Thermoelectric material and thermoelectric module

Abstract

To provide a thermoelectric material that is mainly composed of a half-Heusler type TiNiSn alloy and has excellent thermoelectric properties as a p-type thermoelectric material, and a thermoelectric module that includes the same.SOLUTION: In a thermoelectric material containing a half-Heusler type alloy as a main component, the half-Heusler type alloy has a composition expressed by Ti1-xHfxNiSn (0.1<x≤0.7), and at least a portion of Ni or Sn is substituted by another element, and the total number of valence electrons N satisfies 14<N<17.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermoelectric material and a thermoelectric module. [Background technology]

[0002] Currently, thermal energy is discarded as waste heat in many fields, and proposals have been made to utilize this thermal energy effectively in terms of addressing global warming, etc. Among them, thermoelectric modules made of thermoelectric materials have attracted attention because they can directly convert between thermal energy and electrical energy, do not require complex equipment, and have a small environmental impact.

[0003] A thermoelectric module is constructed by connecting a p-type thermoelectric material (p-type thermoelectric semiconductor) and an n-type thermoelectric material (n-type thermoelectric semiconductor). Known examples of thermoelectric materials include (1) Bi-Te, Pb-Te, and Si-Ge compound semiconductors, (2) Zn-Sb, Co-Sb, and Fe-Sb skutterudite compounds, and (3) TiNiSn alloy and other half-Heusler compounds.

[0004] Among them, the half-Heusler type TiNiSn alloy has a large Seebeck coefficient exceeding -150μV / K and a maximum capacitance of 3mW / mK as an n-type thermoelectric material. 2 High power factor (PF=S 2 It is known that the half-Heusler type TiNiSn alloy exhibits the following properties (σ, S: Seebeck coefficient, σ: electrical conductivity) (Non-Patent Document 1). In addition, the half-Heusler type TiNiSn alloy is inexpensive compared to other thermoelectric materials and has excellent heat resistance, so it is expected to be put to practical use.

[0005] Known techniques relating to thermoelectric materials containing a half-Heusler type TiNiSn alloy include those described in Patent Documents 1 and 2, for example.

[0006] On the other hand, there have been no reports of high thermoelectric performance of TiNiSn alloy as a p-type thermoelectric material. Therefore, when constructing a thermoelectric module using TiNiSn alloy as an n-type thermoelectric material, a method of combining it with a material system with a completely different composition, such as FeNbSb alloy, as a p-type thermoelectric material has been adopted (Non-Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-204835 A [Patent Document 2] JP 2010-157686 A [Non-patent literature]

[0008] [Non-Patent Document 1] Y. Tang, X. Li, LHJ Martin, E. Cuervo Reyes, T. Ivas, C. Leinenbach, S. Anand, M. Peters, GJ Snyder, C. Battaglia, Impact of Ni content on the thermoelectric properties of half-Heusler TiNiSn, Energy Environ. Sci. 11 (2018) 311-320. [Non-Patent Document 2] D. Landmann, Y. Tang, B. Kunz, R. Huber, D. Widner, P. Rickhaus, RN Widmer, HR Elsener, C. Battaglia, Fabrication, characterization, and application-matched design of thermoelectric modules based on Half-Heusler FeNbSb and TiNiSn, J. Appl. Phys. 126 (2019) 085113.

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, when a half-Heusler type TiNiSn alloy is used as the n-type thermoelectric material constituting the thermoelectric module and different materials such as FeNbSb-based alloys are used as the p-type thermoelectric material as in the conventional case, since the thermal conductivity and electrical conductivity are different, there is a problem that the heat balance becomes inhomogeneous and power generation loss occurs. Furthermore, in this case, there are also problems such as an increase in heat transfer loss due to the thermal expansion difference during the power generation operation because the thermal expansion coefficients are different, and a decrease in thermal cycle durability due to the strain caused by the thermal expansion difference.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermoelectric material mainly composed of a half-Heusler type TiNiSn alloy and having excellent thermoelectric characteristics as a p-type thermoelectric material, and a thermoelectric module including the same.

Means for Solving the Problems

[0011] In order to solve the above problems, the following thermoelectric materials and thermoelectric modules are provided. <1>A thermoelectric material containing a half-Heusler type alloy as a main component, wherein the half-Heusler type alloy, Ti 1-x Hf x has a composition represented by NiSn(0.1 < x ≦ 0.7), at least a part of Ni or Sn is substituted with another element, and the total valence electron number N satisfies 14 < N < 17, characterized thermoelectric material. <2>The half-Heusler type alloy has a part of Ni substituted with one or more of Co, Rh, Ir, Fe, and Ru, characterized thermoelectric material of <1> above. <3>The half-Heusler type alloy has a part of Ni substituted with Co, and Ti1-x Hf x Ni 1-y Co y having a composition represented by Sn(0.1 < x ≦ 0.7, 0.1 < y ≦ 0.3) The thermoelectric material of <1>, characterized in that The range of <4>x is 0.2 ≦ x ≦ 0.6, The thermoelectric materials of <1> to <3>, characterized in that A thermoelectric module including an n-type thermoelectric material and a p-type thermoelectric material, wherein the n-type thermoelectric material is a thermoelectric material including a half-Heusler type TiNiSn alloy, and the p-type thermoelectric material is the thermoelectric material of <1>, The thermoelectric module, characterized in that

Advantages of the Invention

[0012] The thermoelectric material of the present invention has a half-Heusler type TiNiSn alloy as a main component and is excellent in thermoelectric properties as a p-type thermoelectric material. The thermoelectric module of the present invention suppresses power generation loss and is excellent in thermal cycle durability.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing the electrical conductivity of a TiNiSn alloy and a TiNi1-yCoySn (y = 0.1 to 0.4) alloy. [Diagram 2] It is a diagram showing the Seebeck coefficient of a TiNiSn alloy and a TiNi1-yCoySn (y = 0.1 to 0.4) alloy. [Diagram 3] It is a diagram showing the thermal conductivity of a TiNiSn alloy and a TiNi1-yCoySn (y = 0.1 to 0.4) alloy. [Figure 4] It is a diagram showing the power factor of a TiNiSn alloy and a TiNi1-yCoySn (y = 0.1 to 0.4) alloy. [Diagram 5] It is a diagram showing the dimensionless performance index ZT of a TiNiSn alloy and a TiNi1-yCoySn (y = 0.1 to 0.4) alloy. [Figure 6]FIG. 1 is a diagram showing the electrical conductivity of Ti1-xHfxNi0.8Co0.2Sn (x=0 to 0.4) alloy. [Figure 7] FIG. 1 is a diagram showing the Seebeck coefficient of a Ti1-xHfxNi0.8Co0.2Sn (x=0 to 0.4) alloy. [Figure 8] FIG. 1 is a diagram showing the thermal conductivity of Ti1-xHfxNi0.8Co0.2Sn (x=0 to 0.4) alloy. [Figure 9] FIG. 1 is a diagram showing the power factor of a Ti1-xHfxNi0.8Co0.2Sn (x=0 to 0.4) alloy. [Figure 10] FIG. 1 is a graph showing the dimensionless figure of merit ZT of the Ti1-xHfxNi0.8Co0.2Sn (x=0 to 0.4) alloy. [Figure 11] FIG. 1 is a diagram showing the electrical conductivity of a Ti1-xHfxNi0.8Co0.2Sn (x=0.5 to 0.7) alloy. [Figure 12] FIG. 1 is a diagram showing the Seebeck coefficient of a Ti1-xHfxNi0.8Co0.2Sn (x=0.5 to 0.7) alloy. [Figure 13] FIG. 1 is a diagram showing the thermal conductivity of Ti1-xHfxNi0.8Co0.2Sn (x=0.5 to 0.7) alloy. [Figure 14] FIG. 1 is a diagram showing the power factor of Ti1-xHfxNi0.8Co0.2Sn (x=0.5 to 0.7) alloy. [Figure 15] FIG. 1 is a graph showing the dimensionless figure of merit ZT of the Ti1-xHfxNi0.8Co0.2Sn (x=0.5 to 0.7) alloy. [Figure 16] FIG. 1 is a diagram showing the electrical conductivity of Ti1-xHfxNi0.7Co0.3Sn (x=0 to 0.5) alloy. [Figure 17] FIG. 1 is a diagram showing the Seebeck coefficient of a Ti1-xHfxNi0.7Co0.3Sn (x=0 to 0.5) alloy. [Figure 18] FIG. 1 is a diagram showing the thermal conductivity of Ti1-xHfxNi0.7Co0.3Sn (x=0 to 0.5) alloy. [Figure 19]FIG. 1 is a diagram showing the power factor of Ti1-xHfxNi0.7Co0.3Sn (x=0 to 0.5) alloy. [Figure 20] FIG. 1 is a graph showing the dimensionless figure of merit ZT of the Ti1-xHfxNi0.7Co0.3Sn (x=0 to 0.5) alloy. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A half-Heusler type TiNiSn alloy containing no dopant has a total valence electron count of 18 (valence electron concentration (VEC) = 6), exhibits semiconductor properties, and exhibits excellent thermoelectric properties. When an element having a different number of valence electrons from that of the main constituent element is doped at one or more sites of the half-Heusler type TiNiSn alloy, the valence electron concentration (number of valence electrons per atom) changes. In the present invention, the term "valence electrons" refers to the number of electrons located in the outermost shell and contributing to chemical bonding, and the term "total number of valence electrons" refers to the sum of the number of valence electrons.

[0015] When part of the main constituent element of a half-Heusler type TiNiSn alloy, which has a total valence electron number of 18 (valence electron concentration (VEC) = 6), is replaced with an element with a smaller number of valence electrons, a half-Heusler type TiNiSn alloy with a total valence electron number less than 18 (valence electron concentration (VEC) = 6) is obtained. When the total valence electron number is less than 18 (valence electron concentration (VEC) = 6), holes are doped, and the half-Heusler type TiNiSn alloy functions as a p-type thermoelectric material.

[0016] However, in the half-Heusler type TiNiSn alloy, for example, by replacing some of the Ni (valence electron number 10) with Co (valence electron number 9) to reduce the total number of valence electrons, it is possible to obtain p-type thermoelectric properties. However, the Seebeck coefficient is small at about 60 μV / K, and the power factor PF is also only 0.1 mW / mK. 2 is low.

[0017] The inventor has found that by controlling the content and the like of Hf, which was considered not to affect the electrical properties because it has the same number of valence electrons as Ti, a thermoelectric material mainly composed of a half-Heusler type TiNiSn alloy and excellent in thermoelectric properties as a p-type thermoelectric material can be obtained, and thus the present invention has been achieved.

[0018] Hereinafter, an embodiment of the thermoelectric material and the thermoelectric module of the present invention will be described.

[0019] <Thermoelectric material> The thermoelectric material of the present invention contains a half-Heusler type alloy as a main component. The thermoelectric material of the present invention may contain inevitable impurities other than the half-Heusler type alloy, but it is preferably less in inevitable impurities that adversely affect the thermoelectric properties. For example, the content of inevitable impurities in the thermoelectric material is preferably 0.05% or less, and more preferably 0.02% by mass or less. Examples of the inevitable impurities include oxygen and nitrogen taken in by reaction with the atmosphere during powder synthesis, or Zr, Mo, V, Fe, Sb, Bi, Pb, etc. mixed as impurities in the raw material metal. Further, the thermoelectric material of the present invention may be a composite of a half-Heusler type alloy and other materials (for example, ceramics, resin, rubber, etc.).

[0020] The half-Heusler type alloy in the thermoelectric material of the present invention is Ti 1-x Hf x It has a composition represented by NiSn(0.1 < x ≦ 0.7). From the viewpoint of realizing excellent p-type thermoelectric properties and suppressing the raw material cost, for the half-Heusler type alloy, the range of x is preferably 0.2 ≦ x ≦ 0.6, more preferably 0.3 ≦ x ≦ 0.5, and particularly preferably 0.4 ≦ x ≦ 0.5.

[0021] Whether the alloy has a half-Heusler type crystal structure can be confirmed, for example, by X-ray diffraction (XRD).

[0022] In addition, in the half-Heusler alloy of the thermoelectric material of the present invention, at least a part of Ni or Sn is substituted with other elements. That is, either one of Ni or Sn may be substituted with other elements, or both Ni and Sn may be substituted simultaneously.

[0023] The type and amount of the element substituted for Ni or Sn are not particularly limited, as long as the total valence electron number of the substituted half-Heusler type TiNiSn alloy is controlled to be 14 < N < 17. When the total valence electron number N is 14 < N < 17, the half-Heusler alloy has a positive Seebeck coefficient S and functions as a p-type thermoelectric material.

[0024] Examples of the element that can substitute for a part of Ni include one or more elements such as Co, Rh, Ir, Fe, Ru, etc. Among them, the element substituted for a part of Ni is preferably Co. In this case, the half-Heusler structure can be stably maintained, it is easy to handle, and the cost can also be suppressed.

[0025] Examples of the element that can substitute for a part of Sn include one or more elements such as B, Al, Ga, In, Zn, Mg, etc.

[0026] The half-Heusler alloy in the thermoelectric material of the present invention is Ti in which a part of Ni is substituted with Co 1-x Hf x Ni 1-y Co y preferably has a composition represented by Sn(0.1 < x ≦ 0.7, 0.1 < y ≦ 0.3). When the half-Heusler alloy has this composition, a thermoelectric material with excellent p-type thermoelectric characteristics can be formed.

[0027] Note that the thermoelectric characteristics of the thermoelectric material are represented by the thermoelectric performance index Z (= S 2 σ / κ, where S: Seebeck coefficient, σ: electrical conductivity, κ: thermal conductivity), the dimensionless performance index ZT represented as the product of the thermoelectric performance index Z and the absolute temperature T indicating its value, and the power factor (PF = S 2σ) can be used to evaluate the

[0028] The thermoelectric material of the present invention has excellent thermoelectric properties as a p-type thermoelectric material. Specifically, the thermoelectric material of the present invention has a Seebeck coefficient of 90 μV / K or more at 500 K to 900 K, preferably 120 μV / K or more, and more preferably 140 μV / K or more. In addition, the thermoelectric material of the present invention has a power factor of 0.5 mW / mK. 2 or more, and in the preferred embodiment, 0.7 mW / mK 2 More preferably, the value is 1.0 mW / mK or more. 2 That's all.

[0029] The method for producing the thermoelectric material of the present invention is not particularly limited and may include the same steps as those of the method for producing a conventional thermoelectric material containing a half-Heusler type TiNiSn alloy. Specifically, in one embodiment of the method for producing the thermoelectric material of the present invention, the method may include, for example, a melting / casting step, a quenching step, and a sintering step.

[0030] The melting and casting process is a process of melting and casting raw materials that are mixed to form a half-Heusler alloy in the thermoelectric material of the present invention. The method of melting the raw materials is not particularly limited, and examples thereof include arc melting, high-frequency melting, and glass tube annealing. Moreover, it is preferable to melt the raw materials in an inert atmosphere to prevent oxidation.

[0031] The quenching step is a step of rapidly solidifying a molten metal obtained by melting raw materials that are mixed to form a half-Heusler alloy in the thermoelectric material of the present invention. The quenching step can be performed, for example, by spraying or dropping the molten metal into a cooling medium using a nozzle.

[0032] The sintering process is a process of pulverizing, shaping, and sintering the ingot obtained in the melting and casting process or the solidified product obtained in the rapid cooling process. When sintering a powdery TiNiSn-based half-Heusler compound, various methods can be used as the sintering method. Specifically, examples of the sintering method include atmospheric pressure sintering, hot pressing, HIP, spark plasma sintering (SPS), etc. The sintering conditions (for example, sintering temperature, sintering time, pressure during sintering, atmosphere during sintering, etc.) can be set as appropriate.

[0033] In the manufacturing method of the thermoelectric material of the present invention, processes other than the above can also be included, or a part of the above processes can be omitted.

[0034] <Thermoelectric module> The thermoelectric module of the present invention includes an n-type thermoelectric material and a p-type thermoelectric material. Usually, the thermoelectric module further includes a substrate and electrodes. Also, the thermoelectric module of the present invention may be in a form in which a plurality of n-type thermoelectric materials and p-type thermoelectric materials are alternately connected in series on a base material.

[0035] In the thermoelectric module of the present invention, the p-type thermoelectric material is the thermoelectric material of the present invention described above. That is, the half-Heusler type alloy constituting the p-type thermoelectric material is Ti 1-x Hf x NiSn (0.1 <x ≦ 0.7), and at least a part of Ni or Sn is substituted with other elements, and the total valence electron number N satisfies 14 <N <17.

[0036] In the thermoelectric module of the present invention, it is preferable that the n-type thermoelectric material is a thermoelectric material containing a half-Heusler type TiNiSn alloy. The half-Heusler type TiNiSn alloy constituting the n-type thermoelectric material is conventionally known and may have a composition excellent in thermoelectric characteristics and is not particularly limited.

[0037] In the thermoelectric module of the present invention, both the n-type thermoelectric material and the p-type thermoelectric material are half-Heusler type TiNiSn alloys. Therefore, in the thermoelectric module of the present invention, the thermal conductivity and electrical conductivity of the n-type thermoelectric material and the p-type thermoelectric material are similar, and the thermal balance is homogenous, so that power generation loss is suppressed. Furthermore, in the thermoelectric module of the present invention, the thermal expansion coefficients of the n-type thermoelectric material and the p-type thermoelectric material are similar, so that heat transfer loss due to the difference in thermal expansion during power generation operation is suppressed, and the occurrence of distortion due to the difference in thermal expansion is suppressed, so that the decrease in thermal cycle durability is also suppressed.

[0038] The thermoelectric material and thermoelectric module of the present invention can be used in, for example, various thermoelectric generators such as solar thermal power generators, seawater temperature difference thermoelectric generators, fossil fuel thermoelectric generators, and generators for regenerating factory exhaust heat or automobile exhaust heat, as well as precision temperature control devices such as photodetectors, laser diodes, field effect transistors, photomultiplier tubes, spectrophotometer cells, and chromatography columns, constant temperature devices, air conditioners, refrigerators, and power sources for clocks.

[0039] The thermoelectric material and thermoelectric module of the present invention are not limited to the above embodiments. EXAMPLES

[0040] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples in any way.

[0041] A half-Heusler type TiNiSn alloy was synthesized using a solid-state reaction to prepare alloy powder. First, metal powders of Ti, Ni, Sn, Co, and Hf were mixed in the desired composition and a sintered body was synthesized by a solid-state reaction in an inert atmosphere. The obtained sintered body was pulverized in a mortar to obtain alloy powder. The obtained alloy powder was then used to produce a sintered body by electric current sintering. Specifically, each step was carried out under the following conditions. (Weighing and mixing of raw materials) Ingredients: Pure metal powder, purity 99.9%, total 6g Mixing: Rotating / revolving mixer (Thinky Corporation ARV-310P) 2000 rpm, 1 min (in a plastic container (Umano Chemical UG container 24 ml)) (Heat treatment) Forming: Uniaxial pressure, φ15mm, 10kN (approx. 60MPa) Heating: 1000℃ (heating rate 200℃ / h), 50h, in argon atmosphere, in magnesia crucible (Crushing) Coarse grinding: Hand grinding in a mortar, 0.5 mm or less Grinding: Automatic mortar (AGB type manufactured by Ishikawa Factory Co., Ltd.), 30 min (Sintering) Electric sintering: 1.2g, 1000℃ (heat rise / decrease 100℃ / min), 10min, in vacuum, φ10 graphite mold A sintered body with a diameter of about 10 mm and a thickness of about 2 mm was obtained.

[0042] The thermoelectric properties (thermal conductivity (laser flash method), electrical conductivity (four-terminal method), and Seebeck coefficient (steady-state method)) of the sintered body were measured, and the power factor (PF = S 2 σ), dimensionless figure of merit ZT (thermoelectric figure of merit Z=S 2 The coefficient σ / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity, was calculated.

[0043] Figures 1 to 5 show the TiNiSn alloy and the TiNi 1-y Co y 6 to 10 are diagrams showing the thermoelectric properties of a TiSn (y=0.1 to 0.4) alloy (reference example). 1-x Hf x Ni 0.8 Co 0.2 11 to 15 show the thermoelectric properties of TiSn (x=0 to 0.4) alloy. 1-x Hf x Ni 0.8 Co 0.2 16 to 20 are diagrams showing the thermoelectric properties of TiSn (x=0.5 to 0.7) alloys. 1-x Hf x Ni 0.7 Co 0.3 FIG. 1 is a diagram showing the thermoelectric properties of a Sn (x=0 to 0.5) alloy.

[0044] As shown in FIGS. 1 to 5, TiNi in which part of Ni is replaced with Co 1-y Co y The Sn alloy has a Seebeck coefficient of approximately 50 to 60 μV / K, and it was confirmed that the p-type thermoelectric characteristics are not sufficient. On the other hand, from the results of FIGS. 1 to 5, when the substitution amount of Co is 0.1, hole doping is insufficient and the conductivity is low, and it turns to n-type due to the contribution of thermally excited electrons at high temperatures. Also, when the substitution amount of Co is 0.4, hole doping becomes excessive, and due to the carrier concentration being too high, metallic properties appear, and although the electrical conductivity is high, the Seebeck coefficient tends to decrease. From these results, it was confirmed that the substitution ratio of Co is preferably 0.2 to 0.3 (0.1 < y ≦ 0.3).

[0045] As shown in FIGS. 6 to 10, Ti in which part of Ni is replaced with Co and part of Ti is replaced with Hf 1-x Hf x Ni 0.8 Co 0.2 The Sn(x = 0.2 to 0.4) alloy was confirmed to exhibit excellent p-type thermoelectric characteristics. On the other hand, Ti 0.9 Hf 0.1 Ni 0.8 Co 0.2 Sn(x = 0.1) was confirmed to have insufficient p-type thermoelectric characteristics.

[0046] As shown in FIGS. 11 - 15, Ti in which part of Ni is replaced with Co and part of Ti is replaced with Hf 1-x Hf x Ni 0.8 Co 0.2 The Sn(x = 0.5 to 0.7) alloy was confirmed to exhibit excellent p-type thermoelectric characteristics. As shown in FIGS. 16 to 20, Ti in which part of Ni is replaced with Co and part of Ti is replaced with Hf 1-x Hf x Ni 0.7 Co 0.3 The Sn(x = 0.2 to 0.5) alloy was confirmed to exhibit excellent p-type thermoelectric characteristics. Among them, Ti 0.5 Hf 0.5 Ni 0.8 Co0.2 Sn(x=0.5) has a Seebeck coefficient exceeding 140μV / K and a power factor of 1.0mW / mK. 2 It was confirmed that Ti exhibits particularly excellent thermoelectric properties. 0.4 Hf 0.6 Ni 0.8 Co 0.2 Sn(x=0.6) and Ti 0.3 Hf 0.7 Ni 0.8 Co 0.2 Sn (x=0.7) also exhibits excellent p-type thermoelectric properties, but no further improvement in the thermoelectric properties was confirmed even when the amount of Hf was increased. Therefore, considering that Hf is an expensive material, it was confirmed that the range of x is preferably 0.3≦x≦0.5 from the viewpoint of balancing thermoelectric properties and cost control.

Claims

1. A thermoelectric material containing a half-Heusler alloy as its main component, The aforementioned half-Heusler type alloy is Ti １－ｘ HF ｘ It has a composition represented by NiSn (0.1 < x ≤ 0.7), At least a portion of Ni or Sn is substituted with another element. It exhibits p-type thermoelectric properties. A thermoelectric material characterized by the following features.

2. The total number of valence electrons N is 14 < N < 18. A thermoelectric material according to feature 1.

3. The aforementioned half-Heusler alloy has a portion of Ni replaced by one or more of Co, Rh, Ir, Fe, and Ru. A thermoelectric material according to feature 1.

4. The aforementioned half-Heusler alloy has some of the Ni replaced by Co, and Ti １－ｘ HF ｘ Ni １－ｙ Co ｙ Having a composition represented by Sn (0.1 < x ≤ 0.7, 0.1 < y ≤ 0.3), A thermoelectric material according to feature 1.

5. The range of x is 0.2 ≤ x ≤ 0.

6. A thermoelectric material according to feature 1.

6. A thermoelectric module comprising an n-type thermoelectric material and a p-type thermoelectric material, The n-type thermoelectric material is a thermoelectric material containing a half-Heusler type TiNiSn alloy, and the p-type thermoelectric material is the thermoelectric material of claim 1. A thermoelectric module characterized by the following features.

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