KR102058196B1 - Thermoelectric material and manufacturing method thereof - Google Patents

Abstract

The present invention discloses a thermoelectric material excellent in thermoelectric conversion performance and a method of manufacturing the same. The thermoelectric material according to the present invention may be represented by the following Chemical Formula 1.
<Formula 1>
Bi _1-xy Ln _x M _y CuOSe _1-z Q _z
In Formula 1, Ln is at least one element of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, M is Ba, Sr, Ca , Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As and Sb is at least one element, Q is at least one element of Te and S, 0 <x <1, 0 ≤ y <1, 0 <x + y <1 and 0 ≦ z <1.

Description

Thermoelectric material and method for manufacturing the same

The present invention relates to a thermoelectric material, and more particularly to a novel thermoelectric material having improved thermoelectric conversion performance and a method of manufacturing the same.

A thermoelectric material is a compound that acts as a semiconductor by combining two or more elements rather than a single element such as silicon or germanium. Such thermoelectric materials have been developed in various types and used in various fields. Typically, a thermoelectric conversion material may be used in a thermoelectric conversion device using a Peltier effect, a light emitting device such as a light emitting diode or a laser diode using the photoelectric conversion effect, and a solar cell.

In particular, the thermoelectric material can be applied to thermoelectric conversion power generation, thermoelectric conversion cooling and the like. Among these, thermoelectric conversion power generation is a form of power generation that converts thermal energy into electrical energy by using thermoelectric power generated by providing a temperature difference to a thermoelectric conversion element. And thermoelectric conversion cooling is a form of cooling which converts electrical energy into thermal energy by taking advantage of the effect that a temperature difference occurs at both ends when a direct current flows through both ends of the thermoelectric conversion element. The thermoelectric material may be implemented to constitute a thermoelectric conversion element to achieve thermoelectric power generation or thermoelectric conversion cooling, wherein the N-type thermoelectric material and the P-type thermoelectric material are electrically in series and thermally parallel. Can be connected to.

Such thermoelectric technology has the advantage that direct and reversible conversion of heat and electricity is possible without using a heat-resistant engine. In particular, recently, as interest in environmentally friendly energy materials has increased, thermoelectric technology has been spotlighted as a notable technology.

The energy conversion efficiency of such a thermoelectric conversion element is largely dependent on ZT, which is a figure of merit of a thermoelectric conversion material, or other factors. Here, ZT may be determined according to Seebeck coefficient, electrical conductivity and thermal conductivity.

Many thermoelectric materials have been proposed and developed to be used as thermoelectric conversion elements. As a typical group, a chalcogenide system, an antimonide system, a clathrate system, a half whisler system, a skutterudite system, etc. are mentioned.

However, in the thermoelectric conversion material proposed so far, it cannot be seen that sufficient thermoelectric conversion performance is secured. Moreover, in recent years, the field of application for thermoelectric conversion materials has been gradually expanded, and the temperature conditions may vary from application to application. However, since thermoelectric conversion performance may vary depending on temperature, each thermoelectric conversion material needs to be optimized for thermoelectric conversion performance in a field in which the thermoelectric conversion material is applied.

In particular, in recent years, the need for a thermoelectric material having high thermoelectric conversion performance is increasing in the low and medium temperature range, such as 50 ℃ to 300 ℃. For example, a thermoelectric material having low performance at low temperature even though it has high performance at high temperature may not be preferable as a thermoelectric material for power generation. This is because even if such a thermoelectric material is applied to a high temperature heat source, some of the material may experience a much lower temperature than a desired temperature due to the temperature gradient generated from the material itself. Therefore, there is a continuous demand for thermoelectric materials having excellent thermoelectric conversion performance in such a temperature range.

Accordingly, the present invention has been made to solve the above problems, and an object thereof is to provide a thermoelectric material excellent in thermoelectric conversion performance and a method of manufacturing the same.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In order to achieve the above object, the present inventors have succeeded in producing a thermoelectric material according to the present invention after repeated studies on the thermoelectric material, and confirmed the excellent characteristics of the thermoelectric material to complete the present invention.

The thermoelectric material according to the present invention may be represented by the following Chemical Formula 1.

<Formula 1>

Bi _1-xy Ln _x M _y CuOSe _1-z Q _z

In Formula 1, Ln is at least one element of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, M is Ba, Sr, Ca , Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As and Sb is at least one element, Q is at least one element of Te and S, 0 <x <1, 0 ≤ y <1, 0 <x + y <1 and 0 ≦ z <1.

Here, Ln of Formula 1 may be La.

In addition, z in Formula 1 may be 0.

In addition, x and y of Formula 1 may be 0 <x + y ≤ 0.1.

In addition, the thermoelectric material manufacturing method according to the present invention, according to the composition of Formula 1 of claim 1, each powder of Bi ₂ O ₃ , Bi, Cu and Se, La, Ce, Pr, Nd, Pm, Sm, Eu, Mixing a powder of at least one of Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu or an oxide thereof to form a mixture; Heat treating the mixture to form a composite; And pressure sintering the composite.

Here, in the mixture forming step, each powder of Bi ₂ O ₃ , Bi, Cu and Se and the powder of La ₂ O ₃ may be mixed.

In addition, the mixture forming step, at least one element or oxides of Ba, Sr, Ca, Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As, Sb, Te and S in the mixture It may further comprise a powder.

In addition, the thermoelectric conversion element according to the present invention may include the thermoelectric material according to the present invention.

According to the present invention, a thermoelectric material excellent in thermoelectric conversion performance can be provided.

In particular, according to one aspect of the present invention, a thermoelectric material having improved Seebeck coefficient may be provided.

Moreover, the thermoelectric material according to the present invention can be said to exhibit excellent thermoelectric conversion performance in the temperature range of 50 ℃ to 300 ℃.

Such thermoelectric materials may be used as another material in place of, or in addition to, conventional thermoelectric materials.

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.
1 is a flowchart schematically illustrating a method of manufacturing a thermoelectric material according to an embodiment of the present invention.
2 is a graph showing the Seebeck coefficient values according to temperature changes, respectively, for thermoelectric materials of Examples and Comparative Examples manufactured according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The thermoelectric material according to the present invention may be represented by the following Chemical Formula 1.

<Formula 1>

Bi _1-xy Ln _x M _y CuOSe _1-z Q _z

In Formula 1, Ln is any one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or two or more elements thereof. to be.

In particular, in Formula 1, Ln may be La.

In Formula 1, M may be any one selected from the group consisting of Ba, Sr, Ca, Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As, and Sb, or two or more elements thereof. to be.

In Formula 1, Q is at least one element of Te and S, and 0 <x <1, 0≤y <1, 0 <x + y <1 and 0≤z <1.

Referring to Chemical Formula 1, the thermoelectric material according to the present invention, together with Bi, Cu, O and Se, Ln (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, One or more of Tm, Yb, and Lu).

In particular, Ln may be included in the form of substituting Bi. That is, in the thermoelectric material according to the present invention, it can be said that at least some sites of Bi are substituted with Ln.

In addition, referring to Chemical Formula 1, the thermoelectric material according to the present invention may include M (at least one of Ba, Sr, Ca, Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As, and Sb). Optionally further may be included. At this time, M may be included in the form of substituting Bi with Ln. That is, some sites of Bi may be substituted with Ln and some other sites of Bi may be substituted with M.

In addition, referring to Chemical Formula 1, the thermoelectric material according to the present invention may further include Q (Te and / or S). In this case, Q may be included in the form of substituting Se. That is, in the thermoelectric material according to the present invention, some sites of Se may be substituted with Te and / or S.

Z in Formula 1 may be 0. In this case, the thermoelectric material according to the present invention may be represented by the following formula.

Bi _1-xy Ln _x M _y CuOSe

In addition, the thermoelectric material according to the present invention may be configured such that x and y of Formula 1 satisfy a relationship of 0 <x + y ≦ 0.1.

In particular, in Formula 1, x may be 0 <x ≦ 0.1. Furthermore, in Chemical Formula 1, x may be 0 <x ≦ 0.05. For example, in Formula 1, x may be 0.02.

Here, when Ln is La, the thermoelectric material according to the present invention may be represented by the following formula.

Bi _0.98-y La _0.02 M _y CuOSe _1-z Q _z

In addition, in Formula 1, y may be 0. In this case, the thermoelectric material according to the present invention may be represented by the following formula.

Bi _1-x Ln _x CuOSe _1-z Q _z

As such, the thermoelectric material according to the present invention is based on Bi-Cu-O-Se, but Bi, Cu, O, and / or Se may be substituted with other elements according to an appropriate composition ratio. And, with such a constitutional feature, the thermoelectric material according to the present invention can be improved thermoelectric conversion performance compared to the conventional thermoelectric material.

1 is a flowchart schematically illustrating a method of manufacturing a thermoelectric material according to an embodiment of the present invention.

Referring to FIG. 1, the method of manufacturing a thermoelectric material according to the present invention may include a raw material mixing step (S110), a heat treatment synthesis step (S120), and a pressure sintering step (S130).

In the step S110, a mixture may be formed by mixing each raw material included in the thermoelectric material. In particular, in step S110, each raw material may be mixed based on Chemical Formula 1.

For example, the step S110 may be weighed such that Bi: Ln: M: Cu: O: Se: Q = 1-xy: x: y: 1: 1: 1-z: z for each element as a molar ratio. Can mix with each other.

For example, when Chemical Formula 1 representing a thermoelectric material according to the present invention is represented by Bi _0.95 Ce _0.04 Sr _0.01 CuOSe _0.9 S _0.1 , in the step S110, Bi, Ce, Sr, Cu, O, Se, and S are molar ratios. And 0.95: 0.04: 0.01: 1: 1: 0.9.0.1.

That is, in the step S110, according to the composition of Formula 1 of claim 1, each powder of Bi ₂ O ₃ , Bi, Cu and Se, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, A mixture may be formed by mixing powders of at least one or more elements of Dy, Ho, Er, Tm, Yb and Lu or their oxides.

In the step S110, each raw material may be mixed in powder form. In this case, the contact area between each element is increased, so that the reaction between each element may be better performed at step S120. However, since the oxygen (O) element itself is easy to exist in the gas phase in the mixing step, O may be included and mixed in the form of oxides of other elements rather than exist alone.

For example, when the thermoelectric material according to the present invention is composed of Bi, La, Cu, O, and Se, the step S110 may include a powder of Bi ₂ O ₃ , Bi, Cu, and Se and a powder of La ₂ O ₃ . Can be mixed with each other. According to this configuration of the present invention, the mixing between the elements can be made well and the reactivity can be improved.

In addition, the thermoelectric material according to the present invention may further include M as a component. At this time, the step S110, the mixture further includes at least one element of Ba, Sr, Ca, Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As and Sb or powder thereof. You can do that.

In addition, the thermoelectric material according to the present invention may further include the above Q in the component. At this time, the step S110, the mixture may further include a powder of at least one or more elements of Te and S or its oxide.

On the other hand, the step S110 may be performed by grinding each pellet in the form of powder (grinding), hand milling (hand milling), etc. and then pelletizing (pelletization). According to this mixing method of the present invention, the mixing is well made, it is possible to make the reaction between the elements in the step S120 better.

In the step S120, by heating the mixture formed in step S110 to cause a reaction between the elements, the composite can be formed. That is, the step S120, by reacting each element included in the mixture may be formed to the compound represented by the formula (1).

For example, the step S120, the heat treatment may be performed to the mixture at a predetermined temperature, for example, a temperature range of 400 ℃ to 650 ℃. In addition, the step S120 may be performed for a predetermined time, for example, 10 hours to 15 hours. For example, in step S120, the mixed raw materials are put in a silica tube, and then maintained at 600 ° C. for 12 hours, thereby allowing each raw material to react with each other to form a composite.

Here, the step S120 may be performed by a melting method or a solid state reaction method.

In the step S130, by sintering the composite formed in the step S120, it is possible to form a sintered body. In addition, such a sintering step may be performed under pressurized conditions. For example, the step S130 may be performed under a pressure condition of 30MPa to 200MPa. In addition, the sintering step may be performed at a predetermined temperature, such as a temperature condition of 300 ℃ to 800 ℃. In addition, the sintering step may be performed for a predetermined time, for example, 1 hour to 15 hours.

Here, step S130 may be performed by a CIP (Cold Isostatic Press) method. That is, the step S130 may be performed by heat treatment after being pressed under a predetermined pressure condition.

The thermoelectric material according to the present invention may have improved thermoelectric conversion performance as compared to the BiCuOTe-based thermoelectric material. In particular, the thermoelectric material according to the present invention may have an improved Seebeck coefficient in the temperature range of 300K to 600K. For example, the thermoelectric material according to the present invention may have a Seebeck coefficient of 400 kW / K or more in a temperature range of 300K to 600K.

The thermoelectric material according to the present invention can be used for thermoelectric conversion elements. That is, the thermoelectric conversion element according to the present invention may include the thermoelectric material according to the present invention, that is, the thermoelectric material represented by Chemical Formula 1.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the embodiment according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1

Powders Bi, Bi ₂ O ₃ , Cu, Se, and La ₂ O ₃ are weighed to a Bi _0.98 La _0.02 CuOSe composition, mixed well in an agate mortar, and then pelletized to form a silica tube Put in. Then, these were vacuum sealed and heated at 600 ° C. for 12 hours to obtain Bi _0.98 La _0.02 CuOSe compound in powder form as an example sample. The sample thus synthesized was molded into a cylinder having a diameter of 4 mm and a length of 15 mm, and pressurized to 200 MPa using CIP. The resultant was then placed in a quartz tube and vacuum sintered for 12 hours. Then, the Seebeck coefficient of the sample was measured at predetermined temperature intervals using ZEM-3 (Ulvac-Rico, Inc) for the sintered cylinder, and the results are shown in FIG. 2 as Example 1. FIG.

Comparative Example 1

Bi, Bi ₂ O ₃ , Cu and Te in powder form were weighed to the BiCuOTe composition, mixed well in an agate mortar and then pelletized into silica tubes. Then, these were vacuum sealed and heated at 600 ° C. for 12 hours to obtain a BiCuOTe compound in powder form as a comparative sample. The comparative sample thus synthesized was molded into a cylinder having a diameter of 4 mm and a length of 15 mm, and pressure was applied at 200 MPa using CIP. The resultant was then placed in a quartz tube and vacuum sintered for 12 hours. Then, about the sintered cylinder, the Seebeck coefficient of the sample was measured at predetermined temperature intervals using ZEM-3 (Ulvac-Rico, Inc), and the results are shown in FIG. 2 as Comparative Example 1. FIG.

Referring to the results of FIG. 2, it can be seen that the Seebeck coefficient of the thermoelectric material of Example 1 is significantly higher over the entire temperature measurement section of approximately 50 ° C. to 300 ° C., compared to the thermoelectric material of Comparative Example 1.

That is, in the case of the thermoelectric material of Example 1, it is shown that the Seebeck coefficient is higher than approximately 400 kHz / K over the temperature range of 300K to 600K. On the other hand, the thermoelectric material of Comparative Example 1 appears to have a Seebeck coefficient of less than approximately 200 mA / K at the same temperature. From these results, it can be seen that the thermoelectric material of Example 1 has an effect of improving the Seebeck coefficient approximately two times or more compared with the thermoelectric material of Comparative Example 1.

Therefore, in the case of a thermoelectric material according to an embodiment of the present invention, that is, a thermoelectric material having Bi, Cu, O, and Se as a basic configuration, and part of Bi is substituted with La, a comparative example composed of Bi, Cu, O, and Te It can be seen that the thermoelectric conversion performance is further improved compared to the thermoelectric material.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

Claims (7)

A thermoelectric material represented by the following formula (1).
<Formula 1>
Bi _1-xy Ln _x M _y CuOSe _1-z Q _z
In Formula 1, Ln is at least one element of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, M is Ba, Sr, Ca , Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As and Sb, at least one or more elements, Q is S as an element for substituting some sites of Se, 0 <x <1, 0 Y <1, 0 <x + y <1 and 0 <z <1. The method of claim 1,
Ln of the general formula (1) is La thermoelectric material, characterized in that. delete The method of claim 1,
X and y in the formula (1), 0 <x + y ≤ 0.1, characterized in that the thermoelectric material. According to the composition of Formula 1 of claim 1, each powder of Bi ₂ O ₃ , Bi, Cu, Se and S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er Mixing a powder of at least one element of Tm, Yb and Lu or an oxide thereof to form a mixture;
Heat treating the mixture to form a composite; And
Pressure sintering the composite
Method for producing a thermoelectric material of claim 1, comprising a. The method of claim 5,
The forming of the mixture further includes a powder of at least one element of Ba, Sr, Ca, Mg, Cd, Hg, Sn, Pb, Mn, Ga, In, Tl, As, and Sb or an oxide thereof in the mixture. The thermoelectric material manufacturing method characterized by the above-mentioned. A thermoelectric conversion element comprising the thermoelectric material according to any one of claims 1, 2 and 4.

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