WO2017069304A1 - Method for manufacturing thermoelectric material and thermoelectric material manufactured thereby - Google Patents

Abstract

Embodiments of the present invention relate to a method for manufacturing a thermoelectric material and a thermoelectric material manufactured thereby, the method being capable of: manufacturing metal ribbons having fine and uniform crystal grains since the metal ribbons are manufactured by using a pressure difference between an upper chamber and a lower chamber, and providing the thermoelectric material having excellent thermoelectric properties since the thermoelectric material is manufactured by using the metal ribbons. In addition, the present invention continuously supplies molten material so as to manufacture the metal ribbons and manufactures the thermoelectric material by using the metal ribbons, thereby enabling the thermoelectric materials to be mass produced so as to improve the productivity of the thermoelectric material.

Description

Method for manufacturing thermoelectric material and thermoelectric material prepared therefrom

The present invention relates to a method for producing a Bi-Te based thermoelectric material and to a thermoelectric material produced by the method.

Thermoelectric technology is a technology for directly converting thermal energy into electrical energy and electrical energy into thermal energy in a solid state, and is applied to thermoelectric power generation that converts thermal energy into electrical energy and thermoelectric cooling that converts electrical energy into thermal energy.

The thermoelectric material used for such thermoelectric power generation and thermoelectric cooling, the better the thermoelectric characteristics, the better the performance of the thermoelectric element. Determining the thermoelectric characteristics, the thermoelectric power (V), Seebeck coefficient (α), Peltier coefficient (π), Thomson coefficient (τ), Nernst coefficient (Q), Ettingshausen coefficient (P), electrical conductivity (σ) ), Output factor (PF), performance index (Z), dimensionless performance index (ZT = α2σT / κ (T is absolute temperature)), thermal conductivity (κ), Lorentz number (L), electrical resistivity (ρ), etc. It is the physical property of. In particular, the dimensionless performance index (ZT) is an important factor in determining thermoelectric conversion energy efficiency, and thermoelectric cooling and thermoelectric power generation are manufactured by using a thermoelectric material having a large value of the performance index (Z = α2σ / κ). It is possible to increase the efficiency of. That is, the thermoelectric material has excellent thermoelectric properties as the Seebeck coefficient and electrical conductivity are high and the thermal conductivity is low.

In view of this, Bi-Te-based thermoelectric materials have a high performance index (Z) in the vicinity of room temperature, and are attracting attention as cooling thermoelectric materials. Conventionally, the Bi-Te-based thermoelectric material has been produced by a method such as single crystal production, casting-crushing, or melt spinning.

However, the Bi-Te-based thermoelectric material manufactured by the single crystal manufacturing method has strong anisotropy in electrical and thermoelectric properties, and has a problem in that raw material loss and workability are inferior because it is easily broken along the wall interface during processing. In addition, the Bi-Te-based thermoelectric material manufactured by the casting-grinding method forms a heterogeneous structure with high segregation, causing segregation after grinding, incorporation of impurities by the grinding media, and coarsening of the tissue. There was a problem that the thermoelectric properties and strength is lowered. In addition, the Bi-Te-based thermoelectric material manufactured by the melt spinning method hardens raw material before injection molding due to the direct influence of a high temperature inert gas (for example, Ar). there was.

An object of the present invention is to provide a novel method of manufacturing a thermoelectric material in order to solve the above problems.

It is also an object of the present invention to provide a thermoelectric material produced by the above production method.

The present invention to achieve the above object, a) forming a master alloy ingot with a raw material comprising a first element and a second element; b) fusing the master alloy ingot in a crucible in an upper chamber to form a melt; c) spinning the melt through a nozzle in a lower chamber to produce a plurality of metal ribbons; And d) injecting and sintering the plurality of metal ribbons into a mold, wherein the pressure of the upper chamber is set higher than the pressure of the lower chamber.

In addition, the present invention provides a thermoelectric material manufactured by the above method.

Moreover, this invention provides the thermoelectric element containing the said thermoelectric material.

According to the present invention, as the metal ribbon is manufactured by using the pressure difference between the upper chamber and the lower chamber, a fine and uniform metal ribbon with crystal grains can be manufactured. Can provide.

In addition, in the present invention, since the molten metal is continuously supplied to manufacture the metal ribbon and the thermoelectric material is manufactured using the same, the mass production of the thermoelectric material is possible, thereby improving productivity of the thermoelectric material.

1 is a reference diagram for explaining a method of manufacturing a thermoelectric material of the present invention.

2 is a reference diagram for describing Embodiment 1 of the present invention.

3 is an image confirming the tissue of the metal ribbon prepared in Example 1 and Comparative Example 1 of the present invention by a scanning electron microscope.

Hereinafter, the present invention will be described.

1. Manufacturing method of thermoelectric material

The present invention forms a metal ribbon by directly adjusting the pressure of one chamber with an inert gas, and using the pressure difference between the two chambers instead of the conventional melt spinning method of manufacturing a thermoelectric material using the same to produce a metal ribbon The present invention relates to a method of manufacturing a new thermoelectric material using the same, which will be described in detail below.

a) forming a master alloy ingot

A mother alloy ingot is formed from the raw material containing a 1st element and a 2nd element. The method of forming the master alloy ingot as the raw material is not particularly limited, but after maintaining the raw material in a vacuum state, the mother alloy ingot may be formed through charging, stirring and dissolving in a furnace. Specifically, the raw material is charged into a quartz tube and sealed using a vacuum pump to maintain a vacuum state. Next, a quartz tube in a vacuum state is charged to the furnace, and stirred and dissolved at a rate of 10 to 15 times / minute at a temperature of 650 to 850 ° C. for 1 to 3 hours to form a master alloy ingot. The size of the mother alloy ingot formed through such a process is not particularly limited, but the diameter (Φ) is 20 to 30, it is preferable that the length is 100 to 150 mm. Moreover, it is preferable that the purity of a master alloy ingot is 5N grade or more. The reason is that since the purity of the master alloy ingot is 5N or higher, it is possible to produce a thermoelectric material having excellent electrical conductivity.

The first element included in the raw material is not particularly limited, but is preferably at least one selected from the group consisting of Bi and Sb, and the second element is not particularly limited, but is at least one selected from the group consisting of Te and Se. It is preferable. Specifically, the raw material of the present invention comprises 50 to 55% by weight Bi, 40 to 45% by weight Te and 3 to 4% by weight of Se, or based on 100% by weight of raw material, based on 100% by weight of raw material, It is preferable to include Bi 10-15 weight%, Sb 25-30 weight%, and Te 55-60 weight%. In consideration of the volatilization of Te in the process of forming the master alloy ingot, it is preferable to add 1 to 2% by weight of Te based on 100% by weight of the raw material when preparing the raw material.

When the raw material includes Bi, Te and Se, the master alloy ingot of the present invention may be an n-type Bi-Te-Se-based alloy ingot. In addition, when the raw material includes Bi, Sb and Te, the mother alloy ingot of the present invention may be a p-type Bi-Sb-Te-based alloy ingot.

Meanwhile, the raw material of the present invention may further include at least one third element selected from the group consisting of Sn, Mn, Ag, and Cu. By further including the third element, the present invention can improve the electrical conductivity and / or the Seebeck properties of the thermoelectric material. At this time, the content of the third element is not particularly limited, but may be 0.001 to 1% by weight based on 100% by weight of the raw material.

b) melt formation

The master alloy ingot is melted in a crucible in the upper chamber to form a melt. Specifically, the mother alloy ingot is charged into a crucible provided in the upper chamber, and a heat source provided around the crucible is heated to 500 to 800 ° C. to form a melt by melting the master alloy ingot. The crucible in the upper chamber is preferably provided as a tilted crucible to continuously supply the melt formed therein. When the melt is formed in the upper chamber as described above, the composition of the master alloy ingot can be maintained as it is, and according to the present invention, a thermoelectric material can be manufactured using a melt in which the composition of the master alloy ingot is maintained as it is.

On the other hand, the upper chamber in which the melt is formed is set to have a pressure higher than the pressure of the lower chamber, which will be described later.

c) metal ribbon manufacturing

The melt is spun through a nozzle in the lower chamber to produce a plurality of metal ribbons. Specifically, the present invention sets a plurality of metal ribbons due to the pressure difference between the upper chamber and the lower chamber (that is, indirectly adjusting the pressure so that the metal ribbon is radiated) by setting the pressure of the upper chamber higher than the pressure of the lower chamber. To prepare, this will be described in detail with reference to FIG. 1 as follows.

The present invention is the upper chamber 10; Lower chamber 20; A flow path 30 connecting the upper chamber 10 and the lower chamber 20; A nozzle 40 provided at one side of the flow path 30; And a plurality of metal ribbons using a melt spinning apparatus including a wheel 50. That is, when the molten material 12 formed in the crucible 11 provided in the upper chamber 10 is injected into the inlet of the flow path 30, the injected melt 12 is lower chamber 20 through the flow path 30. , The moved melt 12 is sprayed onto the wheel 50 through the nozzle 40 in the lower chamber 20, and the sprayed melt 12 is radiated onto the rotating wheel 50, thereby forming a plurality of metals. Ribbon is produced. At this time, since the pressure of the upper chamber 10 is set higher than the pressure of the lower chamber 20, the melt 12 is easily moved from the upper chamber 10 to the lower chamber 20 and the lower chamber 20 It is sprayed through the nozzle in the inside.

As described above, when the metal ribbon is manufactured using the pressure difference between the upper chamber 10 and the lower chamber 20, the metal ribbon having fine and uniform grains (nano blocks) can be obtained. Excellent thermoelectric materials can be provided. In other words, the finer and more uniform the grains of the metal ribbon, the lower the characteristics of the thermoelectric material, in particular, the thermal conductivity can be controlled, the present invention provides a metal ribbon having fine and uniform crystal grains as the metal ribbon is manufactured by the above process. It is possible to obtain a thermoelectric material having low thermal conductivity because the thermoelectric material can be obtained using the same. At this time, since the thermoelectric material having a low thermal conductivity has a high performance index (Z =? 2σ / κ), the present invention can provide a thermoelectric material having excellent thermoelectric characteristics.

The difference (P ₁ -P ₂₎ of the pressure (P ₂₎ of the pressure (P ₁₎ and the lower chamber 20 of the upper chamber 10 is not particularly limited, in consideration of production efficiency and the physical properties of the metallic ribbon, It is preferable that it is 0.1-2 Mpa.

In addition, the wheel 50 to which the melt 12 is radiated is not particularly limited, but may be a copper wheel. At this time, the rotational speed of the wheel 50 is not particularly limited, but considering the length and thickness of the metal ribbon, it is preferably 500 to 2500 rpm.

The metal ribbon formed by the above process is not particularly limited in shape, and has a free side surface that does not touch the wheel 50 and a wheel side surface that touches the wheel 50. The tissue may also be a mixture of amorphous and crystalline tissues. Specifically, the metal ribbon of the present invention preferably has a length of 1 to 5 mm, a thickness of 10 μm or less, and a size of crystal grains (nanoblocks) in the tissue of 250 nm or less. This is because when the length, thickness and grain size of the metal ribbon are within the above ranges, a thermoelectric material having excellent thermoelectric properties can be easily manufactured.

d) pressurized sintering

The plurality of metal ribbons are put into a mold and pressed and sintered. The method of pressurizing and sintering is not particularly limited, and hot press (Hot Press, HP) or spark plasma sintering (Spark Plasma Sintering) and the like. At this time, the conditions for pressurizing and sintering are not particularly limited, but it is preferable to sinter under pressure conditions ranging from 40 to 60 MPa for 3 to 10 minutes at a temperature in the range of 400 to 500 ° C. This is because if the pressure sintering condition is out of the above range, the density of the sintered compact or the volatilization of the raw material may be increased to obtain a thermoelectric material having the required characteristics.

2. Thermoelectric material

The present invention provides a thermoelectric material produced by the above production method. As the thermoelectric material of the present invention is manufactured by the above method, the thermoelectric material is excellent. Specifically, the thermoelectric material of the present invention may have a relative density of 90 to 99%, 0.7-1.0 when the dimensionless performance index (ZT) is n-type, and 0.8-1.5 when the p-type.

On the other hand, the size of the thermoelectric material of the present invention prepared by the manufacturing method is not particularly limited, it may be 2 to 5 mm.

The thermoelectric material of the present invention can be used in various fields, and in particular, it can be usefully used for cooling or low temperature power generation.

3. Thermoelectric element

The present invention provides a thermoelectric element comprising the thermoelectric material. Specifically, the thermoelectric element of the present invention is a thermoelectric element for cooling or low temperature power generation, and particularly, may be usefully used in the electric field and home appliances.

Hereinafter, the present invention will be described in detail with reference to the following Examples. However, the following examples are merely to illustrate the invention, the present invention is not limited by the following examples.

Example 1 Preparation of n-type Thermoelectric Material

Bi 1% by weight to 2% by weight in consideration of volatilization of Te to 53% by weight of Bi, 44% by weight of Te, 3% by weight of Se was charged into a quartz tube and sealed using a vacuum pump. Next, a vacuum quartz tube was charged to the furnace, followed by stirring and dissolving at a rate of 10 times / min at about 750 ° C. for 2 hours to form a mother alloy ingot having a diameter of 30 and a length of 100 mm. .

The master alloy ingot was charged into a crucible in the upper chamber of the melt spinning apparatus, and a melt was formed at a temperature of 680 ° C. At this time, the molten spinning used was a molten spinning of the structure shown in Figure 1, the pressure difference between the upper chamber and the lower chamber was set to be 0.5 MPa.

The melt was spun through a nozzle in the lower chamber to produce a plurality of metal ribbons. At this time, the rotation speed of the copper wheel on which the melt was spun was 1000 rpm. As a result of confirming the size of the prepared metal ribbon, the length was 1 to 5 mm and the average thickness was 8 m (see FIG. 2).

The metal ribbon was placed in a mold and press-sintered at a pressure of 60 MPa for 5 minutes at a temperature of 480 ° C. to prepare a thermoelectric material.

Example 2 Preparation of p-type Thermoelectric Material

A thermoelectric material was manufactured in the same manner as in Example 1, except that a raw material consisting of 13 wt% Bi, 28 wt% Sb, and 59 wt% Te was used.

Comparative Example 1 Preparation of an n-type Thermoelectric Material

A thermoelectric material was manufactured in the same manner as in Example 1, except that the melt spinning device including a single chamber instead of the melt spinning device of FIG. 1 was used. Specifically, the raw material is charged into a crucible in a single chamber, a melt is formed using a heat source consisting of a high frequency coil, and then Ar gas is injected directly into the single chamber at a pressure of 0.5 MPa to inject the melt through a nozzle in a single chamber. A plurality of metal ribbons were prepared by spinning in the same manner, and the process was performed in the same manner as in Example 1.

Comparative Example 2 Preparation of p-type Thermoelectric Material

A thermoelectric material was manufactured in the same manner as in Comparative Example 1, except that a raw material including 13 wt% Bi, 28 wt% Sb, and 59 wt% Te was used.

Experimental Example 1 Grain Check of Metal Ribbon

The crystal grains of the metal ribbons formed in Examples 1 and 2 and Comparative Examples 1 and 2 were confirmed by scanning electron microscopy, and the results are shown in Table 1 below. In addition, the grain image of the metal ribbon formed in Example 1 and Comparative Example 1 is shown in FIG.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Grain (Nano Block) 190.4 nm 219.5 nm 255.4 nm 276.6 nm

Referring to Table 1 and Figure 3, the metal ribbon prepared by the manufacturing method of the present invention can be confirmed that the grain size is 250 nm or less.

Experimental Example 2 Dimensional Performance Index (ZT) Evaluation

The dimensionless performance index of the thermoelectric materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated by the following method, and the results are shown in Table 2 below.

* The dimensionless figure of merit (ZT) is calculated by the following formula (at this time, the temperature is carried out at 25 ℃, 50 ℃, 100 ℃, 150 ℃, 200 ℃ and the maximum dimensionless performance index is indicated)

ZT = α2σT / κ (T: absolute temperature, α: Seebeck coefficient, σ: electrical conductivity, κ: thermal conductivity)

Seebeck coefficient: one side of the specimen is heated with a sub-heater to maintain the temperature difference ΔT at both ends of the specimen at about 10 ° C, and then the potential difference ΔV is measured by using the relationship of α = ΔV / ΔT.

-Conductivity: Measured with 4-point probe by applying AC current of 120 Hz square wave generated by DC chopper to the specimen.

-Thermal conductivity: measured by laser flash method

Example 1 Example 2 Comparative Example 1 Comparative Example 2 ZT 0.83 1.04 0.71 0.92

Referring to Table 2, it can be seen that the thermoelectric material manufactured by the manufacturing method of the present invention has a high dimensionless performance index.

Claims (9)

a) forming a master alloy ingot from a raw material comprising a first element and a second element; b) fusing the master alloy ingot in a crucible in an upper chamber to form a melt; c) spinning the melt through a nozzle in a lower chamber to produce a plurality of metal ribbons; And d) injecting the plurality of metal ribbons into a mold and sintering the mold; And the pressure of the upper chamber is set higher than the pressure of the lower chamber. The method of claim 1, The pressure (P ₁₎ and the difference (P ₁ -P ₂₎ is 0.1 to 2 ㎫ method of producing a thermoelectric material of the pressure (P ₂₎ of the lower chamber of the upper chamber. The method of claim 1, The first element is at least one selected from the group consisting of Bi and Sb, The second element is at least one selected from the group consisting of Te and Se thermoelectric material manufacturing method. The method of claim 1, The master alloy ingot is an n-type Bi-Te-Se-based alloy ingot or a p-type Bi-Sb-Te-based alloy ingot. The method of claim 1, The master alloy ingot further comprises at least one third element selected from the group consisting of Sn, Mn, Ag and Cu. The method of claim 1, A method for producing a thermoelectric material, the grain size of the metal ribbon is 250 nm or less. A thermoelectric material manufactured by the method of any one of claims 1 to 6. A thermoelectric element comprising the thermoelectric material of claim 7. The method of claim 8, Thermoelectric element for cooling power generation.

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