KR101323319B1 - The manufacturing process of Bi-Te-Se thermoelectric materials doped with silver - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bismuth-telelium-selenium-based thermoelectric material to which silver is added, wherein a silver element is added to a Bi-Te-Se-based thermoelectric material as a dopant, and charged into a vacuum ampoule to melt. Step 1; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare a thermoelectric material powder to which a doping material is added; Thermoelectric material to which the doping material is added A fourth step of hot pressing the powder; The manufacturing method of the bismuth-telelium-selenium-type thermoelectric material to which silver is comprised including the 5th step which cuts the thermoelectric material to which the doping material which passed the said 4th step was added is a technical subject matter. Accordingly, there is an advantage in that the thermoelectric properties are improved by adding a silver element to the Bi-Te-Se-based thermoelectric material as a doping material and undergoing a quenching and sintering process and heat treatment.

Description

Manufacturing method of Bi-Te-Se thermoelectric materials doped with silver

The present invention relates to a method for manufacturing a bismuth-telelium-selenium-based thermoelectric material to which silver is added, and more particularly, a predetermined quenching and sintering process by adding a silver element as a dopant to a Bi-Te-Se-based thermoelectric material. In addition, the present invention relates to a method for producing a bismuth-telelium-selenium-based thermoelectric material to which silver is added to improve the thermoelectric properties by heat treatment.

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 thermoelectric power generation and thermoelectric cooling thermoelectric cooling improves the performance of the thermoelectric element as the thermoelectric properties increase. 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 thermoelectric materials, there are a method of adding or replacing various elements (composition control), a method of controlling microstructure (manufacturing process control), a method of introducing abnormal particles or impurities, and the like.

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. .

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

The present applicant is a study on the thermoelectric material as described above in the Korean Patent Office No. 10-2010-99418 in the p-type titled "Method of manufacturing a TE-based thermoelectric material with twins formed by the addition of a doping material and its thermoelectric material" The addition of silver to the Bi-Sb-Te-based thermoelectric material has been selected for thermoelectric material with improved thermoelectric performance.

However, no attempt has been made to improve thermoelectric performance by doping silver to n-type Bi-Te-Se-based thermoelectric materials.

Accordingly, the present invention has been made to solve the above problems of the prior art, the thermoelectric properties of the Bi-Te-Se-based thermoelectric material by adding a silver element as a doping material and undergoing a predetermined quenching and sintering process and heat treatment It is an object of the present invention to provide a method for producing a bismuth-telelium-selenium-based thermoelectric material to which silver is added to improve the efficiency.

The present invention for achieving the above object, the first step of adding a silver element to the Bi-Te-Se-based thermoelectric material as a doping material, and charged into a vacuum ampoule to melt; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare a thermoelectric material powder to which a doping material is added; Thermoelectric material to which the doping material is added A fourth step of hot pressing the powder; The manufacturing method of the bismuth-telelium-selenium-type thermoelectric material to which silver is comprised including the 5th step which cuts the thermoelectric material to which the doping material which passed the said 4th step was added is a technical subject matter.

The Bi-Te-Se-based thermoelectric material is preferably one of the _{Bi 2 Te 2 .85 Se 0 .15} , Bi 2 Te 2 .55 Se 0 .45.

The silver element of the first step is preferably added in a weight ratio of 0.001 to 0.1.

The first step is preferably carried out in an argon gas atmosphere.

The first step is preferably performed for 8 hours to 12 hours at a temperature of 700 ℃ to 1,000 ℃.

The fourth step is preferably performed for 20 minutes to 1 hour under a temperature of 300 ℃ to 500 ℃, a pressure of 100 MPa to 300 MPa.

Accordingly, there is an advantage in that the thermoelectric properties are improved by adding a silver element to the Bi-Te-Se-based thermoelectric material as a doping material and undergoing a quenching and sintering process and heat treatment.

According to the present invention, the thermoelectric properties are improved by adding a silver element to the Bi-Te-Se-based thermoelectric material as a doping material and undergoing a predetermined quenching and sintering process and heat treatment. There is an effect that can be used as a thermoelectric material.

1 shows (a) electrical resistivity, (b) Seebeck coefficient, and (c) power factor of a thermoelectric material in which silver formed according to the first embodiment of the present invention is added to Bi ₂ Te _2.85 Se _0.15 in a weight ratio of 0.05. (d) is a diagram showing thermal conductivity,
FIG. 2 is a diagram illustrating a dimensionless performance index of thermoelectric materials in which silver formed according to the first embodiment of the present invention is added to Bi ₂ Te _2.85 Se _0.15 in a weight ratio of 0.05;
3 shows (a) electrical resistivity, (b) Seebeck coefficient, and (c) power factor of a thermoelectric material in which silver formed according to a second embodiment of the present invention is added to Bi ₂ Te _2.55 Se _0.45 in a weight ratio of 0.01. (d) is a diagram showing thermal conductivity,
FIG. 4 is a diagram illustrating a dimensionless performance index of thermoelectric material in which silver formed according to the second embodiment of the present invention is added to Bi ₂ Te _2.55 Se _0.45 in a weight ratio of 0.01.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating thermoelectric properties of a thermoelectric material to which a doping material is added according to a first embodiment of the present invention and thermoelectric properties of a comparative example, and FIG. 2 is a thermoelectric to which a doping material is formed according to a first embodiment of the present invention. Figure 3 shows the dimensionless performance index of the material and the thermoelectric material of the comparative example, Figure 3 is a diagram showing the thermoelectric characteristics of the thermoelectric material to which the doping material is formed according to the second embodiment of the present invention and the thermoelectric characteristics of the comparative example, Figure 4 Is a diagram showing the dimensionless performance index of the thermoelectric material to which the doping material formed according to the second embodiment of the present invention is added and the thermoelectric material of the comparative example.

As shown in the drawing, a method for producing a bismuth-telelium-selenium-based thermoelectric material to which silver is added according to the present invention is largely added to a Bi-Te-Se-based thermoelectric material by adding a silver element as a dopant, and to a vacuum ampoule. A first step of charging and melting; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare a thermoelectric material powder to which a doping material is added; Thermoelectric material to which the doping material is added A fourth step of hot pressing the powder; And a fifth step of cutting the thermoelectric material to which the doping material passed through the fourth step is added.

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

≪ Embodiment 1 >

First, high purity Bi, Se, Te thermoelectric material and Ag dopant of 99.999% or more are washed with hydrochloric acid, nitric acid, acetone, ethanol, and the like.

That meet the requirements of the following, Bi ₂ Te _{2 .85} ratio of Se _{0 .15} prepare each thermal conductive material, such that the weight ratio of 0.05 to herein (Ag) elements and weighing the respective raw materials by using a precision balance for each of the thermoelectric material To prepare.

Then, the weighed raw materials are charged into a quartz tube, and the internal pressure is 10 ^-5 torr.

When the internal pressure reaches 10 ^-5 torr in vacuum, seal it with argon gas.

The sealed ampoules are placed in a rocking furnace, melted at about 800 ° C. for 10 hours, and then quenched.

The ingot formed through rapid cooling is crushed by a ball milling method to produce a thermoelectric material having a predetermined size by wire cutting after a hot press process at a pressure of 200 MPa for 30 minutes at a temperature of 420 ° C. .

As described above, in the first embodiment, the Bi ₂ Te _{2 .85} Se _{0 .15} thermal conductive material is in the element-doped samples and the comparative examples are not as Bi ₂ Te _{2 .85} Se _{0 .15} thermal element is not doped with Samples were prepared for the material and their thermoelectric properties were investigated.

1 is a diagram showing the thermoelectric properties of the thermoelectric material to which the doping material is added according to the first embodiment of the present invention and the thermoelectric properties of the comparative example, Figure 1 (a) is a view showing the electrical resistivity, Figure 1 (b) 1 is a diagram showing Seebeck coefficient, FIG. 1 (c) is a diagram showing a power factor, and FIG. 1 (d) is a diagram showing thermal conductivity.

Looking at the electrical resistivity value, it can be seen that as the Ag is added, the specific resistivity value is relatively small compared to the case where no Ag is added.

Due to the addition of Ag, the difference in resistivity is constant with temperature, while the Seebeck coefficient difference tends to vary with temperature.

At low temperature, Ag has higher Seebeck coefficient, while at high temperature Ag has lower Seebeck coefficient, but the absolute value of Seebeck coefficient is higher at high temperature when Ag is added. . Therefore, when Ag is added, it has a high power factor due to the absolute value of the Seebeck coefficient and low electrical resistivity improved at high temperatures.

In the case of thermal conductivity, Ag was further lowered at higher temperatures.

2 is a view showing the dimensionless performance index of the thermoelectric material to which the doping material is added according to the first embodiment of the present invention and the dimensionless performance index of the comparative example. It can be seen that the thermoelectric properties are improved compared to the comparative example in which Ag is not added at a high temperature of about 375 K or more due to the absolute coefficient and lower thermal conductivity.

≪ Embodiment 2 >

High-purity Bi, Se, Te thermoelectric materials and Ag doping materials of more than 99.999% are washed with hydrochloric acid, nitric acid, acetone, ethanol and the like.

Then, according to the ratio of Bi ₂ Te _{2 .55} Se _{0 .45} prepare each thermal conductive material, such that the weight ratio of 0.01 to herein (Ag) element and weighing each raw material to the respective thermoelectric material using a precision balance To prepare.

Then, the weighed raw materials are charged into a quartz tube, and the internal pressure is 10 ^-5 torr.

When the internal pressure reaches 10 ^-5 torr in vacuum, seal it with argon gas.

The sealed ampoules are placed in a rocking furnace, melted at about 800 ° C. for 10 hours, and then quenched.

The ingot formed through rapid cooling is crushed by a ball milling method to produce a thermoelectric material having a predetermined size by wire cutting after a hot press process at a pressure of 200 MPa for 30 minutes at a temperature of 420 ° C. .

As described above, in the second embodiment the Bi ₂ Te _{2 .55} Se _{0 .45} thermal conductive material in the element is a Bi ₂ Te _{2 .55} Se _{0 .45} thermally non element is doped as the doped samples and the comparative example by Samples were prepared for the material and their thermoelectric properties were investigated.

3 is a diagram illustrating thermoelectric characteristics of a thermoelectric material to which a doping material is formed according to a second embodiment of the present invention and thermoelectric characteristics of a comparative example, FIG. 3 (a) is a diagram showing an electrical resistivity, and FIG. 3 (b). Figure 3 shows the Seebeck coefficient, Figure 3 (c) shows the power factor (power factor), Figure 3 (d) shows the thermal conductivity.

Looking at the electrical resistivity value, it can be seen that as Ag is added, the resistivity value is relatively smaller than the case where Ag is not added.

Due to the addition of Ag, the difference in resistivity is constant with temperature, while the Seebeck coefficient difference tends to vary with temperature.

At low temperatures, Ag has a higher Seebeck coefficient, while at high temperatures, Ag and non-Ag have similar values.

In addition, even in the case of the power factor, when Ag is added in the high temperature portion, it can be seen that it has a larger value than the comparative example due to the lower electrical resistivity.

In the case of thermal conductivity, Ag was added to the higher temperature, the lower the thermal conductivity.

4 is a diagram illustrating a dimensionless performance index of the thermoelectric material to which the doping material is added according to the second embodiment of the present invention and a dimensionless performance index of the comparative example, in which Ag is not added at a high temperature of about 375 K or more when Ag is added; It can be seen that the thermoelectric properties are improved as compared with the comparative example.

Claims (6)

Adding a silver element to the Bi-Te-Se-based thermoelectric material as a dopant, charging the molten element in a vacuum ampoule; A second step of rapidly cooling the molten raw material to produce an ingot; Crushing the ingot to prepare a thermoelectric material powder to which a doping material is added; Thermoelectric material to which the doping material is added A fourth step of hot pressing the powder; And a fifth step of cutting the thermoelectric material to which the doping material has passed through the fourth step.
The Bi-Te-Se-based thermoelectric material is Bi ₂ Te _2.85 Se _0.15 , Bi ₂ Te _2.55 Se _0.45 characterized in that the bismuth-telelium-selenium-based thermoelectric material is added. delete The method of claim 1, wherein the silver element of the first step is added in a weight ratio of 0.001 to 0.1. The method of claim 3, wherein the first step is performed in an argon gas atmosphere. 5. The method of claim 4, wherein the first step is performed for 8 to 12 hours at a temperature of 700 ° C. to 1,000 ° C. 6. 6. The method of claim 1, wherein the fourth step is performed for 20 minutes to 1 hour at a temperature of 300 ° C. to 500 ° C. and a pressure of 100 MPa to 300 MPa. 7. A method for producing a bismuth-telelium-selenium-based thermoelectric material to which silver is added.

Images