Thermoelectric materials, thermoelectric elements, thermoelectric modules, devices, and methods for manufacturing thermoelectric materials

Abstract

This thermoelectric material includes a matrix represented by the composition formula, A2B3, wherein A of the composition formula is one or more elements selected from the group consisting of Bi and Sb, and B of the composition formula is one or more elements selected from the group consisting of Te, Se, and S. Oxide particles including one or more elements selected from the group of C consisting of Zn, Nb, and Al and telluride particles including one or more elements selected from the group of C are deposited on the inside of the crystal grains of the matrix and / or the crystal grain boundaries of the matrix. The long diameter of the oxide particles is 1 nm to 1000 nm and the short diameter of the oxide particles is 1 nm to 500 nm. The long diameter of the telluride particles is 0.4 μm to 40 μm and the short diameter of the telluride particles is 0.4 μm to 20 μm.

Description

[Technical Field]

[0001] The present invention relates to thermoelectric materials, thermoelectric elements, thermoelectric modules, devices, and methods for manufacturing thermoelectric materials. This application claims priority based on Japanese Patent Application No. 2022-104443, filed in Japan on June 29, 2022, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] Traditionally, materials known as Bi-Te thermoelectric materials have been primarily used. The compositional formula for Bi-Te thermoelectric materials is Bi2Te3, and these materials are composed in which some or all of the Bi sites are replaced with Sb, and some or all of the Te sites are replaced with Se or S.

[0003] The figure of merit Z, which indicates the performance of thermoelectric materials, is given by Z = α 2 It is expressed as σ / κ, where α is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity. In order to improve the figure of merit Z of thermoelectric materials, attempts have been made to reduce the lattice thermal conductivity and improve the carrier mobility, but since both thermal conductivity and the Seebeck coefficient are functions of the carrier concentration, this is often a trade-off.

[0004] Patent Document 1 proposes a thermoelectric material in which Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Y, La, Ce, Nd, Sm, and Mm (mischmetal) are added to a Bi-Te-based thermoelectric material in order to promote the amorphous formation of the crystal and reduce the thermal conductivity.

[0005] Non-patent document 1 describes that adding Zn to a p-type Bi-Te thermoelectric material results in segregated ZnTe, which contributes to a reduction in thermal conductivity.

[0006] Patent Document 2 proposes a thermoelectric material of the p-type Bi-Te-based thermoelectric material that includes multiple zinc oxide nanoparticles within multiple bismuth antimony telluride matrix particles, and zinc antimony modified grain boundaries between multiple bismuth antimony telluride matrix particles. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent No. 3092463 [Patent Document 2] Japanese Patent Application Publication No. 2014-022731 [Non-patent literature]

[0008] [Non-Patent Document 1] Rigui Deng, et.al., Energy Environ. Sci., 2018, 11, 1520 [Overview of the project] [Problems that the invention aims to solve]

[0009] The thermoelectric material described in Patent Document 1 improves its figure of merit by promoting amorphous formation. However, generally speaking, amorphous formation and crystal refinement in Bi-Te-based thermoelectric materials lead to a decrease in thermal conductivity and a decrease in carrier mobility, making it difficult to improve the figure of merit.

[0010] Non-patent document 1 discloses an example demonstrating the effect of segregated ZnTe on reducing thermal conductivity. However, in the case of Zn-doped samples with little oxidation, while the effect of reducing thermal conductivity due to ZnTe precipitation is observed, the carrier mobility also decreases simultaneously, resulting in insufficient improvement in the figure of merit.

[0011] Patent Document 2 describes how mobility is improved by antimony oxide-modified grain boundaries. Zinc antimony-modified grain boundaries are formed in manufacturing methods using solutions such as wet chemical synthesis. Zinc antimony-modified grain boundaries are not formed in the melting method commonly used for mass production of thermoelectric materials, making it unsuitable for mass production. Furthermore, due to the weak brittleness and susceptibility to oxidation of zinc antimony, it is unsuitable for industrial products. In Patent Document 2, zinc oxide is used from the beginning during synthesis, so there is no reduction effect on oxides by Zn, and a large amount of Sb oxide is present at a level easily observable by X-ray diffraction (XRD). Since this Sb oxide can also be a factor in deterioration of properties, it is preferable that it is not included.

[0012] This invention was made in view of the above circumstances, and aims to provide thermoelectric materials, thermoelectric elements, thermoelectric modules, devices, and methods for manufacturing thermoelectric materials having excellent figures of merit. [Means for solving the problem]

[0013] A thermoelectric material according to one embodiment of the present invention has a matrix whose compositional formula is A2B3, wherein A in the compositional formula is one or more elements selected from the group consisting of Bi and Sb, and B in the compositional formula is one or more elements selected from the group consisting of Te, Se, and S, wherein oxide particles containing one or more elements selected from the group consisting of Zn, Nb, and Al, and telluride particles containing one or more elements selected from the group consisting of C, are precipitated inside the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix, the major axis of the oxide particles is 1 nm to 1000 nm, the minor axis of the oxide particles is 1 nm to 500 nm, the major axis of the telluride particles is 0.4 μm to 40 μm, and the minor axis of the telluride particles is 0.4 μm to 20 μm. Furthermore, at least one of the oxide particles and the telluride particles contains at least one of Nb and Al. . [Effects of the Invention]

[0014] According to the above aspects of the present invention, it is possible to provide thermoelectric materials, thermoelectric elements, thermoelectric modules, devices, and methods for manufacturing thermoelectric materials having excellent figures of merit. [Brief explanation of the drawing]

[0015] [Figure 1] This is a flowchart of the method for manufacturing a thermoelectric material according to the embodiment. [Figure 2] This is a diagram illustrating the cutting position of the sample for measurement. [Figure 3] This figure shows the temperature dependence of the Seebeck coefficient α of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 4] This figure shows the temperature dependence of the electrical resistivity ρ of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 5] This figure shows the temperature dependence of the thermal conductivity κ of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 6] This figure shows the temperature dependence of the figure of merit Z of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 7] This figure shows the temperature dependence of the weighted mobility μw of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 8] This figure shows the temperature dependence of the lattice thermal conductivity κlat of a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 9] This figure shows the temperature dependence of the figure of merit Z for a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere and a p-type thermoelectric material prepared by pulverizing an ingot in an inert gas atmosphere. [Figure 10] This figure shows the temperature dependence of Quality factor B for p-type thermoelectric materials prepared by pulverizing an ingot in the atmosphere and p-type thermoelectric materials prepared by pulverizing an inert gas atmosphere (inside a glove box). [Figure 11] This figure shows the distribution of the major axis of zinc telluride particles in a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 12] This figure shows the distribution of the short axis of zinc telluride particles in a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 13] This figure shows the distribution of the major axis of zinc oxide particles in a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 14] This figure shows the distribution of the short axis of zinc oxide particles in a p-type thermoelectric material prepared by pulverizing an ingot in the atmosphere. [Figure 15] This figure shows the results of Sb and O element mapping for thermoelectric materials without Zn addition. [Figure 16] This figure shows the temperature dependence of the thermal conductivity of a p-type thermoelectric material made by adding zinc oxide to the raw material and a p-type thermoelectric material made by adding elemental zinc to the raw material. [Figure 17] This figure shows the dependence of the dimensionless figure of merit ZT of n-type thermoelectric material 2 on the amount of ZnTe at room temperature (325K). [Figure 18] This figure shows the elemental mapping results for n-type thermoelectric material 2. [Figure 19] This figure shows the temperature dependence of the lattice thermal conductivity κlat of Bi2Se0.3Te2.7, n-type thermoelectric material 3, and n-type thermoelectric material 4. [Figure 20] This figure shows the relationship between Quality Factor B and Al content. [Figure 21] This figure shows the temperature dependence of the dimensionless figure of merit ZT for Bi0.45Sb1.55Te3, p-type thermoelectric material 2, and p-type thermoelectric material 3. [Modes for carrying out the invention]

[0016] <Thermoelectric materials> A thermoelectric material according to an embodiment of the present invention has a matrix whose compositional formula is A2B3, where A in the compositional formula is one or more elements selected from the group consisting of Bi and Sb, and B in the compositional formula is one or more elements selected from the group consisting of Te, Se, and S, and at least one of the crystal grains of the matrix and the crystal grain boundaries of the matrix contains oxide particles (hereafter, elements from the group consisting of C, Zn, Nb, and Al) containing one or more elements. The material precipitates oxide particles (hereinafter referred to as "containing oxide particles") and telluride particles containing one or more elements selected from the group C (hereinafter referred to as "telluride particles containing elements from the group C"), with the major axis of the oxide particles containing elements from the group C being 1 nm to 1000 nm, the minor axis of the oxide particles containing elements from the group C being 1 nm to 500 nm, the major axis of the telluride particles containing elements from the group C being 0.4 μm to 40 μm, and the minor axis of the telluride particles containing elements from the group C being 0.4 μm to 20 μm. The thermoelectric material according to this embodiment can be used for both n-type and p-type semiconductors. In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits. Numbers indicated as "less than" or "greater than" are not included in the numerical range. The following describes each element.

[0017] <Matrix> The thermoelectric material according to this embodiment has a composition formula of A2B3, where A in the composition formula is one or more elements selected from the group consisting of Bi and Sb (hereinafter sometimes referred to as the elements of group A), and B in the composition formula is one or more elements selected from the group consisting of Te, Se, and S (hereinafter sometimes referred to as the elements of group B). The ratio of the total number of atoms of the elements of group A to the total number of atoms of the elements of group B (elements of group A:elements of group B) is 2:3. Examples of matrices include Bi2Te3, Sb2Te3, Bi2Se3, Sb2Se3, Bi2S3, Sb2S3, and Bi 0.46 S 1.54 Te3, (Bi 0.225 S 0.775 Examples include 2Te3. It is preferable that the matrix contains Te.

[0018] When using the thermoelectric material according to the embodiment as an n-type semiconductor, it is preferable to increase the ratios of Se and S among the elements of group B in the matrix. Specifically, it is preferable that the atomic ratio of Se and S to Te ((Se + S) / (Te + Se + S)) in the matrix is 0 to 0.33.

[0019] When using the thermoelectric material according to the embodiment as a p-type semiconductor, it is preferable to increase the ratio of Sb among the elements of group A in the matrix. Specifically, it is preferable that the atomic ratio of Bi to Sb (Bi / (Sb + Bi)) in the matrix is 0 to 0.30.

[0020] When using the thermoelectric material according to the embodiment as an n-type semiconductor, it is preferable to contain halogen elements such as Cl, Se, and I. The content of the halogen element is preferably 0.030 at% to 0.20 at% with respect to the entire matrix. More preferably, the content of the halogen element is 0.050 at% to 0.12 at%.

[0021] When using the thermoelectric material according to the embodiment as a p-type semiconductor, the matrix may contain group 14 elements such as Ge, Sn, and Pb. The content of the group 14 element is preferably 0 at% to 0.20 at% with respect to the entire matrix. More preferably, the content of the group 14 element is 0 at% to 0.15 at%. The at% of each element can be analyzed, for example, by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS).

[0022] The matrix of the thermoelectric material according to the embodiment is preferably polycrystalline. It is more preferable that no halo pattern derived from the amorphous phase is visible by X-ray diffraction.

[0023] <Oxide particles containing elements of group C> In the thermoelectric material according to the embodiment, oxide particles containing one or more elements from the group C, selected from the group consisting of Zn, Nb, and Al, are precipitated inside the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix. In the embodiment, it is preferable that the oxide particles containing elements from the group C contain at least Zn. In the embodiment, it is preferable that the oxide particles containing elements from the group C contain at least Nb. In the embodiment, it is preferable that the oxide particles containing elements from the group C contain at least Al. In the embodiment, it is particularly preferable that the oxide particles containing elements from the group C contain at least Zn. The oxide particles containing elements from the group C are, for example, zinc oxide (ZnO) particles. In the thermoelectric material according to the embodiment, it is preferable that the number of oxide particles containing elements from the group C is greater than the number of telluride particles containing elements from the group C. It is preferable that the number of oxide particles containing elements from the group C is greater than the number of individual particles of elements from the group C.

[0024] The major axis of oxide particles containing elements from the C group is 1 nm to 1000 nm. Preferably, the major axis of oxide particles containing elements from the C group is 20 nm to 480 nm. More preferably, the major axis of oxide particles containing elements from the C group is 20 nm to 350 nm. It is sufficient if 75% or more of the oxide particles containing elements from the C group satisfy this numerical range for the major axis. More preferably, 80% or more of the oxide particles containing elements from the C group satisfy this numerical range for the major axis. Even more preferably, 90% or more of the oxide particles containing elements from the C group satisfy this numerical range for the major axis.

[0025] The minor axis diameter of the oxide particles containing the elements of group C is 1 nm to 500 nm. It is preferable that the minor axis diameter of the oxide particles containing the elements of group C is 10 nm to 260 nm. More preferably, the minor axis diameter of the oxide particles containing the elements of group C is 10 nm to 190 nm. Incidentally, it is sufficient that 75% or more of the oxide particles containing the elements of group C satisfy this numerical range of the minor axis diameter. More preferably, 80% or more of the oxide particles containing the elements of group C satisfy this numerical range of the minor axis diameter. Even more preferably, 90% or more of the oxide particles containing the elements of group C satisfy this numerical range of the minor axis diameter.

[0026] <Telluride particles containing the elements of group C> In the thermoelectric material according to the embodiment, telluride particles containing one or more elements from group C selected from the group consisting of Zn, Nb, and Al are precipitated inside the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix. The elements from group C do not easily substitute for A or B sites in A2B3, and do not penetrate between the crystal lattices of A2B3 without significantly changing the carrier concentration, and have a higher ionization tendency than the elements from group A and group B. Since the elements from group C have a higher ionization tendency than the elements from group A and group B, they function as getter materials that absorb oxygen. In the embodiment, it is preferable that the telluride particles containing elements from group C contain at least Zn. Also, in the embodiment, it is preferable that the telluride particles containing elements from group C contain at least Nb. In the embodiment, it is preferable that the telluride particles containing elements from group C contain at least Al. In the embodiment, it is particularly preferable that the telluride particles containing elements from the C group contain at least Zn. The telluride particles are, for example, zinc telluride (ZnTe) particles. At least one of the oxide particles containing elements from the C group and the telluride particles containing elements from the C group may contain at least Zn. At least one of the oxide particles containing elements from the C group and the telluride particles containing elements from the C group may contain at least Nb. At least one of the oxide particles containing elements from the C group and the telluride particles containing elements from the C group may contain at least Al.

[0027] The major axis of telluride particles containing elements from the C group is 0.4 μm to 40 μm. Preferably, the major axis of telluride particles containing elements from the C group is 0.6 μm to 21 μm. More preferably, the major axis of telluride particles containing elements from the C group is 0.6 μm to 15 μm. It is sufficient if 75% or more of the telluride particles containing elements from the C group satisfy this numerical range for the major axis. More preferably, 80% or more of the telluride particles containing elements from the C group satisfy this numerical range for the major axis. Even more preferably, 90% or more of the telluride particles containing elements from the C group satisfy this numerical range for the major axis.

[0028] The minor diameter of the telluride particles containing the elements of Group C is 0.4 μm to 20 μm. It is preferable that the minor diameter of the telluride particles containing the elements of Group C is 0.4 μm to 10.5 μm. More preferably, the minor diameter of the telluride particles containing the elements of Group C is 0.4 μm to 7.5 μm. Note that it is sufficient if 75% or more of the telluride particles containing the elements of Group C satisfy this numerical range of the minor diameter. More preferably, 80% or more of the telluride particles containing the elements of Group C satisfy this numerical range of the minor diameter. Even more preferably, 90% or more of the telluride particles containing the elements of Group C satisfy this numerical range of the minor diameter.

[0029] <Method for Measuring the Major and Minor Diameters of Oxide Particles Containing the Elements of Group C and Telluride Particles Containing the Elements of Group C> The major and minor diameters of the oxide particles containing the elements of group C and the telluride particles containing the elements of group C can be measured, for example, by the following method. The thermoelectric material is processed, for example, by ion milling, focused ion beam (FIB), etc. to obtain a sample for cross-sectional observation. Cross-sectional observation is performed on the obtained sample for cross-sectional observation using a transmission electron microscope (TEM) or a scanning electron microscope (SEM) to obtain a cross-sectional image. In cross-sectional observation, elemental mapping is performed using, for example, an energy dispersive X-ray spectrometer (EDS) attached to TEM. In elemental mapping, particles in which elements of group C and oxygen are detected are regarded as oxide particles containing elements of group C, and particles in which elements of group C and Te are detected are regarded as telluride particles containing elements of group C. Particles in which only elements of group C are detected are regarded as particles of the elements of group C alone. For the obtained elemental mapping image, image processing is performed by setting a threshold value (for example, excluding 5.94% on the background side of the concentration distribution histogram when binarizing) using image analysis software such as ImageJ Fiji so that the contours of the oxide particles and telluride particles become clear. By performing elliptical approximation processing on the obtained oxide particles and telluride particles, the major and minor diameters of the oxide particles containing elements of group C and the telluride particles containing elements of group C can be obtained. Even when the particles to be measured are spherical, elliptical processing is performed in the same manner. For the oxide particles containing elements of group C, 8 fields of view are observed (for example, measurement field: 3.3 μm × 3.3 μm), and for the telluride particles containing elements of group C, 4 fields of view are observed (for example, measurement field: 414 μm × 285 μm), and the range is evaluated from the major and minor diameters of the oxide particles containing elements of group C and the major and minor diameters of the telluride particles containing elements of group C obtained from each mapping image.

[0030] <Content of Zn> The Zn content of the thermoelectric material according to the embodiment is preferably 0.40 to 2.3 at% with respect to the entire thermoelectric material. A more preferable Zn content is 0.40 to 1.2 at%. Even more preferably, it is 0.79 to 1.2 at%. The content of Zn in the thermoelectric material according to the embodiment can be measured, for example, by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Note that the numerical values of the content were rounded to two digits.

[0031] <Content of Al> The Al content of the thermoelectric material according to the embodiment is preferably 1.99 to 3.97 at% with respect to the entire thermoelectric material. The content of Zn in the thermoelectric material according to the embodiment can be measured, for example, by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Note that the numerical values of the content were rounded to three digits.

[0032] <Sb oxide> In the thermoelectric material according to the embodiment, it is preferable that the maximum value of the number density of Sb oxide particles is 31.2 particles / μm 2 or less. It is more preferable that the maximum value of the number density of Sb oxide particles is 12.4 particles / μm 2 or less. Even more preferably, the maximum value of the number density of Sb oxide particles is 1.6 particles / μm 2 or less. Since Sb oxide is preferably less, the lower limit of the number density of Sb oxide particles is 0 particles / mm 2 is. The Sb oxide is, for example, Sb2O3.

[0033] <Bi oxide> In the thermoelectric material according to the embodiment, it is preferable that the maximum value of the number density of Bi oxide particles is 31.2 particles / μm 2 or less. It is more preferable that the maximum value of the number density of Bi oxide particles is 12.4 particles / μm 2 or less. Even more preferably, the maximum value of the number density of Bi oxide particles is 1.6 particles / μm 2The following applies. Although the Sb oxide is less but preferable, the lower limit of the maximum value of the number density of the Bi oxide particles is 0 particles / mm 2 The Bi oxide is, for example, Bi2O3.

[0034] <Method for measuring the number density of Sb oxide particles and Bi oxide particles> The number density of the Sb oxide particles and the Bi oxide particles can be measured, for example, by the following method. The thermoelectric material is processed, for example, with a focused ion beam (FIB) to obtain a sample for cross-sectional observation. The obtained sample for cross-sectional observation is observed with a transmission electron microscope (TEM) or the like to obtain a cross-sectional image. In the cross-sectional observation, elemental mapping is performed with, for example, an energy-dispersive X-ray spectrometer attached to a TEM or the like, and particles in which Sb and oxygen are detected are determined as Sb oxide particles, and particles in which Bi and oxygen are detected are determined as Bi oxide particles. Observation is performed in 8 fields of view (for example, measurement field of view: 3.3 μm × 3.3 μm), and from the number of Sb oxide particles, the number of Bi oxide particles, and the area of the measurement field of view obtained from the cross-sectional image, the number density of the Sb oxide particles and the number density of the Bi oxide particles are calculated. The maximum value among the number densities of the Sb oxide particles in each field of view obtained by the measurement in 8 fields of view is taken as the maximum value of the number density of the Sb oxide particles. The maximum value among the number densities of the Bi oxide particles in each field of view obtained by the measurement in 8 fields of view is taken as the maximum value of the number density of the Bi oxide particles.

[0035] <Oxygen concentration> The oxygen concentration of the thermoelectric material according to the embodiment is preferably 100 ppm or more. A more preferable oxygen concentration is 400 ppm or more. An even more preferable oxygen concentration is 1000 ppm or more. The oxygen concentration of the thermoelectric material can be measured, for example, by the inert gas fusion - nondispersive infrared absorption method (NDIR).

[0036] The thermoelectric material according to the embodiment has been described above. The thermoelectric material according to the embodiment can be used for a thermoelectric element. Further, the thermoelectric element can be used for a thermoelectric module. And the thermoelectric module can be used for devices such as a precision temperature adjustment device and a power generation device.

[0037] <Effects and Effects> In the thermoelectric material according to this embodiment, oxide particles containing elements from the C group (major axis: 1 nm to 1000 nm, minor axis: 1 nm to 500 nm) are deposited inside the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix. Therefore, the lattice thermal conductivity can be reduced without reducing the carrier mobility. This makes it possible to improve the figure of merit Z of the thermoelectric material according to this embodiment.

[0038] In the thermoelectric material according to this embodiment, telluride particles (major axis: 0.4 μm to 40 μm, minor axis: 0.4 μm to 20 μm) containing elements of the C group are precipitated in at least one of the crystal grains of the matrix and at the crystal grain boundaries of the matrix, thereby reducing the lattice thermal conductivity. This makes it possible to improve the figure of merit Z of the thermoelectric material according to this embodiment.

[0039] In the thermoelectric material according to the embodiment, the figure of merit Z of the thermoelectric material according to the embodiment can be further improved by increasing the number of oxide particles containing elements from the C group to more than the number of telluride particles containing elements from the C group.

[0040] The number density of the Sb oxide particles and Bi oxide particles according to the embodiment is 31.2 particles / μm 2 The carrier mobility of the thermoelectric material according to the embodiment can be further improved by doing the following.

[0041] When the oxygen concentration of the thermoelectric material according to the embodiment is 1000 ppm or higher, oxide particles containing an appropriate number of elements from the C group are formed, which can further improve the figure of merit Z.

[0042] <Manufacturing method for thermoelectric materials> Next, a method for manufacturing a thermoelectric material according to the embodiment will be described. The manufacturing method described below is an example of a method for manufacturing a thermoelectric material according to the embodiment, and the present invention is not limited to the method described below. Figure 1 is a flowchart of the method for manufacturing a thermoelectric material according to the embodiment. The method for manufacturing a thermoelectric material according to the embodiment comprises a dissolution and solidification step S1 in which raw materials containing an element from group A, which is at least one selected from the group consisting of Bi and Sb, an element from group B, which is at least one selected from the group consisting of Te, Se, and S, and an element from group C, which is at least one selected from the group consisting of Zn, Nb, and Al are dissolved and solidified to obtain a solidified product; a powder production step S2 in which powder is obtained from the solidified product; and a sintering step S3 in which the powder is sintered. In the dissolution and solidification step S1, at least a portion of one or more elements selected from group C in the raw materials are present as individual elements. Each step will be described below.

[0043] <Melting and solidifying process> In the dissolution and solidification step S1, a raw material containing at least one element selected from group A consisting of Bi and Sb, at least one element selected from group B consisting of Te, Se, and S, and at least one element selected from group C consisting of Zn, Nb, and Al is dissolved and solidified.

[0044] <Raw materials> The raw material contains at least one element selected from group A consisting of Bi and Sb, at least one element selected from group B consisting of Te, Se, and S, and at least one element selected from group C consisting of Zn, Nb, and Al. The raw material may be, for example, a telluride containing yat% of the C group elements, with the atomic ratio of each element determined so that the remainder is a matrix represented by the composition formula A2B3. Here, y in yat% means the atomic concentration of the telluride containing the C group elements relative to all atoms in the raw material. Here, A in the composition formula means at least one element selected from the group consisting of Bi and Sb. Also, B in the composition formula means at least one element selected from the group consisting of Te, Se, and S. Tellurides containing the C group elements include ZnTe, Al2Te3, NbTe 2、 Nb3Te 4、 Examples include NbTe4. Note that tellurides containing elements from the C group do not need to be included as tellurides; it is sufficient if elements from the C group and Te are included in the raw material as elemental compounds. In this embodiment, at least a portion of the elements from the C group in the raw material exist as elemental compounds. It is preferable that elements from the C group are included in the raw material as elemental compounds. It is preferable that each element is uniformly mixed in the raw material. Furthermore, the raw material may also contain the halogen elements and Group 14 elements mentioned above.

[0045] <Heating temperature> In the dissolution and solidification step S1, the raw materials are heated in a vacuum or inert gas at a heating temperature above the melting point of the raw materials and below 1000°C. More preferably, the raw materials are heated in the range of 650°C to 850°C. The heating temperature at this time is, for example, the set temperature of the heating furnace. By heating the raw materials in the range of 650°C to 850°C, each element in the raw materials can be dissolved.

[0046] <Cooking time> The raw materials are heated at the specified heating temperature for a certain period of time. The heating time is not particularly limited as long as the raw materials are completely melted. For example, the heating time can range from 1 hour to 60 hours.

[0047] <Temperature of rise> In the dissolution and solidification step S1, the average heating rate when raising the temperature from room temperature (e.g., 20°C to 30°C) to the heating temperature is preferably, for example, 1°C / min to 20°C / min. To suppress oxidation of the raw materials, it is preferable to raise the temperature of the raw materials in a vacuum or in an inert gas.

[0048] <Cooling rate> In the dissolution and solidification step S1, the raw material is heated for a certain period of time, and then cooled from the heating temperature to room temperature to obtain a solidified product. The average cooling rate when cooling from the heating temperature to room temperature is preferably, for example, 0.1°C / min to 20°C / min.

[0049] <Powder preparation process> In the powder preparation step S2, powder is obtained from the solidified material obtained in the dissolution and solidification step. The solidified material may contain residual air bubbles and may also have elemental segregation. Therefore, the solidified material is powdered. In this process, it is preferable to pulverize the solidified material in the atmosphere or to expose the prepared powder to the atmosphere.

[0050] The method for producing the powder is not particularly limited. Examples of powder production methods include grinding using a mortar and pestle, blender mill, ball mill, atomization, and melt-spun method.

[0051] <Sintering process> In the sintering step S3, a thermoelectric material is obtained by sintering the powder obtained in the powder preparation step S2. The sintering method is not particularly limited. Examples of sintering methods include hot press sintering or pulsed electric current sintering (PECS). In pulsed electric current sintering, the temperature can be rapidly raised to the target level.

[0052] The sintering temperature, sintering pressure, and sintering time are not particularly limited as long as the desired thermoelectric material is obtained. For example, the sintering temperature is preferably 350°C to 550°C. The sintering pressure is preferably, for example, 10 MPa to 90 MPa. The sintering time is preferably, for example, 1 minute to 120 minutes.

[0053] The atmosphere during sintering is not particularly limited as long as the desired thermoelectric material is obtained, but a vacuum or inert gas atmosphere is preferred in order to suppress oxidation during sintering.

[0054] <Effects and Effects> Traditionally, zinc oxide powder was often added before synthesis. In this case, the particle size could never be less than that of the original zinc oxide powder. Furthermore, because zinc oxide has a low specific gravity and a high melting point, it was difficult to evenly disperse zinc oxide particles, as they would remain separated at the bottom of the glass or quartz tube without dissolving or dispersing within the matrix, or the powder particles would aggregate. On the other hand, the method for manufacturing the thermoelectric material of this embodiment allows for the deposition and dispersion of zinc oxide nanoparticles by adding elements from the C group, such as zinc, and Te to the raw materials in excess. In this case, tellurides containing elements from the C group are also precipitated, which can contribute to reducing thermal conductivity and improving the figure of merit.

[0055] The thermoelectric material according to this embodiment can function as an oxygen-absorbing getter material because at least a portion of the elements in the C group in the raw material exist as elemental particles. This allows the maximum number density of Sb oxide particles and Bi oxide particles to be 31.2 particles / μm 2 The following can be done. This will allow for an improvement in the figure of merit Z of the thermoelectric material.

[0056] In the powder preparation process S2, oxidation can be actively promoted by crushing the solidified material in the atmosphere or by exposing it to the atmosphere. This allows the oxygen concentration in the thermoelectric material to be increased to 1000 ppm or more. When the oxygen concentration in the thermoelectric material is 1000 ppm or more, oxide particles containing an appropriate number of elements from the C group are formed, which can further improve the figure of merit Z.

[0057] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention. [Examples]

[0058] Next, embodiments of the present invention will be described. The conditions in the embodiments are merely examples of conditions adopted to confirm the feasibility and effectiveness of the present invention, and the present invention is not limited to these examples of conditions. The present invention can adopt various conditions as long as they do not depart from the spirit of the invention and achieve the objectives of the present invention.

[0059] <Details of the example> Ingots were produced by sealing raw materials containing individual elements of Bi, Sb, Te, Se, Zn, and Al in quartz or Pyrex® glass tubes, according to each composition, and heating, melting, and solidifying them at a temperature of 650°C or higher and 1000°C or lower, which is higher than the melting point of the alloy (588.5°C for Bi2Te3 and 618.5°C for Sb2Te3). The initial compositions were as follows. As a comparative example, ingots were similarly produced with zinc oxide added instead of elemental Zn, but the zinc oxide did not dissolve and was not uniformly dispersed. Also as a comparative example, Bi2Se 0.3 Te 2.7 and Bi 0.45 S 1.55 We also created Te3. Note that the following (Bi x S 1-x )2Te3+y at%ZnTe is (Bi x S 1-x This means that for every 31 moles of 2Te, there are y / 100 moles of ZnTe. 0.45 S 1.55 Te3+y at% AlTe is Bi 0.45 S 1.55 This means that for every 31 moles of Te, there are y / 100 moles of AlTe. 0.45 S 1.55 Te3+y at% Al2Te3 is Bi 0.45 S 1.55This means that for every 1 mole of Te3, there are y / 100 moles of Al2Te3. Similarly, Bi2(Te 0.9 Se 0.1 )3+y at%ZnTe is Bi2(Te 0.9 Se 0.1 This means that for every 31 moles, there are y / 100 moles of ZnTe. (See Bi2Se below) 0.3 Te 2.7 +y at%ZnTe is Bi2Se 0.3 Te 2.7 This means that there are y / 100 moles of ZnTe per mole. BiI3 was added in combination to adjust the carrier concentration, but it does not have any direct effect on improving thermoelectric performance. See Bi2Se below. 0.3 Te 2.7 +y at%AlTe is Bi2Se 0.3 Te 2.7 This means that there are y / 100 moles of AlTe per mole. (See Bi2Se below) 0.3 Te 2.7 +y at%Al2Te3 is Bi2Se 0.3 Te 2.7 This means that for every 1 mole, there are y / 100 moles of Al2Te3. p-type thermoelectric material 1:(Bi x S 1-x )2Te3+y at%ZnTe(x=0.2,0.225,y=0,2,4,6,12) p-type thermoelectric material 2:Bi 0.45 S 1.55 Te3+y at% AlTe(y=4) p-type thermoelectric material 3:Bi 0.45 S 1.55 Te3+y at% Al2Te3(y=2) n-type thermoelectric material 1: Bi2(Te 0.9 Se 0.1 )3+y at%ZnTe(y=0,2,4) N-type thermoelectric material 2: Bi2Se 0.3 Te 2.7 +y at%ZnTe+0.08wt% BiI3(y=0,2,4) N-type thermoelectric material 3: Bi2Se 0.3 Te 2.7 +y at%AlTe(y=2) n-type thermoelectric material 4:Bi2Se 0.3 Te 2.7 +y at%Al2Te3(y=0.5)

[0060] Next, the ingot was processed into powder in the atmosphere or in an inert gas (inside a glove box), and a sintered body (thermoelectric material) was fabricated in an inert gas using a sintering apparatus. Assuming that electric current and heat flow in the direction of pressure or perpendicular to the sintered body, samples for measuring the Seebeck coefficient and electrical resistance, and samples for measuring thermal conductivity were cut from the sintered body as shown in Figure 2.

[0061] <Seebeck coefficient and electrical resistivity> The Seebeck coefficient and electrical resistivity were measured using a thermoelectric property evaluation device (ZEM-3M8) manufactured by Advance Engineering Co., Ltd., in a temperature range from room temperature to 250°C.

[0062] <Measurement of the major and minor axes of zinc oxide particles and zinc telluride particles> Each thermoelectric material was processed by Ar ion milling to obtain a sample for cross-sectional observation. The obtained sample for cross-sectional observation was observed by TEM or SEM, and elemental mapping was performed by EDS. Particles in which zinc and oxygen were detected were defined as oxide particles containing elements of group C (zinc oxide particles), and particles in which zinc and Te were detected were defined as telluride particles containing elements of group C (zinc telluride particles). For the obtained elemental mapping images, using image analysis software ImageJ Fiji, a threshold value (such as excluding 5.94% on the background side of the concentration distribution histogram when binarizing) was set so that the contours of the oxide particles and telluride particles became clear, and image processing was performed. By performing elliptical approximation processing on the obtained oxide particles and telluride particles, the major and minor diameters of the oxide particles containing elements of group C and the telluride particles containing elements of group C were obtained. For the oxide particles, 8 fields of view were observed (measurement field of view: 3.3 μm × 3.3 μm), and for the telluride particles, 4 fields of view were observed (measurement field of view: 414 μm × 285 μm). The range was evaluated from the major and minor diameters of the oxide particles containing elements of group C and the major and minor diameters of the telluride particles containing elements of group C obtained from each cross-sectional image.

[0063] <Measurement of the number density of Sb oxide particles and Bi oxide particles> Each thermoelectric material was processed by a focused ion beam (FIB) to obtain a sample for cross-sectional observation. The obtained sample for cross-sectional observation was observed by TEM, and elemental mapping was performed by EDS. Particles in which Sb and oxygen were detected were defined as Sb oxide particles, and particles in which Bi and oxygen were detected were defined as Bi oxide particles. 8 fields of view were observed (measurement field of view: 3.3 μm × 3.3 μm), and from the number of Sb oxide particles obtained from each cross-sectional image and the area of the measurement field of view, the number density of Sb oxide particles in each field of view was calculated. Among the obtained number densities, the maximum value was taken as the maximum value of the number density.

[0064] <Thermal conductivity> The thermal conductivity was measured by a laser flash apparatus (LFA 467 HyperFlash) manufactured by Netzsch in the temperature range from room temperature to 250 °C.

[0065] <Oxygen concentration> The oxygen concentration of the thermoelectric material prepared as described above was measured using an oxygen / nitrogen analyzer EMGA-920 manufactured by HORIBA Corporation.

[0066] Figure 3 shows the temperature dependence of the Seebeck coefficient α of a p-type thermoelectric material prepared by pulverizing an ingot in air. The horizontal axis of Figure 3 is temperature (°C), and the vertical axis is the Seebeck coefficient α (μV / K). Figure 4 shows the temperature dependence of the electrical resistivity ρ of a p-type thermoelectric material prepared by pulverizing an ingot in air. The horizontal axis of Figure 4 is temperature (°C), and the vertical axis is the electrical resistivity ρ (μΩ·cm). Figure 5 shows the temperature dependence of the thermal conductivity κ of a p-type thermoelectric material prepared by pulverizing an ingot in air. The horizontal axis of Figure 5 is temperature (°C), and the vertical axis is the thermal conductivity κ (mW / (cm·K)). Figure 6 shows the temperature dependence of the figure of merit Z of a p-type thermoelectric material prepared by pulverizing an ingot in air. The horizontal axis of Figure 6 is temperature (°C), and the vertical axis is the figure of merit Z (10 -3 It is / K).

[0067] The results in Figures 3 to 6 are based on the initial values ​​(Bi 0.225 S 0.775 This shows the results when the amount of Zn and Te added (0-12 at%) is varied so that Zn and Te are in a surplus ratio of 1:1 relative to the stoichiometric composition of 2Te3. Specifically, (Bi 0.225 S 0.775 )2Te3+y at%ZnTe is (Bi 0.225 S 0.775x For every 31 moles of 2Te, the amount of ZnTe is y / 100 moles (y: 0 to 12). For example, when ZnTe is 2 at%, the Zn content is 0.40 at% of the total thermoelectric material. When ZnTe is 4 at%, the Zn content is 0.79 at% of the total thermoelectric material. Similarly, when ZnTe is 6 at%, the Zn content is 1.2 at% of the total thermoelectric material. When ZnTe is 12 at%, the Zn content is 2.3 at% of the total thermoelectric material.

[0068] As shown in Figures 3 to 6, the measurement results obtained showed that the Seebeck coefficient α hardly changed even when the amount of excess ZnTe added was increased, indicating that the carrier concentration was similar in all samples. On the other hand, the electrical resistivity ρ and thermal conductivity κ were minimized when y = 4 at% or 6 at% as the amount of excess ZnTe added increased. The figure of merit Z, which is a function of the Seebeck coefficient α, electrical resistivity ρ, and thermal conductivity κ, was maximized when y = 4 at%.

[0069] The Seebeck coefficient α, electrical resistivity ρ, and thermal conductivity κ are all functions of carrier concentration. However, in Bi-Te thermoelectric materials, the electrical resistivity ρ and thermal conductivity κ vary greatly depending on the crystal orientation and scattering source. Therefore, it is difficult to identify the main cause of the change unless the carrier concentration is kept constant. On the other hand, the absolute value of the Seebeck coefficient α is less affected by the crystal orientation and scattering source, and shows almost the same value if the carrier concentration is the same. To more strictly eliminate the influence of carrier concentration on the results in Figures 3 to 6, the Weighted Mobility μ expressed by equation (1) below is used. w and the lattice thermal conductivity κ expressed by equations (2) and (3) below. lat The properties of the above samples were then compared using the following equation (1). In equation (1) below, h is Planck's constant, σ is conductivity, e is elementary charge, and m e k is the mass of the electron. B κ is the Boltzmann constant, T is the absolute temperature, and α is the Seebeck coefficient. In equations (2) and (3) below, κ el σ is the electronic thermal conductivity, L is the Lorentz number, T is the absolute temperature, and σ is the conductivity. These values ​​correspond to the mobility excluding the effect of carrier concentration and the thermal conductivity excluding heat conduction by carriers, respectively.

[0070]

number

[0071] Figure 7 shows Weighted mobility μ wThis shows the temperature dependence. In Figure 7, the horizontal axis is temperature (°C), and the vertical axis is μ w (cm 2 The value is / (V·s)). Figure 8 shows the lattice thermal conductivity κ. lat This shows the temperature dependence. In Figure 8, the horizontal axis is temperature (°C) and the vertical axis is kbp. lat (mW / (cm·K)). Similar to the results in Figures 3 to 6, μ w The ratio was maximized when y=6at%, and κlat was minimized when y=4. In any case, adding excess Zn, which is an element from the Te and C group, resulted in better properties compared to when y=0.

[0072] Next, we compared the case where the ingot was crushed into powder in the atmosphere with the case where the ingot was crushed in an inert gas atmosphere. Figure 9 shows the temperature dependence of the figure of merit Z for p-type thermoelectric materials made by crushing the ingot into powder in the atmosphere and for p-type thermoelectric materials made by crushing the ingot into powder in an inert gas atmosphere (inside a glove box). In Figure 9, the horizontal axis is temperature (°C), and the vertical axis is the figure of merit Z (10°C). -3 The temperature is ( / K). Figure 10 shows the temperature dependence of the Quality factor B of a p-type thermoelectric material prepared by pulverizing an ingot in air and a p-type thermoelectric material prepared by pulverizing an ingot in an inert gas atmosphere (inside a glove box). In Figure 10, the horizontal axis is the amount of ZnTe added (at%), and the vertical axis is the Quality factor B. The Quality factor B is expressed by the following equation (4). In the following equation (4), h is Planck's constant, e is the elementary charge, and m e k is the mass of the electron. B is Boltzmann's constant, T is absolute temperature, μ w Weighted mobility, κ lat This is the lattice thermal conductivity.

[0073]

number

[0074] As shown in Figure 9, the figure of merit of the thermoelectric material was higher when it was ground in air and then powdered compared to when it was ground in an inert gas atmosphere. As shown in Figure 10, when ground in air, the Quality factor B was maximized at a ZnTe concentration of 4 at%, whereas in an inert gas atmosphere, the Quality factor B decreased as the ZnTe concentration increased. These results indicate that adding ZnTe and introducing oxygen can further improve the figure of merit. When the oxygen concentration of thermoelectric materials (without Zn addition, y=0 at%) manufactured under similar conditions to these samples was measured, it was 431 ppm when ground in a glove box and 1150 ppm when ground in air. It is estimated that the oxygen concentration would be similar when ZnTe is added.

[0075] Next, we will describe the results of the crystal structure observation. SEM observation of p-type samples with excess Zn and Te added (6 at%) confirmed that segregated zinc telluride (ZnTe) particles with major axes of 0.4 to 40 μm and minor axes of 0.4 to 20 μm were precipitated inside the crystal grains of the matrix and at least one of the grain boundaries of the matrix. The distribution of major and minor axes of the zinc telluride particles obtained from SEM and EDS is shown in Figures 11 and 12. Figure 11 shows the distribution of major axes of zinc telluride particles. In Figure 11, the horizontal axis shows particle size (μm) and the vertical axis shows frequency (number). Figure 12 shows the distribution of minor axes of zinc telluride particles. In Figure 12, the horizontal axis shows particle size (μm) and the vertical axis shows frequency (number). As shown in Figures 11 and 12, more than 90% of the telluride particles had a major axis of 0.4 μm to 40 μm and a minor axis of 0.4 μm to 20 μm.

[0076] Regarding the thermoelectric material in which zinc telluride was observed, the long axis and short axis of zinc oxide particles were measured by STEM-EDS. Note that zinc oxide particles were deposited in at least one of the interior of the matrix crystal grains and the grain boundaries of the matrix. The obtained results are shown in FIGS. 13 and 14. FIG. 13 shows the distribution of the major diameters of zinc oxide particles. The horizontal axis of FIG. 13 indicates the particle diameter (μm), and the vertical axis indicates the frequency (number). FIG. 14 shows the distribution of the minor diameters of zinc oxide particles. The horizontal axis of FIG. 14 indicates the particle diameter (μm), and the vertical axis indicates the frequency (number). Note that [x, y] on the horizontal axis of FIGS. 13 and 14 indicates that it is more than x and less than or equal to y. More than 90% of the zinc oxide particles had a major diameter of 1 nm to 1000 nm and a minor diameter of 1 nm to 500 nm. Although many zinc oxides were confirmed, no Sb oxide particles were confirmed (number density 0 particles / mm 2 ). Also, the number of Zn single particles was 0, and the number of zinc oxide particles was larger.

[0077] The results of the elemental mapping of Sb when Zn was not added are shown in FIG. 15(a), and the results of the elemental mapping of O are shown in FIG. 15(b). In the thermoelectric material without Zn addition, as shown in FIG. 15, many Sb oxide particles were observed. From this, it was confirmed that by adding elemental zinc, the number of Sb oxide particles in the p-type Bi-Te-based thermoelectric material can be reduced.

[0078] FIG. 16 shows the temperature dependence of the thermal conductivity of the p-type thermoelectric material with zinc oxide added to the raw material and the p-type thermoelectric material with elemental zinc added to the raw material. The horizontal axis of FIG. 16 is the absolute temperature (K), and the vertical axis is the thermal conductivity κ (WK -1 m -1 ). As shown in FIG. 16, when zinc oxide was added to the raw material, the thermal conductivity was hardly reduced. On the other hand, when elemental zinc was added to the raw material, the thermal conductivity was reduced, and the number density of Sb oxide particles was 0 particles / mm 2 . Similarly, the number density of Bi oxide particles was also 0 particles / mm 2Furthermore, when added in the form of zinc oxide, it did not melt, and the distribution of zinc oxide particles was outside the scope of the present invention. From the above, it was confirmed that the performance of thermoelectric materials can be improved by adding elemental zinc as a raw material and allowing it to dissolve and solidify.

[0079] Figure 17 shows the dependence of the dimensionless figure of merit ZT of n-type thermoelectric material 2 on the amount of ZnTe at room temperature (325K). The horizontal axis of Figure 17 represents the amount of ZnTe (at%), and the vertical axis represents the dimensionless figure of merit ZT. As shown in Figure 17, when y=2, the figure of merit was higher than when no ZnTe was added (y=0%).

[0080] Figure 18 shows the elemental mapping results for n-type thermoelectric material 2. As shown in Figure 18, Zn and O were detected in the observed particles, confirming the presence of numerous zinc oxide nanoparticles.

[0081] Figure 19 shows Bi2Se 0.3 Te 2.7 , the lattice thermal conductivity κ of n-type thermoelectric material 3 and n-type thermoelectric material 4 lat The temperature dependence is shown. In Figure 19, the horizontal axis is temperature (°C), and the vertical axis is thermal conductivity κ (mW / (cm·K)). The Al-doped samples tended to have lower lattice thermal conductivity compared to the Al-free samples. Since the Seebeck coefficient, electrical resistivity, and thermal conductivity, which are functions of carrier concentration, also differed significantly among these samples, a Quality factor B, which is an indicator of performance unaffected by carrier concentration, was calculated. Figure 20 shows the relationship between Quality factor B and Al content. In Figure 20, y=1 is the result for n-type thermoelectric material 4, and y=2 is the result for n-type thermoelectric material 3. In the Al-doped samples, the Quality factor values ​​of the y=1 and y=2 samples exceeded those of the Al-free samples, especially in the direction perpendicular to the sintering direction.

[0082] Figure 21 shows Bi 0.45 S 1.55 Figure 21 shows the temperature dependence of the dimensionless figure of merit ZT for Te3, p-type thermoelectric material 2, and p-type thermoelectric material 3. The horizontal axis of Figure 21 is temperature (K). The dimensionless figure of merit ZT for p-type thermoelectric material 3 is Bi0.45 Sb 1.55 It was larger than Te3. From the above, it was confirmed that by adding elemental Al as a raw material and performing melting and solidification, the performance of the thermoelectric material can be improved.

Industrial Applicability

[0083] Since the thermoelectric material according to the embodiment has an excellent figure of merit, it has excellent industrial applicability.

Explanation of Reference Signs

[0084] S1… Melting and solidification process, S2… Powder production process, S3… Sintering process

Claims

1. The empirical formula is A ２ B ３ The matrix is ​​represented as follows, where A in the composition formula is one or more elements selected from the group consisting of Bi and Sb, and B in the composition formula is one or more elements selected from the group consisting of Te, Se, and S. In the interior of the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix, Oxide particles containing one or more elements selected from the group consisting of Zn, Nb, and Al, Telluride particles containing one or more elements selected from the group C above precipitate, The major axis of the oxide particles is 1 nm to 1000 nm. The short axis of the oxide particles is 1 nm to 500 nm. The major axis of the telluride particles is 0.4 μm to 40 μm. The short axis of the telluride particles is 0.4 μm to 20 μm. A thermoelectric material in which at least one of the oxide particles and the telluride particles contains at least one of Nb and Al.

2. A matrix having a composition formula represented as A 2 B 3, wherein A in the composition formula is one or more elements selected from the group consisting of Bi and Sb, and B in the composition formula is one or more elements selected from the group consisting of Te, Se and S, In the interior of the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix, Oxide particles containing one or more elements selected from the group consisting of Zn, Nb, and Al, Telluride particles containing one or more elements selected from the group C above precipitate, The major axis of the oxide particles is 1 nm to 1000 nm. The short axis of the oxide particles is 1 nm to 500 nm. The major axis of the telluride particles is 0.4 μm to 40 μm. The short axis of the telluride particles is 0.4 μm to 20 μm. A thermoelectric material in which the number of oxide particles is greater than the number of telluride particles.

3. A matrix having a composition formula represented as A 2 B 3, wherein A in the composition formula is one or more elements selected from the group consisting of Bi and Sb, and B in the composition formula is one or more elements selected from the group consisting of Te, Se and S, In the interior of the crystal grains of the matrix and at least one of the crystal grain boundaries of the matrix, Oxide particles containing one or more elements selected from the group consisting of Zn, Nb, and Al, Telluride particles containing one or more elements selected from the group C above precipitate, The major axis of the oxide particles is 1 nm to 1000 nm. The short axis of the oxide particles is 1 nm to 500 nm. The major axis of the telluride particles is 0.4 μm to 40 μm. The short axis of the telluride particles is 0.4 μm to 20 μm. A thermoelectric material in which the maximum number density of Sb oxide particles is 31.2 particles / μm² or less, or the maximum number density of Bi oxide particles is 12.4 particles / μm² or less.

4. The thermoelectric material according to any one of claims 1 to 3, wherein at least one of the oxide particles and the telluride particles contains at least Zn.

5. A thermoelectric material according to any one of claims 1 to 3, comprising Zn, wherein the Zn content is 0.40 to 2.3 at%.

6. A thermoelectric material according to any one of claims 1 to 3, comprising Al, wherein the Al content is 1.99 to 3.97 at%.

7. A thermoelectric element using the thermoelectric material described in any one of claims 1 to 3.

8. A thermoelectric module using the thermoelectric element described in claim 7.

9. A device using the thermoelectric module described in claim 8.

10. A method for manufacturing a thermoelectric material according to any one of claims 1 to 3, At least one element selected from the group A consisting of Bi and Sb, At least one element selected from the group B consisting of Te, Se, and S, A dissolution and solidification step to obtain a solidified product by dissolving and solidifying a raw material containing at least one element selected from the group consisting of Zn, Nb, and Al, A powder preparation step to obtain powder from the aforementioned solidified material, A sintering step of sintering the aforementioned powder, Equipped with, A method for producing a thermoelectric material, wherein at least some of the elements selected from the group C in the raw material are present in their elemental form.

11. The method for producing a thermoelectric material according to claim 10, wherein in the powder production step, the solidified material is pulverized in the atmosphere.

12. A method for manufacturing a thermoelectric material according to claim 4, At least one element selected from the group A consisting of Bi and Sb, At least one element selected from the group B consisting of Te, Se, and S, A dissolution and solidification step to obtain a solidified product by dissolving and solidifying a raw material containing Zn and at least one element selected from the group consisting of Nb and Al, A powder preparation step to obtain powder from the aforementioned solidified material, A sintering step of sintering the aforementioned powder, Equipped with, A method for producing a thermoelectric material, wherein at least some of the elements selected from the group C in the raw material are present in their elemental form.

13. The method for producing a thermoelectric material according to claim 12, wherein in the powder production step, the solidified material is pulverized in the atmosphere.

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