KR101323321B1 - MnTe thermoelectric material doped with Sb and manufacturing method thereby - Google Patents

Abstract

The present invention relates to Sb-doped Sb MnTe-based thermoelectric material and a method for manufacturing the same, in the Sb-doped MnTe-based thermoelectric material, having a composition of Mn _{1 - x} Sb _x Te compound, wherein 0.01≤x≤0.2 Sb-doped MnTe system, characterized in that Thermoelectric material is the technical point. In addition, the present invention comprises a first step of weighing each of Sb, Mn and Te in accordance with the composition ratio to charge into a vacuum ampoule and melt; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder; Sb comprising a fourth step of manufacturing the Sb-doped MnTe-based thermoelectric material by sintering the Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder and then hot cutting or after the plasma cutting sintering process to produce Sb-doped MnTe-based thermoelectric material A method for producing a doped MnTe based thermoelectric material is also a technical subject matter. Accordingly, by doping Sb through a predetermined quenching process and hot pressing or discharge plasma sintering process, Sb is doped to MnTe by a certain amount, thereby improving its thermoelectric properties and thus being able to be used as a thermoelectric material having excellent performance.

Description

MnTe thermoelectric material doped with Sb and manufacturing method thereby

The present invention relates to an MnTe-based thermoelectric material doped with Sb for improving thermoelectric characteristics, and an MnTe-doped MnTe for improving thermoelectric properties by doping Sb in MnTe in a predetermined amount. To a thermoelectric material and a manufacturing method thereof.

Generally, thermoelectric technology is a technology to convert heat energy directly into electric energy, and conversely to convert electric energy into heat energy directly in solid state. It is applied to thermoelectric power generation which converts heat energy into electric energy and thermoelectric cooling which converts electric energy into heat energy have.

The thermoelectric material used as the material for the thermoelectric power generation and the thermoelectric cooling increases the performance of the thermoelectric device as the thermoelectric property increases. The determination of the thermoelectric performance is based on the assumption that the thermoelectric performance is determined based on the thermoelectric power V, the Seebeck coefficient?, The Peltier coefficient?, The Thomson coefficient?, The Nernst coefficient Q, the Etchinghausen coefficient P, ), The output factor (PF), the figure of merit (Z), the dimensionless figure of merit (ZT = α ² σT / κ where T is the absolute temperature), thermal conductivity (κ), Lorentz number And resistivity (rho).

Particularly, the dimensionless figure of merit (ZT) is an important factor for determining the thermoelectric conversion energy efficiency. The thermoelectric device is manufactured by using a thermoelectric material having a high performance index (Z =? ² ? /?), It is possible to increase the efficiency of the apparatus. That is, thermoelectric materials have better thermoelectric performance as the Seebeck coefficient, electrical conductivity and thermal conductivity are lower.

Currently commercialized thermoelectric materials have a ZT of about 1 level, and are classified into Bi-Te-based for room temperature, Pb-Te-based, Mg-Si-based, and high-temperature oxide, Fe-Si-based, etc. do.

On the other hand, in order to improve the thermoelectric performance of such a thermoelectric material, a method of adding or replacing various elements (composition control), a method of controlling microstructure (manufacturing process control), abnormal particles or impurities (addition element, substitution element, doping element) ) Can be introduced.

In general, metal-based thermoelectric materials are used in various ways to reduce the thermal conductivity if possible while maintaining the electrical conductivity. On the other hand, attempts have been made to improve the performance index of oxide thermoelectric materials by increasing the Seebeck coefficient.

AgSbTe ₂ Binary Compounds (AgSbTe ₂ )-(mPbTe) (LAST-m) Bulk Including Compounds of Nano-dots on Ag-Sb-rich on Pb-Te Matrix at m = 18 at 700 K Due to the formation, it has a high ZT ≒ 1.7 with a decrease in thermal conductivity due to phonon scattering. Likewise, (GeTe) _x (AgSbTe ₂ ) _100-x (TAGS-x) alloys with chemical compositions similar to LAST have ZT ≒ 1.9 at 800K due to the formation of nano-domains at x = 80. .

In the above results, theoretical and experimental results from various aspects of SbTe-based compounds based on the addition of Ag, which is a common constituent of LAST-m compound and TAGS-x compound, which are high temperature thermoelectric materials exhibiting high thermoelectric properties, Required.

However, no attempt has been made to improve thermoelectric performance by doping Sb into Mn-Te-based thermoelectric materials.

Accordingly, the present invention has been made to solve the problems of the prior art, MnTe by going through a predetermined quenching process and hot press or discharge plasma sintering process by doping Sb to improve the performance index of the MnTe-based thermoelectric material The present invention relates to a MnTe-based thermoelectric material doped with Sb and to a method of manufacturing the same, in which Sb is doped in a predetermined amount to improve its thermoelectric properties.

The present invention for achieving the above object, in the Sb-doped MnTe-based thermoelectric material, has a composition of Mn _{1 - x} Sb _x Te compound, wherein Sb-doped MnTe, characterized in that 0.01≤x≤0.2 system The thermoelectric material is the technical point.

In addition, the present invention comprises a first step of weighing each of Sb, Mn and Te in accordance with the composition ratio to charge and melt in a vacuum ampoule; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder; And sintering the Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder to cut the wire after a hot press or discharge plasma sintering process to produce a Sb-doped MnTe-based thermoelectric material. The manufacturing method of Sb-doped MnTe type thermoelectric material is also a technical subject matter.

Here, the first step is preferably performed for 5 hours to 10 hours at 450 ℃ or more and 600 ℃ or less.

The quenching in the second step is preferably carried out by immersing the ampule in water and quenching it.

The hot press or discharge plasma sintering process of the fourth step is preferably performed at 30 ~ 300MPa for 5 minutes to 3 hours at a temperature of 300 ℃ to 600 ℃.

Accordingly, by doping Sb through a predetermined quenching process and hot pressing or discharging plasma sintering process, Sb is stably doped in MnTe to improve the performance index so as to be an excellent thermoelectric material, thereby improving thermoelectric power generation and thermoelectric cooling. There is an advantage that can be widely used as a thermoelectric material in the field.

The present invention by the above configuration by doping Sb through a predetermined quenching process and hot pressing or discharge plasma sintering process to ensure a certain amount of Sb doped MnTe to improve the performance index to be an excellent thermoelectric material There is an effect that can be widely used as a thermoelectric material in the field of thermoelectric power generation and thermoelectric cooling.

FIG. 1 is a graph illustrating changes in Seebeck coefficient with temperature of Mn _{1 - x} Sb _x Te thermoelectric materials prepared according to examples and comparative examples of the present invention. FIG.
FIG. 2 is a diagram illustrating a change in specific resistance of a Mn _{1 - x} Sb _x Te thermoelectric material prepared according to Examples and Comparative Examples of the present invention.
Figure 3 is a view measuring the change in thermal conductivity according to the temperature of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the Examples and Comparative Examples of the present invention.
Figure 4 is a view measuring the change in the performance index according to the temperature of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the Examples and Comparative Examples of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric material for improving thermoelectric characteristics and a method of manufacturing the same, and particularly, to improve the thermoelectric performance of thermoelectric materials by adding a certain amount of Sb to a MnTe-based thermoelectric material at a doping material level.

Here, the Sb-doped MnTe-based thermoelectric material has a composition of Mn _{1 - x} Sb _x Te, where 0.01 ≦ x ≦ 0.2.

In addition, in the method of manufacturing the Sb-doped MnTe-based thermoelectric material, Sb, Mn and Te are respectively weighed according to the composition ratio, charged into a vacuum quartz tube ampoule coated with thin carbon inside, and melted. The ingot is made by quenching and the ingot is separated from the quartz tube.

Mn _{1 - x} Sb _x Te (0.01≤x≤0.2) powder was prepared by crushing the separated ingot, and the Mn _1-x Sb _x Te (0.01≤x≤0.2) powder was sintered to hot press or discharge plasma sintering. After the process, the wire is cut to prepare an MnTe-based thermoelectric material doped with Sb.

Hereinafter, this will be described in detail.

First, to prepare Mn _{1 - x} Sb _x Te thermoelectric material, pure (99.999%) Sb, Mn and Te are prepared by weighing. Then, the weighed raw materials are charged into a quartz tube ampule whose interior is coated thinly with carbon, and the pressure inside the quartz tube is made to be a vacuum of 10 ^-5 Torr or less by using a rotary vacuum pump and an oil-spreading vacuum pump, The inside of the quartz tube is filled with argon (Ar) gas and sealed at atmospheric pressure. Then, a material having an atomic ratio Mn _{1 - x} Sb _x Te filled with argon gas is present in the quartz tube.

It is melted by high frequency induction melting at a temperature of about 450 ° C. for about 5 hours or more.

As a result, the Sb, Mn and Te materials are uniformly mixed and melted, thereby producing a Mn _{1 - x} Sb _x Te thermoelectric material doped with a certain amount of Sb at Mn sites of MnTe, and the doping content x of Sb is 0.01 or more and 0.2 or less. Very small amount is added.

Here, when the doping content of Sb is greater than 0.2, other effects such as oxidization, precipitation, and segregation increase are increased instead of the addition effect by Sb doping, and when it is less than 0.01, no physical property change is caused by the addition of trace amount. . In particular, since Sb has a very high oxidizing ability, it is very likely to be added in an oxide state when Sb is added and alloyed. Therefore, it is necessary to add Sb as a pure Sb state instead of an oxide state.

Then, in a liquid state dissolved in a high frequency induction melting method Mn _{1 - x} Sb _x Te enters the quartz tube was quenched in water in a spoken wall, to remove the quartz tube Mn _{1 - x} Sb _x Te to obtain an ingot. The Mn _{1 - x} Sb _x Te ingot is crushed to prepare Mn _{1 - x} Sb _x Te in powder form. The prepared Mn _1-x Sb _x Te powder is filled with a screen of about 325 mesh and separated and recovered into a powder of 325 mesh or less.

Then, the Mn _{1 - x} Sb _x Te powder is sintered, and the wire is cut after hot pressing or discharge plasma sintering to manufacture a thermoelectric material having a predetermined size. The hot press or discharge plasma sintering process is performed in the graphite mold for a few minutes or more at a temperature of about 550 ° C. and a pressure of about 30 MPa or more.

Such a manufacturing process makes it easy to control the composition of Sb, thereby controlling the amount of Sb doping added, thereby obtaining a pure Sb-doped Mn _{1 - x} Sb _x Te thermoelectric material.

Hereinafter, preferred embodiments of the present invention will be described.

High purity Sb, Mn, Te of 99.999% or more are washed with hydrochloric acid, nitric acid, acetone, ethanol, etc., and then weighed using a precision balance to the atomic composition ratio Mn _{1 - x} Sb _x Te (0.01≤x≤0.2) Prepare. Here Mn ₁ Sb is doped in a _- in the _x Sb _x Te (0.01≤x≤0.2) thermal conductive material such that the content of doping x is 0.02 of Sb to produce a Mn _{0 .98} Sb _{0 .02} Te.

Here, in the comparative example, each element is weighed and prepared also for MnTe which is 0.

Then, the weighed raw material is charged into a quartz tube ampoule, and the pressure inside the ampoule is 10 ^-5 Torr. It becomes a vacuum state of 10 ^-5 Torr and is filled with argon (Ar) gas. The sealed quartz tube and thereby melting at 450 ℃ for 5 hours using a high frequency induction melting method, wherein a quartz tube inside the liquid Mn _{1 - x} Sb _x Te that is possible example. After soaked quench the quartz tube containing the _x Sb _x Te in the water, to remove the quartz tube Mn _{1 - - 1} Mn in the liquid state to obtain the _x Sb _x Te.

Thereafter, the Mn _{1 - x} Sb _x Te is crushed to prepare a powdered Mn _{1 - x} Sb _x Te, which is then sieved and sintered and hot pressed or discharged at a pressure of 30 MPa at a temperature of 550 ° C. for 5 minutes. The rod-shaped specimen is manufactured through a plasma sintering process and wire-cut to produce a thermoelectric material having a predetermined shape.

As described above, the Sb-doped Mn _{1 - x} Sb _x Te thermoelectric material is formed into a circular plate by cutting the rod-shaped specimen in a direction parallel to the pressing direction to measure physical properties. Generally, physical properties are measured in a direction parallel to the press direction (z direction). The thermal conductivity measurement uses a circular plate shape, and the electrical property measurement uses a rectangular parallelepiped shape sample.

On the other hand, the experimental results were also compared for the case where Sb is not doped for the comparative experiment.

1 is a measurement of the Seebeck coefficient according to the temperature of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the above Examples and Comparative Examples, the Seebeck coefficient is smaller than the comparative example as a whole, but the gap in the middle temperature range It can be seen that the decrease.

Figure 2 is a measurement of the specific resistance according to the temperature of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the above Examples and Comparative Examples, it can be seen that the specific resistance of the embodiment of the present invention is relatively much smaller than the comparative example Can be.

3 is a measurement of the thermal conductivity according to the temperature of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the above Examples and Comparative Examples, the embodiment of the present invention has a lower thermal conductivity than the comparative example And it was found.

4 is a measurement of the change in the performance index (ZT) of the Mn _{1 - x} Sb _x Te thermoelectric material prepared according to the above Examples and Comparative Examples, the performance index according to the embodiment of the present invention as a whole better than the comparative example It was found that the figure of merit improved in all measured temperature ranges compared to the comparative example.

As described above, the Sb-doped Mn _{1 - x} Sb _x Te thermoelectric material manufactured according to the present invention has improved performance index, which can control the amount of Sb doping in the manufacturing of thermoelectric material to improve its thermoelectric characteristics. And it is expected to be widely used as a thermoelectric material in the field of thermoelectric cooling.

Although the above describes a thermoelectric material doped with Sb in MnTe, in the MnTe-based material is MnTe ₂ also exist, and, MnTe was the result doped with Sb ₂ than MnTe _second thermoelectric performance can be obtained improved results, MnTe It is obvious that the construction of the thermoelectric material doped with Sb ₂ also belongs to the scope of the present invention.

Claims (5)

In the Sb-doped MnTe-based thermoelectric material,
Sb-doped MnTe system having a composition of Mn _{1 - x} Sb _x Te compound, wherein 0.01 ≦ x ≦ 0.2 Thermoelectric material. A first step of weighing Sb, Mn, and Te according to the composition ratios, charging the molten Sb, Mn, and Te into a vacuum ampoule;
A second step of rapidly cooling the molten raw material to produce an ingot;
Crushing the ingot to prepare Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder;
And sintering the Mn _{1 - x} Sb _x Te (0.01 ≦ _x ≦ 0.2) powder to cut the wire after a hot press or discharge plasma sintering process to produce a Sb-doped MnTe-based thermoelectric material. Method for producing a Sb-doped MnTe-based thermoelectric material. The method of claim 2, wherein the first step is performed at 450 ° C. or higher and 600 ° C. or lower for 5 hours to 10 hours. The method of claim 3, wherein the quenching of the second step is performed by immersing an ampoule in water to quench the quench. 5. The Sb-doped MnTe system according to claim 4, wherein the hot press or discharge plasma sintering process of the fourth step is performed at 30 to 300 MPa for 5 minutes to 3 hours at a temperature of 300 ° C. to 600 ° C. 6. Method of manufacturing thermoelectric material.

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