JPH06342941A - Manufacture of thermoelectric generator element - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a novel thermoelectric generator in which shortening of a phase transition time is performed and which has an excellent mechanical strength. CONSTITUTION:The method for manufacturing a thermoelectric generator comprises the steps of forming capsule powder containing slave particles made of metal oxide such as CuO, etc., and adhered to peripheries of base particles made of p-type or n-type alpha-FeSi2 powder added with additive element such as Mn, Co, etc., collecting the capsule powder in a predetermined shape, and then carrying out plasma sintering.

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 generator used for a thermocouple or the like.

[0002]

2. Description of the Related Art As is well known, a thermoelectric generator is an element that converts thermoenergy into electric energy by utilizing thermoelectric effect or vice versa. Typical examples are thermocouples and electronic refrigeration elements (Peltier element). Element). This thermocouple uses the Seebeck effect in which two types of metal wires are connected to form a closed circuit, and when two contacts are kept at different temperatures, a thermoelectromotive force is generated between these contacts. On the other hand, the electronic refrigeration element utilizes the Peltier effect in which heat other than Joule heat is generated and absorbed at the contact surface when a current flows through the contact surface between different conductors and semiconductors. -20 ° C
It is often used when precise temperature control is required within the range of plus 70 ° C.

[0003] In addition, some standard combinations of this thermoelectric generator are determined by the JIS standard, and one of them is FeSi thermoelectric generator consisting of a combination of p-type iron silicide and n-type iron silicide. There is an element.

FIG. 4 shows an example of a method of manufacturing this FeSi thermoelectric generator. Briefly explaining this step by step, first, Mn and Co, which are additional elements, are added to Fe and Si, respectively, and these are separately melted at a temperature of 1873K to produce two kinds of ingots, and then a stamp mill. Etc. are separately pulverized and granulated by using, for example, to produce a p-type raw material powder and an n-type raw material powder. And
These raw material powders were put into a molding die, cold pressed, and then sintered at 1433K in a vacuum, and thereafter, this was α-FeSi.
To complete the phase transition from (metal phase) to β-FeSi (semiconductor phase) in the air, heat treatment is performed at 1063K, and the lead wire is brazed or soldered as necessary to complete the process.

[0005]

By the way, in the conventional method for manufacturing a thermoelectric generator as described above, α-FeSi is mixed with β
In addition to the time required for the heat treatment to cause phase transition to —FeSi, there are disadvantages that the current density and mechanical strength are low because there are sparse and dense parts due to the existence of voids between the sintered powders. .

Therefore, the present invention has been devised to effectively solve the above-mentioned problems, and its main purpose is to achieve shortening of the phase transition time and to have excellent mechanical strength. The present invention provides a novel method for manufacturing a thermoelectric generator.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method in which an additional element such as Mn or Co is added to surround a mother particle made of p-type or n-type α-FeSi ₂ powder. , CuO, and the like, to form capsule powder to which child particles made of a metal oxide are attached, and the capsule powder is aggregated in a predetermined shape and plasma-sintered.

[0008]

Since the present invention is the manufacturing method as described above,
It is possible to cause the phase transition at a lower temperature than when only the α-FeSi ₂ powder is subjected to the phase transition. That is, it is considered that oxygen of the metal oxide, which is a child particle, is bonded to carbon adsorbed on the mother particle made of α-FeSi _2, and the reaction heat at that time triggers to lower the phase transition temperature.

4CuO + C ⁺ → 2Cu ₂ O + CO _{2 Further} , when plasma powder is sintered and the capsule powders are aggregated and pressed, the child particles constituting the capsule powders function as a lubricant to fill the voids and density. Is increasing,
The encapsulation serves as a connection when the uniformly dispersed oxides are sintered and improves the mechanical strength. Further, the fluidity and the electrical conductivity of the powder become important when solidified by plasma sintering, and the capsule powder is also excellent in these respects. That is, α-FeSi ₂ used for the mother particles
Is a good conductor and it is easy to overdischarge only partly during electric sintering.
When the oxide, which is an insulator, is uniformly dispersed, the current density is also uniform.

[0010]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1 and Table 1, first, Mn and Co, which are additional elements, are added to Fe and Si, respectively, and these are separately melted at a temperature of 1873 K to prepare two types of ingots. , Using a stamp mill or ball mill, etc.
FeSi ₂ atomized powder having a particle size of about 150 μm was produced. Then, as shown in FIG. 2, this FeSi ₂ atomized powder was used as a mother particle 1, and C around the mother particle 1.
The child particles 2 made of uO and having a particle diameter of about 1 to 2 μm were encapsulated by a well-known technique such as an electrostatic adhesion method and a mechanical impact method to produce a p-type capsule powder and an n-type capsule powder 3. The mixing ratio of CuO in the capsule powder 3 is 2w.
It was set to t%. The melting point of the metal oxide is 50.
It is preferably 0 ° C. or higher and 1200 ° C. or lower and does not easily reduce in air. Further, a particle size of 5 μm or less is convenient for encapsulation.

Next, the thus-encapsulated raw material powder is placed in a mold of a plasma sintering apparatus and sintered at about 650 ° C. in a vacuum atmosphere to convert α-FeSi (metal phase) to β-FeSi. (Semiconductor phase).

As a result, it was confirmed that the CuO-encapsulated powder dislocations at about 715 ° C. This is because the normal non-encapsulated α-FeSi is 727 ° C,
The dislocation temperature will decrease by about 12 ° C. Further, it was confirmed that the density ratio was as high as 97% and the mechanical strength was improved.

Explaining the α → β phase transition, the α phase is a tetragonal metal, while the β phase is an orthorhombic intrinsic semiconductor. β-FeSi ₂ is formed by the encapsulation reaction of α-FeSi ₂ and FeSi ₂ , and this process is usually called a phase transition from α to β. The temperature at this time is called a dislocation temperature and is about 938 ° C. That is, on the higher temperature side than this temperature, it is more stable that Fe and Si have a tetragonal crystal structure, and on the contrary, on the lower temperature side, the orthorhombic crystal structure is lower in internal energy and more stable. From this, it is possible to obtain β-FeSi ₂ by heat-treating α-FeSi ₂ at a temperature lower than the dislocation temperature.

[0015]

[Table 1]

As described above, according to the present invention, the capsule powder in which the child particles made of the metal oxide such as CuO are adhered is formed around the mother particles made of the α-FeSi ₂ powder, and the capsule powder is After being assembled into a predetermined shape, plasma sintering is performed, so α-FeSi is converted to β-Fe.
The heat treatment is shortened to cause the phase transition to Si, and
It will be sintered to high density and mechanical strength will be improved.

[0017]

In summary, the present invention has the following excellent effects.

By encapsulating with a metal oxide, the sintering temperature can be arbitrarily controlled and the phase transition time can be shortened.

When solidified, the density increases and the mechanical strength also improves.

Appropriate electric resistance and fluidity will be exhibited during plasma sintering.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view showing a state in which capsule powders having child particles attached around mother particles are collected.

FIG. 3 is a process drawing showing an example of a conventional method for manufacturing a thermoelectric generator.

[Explanation of symbols]

 1 mother particle 2 child particle 3 capsule powder

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[Procedure amendment]

[Submission date] October 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Method for manufacturing thermoelectric generator

[Claims]

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 generator used for a thermocouple or the like.

[0002]

2. Description of the Related Art As is well known, a thermoelectric generator is an element that converts thermoenergy into electric energy by utilizing thermoelectric effect or vice versa. Typical examples are thermocouples and electronic refrigeration elements (Peltier element). Element). This thermocouple uses the Seebeck effect in which two types of metal wires are connected to form a closed circuit, and when two contacts are kept at different temperatures, a thermoelectromotive force is generated between these contacts. On the other hand, the electronic refrigeration element utilizes the Peltier effect in which heat other than Joule heat is generated and absorbed at the contact surface when a current flows through the contact surface between different conductors and semiconductors. -20 ° C
It is often used when precise temperature control is required within the range of plus 70 ° C.

[0003] In addition, some standard combinations of this thermoelectric generator are determined by the JIS standard, and one of them is FeSi thermoelectric generator consisting of a combination of p-type iron silicide and n-type iron silicide. There is an element.

FIG. 4 shows an example of a method of manufacturing this FeSi thermoelectric generator. Briefly explaining this step by step, first, Mn and Co, which are additional elements, are added to Fe and Si, respectively, and these are separately melted at a temperature of 1873K to produce two kinds of ingots, and then a stamp mill. Etc. are separately pulverized and granulated by using, for example, to produce a p-type raw material powder and an n-type raw material powder. And
These raw material powders were put into a molding die, cold pressed, and then sintered at 1433K in a vacuum, and thereafter, this was α-FeSi.
In order to complete the phase transition from (metal phase) to β-FeSi (semiconductor phase), heat treatment is performed at 1063K in the air, and brazing or soldering the lead wire as needed. Become.

[0005]

By the way, in the conventional method for manufacturing a thermoelectric generator as described above, α-FeSi is mixed with β
In addition to the heat treatment taking a long time to make a phase transition to —FeSi, there are densities due to the presence of voids between the sintered powders, which results in low current density and mechanical strength. .

Therefore, the present invention has been devised in order to effectively solve the above-mentioned problems, and its main purpose is to
It is intended to provide a novel method for manufacturing a thermoelectric generator having excellent mechanical strength while shortening the phase transition time.

[0007]

In order to achieve the above-mentioned object, the present invention provides a method in which an additional element such as Mn or Co is added to surround a mother particle made of p-type or n-type α-FeSi ₂ powder. , CuO, and the like, to form capsule powder to which child particles made of a metal oxide are attached, and the capsule powder is aggregated in a predetermined shape and plasma-sintered.

[0008]

Since the present invention is the manufacturing method as described above,
The phase transition can be performed at a lower temperature than the phase transition of only the α-FeSi ₂ powder. That is, it is considered that oxygen of the metal oxide, which is a child particle, is bonded to carbon adsorbed on the mother particle made of α-FeSi _2, and the reaction heat at that time triggers to lower the phase transition temperature.

4CuO + C ⁺ → 2Cu ₂ O + CO _{2 Further} , when plasma powder is sintered and the capsule powders are aggregated and pressed, the child particles constituting the capsule powders function as a lubricant to fill the voids and density. Is increasing,
The encapsulation serves as a connection when the uniformly dispersed oxides are sintered and improves the mechanical strength. Further, the fluidity and the electrical conductivity of the powder become important when solidified by plasma sintering, and the capsule powder is also excellent in these respects. That is, α-FeSi ₂ used for the mother particles
Is a good conductor and it is easy to overdischarge only partly during electric sintering.
When the oxide, which is an insulator, is uniformly dispersed, the current density is also uniform.

[0010]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0011] Figure 1 and Table 1, first of all, after dissolving them separately at a temperature of 1873K by adding Mn and Co are each added element Fe and Si, Gasua
FeS with a particle size of about 150 μm using a Tomize device
An i ₂ atomized powder was produced. In this atomized equipment
The manufacturing method is as follows.
After mixing additional elements such as Fe, Si and Mn, Co ,
This is melted at high frequency, and the melt is mixed with an inert gas such as Ar.
Those formed by mists cooled under. In addition, these processes
It is performed continuously with one device. Next , this FeSi
₂ Atomizing size powder stamp mill or ball mill
These were separately crushed and granulated by using. Then, as shown in FIG. 2, this FeSi ₂ atomized powder is used as a mother particle 1, and a child particle 2 made of CuO and having a particle size of about 1 to 2 μm is formed around the mother particle 1 by an electrostatic adhesion method,
The p-type capsule powder and the n-type capsule powder 3 were manufactured by encapsulating using a known technique such as a mechanical impact method. still,
The mixing ratio of CuO in this capsule powder 3 was set to 2 wt%. Further, the metal oxide preferably has a melting point of 500 ° C. or higher and 1200 ° C. or lower and is not easily reduced in air. Further, a particle size of 5 μm or less is convenient for encapsulation.

Next, the thus-encapsulated raw material powder is placed in a mold of a plasma sintering apparatus and sintered at about 650 ° C. in a vacuum atmosphere to convert α-FeSi (metal phase) to β-FeSi. was the phase transition to the (semiconductor phase).

[0013] As a result, powder encapsulated with CuO it was confirmed that transition at about 715 ° C.. This is because the normal non-encapsulated α-FeSi is 727 ° C,
The transition temperature will decrease by about 12 ° C. Further, it was confirmed that the density ratio was as high as 97% and the mechanical strength was improved.

Explaining the α → β phase transition , the α phase is a tetragonal metal, while the β phase is an orthorhombic intrinsic semiconductor. β-FeSi ₂ is formed by the encapsulation reaction of α-FeSi ₂ and FeSi ₂ , and this process is usually called the α → β phase transition . Also, and the temperature at this time and transition temperature is about 938 ° C.. That is, on the higher temperature side than this temperature, it is more stable that Fe and Si have a tetragonal crystal structure, and on the contrary, on the lower temperature side, the orthorhombic crystal structure is lower in internal energy and more stable. From this, it is possible to obtain β-FeSi ₂ by heat treating α-FeSi ₂ at a temperature lower than the transition temperature.

[0015]

[Table 1]

As described above, according to the present invention, the capsule powder in which the child particles made of the metal oxide such as CuO are adhered is formed around the mother particles made of the α-FeSi ₂ powder, and the capsule powder is After being assembled into a predetermined shape, plasma sintering is performed, so α-FeSi is converted to β-Fe.
In addition to shortening the heat treatment to cause a phase transition to Si,
It will be sintered to high density and mechanical strength will be improved.

[0017]

In summary, the present invention has the following excellent effects.

By encapsulating with a metal oxide, the sintering temperature can be arbitrarily controlled and the phase transition time can be shortened.

When solidified, the density increases and the mechanical strength also improves.

Appropriate electric resistance and fluidity will be exhibited during plasma sintering.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

FIG. 2 is a partially enlarged view showing a state in which capsule powders having child particles attached around mother particles are collected.

FIG. 3 is a process drawing showing an example of a conventional method for manufacturing a thermoelectric generator.

Process diagram showing a Gasuatoma size method using the invention, FIG
Is.

[Explanation of symbols] 1 mother particle 2 child particle 3 capsule powder

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

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[Figure 1]

[Procedure 3]

[Document name to be corrected] Drawing

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[Figure 4]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Matsumi 8 Tsutana, Fujisawa City Kanagawa Prefecture Isuzu Central Research Institute Co., Ltd. (72) Inventor Masayuki Kato 8th Shelf shelf Fujisawa City Kanagawa Prefecture Isuzu Central Research Co., Ltd. In-house (72) Eiji Okumura Eiji Okumura 8 Tsutana, Fujisawa-shi, Kanagawa Inside Isuzu Central Research Institute

Claims (1)

[Claims] 1. An additive element such as Mn or Co is added, and p
-Type or n-type α-FeSi ₂ powder is formed around a mother particle, and a capsule powder is formed by adhering child particles made of a metal oxide such as CuO, and the capsule powder is formed into a predetermined shape. A method of manufacturing a thermoelectric generator, comprising plasma-sintering after assembling.