JP2007281070A - Thermoelectric transducer, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric transducer composed by surely forming nano-size wires, and to provide its manufacturing method. <P>SOLUTION: A glass template 21 composed by forming a large number of through-holes 22 is prepared (Fig.2(a)). Bismuth as a thermoelectric conversion material is filled into a large number of the through-holes 22 (Fig.2(b)). After heating the glass template 21 over a temperature of softening the glass template 21 and to a temperature over a melting point of the bismuth, the glass template 21 is stretched in an axial direction of the through-holes 22 so as to form nanowires 10 inside the glass template 21 (Fig.2(c), (d)). Then, the stretched glass template 21 is cut into a chip 23 shape (Fig.2(e)). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermoelectric conversion element that converts a temperature difference between two electrodes into an electromotive force, and a manufacturing method thereof.

  In general, thermoelectric conversion elements are known to utilize the Seebeck effect that generates electricity by causing a temperature difference between both ends of a semiconductor. Such a thermoelectric conversion element has a structure in which, for example, a plurality of thermoelectric conversion materials are connected between two electrode plates.

The performance of the thermoelectric conversion element can be obtained as a performance index Z of thermoelectric conversion. That is, the figure of merit Z of thermoelectric conversion is represented by Z = S ² σ / κ. S is the Seebeck coefficient of the thermoelectric conversion material, σ is the electrical conductivity of the thermoelectric conversion material, and κ is the thermal conductivity of the thermoelectric conversion material. The Seebeck coefficient S is approximately represented by S = π ² k _B ² T [ＴD (ε) / ∂ε] / 3eD (ε _F ). k _B is the Boltzmann constant, D (ε) is the density of states of the thermoelectric conversion material, and e is the elementary charge. ε is energy, and ε _F is Fermi energy.

The Seebeck coefficient S increases as the change in state density near Fermi energy (ミ D (ε = ε _F ) / ∂ε) becomes steeper. Moreover, the value of the figure of merit Z of thermoelectric conversion becomes large, so that the value of Seebeck coefficient S is large. On the other hand, it is known that a quantum effect can be expressed in the density of states by making the thermoelectric conversion material into a nanoscale wire shape, and a steep density of states can be realized. Thereby, it is thought that Seebeck coefficient S and by extension, the figure of merit Z of thermoelectric conversion can be increased.

  Then, in order to express a quantum effect, the trial which produces nanowire which is a nanoscale wire has been announced (for example, refer nonpatent literature 1). FIG. 6 is a diagram showing a state of manufacturing a conventional nanowire.

  First, a furnace J2 provided with a heater J1 in a pressure tank (not shown) is prepared, and a liquid Bi (bismuth) thermoelectric material J3 is placed in the furnace J2. Then, the substrate J5 on which the anodized alumina layer J4 having a thickness of several tens of micrometers in which nano-sized (4 to 15 nm) holes are formed is placed in the furnace J2 so that the anodized alumina layer J4 faces the furnace J2 side. Install.

Thereafter, the furnace J2 is heated by the heater J1 to generate steam of the thermoelectric material J3 in the furnace J2, and the lower part (furnace J2 side; temperature T1) and upper part (substrate J5 side; temperature T2) of the anodized alumina layer J4. ) And a temperature difference is successively generated under the condition (T1> T2) in which the lower portion is at a high temperature. Thereby, the vapor | steam of the thermoelectric material J3 is condensed and deposited sequentially toward the board | substrate J5 side from the hole of the anodized alumina layer J4, and Bi nanowire is formed in the hole of the anodized alumina layer J4.
Joseph P. Heremans, “Thermoelectric power, electrical and thermal resistance, and magnetoresistance of nanowire composites.” Mat. Res. Soc. Symp. Pros., Vol. 793, S1.1.1-S1.1.12

  However, in the above conventional technique, since the size of the hole formed in the anodized alumina layer J4 is nano-sized, the evaporated Bi may not enter this hole. For this reason, among the many holes formed in the anodized alumina layer J4, the number of nanowires penetrating the anodized alumina layer J4 is extremely small, and the yield is lowered.

  Even if electrodes are provided at both ends of each wire to form a thermoelectric conversion element, the resistance between the two electrodes is increased because the number of wires is small.

  Moreover, since the thickness of the anodized alumina layer J4 is several tens of micrometers, the length of the formed wire is several tens of micrometers. For this reason, the temperature difference between the two electrodes installed at both ends of the nanowire cannot be obtained, and electricity may not be generated as the thermoelectric conversion element. Furthermore, since the thermal conductivity of the anodized alumina layer J4 that is the base material of the nanowire is good, most of the heat passes through the anodized alumina layer J4 that does not have thermoelectric conversion capability, causing heat loss and thermoelectricity. The performance of the conversion element is lowered.

A mixed film of Al and Si (or Ge) is sputtered on a Si substrate to form Al nanopillars, and then a porous body is formed by etching Al nanopillars with concentrated sulfuric acid. A method of filling a porous body with Bi ₂ Te ₃ has been reported (Japanese Patent Laid-Open No. 2004-193526). However, in this method of forming a wire by electrodeposition, the wire cannot be formed with a good yield as in the above, the wire can be formed only with a thin film base material (mixed film), and the base material has a high thermal conductivity. There is a problem.

  An object of this invention is to provide the thermoelectric conversion element which forms a nanosize wire reliably, and its manufacturing method in view of the said point.

  In order to achieve the above object, according to the first feature of the present invention, a glass base material (21) in which a large number of through holes (22) are formed is prepared (FIG. 2 (a)). Is filled with a thermoelectric conversion material (FIG. 2B). And after heating a preform | base_material to the temperature more than the temperature which a preform | base_material softens and more than melting | fusing point of a thermoelectric conversion material, by extending a preform | base_material in the axial direction of a through-hole, nanowire (10) in a preform | base_material. (FIGS. 2C and 2D). Thereafter, the stretched base material is cut into chips (23) (FIG. 2 (e)).

  In this way, since the thermoelectric conversion material is filled and stretched in a large number of through holes provided in the glass base material, the wire can be reliably formed in the base material. Furthermore, since the nanowire can be spontaneously formed simply by stretching the base material, the nanowire can be reliably formed with a high yield. And the diameter of a nanowire is controllable by controlling the length of the base material to extend.

  In addition, since glass having a low thermal conductivity (about 1 W / mK) is used as the base material, it is possible to suppress performance degradation due to heat loss through the base material. Furthermore, when the stretched base material is used as a chip, the length to be cut can be freely determined, so that a chip having a length of, for example, mm order can be easily formed.

  When the nanowire is formed in the base material as described above, the fixing members (51, 52) are fixed to the surface of the base material where the thermoelectric conversion material is exposed from the through hole and the surface opposite to the surface. Then, the tension members (61, 62) are fixed to the fixing member. And after heating a base material more than the temperature which a base material softens and more than melting | fusing point of a thermoelectric conversion material, a tension | pulling member is moved and a base material is extended.

  Thus, by extending the base material, the portion containing the thermoelectric conversion material in the base material can be linearly extended by the deformation of the fixing member. Moreover, since the through-hole filled with the thermoelectric conversion material among the base materials is sealed with the fixing member, the transpiration of the thermoelectric conversion materials can be prevented when the base material is heated.

  Further, when fixing the fixing member, it is preferable to use the same material as the base material as the fixing member.

  In this way, when the base material is stretched, the base material and the fixing member are stretched at the same coefficient of thermal expansion, so that only the fixing member can be prevented from being stretched, and the base material can be reliably stretched.

  Then, after the base material is cut into chips, electrodes (31, 32) can be formed on both end faces of the chip where the end faces of the nanowires are exposed.

  Thus, by forming the electrode on the chip, the thermoelectric conversion element can be easily connected to, for example, a semiconductor element.

  Moreover, after forming the said electrode, a chip | tip is heated to below the melting temperature of a thermoelectric conversion material, and below the temperature which a base material softens, and it cools slowly after that.

  In this way, by annealing the chip, the crystallinity of the thermoelectric conversion material in the base material can be improved, and thus the characteristics of the thermoelectric conversion element can be improved.

  Further, after the base material is stretched, the molding members (91 to 94) are formed on the side surfaces of the base material after the base material is stretched so that a cross section obtained by cutting the base material perpendicularly to the axial direction of the through hole becomes a square shape. It can also be molded by pressing.

  In this way, a chip having a square cross section can be formed. When a module is formed by arranging a large number of chips in the horizontal direction by such molding, a chip having a square shape can be arranged at a higher density than a chip having a circular cross section, and a unit as a module of a thermoelectric conversion element The power per area can be improved.

  Moreover, the etching process which melt | dissolves the both end surfaces which the end surface of nanowire exposes in a chip | tip can also be performed.

  Thereby, since the nanowire can be exposed from both ends of the chip, when the electrode is formed on the chip where the end of the nanowire is exposed in this way, the electrode and the nanowire can be reliably electrically connected.

  Furthermore, a heating tank (41) is installed in the pressurizing tank (40), and a melt (43) is prepared by melting the thermoelectric conversion material in the heating tank in a state where the atmospheric pressure is reduced from the atmospheric pressure. . Subsequently, the base material in which a large number of through holes are formed is immersed in the melt so that the large number of through holes are covered with the melt. Thereafter, the inside of the pressurization tank is returned to the atmospheric pressure, and an inert gas is introduced into the pressurization tank so that the inside of the pressurization tank is in a pressurized state, and a large number of through holes formed in the base material are inserted. Fill with melt.

  By such a method, the melt can be pushed into the hole by pressure. In this way, the thermoelectric conversion material can be filled into a large number of holes formed in the base material.

  In the second feature of the present invention, a large number of nanowires (10) are provided in a columnar glass member (20), and electrodes are provided at both ends of the nanowire to convert a temperature difference between the electrodes into an electromotive force. It is a thermoelectric conversion element, Comprising: The diameter of nanowire is a diameter which the Seebeck coefficient higher than the Seebeck coefficient which the material which comprises this nanowire has as a bulk expresses by a quantum effect.

  In this way, a large number of nanowires are fixed to a glass member having a low thermal conductivity, electrodes are provided on both ends of the nanowires, and the diameter of the nanowires is set to a diameter that produces a quantum effect, thereby providing a high performance index as a thermoelectric conversion element. realizable.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The thermoelectric conversion element shown in this embodiment is used as an element utilizing the Seebeck effect that generates electricity by generating a temperature difference between two electrodes.

  FIG. 1 is a schematic perspective view of a thermoelectric conversion element according to the first embodiment of the present invention. As shown in FIG. 1, the thermoelectric conversion element S <b> 1 includes a nanowire 10, a glass member 20, and electrodes 31 and 32.

  The nanowire 10 is a wiring that electrically connects the electrodes 31 and 32, and is made of a metal containing, for example, Bi (bismuth) as a thermoelectric conversion material. In this embodiment, an alloy in which Te (tellurium) is doped to Bi by several percent is used as a thermoelectric conversion material. In this way, by doping Te that functions as a carrier into Bi, the thermoelectric conversion characteristics of the nanowire 10 can be adjusted. Such a nanowire 10 has a diameter of, for example, 10 nm and a length of 1 mm.

  In addition, the metal containing Bi indicates not only an alloy containing Bi as described above but also a metal composed of Bi alone. In the following description, Bi refers to Bi doped with Te.

  The glass member 20 forms the outer shape of the thermoelectric conversion element S1, and fixes a large number of nanowires 10 therein. Such a glass member 20 has a cylindrical shape and is made of glass. Moreover, the thermal conductivity of the glass member 20 is about 1 W / mK, and the diameter of the glass member 20 is 1 mm, for example. In the cross section of the glass member 20 in the axial direction of the nanowire 10, the cross-sectional area ratio between the glass member 20 and the nanowire 10 is, for example, 30%.

  The electrodes 31 and 32 are electrically connected to both ends of the nanowire 10. In this embodiment, each electrode 31 and 32 is formed in the both end surfaces of the glass member 20, ie, the both ends of the nanowire 10, by the method of ion plating. As such electrodes 31, 32, for example, Cu (copper), Au (gold), Al (aluminum) or the like is employed. The above is the configuration of the thermoelectric conversion element S1.

  Next, the manufacturing process of the thermoelectric conversion element S1 shown in FIG. 1 will be described with reference to the drawings. FIG. 2 is a diagram showing a manufacturing process of the thermoelectric conversion element S1 shown in FIG. FIG. 3 is a diagram showing a manufacturing process subsequent to FIG.

  In the step shown in FIG. 2A, a glass template 21 is prepared. As shown in FIG. 2A, the glass template 21 has a diameter of 100 mm and a thickness of 1 mm having a large number of through-holes 22 having a diameter of 1 μm.

  Such a glass template 21 can be formed as follows. That is, a double-structured glass rod that is insoluble and soluble in an acid is heated and stretched, and the glass rods are stretched side by side in the horizontal direction. And what was extended is cut | disconnected perpendicularly | vertically with respect to the direction extended, and soluble glass is melt | dissolved with an acid after cutting | disconnection. Thus, the glass template 21 provided with many micron-sized through holes 22 can be formed.

  The glass template 21 corresponds to the base material of the present invention. Moreover, in FIG. 2A, in order to express the through-hole 22 of the glass template 21, although what cut a part of the glass template 21 is drawn, it is not actually cut.

  In the step shown in FIG. 2B, Bi, which is a thermoelectric conversion material, is filled inside each through hole 22 of the glass template 21. First, a Bi lump is placed in a heating tank 41 installed in the pressurizing tank 40, and the glass template 21 is placed on the Bi lump. Next, while evacuating the inside of the pressurizing tank 40 by the vacuum pump 42, the heating tank 41 was heated to a melting point (271.4 ° C.) or higher (for example, up to 300 ° C.) of Bi to melt the Bi lump. The glass template 21 is immersed in the Bi melt 43.

  Thereafter, the evacuation valve 44 is closed and the pressurization pump valve 45 is opened, and the pressurization pump 46 pressurizes and introduces an inert gas such as Ar (argon) into the pressurization tank 40 to several hundred atmospheres. Then, Bi is filled in the through hole 22. And after reducing the temperature of the heating tank 41 to room temperature, the glass template 21 is cut out from the lump of Bi. Thus, a glass template 21 filled with Bi in the through hole 22 is obtained.

  In the step shown in FIG. 2C, the glass template 21 filled with Bi in each through-hole 22 is taken out from the pressurizing tank 40 and attached to a tension machine (not shown). Specifically, first, dummy glasses 51 and 52 are attached to both end faces of the glass template 21 filled with Bi with an adhesive or the like. Furthermore, each dummy glass 51 and 52 is affixed on each workpiece | work 61 and 62 of a tension machine with an adhesive agent.

  The dummy glasses 51 and 52 play a role of extending the vicinity of the end face of the glass template 21 in a straight line by being deformed themselves, and a glass material made of the same material as the glass template 21 is used. Further, when the dummy glasses 51 and 52 are deformed at the connecting portion between the workpieces 61 and 62 and the dummy glasses 51 and 52, the dummy glasses 51 and 52 cause the filler in the through holes 22 of the glass template 21 to flow out. The function of preventing, the function of maintaining the internal pressure of each through-hole 22 to maintain the blockage of the through-hole 22, and the function of preventing the transpiration of the filler are achieved.

  Among these functions, the transpiration prevention function will be described. The vapor pressure of Bi is 133 Pa at 1021 ° C., 1330 Pa at 1136 ° C., and not so high at 600 ° C., but Te has a vapor pressure of 758 Pa at 600 ° C. Therefore, it is necessary to seal each through-hole 22 with the dummy glasses 51 and 52 as described above so that the dope concentration does not change by heating.

  Then, the glass template 21 is heated to a temperature equal to or higher than the temperature at which Bi is melted and the glass template 21 is fluidized (for example, about 600 ° C.), and at least one of the workpieces 61 and 62 is separated so as to separate the dummy glasses 51 and 52. Is moved to stretch the glass template 21 in the axial direction of the through hole 22. The dummy glasses 51 and 52 correspond to the fixing member of the present invention, and the workpieces 61 and 62 correspond to the pulling member of the present invention.

  In the step shown in FIG. 2D, the glass template 21 is stretched. Specifically, at least one of the workpieces 61 and 62 so as to separate the workpieces 61 and 62 of the tension machine in a state where the glass template 21 is heated to a temperature at which Bi is melted and the glass is softened (for example, 600 ° C.). Is moved to stretch the glass template 21.

  When the glass template 21 is stretched in this way, in the dummy glasses 51 and 52 attached to both surfaces of the glass template 21, the surface bonded to the glass template 21 is stretched and deformed together with the glass template 21. Thereby, the through-hole 22 near the end surface of the glass template 21 can be extended linearly.

  As described above, since the size of the through hole 22 of the glass template 21 is 1 μm, in order to set the size of the through hole 22 to, for example, 10 nm, the glass template 21 is stretched until the diameter of the glass template 21 becomes 1 mm. It will be. When the glass template 21 is stretched in this way, the length of the glass template 21 becomes 1 m. If it will be in this state, the glass template 21 will become a column shape, and will be in the state by which many nanowires 10 were formed in the inside.

  In the step shown in FIG. 2E, the glass template 21 stretched as described above is cut into chips. That is, the stretched glass template 21 is cut in the axial direction of the nanowire 10 every desired length (for example, 1 mm) to form the nanowire array chip 23.

  Thereafter, in the step shown in FIG. 3A, electrodes 31 and 32 are formed on both end surfaces of the nanowire array chip 23. In the present embodiment, metal films to be the electrodes 31 and 32 are formed on both end surfaces of each chip 23 using the ion plating apparatus 71.

  First, the ion plating apparatus 71 will be described. As shown in FIG. 3A, the ion plating apparatus 71 is configured such that a metal target 73 and a high frequency discharge coil 74 are installed in a chamber 72. In the chamber 72, the gas in the chamber 72 is sucked by the vacuum pump 75, and the vacuum state is maintained by the vacuum valve 76. Further, the nanowire array chip 23 is fixed by being fitted into a fixing plate 77 provided with a hole having the same diameter as that of the chip 23.

  In the present embodiment, Cu, Au, Al, or the like, which is a raw material for the electrodes 31 and 32, is employed as the metal target 73.

  In such an ion plating apparatus 71, the inside of the chamber 72 is evacuated by the vacuum pump 75, and the metal target 73 is vaporized by irradiating the metal target 73 with an electron beam emitted from an electron gun (not shown). Then, plasma is generated in the chamber 72 by the high-frequency discharge coil 74 to ionize the vaporized metal material. By applying a bias to the fixed plate 77, the ionized metal target 73 is accelerated toward the fixed plate 77, and a metal film is deposited (evaporated) on the end face of the chip 23 facing the metal target 73. Similarly, a metal film is formed on the opposite end face of the chip 23. In this way, the electrodes 31 and 32 are formed.

  According to such a method, since the ionized metal target 73 can be attached to the end face of the chip 23 with high energy, high adhesion between the metal film and the end face of the chip 23 can be obtained.

  Further, by forming the electrodes 31 and 32 that are metal films on both end faces of the nanowire array chip 23, the nanowire 10 in the chip 23 is sealed by the electrodes 31 and 32. That is, the electrodes 31 and 32 also fulfill the function of preventing nanowire transpiration in the step shown in FIG.

  In the step shown in FIG. 3B, a heating / slow cooling process for improving the crystallinity of the nanowire 10 is performed. That is, in the process shown in FIG. 2D, the glass template 21 is heated at a temperature equal to or higher than the melting temperature of Bi and equal to or higher than the softening temperature of the glass template 21 (a temperature higher than the temperature at which the glass template 21 fluidizes). Deformation and the like are likely to occur due to gravity. Therefore, in the step shown in FIG. 2D, there is a possibility that the nanowire 10 is in an amorphous state by rapidly stretching the glass template 21 after the glass template 21 is heated. Therefore, the crystallinity of the nanowire 10 is improved by heating and slowly cooling the chip 23 in this step.

  Specifically, as shown in FIG. 3B, a heating / slow cooling device 81 is prepared. The heating / slow cooling device 81 includes a heater 82, and each chip 23 can be heated by the heater 82. That is, the nanowire array chip 23 on which the electrodes 31 and 32 are formed is placed in the heating / slow cooling device 81. And after heating once to the melting temperature of Bi or more and glass softening temperature or less (for example, 300 degreeC-430 degreeC), it cools to room temperature over about 24 hours, for example. Thereby, the crystallinity of the nanowire 10 can be improved. Thus, the thermoelectric conversion element S1 shown in FIG. 1 is completed.

Subsequently, the performance of the thermoelectric conversion element S1 obtained as described above as a thermoelectric material will be described. As described above, the performance of the thermoelectric conversion material is evaluated by the dimensionless figure of merit ZT. Where T is expressed as absolute temperature (K), Z is expressed as S ² σ / κ, S is Seebeck coefficient (V / K), σ is electrical conductivity (/ Ωm), and κ is thermal conductivity (W / mK).

  The Seebeck coefficient S of the nanowire 10 is extremely high compared to the bulk material because the diameter is nano-size, and the Seebeck coefficient of φ10 nm is 10 times or more that of the bulk material. Thus, about 700 μV / K (bulk is about 50 μV / K) is obtained as the Seebeck coefficient.

On the other hand, the thermal conductivity of Bi is 7.87 W / mK (near room temperature), the thermal conductivity of glass is about 1 W / mK, and considering the case where the cross-sectional area ratio is 30% as described above, the nanowire array chip 23 The overall thermal conductivity κ is about 3.1 W / mK. Further, Bi has an electric conductivity of 0.84 × 10 ⁶ / Ωm (18 ° C.), but glass is an insulator, and the electric conductivity of the nanowire array chip 23 is considered when the cross-sectional area ratio is 30%. Is 0.25 × 10 ⁶ / Ωm. As a result, Z is about 0.04, and the dimensionless figure of merit ZT at 300K is 12, which can be higher than that of a bulk thermoelectric material that usually provides only about 1 ZT.

  As described above, in the present embodiment, the nanowire 10 is inserted into the glass template 21 by filling the through hole 22 of the glass template 21 with Bi; Te, which is a thermoelectric conversion material, and heating and stretching the glass template 21. It is characterized by forming.

  Therefore, since Bi is filled in and stretched in a large number of micron-sized through holes 22 provided in the glass template 21, nano-sized wires can be reliably formed in the glass template 21. Furthermore, since the nanowire 10 can be spontaneously formed simply by stretching the glass template 21, the nanowire 10 can be formed with good yield and reliability. Thus, when forming the nanowire 10, the diameter of the nanowire 10 can also be controlled by controlling the length of the glass template 21 to be stretched.

  Moreover, since the glass template 21 is glass, the thermal conductivity of the glass member 20 of the formed chip 23 is low (about 1 W / mK), and performance degradation due to heat loss through the glass member 20 can be suppressed. . Furthermore, since the length for cutting the stretched glass template 21 can be set freely, for example, a chip 23 having a length on the order of mm can be easily formed. That is, since the distance between the electrodes 31 and 32 can be increased and the temperature difference can be increased, the thermoelectric conversion characteristics can be improved.

  In addition, since it is the method of extending and forming the nanowire 10 as mentioned above, a manufacturing process is also simple and can provide low-cost thermoelectric conversion element S1.

(Second Embodiment)
In the present embodiment, only parts different from the first embodiment will be described. In this embodiment, after the process shown in FIG. 2D, the stretched columnar glass template 21 is arranged in a rectangular shape.

  FIG. 4 is a diagram illustrating a manufacturing process of the thermoelectric conversion element S1 according to the second embodiment of the present invention. This drawing shows a cross section of the glass template 21 stretched in the step of FIG. 4A is a cross-sectional view of the glass template 21 before deformation, and FIG. 4B is a cross-sectional view of the glass template 21 after deformation.

  That is, after finishing the process of FIG.2 (d), in the process shown by Fig.4 (a), four metal mold | dies 91-94 (equivalent to the shaping | molding member of this invention) corresponding to each square-shaped edge | side are shown. Prepare and place each on the side of the glass template 21.

  Then, in the step shown in FIG. 4B, the molds 91 to 94 are moved to the opposite sides, and the molds 91 to 94 are pressed against the side surface of the glass template 21. Thereby, the glass template 21 can be shape | molded so that the cross section of the glass template 21 may become square shape.

  Thereafter, by performing the steps after the step shown in FIG. 2E, the nanowire array chip 23 having a quadrangular cross section can be formed.

  In this way, by manufacturing the nanowire array chip 23 having a quadrangular cross section, when a module is formed by arranging a large number of nanowire array chips 23 in the horizontal direction, the module having a quadrangular shape is more preferable than the chip 23 having a circular cross section. The chips 23 can be arranged with high density. Thereby, the power per unit area obtained as a module using many thermoelectric conversion elements S1 can be made larger than that having a circular cross section.

  As described above, the outer shape of the stretched glass template 21 can be pushed in with the dies 91 to 94 to manufacture the nanowire array chip 23 having a square cross section.

(Third embodiment)
In the present embodiment, only different portions from the above embodiments will be described. The present embodiment is characterized in that both ends of the nanowire 10 are exposed from the glass member 20 after the step shown in FIG.

  FIG. 5 is a diagram illustrating a manufacturing process of the thermoelectric conversion element S1 according to the third embodiment of the present invention. In the present embodiment, the etching process is performed on each chip 23 after the process shown in FIG. Specifically, each chip 23 is immersed in buffered hydrofluoric acid. Thereby, the glass which is the glass member 20 is slightly etched, and the nanowire array chip 23 having the nanowire 10 protruding from the glass member 20 is formed.

  Thus, after exposing the both ends 10a and 10b of the nanowire 10 from the glass member 20, each electrode 31 and 32 is formed in the both end surfaces of the glass member 20 which the both ends 10a and 10b of the nanowire 10 exposed (FIG. 3). (See (a)). Thereby, the electrical connection characteristic of each electrode 31 and 32 and the both ends 10a and 10b of the nanowire 10 can be improved more.

(Other embodiments)
In each said embodiment, you may change the material and size used for the thermoelectric conversion element S1 according to the condition used. Similarly, the size of the glass template 21, the content of the nanowire 10 in the glass member 20, and the like are not limited to the above embodiments.

  In the above embodiment, a method using the ion plating apparatus 71 is adopted as a method of forming the electrodes 31 and 32. However, the method is not limited to this method, and a sputtering or vapor deposition method may be adopted.

  Moreover, although the same material as the glass template 21 is used as the dummy glasses 51 and 52, you may fix with another material. However, when two materials having different coefficients of thermal expansion are stretched, stress or the like may occur on the glass template 21 side. Therefore, it is preferable to use the same material as the glass template 21 as the dummy glasses 51 and 52. .

1 is a schematic perspective view of a thermoelectric conversion element according to a first embodiment of the present invention. It is the figure which showed the manufacturing process of the thermoelectric conversion element which concerns on FIG. FIG. 3 is a diagram illustrating a manufacturing process subsequent to FIG. 2. It is the figure which showed the manufacturing process of the thermoelectric conversion element which concerns on 2nd Embodiment of this invention. It is the figure which showed the manufacturing process of the thermoelectric conversion element which concerns on 3rd Embodiment of this invention. It is the figure which showed the mode of conventional nanowire preparation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Nanowire, 20 ... Glass member, 21 ... Glass template as base material, 22 ... Through-hole, 23 ... Nanowire array chip, 31, 32 ... Electrode, 40 ... Pressurization tank, 41 ... Heating tank, 43 ... Bi fusion Liquid, 51, 52 ... dummy glass as a fixing member, 61, 62 ... work as a pulling member, 91-94 ... mold as a molding member.

Claims (11)

A step of preparing a base material (21) formed of glass and having a large number of through holes (22) formed;
Filling the numerous through holes with a thermoelectric conversion material;
The base material is heated above the melting point of the thermoelectric conversion material at a temperature equal to or higher than the softening temperature of the thermoelectric conversion material, and the base material is stretched in the axial direction of the through hole. 10) forming,
Cutting the stretched base material in a direction perpendicular to the axial direction of the through hole to form a chip (23), and a method for manufacturing a thermoelectric conversion element. In the step of forming the nanowire in the base material,
In the base material, fixing the fixing members (51, 52) to the surface on which the thermoelectric conversion material is exposed from the through hole and the surface opposite to the surface;
Fixing the tension members (61, 62) on the surface of the fixing member opposite to the surface on which the base material is fixed;
The base material is heated to a temperature above the softening temperature of the base material and above the melting point of the thermoelectric conversion material, and at least one of the tension members is moved to stretch the base material so as to separate the tension member. The method of manufacturing a thermoelectric conversion element according to claim 1, further comprising: a process. The method for manufacturing a thermoelectric conversion element according to claim 2, wherein, in the step of fixing the fixing member, the fixing member is made of the same material as the base material. The step of forming the chip includes a step of forming electrodes (31, 32) on both end faces of the chip where the end faces of the nanowires are exposed after cutting the base material. The manufacturing method of the thermoelectric conversion element as described in any one of 1-3. In the step of forming the chip, after the electrode is formed, the chip is heated to a temperature equal to or higher than a melting temperature of the thermoelectric conversion material and equal to or lower than a temperature at which the base material softens, and then gradually cooled. The manufacturing method of the thermoelectric conversion element of Claim 4. In the step of forming the nanowire in the base material, the base material is stretched in the axial direction of the through hole, and then the base material is cut perpendicularly to the axial direction of the through hole. 6. The method of manufacturing a thermoelectric conversion element according to claim 1, wherein a molding member (91 to 94) is pressed against a side surface of the stretched base material so as to be formed. . 7. The method according to claim 1, wherein the step of forming the chip includes a step of performing an etching process for dissolving both end surfaces of the chip where the end surfaces of the nanowires are exposed. 8. A method for manufacturing a thermoelectric conversion element. In the step of filling the numerous through holes with the thermoelectric conversion material,
A heating tank (41) is installed in the pressurizing tank (40), and a melt (43) is prepared by melting the thermoelectric conversion material in the heating tank in a state where the atmospheric pressure is reduced from the atmospheric pressure. Process,
Immersing the base material in which the multiple through-holes are formed in the melt such that the multiple through-holes are covered with the melt;
The inside of the pressurizing tank is returned to atmospheric pressure, and an inert gas is introduced into the pressurizing tank so that the inside of the pressurizing tank is in a pressurized state, and the inside of the numerous through holes formed in the base material The method of manufacturing a thermoelectric conversion element according to claim 1, further comprising a step of filling the melt with the melt. 9. The manufacturing of a thermoelectric conversion element according to claim 1, wherein a metal containing Bi is used as the thermoelectric conversion material in the step of filling the numerous through holes with the thermoelectric conversion material. Method. A columnar glass member (20), a number of nanowires (10) fixed in the glass member and extending in the axial direction of the columnar member, and both end surfaces of the glass member are electrically connected to both end surfaces of the nanowire. A thermoelectric conversion element that converts a temperature difference between the electrodes into an electromotive force by the nanowire,
The diameter of the nanowire is a diameter at which a Seebeck coefficient higher than the Seebeck coefficient that the material constituting the nanowire has as a bulk is expressed by a quantum effect. The thermoelectric conversion element according to claim 10, wherein the thermoelectric conversion material is a metal containing Bi.

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