KR20170139842A - High efficiency nanostructured thermoelectric sintered body and method for fabricating the same - Google Patents

Abstract

The present invention relates to a thermoelectric nano-sintered body formed by using thermoelectric nanopowder through a rapid sintering process, and a manufacturing method thereof. According to the present invention, thermal conductivity is considerably degraded compared to existing commercial thermoelectric materials by a microstructure in which the grain size is controlled at nanoscales, resulting in high density and improved thermoelectric efficiency. The method comprises the steps of: preprocessing thermoelectric nanopowder; and performing heat treatment on the preprocessed thermoelectric nanopowder.

Description

       TECHNICAL FIELD The present invention relates to a high-efficiency thermoelectric nano-sintered body and a method of manufacturing the same.

The present invention relates to a thermoelectric nano-sintered body and a method of manufacturing the same, and more particularly, to a high-efficiency thermoelectric nano-sintered body in which nanocrystalline controlled grains are formed through a pretreatment and a rapid sintering process of a thermoelectric nano powder, .

      Due to the persistent and indiscriminate use of fossil fuels, depletion of fossil energy, such as petroleum and coal, and environmental pollution are accelerating. In order to solve these problems, several international conventions have been concluded to regulate the use of fossil fuels, and alternate energies have been presented and researched as an alternative to fossil energy.

      Unlike the alternative energy goal of not using fossil fuels at all, there are various studies to increase the energy efficiency of fossil fuels. Interest in energy harvesting has been increasing in these studies. Energy harvesting is a research on improving energy efficiency by recovering abandoned waste energy that can not be used in existing energy. It is attempting to recover the heat generated by fossil fuel combustion and convert it into electric energy .

      The thermoelectric material refers to a material exhibiting a thermoelectric effect such as a Seebeck effect. The Jebek effect is a phenomenon in which an electromotive force is formed inside a material due to energy difference between a charge carrier between a high temperature portion and a low temperature portion of the thermoelectric material And it is possible to convert thermal energy into electric energy by the electromotive force according to the temperature difference. Therefore, when a thermoelectric element is installed in a place where waste heat due to the combustion of fossil fuel is generated, energy can be recovered through conversion of waste heat, which has been previously abandoned, into electrical energy.

     In order to achieve high heat-electrical energy conversion efficiency, the thermoelectric properties of the material should be controlled appropriately and the thermoelectric properties of the material can be measured and evaluated with a dimensionless figure of merit (ZT).

           Equation 1

       (sigma is the electrical conductivity, S is the Seebeck coefficient, kappa is the thermal conductivity, and T is the absolute temperature)

       In order to realize a high energy conversion efficiency thermoelectric device, the dimensionless figure of merit ZT must be high. In order to obtain a high ZT, as shown in Equation 1, the material has a high Seebeck coefficient and electrical conductivity, and a low thermal conductivity. . The Seebeck coefficient refers to the magnitude of the electromotive force (S = dV / dT) formed per unit temperature difference. The high Seebeck coefficient forms a high electromotive force even at a small temperature difference, and the high electric conductivity can be used quickly and efficiently I will let you. Also, the temperature difference between the high temperature part and the low temperature part applied to the thermoelectric material can be largely maintained by the low thermal conductivity.

      However, due to the Widemann-Franz law in most materials, the thermal conductivity tends to increase in proportion to the electrical conductivity, and the Seebeck coefficient generally has an inversely proportional relationship with the electrical conductivity. In order to overcome the limitation of such a material itself, a thermoelectric material having a nanoscale microstructure is being studied. When the nanoscale microstructure is implemented in the material, the scattering of the charge carrier is minimized at the interface of each nanoscale microstructure and at the same time, the scattering of the phonon, which is the basic unit of thermal conductivity, is maximized to increase the thermoelectric performance It is known to be able.

    Attempts have been made to form nano precipitates in the material, to sinter fine powder through a ball mill, to incorporate commercial thermoelectric materials and nanopowder, in order to realize nanoscale microstructure in the material. However, in order to form a nano-precipitate, since the heat treatment is required for at least 10 hours at a high temperature of about 700 ° C or more from the stage of preparing the raw material powder before sintering, productivity is deteriorated due to complicated process and high temperature heat treatment for a long time. In addition, the lattice vibration scattering due to nano precipitates is effective only in the lattice vibration having a wavelength of about 10 nm or less. Since the sintered powder by ball milling can only crush to at least several hundred nm, scattering by the precipitates is difficult. Also, due to the high energy ball mill, many defects are generated in the sintered powder, which hinders the thermoelectric properties. Commercial thermoelectric materials and nano powder incorporation methods are also difficult to form uniform nanocrystals in all areas.

     Since the conventional nanoscale microstructure forming method described above can form only a local microstructure having a scale of 10 nm or 500 nm, the lattice vibration scattering center of all the scales can not be formed, do.

      On the other hand, when the nano powder is sintered at a high density, the grain itself of the thermoelectric material can be controlled to several tens to several hundreds of nanometers, and efficient introduction of nanocrystals and formation of nano- It is possible. As a result, the thermal conductivity of the material can be lowered and ultimately a high thermoelectric performance can be obtained.

     In order to solve the above-mentioned problems, a method of realizing a thermoelectric nano-sintered body by rapid sintering of the synthesized thermoelectric nano powder has been proposed. In the method of manufacturing a nano-sintered body by rapid sintering using a thermoelectric nano powder as a raw material, the synthesized thermoelectric nano powder is charged to a graphite mold and sintered. At this time, sintering proceeds to reduce the large surface area of the thermoelectric nano powder. However, in the above method, the sintering is disturbed by the surfactant remaining in the thermoelectric nano powder, and the sintered body of high density is not obtained. The low density sintered body shows low electrical properties and as a result, the thermoelectric properties are not excellent. Also, the mechanical strength is greatly reduced by the pores caused by the low density.

     Thus, a thermoelectric nano-sintered body of nanoscale crystal grains is prepared by rapid sintering of thermoelectric nano powders. The thermoelectric nano-sintered body is pre-treated with thermoelectric nano powders and then subjected to rapid sintering and two-step sintering to suppress volume expansion. Density nano-sized thermoelectric nano-sintered body having a relative density of 10% or more.

Korean Patent No. 10-1264311 Korean Patent No. 10-1323321 Korean Patent No. 10-1346325 Korean Patent No. 10-1409404

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a thermoelectric nano-sintered body exhibiting an efficient lattice vibration scattering property by controlling the size of crystal grains to several tens to several hundreds nm.

In another aspect, the present invention provides a method of manufacturing a thermoelectric nano-sintered body exhibiting an efficient lattice vibration scattering characteristic.

       In order to achieve the above object, the high-efficiency thermoelectric-

The thermoelectric nano powder preferably includes at least one selected from the group consisting of PbTe, Bi ₂ Te ₃ , ZnO, and Cu ₂ S, and the size of the crystal grains formed by heat-treating the thermoelectric nano powder is within 50 to 500 nm. Do. When the thermoelectric nano powder is PbTe, the thermoelectric nano-sintered body has a theoretical density of 8.164 g / cm 3 and a relative density of 99% of theoretical density. According to another aspect of the present invention, there is provided a method of manufacturing a high-efficiency thermoelectric-

Pretreating the thermoelectric nano powder; And

And thermally treating the pretreated thermoelectric nano powder.

It is preferable that the pretreatment is performed at 300 to 400 ° C for 5 minutes to 40 minutes.

The step of heat-

A first heat treatment step of performing rapid sintering at 500 to 700 ° C; And

And a second heat treatment step of performing heat treatment at a lower temperature in the range of 100 to 400 ° C than the first heat treatment step.

In the first heat treatment step, it is preferable to maintain the pressure in a vacuum atmosphere for 1 to 2 hours, and then heat treatment by replacing with Ar atmosphere.

The high-efficiency thermoelectric nano-sintered body according to the present invention is economical because a sintered body can be obtained through short-time sintering as compared with the conventional hot press sintering, and the crystal grain size is controlled within 50 to 500 nm, have. In addition, the high-efficiency thermoelectric-nano-sintered body according to the present invention has the effect of increasing the thermoelectric efficiency by reducing the thermal conductivity.

FIG. 1 is a TEM image of a PbTe thermoelectric nano-sintered body according to an embodiment of the present invention. FIG. 1 (a) shows the diameter of the scale bar when the scale bar is 200 nm, (C) and (d) show the magnitude of the diameter when the scale bar is 20 nm, respectively.
2 is a view showing a graphite mold and a punch used in the rapid sintering process according to an embodiment of the present invention.
FIG. 3 (a) is a TEM image of an initial PbTe nano powder before the process according to the present invention, and FIG. 3 (b) is an XRD analysis of an initial PbTe nano powder before the process according to the present invention.
FIG. 4A is a TEM image of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention, FIG. 4B is a magnitude of the diameter of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention, and FIG. FIG. ₃ is a graph showing the analysis of EDS components of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention. FIG.
FIG. 5A is a TEM image of the pretreated PbTe nano powder according to the present invention, FIG. 5B is XRD analysis of the pretreated PbTe nano powder according to the present invention, and FIG. 5C is a graph showing the XRD analysis of the pretreated PbTe nano powder Lt; RTI ID = 0.0 > FT-IR < / RTI >
FIG. 6 is a graph showing electric conductivity according to temperature of a PbTe thermoelectric nano-sintered body subjected to heat treatment after rapid sintering according to an embodiment of the present invention and volume expansion of PbTe thermoelectric nano-sintered body without thermal treatment after rapid sintering to be.
FIG. 7 is a graph showing the thermal conductivity of a PbTe thermoelectric nano-sintered body according to an embodiment of the present invention and the thermal conductivity of a bulk PbTe thermoelectric material according to a comparative example.

Hereinafter, the present invention will be described in detail.

The present invention relates to a high-efficiency thermoelectric nano-sintered body, and more particularly, to a thermoelectric nano-sintered body having a size of crystal grains formed by heat-treating a thermoelectric nano powder within 50 to 500 nm.

The thermoelectric material is an energy conversion material in which electrical energy is generated when a temperature difference is given between both ends of a material, and a temperature difference is generated between opposite ends when electrical energy is given to the material.

Most thermoelectric materials consist of elements such as Bi, Te, Selenium and Sb. The density, thermal conductivity (S) and figure of merit (ZT) And the like. In discussing the thermoelectric properties of such thermoelectric materials, a dimensionless figure of merit (ZT) is generally considered, which is expressed as shown in Equation (1) below, Which means that the conversion efficiency is high.

     Equation 1

       (sigma is the electrical conductivity, S is the Seebeck coefficient, kappa is the thermal conductivity, and T is the absolute temperature)

In order to realize a high energy conversion efficiency thermoelectric device, the dimensionless figure of merit ZT must be high. In order to obtain a high ZT, as shown in Equation 1, the material has a high Seebeck coefficient and electrical conductivity, and a low thermal conductivity. .

The nano-sintered body according to the present invention is a phenomenon that when the nano-sized powder is heat-treated, the powder is solidified due to binding between the particles, and as the sintering proceeds, the total surface area decreases and the porosity and the water absorption rate decrease.

Thermoelectric nano powder is a nano-sized powder used as a thermoelectric material and is composed of elements such as bismuth (Bi), tellurium (Te), selenium (Se), and antimony (Sb).

The thermoelectric nano powder usable in the present invention preferably includes at least one selected from the group consisting of PbTe, Bi ₂ Te ₃ , ZnO and Cu ₂ S, but is not limited thereto.

PbTe is also called altite, has a molecular weight of 334.80 and is commonly known as an intermediate of thermoelectric materials. Partly low thermal conductivity and electrical conductivity have good performance as thermoelectric material.

Bi ₂ Te ₃ is an intrinsic semiconductor having a molecular weight of 800.83 and a band gap of 0.14 eV, and has excellent thermoelectric properties. Mainly made of diode with alloy of Sb ₂ Te ₃ or Bi ₂ Se ₃ and CPU cooling device. Portable coolers and generators, and detectors for infrared spectroscopes.

ZnO has a molecular weight of 81.38, and due to the difference in diameters of Zn and O ions, a relatively large tetrahedral interspace exists and defects such as Zn interstitial atoms or oxygen vacancies are generated to form electrons, Type semiconductors.

Cu ₂ S, also called calcocite, has a molecular weight of 159.16 and is a dark brown amorphous substance that precipitates when hydrogen sulfide is added to an aqueous solution of copper salt, which is easily converted to colloid and is an electric conductor (an electric or heat-flowable material).

Among the thermoelectric nano powders, when PbTe is used in the present invention, the relative density of the thermoelectric nano-sintered body is preferably 99% of the theoretical density. This is because if the density of the sintered body is decreased as compared with the theoretical density, the mechanical strength of the sintered body is rapidly lowered, which is difficult to use in the thermoelectric device, and the electrical conductivity is also greatly reduced, thereby decreasing the thermoelectric performance of the whole sintered body.

The method for manufacturing a thermoelectric-nano-sintered body of the present invention includes a step of pretreating a thermoelectric-nano powder and a step of heat-treating the pretreated thermo-nano powder.

The pretreatment step of the thermoelectric nano powder is preferably maintained at 300 to 400 ° C for 5 to 40 minutes.

If the temperature and the time of the heat treatment are less than the above-mentioned conditions, it is difficult to efficiently remove the organic matter, and residual organic matter may remain. If the temperature and the time are above the above conditions, agglomeration of the nanopowder itself may occur, Reduction is undesirable. Accordingly, it is difficult to form a high-density nano-sintered body.

The heat treatment in the above manufacturing method may include a first heat treatment step in which rapid sintering is performed at 500 to 700 ° C; And

And a second heat treatment step of performing heat treatment at a lower temperature in the range of 100 to 400 ° C than the first heat treatment step.

The temperature of the first heat treatment step is higher than the temperature of the second heat treatment step to reduce the area of the nanoparticles due to heat energy, that is, rapid sintering. In the second heat treatment step, The volume expansion of the sintered body sintered in the sintered body is suppressed. This makes it possible to form a high-density sintered body in a shorter time.

Therefore, the temperature of the first heat treatment step is preferably 500 to 700 ° C, and the temperature of the second heat treatment step is preferably 100 to 400 ° C lower.

The rapid sintering of the present invention means that the sintered body is manufactured by heat treatment at a temperature of 500 to 700 ° C for 30 minutes in a short time, as compared with the conventional method of performing a heat treatment for at least 10 hours at a high temperature of about 700 ° C or more. Specifically, a method such as atmospheric pressure sintering, hot pressing, hot-isotatic pressing or the like can be used, but the present invention is not limited thereto. A hot press sintering method, preferably a vacuum hot press sintering method, which is capable of producing a sintered body which is close to the theoretical density and which is dense and excellent in the above-mentioned heat treatment method, can be used, but is not limited thereto.

The hot press sintering method is performed by simultaneously adding a high temperature and a high pressure in an oxygen-free vacuum or gas atmosphere. In order to apply such a hot press sintering method, a mold capable of withstanding high temperature and high pressure is required. As a material satisfying this requirement, carbon is mainly used. Among them, a graphite sintered body or a carbon fiber- (C / C composite) is used as a mold. Such a mold is manufactured by processing a graphite or C / C composite block which is pressure-sintered with isobaric pressure into a cylindrical shape (see FIG. 2).

The thermoelectric nano powder is rapidly sintered to suppress the size growth of the powder to 50 nm to 500 nm to form nanoscale crystal grains.

Here, a metal or an alloy is an aggregate of many crystals, and a crystal structure is obtained in its own way, and a portion surrounded by a net mesh is called a crystal grain.

If the heat treated nanopowder is made of a nano-sintered body and controlled to have a grain size of 50 to 500 nm, the surface area can be increased as compared with a conventional thermoelectric material having the same volume. Conventional thermoelectric materials have a grain size of about 1,000 to 20,000 nm. When the grain size of the thermoelectric material is controlled to 50 to 500 nm, the surface area increases to about 2 to 400 times at the same volume. The scattering of the lattice vibration occurs very effectively in the crystal grain surface area, that is, in the grain boundary system, and thus, in the case of the nanosintered body controlled to 50 to 500 nm, the lattice vibration scattering exhibits very low thermal conductivity.

The thermoelectric nano powder has a diameter ranging from 10 to 40 nm and may have a spherical or hexagonal shape. If the diameter of the thermoelectric nano powder is less than the above range, self-agglomeration and sintering may occur during the heat treatment due to a very high surface energy of the thermoelectric nano powder itself, and further, melting may occur. When the diameter is in the above range, it is difficult to obtain a thermoelectric-nano-sintered body having a grain size of 50 to 100 nm through rapid sintering using a hot press, which will be described later.

FIG. 3 (a) is a TEM image of an initial PbTe nano powder before the process according to the present invention, and FIG. 3 (b) is an XRD analysis of an initial PbTe nano powder before the process according to the present invention.

FIG. 4A is a TEM image of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention, FIG. 4B is a magnitude of the diameter of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention, and FIG. FIG. ₃ is a graph showing the analysis of EDS components of the initial Bi ₂ Te ₃ nano powder before the process according to the present invention. FIG. (b), the diameter of the Bi ₂ Te ₃ nano powder is 35 nm.

The synthesized thermoelectric nano powder contains a surfactant containing a carboxyl group and a hydroxyl group. In order to remove residual organic substances such as surfactants, heat treatment is performed before sintering. After the heat treatment, growth of nanoparticles does not occur but only organic substances are effectively removed.

According to the present invention, the nano-sintered body is formed with nano-sized precipitates in addition to nano-scale crystal grains and is effective for scattering lattice vibrations of various wavelength ranges, so that the thermal conductivity is further reduced and the thermoelectric efficiency is increased.

First, the synthesized thermoelectric nano powder is completely dried in a vacuum atmosphere (~ 10 ^-3 Torr) for 1 hour. Then, Ar gas is flowed at 100 sccm by using MFC (Mass Flow Controller). Thereafter, the temperature is raised to 350 ° C at a rate of 50 ° C / m and then maintained at 350 ° C for 20 minutes.

The heat treatment of the pretreated thermoelectric nano powder may include: a first heat treatment step of performing rapid sintering at 500 to 700 ° C;

And a second heat treatment step of performing heat treatment at a lower temperature in the range of 100 to 400 ° C than the first heat treatment step.

Specifically, the nano powder sintered raw material is loaded into the graphite mold and uniaxial pressure of 80 to 100 MPa is applied in a vacuum atmosphere (~ 10 ^-3 Torr). After maintaining the pressure in a vacuum atmosphere for about 1 to 2 hours, the hot press inner chamber is replaced with an Ar atmosphere and Ar pursuit is performed at a rate of about 4.5 L / m. After reaching 600 ° C at a rate of about 20 ° C / m, sintering is carried out for 30 minutes.

Since the nano powder as the raw material for sinter maintains a diameter of 10 to 40 nm before sintering, the sintering driving force for achieving a reduction in surface area is very high, and therefore rapid sintering at 600 ° C. is possible. The driving force of the reduction of the surface area and the pressure of 80 to 100 MPa cause the void space between the nano powder to be consumed and the crystal growth of the sintered body to be relatively small due to the short sintering time.

When the sintering time is more than 30 minutes, crystal grains grow actively and it is difficult to obtain crystal grains having a size of 50 to 500 nm. If the sintering time is less than 30 minutes, sintering between the nano powders can not be accomplished and a high- Not desirable.

At this time, the grain size of the nano-sintered body is controlled to 50 to 500 nm. When the grain size of the commercial thermoelectric material of about 20 μm is reduced to about 50 nm, the grain surface area is increased about 400 times in the same volume. In addition, the grain surface area is doubled when the grain size is reduced to 500 nm compared to the conventional thermoelectric material which controls the grain size of 1 μm in general through a ball mill.

The sintering atmosphere may be a vacuum atmosphere or an Ar atmosphere. However, in a vacuum atmosphere, sublimation phenomenon occurs very actively on the surface of the nano powder as the raw material for sintering, which is a characteristic due to the surface area of a wide nano powder compared with a commercial thermoelectric material. Therefore, the nano-sintered body in a vacuum atmosphere is not preferable because many pores are formed therein and the electrical characteristics are deteriorated.

Finally, the volume expansion of the nano-sintered body is suppressed at a pressure of 80 to 100 MPa at a temperature lower than the range of 100 to 400 DEG C by using a hot press.

Specifically, the sintered body having undergone the rapid sintering is naturally cooled to 350 ° C. together with the graphite mold, and then the sintered body is sintered within 1 hour while maintaining the pressure of 80 to 100 MPa.

When the heat treatment temperature is higher than the above range, the grain size of the sintered body is increased, which makes it difficult to control the grain size. If the heat treatment temperature is lower than the above range, Plastic deformation, crack formation, and fracture of the substrate.

If the heat treatment time is less than the above range, it is difficult to suppress the volume expansion of the nano-sintered body, so that a high-density sintered body can not be manufactured. If the range is over the range, the grain growth of the sintered body occurs It is not preferable for controlling the grain size of the nano-sintered body.

When the thermoelectric nano powder is PbTe, the thermoelectric nano-sintered body has a theoretical density of 8.164 g / cm 3 and a relative density of 99% of theoretical density.

Since the rapid sintering process using the nano powder as a raw material for sintering is performed at a high pressure of about 80 to 100 MPa at a high temperature of about 600 ° C, when the pressure applied to the sintered body is removed in the process of cooling the temperature after the sintering is completed, Expansion occurs. In this case, a thermoelectric sintered body having a relative density of about 90% with respect to the theoretical density is produced. However, the electrical characteristics of the sintered body are very low, which is not desirable for use as a thermoelectric material.

Hereinafter, the present invention will be described in detail by the following examples.

The following examples illustrate the present invention but are not to be construed to limit the scope of the present invention. The following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention. It is provided to fully inform the owner of the scope of the invention.

[Example]

PbTe Of nano powder  Pretreatment

PbTe nanopowder (diameter: about 35 ㎚) prepared on an organic solvent was charged to an alumina boat and pretreated in a quartz tube. The alumina boat was placed in a quartz tube and dried in a vacuum atmosphere (~ 10 ^{- 3} Torr) and at room temperature for 1 hour to sufficiently remove the organic solvent, moisture and hydroxyl groups contained in the nano powder. After heating at 350 ° C at a heating rate of 50 ° C / m, heat treatment was performed for 20 minutes to remove residual organic substances in the nanoparticles such as carboxyl groups.

The size and crystallinity of the nanopowder heat-treated at 350 ℃ were analyzed by TEM and XRD. The presence of residual organic matter was confirmed by FT-IR spectral analysis.

As shown in Fig. 5, (a) (B) shows the XRD analysis of the pretreated PbTe nano powder according to the present invention; and FIG. 6 (b) shows the XRD analysis of the pretreated PbTe nano powder according to the present invention. It shows the PbTe phase which does not change even after the pretreatment. FIG. 5C is a graph showing FT-IR spectrum analysis of the pretreated PbTe nano powder according to the present invention. In FIG. 5C, residual peaks of PbTe nano powder pretreated without organic peak at 1700 cm ^-1 region and 3000 cm ^-1 region Indicating that organic matter has been effectively removed.

Using hot press Of nano powder  Rapid sintering

Using the pretreated nano powder as a raw material for sintering, hot press sintering was carried out through a graphite mold having a diameter of 10 to 20 mm. Specifically, in the hot press chamber, a vacuum atmosphere (~ 10 ^-3 Torr) was maintained for 1 hour, and a pressure of 80 to 100 MPa was applied to the graphite mold. The pressure was applied to the nano powder through a graphite mold and a punch Respectively. Subsequently, the inside of the chamber was replaced with an Ar atmosphere in a vacuum atmosphere, and Ar pursuit was continued at a rate of about 4.5 L / m. Then, the internal temperature of the chamber was raised up to 600 ° C at a rate of 20 ° C / m and maintained for 30 minutes for rapid sintering.

After rapid sintering Nano-sintered  Volume expansion inhibition

The nano-sintered body rapidly sintered at 600 ° C for 30 minutes was then cooled to 350 ° C and heat-treated at 350 ° C for 1 hour while maintaining a pressure of 80-100 MPa.

FIG. 1 is a TEM image of a PbTe thermoelectric nano-sintered body according to an embodiment of the present invention. FIG. 1 (a) shows the diameter of the scale bar when the scale bar is 200 nm, (C) and (d) show the magnitude of the diameter when the scale bar is 20 nm, respectively. It was confirmed that the thermoelectric nano-sintered body had a nanoscale microstructure with a diameter of about 80 nm.

[Comparative Example 1]

And the heat treatment step after the rapid sintering was omitted.

[Experimental Example 1]

After the rapid sintering, the properties of the nano - sintered bodies were compared according to the presence or absence of heat treatment. As shown in FIG. 6, when the heat treatment step after the rapid sintering was omitted, the volume expansion of the nano-sintered body was more than 10% as compared with the sintered body subjected to the heat treatment, and thus the mechanical strength was weak and the electrical conductivity was low.

[Comparative Example 2]

The bulk of the PbTe (about 5 ㎛ in diameter) was purchased from the reagent manufacturer and the thermal conductivity was measured.

[Experimental Example 2]

The thermal conductivity of a PbTe thermoelectric nano-sintered body according to an embodiment of the present invention was compared with commercial bulk PbTe.

As shown in Fig. 7, it was confirmed that the thermal conductivity of the PbTe thermoelectric nano-sintered body was significantly lower than that of commercial bulk PbTe.

Accordingly, the present invention relates to a thermoelectric nano-sintered body formed by a rapid sintering process using a thermoelectric nano powder and a method of manufacturing the same, and the thermal conductivity of the nano- Thereby increasing the density and the efficiency of the thermoelectric conversion.

Claims (11)

A high - efficiency thermoelectric nano - sintered body having a grain size of 50 to 500 nm or less formed by thermally processing a thermoelectric nano powder. The method according to claim 1,
The thermoelectric nano-powder is high-efficiency thermoelectric nano sintered body comprising the PbTe, Bi ₂ Te _3, ZnO, and at least one selected from the group containing Cu ₂ S. 3. The method of claim 2,
Wherein when the thermoelectric nano powder is PbTe, the thermoelectric nano-sintered body has a theoretical density of 8.164 g / cm3 and a relative density of 99% of the theoretical density. Pretreating the thermoelectric nano powder;
And thermally treating the pretreated thermoelectric nano powder. The method of manufacturing a high-efficiency thermoelectric nano-sintered body according to claim 1, 5. The method of claim 4,
Wherein the pre-treating step is performed at 300 to 400 ° C for 5 minutes to 40 minutes. 5. The method of claim 4,
The step of heat-
A first heat treatment step of performing rapid sintering at 500 to 700 ° C;
And a second heat treatment step of performing heat treatment at a lower temperature in a range of 100 to 400 ° C than the first heat treatment step. 5. The method of claim 4,
Wherein the size of the crystal grains formed through the heat treatment is within 50 to 500 nm. 5. The method of claim 4,
The thermoelectric nano-powders PbTe, Bi ₂ Te _3, ZnO and the method for manufacturing a high-efficiency thermoelectric nano sintered body characterized in that it comprises at least one member selected from the group containing Cu ₂ S. 9. The method of claim 8,
Wherein the thermoelectric nano-sintered body has a theoretical density of 8.164 g / cm < 3 > and a relative density of 99% at the theoretical density when the thermoelectric nano powder is PbTe. The method according to claim 6,
Wherein the first heat treatment step comprises maintaining the pressure in a vacuum atmosphere for 1 to 2 hours, replacing the pressure in an Ar atmosphere, and heat-treating the heat-treated nano-sized sintered body. The method according to claim 6,
Wherein the first heat treatment step and the second heat treatment step are performed under a pressure of 80 to 100 MPa.

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