WO2021112268A1 - Method for producing porous thermoelectric material, and thermoelectric element comprising porous thermoelectric material - Google Patents

Abstract

The present invention relates to a porous thermoelectric material including fine pores, a method for producing same, and a thermoelectric element comprising the porous thermoelectric material and thus having improved thermoelectric performance. The present invention allows the size of pores included in a thermoelectric material and the porosity thereof to be easily controlled and, due to the regular pores included in the produced thermoelectric material, does not significantly decrease the electrical conductivity and Seebeck coefficient and yet significantly reduces the thermal conductivity, and thus can improve thermoelectric performance.

Description

Method for manufacturing porous thermoelectric material and thermoelectric device including the porous thermoelectric material

The present invention relates to a porous thermoelectric material including micropores, a manufacturing method thereof, and a thermoelectric device having improved thermoelectric performance including the porous thermoelectric material.

Thermoelectric technology is generally a technology that directly converts thermal energy into electrical energy and electrical energy into thermal energy in a solid state, and is applied in thermoelectric power generation that converts thermal energy into electrical energy and thermoelectric cooling that converts electrical energy into thermal energy. The thermoelectric material used for such thermoelectric power generation and thermoelectric cooling improves the performance of the thermoelectric element as the thermoelectric characteristics increase. The thermoelectric performance is determined by thermoelectromotive force (V), Seebeck coefficient (α), Peltier coefficient (π), Thomson coefficient (τ), Nernst coefficient (Q), Ettingshausen coefficient (P), and electrical conductivity (σ) ), output factor (PF), figure of merit (Z), dimensionless figure of merit (ZT=α2σT/κ (where T is absolute temperature)), thermal conductivity (κ), Lorentz number (L), electrical resistivity ( ρ) and the like. In particular, the dimensionless figure of merit (ZT) is an important factor in determining the thermoelectric conversion energy efficiency. By manufacturing a thermoelectric device using a thermoelectric material having a high figure of merit (Z=α2σ/κ), the efficiency of cooling and power generation can be increased That is, the thermoelectric material has excellent thermoelectric performance as the Seebeck coefficient and electrical conductivity are high and the thermal conductivity is low.

On the other hand, thermoelectric materials are generally manufactured by dissolving and solidifying raw materials constituting the thermoelectric material to prepare a master alloy, then press-molding and sintering the same. These thermoelectric materials have only some differences in manufacturing methods and conditions, and it is difficult to secure desired levels of Seebeck coefficient, electrical conductivity, thermal conductivity, and the like.

The present invention has been devised to solve the above-described problems, and a novel manufacturing method of a thermoelectric material capable of simultaneously realizing performance improvement and reduced usage by reducing thermal conductivity while maintaining electrical conductivity by securing porosity in the thermoelectric material, and the method It is a technical task to provide a porous thermoelectric material manufactured by

Another technical object of the present invention is to provide a thermoelectric device including the aforementioned porous thermoelectric material.

Other objects and advantages of the present invention may be more clearly explained by the following detailed description and claims.

In order to achieve the above technical object, the present invention comprises the steps of (i) dissolving and solidifying a raw material for a thermoelectric material to form a master alloy; (ii) rapidly cooling the mother alloy to form a metal ribbon; (iii) mixing the metal ribbon with a polymer that is thermally decomposed at a predetermined temperature or higher and pulverizing it in an inert atmosphere; and (iv) sintering the pulverized product of step (iii) at a temperature higher than the thermal decomposition temperature of the polymer.

According to one embodiment of the present invention, the thermally decomposable polymer may be pyrolyzed by sintering to form a plurality of pores and removed.

According to one embodiment of the present invention, the thermally decomposable polymer may be selected from the group consisting of a thermoplastic polymer having a thermal decomposition temperature of 200 to 500 °C, a natural polymer, and a water-soluble polymer.

According to one embodiment of the present invention, the thermally decomposable polymer may have a residual carbon content of 5.0% or less after thermal decomposition.

According to an embodiment of the present invention, the thermally decomposable polymer is polymethyl methacrylate (PMMA), polybutyl methacrylate (PBMA), polybromonietide biphenyl (PBB), polyvinyl alcohol (PVA), And it may be at least one selected from the group consisting of ethyl cellulose (EC).

According to one embodiment of the present invention, the thermally decomposable polymer may be a spherical particle having _{an average particle diameter (D 50 ) of 5 to 50 μm.}

According to one embodiment of the present invention, the thermally decomposable polymer may be added in an amount of 0.1 to 2 parts by weight based on the total weight of the metal ribbon.

According to one embodiment of the present invention, in step (iv), the pulverized product of step (iii) may be put into a molding mold and sintered by hot pressing.

According to one embodiment of the present invention, the thermoelectric material may be at least one of a Bi-Te-based thermoelectric material and a Skuttrudite-based thermoelectric material.

According to one embodiment of the present invention, the porous thermoelectric material may have a porosity of 0.1 to 10%, a pore size of 5 to 50 μm, and a density of 90 to 99.9%.

In addition, the present invention provides a porous thermoelectric material manufactured by the above-described method.

In addition, the present invention is a first substrate; a second substrate facing the first substrate; a first electrode and a second electrode respectively disposed between the first substrate and the second substrate; a plurality of thermoelectric legs interposed between the first electrode and the second electrode; and a bonding material disposed between at least one of the first electrode and the thermoelectric leg and between the thermoelectric leg and the second electrode, wherein at least one of the plurality of thermoelectric legs includes the aforementioned porous thermoelectric material. provides

According to one embodiment of the present invention, the bonding material is Sn-based solder; Alternatively, it may have a composition including the Sn-based solder and a metal dendrite having an average branch length of 5 to 50 μm.

According to one embodiment of the present invention, the thermoelectric element may be applied to at least one of cooling, power generation, and a thin film sensor.

According to an embodiment of the present invention, a porous thermoelectric material uniformly containing micropore size and workability can be easily manufactured by using a pyrolyzable polymer as a pore former by a sintering process when manufacturing a thermoelectric material.

In addition, in the present invention, it is economical by reducing the amount of thermoelectric material used compared to non-porous thermoelectric materials, and the thermal conductivity is reduced without significantly lowering the electrical conductivity and Seebeck coefficient due to the regular pores contained in the thermoelectric material. performance can be improved.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a process flowchart of a manufacturing method according to an embodiment of the present invention.

2 is a schematic diagram of a thermoelectric material according to the manufacturing method of the present invention.

3 is an electron micrograph of a thermally decomposable polymer.

4 is a perspective view illustrating a thermoelectric element according to an embodiment of the present invention.

5 is a cross-sectional view of a thermoelectric device according to an embodiment of the present invention.

6 is a graph of the thermal decomposition rate according to the temperature of the thermally decomposable polymer.

7 is a power factor graph using the thermoelectric devices of Examples 1 to 12 and Comparative Example 1. FIG.

8 is a thermoelectric figure of merit graph using the thermoelectric devices of Examples 1 to 12 and Comparative Example 1. FIG.

<Short description of symbols>

100: thermoelectric element

11: insulating substrate

10a: first metal laminate

11a: conductive first substrate

12a: first insulating layer

20a: first electrode

30: porous thermoelectric leg

30a: P-type thermoelectric leg

30b: N-type thermoelectric leg

20b: second electrode

10b: second metal laminate

11b: conductive second substrate

12b: second insulating layer

40: bonding material

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Examples of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, and the scope of the present invention is not limited to the following examples It is not limited to an example. In this case, like reference numerals refer to like structures throughout this specification.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly specifically defined.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar. In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. And in the drawings, for convenience of description, the thickness of some layers and regions are exaggerated.

In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated. In addition, throughout the specification, "on" or "on" means that it includes not only the case where it is located above or below the target part, but also the case where there is another part in the middle, and the direction of gravity must be It does not mean that it is positioned above the reference. And, in the present specification, terms such as “first” and “second” do not indicate any order or importance, but are used to distinguish components from each other.

In addition, throughout the specification, when referred to as "planar", it means when the target part is viewed from above, and "in cross-section" means when viewed from the side when the cross-section of the target part is vertically cut.

In the present invention, when manufacturing a thermoelectric element, a pore former having a high thermal decomposition rate and easy particle size control is mixed with a thermoelectric material to improve thermoelectric properties using a thermoelectric material porous with a predetermined pore size and porosity. do.

As described above, when some pores are included in the thermoelectric material, it does not significantly affect the electrical conductivity, but may induce a decrease in thermal conductivity, thereby improving the thermoelectric performance index (ZT) value. Accordingly, it is possible to manufacture a superior thermoelectric element, and to reduce the amount of thermoelectric material used, thereby reducing costs.

In particular, in the present invention, a thermally decomposable polymer of an organic component that is thermally decomposed in the application temperature range of the sintering process is used as a pore former instead of the conventional complex pore former containing inorganic and organic components. Such a thermally decomposable polymer is mixed with a thermoelectric material powder (eg, a metal ribbon) and pulverized by a ball mill, and then the pulverized product is sintered through a hot press (HP). At this time, since the thermally decomposable polymer is an organic component having a high thermal decomposition rate, the diameter, porosity, etc. of the pores after sintering can be easily controlled by adjusting the particle diameter, content, shape, etc. of the thermally decomposable polymer used. In addition, since residual carbon hardly exists during thermal decomposition, when it is removed by thermal decomposition and/or carbonization by the sintering process, thermal conductivity is reduced through formation of micropores without deterioration of all properties of the thermoelectric element due to the residue and improved thermoelectric performance.

<Manufacturing method of porous thermoelectric material>

Hereinafter, a method for manufacturing a porous thermoelectric material according to an embodiment of the present invention will be described. However, it is not limited only by the following manufacturing method, and the steps of each process may be modified or selectively mixed as needed.

The present invention is to porousize a conventional thermoelectric material used as a thermoelectric material for thermoelectric power generation and cooling. Specifically, the raw material for a thermoelectric material is subjected to rapid solidification (RSP) to form a metal ribbon and then pulverized (e.g., ball mill method) and sintering (eg, hot press), but using a polymer that can be thermally decomposed within the application temperature range of the sintering process as a pore former to prepare a porous thermoelectric material.

For a preferred embodiment of the manufacturing method, (i) dissolving and solidifying a raw material for a thermoelectric material to form a master alloy ('S10 step'); (ii) forming a metal ribbon by rapidly cooling the master alloy ('S20 step'); (iii) mixing the metal ribbon and the thermally decomposable polymer and pulverizing them in an inert atmosphere ('S30 step'); and (iv) sintering the pulverized product of step (iii) at a temperature higher than the thermal decomposition temperature of the polymer ('S40 step').

Meanwhile, FIG. 1 is a conceptual diagram illustrating a method of manufacturing a porous thermoelectric material according to the present invention in each step. Hereinafter, with reference to FIG. 1, the manufacturing method is divided into each process step and described as follows.

(i) master alloy formation step ('S10 step')

This step is a step of mixing, dissolving and solidifying the raw materials of the thermoelectric material according to the stoichiometric ratio constituting the porous thermoelectric material to form a master alloy.

As the thermoelectric material according to the present invention, a conventional thermoelectric material known in the art may be used, and the thermoelectric material is not particularly limited. Non-limiting examples of usable thermoelectric materials include Bi-Te-based, Co-Sb-based, Pb-Te-based, Ge-Tb-based, Si-Ge-based, Sb-Te-based, Sm-Co-based, and transition metal silicide-based materials. , Skuttrudite, Silicide, Half heusler, or a combination thereof. Preferably, it may be a Bi-Te-based or Skuttrudite-based thermoelectric material.

For example, in the case of manufacturing a Bi-Te-based thermoelectric material, Bi, Te, Sb and Se may be used as raw materials for the thermoelectric material in step S10, which may be different depending on the composition for cooling/power generation.

As a usable raw material for a thermoelectric material, Bi and Te are the main components, and depending on the n-type and the p-type, each may have a composition additionally including a Se or Sb component. In one example, the Bi and Te raw material is, may be mixed in a ratio according to the stoichiometric composition of Bi ₂ Te _{3 Wh 0.2,} and preferably be a Bi ₂ Te _{3 Wh 0.15.}

In one embodiment of the present invention, the raw material for a thermoelectric material may include (i) at least one first element selected from the group consisting of Bi and Sb; and a raw material having a composition including one or more second elements selected from the group consisting of Te and Se. More specifically, when the raw material for the n-type thermoelectric material has a Bi-Te-Se-based alloy composition, 50 to 55 wt% of Bi, 40 to 45 wt% of Te, and 3 to 4 wt% of Se based on 100 wt% of the total It may be a composition comprising. In addition, when the raw material for the p-type thermoelectric material is a Bi-Sb-Te alloy composition, the composition may include 10 to 15 wt% of Bi, 25 to 30 wt% of Sb, and 55 to 60 wt% of Te based on 100 wt% of the total. have.

In the present invention, a doping element powder may be added to the composition of the thermoelectric material to be manufactured.

Since the dopant is introduced to allow the Bi-Te-based thermoelectric material to have n-type or p-type characteristics, conventional components in the art that can be used for the n-type or p-type thermoelectric material may be used without limitation. . For example, it may be one or more metals selected from the group consisting of Al, Sn, Mn, Ag, Cu, and Ga. By doping the aforementioned metal component, thermoelectric performance may be improved. At this time, the content of the at least one metal to be doped is not particularly limited, and may be, for example, in the range of 0.001 to 1% by weight based on the total weight.

In the present invention, the size and shape of the thermoelectric material is not particularly limited, but may be in the form of a mass of about 2 to 5 mm in size. In addition, the purity of the thermoelectric material is preferably 5N or more high purity.

For a specific example of step S10, after the above-described raw material for thermoelectric material is charged into a quartz tube, a quartz tube in a vacuum state is charged into a furnace at a temperature of 600 to 1000° C. for 1-10 hours for 10 hours. Stir and dissolve at a rate of ~15 times/min to form the master alloy.

In order to manufacture a ribbon using the rapid solidification method (RSP), it is necessary to prepare a master alloy of a _{uniform thermoelectric material (eg, Bi 2} -Te _{3 system).} Accordingly, the master alloy may be manufactured in a size of Φ 30 * 100 mm or approximately Φ 20 ~ 30 * 100 ~ 150 mm. It may be a Bi-Te-based alloy or a Skuttrudite-based alloy having a high purity of 5N or higher manufactured through the step S10.

(ii) metal ribbon forming step ('S20 step')

In this step, a metal ribbon (eg, Bi-Te-based) having a complex microstructure is prepared through the rapid solidification method (R.S.P) of the mother alloy of the thermoelectric material obtained in the previous step.

For one specific example of step S20, after charging the master alloy ingot into a nozzle installed in the melt spinning equipment, it is completely dissolved using a heating element that can supply heat and continuously maintain it to form a melt, and then to the melt By pressurizing and spraying an inert gas, the melt is brought into contact with the surface of a rotating high-speed rotating wheel to rapidly cool it. Through this, a metal ribbon of a thermoelectric material (eg, Bi-Te-based) is formed.

Here, the heating element is not particularly limited as long as it can continuously supply and maintain heat, and a conventional resistance heating element known in the art may be used. As an example, a resistance heating element that generates heat by receiving a current may be used. As a non-limiting example of the usable resistance heating element, the temperature may be controlled by an electric furnace type heater, for example, a graphite heater.

At this time, the temperature range at which the resistance heating element generates heat is not particularly limited as long as it is a range capable of completely dissolving the master alloy of the thermoelectric material (Bi-Te type), for example, 500 to 800°C, preferably 600 to 700°C. will become

In addition, the type or pressurization range of the inert gas is also not particularly limited, and for example, it is preferable to pressurize the inert gas in the range of 0.1 to 0.5 MPa using argon gas or the like.

In the step S20, the high-speed rotating wheel in contact with the melt may use a conventional wheel known in the art, for example, a copper wheel (Cu wheel). Here, the rotation speed of the high-speed rotating wheel is not particularly limited, and for example, the linear speed of the wheel may be in the range of 5 to 50 m/s. When the above conditions are satisfied, the alloy ribbon of the thermoelectric material having a thin thickness and a microstructure may be formed while the melt in contact with the surface of the wheel is rapidly cooled.

In the present invention, by controlling the cooling rate of the dissolved master alloy, uniform particle size control is possible, and when the cooling rate is generally slow, nano-sized amorphous powder can be prepared, or fine particle powder can be prepared. . In addition, according to the concentration and type of the raw material, it can be manufactured under different manufacturing conditions.

The master alloy that has undergone the above-described process does not become crystalline through a rapid cooling (RSP) process, but is solidified in a state in which an amorphous structure and a crystalline structure are mixed. At this time, if the rapid cooling rate is very fast, it is manufactured in the form of a ribbon, but if the cooling rate is adjusted, powder having a size of several hundred nanometers can be prepared in the form of a half-ribbon simply connected.

A thin-thick thermoelectric material (eg, Bi-Te-based) ribbon may be formed through the rapid cooling in step S20 described above. As an example, the length of the prepared metal ribbon is 5 to 15 mm, the width is 0.5 to 5 mm, and the thickness may be 10 μm or less.

(iii) crushing / crushing step of metal ribbon ('S30 step')

In this step, when the brittle ribbon-like raw material that is rapidly solidified by direct spraying of the dissolved master alloy is crushed, a predetermined thermally decomposable polymer is added to form a nano-sized amorphous fine powder having a fine particle size and shape and thermal decomposition A pulverized product in which the polymer is uniformly mixed is prepared.

At this time, in the present invention, in order to manufacture a porous thermoelectric material, a pyrolytic polymer that is thermally decomposed at a predetermined temperature together with the above-described metal ribbon is added as a pore former and pulverized.

A conventional pore former uses a complex component including both an organic component and an inorganic component. Since the organic component is removed from the pore former after heat treatment to form a pore structure, while the inorganic component remains in the final thermoelectric material, the performance of the thermoelectric material may be deteriorated due to unwanted metal residues. In addition, since the conventional pore former contains inorganic components, it is difficult to control the desired pore size or pore size.

In contrast, the thermally decomposable polymer employed in the present invention is an organic component that is thermally decomposed by forming and sintering processes to be described later without performing a separate heat treatment process to form a plurality of pores and removed at the same time. This thermally decomposable polymer is a pore former that forms a predetermined pore size and pore size in the thermoelectric material, and since the content of residual carbon after sintering is minimized, degradation of the performance of the thermoelectric material due to the residue can be fundamentally prevented. have. In addition, since the thermally decomposable polymer is an organic component that is 100% thermally decomposed during thermal decomposition, the size, shape and porosity of the pores after sintering can be easily controlled by adjusting the average particle diameter, content, shape, etc. of the polymer used.

As long as the thermally decomposable polymer is a material that is thermally decomposed and carbonized and removed by the application temperature of the sintering process to be described later, its components, content, shape, etc. are not particularly limited, and conventional polymers, copolymers, resins, etc. known in the art Can be used. In addition, the use of a monomolecular compound also falls within the scope of the present invention.

For example, the thermally decomposable polymer may be selected from the group consisting of a thermoplastic polymer having a thermal decomposition temperature of 200 to 500°C, a natural polymer, and a water-soluble polymer. In addition, the thermally decomposable polymer may have a residual carbon content of 5.0% or less after thermal decomposition by sintering, specifically 0 to 1.0% or less, more specifically 0 to 0.5% or less based on 100% of the total of the thermally decomposable polymer. .

Non-limiting examples of thermally degradable polymers that can be used include polymethyl methacrylate (PMMA), polybutyl methacrylate (PBMA), polybromonietide biphenyl (PBB), polyvinyl alcohol (PVA), ethyl cellulose. (EC), or a mixture thereof. In addition, polyethylene, polypropylene, glucose, fructose, sucrose, xylose, starch, cellulose, etc. can also be used. PMMA, PBMA, or a mixture thereof having a relatively low decomposition temperature and no residual carbon is preferred. In particular, PMMA, PBMA, etc. are 100% pyrolyzed at about 400 ℃, so almost no residue is generated.

In the present invention, the pore diameter, porosity, pore shape, etc. formed after sintering can be easily adjusted according to the particle diameter, shape, and content thereof of the thermally decomposable polymer used.

Accordingly, the size of the thermally decomposable polymer is not particularly limited, and may be appropriately adjusted in consideration of the porosity and pore size to be formed. For example, the average particle diameter (D ₅₀ ) of the thermally decomposable polymer may be 5 to 50 μm, specifically 5 to 30 μm. And the shape of the thermally decomposable polymer is not particularly limited, and may be, for example, a spherical shape, a triangular or more polygonal shape, a needle shape, a plate shape, or an amorphous shape. It is preferably a spherical particle, and more preferably a spherical particle having excellent sphericity.

In addition, the amount of the thermally decomposable polymer is not particularly limited, and may be added in an amount of 0.1 to 2 parts by weight based on the total weight of the pulverized metal ribbon, for example.

The pulverization process of step S30 may be performed without limitation, and may be pulverized using a ball mill method, for example, a conventional pulverization/pulverization process known in the art. At this time, the particle size of the pulverized powder is not particularly limited, and may be appropriately adjusted within a range known in the art. For example, the average particle diameter of the pulverized product in which the thermoelectric material (eg, Bi-Te-based) and the thermally decomposable polymer are mixed may be adjusted to 100 μm or less, preferably in the range of 10 to 100 μm.

In order to control the oxidation degree of the metal ribbon, the above-described crushing/grinding process is performed in an inert atmosphere. At this time, the type or pressure range of the inert gas is not particularly limited, and for example, nitrogen gas, argon gas, or a mixture thereof may be used.

As described above, as the pulverization is carried out under the condition in which oxygen is not included, the oxygen content in the pulverized powder may be reduced to control the oxidation degree to be low. For example, the pulverized product according to the present invention can reduce the oxygen content by about 30% or more, specifically 30 to 45%, compared to the pulverized product carried out under atmospheric conditions containing oxygen, preferably the The oxygen content in the pulverized product may be controlled to 0.03% or less, preferably in the range of 0.02 to 0.03%.

(iv) forming and sintering step ('S40 step')

In this step, a preform is manufactured by extruding a mixture of the pulverized material of the metal ribbon obtained in the above step and a thermally decomposable polymer, and then, a high-density thermoelectric material is manufactured through pressure sintering.

In this step S40, a molded body having a predetermined shape is manufactured to ensure high density in the pressure sintering process.

The compression process may use a conventional method known in the art, for example, it is preferable to use a cold press or a compressor. In addition, the compression conditions are not particularly limited, and may be appropriately adjusted under conventional compression conditions known in the art.

Then, the green body is sintered to prepare a thermoelectric material having high density and porosity.

As the pressure sintering method that can be used in the present invention, there is a hot press (HP) or the like.

Here, the pressure sintering conditions are not particularly limited, and for example, sintering can be carried out using a Hot Press device under a pressure of 20 to 80 MPa, specifically, a pressure of 40 to 70 MPa, at a temperature of 200 to 500° C. for 40 to 80 minutes. have. If it is smaller than the above-mentioned conditions, it is impossible to have the desired pore size and porosity, and if it exceeds the above-mentioned conditions, the vapor pressure of Te is high and volatilized, making it unsuitable for the intended composition. high.

Meanwhile, FIG. 2 is a schematic diagram showing the structural change of a thermoelectric material including a thermally decomposable polymer according to the molding and sintering steps.

When the step S40 is described with reference to FIG. 2, FIG. 2(a) is a preform manufactured to a predetermined standard through an extrusion process, wherein the preform has a predetermined particle size and shape in a matrix made of a thermoelectric material. It shows a structure in which the polymer is randomly distributed.

Then, when the preform is sintered using a hot press (HP) device, the volume of the polymer is decreased as the thermally decomposable polymer is gradually thermally decomposed and/or carbonized as the temperature rises (see Fig. 2(b)), As a result, when the thermal decomposition of the polymer is completed, a porous structure having a plurality of pores is formed at the location where the polymer is removed (see FIG. 2(c)). The plurality of pores may be regularly distributed or randomly formed, and may have a closed type that is not connected to each other or an open pore structure that is three-dimensionally connected to each other.

The porous thermoelectric material of the present invention prepared through the above-described manufacturing method may have a micropore size and uniform porosity.

For example, the porosity of the porous thermoelectric material may be 0.1 to 10%, specifically 0.5 to 5%. In addition, the pore size included in the porous thermoelectric material can be easily adjusted according to the average particle diameter of the thermally decomposable polymer used. As an example, the pore size may be 5 to 50 μm.

In another embodiment, the porous thermoelectric material may have a relative density of 90 to 99.9%, specifically 92% to 99.9%. In addition, since the pulverization process was performed under an inert gas atmosphere, the degree of oxidation is controlled, so that the oxygen content in the thermoelectric material can be controlled to a predetermined range or less.

<Thermoelectric element>

The thermoelectric element of the present invention is provided with the above-described porous thermoelectric material, and includes all elements for thermoelectric power generation and/or cooling.

A thermoelectric element according to an embodiment of the present invention includes two substrates facing each other; conductive electrodes and a plurality of thermoelectric materials (thermoelectric legs) respectively disposed on upper and lower portions of the two substrates; and a bonding layer disposed between the thermoelectric material and the conductive electrode, wherein at least one of the plurality of thermoelectric legs includes the aforementioned porous thermoelectric material.

Hereinafter, preferred embodiments of the thermoelectric element according to the present invention will be described with reference to the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

4 is a perspective view schematically showing the structure of the thermoelectric element 100 according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view of the thermoelectric element 100 .

4 and 5 , the thermoelectric element 100 includes: a first substrate 11; a second substrate 11 facing the first substrate 11; a first electrode 20a and a second electrode 20b respectively disposed between the first substrate 11 and the second substrate 11; a plurality of thermoelectric legs 30 interposed between the first electrode 20a and the second electrode 20b; and a bonding material 40 disposed between the first electrode 20a and the thermoelectric leg 30 and between the thermoelectric leg 30 and the second electrode 20b.

Hereinafter, each configuration of the thermoelectric element will be described in detail as follows.

The first substrate 11 and the second substrate 11 each generate an exothermic or endothermic reaction when power is applied to the thermoelectric element 100 , and may be made of a conventional electrically insulating material known in the art. For example, each of the first substrate 11 and the second substrate 11 may be a ceramic substrate composed of one or more compositions of _{Al 2} O ₃ , AlN, SiC, and ZrO _{2 .} Alternatively, it may be composed of a high heat-resistance insulating resin or engineering plastic.

In addition, the first substrate 11 and the second substrate 11 may be a metal substrate made of a conventional conductive metal material known in the art. For example, the first substrate 11 and the second substrate 11 may be formed of at least one metal among aluminum (Al), zinc (Zn), copper (Cu), nickel (Ni), and cobalt (Co), respectively. may include.

In this case, when the electrodes 20a and 20b are directly disposed on the first substrate 11 and the second substrate 11, they become electrically conductive, so an electrically insulating material must be interposed therebetween. Accordingly, a first insulating layer (not shown) is formed on one surface of the first substrate 11 on which the first electrode 20a is disposed, and the second substrate 11 on which the second electrode 20b is disposed. A second insulating layer (not shown) is formed on one surface, and the first insulating layer and the second insulating layer are disposed to face each other.

The first insulating layer and the second insulating layer may be the same as or different from each other, and an electrically insulating material that is easy to form a film may be used. For example, the insulating resin may be used alone or a mixture of the insulating resin and the ceramic filler (powder) may be included. For example, each of the first insulating layer and the second insulating layer may be an epoxy resin layer including a ceramic filler.

Each of the first substrate 11 and the second substrate 11 may have a flat plate shape, and the size or thickness thereof is not particularly limited. For example, the thickness of each of the first substrate 11 and the second substrate 11 may be 0.5 to 2 mm, preferably 0.5 to 1.5 mm, more preferably 0.6 to 0.8 mm.

In this case, the positions of the heat absorption and heat generation of the substrate can be changed according to the direction of the current. One of the two substrates is a cold side substrate on which an endothermic reaction occurs, and a heat dissipation pad may be applied to this substrate. The heat dissipation pad may be formed of a silicone polymer or an acrylic polymer, and has a thermal conductivity in the range of 0.5 to 5.0 W/mk, thereby maximizing heat transfer efficiency. It can also act as an insulator. Also, the other one of the two substrates may be a heating part substrate (hot side).

A first electrode 20a and a second electrode 20b are respectively disposed on the first substrate 11 and the second substrate 11 disposed to face each other. That is, the second electrode 20b is disposed at a position opposite to the first electrode 20a.

The material of the first electrode 20a and the second electrode 20b is not particularly limited, and a material used as an electrode in the art may be used without limitation. For example, the first electrode 20a and the second electrode 20b are the same as or different from each other, and each independently aluminum (Al), zinc (Zn), copper (Cu), nickel (Ni), and cobalt. At least one metal of (Co) can be used. In addition, nickel, gold, silver, titanium, etc. may be further included. Its size can also be adjusted in various ways. Preferably, it may be a copper (Cu) electrode.

The first electrode 20a and the second electrode 20b may be patterned in a predetermined shape, and the shape is not particularly limited. In addition, as a method for patterning the first electrode 20a and the second electrode 20b, a conventionally known patterning method may be used without limitation. For example, a lift-off semiconductor process, a deposition method, a photolithography method, etc. may be used.

A plurality of thermoelectric legs 30 are interposed between the first electrode 20a and the second electrode 20b.

Referring to FIG. 1 , the thermoelectric leg 30 includes a plurality of P-type thermoelectric legs 30a and N-type thermoelectric legs 30b, respectively, which are alternately disposed in one direction. As described above, the P-type thermoelectric leg 30a and the N-type thermoelectric leg 30b adjacent in one direction are electrically connected in series with the first electrode 20a and the second electrode 20b, respectively. Each of these thermoelectric legs 30a and 30b includes a thermoelectric semiconductor substrate.

The thermoelectric semiconductor included in the thermoelectric leg 30 may be formed of a conventional thermoelectric material in the art that generates electricity when a temperature difference occurs at both ends when electricity is applied, or when a temperature difference occurs at both ends, and the thermoelectric As long as the material has a regular pore size and porosity having a porosity, it is not particularly limited to a component thereof. For example, one or more thermoelectric semiconductors including at least one element selected from the group consisting of a transition metal, a rare earth element, a group 13 element, a group 14 element, a group 15 element, and a group 16 element may be used. Here, examples of rare earth elements include Y, Ce, La, and the like, and examples of transition metals include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, It may be one or more of Zn, Ag, and Re, and examples of the group 13 element may include at least one of B, Al, Ga, and In, and examples of the group 14 element include C, Si, Ge, Sn, and Pb. may be one or more of the group 15 elements, and examples of the group 15 elements may be at least one of P, As, Sb, and Bi, and examples of the group 16 elements may include one or more of S, Se, and Te.

Usable thermoelectric semiconductors include bismuth (Bi), telerium (Te), cobalt (Co), samarium (Sb), indium (In), and cerium (Ce) having a composition containing at least two or more of cerium (Ce). and, non-limiting examples thereof include Bi-Te-based, Co-Sb-based, Pb-Te-based, Ge-Tb-based, Si-Ge-based, Sb-Te-based, Sm-Co-based, transition metal silicide-based, and Suku. Terdite (Skuttrudite)-based, silicide (Silicide)-based, half whistler (Half heusler), or a combination thereof, and the like. As a specific example, as the Bi-Te-based thermoelectric semiconductor, a (Bi,Sb) ₂ (Te, Se) ₃ thermoelectric semiconductor in which Sb and Se are used as dopants may be exemplified, and as the Co-Sb-based thermoelectric semiconductor, CoSb may be exemplified. _Three -type thermoelectric semiconductor can be exemplified, and AgSbTe ₂ and CuSbTe ₂ can be exemplified as the Sb-Te-based thermoelectric semiconductor, and PbTe, (PbTe)mAgSbTe ₂ and the like can be exemplified as the Pb-Te-based thermoelectric semiconductor. Preferably, it may be composed of a Bi-Te-based or CoSb-based thermoelectric material.

As for the components and structures of the porous thermoelectric material constituting the thermoelectric leg, the description of the porous thermoelectric material shown in FIG. 1 may be applied as it is, and thus a separate description thereof will be omitted. The thermoelectric leg 30 including the P-type thermoelectric leg 30a and the N-type thermoelectric leg 30b may be formed in a predetermined shape, for example, a rectangular parallelepiped shape by a method such as cutting, and applied to a thermoelectric element.

The thermoelectric element 100 according to the present invention includes: between the first electrode 20a and the thermoelectric leg 30 ; and a bonding material 40 disposed between at least one, preferably both, of the thermoelectric leg 30 and the second electrode 20b.

As the bonding material 40, conventional bonding material components known in the art may be used without limitation, and Sn-based solder may be used as an example.

For example, the bonding material 40 may include Sn; A first Sn-based solder composition comprising at least one of Pb, Al, and Zn as a first metal; Alternatively, the first solder may be formed of a Sn-based second solder composition including a second metal of at least one of Ni, Co, and Ag.

For another example, the bonding material 40 may include a metal powder having a dendrite shape in a conventional Sn-based solder known in the art.

Such a metal dendrite is a conductive metal particle having a single main axis and having a shape in which a plurality of branched phases branch vertically or obliquely from the main axis and grow two-dimensionally or three-dimensionally. At this time, a main axis|shaft represents the rod-shaped part used as the base from which several branches branch. The average branched length of these metal dendrites is not particularly limited, and may be, for example, 5 to 50 µm, preferably 5 to 30 µm.

For example, in the metal dendrite, the length of the major axis of the main axis means the total length of the main axis, and may be 5 to 50 µm, specifically 5 to 30 µm. Also, in the metal dendrite, the longest branching length among the plurality of branched phases may be 5 to 30 μm, and specifically, 10 to 25 μm. And the number of branches (number of branches/long diameter) with respect to the major axis of the main axis may be 0.5 to 10 pieces/μm, specifically 1 to 8 pieces/μm. The average particle diameter (D ₅₀ ) of the metal dendrites refers to a two-dimensional size including the major axis length of the dendrites, and may be, for example, 5 to 50 µm, specifically 5 to 30 µm. In addition, the main axis thickness of the dendrite may be 0.3 to 5.0 ㎛. The metal dendrite has a higher specific surface area than the spherical metal particles as it has the above-described structural characteristics. In another embodiment of the present invention, the metal dendrite may have a specific surface area measured by BET measurement of 0.4 to 3.0 m ² /g, specifically 0.5 to 2.0 m ² /g. In addition, the apparent density of the metal dendrite may be 0.5 to 1.5 g/cm 3 , and an oxygen content of 0.35% or less is suitable.

The metal dendrite is not particularly limited to the metal material to be used as long as the above-described structural characteristics and physical properties are satisfied. As a preferred example, copper dendrite (Cu dendrite), silver (Ag) coated copper dendrite (Ag coated Cu dendrite), or a mixture thereof may be used. In particular, copper (Cu) is preferable because it is economical as well as similar in electrical conductivity to silver (Ag).

In the bonding material according to the present invention, the content of the metal dendrite is not particularly limited, and may be included, for example, in an amount of 1 to 40% by weight, preferably 5 to 30% by weight, based on the total weight of the bonding material.

For example, when copper dendrite having an average branch length of 5 to 20 μm is used as the metal dendrite, the content of such copper dendrite is 1 to 40 weight based on the total weight of the bonding material. %, preferably 5 to 30% by weight.

In another embodiment, when using a silver (Ag)-coated copper dendrite having an average branch length of 5 to 20 μm, preferably 10 to 30 μm, as the metal dendrite, relative to the total weight of the bonding material It is preferably included in the range of 10 to 30% by weight.

In the present invention, metal dendrites can be used alone as a bonding material component, and in addition, metal powders having various materials, particle sizes, and/or shapes are further included and mixed as a bonding material component also falls within the scope of the present invention. For example, one or more types of metal powder such as the above-described metal dendrite and spherical shape, needle shape, flake shape, and amorphous shape may be mixed.

Sn-based solder mixed with the above-described metal dendrite may use a conventional Sn-based solder component known in the art. For a preferred example, the Sn-based solder is Sn; It may have a composition including at least one metal among Pb, Al, and Zn. .

Optionally, the thermoelectric element 100 of the present invention may be disposed between the first electrode 20a and the thermoelectric leg 30; and a diffusion barrier layer (not shown) disposed between the thermoelectric leg 30 and the second electrode 20b. Such a diffusion barrier layer can be used without limitation, a conventional component known in the art, for example, tantalum (Ta), tungsten (W), molybdenum (Mo), and includes at least one selected from the group consisting of titanium (Ti) can do.

In the thermoelectric element 100 according to an embodiment of the present invention, the first electrode 20a and the second electrode 20b may be electrically connected to a power supply source. When a DC voltage is applied from the outside, the holes of the p-type thermoelectric leg 30a and the electrons of the n-type thermoelectric leg 30b move, thereby generating heat and endothermic heat at both ends of the thermoelectric leg.

In the thermoelectric element 100 according to another embodiment of the present invention, at least one of the first electrode 20a and the second electrode 20b may be exposed to a heat source. When heat is supplied by an external heat source, electrons and holes move and current flows in the thermoelectric element to generate electricity.

The thermoelectric element according to the above-described embodiment may be manufactured according to a method known in the art. For an embodiment of such a manufacturing method, (a) preparing two insulating substrates; (b) forming a first electrode and a second electrode on one surface of the two insulating substrates, respectively; and (c) disposing the first electrode and the second electrode to face each other, arranging a plurality of porous thermoelectric legs between them, and bonding them using the bonding material. In this case, the manufacturing method is not limited only by the following method or sequence, and steps of each process may be modified or selectively mixed as needed.

As an example of a method of manufacturing a thermoelectric leg using a thermoelectric material in the manufacturing method, a Bi-Te or Skuttrudite-based thermoelectric material is melted using RSP, then a metal ribbon is manufactured, and the metal The ribbon and the thermally decomposable polymer are mixed in a predetermined range and then pulverized, and the pulverized product is molded and hot press sintered to form a porous sintered body. Then, slicing is performed according to the target thickness, and lapping is performed according to the final thickness to adjust the height of the material to within 1/100. After surface coating of Co, Ni, Cr, and W is performed on the surface of the thermoelectric material whose step is controlled, dicing is finally performed according to the size of the material to manufacture the thermoelectric leg.

In addition, a ceramic substrate or a metal substrate is used as the substrate, and a Cu electrode pattern is formed on one surface of the substrate, and then is fixed by heat treatment. In this case, when a metal substrate is used, an insulating resin or a mixture of the insulating resin and a ceramic filler (powder) is applied on one surface of the metal substrate on which the electrode is disposed to prevent conduction.

A plurality of thermoelectric legs are disposed and bonded between the first electrode and the second electrode using the thermoelectric legs and the substrate prepared as described above. Examples of such a bonding material include Sn-based solder; Alternatively, a Sn-based solder paste including the Sn solder and metal dendrite in a predetermined mixing ratio is applied. As a specific example of the bonding step, a bonding material paste is applied to a predetermined thickness according to the pattern of the first electrode 20a, and n-type and p-type thermoelectric legs are arranged thereon. After that, in the case of the opposite electrode (second electrode), the final configuration is completed by placing the previously manufactured n-type and p-type thermoelectric legs in an arrangement in a state where only the bonding material is applied. Then, after heat treatment at 300 to 500 ℃ final bonding, the wire is connected to complete the manufacture of the thermoelectric element.

The above-described thermoelectric leg and/or a thermoelectric element including the same may be provided in a thermoelectric cooling system, a thermoelectric power generation system, and/or a thin-film sensor, and may be applied to at least one of cooling, power generation, and thin-film sensor.

For example, such a thermoelectric power generation system refers to a conventional system that generates power using a temperature difference, and for example, a waste heat furnace, a vehicle thermoelectric power generation system, a solar thermoelectric power generation system, and the like. In addition, the thermoelectric cooling system may include, but is not limited to, a micro cooling system, a general-purpose cooling device, an air conditioner, a waste heat power generation system, and the like. In addition, the thin-film sensor includes all sensor fields using micro-power, such as a thin-film thermoelectric element.

Each configuration and manufacturing method in the field of the thermoelectric power generation system, the thermoelectric cooling system, and/or the thin film type sensor is known in the art, and detailed description thereof will be omitted herein. Also, in the present invention, even though they are denoted by the same reference numerals, they may have different configurations.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited by the following examples.

[Example 1] Preparation of porous thermoelectric material

A thermoelectric material containing Bi, Te, Sb, and Se having a high purity of 4N or higher was prepared in the form of a mass of about 2-5 mm. In the case of p-type, it was made to have a ternary system such as Bi, Te, and Sb. A Φ 30 * 100 mm master alloy ingot was prepared by charging the thermoelectric material with a quartz tube (Quartz) into the locking furnace, stirring and dissolving at 650 to 750 ° C for 2 to 4 hours at a rate of 10 times/min. After that, the master alloy ingot is charged into a nozzle installed in the melt spinning equipment and completely melted at a temperature of about 700 ° C. using a resistance heating element (a structure that surrounds the nozzle as a graphite heater) to form a melt, and then 0.1 ~ By spraying under pressure at 0.5 MPa, a Bi-Te-based metal ribbon was formed as it was rapidly cooled in contact with the surface of a rotating copper wheel (Cu wheel). At this time, the rotational speed of the copper wheel proceeded to 1000 rpm. Thereafter, the formed metal ribbon and a thermally decomposable polymer [polymethyl methacrylate (PMMA) having an average particle diameter of 5 μm] were mixed and pulverized to an average particle diameter of 100 μm or less using a ball mill method in an argon (Ar) atmosphere. The pulverized product was heated to about 525° C. using hot press sintering at a temperature increase rate of 7° C./min, and then sintered by holding for 1 hour and maintaining a pressure of 20 MPa. As a result, a porous thermoelectric material having a high density of 99% or more was manufactured.

[Examples 2 to 12] Preparation of porous thermoelectric material

Examples 2 to 12 were carried out in the same manner as in Example 1, except that during hot press sintering, the pulverized product of the thermoelectric material and polymethyl methacrylate (PMMA) were mixed and used in the composition shown in Table 1 below. Each thermoelectric material was prepared.

	pyrolytic polymer
	Addition amount (parts by weight)	Average particle size (㎛)
Comparative Example 1	0.00	-
Example 1	0.10	5.00
Example 2		20.00
Example 3		50.00
Example 4	0.50	5.00
Example 5		20.00
Example 6		50.00
Example 7	1.00	5.00
Example 8		20.00
Example 9		50.00
Example 10	2.00	5.00
Example 11		20.00
Example 12		50.00
Thermally degradable polymer: PMMA (specific gravity: 1.20 g/cm 3 )

[Comparative Example 1] Preparation of non-porous thermoelectric material

A thermoelectric material containing Bi, Te, Sb, and Se having a high purity of 4N or higher was prepared in the form of a mass of about 2-5 mm. In the case of p-type, it was made to have a ternary system such as Bi, Te, and Sb. A Φ 30 * 100 mm master alloy ingot was prepared by charging the thermoelectric material with a quartz tube (Quartz) into a locking furnace, and then stirring and dissolving at 650 to 750 ° C for 2 to 4 hours at a rate of 10 times/min. After that, the master alloy ingot is charged into a nozzle installed in the melt spinning equipment and completely melted at a temperature of about 700 ° C. using a resistance heating element (a structure that surrounds the nozzle as a graphite heater) to form a melt, and then 0.1 ~ By spraying under pressure at 0.5 MPa, a Bi-Te-based metal ribbon was formed as it was rapidly cooled in contact with the surface of a rotating copper wheel (Cu wheel). At this time, the rotational speed of the copper wheel proceeded to 1000rpm.

Thereafter, the formed metal ribbon was pulverized to have an average particle diameter of 100 μm or less by using a ball mill method in an argon (Ar) atmosphere. A non-porous thermoelectric material having a high density of 99% or more as a result of sintering the pulverized powder by heating the pulverized powder at a temperature increase rate of 7°C/min to about 525°C using hot press sintering, maintaining it for 1 hour and maintaining a pressure of 20MPa was prepared.

[Experimental Example 1] Evaluation of physical properties of thermally decomposable polymers

Meanwhile, FIG. 3 is an electron micrograph of the thermally decomposable polymer used in Examples 3, 6, 9, and 12 of the present application. It was confirmed that the average particle diameter was about 50 μm class spherical particles.

In addition, PMMA, PBMA, PVB, and EC used as thermally decomposable polymers in the present invention were evaluated for thermal decomposition characteristics according to temperature, respectively, and the results are shown in FIG. 6 below.

As a result of the experiment, it was confirmed that the thermal decomposition of PMMA and PBMA was completed without residual carbon when the temperature was raised to about 400°C (see FIG. 6 below).

[Experimental Example 2] Density evaluation of thermoelectric materials

For each thermoelectric material prepared in Examples 1 to 12 and Comparative Example 1, the densities before and after sintering were measured by Archimedes' method, respectively, and the results are shown in Table 2.

	pyrolytic polymer		Density after sintering (g/cm 3 )	Relative density (%)
	Addition amount (parts by weight)	Average particle size (㎛)
Comparative Example 1	0.00	-	6.84	-
Example 1	0.10	5.00	6.82	99.71
Example 2		20.00	6.81	99.56
Example 3		50.00	6.81	99.56
Example 4	0.50	5.00	6.79	99.27
Example 5		20.00	6.78	99.12
Example 6		50.00	6.76	98.83
Example 7	1.00	5.00	6.77	98.98
Example 8		20.00	6.76	98.83
Example 9		50.00	6.72	98.25
Example 10	2.00	5.00	6.50	95.03
Example 11		20.00	6.47	94.59
Example 12		50.00	6.31	92.25

As shown in Table 2, it was found that the density decrease after sintering was not significant up to 1 part by weight of the thermally decomposable polymer.

[Experimental Example 3] Evaluation of thermoelectric material properties

The physical properties of the thermoelectric materials prepared in Examples 1 to 12 and Comparative Example 1 were measured as follows, and the results are shown in Table 3 and FIGS. 7 to 8, respectively.

(1) Measurement of Seebeck coefficient and electrical conductivity: In accordance with JISK 7194, it was measured using ZEM-3 (manufactured by Ulvac-Riko).

(2) Power factor: The power factor was calculated using the measured Seebeck coefficient (S) and electrical conductivity (σ), and the results are shown in FIG. 7 .

[Equation 1] Power factor = (seebeck coefficient)2 * electrical conductivity

(3) Thermoelectric figure of merit: The thermoelectric figure of merit ZT values were compared, and the results are shown in FIG. 8 below. The measured value was compared with the value of 150℃ where the power factor and ZT value had the highest value.

[Equation 2] ZT = (Seebeck coefficient) 2 *Electrical conductivity/thermal conductivity * Temperature

(4) Measurement of thermal conductivity: Measurement of specific heat capacity and thermal conductivity by laser flash method were calculated in accordance with JIS R 1611 and JIS R 1650-3. More specifically, after measuring the thermal diffusivity (D), specific heat (Cp), and density (d) by laser flash method by cutting a disk having a diameter of 10 mm x 1 mm, the thermal conductivity is measured using Equation 3 below did.

[Equation 3] κ = DCpd

	Thermal Conductivity (W/mK)	Electrical Conductivity (/Ωcm)	Seebeck coefficient (μV/K)	Power factor (W/mK^2)	ZT
Comparative Example 1	1.48	932.19	182.09	30.91	0.87
Example 1	1.47	932.26	181.92	30.85	0.89
Example 2	1.46	930.97	181.48	30.66	0.89
Example 3	1.45	929.68	181.05	30.47	0.89
Example 4	1.43	930.32	180.27	30.23	0.90
Example 5	1.40	929.60	179.23	29.86	0.90
Example 6	1.37	926.16	177.67	29.24	0.91
Example 7	1.31	927.80	176.21	28.81	0.93
Example 8	1.26	928.08	174.50	28.26	0.95
Example 9	1.20	922.94	171.79	27.24	0.96
Example 10	1.11	877.06	158.09	21.92	0.83
Example 11	1.03	829.62	144.80	17.39	0.71
Example 12	0.93	765.33	129.24	12.78	0.58

As shown in Table 3 above, the thermoelectric element of the present invention including the porous thermoelectric material reduces the thermal conductivity without significantly lowering the electrical conductivity and Seebeck coefficient due to the regular pore structure contained in the thermoelectric material, thereby improving the thermoelectric performance. It was found that further improvement was possible. Specifically, the decrease in electrical resistance and Seebeck coefficient was not significant until the addition amount of the thermally decomposable polymer was 1 part by weight, whereas the decrease in thermal conductivity was relatively large, so that the thermoelectric performance index (ZT) value was 1 The maximum value was shown when adding parts by weight. In addition, it was found that when particles having an average particle diameter of about 50 μm were used as the thermally decomposable polymer, the maximum value of the thermoelectric performance index compared to the same amount added was shown.

Claims (14)

1. (i) dissolving and solidifying a raw material for a thermoelectric material to form a master alloy;

   (ii) rapidly cooling the mother alloy to form a metal ribbon;

   (iii) mixing the metal ribbon with a polymer that is thermally decomposed at a predetermined temperature or higher and pulverizing it in an inert atmosphere; and

   (iv) sintering the pulverized product of step (iii) at a temperature higher than the thermal decomposition temperature of the polymer;

   A method of manufacturing a porous thermoelectric material comprising a.
2. According to claim 1,

   The thermally decomposable polymer is thermally decomposed by sintering to form a plurality of pores and is removed, a method of manufacturing a porous thermoelectric material.
3. According to claim 1,

   The thermally decomposable polymer is selected from the group consisting of a thermoplastic polymer having a thermal decomposition temperature of 200 to 500 °C, a natural polymer, and a water-soluble polymer, a method for producing a porous thermoelectric material.
4. According to claim 1,

   The method for producing a porous thermoelectric material in which the thermally decomposable polymer has a residual carbon content of 5% or less after thermal decomposition.
5. According to claim 1,

   The thermally decomposable polymer is a group consisting of polymethyl methacrylate (PMMA), polybutyl methacrylate (PBMA), polybromonietide biphenyl (PBB), polyvinyl alcohol (PVA), and ethyl cellulose (EC). At least one selected from, a method for producing a porous thermoelectric material.
6. According to claim 1,

   The thermally decomposable polymer is a spherical particle having an average particle diameter (D ₅₀ ) of 5 to 50 μm, a method for producing a porous thermoelectric material.
7. According to claim 1,

   The method for producing a porous thermoelectric material, wherein the thermally decomposable polymer is added in an amount of 0.1 to 2 parts by weight based on the total weight of the metal ribbon.
8. According to claim 1,

   In the step (iv), the pulverized product of step (iii) is put into a molding mold and sintered by hot pressing, the method for producing a porous thermoelectric material.
9. According to claim 1,

   The method of manufacturing a porous thermoelectric material, wherein the thermoelectric material is at least one of a Bi-Te-based thermoelectric material and a Skuttrudite-based thermoelectric material.
10. According to claim 1,

    The porosity of the porous thermoelectric material is 0.1 to 10%,

    The pore size is 5 to 50 μm,

    The density is 90 to 99.9%, the method of manufacturing a porous thermoelectric material.
11. A porous thermoelectric material manufactured by the method of any one of claims 1 to 10.
12. a first substrate;

    a second substrate facing the first substrate;

    a first electrode and a second electrode respectively disposed between the first substrate and the second substrate; and

    a plurality of thermoelectric legs interposed between the first electrode and the second electrode;

    a bonding material disposed between the first electrode and the thermoelectric leg and between the thermoelectric leg and the second electrode;

    At least one of the plurality of thermoelectric legs is a thermoelectric element including the porous thermoelectric material according to claim 11 .
13. 13. The method of claim 12,

    The bonding material is Sn-based solder; or a thermoelectric element having a composition including the Sn-based solder and a metal dendrite having an average branch length of 5 to 50 μm.
14. 13. The method of claim 12,

    A thermoelectric element applied to at least one of cooling, power generation, and thin film type sensors.

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