JP2000357821A - Manufacture of thermoelectric semiconductor material or element, and manufacture of thermoelectric module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermoelectric semiconductor material or element that is effective for improving thermoelectric performance, and a method for manufacturing a thermoelectric module. SOLUTION: The powder and solvent of a semiconductor material are filled into a rubber tube 42, and both the ends of the rubber tube 42 are fixed by a fixing ring 44 while upper and lower directions are sealed by an upper cover 38 and a lower cover 40. Then, the rubber tube 42 is dipped into an oil bath 46, hydraulic loading is utilized, and the semiconductor material in the rubber tube 42 is uniformly pressed from a side surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thermoelectric semiconductor material or element and a method of manufacturing a thermoelectric module, and more particularly to a method of manufacturing a thermoelectric semiconductor material or element and a method of manufacturing a thermoelectric module effective for improving thermoelectric performance. About.

[0002]

2. Description of the Related Art Conventionally, thermoelectric elements utilizing a thermoelectric phenomenon have been used as heat exchangers and temperature sensors. The thermoelectric phenomenon is a general term for the Peltier effect, the Thompson effect, and the Seebeck effect, and each is described as follows.

[0003] The Peltier effect is a phenomenon in which when a current flows through a junction of dissimilar metals, heat is generated or absorbed at the junction. The Thomson effect is a phenomenon in which a current flows through a metal having a temperature gradient. This is a phenomenon in which heat is generated or absorbed in the metal. The Peltier element used as the electronic cooler is a thermoelectric element using the Peltier effect.

[0004] The Seebeck effect is a phenomenon in which an electromotive force is generated on the high temperature side and the low temperature side of a sample when the junction of dissimilar metals is kept at different temperatures. A thermocouple used as a temperature sensor uses this Seebeck effect. This is a thermoelectric element.

[0005] The thermoelectric element as described above has a simple structure, has stable characteristics, and is easy to handle. Therefore, research and development have been widely conducted for temperature control of a semiconductor laser and application to a small refrigerator. ing.

The material for forming the thermoelectric element is selected from one or two selected from the group consisting of bismuth (Bi) and antimony (Sb) and the group consisting of tellurium (Te) and selenium (Se). One or two alloys are currently in use. These compounds are layered structure compounds, and are semiconductor materials having anisotropic thermoelectric properties due to the crystal structure.

Various techniques such as unidirectional solidification, hot pressing, and extrusion are known as techniques for processing a semiconductor material comprising a layered structure compound as described above to refine crystal grains and improve the degree of orientation. It has been known.

The unidirectional solidification method is a method for producing an ingot having a controlled crystal growth direction, and according to this method, a polycrystalline material having an excellent degree of orientation can be obtained. As a specific example of the directional solidification method, the Bridgman method is known. However, the polycrystalline material produced by the unidirectional solidification method has a problem that the material strength is low. Therefore, it is not preferable to use the polycrystalline material obtained by this method as it is as a thermoelectric semiconductor element.

The hot pressing is a method of compressing ingot material powder or the like in a uniaxial direction to produce a polycrystalline material having improved material strength. The reason for compression in the uniaxial direction is to forcibly align the crystal orientation by an external force. According to these methods, the problem that the material strength of the unidirectional solidification method is low is solved, and a polycrystalline material having excellent orientation can be obtained.

The extrusion method is a method in which a powder or a molded product of the powder is put into a die, and the material in the die is extruded using a punch and compression-molded. As a prior document that discloses this extrusion method, Japanese Patent Application Laid-Open
JP-A-138789, JP-A-8-186299 and JP-A-10-56210. According to this method, since a strong force is applied to the entire material, finer crystal grains can be obtained, and the material strength is also improved.

Therefore, from the viewpoints of crystal orientation and material strength, hot pressing, cold pressing, and extrusion methods are currently widely used as methods for manufacturing thermoelectric semiconductor devices.

[0012]

However, in recent years, a thermoelectric element having better thermoelectric performance has been demanded, and a new technology which is a further development of the above-described conventional technology is required.

Accordingly, an object of the present invention is to provide a method for manufacturing a thermoelectric semiconductor material or element and a method for manufacturing a thermoelectric module, which are effective for improving thermoelectric performance.

[0014]

As means for achieving the above object, the following approach has been taken and will be described here.

First, the crystal structure of a compound having a layered structure, which is a basic matter of the present invention, will be described. Since knowledge of the crystal structure is useful for understanding the present invention, it will be described in detail below.

FIG. 1 is a schematic perspective view showing the crystal structure of a layered structure compound. FIG. 1 shows the crystal structure of a layered structure compound containing a group V element and a group VI element in a composition ratio of 2: 3. Further, the crystal structure shown in the figure has bismuth (Bi) and antimony (Sb) as group V elements.
Are assumed to be selenium (Se) and tellurium (Te) as Group VI elements.

As shown in the figure, the compound of a group V element and a group VI element has a hexagonal structure, and the hexagonal portion in the figure is the basal plane of the layered structure compound, This is the so-called crystal plane. The layered structure compound has a structure in which a large number of C planes are stacked in the C axis direction and spread in the A axis and B axis directions.

Since carriers flow most easily in the direction parallel to the C plane, it can be said that a single crystal of a layered structure compound is the material having the highest electrical anisotropy. However, as described above, since the bonding force between layers of the layered structure compound is weaker than the bonding force in the layer plane, it is not preferable in terms of material strength to use the single crystal as a thermoelectric material.

For example, a bismuth-tellurium-based layered compound has a remarkable cleavage property due to the presence of a weak van der Waals bond between tellurium atoms. Insufficient durability. Therefore, usually, a polycrystal of a layered structure compound is used as a thermoelectric semiconductor material.

FIG. 2 is a schematic perspective view showing a polycrystalline structure of the layered structure compound. As shown in the figure, the polycrystal of the layered structure compound is an aggregate of fine crystal grains 10 and can obtain a material strength superior to that of a single crystal.

In addition, since phonons are scattered at the interface between the crystal grains 10 (hereinafter, referred to as “crystal grain boundaries”), the thermoelectric element formed by the polycrystal composed of the plurality of crystal grains 10 has a thermal conductivity. Rates tend to be lower. Therefore, polycrystal is a preferable structure also in terms of thermoelectric performance.

On the other hand, as described above, since the carrier easily flows along the C-plane of the layered structure compound, as shown in FIG. 2, the C-plane of each crystal grain 10 is entirely along the path of the carrier. The electric resistivity is lowest in the state of standing along (hereinafter, referred to as “standing orientation”). Therefore, in the case of using a polycrystalline material, it is important to make the crystal grains 10 stand up in order to improve the thermoelectric performance.

Here, the thermoelectric performance of the thermoelectric element is expressed by [Equation 1]. Where: Z = index of performance × 10 ⁻³ (1 / K); α = Seebeck coefficient (μV / K); σ = conductivity (μΩ ⁻¹ cm)
^-1 ); κ = thermal conductivity (mW / cmK); ρ = electrical resistivity (μΩ · cm).

Referring to the above equation, miniaturization of the crystal grains 10 to lower the thermal conductivity κ and lowering the electrical resistivity ρ by erecting the crystal grains 10 lead to improvement in thermoelectric performance. You can see that.

In a conventional uniaxial press such as a hot press or a cold press, a kind of upright orientation state is realized by compressing a semiconductor material in a uniaxial direction. As a result, the electric resistivity ρ is reduced. I have.

FIG. 3 is a schematic perspective view showing the orientation tendency of crystal grains by uniaxial pressing. The hexagonal object shown in the figure is a simplified representation of the crystal grain 10 shown in FIG.
Shall represent a surface. As shown in the figure, when a polycrystalline material is pressed in a uniaxial direction, crystal grains 10 contained in the polycrystalline material tend to be uniaxially oriented in a certain direction by a pressure applied from an external force.

At this time, the direction in which the crystal grains 10 are oriented is a direction in which the C plane is perpendicular to the pressing direction. actually,
Although perfect orientation as shown in the figure cannot be obtained, a polycrystalline material processed by uniaxial pressing tends to approach this state.

Conventionally, the orientation direction of the C-plane shown in FIG. 1 is set to the direction of current flow to reduce the electrical resistivity ρ. However, the electrical resistivity ρ of the thermoelectric semiconductor element manufactured by the uniaxial press is not as low as expected, and is expected to be far from the fully oriented state shown in FIG.

Then, the following state was considered by focusing on the point that the idea was changed and the C-plane was not aligned in a fixed direction, but was raised in the direction of carrier movement.

FIG. 4 is a schematic perspective view showing the state of free-standing oriented crystal grains. As shown in the figure, when the traveling direction of the carrier is the Z axis, regardless of how the C plane of the crystal grain 10 is oriented with respect to the X axis and the Y axis, the C plane is the Z axis. Standing along (hereinafter,
"Free standing orientation"), the electrical resistivity p can be reduced.

This free standing orientation is different from the orientation in a fixed direction shown in FIG.
It has the freedom to be oriented in any way with respect to the axis. By allowing such a degree of freedom, it is possible to apply a process deviating from the conventional fixed concept of a uniaxial press.

As a result of repeating the creative act from such a viewpoint, the idea of "pressing in at least three directions orthogonal to one axis (ie, the direction of conduction)" was obtained.
That is, since the C plane of the crystal grain has a property of being oriented in a direction perpendicular to the pressing direction, if pressed from a direction perpendicular to the energizing direction, the C plane of the crystal grain is aligned in parallel with the energizing direction.

However, the same applies to the conventional uniaxial press with respect to the point of "pressing from a direction perpendicular to the energizing direction". However, the above-mentioned idea includes a unique concept of “pressing from at least three directions”, which is different from a conventional uniaxial press. The concept of pressing from these three directions is a concept that can be applied only when the degree of freedom described above is allowed, and cannot be easily conceived from a conventional uniaxial press.

Subsequently, in order to further improve the performance of the thermoelectric semiconductor device, the extrusion method was also studied.
The results are described below.

As described above, the extrusion method is an effective means for refining crystal grains and improving the degree of orientation. However, it has been found that the conventional extrusion method can certainly achieve the fineness, but does not improve the degree of orientation as expected. This is because
It is considered that this is mainly due to the orientation of the extruded material.

That is, as described above, the extruded material used in the extrusion method is obtained by molding a powder (hereinafter, referred to as “powder”).
"Pre-molded body") is common. Since the powder has a different crystal orientation, simply extruding it,
It is considered that the crystal orientation is not uniform before being extruded, and the molding is performed in an insufficient state.

Therefore, a configuration in which the preformed body was extruded after the crystal orientation was aligned was examined. Here, the important point is the relationship between the orientation direction of the pre-molded body and the extrusion direction. In other words, no matter how excellent the orientation of the pre-molded article is, even if the pressure applied to the pre-molded article at the time of extrusion does not utilize the orientation of the pre-molded article, on the contrary, it becomes a cause of disturbing the crystal orientation. is there.

Therefore, in order to define the relationship between the orientation direction of the pre-molded article and the extrusion direction, it is necessary to first fully understand the features of the extrusion method.

As described above, the extrusion method is a method of extruding a polycrystalline material put into a die with a punch.
Since the die used for the extrusion has a drawn shape along the extrusion direction, the polycrystalline material passing through the die is compressed. That is, in the extrusion method, the polycrystalline material receives a normal reaction from the die wall surface and is squeezed in a direction orthogonal to the extrusion direction.

This is an important notion that the extrusion will create the free upright orientation described above in the polycrystalline material. Focusing on this point and further studying, it is possible to obtain an idea that if the crystal orientation of the pre-molded article is made to coincide with the orientation produced by extrusion, the orientation control by extrusion works efficiently. That is,
"The crystal orientation of the pre-formed body is made to coincide with the extrusion direction."

The present invention is based on the two ideas of "pressing in at least three directions perpendicular to one axis" and the two ideas of "coinciding the crystal orientation of the pre-formed body with the extrusion direction". Based on this, it is intended to solve the above-mentioned problem.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Summary of the Invention) One feature of the present invention conceived based on the above idea is that pressing of a semiconductor material containing crystal grains of a layered structure compound is perpendicular to one axis. That is to do from at least three directions. The one axis is an axis corresponding to the direction of conduction of the thermoelectric semiconductor element. Pressing from a direction perpendicular to this axis causes the C plane of the crystal grain to approach a state parallel to the direction of conduction.

Further, by the pressing from at least three directions, free standing orientation of crystal grains is generated in the semiconductor material, and the electric resistivity ρ is reduced. The free standing orientation is an orientation having a relatively high degree of freedom, unlike the uniaxial orientation achieved by a conventional uniaxial press.

The material having the free-standing orientation as described above is useful as a thermoelectric semiconductor material because of its high anisotropy in thermoelectric performance. In addition, since it has a crystal orientation similar to that achieved by the extrusion method, it is also useful as an extrusion material. The present invention in which a free standing orientation is generated can be expressed as a multiaxial press as compared with a conventional uniaxial press.

A second feature of the present invention resides in that the upright axis on the C-plane of the pre-molded article is made coincident with the extrusion direction of the pre-molded article. Since the extrusion method has a characteristic that the C plane of the crystal grain stands in the extrusion direction of the pre-formed body, if the rising axis of the C plane of the pre-formed body is made to coincide with the extrusion direction, it acts on the crystal grain during extrusion. The force is adapted to the crystal orientation of the pre-formed body, and an improvement in the degree of orientation can be expected.

(First Embodiment) A first embodiment of the present invention is an invention for producing a thermoelectric semiconductor material or a thermoelectric semiconductor element having a free standing orientation. Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to FIGS. In the following description, the thermoelectric semiconductor material or thermoelectric semiconductor element manufactured according to the first embodiment will be referred to as a pre-molded body.

FIG. 5 is a schematic perspective view showing an execution state of a step of forming a circular pre-formed body. As shown in the figure, in the first embodiment of the present invention, first, the semiconductor material 12 is pressed from at least three directions orthogonal to one axis. Here, it is assumed that the material outer edge 24 of the semiconductor material 12 has a cylindrical shape. That is, the cylindrical side wall is pressed from at least three directions orthogonal to the central axis of the cylindrical shape.

The pressing at this time may be performed with the upper and lower surfaces of the cylindrical shape being free, and the upper and lower surfaces of the cylindrical shape are provided with supports to restrict the vertical movement of the semiconductor material 12. It may be performed in a state where it is done. If the pressing is performed in a state in which the movement in the vertical direction is restricted, the elongation of the material due to the compression is suppressed, so that the compression ratio is increased and a stronger molded body is obtained.

As shown in the figure, the semiconductor material 12 is
Thin powder 18 produced by a quenching roll method and spherical powder 2 produced by a rapid solidification method such as a centrifugal atomizing method
The concept includes 0 and a pulverized powder 22 produced by pulverizing an ingot obtained by the unidirectional solidification method.

These materials are the above-mentioned compounds having a layered structure. The thin powder 18 is a polycrystalline thin film in which the C plane of crystal grains is oriented perpendicular to the film thickness. Are polycrystalline grains whose C-plane is radially oriented, and
Is a polycrystalline powder in which the C plane of crystal grains is oriented in a certain direction. These polycrystalline materials are all known materials in the field of thermoelectric semiconductors, and a detailed description of the manufacturing method is omitted.

The pressing direction P for pressing the semiconductor material 12 is as follows.
As shown in the figure, it is preferable to set radially with respect to the center axis of the columnar shape, and more preferably to press all the circumferences of the side surfaces simultaneously with a uniform force. The side surface means a surface surrounding the central axis of the cylinder. A method of uniformly pressing the entire circumference of the cylindrical side surface will be described in detail in the following embodiments.

FIG. 6 is a schematic diagram showing the orientation of the pre-molded article obtained by the process shown in FIG. 5A is a plan view of FIG. 5, and FIG. 5B is a side view of FIG. Pre-formed body 13 obtained by the process of FIG.
Is the material outer edge 2 as shown in FIGS.
4 has a shape compressed by pressing.

As a result, the crystal grains 10 stand in a direction perpendicular to the direction in which the crystal grains 10 are pressed, and the central axis of the columnar shape is
Of the C-plane. Then, the obtained pre-formed body 1
3 shows a state in which the crystal grains 10 are freely erected, as shown in the enlarged view of FIG.

If the above-mentioned pressing is performed while heating, the pre-formed body 13 becomes a sintered body, and if it is cut as needed, it can be used as it is as a thermoelectric semiconductor element. Further, if the pre-formed body 13 obtained at this stage is used as an extruded material, a thermoelectric semiconductor having a higher degree of orientation can be obtained. This example will be described later.

FIG. 7 is a schematic perspective view showing an execution state of a step of forming a rectangular pre-formed body. As shown in the figure, the present invention can be applied to a case where the material outer edge 24 of the semiconductor material 12 is rectangular. In this case, the pressing direction P is set to all sides of the rectangle. For example, as shown in the figure, when the material outer edge 24 of the semiconductor material 12 is a rectangular parallelepiped, the pressing direction P is set for each of the four side surfaces of the rectangular parallelepiped. Similarly, in the case where the material outer edge 24 is a polygonal prism such as a pentagonal prism, a hexagonal prism, or the like, if the pressing direction P is set for each of the side surfaces of the polygonal prism, the free upright orientation of the crystal grains can be generated.

FIG. 8 is a schematic view showing the orientation of the pre-molded article obtained by the process shown in FIG. 7A is a plan view of FIG. 7, and FIG. 7B is a side view of FIG. Preformed body 13 obtained by the process of FIG.
Also, similarly to the circular pre-formed body, the material outer edge 24 has a shape compressed by pressing.

As a result, the crystal grains 10 stand in the direction perpendicular to the direction in which the crystal grains 10 are pressed, and the center axis of the rectangular parallelepiped becomes the rising axis of the C plane of the crystal grains 10. Then, the obtained pre-formed body 13
Is a state in which the crystal grains 10 are freely erected as shown in the enlarged view of FIG.

FIG. 9 is a schematic perspective view conceptually showing a phenomenon occurring inside the pre-molded article by the steps shown in FIGS. As shown in the figure, the crystal grains 10 contained in the semiconductor material 12 initially have different directions of the C-plane, but are forcibly erected by pressing from the side, and the C-plane is one axis, that is, one axis. , C are parallel to the upright axis.

At this time, since the crystal grains 10 are pressed so as to be narrowed from the direction surrounding the upright axis of the C plane,
The crystal orientation of the pre-formed body is a free standing orientation. Therefore, if the upright axis of the C plane is set in the direction of conduction, a thermoelectric semiconductor element having a low electric resistivity ρ can be manufactured.

As described above, according to the first embodiment of the present invention, since the semiconductor material composed of the layered structure compound is multiaxially pressed, free upright orientation can be generated in the semiconductor material. As a result, a thermoelectric semiconductor material having a low electric resistivity ρ is obtained, and improvement in thermoelectric performance can be expected.

Since the free upright orientation is similar to the crystal orientation generated by the extrusion method, the pre-formed body manufactured by the first embodiment of the present invention is suitable as an extrusion material. This point will be described in detail in the following second embodiment.

(Second Embodiment) The second embodiment of the present invention is to provide an extrusion method effective for improving the degree of orientation. Note that, in the following description, the same reference numerals are used for components corresponding to the above-described first embodiment, and description thereof is omitted.

FIG. 10 is a perspective view showing an execution state of the circular extrusion step according to the second embodiment of the present invention. As shown in the figure, in the second embodiment of the present invention, the pre-formed body 13 with the C-plane upright oriented is extruded from a die 16 to form an extruded formed body 14 in which the pre-formed body 13 is further compressed.

The important point here is that the upright axis on the C-plane of the pre-molded body 13 and the extrusion direction of the pre-molded body 13 match. This is for the following reason.

First, the extrusion method is a method of extruding a pre-formed body 13 charged with a diameter of A0 in a certain direction and compressing the same into a diameter of A1. During this extrusion, the crystal grains 10 in the pre-formed body 13 are deformed by receiving a vertical drag from the entire periphery of the side wall of the die 16. As a result, the crystal grains 10 in the obtained extruded body 14 have the C-plane standing upright in the extrusion direction. That is, in the extrusion method, the extrusion direction is the upright axis of the C plane.

Therefore, if the crystal orientation of the pre-molded body 13 is made uniform and the upright axis of the C-plane is made to coincide with the extrusion direction, the crystal orientation of the pre-molded body 13 acts in a direction more uniform by the extrusion. The degree is more improved. In the present invention, since the pre-formed body 13 having the upright orientation is extruded along the upright axis, an extruded body 14 having excellent crystal orientation is obtained.

Here, let us consider a case where the crystal orientation of the pre-formed body 13 is a free standing orientation as shown in the enlarged view 1 of FIG. That is, the pre-formed body 13 is formed by the above-described first embodiment. As shown in the enlarged view of FIG. 1, at the stage of the pre-formed body 13, it is not in a completely upright state yet, but when it is extruded from the die 16 and compressed, as shown in the enlarged view 2 in the same figure, a more favorable state is obtained. It stands up. That is, the extrusion works in a direction to further align the crystal orientation of the pre-formed body 13.

Conversely, considering the case where the crystal orientation of the pre-molded body 13 is random, an enormous amount of energy is required to bring this random orientation into an upright state. In many cases, a suitable upright orientation cannot be obtained. Similarly, when there is a large angle difference between the upright axis of the C plane and the extrusion direction, the extrusion only
Since this angle difference cannot be sufficiently filled, the degree of orientation cannot be improved much. That is, the extruded body 14 is formed in a state where the crystal grains that cannot stand up are left. This is a point that has not been recognized so far.

This can be easily understood by considering the following state, for example. In other words, assuming a crystal grain in which the C plane is tilted 90 ° with respect to the pushing direction, this crystal grain gradually rises from the 90 ° tilted state in the process of being extruded.
It is considered that the surface tends to be parallel to the extrusion direction.

Therefore, the larger the angle difference between the orientation of the C-plane and the direction of extrusion, the greater the energy required for the crystal grains to rise, leaving crystal grains that cannot be sufficiently raised during the extrusion process.

Therefore, in the present invention, a certain degree of orientation is given from the stage of the pre-molded body 13 which is a starting material for extrusion, and the orientation direction of the pre-molded body 13 is made to coincide with the extrusion direction. It is in a state where crystal grains are easy to rise. Therefore, it is preferable that the pre-molded article 13 used in the second embodiment of the present invention has high orientation obtained by the above-described first embodiment.

FIG. 11 is a perspective view showing the state of execution of the rectangular extrusion step according to the second embodiment of the present invention. As shown in the figure, the concept of making the upright axis of the C-plane of the pre-formed body 13 coincide with the extrusion direction is not limited to the case where the cylindrical pre-formed body is extruded using the cylindrical die 16, and the rectangular die is used. The present invention can also be applied to a case where a rectangular pre-formed body 13 is extruded using the 16.

In this case, too, the incomplete free standing orientation shown in the enlarged view 1 in the figure is in a suitable state as shown in the enlarged view 2 in the figure. Incidentally, the rectangular die 16 shown in FIG. 12 compresses the pre-formed body 13 in the Y-axis direction to form an extruded body 14 extended in the Z-axis direction. A die 16 having a shape that compresses in both directions of the axis and the Y axis may be used. At this time, the compression ratios in the X-axis direction and the Y-axis direction are the same (that is, A0 / A1 = B
0 / B1).

FIG. 12 is a perspective view showing the state of execution of an extruding step using a laminated material according to the second embodiment of the present invention. As shown in the figure, the pre-molded body 13 may be a laminate of thin powders 18 produced by a quenching roll method. In this case, the thin powder 18 is extruded while the laminating direction and the extruding direction are matched.

As shown in the enlarged view 1 of FIG.
The crystal orientation of 8 is more preferable than that obtained by simply press-molding. If the pre-molded body 13 on which the thin powder 18 is laminated is used, the extrusion is performed in a state where the preferable crystal orientation is maintained. As a result, as shown in the enlarged view 2 in FIG.
An extruded body 14 having a suitable free upright orientation is obtained. The rectangular die 16 shown in FIG. 11 compresses the pre-formed body 13 in both directions of the X-axis and the Y-axis. However, the die 16 has a shape which is compressed only in the Y-axis direction as shown in FIG. May be used.

FIG. 13 is a perspective view showing a step of extruding a pre-formed body formed by a uniaxial press. As shown in the figure, as the pre-formed body 13, one formed by a uniaxial press such as a hot press or a cold press may be used. In the pre-formed body formed by the uniaxial press, since the direction perpendicular to the pressing direction is the upright axis of the C plane, if the upright axis and the extrusion direction match, the extruded body 14 having excellent crystal orientation can be obtained. can get.

Here, the point different from the pre-formed body 13 formed according to the above-described first embodiment is that the pre-formed body 13 formed according to the first embodiment has a free standing orientation, but is formed by a uniaxial press. The pre-formed body 13
As shown in the enlarged view of FIG.

Therefore, taking this point into consideration, when using the pre-formed body 13 whose C-plane is oriented in the Y-axis direction by uniaxial pressing, the die 16 for compressing the pre-formed body 13 only in the Y-axis direction is used. It is considered preferable to use them. This is due to the following reasons.

That is, when a force is applied from the X-axis direction to the crystal grain 10 having the C-plane oriented in the Y-axis direction as shown in the enlarged view of FIG. 1, the C-plane tends to be oriented in the X-axis direction. X on the C side
There is no problem as a standing state even if facing in the axial direction,
Since the energy given to the crystal grains by the extrusion is finite, it is considered that, when the energy is allocated to the operation in which the C plane faces in the X-axis direction, the energy allocation to the operation in which the C plane stands up is reduced accordingly. Because.

In order to improve the thermoelectric performance, it is important to raise the C plane, and it does not matter whether the orientation is uniaxial or free upright. Therefore, supplying energy in a direction contributing to the erecting of the C-plane and preventing unnecessary energy distribution as much as possible leads to an improvement in the degree of orientation.

That is, the upright axis of the C-plane of the pre-molded body 13 and the extrusion direction of the pre-molded body 13 are made to coincide with each other,
By performing the extrusion while matching the direction in which the is compressed, a more suitably erected uniaxial orientation can be obtained as shown in the enlarged view 2 in FIG.

As described above, according to the second embodiment of the present invention, since the extrusion is performed along the upright axis of the C plane, an extruded body 14 having a high degree of orientation can be obtained.

[0083]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Summary) A rubber tube 42 is filled with a semiconductor material powder and a solvent, and both ends of the rubber tube 42 are fixed with fixing rings 44 with the upper cover 38 and the lower cover 40 sealed in the vertical direction. I do. Thereafter, the rubber tube 42 is immersed in an oil bath 46, and the semiconductor material in the rubber tube 42 is evenly pressed from the side using hydraulic pressure (see FIG. 19).

(Preferred Embodiment) The idea of "pressing in at least three directions perpendicular to one axis"
The above-described technical idea of “matching the crystal orientation of the pre-molded product with the extrusion direction” is a very useful idea for improving thermoelectric performance. Here, an example is shown in which this characteristic technical idea is embodied in a mode considered to be industrially preferable. Among the components described above, those that do not need to be particularly described are given the same names and the same reference numerals, and detailed description thereof will be omitted. Further, the embodiment described below is an embodiment of the present invention,
It does not limit the invention.

FIG. 14 is a process chart showing a manufacturing process of the thermoelectric module according to the present embodiment. Hereinafter, the configuration of this manufacturing process will be described with reference to FIG.

First, as shown in the figure, bismuth (Bi), tellurium (Te), selenium (Se) and antimony (Sb), which are raw materials of a semiconductor material, and impurities used as dopants are weighed (step S10). These are put into the crucible 30.

Next, the crucible 30 into which the above-mentioned raw material has been charged is heated to melt the raw material, thereby producing a molten metal as a raw material melt (step S12).

Subsequently, the spherical powder 20 or the thin powder 18 is formed by using the molten metal in the crucible 30, the pulverized powder 22 obtained by coagulating the molten liquid and then pulverized, or a powder comprising a combination thereof. Prepare a material (Step S1)
4). Hereinafter, the spherical powder 20, the pulverized powder 22, and the thin powder 18
Will be described separately.

FIG. 15 is a perspective view showing a method for producing the spherical powder 20. As shown in the figure, when producing the spherical powder 20, the molten metal in the crucible 30 is dropped on a rotating disk 26 rotating at high speed, and the molten metal is scattered by centrifugal force to be rapidly solidified. As a result, a spherical powder 20 having a fine particle size is obtained. Then, the obtained spherical powder 20 is classified and the particle diameters are made uniform, and this is used as the material of the pre-molded body.

FIG. 16 is a process chart showing a method for producing the pulverized powder 22. As shown in the figure, when producing the pulverized powder 22, the molten metal in the crucible 30 is solidified to produce an ingot 32, which is put into a mill 34 and pulverized (step S100).

Then, the powder raw material discharged from the mill 34 is classified by passing through a filter 36 and sized to a powder of about 34 to 108 μm (step S102).

Then, the sized powder is put into a glass ampule under vacuum evacuation, and hydrogen is injected into the glass ampule to set the pressure in the glass ampule to 0.9 atm. Then, this glass ampule is placed in a heating furnace and heated at 350 ° C. for 10 hours to perform hydrogen reduction of the powder (Step S104).

The pulverized powder 22 thus obtained is used as a material for the pre-molded body.

FIG. 17 is a partial cross-sectional view showing a method for producing the thin powder 18. As shown in the figure, when producing the thin powder 18, the molten metal in the crucible 30 is supplied to the nozzle 27, and the molten metal is dropped on the surface of the rotating cooling roll 28.
A thin powder 18 having submicron class crystal grains is produced by a quenching roll method. When a laminate of the thin powders 18 is used as a pre-molded body, the cooling roll 28
A plurality of thin powders 18 formed on the surface and obtained by peeling are laminated in the thickness direction to form a laminate 29.

The preform 13 is formed by pressing the spherical powder 20, the pulverized powder 22, the thin powder 18 or a combination thereof produced as described above in the following procedure (step S16 in FIG. 14). .

FIG. 18 is a perspective view showing a first procedure of the pre-formed body forming step shown in FIG. Pre-molded body 13
As shown in the figure, first, a powder after hydrogen reduction is filled in a rubber tube 42 whose lower end is sealed with a lower cover 40. At this time, a volatile solvent functioning as a lubricant is mixed. Then, the upper end of the rubber tube 42 is sealed with the upper cover 38, and the rubber tube 42 is closed.
Seal both the lower end and the upper end with a fixing ring. Both the upper cover 38 and the lower cover 40 are formed of a rigid body, and restrain the vertical movement of the powder.

FIG. 19 is a perspective view showing a second procedure of the preformed body forming step shown in FIG. As shown in the figure, the powder composed of the spherical powder 20, the pulverized powder 22, the thin powder 18, or a combination thereof is placed in a rubber tube 42.
After that, the upper end of the rubber tube 42 is sealed with a fixing ring 44, and the rubber tube 42 is put into an oil bath 46.

FIG. 20 is a perspective view showing a third procedure of the preformed body forming step shown in FIG. As shown in the figure, after the rubber tube 42 is put into the oil bath 46, the oil in the oil bath 46 is pressed using the punch 48. As a result, the side surface of the rubber tube 42 is deformed by the hydraulic pressure, and the powder in the rubber tube 42 is compressed. At this time, the rubber tube 42 together with the powder is used.
The solvent mixed therein serves as a lubricant, smoothes the movement of the powders, and orients the C plane smoothly.

After that, the compressed powder is taken out from the rubber tube 42, and the solvent contained in the powder is evaporated to obtain a pre-molded body 13. Thereafter, the pre-formed body 13 is extruded by using a cylindrical or rectangular die 16 as shown in FIGS. 10 to 12, thereby forming an extruded body 14 (Step S18 in FIG. 14).

Thereafter, the obtained extruded body 14 is cut into a desired shape to form P-type and N-type thermoelectric semiconductor elements 15 (step S20). The module 100 is assembled (Step S22).

FIG. 21 is a perspective view showing the structure of the thermoelectric module 100 manufactured by the process shown in FIG. As shown in FIG.
-Type thermoelectric semiconductor element 15-1 and N-type thermoelectric semiconductor element 1
A pair of electrodes 50 are fixed to the upper and lower surfaces of 5-2 and manufactured.

At this time, the electrode 50 is connected to the C-type of the P-type thermoelectric semiconductor element 15-1 and the N-type thermoelectric semiconductor element 15-2.
It is disposed at a position penetrated by the upright axis of the surface. With such an arrangement of the electrodes 50, the current supplied via the electrodes 50 flows in a direction parallel to the rising axis of the C plane, that is, in a direction in which the electric resistivity ρ is low.

In the above embodiment, the spherical powder 20 and the pulverized powder 22
Alternatively, the powder made of the thin powder 18 or a combination thereof is used as the material of the pre-molded body 13, but it is preferable to form the pre-molded body using the spherical powder 20. This is considered to be due to the shape of the spherical powder 20.

That is, since the spherical powder 20 is a powder having a minute spherical shape, it has a property that it can easily move even under pressure. Therefore, when the spherical powder 20 is pressed, first, the spherical powder 20 is in a high-density state without any gaps. Then, it is considered that a pre-formed body composed of fine crystal grains having a high degree of orientation can be obtained because the crystal grains are repeatedly destructed and recrystallized by being pressed from the high density state. The spherical powder 20 will be described in more detail as follows.

The spherical powder 20 is clean, spherical and has a small specific surface area without contamination in the powder generation step, and therefore has excellent sinterability and can be easily used even if the powder has a small particle size. A sintered body or a cold compact can be produced. Moreover, since the powder itself is rapidly solidified, it has a fine structure. Therefore, the crystal composition of these preforms is fine crystal grains.

Further, since there is no segregation in the powder and the particle size distribution is narrow, uniform deformation is performed when the preform is subjected to plastic working, and a uniform molded product can be obtained. Further, since the powder is spherical, the powders make point contact with each other. Therefore, in the sintering and plastic working processes, stress concentration occurs at the contact points, and the driving force generated there causes strong destruction and crystal orientation (rotation), thereby forming a high-performance element.

Then, N-type and P-type sintered bodies were formed using the spherical powder produced by the rotating disk method, and the thermoelectric performance was measured. The measuring method and the results are shown below.

(Experiment 1) 0.08 wt% of HgBr ₃ was mixed with Bi ₂ Te _2.7 Se _0.3 , and N-type spherical powders of 10 μm and 50 μm were prepared by a rotating disk method. Thereafter, a pre-compact is formed from the spherical powder by cold pressing and hot pressing. Then, using a rectangular die having an extrusion ratio of 6, the pre-molded body is extruded to form an extruded body. The extrusion temperature at this time is 480 ° C. and 350 ° C., and the extrusion speed is 0.5 mm / min and 2.5 mm / min. The results of this experiment were as follows.

[0109] As can be seen from Table 1, an N-type thermoelectric semiconductor element having a high figure of merit was obtained.

(Experiment 2) A melt of Bi _1.5 Sb _0.5 Te ₃ is prepared, and P-type spherical powders of 10 μm and 50 μm are prepared by a rotating disk method. Thereafter, a pre-compact is formed from the spherical powder by cold pressing and hot pressing. Then, using a rectangular die having an extrusion ratio of 6, the pre-molded body is extruded to form an extruded body. The extrusion temperature at this time was 480 ° C and 3
The extrusion speed is set to 0.5 mm / min and 2.5 mm / min. The results of this experiment were as follows.

[0111] As seen from Table 2, a P-type thermoelectric semiconductor element having a high figure of merit was obtained. Further, by combining an extruded product with an annealing process at a temperature lower by about 0 to 100 ° C. than the extrusion temperature as a post-process, it is possible to further increase the figure of merit.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a crystal structure of a layered structure compound.

FIG. 2 is a schematic perspective view showing a polycrystalline structure of a layered structure compound.

FIG. 3 is a schematic perspective view showing the tendency of crystal grains to be oriented by uniaxial pressing.

FIG. 4 is a schematic perspective view showing a state of a crystal grain in a free standing orientation.

FIG. 5 is a schematic perspective view showing an execution state of a step of forming a circular pre-formed body.

FIG. 6 is a schematic view showing an orientation state of a pre-molded article obtained by the process shown in FIG.

FIG. 7 is a schematic perspective view showing an execution state of a step of forming a rectangular pre-formed body.

FIG. 8 is a schematic view showing an orientation state of a pre-molded article obtained by the process shown in FIG.

FIG. 9 is a schematic perspective view conceptually showing a phenomenon occurring inside the pre-molded article by the steps shown in FIGS. 5 and 7.

FIG. 10 is a perspective view showing an execution state of a circular extrusion step according to a second embodiment of the present invention.

FIG. 11 is a perspective view showing an execution state of a rectangular extrusion step according to a second embodiment of the present invention.

FIG. 12 is a perspective view illustrating an execution state of an extrusion process using a laminated material according to a second embodiment of the present invention.

FIG. 13 is a perspective view showing a step of extruding a pre-formed body formed by a uniaxial press.

FIG. 14 is a process chart illustrating a manufacturing process of the thermoelectric module according to the present embodiment.

FIG. 15 is a perspective view showing a method for producing the spherical powder 20.

FIG. 16 is a process chart showing a method for producing a pulverized powder 22.

FIG. 17 is a partial cross-sectional view showing a method for producing the thin powder 18.

FIG. 18 is a perspective view showing a first procedure of a pre-formed body forming step shown in FIG.

FIG. 19 is a perspective view showing a second procedure of the pre-formed body forming step shown in FIG.

20 is a perspective view showing a third procedure of the pre-molded article forming step shown in FIG.

FIG. 21 is a perspective view showing the structure of a thermoelectric module 100 manufactured by the process shown in FIG.

[Explanation of symbols]

10: crystal grains, 12: semiconductor material, 13: pre-formed body,
14: Extruded body, 15: Thermoelectric semiconductor element, 15-
DESCRIPTION OF SYMBOLS 1 ... P-type thermoelectric semiconductor element, 15-2 ... N-type thermoelectric semiconductor element, 16 ... dice, 18 ... thin powder, 20 ... spherical powder, 22
... ground powder, 24 ... material outer edge, 26 ... rotating disk, 27
... Nozzle, 28 ... Cooling roll, 29 ... Laminate, 30 ... Crucible, 32 ... Ingot, 34 ... Mill, 36 ... Filter, 38 ... Top cover, 40 ... Bottom cover, 42 ... Rubber tube, 44 ... Fixing ring, 46 … Oil bath, 4
8 punch, 50 electrode, 100 thermoelectric module, P
… Pressing direction

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kiyoharu Sasaki 1200 Manda, Hiratsuka-shi, Kanagawa Prefecture Inside Komatsu Manufacturing Co., Ltd. (72) Inventor Keisuke Ikeda 1-20-98 Tsurugaoka, Izumi-ku, Sendai, Miyagi

Claims (13)

[Claims] 1. A method for manufacturing a thermoelectric semiconductor material or device by pressing a semiconductor material (12) containing crystal grains (10) of a layered structure compound, wherein the pressing comprises at least three orthogonal to one axis. A method for manufacturing a thermoelectric semiconductor material or element, wherein the method is performed from two directions. 2. The method for manufacturing a thermoelectric semiconductor material or device according to claim 1, wherein the pressing is performed simultaneously on all side surfaces of the outer edge of the material of the semiconductor material. 3. The method of manufacturing a thermoelectric semiconductor material or device according to claim 1, wherein the pressing causes free standing orientation of the crystal grains. 4. The method for producing a thermoelectric semiconductor material or a device according to claim 1, wherein the semiconductor material is a spherical powder (20) produced by a rapid solidification method. 5. A step of restraining movement along one axis of the semiconductor material (12) including the crystal grains (10) of the layer structure compound, and orthogonal to the one axis while the movement is restrained. Pressing the semiconductor material from at least three directions to produce the thermoelectric semiconductor material or element. 6. A semiconductor material (12) containing crystal grains (10) of a layered structure compound is pressed from at least three directions orthogonal to one axis to form P-type and N-type thermoelectric semiconductor elements. A method for manufacturing a thermoelectric module, comprising: forming; and forming, on the upper and lower surfaces of the P-type and N-type thermoelectric semiconductor elements, a pair of electrodes (50) located on the one axis. 7. A preform (13) containing crystal grains (10) of a layered structure compound is extruded from a die (16),
In the method of manufacturing a thermoelectric semiconductor material or an element, the pre-formed body has a plurality of crystal grains in which a C-plane is oriented upright along one axis, and the extrusion is performed with the one axis of the pre-formed body. A method for producing a thermoelectric semiconductor material or element, wherein the extrusion is performed in the same direction as the extrusion direction of the pre-molded body. 8. A preform (13) containing crystal grains (10) of a layered structure compound is extruded from a die (16),
In the method for producing a thermoelectric semiconductor material or a device, the pre-molded product may be configured such that a C plane is oriented upright along one axis, and the C plane is oriented with respect to another axis orthogonal to the one axis. Having a plurality of crystal grains, wherein the extruding is performed by aligning the one axis of the pre-molded body with the extrusion direction of the pre-molded body, and applying a pressure in a direction parallel to the other axis of the pre-molded body. A method for producing a thermoelectric semiconductor material or device. 9. The thermoelectric device according to claim 7, wherein the pre-formed body is formed by pressing the pre-formed body from at least three directions orthogonal to the one axis. A method for manufacturing a semiconductor material or device. 10. The pre-molded body is formed by laminating thin powders (18) produced by a quenching roll method, and the extruding is performed by matching a laminating axis of the thin powders with the extrusion direction. 9. The method for producing a thermoelectric semiconductor material or device according to claim 7, wherein the method is performed. 11. The thermoelectric semiconductor material according to claim 7, wherein the pre-formed body is formed by pressing a spherical powder (20) produced by a rapid solidification method. Or a method for manufacturing an element. 12. A step of constraining movement along one axis of the semiconductor material (12) including the crystal grains (10) of the layered structure compound, and orthogonal to the one axis with the movement constrained. A thermoelectric semiconductor comprising: pressing the semiconductor material from at least three directions to form a pre-molded body; and pouring the pre-molded body into a die (16) and extruding the same along the one axis. Method of manufacturing a material or element. 13. At least 3 orthogonal to one axis
Pressing a semiconductor material (12) containing crystal grains (10) of a layered structure compound from two directions to form a pre-molded body; and charging the pre-molded body into a die (16), Extruding along to form P-type and N-type thermoelectric semiconductor elements; and a pair of electrodes located on the one axis on the upper and lower surfaces of the P-type and N-type thermoelectric semiconductor elements. Forming a thermoelectric module, the method comprising: