JP2017045841A - Thermoelectric conversion material, thermoelectric conversion element, thermoelectric conversion module and production method for thermoelectric conversion material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the power factor by increasing the Seebeck coefficient (absolute value).SOLUTION: A thermoelectric conversion material is mainly composed of a Si clathrate compound, into the parent phase of which a Nb-Si compound is dispersed as a second phase.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermoelectric conversion material mainly composed of a clathrate compound and a production method thereof.

  Thermoelectric conversion modules using the Seebeck effect convert thermal energy into electrical energy. A thermoelectric conversion module generally has a structure in which a plurality of p-type and n-type thermoelectric conversion materials are alternately electrically connected in series. Thermoelectric conversion is attracting attention as an energy-saving technology in consideration of environmental problems because it can convert waste heat discharged from industrial and consumer processes and moving objects into effective power using the properties of thermoelectric conversion modules. Yes.

The dimensionless figure of merit ZT of the thermoelectric conversion element using the Seebeck effect can be expressed by the following formula [1].
ZT = S ² T / ρκ [1]
In the formula [1], S, ρ, κ, and T represent the Seebeck coefficient, electrical resistivity, thermal conductivity, and measurement temperature, respectively.

  As apparent from the equation [1], in order to improve the performance of the thermoelectric conversion element, it is important to increase the Seebeck coefficient of the element, to decrease the electrical resistivity, and to decrease the thermal conductivity. . Thermoelectric conversion elements using bismuth / tellurium-based materials, silicon / germanium-based materials, lead / tellurium-based materials and the like are known as thermoelectric conversion materials exhibiting a high performance index.

  Each of the above-described thermoelectric conversion elements has problems to be solved. Bismuth-tellurium-based materials have a ZT value that suddenly decreases when the temperature exceeds 100 ° C., and cannot be used as a thermoelectric conversion material at about 200 to 800 ° C. as in waste heat power generation. Bismuth / tellurium and lead / tellurium contain lead and tellurium, which are environmentally hazardous substances.

  Therefore, there is a demand for new thermoelectric conversion materials that have good thermoelectric performance, low environmental impact, and light weight. As one of such new thermoelectric conversion materials, Si-based clathrate compounds have attracted attention.

Several compositions and synthesis methods for Si-based clathrate compounds have already been disclosed. For example, Patent Document 1 discloses a clathrate compound represented by a composition formula Ba ₈ Ga _x Si _46-x (14 ≦ x ≦ 24) and thermoelectric characteristics thereof.

  Patent Document 2 discloses that a P-type Ba—Al—Si clathrate compound has a ZT at 700 K of 1.01. Patent Document 3 discloses that the Ba—Ga—Al—Si clathrate compound has a ZT of 0.4 or more at 800 ° C.

Patent Document 4, the composition formula _{Ba H Ga I Al J Si K} Pd L (7 ≦ H ≦ 8,9 ≦ I ≦ 12,0 ≦ J ≦ 2,33 ≦ K ≦ 35,0 <L ≦ 2, H + I + J + K + L = 54) and a thermoelectric conversion material using the same are disclosed to have a higher ZT than a similar material not containing Pd in a temperature range of room temperature to 600 ° C.

JP 2004-67425 A Japanese Patent No. 4413323 (paragraph 0048, etc.) JP 2012-033867 A JP 2012-256759 A

  However, these clathrate compounds have the following problems. In the technique described in Patent Document 1, ZT is not clear and there is a concern that the performance is low. In the technique described in Patent Document 2, the p-type is disclosed, but the ZT for the n-type is not clear and there is a concern that the performance is low. In the technique described in Patent Document 3, ZT at 600 ° C. is not clear, and further performance improvement is desired, for example, it can be used for waste heat power generation. In the technique described in Patent Document 4, Pd which is a rare element is used, and there is a concern that it is expensive.

In addition to the performance by ZT, the clathrate compound has a characteristic that the lattice thermal conductivity is low. Therefore, in order to improve the thermoelectric characteristics, it is important to improve the power factor. The power factor (PF) is represented by the following formula [2] using the Seebeck coefficient and the electrical resistivity.
PF = S ² / ρ ... [2]

  Therefore, the main object of the present invention is a thermoelectric conversion material mainly composed of a Si-based clathrate compound, and increases the Seebeck coefficient (absolute value) in a temperature range of 600 ° C. that can be used for exothermic power generation, It is an object of the present invention to provide a thermoelectric conversion material capable of improving a power factor and a manufacturing method thereof.

  The inventors have solved the above problem by adding an element that forms an Nb—Si compound to the Si-based clathrate compound.

That is, according to one aspect of the present invention,
Mainly Si-based clathrate compounds,
A thermoelectric conversion material is provided in which an Nb—Si compound is dispersed as a second phase in a matrix phase of the Si-based clathrate compound.

Preferably, the Nb—Si compound is an NbSi ₂ compound.
Preferably, one or more Nb—Si compound particles having a minor axis of 10 nm or more are present per 10,000 μm ² in the mother phase, and the proportion of the particles in the mother phase is 50% or less in area fraction.

Preferably, the Si-based clathrate compound is a Ba—Ga—Al—Si system.
More preferably, in powder X-ray diffraction, the diffraction peak intensity ratio α (%) of the maximum diffraction peak intensity of the Nb—Si compound to the maximum diffraction peak intensity of the Ba—Ga—Al—Si clathrate compound phase. However, 0 <α <22.

According to another aspect of the invention,
A preparation step of adding an element that forms an Nb-Si compound to a raw material for forming an Si-based clathrate compound, and mixing, melting, and solidifying to prepare a clathrate compound having a predetermined composition;
A crushing step of crushing the clathrate compound into fine particles;
A sintering step of sintering the fine particles;
A method for producing a thermoelectric conversion material is provided.

  According to the present invention, the Seebeck coefficient can be increased and the power factor can be improved.

It is a figure which shows the BEI image in the sample of (a) Example 1 and (b) comparative example 1. FIG. (A) It is a perspective view which shows schematic structure of a thermoelectric conversion module, (b) It is sectional drawing which follows the AA line of (a).

(1) Thermoelectric Conversion Material A thermoelectric conversion material according to a preferred embodiment of the present invention is mainly composed of a Si-based clathrate compound, and an Nb—Si compound is dispersed as a second phase in the matrix phase of the Si-based clathrate compound. It has been made.

(1.1) Si-based clathrate compound The Si-based clathrate compound according to the present embodiment is preferably a Ba-Ga-Al-Si-based clathrate compound, more preferably a composition formula Ba _a Ga _b Al _c. Si _d Nb _e (7.77 ≦ a ≦ 8.16, 7.47 ≦ b ≦ 15.21, 0.28 ≦ c ≦ 6.92, 30.35 ≦ d ≦ 32, e = 0) A clathrate compound.

In the Ba-Ga-Al-Si-based clathrate compound according to the present embodiment, the basic lattice is mainly composed of Si clathrate lattice, and Ba element is included in the interior to constitute the clathrate lattice. It has a structure in which some of the atoms are substituted with Ga and Al. Of the composition ratios of Ba _a Ga _b Al _c Si _d Nb _e , the composition ratios b, c, and d of Ga, Al, and Si generally have the following relationship.
b + c + d = 46
If such a relationship is satisfied, the Si-based clathrate compound is realized mainly with a Si-based clathrate compound phase, and can have an ideal crystal structure. Note that the “thermoelectric conversion material” according to the present embodiment is mainly composed of a Si-based clathrate compound (main component) and may contain a small amount of other additives.

(1.2) Nb-Si compound The Nb-Si compound is dispersed as a second phase in the parent phase of the Si-based clathrate compound.
The Nb—Si compound is preferably an NbSi ₂ compound.
Regarding the dispersion of the Nb—Si compound with respect to the parent phase, preferably, there are one or more Nb—Si compound particles having a minor axis of 10 nm or more per 10,000 μm ² in the parent phase, and the proportion of the particles in the parent phase is the area fraction. And 50% or less.

(2) Manufacturing method The manufacturing method of the thermoelectric conversion material concerning preferable embodiment of this invention is mainly,
(2.1) An element that forms an Nb-Si compound dispersed in the matrix of the Si-based clathrate compound is added to the raw material for forming the Si-based clathrate compound, and is mixed, melted, and solidified to have a predetermined composition A preparation step of preparing a clathrate compound of
(2.2) A pulverizing step of pulverizing the clathrate compound into fine particles;
(2.3) a sintering step of sintering the fine particles.

(2.1) Preparation Step In the preparation step, an ingot of a clathrate compound having a predetermined composition and a uniform composition is produced. First, a predetermined amount of raw materials (Ba, Ga, Al, Si, Nb) are weighed and mixed so as to obtain a desired clathrate compound composition. The raw material may be a simple substance, an alloy or a compound, and the shape thereof may be powder, flakes or lumps.

  As the melting time, a time required for all raw materials to be homogeneously mixed in a liquid state is required, but considering the energy required for production, it is desirable that the melting time be as short as possible. Therefore, the melting time is preferably 1 to 100 minutes, more preferably 1 to 10 minutes, and particularly preferably 1 to 5 minutes.

  The method for melting the powder composed of the raw material mixture is not particularly limited, and various methods can be used. Examples of the melting method include heating with a resistance heating element, high frequency induction melting, arc melting, plasma melting, and electron beam melting. As the crucible, graphite, alumina, cold crucible or the like is appropriately used according to the heating method. When melting, it is preferably performed in an inert gas atmosphere or a vacuum atmosphere in order to prevent oxidation of the material. In order to obtain a homogeneously mixed state in a short time, it is preferable that fine powdery raw materials are mixed. However, Ba preferably has a lump shape in order to prevent oxidation. It is also preferable to add mechanical stirring or electromagnetic stirring at the time of melting.

  After melting, ingots may be cast using a mold or solidified in a crucible. In order to homogenize the completed ingot, an annealing treatment may be performed after melting. The annealing treatment time is preferably as short as possible in consideration of energy saving during manufacturing, but a long time is required in consideration of the annealing effect. The treatment time for the annealing treatment is preferably 1 hour or more, more preferably 1 to 10 hours.

  The treatment temperature for the annealing treatment is preferably 700 to 950 ° C, more preferably 850 to 930 ° C. When the processing temperature is less than 700 ° C., there is a problem that homogenization becomes insufficient. When the processing temperature exceeds 950 ° C., concentration segregation due to remelting occurs.

(2.2) Crushing step In the pulverizing step, the ingot obtained in the preparation step can be pulverized using a ball mill or the like to obtain a fine particle clathrate compound. The fine particles obtained are desired to have a fine particle size in order to improve the sinterability. In the present embodiment, the particle diameter of the fine particles is preferably 150 μm or less, more preferably 1 μm or more and 75 μm or less.

  In order to obtain fine particles having a desired particle size, the particle size is prepared after the ingot is pulverized by a ball mill or the like. The particle size may be adjusted by sieving using a ISO 3310-1 standard Lecce test sieve and a Lecce sieve shaker AS200 digit. In addition, it can replace with this grinding | pulverization process, and can also manufacture fine powder using various atomizing methods, such as a gas atomizing method, and a flowing gas evaporation method.

(2.3) Sintering Step In the sintering step, the finely divided clathrate compound obtained in the pulverization step can be sintered to obtain a solid having a uniform shape with few voids. As the sintering method, a discharge plasma sintering method, a hot press sintering method, a hot isostatic pressing method, or the like can be used.

  When using the discharge plasma sintering method, the sintering temperature, which is one condition for the sintering, is preferably 600 to 1000 ° C, more preferably 900 to 1000 ° C. The sintering time is preferably 1 to 10 minutes, more preferably 3 to 7 minutes. The pressure is preferably 40 to 80 MPa, more preferably 50 to 70 MPa.

  When the sintering temperature is less than 600 ° C., the material is not sintered, and when the sintering temperature is 1100 ° C. or more, it is dissolved. When the sintering time is less than 1 minute, the density is low, and when the sintering time exceeds 10 minutes, the sintering is completed and saturated, and it is considered that there is no significance in taking more time. In particular, in the sintering step, the finely divided clathrate compound is heated to the sintering temperature and held at the temperature for the sintering time, and then the clathrate compound is cooled to a temperature before heating. In this case, the process of heating the clathrate compound in the form of fine powder to the sintering temperature and the process of holding at that temperature are brought into a pressurized state, and then the pressurized state is released in the process of cooling the clathrate compound. . According to such pressure operation, it is possible to suppress cracking in the sintering step of the fine powder clathrate compound.

(3) Confirmation of generation of Si-based clathrate compound and Nb-Si compound Whether or not the Si-based clathrate compound and Nb-Si compound were generated by the above-described production method was determined by composition analysis and powder X-ray diffraction (XRD). Can be confirmed.
Specifically, the sintered sample is pulverized again, and diffracted X-rays are measured by a method according to JIS K 0131. The peaks obtained are type 1 clathrate phases (Pm-3n, No. 223) and Nb. If it shows a -Si compound phase, it can be confirmed that a type 1 clathrate compound and an Nb-Si compound were synthesized, respectively.

  In the alloy produced by the above manufacturing method, even if the volume ratio of the Nb—Si compound to the Si-based clathrate compound is too large, it causes deterioration in performance. Therefore, the maximum diffraction peak intensity derived from the structure of the Nb-Si compound in the powder X-ray diffraction peak is the ratio of the diffraction peak intensity to the maximum diffraction peak intensity derived from the structure of the Si-based clathrate compound in the thermoelectric conversion material. α (%) is 0 <α <22.

Moreover, since there are actually a type 1 clathrate phase and only an Nb—Si compound phase and an impurity phase, an impurity peak is also observed.
When the ratio of the impurity phase according to the present embodiment is increased, performance deterioration is caused. Therefore, the diffraction peak intensity ratio of the maximum diffraction peak intensity of the impurity phase to the maximum diffraction peak intensity of the Si-based clathrate compound is 50% or less. Yes, preferably 20% or less, more preferably 10% or less.
In the thermoelectric conversion material according to the present embodiment, “mainly composed of Si-based clathrate compound” means that the diffraction peak intensity ratio of the maximum diffraction peak intensity of the impurity phase to the maximum diffraction peak intensity of the Si-based clathrate compound is 50. % Or less.
The “impurity phase” is a compound phase other than the Si-based clathrate compound phase and the Nb—Si compound phase.

The “diffraction peak intensity” is defined as the product of the peak height of each compound phase measured in powder X-ray diffraction measurement and the half width at the peak.
The “maximum diffraction peak intensity” is the maximum diffraction peak intensity.
“Diffraction peak intensity ratio” is defined as the ratio of the maximum diffraction peak intensity of each compound phase. For example, the diffraction peak intensity ratio α with respect to the maximum diffraction peak intensity (IHS) of the Si-based clathrate compound phase of the maximum diffraction peak intensity (IP) of the Nb—Si compound phase is determined by using the respective maximum diffraction peak intensity, It is defined by the following formula [3].
Diffraction peak intensity ratio α (%) = (IP) / (IHS) × 100 (3)

The maximum diffraction peak intensity is, for example, as follows.
The maximum diffraction peak intensity of the Si-based clathrate compound phase is the diffraction peak intensity derived from the (123) plane of the Ba—Ga—Al—Si-based clathrate compound having the space group Pm-3n (No. 223).
Maximum diffraction peak intensity of NbSi ₂ compound phase is a diffraction peak intensity derived from the (111) plane of the NbSi ₂ compound having a space group _P6 2 22 (No.180).
Using the maximum diffraction peak intensities of these surfaces, the diffraction peak intensity ratio α can be calculated from the above equation [3].

(4) Characteristic Evaluation Test Next, characteristic evaluation for calculating the dimensionless figure of merit ZT of the thermoelectric conversion material manufactured by the above method will be described.
The characteristic evaluation items are Seebeck coefficient S and electrical resistivity ρ. In the characteristic evaluation test, composition analysis, microstructure observation, and sintering density measurement are performed using an electron beam microanalyzer (EPMA-1610 manufactured by Shimadzu Corporation). Various characteristic evaluation samples are cut out and shaped from a cylindrical sintered body of 20 mmφ (diameter 20 mm) × 5 to 20 mm (height 5 to 20 mm).

  “Seebeck coefficient S” and “electric resistivity ρ” are measured by a four-terminal method using a thermoelectric property evaluation apparatus ZEM-3 manufactured by ULVAC-RIKO.

The power factor is also calculated from the above measurement results. The characteristics of the thermoelectric conversion material of the clathrate compound can be evaluated from the calculated power factor. In the thermoelectric conversion material according to the present embodiment, the power factor at 600 ° C. is 0.7 mW / mK ² or more.

(5) Thermoelectric conversion module A thermoelectric conversion module is a module that can have a function of converting thermal energy applied to a thermoelectric conversion element into electrical energy.
As shown in FIG. 2A, the thermoelectric conversion module 60 mainly includes an n-type thermoelectric conversion element 11, a p-type thermoelectric conversion element 12, a high temperature side wiring 41, a low temperature side wiring 42, a high temperature side insulating substrate 51, and a low temperature side insulation. A substrate 52 is used.
As shown in FIG. 2B, in the thermoelectric conversion module 60, the n-type thermoelectric conversion element 11, the p-type thermoelectric conversion element 12, the high-temperature side wiring 41, and the low-temperature side wiring 42 are alternately joined, and the n-type thermoelectric conversion element 11 and the p-type thermoelectric conversion element 12 are electrically arranged in series via a high temperature side wiring 41 and a low temperature side wiring 42.

The n-type thermoelectric conversion element 11 includes a thermoelectric conversion material portion 11a and electrode layers 11b and 11c adjacent thereto. The thermoelectric conversion material part 11a is comprised from the thermoelectric conversion material of said (A). The electrode layers 11b and 11c are layers that enhance the bondability between the thermoelectric conversion material portion 11a, the high temperature side wiring 41, and the low temperature side wiring 42.
The p-type thermoelectric conversion element 12 also includes a thermoelectric conversion material portion 12a and electrode layers 12b and 12c adjacent thereto. The thermoelectric conversion material part 12a is made of a certain thermoelectric conversion material. The electrode layers 12b and 12c are layers that enhance the bondability between the thermoelectric conversion material portion 12a, the high temperature side wiring 41, and the low temperature side wiring 42.
The high temperature side wiring 41 and the low temperature side wiring 42 have a function of electrically connecting the n-type thermoelectric conversion element 11 and the p-type thermoelectric conversion element 12 in series.
The high-temperature side insulating substrate 51 and the low-temperature side insulating substrate 52 have a function of fixing the n-type thermoelectric conversion element 11 and the p-type thermoelectric conversion element 12, the high-temperature side wiring 41 and the low-temperature side wiring 42, and further a thermoelectric conversion module. 60 has a function of receiving heat uniformly.
According to the thermoelectric conversion module 60 described above, when a temperature difference is formed between the high temperature side wiring 41 and the low temperature side wiring 42, electrons or holes excited in the n-type thermoelectric conversion element 11 or the p-type thermoelectric conversion element 12. Moves to the low temperature side wiring 42 so that a current flows.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited by the following Example.

(1) Preparation of sample A high purity Ba having a purity of 2N or higher, high purity Ga and Al having a purity of 3N or higher, a high purity Si having a purity of 3N or higher, and a high purity Nb having a purity of 2N or higher, A raw material mixture was prepared by weighing at a blending ratio of 1.

  The arc mixture is melted in an Ar (argon) atmosphere on a water-cooled copper hearth at a current of 300 A for 1 minute, and then the ingot is inverted in order to eliminate the unevenness of the raw material, and arc melting is performed again. Was repeated 5 times and cooled to room temperature on a water-cooled copper hearth to obtain an ingot having a clathrate compound.

  Thereafter, in order to improve the uniformity of the ingot, annealing treatment was performed at 900 ° C. for 6 hours in an argon atmosphere. The obtained ingot was pulverized using an agate planetary ball mill to obtain fine particles. At this time, the particle size was adjusted using the ISO 3310-1 standard Lecce test sieve and the Lecce shaker AS200 digit so that the average particle size of the obtained particles was 75 μm or less.

  The obtained particles for sintering were pressurized to a pressure of 50 MPa using a discharge plasma sintering method (SPS method), heated to 1000 ° C., and then sintered at 1000 ° C. for 5 minutes. After the sintering was completed, the pressurized state was released, and cooling was performed from 1000 ° C. to room temperature.

  In addition, after the sintering of the particles for sintering was finished, when the pressure state was kept and cooling was performed, cracking occurred, but the pressure state was released after sintering as described above. When cooling from 1000 ° C. to room temperature, such cracks could be suppressed. Considering the deterioration of the sample and the die obtained, it is preferable to hold in a vacuum atmosphere at a cooling temperature of 500 ° C. or higher, but it may be held in an air atmosphere at less than 500 ° C.

  The sample sintered body thus obtained was subjected to composition analysis using an electron beam microanalyzer (EPMA-1610 manufactured by Shimadzu Corporation), and the above-mentioned “(3) Production of Si-based clathrate compound and Nb—Si compound”. The X-ray diffraction of “Confirmation” and the above “(4) Characteristic evaluation test”.

(2) Sample Evaluation (2.1) Composition Analysis and Structure Observation FIG. 1 shows a BEI image of the sample of (a) Example 1 and (b) Comparative Example 1.
In FIG. 1A, a compound having a black contrast was confirmed, and it was confirmed from the element mapping by EPMA that the sample of Example 1 contained Si and Nb. In both of Examples 1 and 2, from the mapping of EPMA, one or more Nb-Si compound particles having a minor axis of 10 nm or more are present per 10,000 μm ² in the parent phase, and the ratio of the particles in the parent phase is also the area. It was also confirmed that the fraction was 50% or less.

The results of composition analysis of the obtained sample are shown in Table 2.
Table 2, in the samples of Examples 1-2 and Comparative Examples 1-2, the desired composition _{Ba a Ga b Al c Si d} Nb e (7.77 ≦ a ≦ 8.16,7.47 ≦ b ≦ 15 .21, 0.28 ≦ c ≦ 6.92, 30.35 ≦ d ≦ 32, e = 0).

(2.2) X-ray diffraction analysis The obtained sample was analyzed by powder X-ray diffraction.
From the obtained results, the diffraction peak intensity ratio of the impurity phase to the Si-based clathrate compound phase was calculated, and it was confirmed that it was 50% or less for all samples. Further, it was confirmed diffraction peaks derived from NbSi ₂ compounds.

From the relationship between strength and 2θ in the obtained samples, in the samples of Examples 1 and 2, it is confirmed that the NbSi ₂ compound is dispersed mainly with the Ba—Ga—Al—Si based clathrate compound. I was able to.

(2.3) Characteristic Evaluation About the obtained sample, characteristic evaluation was performed and the Seebeck coefficient and the electrical resistivity were measured as described in the above “(4) characteristic evaluation test”. From the measurement results of the Seebeck coefficient, it was found that the Seebeck coefficient was negative in all samples, and each sample was n-type.
Furthermore, the power factor was also calculated from the measurement results of Seebeck coefficient and electrical resistivity based on the equation [2].

Table 3 shows the presence of the power factor and the NbSi ₂ compound (dispersion) in the samples of Examples 1-2 and Comparative Examples 1-2.
As shown in Table 3, in the samples of Examples 1 and ² , it can be seen that the power factor is 0.7 mW / mK ² or more.

  From the above, in order to improve the power factor of the Si-based clathrate compound, it is necessary to disperse the Nb—Si compound in the Si-based clathrate compound. According to the present Example, it turns out that it is useful for improving a power factor by disperse | distributing a Nb-Si compound in a Ba-Ga-Al-Si type clathrate compound.

(3) Summary A thermoelectric conversion material mainly composed of a Si-based clathrate compound and in which an Nb—Si compound is dispersed is useful for obtaining a high characteristic with a power factor of 0.7 mW / mK ² or more. I understand that.

11 n-type thermoelectric conversion element 11a thermoelectric conversion material part 11b, 11c electrode layer 12 p-type thermoelectric conversion element 12a thermoelectric conversion material part 12b, 12c electrode layer 41 high temperature side wiring 42 low temperature side wiring 51 high temperature side insulating substrate 52 low temperature side insulating substrate 60 Thermoelectric conversion module

Claims (7)

Mainly Si-based clathrate compounds,
A thermoelectric conversion material, wherein a Nb-Si compound is dispersed as a second phase in a matrix phase of the Si-based clathrate compound. In the thermoelectric conversion material according to claim 1,
Thermoelectric conversion material, wherein the NbSi compound is NbSi ₂ compound. The thermoelectric conversion material according to claim 1 or 2,
One or more particles of the Nb—Si compound having a minor axis of 10 nm or more are present per 10,000 μm ² in the matrix, and the proportion of the particles in the matrix is 50% or less in area fraction. Thermoelectric conversion material. In the thermoelectric conversion material as described in any one of Claims 1-3,
A thermoelectric conversion material, wherein the Si-based clathrate compound is a Ba-Ga-Al-Si-based clathrate compound. A thermoelectric conversion material part composed of the thermoelectric conversion material according to any one of claims 1 to 4, and
An electrode layer adjacent to the thermoelectric conversion material part;
A thermoelectric conversion element comprising: An n-type thermoelectric conversion element and a p-type thermoelectric conversion element are arranged in series via a wiring,
The thermoelectric conversion module according to claim 5, wherein the n-type thermoelectric conversion element is the thermoelectric conversion element according to claim 5. A manufacturing method for manufacturing the thermoelectric conversion material according to any one of claims 1 to 4,
A preparation step of adding an element that forms an Nb-Si compound to a raw material for forming an Si-based clathrate compound, and mixing, melting, and solidifying to prepare a clathrate compound having a predetermined composition;
A crushing step of crushing the clathrate compound into fine particles;
A sintering step of sintering the fine particles;
A method for producing a thermoelectric conversion material, comprising: