KR102014164B1 - Thermoelectric material, and method of manufacturing the same - Google Patents

Abstract

The present invention comprises the steps of applying a thermoelectric paste composition comprising a thermoelectric powder, a binder and a glass frit on a substrate; Primary sintering the thermoelectric paste composition applied on the substrate; And a step of secondary sintering by pressurizing the primary sintered thermoelectric paste composition, and a thermoelectric material manufactured therefrom.

Description

Thermoelectric material and its manufacturing method {Thermoelectric material, and method of manufacturing the same}

The present invention relates to a thermoelectric material and a method for manufacturing the same, and more particularly, to a method for manufacturing a thermoelectric material capable of improving the mechanical strength and thermoelectric properties of the thermoelectric material by improving the density.

The thermoelectric material refers to a material having a Peltier effect and a Seebeck effect, and is a material that can be applied to active cooling and waste heat generation.

The Peltier effect is a phenomenon in which the holes of the p-type material and the electrons of the n-type material move and exotherm across the material when a DC voltage is applied from the outside. The Seebeck effect refers to a phenomenon in which electrons and holes move when heat is supplied from an external heat source, causing electric current to flow in the material to generate electricity.

Active cooling using thermoelectric materials does not generate vibration and noise, and does not require a separate condenser and refrigerant, and its volume is small and environmentally friendly. Therefore, it is used for refrigerant-free refrigerators, air conditioners, and various micro cooling systems. Can be.

Power generation using thermoelectric materials can use waste heat as an energy source and can be applied to various fields such as automobile engines and exhaust systems, waste incinerators, steelworks waste heat, and wearable devices using human body heat.

As a factor for measuring the performance of thermoelectric materials, a dimensionless thermoelectric performance index (ZT) value is used, and various studies have been made to increase the ZT value.

For example, to implement a phonon glass-electron crystal (PGEC), a thermoelectric material having a superlattice between PbTe and PbSeTe or a superlattice structure between Bi ₂ Te ₃ and Sb ₂ Te ₃ has been proposed. However, the manufacturing of such superlattices requires a very precise thin film process, which requires expensive facilities, and no matter how thick the thin film is, only a few hundred nanometers, it is practically difficult to use it as a real thermoelectric power or cooling device. .

The thermoelectric material provided in a conventional thermoelectric power element or a cooling element is a bulk form, and is a bulk form manufactured by pressurizing and firing a thermoelectric powder. However, as the Republic of Korea Patent No. 1286090, the use of the thermoelectric power generation element or cooling element is diversified, the miniaturization of the element, flexibility, light weight, etc. are required, and the thin-structured thermoelectric material to be thinned away from the bulk type thermoelectric material is required. Based on the device development is being made.

Printing techniques can structure thermoelectric materials into a variety of forms, such as microplates or micropillars, can be thickened up to several hundreds of micrometers, can be manufactured in large areas, and are advantageous for integration with high resolution and low cost. Therefore, it is a very advantageous method for commercial manufacture of devices equipped with thermoelectric materials.

However, in the case of thermoelectric structures manufactured by printing, the thermoelectric performance index (ZT) is significantly lower than that of a commercial bulk thermoelectric material, which serves as a limit of improving the efficiency of a device having a thermoelectric material.

Republic of Korea Patent No. 10-1286090 (2013.07.09)

An object of the present invention is to provide a method for manufacturing a thermoelectric material capable of improving the mechanical strength and thermoelectric properties of the thermoelectric material by improving the density, and a thermoelectric material manufactured therefrom.

One aspect of the present invention for achieving the above object is a step of applying a thermoelectric paste composition comprising a thermoelectric material powder, a binder and a glass frit on a substrate; Primary sintering the thermoelectric paste composition applied on the substrate; And pressurizing the primary sintered thermoelectric paste composition to secondary sintering.

In the above aspect, the secondary sintering step may be performed at a pressure condition of 3 to 13 kgf / ㎠, and the secondary sintering step may be performed at a temperature condition of 400 to 800 ℃.

In one aspect, the weight ratio of the thermoelectric powder: binder: glass frit may be 87.2-x: 12.8: x (0 <x ≤ 4), wherein the thermoelectric powder is antimony-tellurium-based (Sb _{2+ x} Te _{3 + x),} bismuth-antimony-telru ryumgye (Bi _y Sb _2-y Te ₃₎ compounds, bismuth-telru ryumgye _{(Bi 2 + x Te 3 +} x) or a bismuth-tellurium-selenium based (Bi ₂ Te _{3 - y} Se _y ) compound.

In addition, another aspect of the present invention relates to a flexible thermoelectric element including a thermoelectric material manufactured according to the above-described method of manufacturing a thermoelectric material, having an electron mobility of 190 cm 2 / Vs or more and a density of 5.2 g / cm 3 or more. A flexible thermoelectric element comprising an N-type thermoelectric material having a P-type thermoelectric material or an electron mobility of 125 cm 2 / Vs or more and a density of 5.2 g / cm 3 or more.

In another aspect, the P-type thermoelectric material and the N-type thermoelectric material may have a peak area ratio of 0.08 to 0.2 on the crystal plane in the planar direction on the XRD.

In another aspect, the thermoelectric performance index (ZT) of the P-type thermoelectric material may be 0.83 or more, and the thermoelectric performance index (ZT) of the N-type thermoelectric material may be 0.50 or more.

In addition, another aspect of the present invention relates to a method for improving thermoelectric efficiency of a thermoelectric device, characterized in that the thermoelectric material having a pore structure is pressurized and densified.

In another aspect, the method of improving the thermoelectric efficiency of the thermoelectric device may satisfy the following Equation 1.

[Relationship 1]

5 ≤ (D ₁ -D ₀ ) / D ₀ × 100

(In relation 1, D ₀ is the density (g / cm 3) of the thermoelectric material before densification, and D ₁ is the density (g / cm 3) of the densified thermoelectric material.)

In the method of manufacturing a thermoelectric material according to the present invention, a high density thermoelectric material may be manufactured by evaporating a binder through a first sintering process and then sintering by applying a pressure at a second time.

Through this, it is possible to manufacture thermoelectric materials with experimental density close to theoretical density and improved mechanical strength, thereby providing thermoelectric materials with greatly improved thermoelectric performance, and improving reproducibility and reliability when manufacturing thermoelectric devices. .

1 briefly illustrates a method of manufacturing a thermoelectric material according to an embodiment of the present invention.
2 is a scanning electron microscope (SEM) image of a P-type thermoelectric material manufactured according to a) Comparative Examples 1 and b) Example 1 of the present invention.
3 a) and b) are X-ray diffraction spectroscopy (XRD) results of the P-type thermoelectric materials prepared according to Examples 1 to 3 and Comparative Example 1, and FIG. XRD is measured in the planar direction of the thermoelectric material, and b) of FIG. 3 is XRD measured in the vertical direction of the thermoelectric material.

Hereinafter, a thermoelectric material and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided by way of example so that the spirit of the invention to those skilled in the art can fully convey. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. Also, like reference numerals denote like elements throughout the specification.

At this time, if there is no other definition in the technical terms and scientific terms used, it has a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs, the gist of the present invention in the following description and the accompanying drawings Descriptions of well-known functions and configurations that may be unnecessarily blurred are omitted.

Existing inventors have printed a paste containing a thermoelectric material powder and a binder through a screen printing process and then sintered it to manufacture a thermoelectric material.

The screen printing process is advantageous for manufacturing large area thermoelectric devices because the area of the thermoelectric material can be adjusted according to the shape of the mask, and the printing resolution of several hundred micrometers to several millimeters enables the integration of devices, thereby allowing a large amount of high-power thermoelectric devices. It has the advantage of being suitable for production.

However, thermoelectric materials manufactured by sintering after screen printing have a problem in that the density is significantly lower than the theoretical density. This is because pores are generated due to evaporation of the binder contained in the paste, so that the mechanical strength of the thermoelectric material is lowered, causing reproducibility and reliability deterioration when the thermoelectric device is manufactured. The thermoelectric performance index is directly connected to the thermoelectric properties. ZT) also has a problem of lowering.

Accordingly, the present inventors attempted to improve the density of the thermoelectric material by reducing the volume of pores formed by evaporation of the binder component, thereby improving the mechanical strength and thermoelectric properties of the thermoelectric material.

Specifically, the method of manufacturing a thermoelectric material according to an embodiment of the present invention comprises the steps of applying a thermoelectric paste composition comprising a thermoelectric material powder, a binder and a glass frit on a substrate; Primary sintering the thermoelectric paste composition applied on the substrate; And pressing the first sintered thermoelectric paste composition to perform second sintering.

As described above, in the method of manufacturing a thermoelectric material according to the present invention, a high-density thermoelectric material may be manufactured by evaporating a binder through a first sintering process and then sintering by applying pressure during the second sintering process.

Through this, it is possible to manufacture thermoelectric materials with experimental density close to theoretical density and improved mechanical strength, thereby providing thermoelectric materials with greatly improved thermoelectric performance, and improving reproducibility and reliability when manufacturing thermoelectric devices. .

Hereinafter, a method of manufacturing a thermoelectric material according to an embodiment of the present invention will be described in more detail.

First, a step of applying a thermoelectric paste composition including a thermoelectric powder, a binder, and a glass frit on a substrate may be performed.

The thermoelectric material powder according to an embodiment of the present invention may vary depending on the type of thermoelectric material to be prepared, and when preparing a P-type thermoelectric material, the thermoelectric material powder is antimony-tellurium-based (Sb _{2 + x} Te _{3 + x} ) or bismuth-antimony-tellurium based (Bi _y Sb _{2 - y} Te ₃ ) compounds, preferably using bismuth-antimony-tellurium based (Bi _y Sb _{2 - y} Te ₃ ) compounds It is more preferable in obtaining this excellent thermoelectric material. In this case, x may be 0 ≦ x ≦ 1, and y may be 0 <y <2.

Alternatively, when the N-type thermoelectric material is to be manufactured, the thermoelectric material powder may use bismuth-tellurium-based (Bi _{2 + x} Te _{3 + x} ) or bismuth-tellurium-selenium-based (Bi ₂ Te _{3 - y} Se _y ) compounds. can, and preferably from bismuth-is more preferable as it give a _{- (y Se y Bi 2 Te} 3) excellent thermal performance is to use a compound material thermally-tellurium selenium-based. In this case, x may be 0 ≦ x ≦ 1, and y may be 0 <y <3.

The binder according to an embodiment of the present invention is to control printing resolution by adjusting the viscosity of the thermoelectric paste composition. For example, polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), a self-crosslinkable acrylic resin Emulsion, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, hydroxy cellulose, methyl cellulose, nitrocellulose, ethyl cellulose, styrene butadiene rubber (SBR), C1-C10 alkyl (meth) acrylate and unsaturated carboxyl Acid copolymers, gelatine, thixotons, starches, polystyrenes, polyurethanes, resins containing carboxyl groups, phenolic resins, mixtures of ethylcellulose and phenolic resins, ester polymers, meta Acrylate polymer, self-crosslinking (meth) acrylic acid copolymer, copolymer having ethylenically unsaturated group, ethylcell Any one or two or more selected from cellulose, acrylate, epoxy resin, and mixtures thereof may be used, but is not necessarily limited thereto.

Glass frit according to an embodiment of the present invention may be a bismuth oxide-based glass containing 60 to 90% by weight of bismuth oxide (Bi ₂ O ₃ ) based on the total weight of the glass frit. Specifically, the bismuth oxide-based glass may include bismuth oxide-zinc oxide-based glass. More specifically, the bismuth oxide-based glass may contain 60 to 85% by weight of Bi ₂ O ₃ and 10 to 20% by weight of ZnO in the total weight of the glass frit, and may include B ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , It may further comprise 1 to 20% by weight of one or two or more oxides selected from CeO ₂ , Li ₂ O, Na ₂ O and K ₂ O. As a more specific example of the bismuth oxide-based glass frit, Bi ₂ O ₃ -ZnO-B ₂ O ₃ glass frit, Bi ₂ O ₃ -ZnO-SiO ₂ -Al ₂ O ₃ glass frit, Bi ₂ O ₃ -ZnO-SiO ₂ -B ₂ O ₃ -La ₂ O ₃ -Al ₂ O ₃ Glass frit, Bi ₂ O ₃ -ZnO-SiO ₂ -B ₂ O ₃ -TiO ₂ Glass frit or Bi ₂ O ₃ -SiO ₂ -B ₂ O ₃ -ZnO-SrO glass frit, and the like, but is not limited thereto.

In addition, it is possible to optimize the properties of the thermoelectric material by appropriately adjusting the content of each component. In one embodiment, the weight ratio of the thermoelectric powder: binder: glass frit may be 87.2-x: 12.8: x (0 <x ≤ 4), and more preferably the weight ratio of the thermoelectric powder: binder: glass frit is 86.2-x: 12.8: 1 + x (0 ≦ x ≦ 1.7). In this range, a thermoelectric material having excellent thermoelectric performance may be manufactured.

In addition to this, the thermoelectric paste composition may further include a solvent for viscosity control, and the solvent may be used without particular limitation as long as it is commonly used in the art. As a specific example, the solvent may be an alcohol solvent, a ketone solvent or a mixed solvent thereof, but is not limited thereto. The amount of the solvent added may be sufficient to dissolve the binder sufficiently and to allow the thermoelectric paste composition to have a desired viscosity.

Next, when the thermoelectric paste composition including the above-mentioned thermoelectric powder, binder and glass frit is prepared, the step of applying it on a substrate may be performed, and the coating may be screen printing, inkjet printing, gravi offset printing or reverse. It may be performed through a method such as offset printing, but may be preferably performed through screen printing.

The thermoelectric structure, which is a printed matter formed by application of the thermoelectric paste composition, may have a shape and size pre-designed for the purpose, and may have a wide variety of shapes and sizes designed due to the methodological characteristics of the printing. As a specific and non-limiting example, a thermoelectric structure may be a thin film (tens of tens to hundreds of nanometers thick), a thick film (several to hundreds of micrometers thick), and a few millimeters of thickness of a disc, an elliptical plate, a triangular to octagonal plate, a circular column. It may be in the shape of an elliptical column, a triangular to octagonal polygonal column, or the like, but the present invention is not limited by the shape of the thermoelectric structure that is a print. The substrate on which the thermoelectric paste composition is applied may be used as long as it is a thermally stable material during heat treatment. In one embodiment, the substrate may be silicon, silicon oxide, sapphire, alumina, mica, germanium or silicon carbide, and the like, but is not limited thereto. In addition, in this case, the substrate may be a substrate on which a component positioned on the upper or lower portion of the thermoelectric material, such as a conductive pattern, is already formed in terms of manufacturing a device including the thermoelectric material.

Next, when the application of the thermoelectric paste composition is completed, the step of first sintering the thermoelectric paste composition applied on the substrate may be performed.

The first sintering step according to an embodiment of the present invention is a process of applying heat so that each component of the thermoelectric paste composition becomes a mass, and the first sintering may be performed through a conventional method in the art.

Specifically, for example, the first sintering step may be performed at a temperature condition of 400 to 800 ℃, more preferably may be carried out at a temperature condition of 450 to 600 ℃. It is better to vary the temperature according to the type of thermoelectric material to be manufactured, and heat treatment at 450 to 520 ° C for P-type thermoelectric material and 500 to 550 ° C for N-type thermoelectric material improves the sintering efficiency. Preferred for the application.

At this time, the process time of the first sintering step may be performed for 30 minutes to 200 minutes, more preferably 50 to 80 minutes, but is not necessarily limited to this, the existing sintering process according to the second sintering step to be performed later Rather, it is desirable to shorten the time somewhat.

In addition, the method of manufacturing a thermoelectric material according to an embodiment of the present invention may further perform a drying step and a binder pyrolysis step before the first sintering step. The drying step is a step of removing liquid components such as a solvent contained in the thermoelectric paste composition, and the binder pyrolysis step is a step of pyrolyzing and removing the binder.

More specifically, the drying step is not particularly limited as long as the thermoelectric paste composition is not sintered, and the used solvent and the like can be sufficiently removed, and in one embodiment, at a temperature of 80 to 150 ° C. Although it may be performed for 30 minutes, the temperature and time conditions may vary depending on the boiling point and vaporization characteristics of the solvent and the like used. In addition, the drying step may be performed at an atmospheric pressure (760 torr), but is not necessarily limited thereto.

The binder pyrolysis step is not particularly limited as long as the thermoelectric paste composition is not sintered, and the binder can be pyrolyzed and removed, and in one embodiment, the binder pyrolysis step is performed at a temperature of 200 to 350 ° C. for 30 minutes to 5 hours. The temperature and time conditions may vary depending on the type of binder used. In addition, the binder pyrolysis step may also be performed in a vacuum state, where the vacuum state may mean, for example, a pressure condition of 1 torr or less, and specifically, for example, a pressure condition of 0.001 to 0.01 torr. Can be.

Next, pressing the first sintered thermoelectric paste composition may be performed to sinter second.

This step is a process for producing a thermoelectric material having a high density (apparent density) by applying pressure to the primary sintered thermoelectric paste composition to reduce the size of the pores.

 In one example according to the present invention, in order to manufacture a thermoelectric material having excellent thermoelectric performance and sufficient mechanical strength, it is preferable to appropriately control the secondary sintering temperature and pressure.

As a specific example, the secondary sintering step may be performed at a pressure condition of 3 to 13 kgf / cm 2, and more preferably at a pressure condition of 5 to 11 kgf / cm 2. In this range, the density of the thermoelectric material may be increased to ensure higher thermoelectric efficiency, and may also have excellent mechanical strength. On the other hand, if the pressure is less than 3 kgf / ㎠, only the surface roughness is improved, the density may not be high, and if the pressure is more than 13 kgf / ㎠, the problem that the orientation of the thermoelectric material may be changed is not good.

In addition, the secondary sintering step may be carried out at a temperature condition of 400 to 800 ℃, more preferably may be carried out at a temperature condition of 450 to 600 ℃. Sintering and densification can be effectively performed in such a range.

At this time, the process time of the second sintering step may be performed for 10 to 120 minutes, more preferably 15 to 60 minutes, but is not necessarily limited thereto.

The present invention also relates to a flexible thermoelectric device including the thermoelectric material manufactured by the above-described method. The thermoelectric material manufactured by the above-described method may have high density and excellent mechanical strength and thus have excellent thermoelectric performance.

More specifically, for example, the flexible thermoelectric device according to an example of the present invention has a P-type thermoelectric material having an electron mobility of 190 cm 2 / Vs or more and a density of 5.2 g / cm 3 or more, or an electron mobility of 125 cm 2 / Vs Or more, and may include an N-type thermoelectric material having a density of 5.2 g / cm 3 or more, more preferably, a P-type thermoelectric material having an electron mobility of 200 to 210 cm 2 / Vs and a density of 5.3 to 5.8 g / cm 3, Alternatively, the electron mobility may be 125 to 140 cm 2 / Vs, and may include an N-type thermoelectric material having a density of 5.3 to 5.8 g / cm 3. As such, as it has a density value close to the theoretical density, it may have excellent electron mobility, and through this, it may have similar thermoelectric characteristics as when using a bulk material as a thermoelectric material.

More specifically, for example, in the thermoelectric material manufactured according to the present invention, the thermoelectric performance index (ZT) of the P-type thermoelectric material may be 0.83 or more, and the thermoelectric performance index (ZT) of the N-type thermoelectric material may be 0.50 or more. More preferably, the thermoelectric performance index (ZT) of the P-type thermoelectric material may be 0.85 or more, and the thermoelectric performance index (ZT) of the N-type thermoelectric material may be 0.55 or more. At this time, the upper limit of the thermoelectric performance index is not particularly limited, but as an example, the upper limit of the thermoelectric performance index (ZT) of the P-type thermoelectric material may be 1, and the upper limit of the thermoelectric performance index (ZT) of the N-type thermoelectric material is 0.8. Can be.

More preferably, the P-type thermoelectric material and the N-type thermoelectric material manufactured according to the above-described method may have a peak area ratio of 0.08 to 0.2 on the crystal plane in the planar direction on XRD, and more. Preferably it may be 0.1 to 0.2. When the peak area ratio of (0015) / (015) on the crystal plane in the planar direction is greater than 0.2, the thermoelectric material may be in a bad orientation, and thus may exhibit low thermoelectric properties.

In addition, the coincidence thermoelectric element may have a conventional structure, and specifically, for example, a thermoelectric material array including one or more P-type thermoelectric materials and N-type thermoelectric materials, spaced apart from each other, and the thermoelectric material array It may be to include an electrode for electrically connecting, and may further include a contact thermal conductor layer, a filling material for filling the empty space between the thermoelectric material array, if necessary.

In addition, the present invention provides a method for improving the thermoelectric efficiency of a thermoelectric device, characterized in that the thermoelectric material having a pore structure is pressurized and densified.

As described above, the thermoelectric paste composition printed on the substrate is subjected to a binder pyrolysis step to remove the binder. At this time, when the binder is pyrolyzed and evaporated and removed, the space occupied by the binder remains as an empty space and the thermoelectric material forms a pore structure. Have. Due to the pore structure, the density and the mechanical strength are lowered, and the thermoelectric efficiency of the thermoelectric element may be lowered.

Accordingly, the thermoelectric material having the pore structure is pressurized and heat-treated to reduce the size of the pores, thereby having a more compact structure and forming a thermoelectric material having improved density, thereby improving thermoelectric efficiency of the thermoelectric device. That is, the densification may mean that the density is improved, and the pore structure is changed to a more compact structure.

Preferably, the method of improving the thermoelectric efficiency of the thermoelectric device may satisfy the following Equation 1.

[Relationship 1]

5 ≤ (D ₁ -D ₀ ) / D ₀ × 100

(In relation 1, D ₀ is the density (g / cm 3) of the thermoelectric material before densification, and D ₁ is the density (g / cm 3) of the densified thermoelectric material.)

As such, by increasing the density through pressure heat treatment, the thermoelectric efficiency of the thermoelectric device may be effectively improved, and the mechanical strength of the thermoelectric device may also be increased, thereby improving the reliability of the device.

More preferably, (D ₁ -D ₀ ) / D ₀ × 100 may be 10 or more, and the lower limit of (D ₁ -D ₀ ) / D ₀ × 100 may be 14 or less. Although the density is effectively made in the above range, the orientation of the thermoelectric material is not changed, so that the thermoelectric efficiency of the thermoelectric element can be improved to the maximum.

Hereinafter, the thermoelectric material and the manufacturing method thereof according to the present invention will be described in more detail with reference to the following examples. However, the following examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto and may be implemented in various forms. Also, unless defined otherwise, all technical and scientific terms have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of effectively describing particular embodiments only and is not intended to be limiting of the invention. Also, the singular forms used in the specification and the appended claims may be intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, the unit of the additive which is not specifically described in the specification may be wt%.

Example 1

First, the N type thermoelectric powder is Bi ₂ Te _{2 . 7} Se _{0 .3} was prepared by crushing the ingot into (KRYOTERM, Russia) the ball miller (planetary ball miller, Retsch, PM -100).

Next, Bi ₂ Te _{2 .} And mixed with the Se _{7 0 .3} thermoelectric material powder 84.5 wt%, 2.7 wt% glass frit, ethyl cellulose-based binder and a mixture of butyl acetate-based vehicle 12.8% by weight of (4-ethyl cellulose: butyl acetate in a weight ratio = 1). Then, the thermoelectric paste composition was prepared by homogenizing for 20 minutes with a stirrer (DAEWHA Tech, PDM-300V). At this time, the glass frit contained 78 wt% of Bi ₂ O ₃ , 19 wt% of ZnO, 1.5 wt% of Al ₂ O _3, and 1.5 wt% of SiO ₂ based on the total weight of the glass frit.

Thereafter, the thermoelectric paste composition was printed on an alumina (Al ₂ O ₃ ) substrate using a screen printer (Automax, 1345TC), and 200 films were formed at a height of about 800 μm through a repeated printing process, and then 110 ° C. The drying process was performed for 10 minutes in an oven.

Next, for pyrolysis of nitrocellulose as a binder, heat treatment was performed at 230 ° C. for 50 minutes in a vacuum state, and then the first sintering process was performed at 510 ° C. for 60 minutes.

Thereafter, the metal block was placed on the primary sintered film and subjected to a secondary sintering process at 500 ° C. for 20 minutes while applying a pressure of 5 kgf / cm 2 to obtain a Bi ₂ Te _2.7 Se _0.3 thermoelectric material having a height of about 650 μm. Was prepared.

Example 2

All the processes except the pressure conditions were changed to 10 kgf / cm 2 in the same manner as in Example 1.

Example 3

All the processes except the pressure conditions were changed to 15 kgf / cm 2 in the same manner as in Example 1.

Example 4

First, P type thermoelectric powder is Bi _{0 . 5} Sb _{1 . 5} Te ₃ ingot (KRYOTERM, Russia) was prepared by grinding with a ball mill (planetary ball miller, Retsch, PM-100).

Next, Bi _{0 . 5} Sb _{1 .} 86.2% by weight of ₅ Te ₃ thermoelectric powder, 1.0% by weight of glass frit, 12.8% by weight of ethylcellulose-based binder and butyl acetate-based mixed vehicle (weight ratio of ethylcellulose to butyl acetate = 1: 1) were mixed. Thereafter, a thermoelectric paste composition was prepared by mixing for 20 minutes with a stirrer (DAEWHA Tech, PDM-300V). At this time, the glass frit contained 78 wt% of Bi ₂ O ₃ , 19 wt% of ZnO, 1.5 wt% of Al ₂ O _3, and 1.5 wt% of SiO ₂ based on the total weight of the glass frit.

Thereafter, the thermoelectric paste composition was printed on an alumina (Al ₂ O ₃ ) substrate using a screen printer (Automax, 1345TC), and the film was formed at a height of about 800 μm through a repeated printing process, followed by an oven at 110 ° C. The drying process was carried out for 10 minutes.

Next, to decompose the ethyl cellulose binder, the heat treatment was performed at 230 ° C. for 50 minutes in a vacuum state, and then the first sintering process was performed at 500 ° C. for 60 minutes.

Thereafter, the metal block was placed on the primary sintered film and subjected to a secondary sintering process at 500 ° C. for 20 minutes while applying a pressure of 5 kgf / cm 2 to obtain a Bi _0.5 Sb _1.5 Te ₃ thermoelectric material having a height of about 650 μm. Was prepared.

Example 5

All the processes except the pressure conditions were changed to 10 kgf / cm 2 in the same manner as in Example 4.

Example 6

All the processes except the pressure condition to 15 kgf / ㎠ proceeded in the same manner as in Example 4.

Comparative Example 1

All the processes except the progress of the secondary sintering process without applying pressure were carried out in the same manner as in Example 1.

Comparative Example 2

All the processes except the progress of the secondary sintering process without applying pressure were carried out in the same manner as in Example 4.

Thermoelectric Characteristic Evaluation

The thermoelectric materials prepared through Examples 1 to 6 and Comparative Examples 1 to 2 were evaluated for thermoelectric properties through the following method, and the results are shown in Table 1 and FIGS. 2 to 3.

1) Electron mobility (cm 2 / Vs): Measured using a hall measurement system (HMS-3000, Ecopia).

2) Density (g / cm 3): The weight was measured using a precision scale with 5 decimal places and the volume was measured using a 3D profiler. Density was derived from the weight and volume ratio.

3) Thermoelectric performance index (ZT): (Seebeck coefficient ² × electrical conductivity / thermal conductivity) × absolute temperature

Seebeck coefficient and electrical conductivity were derived by using Seebeck coefficient and electrical resistance measuring equipment. Specific heat was derived from differential scanning calorimetry (DSC), and thermal diffusivity was derived using thermal diffusometer (LFA). Thermal conductivity was calculated using the density × thermal diffusivity × specific heat of the material.

4) Peak Area Ratio ₍₀₀₁₅₎ / A _{(015) of (0015)} / ₍₀₁₅ ): Derived from the ratio of the integral intensity of peaks with axial components to the strongest integral intensity of the measured XRD peaks. .

pressure
(kgf / ㎠) Electron mobility
(Cm2 / Vs) density
(g / cm 3) ZT A ₍₀₀₁₅₎ / A ₍₀₁₅₎
Horizontal A ₍₀₀₁₅₎ / A ₍₀₁₅₎
Vertical Example 1 5 126.1 5.41 0.51 0.128 0.119 Example 2 10 136.2 5.68 0.58 0.147 0.139 Example 3 15 138.2 5.83 0.54 0.299 0.121 Example 4 5 200.9 5.39 0.82 0.137 0.118 Example 5 10 202.1 5.67 0.89 0.155 0.136 Example 6 15 206.3 5.89 0.84 0.369 0.111 Comparative Example 1 0 122.6 5.10 0.48 0.111 0.100 Comparative Example 2 0 189.1 5.17 0.8 0.103 0.089

As can be seen from Table 1 and FIG. 2 and FIG. 3, it was confirmed that the thermoelectric materials of Examples compared to Comparative Examples 1 and 2 exhibited excellent thermoelectric properties. In particular, as the pressure increases, the electron mobility and density increases. It was confirmed that the increase.

FIG. 2 is an SEM image of each of the thermoelectric materials of Comparative Example 2 and the thermoelectric materials prepared from Example 5, and the thermoelectric materials of Comparative Example 2 prepared without applying pressure were found to have a large number of pores on the thick film surface. . On the other hand, the thermoelectric material of Example 5 sintered under pressure was found to have a more compact structure because pores larger in size compared to Comparative Example 2 significantly reduced.

[Mechanical Characterization]

After bonding each of the thermoelectric materials prepared in Examples 1 to 6 and Comparative Examples 1 to 2 and the copper electrode with a Sn-Ag-Cu-based binder, the strength when the bonded body was broken was measured, and the thermoelectric introduction was sufficiently mechanical. It was confirmed that the bonding part was broken at a strength of about 10 J / m 2 when it had strength and sufficient bonding was made.

As a result of the evaluation, about 70% of the thermoelectric material manufactured according to the present invention normally damaged the junction between the thermoelectric material and the copper electrode at a strength of about 10.0 J / m 2, and about 30% of the thermoelectric material was about 9.0 J / m 2. It is confirmed that the failure rate of the thermoelectric material is about 30% because the thermoelectric material is not broken.

On the other hand, in Comparative Examples 1 and 2, as the density of the thermoelectric material is low, the thermoelectric material, which is about 70 to 80%, breaks the thermoelectric material other than the joint at the strength of about 8.0 J / m 2, resulting in mechanical strength. It was confirmed that the fall, the failure rate of the thermoelectric material was also found to be very high as about 50%.

Although the preferred embodiment of the present invention has been described above, it is clear that the present invention may use various changes, modifications, and equivalents, and that the above embodiments may be appropriately modified in the same manner. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

Claims (10)

Applying a thermoelectric paste composition comprising a thermoelectric powder, a binder, and a glass frit on a substrate;
Primary sintering the thermoelectric paste composition applied on the substrate; And
Pressing the first sintered thermoelectric paste composition under a pressure condition of 5 to 11 kgf / cm 2 to secondary sintering to prepare a thermoelectric material;
Method for producing a thermoelectric material comprising a. delete The method of claim 1,
The secondary sintering step is carried out at a temperature condition of 400 to 800 ℃, the method of manufacturing a thermoelectric material. The method of claim 1,
The thermoelectric material powder: binder: glass frit weight ratio is 87.2-x: 12.8: x (0 <x ≤ 4), the method of manufacturing a thermoelectric material. The method of claim 1,
The thermoelectric material powder is antimony-tellurium-based (Sb _{2 + x} Te _{3 + x} ), bismuth-antimony-tellurium-based (Bi _y Sb _2-y Te ₃ ) compound, bismuth-tellurium-based (Bi _{2 + x} Te _{3 + x} ) or a bismuth-tellurium-selenium-based (Bi ₂ Te _3-y Se _y ) compound, a method for producing a thermoelectric material. P-type thermoelectric material having an electron mobility of 190 cm 2 / Vs or more and a density of 5.2 g / cm 3 or more, or an N-type thermoelectric material having an electron mobility of 125 cm 2 / Vs or more and a density of 5.2 g / cm 3 or more Thermoelectric element. The method of claim 6,
The P-type thermoelectric material and the N-type thermoelectric material is a flexible thermoelectric device having a peak area ratio of (0015) / (015) on the crystal plane in the planar direction on the XRD is 0.08 to 0.2. The method of claim 6,
The thermoelectric performance index (ZT) of the P-type thermoelectric material is 0.83 or more, and the thermoelectric performance index (ZT) of the N-type thermoelectric material is 0.50 or more, flexible thermoelectric device. A thermoelectric material having a pore structure is densified by pressure heat treatment under a pressure condition of 5 to 11 kgf / cm 2, and satisfies the following relational formula 1, wherein the thermoelectric efficiency improvement method of the thermoelectric element.
[Relationship 1]
10 ≤ (D ₁ -D ₀ ) / D ₀ × 100 ≤ 14
(In relation 1, D ₀ is the density (g / cm 3) of the thermoelectric material before densification, and D ₁ is the density (g / cm 3) of the densified thermoelectric material.) delete

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