JP2002353527A - Manufacturing method of thermoelectric material, and thermoelectric material obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric material comprising a skutterudites compound which is acquired by baking a material, to provide it making it larger in size without damages, and to provide a manufacturing method for it which has a thermoelectric performance for a practical use. SOLUTION: Materials are mixed by a mechanical alloying method for turning a part of it into an alloy, and then baking it the first time; this is crushed and mixed for finer particles, which is baked second time; and these are repeated, as required, to manufacture a thermoelectric material whose diameter exceeds 20 mm. At baking, the temperature is raised to a prescribed hot region, which is lower than the baking temperature, when baking is started, then the alloy is gradually raised to the baking temperature range, and it is gradually cooled after completion of baking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric material applied to thermoelectric power generation and thermoelectric cooling and a method for producing the same, and more particularly, to C
The present invention relates to a thermoelectric material comprising a compound having a skutterudite-type crystal structure containing oSb ₃ as a main component and a method for producing the same.

[0002]

2. Description of the Related Art Thermoelectric materials generate heat by directly converting heat to electricity by the Seebeck effect in which a high-temperature carrier diffuses to a low-temperature side when one end of a conductor is heated and a thermoelectromotive force is generated at both ends of the conductor. Alternatively, a material that can be used for thermoelectric cooling by the Peltier effect,
iGe system, GeTe system applied to medium temperature range, ZnSb
Semiconductor materials such as BiTe, BiSb, etc., which are applied to low temperature regions, are known. In recent years, thermoelectric materials comprising various compounds having a skutterudite type crystal structure having higher thermoelectric conversion efficiency have been developed. Is being developed.

The heat generated from this skutterudite compound
For example, Japanese Patent Application Laid-Open No. 11-40860 discloses
As mentioned, CoSb_Three, RhSb_Three, Ir
Sb _ThreeBinary system such as Co_1-XRh_xIr_ySb_ThreeLana
Pseudo quaternary system, Co_1-xM_xSb_ThreePseudo-ternary system (M
Is at least one of Pd, Rh, and Ru, and x = 0.001 to
0.2) is disclosed.

Further, according to the publication, as a method for producing the thermoelectric material, a raw material is pulverized into powder having an average particle diameter of 1 μm or less, and the powder is heated to a temperature of 300 to 700 ° C. and a pressure of 2 MPa.
The pressure sintering is performed within 20 hours. here,
The thermal conductivity of a polycrystalline skutterudite-based thermoelectric material is
By finding that the average crystal grain size is extremely small, the thermal conductivity is greatly reduced, and the average crystal grain size is reduced to 1 μm or less.

[0005] Therefore, the raw material is pulverized into powder having an average particle diameter of 1 µm or less, and at the same time, the growth of crystal grains during sintering is suppressed.
That is, the sintered body is manufactured by pressure sintering at a temperature of 300 to 700 ° C. and a pressure of 2 MPa or more within 20 hours. The upper limit of the sintering temperature is set to 700 ° C.
If it exceeds this, the growth rate of the crystal grains increases, and it becomes difficult to reduce the average crystal grain size of the sintered body to 1 μm or less. The reason for setting the pressure to 2 MPa is that if any of them is less than these values, the mechanical strength of the sintered body will not be sufficiently high. Furthermore, the reason why the upper limit of the time for the pressure sintering is set to 20 hours is that if it exceeds this, the strength of the sintered body does not improve much, and conversely, crystal grains may grow, which is not preferable. And

The preferred sintering temperature and sintering time are 10 to 20 hours at a temperature of 400 to 500 ° C. and 5
A temperature of 00 to 600 ° C. is preferably 2 to 10 hours. To pulverize the raw material into powder having an average particle diameter of 1 μm or less, a mechanical alloying method is employed and the pressure sintering is performed by a plasma discharge sintering method. It is also desirable.

[0007] The publication discloses a specific manufacturing method. According to the description of Example 3, mechanical alloying is used for mixing and pulverizing the raw material powder, and plasma discharge sintering is used for sintering. 200 rpm, 3
The treatment is performed for 0 hours, and the sintering conditions by the plasma discharge sintering method are as follows: sintering temperature is 500 ° C., sintering pressure is 30 MPa, and sintering time is 0.25 (hour). Incidentally, it is stated that in a normal hot press, a sintering pressure of 30 MPa, a pressing temperature of 550 ° C., and a sintering time of 10 hours are required.

[0008]

Generally, this kind of thermoelectric material is obtained by pressing a raw material powder at a high pressure under the pressure and temperature conditions described in the above-mentioned publications and heating it at a high temperature for a long time to obtain a primary powder. Product, eg 3mm, 20m thick
After being manufactured as a disc-shaped sintered body having a diameter of m, this is cut into, for example, 3 mm × 7 mm prismatic chips to obtain a thermoelectric element material.

On the other hand, in order to manufacture a power generation module in which the thermoelectric material and the electrode material are joined and integrated, an extremely large number of thermoelectric elements obtained by cutting a sintered body into chips are required. At present, it takes about one week to manufacture this thermoelectric material. Therefore, it is desirable to obtain the sintered body, which is a thermoelectric material having a diameter as large as possible, from the viewpoint of improving the production efficiency of the power generation module and improving the yield.

However, it is extremely difficult to uniformly distribute the sintering temperature during the manufacture of the sintered body in the radial direction in view of the structure of the manufacturing apparatus which is placed under a high pressure in a closed state. If there is a large difference in the temperature distribution in the radial direction, the composition distribution of the compound during sintering becomes uneven between the central part and the peripheral part, and a large difference occurs in thermal stress, and a large crack occurs after sintering. Not only will the yield be greatly reduced, but it will be impossible to commercialize it.

[0011] Therefore, the sintered body disclosed in the above-mentioned publication also completes sintering in a very short time, for example, plasma discharge sintering is 15 minutes. Although it is considered that the influence of the temperature difference between them is small, the sintered body obtained as in the conventional case is considered to have an upper limit of 20 mm in diameter, though not explicitly stated.

The temperature difference during sintering may be caused by the fact that, for example, atoms to be alloyed or combined often remain alone in the peripheral portion between the central portion and the peripheral portion of the sintered body. Porosity is greater than in the center,
Not only are the physical properties of thermoelectric materials significantly different,
Inconveniences such as a decrease in the density of the entire sample and an increase in brittleness of the peripheral portion occur.

An object of the present invention is to significantly improve the yield of a thermoelectric element obtained by cutting a thermoelectric material made of a sintered body, and at the same time, to provide a large thermoelectric element having a uniform and a performance index not inferior to that of a conventional thermoelectric element. To get the material.

[0014]

Means for Solving the Problems and Functions and Effects The inventors of the present invention considered that in order to achieve the above object, it was first to increase the sintered diameter of a sintered body as a thermoelectric material. However, simply increasing the sintering diameter, as described above, rather causes a large decrease in yield due to cracks. Recognizing that one of the major causes of the cracks is the sintering temperature difference that cannot be controlled from the sintering center to the periphery during sintering, we focus on the distribution of heating amount during sintering. Attempts were made to control as much as possible to increase the temperature from the edge to the periphery or to reduce the temperature distribution. As a result, I learned that the sintering equipment was enlarged and it was not suitable for practical use.

Next, in addition to the non-uniform distribution of the sintering temperature, the distribution of various compound phases having a skutterudite type crystal structure and a single atomic phase distributed in the radial direction of the sintered body are as follows: Based on the presumption that it is not unrelated to not only physical properties but also the occurrence of cracks, various experiments were repeated, and it was found that the above phase distribution, especially the presence of a single atomic phase, makes the intensity distribution non-uniform in addition to physical properties. The conclusion has been reached.

The invention according to claim 1 has been created as a result and has an A-type structure having a skutterudite-type crystal structure.
A method of manufacturing a thermoelectric material containing B ₃ type compound, mixing with the primary alloy by mechanical alloying method raw material powder, by performing the first sintering the mixture under high pressure and high temperature, the burnt A method for producing a skutterudite-based thermoelectric material, comprising pulverizing and mixing the compact, and performing at least a second sintering of the mixture under high pressure and high temperature.

AB_ThreeType compound is AB_Three, A_1-x
M_xB_Three, AB_3-ZC_Z, A_1-xM _xB_3-ZC_ZGeneral
A compound represented by the formula, wherein the element A is Co, Rh, I
one or more of r, B is one of P, As, Sb
As described above, M is an element that substitutes for the element A, x = 0 to 0.2,
Element C penetrates and replaces the skutterudite-type crystal structure
And z = 0 to 0.3. Element that replaces element A
M is one of Pd, Pt, PdPt, and C
Is any of Ni, Te, and Pd.

Here, the most important point in the present invention is as follows.
In order to produce a final sintered body, at least the first mixing and pulverization are performed by a mechanical alloying method, and the resulting sintered body is pressurized and heated, pulverized again, mixed, and added again. It is to obtain a sintered body by applying pressure and heating. In the present invention, a final product may be obtained by repeating the same operation and performing the sintering for the third or more times, without forming the product in the second sintering.

In the second and subsequent grinding and mixing of the sintered body, it is not always necessary to pulverize the powder into a fine powder and partly alloy it. Alternatively, grinding and mixing may be performed in a short time using a planetary ball mill.

As described above, the first sintered body is pulverized, and at least one more sintering is performed using the pulverized material as a raw material, so that the radial component phase distribution in the collected sintered body is obtained. Is not only homogenized, but also a single atomic phase is converted into a compound and disappears, so that a material having excellent physical properties is obtained. Furthermore, surprisingly, for example, a large-diameter sintered body having a diameter of 50 mm having a diameter twice or more that of a sintered body having a diameter of 20 mm, which has been conventionally regarded as a limit, is formed at a high density without generating cracks. In addition, a high-performance thermoelectric material can be manufactured.

In the present invention, any of a hot press method and a plasma sintering method can be employed for the sintering. For example, first, a sintered body is obtained by hot pressing a raw material powder, and after pulverizing the sintered body, a final product is manufactured by using the powder material by a plasma sintering method. The reverse is also possible. Alternatively, it is possible to perform sintering two or more times by a hot press method with pulverization in between, and it is also possible to perform sintering two or more times by plasma sintering with pulverization in between.

According to a second aspect of the present invention, there is provided the method of manufacturing a skutterudite-based thermoelectric material according to the third aspect, wherein the sintering is performed by a plasma discharge sintering method. As described in the above publication, hot press method and plasma discharge sintering method are typical examples of this kind of sintering method. Compared with the hot press method, the plasma discharge sintering method can perform the sintering process in a shorter time and has a small porosity of the obtained sintered body and is excellent in denseness. It is preferable to adopt the conclusion method.

According to a third aspect of the present invention, the heating temperature at the time of sintering is initially increased rapidly to a predetermined high temperature, and then gradually increased until the sintering temperature is reached. After reaching the sintering temperature, a predetermined sintering time elapses, followed by sintering, and then gradual cooling.

In general, when the sintering diameter exceeds 20 mm, if the temperature at the center is set to 740 ° C. in order to obtain a sintered body having a diameter of 50 mm, for example, the temperature at the periphery becomes 6 mm.
It is about 00 ° C, and the difference reaches 100 ° C or more.
When such a large temperature difference occurs between the central portion and the peripheral portion of the sintered body, for example, when manufacturing a skutterudite-based thermoelectric material containing CoSb ₃ as a main component, a low melting point (630 ° C.) is required at the central portion. ) Sb ₃ is is in the molten state, a state close to a solid phase at the periphery.

In addition, apart from other materials, it is known that the formation of CoSb ₃ is severely affected by the temperature and the proportions of Co and Sb. That is,
When the temperature condition is in the range of 623 ° C. to 859 ° C. and the atomic ratio of Co atom is 75% and Sb atom is 25%,
CoSb ₃ is generated for the first time. Therefore, due to the thermal diffusion based on the temperature difference and the distribution unevenness of the generation condition, CoS
The region where b ₃ is generated is not evenly distributed, and in particular, compared to the central portion, there is a strong tendency that the ratio of single phase formation of Sb atoms at the peripheral portion increases.

Therefore, in the present invention, the initial heating gradient is increased, for example, to 600 ° C. in a short time, and then to 740 ° C. in about 2 hours with a gentle temperature gradient, and the required time is reduced. The sintering process is performed while maintaining the same temperature, and the temperature is gradually cooled for 3 to 8 hours. Thus, compared with the conventional case where the temperature is rapidly raised to the sintering temperature and sintering is performed and then quenched, the sintering time is somewhat longer, but the temperature distribution in the radial direction is relaxed, The denseness in the peripheral portion is ensured, and a large-diameter sintered body can be obtained in combination with pulverization and sintering two or more times.

According to a fourth aspect of the present invention, there is provided a skutterudite-based thermoelectric material produced by the production method according to any one of the first to third aspects, wherein the final sintering product form is larger than 20 mm in diameter. A skutterudite-based thermoelectric material characterized by being a disk-shaped sintered body having a diameter.

As described above, a disc-shaped thermoelectric material made of a skutterudite-based sintered body, which is a material of a thermoelectric element, is sintered by using conventional equipment with a radial density distribution of 20 mm or less. It is possible to obtain a sintered body having a diameter distribution larger than the conventional upper limit diameter of 20 mm, having substantially the same radial density distribution as the body and without generating cracks. Is greatly improved, and high productivity is realized.

The invention according to claim 5 is characterized in that the amount of Sb alone by X-ray diffraction with respect to the powder of the sintered body is 1% or less of the maximum peak of the sample. When the presence of Sb alone is small, it means that Sb does not exist alone in the radial direction of the sintered body, which means that impurities such as Sb existing in the sintered body are present. Can be said to mean that a more uniform and nearly single-phase sample was obtained. As a result, the performance and density of the thermoelectric element are high, and the performance of a thermoelectric module manufactured using the thermoelectric element is further improved.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, typical embodiments of the present invention will be described.
A method of manufacturing a thermoelectric material and the heat obtained by the method
The electrical material will be specifically described using drawings and graphs. Departure
Ming AB_ThreeSkutterudite-based thermoelectric material composed of a tertiary compound
The fee is AB_Three, A _1-xM_xB_Three, AB_3-ZC_Z, A_1-x
M_xB_3-ZC_zIncluding compounds represented by the general formula
is there. Here, the element A is Co, Rh, Ir alone or its element.
B is P, As, or Sb alone or a combination thereof.
A combination wherein C is in the skutterudite-type crystal structure
Any of Ni, Te, Pd
M is one of the elements Pd, Pt, and PdPt that replace the element A.
X is 0 to 0.2, z is 0 to 0.3
is there.

In the present embodiment, a thermoelectric material having a skutterudite-type crystal structure containing CoSb ₃ as a main component, which is a typical AB ₃ type compound, will be exemplified. As raw materials, 99.9985% pure Co powder and 99.9999%
% Of granular Sb and weighed at 86.5: 13.5 by weight.
, And mixed by a mechanical alloying method to partially alloy. Next, the particles were classified and the average particle size was adjusted to 38 μm. Using the plasma discharge sintering apparatus, the thus obtained mixed granules are controlled at a sintering pressure of 30 MPa according to the time (min) / temperature (° C.) curve shown by the solid line in FIG. 1 to control the peripheral temperature of the raw material disc. To finish the first sintering,
Was produced with a large diameter. For reference, FIG. 1 shows a general time / temperature curve by a broken line when obtaining a sintered body having a diameter of 20 mm from a conventional thermoelectric raw material of the same quality.

As can be understood from the figure, in the sintering according to the present invention, at the start of sintering, the temperature is quickly raised to a high temperature range just before a predetermined sintering temperature, and then gradually raised to the sintering temperature range. Then, after the required sintering time has elapsed, cooling is started. The cooling at this time is performed gradually over a long time. On the other hand, in the conventional sintering, immediately after the start of sintering, the temperature is raised to a sintering temperature range at a stretch to perform sintering, and the cooling is rapidly cooled in a short time.

That is, according to the plasma discharge sintering method of the present embodiment, as shown by the solid line in FIG. 1, after the temperature is rapidly raised to 600 ° C. in 12 minutes, the sintering temperature is 740 in 95 minutes. C. and slowly sinter for 120 minutes while maintaining the same temperature. Cooling after the completion of this sintering is performed with a total of 21
Cool slowly over 5 minutes.

The temperature rise immediately after the start of sintering is short (12 minutes)
Take some time (95 minutes) after going in
Slowly raise the temperature to 740 ° C, the sintering temperature
Means that the main component of the thermoelectric material according to the present embodiment is CoSb_Threeso
Due to being. CoSb _ThreeIs extremely strict
For example, looking at the component ratio of Co and Sb,
o is 13.5 (% by weight) and one Sb is 86.5
(% By weight) and the synthesis temperature is 623-85.
CoSb for the first time at 9 ° C_ThreeIs generated, for example, C
o was 19.0 (% by weight) and Sb was 81.0 (% by weight).
When the synthesis temperature is in the range of 859 to 919 ° C., CoS
b_TwoIs generated.

For this reason, in this embodiment, the component ratios of Co and Sb are set as described above, and the temperature is raised to around 600 ° C., which is close to the synthesis temperature, in a short time in sintering, so that the temperature distribution of the entire raw material is reduced as much as possible. The temperature was raised to 740 ° C., which is the sintering temperature, over a sufficient time to make the temperature uniform. Further, when the cooling is rapidly performed after the sintering is completed, especially in the large-diameter sintered body according to the present embodiment, a large temperature difference is generated between the center portion and the peripheral edge portion, and the diameter becomes large. A uniform performance distribution in the direction cannot be obtained. Further, due to the large temperature difference, a large thermal stress is generated between the central portion and the peripheral portion, and more single atoms of Sb are present. As a result, not only the thermoelectric performance of the sintered body is low, but also cracks occur frequently.

Therefore, in the present invention, as in the above-described embodiment, at the start of sintering, the temperature is increased to a temperature near the compound formation temperature in a short time, and it takes a necessary time to uniformly heat the entire sintered body. In addition to raising the temperature to the sintering temperature, cooling after sintering is gradually cooled over a sufficient time period such that a difference in thermal stress between the center portion and the peripheral portion of the sintered body does not occur.
However, in the first sintered body thus obtained, although the generation of cracks could be prevented by the sintering conditions described above, the relative density with respect to the theoretical density was as low as 90%, and the Sb A single atom remains, and the performance is inferior to that of a conventional thermoelectric material having a diameter of 20 mm.

In the present embodiment, the sintered body obtained as described above is further crushed, and the crushed material is crushed and mixed by a mixer having a usual rotating blade or a planetary ball mill to obtain an average particle size. A 38 μm mixture was obtained. Next, the same mixture was sintered for the second time using the above-described plasma discharge sintering apparatus. The sintering conditions at this time were the same as those for the first sintering, and the obtained sintered body had a diameter of 50 mm as in the first sintering.

Thus, the two sintering processes are performed.
As shown in FIG. 2, the sintered body having a diameter of mm did not crack, and a thermoelectric material having a relative density of 98% or more of the theoretical density was obtained. The distribution of the thermoelectric performance was uniform in the radial direction, and had the same thermoelectric performance as compared with the conventional sintered body having a diameter of 20 mm shown in FIG.

FIG. 4 shows a sintered body A having a diameter of 50 mm obtained by sintering by the first plasma discharge sintering method according to the present invention, and crushing and mixing the sintered body A under the same conditions. 3 shows the results of a qualitative test with the sintered body B of the present invention obtained by performing the second sintering. In this test, each of the sintered bodies A and B was crushed, and each powder was used as a sample to measure the powder by an X-ray diffraction method. The results are shown by a diffraction intensity distribution.

In this figure, a peak appears where the angle 2θ, which is twice the black angle θ, becomes 28.68 °, which suggests that Sb alone exists in the sintered body. If the peak intensity is lower than 1% with respect to the intensity of the maximum peak (2θ = 31.15) of CoSb _3, the influence on the thermoelectric performance can be ignored. In the first sintered body A, the peak value is about 1%, but in the sintered body B that has been subjected to the second sintering according to the present invention, the peak value is reduced to such a degree that it cannot be visually recognized. From this,
It can be seen how effective the two sinters according to the invention are.

FIGS. 5 to 8 show a sintered body A of substantially the same raw material and having a diameter of 50 mm obtained by the first sintering, and having a diameter of 50 mm obtained by the second sintering according to the present invention. 1 is a graph showing fluctuations in various performances of the thermoelectric material composed of the sintered body B having a diameter of 20 mm and the conventional sintered body C having a diameter of 20 mm obtained by the sintering temperature control indicated by the broken line in FIG. .

In general, the performance of a thermoelectric material is expressed as follows: α is the Seebeck coefficient indicating the magnitude of the thermoelectromotive force generated in the element per unit temperature difference, ρ is the electrical resistivity, and κ is the thermal conductivity. Is represented by Z = α ² / ρ · κ. The figure of merit Z is an important material parameter that determines the thermoelectric conversion efficiency, and the quotient α ² / ρ of the square of the Seebeck coefficient α and the electric resistivity ρ is called an output factor.
The larger the Seebeck coefficient α and the smaller the electrical resistivity ρ, the higher the output factor. The smaller the thermal conductivity κ, the greater the figure of merit Z, and the better the thermoelectric performance.

Referring to these figures, a 50 mm diameter sintered body A obtained by the first sintering, a 50 mm diameter sintered body B obtained by the second sintering according to the present invention, and The conventional 20 m obtained by controlling the sintering temperature indicated by the broken line in FIG.
The thermoelectric performance of the sintered body C having the m diameter is compared.

First, the sintered body B and the sintered body C are compared.
As for the Seebeck coefficient α, in FIG. 5, both values show almost the same value in the entire temperature range (300 to 950 K). Further, looking at the electric resistivity ρ with reference to FIG.
5 times larger. The value of the thermal conductivity κ is determined between the sintered body B and the sintered body C.
Are reversed at 700 K. Below 700 K, the thermal conductivity κ of the sintered body B is higher than that of the sintered body C, and
In the above, the thermal conductivity κ of the sintered body B is lower than that of the sintered body C. In terms of the performance index Z, the sintered body B has a value of 80% or more of the performance index Z of the sintered body C.

Next, the thermoelectric performance of the sintered body B according to the present invention and the sintered body A having the same diameter and obtained by one sintering will be compared with each other with reference to FIGS. As is apparent from these figures, the Seebeck coefficient α of the sintered body B is 15% higher than that of the sintered body A, and the electric resistivity ρ of the sintered body B is 5% lower than that of the sintered body A. I have. The thermal conductivity κ of the sintered body A and that of the sintered body B are almost the same.
Looking at the overall performance index Z, the sintered body B
30% higher than that. The relative density of the sintered body A is 90% of the theoretical density, whereas the relative density of the sintered body B is as high as 98% of the theoretical density, and a dense product is obtained.

The conventional sintered body C was added with 550 in air.
It was confirmed by experiments that the annealing treatment at about 650 ° C. was performed, and the performance index Z of the one subjected to the annealing treatment was improved as compared with the case where the annealing treatment was not performed. From this, improvement of the thermoelectric performance can be expected by performing the annealing treatment even for the large thermoelectric material according to the present invention.

[Brief description of the drawings]

FIG. 1 shows a CoSb3 sintered body in this embodiment and a conventional C
FIG. 4 is a diagram illustrating temperature rise, sintering, and cooling during sintering of an oSb3 sintered body.

FIG. 2 is a plan photograph of a large-diameter CoSb3 sintered body obtained according to this example.

FIG. 3 is a plan photograph of a conventional small-diameter CoSb3 sintered body.

FIG. 4 is an X-ray diffraction diagram showing a change in a single phase of Sb atoms contained in each thermoelectric material when the first and second sintering according to the present invention are completed.

FIG. 5 is a correlation diagram showing a change in the Seebeck coefficient α due to a change in temperature of each electrothermal material when the first and second sintering according to the present invention are completed.

FIG. 6 shows a change in electrical resistivity ρ with temperature change of each thermoelectric material composed of a small-diameter sintered body obtained by the conventional sintering method and a large-diameter sintered body after the first and second sintering according to the present invention. FIG.

FIG. 7 shows a change in thermal conductivity κ due to a temperature change of each thermoelectric material composed of a small-diameter sintered body according to the conventional sintering method and a large-diameter sintered body after the first and second sintering according to the present invention. FIG.

FIG. 8 is a graph showing the change in the figure of merit Z with the temperature change of each thermoelectric material composed of a small-diameter sintered body according to the conventional sintering method and a large-diameter sintered body after the first and second sintering according to the present invention. FIG.

[Explanation of symbols]

A Sintered body of 50 mm diameter obtained by one sintering B Sintered body of 50 mm diameter obtained by two sintering C Conventional sintered body of 20 mm diameter obtained by one sintering

Claims (5)

[Claims] 1. A compound having a skutterudite crystal structure
A method of manufacturing a thermoelectric material containing B ₃ type compound, mixing with the primary alloy by mechanical alloying method raw material powder, by performing the first sintering the mixture under high pressure and high temperature, the burnt A method for producing a skutterudite-based thermoelectric material, comprising: crushing and mixing the compact; and performing at least a second sintering of the mixture under high pressure and high temperature. However, element A is at least one of Co, Rh, and Ir, and B is at least one of P, As, and Sb. 2. The method for producing a skutterudite-based thermoelectric material according to claim 1, wherein the sintering is performed a plurality of times by a plasma discharge sintering method. 3. The sintering comprises rapidly increasing the temperature to a predetermined high temperature, then gradually increasing the temperature to the sintering temperature, and gradually cooling after a required sintering time has elapsed. The method for producing a skutterudite-based thermoelectric material according to claim 1 or 2, wherein: 4. A skutterudite-based thermoelectric material produced by the production method according to claim 1, wherein the final sintered body is a disk having a diameter exceeding 20 mm. Skutterudite-based thermoelectric material. 5. The skutterudite-type thermoelectric material according to claim 4, wherein the amount of Sb alone in the sintered body by powder X-ray diffraction is 1% or less of the maximum peak of the sample.