KR101442018B1 - Alkaline or alkaline earth metal doped indium selenide compound and thermoelectric materials manufactured by compounding the same - Google Patents

Abstract

The present invention relates to a thermoelectric material. In particular, the present invention relates to a compound for an indium selenide thermoelectric element with high efficiency in which alkali and alkaline earth metal that have lower thermal conductivity and a higher Seebeck coefficient compared to common metal or semiconductors are added. According to the present invention, electrical conductivity is increased by adding alkali and alkaline earth metal to the indium selenide thermoelectric material. Therefore, thermoelectric properties of the material are enhanced.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a compound having an alkali and an alkaline earth metal added thereto, and a thermoelectric material prepared by synthesizing the same. BACKGROUND OF THE INVENTION [0001] The present invention relates to an alkaline earth metal alkoxide,

The present invention relates to a thermoelectric material, and more particularly, to a high-efficiency indium-selenide thermoelectric element compound having an alkali and alkaline earth metal added thereto, which has a smaller thermal conductivity and a higher Seebeck coefficient than a general metal or a semiconductor.

The present invention also relates to a thermoelectric material produced by synthesizing such a compound.

Generally, thermoelectric materials are materials that can be applied to active cooling and cogeneration using a Peltier effect and / or a Seebeck effect.

A diagram showing such a Peltier effect is shown in FIG. 1, when the DC voltage is applied to the external power source 120, the electrons of the p-type material 100 and electrons of the n-type material 110 move to generate heat and endothermic .

A diagram showing the Seebeck effect is shown in FIG. Referring to FIG. 2, when heat is supplied from the external heat source 200, electrons and holes move, causing a current to flow in the material, thereby generating electric power.

The active cooling using the thermoelectric material improves the thermal stability of the device, eliminates vibration and noise, and does not use a separate condenser and a refrigerant. Thus, the active cooling is recognized as a small-volume, environmentally friendly method. Application of active cooling using such thermoelectric materials can be applied to a non-refrigerated refrigerator, an air conditioner, and various micro cooling systems. Particularly, when thermoelectric elements are attached to various memory devices, The temperature can be maintained at a uniform and stable temperature, and the performance of the device can be improved.

On the other hand, if the thermoelectric material is used for thermoelectric power generation by using the Seebeck effect, waste heat can be utilized as an energy source, and it can be used as an energy source for automobile engines and exhaust devices, waste incinerators, waste heat of steelworks, Such as the power of the power source, or to collect waste heat and use it in various fields.

As a factor for measuring the performance of the thermoelectric material, the dimensionless figure of merit ZT, which is defined by the following Equation 1, is used.

[Equation 1]

Where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity.

In order to increase the dimensionless figure of merit ZT, a material having high Seebeck coefficient, high electrical conductivity and low thermal conductivity should be sought.

However, a typical Indium Selenide In ₄ Se _3-x thermoelectric material is an n-type crystalline material with a ZT of 1.48 and a current density of about 10 ¹⁸ cm ^-3 . The current density of this level is less than 10 ¹⁹ ~ 10 ²⁰ cm ^-3 , which is the optimum current density of the thermoelectric material, and the thermoelectric property optimization is not achieved.

In order to improve the current density through electron doping, the current density of Indium Selenide In ₄ Se _3-x Cl _0.03 thermoelectric material doped with chlorine was increased to 10 ¹⁹ cm ^-3 and the maximum ZT value was improved to 1.53. The size has been improved to have a wide operating temperature.

However Boltzmann transport from, as in FIG calculation _{In 4 Se 3-x (0.22} eV) and In ₄ Se lot from _{3-x Cl 0.03 (0.34 eV} ) both areas (0.8 eV) has an optimum power factor S ² σ There is a disadvantage that more electron doping must be performed.

3 is a schematic diagram showing the electrical conductivity 330, the Seebeck coefficient 320, and the power factor 310 obtained from the Boltzmann transport calculations of Indium Selenide against the chemical potential.

1. Korean Patent Publication No. 10-2012-0086190 2. Korean Patent No. 10-0663975 3. Korean Patent Publication No. 10-2013-0010848

Disclosure of Invention Technical Problem [8] The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a thermoelectric compound having a high Seebeck coefficient and a very low thermal conductivity.

Another object of the present invention is to provide a thermoelectric material produced by synthesizing a compound for a thermoelectric element.

The present invention provides a thermoelectric compound having a large Seebeck coefficient and a very low thermal conductivity in order to achieve the above problems.

The thermoelectric-element-forming compound is a compound to which an alkali and an alkaline earth metal for a thermoelectric element having a composition represented by the following general formula (1) are added.

(Formula 1)

(A _1-a A ^' _a ) _4-x (B _{1 -b} B ^' _b ) _3-y H _δ

Wherein A is an element selected from the group consisting of alkali metals and alkaline earth metals, B and B 'are different from each other, B is one of S, Se and Te, B 'is an element selected from one of Group 14, Group 15, and Group 16 elements, H is an element selected from one of halogen elements,

Wherein a is 0? A <1,

B is 0? B <1,

X is 0 < x < 1,

Y is 0 < y < 1,

The delta may be 0 < / = &lt; 0.1.

Here, the A may be In or Ga.

The A 'may be at least one selected from the group consisting of Ba, Sr, Ca, Na and Li.

Further, the compound may be a two-dimensional layered structure.

In addition, the compound may form a covalent bond in the in-plane direction, and the interlayer bond may form at least one of an ionic bond and a Van der Waals bond .

Further, it can be characterized that it has an orientation in an out-of-plane direction.

Also, it can be characterized in that it has a lattice distortion in the in-plane direction.

In addition, when the current density of the compound is 10 ¹⁶ / cm ³ to 10 ²⁰ / cm ³ , lattice distortion of the compound occurs due to strong interaction between electrons and neighboring atoms in a specific region .

The method of increasing the current density may be any one of a method of changing physical properties by changing a process condition, a method of adding a doping element, or a method of inducing a defect.

Also, at least one of A and B may be added in an amount less than stoichiometry.

In addition, the A may be arranged in one dimension within the lattice structure.

Further, A 'or B' which is a doping component may be selectively added to A and B which are basic components.

The above-mentioned A 'and B' may be added in the form of a one-component system, a two-component system or a three-component system.

Here, the molar ratio of the two-component system is 1: 9 to 9: 1, and the molar ratio of the three-component system is 1: 0.1 to 0.9: 0.1 to 0.9.

On the other hand, another embodiment of the present invention provides a thermoelectric material prepared by using polycrystalline synthesis method or single crystal growth method.

Here, the polycrystalline synthesis method may be any one of an ampoule method, an arc melting method, and a solid state reaction method.

The single crystal growth method may be any one of a metal flux method, a Bridgeman method, an optical floating zone method, and a vapor transport method. have.

In addition, the thermoelectric element may be characterized in that its cutting direction is perpendicular to the growth direction.

In addition, the current density can be optimized through selective element doping.

It is also possible to further increase the density by using a high-density process.

At this time, the densification step may be any one of a hot pressing method, a spark plasma sintering method, and a hot posing method.

According to the present invention, by adding an alkali metal or an alkaline earth metal to the indium selenide thermoelectric material, the electrical conductivity is improved and the thermoelectric property is increased.

In addition, as another effect of the present invention, the thermoelectric material may be useful for a non-refrigerated refrigerator, an air conditioner, a waste heat power generator, a thermoelectric nuclear power generator for military and aerospace, and a micro cooling system.

1 is a schematic view showing thermoelectric cooling by a general Peltier effect.
Fig. 2 is a schematic diagram showing a thermoelectric power generation by a general Seebeck effect.
3 is a schematic diagram showing the electrical conductivity 330, the Seebeck coefficient 320, and the power factor 310 obtained from the Boltzmann transport calculations of Indium Selenide against the chemical potential in general.
FIG. 4 is a graph showing the electrical resistance of thermoelectric materials In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 according to an embodiment of the present invention.
FIG. 5 is a graph showing the Seebeck coefficient (S) according to the temperature of thermoelectric materials In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 according to an embodiment of the present invention.
6 is a graph showing a power factor (S ² σ) according to temperature of the thermoelectric material In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 according to an embodiment of the present invention.
7 is a graph showing the thermal conductivity (k) of thermoelectric materials In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 according to an embodiment of the present invention.
FIG. 8 is a graph showing the dimensionless figure of merit (ZT) according to the temperature of thermoelectric materials In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 according to an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term "and / or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

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 this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

Hereinafter, a high-efficiency indium-selenide thermoelectric material to which an alkali and an alkaline earth metal are added according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

A useful composition for a thermoelectric material according to one embodiment of the present invention comprises a compound of formula (1)

[Chemical Formula 1]

(A _1-a A ^' _a ) _4-x (B _{1 -b} B ^' _b ) _3-y H _δ

Here, A represents a group 13 element, and A 'represents an element selected from one of an alkali metal and an alkaline earth metal. Further, B and B 'are different from each other, and B can be one of S, Se and Te. B 'represents an element selected from one of Group 14, Group 15, and Group 16 elements, and H represents an element selected as one of halogen elements.

B may have a range of 0? B <1, x may have a range of -1 <x <1, and y may have a range of -1 < y < 1, and? may have a range of 0?? <0.1.

In particular, x may have a range of 0 < x < 1 and y may have a range of 0 < y < Particularly, as the Group 13 element corresponding to A, In or Ga is preferable.

The alkali or alkaline earth metal corresponding to A 'is preferably Ba, Sr, Ca, Na or Li. As B, Se or Te is preferable.

The compound having the composition represented by Formula 1 may have a two-dimensional layer structure, has orientation in a certain direction, and exhibits low thermal conductivity through interlayer van der Waals bonding.

In particular, the compound having the composition of Formula 1 may have a structure without lattice distortion, but lattice distortion may occur according to the change of the current density. In particular, when the current density increases, it is more preferable that the lattice of the compound is distorted by the strong interaction between the electrons and the surrounding atoms in the appropriate region, thereby reducing the thermal conductivity.

For example, when the current density is less than about 10 ¹⁶ / cm ³ , lattice distortion does not occur, but the current density is about 10 ¹⁶ / cm ³ To about 10 &lt; ²⁰ &gt; / cm &lt; ³ &gt; may cause lattice distortion.

As a method of inducing lattice distortion by increasing the current density as described above, a method of changing the physical properties of the compound having the composition represented by Chemical Formula 1 by changing the conditions of the compound, the method of adding the doping element, or the method of inducing defects Method or the like can be used.

As the conditions of the production process for the physical property change, it is possible to control the firing temperature or the firing time in the firing process, or to change the pressure condition, etc. As a method of inducing the flaw, And / or &lt; / RTI &gt; component B in a less than stoichiometric amount.

By changing the current density as described above, the compound of Formula 1 has a lattice distortion in the in-plane direction and an orientation in the out-of-plane direction, thereby exhibiting a low thermal conductivity.

The compound of formula (1) is further improved in the Seebeck coefficient by the low dimensional conduction property because the A component is arranged almost one-dimensionally in the lattice structure and electrons or holes move along this path.

The doping component A 'or B' is selectively added to the basic components A and B of the compound of Formula 1 to improve the electrical conductivity, thereby increasing the ZT value of Equation (1).

The A 'component and the B' component, which are doping components, may be added in the form of a one-component system, a two-component system, or a three-component system, and in a two-component system, a molar ratio thereof may be added in a ratio of 1: 9 to 9: In the case of the three-component system, it may be added at a ratio of 1: 0.1-0.9: 0.1-0.9, but is not limited thereto.

Each of the components constituting the compound of formula (I) combines to form a layered structure. In these layered structures, a covalent bond is formed in-plane, and bonding between these layers is performed by ionic bonding and / To form a Dear Baals bond.

In general, the thermal conductivity (k _tot ) can be distinguished from the thermal conductivity (k _ph ) by the lattice vibration and the thermal conductivity (k _el ) by electrons such as k _tot = k _el + k _ph , Electron thermal conductivity is a dependent variable of electrical conductivity because it is proportional to electrical conductivity (ρ) and temperature (T) according to the Wiedemann-Frantz law as shown in equation (2).

&Quot; (2) &quot;

K _el = LT / ρ

Where T is the temperature, ρ is the electrical conductivity, L = 2.44 × 10 ^-8 ΩW / K ² , and K is the absolute temperature.

Therefore, a good thermoelectric material should have a low lattice thermal conductivity, which can be obtained by controlling the lattice structure.

When the B component deficiency is generated in the compound of Formula 1, the current density increases and the increased current density interferes with the surrounding atoms to distort the lattice and reduce the thermal conductivity. The lattice distortion is caused by strong interaction between electrons and lattice vibrations, and plays a role of reducing thermal conductivity.

Therefore, in the compound of Formula 1, each layer in the in-plane direction forms a strong bond by covalent bonds in the state where lattice distortion exists, and the interlayer bond, that is, the out- Since phonon transmission is difficult in the out-of-plane direction and in-plane lattice distortion is caused in the in-plane and out-of-plane directions, The temperature becomes lower. For example, the compound of Formula 1 can exhibit a thermal conductivity of 2 W / mK or less at room temperature.

As shown in FIG. 3, the compound of Formula 1 has a property that the A component, for example, In is one-dimensionally arranged, thereby exhibiting a low-dimensional conduction characteristic, do.

In general, it is known that the energy state density at the Fermi level increases as the low dimensional conduction characteristic is obtained. If the energy state density has a singular singularity, the SbcEk coefficient increases as shown in Equation (3) below.

&Quot; (3) &quot;

Where S is the Seebeck coefficient, ε is the energy, and E _F is the Fermi energy.

As the compound of Formula 1 has a low dimensional electrical characteristic in the lattice structure, the energy state density at the Fermi level is increased, and it can be interpreted that the compound has a high Seebeck coefficient at the increased energy state density.

Accordingly, the compound of Formula 1 according to an embodiment of the present invention exhibits a low thermal conductivity, and at the same time, a low-dimensional conduction characteristic of the electron increases the Seebeck coefficient. Therefore, the characteristics required as the thermoelectric material are satisfied.

The compound having the above-described formula (1) may have a single crystal or polycrystal structure including lattice distortion as described above. When a compound having the composition of Formula 1 is used as a thermoelectric material, the crystal structure of the single crystal and the polycrystal can affect the properties of the thermoelectric material.

When a compound having the composition of Formula 1 is used as a thermoelectric material, they are cut into a predetermined shape and used, and they may have different properties depending on the cutting direction. For example, when the compound has a single crystal structure, it is preferable that the direction of cutting is perpendicular to the growth direction when the thermoelectric element is formed.

The synthesis method of the compound of formula (1) is divided into a polycrystalline synthesis method and a single crystal growth method.

First, in the polycrystalline synthesis method, there are Ampoule method, Arc melting method, Solid state reaction and the like.

(1) Method of Using Ampoule: The raw material element is put into an ampoule made of a quartz tube or metal, followed by vacuum sealing and heat treatment;

(2) Arc melting method: A method comprising the steps of placing a raw material element in a chamber and discharging an arc in an inert gas atmosphere to melt the raw material element to prepare a sample;

(3) Solid state reaction: A method comprising a step of hardly mixing powders and then heat-treating them, or heat-treating the mixed powders, followed by processing and sintering.

The other one is the metal flux method and the Bridgeman method in the case of the single crystal growth method, and they are briefly described as follows.

(1) Metal flux method: A method comprising a step of growing a crystal by introducing an element which provides an atmosphere so that a raw material element and a raw material element can grow well at a high temperature into a crucible and then heat-treating the raw material at high temperature;

(2) Bridgeman method: The raw material element is placed in a crucible, heated at a high temperature until the raw material element dissolves at the end of the crucible, and slowly moved in a high temperature region to dissolve the sample locally, And allowing the crystal to grow;

(3) Optical floating zone: The raw material element is made into a rod rod and seed rod and feed rod. Then, the feed rod is focused on the light of the lamp and focused on the sample at a locally high temperature. And slowly pulling up the dissolution part upward to grow crystals;

(4) Vapor transport method: The raw material element is placed under the quartz tube, the raw material element is heated, the upper part of the quartz tube is kept at a low temperature, the raw material element is vaporized, &Lt; / RTI &gt;

According to one embodiment of the present invention, any of the various methods described above can be used without any limitation to produce the compound of Formula 1, and there is no particular limitation.

In the above process for preparing the compound of Formula 1 according to an embodiment of the present invention, when 2 band conduction occurs in which electrons and holes coexist by optimizing the current density through selective element doping, Only one of the electrons or the holes causes a conduction characteristic, thereby producing a thermoelectric material having a large power factor and a very small thermal conductivity.

The doping process of the doping element may be performed by adding the doping element as a part of the raw material element in the polycrystalline growth method or the single crystal growth method.

On the other hand, in addition to the doping process of the doping element, the polycrystalline compound may be further subjected to a densification process. Such a high-density process makes it possible to further improve the electrical conductivity.

Examples of the high-density process include the following three processes:

(1) Hot pressing method: a method in which a target powder compound is added to a mold of a predetermined shape and molded at a high temperature, for example, 300 to 800 DEG C and a high pressure, for example, 30 to 300 MPa;

(2) Spark plasma sintering method: a method of sintering a material in a short time by applying a high voltage current, for example, 50 to 500 A, to the powdered compound as a target chain;

(3) Hot Forging Method: A method of extruding and sintering a target chain powder by applying a high temperature, for example, 300 to 700 占 폚 under pressure molding.

By the densification step, the thermoelectric material has a density of 70 to 100% of the theoretical density, preferably 95 to 100% of density, thereby exhibiting an increased ionic conductivity.

The compound of formula (1) as described above exhibits low thermal conductivity through control of the lattice structure and at the same time injects electrons and holes by selective doping treatment to improve the bekking coefficient offset phenomenon of the electron-hole to increase the bekking coefficient A high thermoelectric performance can be expected since the electric conductivity can be improved by optimizing the current density. Therefore, it has an application as an excellent thermoelectric material.

According to another embodiment of the present invention, there is provided a thermoelectric element obtained by molding a thermoelectric material by a method such as cutting.

The thermoelectric element may be a p-type thermoelectric element or an n-type thermoelectric element. Such a thermoelectric element means that the thermoelectric material is formed into a predetermined shape, for example, a rectangular parallelepiped shape.

On the other hand, the thermoelectric element may be an element capable of exhibiting a cooling effect by being applied with a current, or an element capable of exhibiting a power generation effect by a temperature difference.

Example

For the embodiment of the present invention, thermoelectric compound In ₄ Se _2.7 and In 3 _.9 Ba _0.1 Se _2.7 Cl _0.03 were synthesized by the following method using a polycrystalline method.

① In, Se, and Ba elements and InSe ₃ powder are weighed according to composition ratio, put into a quartz tube, and vacuum sealed.

② Heat treatment at 1100 ^o C for 24 hours and at 560 ^o C for 24 hours.

③ For the uniform composition ratio, the ingot is put into agate mortar and powdered, then put into a quartz tube and heat-treated at 560 ^° C for 24 hours.

(4) The ingot is put into agate mortar again, powder is put into the carbon mold, and spark plasma sintering is carried out at 450 ^o C under a pressure of 70 MPa for 5 minutes to produce a sintered body.

(5) Measure the thermal conductivity by processing the sintered body according to the standard specifications.

4 is a graph showing an electric resistance (ρ) according to temperature of thermoelectric materials In ₄ Se _2.7 (420) and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) according to an embodiment of the present invention. In addition, the In ₄ Se _2.7 and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 The figure shows the electrical resistance according to the polycrystalline temperature.

Referring to FIG. 4, the In ₄ Se _2.7 (420) shows a tendency to increase in electrical resistance as the temperature decreases. However, the In _3.9 Ba _0.1 Se _2.7 Cl _0.03 sample doped with Ba and Cl 410) significantly lowered the electrical resistance.

FIG. 5 is a graph showing a Seebeck coefficient (S) according to temperature of thermoelectric material In ₄ Se _2.7 (420) and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) according to an embodiment of the present invention. Referring to FIG. 5, as can be seen, the Seebeck coefficient of In _3.9 Ba _0.1 Se _2.7 Cl _0.03 is smaller than that of In ₄ Se _2.7 , which is understood to be due to the increase of metallicity by doping Ba and Cl.

6 is a graph showing a power factor (S ² σ) according to temperature of the thermoelectric material In ₄ Se _2.7 (420) and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) according to an embodiment of the present invention. Referring to FIG. 6, as a result of the power factor obtained from the measurement of electric resistance and the Seebeck coefficient, the electrical resistance is greatly reduced by Ba and Cl doping, and the power factor (S ² σ) of In _3.9 Ba _0.1 Se _2.7 Cl _0.03 Compared with samples not doped.

FIG. 7 is a graph showing the thermal conductivity (k) of thermoelectric materials In ₄ Se _2.7 (420) and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) according to an embodiment of the present invention. Referring to FIG. 7, as a result of the thermal conductivity, the thermal conductivity (k) of In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) is higher than that of In ₄ Se _{2.7 at} room temperature below 550 K, The thermal conductivity was lower. Accordingly, the results shown in Fig. 8 can be seen.

FIG. 8 is a graph showing the dimensionless figure of merit (ZT) according to the temperature of thermoelectric material In ₄ Se _2.7 (420) and In _3.9 Ba _0.1 Se _2.7 Cl _0.03 (410) according to an embodiment of the present invention. Referring to FIG. 8, the ZT value was increased 1.3 times at 680K by doping Ba and Cl compared to In ₄ Se _2.7 .

100: p-type material
110: n-type material
120: External power source
200: external heat source

Claims (21)

A compound to which alkali and alkaline earth metal for thermoelectric elements having a composition represented by the following formula (1) is added:
(Formula 1)
(A _1-a A ^' _a ) _4-x (B _{1 -b} B ^' _b ) _3-y H _δ
In this formula,
Wherein A is a Group 13 element, A 'is an element selected from the group consisting of an alkali metal or an alkaline earth metal,
B and B 'are different from each other, B is one element of S, Se and Te, B' is an element selected from one of Group 14, Group 15 and Group 16 elements,
H is an element selected from one of halogen elements,
Wherein a is 0? A <1,
B is 0? B <1,
X is 0 < x < 1,
Y is 0 < y < 1,
The delta is 0?? <0.1,
The compound has a two-dimensional layer structure, forms a covalent bond in the in-plane direction, and the interlayer bond forms at least one of an ionic bond and a Van der Waals bond . The method according to claim 1,
Wherein A is In or Ga. The method according to claim 1,
Wherein A 'is at least one selected from the group consisting of Ba, Sr, Ca, Na, and Li.
delete delete The method according to claim 1,
Wherein the alkali and alkaline earth metal have an orientation in an out-of-plane direction. The method according to claim 1,
Wherein the alkali and alkaline earth metals have lattice distortion in the in-plane direction.
The method according to claim 1,
If the current density of 10 ¹⁶ / cm ³ to 10 ²⁰ / cm ³ of the strong interactions with the electrons and the surrounding atoms alkali and alkaline earth metals, characterized in that the lattice strain of the compound occurs in a particular area is added compound.
9. The method of claim 8,
The method of increasing the current density may be any one of a method of changing physical properties by changing process conditions, a method of adding a doping element, or a method of inducing a defect. The alkali and alkaline earth metal &Lt; / RTI &gt;
delete The method according to claim 1,
Wherein A is one-dimensionally arranged in the lattice structure, wherein the alkali and alkaline earth metal are added.
12. The method of claim 11,
Characterized in that A 'or B', which is a doping component, is selectively added to the basic components A and B, to which an alkali and an alkaline earth metal are added.
delete delete A thermoelectric material produced by the polycrystalline synthesis method or the single crystal growth method according to any one of claims 1 to 3, 6 to 9, 11, and 12.
16. The method of claim 15,
Wherein the polycrystalline synthetic method is any one of an ampoule method, an arc melting method, and a solid state reaction.
16. The method of claim 15,
Wherein the single crystal growth method is any one of a metal flux method, a Bridgeman method, an optical floating zone method, and a vapor transport method.
18. The method of claim 17,
Wherein the thermoelectric element is cut perpendicularly to the growth direction when the thermoelectric element is formed.
delete 17. The method of claim 16,
The thermoelectric material produced by any one of the above-mentioned polycrystalline synthesis method of using an ampoule, an arc melting method and a solid state reaction is subjected to hot pressing, spark plasma sintering, Wherein the thermoelectric material is further densified using any one of the high-density processes. delete

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