KR102045716B1 - Electrode material for thermo electric module, thermo electric module including the same and methods for preparing the same - Google Patents

Abstract

The present invention comprises Ti and Cu, the Ti and Cu composition relates to an electrode material for a thermoelectric module according to the following formula 1. The electrode material for a thermoelectric module of the present invention exhibits excellent reliability by reducing the difference in coefficient of thermal expansion with the thermoelectric material. In addition, the electrode material and the scutterudite-based thermoelectric material are bonded by using a high-speed brazing process, thereby realizing an increased interfacial property, thereby improving power generation output performance.
[Equation 1]
xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

Description

Electrode material for thermoelectric module, thermoelectric module including same and manufacturing method thereof {ELECTRODE MATERIAL FOR THERMO ELECTRIC MODULE, THERMO ELECTRIC MODULE INCLUDING THE SAME AND METHODS FOR PREPARING THE SAME}

The present invention relates to an electrode material for a thermoelectric module, a thermoelectric module including the same and a manufacturing method thereof.

Thermoelectric conversion refers to the energy conversion between thermal energy and electrical energy. This is a reversible and direct energy conversion phenomenon of heat and electricity, which is caused by the movement of electrons and / or holes in the thermoelectric material.

Thermoelectric phenomena is a Peltier effect in which heat is dissipated or absorbed at a contact of a dissimilar material by a current applied from the outside to two dissimilar materials connected by a contact, and a dissimilar material connected between the two dissimilar materials connected by a contact. Seebeck effect of generating electromotive force from temperature difference and Thomson effect in which heat is released or absorbed when current flows through a material having a predetermined temperature gradient.

The thermoelectric phenomenon may convert heat generated from a computer, an automobile engine, or various industrial waste heat into electrical energy, and the Peltier effect may be used to implement various cooling systems without using a refrigerant. Recently, as interest in new energy development, waste energy recovery, and environmental protection increases, interest in thermoelectric power is also increasing.

The unit device for thermoelectric power generation is a thermoelectric module, and is generally manufactured in a symmetrical structure of an insulating substrate, an electrode, a thermoelectric material, an electrode, and an insulating substrate. In the case of the high-temperature thermoelectric power module used at a high temperature of 300 ° C. or higher, if the thermal expansion coefficient difference between the constituent materials is large, breakage due to thermal stress may occur. In addition, if a defect structure such as pores is formed at the interface between the thermoelectric material and the electrode, there is a problem that the performance of the thermoelectric power module may be reduced.

The present invention has been made to solve the above problems, to provide an electrode material having almost no difference between the thermoelectric material and the coefficient of thermal expansion and to provide a thermoelectric module and a method of manufacturing the same to maximize the driving reliability.

According to an aspect of the present invention, Ti and Cu, the Ti and Cu composition is provided according to the following formula 1 electrode material for a thermoelectric module.

[Equation 1]

xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

The thermal expansion coefficient of the electrode material may be 9.4 × 10 ^-6 / ℃ to 12.1 × 10 ^-6 / ℃.

According to another aspect of the present invention, the step of weighing and mixing Ti and Cu powder according to Equation 1; And it provides a method of manufacturing an electrode material for a thermoelectric module comprising the step of sintering the mixed powder.

[Equation 1]

xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

The diameter of the Ti and Cu powder may be 10 μm or less.

The sintering may be performed using the discharge plasma sintering method.

The sintering is carried out for 1 to 30 minutes at a vacuum condition of 1.0 × 10 ^-2 torr or less, and the pressure applied to the Ti and Cu powder may be performed at 10 to 60MPa conditions.

The sintering may be performed at a temperature rising rate of 10 to 300 ℃ / min.

According to another aspect of the invention, the upper substrate and the lower substrate to form a heat generation or endotherm; An electrode provided between the upper substrate and the lower substrate to guide the flow of the supplied power; And a plurality of P-type semiconductors and N-type semiconductors spaced apart from each other on one surface of the electrode, wherein the electrode includes Ti and Cu, and the Ti and Cu compositions are provided according to Equation 1 below. .

[Equation 1]

xTi (1-x) Cu (0.65 <x <0.85).

The P-type semiconductor and the N-type semiconductor may be a scrutherite-based semiconductor.

The P-type semiconductor is Fe _{3 . 4} Co _{0 . 6 12} Sb-based, Fe _{3 .4- x} Co _x Sb _{12 0 .6+-based,} and Fe _{3 0 .4+ x} Co _x Sb _{12 .6-} system may be at least one selected from.

Is the N-type semiconductor-based and Co ₄ Sb ₁₂ Co _{4 -} may be at least one selected from _{12-based x} Fe _x Sb.

According to another aspect of the invention, the electrode forming step of forming an upper electrode or a lower electrode on one surface of the upper substrate or lower substrate to form the upper / lower surface of the thermoelectric module; And a bonding step of bonding the P-type semiconductor and the N-type semiconductor to one surface of one of the upper electrode and the lower electrode, wherein the bonding step is performed by a brazing process.

The brazing process may be performed at 600 to 750 ° C.

The brazing process may be performed at a temperature rising rate of 20 ° C./min or more.

The brazing process may be performed for 1 to 30 minutes.

The brazing process may be performed using at least one bonding metal selected from Ag and Cu.

The electrode material for a thermoelectric module of the present invention exhibits excellent reliability by reducing the difference in coefficient of thermal expansion with the thermoelectric material.

In addition, the electrode material and the scutterudite-based thermoelectric material are bonded by using a high-speed brazing process, thereby realizing an increased interfacial property, thereby improving power generation output performance.

FIG. 1 is a scanning electron microscope (SEM) image of a bonding surface of a scutterrudite-based thermoelectric material and a Ti-Cu composite electrode material manufactured according to an embodiment of the present invention.
2 is a result of measuring the power generation output of a thermoelectric module manufactured according to an embodiment of the present invention.
3 is a change evaluation result of the power output density measured for 1000 hours in a temperature difference 400 ℃ condition using a thermoelectric module manufactured according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to an electrode material for a thermoelectric module, a thermoelectric module including the same and a manufacturing method thereof.

According to an aspect of the present invention, Ti and Cu, the Ti and Cu composition is provided according to the following formula 1 electrode material for a thermoelectric module.

[Equation 1]

xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

The inventors of the present invention, while developing a high-temperature thermoelectric power module using a scurterite-based thermoelectric material, when the composition ratio of the composite of Ti and Cu is controlled as in Equation 1, a thermal expansion coefficient similar to that of the scutterite-based thermoelectric material is realized. When applied as an electrode material, it was found that even with a temperature difference of 400 or more, it was possible to manufacture a highly reliable module that does not destroy the interface between the thermoelectric material and the electrode, thereby completing the present invention.

Accordingly, the thermal expansion coefficient of the electrode material may be 9.4 × 10 ^-6 / ℃ to 12.1 × 10 ^-6 / ℃, preferably 9.8 × 10 ^-6 / ℃ to 11.3 × 10 ^-6 / ℃. . The thermal expansion coefficient of the Co ₄ Sb ₁₂ alloy, which is an N-type scrutherite-based thermoelectric material, is in the range of about 10.1 × 10 ⁻⁶ / ° C. to 11.5 × 10 ⁻⁶ / ° C., and Fe _{3 . 4} Co _{0 .} The thermal expansion coefficient of the ₆ Sb ₁₂ based alloy has a value in the range of about 9.8 × 10 ⁻⁶ / ° C. to 11.3 × 10 ⁻⁶ / ° C.

However, since the coefficient of thermal expansion of Cu is about 17 × 10 ⁻⁶ / ° C., the difference in coefficient of thermal expansion is about 40% when Cu is used as an electrode, and thus it is impossible to maintain a stable interface at high temperature. Therefore, through the preparation of a composite with a relatively small thermal expansion coefficient Ti (thermal expansion coefficient of about 8.6 × 10 ^-6 / ℃) it is possible to implement a thermal expansion coefficient of 9.8 ~ 11.5 × 10 ^-6 / ℃ of the scutterite-based thermoelectric material.

As described above, the electrode material according to the present invention is very small compared to other electrode materials having different thermal expansion coefficients from that of the skudrudite-based thermoelectric material used as a semiconductor in the thermoelectric module, so that the interface between the thermoelectric material and the electrode is separated even at a high temperature. There is an advantage that there is no such problem.

Hereinafter, a method of manufacturing an electrode material for a thermoelectric module according to the present invention will be described.

According to another aspect of the invention, the step of weighing and mixing Ti and Cu powder according to the following formula 1; And it provides a method of manufacturing an electrode material for a thermoelectric module comprising the step of sintering the mixed powder.

[Equation 1]

xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

Since the diameters of the Ti and Cu powders are directly related to the properties of the composite, the diameter of the powder is selected in consideration of the density and thermal / mechanical properties of the composite, but preferably 10 μm or less, and more preferably 5 μm or less. When the diameter of the powder exceeds 10 μm, the interfacial density between Ti and Cu, which is characteristic of the composite structure of Ti and Cu, is significantly reduced, so that the desired coefficient of thermal expansion may not be realized.

The composition according to Equation 1 is to reduce the difference in the coefficient of thermal expansion and the scouterite-based alloy, which is a thermoelectric material, as described above, and more preferably to make the difference in thermal expansion coefficient within 15%.

Ti and Cu powders are weighed and mixed to satisfy Equation 1 above. The mixing is not particularly limited, but may be performed using, for example, a mortar, a ball mill, and the like, and preferably, may be performed using a ball mill. When using a ball mill, there is an advantage that can be uniformly mixed while grinding each powder mechanically smaller.

By sintering the mixed Ti and Cu powder to produce a sintered body, an electrode material for a thermoelectric module is manufactured, and the sintering is preferably performed using a spark plasma sintering (SPS) method. The discharge plasma sintering method is a technique capable of synthesizing or sintering a desired material in a short time, and can maintain the characteristic size in the mixed powder even in the sintered agglomerate material.

More specifically, the Ti-Cu mixed powder is charged into a graphite mold, and the chamber inside is vacuumed and pressurized in one axis with a punch, followed by sintering by applying a DC pulse current in a direction parallel to the pressing direction. At this time, the degree of vacuum is preferably 1.0 × 10 ^-2 torr or less to prevent oxidation of the electrode material sintered body.

The sintering is preferably performed at 800 to 1000 ℃, more preferably may be carried out at 850 to 950 ℃. If the sintering temperature is less than 800 ℃ sintered body may not be good due to incomplete sintering, if the sintering temperature is more than 1000 ℃ sintering at the sintering temperature of the above range because the mechanical properties may be lowered due to excessive growth of particles It is desirable to.

Moreover, it is preferable that the temperature increase rate at the time of sintering is 10-300 degreeC / min. If the temperature increase rate is less than 10 ℃ / min has a disadvantage in that the productivity takes a long time, if it exceeds 300 ℃ / min it may be difficult to control the sintering temperature.

The pressure applied to the Ti and Cu powder may be 10 to 60 Mpa. If the pressurization pressure is less than 10MPa, there will be many voids between the mixed powder particles, so that the desired density cannot be obtained.If the pressurization pressure exceeds 60 MPa, further effects cannot be expected. The additional cost of equipment can be increased.

The sintering can be carried out for 1 to 30 minutes, preferably for 1 to 5 minutes. If sintering is performed for an excessively long time, the particle size of Ti and Cu may increase due to particle growth, which may cause a problem in that desired thermal expansion coefficient characteristics are not realized.

According to another aspect of the present invention, there is provided a thermoelectric module to which the electrode material is applied, and more specifically, the upper substrate and the lower substrate to form an upper / lower surface and generate heat or endotherm; An electrode provided between the upper substrate and the lower substrate to guide the flow of the supplied power; And a plurality of P-type semiconductors and N-type semiconductors spaced apart from each other on one surface of the electrode, wherein the electrodes include Ti and Cu, and the Ti and Cu compositions are provided according to the following Equation 1. .

[Equation 1]

xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)

The P-type semiconductor and the N-type semiconductor may be a skutterrudite-based semiconductor, more specifically, the P-type semiconductor is Fe _{3 . 4} Co _{0 . 6 12} Sb-based, Fe _{3 .4- x} Co _x Sb _{12 0 .6+-based,} and _{Fe 3 .4+ x Co 0 .6-} x Sb can use the system _12, etc., but preferably Fe _{3. 4} Co _{0 . 6} Sb _12- based P-type semiconductor, the N-type semiconductor may be used Co ₄ Sb _12- based and Co _{4 - x} Fe _x Sb ₁₂ , etc., preferably Co ₄ Sb _12- based N-type semiconductor have.

As described above, the electrode material of the present invention has an advantage that there is no problem such that the interface between the thermoelectric material and the electrode is separated even at a high temperature due to a small difference in the coefficient of thermal expansion between the scurterite-based thermoelectric material and the electrode.

In addition, according to another aspect of the invention, the electrode forming step of forming an upper electrode or a lower electrode on one surface of the upper substrate or lower substrate to form the upper / lower surface of the thermoelectric module; And a bonding step of bonding the P-type semiconductor and the N-type semiconductor to one surface of one of the upper electrode and the lower electrode, wherein the bonding step is performed by a brazing process.

The composition of the bonding material is very diverse, but in the present invention, it is more preferable to use an alloy containing Ag and Cu as main components and containing elements such as Zn, Sn, In, and Ti.

On the other hand, when the electrode material and the scutterudite thermoelectric element are bonded by using the high-speed brazing process, the increased interfacial characteristics can be realized to show an increased power generation output. Therefore, the electrode material and the skirt are used by the brazing process. It is preferable to join a die-type thermoelectric element.

The brazing process may be performed at 550 to 750 ° C, preferably at 600 to 750 ° C. In general, the brazing process temperature is preferably low, but the process temperature of the metal filler or the high temperature solder for manufacturing a scooter ludite-based thermoelectric module is 550 ° C. or higher and the brazing process temperature is higher than the sintering temperature of the thermoelectric material. When high, since a change may occur in the composition or the microstructure of the thermoelectric material, a problem may occur in which the performance is deteriorated. Therefore, it is preferably performed at 550 to 750.

The brazing process is preferably carried out at a temperature increase rate of 20 ℃ / min or more. Materials such as metal fillers or high temperature solders used in the joining process through the brazing process are preferred to achieve excellent bonding characteristics because it is desirable to achieve a good joining property by rapidly increasing the temperature to reach the joining temperature. It is preferable.

The brazing process is preferably performed for 1 to 30 minutes. Materials such as metal fillers or high temperature solders used in the joining process through the brazing process are preferably carried out for 1 to 30 minutes because it is desirable to achieve a good joining property by rapidly increasing the temperature and reaching the joining temperature. .

Example

Hereinafter, an Example is given and this invention is demonstrated more concretely. The following examples are intended to illustrate the present invention in more detail, and the present invention is not limited thereto.

Example  1 ~ 5: Evaluation of thermal expansion coefficient of electrode material for thermoelectric module

Spherical Ti and Cu powders having an average particle diameter of 5 µm were prepared. Formulas were weighed in xTi (1-x) Cu with x = 0.60, 0.65, 0.70, 0.75, 0.80 and 0.85, respectively, and then mixed and ground using a ball mill. The mixed powder was sintered using a discharge plasma sintering apparatus.

The thermal expansion coefficient measurement results of the Ti-Cu composite electrode material prepared in Examples 1 to 5 and Comparative Example 1 are shown in Table 1 below.

Thermal expansion coefficient (× 10 ^-6 / ℃) Example 1 ( ₃₅ Ti- ₆₅ Cu) ~ 9.4 Example 2 ( ₃₀ Ti- ₇₀ Cu) ~ 10.1 Example 3 ( ₂₅ Ti- ₇₅ Cu) ~ 10.9 Example 4 ( ₂₀ Ti- ₈₀ Cu) ~ 11.5 Example 5 ( ₁₅ Ti- ₈₅ Cu) ~ 12.1 Comparative Example 1 ( ₄₀ Ti- ₆₀ Cu) ~ 8.8 (Skerterite) Co ₄ Sb ₁₂ N-type Semiconductor 10.1-11.5 (Skerterite system) Fe _3.4 Co _0.6 Sb ₁₂ series P type
semiconductor 9.8-11.3

Example  6: Evaluation of Interface Structure of Thermoelectric Module

P-type and N-type scrutherite-based thermoelectric elements and the ₃₀ Ti- ₇₀ Cu composite electrode material according to Example 2 were bonded by a rapid heating brazing process using a high temperature solder.

At this time, the brazing process conditions were carried out under the conditions of the temperature increase rate 100 ℃ / min, the maximum temperature 650 ℃, holding time 5 minutes in vacuum.

The photograph of observing the microstructure of the bonding surface with a scanning electron microscope (SEM) is shown in FIG. 1.

Figure 2 (a) is the interfacial structure of the P-type skauterite-based thermoelectric element and the 30Ti-70Cu composite electrode material prepared in Example 2, (b) is an N-type skaterudite-based thermoelectric element and Example 2 The interfacial structure of 30Ti-70Cu composite electrode material manufactured by As can be seen from the microstructure, it can be seen that an excellent interface structure without any defect structure such as pores is formed.

Example  7: Performance Evaluation of Thermoelectric Modules

The 30Ti-70Cu composite electrode material according to Example 2 was attached onto the alumina substrate, and two pairs of P-type and N-type scutterudite-based thermoelectric elements were bonded by a high temperature soldering process to produce a bicouple thermoelectric module. It was.

For evaluating the performance of the fabricated module, the power generation power was measured at 377.7 ° C., 425.7 ° C., 474 ° C. and 521.8 ° C., and the results are shown in FIG. 2.

In addition, the temperature difference is maintained for about 1000 hours at about 400 ℃ condition to evaluate the change behavior of power generation output density is shown in FIG.

Referring to FIG. 2, a power generation module exhibiting a high power density of about 0.7 W / cm ² based on a temperature difference of 400 ° C. and manufactured by a general brazing process (raising rate of 10 ° C./min, maximum temperature of 650 ° C., holding time of 5 minutes) is shown. It can be seen that the performance is increased by more than 20%.

Referring to FIG. 3, power generation output was slightly increased up to 1 hour required for stabilization of the initial operation of the power generation module, and a very stable behavior without change until 1000 hours after the power density was reduced by 5% by 50 hours. It was confirmed that it was shown.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and changes can be made without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

Claims (17)

delete delete Weighing and mixing Ti and Cu powder according to Equation 1 below; And
Sintering the mixed powder,
Method for producing an electrode material for a thermoelectric module, characterized in that the diameter of the Ti and Cu powder is 10μm or less.
[Equation 1]
xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)
delete The method of claim 3,
The method of manufacturing an electrode material for a thermoelectric module, characterized in that the sintering is performed using the discharge plasma sintering method.
The method of claim 3,
The sintering is carried out for 1 to 30 minutes in a vacuum condition of 1.0 × 10 ^-2 torr or less, the pressure applied to the Ti and Cu powder is a manufacturing method of the electrode material for a thermoelectric module, characterized in that 10 to 60 MPa.
The method of claim 3,
The sintering method of manufacturing an electrode material for a thermoelectric module, characterized in that carried out at 800 to 1000 ℃.
The method of claim 3,
The sintering method of manufacturing an electrode material for a thermoelectric module, characterized in that carried out at a temperature rising rate of 10 to 300 ℃ / min.
An upper substrate and a lower substrate that form upper and lower surfaces and generate heat or endotherm;
An electrode provided between the upper substrate and the lower substrate to guide the flow of the supplied power; And
It comprises a plurality of P-type semiconductor and N-type semiconductor formed spaced apart from each other on one surface of the electrode,
The electrode includes Ti and Cu, the Ti and Cu composition is in accordance with the following formula 1,
The electrode is weighed and mixed according to the following equation 1 Ti and Cu powder; And a step of sintering the mixed powder, wherein the diameters of the Ti and Cu powders are 10 μm or less.
[Equation 1]
xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)
The method of claim 9,
The P-type semiconductor and the N-type semiconductor thermoelectric module, characterized in that the skewrudite-based semiconductor.
The method of claim 10,
The P-type semiconductor is Fe _{3 . 4} Co _{0 .} A thermoelectric module comprising a ₆ Sb _12- based P-type semiconductor.
The method of claim 10,
And the N-type semiconductor is a Co ₄ Sb _12- based N-type semiconductor.
An electrode forming step of forming an upper electrode or a lower electrode on one surface of an upper substrate or a lower substrate forming an upper / lower surface appearance of the thermoelectric module;
And bonding a P-type semiconductor and an N-type semiconductor to one surface of one of the upper electrode and the lower electrode,
The bonding step is performed by a brazing process,
The electrode is weighed and mixed according to the following equation 1 Ti and Cu powder; And sintering the mixed powder,
Method for producing a thermoelectric module of which the diameter of the Ti and Cu powder is 10μm or less.
[Equation 1]
xTi (1-x) Cu (0.65 ≤ x ≤ 0.85)
The method of claim 13,
The brazing process is a method of manufacturing a thermoelectric module, characterized in that performed at 550 to 750 ℃.
The method of claim 13,
The brazing process is a method of manufacturing a thermoelectric module, characterized in that carried out at a temperature increase rate of 20 ℃ / min or more.
The method of claim 13,
Method for producing a thermoelectric module, characterized in that the brazing process is performed for 1 to 30 minutes.
The method of claim 13,
The brazing process is a method of manufacturing a thermoelectric module, characterized in that performed using at least one metal for bonding selected from Ag and Cu.

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