KR102146022B1 - Thermoelectric materials and method for manufacturing the same - Google Patents

Abstract

The present invention discloses a thermoelectric material including a substance of the following composition formula 1 and a substance of the composition formula 2.
[Composition 1]
BiM ₁ M ₂
(In the composition formula 1, the M ₁ and M ₂ is any one of Te, Se or Sb, and M ₁ and M ₂ is a different substance)
[Composition 2]
D
(In the above composition formula 2, the dopant (D) is Bi, M _{1 ,} or M ₂ It is one of them.)

Description

Thermoelectric material and its manufacturing method {THERMOELECTRIC MATERIALS AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to n-type and p-type thermoelectric materials and a method of manufacturing the same.

Bi-Te-based thermoelectric materials have excellent thermoelectric performance near room temperature, so they can solve the heat dissipation problem of highly integrated devices and various sensors, so research on this is active.

Recently, thermoelectric materials having a high performance index (ZT) of thermoelectric materials have been gradually developed, and are used for temperature control of temperature sensitive devices such as semiconductor laser diodes and infrared detection devices using thermoelectric cooling.

In addition, the area is gradually expanding, such as being used for computer-related small coolers, optical communication laser cooling devices, cooling devices for cold and hot water machines, semiconductor temperature control devices, and heat exchangers.

The high performance index (ZT) of the thermoelectric material means that the energy conversion efficiency of the thermoelectric material is high. In order to increase the performance index, it is necessary to increase the electrical conductivity or decrease the thermal conductivity.

In particular, the Seebeck coefficient and electrical conductivity among the functions that influence the performance index (ZT) of a thermoelectric material mainly depend on the scattering of electric charges, and the thermal conductivity mainly depends on the scattering of the phonon. It is necessary to control the characteristics through the control of.

Accordingly, the scattering of electric charges in the thermoelectric material is reduced as much as possible and the scattering of phonons constituting the thermoelectric material is increased to induce a decrease in thermal conductivity, thereby improving the performance index (ZT).

As a method of manufacturing such a thermoelectric material, Korean Patent Laid-Open Publication No. 1997-010993 discloses a method of dissolving Bi powder and Te powder to form an ingot, hot extruding it to form an ingot, and then crushing it to form a powder. have.

However, this manufacturing method has a problem in that a process of separately forming an ingot is added, which complicates the manufacturing process and increases the cost. Therefore, there is an urgent need to develop a technology for manufacturing an excellent thermoelectric material through a simpler process.

The present invention provides a thermoelectric material capable of increasing a performance index with a simple manufacturing method and a manufacturing method thereof.

The thermoelectric material according to the present invention includes a material of Formula 1 and a material of Formula 2 below.

[Composition 1]

BiM ₁ M ₂

(In the composition formula 1, the M ₁ and M ₂ is any one of Te, Se or Sb, and M ₁ and M ₂ is a different substance)

[Composition 2]

D

(In the above composition formula 2, the dopant (D) is Bi, M _{1 ,} or M ₂ It is one of them.)

The thermoelectric material according to the present invention is sintered by mixing the substances of the composition formula 1 and the composition formula 2 with each other in a powder state.

In the thermoelectric material according to the present invention, the addition amount of the material represented by the composition formula 2 may be 0.01 wt% to 0.2 wt% based on the total weight of the material represented by the composition formula 1.

In the thermoelectric material according to the present invention, the material of Formula 1 may satisfy Formula 3 below.

[Composition 3]

Bi ₂ Te _3-x Se _x

(At this time, the variable x is 0.1<x<0.4.)

In the thermoelectric material according to the present invention, the material of Formula 1 may satisfy Formula 4 below.

[Composition 4]

Bi _{2 - y} Sb _y Te ₃

(At this time, the variable y is 1.2<y<1.8.)

The method for manufacturing a thermoelectric material according to the present invention includes the steps of manufacturing an ingot by melting a plurality of constituent elements constituting an n-type or p-type thermoelectric material; Pulverizing the ingot to prepare a powder; Mixing the pulverized powder with a dopant, which is one of the plurality of constituent elements; And sintering the powder mixed with the dopant.

In the thermoelectric material manufacturing method according to the present invention, the n-type thermoelectric material constituent elements include Bi, Se, and Te, and the p-type thermoelectric material constituent elements include Bi, Sb, and Te.

In the method for manufacturing a thermoelectric material according to the present invention, the dopant is included in an amount of 0.01 wt% to 0.2 wt% based on the total weight of the powder.

In the method for manufacturing a thermoelectric material according to the present invention, the average particle diameter of the dopant may be 200 μm or less.

In the method of manufacturing a thermoelectric material according to the present invention, the components of the thermoelectric material include Bi, Se, and Te, and the dopant may be Te.

In the thermoelectric material manufacturing method according to the present invention, the thermoelectric material constituent elements include Bi, Sb, and Te, and the dopant may be Te.

According to the present invention, after forming an ingot, by adding a small amount of n-type or p-type constituent elements to form a heterogeneous system, it is possible to increase the performance index (ZT) of the thermoelectric material.

Further, according to the present invention, a general thermoelectric material manufacturing process can be used as it is, thereby reducing manufacturing cost.

1 is a flowchart of a method for manufacturing a thermoelectric material according to the present invention,
2 is a SEM photograph of a material represented by the composition formula 1 prepared according to the present invention,
3 is a graph measuring a figure of merit according to temperature of a thermoelectric material manufactured according to the present invention.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present invention, terms such as "comprises" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

The thermoelectric material according to the present invention includes a material of Formula 1 and a material of Formula 2 below.

[Composition 1]

BiM ₁ M ₂

[Composition 2]

D

At this time, in the composition formula 1 M ₁ and M ₂ is any one of Te, Se or Sb, and M ₁ and M ₂ is different. Therefore, when M ₁ is Te, M ₂ may be selected as either Se or Sb. In addition, the dopant (D) in the composition formula 2 is Bi, M _{1 ,} or M ₂ Any one can be selected. Therefore, the thermoelectric material may have a composition of BiM ₁ M ₂ :D by doping the material of the composition formula 1 with the material of the composition formula 2.

Specifically, in the case of an n-type thermoelectric material, the material of composition formula 1 may be expressed as Bi ₂ Te _3-x Se _x . At this time, it is preferable that the variable x has a range of 0.1<x<0.4. When the range of x is less than 0.1 or greater than 0.4, there is a problem that the composition of Te or Se becomes too large or small, and the performance of the thermoelectric material is deteriorated.

Further, when the thermoelectric material is p-type, material of the formula 1 is a Bi _{2 -} can be represented by _y Sb _y Te _3. In this case, it is preferable that the variable y has a range of 1.2<y<1.8. When the range of y is less than 1.2 or greater than 1.8, there is a problem that the composition of Bi or Sb becomes too large or small, and the performance of the thermoelectric material is deteriorated.

D of the composition formula 2 is a dopant in the form of a powder to be mixed in the composition formula 1, specifically, may be selected from any one of the substances of the composition formula 1. Accordingly, in the case of the n-type thermoelectric material, any one of Bi, Te, and Se may be selected as the material of the composition formula 2, and in the case of the p-type thermoelectric material, any one of Bi, Te, or Sb may be selected. In the thermoelectric material, both the material of the composition formula 1 and the material of the composition formula 2 are formed in a powder formulation and are sintered to form a heterogeneous system.

Table 1 below is a table in which the electrical conductivity, Seeback coefficient, thermal conductivity, and thermoelectric performance index (ZT) are changed according to the addition of the dopant in the n-type thermoelectric material. The experiment was conducted continuously by increasing the amount of Te particles added to the powder of the composition formula 1 based on the n-type thermoelectric material.

Dopant
(wt%) Electrical conductivity
(10 ⁴ S/m) Seebeck coefficient
(10 ^-4 V/K) Thermal conductivity
(W/mk) ZT Experimental Example 1 0.00 7.30 -1.66 1.11 0.68 Experimental Example 2 0.01 7.00 -1.87 1.11 0.82 Experimental Example 3 0.05 6.97 -1.90 1.12 0.83 Experimental Example 4 0.07 7.05 -1.86 1.18 0.77 Experimental Example 5 0.1 7.52 -1.72 1.16 0.71 Experimental Example 6 0.2 9.33 -1.59 1.24 0.71 Experimental Example 7 0.5 10.77 -1.47 1.39 0.62 Experimental Example 8 1.0 12.94 -1.26 1.48 0.51 Experimental Example 9 1.2 17.50 -1.01 2.38 0.28

When referring to Table 1, in the case of Experimental Example 1 without the dopant added, it can be seen that the performance index (ZT) is 0.68, and in Experimental Examples 2 to 6, it can be seen that the performance index increases as the addition amount of the dopant increases. have. At this time, the thermoelectric performance index (ZT) is determined by the following relational equation 1.

[Relationship 1]

Number of thermal cells (ZT) = (σs ² /k)T

(Where σ is the electrical conductivity, s is the Seebeck coefficient, k is the thermal conductivity, and T is the temperature.)

Referring back to Table 1, in the case of Experimental Examples 2 to 6, the absolute value of the Seebeck coefficient and the increase in electrical conductivity were relatively large as the amount of dopant was increased, whereas the increase in thermal conductivity was relatively small. It can be seen that the thermoelectric figure of merit calculated according to the relational equation 1 has increased overall.

However, in the case of Experimental Examples 7 to 9, it can be seen that as the amount of the dopant increases, the thermal conductivity rapidly increases and the absolute value of the Seebeck coefficient decreases, thereby significantly reducing the thermoelectric performance index. Therefore, the dopant is preferably contained in an amount of 0.01 wt% to 0.2 wt% based on the total mass of the powder prepared according to the composition formula 1.

1 is a flowchart of a method for manufacturing a thermoelectric material according to the present invention, and FIG. 2 is a SEM photograph of a material represented by Formula 1 manufactured according to the present invention.

Referring to FIG. 1, the method of manufacturing a thermoelectric material according to the present invention includes the step of manufacturing an ingot by melting a plurality of constituent elements constituting an n-type or p-type thermoelectric material (S10), and pulverizing the ingot to produce a powder. (S20), adding a dopant, which is one of the plurality of constituent elements, to the pulverized powder (S30), and sintering the powder to which the dopant is added (S40).

First, in the step of manufacturing an ingot (S10), each element constituting the n-type or p-type thermoelectric material is melted and cooled to manufacture an ingot. At this time, the constituent elements of the n-type thermoelectric material are Bi, Se, and Te, and the constituent elements of the p-type thermoelectric material are Bi, Sb, and Te, so each constituent element is weighed to match the composition ratio of the thermoelectric material.

Specifically, in the case of n-type Bi ₂ Te _{3 - x} Se _y Each element is weighed according to the composition of (0.1<x<0.4), and in the case of p-type, each element is weighed according to the composition of Bi _{2 -y} Sb _y Te ₃ (1.2<y<1.8). Thereafter, each of the weighed constituent elements is uniformly mixed, melted in a high-temperature melting furnace, and then cooled to prepare an ingot.

After the step of producing the powder (S20), the manufactured ingot is pulverized by a ball mill to prepare a powder. At this time, the average particle diameter of the particles is 1 to 10 μm, and the aggregated particles formed by agglomeration of the pulverized particles have an average particle diameter of 200 μm or more as shown in FIG. 2.

The step of adding a dopant (S30) is a step of adding a dopant to the pulverized powder. In the case of n-type, one of the constituent elements Bi, Se, and Te is added, and in the case of p-type, the constituent elements Bi, Sb, And Te is added.

The dopant to be added is preferably spherical particles having an average particle diameter of 200 μm or less. Since the size of the aggregated particles is at least 200㎛, if the average particle diameter of the dopant powder is larger than the size of the aggregated particles, the grain size becomes too large and there is a problem that the phonon scattering effect decreases. .

After sintering (S40), the dopant-added powder is put in a carbon mold and sintered for 1 to 30 minutes at a temperature of 400 to 550°C. At this time, a spark plasma sintering (SPS) method may be used, and the sintering pressure may be adjusted to 35 MPa to 60 MPa.

Hereinafter, the present invention will be described in detail through examples for making the present invention, but this is only provided to aid understanding of the present invention, and the present invention is not limited thereto.

[Comparative Example 1]

After weighing each raw material to have a composition of Bi ₂ Se _{0 .15} Te _{2 .85} of n-type thermoelectric material, it was charged into a furnace and melted for 5 to 15 hours at a temperature of 600 to 900°C in an Ar inert atmosphere. Then, it was cooled to form an ingot. The prepared ingot was pulverized to a size of 1 to 10 μm by a ball mill method, and then the powder was put in a carbon mold and sintered at a temperature of 400 to 450° C. at a pressure of 35 to 60 MPa for 30 minutes to prepare an n-type thermoelectric material.

[Example 1]

After weighing each raw material to have a composition of Bi ₂ Se _{0 .15} Te _{2 .85} of n-type thermoelectric material, it was charged into a furnace and melted for 5 to 15 hours at a temperature of 600 to 900°C in an Ar inert atmosphere. Then, it was cooled to form an ingot. The prepared ingot was pulverized to a size of 1 to 10 μm by a ball mill method, and 0.02 wt% of Te particles of 200 μm or less were added in a small amount, and then mixed unevenly. Then, the powder was put in a carbon mold and sintered for 30 minutes at a temperature of 400 to 450°C at a pressure of 35 to 60 MPa to prepare an n-type thermoelectric material.

[Example 2]

Bi _{0 .5} of the P-type thermoelectric material _{1 .5} Sb Te ₃ composition have a After weighing the respective raw materials, charging them to the furnace (Furnace), and molten for 5 to 15 hours in Ar inert atmosphere to a temperature of 600 to 900 ℃ After cooling, an ingot was formed. The prepared ingot was pulverized to a size of 1 to 10 μm by a ball mill method, and 0.02 wt% of Te particles of 200 μm or less were added in a small amount, and then mixed unevenly. Then, the powder was put in a carbon mold and sintered at a temperature of 400 to 450°C for 30 minutes at a pressure of 35 to 60 MPa to prepare a P-type thermoelectric material.

As can be seen from FIG. 3, the number of thermoelectric cells of the thermoelectric material prepared according to Comparative Example 1 was about 0.56 at room temperature (25°C), but the thermoelectric material prepared by Example 1 was about 0.62 at room temperature. You can see that the performance has improved. In addition, even when the temperature is increased to 150°C, the thermoelectric material prepared according to Comparative Example 1 has a number of thermoelectric cells of about 0.7, but the thermoelectric material prepared according to Example 1 has a number of thermoelectric cells of about 0.8, so that thermoelectric performance is improved even at high temperatures. You can see excellence.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the claims are also included in the scope of the present invention. It belongs to.

Claims (12)

manufacturing an ingot by melting constituent elements constituting an n-type or p-type thermoelectric material;
Pulverizing the ingot to prepare a powder;
Mixing the pulverized powder with a dopant, which is one of the constituent elements; And
Sintering the powder mixed with the dopant; Including,
The average particle diameter of the dopant is less than or equal to the average particle diameter of the pulverized powder,
The pulverized powder satisfies the following composition formula 1,
The dopant is a method of manufacturing a thermoelectric material satisfying the following composition formula 2.
[Composition 1]
BiM ₁ M ₂
(In the composition formula 1, the M ₁ and M ₂ is any one of Te, Se or Sb, and M ₁ and M ₂ is a different substance)
[Composition 2]
D
(In the above composition formula 2, the dopant (D) is any one of Bi, M _1, or M _2. )
delete delete The method of claim 1, wherein in the step of mixing the dopant,
The dopant is added in an amount of 0.01 wt% to 0.2 wt% based on the total weight of the pulverized powder.
The method of claim 1,
The method of manufacturing a thermoelectric material having an average particle diameter of the dopant is 200 μm or less.
The method of claim 1,
The method of manufacturing a thermoelectric material in which the dopant is Te.
delete delete delete delete delete delete

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