JP4166927B2 - Thermoelectric material manufacturing method, thermoelectric material, and thermoelectric material manufacturing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoelectric material manufacturing method, a thermoelectric material, and a thermoelectric material manufacturing apparatus, and in particular, a thermoelectric material manufacturing method for manufacturing a thermoelectric material including a scattering center that scatters phonons and a base material, Bi, A base material containing at least two elements selected from Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Te, Fe, Mn, Co, and Si, a scattering center that scatters phonons, The present invention relates to a thermoelectric material manufacturing apparatus that manufactures a thermoelectric material that includes a thermoelectric material that is a composite material made of a material, a scattering center that scatters phonons, and a base material.
[0002]
[Prior art]
Conventionally, in this type of thermoelectric material, a figure of merit Z representing the performance of the thermoelectric material is defined as follows.
[0003]
[Expression 1]
Z = σ * α ² / κ
In this equation, σ is electrical conductivity, α is the Seebeck coefficient, and κ is thermal conductivity. The thermal conductivity κ is given by the sum of the one caused by vibrations of the nuclei themselves constituting the substance (phonon thermal conductivity) and the one caused by the movement of carriers (electrons or holes) (carrier thermal conductivity).
[0004]
In order to obtain a thermoelectric material having a large figure of merit Z, various manufacturing methods have been proposed. In particular, as a method for reducing the thermal conductivity κ, a thermoelectric material including a scattering center that scatters phonons has been proposed. As a method for producing such a thermoelectric material, there has been proposed a method in which a powder of a scattering center is mixed with a mechanically pulverized and powdered base material and then sintered (for example, JP-A-9-74229). Such).
[0005]
[Problems to be solved by the invention]
However, when the powder obtained by mechanically pulverizing the thermoelectric material is sintered, the average crystal grain size is increased, the scattering center is unevenly distributed, the phonon mean free path is increased, and the phonon thermal conductivity is increased. As a result, the thermal conductivity κ increases. Moreover, it is difficult to obtain a high-performance thermoelectric material due to impurities being mixed during pulverization. There is also a problem that the number of manufacturing steps increases.
[0006]
One object of the method for producing a thermoelectric material of the present invention is to produce a thermoelectric material having a high figure of merit. Another object of the thermoelectric material of the present invention is to have a high figure of merit. Another object of the thermoelectric material manufacturing apparatus of the present invention is to be an apparatus capable of manufacturing a material having a high performance index.
[0007]
[Means for Solving the Problems]
The method for producing a thermoelectric material of the present invention is a method for producing a thermoelectric material comprising a scattering center that scatters phonons and a base material, wherein the mixture melt of the scattering center and the base material And a rocking cooling step of cooling the mixture while being swung in a container.
[0008]
In the method for producing a thermoelectric material of the present invention, the mixture melt of the scattering center substance and the base material that scatters phonons is oscillated and cooled, so that the scattering center substance is uniformly dispersed in the mixture. Therefore, in the manufactured thermoelectric material, the mean free path of phonons is reduced, and the phonon thermal conductivity is reduced. On the other hand, the produced thermoelectric material solidifies in the absence of a stable liquid surface, so that crystal growth is suppressed, the average crystal grain size is reduced, phonon thermal conductivity is further reduced, and thus thermal conductivity κ is reduced. . Further, the gap between crystal grains is reduced, and the electrical conductivity σ is kept high. As a result, a thermoelectric material with a high figure of merit can be manufactured. Note that the scattering center may not be decomposed by the base material and may not react with the molten base material.
[0009]
In the manufacturing method of the thermoelectric material of the present invention, the scattering center is selected from any one of B, C, Si, and P, or B, C, Si, N, Zr, Ti, O, Mo, and W. It is also possible to provide a powder particle of a compound containing at least two kinds of elements, and an addition step of adding the powder particle to the base material and a melting step of melting the base material. Compared to the method in which the base material is melted and cooled after the scattering center is added to the base material, and the base material is pulverized into powder and then mixed with the scattering center, the scattering center is uniform in the thermoelectric material. It is possible to produce a thermoelectric material that is dispersed in the substrate and contains less impurities.
[0010]
In the method for producing a thermoelectric material of the present invention, the scattering center is a bubble of an inert gas or a reducing gas, and melts the base material and introduces the bubbles into the melted base material. , Can also be provided. Compared with the method in which the scattering material is introduced when the matrix is melted, and then the matrix is cooled, the thermoelectric material is less mixed with impurities compared to the method in which the matrix is pulverized into powder and then mixed with the scattering material. Can be manufactured.
[0011]
In the method for producing a thermoelectric material of the present invention, the swing cooling step may be a step of swinging the mixture and cooling the mixture in a state where a temperature gradient is provided in the mixture. By providing a temperature gradient when the mixture cools, it is possible to give direction to the crystallization of the mixture, and the crystallization can be promoted uniformly regardless of the ambient temperature and the surface state of the mixture.
[0012]
In this method for producing a thermoelectric material of the present invention, the container is provided with a stirrer inside, and the swing cooling step swings the mixture by stirring the mixture with the stirrer and the mixture. It can also be a process of cooling. The scattering center is more uniformly dispersed in the thermoelectric material by the stirring bar inside the container. In addition, the amount of rocking of the molten mixture increases, and a more stable liquid level is less likely to occur.
[0013]
In the method for producing a thermoelectric material of the present invention, the swing cooling step may be a step of swinging the mixture by rotating and cooling the mixture. By rotating the container, the scattering center can be dispersed in the thermoelectric material, and can be easily swung while the mixture is sealed in the container.
[0014]
In the manufacturing method of the thermoelectric material according to the present invention, the swing cooling step rotates the container at a rotational speed of 5 to 3000 rotations / minute, changes the rotation direction of the container, rotates and stops the container. And the mixture can be swung and the mixture can be cooled. By changing the rotation state of the container in this way, the scattering center is more uniformly dispersed in the thermoelectric material. Further, it becomes difficult to form a stable liquid surface when the thermoelectric material is solidified, and a thermoelectric material having a smaller average crystal grain size can be produced.
[0015]
In the manufacturing method of the thermoelectric material of the present invention, the swing cooling step swings the mixture and cools the mixture by tilting the rotation axis of the container with respect to the direction of gravity and rotating the container. It can also be a process. By tilting the rotation axis of the container with respect to the direction of gravity, the amount of rocking of the molten mixture in the container becomes larger and the scattering center is more uniform than when the rotation axis of the container is in the direction of gravity. Disperse in thermoelectric material. Moreover, it becomes difficult to produce a stable liquid level in the molten mixture.
[0016]
In the thermoelectric material manufacturing method of the present invention, the swing cooling step swings the mixture and cools the mixture by rotating the container with the rotation axis of the container perpendicular to the direction of gravity. It can also be set as the process to do. By making the rotation axis of the container perpendicular to the direction of gravity, the amount of rocking of the molten mixture in the container becomes larger, and the scattering center is more uniformly dispersed in the thermoelectric material. Moreover, it becomes difficult to produce a stable liquid level in the molten mixture.
[0017]
The thermoelectric material of the present invention includes a base material containing at least two elements selected from Bi, Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Te, Fe, Mn, Co, and Si, A scattering center material that scatters phonons, wherein the mixture has an average crystal grain size of 2 μm to 20 μm, a filling rate of 95 to 100%, and the scattering center material. Is uniformly dispersed in the base material.
[0018]
In the thermoelectric material of the present invention, the average crystal grain size of the base material is small compared with the thermoelectric material produced by pulverization and sintering into a bulk shape, and is considered to be about 2 μm to 20 μm. For this reason, phonon scattering at the crystal grain boundary increases and phonon thermal conductivity is reduced. Further, the scattering center is taken into the crystal grains of the base material and uniformly dispersed throughout the thermoelectric material. As a result, phonon scattering is further increased, phonon thermal conductivity is further reduced, and consequently thermal conductivity κ is reduced. Moreover, the filling rate of the manufactured thermoelectric material is about 95 to 100%, which is close to about 100% as in the case of the melted material, and the electrical conductivity σ is kept high. As a result, the thermoelectric material has a high figure of merit.
[0019]
In the thermoelectric material of the present invention, the base material may be made of a thermoelectric semiconductor melting material.
[0020]
In the thermoelectric material of this reference form of the present invention, the scattering center is selected from any one of B, C, Si, and P, or B, C, Si, N, Zr, Ti, O, Mo, and W. It can also consist of a compound containing at least two or more elements, or it can consist of bubbles of inert gas or reducing gas.
[0021]
The thermoelectric material manufacturing apparatus of the present invention is a thermoelectric material manufacturing apparatus that manufactures a thermoelectric material including a scattering center object that scatters phonons and a base material, and encloses a mixture melt of the scattering center object and the base material. And a swing cooling means for swinging the container to swing the mixture and cooling the mixture.
[0022]
In the thermoelectric material manufacturing apparatus of the present invention, since the mixture melt containing the scattering center and the base material is swung and cooled, the scattering center is uniformly dispersed in the thermoelectric material. Since the scattering center scatters phonons, the mean free path of phonons is reduced and the phonon thermal conductivity is reduced. In addition, since the mixture solidifies without a stable liquid surface, crystal growth is suppressed, and the average crystal grain size becomes small. Therefore, phonon scattering at the crystal grain boundary increases, and the phonon thermal conductivity is further reduced, and consequently the thermal conductivity κ is reduced. Further, since the gap between the crystal grains becomes small, the electrical conductivity σ is kept high. As a result, a thermoelectric material with a high figure of merit can be manufactured.
[0023]
In the thermoelectric material manufacturing apparatus of the present invention, the scattering center is a bubble of an inert gas or a reducing gas, and includes gas introduction means for introducing the gas into the molten base material. You can also. Introducing a scattering center when the base material melts, and then cooling the mixture of the scattering center and the base material, so that the base material is pulverized into powder and then mixed with the scattering center, The amount of impurities mixed in the thermoelectric material is reduced.
[0024]
The thermoelectric material manufacturing apparatus according to the present invention may include a temperature gradient setting unit that sets a temperature gradient in the mixture in the container. Since a temperature gradient can be set in the mixture, directionality can be given to the crystallization of the mixture, and crystallization can be promoted uniformly regardless of the ambient temperature and the surface state of the mixture.
[0025]
In the thermoelectric material manufacturing apparatus of the present invention, a stirrer for stirring the mixture may be provided inside the container. The amount of rocking of the melted mixture can be increased by the stirring bar inside the container, and the scattering center can be uniformly dispersed in the thermoelectric material, and a more stable liquid surface can be less likely to occur.
[0026]
In the thermoelectric material manufacturing apparatus of the present invention, the swing cooling means may be means for rotating the container to swing the mixture and to cool the mixture. By rotating the container, the mixture can be easily swung while the mixture is sealed in the container.
[0027]
In the thermoelectric material manufacturing apparatus of the present invention, the oscillating cooling means may include a rotation state control means for controlling the rotation state of the container. By controlling the rotation state of the container, it is possible to produce a thermoelectric material having a smaller average crystal grain size by making the container into a rotation state in which a stable liquid surface is difficult to form when the mixture is solidified. The control of the rotation state includes control such as changing the rotation speed of the container, changing the rotation direction of the container, rotating the container, and stopping the container.
[0028]
In the thermoelectric material manufacturing apparatus of the present invention, the swing cooling means may include a rotation axis tilting means for tilting the rotation axis of the container with respect to the direction of gravity. By tilting the rotation axis of the container with respect to the direction of gravity, the scattering center is uniformly dispersed in the thermoelectric material as compared with the case where the rotation axis of the container is in the direction of gravity, and the molten mixture in the container The amount of rocking is increased and a stable liquid level is less likely to occur.
[0029]
In the thermoelectric material manufacturing apparatus of the present invention, the swing cooling means may be means for rotating the container on a rotation axis perpendicular to the direction of gravity. By making the rotation axis of the container perpendicular to the direction of gravity, the amount of rocking of the molten mixture in the container becomes larger, the scattering center is uniformly dispersed in the thermoelectric material, and a stable liquid surface is generated. It becomes difficult.
[0030]
In the thermoelectric material manufacturing apparatus of the present invention, the swing cooling means may be a magnetic stirrer.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.
[0032]
FIG. 1 is a schematic view showing a configuration of a thermoelectric material manufacturing apparatus 100 of the present embodiment. The thermoelectric material manufacturing apparatus 100 includes an iron sample tube 14 in which a glass container 12 enclosing a BiTe mixture melt 10 is housed, a furnace tube 16 in which the sample tube 14 is housed, and a sample tube 14 in the furnace. A rod-shaped sample tube holder 18 fixed at the center of the tube 16, a gas inlet 20 for introducing an inert gas or reducing gas such as Ar gas or Ar-diluted hydrogen gas into the furnace tube 16, and such a gas A gas exhaust port 23 for exhausting the outside of the furnace tube 16, a temperature-adjustable heater 24 surrounding the furnace tube 16 concentrically and heating the left side toward the drawing of the furnace tube 16, and the right side facing the drawing of the furnace tube 16. A heater 26 for heating, a part of the furnace tube 16, a heater 24 and a housing 28 for enclosing the heater 26, a drive belt 32 provided in the furnace tube 16, a motor 34 for driving the drive belt 32, and the housing 28 And motor 3 Comprising DOO a pedestal 36 which is fixed a shaft 38 for fixing one end of the gantry 36 to the installation base 37, a pulley 42 which is driven to secure the other end of the frame 36 by a motor (not shown).
[0033]
The furnace tube 16 rotates together with the internal sample tube 14 and the sample tube retainer 18 by a drive belt 32 driven by a drive circuit 30 controlled by the controller 21. The drive belt 32 can change the rotation direction, the rotation speed, and the like of the furnace tube 16 based on a control signal from the controller 21. Here, the change of the rotation direction includes reversal of the rotation direction, stop of rotation, and the like.
[0034]
The gantry 36 can be tilted with the shaft 38 as a fulcrum by the rotation of the pulley 42 driven by the drive circuit 31 based on the control signal from the controller 21. As the gantry 36 is inclined, the casing 28, the sample tube 14, and the motor 34 are also inclined. The furnace tube 16 can be rotated by the drive belt 32 even when the gantry 36 is inclined.
[0035]
The heater 24 and the heater 26 are measured by a sheath thermocouple 50 and a sheath thermocouple 52 provided between each heater and the furnace tube 16, and temperature measurement data is input to the controller 21. The controller 21 controls the heater controller 22 based on the temperature measurement data, can adjust the temperature of the heater 24 and the heater 26, and can set a temperature gradient in the longitudinal direction of the furnace tube 16.
[0036]
2 is a plan view of the container 12, and FIG. 3 is a cross-sectional view taken along line AA in FIG. The container 12 has a plurality of protrusions 40 provided on the inner wall extending in the longitudinal direction of the container 12. The protrusion 40 can agitate the melted BiTe mixture melt inside the container 12 as it rotates.
[0037]
Next, a method for manufacturing a thermoelectric material using the thermoelectric material manufacturing apparatus 100 will be described. FIG. 4 is a diagram showing a manufacturing process of the thermoelectric material. First, a base material powder of BiTe-based material containing Bi and Te and powder particles of B serving as a scattering center are mixed and sealed in a glass container 12 in a vacuum or an inert atmosphere (step S10). The glass container 12 is enclosed in an iron sample tube 14 to prevent breakage. The sample tube 14 is inserted into the furnace tube 16, supported by the sample tube holder 18, and then enclosed in the furnace tube 16.
[0038]
Next, the heater controller 22 operates the heater 24 and the heater 26 based on the control signal of the controller 21 to heat the sample tube 14 and heat and melt the base material to form a BiTe mixture melt (step S12). . Since the melting point of B is higher than that of the BiTe-based material, the BiTe mixture melt is in a state of remaining as powder particles in the molten BiTe-based material. At this time, it is also possible to send a control signal from the controller 21 to the drive circuit 30, drive the motor 34 by the drive circuit 30, rotate the drive belt 32, and rotate the furnace tube 16. By rotating the furnace tube 16, the B powder particles are uniformly dispersed in the BiTe mixture melt, and the composition of the BiTe mixture melt is also uniform.
[0039]
Next, the furnace tube 16 is rotated and Ar gas is supplied from the gas inlet 20 into the furnace tube 16, and the container 12 is rotated at 5 to 3000 rotations / minute to swing the BiTe mixture melt with Ar gas. Cool (step S14). The BiTe mixture melt is solidified in a state where the B powder is uniformly dispersed in the BiTe mixture melt, and becomes a thermoelectric material. The rotation direction and the number of rotations of the furnace tube 16 can be changed by driving the motor 34 with the drive circuit 30 based on the control signal sent from the controller 21. At this time, the B powder can be uniformly dispersed in the BiTe mixture melt, and the rotation direction can be selected such that a stable liquid surface does not occur in the BiTe mixture melt when the BiTe mixture melt is cooled. In addition, the rotational speed of the BiTe mixture melt is often inconsistent with the rotational speed set for the furnace tube 16 due to its viscosity and friction with the vessel 12, so the rotational speed of the furnace tube 16 is set high and the BiTe mixture melt is set. Can be vigorously stirred. Moreover, since the protrusion 40 exists in the container 12, the BiTe mixture melt can be stirred strongly. In this way, in step S14, B powder is uniformly dispersed in the BiTe mixture melt and cooled so that a stable liquid surface is not formed in the BiTe mixture melt, so that B is uniformly contained in the manufactured thermoelectric material. And the crystallization of the BiTe mixture melt can be promoted uniformly. In Step S14, since the BiTe mixture melt is crystallized in a state where the solid and the liquid are mixed, the filling rate of the manufactured thermoelectric material is close to 100%, about 95 to 100%, and there is a gap between the crystal grains. Does not occur.
[0040]
The manufactured BiTe-based thermoelectric material is considered to have a smaller average crystal grain size of the BiTe-based material that is the base material and about 2 μm to 20 μm compared with the thermoelectric material that is pulverized and sintered and manufactured in bulk. For this reason, phonon scattering at the crystal grain boundary increases and phonon thermal conductivity is reduced. Further, the B particles that are the scattering center are taken into the crystal grains of the BiTe-based material that is the base material, and are uniformly dispersed throughout the thermoelectric material. As a result, the phonon scattering is further increased, the phonon thermal conductivity is further reduced, and consequently the thermal conductivity κ is reduced. Moreover, the filling rate of the manufactured thermoelectric material is about 95 to 100%, which is close to 100% like the melted material, and the electrical conductivity σ is kept high. As a result, the thermoelectric material has a high figure of merit.
[0041]
In the manufacturing method of the thermoelectric material of the present embodiment, the rotation axis of the furnace tube 16, that is, the rotation axis of the container 12 is set to be perpendicular to the horizontal direction of the gantry 36, that is, the direction of gravity applied to the furnace tube 16. It is also possible to rotate the furnace tube 16 by tilting the gantry 36 by controlling the pulley 42 and tilting the rotation axis of the container 12 from the direction perpendicular to the direction of gravity applied to the container 12. By tilting the rotation axis of the container 12 with respect to the direction of gravity, the amount of rocking of the molten BiTe mixture in the container 12 becomes larger than when the rotation axis of the container 12 is set to the direction of gravity, and a stable liquid level is generated. It becomes difficult. As a result, since crystallization proceeds uniformly, a thermoelectric material having a low thermal conductivity κ and a high figure of merit can be manufactured.
[0042]
In the thermoelectric material manufacturing method of the present embodiment, the BiTe mixture can be cooled by controlling each of the heater 24 and the heater 26 during cooling in step S14 to provide a temperature gradient in the BiTe mixture. For example, in FIG. 1, the temperature on the left side of the container 12 can be increased and the temperature on the right side can be decreased. Thus, by appropriately setting the temperature gradient in the BiTe mixture melt, it is possible to give direction to the crystallization of the mixture melt, and to promote the crystallization uniformly regardless of the ambient temperature and the surface state of the mixture. Can do.
[0043]
In the manufacturing method of the thermoelectric material of the present embodiment, the B powder is dispersed in the molten BiTe-based material base material, but the scattering center is a powder and is decomposed by the base material or reacts with the base material. A compound containing at least two or more selected from C, Si, P alone or B, C, Si, N, Zr, Ti, O, Mo, W in addition to B, For example, B _x C _1-x , BN, ZrB ₂ , TiB ₂ , ZrC, TiC, SiC, Si ₃ N ₄ , SiO ₂ , MoSi ₂ , and WSi ₂ can be used.
[0044]
In the thermoelectric material manufacturing apparatus 100 of the present embodiment, the container 12 is provided with the protrusion 40 that stirs the BiTe mixture on the inner wall. However, as shown in FIG. 5, the stirring blade 50 may be provided at the center of the container 12. . The stirring blade 50 extends in the longitudinal direction of the container 12. Further, as shown in FIG. 6, a stirring ball made of a material having a specific gravity greater than that of the BiTe mixture melt in the container, does not react with the BiTe mixture melt, and does not affect the composition of the BiTe mixture melt. 52 can also be entered. Since the stirring ball 52 rotates with the rotation of the container 12, the BiTe mixture melt can be stirred more greatly, and the powder particles of B can be uniformly dispersed in the BiTe mixture melt and it becomes difficult to form a stable liquid surface. The larger the particle diameter of the stirring ball 52, the higher the stirring effect. However, since the stirring ball 52 remains inside when the BiTe mixture melt is solidified, the diameter is sufficiently smaller than the diameter of the container 12, and preferably It is preferable that it is 1/4 or less of the diameter of the container 12.
[0045]
As the scattering center, an inert gas or reducing gas such as Ar gas or Ar-diluted hydrogen can be introduced in addition to the powder. When introducing such a gas, it is preferable to use a magnetic stirrer in which the stirring bar in the container rotates by applying a rotating magnetic field from the outside. FIG. 7 is a diagram showing a schematic configuration of a thermoelectric material manufacturing apparatus 200 according to the second embodiment using a magnetic stirrer. The thermoelectric material manufacturing apparatus 200 includes a vessel 12 that encloses the BiTe mixture melt 10, a gas introduction pipe 80 that is wound around the vessel 12 and introduces gas from the lower portion of the vessel 12, and a gas provided at the upper portion of the vessel 12. The gas exhaust pipe 82 for exhausting the gas, the stirrer 70 in which the magnet is coated with a material that does not react with the BiTe mixture, the furnace chamber 17 in which the container 12 is housed, and the furnace chamber 17 are concentric. In the drawing of the furnace chamber 17, a temperature-adjustable heater 72 that heats the upper side in the drawing, a heater 74 that heats the lower side toward the drawing of the furnace chamber 17, and a casing that encloses the furnace chamber 17, the heater 72, and the heater 74. 28, a gantry 36 having a magnet (not shown) that generates a rotating magnetic field therein, and sheath thermocouples 50 and 52 that are embedded in the container 12 and measure the temperature of the container 12. In the thermoelectric material manufacturing apparatus 200, the BiTe mixture melt 10 can be swung by rotating the stirring bar 70 by the rotating magnetic field generated by the magnet of the gantry 36. Further, when the BiTe mixture melt 10 is swung, the introduced gas bubbles are taken in and solidified in that state, so that the gas bubbles remain in the BiTe thermoelectric material, which becomes the scattering center. Can do. In addition to the magnetic stirrer, a high-frequency induction heating furnace in which a coil is set around a vessel in which a BiTe mixture is sealed and a high frequency is applied to generate an induction current in the melt can be used. In the high-frequency induction heating furnace, the BiTe mixture melt can be heated by the induction current, and the BiTe mixture melt can be stirred by the Lorentz force received by the induction current. By this agitation, the introduced gas bubbles are taken in and solidified in that state, so that the gas bubbles remaining in the BiTe-based thermoelectric material become a scattering center, and the thermal conductivity of the thermoelectric material can be reduced.
[0046]
The thermoelectric material of each embodiment uses Bi and Te as raw materials, but in addition thereto, an element selected from Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Fe, Mn, Co, and Si Can also contain at least two or more. In particular, a chalcogenite-based raw material of a combination of at least one of Bi, Sb, Ag, Pb, Ge, Cu, Sn, As and Se or Te, or a combination of any one of Fe, Mn, Co, Ge and Si Silicide-based raw materials and BiSb-based materials are suitable.
[0047]
【The invention's effect】
As described above, in the thermoelectric material manufacturing method and thermoelectric material manufacturing apparatus of the present invention, when manufacturing a thermoelectric material in which a scattering center object that scatters phonons is added to the base material, the scattering center object and the base material Since the mixture melt is swung and the mixture is cooled, the scattering center can be uniformly dispersed in the thermoelectric material. Further, since the mixture is solidified without a stable liquid surface, the crystal grain size of the base material of the manufactured thermoelectric material is reduced. As a result, the mean free path of phonons is reduced, the phonon thermal conductivity is reduced, and consequently the thermal conductivity κ is reduced. Further, the gap between the crystal grains is as small as the melted material, and the electrical conductivity σ is kept high. As a result, a thermoelectric material having a high figure of merit can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of a thermoelectric material manufacturing apparatus 100 of the present embodiment.
FIG. 2 is a plan view of the container 12. FIG.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a diagram showing a manufacturing process of the thermoelectric material of the present embodiment.
5 is a cross-sectional view of the container 12 provided with a stirring blade 50. FIG.
6 is a cross-sectional view of the container 12 provided with a stirring ball 52. FIG.
FIG. 7 is a schematic view showing a configuration of a thermoelectric material manufacturing apparatus 200 according to a second embodiment.
[Explanation of symbols]
10 BiTe mixture melt, 12 container, 14 sample tube, 16 furnace tube, 17 furnace chamber, 21 controller, 22 heater controller, 30, 31 drive circuit, 24, 26 heater, 32 drive belt, 40 protrusion, 42 Pulley, 100, 200 Thermoelectric material manufacturing equipment.

Claims (21)

A thermoelectric material manufacturing method for manufacturing a thermoelectric material including a scattering center and a base material that scatters phonons,
A rocking cooling step of cooling the mixture while shaking the mixture melt of the scattering center and the base material in a container ;
The scattering center is a compound containing at least two elements selected from B, C, Si, P alone or B, C, Si, N, Zr, Ti, O, Mo, W. Powder particles,
Furthermore, an addition step of adding the powder particles to the base material;
A melting step of melting the base material;
A method for producing a thermoelectric material, comprising: A thermoelectric material manufacturing method for manufacturing a thermoelectric material including a scattering center and a base material that scatters phonons,
A rocking cooling step of cooling the mixture while shaking the mixture melt of the scattering center and the base material in a container ;
The scattering center is an inert gas or reducing gas bubble,
Furthermore, the manufacturing method of the thermoelectric material characterized by including the melting | fusing process which introduce | transduces the bubble of the said gas into the molten base material while melting the base material. 3. The thermoelectric material according to claim 1, wherein the swing cooling step is a step of swinging the mixture in a state where a temperature gradient is provided in the mixture and cooling the mixture. Production method. It is a manufacturing method of the thermoelectric material given in any 1 paragraph of Claims 1-3 ,
The container is provided with a stirring bar inside,
The method for producing a thermoelectric material is characterized in that the rocking cooling step is a step of rocking the mixture by stirring the mixture with the stirrer and cooling the mixture. Said oscillating cooling step, the thermoelectric material according to any one of claims 1 to 4, characterized in that a step of cooling the mixture while oscillating the mixture by rotating the container Production method. Said oscillating cooling step of claim 5, characterized in that the step of cooling the mixture while oscillating the mixture by rotating the container at a rotational speed of 5 to 3000 rev / min Thermoelectric material manufacturing method. 6. The method of manufacturing a thermoelectric material according to claim 5 , wherein the rocking cooling step is a step of rocking the mixture while changing a rotation direction of the container and cooling the mixture. 6. The method of manufacturing a thermoelectric material according to claim 5 , wherein the swing cooling step is a step of swinging the mixture while repeating rotation and stop of the container and cooling the mixture. Said oscillating cooling step, claim 5, characterized in that the step of cooling the mixture while oscillating the mixture by rotating the container is inclined rotation axis of said container with respect to the direction of gravity method for producing a thermoelectric material according to any one of 1-8. The rocking cooling step is a step of rocking the mixture and cooling the mixture by rotating the container with the rotation axis of the container perpendicular to the direction of gravity. method for producing a thermoelectric material according to any one of 5-8. A base material containing at least two elements selected from Bi, Sb, Ag, Pb, Ge, Cu, Sn, As, Se, Te, Fe, Mn, Co, and Si, and a scattering center that scatters phonons A thermoelectric material produced from a mixture comprising:
The mixture has an average crystal grain size of 2 μm to 20 μm and a filling rate of 95 to 100%,
The scattering center is composed of bubbles of an inert gas or a reducing gas, and the scattering center is uniformly dispersed in the base material. The thermoelectric material according to claim 11 , wherein the base material is made of a thermoelectric semiconductor melting material. A thermoelectric material manufacturing apparatus for manufacturing a thermoelectric material including a scattering center and a base material that scatters phonons,
A container for enclosing a mixture melt of the scattering center and the base material;
Rocking cooling means for rocking the container and rocking the mixture and cooling the mixture;
A thermoelectric material manufacturing apparatus comprising: The thermoelectric material manufacturing apparatus according to claim 13 ,
The scattering center is an inert gas or reducing gas bubble,
A gas introduction means for introducing the gas into the base material in a molten state;
A thermoelectric material manufacturing apparatus comprising: The thermoelectric material manufacturing apparatus according to claim 13 or 14 , further comprising temperature gradient setting means for setting a temperature gradient in the mixture in the container. Thermoelectric material production apparatus according to any one of claims 13 to 15, characterized in that the stirrer for stirring the mixture in the interior of the container is provided. The rocking cooling means, thermoelectric material production apparatus according to any one of claims 13 to 16, characterized in that while oscillating the mixture by rotating the container is a means for cooling the mixture. The thermoelectric material manufacturing apparatus according to claim 17 , wherein the swing cooling means includes a rotation direction control means for controlling a rotation direction of the container. The thermoelectric material manufacturing apparatus according to claim 17 or 18 , wherein the swing cooling means includes a rotation axis inclination means for inclining the rotation axis of the container with respect to a gravitational direction. The thermoelectric material manufacturing apparatus according to claim 17 or 18 , wherein the swing cooling means is means for rotating the container with a rotation axis perpendicular to the direction of gravity. The thermoelectric material manufacturing apparatus according to claim 16 , wherein the swing cooling means is a magnetic stirrer.

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