KR20190021549A - Composite thermoelectric materials and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a composite thermoelectric material having a form in which FeTe_2 and Fe-rich phase nanoparticles, which are a heterogeneous phase, are dispersed in a Bi_xSb_(2-x)Te_3 (herein, X is a real number smaller than 2) thermoelectric semiconductor, and to a manufacturing method thereof. According to the present invention, the composite thermoelectric material has a form in which FeTe_2 and Fe-rich phase nanoparticles, which are a heterogeneous phase, are dispersed in a Bi_xSb_(2-x)Te_3 (herein, X is a real number smaller than 2) thermoelectric semiconductor, thereby improving thermoelectric performance by improvement of an output factor and reduction in thermal conductivity.

Description

TECHNICAL FIELD The present invention relates to a composite thermoelectric material and a manufacturing method thereof,

The present invention relates to a thermoelectric material and a method of manufacturing the same, and more particularly, Bi _x Sb _{2 -x} Te ₃ (where X is a real number smaller than 2) of the thermally yijongsang FeTe ₂ nanoparticles and Fe nanoparticles on the semiconductor (Fe- rich phase nanoparticle dispersed therein, thereby improving the output factor and reducing the thermal conductivity, thereby improving the thermoelectric performance, and a method of manufacturing the composite thermoelectric material.

The thermoelectric phenomenon was first discovered by the German physicist TJ Seebeck in a circuit made up of two different conductors. When a different temperature is applied to a contact point between conductors, current or voltage is generated. The heat flow from the place to the cold generates the current. This phenomenon is called the Seebeck effect.

In France, Zhang Shah, Atanaspelte, discovered another important thermoelectric phenomenon: when a direct current flows through a circuit composed of different conductors, one side of the junction between the different conductors is heated according to the direction of the current, The other is the phenomenon of cooling. This is called the Peltier effect.

William Thompson found that the Peltier effect and the Seebeck effect are related to each other, and the correlation between them is summarized. In this process, when a potential difference is applied to both ends of a rod made of a single conductor, heat absorption (Thomson Effect) that the release will occur.

Thermoelectric devices, which are called by various names, such as thermoelectric modules, Peltier devices, Thermoelectrical Coolers (TECs), and ThermoElectric Modules (TEMs), are small heat pumps (which absorb heat from cold heat sources) Thereby giving heat to a high-temperature heat source). When a DC voltage is applied to both ends of the thermoelectric element, heat is transferred from the heat absorbing portion to the heat generating portion, and accordingly, the temperature of the heat absorbing portion is lowered and the temperature of the heat generating portion is increased over time. At this time, if the polarity of the applied voltage is changed, the heat absorbing portion and the heat generating portion are exchanged with each other and the heat flow is reversed.

A typical thermoelectric element is a pair of N-type and P-type thermoelectric semiconductor elements, and in a typical model, 127 pairs of elements are used. When a direct current (DC) voltage is applied to both ends, the heat moves according to the flow of electrons in the N type and the flow in the hole in the P type, so that the temperature of the heat absorbing part is lowered. Because there is a difference in the potential energy of the electrons in the metal, in order for the electrons to move from the metal in the low state of the potential state to the metal in the high state, the heat energy is taken away from the contact point, . This endothermic (cooling) is proportional to the current flow and the number of thermoelectric couple (N, P type 1 pair).

Currently, the energy used is fossil fuel, petroleum, nuclear power, etc., and is used as a source of electric energy. However, it is necessary to develop alternative energy by depletion of resource energy. In addition, most of the electric power generated by the generator is converted into electrical energy through mechanical energy, but the conversion efficiency of the energy is difficult to exceed a certain limit (for example, 40%). In recent years, thermoelectric power generation technologies having advantages such as thermoelectric generation using thermoelectric elements and recycling of waste heat energy using thermoelectric elements have been attracting attention as energy problems.

Korean Patent Publication No. 10-1198260

SUMMARY OF THE INVENTION The object of the present invention is to provide a ferroelectric semiconductor device in which FeTe ₂ nanoparticles and Fe nanoparticles dispersed in a thermoelectric semiconductor are dispersed in Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) And the thermoelectric performance can be improved by improving the output factor and reducing the thermal conductivity, and a method of manufacturing the composite thermoelectric material.

The present invention relates to a composite body in which FeTe ₂ nanoparticles and Fe-rich phase nanoparticles, which are heterogeneous, are dispersed in a thermoelectric semiconductor, Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) Thermoelectric material.

It is preferable that the FeTe ₂ nanoparticles and the Fe nanoparticles are contained in the composite thermoelectric material in an amount of 0.1 to 20.0 mol% based on the Bi _x Sb _{2 -x} Te ₃ thermoelectric semiconductor.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

Further, the present invention relates to a method for producing an FeTe ₂ -based alloy by mixing Bi, Sb and Te, which are raw metal materials, of a composition of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2) A step of preparing a composite raw material by mixing Fe and Te which are Fe and Te in a composition ratio, synthesizing an ingot-type composite thermoelectric material by using the composite raw material, forming a composite thermoelectric material powder by rapid solidification using a rapid solidification method, and sintering the composite thermoelectric material powder to obtain a composite thermoelectric material, wherein the composite thermoelectric material comprises Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2), characterized in that the composite body forming the form in which the yijongsang of FeTe ₂ nanoparticles and nanoparticles Fe (Fe-rich phase nanoparticle) dispersed in the thermoelectric semiconductor It provides a process for the preparation of all materials.

Fe and Te, which are the raw metals constituting the composition of FeTe ₂ , are in a range of 0.1 to 20.0% relative to the total molar amount of Bi, Sb and Te, which are the starting metal constituting the composition of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2) Mol%.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

The step of forming the composite thermoelectric material powder may include melting the ingot-type composite thermoelectric material and injecting the molten composite thermoelectric material onto a rotating wheel through a nozzle to rapidly solidify the composite thermoelectric material powder to obtain a composite thermoelectric material powder having a ribbon-like shape .

The shape of the ribbon may have a thickness of 100 nm to 10 mu m, a width of 100 mu m to 5 cm, and a length of 100 mu m to 5 cm.

The sintering can be performed by spark plasma sintering or hot press sintering. The sintering is preferably performed in a vacuum atmosphere at a temperature of 300 to 800 ° C. and a pressure of 1 to 100 MPa .

The present invention also provides a method for producing a composite thermoelectric material, comprising: preparing a composite material by mixing a Bi-Sb-Te system thermoelectric semiconductor and FeTe ₂ ; synthesizing an ingot type composite thermoelectric material by using the composite material; Rapidly solidifying the composite thermoelectric material in an ingot form using a rapid solidification method to form a composite thermoelectric material powder and sintering the composite thermoelectric material powder to obtain a composite thermoelectric material, The complex type thermoelectric material has a structure in which FeTe ₂ nanoparticles and Fe-rich phase nanoparticles, which are heterogeneous, are dispersed in a thermoelectric semiconductor, Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) Wherein the thermoelectric material is a thermosetting thermoplastic elastomer.

The FeTe ₂ is preferably mixed with 0.1 to 20.0 mol% of the Bi-Sb-Te based thermoelectric semiconductor.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

The step of forming the composite thermoelectric material powder may include melting the ingot-type composite thermoelectric material and injecting the molten composite thermoelectric material onto a rotating wheel through a nozzle to rapidly solidify the composite thermoelectric material powder to obtain a composite thermoelectric material powder having a ribbon-like shape .

The shape of the ribbon may have a thickness of 100 nm to 10 mu m, a width of 100 mu m to 5 cm, and a length of 100 mu m to 5 cm.

The sintering can be performed by spark plasma sintering or hot press sintering. The sintering is preferably performed in a vacuum atmosphere at a temperature of 300 to 800 ° C. and a pressure of 1 to 100 MPa .

According to the composite-type thermoelectric material of the present invention, FeTe ₂ nanoparticles and Fe-rich phase nanoparticles, which are heterogeneous, are dispersed in a thermoelectric semiconductor of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) The thermoelectric performance can be improved by improving the output factor and reducing the thermal conductivity.

The composite thermoelectric material of the present invention has a thermoelectric power generation using a voltage generated by a Seebeck effect when a temperature difference between the two ends of the material is given, And may be applied to thermoelectric cooling using a Peltier effect in which heat is absorbed by the other side.

FIGS. 1 and 2 are diagrams showing X-ray diffraction (XRD) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
3A is a graph showing the relationship between the total molar amount of Bi, Sb, and Te as a raw material metal constituting the composition of the Bi-Sb-Te based thermoelectric semiconductor, Fe and Te, which are the raw materials of FeTe ₂ , FIG. 3B is a high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image, FIG. 3C is a HAADF-STEM image and FIG. TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) element map (TEM-EDS elemental maps).
Figure 4a is mixed to achieve a 8 mol% compared to the total molar content of the composition forming raw material metal of Fe and Te of FeTe ₂ Bi-Sb-Te based thermoelectric raw material metal constituting the composition of the semiconductor Bi, Sb and Te in accordance with Experimental Example 2 FIG. 4B is a high resolution HAADA-STEM image, FIG. 4C is a HAADF-STEM image, and TEM-EDS is a high resolution HAADA-STEM image of a composite thermoelectric material Show element-maps (TEM-EDS elemental maps).
5 is a graph showing the electrical conductivity () of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
6 is a graph showing the shear modulus (S) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
7 is a graph showing the relationship between FeTe ₂ and Bi _{0 . 4} Sb _{1 . 6} > Te < _{3 &} gt ;.
8 is a graph showing the output factor (PF) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
9 is a graph showing the thermal conductivity (k) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
10 is a graph showing the lattice thermal conductivity (k) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.
11 is a graph showing the thermoelectric performance index (ZT) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

Hereinafter, the term " nano " refers to a size of nanometer units and a size of 1 to 1000 nm, and a term " nanoparticle " refers to particles having a size of 1 to 1000 nm.

Composite body according to an embodiment of the present invention thermal material _{is, Bi x Sb 2 - x Te} 3 ( where X is a small real number greater than 2) of FeTe ₂ nanoparticles and Fe nanoparticles yijongsang the thermoelectric semiconductor (Fe-rich phase nanoparticle ) Are dispersed.

It is preferable that the FeTe ₂ nanoparticles and the Fe nanoparticles are contained in the composite thermoelectric material in an amount of 0.1 to 20.0 mol% based on the Bi _x Sb _{2 -x} Te ₃ thermoelectric semiconductor.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

A method of producing a composite thermoelectric material according to a preferred embodiment of the present invention includes the steps of preparing Bi, Sb and Te as raw materials of a composition of Bi _x Sb _2-x Te ₃ (where X is a real number smaller than 2) Mixing Fe and Te, which are the raw materials of FeTe ₂ , in accordance with a composition ratio, preparing a composite raw material, synthesizing an ingot-type composite thermoelectric material using the composite raw material, , Rapidly solidifying the ingot-type composite thermoelectric material using a rapid solidification method to form a composite thermoelectric material powder, and sintering the composite thermoelectric material powder to obtain a composite-type thermoelectric material and the composite body thermoelectric material is _{Bi x Sb 2 - x Te 3} ( where X is a real number smaller than 2) of FeTe ₂ nanoparticles and nanoparticles Fe (Fe-rich phase nanoparticle) is being dispersed in the thermoelectric semiconductor yijongsang Constitute a form.

Fe and Te, which are the raw metals constituting the composition of FeTe ₂ , are in a range of 0.1 to 20.0% relative to the total molar amount of Bi, Sb and Te, which are the starting metal constituting the composition of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2) Mol%.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

The step of forming the composite thermoelectric material powder may include melting the ingot-type composite thermoelectric material and injecting the molten composite thermoelectric material onto a rotating wheel through a nozzle to rapidly solidify the composite thermoelectric material powder to obtain a composite thermoelectric material powder having a ribbon-like shape .

The shape of the ribbon may have a thickness of 100 nm to 10 mu m, a width of 100 mu m to 5 cm, and a length of 100 mu m to 5 cm.

The sintering can be performed by spark plasma sintering or hot press sintering. The sintering is preferably performed in a vacuum atmosphere at a temperature of 300 to 800 ° C. and a pressure of 1 to 100 MPa .

A method of manufacturing a composite thermoelectric material according to an embodiment of the present invention includes the steps of preparing a composite material by mixing a Bi-Sb-Te system thermoelectric semiconductor with FeTe _2, and mixing the ingot with the composite material, A step of rapidly solidifying the ingot-type composite thermoelectric material using a rapid solidification method to form a composite thermoelectric material powder, and a step of sintering the composite thermoelectric material powder and a step of obtaining a composite body type thermoelectric material, the composite body type thermoelectric material is _{Bi x Sb 2 - x Te 3} ( where X is a small real number greater than 2) of FeTe ₂ nanoparticles and Fe nanoparticles yijongsang the thermoelectric semiconductor (Fe -rich phase nanoparticle) is dispersed in the thermosetting material.

The FeTe ₂ is preferably mixed with 0.1 to 20.0 mol% of the Bi-Sb-Te based thermoelectric semiconductor.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

The step of forming the composite thermoelectric material powder may include melting the ingot-type composite thermoelectric material and injecting the molten composite thermoelectric material onto a rotating wheel through a nozzle to rapidly solidify the composite thermoelectric material powder to obtain a composite thermoelectric material powder having a ribbon-like shape .

The shape of the ribbon may have a thickness of 100 nm to 10 mu m, a width of 100 mu m to 5 cm, and a length of 100 mu m to 5 cm.

The sintering can be performed by spark plasma sintering or hot press sintering. The sintering is preferably performed in a vacuum atmosphere at a temperature of 300 to 800 ° C. and a pressure of 1 to 100 MPa .

Hereinafter, a composite thermoelectric material according to a preferred embodiment of the present invention will be described more specifically.

Thermoelectric power generation using the Seebeck effect is environmentally friendly because it has high reliability, high output stability, and does not generate carbon dioxide (CO ₂ ). Thermoelectric cooling using the Peltier effect enables precise temperature control, It is not only noise-free, but also eco-friendly because it is cooling that does not generate freon gas.

Despite these advantages, however, thermoelectric elements exhibit a low utilization rate compared to their potential use due to their low thermoelectric properties (thermoelectric materials).

A parameter for evaluating the performance of the thermoelectric material is required, which can be expressed by the figure of merit Z, and the figure of merit Z can be expressed by the following equation (1).

In the above equation (1),? Is the Seebeck coefficient,? Is the electrical resistivity, and K is the thermal conductivity.

As shown in Equation (1), the characteristics of the thermoelectric material are better as the electric conductivity and the thermal conductivity are lower. Generally, the figure of merit Z is obtained by multiplying this value by the temperature T rather than directly using the dimensionless thermoelectric performance index ZT.

&Quot; (2) "

The performance of the thermoelectric material can be expressed by the dimensionless thermoelectric performance index ZT. Not only the usable thermoelectric material is determined depending on the temperature of the heat source, but also the thermoelectric power (S) and the electric conductivity σ) and the thermal conductivity (k) are different, and the thermoelectric performance index as a whole is a function of temperature. However, due to the interdependence of electrical conductivity ( ? ), Thermoelectric power (S), and thermal conductivity (k), the performance has been limited.

In the composite thermoelectric material according to the preferred embodiment of the present invention, since the thermoelectric semiconductor material contains FeTe ₂ nanoparticles and Fe nanoparticles which are heterogeneous, the thermoelectric performance can be improved by reducing the thermal conductivity.

The composite-type thermoelectric material according to the preferred embodiment of the present invention is formed by dissimilar FeTe ₂ nanoparticles and Fe-rich phase nanoparticles dispersed in a thermoelectric semiconductor as a parent phase.

The thermoelectric semiconductor material 120 may include a Bi-Se-Te-based compound. The Bi-Sb-Te compound is Bi _x Sb _2-x Te ₃ (where X is a real number smaller than 2).

It is preferable that the FeTe ₂ nanoparticles and the Fe nanoparticles are contained in the composite thermoelectric material in an amount of 0.1 to 20.0 mol% based on the Bi _x Sb _{2 -x} Te ₃ thermoelectric semiconductor.

The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.

The Fe nanoparticles have a size of 1 to 100 nm.

The FeTe ₂ nanoparticles and the Fe nanoparticles distributed in the thermoelectric semiconductor can improve the thermoelectric performance index by improving the output factor due to the increase of the whitening coefficient and decreasing the thermal conductivity through the phonon scattering. Since there is no significant decrease in the electrical conductivity, it is possible to improve the thermoelectric performance index.

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

Bi, Sb and Te, which are the raw materials of the composition of the Bi-Sb-Te system thermoelectric semiconductor, are mixed according to a desired composition ratio, and Fe and Te, which are the raw materials of FeTe ₂ , are mixed to prepare a composite raw material do. Fe and Te, which are the raw materials of the composition of FeTe _{2, are in a range} of 0.1 to 20.0 mol% based on the total molar amount of Bi, Sb and Te, which are the starting metal constituting the composition of the Bi-Sb-Te system thermoelectric semiconductor, 12.0 mol% is preferably mixed. The Bi-Sb-Te-based thermoelectric semiconductor is an example of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2). For example, Bi, Sb and Te, which are raw materials metals, are mixed so as to have a composition formula of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2), and Fe and Fe, which constitute the composition of FeTe ₂ , Te is mixed according to the composition ratio to prepare a composite raw material.

As another example, the composite raw material may be prepared by mixing Bi-Sb-Te based thermoelectric semiconductor and FeTe ₂ . In this case, the Bi-Sb-Te-based thermoelectric semiconductor and the FeTe ₂ may be in powder form, but are not limited thereto and may be in a bulk form (for example, in a lump form). The FeTe ₂ is preferably mixed with 0.1 to 20.0 mol%, more preferably 1 to 12.0 mol% of the Bi-Sb-Te based thermoelectric semiconductor. The Bi-Sb-Te-based thermoelectric semiconductor is an example of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2).

An ingot-type composite thermoelectric material is synthesized using the composite raw material. The ingot-type composite thermoelectric material can be obtained by placing the composite raw material in a quartz tube and vacuum-sealing the same, melting and quenching the quartz tube. The melting and cooling are performed at a temperature of about 900 to 1200 DEG C for 10 minutes to 48 hours and then held at a temperature of about 500 to 700 DEG C lower than the melting temperature for stabilization for 10 minutes to 12 hours, Followed by quenching.

The ingot-type composite thermoelectric material is rapidly solidified using a rapid solidification method to form a composite thermoelectric material powder.

The rapid solidification method may be a melt spinning method, a gas atomization method, a plasma deposition method, a centrifugal atomization method, a splat quenching method, or the like. But it is not necessarily limited to, and can be used as a rapid solidification method in the art.

As a specific example of the rapid solidification method, a melt spinning method will be described in detail. The melt spinning method is a method of melting raw materials and spraying (or dropping) them onto a wheel rotating at a high speed through a nozzle to rapidly solidify the raw materials. The apparatus for melt spinning comprises a melting furnace for melting a raw material, a heating means provided around the melting furnace, a pressure supply means provided at an upper portion of the melting furnace for applying pressure to the melted material and extruding the molten material into the nozzle, A nozzle provided at a lower portion of the melting furnace to eject molten material and a rotating wheel provided under the nozzle to rapidly solidify the molten material to be injected (dropped) through the nozzle into a ribbon shape. A rotary pump for making the chamber into a vacuum atmosphere, and the like. The melting furnace, the nozzle and the rotating wheel are provided in a vacuum chamber. An inert gas such as argon (Ar) is supplied into the vacuum chamber. The pressure in the vacuum chamber may be about 0.001 to 0.95 bar. The wheel may be made of a metal such as copper (Cu) or a metal alloy, and is rotated at a speed of about 100 to 5000 rpm. Cooling water may be connected to the inside of the wheel to maintain a low temperature. An apparatus for such a molten spinning method may be a commercially available apparatus. The composite thermoelectric material of the ingot type is melted and sprayed onto a rotating wheel through a nozzle using the above-described melt spinning method to perform rapid solidification to obtain a ribbon-shaped composite thermoelectric material powder. The thus-prepared composite thermoelectric material powder is a composite of a Bi-Sb-Te thermoelectric semiconductor and FeTe ₂ , and has a ribbon-like shape having a length larger than the thickness. The shape of the ribbon shape preferably has a thickness of 100 nm to 10 mu m, a width of 100 mu m to 5 cm, and a length of 100 mu m to 5 cm.

The composite thermoelectric material powder may be pulverized. The pulverization may be performed by ball milling, attrition milling, high energy milling, zet milling, grinding in a mortar, or the like. But the present invention is not limited thereto, and any method that can be used in the art can be used as a method of producing powder by dry pulverization.

Hereinafter, the pulverization process by the ball mill method will be specifically described. The composite thermoelectric material powder is charged into a ball milling machine and mixed. The mixture is rotated at a constant speed using a ball miller to pulverize the composite thermoelectric material powder while uniformly mixing. The ball used for the ball mill may be a ball made of a ceramic such as alumina or zirconia, and the balls may be all the same size or may be used together with balls having two or more sizes. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are adjusted so as to be crushed to the target particle size. For example, the size of the balls may be set in a range of about 1 mm to 50 mm in consideration of the size of the particles, and the rotational speed of the ball miller may be set in a range of about 100 to 500 rpm. The ball mill is preferably carried out for 1 to 48 hours in consideration of the target particle size and the like.

The composite thermoelectric material powder is sintered using spark plasma sintering, hot press sintering, or the like. The sintering is preferably performed at a temperature of 300 to 800 DEG C under a vacuum of 1 to 100 MPa for 1 to 10 minutes in a vacuum atmosphere. However, the sintering is not necessarily limited to these conditions, It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof. In the sintering process, a heterophase is precipitated in a secondary phase to form a composite thermoelectric material.

The composite thermoelectric material thus produced has a structure in which the secondary phase nanoparticles are formed on the mother phase. The parent phase is composed of a Bi-Sb-Te system thermoelectric semiconductor, and the secondary phase nanoparticles consist of _two kinds of FeTe ₂ nanoparticles and Fe nanoparticles (Fe-rich phase nanoparticles). The composite thermoelectric material has excellent properties of thermoelectric performance index. The FeTe ₂ nanoparticles and the Fe nanoparticles distributed in the thermoelectric semiconductors can improve the thermoelectric performance index by increasing the Seebeck coefficient due to the energy band control and reducing the thermal conductivity through phonon scattering. Since there is no significant decrease in the electrical conductivity, it is possible to improve the thermoelectric performance index.

Hereinafter, experimental examples according to the present invention will be specifically shown, and the present invention is not limited by the following experimental examples.

<Experimental Example 1>

Bi _{0 . 4} Sb _{1 . 6} Te ₃ were mixed with each other according to the composition ratio to prepare raw materials.

The raw material was placed in a quartz tube, vacuum-sealed, and then melted and cooled to produce an ingot-type thermoelectric material. Melting and cooling were carried out at 1100 ° C for 4 hours, followed by holding at 600 ° C for 1 hour, followed by quenching with water at room temperature.

The thermoelectric material of the ingot form was rapidly solidified by a melt spinning method to prepare a ribbon-shaped thermoelectric material powder. In the melt spinning, the thermoelectric material in the form of an ingot was melted in the chamber and ejected onto a Cu wheel through a nozzle. The inside of the chamber was an argon (Ar) gas atmosphere, the chamber pressure was 0.4 bar, the diameter of the Cu wheel was 250 mm, and the rotation speed of the Cu wheel was 1000 rpm.

The ribbon-shaped thermoelectric material powder was pulverized in a mortar to prepare a thermoelectric material powder.

A thermoelectric material was prepared by spark plasma sintering of the thermoelectric material powder. The spark plasma sintering was performed at 400 DEG C for 3 minutes under a pressure of 60 MPa and a vacuum condition.

<Experimental Example 2>

Bi _{0 . 4} Sb _{1 . 6} Te ₃ were mixed in accordance with the composition ratios, and Fe and Te, which are the raw materials of FeTe ₂ , were mixed to prepare a composite raw material. Fe and Te, which are the raw materials of the composition of FeTe ₂ , are 2, 4, 8, and 11 mol%, respectively, relative to the total molar amount of Bi, Sb and Te, which are the starting metal constituting the composition of the Bi-Sb- .

The composite raw material was placed in a quartz tube, vacuum-sealed, and then melted and cooled to prepare an ingot-type composite thermoelectric material. Melting and cooling were carried out at 1100 ° C for 4 hours, followed by holding at 600 ° C for 1 hour, followed by quenching with water at room temperature.

The composite thermoelectric material in the ingot form was rapidly solidified by a melt spinning method to prepare a ribbon-shaped composite thermoelectric material powder. In the melt spinning, the composite thermoelectric material in the form of an ingot was melted in the chamber and ejected onto a Cu wheel through a nozzle. The inside of the chamber was an argon (Ar) gas atmosphere, the chamber pressure was 0.4 bar, the diameter of the Cu wheel was 250 mm, and the rotation speed of the Cu wheel was 1000 rpm.

The ribbon-shaped composite thermoelectric material powder was pulverized in a mortar bowl to prepare a composite thermoelectric material powder.

The composite thermoelectric material was prepared by spark plasma sintering of the composite thermoelectric material powder. The spark plasma sintering was performed at 400 DEG C for 3 minutes under a pressure of 60 MPa and a vacuum condition.

FIGS. 1 and 2 are diagrams showing X-ray diffraction (XRD) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2. FIG. In FIG. 1 and FIG. 2, 'BST' is for the thermoelectric material produced according to Experimental Example 1, and 'BST-2% FeTe ₂ ' is Fe and Te, which are the raw metals forming the composition of FeTe ₂ according to Experimental Example 2, BST-4% FeTe ₂ 'is a composite type thermoelectric material prepared by mixing 2 mol% of the total molar amount of Bi, Sb and Te, which are the raw metals of the composition of the -Sb-Te thermoelectric semiconductor. According to Example 2, Fe and Te, which are the raw materials of FeTe ₂ , were mixed to make 4 mol% based on the total molar amount of Bi, Sb and Te, which are the raw metals of the composition of the Bi-Sb- BST-8% FeTe ₂ 'is a raw material metal that forms the composition of FeTe ₂ , and Fe and Te which are the raw materials of the composition of Bi-Sb-Te based thermoelectric semiconductor are Bi, Sb And 8 mol% based on the total molar content of Te. BST-11% FeTe ₂ 'is the raw material metal constituting the composition of FeTe ₂ according to Experimental Example 2, and Fe and Te are the raw materials of Bi, Sb and Te which are the raw metal constituting the composition of the Bi-Sb- To 11 mol% based on the molar content of the composite material.

1 and 2, FeTe ₂ crystal phase was observed in the composite thermoelectric material prepared according to Experimental Example 2. In particular, when Fe and Te, which are the raw materials of FeTe ₂ , were added in an amount of 4 mol% or more It was confirmed that FeTe ₂ crystal peak clearly appeared.

3A is a graph showing the relationship between the total molar amount of Bi, Sb, and Te as a raw material metal constituting the composition of the Bi-Sb-Te based thermoelectric semiconductor, Fe and Te, which are the raw materials of FeTe ₂ , FIG. 3B is a high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image, FIG. 3C is a HAADF-STEM image and FIG. TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) element map (TEM-EDS elemental maps).

Figure 4a is mixed to achieve a 8 mol% compared to the total molar content of the composition forming raw material metal of Fe and Te of FeTe ₂ Bi-Sb-Te based thermoelectric raw material metal constituting the composition of the semiconductor Bi, Sb and Te in accordance with Experimental Example 2 FIG. 4B is a high resolution HAADA-STEM image, FIG. 4C is a HAADF-STEM image, and TEM-EDS is a high resolution HAADA-STEM image of a composite thermoelectric material Show element-maps (TEM-EDS elemental maps).

Referring to FIGS. 3A to 4C, secondary nanoparticles are formed on the parent phase to show the structure. It was observed that FeTe ₂ nanoparticles were formed in the core and Fe nanoparticles were formed. The FeTe ₂ nanoparticles have a size of 10 nm to 1 탆, and the Fe-rich phase nanoparticles have a size of 1 to 100 nm.

FIG. 5 is a graph showing the electrical conductivity () of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2, FIG. 6 is a graph showing the electric conductivity is a graph showing the Seebeck coefficient (S) of the composite body type thermoelectric material prepared according to 2, Figure 7 is FeTe and Bi _{2 0. 4} Sb _{1 . 6} Te ₃ is a graph showing the Seebeck coefficient (S) according to the charge density, Figure 8 shows the output factor (PF) of the composite body type thermoelectric material prepared according to the thermal transfer material in Experiment Example 2 produced according to Experimental Example 1 FIG. 9 is a graph showing the thermal conductivity (k) of the thermoelectric material produced according to Experimental Example 1 and the composite thermoelectric material prepared according to Experimental Example 2, and FIG. 10 is a graph showing the thermal conductivity Fig. 11 is a graph showing the lattice thermal conductivity (k) of the composite thermoelectric material produced according to Experimental Example 2. Fig. 11 is a graph showing the lattice thermal conductivity (k) of the thermoelectric material produced according to Experimental Example 1 and the thermoelectric This figure shows the performance index (ZT). 5, 6, and 8 to 11, 'BST' refers to the thermoelectric material produced according to Experimental Example 1, 'BST-2% FeTe ₂ ' corresponds to the FeTe ₂ composition according to Experimental Example 2, BST-4 is a composite type thermoelectric material prepared by mixing Fe and Te, which are Fe, and Te, in an amount of 2 mol% based on the total molar amount of Bi, Sb and Te, which are the raw metals of the composition of the Bi-Sb- % FeTe ₂ 'was prepared in the _{same manner} as in Experimental Example 2 except that Fe and Te, which are the raw materials of the composition of FeTe ₂ , were 4 mol% based on the total molar amount of Bi, Sb and Te, which are the starting metal constituting the composition of the Bi-Sb- 'BST-8% FeTe ₂ ' is a mixed-type thermoelectric material prepared by mixing Fe and Te, which are the raw materials of the composition of FeTe ₂ according to Experimental Example 2, with a composition of Bi-Sb-Te thermoelectric semiconductor And 8 mol% based on the total molar amount of Bi, Sb and Te, which are raw material metals, I are for the _{material, 'BST-11% FeTe 2} ' is in the composition forming raw material metal of Fe and Te of FeTe ₂ raw material metals forming a composition of Bi-Sb-Te based thermoelectric semiconductor according to Experimental Example 2 Bi, Sb, and Te of 11 mol% based on the total molar content of the thermoelectric material.

Referring to Figure 5 to Figure 11, a Bi-Sb-Te based thermoelectric semiconductor _{(Bi 0. 4 Sb 1.} 6 Te 3 Thermoelectric Semiconductor) in FeTe ₂ by introducing the Seebeck coefficient increases and the power factor increases, the thermal conductivity reduction effects It is judged to be visible. It is considered that the anti-Seebeck coefficient increases due to band alignment between the parent phase (Bi _0.4 Sb _1.6 Te ₃ thermoelectric semiconductor) and FeTe ₂ .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

Claims (13)

Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) Composite body thermoelectric materials in which heterogeneous FeTe ₂ nanoparticles and Fe-rich phase nanoparticles are dispersed in a thermoelectric semiconductor.
The composite thermoelectric material according to claim 1, wherein the FeTe ₂ nanoparticles and the Fe nanoparticles are contained in the composite thermoelectric material in an amount of 0.1 to 20.0 mol% based on the Bi _x Sb _{2 - x} Te ₃ thermoelectric semiconductor. Material.
The composite thermoelectric material according to claim 1, wherein the FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.
The composite thermoelectric material according to claim 1, wherein the Fe nanoparticles have a size of 1 to 100 nm.
Bi, Sb and Te which are the raw materials of the metal constituting the composition of Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than 2) are mixed in accordance with the composition ratio, and Fe and Te, which are the raw metals forming the composition of FeTe ₂ , To prepare a composite raw material;
Synthesizing an ingot-type composite thermoelectric material using the composite material;
Rapidly solidifying the ingot-type composite thermoelectric material using a rapid solidification method to form a composite thermoelectric material powder; And
And sintering the composite thermoelectric material powder to obtain a composite thermoelectric material,
The complex type thermoelectric material has a structure in which FeTe ₂ nanoparticles and Fe-rich phase nanoparticles, which are heterogeneous, are dispersed in a thermoelectric semiconductor, Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) Wherein the composite thermoelectric material is a thermoelectric material.
Preparing a composite raw material by mixing a Bi-Sb-Te system thermoelectric semiconductor and FeTe ₂ ;
Synthesizing an ingot-type composite thermoelectric material using the composite material;
Rapidly solidifying the ingot-type composite thermoelectric material using a rapid solidification method to form a composite thermoelectric material powder; And
And sintering the composite thermoelectric material powder to obtain a composite thermoelectric material,
The complex type thermoelectric material has a structure in which FeTe ₂ nanoparticles and Fe-rich phase nanoparticles, which are heterogeneous, are dispersed in a thermoelectric semiconductor, Bi _x Sb _{2 - x} Te ₃ (where X is a real number smaller than ₂ ) Wherein the composite thermoelectric material is a thermoelectric material.
6. The method of claim 5, wherein Fe and Te, which are the raw materials of the composition of FeTe ₂ , are the total of Bi, Sb, and Te, which are the raw metal constituting the composition of Bi _x Sb _2-x Te ₃ (where X is a real number smaller than 2) Wherein the molar content of the thermoplastic elastomer is in the range of 0.1 to 20.0 mol% based on the molar content.
[7] The method according to claim 6, wherein the FeTe ₂ is mixed with 0.1 to 2.0 mol% of the Bi-Sb-Te based thermoelectric semiconductor.
The composite thermoelectric material according to claim 5 or 6, wherein the FeTe ₂ nanoparticles have a size of 10 nm to 1 탆.
The composite thermoelectric material of claim 5 or 6, wherein the Fe nanoparticles have a size of 1 to 100 nm.
[7] The method according to claim 5 or 6, wherein the step of forming the composite thermoelectric material powder comprises melting the ingot-type composite thermoelectric material and spraying the molten composite thermoelectric material onto a rotating wheel through a nozzle to rapidly solidify the composite thermoelectric material powder, To obtain a material powder. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
The composite thermoelectric material manufacturing method according to claim 11, wherein the shape of the ribbon shape has a thickness of 100 nm to 10 m, a width of 100 m to 5 cm, and a length of 100 m to 5 cm.
The method according to claim 5 or 6, wherein the sintering is performed using spark plasma sintering or hot press sintering,
Wherein the sintering is performed in a vacuum atmosphere at a temperature of 300 to 800 DEG C and a pressure of 1 to 100 MPa.

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