JPH0918061A - Manufacture of thermoelectric conversion material - Google Patents

Abstract

PURPOSE: To manufacture an alloy thermoelectric conversion element, which has a remarkably high processing yield at the time of machining and has stably a high performance index. CONSTITUTION: In an alloy ingot, which is produced by a fusing method and contains two kinds or more of elements selected from among elements of Bi, Te, Se and Sb as its main components, or by a fusing method and contains any one or more kinds of elements selected from among elements of Bi, Te, Se and Sb, the alloy, or an arbitrary shaped material cut out from the alloy ingot, without being ground, is burned by an uniaxial pressing method at a pressure of about 3000kg/cm<2> or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoelectric conversion material.

[0002]

2. Description of the Related Art Bi-Te based alloys are known as materials having high thermoelectric properties near room temperature. Since this thermoelectric property exhibits anisotropy with respect to the crystal axis, a method for producing a thermoelectric conversion material that sufficiently expresses this anisotropy has been studied,
For example, when a metal such as Bi or Te is melted in an ampoule filled with an inert gas and unidirectionally solidified by utilizing a temperature gradient, that is, a solidified material called an ingot material is produced to obtain a figure of merit. It is known that high thermoelectric conversion characteristics exceeding 2.7 × 10 ^-3 K ^-1 can be obtained. The figure of merit is a parameter expressed by the following equation. The higher the figure of merit, the better the thermoelectric conversion characteristics. Performance index = (Thermoelectromotive force) ² × (Electrical conductivity) / (Thermal conductivity)

Since the crystallites of this ingot are mainly bonded by atomic force, it is difficult to obtain a material having a strength sufficient to withstand the mechanical processing required for producing a practical member, and the processing yield is high. Is extremely low. Further, the thermoelectric element made of the ingot material has a problem that the resistance value and the thermoelectric characteristic are likely to change due to the influence of temperature and humidity, and further, the durability is deteriorated in long-term use.

As a method for avoiding these problems, it has been attempted to manufacture a sintered body by hot pressing a powder obtained by crushing and classifying a molten material with a hot press machine. In general, sintering by hot pressing can achieve high densification even for a difficult-to-sinter material, and at the same time can suppress grain growth, so that a sintered body can be manufactured without lowering strength. Further, the uniaxial pressure tends to cause the sintered crystal to be oriented in a direction perpendicular to the pressure direction.

However, according to this method, the metal particles are easily oxidized at the time of pulverization and classification, and the sintered body obtained by sintering such particles remarkably deteriorates the thermoelectric properties. Further, generally, with the pressure that can be generated by the hot pressing apparatus, the crystals in the Bi-Te based alloy sintered body cannot be perfectly oriented in a certain direction, and are affected by the remaining crystals of low characteristic orientation. The figure of merit of the sintered body can only be as low as about 2.2 to 2.4 × 10 ⁻³ K ⁻¹ .

[0006]

As described above, it is extremely difficult to obtain a thermoelectric conversion material capable of stably maintaining a high figure of merit with a high production yield in any of the production methods that have been tried so far. there were.

[0007]

In order to solve the above-mentioned problems, the inventors of the present invention have focused on not only the chemical composition of the material but also the crystal orientation, which has a great influence on the thermoelectric properties. Focused on the relationship between the material strength and the bonding state of crystals, and further studied the alteration of the material composition from the viewpoint of eliminating the factors. As a result, the yield during machining is dramatically improved by pressing and sintering the alloy ingot produced by the melting method at a high pressure in a certain direction without crushing, and the excellent figure of merit is stably maintained. The inventors have found that a thermoelectric conversion material having excellent durability can be easily manufactured, and have completed the present invention.

That is, according to the present invention, any one of Bi, Te, Se, and Sb produced by solidifying through a melting process is used.
An alloy lump containing at least one kind of component, or at least one of Bi, Te, Se, and Sb produced by solidifying through a melting process as a main component and the remaining component as a periodic table 3A to 7
In an alloy lump containing at least two metals selected from Group A, Group 8, 1B to 4B, and 7B except for boron and carbon, the alloy lump, or from the alloy lump It is a method for producing a thermoelectric conversion material, which comprises uniaxially pressure-sintering a cut molded product without crushing it.

The alloy according to the present invention is a mixture of a plurality of kinds of metals, or a nonmetal element contained in the alloy, the structure of which is solid solution, eutectic or intermetallic compound,
Alternatively, they are a mixture. The specific component of the alloy targeted by the present invention may be any material component as long as it can obtain thermoelectric conversion characteristics. Typical examples thereof are Bi, Te, Se and Sb. Either 2
Seed-based component systems, such as the well-known Bi-Te system, Sb-
There are binary alloys such as Te-based, Bi-Se-based, Bi-Sb-based, etc., and such binary alloys do not contain the third component from Bi, Te, Se, Sb. One component selected and added as a ternary alloy, or Bi-Te-Se-
Sb quaternary alloys can also have similar thermoelectric properties and are therefore the subject of the present invention.

Further, each component of Bi, Te, Se and Sb, or a component composed of two or more of them is selected from the groups 3A to 7A, 8 group, 1B to 4B group and 7B group of the periodic table. One or more components other than boron and carbon, ie S
c, Y, La, Ce, Pr, Nd, Sm, Eu, Gd,
Tb, Dy, Ho, Er, Tm, Yb, Lu, Ti, Z
r, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe,
Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, A
g, Au, Zn, Cd, Hg, Al, Ga, In, Tl, S
Even when alloying with components such as i, Ge, Sn, Pb, F, Cl, Br and I, B contained in the alloy is included.
The total amount of i, Te, Se, and Sb components is approximately 90% by weight.
In the case of a degree or more, generally, it is possible to have relatively good thermoelectric conversion characteristics, and this case is also an object of the present invention.

The alloy ingot of the present invention is usually a simple substance of each metal of the above components, an alloy of two or more of the above components, and a composition capable of forming a metal or an alloy of the above components by heat melting treatment, and more particularly, , Cu for forming an impurity level called a dopant and imparting properties as a semiconductor
I, HgBr ₂ , HgCl ₂ , HgI ₂ , CuF ₂ , SbI
₃ , 700, BiI _{3 and} other compounds, which are appropriately selected from the component sources, are placed in a quartz ampoule and heated in an electric furnace for approximately 700
It is prepared by melting at 0 ° C and then cooling and solidifying. Here, in solidifying the melt, an alloy ingot in which crystals are oriented in a certain direction is produced by an operation such as unidirectional solidification in which cooling is performed while maintaining a constant temperature gradient at the upper and lower ends of the melt. More preferably, the solidified product is treated by the zone melting method,
It is preferable to produce an alloy ingot having higher purity and orientation.

It is desirable that the pressing direction be horizontal to the crystal orientation direction of the alloy without crushing any of the alloy ingot thus produced or the molded product cut out from the alloy ingot into a desired shape. Is installed in the hot pressurizer so that it is in the vertical direction, and uniaxial pressure is applied, that is, pressure is applied in one direction to the material to be fired, or pressure from two directions that are coaxial with each other at 180 °. And sinter.

The pressure of pressure sintering is 3000 Kg / cm ²
When the above pressure is applied to sinter, it is possible to manufacture a high-strength sintered body that can sufficiently withstand mechanical processing while maintaining the crystal orientation state before sintering. The mechanical strength can be further increased by increasing the applied pressure here, but if the pressure value is not reached, a sintered body having sufficient strength cannot be obtained. Such pressure cannot be obtained by an ordinary hot press device, and an ultrahigh pressure heating device such as a piston cylinder type, a flat belt type, a girdle type, a Bridgman type, or a cubic anvil type is used.

The temperature of pressure sintering is 300 ° C. or higher and 500 ° C.
The following is desirable. If it is less than 300 ° C, densification does not proceed sufficiently and it becomes difficult to obtain a high-strength sintered body, and if it exceeds 500 ° C, melting of the alloy is likely to occur, which is not preferable.

The pressure sintering can be carried out in the atmosphere or under a reduced pressure vacuum, but since the surface of the material may be oxidized or a high vapor pressure component may be volatilized, the atmosphere should be kept under an inert gas atmosphere. It is desirable to use one gas or two or more gases selected from nitrogen gas.

[0016]

In the production method of the present invention, since the pulverization step is not performed, it is possible to avoid the powder state in which the surface area is large and the surface energy is high, so that the powder state is easily oxidized, and the deterioration of the property due to the oxide formation is sufficiently performed. Can be prevented.

In the uniaxial pressure sintering, in addition to hot pressing in a certain direction, a crystalline ingot having an orientation can be made into a sintered body in which the orientation is maintained. ,
The crystal orientation can be made more perfect and excellent thermoelectric properties can be exhibited. Further, the pressurization and the sintering are performed at the same time, so that the respective crystals are bonded very strongly to form a highly dense and high-strength sintered body. This strength is a material strength that can sufficiently withstand the mechanical processing that is essential to the production of a member as a thermoelectric conversion element, and contributes to the improvement of mechanical durability.

[0018]

EXAMPLES Hereinafter, examples according to the present invention and comparative examples outside the scope of the present invention will be described together. [Example 1] Bi, Te, and
Powders of Sb and Se were respectively 484.75 g, 468.
A mixture of 60 g, 31.39 g, 15.26 g and 1.15 g of HgBr ₂ as an n-type dopant was weighed and mixed, and the mixture was sealed in a quartz ampoule in an argon atmosphere. This was placed in an electric furnace, melted and stirred at 700 ° C., and then cooled and solidified to near room temperature while maintaining a temperature gradient of 5 ° C./cm between the upper and lower ends of the ampoule, to obtain an n-type ingot material. It was made. A 20 × 25 × 6 mm rectangular parallelepiped is cut out from this ingot, and this rectangular parallelepiped molded product is subjected to a unidirectional pressure in a direction perpendicular to the crystal orientation direction in an argon atmosphere at 35 ° C.
An n-type sintered body was produced by performing pressure sintering with a piston-cylinder type ultra-high pressure heating device under conditions of 0 ° C. and 3000 Kg / cm ² .

Regarding the figure of merit of this sintered body, the electrical conductivity of the sample of 4 × 4 × 20 mm cut out from this sintered body was measured by the direct current 4-terminal method. Similarly, the sample of 4 × 4 × 4 mm cut out was quartz. Was calculated from the values of the thermal conductivity and the thermoelectromotive force measured by the relative method using the standard as 2.9 ×
It was 10 ^-3 K ^-1 . Further, after performing Ni electroless plating on each of the 20 sintered bodies, a cross section of 2 was obtained by a surface grinding machine with a diamond wheel having a thickness of 0.7 mm, a peripheral speed of 2600 m / min, and a cut amount of 30 μm. ×
It processed so that it might become a rectangular parallelepiped shape which is 2 mm. We investigated the occurrence of cracks and chipping (chips and shattering) and the plating covering state of the sintered body after processing.
No crack or chipping was generated in any of the sintered bodies, and the plating was not peeled at all, and the processing yield was 100%.

[Embodiment 2] In each case, powders of Bi, Te, Sb and Se having a purity of 99.99% are respectively 484.75.
g, 468.60 g, 31.39 g, 15.26 g, and weighed and mixed. The mixture was sealed in a quartz ampoule under an argon atmosphere. It was placed in an electric furnace and melted at 700 ° C.
After stirring, 5 ° C / c between the upper and lower ends of the ampoule
Cooling to near room temperature while maintaining the temperature gradient of m, a p-type ingot was produced. From this ingot, 20 x 25 x 6 mm
A total of 60 rectangular parallelepiped molded products were cut out, and the temperature was 300 ° C. in an argon atmosphere under a pressurizing condition of 8000 Kg / cm ² so that a pressure in one direction was applied in a direction perpendicular to the crystal orientation direction. , 400 ° C., and 500 ° C. were individually pressure-sintered by a piston-cylinder type ultra-high pressure heating device to produce 20 p-type sintered bodies of each of three types having different sintering temperatures.

The performance indexes of these three kinds of sintered bodies were measured by the same method as in Example 1, and all 3.0
It was × 10 ^-3 K ^-1 . Further, Ni electroless plating was performed on these sintered bodies under the same conditions and method as in Example 1, and then processed by a surface grinder to have a rectangular parallelepiped shape having a cross section of 2 × 2 mm. . The occurrence of cracks and chippings and the covering state of the plating were examined for each sintered body after processing. No cracks or chippings were found in all the sintered bodies, but sintering was performed at 300 ° C and 400 ° C. A partial peeling of the plating was observed in each of the sintered bodies, and the processing yields of these sintered bodies were all 95%.
In the sintered body at 500 ° C., peeling of the plating was not observed at all, and the processing yield was 100%.

[Embodiment 3] Each of powders of Bi, Te, Sb, and Se having a purity of 99.99% is 484.75.
g, 468.60 g, 31.39 g, 15.26 g, and 1.15 g of n-type dopant HgBr ₂ were weighed and mixed, and the mixture was sealed in a quartz ampoule in an argon atmosphere. This was melted and solidified in the same manner as in Example 1, and impurities were removed and crystal orientation was improved by a zone melting method using a Bridgman-Stockburger furnace to produce an n-type ingot material. 20 × from this ingot
A 25 × 6 mm rectangular parallelepiped is cut out, and this molded product is applied with a piston-cylinder type ultra-high pressure heating device in an argon atmosphere under the conditions of 380 ° C. and 6000 Kg / cm ² so that pressure is applied in one direction perpendicular to the crystal orientation direction. An n-type sintered body was produced by performing pressure sintering.

The performance index of this sintered body was measured by the same method as in Example 1 and found to be 3.1 × 10 ^-3 K ^-1 .
After performing Ni electroless plating on each of the 20 sintered bodies, a cross section of 2 × 2 mm was obtained by a surface grinding machine under the conditions of a peripheral speed of 2600 m / min and a cutting depth of 30 μm using a diamond wheel having a thickness of 0.7 mm. Was processed into a rectangular parallelepiped shape. When the sintered body after processing was examined for cracks and chippings and the covering state of the plating, cracks and chippings did not occur at all, plating did not peel off at all, and the processing yield was 100%.

Further, with respect to the sintered body produced under the same conditions and method as described above, only the cut amount was 5, 10, 20, 4
The values were 0 and 50 μm, and other conditions were the same as above, and the processing yield was examined with respect to changes in the depth of cut. As a result, cracks and chippings did not occur at any cutting depth, and plating was not peeled off, and the processing yields were all 100%.

From the n-type sintered body produced here, 4
A 4x20mm rectangular parallelepiped is cut out, and a lead wire is soldered to both end faces of the rectangular parallelepiped, and a current of 2A is applied while inverting the polarity every minute in a constant temperature and humidity chamber at a temperature of 40 ° C and a relative humidity of 93%. When a durability test was continuously performed, the specific resistance (Ω
The change in cm) was hardly seen, and stable properties were exhibited.

[0026]

FIG.

[Embodiment 4] Each of powders of Bi, Te, Sb, and Se having a purity of 99.99% was 484.75.
g, 468.60 g, 31.39 g, 15.26 g, and weighed and mixed. The mixture was sealed in a quartz ampoule under an argon atmosphere. In the same procedure as in Example 3, a p-type ingot was prepared by removing impurities and improving the crystal orientation by the zone melting method. 20 x 25 from this ingot
A rectangular parallelepiped of 6 mm is cut out, and this molded product is heated by a piston cylinder type ultra-high pressure heating device under an argon atmosphere at 380 ° C. and 6000 Kg / cm ² so that a pressure in one direction is applied in a direction perpendicular to the crystal orientation direction. Pressure sintering,
A p-type sintered body was obtained.

When the performance index of this sintered body was measured by the same method as in Example 1, it was 3.1 × 10 ^-3 K ^-1 .
Moreover, under the same conditions and method as in Example 1, the sintered body was N
i After electroless plating, the cross section is 2 × with a surface grinder
It processed so that it might become a rectangular parallelepiped shape which is 2 mm. When the sintered body after processing was examined for cracks and chippings and the covering state of the plating, cracks and chippings did not occur at all, plating did not peel off at all, and the processing yield was 100%.

[Embodiment 5] In each case, powders of Bi, Te, Sb and Se having a purity of 99.99% are respectively 484.75.
g, 468.60 g, 31.39 g, 15.26 g, and weighed and mixed. The mixture was sealed in a quartz ampoule under an argon atmosphere. It was placed in an electric furnace and melted at 700 ° C.
After stirring, 5 ° C / c between the upper and lower ends of the ampoule
Cooling to near room temperature while maintaining the temperature gradient of m, a p-type ingot was produced. From this ingot, 20 x 25 x 6 mm
A total of 40 rectangular parallelepiped molded articles are cut out, and the molded article is pressed in one direction in a direction perpendicular to the crystal orientation direction.
All are 400 degrees Celsius in argon atmosphere, only pressure is 300
The condition of the two types of 0 kg / cm ² and 10000 kg / cm ^2, subjected to pressure sintering by the piston cylinder-type ultrahigh pressure heating apparatus at individual condition, sintering pressures of two different p-type sintered bodies each 20 pieces were produced.

The performance indexes of these sintered bodies were measured by the same method as in Example 1. All were 3.0 × 10 ^-3 K ^-1.
Met. After performing Ni electroless plating on each of the 20 sintered bodies, a cross section of 2 × 2 mm was obtained by a surface grinding machine under the conditions of a peripheral speed of 2600 m / min and a cutting depth of 30 μm using a diamond wheel having a thickness of 0.7 mm. Was processed into a rectangular parallelepiped shape. The state of cracks and chippings and the state of plating covering of the sintered body after processing were examined. No peeling of the plating was observed in all the sintered bodies, but ^{2 was found in} the sintered body of 3000 kg / cm 2.
Only one piece showed chipping, and the processing yield was 90%. With respect to the sintered body of 10000 Kg / cm ² , there was no problem with cracking or chipping, and the processing yield was 1
00%.

[Embodiment 6] Powders of Bi, Te, Sb, and Se having a purity of 99.99% are respectively 484.75.
g, 468.60 g, 31.39 g, 15.26 g, and weighed and mixed. The mixture was sealed in a quartz ampoule under an argon atmosphere. It was placed in an electric furnace and melted at 700 ° C.
After stirring, 5 ° C / c between the upper and lower ends of the ampoule
Cooling to near room temperature while maintaining the temperature gradient of m, a p-type ingot was produced. From this ingot, 20 x 25 x 6 mm
Cut out a rectangular parallelepiped, and apply a unidirectional pressure to this molded product in a direction perpendicular to the crystal orientation direction.
At 000 Kg / cm ² , the atmosphere is nitrogen gas, nitrogen-argon mixed gas (volume ratio about 1: 1), and helium gas are pressure-sintered by a piston-cylinder type ultra-high pressure heating device, and a sintering atmosphere is obtained. Three different types of p-type sintered bodies were prepared. When the figure of merit of these sintered bodies was measured, they were all 3.0 × 10 ⁻³ K ⁻¹ .

[Embodiment 7] 529.20 g of Bi and Te powders having a purity of 99.99% and 478.
02g, and SbI ₃ and HgBr ₂ which are n-type dopants
0.6 g and 0.55 g of and were weighed and mixed, and the mixture was sealed in a quartz ampoule in an argon atmosphere. This was placed in an electric furnace, melted and stirred at 700 ° C., and then cooled to near room temperature while maintaining a temperature gradient of 5 ° C./cm between the upper and lower ends of the ampoule to produce an n-type ingot material. did.
A rectangular parallelepiped having a size of 20 × 25 × 6 mm was cut out from this ingot, and the rectangular parallelepiped molded product was subjected to unidirectional pressure in a direction perpendicular to the crystal orientation direction at 350 ° C. in an argon atmosphere,
An n-type sintered body was produced by performing pressure sintering with a piston-cylinder type ultra-high pressure heating device under the condition of 3000 kg / cm ² . When the figure of merit of this sintered body was measured, 2.
It became 8 × 10 ⁻³ K ⁻¹ . Further, when the processing yield was examined for the 20 sintered bodies under the same conditions and methods as in Example 1, the processing yield was 100%.

[Embodiment 8] In the same manner as in Embodiment 1, n
A mold ingot was produced. 20 × 25 × 6m from this ingot
m rectangular parallelepiped is cut out, and this rectangular parallelepiped shaped product is pressed by a piston cylinder type ultra-high pressure heating device in an argon atmosphere at 380 ° C. and 3500 Kg / cm ² so that pressure in one direction is applied in a direction parallel to the crystal orientation direction. An n-type sintered body was produced by performing sintering. When the processing yield of this sintered body was examined under the same conditions and methods as in Example 1, the processing yield was 100%.

[Embodiment 9] 52.20 g of Bi and Te powders having a purity of 99.99% and 478.
02g, and SbI ₃ and HgBr ₂ which are n-type dopants
0.6 g and 0.55 g of and were weighed and mixed, and the mixture was sealed in a quartz ampoule in an argon atmosphere. This was placed in an electric furnace, melted and stirred at 700 ° C., and then cooled to near room temperature while maintaining a temperature gradient of 5 ° C./cm between the upper and lower ends of the ampoule to produce an n-type ingot material. did.
From this ingot, a cylinder with a diameter of 6 mm was cut out, and this cylinder molded product was subjected to unidirectional pressure in a direction perpendicular to the crystal orientation direction at 320 ° C. and 50000 Kg / cm ² ,
Pressure sintering was performed with a flat belt type ultra-high pressure heating device to produce an n-type sintered body.

After electroless plating of Ni on each of the 20 sintered bodies, a diamond wheel having a thickness of 0.7 mm was used to produce a peripheral speed of 2600 m / min and a cutting depth of 30 μm.
Under the above conditions, the cross-section was processed by a surface grinder so as to have a 2 × 2 mm shape. We investigated the occurrence of cracks and chippings (chips and shattering) and the coating state of the plated sintered bodies, and found that all of the sintered bodies did not show cracks, chippings, or peeling of the plating. The processing yield was 100%.

[Comparative Example 1] In the same manner as in Example 1, n
A mold ingot was produced. Performance index of this ingot is 2.9x
It became 10 ^-3 K ^-1 . Further, without pressing and sintering this ingot, 20 disc-shaped objects having a thickness of 4 mm were cut out in a direction perpendicular to the crystal growth direction and subjected to Ni electroless plating, and then, as in Example 1. Under the same conditions, it was processed by a surface grinder to have a rectangular parallelepiped shape having a cross section of 2 × 2 mm. The state of cracks and chippings and the state of plating covering were investigated for the shape after processing. Total of 1 if either or both cracks and chippings occurred
There were two pieces, and the processing yield was 40% or less.

[Comparative Example 2] In the same manner as in Example 2, p
A mold ingot was produced. The figure of merit of this ingot is 3.0 x
It became 10 ^-3 K ^-1 . When the processing yield of 20 unsintered samples was examined under the same conditions and method as in Comparative Example 1 without pressurizing and sintering this ingot, chipping and cracks were found in 11 samples, and the processing yield was Was 45%.

Comparative Example 3 In the same manner as in Example 3, n
A mold ingot was produced. When the processing yield was examined under the same conditions and methods as in Comparative Example 1 without pressurizing and sintering this ingot, it was 50%. Also, from this ingot, 4x
Cut out a 4 × 20 mm rectangular parallelepiped, solder lead wires to both ends of it, and continue applying a current of 2 A while reversing the polarity every minute in a constant temperature and humidity chamber at a temperature of 40 ° C. and a relative humidity of 93%. When a durability test was performed, as shown in FIG. 2, an increase in specific resistance (Ωcm) of about 15% was observed by the time elapsed from the start of the test up to 300 hours, and deterioration of the material due to moisture absorption from the atmosphere was observed. confirmed.

[0039]

FIG. 2

[Comparative Example 4] In the same manner as in Example 4, p
A mold ingot was produced. When the processing yield of 20 unsintered samples was examined under the same conditions and method as in Comparative Example 1 without press-sintering this ingot, the processing yield was 55%.

[Comparative Example 5] In the same manner as in Example 5, p
A mold ingot was produced. From this ingot, 20 x 25 x 6
20 pieces of rectangular parallelepiped molded product of mm are cut out, and the molded product is pressed in one direction in a direction perpendicular to the crystal orientation direction.
Both are 400 ° C and 300 Kg / cm in an argon atmosphere.
^An n-type sintered body was produced by performing pressure sintering with a hot press machine under the condition of ² . When the processing yield of this sintered body was examined under the same conditions and method as in Example 1, 11 pieces were found to be damaged by cracks or chippings.
No cracks or chippings were found, but there were four with peeling of the plating, and the processing yield was 25.
It became a very low percentage.

[Comparative Example 6] In the same manner as in Example 3, n
A mold ingot was produced. This ingot was ground in a mortar in the air and classified with a stainless sieve into particles having a particle size of 75 μm or more and less than 150 μm. The particles were filled in a graphite mold shielded with a boron nitride film and pressure-sintered under the same conditions as in Example 3 to produce an n-type sintered body. The figure of merit of this sintered body is 2.3 × 10 ^-3 K ^-1, which is about 26% of the figure of merit of the ingot before sintering (3.1 × 10 ^-3 K ^-1 ). Fell.

[0043]

According to the manufacturing method of the present invention, it is possible to obtain a thermoelectric conversion material having a high thermoelectric property, which has heretofore been impossible, with an excellent manufacturing yield. In particular, a large yield improvement in the processing process can bring about not only a production cost but also a material cost reduction. In addition, since the present manufacturing method can obtain a thermoelectric conversion material having excellent durability, a thermoelectric conversion element having a longer life and stable properties, which is desired for use in thermoelectric cooling, thermoelectric power generation, temperature sensors, etc. Very suitable for the production of Furthermore, it may be sufficiently applicable to the production of high-performance small elements, which has been extremely difficult until now. For example, a field requiring highly accurate temperature control in a minute space, that is, a laser for optical communication. Also in applications such as temperature control of a diode, it is possible to manufacture a small element that enables more precise temperature control as compared with a known sintered body element.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of durability of a thermoelectric conversion material manufactured by the present invention.

FIG. 2 is an explanatory diagram of durability of a thermoelectric conversion material manufactured by a conventional method without using the present invention.

Front page continuation (72) Inventor Hirotaka Senba 2-4 Daisaku, Sakura City, Chiba Prefecture Chichibu Onoda Central Research Institute, Inc.

Claims (6)

[Claims] 1. An alloy lump containing any two or more of Bi, Te, Se, and Sb, which are produced by solidifying through a melting process, or Bi, Te, which is produced by solidifying through a melting process. The main component is at least one of Se and Sb, and the remaining components are periodic groups 3A to 7A, 8 and 1
In an alloy lump containing at least two kinds of metals selected from the group B to 4B and 7B except for boron and carbon, crushing the alloy lump or a molded product cut out from the alloy lump. A method for producing a thermoelectric conversion material, which comprises performing uniaxial pressure sintering without performing. 2. The pressure for pressure sintering is about 3000 Kg / cm.
^{It is 2} or more, The manufacturing method of the thermoelectric conversion material of Claim 1 characterized by the above-mentioned. 3. The pressure sintering temperature is 300 ° C. or higher and 500 ° C.
It is the following, The manufacturing method of the thermoelectric conversion material of Claim 1 characterized by the following. 4. The method for producing a thermoelectric conversion material according to claim 1, wherein the pressure sintering atmosphere is composed of one or more gases selected from an inert gas and a nitrogen gas. . 5. The method for producing a thermoelectric conversion material according to claim 1, wherein the solidification is unidirectional solidification. 6. The method for producing a thermoelectric conversion material according to claim 1, wherein zone melting treatment is performed after solidification.