JP5915356B2 - Thermoelectric generator - Google Patents

Description

  The present invention relates to a thermoelectric power generation element that converts thermal energy into electrical energy.

Conventionally, a thermoelectric power generation element that converts thermal energy into electrical energy using a phenomenon in which thermoelectrons are emitted from a high-temperature electrode surface has been proposed in, for example, Patent Document 1 below.
In addition, when diamond semiconductor is used for the emitter (emitter electrode) and collector (collector electrode) of the thermoelectron generator, extremely high-efficiency thermoelectron emission from the surface of each electrode due to the negative electron affinity (NEA) effect. Therefore, it is known that high-efficiency power generation is possible at a lower temperature than metal.

  Further, a technique is known in which a metal such as tungsten is used as a material for an electrode of a thermoelectric power generation element, and Se (cesium) gas is enclosed to generate power in order to reduce the work function.

  In the thermoelectric generator described above, in order to obtain high power generation performance, the emitter electrode and the collector electrode are arranged to face each other so that there is no contact between the electrodes in a vacuum or the like, and the distance between the electrodes is constant. It is set to keep. In principle, it is known that the power generation efficiency is improved as the distance between the electrodes is reduced.

  Further, in the thermoelectric power generation element, in order to prevent back emission (thermal electron emission from the collector electrode) due to the temperature rise of the collector electrode, the temperature of the emitter electrode is set to a high temperature such as 1000 to 2000 ° C., for example. On the other hand, it is known that the temperature of the collector electrode needs to be set to a temperature sufficiently lower than that of the emitter electrode, for example, 500 ° C. or lower.

JP 2004-349398 A

  However, conventionally, the same material (for example, a similar electrode material or a similar holding member that holds each electrode) is used for the emitter electrode side member and the collector electrode side member, but as described above, Since the set temperatures of the respective electrodes are different, for example, there is a possibility that a difference in thermal expansion occurs between both the holding members, and the holding members are distorted to cause a short circuit between the electrodes.

In order to prevent this short circuit, it is conceivable to secure a sufficient distance by setting the distance between the electrodes to several hundreds μm. However, the power generation performance deteriorates as the distance is increased.
This invention is made | formed in view of the said subject, and it aims at providing the thermoelectric generation element which can prevent the short circuit with an emitter electrode and a collector electrode.

  The present invention includes an emitter electrode to which heat from a heat source is applied, and a collector electrode that is disposed opposite to the emitter electrode with a space therebetween and captures thermal electrons from the emitter electrode, and is provided between the emitter electrode and the collector electrode. The present invention relates to a thermionic power generation element that converts thermal energy into electrical energy using thermionic electrons that move through the.

  In particular, the present invention includes an emitter holding part that holds the emitter electrode and a collector holding part that holds the collector electrode, and at the operating temperature of the thermoelectric generator so that the emitter electrode and the collector electrode do not come into contact with each other. The thermal expansion coefficient of a part or the whole of the emitter holding part is set to be smaller than the thermal expansion coefficient of a part or the whole of the collector holding part.

  That is, in the present invention, even when the emitter electrode and the collector electrode are arranged close to each other, the thermal expansion coefficient of the emitter holding part on the high temperature side is set smaller than the thermal expansion coefficient of the collector holding part on the low temperature side. Therefore, even when both holding parts are deformed by heat, the difference in deformation of each holding part is small (compared to the conventional one having the same thermal expansion coefficient), and the degree of deformation is the same. Therefore, since the distance between the electrodes held by both holding portions is not easily changed, a short circuit between the electrodes can be prevented.

In addition, since the present invention can prevent a short circuit between the electrodes, the distance between the electrodes can be reduced, and thus there is an advantage that the power generation efficiency is high.
Here, the collector holding part and the emitter holding part are structures that can hold the emitter electrode and the collector electrode and define their positions (opposing positions). The thermal expansion coefficient (thermal expansion coefficient) indicates a linear thermal expansion coefficient (the same applies hereinafter).

It is explanatory drawing which shows typically the cross section which fractured | ruptured the thermoelectric power generation element of Example 1 along the lamination direction of each member. It is explanatory drawing which shows typically the cross section which fractured | ruptured the thermoelectric power generation element of Example 2 along the lamination direction of each member. It is explanatory drawing which shows typically the cross section which fractured | ruptured the thermoelectric power generation element of Example 3 along the lamination direction of each member. It is explanatory drawing which shows typically the cross section which fractured | ruptured the thermoelectric power generation element of Example 4 along the lamination direction of each member. It is explanatory drawing which shows typically the cross section which fractured | ruptured the thermoelectric power generation element of Example 5 along the lamination direction of each member.

Next, an embodiment of the present invention will be described.
[Embodiment]
<Configuration of electrode>
Examples of the emitter electrode and the collector electrode include an electrode made of a metal such as W (tungsten) and an electrode made of a semiconductor formed on a substrate. Note that the emitter electrode and the collector electrode may be made of different materials.

  Among these, when a semiconductor is used as a material for an electrode (particularly, an emitter electrode), the work function is smaller than when a metal material such as W is used, and therefore at a lower temperature than when the metal is used. Thermal electrons can be emitted. Thereby, since the temperature of an electrode (hence, holding | maintenance part) can be made low, as a result, the thermal expansion of a holding | maintenance part can be suppressed and the short circuit between electrodes can be prevented effectively.

Examples of the semiconductor include diamond, Si, BN, SiC, GaN, CNT (carbon nanotube) semiconductor (or compound semiconductor), ZnO, BaO, Sc ₂ O ₃ , WO _x , NbO _x , TaO _x , AgO _{x, and the} like. An oxide semiconductor can be given.

  In particular, diamond is a material having a negative electron affinity and can improve power generation efficiency at a low temperature as compared with metal. That is, the diamond semiconductor can emit thermoelectrons at a lower temperature than conventional. Therefore, even when both holding parts that hold both electrodes arranged close to each other are deformed by heat, the distance between the electrodes held by both holding parts is also difficult to change, effectively preventing a short circuit between the electrodes. can do.

  Furthermore, by making the dopant concentration of the emitter electrode higher than that of the collector electrode, the temperature condition applied to both electrodes (ie, the temperature of the emitter electrode and the temperature difference between the two electrodes) and the dopant concentration are the same. The number of thermionic electrons emitted from the collector electrode can be reduced. As a result, the temperature of the collector electrode can be increased, so that the temperature difference between the emitter electrode and the collector electrode can be reduced, and thus the difference in thermal expansion between the holding portions can be reduced. Can be prevented.

As the dopant concentration, for example, the short-circuit can be effectively prevented by increasing the dopant concentration of the emitter electrode by 10 times or more than the dopant concentration of the collector electrode.
Further, N (nitrogen) can be added to the emitter electrode and the collector electrode as the dopant. Further, P (phosphorus) can be added to the emitter electrode, and N can be added to the collector electrode. Furthermore, Sb (antimony) can be added to the emitter electrode, and N can be added to the collector electrode.
<Configuration of holding unit>
-As the emitter holding part, a configuration comprising an emitter intermediate layer for holding the emitter electrode and an emitter holding member for holding the emitter intermediate layer, that is, an emitter intermediate layer is provided between the emitter electrode and the emitter holding member. Can be adopted.

  In this case, it is desirable that the thermal expansion coefficient of the emitter intermediate layer is the thermal expansion coefficient between the emitter electrode and the emitter holding member. As a result, the thermal stress applied to the emitter electrode can be relaxed and the distortion due to the heat of the emitter electrode can be reduced (compared to the case where there is no emitter intermediate layer), thereby further preventing a short circuit between the electrodes.

Further, the emitter intermediate layer may be omitted, and the emitter electrode may be held by the emitter holding member. Thereby, a structure can be simplified.
On the other hand, the collector holding portion includes a collector intermediate layer that holds the collector electrode and a collector holding member that holds the collector intermediate layer, that is, a collector intermediate layer between the collector electrode and the collector holding member. The provided structure can be adopted.

  In this case, it is desirable that the thermal expansion coefficient of the collector intermediate layer is a thermal expansion coefficient between the collector electrode and the collector holding member. Thereby, the thermal stress applied to the collector electrode can be relieved and the distortion due to the heat of the collector electrode can be reduced, so that a short circuit between the electrodes can be prevented.

Further, the collector intermediate layer may be omitted, and the emitter electrode may be held by the collector holding member. Thereby, a structure can be simplified.
As materials of the emitter holding member and the collector holding member, and their thermal expansion coefficients (× 10 ⁻⁶ / ° C.) at 20 ° C., for example, Mo (4.9), Ti (8.5), Ta (6 .3), Cr (6.2), W (4.3), Co (12.4), Ni (12.8), Fe (10), Ir (6.5) and the like. That is, a material that meets the above-described conditions of the thermal expansion coefficient can be appropriately selected from the materials of these holding members.

  For example, as a combination of the collector holding member and the collector electrode and the emitter holding member and the emitter electrode, the combinations shown in Table 1 below can be considered. In addition, in the temperature range of 300-600 degreeC, for example, since the magnitude relationship of the following thermal expansion coefficient does not change, in the following Table 1, the thermal expansion coefficient in 20 degreeC was mentioned as an example (the following Table 2 is also the same).

  In addition, as a combination of the collector holding member, the collector intermediate layer, and the collector electrode, and the emitter holding member, the emitter intermediate layer, and the emitter electrode, combinations shown in Table 2 below can be considered.

  -Furthermore, as the collector intermediate layer and the emitter intermediate layer, a single layer having a single thermal expansion coefficient can be mentioned, but a plurality of layers having different thermal expansion coefficients may be combined, and the thermal expansion coefficient gradually increases. Different so-called gradient materials may be used. In this case, it is desirable to set so as to gradually approach the thermal expansion coefficients on both sides (in the thickness direction) of each intermediate layer.

Hereinafter, a thermionic power generation element of Example 1 of the present invention will be described.
This thermoelectric power generation element converts thermal energy into electrical energy by using thermoelectrons that move between a pair of electrodes arranged opposite to each other.

a) First, the configuration of the thermoelectric generator of Example 1 will be described.
As shown in FIG. 1, the thermoelectric generator 1 of the first embodiment is a tubular element 1 having a hollow interior 2, and is a flat emitter electrode 3 and a collector electrode 5 that are opposed to each other and arranged in parallel. An emitter holding part 7 for holding the emitter electrode 3 from the outside (lower part of the figure), a collector holding part 9 for holding the collector electrode 5 from the outside (upper part of the figure), an emitter holding part 7 and a collector holding part 9 and a cylindrical insulating member 11 disposed between the holding portions 7 and 9.

That is, the thermoelectric generator 1 has an airtight structure in which the opening in the vertical direction of the figure of the cylindrical insulating member 11 is closed with the emitter holding part 7 and the collector holding part 9.
The emitter holding portion 7 includes an emitter holding member 13 which is a flat housing fixed to the insulating member 11, and an emitter holding member 13 and an emitter electrode on the inside 2 side of the central portion of the emitter holding member 13. 3 and a flat emitter substrate 15 disposed between the two.

  Similarly, the collector holding portion 9 includes a collector holding member 17 that is a flat casing fixed to the insulating member 11, and a collector holding member 17 and a collector on the inside 2 side of the central portion of the collector holding member 17. A flat collector substrate 19 disposed between the electrodes 5 is provided.

  Of these, the emitter electrode 3 is made of a diamond semiconductor thin film formed on the emitter substrate 15. Similarly, the collector electrode 5 is made of a diamond semiconductor thin film formed on the collector substrate 19.

  As the emitter substrate 15 and the collector substrate 19, a substrate having conductivity and heat resistance such as a diamond substrate, a Si (silicon) substrate, or a Mo (molybdenum) substrate can be used. When a diamond substrate is used, for example, a 3 mm square substrate can be used, and when a Mo substrate is used, for example, a 1 inch square substrate can be used. In the first embodiment, an example using Mo substrates will be described. However, these substrates may be omitted.

  The emitter holding member 13 is a square metal plate (for example, thickness 0.5 mm × one side 50 mm) made of, for example, Mo having a smaller coefficient of thermal expansion than the collector holding member 17, and the outer periphery of the emitter holding member 13 is insulated from the insulation. It is fixed to the member 11.

  Similarly, the collector holding member 17 is a square metal plate made of, for example, Ti (for example, thickness 05 mm × one side 50 mm), and the outer periphery of the collector holding member 17 is fixed to the insulating member 11.

Further, the insulating member 11 is a spacer cross section of the square-shaped tubular example of Al ₂ O _3, the emitter electrode 3 (in the same drawing side) surface and the collector electrode 5 (in the figure the lower side ) The dimension (in the vertical direction in the figure) is set so that the surface maintains a parallel interval (space) 21 having a predetermined dimension (for example, 20 μm).

The emitter holding member 13 and the collector holding member 17 are electrically connected by a circuit 25 via a load 23.
b) Here, a method for manufacturing the thermoelectric generator 1 of the first embodiment will be briefly described.

  First, when forming each electrode 3 and 5 on each board | substrate 15 and 19, a diamond semiconductor thin film is formed on each board | substrate 15 and 19 by CVD method or a sputtering method, for example. Note that microwave plasma CVD, RF plasma CVD, DC plasma CVD, RF plasma sputtering, DC plasma sputtering, or the like may be used.

  The diamond constituting the diamond semiconductor thin film may be either single crystal or polycrystal. For example, when a diamond substrate produced by high pressure synthesis is used, a diamond semiconductor thin film formed on the diamond substrate by, for example, a CVD method becomes a single crystal. The thickness of the diamond semiconductor thin film is not particularly limited because the film thickness dependence on the thermionic emission characteristics has not been confirmed. However, when the diamond semiconductor thin film is formed with the same thickness on the entire surface of the substrates 15 and 19 without deviation. preferable.

  In the emitter electrode 3 and the collector electrode 5 formed in this way, the portions of the substrates 15 and 19 are joined to the emitter holding member 13 or the collector holding member 17 by welding or brazing, for example, to become an integral member. .

  Then, the emitter holding member 13 and the collector holding member 17 are arranged so that the emitter electrode 3 and the collector electrode 5 face each other so as to close the opening portion of the cylindrical insulating member 11, and the insulating member 11. And the holding members 13 and 17 are joined together by, for example, direct joining and hermetically integrated.

c) Next, the main part of the thermoelectric generator 1 of the first embodiment will be described.
In this embodiment, the emitter electrode 3 side, that is, the emitter holding member 13, the emitter substrate 15, and the emitter electrode 3 are maintained at a high temperature of, for example, 600 ° C., and the collector electrode 5 side, that is, the collector holding member 17, the collector substrate 19. The collector electrode 5 is kept at a low temperature of 300 ° C., for example, 300 ° C. lower than the emitter electrode 3 side.

By setting the temperature, the thermoelectrons emitted from the emitter electrode 3 are captured by the collector electrode 5 to generate power.
Particularly in this embodiment, the thermal expansion coefficient of the emitter holding member 13 is set to be smaller than the thermal expansion coefficient of the collector holding member 17 at the operating temperature of the thermoelectric generator 1.

Specifically, the thermal expansion coefficient at 600 ° C. of Mo constituting the emitter holding member 13 is 4.5 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient at 300 ° C. of Ti constituting the collector holding member 17 is 10 × 10 ⁻⁶ / ° C. The thermal expansion coefficient of the emitter holding member 13 is smaller than the thermal expansion coefficient of the collector holding member 17.

  Therefore, even when the emitter electrode 3 and the collector electrode 5 are arranged close to each other as in this embodiment, the thermal expansion coefficient of the emitter holding member 13 on the high temperature side is the heat of the collector holding member 17 on the low temperature side. Since it is smaller than the expansion coefficient, even when both holding members 13 and 17 are deformed by heat, the difference in deformation of the holding members 13 and 17 is small, and the degree of deformation is the same. Therefore, since the distance 21 between the emitter electrode 3 and the collector electrode 5 held by the holding members 13 and 17 is not easily changed, a short circuit between the electrodes 3 and 5 can be prevented.

Further, in this embodiment, since a short circuit between the electrodes 3 and 5 can be prevented, the interval 21 between the electrodes 3 and 5 can be reduced, and thus there is an advantage that the power generation efficiency is high.
Further, in this embodiment, the collector substrate 19 made of Mo has a thermal expansion coefficient (at 300 ° C.) of 4.5 × 10 ⁻⁶ / ° C., and the thermal expansion at the same temperature of the collector electrode 5 made of a diamond semiconductor thin film. This is an intermediate value between a coefficient of 2.3 × 10 ⁻⁶ / ° C. and a coefficient of thermal expansion of 10 × 10 ⁻⁶ / ° C. at the same temperature of the collector holding member 17 made of Ti. That is, the thermal expansion coefficient of the collector substrate 19 is between the thermal expansion coefficient of the collector electrode 5 on both sides thereof and the thermal expansion coefficient of the collector holding member 17 (intermediate).

  Therefore, even when the temperature is as high as 300 ° C., the collector substrate 19 exhibits the function of an intermediate layer that relieves thermal stress, so that the collector electrode 5 is not easily distorted. There is an effect that a short circuit can be prevented.

d) Next, a modification of the first embodiment will be described.
For example, N is added as a dopant to the diamond semiconductor thin film constituting the emitter electrode 3 and the collector electrode 5, but the dopant concentration of the emitter electrode 3 may be higher than the dopant concentration of the collector electrode 5.

  In this case, compared with the case where the temperature conditions of both the electrodes 3 and 5 (that is, the temperature of the emitter electrode 3 and the temperature difference between the electrodes 3 and 5) and the dopant concentration are the same, the thermoelectrons emitted from the collector electrode 5 are reduced. The number can be reduced. As a result, the temperature of the collector electrode 5 can be increased, so that the temperature difference between the emitter electrode 3 and the collector electrode 5 can be reduced, and hence the difference in thermal expansion between the holding members 13 and 17 can be reduced. A short circuit between the electrodes 3 and 5 can be effectively prevented.

Next, the second embodiment will be described, but the description of the same contents as the first embodiment will be simplified. In addition, the same code | symbol is attached | subjected to the structure similar to Example 1. FIG.
As shown in FIG. 2, the thermoelectric conversion element 31 of the second embodiment includes an emitter holding portion 7 that holds the emitter electrode 3, a collector holding portion 9 that holds the collector electrode 5, as in the first embodiment. And an insulating member 11.

  In particular, in this embodiment, the emitter holding portion 7 includes an emitter intermediate layer 33 bonded to both the members 15 and 13 between the emitter substrate 15 on which the emitter electrode 3 is formed and the emitter holding member 13.

  Similarly, the collector holding portion 9 includes a collector intermediate layer 35 bonded to both the members 19 and 17 between the collector substrate 19 on which the collector electrode 5 is formed and the collector holding member 17.

The emitter substrate 15 is made of Si having a thermal expansion coefficient (at 600 ° C.) of 4.1 × 10 ⁻⁶ / ° C., and the emitter holding member 13 has a thermal expansion coefficient of 7.2 × 10 (at 600 ° C.). ^-6 / consist ° C. of Ta, further emitter interlayer 33, the thermal expansion coefficient (600 ° C.) of intermediate the emitter substrate 15 and the emitter holding member 13 is made of W of 5 × 10 ^-6 / ° C..

Similarly, the collector substrate 19 is made of Si having a thermal expansion coefficient (300 ° C.) of 3.5 × 10 ⁻⁶ / ° C., and the collector holding member 17 has a thermal expansion coefficient of 11 × 10 ⁻ (300 ° C.). ^The collector intermediate layer 35 is made of Cr having an intermediate (300 ° C.) thermal expansion coefficient of 9 × 10 ⁻⁶ / ° C. between the collector substrate 19 and the collector holding member 17.

The materials of the emitter electrode 3 and the collector electrode 5 are the same as those in the first embodiment.
Therefore, in this embodiment, the same effects as those of the first embodiment are obtained, and the emitter intermediate layer 33 and the collector intermediate layer 35 have a thermal expansion coefficient that is intermediate between the thermal expansion coefficients of the members on both sides thereof. It functions as an intermediate layer that relieves heat. Thereby, since the emitter electrode 3 and the collector electrode 5 are not easily distorted, there is an effect that a short circuit between the electrodes 3 and 5 can be more effectively prevented.

  In addition, in this embodiment, the thermal expansion coefficients of the emitter substrate 15 and the emitter intermediate layer 33 are set between the thermal expansion coefficient of the emitter electrode 3 and the thermal expansion coefficient of the emitter holding member 13. The emitter intermediate layer 33 also functions as an intermediate layer that relieves thermal stress.

  Similarly, the coefficient of thermal expansion between the collector substrate 19 and the collector intermediate layer 35 is set between the coefficient of thermal expansion of the collector electrode 5 and the coefficient of thermal expansion of the collector holding member 17. The layer 35 also has a function as an intermediate layer that relieves thermal stress.

  In addition, the thermal expansion coefficient of the emitter substrate 15 and the thermal expansion coefficient of the emitter intermediate layer 33 are set such that the closer to the emitter electrode 3 or the emitter holding member 13, the closer the thermal expansion coefficient.

  Similarly, the thermal expansion coefficient of the collector substrate 19 and the thermal expansion coefficient of the collector intermediate layer 35 are set such that the closer to the collector electrode 5 or the collector holding member 17, the closer the thermal expansion coefficient.

  That is, in this way, the thermal expansion coefficients of the substrates 15 and 19 and the intermediate layers 33 and 35 sandwiched therebetween are set so as to gradually change (along the stacking direction). However, the thermal stress is preferably relaxed, and a short circuit can be further prevented.

Next, the third embodiment will be described, but the description of the same contents as the second embodiment will be simplified. In addition, the same code | symbol is attached | subjected to the structure similar to Example 2. FIG.
As shown in FIG. 3, the thermoelectron conversion element 41 of the third embodiment includes an emitter holding portion 7 that holds the emitter electrode 3, a collector holding portion 9 that holds the collector electrode 5, as in the second embodiment. And an insulating member 11.

  In this embodiment, the emitter holding unit 7 includes the emitter substrate 15 on which the emitter electrode 3 is formed, the emitter intermediate layer 33 bonded to the emitter substrate 15, and the emitter holding member 13 bonded to the emitter intermediate layer 33. It consists of and.

  Similarly, the collector holding unit 9 includes a collector substrate 19 on which the collector electrode 5 is formed, a collector intermediate layer 35 bonded to the collector substrate 19, and a collector holding member 17 bonded to the collector intermediate layer 35. ing.

In particular, in this embodiment, the emitter intermediate layer 33 has an inner emitter intermediate layer 33a made of W with a thermal expansion coefficient (600 ° C.) of 5 × 10 ⁻⁶ / ° C. and a thermal expansion coefficient of 5.degree. And an outer emitter intermediate layer 33b made of Mo at 3 × 10 ⁻⁶ / ° C.

That is, the thermal expansion coefficient of the outer emitter intermediate layer 33b is set larger than the thermal expansion coefficient of the inner emitter intermediate layer 33a.
Similarly, the collector intermediate layer 35 has an inner collector intermediate layer 35a made of W having a thermal expansion coefficient of 4.6 × 10 ⁻⁶ / ° C. (300 ° C.) and a thermal expansion coefficient of 9 × 10 ⁶ (300 ° C.). ^-6 / ° C outer collector intermediate layer 35b.

That is, the thermal expansion coefficient of the outer collector intermediate layer 35b is set larger than that of the inner collector intermediate layer 35a.
Thereby, in the present embodiment, there are advantages that the same effects as in the first embodiment can be obtained, the thermal stress can be further reduced, and the short circuit between the electrodes 3 and 5 can be further greatly reduced.

  The inner emitter intermediate layer 33a, the outer emitter intermediate layer 33b, and the inner collector intermediate layer 35a and the outer collector intermediate layer 35b may be formed by laminating plate materials made of each material and joining them by, for example, thermal diffusion. Good.

  The emitter intermediate layer 33 and the collector intermediate layer 25 may be made of a so-called gradient material. The gradient material is a material in which the thermal expansion coefficient is gradually changed by gradually changing the composition of the material in the thickness direction.

Next, the fourth embodiment will be described, but the description of the same contents as the first embodiment will be simplified. In addition, the same code | symbol is attached | subjected to the structure similar to Example 1. FIG.
As shown in FIG. 4, the thermoelectron conversion element 51 of the fourth embodiment is different from the first embodiment in that the emitter electrode 3 and the collector electrode 5 are made of a metal material, and each is an emitter holding portion 7. ) An emitter holding member 13 and a collector holding member 17 (which is the collector holding portion 9) are joined.

In this embodiment, the emitter electrode 3 and the collector electrode 5 are made of W, the emitter holding member 13 is made of Cr, and the collector holding member 17 is made of Fe.
Therefore, the thermal expansion coefficient of the emitter holding member 13 (600 ° C.) is 12 × 10 ⁻⁶ / ° C., which is smaller than the thermal expansion coefficient of the collector holding member 17 (300 ° C.) of 15 × 10 ⁻⁶ / ° C. The same effects as those of the first embodiment are obtained.

Next, the fifth embodiment will be described, but the description of the same contents as the first embodiment will be simplified. In addition, the same code | symbol is attached | subjected to the structure similar to Example 1. FIG.
As shown in FIG. 5, the thermoelectric conversion element 61 of the fifth embodiment is similar to the first embodiment in that the emitter electrode 3, the emitter holding portion 7 including the emitter substrate 15 and the emitter holding member 13, and the collector electrode. 5 and a collector holding portion 9 including a collector substrate 19 and a collector holding member 17.

  In particular, in this embodiment, the emitter-side heat choke portion (which prevents the thermal diffusion to the low temperature side and relaxes the thermal stress) from the end on the outer peripheral side of the emitter holding member 13 downward in FIG. 63 is extended.

  Similarly, from the end on the outer peripheral side of the collector holding member 17 toward the lower side in the figure, a collector-like heat choke portion 65 (which prevents thermal diffusion to the low temperature side and relaxes thermal stress) is provided. The emitter-side heat choke portion 63 extends concentrically in parallel.

  The tip side of the emitter-side heat choke part 63 and the collector-side heat choke part 65 (lower side in the figure) is integrated with an annular insulating member 67 so as to close the internal space 69 of the thermoelectric conversion element 61. It is joined.

  In the present embodiment, the same effect as in the first embodiment is achieved, and the relaxation of the thermal stress is realized to a considerable degree by setting the thermal expansion coefficients of the emitter holding member 13 and the collector holding member 17. Both heat choke parts 63 and 65 can be reduced in size compared with the past. As a result, the thermoelectric conversion element 61 itself can be downsized.

  In addition, this invention is not limited to the said embodiment and an Example at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from this invention.

DESCRIPTION OF SYMBOLS 1, 31, 41, 51, 61 ... Thermionic power generation element 3 ... Emitter electrode 5 ... Collector electrode 7 ... Emitter holding part 9 ... Collector holding part 13 ... Emitter holding member 17 ... Collector holding member 21 ... Space (space | interval)
33 ... Emitter intermediate layer 35 ... Collector intermediate layer

Claims (6)

An emitter electrode (3) to which heat from a heat source is applied;
A collector electrode (5) disposed opposite to the emitter electrode (3) with a space (21) therebetween, and capturing the thermal electrons from the emitter electrode (3);
A thermoelectron generator (1, 31, 41, 51, 61) that converts thermal energy into electrical energy using thermoelectrons moving between the emitter electrode (3) and the collector electrode (5). ) And
An emitter holder (7) for holding the emitter electrode (3);
A collector holding part (9) for holding the collector electrode (5);
With
In order to prevent the emitter electrode (3) and the collector electrode (5) from coming into contact with each other, one of the emitter holding portions (7) is used at the operating temperature of the thermoelectric generator (1, 31, 41, 51, 61). The thermal expansion coefficient of the part or the whole is set smaller than the thermal expansion coefficient of a part or the whole of the collector holding part (9).   The thermionic power generation element according to claim 1, wherein a semiconductor material is used as a material for the emitter electrode (3) and the collector electrode (5).   The thermoelectric power generation element according to claim 2, wherein the semiconductor is a diamond semiconductor.   The dopant concentration of the semiconductor impurity added to the semiconductor material used for the emitter electrode (3) is higher than the dopant concentration of the semiconductor impurity added to the semiconductor material of the collector electrode (5). Item 3. The thermoelectric generator of item 1 or 2. The emitter holding portion (7) includes an emitter intermediate layer (33) that holds the emitter electrode (3), and an emitter holding member (13) that holds the emitter intermediate layer (33) .
The said emitter intermediate | middle layer (33) has a thermal expansion coefficient between the said emitter electrode (3) and the said emitter holding member (13), The any one of Claims 1-4 characterized by the above-mentioned. Thermoelectric power generation element. The collector holding part (7) includes a collector intermediate layer (35) for holding the collector electrode (5), and a collector holding member (17) for holding the collector intermediate layer (35),
The collector intermediate layer (35) has a coefficient of thermal expansion between the collector electrode (5) and the collector holding member (17). Thermoelectric power generation element.

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