Cr2Te3 THERMOELECTRIC MATERIALS AND PREPARING METHOD THEREOF

Abstract

The present invention relates to a Cr2Te3-based thermoelectric material and a method for manufacturing the same. More specifically, it relates to an intermetallic compound Cr2Te3 thermoelectric material synthesized with Cr and Te in a compositional ratio of 2 to 3 for the purpose of thermoelectric material applications, and a method for manufacturing a thermoelectric material doped with Ti and Ge to improve thermoelectric properties. A homogeneous Cr-Te-based thermoelectric material can be manufactured by utilizing the solid-liquid reaction, solid-solid reaction, heat treatment, and hot compression or discharge plasma sintering processes, which are the methods for manufacturing the Ti and Ge-doped Cr-Te-based thermoelectric material of the present invention.

Description

Technology Field

[0001] The present invention relates to a Cr2Te3-based thermoelectric material and a method for manufacturing the same. More specifically, it relates to a method for manufacturing an intermetallic compound Cr2Te3 thermoelectric material synthesized with Cr and Te in a compositional ratio of 2 to 3 for the purpose of thermoelectric material applications, and a thermoelectric material doped with Ti and Ge. Background Technology

[0003] Thermoelectric technology refers to energy harvesting technology that utilizes the Seebeck effect, which directly and reversibly converts input thermal energy into electrical energy, or the Peltier effect, which uses input electrical energy to create a temperature difference. This thermoelectric technology is used to improve energy efficiency.

[0004] Thermoelectric technology is applied as thermoelectric devices, and their forms are diverse. Although this invention describes a standard thermoelectric power generation device, film-type thermoelectric power generation devices can also be fabricated by utilizing single-phase powder. The energy conversion efficiency of the thermoelectric device is It is expressed as such, and in order to obtain high energy conversion efficiency, the invention of materials exhibiting a high zT is required. zT is a dimensionless performance index used to evaluate the thermoelectric performance of thermoelectric materials, where ZT=S 2 It is defined as σT / κ. Here, S, σ, T, and κ are the Seebeck coefficient, electrical conductivity, absolute temperature, and thermal conductivity, respectively. The product of the square of the Seebeck coefficient and the electrical conductivity is called the power factor, and to obtain a high ZT, a high power factor and low thermal conductivity are required simultaneously.

[0005] Metal chalcogenides, which are intermetallic compounds composed of transition metals and chalcogen elements, have been primarily studied as materials exhibiting high power factors. Among these, materials with layered structures have been reported to exhibit low lattice thermal conductivity due to bond anisotropy. Metal chalcogenides such as SnSe and Bi2Te3 are layered metal chalcogenides that display high thermoelectric properties. Cr2Te3 has previously been synthesized in thin film form and mainly studied as a magnetic material; however, since it has been reported to possess a layered structure, it was expected to exhibit low lattice thermal conductivity. Although it needs to be synthesized in a bulk form for the fabrication of standard thermoelectric devices, it is difficult to determine an appropriate synthesis process due to the significant difference in melting points between Cr and Te.

[0006] Therefore, to solve these problems, the present invention optimized the bulk single-phase synthesis process by introducing pulverization, cold compression, and heat treatment processes following a solid-liquid reaction, and completed the invention by reporting the thermoelectric properties of Cr2Te3 for the first time. Additionally, Ti and Ge were doped to enhance the thermoelectric properties. Prior art literature

[0008] Republic of Korea Published Patent No. 10-2011-0004362 The problem to be solved

[0009] The present invention was devised to manufacture a single-phase thermoelectric material through process optimization of a Cr2Te3 intermetallic compound, and the objective of the present invention is to provide a method for manufacturing a Cr2Te3-based thermoelectric material doped with Ti or Ge.

[0010] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0012] To achieve the above objective, the present invention provides a Cr2Te3-based thermoelectric material characterized by being represented by the following general formula 1.

[0013] [General Formula 1]

[0014] Cr 2-x M x Te3

[0015] In the above general formula 1, M is Ti or Ge, and 0 ≤ x ≤ 0.2.

[0016] The above Cr2Te3-based thermoelectric material is Cr 2-x Ti x Te3 or Cr 2-x Ti x It has a compound composition of Te3, characterized in that 0≤x≤0.2.

[0017] The above Cr2Te3-based thermoelectric material is characterized by having a lattice thermal conductivity of 0.5 W / mK or less at 500 K or higher.

[0018] In addition, the present invention comprises the steps of: weighing raw materials Cr, Te, and M (M = Ti or Ge) and loading them into a quartz tube and sealing it; melting the raw materials Cr, Te, and M (M = Ti or Ge); rapidly cooling the molten raw materials; pulverizing the rapidly cooled raw materials; cold-compressing the pulverized raw materials; and heat-treating the cold-compressed raw materials to Cr 2-x M x A step of manufacturing a Te3 (M = Ti or Ge, 0≤x≤0.2) ingot; the heat-treated Cr 2-x M x A step of preparing powder by crushing a Te3 (M = Ti or Ge, 0≤x≤0.2) ingot; and the prepared Cr 2-x M x A method for manufacturing a Cr2Te3-based thermoelectric material is provided, characterized by including the step of sintering Te3 (M = Ti or Ge, 0≤x≤0.2) ingot powder.

[0019] The step of melting the above raw materials Cr, Te, and M (M = Ti or Ge) is characterized by being performed for 10 to 72 hours at a temperature range of 850 K to 1300 K.

[0020] The step of pulverizing the above-mentioned rapidly cooled raw material is characterized by selecting one of a mortar and pestle, a planetary ball mill, and a SPEX mill to pulverize the material.

[0021] The step of cold compressing the powdered raw material is characterized by performing cold compression for 5 minutes to 30 minutes at a pressure range of 30 MPa to 100 MPa.

[0022] The above cold-compressed raw material is heat-treated to Cr 2-x M x The step of manufacturing the Te3 ingot is characterized by being performed in an inert atmosphere or a reducing atmosphere.

[0023] The above cold-compressed raw material is heat-treated to Cr 2-x M x The step of manufacturing the Te3 ingot is characterized by being performed for 1 to 5 days.

[0024] The above-mentioned manufactured Cr 2-x M x The step of sintering Te3 (M = Ti or Ge, 0≤x≤0.2) ingot powder is characterized by being performed in a temperature range of 600 K to 1100 K.

[0025] The above-mentioned manufactured Cr 2-x M x The step of sintering Te3 (M = Ti or Ge, 0≤x≤0.2) ingot powder is characterized by being performed for 5 minutes to 2 hours at a pressure range of atmospheric pressure to 200 MPa. Effects of the invention

[0027] By means of the solution to the above problem, a homogeneous Cr-Te-based thermoelectric material can be produced by using a solid-liquid reaction, a solid-solid reaction, a heat treatment, and a hot compression or discharge plasma sintering process, which is a method for producing a Cr-Te-based thermoelectric material doped with Ti and Ge according to the present invention.

[0028] In addition, the Cr-Te-based thermoelectric material manufactured according to the present invention exhibits a low lattice thermal conductivity of at least 0.31 W / mK, which has the effect of being applicable to effective thermoelectric material synthesis design that can be utilized as a thermoelectric element for medium and low temperatures.

[0029] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims. Brief explanation of the drawing

[0031] Figure 1 is a schematic diagram showing the process of manufacturing a Cr2Te3-based thermoelectric material according to an embodiment of the present invention. Figure 2 shows the results of the X-ray diffraction patterns of Cr2Te3 thermoelectric materials prepared according to the comparative example and embodiment of the present invention. FIG. 3 shows Cr manufactured according to an embodiment of the present invention 2-x M x This shows the results of the X-ray diffraction pattern of the Te3 (M= Ti or Ge; 0≤x≤0.20) thermoelectric material. FIG. 4 shows Cr manufactured according to an embodiment of the present invention 2-x M x This shows the electrical conductivity of the thermoelectric material Te3 (M = Ti or Ge; 0≤x≤0.20) as a function of temperature. FIG. 5 shows Cr manufactured according to an embodiment of the present invention 2-x M x This shows the Seebeck coefficient according to temperature of the thermoelectric material Te3 (M = Ti or Ge; 0≤x≤0.20). FIG. 6 is a Cr manufactured according to an embodiment of the present invention2-x M x This shows the thermal conductivity of the thermoelectric material Te3 (M = Ti or Ge; 0≤x≤0.20) as a function of temperature. FIG. 7 shows Cr manufactured according to an embodiment of the present invention 2-x M x This shows the lattice thermal conductivity of the Te3 (M= Ti or Ge; 0≤x≤0.20) thermoelectric material according to temperature. FIG. 8 shows Cr manufactured according to an embodiment of the present invention 2-x M x This shows the performance index zT of the thermoelectric material according to temperature (M= Ti or Ge; 0≤x≤0.20). FIG. 9 shows a graph of process temperature and time during the manufacture of a Cr2Te3-based thermoelectric material according to the present invention, and the structure of the Cr2Te3-based thermoelectric material manufactured accordingly. Specific details for implementing the invention

[0032] The terms used in this invention have been selected based on currently widely used general terms, taking into account their functions within the invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0033] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0034] When a part of a specification is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0035] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0037] The present invention will be described in detail below.

[0039] The present invention provides a Cr2Te3-based thermoelectric material characterized by being represented by the following general formula 1.

[0040] [General Formula 1]

[0041] Cr 2-x M x Te3

[0042] In the above general formula 1, M is Ti or Ge, and 0 ≤ x ≤ 0.2.

[0043] The above Cr2Te3-based thermoelectric material is characterized by having Cr and Te as main components and being doped with Ti and Ge.

[0044] The above Cr2Te3-based thermoelectric material is Cr 2-x Tix Te3 or Cr 2-x Ge x It has a compound composition of Te3, characterized in that 0≤x≤0.2.

[0045] The above Cr2Te3-based thermoelectric material is characterized by having a lattice thermal conductivity of 0.5 W / mK or less at 500 K or higher.

[0046] The above Cr2Te3-based thermoelectric material is characterized by being manufactured through a solid-liquid reaction at 850 K or higher and 1300 K or lower.

[0047] In addition, the present invention comprises the steps of: weighing raw materials Cr, Te, and M (M = Ti or Ge) and loading them into a quartz tube and sealing it; melting the raw materials Cr, Te, and M (M = Ti or Ge); rapidly cooling the molten raw materials; pulverizing the rapidly cooled raw materials; cold-compressing the pulverized raw materials; and heat-treating the cold-compressed raw materials to Cr 2-x M x A step of manufacturing a Te3 (M = Ti or Ge, 0≤x≤0.2) ingot; the heat-treated Cr 2-x M x A step of preparing powder by crushing a Te3 (M = Ti or Ge, 0≤x≤0.2) ingot; and the prepared Cr 2-x M x A method for manufacturing a Cr2Te3-based thermoelectric material is provided, characterized by including the step of sintering Te3 (M = Ti or Ge, 0≤x≤0.2) ingot powder.

[0048] Figure 1 shows a schematic diagram of the process for manufacturing a Cr2Te3-based thermoelectric material according to the present invention.

[0049] In the present invention, the step of weighing the raw material, loading it into a quartz tube, and sealing it involves using a rotary vacuum pump to reduce the pressure inside the quartz tube to 10 -3It can be filled to a vacuum state of Torr. The above vacuum state is achieved by filling with argon (Ar) gas up to atmospheric pressure and then again 10 -3 It can be sealed by creating a vacuum of Torr. Preferably, after filling with the argon (Ar) gas up to atmospheric pressure, again 10 -3 The process of creating a vacuum of Torr can be repeated four times to purge impurity gases from the quartz tube with argon gas.

[0050] The step of melting the above raw materials Cr, Te, and M (M = Ti or Ge) is characterized by being performed for 10 to 72 hours at a temperature range of 850 K to 1300 K. Preferably, it may be performed for 10 to 40 hours at a temperature range of 900 K to 1200 K, but is not limited thereto.

[0051] The step of rapidly cooling the molten raw material can utilize air cooling or furnace cooling, but it is more preferable to rapidly cool it by placing it in water.

[0052] The step of pulverizing the above-mentioned rapidly cooled raw material is characterized by selecting one of a mortar and pestle, a planetary ball mill, and a SPEX mill to pulverize the material. Through the pulverization step, a raw material powder having a diameter of 40 μm to 50 μm or less can be obtained.

[0053] The step of cold-compressing the powdered raw material may utilize any one of hot compression (hot press), spark plasma, and hydraulic press, and is preferably carried out in a chamber with an argon atmosphere.

[0054] The step of cold compressing the powdered raw material is characterized by performing cold compression for 5 minutes to 30 minutes at a pressure range of 30 MPa to 100 MPa. Preferably, cold compression may be performed for 10 minutes to 25 minutes at a pressure range of 50 MPa to 90 MPa, but is not limited thereto.

[0055] The above cold-compressed raw material is heat-treated to Cr 2-x M x The step of manufacturing Te3 ingots is characterized by being performed in an inert atmosphere or a reducing atmosphere. Preferably, it is characterized by being performed in an inert atmosphere comprising any one selected from the group consisting of argon, xenon, and helium, or in a reducing atmosphere comprising any one selected from the group consisting of hydrogen and carbon monoxide.

[0056] The above cold-compressed raw material is heat-treated to Cr 2-x M x The step of manufacturing the Te3 ingot is characterized by being performed for 1 to 5 days.

[0057] The above heat-treated ingot can be slowly cooled to room temperature in a box electric furnace.

[0058] The thermoelectric material ingot obtained through the above process is Cr 2-x M x It may have a compound composition of Te3, where M=Ti or Ge and 0 ≤ x ≤ 0.2.

[0059] The above heat-treated Cr 2-x M x The step of grinding a Te3 (M = Ti or Ge, 0≤x≤0.2) ingot to produce powder is characterized by selecting one of a mortar and pestle, a planetary ball mill, and a SPEX mill to pulverize the powder. Through the pulverization step, a raw material powder having a diameter of 40 μm to 50 μm or less can be obtained.

[0060] The above ingot powder itself has thermoelectric properties and can be fabricated into a thermoelectric device by forming a composite with a conductive polymer film, but it is preferable to fabricate a thermoelectric leg through sintering and apply it as a device.

[0061] The above-mentioned manufactured Cr 2-x M x The step of sintering Te3 (M = Ti or Ge, 0≤x≤0.2) ingot powder is characterized by being performed in a temperature range of 600 K to 1100 K. Preferably, it can be performed in a temperature range of 650 K to 800 K, but is not limited thereto.

[0062] The above-mentioned manufactured Cr 2-x M x The step of sintering Te3 (M = Ti or Ge, 0 ≤ x ≤ 0.2) ingot powder is characterized by being performed for 5 minutes to 2 hours at a pressure range of atmospheric pressure to 200 MPa. Preferably, it may be performed for 20 minutes to 1 hour at a pressure range of 50 MPa to 90 MPa, but is not limited thereto.

[0063] The step of sintering the above ingot powder can be performed in an argon atmosphere.

[0064] The above sintering can be carried out by hot pressing or spark plasma methods.

[0065] The above-mentioned sintered Cr 2-x M x To measure the thermoelectric properties of Te3 (M = Ti or Ge, 0 ≤ x ≤ 0.2) thermoelectric materials, the material may be cut in a direction parallel to the press direction to fit the analysis equipment, but is not limited thereto.

[0066] By the manufacturing method described above, the Cr-Te-based thermoelectric material is Cr 2-x M xA homogeneous Cr-Te-based thermoelectric material can be obtained having a compound composition of Te3, wherein M = Ti or Ge and 0 ≤ x ≤ 0.2, and exhibiting a low lattice thermal conductivity of at least 0.31 W / mK, it can be fabricated as a thermoelectric material that can be utilized as a medium-temperature thermoelectric element.

[0068] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0070] <Example 1>

[0071] As shown in the schematic diagram of thermoelectric material fabrication in Fig. 1, the thermoelectric material raw materials Cr, Te, and M (M = Ti or Ge) are weighed according to their atomic composition ratios and loaded into a quartz tube, and the pressure inside the quartz tube is reduced to 10 using a rotary vacuum pump -3 After creating a vacuum of approximately Torr, fill with argon (Ar) gas up to atmospheric pressure, then 10 -3 Create a vacuum of approximately Torr. Repeat the above process 4 times to purify the impurity gases inside the quartz tube with argon gas, and 10 -3 A vacuum was created to the Torr level and sealed. The quartz tube was placed in a oscillating electric furnace and melted at 1173 K for 24 hours. Afterward, the quartz tube was rapidly cooled by immersing it in water, and then a homogeneous powder was prepared by sieving it through a 45 μm diameter sieve using an alumina mortar and pestle. The prepared powder was loaded into a tungsten mold, and using a rotary vacuum pump, 10 -3 A vacuum of Torr was created. After filling with argon (Ar) gas up to atmospheric pressure, 10 again -3A vacuum of Torr was created. This process was repeated four times to purify the chamber of impurities using argon gas, and the mixture was compressed at a pressure of 70 MPa for 20 minutes. Subsequently, the compressed powder was loaded into a quartz tube, and the pressure inside the quartz tube was reduced to 10 using a rotary vacuum pump. -3 After creating a vacuum of approximately Torr, fill with argon (Ar) gas up to atmospheric pressure, then 10 -3 A vacuum of approximately Torr was created. The above process was repeated four times to purge impurity gases from the quartz tube using argon gas, and the tube was sealed after creating a vacuum of 10⁻³ Torr. Subsequently, it was placed in a box furnace and heat-treated at 713 K for three days, after which the quartz tube was slowly cooled to room temperature inside the furnace. The quartz tube was removed to obtain homogeneous Cr 2-x M x Secure Te3 powder ingots. Cr 2-x M x Te3 ingots are ground and Cr in powder form with a particle size of 45 μm or less 2-x M x Te3 was prepared. Cr in powder form 2-x M x Te3 powder was loaded into a tungsten mold and subjected to a hot press or spark plasma sintering process in an Ar atmosphere at 713 K and a pressure range of 70 MPa for 30 minutes, and the sintered Cr 2-x M x To measure the thermoelectric properties of Te3, cut Cr in a direction parallel to the press direction to fit the analysis equipment 2-x M x A thermoelectric material having a composition ratio of Te3 was prepared. Example 1 refers to a thermoelectric material with a composition ratio of Cr2Te3 where x=0.

[0073] <Example 2>

[0074] Cr, Te, and Ti, which are raw materials for the thermoelectric material, were weighed according to their atomic composition ratios, and Cr was manufactured using the same process as in Example 1. 1.8 Ti 0.2 A thermoelectric material having a composition ratio of Te3 was manufactured.

[0076] <Example 3>

[0077] Cr, Te, and Ge, which are raw materials for the thermoelectric material, were weighed according to their atomic composition ratios, and Cr was manufactured using the same process as in Example 1. 1.8 Ge 0.2 A thermoelectric material having a composition ratio of Te3 was manufactured.

[0079] <Comparative Example 1>

[0080] As shown in the schematic diagram of thermoelectric material fabrication in Fig. 1, the thermoelectric material raw materials Cr, Te, Ti, and Ge are weighed according to their atomic composition ratios and loaded into a quartz tube, and the pressure inside the quartz tube is reduced to 10 using a rotary vacuum pump -3 After creating a vacuum of approximately Torr, fill with argon (Ar) gas up to atmospheric pressure, then 10 -3 A vacuum of approximately Torr was created. The above process was repeated four times to purify the impurity gases inside the quartz tube with argon gas, and 10 -3 It was sealed under a vacuum at the Torr level. The quartz tube was placed in a pulsating electric furnace and melted at 1173 K for 24 hours. Afterward, the quartz tube was quenched by immersion in water, then placed in a box electric furnace for heat treatment at 713 K for 3 days, after which the quartz tube was slowly cooled to room temperature inside the box electric furnace. The quartz tube was removed to obtain homogeneous Cr 2-x M x Te3 powder ingots were secured. Cr 2-x M x Te3 ingots are ground and Cr in powder form with a particle size of 45 μm or less 2-x M x Te3 was prepared. Cr in powder form 2-x M xTe3 was loaded into a tungsten mold and subjected to a hot press or spark plasma sintering process in an Ar atmosphere for 30 minutes at a pressure range of 70 MPa and 713 K, and the sintered Cr 2-x M x To measure the thermoelectric properties of Te3, cut Cr in a direction parallel to the press direction to fit the analysis equipment 2-x M x A thermoelectric material having a composition ratio of Te3 was manufactured. Comparative Example 1 refers to a thermoelectric material with a composition ratio of Cr2Te3 where x=0.

[0082] <Experimental Example 1> Review of Process Validity

[0083] The X-ray diffraction patterns of the Cr2Te3 compositions prepared according to Example 1 and Comparative Example 1 of the present invention were analyzed. As shown in Fig. 2, in the case of Example 1, which includes powdering, compression, and heat treatment processes, it can be confirmed that all peaks have a hexagonal crystal structure and are indexed to the Cr2Te3 (PDF#29-0458) peak. In contrast, in the peaks of the Cr2Te3 composition prepared according to Comparative Example 1, which is heat-treated without powdering or compression processes, peaks corresponding to Cr-rich CrTe and Te-rich CrTe3 were detected, indicating that obtaining single-phase Cr2Te3 is not effective. The effectiveness of the process optimized in the present invention was confirmed by the fact that a large volume (20g) or more of single-phase Cr2Te3 can be produced.

[0085] <Experimental Example 2> Phase Analysis

[0086] Cr prepared in Examples 1, 2, and 3 of the present invention above 2-x M x The X-ray diffraction patterns of the Te3 (M= Ti, Ge; x=0, 0.2) composition were analyzed. As shown in Fig. 3, the Cr2Te3 composition of Example 1 and the Cr of Example 2 1.8 Ti 0.2 Te3 composition and Cr of Example 31.8 Ge 0.2 In all Te3 compositions, it can be confirmed that the major peak has a hexagonal crystal structure and is indexed to the CCr2Te3 (PDF#29-0458) peak. In the case of Example 2, it was confirmed that the lattice constant changes due to the substitution of Ti, and it can be confirmed that Ti readily substitutes for the Cr sites in Cr2Te3. In the case of Example 3, it can be confirmed that the doped Ge forms a secondary phase of Cr2Ge2Te6 and is not readily substituted within the lattice.

[0088] <Experimental Example 3> Electrical Conductivity Analysis

[0089] Cr prepared according to Examples 1, 2, and 3 of the present invention above 2-x M x The electrical conductivity of Te3 (M = Ti, Ge; x = 0, 0.2) as a function of temperature is shown in Fig. 4. As a result, as shown in Fig. 4, the comparative example and the examples generally exhibited metallic behavior in which electrical conductivity decreased as temperature increased. The Cr2Te3 composition of Example 1 showed an electrical conductivity of 2000 S / cm at room temperature, whereas both Examples 2 and 3 showed low electrical conductivity of 1000 S / cm. In the case of Example 2, the substituted Ti inhibited the formation of vacancies in the matrix phase, and Ti 3+ The electrical conductivity decreased significantly due to the reduction in charge carrier concentration caused by the provision of extra electrons. In Example 3, a secondary phase of Cr2Ge2Te6 was formed as shown in Fig. 2, which was reported to be a p-type semiconductor material with a high hole concentration. Consequently, the electrical conductivity decreased as the charge carrier concentration decreased due to the formation of the p-type semiconductor Cr2Ge2Te6 existing as a secondary phase. Additionally, in Example 3, the electrical conductivity showed a slight increase as the temperature increased, which is because a bipolar phenomenon occurred as electrons were excited by thermal energy in the semiconductor-type Cr2Ge2Te6.

[0091] <Experimental Example 4> Seebeck Coefficient Analysis

[0092] Cr prepared in Examples 1, 2, and 3 of the present invention above 2-x M x Figure 5 shows the Seebeck coefficient of Te3 (M= Ti, Ge; x=0, 0.2) as a function of temperature. The Seebeck coefficients of Examples 1, 2, and 3 are positive, indicating a p-type semiconductor in which holes play a major role in charge transport. Together with the results in Figure 3, this can be interpreted as a p-type degenerate semiconductor. Charge carrier concentration has a significant effect on the Seebeck coefficient; at room temperature, the Seebeck coefficient in Example 1 was around 3 μV / K, while the room temperature Seebeck coefficients for Examples 2 and 3 were around 9 μV / K. As the temperature increased, the Seebeck coefficient showed an increasing trend, and in the case of Example 3, the Seebeck coefficient recorded a peak value of 22 μV / K at 623 K.

[0094] <Experimental Example 5> Thermal Conductivity Analysis

[0095] Cr prepared in Examples 1, 2, and 3 of the present invention above 2-x M x Figure 6 shows the thermal conductivity of Te3 (M= Ti, Ge; x=0, 0.2) as a function of temperature. The thermal conductivity at room temperature decreased from ~1.56 W / mK in Example 1 to ~1.30 W / mK in Example 2. This decrease is mainly attributed to a decrease in electronic thermal conductivity. The decrease in electronic thermal conductivity is due to the reduction in charge carrier concentration caused by Ti doping, which lowers electrical conductivity. The thermal conductivity of Example 3 at room temperature increased to 1.90 W / mK. This is due to the high thermal conductivity of Cr2Ge2Te6, which has semiconductor properties. Although electrical conductivity decreased with increasing temperature, electronic thermal conductivity calculated by Wiedemann-Franz's law increased; accordingly, thermal conductivity in Examples 1, 2, and 3 increases with increasing temperature.

[0097] <Experimental Example 6> Analysis of Lattice Thermal Conductivity

[0098] Cr prepared in Examples 1, 2, and 3 of the present invention above 2-x M x Figure 7 shows the thermal conductivity of Te3 (M = Ti, Ge; x = 0, 0.2) as a function of temperature. The thermal conductivity of Example 1 at room temperature was recorded at ~0.56 W / mK, and at a high temperature of 673 K, it gradually decreased to ~0.31 W / mK. This indicates that the lattice thermal conductivity characteristics exhibited low bonding anisotropy due to the layered structure of Cr2Te3. The thermal conductivity of Example 2 at room temperature was recorded at ~0.85 W / mK, and at a high temperature of 673 K, it gradually increased to ~0.91 W / mK. This is because the analysis results in Figure 2 showed that Ti was inserted not only at Cr sites but also between layers, which altered the layered structure and contributed to the increase in lattice thermal conductivity. In Example 3, the thermal conductivity at room temperature was recorded at ~1.42 W / mK, and at a high temperature of 673 K, it gradually increased to ~1.61 W / mK. This is due to the bipolar phenomenon of Cr2Ge2Te6, which has semiconductor properties.

[0100] <Experimental Example 7> Performance Index Analysis

[0101] Cr prepared in Examples 1, 2, and 3 of the present invention above 2-x M x Figure 8 shows the performance index of Te3 (M= Ti, Ge; x=0, 0.2) according to temperature. The highest performance index recorded in Example 1 was 0.012 at 623 K. In Examples 2 and 3, which were doped with Ti and Ge, the performance index improved in all temperature ranges except 623 K, and the average performance index of Example 1 was 0.0043, while Example 2 was 0.0056 and Example 3 was 0.0051.

[0103] Specific embodiments of the present invention have been examined so far. Those skilled in the art will understand that the present invention may be embodied in modified forms without departing from the essential characteristics of the invention. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the claims, not by the foregoing description, and all variations within the scope of equivalents should be interpreted as being included in the present invention.

Claims

Claim 1 A Cr2Te3-based thermoelectric material characterized by being represented by the following general formula 1. [General Formula 1]Cr 2-x M x In the above general formula 1, M is Ti or Ge, and 0 < x ≤ 0.

2. Claim 2 In claim 1, the above Cr2Te3-based thermoelectric material is Cr 2-x Ti x Te3 or Cr 2-x Ge x A Cr2Te3-based thermoelectric material characterized by having a compound composition of Te3, wherein 0 < x ≤ 0.

2. Claim 3 The Cr2Te3-based thermoelectric material according to claim 1, characterized in that the lattice thermal conductivity is 0.5 W / mK or less at 500 K or higher. Claim 4 The raw materials Cr, Te, and M (M = Ti or Ge) are Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤ 0.2)의 조성비가 되도록 칭량하여 석영관에 장입하여 밀봉하는 단계;상기 원료물질인 Cr, Te 및 M(M= Ti 또는 Ge)을 용융하는 단계; 상기 용융된 원료물질을 급냉하는 단계;상기 급냉처리된 원료물질을 분말화하는 단계;상기 분말화된 원료물질을 냉간 압축하는 단계; 상기 냉간 압축처리된 원료물질을 열처리하여 Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳을 제조하는 단계; 상기 열처리된 Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳을 분쇄하여 분말을 제조하는 단계; 및상기 제조된 Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳 분말을 소결하는 단계;를 포함하고,상기 분말화된 원료물질을 냉간 압축하는 단계는, 30 MPa 내지 100 MPa의 압력범위에서 5 내지 30 분 동안 냉간 압축을 수행하는 것을 특징으로 하는 Cr2Te3계 열전재료 제조방법. Claim 5 A method for manufacturing a Cr2Te3-based thermoelectric material according to claim 4, wherein the step of melting the raw materials Cr, Te, and M (M = Ti or Ge) is performed for 10 to 72 hours at a temperature range of 850 K to 1300 K. Claim 6 A method for manufacturing a Cr2Te3-based thermoelectric material according to claim 4, wherein the step of pulverizing the raw material subjected to rapid cooling treatment is characterized by selecting one of a mortar and pestle, a planetary ball mill, and a SPEX mill to pulverize the material. Claim 7 delete Claim 8 In paragraph 4, the above cold-compressed raw material is heat-treated to Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳을 제조하는 단계는, 비활성 분위기 또는 환원성 분위기에서 수행하는 것을 특징으로 하는 Cr2Te3계 열전재료 제조방법. Claim 9 In paragraph 4, the above cold-compressed raw material is heat-treated to Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳을 제조하는 단계는, 1일 내지 5일 동안 수행하는 것을 특징으로 하는 Cr2Te3계 열전재료 제조방법. Claim 10 In paragraph 4, the above-mentioned manufactured Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳 분말을 소결하는 단계는, 600 K 내지 1100 K의 온도 범위에서 수행하는 것을 특징으로 하는 Cr2Te3계 열전재료 제조방법. Claim 11 In paragraph 4, the above-mentioned manufactured Cr 2-x M x Te3(M = Ti or Ge, 0 <x≤0.2) 잉곳 분말을 소결하는 단계는, 상압 내지 200 MPa의 압력 범위에서 5분 내지 2시간 동안 수행하는 것을 특징으로 하는 Cr2Te3계 열전재료 제조방법.

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