JPH03108781A - Manufacture of thermoelectric transducer - Google Patents

Abstract

PURPOSE:To acquire a variety of quality thermoelectric transducers at a low cost effectively and readily by mixing and grinding a metallic powder which contains at least bismuth and a metallic powder which contains at least tellurium and by controlling a grinding time when formation and sintering are carried out. CONSTITUTION:For example, a mixture whose starting raw material composition consists of (Bi2Se3)0.05(Sb2Te3)0.10(Bi3Te3)0.85 is introduced to a pod of an agate planetary ball mill together with SbI3. Ethanol is added as a medium and grinding and mixing are carried out in a condition of the number of revolutions of 600rpm for 20, 40, 60, 80, 100 hours, respectively. Each of acquired compositions having different grinding and mixing times is formed to a chip by single shaft press formation device, and sintered in a condition of argon air flow to form a sintered body. A grinding time is selected properly to acquire desired P-type or N-type characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a thermoelectric conversion element, and more specifically, the present invention relates to a method for manufacturing a thermoelectric conversion element, and more specifically, it relates to a method for manufacturing a thermoelectric conversion element. High-quality P-type, N-type, or P- The present invention relates to a method for manufacturing a thermoelectric conversion element, which has advantages such as being able to efficiently obtain an N-junction type element at low cost.

[Prior art and problems to be solved by the invention] In recent years, sintered bodies made of bismuth and tellurium (for example, those whose composition is Bi2Te:+ type or those with an excess of 81 or Te) or In addition to these, for example, sintered bodies of various compositions containing other metals or metalloids such as antimony and selenium [e.g. (Bi, Sb) 2(
Te, Se) 3 or compositions containing these as basic components] are being used as P-type, N-type, or PN junction type thermoelectric conversion elements.

As methods for controlling the P-type and N-type, two methods are known: (1) changing the composition (raw material composition) and (2) changing the sintering temperature.

The method 1. (2) is based on the general idea that basically only either P-type or N-type can be obtained with the same composition, and is widely used in the semiconductor field.

However, in method (2) above, in order to effectively control P and N, the raw material system is too complex, and the composition and purity of each must be precisely adjusted.
Moreover, it is generally difficult to sinter P-type and N-type simultaneously;
There are problems such as the need to manufacture the -N junction element secondarily.

On the other hand, the method (2) has the advantage that either P-type or N-type elements can be obtained from the same raw material composition. For example, when a B i 2Te type 3 composition is sintered at 300 to 450°C, it becomes N type, and 5
It is known that when sintered at 00°C or higher, it becomes P-type (in this case, it becomes P-type at 300°C or lower, but the P-type strength is weak and is not practical).

However, in this method (2), extremely high temperatures are required to obtain a practical device with controlled P and N (P-type in the example), and high-pressure sintering equipment is required. ,
It is economically disadvantageous because the energy and equipment costs are large, and the process is complicated depending on the P type and N type because the sintering temperature must be set to significantly different temperatures for each of the P type and N type. There are problems such as: Moreover, in this method (2), not only in the above example but generally, P type and N type cannot be obtained by simultaneous sintering.

Therefore, to obtain a P-N junction element, one has to rely on secondary processing, which increases the cost and further complicates the process. Furthermore, in the method (■) above, P
, N control is determined by the sintering temperature, so the sintering temperature cannot be changed freely, and as a result, it is difficult to freely control other properties such as the strength of the obtained sintered body by the sintering temperature. Become.

As described above, the conventional method for manufacturing bismuth-tellurium thermoelectric conversion elements has various serious problems as described above.

The present invention has been made in view of the above circumstances.

The purpose of the present invention is to solve the above-mentioned problems, to easily control P and N from raw materials of the same composition and purity without changing the sintering temperature, and to unify the raw materials. It is also possible to obtain high-quality P-type and N-type devices separately or by simultaneous sintering, and furthermore, it is also possible to manufacture PN junction devices primarily by simultaneous integral sintering. It is an object of the present invention to provide a method for manufacturing a thermoelectric conversion element which is extremely advantageous in practice and has various advantages such as being able to efficiently obtain various types of these elements through a simple process.

[Means for Solving the Problems] The present invention for solving the problems described above provides a method for manufacturing a thermoelectric conversion element containing bismuth and tellurium, in which a metal powder containing at least bismuth and a metal powder containing at least tellurium are used. This method of manufacturing a thermoelectric conversion element is characterized in that the grinding time is controlled during mixing and pulverizing powder, molding, and sintering.

In the present invention, metal powder containing at least bismuth and metal powder containing at least tellurium are used as raw materials. The metals used as the metal powder include bismuth and tellurium, or one or more other metals in addition to these. As other metals, various metals or semimetals can be used, and specific examples include antimony and selenium.

These metals are usually used as single metals, but they may also be used in advance as a mixture or composition of two or more of them, bismuth-based and tellurium-based.

The purity of the various metals used as the metal powder is
As a single metal, it is usually desirable to make it 98% or more.

The shape of the metal powder to be subjected to the pulverization is preferably particulate, and the particle size of the metal powder is not particularly limited as long as it can be sufficiently pulverized and mixed, but usually 100 mesh passes, preferably 150 mesh passes. It belongs to Metsuyupass. It is preferable that the metal powder having a large particle size is adjusted in advance to the above particle size range by means such as pulverization.

Furthermore, it is desirable to add an appropriate amount of dopani to the metal powder. As this dopant, conventionally used dopants can be added according to the usual method, but for example, if the thermoelectric conversion element is made into N type by the usual method (7), SbI:+ , Cu
Te, Cu2S, CuI, CuBr, AgBr, etc. can be used, and if the thermoelectric conversion element is made into P type according to the usual method, Te, Cd, Sb, P
b, As, Ei, etc. can be used. The amount of this dopant added cannot be determined unconditionally depending on the type of metal powder, the mixing ratio, the type of dopant material, etc., but it is usually 0.01N10 mol%,
The content is preferably 0.05 to 5 mol%.

In the method of the present invention, each of the metal powders is mixed and pulverized in a predetermined ratio to form a composition, and this composition is molded and sintered to form a thermoelectric conversion element itself or a thermoelectric conversion element. A P-type or N-type sintered body (an element or its element material) as a material for an element is manufactured.

For example, if antimony and/or selenium are used in addition to bismuth and tellurium, an example of a particularly preferable metal composition is as follows: The composition containing the proportions expressed, or the following formula (Bio
9osbo, to)2 (Teo95Seo, o5)
Examples include a composition containing powder of a simple metal at a ratio expressed by 3.

Note that, if necessary, additives other than the above-mentioned metal components can also be blended in appropriate amounts. For example, in addition to the metal, a halide, preferably an iodide, of the metal used, such as SbI3, is used as a dopant, for example, 2.
It is blended in a proportion of 0% by weight or less, preferably about 0.1 to 1.0% by weight.

For example, 0% SbI3 is added to the mixture of metal powders in the proportion represented by (Bio25sbo75)2Te3 as shown in the previous example.
．． The composition added at a ratio of 33% by weight, or the above-mentioned (Bio9osbo, to)2(Teo95Se)
o, o5) Sb in a mixture of metal powders in the proportions expressed
Particularly preferred raw material compositions include compositions in which 0.25% by weight of I3 is added.

Even if the mixing of the metal powder is performed in advance prior to pulverization,
It may be carried out at the same time as the pulverization, but in any case, the pulverization is carried out so that the raw metal powder is well mixed.

There are no particular restrictions on the pulverizer used for this mixing and pulverization, as long as it is a pulverizer mixer that can simultaneously and sufficiently perform pulverization and mixing, and usually a high-speed ball mill type pulverizer such as a planetary ball mill is used. etc. can be suitably used.

Such pulverization and mixing using a high-speed ball mill can be performed under various conditions.

For example, 100 μm of metal powder with an average particle size of about 3 to 100 μm
When using about 0 g, the following examples can be given as conditions under which it can be used suitably.

That is, in a planetary ball mill having an agate pot with an inner diameter of about 70 mm and a depth of about 100 mm, for example, metal powder of a predetermined composition, an additive such as SbI3, and ethanol as a solvent are added at a rate of 0.5 per gram of metal powder.
ml, and use these as poles with a diameter of 10mm.
About 20 pieces with a diameter of about 3mm and 10 pieces with a diameter of about 3mm
The contents are pulverized using about 0 pieces, for example, at a rotation speed of about 600 rpm, for a pulverization time (i.e., pulverization and mixing time) selected from a time range of usually 5 to 200 hours, preferably 10 to 100 hours. An example of a suitable method is a method of mixing.

One of the important points in the method of the present invention is that the sintered body (thermoelectric conversion element) obtained by adjusting the grinding time (pulverization mixing time) from raw materials of the same composition is not limited to the specific example described in "-0". or thermoelectric conversion element material) P type,
The point is that N-type control is performed.

The grinding time (grinding and mixing time) to control this P type or N type depends on other factors such as the composition of the raw materials used, the particle size of the metal powder, the type of mixing grinder, and other grinding conditions. Therefore, it cannot be specified uniformly. Also, depending on the difference in the grinding time (pulverization mixing time), it may become P type,
Alternatively, the reason why the particles become N-type is not clear at present, although it is thought that there are differences in the particle size of the pulverized particles obtained by pulverization, differences in interaction between the particles of the pulverized particles, etc.

Therefore, the pulverization time (pulverization mixing time) may be appropriately selected so as to obtain the desired P-type or N-type characteristics. However, as a guideline, the average particle size after mixing and pulverization should be controlled to be larger or smaller than the standard of 1 to 2 ml.

The composition (P-type precursor and/or N-type precursor) obtained by adjusting the pulverization time (pulverization mixing time) as described above is molded into a desired shape and structure by a conventional method such as press molding. Form into.

There are no particular restrictions on this molding method, and it can be performed using various molding devices under various conditions and methods, but usually, it is press-formed using a uniaxial press molding machine commonly used in this field. Press molding is performed at a pressure of about 0.5 to 5 ton/cm2. Furthermore, it can be further processed into various complex structures as required.

During this press molding or molding process, the P-type composition and N-type composition obtained by adjusting the grinding time are used to mold the P-type composition alone and the N-type composition alone. Or, for example, P as illustrated in FIG.
P-N junction element l in which mold part 2 and N-type part 3 are integrally molded
It may be formed into a P-N junction type molded product having a structure obtained by simultaneous sintering. For example, as illustrated in FIG. 2, an indirect type P-N where a P-type part 2 and an N-type part 3 are indirectly joined via a conductor such as copper or a conductive material 4 such as a semiconductor is also available. The joining element 1' may be molded into an indirect PN junction type molding having a structure obtained by simultaneous sintering, or may be molded into a molding having any other desired shape and structure.

The various molded products obtained as described above are sintered,
A sintered body (element or element material) having the predetermined shape and structure is obtained.

The sintering temperature and sintering time cannot be unconditionally defined because they vary depending on other conditions such as the composition of the raw materials, but are usually 300 to 600°C, preferably 400 to 520°C.
It is appropriate to carry out the sintering within the temperature range of °C for usually 0.5 hours or more, preferably 0.5 to 30 hours (for example, about 10 hours).

If the sintering temperature is too low, the P-type or N-type strength may become insufficient, or the sintered body may not have sufficient strength. On the other hand, if the sintering temperature is too high, the strength of the P-type or N-type may decrease, or the energy cost may increase, which may be disadvantageous.

There are no particular restrictions on the atmosphere during the sintering, but it is usually preferable to carry out the sintering in an inert (gas) atmosphere such as argon or nitrogen or in an inert gas stream.

There is no particular restriction on the pressure at which the sintering is performed, and for example, the sintering can be suitably carried out under normal pressure such as atmospheric pressure.

In the following manner, P-type and N-type thermoelectric conversion elements can be sintered separately or simultaneously. In any case, P-type and N-type products can be sintered using the same furnace and under the same temperature and other conditions.
The process can be significantly simplified, especially for P-type and N-type
The process can be made simpler if the mold is obtained by co-sintering.

The P-type and N-type elements thus obtained can be processed into a P-N junction type according to a conventional method, if necessary.

However, in the method of the present invention, P 4 type and N type can be obtained by simultaneous sintering as described above.
As described above, by sintering the P-N bonding molded product as it is, for example, the P-N bonding type shown in FIGS.
P-N junction type elements or element materials of various shapes and configurations such as junction type elements can be directly obtained. By employing this method, the manufacturing process of the PN junction element can be further simplified significantly.

Note that the various elements or element materials obtained in this way can be made into desired products as they are or by further processing as necessary.

Further, according to the method of the present invention, the various devices described above can be manufactured using the same raw material composition.

Therefore, the raw materials (composition and purity) can be standardized, and there is no need to separately set and adjust the raw material system for P-type and N-type, which greatly simplifies the process of setting and adjusting the raw material system. can do.

With the simplification of the manufacturing process and the raw material system mentioned above, the manufacturing cost can be significantly reduced.

The P-type, N-type, and P-N junction type devices obtained in the following manner can be suitably used in various fields of use, such as electric/electronic component electronic cooling devices, etc. .

[Examples] Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Examples 1 to 5) Starting material composition is (Bi 2se3) o, o 5(S
b2Te3)o, to(Bi3Te3)o85, and weigh each elemental metal (150 menshu buff) so that the total amount is 100g, and combine them with
It was introduced into the bod of a planetary ball mill (inner diameter 70 mm, depth 100 mm, made of agate) together with Hoshi no 5b13 to give a concentration of 0.25% by weight, and 0.5 ml of ethanol was used as a medium.
20 poles with a diameter of 10 mm and 100 balls with a diameter of 3 mm, the rotation speed was 60 Or.
The mixture was pulverized and mixed for 20, 40, 60 and 6 80, 100 hours under the conditions of pm.

The obtained compositions with different pulverization and mixing times were -
Press pressure 2.9tOn/Cff by axial press molding machine
3. under 12 conditions. OX3. It was molded into a chip of OX 1.5 mm.

The obtained molded product was sintered for 10 hours under the conditions of 460°C, 1 atmospheric pressure, and argon flow (2.0 degrees/m1n) to obtain a sintered body.

The Seebeck coefficient of each of the obtained sintered bodies was evaluated.

These results are shown in Table 1 along with the average particle diameter of the particles after pulverization and mixing and the pulverization and mixing time.

Table 1 Average particle size during pulverization Type Seebeck distance/hr Diameter/gm Coefficient ()LV/K) Example 1 20 2.4 P type 300 Example 2 40 2. OP type 230 Example 3 60
1.4 P type 5° Example 4801. IN
Type -215 Example 5 100 0.9 N type -280
Reference Example* -1 --N Type -220*Melted and Mixed [Effects of the Invention] As detailed above, according to the present invention, the following effects can be achieved.

(2) P and N control can be easily performed by adjusting the grinding time, which is a simple operation with low energy cost, even without changing the sintering temperature, based on the composition and purity of the raw material.

■Since P-type and N5 can be obtained simultaneously or separately in the same sintering furnace under the same temperature and other conditions, the process and equipment can be significantly simplified, especially P-type and N-type. By adopting a method of obtaining by simultaneous sintering, the manufacturing process can be further simplified and process efficiency can be significantly improved.

■P-N junction type elements can be obtained directly by simultaneous sintering without relying on secondary processing as in the past.
By adopting this method, the manufacturing process can be significantly simplified and the process efficiency can be greatly improved.

Furthermore, modularization becomes possible.

(2) Since raw material systems of the same composition and purity can be used for P-type and N-type, the setting and adjustment process of the raw material systems is significantly simplified, and high-quality devices can be easily manufactured.

■Since the sintering temperature does not need to be extremely high, energy costs and equipment costs can be significantly reduced.

Due to the above points, etc., according to the present invention, high quality P type, N type
Provides a method for manufacturing % electric conversion elements that is extremely advantageous in practice and has various advantages such as being able to manufacture various type and P-N junction type thermoelectric conversion elements efficiently and easily at low cost. can do.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the structure of a PN junction element obtained by the method of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the structure of an indirect PN junction element obtained by the method of the present invention. 1...φF'-N junction element, 1"...Indirect type P-N junction element, 2...P type part, 3...N type part, 4...
・Conductive material. 0

Claims (2)

[Claims] (1) In a method for manufacturing a thermoelectric conversion element containing bismuth and tellurium, the grinding time is required when mixing and grinding, molding, and sintering a metal powder containing at least bismuth and a metal powder containing at least tellurium. 1. A method for manufacturing a thermoelectric conversion element, characterized by controlling. (2) In a method for manufacturing a thermoelectric conversion element containing bismuth and tellurium, a metal powder containing at least bismuth, a metal powder containing at least tellurium, and a dopant are mixed, pulverized, and pulverized during molding and sintering. A method for manufacturing a thermoelectric conversion element characterized by controlling time.