KR101302490B1 - An Method for fabricating thermoelectric thick film made from thermoelectric powder having a bimodal size distribution - Google Patents

Abstract

A thermal starch having a bee distribution particle according to the present invention, which must include at least one of tellurium (Te) and bismuth (Bi), and containing at least one of antimony (Sb) and selenium (Se) different milling By pulverizing and mixing a plurality of times according to the conditions characterized in that the particle size is formed to be distributed beekeeping.

Description

An method for fabricating thermoelectric thick film made from thermoelectric powder having a bimodal size distribution}

The present invention relates to a thermoelectric powder in which bee particles are distributed in different sizes, and a thermoelectric thick film using the same.

In addition, the present invention is a method of manufacturing a thermal starch powder so that a bee distribution in different sizes can be produced by sequentially applying a milling process of different conditions to a single material prepared, and a thermoelectric material using the thermal starch powder as a raw material A method for producing a thick film.

A thermoelectric material is an energy conversion material that generates electrical energy when a temperature difference is provided between opposite ends of a material, and generates a temperature difference between opposite ends of the material when electrical energy is applied to the material.

These thermoelectric materials were found in the early 19th century after the discovery of the thermoelectric phenomenon Seebeck effect, Peltier effect and Thomson effect. From the latter half of the 1930s, along with the development of semiconductors, It has been developed as a thermoelectric material and recently it has been used as a special power source device for thermal wallpaper in the mountains, for space use, military use, and for precise temperature control in a semiconductor laser diode or an infrared ray detecting device using thermoelectric cooling, , An optical fiber laser cooling device, a cooling device for a cold / hot water heater, a semiconductor temperature control device, a heat exchanger, and the like.

In order to improve the thermoelectric performance index of such a thermoelectric material, ZT = (σα ² / κ) T value, which is a dimensionless performance index, should be improved.

(α: Seebeck coefficient, σ: electric conductivity, κ: thermal conductivity)

The higher the performance index of the thermoelectric material means that the higher the energy conversion efficiency of the thermoelectric material, it is necessary to increase the electrical conductivity and Seebeck coefficient or to reduce the thermal conductivity.

In general, the electrical and thermal conductivity of a material depends on each other. That is, a thermoelectric material having low electrical conductivity is known to have low thermal conductivity.

However, in the case of thermoelectric materials, an appropriate combination of high electrical conductivity and low thermal conductivity is needed, as can be seen from the above-mentioned performance index (ZT). Among the functions that influence the figure of merit, Seebeck coefficient and electrical conductivity mainly depend on scattering of charge, and thermal conductivity mainly depends on scattering of phonon. There is a need.

More specifically, the scattering of charges in the thermoelectric material may be reduced as much as possible, and the scattering of phonons constituting the thermoelectric material may be increased to induce thermal conductivity to decrease, thereby improving the performance index.

 Recently, it has been widely used as a special power supply device using thermoelectric power generation, and precise temperature control using thermoelectric cooling or computer related compact cooler, optical communication laser cooling device, cold / hot water cooling device, semiconductor temperature control device, etc. Is being used.

A thermoelectric module is a bulk module for assembling pieces of a few mm size obtained by cutting and processing a bulk thermoelectric material, a thin film module composed of a thermoelectric material having a thickness of 10 μm or less, and a thick film having a height of tens to 500 μm. It can be divided into type modules.

Among the various modules, the thick film module has been attracting much attention as a thin and light electronic device or a CPU cooling control device in the field of thermoelectric cooling. That is, the thickness of the thermoelectric material limited in the thin film module is difficult to effectively remove the heat flux generated during the operation of the module. This requires a thick film of at least several tens of micrometers in height.

However, in forming a thick film module, the conventional thin film process is difficult to obtain a thick film of several tens of micrometers or more due to the slow deposition rate. Similarly, conventional bulk is burdened by the technology and cost of processing thermoelectric elements of tens to hundreds of microns in size.

Therefore, in recent years, a screen printing process has been used to manufacture a thick film module.

For example, Korean Patent Laid-Open No. 10-2008-0093512 discloses a method of manufacturing a thermoelectric module in which a P-type semiconductor and an N-type semiconductor are formed by a screen printing process so that a thin film can be formed. Korean Patent Publication No. 10-2009-0035317 Discloses a thermoelectric module in which an insulating layer provided between an upper substrate and a lower substrate and electrodes, and a P-type semiconductor and an N-type semiconductor can be formed by a screen printing process.

The above technique requires a paste formed by mixing a thermoelectric powder having thermoelectric properties with an organic solvent to form a P-type semiconductor and an N-type semiconductor by a screen printing process.

However, the thermoelectric powders constituting the P-type semiconductor and the N-type semiconductor are composed of only unimodal particles having the same size, and it is difficult to homogeneously mix with an organic solvent to form a paste for screen printing.

Inhomogeneous mixing between the organic solvent and the powder causes a local shrinkage difference during the heat treatment for removing the organic solvent and the sintering process of the powder, so that cracks are easily formed on the surface of the screen-printed thick film as shown in FIG. The performance index of the thermoelectric module is deteriorated.

FIG. 1 is an enlarged view of a surface of a paste obtained by screen printing a paste prepared by mixing a powder of unimodal particles with an organic binder.

An object of the present invention is to solve the conventional problems, it is possible to manufacture a paste having a high density when mixing with the organic solvent according to the bead containing particles in different sizes, it is possible to form a thick film using a screen printing process In addition, the present invention is to provide a thermoelectric powder with improved thermoelectric efficiency.

It is another object of the present invention to provide a method for producing a thermal starch powder so that a bee distribution can be produced in different sizes by sequentially applying different milling processes to a single prepared material.

It is still another object of the present invention to provide a thermoelectric film based on a thermopowder powder that is thickened by a screen printing process using a thermoelectric powder to prevent cracking in advance and maximize thermoelectric efficiency.

It is still another object of the present invention to provide a method for producing a thermo- thick film based on a thermo-powder in which the production process of the thermo- thick film is simplified to improve productivity.

The thermoelectric powder having the bee-distributing particles according to the present invention is characterized in that the raw powder containing at least one of antimony (Sb) and selenium (Se), which contains tellurium (Te) and bismuth (Bi) And is pulverized and mixed a plurality of times according to the conditions, so that the particle size is formed so as to be be distributed.

The relatively large particles are characterized by being three times larger than the size of the small particles.

The thermoelectric conversion film formed from the thermoelectric powder having the bee-distributing particles according to the present invention as a raw material must contain at least one of tellurium (Te) and bismuth (Bi) and at least one of antimony (Sb) and selenium The thermoelectric powders having bee-distributing particles formed by pulverizing and mixing the raw material powders a plurality of times in accordance with different milling conditions so that the particle sizes are be distributed, are prepared, and the thermoelectric powders and the organic binder are mixed and screen- And is formed by sintering.

And the thermoelectric converting film has an electrical resistance of 2 x 10 <" ⁵ > [Omega] m or less.

The relatively large particles are characterized by being three times larger than the size of the small particles.

Wherein the thermoelectric thick film has a Seebeck coefficient of 120 to 150 kK- ¹ .

A method for producing a thermoelectric powder having bee-distributing particles according to the present invention comprises preparing a raw material powder containing at least one of tellurium (Te) and bismuth (Bi) and containing at least one of antimony (Sb) and selenium (Se) A first powder pulverizing step of pulverizing and mixing the raw material powder by ball milling, and a second heat pulverizing step of subjecting the pulverized and mixed powder to ball milling under different conditions from the first powder pulverizing step, And a second powder pulverizing step of producing a powder.

In the first powder milling step, the raw material powder is ball milled with zirconia balls at a weight ratio of 8: 1 to 10: 1.

And the first powder milling step is performed at a rotation speed of 450 rpm for 2 hours to 4 hours.

And the second powder milling step is carried out at a rotation speed of 300 rpm for 1 hour.

A method for producing a thermoelectric conversion film using a thermoelectric powder having particles having bee-distributing particles according to the present invention as a raw material is characterized in that it contains at least one of tellurium (Te) and bismuth (Bi) and at least one of antimony (Sb) and selenium A first powder milling step of milling and mixing the raw material powder by ball milling; and a step of milling the milled and mixed powder by ball milling under conditions different from those of the first powder milling step A second powder pulverizing step of producing a thermoelectric powder having a particulate distribution having a bead distribution, a paste producing step of mixing the thermoelectric powder with an organic binder to produce a thermoelectric paste, a step of screen printing the thermoelectric paste to form a thermoformed article A binder removal step of removing the binder by heat treatment of the thermoformed article, a step of forming a powder sintered body by heat treatment of the thermoformed article from which the binder has been removed, Thick film composed of a heat-producing step for producing a thermally thick film by pressing and heating a sintering step, and the powder sintered body.

And the first powder milling step is performed at a rotation speed of 450 rpm for 2 hours to 4 hours.

And the second powder milling step is carried out at a rotation speed of 300 rpm for 1 hour.

The paste is produced by mixing 80 to 85% by weight of thermoelectric powder and 15 to 20% by weight of an organic binder to prepare a paste.

And the binder removing step is performed in an air atmosphere of 350 DEG C or less.

The step of forming the thermally conductive thick film is a process of removing the oxide contained in the thermally conductive thick film by performing the hydrogen reduction in the atmosphere.

As described above, the present invention provides a thermoelectric powder having particles to bee distributed and a thermoelectric film using the same as a raw material, and a method for preparing the same, wherein the particles are distributed in a different size to obtain a thermal powder having high densities. The powder is a raw material to form a thermoelectric film using a screen printing process, and relates to a method for producing the thermoelectric powder and the thermoelectric film.

Since the thermoelectric powder has a high density, it is possible to form a thick film at a high density in the screen printing process and to prevent cracking from occurring in the heat treatment or sintering.

Further, the heat transfer efficiency can be maximized.

In addition, since the milling process with different conditions is sequentially applied to the single-sized material, it is possible to manufacture the thermoelectric powder in which beads are distributed in different sizes, which simplifies the manufacturing process.

FIG. 1 is a magnified view of a surface of a paste prepared by screen printing a mixture of unimodal particles and an organic binder. FIG.
2 is an enlarged photograph of a P-type thermoelectric powder prepared according to a preferred embodiment of the present invention.
3 is a graph showing the particle size distribution of the P-type thermoelectric powder of FIG.
4 is an enlarged photograph of an N-type thermoelectric powder prepared according to a preferred embodiment of the present invention.
5 is a graph showing the particle size distribution of the N-type thermoelectric powder of FIG.
6 is a process flow diagram showing a method for producing a thermoelectric powder having bee-distributing particles according to the present invention.
FIG. 7 is a graph showing changes in particle size distribution and XRD graphs according to the order of manufacturing process of the P-type thermoelectric powder in the method for producing thermoelectric powders having bead-distributing particles according to the present invention.
FIG. 8 is a graph showing the change in particle size distribution and the XRD graph according to the order of manufacturing process of the N-type thermogravimetric powder in the method for producing thermoelectric powder having bead distribution particles according to the present invention.
Fig. 9 is an enlarged photograph showing the surface of a thermoelectric conversion film using a thermoelectric powder having bee-blooming particles according to the present invention as a raw material.
10 is a flow chart showing a process for producing a thermoelectric conversion film using thermoelectric powders having bee-blooming particles according to the present invention as raw materials.
11 is a graph comparing the electrical resistance values of the P-type thermoelectric converting films among the thermoelectric converting films prepared by using the thermoelectric powders having the bee-distributing particles according to the present invention as a raw material.
12 is a graph comparing the figure of merit (ZT) of the N-type thermoelectric converting thick film in the thermoelectric converting film made from the thermoelectric powder having the bee-distributing particles according to the present invention, with the comparative example.

Hereinafter, a thermoelectric powder 100 having bee-distributing particles according to the present invention will be described with reference to FIGS. 2 to 5 attached hereto.

FIGS. 2 and 3 are enlarged views of a P-type thermoelectric powder and a graph showing particle size distribution of a P-type thermoelectric powder produced according to a preferred embodiment of the present invention. FIGS. 4 and 5 show a preferred embodiment An enlarged photograph of the N-type thermoelectric powder prepared according to the example and a graph showing the particle size distribution of the N-type thermoelectric powder are shown.

The thermoelectric material according to the present invention has a beehive distribution in which powders having different particle sizes are mixed with each other as shown in FIG. 2 and FIG. 4, and necessarily contains tellurium (Te) and bismuth (Bi) Sb) and selenium (Se) are pulverized and mixed many times according to different milling conditions.

Since powders of two different sizes can be densely packed in powder as a small powder exists between powders having a relatively large particle size even when a paste is formed, it is possible to form a thermally conductive thick film having a high density in the screen printing process Reference numeral 200).

That is, as shown in FIG. 3, in the case of the P-type thermoelectric powder 100, the powder having a particle size of about 0.4 탆 and the powder having a particle size of about 2 탆 are configured to have a maximum volume with respect to the volume of the entire powder resulting in a bimodal particle.

As shown in Fig. 5, in the case of the N-type thermoelectric powder 100, the powder having a particle size of about 0.45 占 퐉 and the powder having a particle size of about 2 占 퐉 are configured to have a maximum volume with respect to the volume of the entire powder resulting in a bimodal particle.

Accordingly, the thermoelectric powder 100 has a particle size difference of three times or more as compared with particles of different sizes having the largest volume.

The thermoelectric powders produced according to the preferred embodiment of the present invention have a Seebeck coefficient of at least 285 KK- ¹ .

Hereinafter, a method of manufacturing the thermoelectric powder will be described with reference to FIG.

Fig. 6 shows a process flow chart showing a method for producing a thermoelectric powder having bee-blooming particles according to the present invention.

As shown in the drawing, the thermoelectric powder necessarily contains tellurium (Te) and bismuth (Bi) and contains at least one of antimony (Sb) and selenium (Se) (S200) for milling and mixing the raw material powder by ball milling, and a second powder milling step (S200) for preparing a milled and mixed powder by subjecting the milled and mixed powder to a different condition from the first powder milling step And a second powder milling step (S300) for producing a thermoelectric powder having a granular shape that is ball-milled by ball milling.

The raw material powder preparing step (S100) is a process of preparing a powder that can be used as an N-type thermoelectric material and a P-type thermoelectric material, and can be implemented by various methods.

The first powder milling step (S200) is a process for ball milling and pulverizing the raw material powder, and is a process for producing a powdered powder having a particle size larger than that of thermoelectric powder having a maximum particle size distribution.

In the embodiment of the present invention, the first powder milling step (S200) is a ball milling process using a planetary milling machine. A P-type or N-type thermoelectric powder is mixed with a 1-cm diameter zirconia ball at a weight ratio of 8: 1 and milled in a 250 cc zirconia milling vessel.

The first ball milled powder in the first powder milling step (S200) is capable of producing thermoelectric powders having bee-distributing particles through a second powder milling step (S300).

The particle size distribution of the thermoelectric powders of the preferred embodiment prepared through the first powder milling step (S200) and the second powder milling step (S300) and the thermoelectric powders of the comparative example will be described with reference to FIGS. 7 and 8 attached hereto.

Fig. 7 is a graph showing the change in particle size distribution and the XRD graph according to the order of manufacturing process of the P-type thermoelectric powder in the method for producing thermoelectric powders having bee-distributing particles according to the present invention, and Fig. In the method for producing thermoelectric powder, the particle size distribution change and the XRD graph according to the order of manufacturing process of the N-type thermoelectric powder are shown.

In a preferred embodiment of the present invention, the raw material powder is subjected to a first powder milling step (S200) at a rotation speed of 450 rpm for 2 hours to 4 hours, at a second powder milling step (S300) at a rotation speed of 300 rpm for 1 hour Lt; / RTI >

As a result, it was confirmed that the particles having the largest volume had bee-like distribution as shown in the right graph of Figs. 7 and 8.

On the other hand, the conditions of the second powder milling step (S300) are the same, and the powders of the comparative examples having different execution times in the first powder milling step (S200) have unimodal particle size distribution Respectively.

Hereinafter, a thermoelectric conversion film prepared using the thermoelectric powder as a raw material will be described with reference to FIG. 9 attached hereto.

Fig. 9 is an enlarged photograph showing the surface of a thermoelectric conversion film using a thermoelectric powder having bee-blooming particles according to the present invention as a raw material.

As shown in the drawing, the thermoelectric conversion layer is formed by mixing a thermoelectric powder with an organic binder to prepare a paste, forming a thermoformed body by a screen printing method, removing the organic binder, and sintering and press molding.

More specifically, the thermoelectric powder was mixed at a weight ratio of 80:20 with respect to the organic binder in the case of the P type and at a ratio of 85:15 with respect to the organic binder in the case of the N type, to prepare a paste.

The thermoelectric conversion layer was formed according to the same procedure and conditions as the thick film of the comparative example of FIG. 1, and the raw powders were different from each other.

That is, in the thermoelectric conversion film prepared by using the thermoelectric powder (thermoelectric powder having bee-busting particles) of the preferred embodiment of the present invention as a raw material powder, cracks were not generated as shown in FIG. 9, but the thermoelectric powders of the comparative example (unimodal )) As a raw material powder, cracks occurred in the thick film.

This is because homogeneous mixing can be performed when thermoelectric powders having bee-like distribution are mixed at the time of mixing the organic binder and the thermoelectric powder, and portions having only the organic binder are removed, so that powders of different sizes existing in the paste are densely It is believed that it was filled.

Hereinafter, a method of manufacturing the thermoelectric conversion film will be described with reference to FIG.

FIG. 10 is a flow chart showing a process for producing a thermoelectric conversion film in which thermoelectric powders having bee-distributing particles according to the present invention are used as raw materials.

As shown in the accompanying drawings, the thermoelectric powders obtained through the raw material powder preparation step (S100), the first powder milling step (S200), and the second powder milling step (S300) And is then pasted.

In the embodiment of the present invention, the organic binder is made of a material containing Terpineol, Ehyl Cellosolve or the like as a main solvent, and the paste is formed through a printing step (S500) employing a screen printing method to form a thermoformed body do.

Then, the thermoformed article is removed through a binder removal step (S600), the organic binder is removed, and the thermoelectric conversion film is completed by performing the powder sintering step (S700).

At this time, the powder sintering step (S700) performed a process of removing the binder in an air atmosphere at 350 ° C or less at which the tellurium (Te) does not volatilize.

In the present invention, the performance of the comparative example and the embodiment were compared under the same conditions (S800) for preparing a thermoelectric thick film by hot pressing under pressure and heating conditions.

In the hot-pressing step S800, a hydrogen-reducing atmosphere was adopted, and oxides in oxidized bismuth (Bi), tellurium (Te), antimony (Sb) and selenium (Se) powders were removed.

FIG. 11 is a graph comparing the electrical resistance values of the P-type thermoelectric converting films among the thermoelectric converting films prepared by using the thermoelectric powders having the bee-distributing particles according to the present invention as raw materials, and FIG. 12 is a graph (ZT) for the N type thermoelectric thick film among the thermoelectric thick films prepared by using the thermoelectric powder having the particles as the raw materials.

As shown in FIG. 11, the thermoelectric thick film produced according to the embodiment has an electrical resistance of 2 × 10 ^-5 Ωm or less, whereas the thick film of the comparative example has an electrical resistance close to 8 × 10 ^-5 Ωm, Electrical properties.

As a result of comparing the whiteness coefficients as shown in FIG. 12, the increase in the pressure during the thermoelectric thick film manufacturing step (S800) showed a constant Ge Bak coefficient of 285 ㎶ K ^{- 1} or more.

On the other hand, the thick film of the comparative example exhibits a Seebeck coefficient of 120 or more and 150 ㎶K ^{- 1} or less, which is significantly lower than that of the embodiment.

As a result, it can be seen that the thermoelectric layer formed from the thermoelectric powder having the bead distribution particles has a higher thermoelectric performance than the thick layer formed from the thermoelectric powder having the particles other than the thermoelectric powder.

The embodiments of the present invention described above are only concrete examples of the technical idea of the present invention, and the conditions such as the execution time, rotation speed, particle size and the like in the manufacturing process can be selectively changed by those skilled in the art.

100. Thermoelectric powder 200. Thermoelectric thick film
S100. Preparation of raw material powder S200. The first powder milling step
S300. Second powder milling step S400. Paste manufacturing step
S500. Printing step S600. Binder removal steps
S700. Powder sintering step S800. Thermoelectric thick film manufacturing step

Claims (16)

delete delete delete delete delete delete delete delete delete delete A raw material powder preparation step of preparing raw material powder which necessarily contains tellurium (Te) and bismuth (Bi) and which contains at least one of antimony (Sb) and selenium (Se)
A first powder grinding step of grinding and mixing the raw powder by milling;
A second powder grinding step of preparing a thermally-powder having a particulate form in which the milled and mixed powder is ball milled under a different condition from the first powder grinding step to produce a bee distribution;
A paste manufacturing step of preparing a thermoelectric paste by mixing the thermoelectric powder in an organic binder;
A printing step of forming a thermoform by screen printing the thermoelectric paste;
A binder removal step of removing the binder by heat treating the thermoformed body;
A powder sintering step of thermally treating the thermoformed body from which the binder is removed to form a powder sintered body,
And a thermoelectric film manufacturing step of producing a thermoelectric film by pressurizing and heating the powder sintered body. The method of claim 11, wherein the first powder grinding step,
A method of producing a thermoelectric film based on a thermoelectric powder having a beekeeping distribution, characterized in that carried out for 2 to 4 hours at a rotational speed of 450 rpm. The method of claim 12, wherein the second powder grinding step,
A method of producing a thermoelectric film based on a thermoelectric powder having a beekeeping particles, characterized in that carried out for 1 hour at a rotational speed of 300 rpm. The method of claim 13, wherein the paste manufacturing step,
A method of manufacturing a thermoelectric film based on a thermoelectric powder having a beekeeping distribution, characterized in that the paste is prepared by mixing 80 to 85% by weight of the thermal starch and 15 to 20% by weight of the organic binder. 15. The method of claim 14, wherein the binder removal step is performed in an air atmosphere of 350 DEG C or lower. The method of claim 15, wherein the thermoelectric film manufacturing step,
A method of producing a thermoelectric film based on a thermoelectric powder having a beekeeping distribution, characterized in that the process is carried out in a hydrogen reduction atmosphere to remove the oxide contained in the thermoelectric film.

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