JPH08178758A - Thermoelectric material and production thereof - Google Patents

Abstract

PURPOSE: To produce a lightweight thermoelectric material having high conductivity suitable for environmental protection by composing the thermoelectric material of a composite of a quasicrystal of aluminum based alloy and a good electric conductor of aluminum having fcc structure. CONSTITUTION: A p-type thermoelectric material 3 and an n-type thermoelectric material 4, sandwiched by a pair of ceramic plates 1 are composed of a composite of a quasicrystal of a lightweight aluminum(Al) based alloy having specific gravity of 2.5-3.5 g/cm and a good electric conductor of Al or the like having fcc structure. The thermoelectric material 3, 4 having such structure is light in weight, causes no contamination of environment, excellent in the figure of merit because the quasicrystal of Al group is contained, and exhibits high conductivity because a good electric conductor is contained. Since the quasicrystal and the electric good conductor are made of similar material when Al of fcc structure is employed as the good electric conductor, bonding strength is enhanced at the interface thus enhancing the strength of the thermoelectric material 3, 4. The electric good conductor may be made of Ag, Au, Cu, etc., in addition to Al of fcc structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is lightweight utilizing the thermoelectric properties of quasicrystals and the electrical conductivity of aluminum.
The present invention relates to a thermoelectric material such as a thermoelectric element suitable for environmental protection and a method for manufacturing the same.

[0002]

2. Description of the Related Art A typical Peltier effect element (thermoelectric element) suitable for use at room temperature has a composition mainly containing Bi, Sb, Te or Se.

FIG. 1 is a schematic view showing a thermoelectric element module. P-type thermoelectric material 3 between a pair of ceramic plates 1
And n-type thermoelectric material 4 are sandwiched between them, and electrodes 2 are provided between the ceramic plate 1 and the p-type thermoelectric material 3 and the n-type thermoelectric material 4, respectively.

The p-type and n-type thermoelectric materials 3 and 4 are B
The material is mainly composed of i, Sb, Te or Se.

[0005]

However, since these conventional thermoelectric materials are toxic elements such as Bi, Sb, Te and Se, they have a drawback that they are likely to have a bad influence on the environment. Also, these thermoelectric materials have a specific gravity of 6.7 g.
Since it is / cm ³ , it also has the drawback of being heavy. Further, these conventional thermoelectric materials also have a problem of low electrical conductivity.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a thermoelectric material which is lightweight and has high electrical conductivity, and which is suitable for environmental protection, and a method for manufacturing the same.

[0007]

The thermoelectric material according to the present invention is characterized by comprising a composite of a quasicrystal of an aluminum-based alloy and a good electrical conductor. This good electrical conductor is f
There is a cc structure of aluminum.

In the method for producing a thermoelectric material according to the present invention, an aluminum-based alloy is rapidly cooled by a liquid quenching method or a gas atomizing method to obtain a ribbon, flakes or powder, which is directly or heat-treated to be a quasicrystalline phase. After that, it is characterized in that it is mixed with a good electric conductor and solidified by hot pressing or extrusion.

[0009]

In the present invention, the specific gravity is 2.5 to 3.5 g /
Since a composite of a quasi-crystal made of an aluminum-based alloy, which is light in cm ^3, and a good electric conductor made of aluminum or the like having an fcc structure is used as a thermoelectric material, it is lightweight and
Suitable for environmental protection. Further, since this thermoelectric material contains aluminum-based quasicrystals, the figure of merit is excellent. Furthermore, since it also contains a good electrical conductor, it has high conductivity.

When aluminum having an fcc structure is used as the good electrical conductor, the quasicrystal and the good electrical conductor are materials of the same system, so that the interface between the two becomes strong and the strength of the thermoelectric material becomes high.

[0011]

EXAMPLES Next, the thermoelectric material of the present invention will be described in more detail. Examples of good electric conductors include Ag, Au, Cu, and the like, in addition to aluminum having an fcc structure. this house,
Considering the strength of the thermoconductive material, it is preferable to use Al. From the viewpoint of conductivity, Au or Ag is preferable, but in order to satisfy both high conductivity and low cost, A or Ag is preferable.
g is preferred.

The following are examples of aluminum-based quasicrystals. (1) Al _100-x Mn _x (20 ≦ x ≦ 23 atomic%) (2) Al _100-x Cr _x (14 ≦ x ≦ 16 atomic%) (3) Al _100-x V _x (16 ≦ x ≦) 18 atom%) (4) Al _100-x Mo _x (8 ≦ x12 atom%) (5) Al ₇₄ Mn ₂₀ Si ₆ (6) Al ₇₂ Mn ₂₀ Si ₈ (7) Al ₅₅ Mn ₂₅ Si ₂₀ (8) Al ₇₅ Cu ₁₅ V ₁₀ (9) Al ₇₅ Fe ₁₅ Ni ₁₀ (10) Al ₇₀ Ni ₁₅ Co ₁₅ (11) Al ₆₅ Cu ₂₀ Fe ₁₅ (12) Al ₆₅ Cu ₂₀ Ru ₁₅ (13) Al ₆₅ Cu ₂₀ Os ₁₅ (14) Al ₆₅ Cu ₂₀ Cr ₁₅ (15) Al ₆₅ Cu ₂₀ Mn ₁₅ (16) Al ₇₀ Pd ₂₀ Mn ₁₀ (17) Al ₇₀ Pd ₂₀ Re ₁₀ (18) Al ₇₅ Pd ₁₅ Fe ₁₀ (19) Al ₇₅ Pd ₁₅ Ru ₁₀ (20) Al ₇₅ Pd ₁₅ Os _{10 (21) Al 75} Cu ₁₅ Co ₂₀ (22) Al ₅₆ Li ₃₃ Cu ₁₁ (23) Al ₆₀ Li ₃₀ Cu ₁₀ (24) Al ₆₀ Li ₃₀ Au ₁₀ (25) Al ₅₀ Mg ₄₀ Cu ₁₀ (26) Al ₅₂ Mg ₁₈ Pd ₃₀ (27) Al ₄₃ Mg ₄₃ Pd ₁₄ (28) Al ₅₃ Mn ₂₀ Si ₂₇ (29) Al ₅₀ Mg ₃₅ Ag ₁₅ (30) Al ₅₀ Mg ₂₅ Li ₂₅ (31) Al ₇₃ Pd ₂₀ Mn ₇

The proportion of aluminum-based quasicrystals in the thermoelectric material is preferably 50 to 95% by volume. This is because from the viewpoint of strength of the thermoelectric material, it is preferable that the proportion of the aluminum reference crystal is 50% by volume or more.
Further, if the proportion of the quasicrystal exceeds 95% by volume, the strength of the module becomes insufficient due to embrittlement, so the proportion of the quasicrystal is preferably 95% by volume or less.

Quasicrystals of these aluminum-based alloys (1) to (32) can be obtained by a liquid quenching method. The quasi-crystals of aluminum-based alloys (8), (26), (28) were made into an amorphous phase by the liquid quenching method, and then 650 to 820K
A quasicrystal can be obtained by performing a heat treatment for 60 to 600 seconds.

Further, the aluminum base alloys (9) to (22) are
A quasicrystal can be formed by a cooling method such as water cooling, oil cooling, or furnace cooling without quenching by the liquid quenching method.

This quasi-crystalline phase is a thin ribbon,
It can be obtained by obtaining thick pieces or powder, or by further heat treating it. Further, a gas atomizing method can be applied instead of the liquid quenching method.
Then, the quasi-crystalline phase is solidified and molded by a pot press, an extrusion method, or the like to obtain a thermoelectric material.

Next, the method for producing the quasi-crystalline phase made of this aluminum-based alloy will be specifically described. FIG. 2 is a diagram for explaining the liquid quenching method. A quartz nozzle 1 is arranged above a copper roller 2, and a molten aluminum-based alloy 3 is stored in the quartz nozzle 1.

Then, from the lower end 5 of the quartz nozzle 1 to the molten metal 3
Is supplied onto the copper roller 2, and the copper roller 2 is rotationally driven in the direction of the arrow, the molten metal 3 is rapidly cooled by the copper roller 2, and the ribbon 4 is obtained.

FIG. 3 is a diagram showing the gas atomizing method.
Molten metal is stored in a crucible 11 for holding molten metal.
A trickle stream 14 of molten metal flows out from the center of the lower wall of 1. The spray nozzle 13 is provided on the lower surface of the crucible 11.
Are arranged, and the molten metal trickle 1 is discharged from the spray nozzle 13.
High-pressure gas is sprayed toward No. 4.

In this gas atomizing method, the molten metal fine stream 14 is rapidly cooled and pulverized at the pulverization point 15 to which the high pressure gas 2 is sprayed. The powdered aluminum-based alloy is cooled in the process of falling from the powdering point 15.

The quenched ribbon 4 obtained according to FIG. 2 or the powder obtained according to FIG.
It is crushed, classified, and then solidified and molded.

This solidification molding can be performed by a pressing method or an extrusion method. For example, the solidification molding conditions by pressing are as follows: press pressure P, press temperature P:
Process for more than a minute.

300 kgf / cm ² ≦ P ≦ 8000 kgf / cm ² room temperature ≦ T ≦ 450 ° C. On the other hand, in the case of solidification molding by an extrusion method, the extrusion temperature T is set to the following conditions. That is, in extrusion, the extrusion temperature is set to room temperature or higher, for example, 450 ° C. (723 K) or lower.
The extrusion ratio is, for example, 5 to 20.

It is preferable to preheat before the extrusion step. The preheating conditions are, for example, 240 seconds in the case of an oil bath of 573K or less and 900 seconds in the case of an electric furnace of 573 to 725K.

The extrusion ratio is 5 to 20. This extrusion ratio is a measure of the degree of deformation of the material during extrusion processing, and the extrusion ratio is the cross-sectional area at the beginning of the material, A,
The cross-sectional area after extrusion is represented by A / a. The extrusion ratio may be evaluated by the cross-sectional reduction rate. Also,
The extrusion ratios 5 to 20 are those when the die half angle is 30 ° and the extrusion speed (ram speed) is 5 mm / sec.

The extruded billet has the structure shown in FIG.
That is, the container 20 is made of aluminum or copper having an outer diameter of 23 mm and an inner diameter of 20 mm, and 5 g of each powder is added to the container 20 by cold pressing at a pressure of 250 MPa, a total of 20 to 25 g of powder 21 being about 78%. Packed at a filling rate of
After the spacers 22 are arranged, a vacuum of 1 × 10 ⁻³ Pa is applied for about 21.6 ks, and then Ar gas is substituted.
After that, the plug 23 is arranged, and the gap between the plug 23 and the inner surface of the container 20 is sealed by the epoxy or ceramic adhesive 24. In this way, an extruded billet is obtained.

FIG. 5 is a diagram showing an outline of the impact molding method.
The spar ring 3 is attached to one end of the cylindrical holder 31.
A container 33 is installed with the opening of the container 33 facing the other end of the holder 31, the powder 34 is stored in the container 33, and the plug 35 encloses the powder 34. Then, a propulsion body 37 is ejected from the impact gun toward the plug 35, and the flyer 36 fixed to the propulsion body 37 is caused to collide with the plug 35 at a predetermined speed. The impact pressure is 20 to 200 GPa, and the impact force causes the powder 34 to be instantaneously solidified and molded.

The solidified aluminum-based alloy is cut into a predetermined shape and then modularized.

The figure of merit Z of the thermoelectric material is represented by Z = α ² σ / κ. Here, α is thermoelectromotive force, σ is electrical conductivity, and κ is thermal conductivity. In this example, since the quasicrystal is included, the thermoelectromotive force is 20 to 5 unlike the ordinary crystal material.
It increases to 0 times and the thermoelectromotive force κ decreases to 1/50 to 1/100. Moreover, the Al phase improves the conductivity σ, and as a result the performance index Z is improved.

Next, the results of actually producing thermoelectric materials according to the examples of the present invention and examining the characteristics thereof will be described in comparison with comparative examples. This thermoelectric material is represented by the general formula Al _X Q _Y , and in the following Tables 1 and 2, the composition column shows the composition of Q. Further, the composition of this thermoelectric material was shown by the amount X (% by weight) of Al. Therefore, the amount Y of Q (% by weight) is 1
00-X. However, all measurement temperatures are room temperature. The properties of these thermoelectric materials are shown in Table 1 (Examples of the present invention) and Table 2 (Comparative Examples) below. Also, | α | is the absolute value of the thermoelectromotive force α, ρ is the specific resistance, and Z is the figure of merit.

[0031]

[Table 1]

[0032]

[0033]

[Table 2]

[0034]

From the comparison of these Tables 1 and 2, the thermoelectric materials according to the examples of the present invention have a high figure of merit, whereas the thermoelectric materials of the comparative examples have a low figure of merit.

Next, the thermoelectromotive force, the specific resistance and the figure of merit of the Ag _X Q _Y based thermoelectric material are shown in Table 3 (Examples) and Table 4 (Comparative Examples) below.

[0037]

[Table 3]

[0038]

[0039]

[Table 4]

[0040]

From the comparison of these Tables 3 and 4, the thermoelectric materials according to the examples of the present invention have a high figure of merit, whereas the thermoelectric materials of the comparative examples have a low figure of merit.

[0042]

As described above, the present invention is a thermoelectric material composed of a composite of a quasicrystal of an aluminum-based alloy and a good electrical conductor, and therefore has the excellent effects of being lightweight and having high conductivity. Play. Further, these constituent elements have an advantage that they do not pollute the environment.

[Brief description of drawings]

[0043]

FIG. 1 is a schematic view showing an example of a thermoelectric element.

[0044]

FIG. 2 is a schematic diagram illustrating a liquid quenching method.

[0045]

FIG. 3 is a schematic diagram illustrating a gas atomizing method.

[0046]

FIG. 4 is a diagram illustrating a method for manufacturing an extrusion billet.

[0047]

FIG. 5 is a diagram illustrating an impact molding method.

[0048]

[Explanation of symbols]

1: ceramic plate, 2: electrode, 3: p-type thermoelectric material, 4:
n-type thermoelectric material, 5: quartz nozzle, 6: copper roll, 7:
Molten metal, 8: ribbon, 11: crucible for holding molten metal, 12: high-pressure gas, 13: spray nozzle, 14: narrow stream of molten metal, 15: powdering point, 16: powder, 20: container, 21: powder, 22: Spacer, 23: Plug, 24: Adhesive, 31: Holder, 3
2: sparring ring, 33: container, 34: powder, 35: plug, 36: flyer, 37: propellant

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 35/20 // H01B 1/02 B

Claims (3)

[Claims] 1. A thermoelectric material comprising a composite of a quasi-crystal of an aluminum-based alloy and a good electric conductor. 2. The thermoelectric material according to claim 1, wherein the good electrical conductor is aluminum having an fcc structure. 3. An aluminum-based alloy is rapidly cooled by a liquid quenching method or a gas atomizing method to obtain a ribbon, flakes or powder, which is directly or heat-treated to obtain a quasicrystalline phase, and then mixed with a good electrical conductor to be hot. A method for producing a thermoelectric material, which comprises solidifying by pressing or extrusion.