claims 8 to 12, wherein the plated layer has an average crystal grain size of 0.1 µm or more and 500 µm or less.   The thermoelectric conversion module according to claim 8, wherein at least a part of the plating layer is an inclined material in which a linear expansion coefficient changes gently. A thermoelectric conversion system comprising a thermoelectric conversion member, an electrode member, a diffusion prevention layer provided between the thermoelectric conversion member and the electrode member, and current extraction means,
The thermoelectric conversion member has a filled skutterudite structure and is made of a thermoelectric conversion material containing Sb,
The diffusion prevention layer is a plating layer that is provided in contact with the thermoelectric conversion member and includes at least one element of Cr, Mo, and W, and has a thickness of 0.1 μm or more and 500 μm or less. system. The thermoelectric conversion material is represented by R _r T _t X _x (0 <r ≦ 1, 3 ≦ t ≦ 5, 0 <x ≦ 15),
R is a rare earth element, an alkali metal element, an alkaline earth metal element, and a Group 13 element;
T is a transition metal element,
The thermoelectric conversion system according to claim 15, wherein X is Sb.   The plating layer is at least one selected from the group consisting of Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, W—Co, and W—Ni. The thermoelectric conversion system of Claim 15 or 16 which consists of these alloys.   The plating layer includes at least two plating layers, and each plating layer includes Cr, Cr—Fe, Cr—Co, Cr—Ni, Mo—Fe, Mo—Co, Mo—Ni, W—Fe, and W. The thermoelectric conversion system according to any one of claims 15 to 17, which is made of a metal selected from the group consisting of -Co and W-Ni.   The thermoelectric conversion system according to claim 15, wherein the plated layer includes a ternary alloy composed of three elements selected from the group consisting of Cr, Mo, W, Fe, Co, and Ni.   The thermoelectric conversion system according to any one of claims 15 to 19, wherein the plating layer has an average crystal grain size of 0.1 µm or more and 500 µm or less.   The thermoelectric conversion system according to claim 15, wherein at least a part of the plating layer is an inclined material in which a linear expansion coefficient changes gently.

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