Thermoelectric conversion materials, thermoelectric power generation modules using thermoelectric conversion materials, and Peltier cooling modules

Abstract

To provide a thermoelectric conversion material having a high dimensionless thermoelectric figure of merit over a wide temperature range, and a thermoelectric power generation module and a Peltier cooling module using the thermoelectric conversion material.SOLUTION: A thermoelectric conversion material according to the present invention includes a base material containing PbTe, and at least one element selected from the group consisting of elements whose ionic radius with a valence of +1 is smaller than the ionic radius of Pb with a valence of +2, which is contained in the base material, and the element whose ionic radius with a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 is contained in the base material as an ion with a valence of +1, and the content is more than 0at% and less than 10.0at%.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion material, a thermoelectric power generation module using the thermoelectric conversion material, and a Peltier cooling module. [Background technology]

[0002] Thermoelectric conversion is the direct conversion of thermal energy to electrical energy using a solid-state semiconductor element. Thermoelectric conversion is a general term for thermoelectric power generation and Peltier cooling. Thermoelectric power generation using thermoelectric conversion is based on the Seebeck effect. tree By using a thermoelectric power generation module, electricity can be generated from unused thermal energy such as waste heat from automobiles, industrial furnaces, and data centers, making a significant contribution to overcoming the energy crisis and reducing carbon dioxide emissions.

[0003] On the other hand, thermoelectric (Peltier) cooling, which uses thermoelectric conversion, uses the Peltier effect to create a heat flow in conjunction with the flow of electric current. Peltier cooling modules that use the Peltier effect have no moving parts, so they have a long lifespan, can be made compact, and are easy to carry.

[0004] Thermoelectric conversion modules (thermoelectric power generation modules and Peltier cooling modules) require thermoelectric conversion materials that can directly convert thermal energy to electrical energy. The performance of a thermoelectric conversion material is expressed by the dimensionless thermoelectric figure of merit ZT, specifically, ZT=S 2 T / (ρκ total ) where Z is the thermoelectric figure of merit of the thermoelectric material, T is the absolute temperature, S is the Seebeck coefficient of the thermoelectric material, ρ is the electrical resistivity of the thermoelectric material, and κ total is the thermal conductivity of the thermoelectric material. total is κ total =κ lat +κ ele It is expressed as κ lat is the lattice thermal conductivity, and κ ele is the electronic thermal conductivity.

[0005] The performance of thermoelectric power generation modules and Peltier cooling modules is determined by the average value of the dimensionless figure of merit ZT in the temperature range that the thermoelectric conversion module operates in. Lead telluride PbTe exhibits a relatively high ZT in the mid-to-high temperature range (600K to 900K), making it an advantageous material for maximizing the average value of ZT in the 600K to 900K temperature range.

[0006] Patent Document 1 discloses a thermoelectric conversion material comprising a base material containing PbTe, and nano-precipitates in the base material containing at least one element (M) selected from the group consisting of C, Si, Ge and Sn, and at least one element (A) selected from the group consisting of Group 1 elements, Group 11 elements and Group 13 elements, 1-x-y A y M x The thermoelectric conversion material is disclosed as being represented by the composition formula Te, where x and y represent the atomic ratios of M and A, respectively, to the total amount of Pb, M, and A, where x is 0.002 or more and 0.012 or less, and y is greater than 0 and 0.1 or less.

[0007] Non-Patent Document 1 describes a thermoelectric conversion material, which is a base material containing PbTe, a base material containing Ga, and a Pb 1-x Ga x A thermoelectric conversion material is disclosed that is expressed by the composition formula Te, where x is 0.005 or more and 0.035 or less. The dimensionless thermoelectric figure of merit ZT of this material increases with temperature from room temperature to 750 K, but begins to decrease at higher temperatures, so the average dimensionless thermoelectric figure of merit ZT at temperatures between 600 K and 900 K remains low.

[0008] Non-Patent Document 2 describes a thermoelectric conversion material, which is a base material containing PbTe and a base material containing Cu, x A thermoelectric conversion material is disclosed that has the composition formula Cu2Te, where x is 0.02 or more and 0.065 or less. The dimensionless thermoelectric figure of merit ZT of this material increases with temperature from room temperature to 750K, but begins to decrease at higher temperatures, so the average dimensionless thermoelectric figure of merit ZT at temperatures between 600K and 900K remains low. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6923182 [Non-patent literature]

[0010] [Non-Patent Document 1] XL Su, SQ Hao, TP Bailey, S. Wang, I. Hadar, GG Tan, T.-B. Song, QJ Zhang, C. Uher, C. Wolverton, XF Tang, and MG Kanatzidis, “Weak electron phonon coupling and deep level impurity for high thermoelectric performance Pb1-xGaxTe”, Advanced Energy Materials, Vol. 8, pp 1800659:1-11, 2018. [Non-patent document 2] Y. Xiao, HJ Wu, W. Li, MJ Yin, YL Pei, Y. Zhang, LW Fu, YX Chen, SJ Pennycook, L. Huang, JQ He, and L.-D. Zhao, “Remarkable roles of Cu to synergistically optimize phonon and carrier transport in n-type PbTe-Cu2Te”, Journal of the American Chemical Society, Vol. 139, pp 18732-18738, 2017. Summary of the Invention [Problem to be solved by the invention]

[0011] However, adjusting the electrical and thermal properties of thermoelectric conversion materials is not easy, and it is necessary to explore combinations of elements to optimize the dimensionless thermoelectric figure of merit ZT.

[0012] The present invention has been made to solve the above-mentioned problems, and aims to provide a thermoelectric conversion material that has a high dimensionless thermoelectric figure of merit ZT over a wide temperature range, and a thermoelectric power generation module and a Peltier cooling module that use the thermoelectric conversion material. [Means for solving the problem]

[0013] In order to solve the above problems, one aspect of the present invention provides the following means. (1) A thermoelectric conversion material according to one embodiment of the present invention includes a base material containing PbTe, and at least one element selected from the group consisting of elements contained in the base material and having an ionic radius of +1 smaller than the ionic radius of Pb having a valence of +2, wherein the element having an ionic radius of +1 smaller than the ionic radius of Pb having a valence of +2 is contained in the base material as an ion with a valence of +1, and the content of the element is more than 0 at% and less than 10.0 at%. Pb 1-x A x M z T e wherein A is at least one element selected from the group consisting of Group 13 elements, M is at least one element selected from the group consisting of Group 1 elements, Group 10 elements, and Group 11 elements, x is 0.02 or more and 0.04 or less, z is more than 0 and less than 0.10, and the Seebeck coefficient S is -210 μVK at 600 K to 900 K. -1 and the electrical resistivity ρ is 35 μΩm or less. It is characterized by: (2) The thermoelectric conversion material according to (1), which is an n-type semiconductor. (3) A is at least one element selected from the group consisting of B, Al, Ga, and In. The thermoelectric conversion material according to (1) or (2) above. (4) The method according to any one of (1) to (3), wherein M is at least one element selected from the group consisting of Li, Na, Pd, Cu, and Ag. The thermoelectric conversion material described herein. (5) wherein A is Ga. (3) The thermoelectric conversion material according to claim 1. (6) wherein M is Cu (4) The thermoelectric conversion material according to claim 1. (7)The z is greater than 0 and not greater than 0.04. (1)~(6) The thermoelectric conversion material according to any one of claims 1 to 4. (8) The x is 0.02. (1)~(7) The thermoelectric conversion material according to any one of claims 1 to 4. (9) The z is 0.01 or more and 0.04 or less. (7) The thermoelectric conversion material according to claim 1. (10) The average value of the dimensionless thermoelectric figure of merit ZT between 600K and 900K is greater than 1.00. (1)~(9) The thermoelectric conversion material according to any one of claims 1 to 4. (11) (1)~ (10) A thermoelectric power generation module comprising the thermoelectric conversion material according to any one of claims 1 to 4. (12) (1)~ (10) 10. A Peltier cooling module comprising the thermoelectric conversion material according to any one of claims 1 to 9. [Effects of the Invention]

[0014] The present invention provides a thermoelectric conversion material having a high dimensionless thermoelectric figure of merit over a wide temperature range, as well as a thermoelectric power generation module and a Peltier cooling module that use the thermoelectric conversion material. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 shows a scanning electron microscope (SEM) photograph and elemental mapping by energy dispersive X-ray analysis (EDS) of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 2] FIG. 2 is a diagram showing a powder X-ray diffraction pattern of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 3] FIG. 3 is a graph showing the temperature dependence of the Seebeck coefficient of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 4]FIG. 4 is a graph showing the temperature dependence of the electrical resistivity of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 5] FIG. 5 is a diagram showing the temperature dependence of the power factor of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 6] FIG. 6 is a graph showing the temperature dependence of the thermal conductivity of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 7] FIG. 7 is a graph showing the temperature dependence of the lattice thermal conductivity of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 8] FIG. 8 is a graph showing the temperature dependence of the dimensionless thermoelectric figure of merit of a thermoelectric conversion material according to an experimental example of the present invention. [Figure 9] FIG. 9 is a schematic diagram of a thermoelectric power generation module according to an embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram of a Peltier cooling module according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] There are two methods to improve the ZT of thermoelectric materials. One is to increase the power factor (S 2 / ρ), especially to reduce the electrical resistivity ρ.

[0017] Electrical resistivity ρ, charge carrier concentration n, and carrier mobility μ and The relationship between -1 =neμ, where e represents the carrier charge. It is difficult to reduce the electrical resistivity ρ of n-type PbTe in the temperature range of 600K to 900K for the following two reasons. First, it is difficult to optimize the carrier concentration n. Second, because carriers are scattered by pores, precipitates, and doped atoms in the structure, materials with a high concentration of pores, precipitates, and doped atoms typically have a low carrier mobility μ. For these two reasons, ZT of conventional n-type PbTe peaks around 700K, and at around 900K, ZT drops by about 50% compared to the peak.

[0018] Another way to improve the dimensionless figure of merit ZT is to improve the lattice thermal conductivity κ, which represents the conduction performance of heat (phonons) carried by lattice vibrations in a solid. lat The lattice thermal conductivity κ can be reduced by precipitating nano- or micro-sized precipitates in thermoelectric materials that can efficiently scatter heat-carrying quanta (phonons). lat It is known that nano- and micro-sized precipitates can reduce the carrier mobility. However, it is not easy to form nano- and micro-sized precipitates that cause effective phonon scattering, and it is necessary to explore combinations of elements to optimize the formation of nano- and micro-sized precipitates. If the amount of nano- and micro-sized precipitates is too large, it will affect carrier mobility, so the amount must be less than a certain value.

[0019] The present inventors have investigated the above points and found that by incorporating into PbTe an element whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb at a valence of +2, the thermoelectric conversion material has a high dimensionless thermoelectric figure of merit over a wide temperature range.

[0020] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. First, a thermoelectric conversion material according to an embodiment of the present invention will be described.

[0021] <Thermoelectric conversion materials> A thermoelectric conversion material according to an embodiment of the present invention includes a base material containing PbTe and at least one element contained in the base material and selected from the group consisting of elements having an ionic radius when the valence is +1 that is smaller than the ionic radius of Pb having a valence of +2, wherein the content of the at least one element selected from the group consisting of elements having an ionic radius when the valence is +1 that is smaller than the ionic radius of Pb having a valence of +2 is more than 0 at% and less than 10.0 at%.

[0022] (base material) A thermoelectric conversion material according to an embodiment of the present invention has a substrate. The substrate contains PbTe. PbTe is lead telluride. The crystal structure of PbTe may be NaCl type. PbTe may be single crystal or polycrystalline. The substrate preferably consists of PbTe, a donor or acceptor, and impurities. The substrate preferably contains as few impurities as possible. PbTe is a compound containing Pb and Te.

[0023] (Explanation of M: An element whose ionic radius with a valence of +1 is smaller than the ionic radius of Pb, which has a valence of +2.) In a thermoelectric conversion material according to an embodiment of the present invention, the base material contains at least one element selected from the group consisting of elements whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2. The content of elements whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 is greater than 0 at% and less than 10.0 at%. Here, the content of elements whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 refers to the content of elements whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 relative to the total mass of the thermoelectric conversion material.

[0024] In an embodiment of the present invention, an element whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 exists as an ion with a valence of +1 in the base material. Furthermore, an element whose ionic radius is smaller than the ionic radius of Pb with a valence of +2 refers to an element whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb contained in PbTe. Pb is essentially present as a +2 ion in PbTe. The ionic radius of an element whose ionic radius at a valence of +1 is smaller than that of Pb with a valence of +2 is the ionic radius when the valence is +1. In other words, an element whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 refers to an element that can exist as a +1 ion in PbTe and is smaller than the ionic radius of Pb with a valence of +2 contained in PbTe when in the +1 ionic state. One or more elements whose ionic radius at a valence of +1 is smaller than the ionic radius of Pb with a valence of +2 may be contained in the base material.

[0025] According to the thermoelectric conversion material of this embodiment, the base material contains an element whose ionic radius when the valence is +1 is smaller than the ionic radius of Pb whose valence is +2, thereby reducing the electrical resistivity of the thermoelectric conversion material. This increases the power factor of the thermoelectric conversion material. Furthermore, the lattice thermal conductivity is reduced. Therefore, the dimensionless figure of merit ZT of the thermoelectric conversion material in the temperature range of 600 K to 900 K is increased. When the content of the element whose ionic radius when the valence is +1 is smaller than the ionic radius of Pb whose valence is +2 exceeds 0 at%, the effect of reducing the electrical resistivity of the thermoelectric conversion material is enhanced. The content of the element whose ionic radius when the valence is +1 is smaller than the ionic radius of Pb whose valence is +2 may exceed 0 at%, but is preferably 0.1 at% or more, more preferably 0.5 at% or more, and even more preferably 1.0 at% or more.

[0026] When the content of elements whose ionic radius of valence +1 is smaller than that of Pb whose valence is +2 is less than 10.0 at%, the effect of reducing the electrical resistivity ρ is increased. This increases the power factor S of the thermoelectric conversion material. 2 / ρ increases, and the lattice thermal conductivity decreases. Therefore, the dimensionless figure of merit ZT of the thermoelectric conversion material in the temperature range of 600 K to 900 K increases. As a result, a thermoelectric conversion material with high thermoelectric conversion efficiency can be provided. The content of elements whose ionic radius when valence is +1 is smaller than the ionic radius of Pb when valence is +2 may be less than 10.0 at% and is preferably 6.0 at% or less, more preferably 5.0 at% or less, and even more preferably 4.0 at% or less.

[0027] The thermoelectric conversion material according to the embodiment of the present invention may be a p-type semiconductor or an n-type semiconductor. The thermoelectric conversion material according to the present embodiment has a content of elements having a valence of +1 and an ionic radius smaller than that of Pb of more than 0 at % and less than 10.0 at %, and therefore has a power factor S 2Because / ρ increases and the lattice thermal conductivity decreases, the dimensionless figure of merit ZT increases over a wide temperature range of 600 K to 900 K. Since the ionic radius of an element with a valence of +1 is smaller than the ionic radius of Pb, which has a valence of +2, the element has a valence of +1, and therefore provides n-type (negatively charged) charge carriers, a higher dimensionless figure of merit ZT is achieved when the thermoelectric conversion material is an n-type semiconductor.

[0028] The thermoelectric conversion material according to an embodiment of the present invention is Pb 1-x A x M z The compound may be represented by the composition formula Te. A may be at least one element selected from the group consisting of Group 13 elements. M may be at least one element selected from the group consisting of Group 1 elements, Group 10 elements, and Group 11 elements.

[0029] When A is at least one element selected from the group consisting of Group 13 elements, n-type charge carriers (electrons) can be generated in PbTe. A may exist in the state of a +3 ion in PbTe. A acts as a donor that provides n-type charge carriers.

[0030] M is at least one element selected from the group consisting of Group 1 elements, Group 10 elements, and Group 11 elements, and M occupies Pb vacancies and interstitial sites of PbTe, optimizing the carrier concentration and improving the carrier mobility. This reduces the electrical resistivity ρ. Therefore, the power factor S of the thermoelectric conversion material 2 / ρ can be further improved. As a result, the dimensionless figure of merit ZT of the thermoelectric conversion material is further improved. M may be an element whose ionic radius when the valence is +1 is smaller than the ionic radius of Pb when the valence is +2.

[0031] In the thermoelectric conversion material according to the embodiment of the present invention, it is more preferable that A is at least one element selected from the group consisting of Group 13 elements, and M is at least one element selected from the group consisting of Group 1, Group 10, and Group 11 elements. This allows nano- and micro-sized pores and precipitates to be dispersed in PbTe. As a result, heat-carrying quanta (phonons) can be scattered more efficiently. This further reduces the lattice thermal conductivity of the thermoelectric conversion material. As a result, the dimensionless figure of merit (ZT) of the thermoelectric conversion material is further improved.

[0032] A is preferably at least one element selected from the group consisting of B, Al, Ga, and In. This can further improve the carrier concentration of the thermoelectric conversion material. As a result, the dimensionless figure of merit ZT of the thermoelectric conversion material is further improved. B, Al, Ga, and In may exist in the state of +3 ions in PbTe.

[0033] M is preferably at least one element selected from the group consisting of Li, Na, Pd, Cu, and Ag. This further enhances the effects of optimizing the carrier concentration and improving carrier mobility. As a result, the dimensionless figure of merit ZT of the thermoelectric conversion material is further improved. Li, Na, Pd, Cu, and Ag may exist in PbTe as +1 ions, and their ionic radii are smaller than the ionic radius of Pb, which has a valence of +2.

[0034] In the thermoelectric conversion material according to an embodiment of the present invention, it is more preferable that A is at least one element selected from the group consisting of B, Al, Ga, and In, and M is at least one element selected from the group consisting of Group 1 elements, Li, Na, Pd, Cu, and Ag. This allows nano- and micro-sized pores and precipitates to be effectively dispersed in PbTe, allowing heat-carrying quanta (phonons) to be scattered more efficiently. As a result, the dimensionless figure of merit (ZT) of the thermoelectric conversion material is further improved.

[0035] More preferably, A is Ga. More preferably, M is Cu. More preferably, A is Ga and M is Cu. This further improves the dimensionless figure of merit ZT of the thermoelectric conversion material.

[0036] In the thermoelectric conversion material according to an embodiment of the present invention, Pb 1-x A x M z x in Te may be greater than 0, preferably greater than 0.01, and more preferably 0.02. When x is greater than 0, electrons, which are n-type charge carriers, can be generated, making it an n-type semiconductor. Also, x may be 0.04 or less, preferably 0.03 or less, and more preferably 0.02. When x is 0.04 or less, it becomes an n-type semiconductor.

[0037] The thermoelectric conversion material according to an embodiment of the present invention is Pb 1-x A x M z The value of z in Te may be greater than 0, and is preferably 0.001 or greater, more preferably 0.005 or greater, and even more preferably 0.01 or greater. When z is greater than 0, the value of z in the thermoelectric conversion material is Medium and high temperature range (600K~900K) The dimensionless figure of merit ZT at this temperature is further improved. Furthermore, z may be less than 0.10, and is preferably 0.08 or less, more preferably 0.06 or less, more preferably 0.05 or less, and even more preferably 0.04 or less. When z is less than 0.10, the thermoelectric conversion material Medium and high temperature range The dimensionless figure of merit ZT at

[0038] In the thermoelectric conversion material according to an embodiment of the present invention, Pb 1-x A x M z M in Te may exist in Pb vacancies and interstitial sites of PbTe. The state in which M exists in Pb vacancies refers to a state in which M occupies vacancies generated at Pb sites in the superlattice of PbTe. The state in which M exists in PbTe as an interstitial element refers to a state in which M exists in interstitial sites in the superlattice of PbTe where Pb and Te do not normally exist. Pb1-x A x M z The presence of Pb vacancies in Te and interstitial sites in PbTe optimizes the carrier concentration and improves the carrier mobility. Medium and high temperature range The dimensionless figure of merit ZT at

[0039] In the thermoelectric conversion material according to an embodiment of the present invention, the Seebeck coefficient S is -210 μVK in the temperature range of 600 K to 900 K. -1 May be greater than -180μVK -1 It is preferable that it is equal to or greater than -170μVK. -1 More preferably, it is -160μVK or more. -1 More preferably, it is -150 μVK or more. -1 It is even more preferable that the temperature is -210μVK or more in the temperature range of 600K to 900K. -1 Above this, the Seebeck coefficient S is -210μVK in the temperature range of 600K to 900K. -1 This means that the Seebeck coefficient S is -210μVK in the temperature range of 600K to 900K. -1 As a result, the thermoelectric conversion material Medium and high temperature range The dimensionless figure of merit ZT at

[0040] In the thermoelectric conversion material according to the embodiment of the present invention, the electrical resistivity ρ may be 35 μΩm or less, preferably 28 μΩm or less, more preferably 24 μΩm or less, even more preferably 21 μΩm or less, and even more preferably 19 μΩm or less in the temperature range of 600 K to 900 K. An electrical resistivity ρ of 35 μΩm or less in the temperature range of 600 K to 900 K means that the electrical resistivity ρ is 35 μΩm or less throughout the temperature range of 600 K to 900 K. By having the electrical resistivity ρ of 35 μΩm or less in the temperature range of 600 K to 900 K, the thermoelectric conversion material Medium and high temperature range The dimensionless figure of merit ZT at

[0041] In the thermoelectric conversion material according to an embodiment of the present invention, the average value of the dimensionless thermoelectric figure of merit ZT from 600K to 900K is preferably greater than 1.00, more preferably 1.05 or greater, even more preferably 1.10 or greater, and even more preferably 1.15 or greater. This further improves the thermoelectric conversion efficiency of the thermoelectric conversion material. The average value of the dimensionless thermoelectric figure of merit ZT from 600K to 900K means the average value of the dimensionless thermoelectric figure of merit ZT from 600K to 900K.

[0042] The thermoelectric conversion material according to the embodiment of the present invention has a high dimensionless thermoelectric figure of merit over a wide temperature range. Furthermore, by including at least one element selected from the group consisting of Group 13 elements, the Pb content in the thermoelectric conversion material can be further reduced. Therefore, a thermoelectric conversion material with even less toxicity can be provided.

[0043] <Thermoelectric power generation module> Next, a thermoelectric power generation module according to an embodiment of the present invention will be described.

[0044] Fig. 9 is a schematic diagram of a thermoelectric power generation module according to an embodiment of the present invention. As shown in Fig. 9, a thermoelectric power generation module 30 according to an embodiment of the present invention includes a p-type thermoelectric conversion material 10a, an n-type thermoelectric conversion material 10b, an upper junction electrode 31 in contact with one side of each of the p-type thermoelectric conversion material 10a and the n-type thermoelectric conversion material 10b, a lower junction electrode 32 in contact with the other side of the p-type thermoelectric conversion material 10a, and a lower junction electrode 33 in contact with the other side of the n-type thermoelectric conversion material 10b. As shown in Fig. 9, the entire thermoelectric power generation module 30 has a π-shaped configuration.

[0045] The p-type thermoelectric conversion material 10a may be a thermoelectric conversion material described in the embodiment of the present invention, or a known p-type thermoelectric conversion material. The n-type thermoelectric conversion material 10b uses a thermoelectric conversion element described in the embodiment of the present invention. The upper junction electrode 31, the lower junction electrode 32, and the lower junction electrode 33 may be made of a material with good electrical and thermal conductivity, such as copper (Cu). The thickness is not particularly limited, but is preferably about 1 mm, taking into account mechanical strength.

[0046] In the thermoelectric power generation module 30, a high-temperature body is brought into contact with the upper junction electrode 31, and a temperature difference is generated between the lower junction electrode 32 and the lower junction electrode 33. This increases the carrier concentration in the p-type thermoelectric conversion material 10a and the n-type thermoelectric conversion material 10b that are in contact with the upper junction electrode 31. As a result, carriers diffuse toward the lower junction electrode 32 and the lower junction electrode 33, respectively. This causes a current to flow from the lower junction electrode 33 to the lower junction electrode 32 via the n-type thermoelectric conversion material 10b, the upper junction electrode 31, and the p-type thermoelectric conversion material 10a. As a result, a positive voltage is generated in the lower junction electrode 32 relative to the lower junction electrode 33. This allows power to be extracted by connecting an external load 34 to the lower junction electrode 32 and the lower junction electrode 33.

[0047] According to the thermoelectric power generation module 30 of this embodiment, it is possible to provide a thermoelectric power generation module 30 having high power generation performance. In addition, it is possible to provide a thermoelectric power generation module with less toxicity.

[0048] <Peltier cooling module> Fig. 10 is a schematic diagram of a Peltier cooling module according to an embodiment of the present invention. As shown in Fig. 10, a Peltier cooling module 50 according to an embodiment of the present invention includes a p-type thermoelectric conversion material 10a, an n-type thermoelectric conversion material 10b, an upper junction electrode 31 in contact with one side of each of the p-type thermoelectric conversion material 10a and the n-type thermoelectric conversion material 10b, a lower junction electrode 32 in contact with the other side of the p-type thermoelectric conversion material 10a, and a lower junction electrode 33 in contact with the other side of the n-type thermoelectric conversion material 10b. In this embodiment, components identical to those in the above-described embodiment are designated by the same reference numerals, and their description will be omitted, with only differences being described.

[0049] A positive voltage is applied to the lower junction electrode 33 and a negative voltage is applied to the lower junction electrode 32 through the external power supply unit 51 to operate the Peltier cooling module.

[0050] In the Peltier cooling module 50, current supplied by the external power supply unit 51 flows in the order of from the lower junction electrode 33 to the n-type thermoelectric conversion material 10b, the upper junction electrode 31, the p-type thermoelectric conversion material 10a, and the lower junction electrode 32, thereby absorbing heat from the object to be cooled on the upper junction electrode 31 side. In the n-type thermoelectric conversion material 10b, electrons serving as charge carriers on the upper junction electrode 31 side absorb energy and release the energy on the lower junction electrode 33 side, and in the p-type thermoelectric conversion material 10a, holes serving as charge carriers on the upper junction electrode 31 side absorb energy and release it on the lower junction electrode 32 side, thereby cooling the object to be cooled.

[0051] According to the Peltier cooling module 50 of this embodiment, it is possible to realize a Peltier cooling module 50 having high cooling performance. In addition, it is possible to provide a Peltier cooling module with less toxicity.

[0052] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Example]

[0053] <Experimental Example 1> (Preparation of thermoelectric conversion materials) The raw materials, lead (Pb) 6.02g, gallium (Ga) 0.04g, and tellurium (Te) 3.78g, were vacuum sealed in a quartz tube. The raw materials vacuum sealed in the quartz tube were reacted at 1323K, and a total of 9.84g of Pb was produced. 0.98 Ga 0.02 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 A portion of the Te polycrystalline sample was crushed into powder and then subjected to X-ray diffraction (CuKα radiation, 40 kV, 10 mA) to identify Pb 0.98 Ga 0.02 The phase of Te was evaluated. 0.98 Ga 0.02 The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 99% of the theoretical density) was obtained.

[0054] (Measurement of the dimensionless figure of merit ZT) The Seebeck coefficient S (μVK) of the thermoelectric conversion material compact in a predetermined temperature range (from room temperature of approximately 300 K to approximately 900 K) -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m-1 The results are shown in Figures 5 and 7.

[0055] The electrical resistivity ρ was measured by the four-terminal method.

[0056] The Seebeck coefficient S was measured specifically by the following method. The Seebeck coefficient S is the electromotive force V that occurs when a temperature gradient ΔT exists in a thermoelectric conversion material. E Measure S=(V E ΔT -1 )-S wire It was calculated from the formula where S wire is the absolute Seebeck coefficient of the metal probe used to measure the electromotive force.

[0057] Thermal conductivity κ total was measured by the flash method.

[0058] <Experimental Example 2> The raw materials, lead (Pb) 6.11 g, gallium (Ga) 0.04 g, copper (Cu) 0.02 g, and tellurium (Te) 3.84 g, were vacuum-sealed in a quartz tube. The raw materials vacuum-sealed in the quartz tube were reacted at 1323 K, and a total of 10.01 g of Pb was produced. 0.98 Ga 0.02 Cu 0.01 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu 0.01 A portion of the Te polycrystalline sample was crushed into powder and then subjected to X-ray diffraction (CuKα radiation, 40 kV, 10 mA) to identify Pb 0.98 Ga 0.02 Cu 0.01 The phase of Te was evaluated. 0.98 Ga 0.02 Cu 0.01 The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.01 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 98% of the theoretical density) was obtained.

[0059] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0060] <Experimental Example 3> The raw materials, lead (Pb) 6.07g, gallium (Ga) 0.04g, copper (Cu) 0.04g, and tellurium (Te) 3.81g, were vacuum sealed in a quartz tube. The raw materials vacuum sealed in the quartz tube were reacted at 1323K, and a total of 9.96g of Pb was produced. 0.98 Ga 0.02 Cu 0.02 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu 0.02 A portion of the Te polycrystalline sample was crushed into powder and then subjected to X-ray diffraction (CuKα radiation, 40 kV, 10 mA) to identify Pb 0.98 Ga 0.02 Cu 0.02 The phase of Te was evaluated. 0.98 Ga 0.02 Cu 0.02 The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.02A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 98% of the theoretical density) was obtained.

[0061] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0062] <Experimental Example 4> The raw materials, lead (Pb) 6.07g, gallium (Ga) 0.04g, copper (Cu) 0.06g, and tellurium (Te) 3.81g, were vacuum sealed in a quartz tube. The raw materials vacuum sealed in the quartz tube were reacted at 1323K, and a total of 9.98g of Pb was produced. 0.98 Ga 0.02 Cu 0.03 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu 0.03 A portion of the Te polycrystalline sample was crushed into powder and then subjected to X-ray diffraction (CuKα radiation, 40 kV, 10 mA) to identify Pb 0.98 Ga 0.02 Cu 0.03 The phase of Te was evaluated. 0.98 Ga 0.02 Cu 0.03The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.03 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 99% of the theoretical density) was obtained.

[0063] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0064] <Experimental Example 5> The raw materials, lead (Pb) 6.09 g, gallium (Ga) 0.04 g, copper (Cu) 0.08 g, and tellurium (Te) 3.83 g, were vacuum-sealed in a quartz tube. The raw materials vacuum-sealed in the quartz tube were reacted at 1323 K, and a total of 10.0 g of Pb was produced. 0.98 Ga 0.02 Cu 0.04 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu 0.04 A portion of the Te polycrystalline sample was crushed into powder and then subjected to X-ray diffraction (CuKα radiation, 40 kV, 10 mA) to identify Pb 0.98 Ga 0.02Cu 0.04 The phase of Te was evaluated. The results of X-ray diffraction measurements are shown in Figure 2. 0.98 Ga 0.02 Cu 0.04 The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.04 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 98% of the theoretical density) was obtained.

[0065] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0066] <Experimental Example 6> The raw materials, lead (Pb) 6.05 g, gallium (Ga) 0.04 g, copper (Cu) 0.11 g, and tellurium (Te) 3.80 g, were vacuum-sealed in a quartz tube. The raw materials vacuum-sealed in the quartz tube were reacted at 1323 K, resulting in a total of 10.0 g of Pb. 0.98 Ga 0.02 Cu 0.06 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu0.06 The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.06 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 99% of the theoretical density) was obtained.

[0067] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0068] <Experimental Example 7> The raw materials, lead (Pb) 6.02 g, gallium (Ga) 0.04 g, copper (Cu) 0.19 g, and tellurium (Te) 3.78 g, were vacuum-sealed in a quartz tube. The raw materials vacuum-sealed in the quartz tube were reacted at 1323 K, and a total of 10.0 g of Pb was produced. 0.98 Ga 0.02 Cu 0.10 A polycrystalline Te sample was obtained. 0.98 Ga 0.02 Cu 0.10The polycrystalline Te powder was placed in a graphite die, and the die was inserted into a sintering apparatus. The sintering apparatus was used to sinter the Pb sintered sample at 773 K under a uniaxial pressure of 30 MPa in vacuum for 1 h. 0.98 Ga 0.02 Cu 0.10 A polycrystalline Te sample was processed, and as a result, a compact of thermoelectric conversion material with high density (over 99% of the theoretical density) was obtained.

[0069] Next, in the same manner as in Experimental Example 1, the Seebeck coefficient S (μVK -1 ), electrical conductivity ρ (μΩm), and thermal conductivity κ total (WK -1 m -1 ) was measured. Seebeck coefficient S (μVK -1 The measurement results of ) are shown in Figure 3. The measurement results of electrical conductivity ρ (μΩm) are shown in Figure 4. The thermal conductivity κ total (WK -1 m -1 The measurement results of ZT are shown in Figure 6. The dimensionless figure of merit ZT is ZT=S 2 T / (ρκ total The calculation results of the dimensionless figure of merit ZT are shown in Figure 8. The power factor S 2 / ρ(μWK -2 m -1 ) and lattice thermal conductivity κ lat (WK -1 m -1 The results are shown in Figures 5 and 7.

[0070] For Experimental Examples 1 and 3, observation was performed using a scanning electron microscopy (SEM) and element mapping was performed using energy dispersive spectroscopy (EDS).

[0071] FIG. 1 shows a scanning electron microscope (SEM) photograph and elemental mapping by energy dispersive X-ray analysis (EDS) of a thermoelectric conversion material according to an experimental example of the present invention. (a) in FIG. 1 is an SEM photograph of Experimental Example 1. (b) in FIG. 1 is an SEM photograph of Experimental Example 3. (c) in FIG. 1 is elemental mapping by EDS of Experimental Example 3. As shown in (a) in FIG. 1, the structure of the thermoelectric conversion material of Experimental Example 1 had few defects. On the other hand, as shown in (b) in FIG. 1, the structure of the thermoelectric conversion material of Experimental Example 3, to which Cu was added, had many pores with sizes of 100-300 nm and precipitates with sizes up to 2 μm. The precipitates were uniformly distributed in the structure of the thermoelectric conversion material. (c) in FIG. 1 shows that the precipitates observed in the structure of the thermoelectric conversion material of Experimental Example 3 were a Cu-Ga-Te phase. Furthermore, it was found that the precipitates observed in the structure of the thermoelectric conversion material of Experimental Example 3 contained almost no Pb. The pores present in the structure of the thermoelectric conversion material of Experimental Example 3 and the precipitates made of Cu-Ga-Te phases can scatter heat-carrying phonons.

[0072] Fig. 2 shows the powder X-ray diffraction patterns of the thermoelectric conversion materials according to the experimental examples of the present invention. As shown in Fig. 2, it was clear that all of the thermoelectric conversion materials from Experimental Example 1 to Example 5 were composed of NaCl-type PbTe. No diffraction peaks of a second phase were observed. In other words, the amount of the second phase in the thermoelectric conversion materials from Experimental Example 1 to Example 5 was below the detection limit of the measuring device.

[0073] Table 1 shows the results of measuring the carrier concentration and carrier mobility at room temperature for the thermoelectric conversion materials of Experimental Example 1 to Example 5.

[0074] [Table 1]

[0075] As shown in Table 1, the carrier concentration at room temperature increased with increasing Cu content. When z was 0, the carrier concentration at room temperature was 1.2 × 10 19 cm -3However, when z is 0.04, the carrier concentration at room temperature is 2.1 × 10 19 cm -3 This is thought to be due to Cu occupying interstitial sites and acting as a donor. When z is 0.02 or less, the carrier mobility at room temperature increases with increasing Cu content. This is thought to be due to Cu occupying Pb vacancies and reducing the scattering of electron carriers. On the other hand, when the Cu content is high, for example, when z is greater than 0.02, the scattering of electron carriers increases due to vacancies and Cu-Ga-Te precipitates, resulting in a decrease in carrier mobility at room temperature.

[0076] The Seebeck coefficients of the samples of Examples 1 to 7 show a negative sign in the temperature range from 300 K to 900 K, demonstrating that the materials are n-type semiconductors. The relationship between the Seebeck coefficient S and the carrier concentration n is S∝m * T(π / 3n) 2 / 3 where m * is the effective mass of the carrier. Comparing all experimental examples within the measured temperature range, the carrier concentration tends to increase as the Cu content increases. Therefore, due to the above-mentioned relationship, the Seebeck coefficient S tended to decrease as the Cu content increased, as shown in Figure 3. In particular, the decrease in the Seebeck coefficient S was significant above 600 K (at 900 K, the Seebeck coefficient of the sample in Experimental Example 4, which contained 3% Cu, decreased by about 20% compared to the Seebeck coefficient S of the sample in Experimental Example 1, which did not contain Cu). This is thought to be because the contained Cu dissolved in the matrix and occupied interstitial sites.

[0077] FIG. 4 is a diagram showing the temperature dependence of the electrical resistivity of thermoelectric conversion materials according to Experimental Examples of the present invention. As shown in FIG. 4, in the entire temperature range from 600 K to 900 K, the electrical resistivity ρ of the samples of Experimental Examples 2 to 7 containing Cu was smaller than the electrical resistivity ρ of the sample of Experimental Example 1 containing no Cu. In particular, the effect of reducing the electrical resistivity ρ was remarkable above 600 K (at 900 K, the electrical resistivity ρ of the sample of Experimental Example 4 containing 3% Cu was 100% lower than that of the sample of Experimental Example 1 containing no Cu). The electrical resistivity ρ isThe sample containing Cu had a high carrier concentration n and carrier mobility μ, and therefore a low electrical resistivity ρ. The rate of increase in electrical resistivity in the temperature range of 600K to 900K was due to the increase in Cu occupying the interstitial sites of PbTe as the temperature increased. +1 This is thought to be because the carrier concentration n increased.

[0078] 5 is a diagram showing the temperature dependence of the power factor of the thermoelectric conversion material according to the experimental examples of the present invention. As shown in FIG. 5, in the samples of Experimental Examples 2 to 7 containing Cu, the electrical resistivity ρ and the Seebeck coefficient S were optimized, and the power factor S at 600 K or higher was 2 / ρ increased (at 900 K, the power factor S 2 This is because the power factor S 2 This shows that / ρ can be further increased.

[0079] Fig. 6 shows the thermal conductivity of thermoelectric conversion materials according to experimental examples of the present invention, and Fig. 7 shows the temperature dependence of lattice thermal conductivity. As shown in Fig. 7, the lattice thermal conductivity κ of the samples of Experimental Examples 2 to 7 containing Cu was lat is the lattice thermal conductivity κ of the sample of Experimental Example 1 that does not contain Cu. lat This is because the inclusion of Cu generates pores with a size of 100-300 nm and precipitates with a size of up to 2 μm, which increases the scattering of phonons and reduces the lattice thermal conductivity κ lat On the other hand, the electronic thermal conductivity κ of the Cu-containing experimental example ele The reason why the electron thermal conductivity κ ele and electrical resistivity ρ is κ ele =LT / ρ, the electronic thermal conductivity κ of the Cu-containing sample ele is the electronic thermal conductivity κ of the sample of Experimental Example 1 that does not contain Cu. ele where L is the Lorentz number. High electronic thermal conductivity κ ele Low lattice thermal conductivity κ latAs a result, as shown in FIG. 6, the thermal conductivity κ of the samples of Experimental Examples 2 to 7 containing Cu is total is the thermal conductivity κ of the sample of Experimental Example 1 that does not contain Cu total was slightly higher than

[0080] FIG. 8 shows the temperature dependence of the dimensionless thermoelectric figure of merit (ZT) of a thermoelectric conversion material according to an experimental example of the present invention. As shown in FIG. 8, by incorporating Ga and Cu into PbTe and synergistically optimizing the carrier concentration, carrier mobility, and thermal conductivity, we succeeded in achieving a flat and high dimensionless figure of merit (ZT) in the temperature range of 600 K to 900 K. The samples of Experimental Examples 2, 3, Example 4, and Example 5 had an average dimensionless figure of merit (ZT) of over 1.10 in the mid- to high-temperature range, and the sample of Experimental Example 4 had an average dimensionless figure of merit (ZT) of 1.15 in the mid- to high-temperature range, which is extremely high for an n-type thermoelectric conversion material. The sample of Experimental Example 1 contained only Ga, and therefore was unable to synergistically optimize the carrier concentration, carrier mobility, and thermal conductivity, resulting in an average dimensionless figure of merit (ZT) of only 1.0 in the mid- to high-temperature range. The samples of Experimental Example 6 and Example 7 contain Ga and Cu, but the amount of Cu is too high, and the power factor in particular is not improved, so the dimensionless figure of merit ZT is below 1.10 on average in the medium to high temperature range.

[0081] In addition to Cu, Group 1 elements, Group 10 elements, and Group 11 elements also have the effect of optimizing the carrier concentration in PbTe, further improving carrier mobility, and further reducing the electrical resistivity ρ. This is thought to be because Group 1 elements, Group 10 elements, and Group 11 elements exist as +1 ions in PbTe and have smaller ionic radii than Pb, and therefore have the same effect as Cu, occupying Pb vacancies and interstitial sites in PbTe. Examples of Group 1 elements, Group 10 elements, and Group 11 elements other than Cu include Li +1 , Na +1 , Pd +1 , Ag +1 Li in PbTe +1 , Na +1When containing, it is also possible to prepare a p-type thermoelectric conversion material.

[0082] Group 13 elements other than Ga have the same electronic structure as Ga. Therefore, other than Ga, Group 13 elements also have the effect of increasing the carrier concentration and dispersing precipitates in PbTe. As a result, Group 13 elements other than Ga also have the effect of increasing the lattice thermal conductivity κ lat It is thought that B has the effect of reducing +3 , Al +3 , and In +3 Examples include:

[0083] When a p-type thermoelectric conversion material is used, the effect of increasing the dimensionless figure of merit ZT described above can be obtained, just as with an n-type thermoelectric conversion material. This is thought to be because both n-type PbTe and p-type PbTe have the same NaCl-type crystal structure. In other words, by using the n-type thermoelectric conversion material and p-type thermoelectric conversion material according to the embodiment of the present invention, a thermoelectric conversion device with high thermoelectric conversion efficiency can be manufactured by simply adjusting a few components.

[0084] Throughout this specification, when a part is described as "having" or "comprising" a certain element, this does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0085] Furthermore, the term "unit" used in the specification means a unit that processes at least one function or operation, which may be embodied as hardware or software, or as a combination of hardware and software.

[0086] Furthermore, the term "connection" refers to an electrical connection. An electrical connection means that power or an electrical signal can be transmitted. The electrical connection may be a connection via components such as a cable, resistor, capacitor, diode, or circuit breaker.

[0087] In addition, the components in the above-described embodiment may be replaced with known components as appropriate within the scope of the present invention. Furthermore, the above-described modifications may be combined as appropriate. [Explanation of symbols]

[0088] 10a p-type thermoelectric conversion material 10b n-type thermoelectric conversion material 30 Thermoelectric power generation module 31 Upper junction electrode 32 Lower junction electrode 33 Lower junction electrode 34 External Load 50 Peltier cooling module 51 External power supply section

Claims

1. a substrate comprising PbTe; At least one element selected from the group consisting of elements contained in the base material and having an ionic radius of +1 that is smaller than the ionic radius of Pb that has a valence of +2; the element having an ionic radius of +1 valence smaller than the ionic radius of Pb having a valence of +2 is contained in the base material as an ion having a valence of +1, and the content thereof is more than 0 at % and less than 10.0 at %, It is represented by the composition formula Pb 1-x A x M z T e , A is at least one element selected from the group consisting of Group 13 elements, M is at least one element selected from the group consisting of Group 1 elements, Group 10 elements, and Group 11 elements; x is equal to or greater than 0.02 and equal to or less than 0.04, and z is greater than 0 and less than 0.10; A thermoelectric conversion material characterized in that, at 600K to 900K, the Seebeck coefficient S is -210 μVK −1 or more and the electrical resistivity ρ is 35 μΩm or less.

2. It is an n-type semiconductor The thermoelectric conversion material according to claim 1 .

3. A is at least one element selected from the group consisting of B, Al, Ga, and In. The thermoelectric conversion material according to claim 1 or 2.

4. The M is at least one element selected from the group consisting of Li, Na, Pd, Cu, and Ag. The thermoelectric conversion material according to any one of claims 1 to 3.

5. The A is Ga. The thermoelectric conversion material according to claim 3 .

6. The M is Cu. The thermoelectric conversion material according to claim 4 .

7. The z is greater than 0 and equal to or less than 0.

06. The thermoelectric conversion material according to any one of claims 1 to 6.

8. The x is 0.

02. The thermoelectric conversion material according to any one of claims 1 to 7.

9. The z is 0.01 or more and 0.04 or less. The thermoelectric conversion material according to claim 7 .

10. The thermoelectric conversion material according to any one of claims 1 to 9, characterized in that the average value of the dimensionless thermoelectric figure of merit ZT from 600K to 900K exceeds 1.

00.

11. A thermoelectric power generation module comprising the thermoelectric conversion material according to any one of claims 1 to 10.

12. A Peltier cooling module comprising the thermoelectric conversion material according to any one of claims 1 to 10.

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