JP3136657B2 - Thermoelectric element manufacturing method - Google Patents

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 element.

[0002]

2. Description of the Related Art A thermoelectric element is an element for converting thermal energy into electric energy. As shown in FIG. 5, a p-type semiconductor 1 and an n-type semiconductor 2 are joined in a U-shape, and a p-type The n-junction 3 is exposed to high temperature to generate power.

[0003] Various semiconductor materials have been developed as shown in Table 1, and in the production thereof, these powders are generally formed by sintering under pressure.

[0004]

[Table 1]

[0005]

By the way, in the thermoelectric element, the pn junction 3
(Small cross section) is required. However, when the thickness is reduced, a concentrated load is applied to the pn junction 3, and the strength becomes severe.

In view of the above circumstances, the present invention has been made in order to provide a method for manufacturing a thermoelectric element having a strong pn junction.

As a prior art to be compared with the present invention,
There is a "method of manufacturing a thermoelectric element" (Japanese Patent Publication No. 54-41315). However, in this method, a green compact in which a p-type or n-type compound powder is mixed is simply pressure-sintered to form a pn junction. Therefore, it is considered that there is a problem in reliability such as strength.

Further, "Electrothermal conversion element" (JP-A-2-106)
No. 079) discloses a method of forming a coating layer made of a material constituting a semiconductor around particles made of a low thermal conductive material by plating or fusion and sintering the coating layer. Special process is required, and the manufacturing process may be complicated.

Further, "Thermoelectric conversion element and its manufacturing method"
(Japanese Patent Application Laid-Open No. 61-203687) discloses a method in which a semiconductor thin film is laminated on both sides of a heat-resistant insulating thin plate, sandwiched between sintered plates of semiconductor powder, and joined by thermal diffusion. Since several sintering and film forming steps are required, it is inevitable that the steps become complicated and costly.

[0010] The present invention has been made on the assumption that there is no such concern in the conventional proposal.

[0011]

According to the present invention, when manufacturing a thermoelectric element in which a p-type semiconductor and an n-type semiconductor are appropriately joined, a substance having low conductivity among components of both semiconductors is used as a core particle, After forming capsule particles using a substance having high conductivity as coating particles, the powder of the capsule particles is subjected to plasma sintering to form a pn junction.

[0012]

According to the above-mentioned method, since the components of the pn junction are common to the p-type semiconductor and the n-type semiconductor, the sintering reaction is promoted and the particles are uniformly dispersed.

[0013]

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

FIGS. 1 and 2 show a first embodiment of a method of manufacturing a thermoelectric element according to the present invention, in which FeSi ₂ is used as a p-type semiconductor 11 and Co as an n-type semiconductor 12.
This is a case where Si is used.

First, among the components of the semiconductors 11 and 12, Fe was selected as a substance having low conductivity (high electric resistance), and Co was selected as a substance having high conductivity (low electric resistance), as shown in FIG. Thus, the capsule particles 1 in which the Fe particles 13 are the core particles 14 and the Co particles 15 are the coating particles 16
7 is manufactured. In this manufacturing process, the diameter of the Fe particles 13 is about 40 μm, and the diameter of the Co particles 15 is about 1 μm, and the Co particles 15 are attached to the Fe particles 13. This adhering force is based on a known van der Waals force. The Fe particles 13 thus surrounded by the Co particles 15
Is placed in a container (not shown) equipped with a rotary blade of 2,000 to 7,000 rpm, and is centrifugally rolled for 1 to 5 minutes to give an impact force by an air current. Due to this impact action, the attached Co particles 15 are firmly adhered to the surface of the Fe particles 13, and desired capsule particles 17 are obtained.

Next, the main body portions 18 and 19 of the thermoelectric element are sintered with FeSi ₂ and CoSi powders, respectively. Then, a green compact having the shape of the pn junction 20 with the powder of the capsule particles 17 is inserted between the sintered bodies, and set in a sintering apparatus (not shown) for performing a plasma sintering method. And plasma sintering. This process includes FeSi ₂ powder, capsule powder,
The CoSi powder may be sequentially packed in a predetermined form and simultaneously plasma integrally sintered.

Thus, the pn junction 20 becomes the capsule particle 1
7, a thermoelectric element formed by sintering is obtained.
Since the component 0 is common to the main body portions 18 and 19, the sintering reaction is promoted and the interface strength is increased. Since plasma sintering is performed in a state where the Fe particles 13 and the Co particles 15 are uniformly dispersed, a strong sintered product can be obtained.
Further, since the highly conductive Co particles 15 were used as the coated particles,
Electrons easily flow, and a high-performance thermoelectric element can be obtained.

In this embodiment, the capsule particles 17 are
e particles 13 and Co particles 15 were used.
The coating particles may be Si particles. If you do this,
The bonding surface of the pn junction is Si, and the S
Since it always comes into contact with the i component, the bonding strength is further improved.

Alternatively, the pn junction 20 may be formed by using both the capsule particles of the combination of Fe / Co and Fe / Si described above.

Next, a second embodiment of the present invention will be described with reference to FIG. In this manufacturing method, the high thermal conductivity and high electric conductivity ceramic particles 31 are provided on the pn junction 20 composed of the capsule particles 17 of the first embodiment, and the low thermal conductivity is provided on the lower end portions 32 of the main body portions 18 and 19. Electrically conductive ceramic particles 33
Are mixed and added, and sintering is performed.

The background of the second embodiment is as follows. In the thermoelectric element, the high temperature side p
The −n junction 20 needs to be as hot as possible (high heat sensitivity), and the lower end 32 on the low temperature side needs to be as low temperature as possible (low heat sensitivity). That is, it is desirable that the temperature gradient is large. According to the second embodiment, a strong temperature gradient can be obtained with the strong pn junction 20. When the ceramic particles 31 and 33 are added, they may be added at a constant concentration or mixed with an appropriate concentration gradient. The high heat conductive high electric conductive ceramic particles 31 include TiB ₂ and ZrB ₂ , and the low heat conductive high electric conductive ceramic particles 33 include ZnC, SiC, Zr
O _2, and the like.

Next, a third embodiment of the present invention will be described with reference to FIG. This manufacturing method uses capsule particles also in the main body shown in the first embodiment. That is, when forming the main body 41 of the p-type semiconductor, Fe
Capsule particles are produced in the same manner as in the first embodiment, in which the particles are core particles and the Si particles having a smaller diameter are coated particles, and this powder is formed into a predetermined shape and plasma-sintered. At this time, the molar ratio of these Fe particles and Si particles was 1: 2
And keep it. The chemical reaction accompanying this sintering produces FeSi _{2 as a} semiconductor compound. Also, the main body 4 of the n-type semiconductor
2 was formed by sintering capsule particles using Co particles as core particles and the same moles of Si particles as coated particles,
Get. Then, a compact of Fe / Co or Fe / Si capsule particles to be the pn junction 20 is inserted between these sintered bodies and plasma sintered to manufacture a thermoelectric element.

According to the third embodiment, the main body 41,
Since the Fe particles, Si particles, and Co particles, which are the 42 component particles, are uniformly dispersed, electron mobility and heat conduction characteristics are stabilized in the cross-sectional direction and the longitudinal direction. In addition, in the combination of the core particles and the coated particles, by using a material having a small electric resistance or a material having a low thermal conductivity as the coated particles, it is possible to form a passage for electrons or to reduce scattering of electrons due to lattice vibration. That is, it is possible to obtain a thermoelectric element in which electrons flow more easily and a temperature gradient is larger than before, and the thermoelectric characteristics can be improved.

In the above embodiment, the case where FeSi ₂ is used as the material of the p-type semiconductor and CoSi is used as the n-type semiconductor has been described. However, the present invention is not limited to this. Applicable in any other combination. The combination of the core particles and the coating particles of the capsule particles at the pn junction can be selected as described in the table.

[0025]

[Table 2]

[0026]

In summary, according to the present invention, the following excellent effects are exhibited.

Among the components of the p-type semiconductor and the n-type semiconductor, capsule particles are formed by using a substance having low conductivity as core particles and a substance having high conductivity as coating particles. Since the joint is formed, the sintering reaction is promoted, and the component particles are uniformly dispersed, so that a thermoelectric element having a strong pn junction can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a capsule particle for explaining a first embodiment of a method for manufacturing a thermoelectric element according to the present invention.

FIG. 2 is a side view of a thermoelectric device including a pn junction manufactured by the capsule particles of FIG. 1;

FIG. 3 is a side view of a thermoelectric element for explaining a second embodiment of the present invention.

FIG. 4 is a side view of a thermoelectric element for explaining a third embodiment of the present invention.

FIG. 5 is a side view showing a conventional thermoelectric element.

[Explanation of symbols]

 Reference Signs List 11 p-type semiconductor 12 n-type semiconductor 14 core particle 16 coated particle 17 capsule particle 20 pn junction

Continuation of the front page (56) References JP-A-50-115077 (JP, A) JP-A-2-27779 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 35 / 32 G01K 7/02

Claims (1)

(57) [Claims] When manufacturing a thermoelectric element in which a p-type semiconductor and an n-type semiconductor are appropriately joined, a substance having a low conductivity among the components of the two semiconductors is used as a core particle, and a substance having a high conductivity is used as a coating particle. A method for manufacturing a thermoelectric element, comprising forming capsule particles by forming a pn junction by plasma sintering the powder of the capsule particles.