JP2006237460A - Process for producing thermoelectric material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a thermoelectric material in which the figure of merit is enhanced by employing a thermoelectric material of ultrafine particles having single nano size thereby reducing thermal conductivity significantly. <P>SOLUTION: The process for producing a thermoelectric material comprises a step for forming a deposition film by simultaneous deposition method where the thermoelectric material and a polymer are heated simultaneously and deposited while performing vapor phase mixture, a step for collecting the thermoelectric material by removing the polymer from the deposition film, and a step for sintering the collected thermoelectric material wherein a thermoelectric material having an ultrafine crystal grain size can be produced by vapor phase mixture. Furthermore, the figure of merit can be enhanced because phonon thermal conductivity is reduced sharply by phonon dispersion when the thermoelectric material is sintered. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a thermoelectric material that converts heat into electricity.

In general, there are various thermoelectric materials such as PbTe, skutterudite, and perovskite, but Bi ₂ Te ₃ , Bi ₂ Se _3, and Sb ₂ Te ₃ are materials that exhibit the greatest ability near room temperature. Thermoelectric materials such as V-VI group, such as sensor elements, optical elements, semiconductor circuits such as LSI substrates, cooling of electronic equipment used in space stations, precise temperature control of laser diodes, etc. are required However, it is used.

For consumer use, it is used to cool hotel refrigerators and wine cellars, taking advantage of its low noise characteristics and low vibration. On the contrary, it is also used for thermoelectric power generation that generates electricity from heat, and the use of waste heat especially near room temperature does not surpass the Bi ₂ Te ₃ system. In addition, examples of a relatively large capacity near room temperature include strongly correlated thermoelectron-based NaCo ₂ O ₄ and half-Heusler-based thermoelectric materials, which are still not as good as those of Bi ₂ Te ₃ .

The Bi ₂ Te ₃ compound that exhibits the greatest ability near room temperature has a large anisotropy in physical properties with a layered structure containing 2 and 3 atoms of Bi and Te, respectively, in the unit cell of the rhombohedral crystal. . In this structure, there are three pairs of Te atom layers overlapping in the c-axis direction of hexagonal crystal display, and this Te-Te atom bond is a van der Waals bond, so it is a covalent bond, an ionic bond or a mixed bond thereof. It is significantly weaker than the bond between other bonded atoms and easily cleaves. Also, the electrical characteristics are high in a direction perpendicular to the c-axis direction (parallel to the c-plane).

  The figure of merit Z representing the characteristics of the thermoelectric material is represented by the product of the square of the Seebeck coefficient S and the electrical conductivity σ divided by the thermal conductivity κ, as shown in the following equation.

Z = S ² · σ / κ
Therefore, in order to increase the figure of merit Z, it is necessary to increase S ² · σ (the product of the square of the Seebeck coefficient S and the electrical conductivity σ) and decrease the thermal conductivity κ.

  The melted material produced by unidirectional solidification by the Bridgman method or the like that is generally used has a crystal orientation that is not as high as that of a single crystal material. Therefore, electrical conductivity is high. However, since the crystal grain size is very large, the effect of decreasing the thermal conductivity due to phonon scattering is small and the thermal conductivity is large. Moreover, since it is easy to cleave at c surface, material strength is very low.

  On the other hand, a sintered material produced by refining a thermoelectric material by mechanical alloying or gas atomization and unidirectionally pressing and sintering the fine crystal has excellent material strength and is perpendicular to the pressing direction ( It is known that c-planes are aligned in a (right angle) direction (see, for example, Patent Document 1).

  Further, the thermal conductivity can be reduced by phonon scattering at the grain boundaries of the fine particles. Simply put, the finer the particle size, the greater the phonon scattering effect, and the smaller the phonon thermal conductivity. Other methods for reducing the crystal grain size include a gas atomizing method and a super rapid cooling method (see, for example, Patent Document 2).

  Furthermore, these methods have a much lower crystal orientation of the sintered material than the Bridgman method, and the electrical conductivity is reduced, so that they are offset as a result and the figure of merit exceeds that of the unidirectional solidified material. Absent.

Therefore, as means for improving the crystal orientation of the fine crystal sintered body, there are methods by upset forging by hot plastic deformation and hot extrusion (for example, see Patent Document 3).
Japanese Patent Laid-Open No. 62-264682 JP 2002-26403 A JP-A-10-178218

  However, in the fine particle manufacturing methods of Patent Document 1 and Patent Document 2 described above, the average particle diameter of crystals is about 1 to 30 μm, the phonon scattering effect is not sufficient, and impurities are easily mixed.

  Further, when the hot plastic deformation described in Patent Document 3 is performed, the crystal orientation is improved, but in the process, the grain size of several μm grows to several tens of μm, so that the heat conduction is reduced by reducing the phonon scattering effect. However, there is a problem that the figure of merit decreases even if the crystal orientation is uniform.

  The object of the present invention is to remarkably improve the thermal conductivity reduction effect by making the thermoelectric material ultrafine, and also to keep the crystal grain size small even during hot plastic deformation. An object of the present invention is to provide a method for producing a thermoelectric material that improves crystal orientation while reducing conductivity and improves a figure of merit.

  In order to solve the above-mentioned conventional problems, the method for producing a thermoelectric material of the present invention is a method for producing a thermoelectric material, in which vapor deposition is performed while vapor-phase mixing is performed by simultaneously heating the thermoelectric material and a polymer. A vapor deposition process for producing a vapor deposition film by a method, a recovery process for recovering the thermoelectric material by removing the polymer from the vapor deposition film, and a sintering process for sintering the recovered thermoelectric material. It is what.

  Thus, a thermoelectric material having an ultrafine crystal grain size can be produced by gas phase mixing. Moreover, by sintering the thermoelectric material, phonon scattering is increased and phonon thermal conductivity is greatly reduced, so that the figure of merit can be improved.

  Furthermore, since the thermoelectric material is taken into the polymer, the opportunity for the thermoelectric material to come into contact with oxygen is drastically reduced until the polymer is removed. There is little change.

  The method for producing a thermoelectric material of the present invention is characterized in that the thermoelectric material is a single nanoparticle.

  In other words, with single nanoparticles of 10 nm or less, the grain boundary area is remarkably increased, the thermal conductivity is greatly reduced, the hardness is lowered by the reverse Hall Petch effect, and deformation due to grain boundary sliding is likely to occur, thereby improving workability. To do.

  Thereby, an ultrafine thermoelectric material can be produced, and a method for producing a thermoelectric material with greatly reduced thermal conductivity and improved thermoelectric performance can be provided.

  The method for producing a thermoelectric material of the present invention is a thermoelectric material having an ultrafine particle size of a single nano level by producing a thermoelectric material and a polymer by simultaneous evaporation method in which vapor deposition is performed by gas phase mixing and vapor deposition. The phonon scattering effect due to grain boundary scattering can be exhibited very effectively, the thermal conductivity can be greatly reduced, and the figure of merit can be improved. In addition, since it is taken into the polymer film during vapor deposition, contact with oxygen can be prevented, and by reducing the time for contact with oxygen as much as possible, oxidation of the thermoelectric material can be prevented and impurities can be mixed. There is little change in performance.

  In addition, since the thermoelectric material manufacturing method of the present invention is an ultrafine particle, when performing hot plastic deformation, even if the particle size increases due to grain growth, the particle size is sufficiently small, and the electric conduction due to improved orientation is achieved. The figure of merit is remarkably improved by the improvement of the rate and the effect of reducing the thermal conductivity by phonon scattering.

  The invention according to claim 1 is a vapor deposition process in which a vapor deposition film is formed by simultaneous evaporation method in which a thermoelectric material and a polymer are heated at the same time to perform vapor phase mixing, and the polymer is removed from the vapor deposition film. This is a method for producing a thermoelectric material comprising a recovery step of recovering the thermoelectric material and a sintering step of sintering the recovered thermoelectric material.

  By this method, a thermoelectric material having an ultrafine crystal grain size of less than 1 μm, which is difficult to obtain by other production methods, can be produced by gas phase mixing. By sintering the thermoelectric material, phonon scattering is large and phonon thermal conductivity is greatly reduced, so that the figure of merit can be improved.

  Further, according to such a method, since the thermoelectric material is taken into the polymer, the opportunity for the thermoelectric material to contact oxygen is drastically reduced until the polymer is removed. Little contamination and little change in performance.

  Further, the vapor deposition step is preferably performed in a vacuum, an inert gas, or a rare gas, and the thermoelectric material recovery step is preferably performed in a vacuum, an inert gas, or a rare gas.

  The sintering process is not particularly limited, such as a hot pressing method, a cold pressing method, an SPS sintering method, an HIP method, and a CIP method, and a plurality of sintering steps may be performed.

  The invention according to claim 2 is the one in which the thermoelectric material recovered in the recovery step is a single nanoparticle.

  As a result, in single nanoparticles of 10 nm or less, the grain interfacial area is remarkably increased, the thermal conductivity is greatly reduced, the hardness is lowered due to the reverse Hall Petch effect, and deformation due to grain boundary sliding is likely to occur. Will improve.

  The invention according to claim 3 is the one in which the polymer is a thermoplastic polymer, and the thermoplastic polymer can be easily deposited and dissolved in a solvent, so that the process can be simplified.

  Furthermore, the type of the polymer is not particularly limited, but a polymer having a lower molecular weight and a simple structure is easier to deposit, and for example, polyvinyl alcohol is suitable.

  According to a fourth aspect of the present invention, in the recovery step, the polymer is removed by dissolving the polymer with a solvent.

  In this way, since the polymer can be removed with high precision by washing well after dissolution, it is possible to eliminate the influence on the performance degradation of the thermoelectric material such that the polymer is deposited during sintering.

  The type of the solvent is not particularly limited, but a solvent that does not affect the thermoelectric material and dissolves the polymer quickly is preferable.

  The invention according to claim 5 maximizes the performance of the thermoelectric material near room temperature by using a thermoelectric material manufacturing method using a thermoelectric material containing at least two or more from the group consisting of bismuth, antimony, tellurium and selenium. The thermoelectric material with excellent cooling efficiency can be provided.

The invention according to claim 6 includes at least a deformation step in which the thermoelectric material is hot plastically deformed in the sintering step, and the Bi ₂ Te ₃ series thermoelectric material is anisotropic and external From the deformation process, the crystal orientation is improved and the thermoelectric performance can be improved.

  According to the seventh aspect of the invention, the hot plastic deformation is performed by hot rolling, and the crystal is stretched in the rolling direction by the rolling and the crystal is oriented to improve the thermoelectric performance.

  In the invention according to claim 8, the hot plastic deformation is performed by hot extrusion, and the crystal orientation is improved in the direction parallel to the extrusion direction by the extrusion, and the thermoelectric performance is improved.

  The invention according to claim 9 is the one in which the hot plastic deformation is performed by ECAE processing, and the hot plastic deformation is ECAE (Equal-Channel Angular Extraction) processing, whereby a strong shear stress is applied to the crystal. Since miniaturization occurs, the influence of grain growth due to hot working can be suppressed, and a high-performance thermoelectric material can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic diagram of a co-evaporation method according to Embodiment 1 of the present invention.

  In FIG. 1, a thermoelectric material 2 and a polymer 3 are placed in separate containers 2 a and 3 a in a chamber 1. The inside of the chamber 1 is replaced with a rare gas 4 and adjusted to a reduced pressure atmosphere. Each of the containers 2a and 3a is provided with a heater 5 for heating. By heating the thermoelectric material 2 and the polymer 3 with the heater 5, they are vaporized and mixed in a gas phase state, A vapor deposition film 6 is formed in the chamber 1.

  FIG. 2 is a schematic diagram of the deposited film in the first embodiment of the present invention.

  In FIG. 2, the vapor deposition film 6 is in a state where the thermoelectric material fine particles 8 are dispersed in the polymer vapor deposition film 7. Since the thermoelectric material fine particles 8 are mixed in the gas phase, very fine single nano-sized particles are formed.

  FIG. 3 is a schematic diagram showing a thermoelectric material microparticle recovery step in Embodiment 1 of the present invention.

  In FIG. 3, only the polymer vapor deposition film 7 is dissolved by immersing the vapor deposition film 6 in the solvent 10 filled in the container 9 as shown in FIG. As a result, the thermoelectric material fine particles 8 can be separated and recovered as shown in FIG.

  These steps are performed in the absence of oxygen such as a rare gas atmosphere, and the recovered thermoelectric material fine particles 8 are dried well.

  FIG. 4 is a schematic diagram showing a sintering process by spark plasma sintering in Embodiment 1 of the present invention.

  In FIG. 4, a pulse energization pressure sintering apparatus (discharge plasma sintering apparatus) 11 is a pair of upper and lower sides, each having an electrode 12 and a pressure cell 16. The thermoelectric material fine particles 8 recovered in the above-described recovery step are enclosed in a space 17 provided in the die 14 and punches 13 are provided on the upper and lower sides. The pressurization cell 16 can move up and down, and after filling the thermoelectric material fine particles 8, the pressurization cell 16 is moved in the opposite direction (up and down direction) as indicated by arrows A and B in the figure, and the thermoelectric material fine particles 8 are moved. A pulse current 15 is applied to the electrode 12 while pressurizing in a uniaxial direction (vertical direction in the figure) with a predetermined pressure. As a result, a pulse current also flows through the thermoelectric material fine particles 8. In this way, by applying the pulse current 15 to the thermoelectric material fine particles 8, Joule heat is generated inside the thermoelectric material fine particles 8, and heat is generated from the thermoelectric material fine particles 8 by the generation of the Joule heat.

  Then, after the temperature of the thermoelectric material fine particles 8 reaches a predetermined temperature, the temperature is maintained for a predetermined time, and the thermoelectric material is sintered.

  The thermoelectric material (sintered body) produced as described above can reduce thermal conductivity and improve thermoelectric performance.

  Example 1 to Example 3 show the performance evaluation results of the thermoelectric material sintered bodies produced by the above-described methods by changing the types of the thermoelectric material and polymer. As Comparative Example 1 and Comparative Example 2, a thermoelectric material produced by a mechanical alloying method and produced by a pulse current pressure sintering method was used.

Using (Bi ₂ Te ₃ ) ₂₀ (Sb ₂ Te ₃ ) ₈₀ as a thermoelectric material, a vapor deposition film 6 containing ultrafine particles was prepared by simultaneous vapor deposition with polyvinyl alcohol, and the polyvinyl alcohol was removed with acetone. At this time, the crystal grain size was about 5 to 10 nm. And when the thermoelectric performance of the sintered compact produced by 673K, 50MPa, and the pulse-current pressurization sintering method for 10 minutes was measured, Seebeck coefficient was 2.2 * 10 < ^-4 > [V / K], and electrical conductivity was. The thermal conductivity was 5.7 × 10 ⁴ [1 / Ω · m], the thermal conductivity was 0.87 [W / m · K], and the figure of merit was 3.17 × 10 ⁻³ [1 / K].

  This is considered that the thermal conductivity was reduced by phonon scattering.

Using (Bi ₂ Te ₃ ) ₂₅ (Sb ₂ Te ₃ ) ₇₅ as a thermoelectric material, a vapor deposition film 6 containing ultrafine particles was prepared by simultaneous vapor deposition with polystyrene, and the polystyrene was removed with toluene. At this time, the crystal grain size was about 8 to 15 nm. And when the thermoelectric performance of the sintered compact produced by the 673K, 50MPa, pulse current pressurization sintering method for 10 minutes was measured, Seebeck coefficient was 2.1 * 10 < ^-4 > [V / K], and electrical conductivity was 5. It was 5 × 10 ⁴ [1 / Ω · m], the thermal conductivity was 0.83 [W / m · K], and the figure of merit was 2.92 × 10 ⁻³ [1 / K].

  This is considered that the thermal conductivity was reduced by phonon scattering.

Using (Bi ₂ Te ₃ ) ₉₀ (Bi ₂ Se ₃ ) ₁₀ as a thermoelectric material, a vapor deposition film 6 containing ultrafine particles was prepared by simultaneous vapor deposition with polyvinyl alcohol, and the polyvinyl alcohol was removed with acetone. At this time, the crystal grain size was about 4 to 10 nm. And when the thermoelectric performance of the sintered compact produced by the 673K, 50MPa, 10 minutes pulse-current pressurization sintering method was measured, Seebeck coefficient was -2.3x10 < ^-4 > [V / K], and electrical conductivity was 3. ^{.5 × 10 4 [1 / Ω} · m], the thermal conductivity of 0.89 [W / m · K] , the performance index was ^{2.08 × 10 -3 [1 / K} ].

  This is considered that the thermal conductivity was reduced by phonon scattering.

(Embodiment 2)
FIG. 5 is a schematic diagram of hot rolling in Embodiment 2 of the present invention.

  In FIG. 5, the hot rolling process in the second embodiment is a process for obtaining a rolled body 21 using a die 18, a punch 19, and a green compact 20 of the thermoelectric material 8. FIG. 5A shows a state before hot rolling, and FIG. 5B shows a state after hot rolling.

  About the hot rolling process comprised as mentioned above, the operation | movement is demonstrated below.

  First, the thermoelectric material fine particles 8 obtained by the method shown in Embodiment 1 are put in a die 18 with the punch 19 sandwiched between the upper and lower sides, and the green compact 20 is produced and installed by pressurizing the punch 19.

  Then, after raising the temperature with a temperature raising device (not shown), the green compact 20 is rolled in a direction perpendicular to the pressing direction by pressing the punch 19 from above and below, and as a result, a rolled body 21 is obtained. It is done.

  The thermoelectric material (rolled body 21) produced as described above can reduce the thermal conductivity, improve the crystal orientation, and improve the thermoelectric performance.

  Example 4 shows the performance evaluation results of the thermoelectric material sintered body produced by the hot rolling process described above.

Using (Bi ₂ Te ₃ ) ₂₀ (Sb ₂ Te ₃ ) ₈₀ as a thermoelectric material, a vapor deposition film 6 containing ultrafine particles was prepared by simultaneous vapor deposition with polyvinyl alcohol, and the polyvinyl alcohol was removed with acetone. At this time, the crystal grain size was about 5 to 10 nm. When the thermoelectric performance of the sintered body produced by hot rolling was measured by heating at 673 K, the Seebeck coefficient was 1.9 × 10 ⁻⁴ [V / K], and the electrical conductivity was 8.6 × 10 ⁴ [1. / Ω · m], thermal conductivity was 0.93 [W / m · K], and the figure of merit was 3.34 × 10 ⁻³ [1 / K].

  This is considered that the thermal conductivity was reduced by phonon scattering and the orientation was improved.

(Embodiment 3)
FIG. 6 is a schematic diagram of hot extrusion processing in Embodiment 3 of the present invention.

  In FIG. 6, the hot rolling process according to the third embodiment includes a die 23 having a space 23 filled with a green compact 24 of thermoelectric material fine particles 8 and having an opening 26 having a smaller diameter than the space 23 on the bottom surface. 22 and a punch 25 that pressurizes the thermoelectric material fine particles 8 in the space 23, and a process of obtaining an extruded product 27 from the opening 26.

  6A shows a state before hot extrusion, and FIG. 6B shows a state after hot extrusion.

  Next, the hot extrusion processing operation in FIG. 6 will be described.

  First, the thermoelectric material fine particles 8 are pulverized and compressed in advance by a compacting device (not shown) to form a compact 24. Then, the green compact 24 is filled and installed in the space 23 of the mold 22.

  Then, the green compact 24 is heated and heated by a temperature raising device (not shown), and then the punch 25 is pressurized downward in the drawing.

  As a result, the green compact 24 is pressurized in the space 23 in the mold 22 and is discharged as an extruded product 27 from the opening 26 under the mold 22.

  The thermoelectric material (extruded product 27) produced as described above can reduce thermal conductivity, improve crystal orientation, and improve thermoelectric performance.

  Example 5 shows the performance evaluation results of the thermoelectric material sintered body (extruded product 27) produced by the hot extrusion process.

Using (Bi ₂ Te ₃ ) ₂₀ (Sb ₂ Te ₃ ) ₈₀ as a thermoelectric material, a vapor deposition film containing ultrafine particles was prepared by simultaneous vapor deposition with polyvinyl alcohol, and the polyvinyl alcohol was removed with acetone. At this time, the crystal grain size was about 5 to 10 nm. When the thermoelectric performance of the sintered body produced by hot extrusion was measured by heating at 673 K, the Seebeck coefficient was 1.9 × 10 ⁻⁴ [V / K], and the electrical conductivity was 9.3 × 10 ⁴ [1. / Ω · m], the thermal conductivity was 0.98 [W / m · K], and the figure of merit was 3.43 × 10 ⁻³ [1 / K].

  This is considered that the thermal conductivity was reduced by phonon scattering and the orientation was improved.

(Embodiment 4)
FIG. 7 is a schematic diagram of a process called ECAE (Equal-Channel Angular Extension) (hereinafter referred to as ECAE process) in Embodiment 4 of the present invention.

  In FIG. 7, the ECAE processing in the fourth embodiment is a mold having an entrance 29 a side and an exit 29 b at both ends, and a space 29 formed so that the directions of the entrance 29 a and the exit 29 b are different from each other by an angle θ. 28 and the punch 31 that pressurizes the green compact 30 of the thermoelectric material fine particles 8 filled in the space 29 to obtain the green compact 30 pressurized from the outlet 29b.

  Next, the ECAE processing operation in FIG. 7 will be described.

  First, the thermoelectric material fine particles 8 are pulverized and compressed in advance by a compacting device (not shown) to form a compact 24 in advance. Then, the green compact 30 is filled and installed in the space 29 of the mold 28.

  Then, the green compact 30 is heated and heated by a temperature raising device (not shown), and then the punch 31 is pressurized downward in the drawing.

  As a result, the green compact 30 is pressurized in the space 29 in the mold 28 and is pushed obliquely downward from the outlet 29 b of the mold 28. At the time of the extrusion, a very large shear stress is applied to the green compact 30, so that the green compact 30 is extruded while being miniaturized. Here, the orientation is further improved by making the hole diameter on the outlet 29b side smaller than the hole diameter on the inlet 29a side.

  The thermoelectric material (the green compact 30 discharged from the outlet 29b) manufactured as described above can reduce the thermal conductivity, improve the crystal orientation, and further improve the thermoelectric performance.

  Example 6 shows the performance evaluation results of the thermoelectric material sintered body (the green compact 30 discharged from the outlet 29b) produced by the hot extrusion process.

Using (Bi ₂ Te ₃ ) ₂₀ (Sb ₂ Te ₃ ) ₈₀ as a thermoelectric material, a vapor deposition film containing ultrafine particles was prepared by simultaneous vapor deposition with polyvinyl alcohol, and the polyvinyl alcohol was removed with acetone. At this time, the crystal grain size was about 5 to 10 nm. When the thermoelectric performance of the sintered body produced by ECAE processing was measured by heating at 673 K, the Seebeck coefficient was 1.9 × 10 ⁻⁴ [V / K], and the electrical conductivity was 9.0 × 10 ⁴ [1 / Ω. M], thermal conductivity was 0.91 [W / m · K], and the figure of merit was 3.57 × 10 ⁻³ [1 / K].

  This is considered that the thermal conductivity was reduced by phonon scattering and the orientation was improved.

  Next, the comparative example with respect to the gas adsorbent of this invention and a heat insulating body is shown. The evaluation method is a method according to each of the above examples.

(Comparative Example 1)
A sintered body was produced by a mechanical alloying method using (Bi ₂ Te ₃ ) ₂₀ (Sb ₂ Te ₃ ) ₈₀ as a thermoelectric material. At this time, the crystal grain size was about 2 to 30 μm.

And when the thermoelectric performance of the sintered compact produced by 673K, 50MPa, and the pulse-current pressurization sintering method for 10 minutes was measured, Seebeck coefficient was 2.2 * 10 < ^-4 > [V / K], and electrical conductivity was. The thermal conductivity was 5.9 × 10 ⁴ [1 / Ω · m], the thermal conductivity was 1.01 [W / m · K], and the figure of merit was 2.83 × 10 ⁻³ [1 / K].

(Comparative Example 2)
A sintered body was produced by a mechanical alloying method using (Bi ₂ Te ₃ ) ₉₀ (Bi ₂ Se ₃ ) ₁₀ as a thermoelectric material. At this time, the crystal grain size was about 2 to 28 μm.

Then, 673 K, 50 MPa, the Seebeck coefficient was measured the thermoelectric performance of the sintered body produced by the pulse current pressure sintering method 10 minutes ^{-2.1 × 10 -4 [V / K} ], the electrical conductivity It was 3.4 × 10 ⁴ [1 / Ω · m], the thermal conductivity was 1.09 [W / m · K], and the figure of merit was 1.38 × 10 ⁻³ [1 / K].

  As described above, the method for producing a thermoelectric material according to the present invention can reduce thermal conductivity by producing a thermoelectric material having an ultrafine single nano-size particle size, and has excellent thermoelectric performance. Thermoelectric materials can be manufactured, and can be applied to freezing refrigerators and refrigeration equipment, sensor devices, optical devices, semiconductor circuits such as LSI substrates, precision temperature control such as laser diodes, and thermoelectric power generation it can.

Schematic diagram of co-evaporation method in Embodiment 1 according to the method for producing a thermoelectric material of the present invention Schematic diagram of the deposited film in the first embodiment (A) Schematic diagram before separation of thermoelectric material particles in the recovery step of thermoelectric material particles in the first embodiment (b) Schematic diagram after separation of thermoelectric material particles in the recovery step Schematic diagram showing a sintering process by spark plasma sintering in the first embodiment (A) Schematic diagram showing the state before hot rolling in Embodiment 2 of the present invention (b) Schematic diagram showing the state after hot rolling (A) The schematic diagram which shows the state before the process of the hot extrusion process in Embodiment 3 of this invention (b) The schematic diagram which shows the state after the process of the same hot extrusion process Schematic diagram of ECAE processing in Embodiment 4 of the present invention

Explanation of symbols

1 Chamber 2 Thermoelectric Material 3 Polymer 4 Noble Gas 5 Heater 6 Vapor Deposition Film 7 Polymer Vapor Deposition Film 8 Thermoelectric Material Fine Particles 9 Container 10 Solvent 11 Discharge Plasma Sintering Device 12 Electrode 13 Punch 14 Dice 15 Pulse Current 16 Pressurized Cell 17 Space 18 Die 19 Punch 20 Compact 21 Rolled body 22 Mold 23 Space 24 Compact 25 Punch 26 Opening 27 Extrusion product 28 Mold 29 Space 30 Compact 31 Punch

Claims (9)

  A vapor deposition process for producing a vapor deposition film by a co-evaporation method in which vapor deposition is performed while gas phase mixing is performed by simultaneously heating a thermoelectric material and a polymer, and recovery for recovering the thermoelectric material by removing the polymer from the vapor deposition film. A method for producing a thermoelectric material comprising a step and a sintering step of sintering the recovered thermoelectric material.   The method for producing a thermoelectric material according to claim 1, wherein the thermoelectric material recovered in the recovery step is a single nanoparticle.   The method for producing a thermoelectric material according to claim 1, wherein the polymer is a thermoplastic polymer.   The method for producing a thermoelectric material according to any one of claims 1 to 3, wherein in the recovery step, the polymer is removed by dissolving the polymer with a solvent.   The method for producing a thermoelectric material according to any one of claims 1 to 4, wherein a thermoelectric material containing at least two from the group consisting of bismuth, antimony, tellurium, and selenium is used.   The method for producing a thermoelectric material according to claim 1, wherein the sintering step includes at least a deformation step in which the thermoelectric material is hot plastically deformed.   The method for producing a thermoelectric material according to claim 6, wherein the hot plastic deformation is performed by hot rolling.   The method for producing a thermoelectric material according to claim 6, wherein the hot plastic deformation is performed by hot extrusion.   The method for producing a thermoelectric material according to claim 6, wherein the hot plastic deformation is performed by ECAE processing.

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