KR102259535B1 - Thermoelectric materials with improved thermal conductivity and thermoelectric merit figure - Google Patents

Abstract

The present invention relates to a thermoelectric material and a thermoelectric device. In particular, the present invention relates to the thermoelectric material including a compound represented by a chemical formula 1 and the thermoelectric device including the same. The chemical formula 1 is Bi(2-x-y)CuxSbyTe(3-j)Sj. In the chemical formula 1, each of the x, y, and j has the following ranges that 0 < x <= 0.02, 0 < y < 2, 0 < x + y < 2, 0 < j <= 0.5.

Description

Thermoelectric materials with improved thermal conductivity and thermoelectric merit figure

The present invention relates to a thermoelectric material and a thermoelectric device including the same.

The present invention is a result of the following tasks.

[Project identification number] SRFC-MA1701-05

[Name of department] Samsung Electronics Co., Ltd.

[Research and Management Specialized Institution] Samsung Electronics Future Technology Development Center

Recently, problems have arisen due to the use of fossil fuels and nuclear power generation, and accordingly, new and renewable energy fields including thermoelectric materials and solar energy are gradually emerging. Among them, thermoelectric materials have been studied for a long time because they can directly and reversibly convert thermal energy such as waste heat and geothermal heat into electrical energy.

A thermoelectric material is a material having a thermoelectric effect, which is a direct and reversible conversion phenomenon between thermal energy and electrical energy generated by the movement of electrons or holes in the material by heat (temperature difference).

The thermoelectric phenomenon is caused by the diffusion of carriers (electrons or holes) by the heat formed due to the temperature gradient occurring at both ends of the material to form a potential difference, or by conversely applied electric energy, the carriers move with heat, resulting in a temperature difference at both ends of the material. A direct and reversible reaction that forms It uses the thermoelectric effect to generate electricity from a temperature difference, or to measure the temperature of a material and to control the temperature, such as heating or cooling.

The thermoelectric phenomenon is largely divided into the Seebeck effect and the Peltier effect. The Seebeck effect is a phenomenon in which two materials (metal or semiconductor) are connected to form a closed circuit, and when a temperature difference is applied to both ends of the material, a potential difference is generated to generate electric power. The cause of this Seebeck effect is that the carrier concentration increases at a relatively high temperature portion when a temperature difference is given to both ends of the material. Due to the difference in carrier concentration, a potential difference is generated, thereby generating electrical energy. This Seebeck effect is expressed as a Seebeck coefficient (S). The Peltier effect is that when two elements are connected, a closed circuit is formed between two points, and when current flows, one side emits heat and the other side absorbs heat. This principle is because carriers move and generate a potential difference when current flows.

The most developed field of system technology using thermoelectric materials is the aerospace field, which is mainly used as a generator for spacecraft. In addition, thermoelectric materials are being applied to overall industries such as automobiles, home appliances, and medical fields. Recently, a thermoelectric element applied with a thermoelectric material has been developed to obtain energy by utilizing the body temperature of a person. When a system to which such a thermoelectric element is applied is completed, it can be used as a power source for wearable devices or Internet of Things devices, and as a hardware platform. watching. Furthermore, the thermoelectric material may be made of a device coupled with a body temperature or a pulse sensor. As such, thermoelectric materials are currently being applied to various fields of industry, and as the performance of thermoelectric materials gradually increases in the future, the size of the market will also gradually expand.

However, research on thermoelectric materials having excellent performance so that the industrial applicability can be excellent compared to the wide application of the above thermoelectric materials is still insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoelectric material having excellent thermoelectric performance and a thermoelectric device including the thermoelectric material.

According to one aspect of the present invention, there is provided a thermoelectric material including a compound represented by the following Chemical Formula 1:

[Formula 1]

Bi _(2-xy) Cu _x Sb _y Te _(3-j) S _j

In Formula 1, x, y, and j each have the following ranges:

0 < x ≤ 0.02, 0 < y < 2, 0 < x + y < 2, 0 < j ≤ 0.5.

According to one embodiment of the present invention, the thermoelectric material is characterized in that 1 < y < 2.

According to another embodiment of the present invention, the thermoelectric material is characterized in that 0 < j ≤ 0.2.

According to another embodiment of the present invention, the thermoelectric material is characterized in that it has a lattice thermal conductivity of less than 0.6 W/mk at 300 K.

According to another embodiment of the present invention, the thermoelectric material is characterized in that it has an overall thermal conductivity of less than 1.5 W/mk at 300 K.

According to another aspect of the present invention, there is provided a thermoelectric device including the thermoelectric material.

The thermoelectric material according to the present invention is a factor determining thermoelectric performance such as electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ) by doping S in the Te site of the Cu-Bi-Sb-Te-based thermoelectric material. appears excellent. Additionally, the thermoelectric material according to the present invention may simultaneously provide high electrical conductivity and low thermal conductivity compared to conventional thermoelectric materials, and consequently may have increased thermoelectric performance. By using the thermoelectric material of the present invention exhibiting such excellent thermoelectric performance, the performance of various products to which the thermoelectric material is applied, such as a wearable device or a sensor, may be improved.

1 is an X-ray diffraction analysis graph of a thermoelectric material prepared in an embodiment of the present invention.
2 is a graph of lattice constants (a-axis, c-axis) of a thermoelectric material manufactured in an embodiment of the present invention.
3 is a graph of the electrical conductivity (σ) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.
4 is a graph of the Seebeck coefficient (S) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.
5 is a graph of the power factor (PF) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.
^{6 is a density-of-state effective mass (m *} ) graph at 300K of the thermoelectric material manufactured in the embodiment of the present invention according to the S doping amount.
7 is a weighted mobility (U) graph of the valence band (VB) and conduction band (CB) at 300K of the thermoelectric material manufactured in the embodiment of the present invention according to the S doping amount.
8 is a graph of _{the total thermal conductivity (κ tot} ) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.
9 is a graph of _{the lattice thermal conductivity (κ latt} ) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.
10 is a graph of the thermoelectric performance index (zT) of the thermoelectric material manufactured in the embodiment of the present invention according to the absolute temperature and the S doping amount.

Hereinafter, the terms used in the present application are used only to describe specific embodiments and are not intended to limit the present invention. Unless otherwise defined, all terms used herein including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

Throughout the specification, when a part "includes" or "contains" a certain element, it means that other elements may be further included unless otherwise defined.

Hereinafter, a thermoelectric material and a thermoelectric element according to embodiments of the present invention will be described in more detail.

1. Thermoelectric material

According to one aspect of the present invention, there is provided a thermoelectric material including a compound represented by the following Chemical Formula 1:

[Formula 1]

Bi _(2-xy) Cu _x Sb _y Te _(3-j) S _j

In Formula 1, x, y, and j each have the following ranges:

0 < x ≤ 0.02, 0 < y < 2, 0 < x + y < 2, 0 < j ≤ 0.5.

The energy conversion efficiency of the thermoelectric material, that is, the performance of the thermoelectric semiconductor, may be expressed as a dimensionless thermoelectric figure of merit (zT) as shown in Equation 1 below.

[Equation 1]

zT is the thermoelectric figure of merit, σ is the electrical conductivity (S/cm), S is the Seebeack coefficient (μV/K), κ is the thermal conductivity (W/mK), and T is the absolute temperature ( Absolute temperature, K), and the product (σS ² ) of electrical conductivity (σ) and Seebeck coefficient (S) is expressed as a power factor (PF) (Power factor, mW/mK ² ).

The thermoelectric figure of merit (zT) of the thermoelectric material is expressed as in Equation 1, and in order to increase this, the power factor (PF, σS ² ) is increased by increasing the electrical conductivity (σ) and the Seebeck coefficient (S), and the thermal conductivity There is a method of reducing (κ). However, since the electrical conductivity (σ) and the Seebeck coefficient (S) have a trade-off relationship depending on the carrier concentration, it is difficult to simultaneously increase them. Therefore, it is necessary to increase the thermoelectric figure of merit (zT) by reducing the thermal conductivity (κ), that is, the total thermal conductivity (κ _{tot ).}

On the other hand, _{the contributions of the total thermal conductivity (κ tot} ) can be expressed by the following equation.

κ _{tot =} κ _{elec +} κ _{bp +} κ _latt

where κ _elec is the electronic thermal conductivity, κ _bp is the bipolar thermal conductivity, κ _latt is the lattice thermal conductivity, and the _{contributions of the total thermal conductivity (κ tot} ) are correlated with each other. In order to increase the thermoelectric figure of merit (zT), _{it is necessary to reduce the total thermal conductivity (κ tot} ). If the electron thermal conductivity (κ _elec ) is reduced, the movement of electrons and holes is also restricted, so that the electrical conductivity (σ) is lowered as well, and thus the power factor PF is lowered, and as a result, the thermoelectric figure of merit zT cannot be increased. Therefore, it is advantageous to increase the thermoelectric figure of merit (zT) to lower the lattice thermal conductivity (κ _latt ) instead of the electron thermal conductivity (κ _{elec ).} By doping S in the thermoelectric material according to the present invention, it can have high electrical conductivity and low thermal conductivity due to low lattice thermal conductivity compared to conventional thermoelectric materials, thereby increasing thermoelectric performance.

In Chemical Formula 1 of the present invention, the amount of x, that is, Cu atoms may have a range of 0 < x ≤ 0.02, specifically 0.005 ≤ x ≤ 0.02. Here, Cu shows two major aspects in the thermoelectric material. First, most Cu is substituted with Sb. Second, a small amount of Cu is intercalated into the van der Waals gap of the quintuple layer. The formation of two different point defects increases the thermoelectric power factor by increasing the hole concentration to a range having an optimum value in the trade-off relationship of electrical conductivity and Seebeck coefficient, with increased density of states and effective mass, and at the same time, a complex crystal structure Reduce the thermal conductivity by enhanced phonon scattering due to , and suppress the bipolar contribution. Accordingly, by doping Cu as in Formula 1, thermoelectric performance may be increased.

In Chemical Formula 1 of the present invention, the amount of y, that is, the Sb atom may have a range of 0 < y < 2, specifically, 1 < y < 2 . Also, the amount of Bi atoms decreases by the amount substituted by the Sb. Accordingly, the amount of Bi atoms may have a range of 0 < 2-y < 2 depending on the amount of Sb atoms.

In Formula 1 of the present invention, j, that is, the amount of S atoms may have a range of 0 < j ≤ 0.5. Specifically, in Formula 1, j may be in the range of 0 < j ≤ 0.2, more specifically in the range of 0 < j ≤ 0.1, even more specifically in the range of 0 < j < 0.1, or 0 < j ≤ 0.07. Also, the amount of Te atoms may be equal to 3 minus the amount of S atoms (ie, 3-j in Formula 1). As such, by doping S in the Te site of the Cu-Bi-Sb-Te-based thermoelectric material, the thermoelectric material may have an increased thermoelectric figure of merit (zT) compared to the composition in which S is not doped, and this S doping The effect of can be confirmed in the following evaluation examples and drawings.

According to one embodiment of the present invention, the thermoelectric material is characterized in that 1 < y < 2 and 0 < j ≤ 0.2. In Chemical Formula 1 of the present invention, j, that is, the amount of S atoms may have a range of 0 < j ≤ 0.2. Specifically, the thermoelectric figure of merit (zT) of the thermoelectric material of the present invention varies depending on the amount of doped S atoms, and in particular, the electrical conductivity (σ), which is a component in the equation required to calculate the thermoelectric figure of merit (zT). ), Seebeck coefficient (S) and thermal conductivity (κ) are improved by doping of S atoms is shown in Figs. 3, 4, and 8 below. In particular, it is shown in FIGS. 8 and 9 that the lattice thermal conductivity (κ _latt ) and the total thermal conductivity (κ _tot ) are improved as the amount of doped S atoms increases.

2. Thermoelectric element

According to another aspect of the present invention, there is provided a first electrode, a second electrode at least partially opposite to the first electrode, and a thermoelectric material as described above interposed between the first electrode and the second electrode. There is provided a thermoelectric element comprising. The first electrode may be positioned between the thermoelectric material and the heat source. The thermoelectric material includes a p-type thermoelectric material and an n-type thermoelectric material. The thermoelectric material of the present invention may be used as the n-type thermoelectric material or the p-type thermoelectric material, and specifically may be used as the p-type thermoelectric material. The first electrode is connected to the p-type thermoelectric material and the n-type thermoelectric material, and the p-type thermoelectric material and the n-type thermoelectric material are spaced apart from each other. In the thermoelectric element, when the thermoelectric material receives heat from a heat source, holes in the p-type thermoelectric material and electrons in the n-type thermoelectric material move toward the second electrode, respectively, and the generated electromotive force is in the form of electrical energy. can be saved.

Hereinafter, various embodiments and evaluation examples of the present invention will be described in detail. However, the following examples are only some examples of the present invention, and the present invention should not be construed as being limited to the following examples.

3. Examples

The following method was used to prepare the thermoelectric material of the present invention:

Example 1: Bi _0.49 Cu _0.01 Sb _1.5 Te ₃

After weighing high-purity raw materials (Cu, Bi, Sb, Te) according to the composition ratio, it was vacuum-sealed in Quartz so that the total weight was 20 g. The sealed sample was kept in a muffle furnace at a temperature of 1150° C. for 20 hours. After putting the ball and material in a jar so that the ratio was 1:5, ball milling (SPEX mill - 8000M) was performed for 10 minutes in an Ar atmosphere. (The jar and ball are stainless steel.) Weigh the sample to 6.8 g Thus, sintering (spark plasma sintering, Dr.sinter SPS-2040) was performed at 60 MPa and 430 ° C. for 5 minutes.

Example 2: Bi _0.49 Cu _0.01 Sb _1.5 (Te _2.99 S _0.01 )

High purity raw materials (Cu, Bi, Sb, Te, S) were weighed according to the composition ratio to obtain a composition of _{Bi 0.49} Cu _0.01 Sb _1.5 (Te _2.99 S _{0.01 ), and then synthesized and sintered in the same manner as in Example 1.} .

Example 3: Bi _0.49 Cu _0.01 Sb _1.5 (Te _2.97 S _0.03 )

High purity raw materials (Cu, Bi, Sb, Te, S) were weighed according to the composition ratio to obtain a composition of _{Bi 0.49} Cu _0.01 Sb _1.5 (Te _2.97 S _{0.03 ), and then synthesized and sintered in the same manner as in Example 1.} .

Example 4: Bi _0.49 Cu _0.01 Sb _1.5 (Te _2.95 S _0.05 )

High purity raw materials (Cu, Bi, Sb, Te, S) were weighed according to the composition ratio to obtain a composition of _{Bi 0.49} Cu _0.01 Sb _1.5 (Te _2.95 S _{0.05 ), and then synthesized and sintered in the same manner as in Example 1.} .

Example 5: Bi _0.49 Cu _0.01 Sb _1.5 (Te _2.93 S _0.07 )

High purity raw materials (Cu, Bi, Sb, Te, S) were weighed according to the composition ratio to obtain a composition of _{Bi 0.49} Cu _0.01 Sb _1.5 (Te _2.93 S _{0.07 ), and then synthesized and sintered in the same manner as in Example 1.} .

Example 6: Bi _0.49 Cu _0.01 Sb _1.5 (Te _2.9 S _0.1 )

High purity raw materials (Cu, Bi, Sb, Te, S) were weighed according to the composition ratio to obtain a composition of _{Bi 0.49} Cu _0.01 Sb _1.5 (Te _2.9 S _{0.1 ), and then synthesized and sintered in the same manner as in Example 1.} .

4. Evaluation example

Evaluation Example 1: XRD pattern

In order to measure the structural properties of the thermoelectric material of the present invention, X-ray diffraction analysis and XRD (X-ray diffraction) were used. X-ray diffraction is a phenomenon in which when a material is exposed to X-rays, diffraction occurs at a specific angle and crystal plane of the material. X-ray diffraction analysis is to measure an angle between an X-ray and a material and the intensity of a diffracted X-ray by using this diffraction phenomenon of X-rays, and analyze it through Bragg's diffraction law. Through this X-ray diffraction analysis, the crystal structure, lattice constant, phase analysis and orientation of the material can be confirmed.

Through this, the secondary phase was confirmed and the structural properties were analyzed by calculating the lattice constant. In this analysis method, in all examples, a single phase was observed without a secondary phase. When the lattice constant was calculated through the XRD measurement result, it was observed that both the a-axis and the c-axis lattice constant decreased as the S doping increased. This is due to the difference in ionic radii between Te and S. As a result, it is judged that the distortion of the lattice has occurred due to the doping of S, which can prove that S is successfully substitutionally doped at the Te site. This is shown through the XRD data graph of FIG. 1 and the lattice constant value graph of FIG. 2 .

Evaluation Example 2: Electrical Conductivity (σ)

To measure the electrical conductivity (σ) of the thermoelectric material of the present invention, ZEM-3 was used. The electrical conductivity (σ) of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 3 according to the absolute temperature. Electrical conductivity (σ) increased with decreasing temperature in all examples depending on the amount of S. According to FIG. 3, as the amount of doped S increases, the electrical conductivity (σ) continuously increases in the range of 0 < x < 0.05, and the electrical conductivity (σ) gradually decreases in the range of 0.05 ≤ x ≤ 0.1. .

Evaluation Example 3: Seebeck coefficient (S)

In order to measure the Seebeck coefficient (S) of the thermoelectric material of the present invention, ZEM-3 was used. The Seebeck coefficient (S) of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 4 according to the absolute temperature. In the range where the amount of doped S is 0 < x ≤ 0.05, the Seebeck coefficient (S) maintains a relatively constant value and does not show a large change. In particular, the value of the Seebeck coefficient (S) is constant in a low temperature region. According to FIG. 4 , when the amount of doped S is 0.07 or more, the Seebeck coefficient S gradually increases.

Evaluation Example 4: Power Factor (P.F)

In order to measure the power factor (P.F) of the thermoelectric material of the present invention, the electrical conductivity (σ) and the Seebeck coefficient (S) are required. The power factor (P.F) of the thermoelectric material of the present invention was calculated using the electrical conductivity (σ) and the Seebeck coefficient (S) measured in the evaluation examples 2 and 3 above. The power factor (P.F) of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 5 according to the absolute temperature. The power factor (P.F) value increased as S was doped. As the amount of doped S increases to 0.01, the value of the power factor P.F increases due to the increase of the electrical conductivity σ and the maintenance of the Seebeck coefficient S. As the amount of doped S increases more than 0.01, the power factor (P.F) value decreases, but up to the doping amount of 0.03, the power factor (P.F) value is higher than that of the undoped composition.

Evaluation Example 5: Density of State Effective Mass (m) ^* )

The density of states effective mass (m ^* ) affects the charge transport ability, so improvement of the density of states effective mass tends to contribute to the improvement of the thermoelectric performance. In order to calculate the density-of-state effective mass (m ^* ) of the thermoelectric material of the present invention, the electrical conductivity (σ) and the Seebeck coefficient (S) are required. Using the electrical conductivity (σ) and Seebeck coefficient (S) measured in Evaluation Examples 2 and 3 above, the density of state effective mass (m ^* ) of the thermoelectric material of the present invention was calculated by applying it to the single parabolic band model. . ^{The density of states effective mass (m *} ) at 300 K of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 6 . The density of states effective mass (m ^* ) value increased by doping with S. As the amount of doped S increases, the density of states effective mass (m ^* ) continuously increases in the range of 0 < x ≤ 0.07, and the density of states effective mass (m ^* ) gradually decreases in the range of 0.07 < x ≤ 0.1. do.

Evaluation Example 6: Weighted mobility (U)

Since the weighted mobility (U) affects the charge transport ability, the improvement of the weighted mobility tends to contribute to the improvement of the thermoelectric performance. In order to calculate the weighted mobility (U) of the thermoelectric material of the present invention, the electrical conductivity (σ) and the Seebeck coefficient (S) are required. Using the electrical conductivity (σ) and Seebeck coefficient (S) measured in Evaluation Examples 2 and 3 above, the valence band (VB) and conduction band (CB) of the thermoelectric material of the present invention by applying to the single parabolic band model The weighted mobility (U) was calculated. The weighted mobility (U) of the valence band (VB) and conduction band (CB) at 300 K of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 7 . The weighted mobility (U) value increased with S doping. As the amount of doped S increases, in the range of 0 < x < 0.05, the weighted mobility (U) of the valence band (VB), which is involved in the physical properties of holes, which is the main charge transporter, increases compared to before doping, and 0.05 ≤ x ≤ In the range of 0.1, the weighted mobility U of the valence band VB gradually decreases.

Evaluation Example 7: Thermal Conductivity (κ)

A lower thermal conductivity tends to improve the thermoelectric figure of merit of a thermoelectric material. _{In order to measure the total thermal conductivity (κ tot} ) of the thermoelectric material of the present invention, thermal diffusivity, specific heat, and density are required. In order to measure the thermal diffusivity, LFA-465 (Netzsch) was used. _{The total thermal conductivity (κ tot} ) was calculated using the thermal diffusivity, specific heat, and density measured by the above method. _{The overall thermal conductivity (κ tot} ) of all examples as a function of the amount of S is shown in FIG. 8 as a function of the absolute temperature. As the amount of doped S increases, the total thermal conductivity (κ _tot ) gradually decreases over the entire temperature range. To examine the causes of these changes, the contributions of the total thermal conductivity (κ _tot ) were analyzed.

First, based on the single parabolic band model, the Lorentz number was calculated through Equation 2 below using the Seebeck coefficient to obtain the electron thermal conductivity.

[Equation 2]

L = 1.5 + exp(-|S|/116)

The calculated electronic thermal conductivity increased until the doping amount of S was 0.01, and then gradually decreased thereafter.

Second, the bipolar thermal conductivity can be predicted with the single parabolic band model and the Boltzmann transport equation. The predicted bipolar thermal conductivity decreased slightly until the S doping amount was 0.01, but after that it appeared to be a constant value without further change. This can be interpreted that S has little effect on bipolar conduction.

On the other hand, the lattice thermal conductivity shows a tendency to gradually decrease as the doping of S increases, the point defect scattering increases. This can be confirmed through FIG. 9 below.

Evaluation Example 8: Thermoelectric performance index (zT)

In order to measure the thermoelectric figure of merit (zT) of the thermoelectric material of the present invention, a power factor (PF) and thermal conductivity (κ) are required. The thermoelectric figure of merit (zT) of the thermoelectric material of the present invention was calculated using the electrical conductivity (σ) and the Seebeck coefficient (S) measured in Evaluation Examples 4 and 5 above. The thermoelectric figure of merit (zT) of the thermoelectric materials prepared in Examples 1 to 6 according to the amount of S is shown in FIG. 10 according to the absolute temperature. As shown in FIG. 10 , the S-doped thermoelectric material composition exhibits a higher thermoelectric figure of merit (zT) compared to the basic composition. As the amount of doped S increases, in the range of 0 ≤ x ≤ 0.03, the density of states effective mass (m ^* ) and the weighted mobility (U) of the valence band (VB), which contribute to the transport ability of holes, which are the main charge transporters, are Compared to before doping, the thermoelectric figure of merit (zT) increased due to the improvement of electrical properties, and in the range of 0.03 ≤ x ≤ 0.07, the thermoelectric figure of merit (zT) was increased due to the improvement of thermal properties due to the reduction effect of the _{total thermal conductivity (κ tot )} ) increased.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that you can.

Claims (6)

A thermoelectric material comprising a compound represented by the following formula (1):
[Formula 1]
Bi _(2-xy) Cu _x Sb _y Te _(3-j) S _j
In Formula 1, x, y, and j each have the following ranges:
0 < x ≤ 0.02, 0 < y < 2, 0 < x + y < 2, 0 < j ≤ 0.03. The thermoelectric material according to claim 1 , wherein 1 < y < 2 . delete The thermoelectric material of claim 1 having a lattice thermal conductivity of less than 0.6 W/mk at 300 K. The thermoelectric material of claim 1 having an overall thermal conductivity of less than 1.5 W/mk at 300 K. A thermoelectric element comprising the thermoelectric material according to claim 1 .

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