阅读说明：本技术 热电材料和包含其的热电装置 (Thermoelectric material and thermoelectric device including the same ) 是由 金宰贤 李秀贞 李艺瑟 朴哲凞 于 2019-05-08 设计创作，主要内容包括：根据本发明的热电材料是p型方钴矿,并且包含Fe和Sb元素。在p型方钴矿粉末的烧结期间添加少量的Al,从而将p型方钴矿和Al一起烧结,并因此在热电材料中生成少量的AlSb,从而使降低热电材料性能的FeSb<Sub>2</Sub>组分的生成最小化。因此,热电材料可以有利地用于包含热电材料的热电装置中。(The thermoelectric material according to the present invention is p-type skutterudite, and contains Fe and Sb elements. Adding a small amount of Al during sintering of the p-type skutterudite powder to sinter the p-type skutterudite and Al together, and thus generating a small amount of AlSb in the thermoelectric material, thereby causing FeSb that degrades the performance of the thermoelectric material 2 The generation of components is minimized. Thus, the thermoelectric material may be advantageously used in a thermoelectric device comprising the thermoelectric material.)

1. A thermoelectric material, comprising:

a p-type skutterudite material of the following chemical formula 1,

greater than 0 wt% and 7.5 wt% or less AlSb, and

FeSb in an amount of more than 0 wt% and 20 wt% or less₂：

[ chemical formula 1]

(M)_m(Fe)_a(A′)_a′(Co)_b(B′)_b′(Sb)_c(C′)_c′

In the chemical formula 1, the first and second,

m is at least one element selected from the group consisting of S, In, Nd, Pr, Ce, Yb, La, Sr, Ba, Ca, Sm, Eu and Gd,

0＜m＜1.5，

a' is at least one of elements selected from Ni, Mn, Tc and Pd,

1< (a + a ') is less than or equal to 4, and 0< a' <1,

b' is at least one of elements selected from Ni, Ru, Os, Ir and Pt,

0< (b + b ') <3, and 0. ltoreq. b' <1,

c' is at least one of elements selected from Sn and Te, and

11< (c + c ') <13.5, and 0. ltoreq. c' < 1.

2. The thermoelectric material of claim 1, wherein

m is 0.5 to 1.0.

3. The thermoelectric material of claim 1, wherein

The AlSb is included in an amount of 1 to 5 wt%.

4. The thermoelectric material of claim 1, wherein

The FeSb₂Included in an amount of 5 to 15 wt%.

5. A method for producing a thermoelectric material according to any one of claims 1 to 4, the method comprising the steps of:

1) mixing M, Fe, A ', Co, B', Sb and C 'in a molar ratio of M: a': B ': C', and then heating and heat-treating the mixture to produce an ingot;

2) pulverizing the ingot produced above to produce a powder; and

3) mixing the pulverized powder with an Al powder in an amount of more than 0 to 1.5% by weight relative to the weight of the powder, and then sintering:

wherein M, A ', B', C ', m, a', B ', C and C' are as defined according to any one of claims 1 to 4.

6. The method of claim 5, wherein

The heating temperature of step 1) is 600 ℃ to 1400 ℃.

7. The method of claim 5, wherein

The heat treatment temperature of the step 1) is 500 ℃ to 800 ℃.

8. The method of claim 5, wherein

The amount of Al added in step 3) is 0.5 to 1.0 wt% with respect to the weight of the powder.

9. The method of claim 5, wherein

The sintering temperature of step 3) is 500 ℃ to 900 ℃.

10. A thermoelectric device comprising the thermoelectric material according to any one of claims 1 to 4.

Technical Field

Cross Reference to Related Applications

This application claims the benefit of the filing date of korean patent application No. 10-2018-0066825, filed on 11.6.2018 to the korean intellectual property office, the entire contents of which are incorporated herein by reference.

The present invention relates to a thermoelectric material that minimizes the content of a component that reduces thermoelectric performance, and a thermoelectric device including the same.

Background

Recently, as interest in development and conservation of alternative energy sources increases, research and study on high-efficiency energy conversion materials are actively being conducted. In particular, research into thermoelectric materials that are thermoelectric energy conversion materials is being accelerated.

These thermoelectric materials are metal or ceramic materials having a function of directly converting heat into electricity or vice versa, and have an advantage that power can be generated even without moving parts when a temperature difference is applied. After their thermoelectric phenomena, i.e., Seebeck (Seebeck) effect, Peltier (Peltier) effect, and tombuston (Thomson) effect, were discovered in the beginning of the 19 th century, these thermoelectric materials have been developed to have high thermoelectric performance indexes with the progress of semiconductors since the end of the 30 th century.

Meanwhile, as a next-generation material having thermoelectric energy conversion characteristics, skutterudite compounds have been studied. Skutterudite compounds have great potential as materials expected to improve their thermoelectric energy conversion characteristics by lowering the lattice thermal conductivity.

Meanwhile, a method for producing a thermoelectric material containing skutterudite generally includes three stages in which a raw material is first heated under various conditions according to the chemical composition of a target thermoelectric material and is subjected to a heat treatment to synthesize an ingot-shaped material. It is pulverized and classified to produce powder, and then the powder is sintered at high temperature and high pressure to produce thermoelectric materials.

In addition, the production method including synthesis, pulverization, classification, and sintering as described above is expensive to apply to a continuous process, and therefore, in industrial production, first, thermoelectric material powder is mass-produced as described above in consideration of economic efficiency, and then, the powder is sintered to produce a thermoelectric material. In other words, as mass production becomes possible, the production process of the powder is more economical, and the sintering process of the powder has a long processing time due to high-temperature processing characteristics. Therefore, a considerable amount of time is spent between the mass production process and the sintering process of the powder, and thus the powder is inevitably stored for a long time.

Meanwhile, the present inventors found that the properties of the finally produced thermoelectric material greatly depend on the storage conditions of the skutterudite powder produced by the above-described method. In particular, as described in detail below, it has been determined that a material that degrades the performance of a thermoelectric material is found in the thermoelectric material produced when skutterudite powder is stored for a long period of time.

In this regard, the present inventors have intensively studied a method for preventing the performance degradation of a thermoelectric material even when the thermoelectric material is produced after the powder is stored for a long time as described above, and as a result, found that the above-described problems are solved when the thermoelectric material and the production method thereof as described below are used, thereby completing the present invention.

Disclosure of Invention

Technical problem

An object of the present invention is to provide a thermoelectric material and a thermoelectric element including the thermoelectric material, in which the content of a component that degrades thermoelectric performance is minimized.

Technical scheme

In order to achieve the above object, one embodiment of the present invention provides a thermoelectric material comprising: a p-type skutterudite material of the following chemical formula 1, more than 0% by weight and 7.5% by weight or less of AlSb, andFeSb in an amount of more than 0 wt% and 20 wt% or less₂：

[ chemical formula 1]

(M)_m(Fe)_a(A')_a'(Co)_b(B')_b'(Sb)_c(C')_c'

In the chemical formula 1, the first and second,

m is at least one element selected from the group consisting of S, In, Nd, Pr, Ce, Yb, La, Sr, Ba, Ca, Sm, Eu and Gd,

0<m<1.5，

a' is at least one of elements selected from Ni, Mn, Tc and Pd,

1< (a + a ') > is less than or equal to 4, and a' is more than or equal to 0 and less than 1,

b' is at least one of elements selected from Ni, Ru, Os, Ir and Pt,

0< (b + b ') <3, and 0. ltoreq. b' <1,

c' is at least one of elements selected from Sn and Te, and

11< (c + c ') <13.5, and 0 ≦ c' < 1.

As used herein, the term 'p-type skutterudite material' refers to a compound represented by chemical formula 1 as defined above, and corresponds to a main component of the thermoelectric material in the present invention.

The p-type skutterudite-based thermoelectric material as described above is generally produced by a method for producing a thermoelectric material, the method comprising the steps of: the raw material is heated under various conditions according to chemical composition, subjected to heat treatment to produce an ingot-shaped material, the resulting material is pulverized and classified to produce a powder, and then the powder is sintered at high temperature and high pressure. In industrial production, for economic reasons, skutterudite materials are produced by mass-producing powders and then sintering them. In this process, sintering is performed after the powder is stored for a long time. The long-term storage causes a problem that the performance of the thermoelectric material is greatly deteriorated.

In particular, the "p-type skutterudite" of the present invention contains Fe and Sb elements. Although not limited in theory, the performance degradation of the thermoelectric material as described above is attributed to FeSb due to long-term storage₂As in the examples of the invention and comparative examples. In addition, the "p-type skutterudite" of the present invention also contains Co element, and thus FeSb₂May also be (Fe/Co) Sb₂Exist in the form of (1). Thus, the FeSb described herein₂Means further comprising (Fe/Co) Sb₂。

Therefore, according to the present invention, in the production of thermoelectric materials, a small amount of Al is added during sintering of p-type skutterudite powder and sintered together, and thus a small amount of AlSb is generated in the thermoelectric materials. As a result, FeSb which degrades the performance of the thermoelectric material can be reduced₂And (4) generating.

Preferably, m is 0.5 to 1.0. Further, preferably, M is Nd.

a is preferably 2. ltoreq. a.ltoreq.4, and most preferably 3.

b is preferably 0.5. ltoreq. b.ltoreq.2, and most preferably 1.

c is preferably 11.5. ltoreq. c.ltoreq.12.5, and most preferably 12.

a ', b ' and c ' mean the amounts of elements that undergo substitution and enter the Fe, Co and Sb sites, respectively. a ', b', and c 'are each less than 1, and when a', b ', and c' are 0, it means that there is no substitution element.

Meanwhile, AlSb and FeSb₂The content of (b) means based on the total mass of the thermoelectric material described above. For example, when AlSb and FeSb₂When included at 5 wt% respectively, it means that the thermoelectric material contains 5 wt% of AlSb, 5 wt% of FeSb₂And 90 wt% of a p-type skutterudite material.

As described below, AlSb is generated by adding Al during the production of the thermoelectric material, and is included in the thermoelectric material of the present invention in an amount of more than 0 wt% and 7.5 wt% or less. Although not limited in theory, when sintered with Al, Al combines with Sb to form AlSb, thereby suppressing FeSb₂As a result, the performance of the thermoelectric material can be prevented from deteriorating.

FeSb with increased AlSb production₂The generation of (a) is reduced, and as the generation amount of AlSb increases, the performance of the thermoelectric material improves. However, when the amount of AlSb produced is too large, the properties of the thermoelectric materialCan deteriorate. Therefore, preferably, the generation amount of AlSb in the thermoelectric material is preferably 7.0 wt% or less, 6.5 wt% or less, 5.0 wt% or less, 4.5 wt% or less, or 4.0 wt% or less. Further, preferably, in the thermoelectric material, the generation amount of AlSb is preferably 0.5 wt% or more, 1.0 wt% or more, or 1.5 wt% or more.

FeSb because of the production of AlSb₂The amount of production of (2) is reduced. Preferably, in the thermoelectric material, FeSb₂Is 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, 16 wt% or less, 15 wt% or less, 14 wt% or less, 13 wt% or less, or 12 wt% or less.

Another embodiment of the present invention provides a method for producing the above thermoelectric material, comprising the steps of:

1) mixing M, Fe, A ', Co, B', Sb and C 'in a molar ratio of M: a: a': B: B ': C: C', and then heating and heat-treating the mixture to produce an ingot;

2) pulverizing the ingot produced above to produce a powder; and

3) mixing the pulverized powder with more than 0 to 1.5% by weight of Al powder with respect to the weight of the powder, and then sintering it:

wherein M, A ', B', C ', m, a', B ', C, and C' are as defined above.

Step 1 is a step of mixing the components of the thermoelectric material and heating and heat-treating the mixture to produce an ingot.

Preferably, the heating temperature is 600 ℃ to 1400 ℃. Preferably, the heating time is 10 hours to 200 hours. Preferably, the heat treatment temperature is 500 ℃ to 800 ℃. Preferably, the heat treatment time is 10 hours to 200 hours. Thereby, the components of the thermoelectric material are finally melted to prepare an ingot-shaped material.

Step 2 is a step of pulverizing the ingot produced in step 1 to produce a powder.

The powder may be pulverized to a particle size of 100 μm or less, and a classification step may be added as necessary. As the pulverizing/classifying method and apparatus therefor, methods and apparatuses used in the field of inorganic materials can be applied without limitation.

Step 3 is a step of sintering the pulverized powder produced in step 2.

As described above, step 2 and step 3 are difficult to apply in a continuous process, in industrial production, and therefore, thermoelectric materials are produced by: the powders as in step 1 and step 2 are mass-produced and then sintered as in step 3. This greatly affects the performance of the thermoelectric material depending on the conditions under which the powder is stored between step 2 and step 3.

However, in the present invention, the content of the component that degrades the performance of the thermoelectric material can be minimized by adding Al to the powder and sintering together as in step 3.

The amount of Al added is determined by the amount of AlSb and FeSb in the thermoelectric material₂The content of (c). Therefore, by adjusting the amount of Al added, AlSb and FeSb can be adjusted₂The content of (a). Preferably, Al is added in an amount of 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, or 0.5 wt% or more, and 1.4 wt% or less, 1.3 wt% or less, 1.2 wt% or less, 1.1 wt% or less, or 1.0 wt% or less, relative to the powder produced in step 1.

Sintering may be performed using spark plasma sintering at a temperature of about 500 ℃ to 900 ℃. Preferably, the sintering temperature is 600 ℃ to 680 ℃. Further, the sintering time is preferably 1 minute to 600 minutes at a pressure of 0.1MPa to 100 MPa.

Yet another embodiment of the present invention provides a thermoelectric device comprising the thermoelectric material described above.

Advantageous effects

As described above, the thermoelectric material according to the present invention minimizes the content of the component that degrades thermoelectric performance, and thus can be effectively used for a thermoelectric device including the same.

Drawings

Fig. 1 shows XRD patterns of thermoelectric materials produced in examples according to the present invention and comparative examples.

Detailed Description

Hereinafter, preferred embodiments are provided to facilitate understanding of the present invention. However, the following examples are provided only for better understanding of the present invention, and the scope of the present invention is not limited thereto.

Comparative example 1

(step 1)

High-purity raw materials of Nd, Fe, Co and Sb were weighed in a glove box at a molar ratio of 0.9:3.0:1.0:12.1, placed in a graphite crucible, and then charged in a quartz tube. As for Sb, Sb was added at a molar ratio of 0.1 due to volatilization. The inside of the quartz tube is sealed under a vacuum state. Then, the raw material was heated at 1000 ℃ to 1200 ℃ and kept in a constant temperature state in the furnace for 24 hours. Subsequently, the quartz tube is naturally cooled to room temperature to form an ingot, and then it is maintained in a constant temperature state in a furnace of 600 to 750 ℃ for 120 hours and subjected to heat treatment. The heat-treated ingot material is pulverized and classified into a powder having a particle size of 75 μm or less.

(step 2)

The powder produced in step 1 was stored in a glove box having an oxygen concentration of 1ppm or less for 6 months.

(step 3)

7g of the powder produced in step 2 was put into a 0.5-inch SUS die and cold-pressed at a pressure of 0.5 ton to 1 ton to prepare pSKD pellets. The prepared pellets were placed in a 0.5-inch carbonaceous mold and subjected to high-temperature pressurization by a Spark Plasma Sintering (SPS) apparatus at 650 ℃ and 50MPa for 10 minutes to prepare a 0.5-inch pSKD sintered body.