JP2002185052A - Method of manufacturing thermoelectric semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the uniform material of the thermoelectric semiconductor in a bismuth-tellurium base with a large orientation degree. SOLUTION: This method of manufacturing a thermoelectric semiconductor 11 should include a process for fusing a bismuth-tellurium-based raw material, a process for cooling the fused raw material for obtaining an alloy, a process for grinding the alloy, a process for pressing the ground alloy by hot press for forming the thermoelectric semiconductor made of a thin plate, and a process for overlapping a plurality of thermoelectric semiconductors 1 for repressing by hot press from a vertical direction to the thin-plate surface of the thermoelectric semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermoelectric semiconductor such as a semiconductor laser module for optical communication, a semiconductor amplifier module, an external modulator module and a receiving module.

[0002]

2. Description of the Related Art As this kind of prior art, Japanese Patent No. 284 is disclosed.
No. 7123. This technology relates to a method for producing a thermoelectric material containing two or three elements selected from the group consisting of bismuth, tellurium, and selenium and antimony as main components and adding additives to these elements. A method for producing a thermoelectric material, comprising sintering an alloy powder obtained by dissolving and pulverizing the elements and additives to a hot press density ratio of 97% or more.

In order to improve the mass productivity of the bismuth-tellurium-based thermoelectric material, a zone melting method (a method in which a raw material or an alloy is put in an ampule and sealed, and a part of the alloy is melted by a heater from the outside of the ampule and unidirectionally solidified). Hot press is proposed as a new method that can be used instead of the method of producing materials.

[0004]

[Problems to be solved by the invention] However, Bi2Te3
Proceeding of the Physical
As shown in Society Vol.78, p838-844 (1961), the crystal flows in a direction parallel to the (0,0,15) plane, and in a direction perpendicular to the (0,0,15) plane. The electric conductivity differs by 1.4 times for the P-type and 3 times for the N-type when a current is passed through the P-type.

[0005] Therefore, as compared with the unidirectionally solidified material having the same composition, the performance index of the above-mentioned hot press material of the prior art is clearly reduced due to the decrease in the degree of crystal orientation. Furthermore, since the degree of orientation is the largest on the punch surface (hot pressing surface) and becomes smaller at the center of the material, the higher the height of the bulk produced by hot pressing, the more the dispersion of the figure of merit within the bulk increases. To increase.

There has been a problem that cutting out a thermoelectric semiconductor made of such a material as a chip is a primary cause of performance variations.

The present invention has solved the above-mentioned problems, and the orientation degree when hot pressing in the prior art is the largest on the punch surface and decreases from the punch surface to the center of the material.
In order to solve the problem of thermoelectric semiconductors, in which the minimum degree of orientation becomes smaller in inverse proportion to the thickness of the material, a thin plate of, for example, 3 mm or less is produced by hot pressing, and they are stacked and hot-pressed again. An object of the present invention is to provide a method of manufacturing a thermoelectric semiconductor capable of obtaining a uniform material having a large degree.

[0008]

Means for Solving the Problems In order to solve the above-mentioned technical problem, the invention of claim 1 is to provide a plurality of thin plate-like thermoelectric semiconductors obtained by hot pressing by pressing again by hot pressing. This is a method for manufacturing a thermoelectric semiconductor.

According to the first aspect of the present invention, a uniform material having a high degree of orientation can be obtained.

[0010] In order to solve the above technical problems, the invention of claim 2 comprises a step of melting a bismuth-tellurium-based raw material, a step of cooling the molten raw material to obtain an alloy, Pulverizing, pressing the pulverized alloy by hot pressing to form a thermoelectric semiconductor composed of a thin plate, stacking a plurality of the thermoelectric semiconductors, and again from a direction perpendicular to the thin plate surface of the thermoelectric semiconductor. And a pressing step by a hot press.

According to the second aspect of the present invention, a uniform material of a thermoelectric semiconductor having a large degree of orientation of a bismuth-tellurium system can be obtained.

According to a third aspect of the present invention, there is provided a thermoelectric semiconductor according to the first or second aspect, wherein the thickness of the thermoelectric semiconductor formed of the thin plate is 3 mm or less. This is a method for manufacturing a semiconductor.

According to the third aspect of the present invention, in addition to the effects of the first and second aspects, there is an effect that a uniform thermoelectric semiconductor having a higher degree of orientation can be obtained.

According to a fourth aspect of the present invention, there is provided a thermoelectric semiconductor according to the third aspect, wherein the thickness of the thermoelectric semiconductor is 0.5 to 3 mm. It is a manufacturing method of.

According to the invention of claim 4, in addition to the effect of claim 3, there is an effect that a uniform thermoelectric semiconductor having a higher degree of orientation can be obtained. If the thickness is less than 0.5 mm, when hot pressing is performed, chipping appears in the thermoelectric semiconductor and sintering is difficult. If it is larger than 3 mm, the degree of orientation of the whole sintered body is reduced.

According to a fifth aspect of the present invention, there is provided a thermoelectric semiconductor according to the first or second aspect, wherein the thermoelectric semiconductor comprising a plurality of thin plates is stacked. It is a manufacturing method of.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Bismuth, tellurium, selenium purity 99.9
Raw materials of 99% or more are mixed at a predetermined ratio, SbI ₃ (antimony triiodide) is added, and the mixture is put in a quartz tube and sealed at a vacuum of 10 ⁻³ Pa.

The quartz tube was melt-stirred at 800 ° C. for 1 hour.
After stirring, the furnace is cooled to obtain an alloy. The temperature of 800 ° C
The degree is Bi₂(Te_1-xSe_x)₃The maximum melting point of
Bi ₂Se₃At 100 ° C at 700 ° C
Specified.

The alloy was pulverized by a cutter mill or the like, bismuth placed only below the powder 90 micron die by a sieve, tellurium, at a temperature of 480 ° C. of melting point 590 ° C. vicinity of selenium, a pressure of 300~500kg / cm ³ Press. 300
If less than kg / cm ³ , the density of the sintered body will be low,
If it is larger than / cm ³ , the strength of a die such as a die or a punch will be insufficient.

By performing hot pressing using upper and lower punches, a thin plate-shaped sintered body 1 having a diameter of 20 mm and a height of 1 mm is obtained. The thermoelectric semiconductor 1 made of the thin plate-shaped sintered body has a state in which the surface and the inside of the thin plate are crushed by the upper and lower punches and the crystal is crushed, and the degree of crystal orientation is high.

The thermoelectric semiconductor 1 made of the thin plate-like sintered body
As shown in FIG. 1, 20 dies are stacked on the lower punch 3B of the punch 3 and a plurality of dies 2 on which a plurality of thermoelectric semiconductors 1 can be mounted.
Insert

The thermoelectric semiconductor 1 placed on the lower punch 3B is hot-pressed at 480 ° C. and 400 kg / cm ³ by the upper punch 3A. In this case, the thermoelectric semiconductor 1 which is a sintered body is pressed again by a hot press from a direction perpendicular to the thin plate surface 1A. Therefore, the pressed thermoelectric semiconductor 10 made of a thin plate having a height of 20 mm is in a state of being compressed to a height of about 19.2 to 3 mm.

Further, a rectangular body of 2 mm × 2 mm × 13 mm cut out from the vicinity of the thermoelectric semiconductor 11 slightly lowered from the upper surface, the inside, and the vicinity slightly raised from the lower surface, was taken out, and the obtained thermoelectric semiconductor sample was obtained. Degree of orientation for S,
The Seebeck coefficient, electrical conductivity, and thermal conductivity were measured, and the following equation (performance index) = (Seebeck coefficient) ² × (electric conductivity)
When the figure of merit is calculated from the following formulas, the thermoelectric semiconductor of the present invention obtained from the production method of the present invention from the following Examples 1 and 2 has a high degree of orientation, a high figure of merit, and a thermoelectric semiconductor. Suitable as a semiconductor.

The reason for this is that the thermoelectric semiconductor made of a thin plate-shaped sintered body has a high degree of orientation one by one, and is hot-pressed by superimposing them. This is because the degree of orientation is high even inside the thermoelectric semiconductor.

Example 1 Bismuth, tellurium and selenium
Bi materials with a purity of 99.999% or more_TwoTe_2.85Se _0.15
0.1% SbI_ThreeAnd put in a quartz tube
0^-3The tube was sealed at a vacuum of Pa.

This quartz tube was melted and stirred at 800 ° C. for 1 hour,
The furnace was cooled to obtain an alloy. The alloy is pulverized with a cutter mill, and only the powder having a size of 90 μm or less is sieved into a die.
Φ20m by hot pressing at 80 ℃, 400kg / cm ³
m, a thermoelectric semiconductor 1 made of a sintered body having a height of 1 mm was obtained.

As shown in FIG. 1, twenty thermoelectric semiconductors 1 made of this sintered body were stacked and hot pressed again under the same conditions to obtain a thermoelectric semiconductor 11 made of a sintered body having a diameter of 20 mm and a height of 20 mm. .

Further, a 2 mm × 2 mm × 13 mm rectangular body cut out from the vicinity of the thermoelectric semiconductor 10 slightly lowered from the upper surface, the inside, and the vicinity slightly raised from the lower surface, was taken out, and the obtained thermoelectric semiconductor sample was obtained. Degree of orientation for S,
The performance index of the Seebeck coefficient, the electric conductivity, and the thermal conductivity was calculated by the following equation.

(Performance index) = (Seebeck coefficient)^Two×
(Electrical conductivity) / (Thermal conductivity) <Example 2> Bismuth, tellurium, selenium purity 99.9
Bi over 99% of raw materials₂Sb_2.85Te _0.15Mix at the ratio of
0.1 wt% SbI₃, And put in a quartz tube.
^-3The tube was sealed at a vacuum of Pa.

The quartz tube was melted and stirred at 800 ° C. for 1 hour,
The furnace was cooled to obtain an alloy. The alloy is pulverized with a cutter mill, and only powder having a size of 90 μm or less is put into a die by a sieve.
Φ20m by hot pressing at 80 ℃, 400kg / cm3
A thermoelectric semiconductor made of a sintered body having a height of 1 mm and a height of 1 mm was obtained.

As shown in FIG. 1, 20 such sintered bodies were stacked, and were placed in an argon gas containing 20% hydrogen at 480 ° C.
Hot press at 400kg / cm3, φ20mm, height 2
A thermoelectric semiconductor 12 of 0 mm was obtained.

Further, in the same manner as in Example 1, a portion slightly lower than the upper surface portion of the thermoelectric semiconductor 12 made of this sintered body,
2 cut out from the inner, slightly raised from the lower part
A rectangular body of mm × 2 mm × 13 mm was taken out, and the performance index of the obtained thermoelectric semiconductor sample S was calculated for the degree of orientation, Seebeck coefficient, electric conductivity, and thermal conductivity according to the following equation.

<Comparative Example 1> Bi ₂ Te _2.85 Se _0.15 was used as a raw material having a purity of 99.999% or more of bismuth, tellurium, and selenium.
Of added SbI ₃ of 0.1 wt% were blended in a ratio, and sealed tube in a vacuum of 10-3Pa placed in a quartz tube. This quartz tube is 800
The mixture was melt-stirred at a temperature of 1 hour and cooled in a furnace to obtain an alloy.

The alloy is pulverized with a cutter mill, and only a powder having a size of 90 μm or less is put into a die by a sieve, and the powder is placed at 480 ° C.
Φ20mm, height 2 by hot pressing at 400kg / cm3
A thermoelectric semiconductor 1 made of a 0 mm sintered body was obtained.

Further, as in Examples 1 and 2, 2 mm × 2 mm × 13 cut out from the vicinity of the thermoelectric semiconductor 13 made of this sintered body, which is slightly lowered from the upper surface, the inside, and the vicinity which is slightly raised from the lower surface. mm was taken out, and for the obtained thermoelectric semiconductor sample S3, the degree of orientation, the Seebeck coefficient, the electric conductivity, and the thermal conductivity were calculated by the following formulas.

Table 1 shows the characteristic evaluation results of Examples 1 and 2 and Comparative Example 1. The numerical values of each Example and Comparative Example are those of the thermoelectric semiconductor 1.
The average value of three pieces, each of which is cut out from 1, 12, and 13, respectively, is shown.

[0038]

[Table 1] As can be seen from Table 1, in Example 1, the Seebeck coefficient and the electrical conductivity increased, and the figure of merit improved by 10%, as compared with the sintered body of Comparative Example 1 because the degree of orientation increased. Also,
In Example 2, although the degree of orientation was the same as in Comparative Example 2, it is considered that the performance was improved due to the decrease in the oxygen content. (Proceedings, ICT99, 18th International Confer
ence on Thermoelectrics (1999) p717-720) It is described in the above literature that the mobility of electrons decreases when oxygen is mixed. That is, it is considered that the reduction of hydrogen reduces the amount of mixed oxygen and improves the figure of merit.

[0039] This is derived from the formula of Zαm ^{* 3/2} μ _{/ k ph.} Where m is the effective mass, μ is the electron mobility, k
_ph is the lattice conductivity.

[0040]

As described above, the present invention relates to a method for manufacturing a thermoelectric semiconductor obtained by pressing a plurality of thin plate-like thermoelectric semiconductors obtained by hot pressing again by hot pressing. And a uniform material having a large value can be obtained.

More specifically, a step of melting a bismuth-tellurium raw material, a step of cooling the molten raw material to obtain an alloy, a step of pulverizing the alloy, and a step of hot-dipping the pulverized alloy Forming a thermoelectric semiconductor formed of a thin plate by pressing with a press, and pressing again by hot pressing from a direction perpendicular to the thin plate surface of the thermoelectric semiconductor by stacking a plurality of the thermoelectric semiconductors Therefore, a uniform material of a thermoelectric semiconductor having a high degree of orientation in a bismuth-tellurium system can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method for manufacturing a thermoelectric semiconductor according to the present invention.

FIG. 2 is a conceptual diagram of a thermoelectric semiconductor sample cut out from a thermoelectric semiconductor obtained by the manufacturing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermoelectric semiconductor of a thin plate shape 2 ... Dice 2A ... Die hole 3 ... Punch 3A ... Upper punch 3B ... Lower punch 12, 13 ... Thermoelectric semiconductor S1, S2, S3 ... Thermoelectric semiconductor sample

Claims (4)

[Claims] 1. A method for manufacturing a thermoelectric semiconductor obtained by pressing a plurality of thin plate-like thermoelectric semiconductors obtained by hot pressing again by hot pressing. 2. A step of melting a bismuth-tellurium raw material, a step of cooling the molten raw material to obtain an alloy, a step of pulverizing the alloy, and pressing the pulverized alloy by a hot press. And forming a plurality of thermoelectric semiconductors by laminating the thermoelectric semiconductors, and pressing the thermoelectric semiconductors again by hot pressing from a direction perpendicular to the thin plate surface of the thermoelectric semiconductors. Manufacturing method of thermoelectric semiconductor. 3. The thermoelectric semiconductor comprising the thin plate has a thickness of 3
3. The method for producing a thermoelectric semiconductor according to claim 1, wherein the diameter is not more than mm. 4. 4. The method for producing a thermoelectric semiconductor according to claim 3, wherein the thickness of the thermoelectric semiconductor formed of the thin plate is 0.5 to 3 mm.