KR101869427B1 - Nano-thermoelectric powder and thermoelectric device using the same - Google Patents

Abstract

The present invention relates to a method of synthesizing a thermoelectric powder at a nano-scale, which can replace the conventional process of producing an ingot requiring high energy and crushing it to obtain a thermoelectric powder. In addition, the thermoelectric device manufactured using the thermoelectric powder according to the synthesis method of the present invention shows improved thermoelectric performance as compared with the conventional thermoelectric device.

Description

TECHNICAL FIELD The present invention relates to a nano-thermoelectric powder and a thermoelectric device using the same,

Nano-sized thermoelectric powders, a method of synthesizing the same, a bulk-type thermoelectric device having a nanostructure using the same, and a method of manufacturing the same.

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

Bi-Te thermoelectric materials are used as means for solving heat dissipation problems of highly integrated devices and various sensors due to excellent thermoelectric performance at room temperature, and they are mainly manufactured by one-way solidification method or single crystal growth method. However, a thermoelectric device using a casting method such as a one-direction solidification method or a single crystal growth method is disadvantageous in that it has a high cost due to an increase in a production cost due to a reduction in a recovery rate in processing and module manufacturing,

In order to overcome such problems, researches on powder metallurgy process have been actively carried out. However, the micro-thermoelectric powders obtained by preparing and crushing the conventional ingot have control of densification of texture, size of grain and crystallographic anisotropy Therefore, it is difficult to control the thermoelectric performance.

SUMMARY OF THE INVENTION The present invention provides a nano thermoelectric powder for solving the above problems.

The present invention also provides a method of synthesizing the nano-thermoelectric powder.

The present invention also provides a thermoelectric device using the nano-sized thermoelectric powder.

The present invention also provides a method of manufacturing a thermoelectric device using the nano thermoelectric powder.

The present invention provides a nano thermoelectric powder having an average particle size of 20 to 200 nm.

The nano thermoelectric powder includes at least one selected from Bi, Te, Sb and Se.

The nano thermoelectric powder may contain P in an amount of 5 to 30% by weight of Bi, 50 to 70% by weight of Te and 20 to 35% by weight of Sb, and may contain 45 to 60% by weight of Bi, By weight, and 0.1 to 10% by weight, respectively, so as to have N-type characteristics.

The present invention provides a thermoelectric device obtained by sintering the nano thermoelectric powder.

The nano thermoelectric powder according to the present invention comprises (a) adjusting the pH of the solvent from neutral to basic; (b) adding a thermoelectric powder raw material to the solvent; (c) further adding a reducing agent to the solvent to which the thermoelectric powder raw material is added to prepare a thermoelectric powder forming composition; And (d) synthesizing a nano thermoelectric powder from the thermoelectric powder-forming composition.

In the step (a), the pH may be adjusted to 8 to 11 by adding a base such as NaOH or KOH to the aqueous solution.

The thermoelectric powder raw material in the step (b) may be a raw material capable of producing a P-type thermoelectric powder including a raw material of Bi, a raw material of Te, and a raw material of Sb.

More specifically, the thermoelectric powder raw material in the step (b) is a raw material of Bi 5 to 30% by weight, the raw material of Te 50 to 70% by weight, and the raw material of Sb 20 to 35% by weight.

The thermoelectric powder raw material in the step (b) may be a raw material capable of producing an N-type thermoelectric powder including a raw material of Bi, a raw material of Te, and a raw material of Se.

More specifically, the thermoelectric powder raw material in the step (b) includes N-type thermoelectric material containing 45 to 60% by weight of the raw material of Bi, 35 to 50% by weight of the raw material of Te and 0.1 to 10% by weight of the raw material of Se. It may be a powder raw material.

The raw material of Bi, Te, Sb and Se is one can be used, but not limited to, use in the art, non-limiting examples, a raw material of the Bi is Bi, BiF _3, BiF _5, BiCl _3, BiBr _{3, BiI 3, Bi 2 O 3,} Bi (OH) 3, BiOCl, BiOI, BiONO 3, Bi (NO 3) 3, Bi (NO 3) 3 · xH 2 O (x is a natural number), BiPO _4, (BiO) there may be mentioned ₂ CO ₃ or the like, to a raw material for the Te is such as _{Te, TeO 2, TeO 3,} Te (OH) 6, Na 2 TeO 3, K 2 TeO 3, TeI 4, TeBr 4, TeCl 4 there may be mentioned, as a raw material of the Sb is and the like Sb, SbOCl, SbCl _3, SbCl _5, Sb ₂ O _3, Sb ₂ O _5, Sb ₂ O _4, SbBr _3, SbF _3, SbF _5, Examples of the raw material of Se include Se, SeO ₂ , Na ₂ SeO ₃ , K ₂ SeO ₃ , H ₂ SeO ₄ , SeOCl ₂ , SeS ₂ , SeBr ₄ and SeCl ₄ .

The reducing agent and suitable to add parts of 0.2 to 10 parts by weight based on 100 parts by weight of the heat-powder raw material, one can be used without limitation so long used in the art, non-limiting example, NaBH _4, KBH ₄ or N ₂ H _{4 ·} H ₂ O can be used.

At least one additive such as ethylenediaminetetraacetic acid (EDTA), cetyltrimethylammonium bromide (CTAB), sodium dodecylammonium sulfate (SDS), or sodium dodecylbenzene sulfate (SDBS) may be added to the thermoelectric powder forming composition of step (c) .

The nano thermoelectric powder can be synthesized by reacting the thermoelectric powder forming composition of step (d) at a temperature of 60 to 100 ° C for 5 to 24 hours.

It is preferable that the reaction is performed in an inert gas atmosphere of nitrogen or argon because it can improve the yield of the nano thermoelectric powder and prevent impurities from being contained in the nano thermoelectric powder and oxidation.

The method of synthesizing the nano-sized thermoelectric powder may further include (e) washing and drying the nano-sized thermoelectric powder after the steps (a) to (d).

The nano thermoelectric powder having an average particle size of 20 to 200 nm can be obtained by the above-described synthesis method of the nano thermoelectric powder.

The present invention further provides a method of manufacturing a thermoelectric device, further comprising the step of (f) sintering the thermoelectric device after the step of synthesizing the nano thermoelectric powder.

The sintering may be carried out by SPS (Spark Plasma Sintering) equipment by placing nano thermoelectric powder in a graphite die.

The shape of the thermoelectric element manufactured according to the method of manufacturing the thermoelectric element may be a pellet type in a bulk form.

The present invention also provides P-type and N-type thermoelectric elements manufactured according to the method of manufacturing the thermoelectric element.

A bulk type thermoelectric element having a nanostructure manufactured by using the nano thermoelectric powder according to the present invention improves the scattering effect of phonon and has excellent thermoelectric performance. In addition, when the nano thermoelectric powder is used, Not only does it greatly reduce energy, but it also simplifies the manufacturing process.

FIG. 1 schematically shows a process of making a conventional thermoelectric device.
FIG. 2 is a schematic view showing a process of making a thermoelectric device according to the present invention.
FIG. 3 is a schematic view illustrating a process of making a thermoelectric device by sintering a nano thermoelectric powder synthesized according to an embodiment of the present invention.

The present invention relates to nano-sized thermoelectric powders and methods for their synthesis.

In the prior art (see FIG. 1), a process for producing a thermoelectric element and a process for preparing an ingot and pulverizing the ingot to obtain a fine thermoelectric powder (average particle size: about 100 μm) was required. High energy was required.

However, according to the present invention (refer to FIG. 2), since nano-sized thermoelectric powders can be obtained in accordance with the method of synthesizing nano thermoelectric powders instead of the above-mentioned process, energy for manufacturing thermoelectric elements is greatly reduced, The manufacturing process of the device can be shortened, and the thermoelectric device according to the present invention has excellent thermoelectric properties.

Hereinafter, the present invention will be described in detail. However, the examples described below can be modified in various other forms, and the scope of the present invention should not be construed as being limited due to the above-mentioned examples. The following examples are provided to more fully describe the present invention to those skilled in the art. Therefore, the constituent elements and the like in the drawings are exaggerated in order to emphasize a clearer description, and elements denoted by the same symbols in the drawings denote the same elements.

The nano-sized thermoelectric powder according to the present invention has an average particle size of about 20 to 200 nm.

The nano thermoelectric powder is composed of Bi, Te, Sb, Se, etc., and the content of the nano thermoelectric powder can be controlled to obtain a nano thermoelectric powder having P type or N type characteristics.

The nano-sized thermoelectric powder having the P-type characteristics may contain 5 to 30% by weight of Bi, 50 to 70% by weight of Te and 20 to 35% by weight of Sb, and particularly 9.6 to 21.3% by weight of Bi, 58.7% by weight and Sb 23.0% to 31.8% by weight are preferable because a P-type thermoelectric powder having a high thermoelectric performance can be obtained.

The nano-sized thermoelectric powders having the N-type characteristics may contain 45 to 60% by weight of Bi, 35 to 50% by weight of Te and 0.1 to 10% by weight of Se, in particular, Bi 52.5 to 53.5% 46.5% by weight and Se 0.9 to 4.1% by weight is preferable because an N-type thermoelectric powder having a high thermoelectric performance can be obtained.

The thermoelectric element according to the present invention can be obtained by sintering the nano thermoelectric powder, and the thermoelectric element thus obtained has excellent thermoelectric performance.

In the nano-thermoelectric powder according to the present invention,

(a) adjusting the pH of the solvent from neutral to basic;

(b) adding a thermoelectric powder raw material to the solvent;

(c) further adding a reducing agent to the solvent to which the thermoelectric powder raw material is added to prepare a thermoelectric powder forming composition; And

(d) synthesizing nano thermoelectric powders from the thermoelectric-powder-forming composition.

In the step (a), a base such as NaOH or KOH is added to the aqueous solution to adjust the pH to 8 to 11 (a), since the nano thermoelectric powder is advantageously ionized at a neutral to basic pH, .

The thermoelectric powder raw material in the step (b) may be a raw material of Bi, a raw material of Te, a raw material of P, a raw material of Bi, a raw material of Te and a raw material of Se, Type thermoelectric powder raw material containing N-type thermoelectric powder.

When the thermoelectric powder raw material is a P-type thermoelectric powder raw material, 5 to 30% by weight of raw material of Bi, 50 to 70% by weight of raw material of Te and 20 to 35% by weight of raw material of Sb are contained In particular, in a content of 9.6 to 21.3% by weight of a raw material of Bi, 55.6 to 58.7% by weight of a raw material of Te and 23.0 to 31.8% by weight of a raw material of Sb to obtain a P-type thermoelectric powder having a high thermoelectric performance .

The P-type thermoelectric powder raw material is mixed according to the above-mentioned contents and put into a solvent whose pH is controlled in step (a).

In the case where the thermoelectric powder raw material is an N-type thermoelectric powder raw material, it is contained in an amount of 45 to 60 wt% of raw material of Bi, 35 to 50 wt% of raw material of Te, and 0.1 to 10 wt% of raw material of Se In particular, in the content of 52.5 to 53.5% by weight of raw material of Bi, 42.4 to 46.5% by weight of raw material of Te and 0.9 to 4.1% by weight of raw material of Se to obtain an N-type thermoelectric powder having a high thermoelectric performance .

The N-type thermoelectric powder raw material is mixed according to the above-mentioned contents and put into a solvent whose pH is controlled in step (a).

The thermoelectric powder raw material may be any of those used in the art as long as it is used as a P type or N type thermoelectric powder raw material.

Non-limiting examples, a raw material of the Bi is _{Bi, BiF 3, BiF 5,} BiCl 3, BiBr 3, BiI 3, Bi 2 O 3, Bi (OH) 3, BiOCl, BiOI, BiONO 3, Bi (NO 3) ₃ , Bi (NO ₃ ) ₃ .xH ₂ O (x is a natural number), BiPO ₄ , (BiO) ₂ CO ₃ and the like.

As a non-limiting example, the raw materials of Te include Te, TeO ₂ , TeO ₃ , Te (OH) ₆ , Na ₂ TeO ₃ , K ₂ TeO ₃ , TeI ₄ , TeBr ₄ and TeCl ₄ .

Non-limiting examples, a raw material of the Sb is the like _{Sb, SbOCl, SbCl 3, SbCl} 5, Sb 2 O 3, Sb 2 O 5, Sb 2 O 4, SbBr 3, SbF 3, SbF 5.

Non-limiting examples, the raw materials of the Se has, and the like _{Se, SeO 2, Na 2 SeO} 3, K 2 SeO 3, H 2 SeO 4, SeOCl 2, SeS 2, SeBr 4, SeCl 4.

The reducing agent added in the step (c) is added in an amount of 0.2 to 10 parts by weight based on 100 parts by weight of the thermoelectric powder raw material. When the amount of the reducing agent is less than 0.2, the amount of the unreacted material may remain because the reduction is not performed. When the amount of the reducing agent is more than 10, a desired amount of side reaction occurs. Or amorphous form, so that the resultant product can not be synthesized.

The reducing agent can be used without limitation as long as it is used in the art. Non-limiting examples of the reducing agent include NaBH ₄ , KBH _4, and N ₂ H ₄ .H ₂ O.

The thermoelectric powder-forming composition of the step (c) may further contain additives such as ethylenediaminetetraacetic acid (CTE), cetyltrimethylammonium bromide (CTAB), sodium dodecylammonium sulfate (SDS), or sodium dodecylbenzene sulfate (SDBS).

The addition of the additive is preferable in that it is possible to synthesize well-dispersed nano thermoelectric powders of uniform size.

In the step (d) The nano thermoelectric powder can be synthesized by reacting the thermoelectric powder forming composition at a temperature of 60 to 100 ° C for 5 to 24 hours.

The step (d) is preferably performed under an inert gas atmosphere of nitrogen or argon. When the nano-thermal conductive powder is formed in an inert gas atmosphere, it is possible to improve the yield of the nano-thermal conductive powder and to prevent impurities from being contained in the nano- can do.

The method for synthesizing nano thermoelectric powders may further comprise, after step (d)

(e) washing and drying the nano-sized thermoelectric powder.

In the step (e), the nano-thermal powder may be washed with water and / or ethanol. The drying may be performed at room temperature or 50 to 80 ° C for 1 to 24 hours.

By the step (e), a more pure thermoelectric powder can be obtained.

The size of the nano-sized thermoelectric powder by the method of synthesizing the nano-sized thermoelectric powder according to the present invention is determined according to the pH of the thermoelectric-powder-forming composition, the synthesis reaction temperature and time of the nano-sized thermoelectric powder and the concentration of the reducing agent, Has an average particle size of 20 to 200 nm. When a thermoelectric device is manufactured using the nano thermoelectric powder of this range, the scattering effect of the phonon can be improved, and the excellent thermoelectric performance can be expected due to the effect of lowering the thermal conductivity.

The thermoelectric element according to the present invention is produced by sintering the nano thermoelectric powder by the above-mentioned synthesis method.

The sintering method can be used without limitation as long as it is used in the art to make a thermoelectric element 20. The nano thermoelectric powder 10 is placed in a graphite die and sintered using an SPS (Spark Plasma Sintering) The device 20 can be manufactured.

The thermoelectric device 20 manufactured by the method of manufacturing the thermoelectric device 20 according to an embodiment of the present invention may be in the form of a bulk pellet, as shown in FIG.

The P-type thermoelectric element and the N-type thermoelectric element having excellent thermoelectric performance can be provided according to the method of manufacturing the thermoelectric element.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the examples, but is used for the purpose of describing the present invention only. And are not used to limit the scope of the present invention. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Synthetic example  One

A solution of pH 10 was made by adding 0.8 g of NaOH to the aqueous solution. To this solution, 9.6 to 21.3% by weight of BiCl ₃ , 55 to 58.7% by weight of Te and 23.0 to 31.8% by weight of Sb were added, and 0.5 to 10 parts by weight of NaBH ₄ was further added to 100 parts by weight of the thermoelectric powder raw material, Forming composition.

The thermoelectric powder-forming composition was reacted at a temperature of 90 ° C for 12 hours, washed with water and ethanol, and dried at 60 ° C for 5 hours to prepare a P-type nano-thermoelectric powder.

The average particle size of the prepared P-type thermoelectric powder was 50 nm.

Synthetic example  2

A solution of pH 10 was made by adding 0.8 g of NaOH to the aqueous solution. To the solution was added 52.5 to 53.5% by weight of BiCl ₃ , 42.4 to 46.5% by weight of Te and 0.9 to 4.1% by weight of Se, and 0.5 parts by weight of NaBH _{4 based} on 100 parts by weight of the thermoelectric powder raw material, .

The thermoelectric powder-forming composition was reacted at 90 ° C for 12 hours, washed with water and ethanol, and dried at 60 ° C for 5 hours to prepare an N-type nano-thermoelectric powder.

The average particle size of the prepared N-type thermoelectric powder was 50 nm.

Example  One

The P-type nano thermoelectric powder prepared in Synthesis Example 1 was placed in a graphite die and sintered at a pressure of 50 MPa and a temperature of 330 ° C for 10 minutes using a SPS (Spark Plasma Sintering) apparatus to prepare a P-type pellet type thermoelectric device.

The n-type nano thermoelectric powder prepared in Synthesis Example 2 was placed in a graphite die and sintered at a pressure of 30 MPa and a temperature of 400 ° C for 10 minutes using a SPS (Spark Plasma Sintering) apparatus to prepare an N-type pellet type thermoelectric device.

Comparative Example  One

A conventional thermoelectric device using an ingot.

Experimental Example

The thermoelectric performance ZT value of the thermoelectric device manufactured in Comparative Example 1 was 0.7 to 0.9 and the thermoelectric performance ZT value of the thermoelectric device manufactured in Example 1 was 1.0 to 1.2, It was confirmed that the thermoelectric properties of the device were excellent.

10 nano thermoelectric powder
20 Thermoelectric element

Claims (27)

delete delete delete delete delete (a) adjusting the pH of the solvent from neutral to basic;
(b) adding a thermoelectric powder raw material to the solvent;
(c) further adding a reducing agent to the solvent to which the thermoelectric powder raw material is added to prepare a thermoelectric powder forming composition; And
(d) synthesizing a nano-thermoelectric powder from the thermoelectric-powder-forming composition,
The reducing agent is added in an amount of 0.2 to 10 parts by weight based on 100 parts by weight of the thermoelectric powder raw material,
The thermoelectric-powder-forming composition of (c) further comprises at least one additive selected from the group consisting of EDTA, CTAB, SDS and SDBS so that the thermoelectric powder of a uniform size is well dispersed. . The method according to claim 6,
Wherein the step (a) is a step of adjusting the pH to 8 to 11 by adding NaOH or KOH to the aqueous solution. The method according to claim 6,
Wherein the thermoelectric powder raw material in step (b) is a P-type thermoelectric powder raw material including a raw material of Bi, a raw material of Te, and a raw material of Sb. 9. The method of claim 8,
The thermoelectric powder raw material in the step (b) is a raw material of Bi 5 to 30% by weight of the raw material of Te, 50 to 70% by weight of the raw material of Te, and 20 to 35% by weight of the raw material of Sb. The method according to claim 6,
Wherein the thermoelectric powder raw material in step (b) is an N-type thermoelectric powder raw material including a raw material of Bi, a raw material of Te, and a raw material of Se. 11. The method of claim 10,
The thermoelectric powder raw material in the step (b) is an N-type thermoelectric powder raw material containing 45 to 60% by weight of the raw material of Bi, 35 to 50% by weight of the raw material of Te, and 0.1 to 10% by weight of the raw material of Se. ≪ / RTI > The method according to any one of claims 8 to 11,
Raw material of the Bi is _{Bi, BiF 3, BiF 5,} BiCl 3, BiBr 3, BiI 3, Bi 2 O 3, Bi (OH) 3, BiOCl, BiOI, BiONO 3, Bi (NO 3) 3, Bi ( NO ₃ ) ₃ .xH ₂ O (x is a natural number), BiPO _4, and (BiO) ₂ CO ₃ . The method according to any one of claims 8 to 11,
Wherein the raw material of Te is at least one selected from the group consisting of Te, TeO ₂ , TeO ₃ , Te (OH) ₆ , Na ₂ TeO ₃ , K ₂ TeO ₃ , TeI ₄ , TeBr ₄ and TeCl ₄ Synthesis method of nano thermoelectric powder. 10. The method according to claim 8 or 9,
Raw material of the Sb is characterized in that at least one member selected from the group consisting of _{Sb, SbOCl, SbCl 3, SbCl} 5, Sb 2 O 3, Sb 2 O 5, Sb 2 O 4, SbBr 3, SbF 3 and SbF ₅ A method for synthesizing nano thermoelectric powder. The method according to claim 10 or 11,
Wherein the raw material of Se is at least one selected from the group consisting of Se, SeO ₂ , Na ₂ SeO ₃ , K ₂ SeO ₃ , H ₂ SeO ₄ , SeOCl ₂ , SeS ₂ , SeBr ₄ and SeCl ₄ . (Method of synthesizing thermoelectric powder). delete The method according to claim 6,
Wherein the reducing agent is at least one selected from the group consisting of NaBH ₄ , KBH _4, and N ₂ H ₄揃 H ₂ O. delete The method according to claim 6,
Wherein the thermoelectric powder-forming composition of step (d) is reacted at a temperature of 60 to 100 ° C for 5 to 24 hours. 20. The method of claim 19,
Wherein the reaction is carried out in an inert gas atmosphere of nitrogen or argon. The method according to claim 6,
The method for synthesizing the nano-thermoelectric powder may further comprise, after steps (a) to (d)
(e) washing and drying the nano-sized thermoelectric powder. The method according to claim 6,
Wherein the nano-sized thermoelectric powder has an average particle size of 20 to 200 nm. A nano thermoelectric powder synthesized according to the synthesis method of claim 6,
(f) sintering to form a thermoelectric device. 24. The method of claim 23,
Wherein the sintering is performed by spark plasma sintering (SPS) equipment in which a nano-sized thermoelectric powder is placed in a graphite die 24. The method of claim 23,
Wherein the thermoelectric device manufactured according to the method of manufacturing the thermoelectric device is a bulk pellet. A P-type thermoelectric device manufactured by the method for manufacturing a thermoelectric device according to claim 23. An N-type thermoelectric device manufactured by the method for manufacturing a thermoelectric device according to claim 23.

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