JP6593870B2 - Thermoelectric conversion material, thermoelectric power generation element using the same, and Peltier cooling element - Google Patents

Description

  The present invention relates to a thermoelectric conversion material, a thermoelectric power generation element using the material, and a Peltier cooling element.

  Thermoelectric conversion is a technology that mutually converts thermal energy and electrical energy using a solid element. The technology that converts thermal energy into electrical energy is called thermoelectric power generation and is based on the Seebeck effect, which is one of the thermoelectric effects. On the other hand, the conversion from electrical energy to thermal energy originates from the Peltier effect and is applied to cooling and precision temperature control. These power generators and temperature control devices do not have mechanical moving parts, and have the advantages of quietness, no vibration, and long life.

In thermoelectric power generation, the temperature difference between both ends of a solid element is directly converted into electrical energy. This method is a power generation technology that is more environmentally friendly than power generation using fossil fuels. If this thermoelectric power generation can be used to recover a huge amount of unused thermal energy that is discarded from factories and automobiles and generate electricity from it, it will reduce fossil fuel consumption, that is, reduce CO ₂ emissions. It can greatly contribute to energy saving.

  Peltier cooling (electronic cooling) uses a phenomenon in which one end of an element is cooled when a direct current is applied to the thermoelectric conversion element. This cooling has the advantage of not requiring a refrigerant such as Freon gas and precise control of the cooling temperature based on current control.

In such a thermoelectric conversion material, the performance as an element can be obtained as the dimensionless figure of merit ZT of the thermoelectric conversion material. The dimensionless figure of merit ZT of the thermoelectric conversion material is represented by ZT = S ² T / ρκ. Z is the figure of merit of the thermoelectric conversion material, S is the Seebeck coefficient of the thermoelectric conversion material, T is the absolute temperature, ρ is the electrical resistivity of the thermoelectric conversion material, and κ is the thermal conductivity of the thermoelectric conversion material.

Here, a high-performance thermoelectric conversion material based on a copper sulfide mineral has been proposed. More specifically, for example, a thermoelectric conversion material represented by Cu _12-X M _X Sb ₄ S ₁₃ (when M is Zn, 0 <X <2.0, and when M is Fe, 0 < When X <1.5 and M is Ni, 0 ≦ X ≦ 2.0) is proposed. And the dimensionless figure of merit ZT in 400 degreeC of this thermoelectric conversion material is 0.5-0.9, and it is described that the high dimensionless figure of merit ZT is shown (for example, patent documents 1, nonpatent literature 1). reference).

  Further, antimony-tellurium and bismuth-tellurium have been proposed as thermoelectric conversion materials. The thermoelectric conversion material has a dimensionless figure of merit ZT at room temperature of about 1, and is described as exhibiting a high dimensionless figure of merit ZT. Furthermore, it is described that a material containing lead-tellurium and antimony exhibits a high dimensionless figure of merit ZT in the range of room temperature to 400 ° C. (see, for example, Non-Patent Document 2).

International Publication No. 2014/008414

Koichiro Suekuni, Kojiro Tsuruta, Masaru Kunii, Hirotaka Nishiate, Eiji Nishibori, Sachiko Maki, Michihiro Ohta, Atsushi Yamamoto, and Mikio Koyano, "High-performance thermoelectric mineral Cu12-xNixSb4S13tetrahedrite", Journal of Applied Physics, No. 113, 04371 ~ 5 pages, doi: 10.1063 / 1.4789389, January 2013 G. Jeffrey Snyder, Eric S. Toberer, "Complex thermoelectric materials", Nature Materials, No. 7, pp. 105-114, doi: 10.1038 / nmat2090, February 2008

  The thermoelectric conversion materials described in Patent Document 1 and Non-Patent Document 1 contain antimony that is a toxic element, and the thermoelectric conversion material described in Non-Patent Document 2 also contains lead that is a toxic element. And antimony was included, so it was a problem from an environmental friendly point of view.

  In addition, the thermoelectric conversion material described in Non-Patent Document 2 contains tellurium, which is an element with a small amount of crustal reserves. Therefore, with such a thermoelectric conversion material, a wide range of practical use of thermoelectric power generation is not easy. There was a problem.

  Furthermore, since heavy elements (heavy elements) such as lead, tellurium, bismuth, and antimony are included, the density per unit volume of the thermoelectric conversion element increases, and the weight of the entire power generation system increases. As a result, in the field where weight reduction is desired (for example, automobiles, etc.), there has been a problem that the demerit of an increase in weight due to mounting of a thermoelectric power generation system is large.

  Therefore, the present invention has been made in view of such a point, and is composed of an element having low toxicity and a large amount of crustal reserves, and has a high dimensionless figure of merit ZT, and can cope with weight reduction. And a thermoelectric power generation element and a Peltier cooling element using the same.

  In order to achieve the above object, the thermoelectric conversion material of the present invention is represented by the following formula (1).

（式中、ＭはＭｎ、Ｆｅ、Ｃｏ、Ｎｉ、及びＺｎから選ばれる少なくとも１種であり、ＡはＶ、Ｎｂ、及びＴａから選ばれる少なくとも１種であり、ＥはＳｉ、Ｇｅ、及びＳｎから選ばれる少なくとも１種であり、Ｘは０以上５以下である。）

(In the formula, M is at least one selected from Mn, Fe, Co, Ni, and Zn, A is at least one selected from V, Nb, and Ta, and E is Si, Ge, and Sn) At least one selected from X, and X is 0 or more and 5 or less.)

  According to the thermoelectric conversion material of the present invention, it is possible to provide a thermoelectric conversion material that is composed of an element having low toxicity and a large amount of crustal reserves and that exhibits a high dimensionless figure of merit ZT and can cope with weight reduction. Become.

  Hereinafter, the thermoelectric conversion material of the present invention will be described. In the present invention, a sulfide represented by the following general formula (2) is used as the thermoelectric conversion material.

This sulfide has a crystal structure similar to that of corusa ore (Cu _24-26 V ₂ (As, Sn, Sb) ₆ S ₃₂ ), but this corrosa ore has been used as a thermoelectric conversion material until now.・ Not considered.

  And as a result of the present inventor's extensive research, the thermoelectric conversion material represented by the general formula (2) has a low thermal conductivity, a high Seebeck coefficient and a low electrical resistivity in a temperature range of 120 to 400 ° C. It has become clear that it is expressed, that is, it exhibits a high dimensionless figure of merit ZT, and it has been found that the above-mentioned problems can be solved, thereby completing the present invention.

  And by using such a sulfide as a thermoelectric conversion material, it is mainly composed of sulfur and copper with low toxicity and a large amount of crustal reserves, and also exhibits a high dimensionless figure of merit ZT, corresponding to weight reduction It becomes possible to provide a possible thermoelectric conversion material.

  Here, from the viewpoint of achieving a high Seebeck coefficient and a low electrical resistivity, the metal M in the general formula (2) is preferably Zn having an electronic configuration similar to Cu. As the metal M, Mn, Fe, Co, and Ni that have an electron in a 3d orbital and can take a divalent ion state can be used as in the case of Zn.

  Further, from the viewpoint of charge balance, the range of X relating to the metal M in the general formula (2) is preferably 0 or more and 5 or less, and from the viewpoint of achieving a high Seebeck coefficient and low electrical resistivity, 0 or more and 4 or less. More preferred.

Note that the range of X in Cu _26-x M _x A ₂ E ₆ S ₃₂ is determined by the charge balance of Cu ⁺ , M ²⁺ , A ⁵⁺ , or E ⁴⁺ (Si ⁴⁺ , Ge ⁴⁺ , Sn ⁴⁺ ) and S ^2−. It is preferable to do.

  For example, if X = 0, the sum of charges is -4, so the material exhibits metallic electrical characteristics, and if X = 4, the sum of charges is 0, so the material is semiconductive. Characteristics. Since the thermoelectric material is required to have an intermediate charge carrier density between a metal and a semiconductor, the range of X is preferably 0 or more and 4 or less.

  Further, from the viewpoint of achieving a high Seebeck coefficient and a low electrical resistivity, the metal A in the general formula (2) is preferably at least one selected from V, Nb, and Ta which are Group 5 transition metals. .

  Further, from the viewpoint of reducing the thermal conductivity, the metal E in the general formula (2) is at least one selected from Si, Ge, and Sn having a large difference in atomic weight and atomic radius with respect to Cu and S. preferable.

In addition, the thermoelectric conversion material represented by the general formula (2) can cope with the weight reduction of the thermoelectric conversion material because the main components thereof are Cu and S having a small atomic weight. In the case of mounting, since it is preferable that the weight is lighter, the mass density per unit volume of the thermoelectric conversion material represented by the general formula (2) is lead-tellurium, antimony- It is preferably 5 g / cm ³ or less, which is sufficiently lower than the density of tellurium or bismuth-tellurium (6.5 to 8.3 g / cm ³ ).

  Further, a general thermoelectric power generation module and a Peltier cooling module have a π-shape, and are composed of a thermoelectric element made of n-type and p-type thermoelectric conversion materials, an electrode material for joining them, and an insulating material. . As the p-type thermoelectric element, a thermoelectric conversion material represented by the general formula (2) can be used.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

(Example 1)
(Production of thermoelectric conversion material)
First, Cu (1.2386 g), Zn (0.0510 g), V (0.0794 g), Sn (0.5553 g), and S (0.8000 g) as raw materials are vacuum sealed in a quartz tube. , it is reacted in 1100 ° _C., to give 2.7244g of polycrystalline samples of _{Cu 25 ZnV 2 Sn 6 S 32} . The obtained polycrystalline sample was identified by powder X-ray diffraction and electron probe microelement analysis.

  Next, the polycrystalline sample was pulverized into a pellet and subjected to annealing at 800 ° C. to remove impurities. Thereafter, the obtained polycrystalline sample was pulverized again and sintered under conditions of 800 ° C. and 50 MPa to obtain a high-density polycrystalline sample with few voids.

(Calculation of dimensionless figure of merit ZT for thermoelectric conversion)
Next, in a predetermined temperature range (room temperature of about 30 ° C. to about 390 ° C.), the obtained polycrystalline sample has an electrical resistivity ρ [μΩm], Seebeck coefficient S [μV / K], and thermal conductivity κ [ W / Km] was measured, and the dimensionless figure of merit ZT of thermoelectric conversion was determined from the equation ZT = S ² T / ρκ. The results are shown in Table 1.

(Example 2)
(Production of thermoelectric conversion material)
First, Cu (1.2882 g), V (0.0794 g), Ge (0.3398 g), and S (0.8000 g) as raw materials are vacuum sealed in a quartz tube and reacted at 1100 ° C. A 2.0574 g polycrystalline sample of Cu ₂₆ V ₂ Ge ₆ S ₃₂ was obtained. The obtained polycrystalline sample was identified by powder X-ray diffraction and electron probe microelement analysis.

  Next, the polycrystalline sample was pulverized into a pellet and subjected to annealing at 800 ° C. to remove impurities. Thereafter, the obtained polycrystalline sample was pulverized again and sintered under conditions of 800 ° C. and 50 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The results are shown in Table 2.

Example 3
(Production of thermoelectric conversion material)
First, Cu (1.6365 g), Nb (0.1842 g), Si (0.1667 g), and S (1.0178 g) as raw materials are vacuum-sealed in a quartz tube and reacted at 1050 ° C. 3.0052 g of a polycrystalline sample of Cu ₂₆ Nb ₂ Si ₆ S ₃₂ was obtained. The obtained polycrystalline sample was identified by powder X-ray diffraction.

  Next, the powdered polycrystalline sample was sintered under the conditions of 850 ° C. and 70 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The above results are shown in Table 3.

(Example 4)
(Production of thermoelectric conversion material)
First, Cu (1.2882 g), V (0.0794 g), Sn (0.5553 g), and S (0.8000 g) as raw materials are sealed in a quartz tube and reacted at 1100 ° C. 2.7229 g of a polycrystalline sample of Cu ₂₆ V ₂ Sn ₆ S ₃₂ was obtained. The obtained polycrystalline sample was identified by powder X-ray diffraction and electron probe microelement analysis.

  Next, the polycrystalline sample was pulverized into a pellet and subjected to annealing at 800 ° C. to remove impurities. Thereafter, the obtained polycrystalline sample was pulverized again and sintered under conditions of 800 ° C. and 50 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The results are shown in Table 4.

(Example 5)
(Production of thermoelectric conversion material)
First, Cu (1.1891 g), Zn (0.1019 g), V (0.0794 g), Sn (0.5553 g), and S (0.8000 g) as raw materials are vacuum-sealed in a quartz tube. , it is reacted in 1100 ° _C., to give 2.7258g of polycrystalline samples of _{Cu 24 Zn 2 V 2 Sn 6} S 32. The obtained polycrystalline sample was identified by powder X-ray diffraction and electron probe microelement analysis.

  Next, the polycrystalline sample was pulverized into a pellet and subjected to annealing at 800 ° C. to remove impurities. Thereafter, the obtained polycrystalline sample was pulverized again and sintered under conditions of 800 ° C. and 50 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The results are shown in Table 5.

(Example 6)
(Production of thermoelectric conversion material)
First, Cu (1.1395 g), Zn (0.1529 g), V (0.0794 g), Sn (0.5553 g), and S (0.8000 g) as raw materials are vacuum-sealed in a quartz tube. , it is reacted in 1100 ° _C., to give 2.7272g of polycrystalline samples of _{Cu 23 Zn 3 V 2 Sn 6} S 32. The obtained polycrystalline sample was identified by powder X-ray diffraction and electron probe microelement analysis.

  Next, the polycrystalline sample was pulverized into a pellet and subjected to annealing at 800 ° C. to remove impurities. Thereafter, the obtained polycrystalline sample was pulverized again and sintered under conditions of 800 ° C. and 50 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The results are shown in Table 6.

(Example 7)
(Production of thermoelectric conversion material)
First, Cu (1.3865 g), Nb (0.1560 g), Sn (0.5986 g), and S (0.8610 g) as raw materials are vacuum-sealed in a quartz tube and reacted at 1050 ° C. Then, 3.0021 g of a polycrystalline sample of Cu ₂₆ Nb ₂ Sn ₆ S ₃₂ was obtained. The obtained polycrystalline sample was identified by powder X-ray diffraction.

  Next, the powdered polycrystalline sample was sintered under the conditions of 700 ° C. and 70 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. The results are shown in Table 7.

(Example 8)
(Production of thermoelectric conversion material)
First, Cu (1.3943 g), V (0.0656 g), Ta (0.00768 g), Sn (0.6055 g), and S (0.8690 g) as raw materials are vacuum sealed in a quartz tube. , it is reacted in 1050 ° _C., to give 3.0112g of polycrystalline samples of _{Cu 26 V 1.5 Ta 0.5 Sn 6} S 32. The obtained polycrystalline sample was identified by powder X-ray diffraction.

  Next, the powdered polycrystalline sample was sintered under the conditions of 700 ° C. and 70 MPa to obtain a high-density polycrystalline sample with few voids.

  Next, the dimensionless figure of merit ZT of thermoelectric conversion was calculated in the same manner as in the first embodiment described above. Table 8 shows the above results.

  As shown in Table 1, the thermoelectric conversion material of Example 1 shows a dimensionless figure of merit ZT of 0.2 or more in a temperature range of 170 to 386 ° C., and particularly 0 at a temperature of 364 ° C. or more. It can be seen that it exhibits a high dimensionless figure of merit ZT of 4 or higher.

  Further, as shown in Table 2, the thermoelectric conversion material of Example 2 shows a dimensionless figure of merit ZT of 0.2 or more in the temperature range of 76 to 389 ° C., and particularly at a temperature of 172 ° C. or more. It can be seen that a high dimensionless figure of merit ZT of 0.4 or more is shown.

  Further, as shown in Table 3, the thermoelectric conversion material of Example 3 shows a dimensionless figure of merit ZT of 0.2 or more in the temperature range of 122 to 387 ° C., and particularly at a temperature of 267 ° C. or more. It can be seen that a high dimensionless figure of merit ZT of 0.4 or more is shown.

  Further, as shown in Table 4, the thermoelectric conversion material of Example 4 shows a dimensionless figure of merit ZT of 0.2 or more in a temperature range of 125 to 391 ° C., and particularly at a temperature of 320 ° C. or more. It can be seen that a high dimensionless figure of merit ZT of 0.4 or more is shown.

  Moreover, as shown in Table 5, it can be seen that the thermoelectric conversion material of Example 5 exhibits a dimensionless figure of merit ZT of 0.2 or more in the temperature range of 216 to 383 ° C.

  Further, as shown in Table 6, it can be seen that the thermoelectric conversion material of Example 6 exhibits a dimensionless figure of merit ZT of 0.2 or more in the temperature range of 368 to 390 ° C.

  Further, as shown in Table 7, the thermoelectric conversion material of Example 7 shows a dimensionless figure of merit ZT of 0.2 or more in the temperature range of 123 to 388 ° C., and particularly at a temperature of 292 ° C. or more. It can be seen that a high dimensionless figure of merit ZT of 0.4 or more is shown.

  Furthermore, as shown in Table 8, the thermoelectric conversion material of Example 8 shows a dimensionless figure of merit ZT of 0.2 or more in a temperature range of 101 to 390 ° C., and particularly at a temperature of 246 ° C. or more. It can be seen that a high dimensionless figure of merit ZT of 0.4 or more is shown.

  Further, as shown in Tables 1 to 8, it can be seen that the thermoelectric conversion materials of Examples 1 to 8 exhibit a high dimensionless figure of merit ZT with good reproducibility in a predetermined temperature range.

  From the above, the thermoelectric conversion materials in Examples 1 to 8 show a high dimensionless figure of merit ZT in a predetermined temperature range (76 ° C. to 391 ° C.), and are composed of low toxicity and a large amount of crustal reserves. In addition, it can be seen that the thermoelectric conversion material can be reduced in weight.

  Examples of utilization of the present invention include thermoelectric conversion materials, thermoelectric power generation elements using the materials, and Peltier cooling elements.

Claims (6)

A thermoelectric conversion material represented by the following formula (1).

(In the formula, M is at least one selected from Mn, Fe, Co, Ni, and Zn, A is at least one selected from V, Nb, and Ta, and E is Si, Ge, and Sn) At least one selected from X, and X is 0 or more and 5 or less.)   The thermoelectric conversion material according to claim 1, wherein the M is Zn.   The thermoelectric conversion material according to claim 1, wherein the X is 0 or more and 4 or less. 4. The thermoelectric conversion material according to claim 1, wherein a dimensionless figure of merit (ZT) is 0.2 to 0.73 at 76 to 390 ° C. 5.   The thermoelectric power generation element formed with the thermoelectric conversion material of any one of Claims 1-4.   The Peltier cooling element formed with the thermoelectric conversion material of any one of Claims 1-4.