KR102432442B1 - Thermoelectric material powder manufacturing method using rapid solidification - Google Patents

Abstract

The thermoelectric material powder manufacturing method using the rapid solidification method according to an embodiment of the present invention contains antimony (Sb), and is 1/120 or more and 10/120 or less higher than the final content of Sb in the thermoelectric material powder to be finally manufactured. Raw material preparation step of preparing a powder raw material having an Sb content; vacuum sealing and melting the powder raw material to make a molten solution; making a solidified product by solidifying the molten solution by a rapid solidification method; A raw material powder manufacturing step of pulverizing the coagulated product and the step of sintering.

Description

Thermoelectric material powder manufacturing method using rapid solidification

The present invention relates to a method for manufacturing a thermoelectric material powder using a rapid solidification method. More particularly, it relates to a method for manufacturing a thermoelectric material powder using a rapid solidification method for preparing a powder having an accurate composition ratio by pre-compensating for loss of volatile metals occurring during the rapid solidification method.

Thermoelectric phenomenon is a phenomenon in which current or voltage is generated when different temperatures are applied to the contact points between conductors in a circuit composed of two different conductors. This phenomenon is called the Seebeck effect.

A general thermoelectric element is a basic unit of a pair of p-type and n-type thermoelectric semiconductor elements.

The thermoelectric efficiency of the thermoelectric element is known as Equation 1

Here, S is the Seebeck coefficient, σ is the electrical conductivity, S ² σ is the output factor, κ _E is the electronic thermal conductivity, κ _L is the lattice thermal conductivity, and T is the absolute temperature.

As can be seen from Equation 1, the higher the output factor, the better the thermoelectric efficiency, and the lower the lattice thermal conductivity, the better the thermoelectric efficiency. Here, the output factor is proportional to the electrical conductivity, so if the same material is used, the thermoelectric efficiency can be increased by improving the electrical conductivity.

Here, the Seebeck coefficient may be calculated according to the Pisarenko relation. The Pisarenko relation is the same as Equation (2).

Here, k _B is the Boltzmann constant, m ^* _d is the effective mass, n is the carrier concentration, q is the charge, and h is the Planck constant. As can be seen from Equation 2, as the effective mass increases, the Seebeck coefficient increases, and the thermoelectric efficiency increases.

As a thermoelectric material with low lattice thermal conductivity, there is a Skutterudite (SKD) material.

SKD compounds having the formula MX ₃ (M=Co, Rh, or Ir; X=P, As, or Sb) contain two voids in the unit cell, a heteroatom called rattler(R). The lattice thermal conductivity can be lowered through the rattling effect, which fills the voids with (transition metal) and vibrates independently of other atoms. Among SKD-based materials, CoSb ₃ has adequate bandgap energy and high carrier mobility, and is composed of eco-friendly low-cost elements, making it suitable as a thermoelectric material for medium temperature.

CoSb ₃ material has p-type and n-type like general thermoelectric devices. In the p-type semiconductor, holes in the balance band are the main carriers, and in the n-type semiconductor, electrons in the conduction band are the main carriers. Here, in the case of antimony (Sb), the outermost electron is a 5p orbital, which has a dominant influence on the balance band of p-type CoSb ₃ . In this case, when the 5p orbital of Sb acts as a balance band, since the effective mass of the carrier is very low, there is a problem in that the Seebeck coefficient is low. In other words, when used as a p-type device, there is a problem in that the performance is very low. Therefore, iron (Fe) is substituted for Co to increase the effective mass of the balance band. Through this, by using the 3d orbital of Fe, there is an effect that the effective mass is increased and the Seebeck coefficient is relatively high. In other words, a p-type material with an increased Seebeck coefficient has been proposed by improving the CoSb ₃ -based material.

On the other hand, when the SKD-based thermoelectric material is manufactured by the general melting and sintering process, the grain size is large, so that the problem of phonon scattering occurs. The scattering of phonons means that the lattice thermal conductivity is increased. Therefore, the thermoelectric efficiency is greatly reduced by Equation (1). In order to solve this problem, a method of reducing the grain size to the nano level was sought. One of the methods applied to reduce the grain size is the rapid solidification method. If the rapid solidification method is used, since the ceramic grain size is solidified before growth, it is possible to obtain a grain size at a level at which electron scattering is difficult to occur.

However, when the SKD-based thermoelectric device is manufactured using the rapid solidification method, the metal loss occurring in the solidification process is different for each component, so that the exact initial composition and the composition of the product are different. Therefore, there is a problem that an unexpected secondary phase is generated during design.

Therefore, there is a need for a manufacturing method and recipe for compensating for metal loss when manufacturing an SKD-based thermoelectric device using the rapid solidification method.

1) Republic of Korea Patent No. 10-1468991 (November 28, 2014)

The present invention provides a manufacturing method capable of maintaining a precise content ratio and a single phase in a manufacturing method for manufacturing a thermoelectric device containing Sb by utilizing a rapid solidification method.

As a technical means for achieving the above-described technical problem, the thermoelectric material powder manufacturing method using the rapid solidification method according to an embodiment of the present invention contains antimony (Sb), and the Sb of the thermoelectric material powder to be finally manufactured is Raw material preparation step of preparing a powder raw material having an Sb content higher than 1/120 or more and 10/120 or less than the final content A step of vacuum sealing and melting the powder raw material to make an ingot to make a coagulated product and a raw material powder manufacturing step of pulverizing the coagulated product, and sintering.

The powder raw material may further include neodymium (Nd), iron (Fe) and cobalt (Co).

The powder raw material may have a ratio of Nd:Fe:Co of 0.9:3.5:0.5, and a ratio of Sb of 4.9:12.1 or more and 13 or less with respect to all of them.

The step of vacuum sealing and melting the powder raw material to make an ingot may include putting the powder raw material into a refractory-coated crucible and sealing the powder raw material while maintaining a vacuum degree of 10 ^-2 Torr or less.

The refractory material may be carbon.

The crucible may be a quartz tube.

The step of vacuum sealing and melting the powder raw material to make an ingot may include heating a crucible containing the powder raw material in a high frequency induction melting furnace.

The high-frequency induction melting furnace can heat the crucible at a frequency of 6kw or more and 8kw or less, 30kHz or more and 50kHz or less.

In the step of vacuum-sealing and melting the powder raw material to make an ingot, the powder raw material may be vacuum sealed and melted by heating for 70 minutes or more.

The step of vacuum sealing and melting the powder raw material to make an ingot may further include air-cooling the powder raw material for a period of 10 minutes or more and 30 minutes or less after the powder raw material is melted.

The step of re-melting the ingot and solidifying it by a rapid solidification method to form a solidified product may be any one of a melt spinning method, a gas atomization method, a plasma deposition method, a centrifugal spraying method, and a splat quenching method.

The step of re-melting the ingot and solidifying it by a rapid solidification method to make a solidified product may include spraying the re-melted melt on the side of the rotating disk.

The rotating disk may rotate at a speed of 500 or more and 4000 rpm or less.

The spraying of the re-melted melt may be performed in an argon atmosphere.

The spraying of the re-melted melt may be performed at a pressure of 0.5 bar or less.

The rotating disk may be made of copper.

The rotating disk may have a diameter of 30 cm or more.

In the spraying of the re-melted melt, the re-melted melt may be sprayed using a nozzle.

The sintering may be performed by a discharge plasma sintering method.

The sintering step may be sintered at a pressure of less than 0.5 bar at a temperature of 900 K or more and a pressure of 45 MPa or more for 10 minutes or more.

According to an embodiment of the present invention, even when the rapid solidification method is used, the ratio of Sb included in the finished product can be controlled to match the target ratio by adding an amount higher than the product ratio of highly volatile Sb.

According to an embodiment of the present invention, it is possible to minimize the addition of foreign substances in the manufacturing process.

1 is a flowchart illustrating a method of manufacturing a thermoelectric material powder according to an embodiment of the present invention.
2 is a cross-sectional view for explaining the vacuum sealing and melting step of the raw material in the actual manufacturing example of the manufacturing method of the thermoelectric material powder according to an embodiment of the present invention.
3 and 4 are perspective views and photographs for explaining a rapid solidification method in an actual manufacturing example of a method for manufacturing a thermoelectric material powder according to an embodiment of the present invention.
5 is an overall XRD and photograph of samples prepared according to a method for manufacturing a thermoelectric material powder according to an embodiment of the present invention.
6 (a) is an XRD graph of 31° to 36° for secondary phase analysis of samples prepared according to the method of manufacturing a thermoelectric material powder according to an embodiment of the present invention, and (b) is an embodiment of the present invention It is an XRD graph of 38° to 41° for secondary phase analysis of samples prepared according to the method for preparing thermoelectric material powder according to
7 is a graph of quantitative analysis of Sb in which the quantity of a ribbon sample is analyzed after rapid solidification in samples prepared according to the method for manufacturing a thermoelectric material powder according to an embodiment of the present invention.
8 is a SEM photograph showing the cross-sectional microstructure according to the rapid solidification method of samples prepared according to the method for producing a thermoelectric material powder according to an embodiment of the present invention.
Figure 9 (a) is a graph showing the electrical conductivity of each temperature of the samples prepared according to the manufacturing method of the thermoelectric material powder according to an embodiment of the present invention, (b) is a graph showing the Seebeck coefficient for each temperature, (c) ) is a graph showing the output factors for each temperature.
10 (a) is a graph showing the thermal conductivity of samples prepared according to the manufacturing method of the thermoelectric material powder according to an embodiment of the present invention for each temperature, (b) is a graph showing the value of ZT for each temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

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

1, the thermoelectric material powder manufacturing method using the rapid solidification method according to an embodiment of the present invention contains antimony (Sb), and 1/120 or more than the final content of Sb in the final manufactured thermoelectric material powder Raw material preparation step (S110) of preparing a powder raw material having a high Sb content of 10/120 or less, vacuum sealing and melting the powder raw material to make an ingot (S120), re-melting the ingot and solidifying it by rapid solidification It includes a step of making water (S130), a step of preparing a raw powder for pulverizing the coagulated product (S140), and a step of sintering (S150).

The biggest feature of the present invention is that it increases the scattering of phonons by adjusting the grain size to a nanometer size by the rapid solidification method, and that a secondary phase is not generated by compensating for the disappearance deviation by element occurring during the rapid solidification method is in

In the step of preparing the raw material (S110), a powder raw material suitable for the combination ratio of the thermoelectric material is prepared. The powder raw material may be a Skutterudite (hereinafter, SKD)-based thermoelectric material. Accordingly, the powder raw material may include Sb and may include cobalt (Co). On the other hand, in order to make a SKD-based thermoelectric element in which a part of Co is substituted with iron (Fe), a part of Co can be substituted with Fe, and Nd is further included when making an SKD-based thermoelectric element in which R is neodymium (Nd). can do.

Nd, Fe, and Co are hardly lost even when the rapid solidification method is applied. Therefore, Nd, Fe, and Co may be prepared in a ratio of 0.9:3.5:0.5 similar to that of the conventional SKD-based thermoelectric material.

In the SKD-based thermoelectric material, when the sum of the atomic ratios of Fe and Co is 4, the theoretical content ratio of Sb is 12. When the rapid solidification method is applied, a large amount of Sb evaporates and disappears. Therefore, in order to compensate for this, Sb may be prepared at a content ratio greater than 12. Specifically, it may be prepared as much as a content ratio of 12.1 or more and 13 or less to which a content of 1/120 or more and 10/120 or less is added.

In the vacuum sealing and melting step ( S120 ), the powder raw material is vacuum sealed, and the powder raw material is heated and melted.

The powder raw material is put in a crucible coated with a refractory material, and it can be sealed while maintaining a vacuum degree of 10 ^-2 Torr or less. Since the powder raw material may react with the crucible during the heating process, it is preferable to put it in a crucible coated with a refractory material. The crucible may be made of a material having high thermal conductivity and high durability and fire resistance, and may be, for example, a quartz tube. In addition, the refractory material for coating the crucible may be carbon.

Since the powder raw material may be oxidized, it is preferable to melt in a reducing atmosphere. Therefore, it is preferable to be sealed at a high degree of vacuum.

In the crucible, the powder raw material is heated and melted. Specifically, the powder raw material may be heated in a high frequency induction melting furnace. Since the heating means is physically separated from the powder raw material, the high frequency induction melting furnace is particularly suitable for melting powder raw materials because the possibility of mixing with foreign substances is low.

High frequency induction melting furnace can melt powder raw materials with power of 6kw or more and 8kw or less. The lower limit of the electric power applied to the high frequency induction furnace may vary depending on the insulation performance of the high frequency induction furnace. In the case of using a melting furnace as a general thermal insulation means, it is preferable to apply heat of 6 kw or more, and when heat of 8 kw or more is applied, there is a problem in that the thermal efficiency is lowered.

High frequency induction melting furnace may use a frequency of more than medium frequency, specifically, a frequency of 30 kHz or more and 50 kHz or less may be used. In the high-frequency induction melting technology, the application frequency changes depending on whether the material to which induction electricity is applied is a metal or a non-metal. However, high frequency or radio frequency (10 kHz to 500 kHz) may be used as heating for a general non-metallic crucible.

The heating time may vary depending on the applied power and frequency, and the material of the crucible. For example, it may be heated for a time period of 70 minutes or more until all powder raw materials are melted.

After the melting is completed, the melt in which the raw material is melted may be air-cooled for a period of 10 minutes or more and 30 minutes or less. As the melting proceeds, air or the like between the powder raw materials is included in the melt. Since the melt has a high viscosity, there are cases in which air or the like cannot escape during melting. Therefore, it is possible to air-cool the melt for a certain period of time to discharge air or the like inside the melt to the surface. When the melt solidifies through air cooling, the ingot is completed.

The ingot is re-melted and a solidified product is prepared by a rapid solidification method (S130).

Although it is preferable to solidify directly by the rapid solidification method in an induction melting furnace having a quartz tube, in reality, the equipment for applying the induction melting furnace and the rapid solidification method is different in many cases. Therefore, the ingot manufactured in the induction melting furnace is put into a carbon crucible within the rapid solidification defense that can use the rapid heating method and melted by the induction melting method to make a melt. It is then solidified by a rapid solidification method.

The rapid solidification method is a method of solidifying a molten material by rapidly cooling it. When solidification occurs quickly, the size of microstructures such as grains becomes smaller. When it solidifies rapidly, each atom does not have enough time to move to crystallize.

When the grain size is large, phonons are scattered on the grain surface when they pass through the grain. In other words, when the thermoelectric material powder is manufactured using the rapid solidification method, phonon scattering is increased, thereby reducing lattice thermal conductivity, and thus the Seebeck coefficient is improved.

Any method may be used for the rapid solidification method. In other words, any one of a typical rapid solidification method such as a melt spinning method, a gas atomization method, a plasma deposition method, a centrifugal spray method, and a splat quenching method may be used.

The double melt spinning method is particularly advantageous because it can solidify a large amount of melt at a high speed.

The melt spinning method may be a method of spraying a melt with a nozzle on the side of the disk rotating at high speed. The disk is 50 cm or more, and it is preferable to rotate at a speed of 500 or more and 4000 rpm or less. The disk may be made of a material such as copper having high thermal conductivity.

The melt spinning method is a method of instantaneous solidification by spraying a molten solution on a cold object. At this time, when a large amount of molten liquid is sprayed on a cold object, the temperature of the cold object increases, so that a problem of lowering of the melting efficiency may occur. In this case, the degree of cooling can be uniformed by rotating the cold object.

Therefore, in the melt spinning method, the rotational speed and radius of a rotating object are closely related to the jetting speed. This is because the higher the rotation speed and the larger the radius, the greater the heat capacity for cooling the molten liquid sprayed at a specific moment. With respect to a speed of 1 mL/min or less, which is a general injection speed, a disk having a diameter of 30 cm or more and a speed of 500 or more and 4000 rpm or less is preferable. It is preferable to use a nozzle because only a very small amount must be continuously sprayed.

The melt spinning method is preferably performed in a reducing atmosphere. Specifically, it may be carried out in an argon atmosphere. In addition, it may be carried out at a pressure of 0.5 bar or less in order to reduce the phenomenon that the spray liquid is scattered in all directions.

Since the melt is sprayed into the air, the raw material may be oxidized during solidification. To prevent this, a reducing atmosphere is suitable for air, and it is preferable to perform in an environment close to vacuum in order to reduce air resistance even when a small amount of melt is strongly sprayed.

The solidified material solidified on the surface of the rotating object by the melt spinning method is collected and pulverized to prepare a raw material powder (S140). The grinding method may be any method. Since the solidified material is in the form of a ribbon with thin films overlapping, it can be crushed with relatively little force. Accordingly, as the grinding method, various methods such as ball milling, attribution milling, high energy milling, and jet milling may be used.

Thereafter, the pulverized solid is sintered (S150). The method of sintering is not particularly limited, but a method in which recrystallization does not occur during the sintering process is preferable. Specifically, it may be at least one of spark plasma sintering and hot press sintering.

Spark plasma sintering, in which the powder is sintered by generating spark plasma, is sintered by heating in a short time, so it is possible to minimize the time for particles to move and recrystallize. Spark plasma sintering may be performed at a temperature of 300°C or higher and 800°C or lower.

Hot press sintering is a method of increasing the sintering speed by applying pressure to the powder to reduce the movement distance of particles on the contact surface. Hot press sintering can be combined with various heating methods. For example, spark plasma sintering and hot press sintering may be used together.

Hot press sintering can be performed at a low pressure of 1 Pa or more and 100 Pa or less. A vacuum of 1 Pa or less is difficult to maintain and sublimation may occur. Oxidation is highly likely to occur at pressures above 100Pa. The hot press sintering may be performed for a time of 5 minutes or more and 60 minutes or less, but the time may be flexibly determined according to the temperature of the spark plasma sintering and the pressure applied to the hot press sintering.

The thermoelectric material powder according to an embodiment of the present invention can be obtained by the above-described method. The inventors of the present invention prepared the thermoelectric material powder according to the thermoelectric material powder manufacturing method according to the embodiment of the present invention, The physical properties of the thermoelectric material powder were measured.

Hereinafter, actual manufacturing examples according to the method for manufacturing the thermoelectric material powder according to an embodiment of the present invention and measured values of physical properties of the thermoelectric material powder samples prepared according to the method will be described with reference to FIGS. 2 to 10 .

2 is a cross-sectional view for explaining the vacuum sealing of the raw material and the ingot manufacturing step in the actual manufacturing example of the method for manufacturing the thermoelectric material powder according to an embodiment of the present invention.

<Production Example>

First, a powder raw material was prepared. In one embodiment of the present invention, as a starting material of Nd _0.9 Fe _3.5 Co _0.5 Sb ₁₂ Nd (Alfa Aesar, 99.1%), Fe (Alfa Aesr, 99.9%), Co (Alfa Aesar, 99.95%), Sb (High Purity Chemical, 99.999%) was used.

The present invention is characterized in that the composition of the finished product is precisely controlled by compensating in advance the content of Sb lost in the manufacturing process. The inventors of the present invention prepared the thermoelectric material powder samples shown in [Table 1] according to the Sb content in order to confirm the generation of the secondary phase and the thermoelectric effect characteristics for each compensation content of Sb.

sample No. Relative content ratio of Nd:Fe:Co Sb content ratio A 0.9:3.5:0.5 12.0 B 12.2 C 12.4 D 12.6 E 13

Thereafter, the powder raw material was put into the quartz tube 210 coated with carbon 220 . The quartz tube 210 was placed in the chamber 230, and the chamber 230 was sealed while maintaining a vacuum degree of about 10 ^-3 Torr or less. A high-frequency induction melting furnace 240 was provided around the chamber 230 to heat the inner quartz tube 210 .

The sealed quartz tube 210 was induction-melted using a high-frequency induction melting furnace 240 at a power and frequency of 7kW/40kHz for about 90 minutes, and then melted and air-cooled to minimize shrinkage and pores to prepare an ingot.

3 and 4 are perspective views and photographs for explaining a rapid solidification method in an actual manufacturing example of a method for manufacturing a thermoelectric material powder according to an embodiment of the present invention.

In these examples, a ribbon-shaped sample was prepared by using a melt spinning method as a rapid solidification method. After the powder raw material is melted in the chamber, the solidified ingot is transferred to a carbon crucible and melted by induction melting. The molten solution 310 produced in this way was ejected on the side of the rotating disk 340 made of copper using a carbon crucible as a syringe 320 and a hole provided at the bottom of the carbon crucible as a nozzle 330 . The inside of the chamber 230 was an argon atmosphere, and the chamber 230 pressure was maintained at 0.4 bar. The rotational speed of the rotating disk 340 made of copper was maintained at 500 to 4000 rpm.

The prepared ribbon was made into powder by grinding using a mortar and rod. Then, the prepared powder was sintered using a discharge plasma sintering equipment. Specifically, pellets were prepared by sintering by applying a pressure of 50 MPa for 10 minutes at a temperature of 963 K in a vacuum atmosphere.

5 is an overall XRD and photographic graph of samples prepared according to a method of manufacturing a thermoelectric material powder according to an embodiment of the present invention.

In FIG. 5, a value of x means an additional Sb content of each sample. That is, it means a content ratio that is added more than the final content of Sb. The alphabet next to the x value means the sample number in [Table 1].

In sample B where x=0.2, it can be seen that the 34.7° peak seen in sample A disappears. For a more detailed description of this, refer to FIG. 6 .

6 (a) is an XRD graph of 31° to 36° for secondary phase analysis of samples prepared according to the method of manufacturing a thermoelectric material powder according to an embodiment of the present invention, and (b) is an embodiment of the present invention It is an XRD graph of 38° to 41° for secondary phase analysis of samples prepared according to the method for preparing the thermoelectric material powder according to

Referring to (a) of FIG. 6 , it can be confirmed that FeSb ₂ was formed at 31.9°, 33.6°, and 34.7° of sample A with x=0. In Sample A, the FeSb ₂ phase is a secondary phase generated because the SKD phase cannot be formed due to the lack of Sb. In this way, when Fe is lost in the secondary phase and becomes insufficient in the SKD phase, the conduction characteristics are reduced and the thermoelectric effect may be deteriorated.

In the case of samples B to F in which x=0.2 exceeds Sb, a secondary phase is not generated because Sb is sufficiently supplied.

Referring to (b) of FIG. 6 , the peak of unreacted Sb in samples C to F exceeding x=0.4 was found at 41°. Through this, it can be seen that an independent phase of Sb was generated in samples C to F. In the SKD-based thermoelectric element, the independent phase of Sb does not significantly affect the thermoelectric efficiency, but rather serves to improve electrical conductivity. Accordingly, there is an effect of increasing the Seebeck effect.

7 is a graph of quantitative analysis of Sb obtained by analyzing the quantity of ribbon samples after rapid solidification in samples prepared according to the method for preparing thermoelectric material powder according to an embodiment of the present invention.

The nominal composition of the Sb content on the graph has a lower value than the actual composition, because of the amount lost during the rapid solidification process. It can be seen that when X=0.2, that is, when Sb is contained in a ratio of 12.2, the actual content is close to 12, which is a ratio in the crystal structure.

8 is a SEM photograph showing the cross-sectional microstructure according to the rapid solidification method of samples prepared according to the method for manufacturing the thermoelectric material powder according to an embodiment of the present invention.

The present invention suppresses the current scattering effect of the grain by controlling the grain size of the thermoelectric material powder to the nano level using the rapid solidification method. As shown in the SEM photograph, samples A to E were all prepared using the rapid solidification method, so that the grains on the surface were controlled to have a uniform size of 1 μm or less.

Figure 9 (a) is a graph showing the electrical conductivity of each temperature of the samples prepared according to the manufacturing method of the thermoelectric material powder according to an embodiment of the present invention, (b) is a graph showing the Seebeck coefficient for each temperature, (c) ) is a graph showing the output factors for each temperature.

Referring to (a) of FIG. 9 , it can be confirmed that the electrical conductivity is improved as the content of Sb increases in the temperature range from 300K to 500K. In particular, in the case of samples C, D, and E, it can be seen that the electrical conductivity is improved in all temperature ranges.

Referring to FIG. 9B , it can be seen that the Seebeck coefficient of samples B to E is improved compared to that of sample A, although there is no trend in the change of the Seebeck coefficient.

Referring to (c) of FIG. 9 , it can be seen that the output factor also has the same graph form as the Seebeck coefficient, and the sample D with x=0.6 has the maximum value.

10 (a) is a graph showing the thermal conductivity of samples prepared according to the manufacturing method of the thermoelectric material powder according to an embodiment of the present invention for each temperature, (b) is a graph showing the value of ZT for each temperature.

Referring to (a) of FIG. 10 , the thermal conductivity of Sample B has a minimum value in all temperature regions.

Referring to (b) of FIG. 10 , in the graph of sample B where x=0.2, ZT has a maximum value of 0.91 when 768K. This is because, as described above, the Seebeck coefficient has a higher value as the thermal conductivity is lower.

Since the sample A with x=0 has the lowest ZT over the entire temperature range, there is an effect that the ZT is increased in the section where x is greater than 0 and x=1 or less. ZT has a maximum value at x=0.2, but the effect of increasing ZT occurs even at x=0.1 or higher. Therefore, in the present specification, the range in which the effect of the invention occurs is limited to 1/120 or more and 10/120 or less of the theoretical content ratio of Sb in the claims.

According to an embodiment of the present invention, in the process of manufacturing a thermoelectric element containing Sb through a process of solidifying it by a rapid solidification method, by increasing the content of Sb in the powder raw material than the content of the final Sb, the material of the thermoelectric element It is possible to precisely control the final content ratio of each star.

According to an embodiment of the present invention, in the process of manufacturing a thermoelectric element containing Sb through a process of solidifying by a rapid solidification method, by increasing the content of Sb of the powder raw material than the content of the final Sb, the electricity of the thermoelectric element Conductivity can be improved.

According to an embodiment of the present invention, in the process of manufacturing a thermoelectric element containing Sb through a process of solidifying by a rapid solidification method, the content of Sb of the powder raw material is increased than the content of the final Sb, thereby reducing thermal conductivity and increase the Seebeck coefficient.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and likewise components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be interpreted as being included in the scope of the present invention. do.

210: quartz tube 220: carbon coating
230: chamber 240: high frequency induction melting furnace
310: melt 320: syringe
330: nozzle 340: rotating disk

Claims (20)

It contains antimony (Sb), neodymium (Nd), iron (Fe) and cobalt (Co), and considering the total content of the iron (Fe) and the cobalt (Co) raw materials, the final manufactured thermoelectric material powder a raw material preparation step of preparing a powder raw material having an Sb content as high as 1/120 or more and 10/120 or less than the final content of Sb;
vacuum sealing and melting the powder raw material to make an ingot;
re-melting the ingot and solidifying it by a rapid solidification method to make a solidified product;
A raw material powder manufacturing step of pulverizing the coagulated product, and
sintering;
The powder raw material is characterized in that the ratio of Nd:Fe:Co is 0.9: 3.5: 0.5, and the ratio of Sb is 4.9:12.1 or more and 13 for all of them,
Thermoelectric material powder manufacturing method using rapid solidification method. delete delete According to claim 1,
The step of vacuum sealing and melting the powder raw material to make an ingot,
Thermoelectric material powder manufacturing method using rapid solidification method, characterized in that it comprises the step of putting the raw material powder into a crucible coated with a refractory material and sealing the vacuum degree of 10 ^-2 Torr or less. 5. The method of claim 4,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the refractory material is carbon. 5. The method of claim 4,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the crucible is a quartz tube. According to claim 1,
The step of vacuum sealing and melting the powder raw material to make an ingot,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that it comprises the step of heating the crucible containing the powder raw material in a high-frequency induction melting furnace. 8. The method of claim 7,
The high-frequency induction melting furnace is a thermoelectric material powder manufacturing method utilizing a rapid solidification method, characterized in that the crucible is heated at a frequency of 6kw or more and 8kw or less, 30kHz or more and 50kHz or less. 8. The method of claim 7,
The step of vacuum sealing and melting the powder raw material to make an ingot,
A thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that the powder raw material is vacuum sealed and melted by heating for 70 minutes or more. According to claim 1,
The step of vacuum sealing and melting the powder raw material to make an ingot,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that it further comprises the step of air-cooling the powder raw material is melted and the melted raw powder raw material for a time period of 10 minutes or more and 30 minutes or less. According to claim 1,
The step of re-melting the ingot and solidifying it by a rapid solidification method to make a solidified product,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the rapid solidification method is any one of a melt spinning method, a gas atomization method, a plasma deposition method, a centrifugal spray method, and a splat quenching method. 12. The method of claim 11,
The step of re-melting the ingot and solidifying it by a rapid solidification method to make a solidified product,
Thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that it comprises the step of spraying the re-melted melt on the side of the rotating disk. 13. The method of claim 12,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the rotating disk rotates at a speed of 500 or more and 4000 rpm or less. 13. The method of claim 12,
The step of spraying the re-melted melt is a thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that it is performed in an argon atmosphere. 13. The method of claim 12,
The step of spraying the re-melted melt is a thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that performed at a pressure of 0.5 bar or less. 13. The method of claim 12,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the rotating disk is made of copper. 13. The method of claim 12,
Thermoelectric material powder manufacturing method using the rapid solidification method, characterized in that the rotating disk has a diameter of 30 cm or more. 13. The method of claim 12,
The step of spraying the re-melted melt is
Thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that the re-melted melt is sprayed using a nozzle. According to claim 1,
The sintering step
A thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that sintering is performed by a discharge plasma sintering method. 20. The method of claim 19,
The sintering step
Thermoelectric material powder manufacturing method using a rapid solidification method, characterized in that it comprises the step of sintering at a temperature of 900K or more at an atmospheric pressure of 0.5 bar or less and a pressure of 45 MPa or more for 10 minutes or more.

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