WO2024079811A1 - Thermoelectric conversion device - Google Patents

Thermoelectric conversion device Download PDF

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Publication number
WO2024079811A1
WO2024079811A1 PCT/JP2022/038027 JP2022038027W WO2024079811A1 WO 2024079811 A1 WO2024079811 A1 WO 2024079811A1 JP 2022038027 W JP2022038027 W JP 2022038027W WO 2024079811 A1 WO2024079811 A1 WO 2024079811A1
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thermoelectric conversion
conversion film
temperature
composition
substrate
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PCT/JP2022/038027
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French (fr)
Japanese (ja)
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敦 塚▲崎▼
宏平 藤原
純一 塩貝
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国立大学法人東北大学
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Priority to PCT/JP2022/038027 priority Critical patent/WO2024079811A1/en
Publication of WO2024079811A1 publication Critical patent/WO2024079811A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
    • H02N11/00—Generators or motors not provided for elsewhere; Alleged perpetua mobilia obtained by electric or magnetic means
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N15/00—Thermoelectric devices without a junction of dissimilar materials; Thermomagnetic devices, e.g. using the Nernst-Ettingshausen effect
    • H10N15/20—Thermomagnetic devices using thermal change of the magnetic permeability, e.g. working above and below the Curie point
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N59/00—Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00

Definitions

  • the present invention relates to a thermoelectric conversion device.
  • Thermoelectric conversion technology is attracting attention as an essential technology for energy recycling, energy conservation, and advanced IoT technology.
  • Thermoelectric conversion technology is used to generate thermoelectromotive force for a variety of applications, such as power generation from exhaust heat recovery in factories and automobiles, monitoring with heat flow sensors, and power generation using the temperature difference between body heat and the outside air.
  • thermoelectromotive force generated by thermoelectric conversion is widely due to the Seebeck effect.
  • semiconductor materials with a high Seebeck coefficient.
  • the direction in which the thermoelectromotive force is generated is the same as (parallel to) the direction of the temperature difference, there are often restrictions on the element design, such as the need for a three-dimensional element structure to increase the electromotive force.
  • semiconductor materials that generate high thermoelectromotive force are often composed of rare and toxic elements. Semiconductor materials are also known to be mechanically fragile, and improvements are required from the perspective of reducing environmental impact and making them more flexible.
  • thermoelectric materials that generate thermoelectromotive force due to the anomalous Nernst effect have been attracting attention (Patent Document 1, etc.).
  • the difference is that the thermoelectromotive force due to the Seebeck effect is generated parallel to the direction of the temperature gradient, whereas the thermoelectromotive force due to the anomalous Nernst effect is generated perpendicular to both the direction of the temperature gradient and the magnetization direction of the sample.
  • the thermoelectromotive force is generated in the X-axis direction. Therefore, by devising the shape, size, arrangement, etc. of the thermoelectric material, it is possible to adjust the magnitude of the thermoelectromotive force while also making it possible to utilize an element structure different from that of conventional thermoelectric conversion devices using the Seebeck effect.
  • Non-Patent Document 1 Materials that have been reported so far as exhibiting excellent thermoelectric properties due to the anomalous Nernst effect are crystalline bulk samples and crystalline thin film samples, but they generally require high-temperature treatment in the manufacturing process (e.g., Non-Patent Document 1, etc.). Therefore, it is difficult to form a thin film at room temperature on a flexible organic polymer substrate or a general-purpose glass substrate. In addition, some materials are difficult to form thin films while maintaining their crystal structure. In addition, in recent years, flexible thermoelectric conversion elements in which Fe, Ni, Cr, Al, or the like is dispersed in a polymer have been reported (e.g., Patent Document 2).
  • thermoelectric conversion material consisting of a single component that can be mounted on a substrate as an element is required.
  • the present invention was made in consideration of the above circumstances, and aims to provide a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
  • the present invention adopts the following measures.
  • thermoelectric conversion device comprises a substrate, a thermoelectric conversion film formed on one surface of the substrate, a first temperature applying means for applying a temperature to the substrate side of the thermoelectric conversion film, and a second temperature applying means for applying a temperature to the side of the thermoelectric conversion film opposite the substrate that is different from the temperature of the substrate side, and the thermoelectric conversion film has an amorphous structure made of a composition containing Fe and Sn.
  • the present invention provides a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
  • FIG. 1 is a perspective view of a thermoelectric conversion device according to an embodiment of the present invention.
  • FIG. 2 is a perspective view of a thermoelectric conversion device according to an application example 1 of the embodiment.
  • FIG. 11 is a perspective view of a thermoelectric conversion device according to an application example 2 of the same embodiment.
  • 1 shows the results of measuring the X-ray diffraction pattern of a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe x Sn 1-x , where (a) to (f) show the results when x is 0.42, 0.52, 0.60, 0.65, 0.74, 0.84, and 0.87, respectively.
  • FIG. 1 is a graph showing the relationship between the anomalous Nernst coefficient S xy and the Fe composition ratio x in thermoelectric conversion films formed on a glass substrate and represented by the composition formulas Fe x Sn 1-x and Fe x ( Aly Sn 1-y ) 1-x.
  • the white circles are graphs showing the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 .
  • 1 is a graph showing the relationship between lateral thermal conductivity ⁇ xy and Fe composition ratio x in thermoelectric conversion films formed on a glass substrate and represented by the composition formulas Fe x Sn 1-x and Fe x (Al y Sn 1-y ) 1-x.
  • the white circles represent the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 .
  • 1 is a graph showing the relationship between the Hall angle ⁇ xy / ⁇ xx and the Fe composition ratio x in a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe x Sn 1- x.
  • the white circles represent the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 .
  • 1 shows the results of measuring an X-ray diffraction pattern of a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 .
  • 1 shows a transmission electron microscope image of a thermoelectric conversion film represented by a composition formula Fe 0.60 Sn 0.40 formed on an Al 2 O 3 substrate.
  • 1 shows a transmission electron microscope image of a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe 0.491 Sn 0.278 Ta 0.231 .
  • thermoelectric conversion device according to an embodiment of the present invention will be described in detail below with reference to the drawings.
  • the drawings used in the following description may show enlarged characteristic parts for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of the components may not be the same as in reality.
  • the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and may be modified as appropriate within the scope of the present invention.
  • thermoelectric conversion device 1 is a perspective view of a thermoelectric conversion device 100 according to an embodiment of the present invention.
  • the thermoelectric conversion device 100 mainly includes a substrate 101, a thermoelectric conversion film 102, a first electrode 103, a second electrode 104, a first temperature application means 105, and a second temperature application means 106.
  • a Z axis perpendicular to one surface (principal surface) 101a of the substrate, and an X axis and a Y axis perpendicular to each other in a plane parallel to the surface 101a are defined.
  • the substrate 101 is not limited in shape, but is preferably flat.
  • the material of the substrate 101 may be any material capable of forming the thermoelectric conversion film 102, and is determined according to the material of the thermoelectric conversion film 102.
  • the thermoelectric conversion film 102 made of a metal material is used, so that the substrate material may be, for example, Al 2 O 3 , SiO 2 , MgO, SrTiO 3 , glass, polymer, or the like.
  • an amorphous substrate such as glass, which does not have the effect of promoting thin film crystallization due to the matching of crystal orientation and lattice constant, as the substrate.
  • flexibility is required for the substrate 101, it is preferable to use, for example, an organic material, a polymer film, a resin film, or the like, which has low thermal conductivity, insulating properties, and is flexible.
  • the thermoelectric conversion film 102 is formed on one surface 101a of the substrate, and is made of an Fe-Sn composition containing Fe (iron) and Sn (tin).
  • This composition is expressed by the composition formula Fe x Sn 1-x , where 0.4 ⁇ x ⁇ 0.9.
  • a film of the Fe-Sn composition can be formed on any substrate at room temperature (about 25 to 30° C.), and is inexpensive and environmentally friendly.
  • the thermoelectric conversion film 102 has magnetism due to Fe, and therefore exhibits the anomalous Nernst effect when magnetized in a specific direction and subjected to a temperature gradient.
  • the anomalous Nernst effect is a phenomenon in which an electric field (electromotive force) is generated in the cross product direction of the temperature gradient and magnetization.
  • an electric field electroactive force
  • thermoelectromotive force coefficient exceeding 1 ⁇ V/K
  • a magnetic field is applied by a magnetic field application means (not shown) in a direction parallel to one surface of the substrate to magnetize the thermoelectric conversion film 102, but the direction of magnetization may be freely set depending on the application, and for example, the film may be magnetized in a direction perpendicular to one surface of the substrate.
  • Methods for controlling the magnetization direction include a method in which a magnetic field generating means such as a magnet is placed around the film to apply a magnetic field in a predetermined direction to the part to be magnetized, as well as a method in which light in a polarized state corresponding to the magnetization direction is irradiated onto the part to be magnetized.
  • the composition may further include an element A selected from transition elements such as Ta (tantalum), W (tungsten), Pt (platinum), Mo (molybdenum), and Mn (manganese) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction.
  • transition elements such as Ta (tantalum), W (tungsten), Pt (platinum), Mo (molybdenum), and Mn (manganese) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction.
  • the composition is represented by a composition formula Fe x-y Sn 1-x-z A y+z , where 0.4 ⁇ x ⁇ 0.9, 0.05 ⁇ y ⁇ 0.6, and 0.05 ⁇ z ⁇ 0.4.
  • the composition may further include an element B selected from magnetic elements such as typical elements such as In (indium), Al (aluminum), Ge (germanium), Si (silicon), and Ga (gallium) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction.
  • element B selected from magnetic elements such as typical elements such as In (indium), Al (aluminum), Ge (germanium), Si (silicon), and Ga (gallium) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction.
  • the composition is represented by the formula Fe x-y Sn 1-x-z B y+z , where 0.4 ⁇ x ⁇ 0.9, 0.05 ⁇ y ⁇ 0.6, and 0.05 ⁇ z ⁇ 0.4.
  • thermoelectric conversion film 102 The shape of the thermoelectric conversion film 102 is determined depending on the application. In this embodiment, a thermoelectric conversion film 102 having a shape that extends in one direction (X direction) is exemplified.
  • the thickness of the thermoelectric conversion film 102 is not limited, but is preferably 4 nm or more and 1000 nm or less. The Seebeck coefficient and the anomalous Nernst coefficient do not depend on the thickness of the thermoelectric conversion film 102.
  • the thermoelectric conversion film 102 has a mostly amorphous (non-crystalline, glass) structure, is a soft magnetic material, is flexible, and has high mechanical strength (tensile strength, toughness, hardness, etc.) and corrosion resistance.
  • the fact that the thermoelectric conversion film 102 has an amorphous structure can be indirectly confirmed, for example, by performing X-ray diffraction measurement. If no sharp peak due to Bragg reflection is observed in the X-ray diffraction pattern obtained by the measurement, that is, if the peak value due to Bragg reflection is equivalent to the noise (signal-to-noise ratio (S/N ratio) is 30 or less), it can be determined that the thermoelectric conversion film 102 has an amorphous structure.
  • the amorphous structure preferably accounts for 50% or more of the volume ratio of the thermoelectric conversion film 102.
  • thermoelectric conversion device 100 By using a flexible substrate 101, the flexibility of the thermoelectric conversion device 100 can be increased.
  • the flexibility of the thermoelectric conversion device 100 can be confirmed, for example, by using a jig with a curved surface. That is, if the thermoelectric conversion device 100 is attached in a bent state to the curved surface of the jig and a state in which no cracks occur in the substrate 101 and the thermoelectric conversion film can be maintained, then it can be determined that the thermoelectric conversion device 100 is flexible.
  • the thermoelectric conversion film 102 may be an almost completely amorphous structure (90% or more of the total volume), or may have microcrystals with a plurality of nanocrystalline portions (nanocrystalline portions) distributed within the amorphous structure. As long as the thermoelectric conversion film 102 contains 50% or more of an amorphous structure, the volume ratio of the nanocrystalline structure in the thermoelectric conversion film 102 is not particularly limited.
  • the first electrode 103 and the second electrode 104 are made of a conductive material such as indium, gold or silver paste, a metal conductor such as gold or aluminum, or a vapor-deposited film of gold or platinum.
  • the first electrode 103 is connected to a part of the thermoelectric conversion film 102 (the left end in FIG. 1 ), and the second electrode 104 is connected to another part of the thermoelectric conversion film 102 (the right end in FIG. 1 ).
  • the first electrode 103 and the second electrode 104 are configured to output the thermoelectromotive force generated between the first electrode 103 and the second electrode 104. It should be noted that the first electrode 103 and the second electrode 104 do not need to be provided in cases where electric power is directly extracted.
  • the first temperature applying means 105 and the second temperature applying means 106 are means (such as a commercially available temperature regulator) for applying temperature to a predetermined portion of the thermoelectric conversion film 102.
  • the first temperature applying means 105 is disposed so as to apply the temperature of the substrate 101 side (lower side in FIG. 1) of the thermoelectric conversion film 102, and is connected to the thermoelectric conversion film 102 via the substrate 101.
  • the second temperature applying means 106 is disposed so as to apply the temperature of the side opposite the substrate 101 of the thermoelectric conversion film 102 (upper side in FIG. 1), and is directly connected to the thermoelectric conversion film 102.
  • the first temperature providing means 105 and the second temperature providing means 106 are not limited to devices such as a heat source such as a heater or a heat bath or a refrigerant that passes electricity through a resistor that accurately adjusts the temperature, but may also be waste heat generated by friction or industry, or heat from the surrounding environment such as human body temperature or air temperature. Any device may be used as long as it generates a different temperature difference that is a significant temperature difference between the first temperature providing means 105 and the second temperature providing means 106.
  • the direction of the temperature gradient ⁇ T is the Z-axis direction
  • the direction of the magnetization M is the Y-axis direction
  • the thermoelectromotive force due to the anomalous Nernst effect is generated in the X-axis direction, which is parallel to one surface 101a of the substrate. Therefore, by forming the thermoelectric conversion film 102 long in the X-axis direction, the obtained thermoelectromotive force can be increased.
  • thermoelectric conversion device 100 of this embodiment can be manufactured mainly through the following steps.
  • thermoelectric conversion film 102 is formed on one surface 101a of the substrate by using a known film formation method such as a sputtering method.
  • a film formation method such as a sputtering method.
  • an RF magnetron sputtering device and a mosaic target in which 10 mm square Fe chips are arranged on a 2-inch diameter Sn disk can be used, and the conditions are as follows: substrate temperature: room temperature, RF output: 50 W, Ar gas pressure: 0.5 Pa, and target-substrate distance: 100 mm. Under these film formation conditions, a thermoelectric conversion film 102 having an amorphous structure can be obtained.
  • the conditions may be set to a substrate temperature of 0° C. or higher and 400° C. or lower, an RF output of 5 to 200 W, an Ar gas pressure of 0.01 to 10 Pa, and a target-substrate distance of 50 to 200 mm.
  • the formed thermoelectric conversion film 102 is processed into a desired shape using a photolithography method or the like.
  • the processed thermoelectric conversion film 102 may be subjected to a heat treatment at a temperature of 0° C. or more and 400° C. or less, at which crystallization does not occur, for 0 to 24 hours.
  • the thermoelectric conversion film 102 of the present invention can also be manufactured by a manufacturing method such as vacuum deposition, electron beam deposition, molecular beam epitaxy, chemical vapor deposition, electrodeposition, or the like.
  • a known film formation method such as sputtering is used to form the first electrode 103 and the second electrode 104 connected to the thermoelectric conversion film 102.
  • the film formation conditions are the same as those for forming the thermoelectric conversion film.
  • the formed first electrode 103 and second electrode 104 are processed into a desired shape using a photolithography method or the like.
  • the processed first electrode 103 and second electrode 104 may be subjected to a heat treatment.
  • thermoelectric conversion device 100 is obtained.
  • the thermoelectric conversion device 100 of this embodiment has a thermoelectric conversion film 102 made of a composition combining Fe and Sn, and has excellent thermoelectric properties due to the anomalous Nernst effect. Furthermore, since the thermoelectric conversion film 102 of this embodiment has an amorphous structure for the most part, is highly flexible, and can be formed on various substrates at room temperature, the thermoelectric conversion device 100 of this embodiment can be used as a flexible device. Furthermore, the thermoelectric conversion film 102 of this embodiment has an amorphous structure for the most part, can be formed on any substrate at room temperature, is inexpensive, and is environmentally friendly. Furthermore, the Fe and Sn that make up the thermoelectric conversion film are low-toxicity materials, and therefore have a smaller environmental impact than when semiconductor materials such as bismuth and tellurium are used.
  • thermoelectric conversion film 102 When a temperature gradient is applied in the Z-axis direction to the thermoelectric conversion film 102 magnetized in the Y-axis direction as in this embodiment, a thermoelectromotive force due to the anomalous Nernst effect is generated in the X-axis direction parallel to one surface 101a of the substrate. Therefore, the magnitude of the generated thermoelectromotive force can be controlled by adjusting the size of the thermoelectric conversion film 102 in the X-axis direction.
  • thermoelectric conversion film 102 has a positive anomalous Nernst coefficient, and is magnetized in the positive direction of the Y axis (+Y direction), generating a thermoelectromotive force in the positive direction of the X axis (+X direction).
  • a thermoelectric conversion film 102 with a negative anomalous Nernst coefficient is magnetized in the positive direction of the Y axis (+Y direction)
  • a thermoelectromotive force is generated in the negative direction of the X axis (-X direction).
  • the thermoelectric conversion device 100 of this embodiment can be used in a variety of applications by combining such thermoelectric conversion films with anomalous Nernst coefficients of different signs.
  • thermoelectric conversion films containing Fe and Sn exhibit a significant anomalous Nernst effect even when amorphous.
  • Previous research has focused on crystalline materials to investigate the cause of the anomalous Nernst effect, but the cause remains unknown.
  • thermoelectric conversion films containing Fe and Sn While investigating the cause of the anomalous Nernst effect of thermoelectric conversion films containing Fe and Sn, the present inventors discovered that even thermoelectric conversion films composed entirely of amorphous materials exhibit a significant anomalous Nernst effect. Based on other analytical results, the present inventors believe that the cause of this is that in Fe and Sn, the kagome lattice, which is the basic structure of the Fe 3 Sn crystal mentioned in Non-Patent Document 1, is maintained in the short-distance region of nearest neighbor even in amorphous samples, and other analytical results support this.
  • the present inventors speculate that in Fe and Sn, the short-distance order of the kagome lattice exists at the nearest neighbor level, and the existence of this short-distance order contributes to the electronic state, leading to the manifestation of a large anomalous Nernst effect.
  • thermoelectric conversion device 110 is a perspective view of a thermoelectric conversion device 110 according to Application Example 1 of this embodiment.
  • the thermoelectric conversion film 102 is configured by combining two patterns of magnetic materials having different signs of the anomalous Nernst coefficient.
  • the other configuration of the thermoelectric conversion device 110 is similar to that of the thermoelectric conversion device 100, and at least the thermoelectric conversion device 110 has the same effects as the thermoelectric conversion device 100.
  • the same reference numerals are used to indicate parts corresponding to those of the thermoelectric conversion device 100.
  • the first temperature applying means 105 and the second temperature applying means 106 are omitted from the illustration.
  • the thermoelectric conversion film 102 of Application Example 1 has a wavy pattern 107 on one surface 101a of the substrate, and is composed of a plurality of first patterns (first magnetic bodies) 102A extending substantially parallel in the same direction (here, the Y-axis direction), and a second pattern 102B connecting adjacent first patterns 102A.
  • Adjacent first patterns 102A have anomalous Nernst coefficients of different signs.
  • one has an anomalous Nernst coefficient S XY + and magnetization M A of a positive sign
  • the other has an anomalous Nernst coefficient S XY - and magnetization M B of a negative sign.
  • the direction of magnetization M A and the direction of magnetization M B are the same.
  • thermoelectromotive force is generated in the negative direction of the Y axis (-Y direction), which is the direction of the cross product of the temperature gradient ⁇ T and the magnetization M.
  • a thermoelectromotive force is generated in the positive direction of the Y axis (+Y direction), which is the opposite direction to the cross product of the temperature gradient ⁇ T and the magnetization M.
  • thermoelectromotive force in the multiple first patterns 102A lined up in the X-axis direction alternates in the order of the patterns.
  • all of the first patterns 102A are connected in series via the second patterns 102B, and a current path is formed from one end 107a to the other end 107b of the wavy pattern 107.
  • thermoelectric conversion device 100 of this embodiment can be used in a variety of applications by combining such thermoelectric conversion films with different magnetization directions.
  • FIG. 3 is a perspective view of a thermoelectric conversion device 120 according to application example 2 of this embodiment.
  • the thermoelectric conversion film 102 is configured by combining two patterns of magnetic materials with different magnetization directions.
  • the other configuration of the thermoelectric conversion device 120 is the same as that of the thermoelectric conversion device 100, and at least provides the same effects as the thermoelectric conversion device 100. Parts corresponding to those in the thermoelectric conversion device 100 are indicated by the same reference numerals.
  • the first temperature applying means 105 and the second temperature applying means 106 are not shown.
  • the thermoelectric conversion film 102 of the application example 2 has a wavy pattern on one surface 101a of the substrate, and is composed of a plurality of first patterns (first magnetic bodies) 102C extending substantially parallel in the same direction (here, the Y-axis direction), and a second pattern (second magnetic body) 102D connecting adjacent first patterns 102C. Adjacent first patterns 102C are magnetized in opposite directions.
  • one of the two adjacent first patterns 102C has a magnetization M C in the + direction of the X-axis (+X direction), and the other has a magnetization M D in the - direction of the -X-axis (-X direction).
  • thermoelectromotive force is generated in the negative direction of the Y axis (-Y direction), which is the cross product direction of the temperature gradient ⁇ T and the magnetization M C.
  • a thermoelectromotive force is generated in the positive direction of the Y axis (+Y direction), which is the opposite direction to the cross product of the temperature gradient ⁇ T and the magnetization M D.
  • thermoelectromotive force in the multiple first patterns 102C arranged in the X-axis direction alternates depending on the arrangement.
  • all of the first patterns 102C are connected in series via the second patterns 102D, and a current path is formed from one end 107a to the other end 107b of the wavy pattern 107.
  • thermoelectric conversion device of the present invention using a thermoelectric conversion film composed only of amorphous material
  • thermoelectric conversion film composed only of amorphous material
  • composition Dependence A plurality of samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric properties were measured.
  • a glass substrate was used as the base material. The reason for using a glass substrate in this example is that if a crystalline substrate is used, it may be affected by the substrate and may partially crystallize (microcrystal formation).
  • a thin film (thickness 28 to 46 nm) made of a composition represented by the composition formula Fe x Sn 1-x was used as the thermoelectric conversion film.
  • thermoelectric conversion film that was almost 100% composed only of amorphous.
  • the amorphous structure was confirmed by an X-ray diffraction device (SmartLab manufactured by Rigaku Co., Ltd. and Empyrean manufactured by Spectris Malvern Panalytical Co., Ltd.).
  • a member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
  • thermoelectric conversion film A magnetic field (magnetic field applied perpendicular to the surface) was applied in the thickness direction of the thermoelectric conversion film to seven samples with Fe composition ratios x of 0.42, 0.52, 0.60, 0.65, 0.74, 0.84, and 0.87, and the temperatures of one end and the other end in the direction perpendicular to the magnetic field were set to 300 K using the first temperature application means and the second temperature application means, respectively.
  • first temperature application means side the other end (second temperature application means side) of the thermoelectric conversion film
  • the Hall voltage generated between the electrodes due to the anomalous Hall effect was measured.
  • the measurement results are shown in the graph of Fig. 5.
  • the horizontal axis of the graph indicates the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph indicates the Hall resistivity ⁇ yx [ ⁇ cm]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the Hall resistivity.
  • thermoelectric conversion film In seven samples, a magnetic field was applied in the thickness direction of the thermoelectric conversion film, and the temperature of one end side was maintained at about 302 K by the first temperature applying means in the direction perpendicular to the magnetic field without passing a current, while the temperature of the other end side was adjusted to about 307 K by the second temperature applying means.
  • first temperature applying means a sample holder of a refrigerator (VersaLab manufactured by Quantum Design) was used as a heat bath, and as the second temperature applying means, heating by applying current to a resistor was used.
  • the temperature difference generated in the sample was calculated by measuring the resistance of a Pt/Ti bilayer film formed on the same substrate as the thermoelectric conversion film, and by referring to a resistance-temperature dependency curve obtained in advance, the temperature at multiple points on the substrate was calculated. At this time, the thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect was measured.
  • the horizontal axis of the graph represents the magnetic field (T) applied perpendicular to the surface
  • the vertical axis of the graph represents the anomalous Nernst coefficient S xy [ ⁇ V ⁇ K ⁇ 1 ].
  • the relationship between the anomalous Nernst coefficient S xy and the thermoelectromotive force V xy is defined by the following formula (1) using the inter-electrode distance W used in the measurement and the temperature gradient ( ⁇ T) x in the x-axis direction.
  • the anomalous Hall effect was measured by the above-mentioned procedure, and the Hall angle ⁇ xy / ⁇ xx was calculated from the Hall resistivity ⁇ yx and the electrical resistivity ⁇ xx .
  • the Hall conductivity ⁇ xy and the electrical conductivity ⁇ xx are defined by the following formulas (2, 3).
  • ⁇ xy ⁇ yx / ( ⁇ xx 2 + ⁇ yx 2 ) (2)
  • ⁇ xx ⁇ xx / ( ⁇ xx 2 + ⁇ yx 2 ) (3)
  • ⁇ yx Hall resistivity ⁇ xx : Electrical resistivity
  • the anomalous Nernst effect was measured by the above-mentioned procedure, and the anomalous Nernst coefficient S xy and the transverse thermal conductivity ⁇ xy were calculated from the thermoelectromotive force V xy .
  • the black circles in Figures 7 to 9 are graphs showing the calculation results.
  • the horizontal axis shows the Fe composition ratio Fe/total constituent elements (atomic ratio).
  • FIG. 7 is a graph showing the relationship between the composition ratio of Fe and the anomalous Nernst coefficient.
  • the vertical axis of the graph shows the anomalous Nernst coefficient ( ⁇ V ⁇ K ⁇ 1 ).
  • the anomalous Nernst coefficient is an index of the performance of a thermoelectric conversion film that converts a temperature gradient into an electromotive force.
  • the larger the composition ratio x of Fe the larger the anomalous Nernst coefficient S xy .
  • the composition ratio x of Fe is 0.74 or more, it exceeds 1.0 ⁇ V ⁇ K ⁇ 1 , and it can be seen that the material has excellent thermoelectric properties comparable to the values reported for crystalline bulk Fe 3 Sn (see Non-Patent Document 1).
  • the composition ratio x of Fe is 0.87, the anomalous Nernst coefficient shows a maximum value of 2.00 ⁇ V ⁇ K ⁇ 1 .
  • the transverse thermal conductivity ⁇ xy (A/mK).
  • the transverse thermal conductivity ⁇ xy defined by formula (4) is the component (second term) due to the essential anomalous Nernst effect plus the component (first term) contributed by carriers (electrons and holes) generated by the Seebeck effect through the anomalous Hall effect. From the graph of FIG. 8, it can be seen that the transverse thermal conductivity ⁇ xy also tends to increase as the composition ratio x of Fe increases, similar to the anomalous Nernst coefficient.
  • FIG. 9 is a graph showing the relationship between the composition ratio of Fe and the Hall angle.
  • the vertical axis of the graph shows the tangent of the Hall angle ⁇ xy / ⁇ xx .
  • Example 1-2 [Dependence on composition elements]
  • a thermoelectric conversion film was obtained using a sputtering method, in which aluminum (Al) was used as an impurity, and the thin film (thickness 43 nm) made of a composition represented by the composition formula Fe x (Al y Sn 1-y ) 1-x was also made of only amorphous.
  • Al aluminum
  • the thin film thin film made of a composition represented by the composition formula Fe x (Al y Sn 1-y ) 1-x was also made of only amorphous.
  • Al modulates the electronic state near the Fermi state that contributes to the anomalous Nernst effect through modulation of spin-orbit interaction and carrier density.
  • a member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
  • Example 11 is a graph showing the measurement results.
  • thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect of the thin film of the composition containing aluminum as an impurity in Example 1-2 was measured.
  • FIG. 12 is a graph showing the measurement results.
  • Example 7 For comparison, the results of the thin film of the composition containing aluminum as an impurity in Example 1-2 are shown superimposed as white circles on the graph in Figure 7, which shows the relationship between the Fe composition ratio and the anomalous Nernst coefficient, the graph in Figure 8, which shows the relationship between the Fe composition ratio and the lateral thermal conductivity, and the graph in Figure 9, which shows the relationship between the Fe composition ratio and the Hall angle, for the FeSn of Example 1-1.
  • the amorphous thin film made of FeSn of the present invention has the potential to greatly improve the characteristics of a thermoelectric conversion device by adding, as an impurity, an element selected from transition elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction, and typical elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction, particularly non-magnetic elements such as aluminum and indium. Other elements will be shown in the experiments below.
  • Example 2-1 Thermoelectric conversion device of the present invention using amorphous thermoelectric conversion film containing microcrystals
  • composition Dependence the characteristics in the case where an amorphous thermoelectric conversion film containing microcrystals is used are examined. A number of samples of amorphous thermoelectric conversion films containing microcrystals were manufactured, and their thermoelectric properties were measured. Considering various applications of thermoelectric conversion devices, a sapphire Al 2 O 3 substrate, which is a general-purpose base material, was used.
  • a thin film (thickness 32-53 nm) made of a composition represented by the composition formula Fe x Sn 1-x could be formed on the Al 2 O 3 substrate as an amorphous thermoelectric conversion film containing microcrystals. From observations using a transmission microscope, etc., the proportion of microcrystals was estimated to be about 5-50% of the total. The proportion of microcrystals tended to increase as the composition proportion of Fe increased. A member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
  • thermoelectric conversion film A magnetic field (magnetic field applied perpendicular to the surface) was applied in the thickness direction of the thermoelectric conversion film to seven samples with Fe composition ratios x of 0.44, 0.51, 0.60, 0.65, 0.73, 0.84, and 0.87, and the temperatures of one end and the other end in the direction perpendicular to the magnetic field were set to 300 K using the first temperature application means and the second temperature application means, respectively.
  • first temperature application means side the other end (second temperature application means side) of the thermoelectric conversion film
  • the Hall voltage generated between the electrodes due to the anomalous Hall effect was measured.
  • the measurement results are shown in the graph of Fig. 13.
  • the horizontal axis of the graph indicates the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph indicates the Hall resistivity ⁇ yx [ ⁇ cm]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the Hall resistivity.
  • thermoelectric conversion film In seven samples, a magnetic field was applied in the thickness direction of the thermoelectric conversion film, and a current was not applied. In the direction perpendicular to the magnetic field, the temperature of one end side was maintained at about 300 K by the first temperature application means, while the temperature of the other end side was adjusted to about 306 K by the second temperature application means.
  • first temperature application means a sample holder of a refrigerator (VersaLab manufactured by Quantum Design) was used as a heat bath, and as the second temperature application means, current heating to a resistor was used. At this time, the thermoelectromotive force generated between the electrodes due to the anomalous Nernst effect was measured.
  • the temperature gradient generated in the sample was estimated from a calibration curve of the relationship between the applied current and the temperature difference evaluated separately using an Al 2 O 3 substrate equipped with a resistance thermometer. The temperature gradient of 0.937 K mm -1 estimated from this calibration curve was used.
  • the horizontal axis of the graph represents the magnetic field (T) applied perpendicular to the surface
  • the vertical axis of the graph represents the anomalous Nernst coefficient S xy [ ⁇ V ⁇ K ⁇ 1 ]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the anomalous Nernst coefficient. It can also be seen that a large anomalous Nernst coefficient occurs at a certain composition ratio, depending on the Fe composition ratio.
  • Example 15 to 17 are graphs showing the calculation results. In each graph, the horizontal axis shows the composition ratio of Fe Fe/total constituent elements (atomic ratio).
  • FIG. 15 is a graph showing the relationship between the composition ratio of Fe and the anomalous Nernst coefficient.
  • the vertical axis of the graph shows the anomalous Nernst coefficient ( ⁇ V ⁇ K ⁇ 1 ).
  • the anomalous Nernst coefficient S xy increases as the composition ratio x of Fe increases.
  • the composition ratio x of Fe is 0.6 or more, it exceeds 1.0 ⁇ V ⁇ K ⁇ 1 , and it can be seen that the material has excellent thermoelectric properties comparable to the values reported for crystalline bulk Fe 3 Sn (Sci. Adv. is cited as a non-patent document).
  • the composition ratio x of Fe is 0.87, the anomalous Nernst coefficient shows a maximum value of 2.80 ⁇ V ⁇ K ⁇ 1 .
  • FIG 16 is a graph showing the relationship between the Fe composition ratio and the transverse thermal conductivity.
  • the vertical axis of the graph shows the transverse thermal conductivity ⁇ xy (A/mK).
  • the transverse thermal conductivity ⁇ xy also tends to increase as the Fe composition ratio x increases, similar to the anomalous Nernst coefficient.
  • thermoelectric conversion device of the present invention Three samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric characteristics were measured.
  • the Fe composition ratio x in the three samples was 0.60, 0.60, and 0.60, and the thickness t of the thermoelectric conversion film was 20 nm, 40 nm, and 100 nm.
  • the other configurations were the same as in Example 2-1.
  • thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect was measured in the same manner as described in Example 1-1.
  • the thermoelectric coefficient S xy was calculated using the measurement results. The calculation results are shown in Table 1. It can be seen that the anomalous Nernst coefficient S xy is almost constant regardless of the thickness t of the thermoelectric conversion film.
  • thermoelectric conversion devices of Example 2-2 one in which the thermoelectric conversion film was made of a composition represented by the composition formula Fe0.60Sn0.40 and was fabricated on an Al2O3 substrate was selected, and the surface of the thermoelectric conversion film was observed using a transmission electron microscope.
  • Figure 18 is an enlarged image of a portion of the observed surface. It can be seen that crystalline portions 108B are scattered in the thermoelectric conversion film having a mainly amorphous structure 108A.
  • thermoelectric conversion device of the present invention A plurality of samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric properties were measured.
  • An Al2O3 substrate was used as the base material.
  • a thin film made of a composition containing three elements was used as the thermoelectric conversion film.
  • the composition formula of the composition was Fe0.415Ta0.218Sn0.367 , Fe0.511Ta0.217Sn0.272 , Fe0.717In0.034Sn0.349, Fe0.697Al0.098Sn0.205 , and Fe0.768Al0.112Sn0.120 .
  • a member made of indium was used as the electrode.
  • the thermoelectromotive force Vxy generated between the electrodes due to the anomalous Nernst effect was measured, and the anomalous Nernst coefficient Sxy was calculated using the measurement results. The calculation results are shown in Table 2.
  • the anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.415 is about 0.25 in the case of the Fe--Sn composition (FIG. 15), whereas it is 0.90 in the case of the Fe--Sn--Ta composition (Table 2).
  • the anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.511 is about 0.4 in the case of the Fe--Sn composition (FIG. 15), whereas it is 1.22 in the case of the Fe--Sn--Ta composition.
  • the anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.717 is about 1.5 in the case of the Fe--Sn composition (FIG. 15), whereas it is 1.33 in the case of the Fe--Sn--In composition (Table 2).
  • the anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.697 is about 1.4 in the case of the Fe--Sn composition (FIG. 6), whereas it is 2.40 in the case of the Fe--Sn--Al composition (Table 2).
  • the anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.768 is about 1.8 in the case of an Fe--Sn composition (FIG. 15), whereas it is 2.80 in the case of an Fe--Sn--Al composition (Table 2).
  • the anomalous Nernst coefficient can be significantly increased.
  • Al causes a significant increase in the anomalous Nernst coefficient.
  • this result is thought to be due to the fact that the electronic state near the Fermi level that contributes to the anomalous Nernst effect is modulated, thereby enhancing the anomalous Nernst coefficient, which is an index of the performance of the thermoelectric conversion film.
  • other transition elements are often added as impurities from the viewpoint of modulating magnetic interactions, but the present invention achieves great effects with Al, a typical element that is less expensive than the transition element Ta.
  • the Fe-Sn composition of the present invention is an inexpensive material and is likely to achieve a significant increase in the anomalous Nernst coefficient.
  • the characteristics of the thermoelectric conversion device can be greatly improved by adding an element selected from among transition elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction as an impurity, and typical elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction.
  • thermoelectric conversion films of Example 2-3 one in which the thermoelectric conversion film was made of a composition represented by the composition formula Fe0.491Sn0.278Ta0.231 was selected, and the surface of the thermoelectric conversion film was observed using a transmission electron microscope.
  • Figure 19 is an enlarged image of a part of the observed surface. It can be seen that crystalline portions 109B are scattered in the thermoelectric conversion film having a mainly amorphous structure 109A.
  • thermoelectric conversion films obtained by dispersing metals in crystalline bulks, thin films, and polymers, but in the present invention, a high-performance thermoelectric conversion film was obtained from a magnetic thin film made of only an amorphous structure.
  • thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, can be manufactured at room temperature, and can be made compact as an element.
  • transition elements, typical elements, etc. can greatly improve the characteristics of thermoelectric conversion devices, so depending on the composition, revolutionary improvements in performance can be expected.
  • inexpensive typical elements such as Al can be expected to improve performance, making it possible to provide inexpensive, high-performance thermoelectric conversion devices.
  • the present invention provides a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
  • Thermoelectric conversion device 101 Substrate 101a... One surface of substrate 102... Thermoelectric conversion film 103... First electrode 104... Second electrode 105... First temperature application means 106... Second temperature application means 107... Wavy pattern 107a... One end of wavy pattern 107b... Other end of wavy pattern 108A, 109A... Amorphous structure 108B, 109B... Crystalline portion E... Thermoelectromotive force M... Magnetization ⁇ T... Temperature gradient

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Abstract

A thermoelectric conversion device (100) comprises: a substrate (101); a thermoelectric conversion film (102) formed on one surface (101a) of the substrate; a first temperature setting means (105) that sets the temperature of the thermoelectric conversion film (102) on the substrate (101) side; and a second temperature setting means (106) that sets the temperature of the thermoelectric conversion film (102) on the reverse side of the substrate (101) to a temperature different from the temperature on the substrate side. The thermoelectric conversion film (102) has an amorphous structure composed of a composition containing Fex and Sn1-x (0.4 ≤x≤ 0.9).　

Description

熱電変換装置Thermoelectric conversion device
　本発明は、熱電変換装置に関する。 The present invention relates to a thermoelectric conversion device.
　エネルギーリサイクル、省エネルギー化、ＩoＴ技術の高度化に不可欠な技術として、熱電変換の技術が注目されている。熱電変換の技術は、工場や自動車の排熱回収による発電、熱流センサによるモニタリング、体温と外気との温度差を利用した発電等の様々な用途で、熱起電力を発生させることに使われている。 Thermoelectric conversion technology is attracting attention as an essential technology for energy recycling, energy conservation, and advanced IoT technology. Thermoelectric conversion technology is used to generate thermoelectromotive force for a variety of applications, such as power generation from exhaust heat recovery in factories and automobiles, monitoring with heat flow sensors, and power generation using the temperature difference between body heat and the outside air.
　熱電変換で発生させる熱起電力としては、ゼーベック効果に起因したものが広く用いられている。ゼーベック効果による熱電変換を行う場合、高いゼーベック係数を有する半導体材料を用いるのが一般的である。しかしながら、熱起電力の発生方向が、温度差の付く方向と同じ方向（平行）であるため、高起電力化には立体的な素子構造が必要であるなど、素子設計上の制限が加わることが多い。また、高い熱起電力が生じる半導体材料は、希少性、毒性を有する元素から構成されることが多い。また、半導体材料は、機械的に脆いことが知られており、環境負荷の低減、フレキシブル化の観点から、改善が求められている。 The thermoelectromotive force generated by thermoelectric conversion is widely due to the Seebeck effect. When performing thermoelectric conversion using the Seebeck effect, it is common to use semiconductor materials with a high Seebeck coefficient. However, since the direction in which the thermoelectromotive force is generated is the same as (parallel to) the direction of the temperature difference, there are often restrictions on the element design, such as the need for a three-dimensional element structure to increase the electromotive force. Furthermore, semiconductor materials that generate high thermoelectromotive force are often composed of rare and toxic elements. Semiconductor materials are also known to be mechanically fragile, and improvements are required from the perspective of reducing environmental impact and making them more flexible.
　近年では、異常ネルンスト効果に起因して熱起電力を発生させる熱電材料が注目を集めている（特許文献１等）。ゼーベック効果による熱起電力は、温度勾配の向きに平行に発生するのに対し、異常ネルンスト効果による熱起電力は、温度勾配の向きと試料の磁化方向の両方に垂直な方向に発生する点で異なる。例えば、Ｙ軸方向に配向した磁化を有する熱電材料のＺ軸方向に温度勾配がある場合、熱起電力は、Ｘ軸方向に発生する。したがって、熱電材料の形状、大きさ、配置等を工夫することにより、熱起電力の大きさの調整を可能にしつつ、ゼーベック効果による従来の熱電変換装置とは異なる素子構造の活用も可能にすることができる。 In recent years, thermoelectric materials that generate thermoelectromotive force due to the anomalous Nernst effect have been attracting attention (Patent Document 1, etc.). The difference is that the thermoelectromotive force due to the Seebeck effect is generated parallel to the direction of the temperature gradient, whereas the thermoelectromotive force due to the anomalous Nernst effect is generated perpendicular to both the direction of the temperature gradient and the magnetization direction of the sample. For example, when there is a temperature gradient in the Z-axis direction of a thermoelectric material with magnetization oriented in the Y-axis direction, the thermoelectromotive force is generated in the X-axis direction. Therefore, by devising the shape, size, arrangement, etc. of the thermoelectric material, it is possible to adjust the magnitude of the thermoelectromotive force while also making it possible to utilize an element structure different from that of conventional thermoelectric conversion devices using the Seebeck effect.
　異常ネルンスト効果による優れた熱電特性を示す物質として、これまでに報告されているものは、結晶性バルク試料と結晶性薄膜試料であるが、その製造過程において高温処理を必要とすることが一般的である（例えば、非特許文献１等）。そのため、可撓性を有する有機ポリマー基板上や汎用的なガラス基板上に、室温で薄膜形成することが難しい。また、物質によっては、結晶構造を維持したまま薄く形成することが難しいものもある。
　また、近年、ポリマー中に、Ｆｅ、Ｎｉ、Ｃｒ、Ａｌ等を分散させたフレキシブルな熱電変換素子の報告があるが（例えば、特許文献２）、このような形態のものはポリマーと金属粒子という異なる材質の混合物であることから、熱的な安定性に問題があり、応用に不向きである。
　他の素子と組み合わせて小型の熱電モジュール等として用いるためには、基材上に素子として搭載することのできる、単一の構成物からなる薄膜形状の熱電変換材料が求められる。 Materials that have been reported so far as exhibiting excellent thermoelectric properties due to the anomalous Nernst effect are crystalline bulk samples and crystalline thin film samples, but they generally require high-temperature treatment in the manufacturing process (e.g., Non-Patent Document 1, etc.). Therefore, it is difficult to form a thin film at room temperature on a flexible organic polymer substrate or a general-purpose glass substrate. In addition, some materials are difficult to form thin films while maintaining their crystal structure.
In addition, in recent years, flexible thermoelectric conversion elements in which Fe, Ni, Cr, Al, or the like is dispersed in a polymer have been reported (e.g., Patent Document 2). However, such elements are a mixture of different materials, namely, a polymer and metal particles, and therefore have problems with thermal stability and are unsuitable for practical applications.
In order to use the material in combination with other elements as a small thermoelectric module or the like, a thin-film thermoelectric conversion material consisting of a single component that can be mounted on a substrate as an element is required.
特開２０２０－０９８８６０号公報JP 2020-098860 A 特開２０２１－１２８９９９号公報JP 2021-128999 A
　本発明は上記事情に鑑みてなされたものであり、優れた熱電特性および可撓性を有し、環境負荷が小さく、かつ室温で製造することが可能な熱電変換装置を提供することを目的とする。 The present invention was made in consideration of the above circumstances, and aims to provide a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
　上記課題を解決するため、本発明は以下の手段を採用している。 To solve the above problems, the present invention adopts the following measures.
　本発明の一態様に係る熱電変換装置は、基材と、前記基材の一面に形成された熱電変換膜と、前記熱電変換膜の前記基材側の温度を付与する第一温度付与手段と、前記熱電変換膜の前記基材と反対側の温度を前記基材側の温度と異なる温度に付与する第二温度付与手段と、を備え、前記熱電変換膜は、ＦｅとＳｎを含む組成物からなるアモルファス構造を有する。 A thermoelectric conversion device according to one embodiment of the present invention comprises a substrate, a thermoelectric conversion film formed on one surface of the substrate, a first temperature applying means for applying a temperature to the substrate side of the thermoelectric conversion film, and a second temperature applying means for applying a temperature to the side of the thermoelectric conversion film opposite the substrate that is different from the temperature of the substrate side, and the thermoelectric conversion film has an amorphous structure made of a composition containing Fe and Sn.
　本発明は、優れた熱電特性および可撓性を有し、環境負荷が小さく、かつ室温で製造することが可能な熱電変換装置を提供することができる。 The present invention provides a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
本発明の一実施形態に係る熱電変換装置の斜視図である。1 is a perspective view of a thermoelectric conversion device according to an embodiment of the present invention. 同実施形態の応用例１に係る熱電変換装置の斜視図である。FIG. 2 is a perspective view of a thermoelectric conversion device according to an application example 1 of the embodiment. 同実施形態の応用例２に係る熱電変換装置の斜視図である。FIG. 11 is a perspective view of a thermoelectric conversion device according to an application example 2 of the same embodiment. ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜のＸ線回折パターンの測定結果である。（ａ）～（ｆ）は、それぞれｘを０．４２、０．５２、０．６０、０．６５、０．７４、０．８４、０．８７とした場合の結果を示す。1 shows the results of measuring the X-ray diffraction pattern of a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe x Sn 1-x , where (a) to (f) show the results when x is 0.42, 0.52, 0.60, 0.65, 0.74, 0.84, and 0.87, respectively. ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜の異常ホール抵抗率ρｙｘと面直印加磁場の関係を示すグラフである。ｘ＝０．４２～０．８７の結果を示す。1 is a graph showing the relationship between the anomalous Hall resistivity ρ yx of a thermoelectric conversion film formed on a glass substrate and expressed by the composition formula Fe x Sn 1-x , and the magnetic field applied perpendicular to the surface, showing the results for x=0.42 to 0.87. ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜の異常ネルンスト係数Ｓｘｙと面直印加磁場の関係を示すグラフである。ｘ＝０．４２～０．８７の結果を示す。1 is a graph showing the relationship between the anomalous Nernst coefficient S xy of a thermoelectric conversion film formed on a glass substrate and expressed by the composition formula Fe x Sn 1-x , and the magnetic field applied perpendicular to the surface, showing the results for x=0.42 to 0.87. ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘおよびＦｅｘ（ＡｌｙＳｎ１－ｙ）１－ｘで表される熱電変換膜における異常ネルンスト係数ＳｘｙとＦｅの組成比ｘの関係を示すグラフである。図中、黒丸はＦｅｘＳｎ１－ｘにおけるｘ＝０．４２～０．８７の結果を示すグラフである。白丸はＡｌをドープした、Ｆｅ0.77（Ａｌ0.48Ｓｎ0.52）0.23の結果を示すグラフである。 1 is a graph showing the relationship between the anomalous Nernst coefficient S xy and the Fe composition ratio x in thermoelectric conversion films formed on a glass substrate and represented by the composition formulas Fe x Sn 1-x and Fe x ( Aly Sn 1-y ) 1-x. In the figure, the black circles are graphs showing the results for x = 0.42 to 0.87 in Fe x Sn 1-x . The white circles are graphs showing the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 . ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘおよびＦｅｘ（ＡｌｙＳｎ１－ｙ）１－ｘで表される熱電変換膜における横熱伝導度αｘｙとＦｅの組成比ｘの関係を示すグラフである。黒丸はＦｅｘＳｎ１－ｘにおけるｘ＝０．４２～０．８７の結果を示すグラフである。白丸はＡｌをドープした、Ｆｅ0.77（Ａｌ0.48Ｓｎ0.52）0.23の結果を示すグラフである。 1 is a graph showing the relationship between lateral thermal conductivity α xy and Fe composition ratio x in thermoelectric conversion films formed on a glass substrate and represented by the composition formulas Fe x Sn 1-x and Fe x (Al y Sn 1-y ) 1-x. The black circles represent the results for x = 0.42 to 0.87 in Fe x Sn 1-x . The white circles represent the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 . ガラス基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜におけるホール角σｘｙ／σｘｘとＦｅの組成比ｘの関係を示すグラフである。黒丸はＦｅｘＳｎ１－ｘにおけるｘ＝０．４２～０．８７の結果を示すグラフである。白丸はＡｌをドープした、Ｆｅ0.77（Ａｌ0.48Ｓｎ0.52）0.23の結果を示すグラフである。1 is a graph showing the relationship between the Hall angle σ xy /σ xx and the Fe composition ratio x in a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe x Sn 1- x. The black circles represent the results for x = 0.42 to 0.87 in Fe x Sn 1-x . The white circles represent the results for Al-doped Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 . ガラス基板上に作製された組成式Ｆｅ0.77（Ａｌ0.48Ｓｎ0.52）0.23で表される熱電変換膜のＸ線回折パターンの測定結果である。1 shows the results of measuring an X-ray diffraction pattern of a thermoelectric conversion film formed on a glass substrate and represented by the composition formula Fe 0.77 (Al 0.48 Sn 0.52 ) 0.23 . ガラス基板上に作製された組成式Ｆｅｘ（ＡｌｙＳｎ１－ｙ）１－ｘ（ｘ＝０．７４、ｙ＝０．４８）で表される熱電変換膜の異常ホール抵抗率ρｙｘと面直印加磁場の関係を示すグラフである。 1 is a graph showing the relationship between the anomalous Hall resistivity ρ yx and the magnetic field applied perpendicular to the surface of a thermoelectric conversion film formed on a glass substrate and represented by a composition formula Fe x (Al y Sn 1-y ) 1-x (x=0.74, y=0.48). ガラス基板上に作製された組成式Ｆｅｘ（ＡｌｙＳｎ１－ｙ）１－ｘ（ｘ＝０．７７、ｙ＝０．４８）で表される熱電変換膜の異常ネルンスト係数Ｓｘｙと面直印加磁場の関係を示すグラフである。1 is a graph showing the relationship between the anomalous Nernst coefficient S xy and the magnetic field applied perpendicular to the surface of a thermoelectric conversion film formed on a glass substrate and represented by a composition formula Fe x ( AlySn 1-y ) 1-x (x=0.77, y=0.48). Ａｌ２Ｏ３基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜の異常ホール抵抗率ρｙｘと面直印加磁場の関係（ｘ＝０．４４～０．８７）を示すグラフである。 1 is a graph showing the relationship between the anomalous Hall resistivity ρ yx and the magnetic field applied perpendicular to the surface (x=0.44 to 0.87) of a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe x Sn 1-x. Ａｌ２Ｏ３基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜の異常ネルンスト係数Ｓｘｙと面直印加磁場の関係（ｘ＝０．４４～０．８７）を示すグラフである。 1 is a graph showing the relationship between the anomalous Nernst coefficient S xy and the magnetic field applied perpendicular to the surface (x=0.44 to 0.87) of a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe x Sn 1-x. Ａｌ２Ｏ３基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜における異常ネルンスト係数ＳｘｙとＦｅの組成比ｘの関係（ｘ＝０．４４～０．８７）を示すグラフである。1 is a graph showing the relationship between the anomalous Nernst coefficient S xy and the Fe composition ratio x (x=0.44 to 0.87) in a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe x Sn 1 -x. Ａｌ２Ｏ３基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜における横熱伝導度αｘｙとＦｅの組成比ｘの関係（ｘ＝０．４４～０．８７）を示すグラフである。1 is a graph showing the relationship between lateral thermal conductivity α xy and Fe composition ratio x (x=0.44 to 0.87) in a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe x Sn 1-x . Ａｌ２Ｏ３基板上に作製された組成式ＦｅｘＳｎ１－ｘで表される熱電変換膜におけるホール角σｘｙ／σｘｘとＦｅの組成比ｘの関係（ｘ＝０．４４～０．８７）を示すグラフである。 1 is a graph showing the relationship between the Hall angle σ xy /σ xx and the Fe composition ratio x (x=0.44 to 0.87) in a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe x Sn 1-x. Ａｌ２Ｏ３基板上に作製された組成式Ｆｅ０．６０Ｓｎ０．４０で表される熱電変換膜の透過型電子顕微鏡像を示す。1 shows a transmission electron microscope image of a thermoelectric conversion film represented by a composition formula Fe 0.60 Sn 0.40 formed on an Al 2 O 3 substrate. Ａｌ２Ｏ３基板上に作製された組成式Ｆｅ０．４９１Ｓｎ０．２７８Ｔａ０．２３１で表される熱電変換膜の透過型電子顕微鏡像を示す。1 shows a transmission electron microscope image of a thermoelectric conversion film formed on an Al 2 O 3 substrate and represented by a composition formula Fe 0.491 Sn 0.278 Ta 0.231 .
　以下、本発明を適用した実施形態に係る熱電変換装置について、図面を用いて詳細に説明する。なお、以下の説明で用いる図面は、特徴を分かりやすくするために、便宜上特徴となる部分を拡大して示している場合があり、各構成要素の寸法比率などが実際と同じであるとは限らない。また、以下の説明において例示される材料、寸法等は一例であって、本発明はそれらに限定されるものではなく、その要旨を変更しない範囲で適宜変更して実施することが可能である。 The thermoelectric conversion device according to an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show enlarged characteristic parts for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of the components may not be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them, and may be modified as appropriate within the scope of the present invention.
（熱電変換装置）
　図１は、本発明の一実施形態に係る熱電変換装置１００の斜視図である。熱電変換装置１００は、主に、基材１０１と、熱電変換膜１０２と、第一電極１０３と、第二電極１０４と、第一温度付与手段１０５と、第二温度付与手段１０６と、を備える。ここで、基材の一面（主面）１０１ａに垂直なＺ軸と、一面１０１ａに平行な面内おいて互いに直交するＸ軸とＹ軸を定義する。 (Thermoelectric conversion device)
1 is a perspective view of a thermoelectric conversion device 100 according to an embodiment of the present invention. The thermoelectric conversion device 100 mainly includes a substrate 101, a thermoelectric conversion film 102, a first electrode 103, a second electrode 104, a first temperature application means 105, and a second temperature application means 106. Here, a Z axis perpendicular to one surface (principal surface) 101a of the substrate, and an X axis and a Y axis perpendicular to each other in a plane parallel to the surface 101a are defined.
　基材１０１は、形状が限定されることはないが、平板状であることが好ましい。基材１０１の材料としては、熱電変換膜１０２を形成できるものであればよく、熱電変換膜１０２の材料に合わせて決定される。本実施形態では金属材料からなる熱電変換膜１０２を用いるため、基材の材料としては、例えば、Ａｌ２Ｏ３、ＳｉＯ２、ＭｇＯ、ＳｒＴｉＯ３、ガラス、ポリマー等を用いることができる。基材は、結晶方位や格子定数のマッチング等による薄膜結晶化を促進する効果をもたない、ガラス等の非晶質の基板を用いる方が、良質なアモルファス膜を得るには好適である。基材１０１に可撓性が求められる場合には、例えば、熱伝導率が低く絶縁性を有し、かつ可撓性のある有機材料、高分子フィルム、樹脂フィルム等を用いることが好ましい。 The substrate 101 is not limited in shape, but is preferably flat. The material of the substrate 101 may be any material capable of forming the thermoelectric conversion film 102, and is determined according to the material of the thermoelectric conversion film 102. In this embodiment, the thermoelectric conversion film 102 made of a metal material is used, so that the substrate material may be, for example, Al 2 O 3 , SiO 2 , MgO, SrTiO 3 , glass, polymer, or the like. In order to obtain a good quality amorphous film, it is preferable to use an amorphous substrate such as glass, which does not have the effect of promoting thin film crystallization due to the matching of crystal orientation and lattice constant, as the substrate. When flexibility is required for the substrate 101, it is preferable to use, for example, an organic material, a polymer film, a resin film, or the like, which has low thermal conductivity, insulating properties, and is flexible.
　熱電変換膜１０２は、基材の一面１０１ａに形成され、Ｆｅ（鉄）とＳｎ（錫）を含むＦｅ－Ｓｎ組成物からなる。この組成物は、組成式ＦｅｘＳｎ１－ｘ、０．４ ≦ｘ≦ ０．９で表される。Ｆｅの組成比ｘが大きいほど、高い磁化を有する。特に、０．８ ≦ｘ≦ ０．９であることが好ましい。Ｆｅ－Ｓｎ組成物の膜は、室温（約２５～３０℃）であらゆる基材上に形成することができ、安価で環境調和性に優れている。 The thermoelectric conversion film 102 is formed on one surface 101a of the substrate, and is made of an Fe-Sn composition containing Fe (iron) and Sn (tin). This composition is expressed by the composition formula Fe x Sn 1-x , where 0.4≦x≦0.9. The larger the Fe composition ratio x, the higher the magnetization. In particular, 0.8≦x≦0.9 is preferable. A film of the Fe-Sn composition can be formed on any substrate at room temperature (about 25 to 30° C.), and is inexpensive and environmentally friendly.
　熱電変換膜１０２は、Ｆｅに起因した磁性を有するため、所定の方向に磁化させ、温度勾配を与えることによって異常ネルンスト効果を示す。異常ネルンスト効果は、温度勾配と磁化の外積方向に電界（起電力）が発生する現象である。実施例として後述するように、ＦｅとＳｎを組み合わせることにより、巨大な異常ネルンスト効果を示し、１μＶ／Ｋを超える熱起電力係数（異常ネルンスト係数）が得られる。 The thermoelectric conversion film 102 has magnetism due to Fe, and therefore exhibits the anomalous Nernst effect when magnetized in a specific direction and subjected to a temperature gradient. The anomalous Nernst effect is a phenomenon in which an electric field (electromotive force) is generated in the cross product direction of the temperature gradient and magnetization. As will be described later as an example, by combining Fe and Sn, a huge anomalous Nernst effect is exhibited, and a thermoelectromotive force coefficient (anomalous Nernst coefficient) exceeding 1 μV/K can be obtained.
　ここでは基材の一面と平行な方向に、不図示の磁場印加手段で磁場を印加し、熱電変換膜１０２を磁化させている場合を例示しているが、磁化させる方向は用途に応じて自由に設定してよく、例えば、基材の一面と垂直な方向に磁化してもよい。磁化方向を制御する方法としては、磁石等の磁場発生手段を周囲に配置して、磁化させる部分に、所定の方向の磁場を作用させる方法の他に、磁化方向に対応する偏光状態の光を、磁化させる部分に照射する方法等が挙げられる。 In this example, a magnetic field is applied by a magnetic field application means (not shown) in a direction parallel to one surface of the substrate to magnetize the thermoelectric conversion film 102, but the direction of magnetization may be freely set depending on the application, and for example, the film may be magnetized in a direction perpendicular to one surface of the substrate. Methods for controlling the magnetization direction include a method in which a magnetic field generating means such as a magnet is placed around the film to apply a magnetic field in a predetermined direction to the part to be magnetized, as well as a method in which light in a polarized state corresponding to the magnetization direction is irradiated onto the part to be magnetized.
　組成物には、さらに、磁気的相互作用およびスピン軌道相互作用の変調を通して異常ネルンスト効果による起電力を増強する可能性を有するＴａ（タンタル）、Ｗ（タングステン)、Ｐｔ（白金）、Ｍｏ（モリブデン)、Ｍｎ（マンガン)などの遷移元素から選択される元素Ａを含んでもよい。この場合の組成物は、組成式Ｆｅｘ―ｙＳｎ１－ｘ－ｚＡｙ＋ｚ、０．４≦ｘ≦０．９、０．０５≦ｙ≦０．６、０．０５≦ｚ≦０．４で表される。また、組成物には、さらに、キャリア密度およびスピン軌道相互作用の変調を通して、異常ネルンスト効果による起電力を増強する可能性を有するＩｎ（インジウム）、Ａｌ（アルミニウム）、Ｇｅ（ゲルマニウム)、Ｓｉ（シリコン)、Ｇａ（ガリウム)などの典型元素等の磁性元素から選択される元素Ｂを含んでもよい。この場合の組成物は、組成式Ｆｅｘ―ｙＳｎ１－ｘ－ｚＢｙ＋ｚ、０．４≦ｘ≦０．９、０．０５≦ｙ≦０．６、０．０５≦ｚ≦０．４で表される。 The composition may further include an element A selected from transition elements such as Ta (tantalum), W (tungsten), Pt (platinum), Mo (molybdenum), and Mn (manganese) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction. In this case, the composition is represented by a composition formula Fe x-y Sn 1-x-z A y+z , where 0.4≦x≦0.9, 0.05≦y≦0.6, and 0.05≦z≦0.4. The composition may further include an element B selected from magnetic elements such as typical elements such as In (indium), Al (aluminum), Ge (germanium), Si (silicon), and Ga (gallium) that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction. In this case, the composition is represented by the formula Fe x-y Sn 1-x-z B y+z , where 0.4≦x≦0.9, 0.05≦y≦0.6, and 0.05≦z≦0.4.
　熱電変換膜１０２の形状は、用途に応じて決定される。本実施形態では、一方向（Ｘ方向）に延材する形状の熱電変換膜１０２を例示している。熱電変換膜１０２の厚みについては、限定されないが、４ｎｍ以上１０００ｎｍ以下であることが好ましい。なお、ゼーベック係数および異常ネルンスト係数は、熱電変換膜１０２の厚みには依存しない。 The shape of the thermoelectric conversion film 102 is determined depending on the application. In this embodiment, a thermoelectric conversion film 102 having a shape that extends in one direction (X direction) is exemplified. The thickness of the thermoelectric conversion film 102 is not limited, but is preferably 4 nm or more and 1000 nm or less. The Seebeck coefficient and the anomalous Nernst coefficient do not depend on the thickness of the thermoelectric conversion film 102.
　熱電変換膜１０２は、大部分がアモルファス（非晶質、ガラス）構造を有し、軟磁性体であり、可撓性を有し、機械的な強度（引っ張り強度、靭性、硬度等）、および耐食性が高い。熱電変換膜１０２がアモルファス構造を有することは、例えば、Ｘ線回折測定を行うことによって間接的に確認することができる。測定によって得られるＸ線回折パターンにおいて、ブラッグ反射による鋭いピークが見られない場合、すなわち、ブラッグ反射に伴うピーク値が、ノイズと同等（信号雑音比（Ｓ／Ｎ比）が３０以下）の場合に、熱電変換膜１０２がアモルファス構造を有すると判断することができる。アモルファス構造は、熱電変換膜１０２の体積比率で、５０％以上含まれるのが好ましい。 The thermoelectric conversion film 102 has a mostly amorphous (non-crystalline, glass) structure, is a soft magnetic material, is flexible, and has high mechanical strength (tensile strength, toughness, hardness, etc.) and corrosion resistance. The fact that the thermoelectric conversion film 102 has an amorphous structure can be indirectly confirmed, for example, by performing X-ray diffraction measurement. If no sharp peak due to Bragg reflection is observed in the X-ray diffraction pattern obtained by the measurement, that is, if the peak value due to Bragg reflection is equivalent to the noise (signal-to-noise ratio (S/N ratio) is 30 or less), it can be determined that the thermoelectric conversion film 102 has an amorphous structure. The amorphous structure preferably accounts for 50% or more of the volume ratio of the thermoelectric conversion film 102.
　可撓性を有する基材１０１を用いることにより、熱電変換装置１００としての可撓性を高めることができる。熱電変換装置１００としての可撓性については、例えば、曲面を有する治具を用いて確認することができる。すなわち、治具の曲面部分に対し、熱電変換装置１００を曲げた状態で貼り付け、基材１０１および熱電変換膜に亀裂が発生しない状態を維持できれば、この熱電変換装置１００が可撓性を有すると判断することができる。 By using a flexible substrate 101, the flexibility of the thermoelectric conversion device 100 can be increased. The flexibility of the thermoelectric conversion device 100 can be confirmed, for example, by using a jig with a curved surface. That is, if the thermoelectric conversion device 100 is attached in a bent state to the curved surface of the jig and a state in which no cracks occur in the substrate 101 and the thermoelectric conversion film can be maintained, then it can be determined that the thermoelectric conversion device 100 is flexible.
　熱電変換膜１０２は、ほぼ完全な（全体積の９０％以上）アモルファス構造であってもよく、また、アモルファス構造中に複数のナノ結晶構造を有する部分（ナノ結晶部分）が分布した微結晶を有していてもよい。熱電変換膜１０２中にアモルファス構造が５０％以上含まれていれば、ナノ結晶構造の熱電変換膜１０２中の体積比率は特に限定されない。 The thermoelectric conversion film 102 may be an almost completely amorphous structure (90% or more of the total volume), or may have microcrystals with a plurality of nanocrystalline portions (nanocrystalline portions) distributed within the amorphous structure. As long as the thermoelectric conversion film 102 contains 50% or more of an amorphous structure, the volume ratio of the nanocrystalline structure in the thermoelectric conversion film 102 is not particularly limited.
　第一電極１０３および第二電極１０４は、インジウム、金や銀のペースト、金やアルミニウムなどの金属の導線、金や白金の蒸着膜等の導電材料からなる。第一電極１０３は熱電変換膜１０２の一部（図１では左端部）に接続され、第二電極１０４は熱電変換膜１０２の他の一部（図１では右端部）に接続される。第一電極１０３と第二電極１０４との間で発生する熱起電力を、出力するように構成されている。
　なお、第一電極１０３及び第二電極１０４は、直接電力を取り出す場合などには、設けなくてもよい。 The first electrode 103 and the second electrode 104 are made of a conductive material such as indium, gold or silver paste, a metal conductor such as gold or aluminum, or a vapor-deposited film of gold or platinum. The first electrode 103 is connected to a part of the thermoelectric conversion film 102 (the left end in FIG. 1 ), and the second electrode 104 is connected to another part of the thermoelectric conversion film 102 (the right end in FIG. 1 ). The first electrode 103 and the second electrode 104 are configured to output the thermoelectromotive force generated between the first electrode 103 and the second electrode 104.
It should be noted that the first electrode 103 and the second electrode 104 do not need to be provided in cases where electric power is directly extracted.
　第一温度付与手段１０５、第二温度付与手段１０６は、熱電変換膜１０２の所定部分に温度を付与する手段（市販の温度調節器等）である。第一温度付与手段１０５は、熱電変換膜１０２の基材１０１側（図１では下側）の温度を付与するように配置され、基材１０１を介して熱電変換膜１０２に接続されている。第二温度付与手段１０６は、熱電変換膜１０２の基材１０１と反対側（図１では上側）の温度を付与するように配置され、直接、熱電変換膜１０２に接続されている。ここでは、相対的に、第一温度付与手段１０５側の温度を高く設定し、第二温度付与手段１０６側の温度を低く設定し、第二温度付与手段１０６側から第一温度付与手段１０５側に向かって温度勾配∇Ｔが生じる場合を例示している。
　なお、第一温度付与手段１０５、第二温度付与手段１０６は、温度を正確に調整する抵抗に、通電するヒータなど熱源や熱浴、冷媒のような機器に限らず、摩擦、産業などで発生するなどの廃熱や人の体温、気温などの周辺環境の熱であってもよい。第一温度付与手段１０５、第二温度付与手段１０６の間で、有意な温度差となる異なる温度差が生じるものであれば、どのようなものを用いてもよい。 The first temperature applying means 105 and the second temperature applying means 106 are means (such as a commercially available temperature regulator) for applying temperature to a predetermined portion of the thermoelectric conversion film 102. The first temperature applying means 105 is disposed so as to apply the temperature of the substrate 101 side (lower side in FIG. 1) of the thermoelectric conversion film 102, and is connected to the thermoelectric conversion film 102 via the substrate 101. The second temperature applying means 106 is disposed so as to apply the temperature of the side opposite the substrate 101 of the thermoelectric conversion film 102 (upper side in FIG. 1), and is directly connected to the thermoelectric conversion film 102. Here, the temperature on the first temperature applying means 105 side is set relatively high, and the temperature on the second temperature applying means 106 side is set relatively low, and a temperature gradient ∇T is generated from the second temperature applying means 106 side to the first temperature applying means 105 side is illustrated.
The first temperature providing means 105 and the second temperature providing means 106 are not limited to devices such as a heat source such as a heater or a heat bath or a refrigerant that passes electricity through a resistor that accurately adjusts the temperature, but may also be waste heat generated by friction or industry, or heat from the surrounding environment such as human body temperature or air temperature. Any device may be used as long as it generates a different temperature difference that is a significant temperature difference between the first temperature providing means 105 and the second temperature providing means 106.
　本実施形態では、温度勾配∇Ｔの方向がＺ軸方向であり、かつ磁化Ｍの方向がＹ軸方向であるため、異常ネルンスト効果による熱起電力は、基材の一面１０１ａに平行なＸ軸方向に発生する。そのため、Ｘ軸方向において熱電変換膜１０２を長く形成することにより、得られる熱起電力を高めることができる。 In this embodiment, the direction of the temperature gradient ∇T is the Z-axis direction, and the direction of the magnetization M is the Y-axis direction, so the thermoelectromotive force due to the anomalous Nernst effect is generated in the X-axis direction, which is parallel to one surface 101a of the substrate. Therefore, by forming the thermoelectric conversion film 102 long in the X-axis direction, the obtained thermoelectromotive force can be increased.
（熱電変換装置の製造方法）
　本実施形態の熱電変換装置１００は、主に、次の工程を経て製造することができる。 (Method for manufacturing a thermoelectric conversion device)
The thermoelectric conversion device 100 of this embodiment can be manufactured mainly through the following steps.
［熱電変換膜の形成］
　スパッタリング法等の公知の成膜方法を用いて、基材の一面１０１ａに熱電変換膜１０２を形成する。成膜条件の一例として、ＲＦマグネトロンスパッタリング装置と直径２インチのＳｎディスク上に１０ｍｍ角のＦｅチップを配置したモザイクターゲットを用いて、基板温度室温、ＲＦ出力５０Ｗ、Ａｒガス圧０．５Ｐａ、ターゲット・基板間距離１００ｍｍに設定することができる。この成膜条件により、アモルファス構造を有する熱電変換膜１０２が得られる。結晶化しない範囲において、用途に応じて薄膜の堆積速度等を調整するために、基板温度０℃以上、４００℃以下、ＲＦ出力５～２００Ｗ、Ａｒガス圧０.０１～１０Ｐａ、ターゲット・基板間距離５０～２００ｍｍに設定しても良い。
　続いて、フォトリソグラフィ法等を用いて、形成した熱電変換膜１０２を所望の形状になるように加工する。
なお、加工した熱電変換膜１０２に対し、結晶化しない０℃以上、４００℃以下の温度で、０～２４時間の熱処理を行ってもよい。
　なお、本発明の熱電変換膜１０２は、真空蒸着法、電子ビーム蒸着法、分子線エピタキシー法、化学気相成長法、電析、電着などの製造方法であっても、製造可能である。 [Formation of thermoelectric conversion film]
A thermoelectric conversion film 102 is formed on one surface 101a of the substrate by using a known film formation method such as a sputtering method. As an example of film formation conditions, an RF magnetron sputtering device and a mosaic target in which 10 mm square Fe chips are arranged on a 2-inch diameter Sn disk can be used, and the conditions are as follows: substrate temperature: room temperature, RF output: 50 W, Ar gas pressure: 0.5 Pa, and target-substrate distance: 100 mm. Under these film formation conditions, a thermoelectric conversion film 102 having an amorphous structure can be obtained. In order to adjust the deposition rate of the thin film according to the application within a range in which crystallization does not occur, the conditions may be set to a substrate temperature of 0° C. or higher and 400° C. or lower, an RF output of 5 to 200 W, an Ar gas pressure of 0.01 to 10 Pa, and a target-substrate distance of 50 to 200 mm.
Next, the formed thermoelectric conversion film 102 is processed into a desired shape using a photolithography method or the like.
The processed thermoelectric conversion film 102 may be subjected to a heat treatment at a temperature of 0° C. or more and 400° C. or less, at which crystallization does not occur, for 0 to 24 hours.
The thermoelectric conversion film 102 of the present invention can also be manufactured by a manufacturing method such as vacuum deposition, electron beam deposition, molecular beam epitaxy, chemical vapor deposition, electrodeposition, or the like.
［電極の形成］
　スパッタリング法等の公知の成膜方法を用いて、熱電変換膜１０２に接続される第一電極１０３、第二電極１０４を形成する。成膜の条件は、熱電変換膜の形成と同様である。
　続いて、フォトリソグラフィ法等を用いて、形成した第一電極１０３、第二電極１０４を所望の形状になるように加工する。
　なお、加工した第一電極１０３、第二電極１０４に対して熱処理を行ってもよい。 [Formation of electrodes]
A known film formation method such as sputtering is used to form the first electrode 103 and the second electrode 104 connected to the thermoelectric conversion film 102. The film formation conditions are the same as those for forming the thermoelectric conversion film.
Next, the formed first electrode 103 and second electrode 104 are processed into a desired shape using a photolithography method or the like.
The processed first electrode 103 and second electrode 104 may be subjected to a heat treatment.
［温度付与手段の配置］
　基材１０１から見て熱電変換膜１０２と反対側に、第一温度付与手段１０５（装置）を配置する。また、熱電変換膜１０２から見て基材１０１と反対側に、第二温度付与手段１０６（装置）を配置する。これにより、本実施形態の熱電変換装置１００が得られる。 [Arrangement of temperature applying means]
A first temperature application means 105 (device) is disposed on the opposite side of the thermoelectric conversion film 102 from the substrate 101. A second temperature application means 106 (device) is disposed on the opposite side of the substrate 101 from the thermoelectric conversion film 102. In this manner, the thermoelectric conversion device 100 of the present embodiment is obtained.
　以上のように、本実施形態の熱電変換装置１００は、熱電変換膜１０２がＦｅとＳｎを組み合わせた組成物からなり、異常ネルンスト効果による優れた熱電特性を有する。さらに、本実施形態の熱電変換膜１０２の大部分がアモルファス構造を有しており、可撓性が高く、様々な基材上に室温で形成できるため、本実施形態の熱電変換装置１００は、フレキシブルデバイスとして活用することができる。また、本実施形態の熱電変換膜１０２は、大部分がアモルファス構造を有し、室温であらゆる基材上に形成することができ、安価で環境調和性に優れている。また、熱電変換膜を構成するＦｅとＳｎは、毒性が低い材料であるため、ビスマス、テルル等の半導体材料を用いる場合に比べて環境負荷が小さい。 As described above, the thermoelectric conversion device 100 of this embodiment has a thermoelectric conversion film 102 made of a composition combining Fe and Sn, and has excellent thermoelectric properties due to the anomalous Nernst effect. Furthermore, since the thermoelectric conversion film 102 of this embodiment has an amorphous structure for the most part, is highly flexible, and can be formed on various substrates at room temperature, the thermoelectric conversion device 100 of this embodiment can be used as a flexible device. Furthermore, the thermoelectric conversion film 102 of this embodiment has an amorphous structure for the most part, can be formed on any substrate at room temperature, is inexpensive, and is environmentally friendly. Furthermore, the Fe and Sn that make up the thermoelectric conversion film are low-toxicity materials, and therefore have a smaller environmental impact than when semiconductor materials such as bismuth and tellurium are used.
　本実施形態のように、Ｙ軸方向に磁化させた熱電変換膜１０２に対し、Ｚ軸方向に温度勾配を与える場合、異常ネルンスト効果による熱起電力は、基材の一面１０１ａに平行なＸ軸方向に発生する。したがって、熱電変換膜１０２のＸ軸方向のサイズを調整することにより、発生する熱起電力の大きさを制御することができる。 When a temperature gradient is applied in the Z-axis direction to the thermoelectric conversion film 102 magnetized in the Y-axis direction as in this embodiment, a thermoelectromotive force due to the anomalous Nernst effect is generated in the X-axis direction parallel to one surface 101a of the substrate. Therefore, the magnitude of the generated thermoelectromotive force can be controlled by adjusting the size of the thermoelectric conversion film 102 in the X-axis direction.
　図１では、熱電変換膜１０２の異常ネルンスト係数の符号が正であって、熱電変換膜１０２をＹ軸の＋方向（＋Ｙ方向）に磁化させ、Ｘ軸の＋方向（＋Ｘ方向）に熱起電力が発生する場合を例示している。これに対し、異常ネルンスト係数の符号が負である熱電変換膜１０２を、Ｙ軸の＋方向（＋Ｙ方向）に磁化させた場合には、Ｘ軸の－方向（－Ｘ方向）に熱起電力が発生する。本実施形態の熱電変換装置１００は、このような異常ネルンスト係数の符号が異なる熱電変換膜を組み合わせることによって、様々な応用が可能となる。 In FIG. 1, the thermoelectric conversion film 102 has a positive anomalous Nernst coefficient, and is magnetized in the positive direction of the Y axis (+Y direction), generating a thermoelectromotive force in the positive direction of the X axis (+X direction). In contrast, when a thermoelectric conversion film 102 with a negative anomalous Nernst coefficient is magnetized in the positive direction of the Y axis (+Y direction), a thermoelectromotive force is generated in the negative direction of the X axis (-X direction). The thermoelectric conversion device 100 of this embodiment can be used in a variety of applications by combining such thermoelectric conversion films with anomalous Nernst coefficients of different signs.
　本発明は、Ｆｅ、Ｓｎを含有する、熱電変換膜は、アモルファスでも有意な異常ネルンスト効果を奏することを見出したものである。これまでの研究では、異常ネルンスト効果の原因について、結晶性のものを中心について調べられてきたが、原因は不明なままであった。 The present invention is based on the discovery that thermoelectric conversion films containing Fe and Sn exhibit a significant anomalous Nernst effect even when amorphous. Previous research has focused on crystalline materials to investigate the cause of the anomalous Nernst effect, but the cause remains unknown.
　本発明者は、Ｆｅ、Ｓｎを含有する熱電変換膜の、異常ネルンスト効果の原因について探るうち、全てアモルファスで構成した熱電変換膜であっても、有意な異常ネルンスト効果を示すことを発見した。
　本発明者らは、他の解析結果などから、この原因は、Ｆｅ、Ｓｎでは、非特許文献１で言及されているＦｅ３Ｓｎ結晶の基本構造であるカゴメ格子が、アモルファス試料でも、最近接程度の短距離領域では、維持されているのではないかと考えており、他の解析からもそれを裏付ける結果を得ている。つまり、本発明者らは、Ｆｅ、Ｓｎでは、最近接レベルではカゴメ格子の短距離秩序が存在し、この短距離秩序の存在が電子状態に寄与することで、大きな異常ネルンスト効果の発現につながっているのではないかと推測している。 While investigating the cause of the anomalous Nernst effect of thermoelectric conversion films containing Fe and Sn, the present inventors discovered that even thermoelectric conversion films composed entirely of amorphous materials exhibit a significant anomalous Nernst effect.
Based on other analytical results, the present inventors believe that the cause of this is that in Fe and Sn, the kagome lattice, which is the basic structure of the Fe 3 Sn crystal mentioned in Non-Patent Document 1, is maintained in the short-distance region of nearest neighbor even in amorphous samples, and other analytical results support this. In other words, the present inventors speculate that in Fe and Sn, the short-distance order of the kagome lattice exists at the nearest neighbor level, and the existence of this short-distance order contributes to the electronic state, leading to the manifestation of a large anomalous Nernst effect.
　短距離秩序が存在し、異常ネルンスト効果が生じるのであれば、結晶化させる必要もなく、また、他の金属をドープさせる手法にも自由度が生まれ、これまでにない、異常ネルンスト効果が生じる安価な熱電変換素子を得ることができる。 If short-range order exists and the anomalous Nernst effect occurs, there is no need to crystallize the material, and there is also more freedom in the method of doping with other metals, making it possible to obtain an inexpensive thermoelectric conversion element that generates the anomalous Nernst effect, something that has never been done before.
　［熱電変換装置の具体的な構造の応用例］
　図２は、本実施形態の応用例１に係る熱電変換装置１１０の斜視図である。熱電変換装置１１０では、熱電変換膜１０２が、異常ネルンスト係数の符号が異なる二つの磁性体のパターンを組み合わせて構成されている。熱電変換装置１１０の他の構成は、熱電変換装置１００と同様であり、少なくとも熱電変換装置１００と同様の効果を奏する。熱電変換装置１００と対応する箇所については、同じ符号で示している。ここでは、第一温度付与手段１０５とおよび第二温度付与手段１０６の図示を省略している。 [Application examples of specific structures of thermoelectric conversion devices]
2 is a perspective view of a thermoelectric conversion device 110 according to Application Example 1 of this embodiment. In the thermoelectric conversion device 110, the thermoelectric conversion film 102 is configured by combining two patterns of magnetic materials having different signs of the anomalous Nernst coefficient. The other configuration of the thermoelectric conversion device 110 is similar to that of the thermoelectric conversion device 100, and at least the thermoelectric conversion device 110 has the same effects as the thermoelectric conversion device 100. The same reference numerals are used to indicate parts corresponding to those of the thermoelectric conversion device 100. Here, the first temperature applying means 105 and the second temperature applying means 106 are omitted from the illustration.
　応用例１の熱電変換膜１０２は、基材の一面１０１ａにおいて、波状のパターン１０７を有し、同じ方向（ここではＹ軸方向）に、略平行に延在する複数の第一パターン（第一磁性体）１０２Ａと、隣接する第一パターン１０２Ａ同士を連結する第二パターン１０２Ｂと、で構成される。隣接する第一パターン１０２Ａ同士が、互いに異なる符号の異常ネルンスト係数を有する。ここでは、隣接する二つの第一パターン１０２Ａのうち、一方が正の符号の異常ネルンスト係数ＳＸＹ ＋および磁化ＭＡを有し、他方が負の符号の異常ネルンスト係数ＳＸＹ －および磁化ＭＢを有する。磁化ＭＡの方向と磁化ＭＢの方向は同じである。 The thermoelectric conversion film 102 of Application Example 1 has a wavy pattern 107 on one surface 101a of the substrate, and is composed of a plurality of first patterns (first magnetic bodies) 102A extending substantially parallel in the same direction (here, the Y-axis direction), and a second pattern 102B connecting adjacent first patterns 102A. Adjacent first patterns 102A have anomalous Nernst coefficients of different signs. Here, of two adjacent first patterns 102A, one has an anomalous Nernst coefficient S XY + and magnetization M A of a positive sign, and the other has an anomalous Nernst coefficient S XY - and magnetization M B of a negative sign. The direction of magnetization M A and the direction of magnetization M B are the same.
　正の符号の異常ネルンスト係数を有する第一パターン１０２Ａでは、温度勾配∇Ｔと磁化Ｍの外積方向であるＹ軸の－方向（－Ｙ方向）に、熱起電力が発生する。一方、負の符号の異常ネルンスト係数を有する第一パターン１０２Ａでは、温度勾配∇Ｔと磁化Ｍの外積と反対方向であるＹ軸の＋方向（＋Ｙ方向）に、熱起電力が発生する。 In the first pattern 102A having a positive anomalous Nernst coefficient, a thermoelectromotive force is generated in the negative direction of the Y axis (-Y direction), which is the direction of the cross product of the temperature gradient ∇T and the magnetization M. On the other hand, in the first pattern 102A having a negative anomalous Nernst coefficient, a thermoelectromotive force is generated in the positive direction of the Y axis (+Y direction), which is the opposite direction to the cross product of the temperature gradient ∇T and the magnetization M.
　したがって、Ｘ軸方向に並ぶ複数の第一パターン１０２Ａにおいて、発生する熱起電力の方向が、並び順に交互に変わる。そのため、全ての第一パターン１０２Ａが、第二パターン１０２Ｂを介して直列接続され、波状のパターン１０７の一端１０７ａから他端１０７ｂまでの電流パスが形成される。第一パターン１０２Ａの数が多いほど、長い電流パスが形成されるため、より大きい熱起電力を発生させることができる。 Therefore, the direction of the generated thermoelectromotive force in the multiple first patterns 102A lined up in the X-axis direction alternates in the order of the patterns. As a result, all of the first patterns 102A are connected in series via the second patterns 102B, and a current path is formed from one end 107a to the other end 107b of the wavy pattern 107. The more first patterns 102A there are, the longer the current path that is formed, and therefore the greater the thermoelectromotive force that can be generated.
　図１では、熱電変換膜１０２の異常ネルンスト係数の符号が正であって、熱電変換膜１０２をＹ軸の＋方向（＋Ｙ方向）に磁化させ、Ｘ軸の＋方向（＋Ｘ方向）に熱起電力が発生する場合を例示している。これに対し、同符号の異常ネルンスト係数を有する熱電変換膜１０２を、Ｙ軸の－方向（－Ｙ方向）に磁化させた場合には、Ｘ軸の－方向（－Ｘ方向）に熱起電力が発生する。本実施形態の熱電変換装置１００は、このような磁化方向が異なる熱電変換膜を組み合わせることによって、様々な応用が可能となる。 In FIG. 1, the sign of the anomalous Nernst coefficient of the thermoelectric conversion film 102 is positive, and the thermoelectric conversion film 102 is magnetized in the + direction of the Y axis (+Y direction), generating a thermoelectromotive force in the + direction of the X axis (+X direction). In contrast, when a thermoelectric conversion film 102 having an anomalous Nernst coefficient of the same sign is magnetized in the - direction of the Y axis (-Y direction), a thermoelectromotive force is generated in the - direction of the X axis (-X direction). The thermoelectric conversion device 100 of this embodiment can be used in a variety of applications by combining such thermoelectric conversion films with different magnetization directions.
　図３は、本実施形態の応用例２に係る熱電変換装置１２０の斜視図である。熱電変換装置１２０では、熱電変換膜１０２が、磁化方向が異なる二つの磁性体のパターンを組み合わせて構成されている。熱電変換装置１２０の他の構成は、熱電変換装置１００と同様であり、少なくとも熱電変換装置１００と同様の効果を奏する。熱電変換装置１００と対応する箇所については、同じ符号で示している。ここでは、第一温度付与手段１０５とおよび第二温度付与手段１０６の図示を省略している。 FIG. 3 is a perspective view of a thermoelectric conversion device 120 according to application example 2 of this embodiment. In the thermoelectric conversion device 120, the thermoelectric conversion film 102 is configured by combining two patterns of magnetic materials with different magnetization directions. The other configuration of the thermoelectric conversion device 120 is the same as that of the thermoelectric conversion device 100, and at least provides the same effects as the thermoelectric conversion device 100. Parts corresponding to those in the thermoelectric conversion device 100 are indicated by the same reference numerals. Here, the first temperature applying means 105 and the second temperature applying means 106 are not shown.
　応用例２の熱電変換膜１０２は、基材の一面１０１ａにおいて、波状のパターンを有し、同じ方向（ここではＹ軸方向）に、略平行に延在する複数の第一パターン（第一磁性体）１０２Ｃと、隣接する第一パターン１０２Ｃ同士を連結する第二パターン（第二磁性体）１０２Ｄと、で構成される。隣接する第一パターン１０２Ｃ同士が、互いに反対の方向に磁化されている。ここでは、隣接する二つの第一パターン１０２Ｃのうち、一方がＸ軸の＋方向（＋Ｘ方向）の磁化ＭＣを有し、他方が－Ｘ軸の－方向（－Ｘ方向）の磁化ＭＤを有する。 The thermoelectric conversion film 102 of the application example 2 has a wavy pattern on one surface 101a of the substrate, and is composed of a plurality of first patterns (first magnetic bodies) 102C extending substantially parallel in the same direction (here, the Y-axis direction), and a second pattern (second magnetic body) 102D connecting adjacent first patterns 102C. Adjacent first patterns 102C are magnetized in opposite directions. Here, one of the two adjacent first patterns 102C has a magnetization M C in the + direction of the X-axis (+X direction), and the other has a magnetization M D in the - direction of the -X-axis (-X direction).
　＋Ｘ方向に磁化されている第一パターン１０２Ｃでは、温度勾配∇Ｔと磁化ＭＣの外積方向であるＹ軸の－方向（－Ｙ方向）に、熱起電力が発生する。一方、－Ｘ方向に磁化されている第一パターン１０２Ｄでは、温度勾配∇Ｔと磁化ＭＤの外積と反対方向であるＹ軸の＋方向（＋Ｙ方向）に、熱起電力が発生する。 In the first pattern 102C magnetized in the +X direction, a thermoelectromotive force is generated in the negative direction of the Y axis (-Y direction), which is the cross product direction of the temperature gradient ∇T and the magnetization M C. On the other hand, in the first pattern 102D magnetized in the -X direction, a thermoelectromotive force is generated in the positive direction of the Y axis (+Y direction), which is the opposite direction to the cross product of the temperature gradient ∇T and the magnetization M D.
　したがって、Ｘ軸方向に並ぶ複数の第一パターン１０２Ｃにおいて、発生する熱起電力の方向が、並び順に交互に変わる。そのため、全ての第一パターン１０２Ｃが、第二パターン１０２Ｄを介して直列接続され、波状のパターン１０７の一端１０７ａから他端１０７ｂまでの電流パスが形成される。第一パターン１０２Ｃの数が多いほど、長い電流パスが形成されるため、より大きい熱起電力を発生させることができる。 Therefore, the direction of the generated thermoelectromotive force in the multiple first patterns 102C arranged in the X-axis direction alternates depending on the arrangement. As a result, all of the first patterns 102C are connected in series via the second patterns 102D, and a current path is formed from one end 107a to the other end 107b of the wavy pattern 107. The more first patterns 102C there are, the longer the current path that is formed, and therefore the greater the thermoelectromotive force that can be generated.
　以下、実施例により、本発明の効果をより明らかなものとする。なお、本発明は、以下の実施例に限定されるものではなく、その要旨を変更しない範囲で適宜変更して実施することができる。 The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples, and can be modified as appropriate without departing from the gist of the present invention.
（実施例１－１：アモルファスのみで構成した熱電変換膜を用いた本発明の熱電変換装置）
［組成依存性］
　本発明の熱電変換装置のサンプルを複数製造し、それらの熱電特性を測定した。基材として、ガラス基板を用いた。なお、この実施例でガラス基板を用いたのは、結晶性の基板を用いると、基板の影響を受け、部分的に結晶化（微結晶形成）する可能性があるためである。熱電変換膜として、組成式ＦｅｘＳｎ１－ｘで表される組成物からなる薄膜（厚み２８～４６ｎｍ）を用いた。ＲＦマグネトロンスパッタリング装置（エイコー社製ＥＳ－２５０）を用い、スパッタリング法により薄膜成長を行うことで、ほぼ１００％、アモルファスのみで構成した熱電変換膜を得ることができた。アモルファス構造の確認は、Ｘ線回折装置（リガク社製ＳｍａｒｔＬａｂおよびスペクトリス・マルバーン・パナリティカル社製Ｅｍｐｙｒｅａｎ）で行った。ＦｅｘＳｎ１－ｘは、結晶化した場合、通常、非特許文献１に記載のようにカゴメ格子の結晶構造を構成するが、図４（ａ）～（ｇ）に示すＸ線回折では、ｘ＝０．４２～０．８７の薄膜において、それら結晶に由来する鋭いピークは観測されなかった。異常ホール効果および異常ネルンスト効果を検出するための電極として、インジウムからなる部材を用いた。 (Example 1-1: Thermoelectric conversion device of the present invention using a thermoelectric conversion film composed only of amorphous material)
[Composition Dependence]
A plurality of samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric properties were measured. A glass substrate was used as the base material. The reason for using a glass substrate in this example is that if a crystalline substrate is used, it may be affected by the substrate and may partially crystallize (microcrystal formation). A thin film (thickness 28 to 46 nm) made of a composition represented by the composition formula Fe x Sn 1-x was used as the thermoelectric conversion film. By using an RF magnetron sputtering device (ES-250 manufactured by Eiko Co., Ltd.) to grow a thin film by a sputtering method, it was possible to obtain a thermoelectric conversion film that was almost 100% composed only of amorphous. The amorphous structure was confirmed by an X-ray diffraction device (SmartLab manufactured by Rigaku Co., Ltd. and Empyrean manufactured by Spectris Malvern Panalytical Co., Ltd.). When Fe x Sn 1-x is crystallized, it usually forms a Kagome lattice crystal structure as described in Non-Patent Document 1, but in the X-ray diffraction shown in Figures 4(a) to (g), no sharp peaks derived from these crystals were observed in the thin films with x = 0.42 to 0.87. A member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
　Ｆｅの組成比ｘが０．４２、０．５２、０．６０、０．６５、０．７４、０．８４、０．８７、である７個のサンプルに対し、熱電変換膜の厚み方向に磁場（面直印加磁場）を印加し、磁場と直交する方向における一端側、他端側の温度を、それぞれ第一温度付与手段、第二温度付与手段を用いて３００Ｋとした。ここで、熱電変換膜の一端側（第一温度付与手段側）から他端側（第二温度付与手段側）へ電流を流したときに、異常ホール効果によって電極間に発生するホール電圧を測定した。 A magnetic field (magnetic field applied perpendicular to the surface) was applied in the thickness direction of the thermoelectric conversion film to seven samples with Fe composition ratios x of 0.42, 0.52, 0.60, 0.65, 0.74, 0.84, and 0.87, and the temperatures of one end and the other end in the direction perpendicular to the magnetic field were set to 300 K using the first temperature application means and the second temperature application means, respectively. Here, when a current was passed from one end (first temperature application means side) to the other end (second temperature application means side) of the thermoelectric conversion film, the Hall voltage generated between the electrodes due to the anomalous Hall effect was measured.
　図５は、その測定結果を示すグラフである。グラフの横軸は面直印加磁場（Ｔ）を示し、グラフの縦軸はホール抵抗率ρｙｘ［μΩ・ｃｍ］を示す。このグラフから、磁場印加に伴う磁化方向の変化が、ホール抵抗率に反映されていることが分かる。 The measurement results are shown in the graph of Fig. 5. The horizontal axis of the graph indicates the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph indicates the Hall resistivity ρ yx [μΩ·cm]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the Hall resistivity.
　７個のサンプルにおいて、熱電変換膜の厚み方向に磁場を印加し、電流は流さずに、磁場と直交する方向において、一端側の温度を第一温度付与手段により約３０２Ｋに維持しつつ、他端側の温度を第二温度付与手段により約３０７Ｋに調整した。第一温度付与手段として、冷凍機（カンタムデザイン社製VersaLab）の試料ホルダーを熱浴に用い、第二温度付与手段として、抵抗への通電加熱を用いた。試料に生じる温度差は、熱電変換膜と同一の基板上に形成したＰｔ／Ｔｉの二層膜の抵抗を測定し、予め取得しておいた抵抗―温度依存性曲線を参照することで、基板上の複数点での温度を求めることで算出した。このとき、異常ネルンスト効果によって、電極間に発生する熱起電力Ｖｘｙを測定した。 In seven samples, a magnetic field was applied in the thickness direction of the thermoelectric conversion film, and the temperature of one end side was maintained at about 302 K by the first temperature applying means in the direction perpendicular to the magnetic field without passing a current, while the temperature of the other end side was adjusted to about 307 K by the second temperature applying means. As the first temperature applying means, a sample holder of a refrigerator (VersaLab manufactured by Quantum Design) was used as a heat bath, and as the second temperature applying means, heating by applying current to a resistor was used. The temperature difference generated in the sample was calculated by measuring the resistance of a Pt/Ti bilayer film formed on the same substrate as the thermoelectric conversion film, and by referring to a resistance-temperature dependency curve obtained in advance, the temperature at multiple points on the substrate was calculated. At this time, the thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect was measured.
　図６は、その測定結果を示すグラフである。グラフの横軸は面直印加磁場（Ｔ）を示し、グラフの縦軸は異常ネルンスト係数Ｓｘｙ［μＶ・Ｋ－１］を表す。異常ネルンスト係数Ｓｘｙと熱起電力Ｖｘｙの関係は、測定に用いた電極間距離Ｗ、ｘ軸方向の温度勾配（∇Ｔ）ｘを用いて、下記の式（１）で定義される。
　　　　　　　　Ｓｘｙ＝Ｖｘｙ／Ｗ／（∇Ｔ）ｘ　　　　　　　（１）
　図６のグラフから、磁場印加に伴う磁化方向の変化が、異常ネルンスト係数に反映されていることが分かる。また、ＦｅとＳｎの組成比に依存して、ある組成比において、大きい異常ネルンスト係数が発生していることが分かる。 6 is a graph showing the measurement results. The horizontal axis of the graph represents the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph represents the anomalous Nernst coefficient S xy [μV·K −1 ]. The relationship between the anomalous Nernst coefficient S xy and the thermoelectromotive force V xy is defined by the following formula (1) using the inter-electrode distance W used in the measurement and the temperature gradient (∇T) x in the x-axis direction.
S xy = V xy /W/(∇T) x (1)
6, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the anomalous Nernst coefficient. It can also be seen that a large anomalous Nernst coefficient occurs at a certain composition ratio depending on the composition ratio of Fe and Sn.
　実施例１－１として製造した全てのサンプルに対し、前述の手順で異常ホール効果を測定し、ホール抵抗率ρｙｘおよび電気抵抗率ρｘｘから、ホール角σｘｙ／σｘｘを算出した。ホール伝導度σｘｙおよび電気伝導度σｘｘは、下記の式（２、３）で定義される。
　　　　　　　　σｘｙ＝ρｙｘ／（ρｘｘ ２＋ρｙｘ ２）　　　　　　（２）
　　　　　　　　σｘｘ＝ρｘｘ／（ρｘｘ ２＋ρｙｘ ２）　　　　　　（３）
　　　　　　　　　　　ρｙｘ：ホール抵抗率
　　　　　　　　　　　ρｘｘ：電気抵抗率 For all samples manufactured as Example 1-1, the anomalous Hall effect was measured by the above-mentioned procedure, and the Hall angle σ xy /σ xx was calculated from the Hall resistivity ρ yx and the electrical resistivity ρ xx . The Hall conductivity σ xy and the electrical conductivity σ xx are defined by the following formulas (2, 3).
σ xy = ρ yx / (ρ xx 2 + ρ yx 2 ) (2)
σ xx = ρ xx / (ρ xx 2 + ρ yx 2 ) (3)
ρ yx : Hall resistivity ρ xx : Electrical resistivity
　実施例１－１として製造した全てのサンプルに対し、前述の手順で異常ネルンスト効果を測定し、熱起電力Ｖｘｙから、異常ネルンスト係数Ｓｘｙ、横熱伝導度αｘｙを算出した。横熱伝導度αｘｙは、下記の式（４）で定義される。
　　　　　　　　αｘｙ＝σｘｙＳｘｘ＋σｘｘＳｘｙ　　　　（４）
　　　　　　　　　　　σｘｙ：ホール伝導度
　　　　　　　　　　　Ｓｘｘ：ゼーベック係数
　　　　　　　　　　　σｘｘ：電気伝導度
　　　　　　　　　　　Ｓｘｙ：異常ネルンスト係数 For all samples manufactured as Example 1-1, the anomalous Nernst effect was measured by the above-mentioned procedure, and the anomalous Nernst coefficient S xy and the transverse thermal conductivity α xy were calculated from the thermoelectromotive force V xy . The transverse thermal conductivity α xy is defined by the following formula (4).
α xy = σ xy S xx + σ xx S xy (4)
σ xy : Hall conductivity S xx : Seebeck coefficient σ xx : Electrical conductivity S xy : Anomalous Nernst coefficient
　図７～９の黒丸は、その算出結果を示すグラフである。いずれのグラフにおいても、横軸はＦｅの組成比Ｆｅ／全構成元素（原子比）を示している。 The black circles in Figures 7 to 9 are graphs showing the calculation results. In each graph, the horizontal axis shows the Fe composition ratio Fe/total constituent elements (atomic ratio).
　図７は、Ｆｅの組成比と異常ネルンスト係数との関係を示すグラフである。グラフの縦軸は、異常ネルンスト係数（μＶ・Ｋ－１）を示している。異常ネルンスト係数は、温度勾配を起電力へと変換する熱電変換膜の性能の指標である。図７のグラフでは、Ｆｅの組成比ｘが大きいほど、異常ネルンスト係数Ｓｘｙが大きくなっている。Ｆｅの組成比ｘが０．７４以上で１．０μＶ・Ｋ－１を超えており、結晶性バルクＦｅ３Ｓｎで報告されている値（非特許文献１参照。）に匹敵する優れた熱電特性を有することが分かる。Ｆｅの組成比ｘが０．８７のとき、異常ネルンスト係数は、最大値２．００μＶ・Ｋ－１を示している。 FIG. 7 is a graph showing the relationship between the composition ratio of Fe and the anomalous Nernst coefficient. The vertical axis of the graph shows the anomalous Nernst coefficient (μV·K −1 ). The anomalous Nernst coefficient is an index of the performance of a thermoelectric conversion film that converts a temperature gradient into an electromotive force. In the graph of FIG. 7, the larger the composition ratio x of Fe, the larger the anomalous Nernst coefficient S xy . When the composition ratio x of Fe is 0.74 or more, it exceeds 1.0 μV·K −1 , and it can be seen that the material has excellent thermoelectric properties comparable to the values reported for crystalline bulk Fe 3 Sn (see Non-Patent Document 1). When the composition ratio x of Fe is 0.87, the anomalous Nernst coefficient shows a maximum value of 2.00 μV·K −1 .
　以上の結果から、現在、一般に、熱電変換装置の性能を表す際に、大きな異常ネルンスト係数とされるのは、１．０μＶ・Ｋ－１以上であるので、組成式ＦｅｘＳｎ１－ｘからなるアモルファス薄膜の熱電変換装置としては、０．７≦ｘ≦０．９の範囲であれば、十分な効果が期待できると言える。
　なお、Ｆｅ単体では、異常ネルンスト係数は、－０．２０～－０．４５μＶ・Ｋ－１となることが知られており（J. Weischenberg et al., Phys. Rev. B 87, 060406 (R) (2013), W. Zhou and Y. Sakuraba, Appl. Phys. Express 13, 043001 (2020)）、この異常ネルンスト効果は、ＦｅＳｎアモルファス薄膜での効果と認められる。 From the above results, since a large anomalous Nernst coefficient of 1.0 μV·K −1 or more is generally currently used to express the performance of a thermoelectric conversion device, it can be said that a sufficient effect can be expected for a thermoelectric conversion device of an amorphous thin film made of the composition formula Fe x Sn 1-x if the range of 0.7≦x≦0.9.
In addition, it is known that the anomalous Nernst coefficient of Fe alone is -0.20 to -0.45 μV·K -1 (J. Weischenberg et al., Phys. Rev. B 87, 060406 (R) (2013), W. Zhou and Y. Sakuraba, Appl. Phys. Express 13, 043001 (2020)), and this anomalous Nernst effect is recognized as an effect in FeSn amorphous thin films.
　図８は、Ｆｅの組成比と横熱伝導度との関係を示すグラフである。グラフの縦軸は、横熱伝導度αｘｙ（Ａ／ｍＫ）を示している。式（４）で定義した横熱伝導度αｘｙは、本質的な異常ネルンスト効果による成分（第二項）に、ゼーベック効果から生じるキャリア（電子・正孔）が異常ホール効果を介して寄与する成分（第一項）を加えたものである。図８のグラフから、横熱伝導度αｘｙについても、異常ネルンスト係数と同様に、Ｆｅの組成比ｘが大きいほど、大きくなる傾向が見られる。 8 is a graph showing the relationship between the composition ratio of Fe and the transverse thermal conductivity. The vertical axis of the graph shows the transverse thermal conductivity α xy (A/mK). The transverse thermal conductivity α xy defined by formula (4) is the component (second term) due to the essential anomalous Nernst effect plus the component (first term) contributed by carriers (electrons and holes) generated by the Seebeck effect through the anomalous Hall effect. From the graph of FIG. 8, it can be seen that the transverse thermal conductivity α xy also tends to increase as the composition ratio x of Fe increases, similar to the anomalous Nernst coefficient.
　図９は、Ｆｅの組成比とホール角との関係を示すグラフである。グラフの縦軸は、ホール角の正接σｘｙ／σｘｘを示している。ホール角の正接σｘｙ／σｘｘは、ホール効果による電子軌道の捻じ曲がりの強さの指標を示すものである。図９のグラフから、ホール角の正接σｘｙ／σｘｘは、ｘ＝０．７５付近（０．６～０．７５）でブロードなピークを示すことが分かる。 9 is a graph showing the relationship between the composition ratio of Fe and the Hall angle. The vertical axis of the graph shows the tangent of the Hall angle σ xy /σ xx . The tangent of the Hall angle σ xy /σ xx indicates an index of the strength of the twisting of the electron orbital due to the Hall effect. From the graph of FIG. 9, it can be seen that the tangent of the Hall angle σ xy /σ xx shows a broad peak near x = 0.75 (0.6 to 0.75).
（実施例１－２）
［組成元素依存性］
　実施例１－２では、熱電変換装置の特性の向上に向けて異常ネルンスト係数を増強すべく、スパッタリング法を用いて、不純物としてアルミニウム（Ａｌ）を組成式Ｆｅｘ（ＡｌｙＳｎ１－ｙ）１－ｘで表される組成物からなる薄膜（厚み４３ｎｍ）についてもアモルファスのみで構成した熱電変換膜を得た。Ａｌはスピン軌道相互作用やキャリア密度等の変調を通して、異常ネルンスト効果に寄与するフェルミ状態近傍の電子状態を変調するものと期待される。図１０に示すＸ線回折では、ｘ＝０．７７、ｙ＝０．４８の薄膜において、結晶に由来する鋭いピークは観測されなかった。
　異常ホール効果および異常ネルンスト効果を検出するための電極としてインジウムからなる部材を用いた。 (Example 1-2)
[Dependence on composition elements]
In Example 1-2, in order to enhance the anomalous Nernst coefficient to improve the characteristics of the thermoelectric conversion device, a thermoelectric conversion film was obtained using a sputtering method, in which aluminum (Al) was used as an impurity, and the thin film (thickness 43 nm) made of a composition represented by the composition formula Fe x (Al y Sn 1-y ) 1-x was also made of only amorphous. It is expected that Al modulates the electronic state near the Fermi state that contributes to the anomalous Nernst effect through modulation of spin-orbit interaction and carrier density. In the X-ray diffraction shown in FIG. 10, no sharp peaks derived from crystals were observed in the thin film with x = 0.77 and y = 0.48.
A member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
　Ｆｅの組成比ｘが０．７７かつＳｎとＡｌが占める０．２３の内のＡｌの組成比ｙが０．４８である１個のサンプルに対し、実施例１－１の手順と同様の手順で、実施例１－２の、不純物としてアルミニウムを含む組成物の薄膜の異常ホール効果によって電極間に発生するホール電圧を測定した。図１１は、その測定結果を示すグラフである。 For one sample with an Fe composition ratio x of 0.77 and an Al composition ratio y of 0.48 out of the 0.23 occupied by Sn and Al, the Hall voltage generated between the electrodes due to the anomalous Hall effect of the thin film of the composition containing aluminum as an impurity in Example 1-2 was measured using a procedure similar to that of Example 1-1. Figure 11 is a graph showing the measurement results.
　実施例１－１の手順と同様の手順で、実施例１－２の、不純物としてアルミニウムを含む組成物の薄膜の異常ネルンスト効果によって電極間に発生する熱起電力Ｖｘｙを測定した。図１２は、その測定結果を示すグラフである。 In a similar manner to that of Example 1-1, the thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect of the thin film of the composition containing aluminum as an impurity in Example 1-2 was measured. FIG. 12 is a graph showing the measurement results.
　比較のため、実施例１－２の、不純物としてアルミニウムを含む組成物の薄膜の結果を、実施例１－１のＦｅＳｎからなる、Ｆｅの組成比と異常ネルンスト係数の関係を示す図７のグラフ、Ｆｅの組成比と横熱伝導率の関係を示す図８のグラフ、及び、Ｆｅの組成比とホール角の関係を図９のグラフにそれぞれ白丸として重畳して示す。 For comparison, the results of the thin film of the composition containing aluminum as an impurity in Example 1-2 are shown superimposed as white circles on the graph in Figure 7, which shows the relationship between the Fe composition ratio and the anomalous Nernst coefficient, the graph in Figure 8, which shows the relationship between the Fe composition ratio and the lateral thermal conductivity, and the graph in Figure 9, which shows the relationship between the Fe composition ratio and the Hall angle, for the FeSn of Example 1-1.
　実施例１－１で用いたＦｅの組成比が同程度のｘ＝０．７４の熱電変換膜に比べ、実施例１－２のｘ＝０．７７、ｙ＝０．４８の熱電変換膜は高い異常ネルンスト係数と横熱伝導率が示している。この結果から、同量のＦｅの組成比に対してアルミニウムを添加することで、異常ネルンスト効果に寄与するフェルミ準位近傍の電子状態が変調され、熱電変換膜の性能の指標である異常ネルンスト係数を増強できることが分かった。
　このように、本発明のＦｅＳｎからなるアモルファス薄膜は、不純物として磁気的相互作用およびスピン軌道相互作用の変調を通して異常ネルンスト効果による起電力を増強する可能性を有する遷移元素、キャリア密度およびスピン軌道相互作用の変調を通して、異常ネルンスト効果による起電力を増強する可能性を有する典型元素、特に、アルミニウム、インジウム等の非磁性元素等から選択される元素を加えることにより、熱電変換装置の特性を大きく向上させる可能性がある。
　他の元素については、後述の実験で示す。 Compared to the thermoelectric conversion film with the same Fe composition ratio of x = 0.74 used in Example 1-1, the thermoelectric conversion film with x = 0.77 and y = 0.48 in Example 1-2 shows a high anomalous Nernst coefficient and lateral thermal conductivity. From this result, it was found that by adding aluminum to the same amount of Fe composition ratio, the electronic state near the Fermi level that contributes to the anomalous Nernst effect is modulated, and the anomalous Nernst coefficient, which is an index of the performance of the thermoelectric conversion film, can be enhanced.
In this way, the amorphous thin film made of FeSn of the present invention has the potential to greatly improve the characteristics of a thermoelectric conversion device by adding, as an impurity, an element selected from transition elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction, and typical elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction, particularly non-magnetic elements such as aluminum and indium.
Other elements will be shown in the experiments below.
（実施例２－１：微結晶を含むアモルファス熱電変換膜を用いた本発明の熱電変換装置）
［組成依存性］
　実施例２－１では、微結晶を含むアモルファス熱電変換膜を用いた場合の特性について検討する。
　微結晶を含むアモルファス熱電変換膜のサンプルを複数製造し、それらの熱電特性を測定した。熱電変換装置の様々な用途を考慮して、汎用的な基材であるサファイアＡｌ２Ｏ３基板を用いた。スパッタリング法を用いて、組成式ＦｅｘＳｎ１－ｘで表される組成物からなる薄膜（厚み３２～５３ｎｍ）を、微結晶を含むアモルファス熱電変換膜としてＡｌ２Ｏ３基板上に形成することができた。透過型顕微鏡観察などから、微結晶の割合は全体の約５～５０％と見積もられた。Ｆｅの組成割合が多いほど、微結晶の割合は増加する傾向にあった。異常ホール効果および異常ネルンスト効果を検出するための電極としてインジウムからなる部材を用いた。 (Example 2-1: Thermoelectric conversion device of the present invention using amorphous thermoelectric conversion film containing microcrystals)
[Composition Dependence]
In Example 2-1, the characteristics in the case where an amorphous thermoelectric conversion film containing microcrystals is used are examined.
A number of samples of amorphous thermoelectric conversion films containing microcrystals were manufactured, and their thermoelectric properties were measured. Considering various applications of thermoelectric conversion devices, a sapphire Al 2 O 3 substrate, which is a general-purpose base material, was used. Using a sputtering method, a thin film (thickness 32-53 nm) made of a composition represented by the composition formula Fe x Sn 1-x could be formed on the Al 2 O 3 substrate as an amorphous thermoelectric conversion film containing microcrystals. From observations using a transmission microscope, etc., the proportion of microcrystals was estimated to be about 5-50% of the total. The proportion of microcrystals tended to increase as the composition proportion of Fe increased. A member made of indium was used as an electrode for detecting the anomalous Hall effect and the anomalous Nernst effect.
　Ｆｅの組成比ｘが０．４４、０．５１、０．６０、０．６５、０．７３、０．８４、０．８７である７個のサンプルに対し、熱電変換膜の厚み方向に磁場（面直印加磁場）を印加し、磁場と直交する方向における一端側、他端側の温度を、それぞれ第一温度付与手段、第二温度付与手段を用いて３００Ｋとした。ここで、熱電変換膜の一端側（第一温度付与手段側）から他端側（第二温度付与手段側）へ電流を流したときに、異常ホール効果によって電極間に発生するホール電圧を測定した。 A magnetic field (magnetic field applied perpendicular to the surface) was applied in the thickness direction of the thermoelectric conversion film to seven samples with Fe composition ratios x of 0.44, 0.51, 0.60, 0.65, 0.73, 0.84, and 0.87, and the temperatures of one end and the other end in the direction perpendicular to the magnetic field were set to 300 K using the first temperature application means and the second temperature application means, respectively. Here, when a current was passed from one end (first temperature application means side) to the other end (second temperature application means side) of the thermoelectric conversion film, the Hall voltage generated between the electrodes due to the anomalous Hall effect was measured.
　図１３は、その測定結果を示すグラフである。グラフの横軸は面直印加磁場（Ｔ）を示し、グラフの縦軸はホール抵抗率ρｙｘ［μΩ・ｃｍ］を示す。このグラフから、磁場印加に伴う磁化方向の変化が、ホール抵抗率に反映されていることが分かる。 The measurement results are shown in the graph of Fig. 13. The horizontal axis of the graph indicates the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph indicates the Hall resistivity ρ yx [μΩ·cm]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the Hall resistivity.
　７個のサンプルにおいて、熱電変換膜の厚み方向に磁場を印加し、電流は流さずに、磁場と直交する方向において、一端側の温度を第一温度付与手段で約３００Ｋに維持しつつ、他端側の温度を第二温度付与手段で約３０６Ｋに調整した。第一温度付与手段として、冷凍機（カンタムデザイン社製VersaLab）の試料ホルダーを熱浴に用い、第二温度付与手段として、抵抗への通電加熱を用いた。このとき、異常ネルンスト効果によって、電極間に発生する熱起電力を測定した。試料に生じる温度勾配は、抵抗温度計を搭載したＡｌ２Ｏ３基板を用いて別途評価した印加電流と温度差の関係の較正曲線から見積もった。この較正曲線から見積もった温度勾配０．９３７Ｋ・ｍｍ－１を用いた。 In seven samples, a magnetic field was applied in the thickness direction of the thermoelectric conversion film, and a current was not applied. In the direction perpendicular to the magnetic field, the temperature of one end side was maintained at about 300 K by the first temperature application means, while the temperature of the other end side was adjusted to about 306 K by the second temperature application means. As the first temperature application means, a sample holder of a refrigerator (VersaLab manufactured by Quantum Design) was used as a heat bath, and as the second temperature application means, current heating to a resistor was used. At this time, the thermoelectromotive force generated between the electrodes due to the anomalous Nernst effect was measured. The temperature gradient generated in the sample was estimated from a calibration curve of the relationship between the applied current and the temperature difference evaluated separately using an Al 2 O 3 substrate equipped with a resistance thermometer. The temperature gradient of 0.937 K mm -1 estimated from this calibration curve was used.
　図１４は、その測定結果を示すグラフである。グラフの横軸は面直印加磁場（Ｔ）を示し、グラフの縦軸は異常ネルンスト係数Ｓｘｙ［μＶ・Ｋ－１］を表す。このグラフから、磁場印加に伴う磁化方向の変化が、異常ネルンスト係数に反映されていることが分かる。また、Ｆｅの組成比に依存して、ある組成比において、大きい異常ネルンスト係数が発生していることが分かる。 14 is a graph showing the measurement results. The horizontal axis of the graph represents the magnetic field (T) applied perpendicular to the surface, and the vertical axis of the graph represents the anomalous Nernst coefficient S xy [μV·K −1 ]. From this graph, it can be seen that the change in magnetization direction caused by the application of a magnetic field is reflected in the anomalous Nernst coefficient. It can also be seen that a large anomalous Nernst coefficient occurs at a certain composition ratio, depending on the Fe composition ratio.
　実施例２－１として製造した全てのサンプルに対し、実施例１－１に記載した手順と同様の手順で異常ホール効果を測定し、ホール抵抗率ρｙｘおよび電気抵抗率ρｘｘから、ホール角σｘｙ／σｘｘを算出した。また、実施例１－１に記載した手順と同様の手順で異常ネルンスト効果を測定し、熱起電力Ｖｘｙから、異常ネルンスト係数Ｓｘｙ、横熱伝導度αｘｙを算出した。図１５～１７は、その算出結果を示すグラフである。いずれのグラフにおいても、横軸はＦｅの組成比Ｆｅ／全構成元素（原子比）を示している。 For all samples manufactured as Example 2-1, the anomalous Hall effect was measured in the same manner as described in Example 1-1, and the Hall angle σ xy /σ xx was calculated from the Hall resistivity ρ yx and the electrical resistivity ρ xx . The anomalous Nernst effect was also measured in the same manner as described in Example 1-1, and the anomalous Nernst coefficient S xy and the transverse thermal conductivity α xy were calculated from the thermoelectromotive force V xy . Figures 15 to 17 are graphs showing the calculation results. In each graph, the horizontal axis shows the composition ratio of Fe Fe/total constituent elements (atomic ratio).
　図１５は、Ｆｅの組成比と異常ネルンスト係数との関係を示すグラフである。グラフの縦軸は、異常ネルンスト係数（μＶ・Ｋ－１）を示している。図１５のグラフでは、Ｆｅの組成比ｘが大きいほど、異常ネルンスト係数Ｓｘｙが大きくなっている。Ｆｅの組成比ｘが０．６以上で１．０μＶ・Ｋ－１を超えており、結晶性バルクＦｅ３Ｓｎで報告されている値（非特許文献としてSci. Adv.を引用）に匹敵する優れた熱電特性を有することが分かる。Ｆｅの組成比ｘが０．８７のとき、異常ネルンスト係数は、最大値２．８０μＶ・Ｋ－１を示している。 FIG. 15 is a graph showing the relationship between the composition ratio of Fe and the anomalous Nernst coefficient. The vertical axis of the graph shows the anomalous Nernst coefficient (μV·K −1 ). In the graph of FIG. 15, the anomalous Nernst coefficient S xy increases as the composition ratio x of Fe increases. When the composition ratio x of Fe is 0.6 or more, it exceeds 1.0 μV·K −1 , and it can be seen that the material has excellent thermoelectric properties comparable to the values reported for crystalline bulk Fe 3 Sn (Sci. Adv. is cited as a non-patent document). When the composition ratio x of Fe is 0.87, the anomalous Nernst coefficient shows a maximum value of 2.80 μV·K −1 .
　図１６は、Ｆｅの組成比と横熱伝導度との関係を示すグラフである。グラフの縦軸は、横熱伝導度αｘｙ（Ａ／ｍＫ）を示している。このグラフから、横熱伝導度αｘｙについても、異常ネルンスト係数と同様に、Ｆｅの組成比ｘが大きいほど、大きくなる傾向が見られる。 16 is a graph showing the relationship between the Fe composition ratio and the transverse thermal conductivity. The vertical axis of the graph shows the transverse thermal conductivity α xy (A/mK). As can be seen from this graph, the transverse thermal conductivity α xy also tends to increase as the Fe composition ratio x increases, similar to the anomalous Nernst coefficient.
　図１７は、Ｆｅの組成比とホール角との関係を示すグラフである。このグラフから、ホール角の正接σｘｙ／σｘｘは、ｘ＝０．７０付近に加えて、ｘ＝０．８５付近でもピークを示すことが分かる。 17 is a graph showing the relationship between the composition ratio of Fe and the Hall angle. From this graph, it can be seen that the tangent of the Hall angle σ xy /σ xx shows a peak not only near x=0.70 but also near x=0.85.
（実施例２－２）
［膜厚依存性］
　本発明の熱電変換装置のサンプルを３個製造し、それらの熱電特性を測定した。３個のサンプルにおけるＦｅの組成比ｘを０．６０、０．６０、０．６０、熱電変換膜の厚みｔを２０ｎｍ、４０ｎｍ、１００ｎｍとした。その他の構成については、実施例２－１と同様とした。 (Example 2-2)
[Thickness Dependence]
Three samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric characteristics were measured. The Fe composition ratio x in the three samples was 0.60, 0.60, and 0.60, and the thickness t of the thermoelectric conversion film was 20 nm, 40 nm, and 100 nm. The other configurations were the same as in Example 2-1.
　３個のサンプルにおいて、実施例１－１に記載の手順と同様の手順で異常ネルンスト効果によって電極間に発生する熱起電力Ｖｘｙを測定した。測定結果を用いて熱電係数Ｓｘｙを算出した。この算出結果を表１に示す。異常ネルンスト係数Ｓｘｙは、熱電変換膜の厚みｔによらず、ほぼ一定であることが分かる。 For the three samples, the thermoelectromotive force V xy generated between the electrodes due to the anomalous Nernst effect was measured in the same manner as described in Example 1-1. The thermoelectric coefficient S xy was calculated using the measurement results. The calculation results are shown in Table 1. It can be seen that the anomalous Nernst coefficient S xy is almost constant regardless of the thickness t of the thermoelectric conversion film.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
［膜の画像観察］
　実施例２－２の熱電変換装置のうち、熱電変換膜が組成式Ｆｅ０．６０Ｓｎ０．４０で表される組成物からなり、Ａｌ２Ｏ３基板上に作製されたものを選択し、透過型電子顕微鏡を用いて熱電変換膜の表面を観察した。図１８は、観察した表面の一部を拡大した画像である。主にアモルファス構造１０８Ａを有する熱電変換膜の中に、結晶部分１０８Ｂが点在していることが分かる。 [Image observation of the membrane]
Among the thermoelectric conversion devices of Example 2-2, one in which the thermoelectric conversion film was made of a composition represented by the composition formula Fe0.60Sn0.40 and was fabricated on an Al2O3 substrate was selected, and the surface of the thermoelectric conversion film was observed using a transmission electron microscope. Figure 18 is an enlarged image of a portion of the observed surface. It can be seen that crystalline portions 108B are scattered in the thermoelectric conversion film having a mainly amorphous structure 108A.
（実施例２－３）
［組成元素依存性］
　本発明の熱電変換装置のサンプルを複数製造し、それらの熱電特性を測定した。基材として、Ａｌ２Ｏ３基板を用いた。熱電変換膜として、三つの元素を含む組成物からなる薄膜を用いた。組成物の組成式を、Ｆｅ０．４１５Ｔａ０．２１８Ｓｎ０．３６７、Ｆｅ０．５１１Ｔａ０．２１７Ｓｎ０．２７２、Ｆｅ０．７１７Ｉｎ０．０３４Ｓｎ０．３４９、Ｆｅ０．６９７Ａｌ０．０９８Ｓｎ０．２０５、Ｆｅ０．７６８Ａｌ０．１１２Ｓｎ０．１２０とした。電極としてインジウムからなる部材を用いた。異常ネルンスト効果によって電極間に発生する熱起電力Ｖｘｙを測定し、測定結果を用いて異常ネルンスト係数Ｓｘｙを算出した。この算出結果を表２に示す。 (Example 2-3)
[Dependence on composition elements]
A plurality of samples of the thermoelectric conversion device of the present invention were manufactured, and their thermoelectric properties were measured. An Al2O3 substrate was used as the base material. A thin film made of a composition containing three elements was used as the thermoelectric conversion film. The composition formula of the composition was Fe0.415Ta0.218Sn0.367 , Fe0.511Ta0.217Sn0.272 , Fe0.717In0.034Sn0.349, Fe0.697Al0.098Sn0.205 , and Fe0.768Al0.112Sn0.120 . A member made of indium was used as the electrode. The thermoelectromotive force Vxy generated between the electrodes due to the anomalous Nernst effect was measured, and the anomalous Nernst coefficient Sxy was calculated using the measurement results. The calculation results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　図１５のグラフと表２の測定結果について、Ｆｅの組成比を基準にして次のように比較することができる。 The graph in Figure 15 and the measurement results in Table 2 can be compared as follows, based on the Fe composition ratio.
　Ｆｅの組成比が約０．４１５であるときの異常ネルンスト係数Ｓｘｙは、Ｆｅ－Ｓｎ組成の場合（図１５）には０．２５程度であるのに対し、Ｆｅ－Ｓｎ－Ｔａ組成の場合（表２）には０．９０になっている。 The anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.415 is about 0.25 in the case of the Fe--Sn composition (FIG. 15), whereas it is 0.90 in the case of the Fe--Sn--Ta composition (Table 2).
　Ｆｅの組成比が約０．５１１であるときの異常ネルンスト係数Ｓｘｙは、Ｆｅ－Ｓｎ組成の場合（図１５）には０．４程度であるのに対し、Ｆｅ－Ｓｎ－Ｔａ組成の場合には１．２２になっている。 The anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.511 is about 0.4 in the case of the Fe--Sn composition (FIG. 15), whereas it is 1.22 in the case of the Fe--Sn--Ta composition.
　Ｆｅの組成比が約０．７１７であるときの異常ネルンスト係数Ｓｘｙは、Ｆｅ－Ｓｎ組成の場合（図１５）には１．５程度であるのに対し、Ｆｅ－Ｓｎ－Ｉｎ組成の場合（表２）には１．３３になっている。 The anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.717 is about 1.5 in the case of the Fe--Sn composition (FIG. 15), whereas it is 1.33 in the case of the Fe--Sn--In composition (Table 2).
　Ｆｅの組成比が約０．６９７であるときの異常ネルンスト係数Ｓｘｙは、Ｆｅ－Ｓｎ組成の場合（図６）には１．４程度であるのに対し、Ｆｅ－Ｓｎ－Ａｌ組成の場合（表２）には２．４０になっている。 The anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.697 is about 1.4 in the case of the Fe--Sn composition (FIG. 6), whereas it is 2.40 in the case of the Fe--Sn--Al composition (Table 2).
　Ｆｅの組成比が約０．７６８であるときの異常ネルンスト係数Ｓｘｙは、Ｆｅ－Ｓｎ組成の場合（図１５）には１．８程度であるのに対し、Ｆｅ－Ｓｎ－Ａｌ組成の場合（表２）には２．８０になっている。 The anomalous Nernst coefficient S xy when the composition ratio of Fe is about 0.768 is about 1.8 in the case of an Fe--Sn composition (FIG. 15), whereas it is 2.80 in the case of an Fe--Sn--Al composition (Table 2).
　これらの比較から、Ｆｅ－Ｓｎ組成物にＴａ、Ａｌをドープした場合には、異常ネルンスト係数を大幅に高められることが分かる。特に、Ａｌは、異常ネルンスト係数の大幅な増加がみられる。この結果は、前述のように、異常ネルンスト効果に寄与するフェルミ準位近傍の電子状態が変調され、熱電変換膜の性能の指標である異常ネルンスト係数を増強できるためと考えられる。
　遷移元素を主成分とする磁性材料の特性向上には、磁気的相互作用を変調する観点から他の遷移元素を不純物として添加することが多いが、本発明は、遷移元素のＴａよりコストが安い、典型元素のＡｌで大きな効果を得ている。そのため、本発明のＦｅ－Ｓｎ組成物は、安価な材料で、異常ネルンスト係数の大幅な増加が見込める可能性がある。
　このように、本発明のＦｅＳｎからなるアモルファス薄膜は、微結晶粒子を含んでいる場合であっても、不純物として磁気的相互作用およびスピン軌道相互作用の変調を通して異常ネルンスト効果による起電力を増強する可能性を有する遷移元素、キャリア密度およびスピン軌道相互作用の変調を通して、異常ネルンスト効果による起電力を増強する可能性を有する典型元素等から選択される元素を加えることにより、熱電変換装置の特性を大きく向上させる可能性がある。 From these comparisons, it can be seen that when the Fe-Sn composition is doped with Ta or Al, the anomalous Nernst coefficient can be significantly increased. In particular, Al causes a significant increase in the anomalous Nernst coefficient. As mentioned above, this result is thought to be due to the fact that the electronic state near the Fermi level that contributes to the anomalous Nernst effect is modulated, thereby enhancing the anomalous Nernst coefficient, which is an index of the performance of the thermoelectric conversion film.
To improve the properties of magnetic materials mainly composed of transition elements, other transition elements are often added as impurities from the viewpoint of modulating magnetic interactions, but the present invention achieves great effects with Al, a typical element that is less expensive than the transition element Ta. Therefore, the Fe-Sn composition of the present invention is an inexpensive material and is likely to achieve a significant increase in the anomalous Nernst coefficient.
Thus, even if the amorphous thin film made of FeSn of the present invention contains microcrystalline particles, the characteristics of the thermoelectric conversion device can be greatly improved by adding an element selected from among transition elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of magnetic interaction and spin-orbit interaction as an impurity, and typical elements that have the potential to enhance the electromotive force due to the anomalous Nernst effect through modulation of carrier density and spin-orbit interaction.
［膜の画像観察］
　実施例２－３の熱電変換装置のうち、熱電変換膜が組成式Ｆｅ０．４９１Ｓｎ０．２７８Ｔａ０．２３１で表される組成物からなるものを選択し、透過型電子顕微鏡を用いて熱電変換膜の表面を観察した。図１９は、観察した表面の一部を拡大した画像である。主にアモルファス構造１０９Ａを有する熱電変換膜の中に、結晶部分１０９Ｂが点在していることが分かる。 [Image observation of the membrane]
Among the thermoelectric conversion devices of Example 2-3, one in which the thermoelectric conversion film was made of a composition represented by the composition formula Fe0.491Sn0.278Ta0.231 was selected, and the surface of the thermoelectric conversion film was observed using a transmission electron microscope. Figure 19 is an enlarged image of a part of the observed surface. It can be seen that crystalline portions 109B are scattered in the thermoelectric conversion film having a mainly amorphous structure 109A.
（効果等）
　本発明の実施例により、Ｆｅ、Ｓｎからなる、ほぼアモルファス構造の薄膜で大きな熱起電力を観測した。従来、結晶性のバルクや薄膜、ポリマーに金属等を分散させたもので、熱電変換膜が得られた報告はあったが、本発明では、アモルファス構造のみからなる磁性薄膜で、高性能の熱電変換膜を得ることができた。特に、組成式ＦｅｘＳｎ１－ｘ、０．７≦ｘ≦０．９で表されるアモルファス薄膜において、異常ネルンスト係数（異常ネルンスト効果に基づく熱電変換装置の性能指数の一つ）として、１．０μＶ・Ｋ－１を超える大きな値を得ることができた。
　これにより、優れた熱電特性および可撓性を有し、環境負荷が小さく、かつ室温で製造すること及び素子として小型化が可能な熱電変換装置を提供することができる。 (Effects, etc.)
According to the embodiment of the present invention, a large thermoelectromotive force was observed in a thin film of a nearly amorphous structure made of Fe and Sn. Conventionally, there have been reports of thermoelectric conversion films obtained by dispersing metals in crystalline bulks, thin films, and polymers, but in the present invention, a high-performance thermoelectric conversion film was obtained from a magnetic thin film made of only an amorphous structure. In particular, in an amorphous thin film represented by the composition formula Fe x Sn 1-x , 0.7≦x≦0.9, a large value exceeding 1.0 μV·K −1 was obtained as the anomalous Nernst coefficient (one of the performance indices of a thermoelectric conversion device based on the anomalous Nernst effect).
This makes it possible to provide a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, can be manufactured at room temperature, and can be made compact as an element.
　また、微結晶を含んでいても、性能に大きな変化がないことから、製造の汎用性が高く、かつ、安価に製造ができる。 In addition, even if it contains microcrystals, there is no significant change in performance, making it highly versatile and inexpensive to manufacture.
　さらに、添加物として遷移元素、典型元素等を含むことで、熱電変換装置の特性を大きく向上させる可能性があることから、組成によっては、革新的な性能の向上が期待できる。特に、安価なＡｌ等の典型元素を含ませることで、性能の向上が期待でき、安価で、高性能な、熱電変換装置を提供することができる。 Furthermore, the inclusion of transition elements, typical elements, etc. as additives can greatly improve the characteristics of thermoelectric conversion devices, so depending on the composition, revolutionary improvements in performance can be expected. In particular, the inclusion of inexpensive typical elements such as Al can be expected to improve performance, making it possible to provide inexpensive, high-performance thermoelectric conversion devices.
　本発明は、優れた熱電特性および可撓性を有し、環境負荷が小さく、かつ室温で製造することが可能な熱電変換装置を提供することができる。 The present invention provides a thermoelectric conversion device that has excellent thermoelectric properties and flexibility, has a small environmental impact, and can be manufactured at room temperature.
１００、１１０、１２０・・・熱電変換装置
１０１・・・基材
１０１ａ・・・基材の一面
１０２・・・熱電変換膜
１０３・・・第一電極
１０４・・・第二電極
１０５・・・第一温度付与手段
１０６・・・第二温度付与手段
１０７・・・波状のパターン
１０７ａ・・・波状のパターンの一端
１０７ｂ・・・波状のパターンの他端
１０８Ａ、１０９Ａ・・・アモルファス構造
１０８Ｂ、１０９Ｂ・・・結晶部分
Ｅ・・・熱起電力
Ｍ・・・磁化
∇Ｔ・・・温度勾配 100, 110, 120... Thermoelectric conversion device 101... Substrate 101a... One surface of substrate 102... Thermoelectric conversion film 103... First electrode 104... Second electrode 105... First temperature application means 106... Second temperature application means 107... Wavy pattern 107a... One end of wavy pattern 107b... Other end of wavy pattern 108A, 109A... Amorphous structure 108B, 109B... Crystalline portion E... Thermoelectromotive force M... Magnetization ∇T... Temperature gradient

Claims (7)

  1. 　基材と、
    　前記基材の一面に形成された熱電変換膜と、
    　前記熱電変換膜の前記基材側の温度を付与する第一温度付与手段と、
    　前記熱電変換膜の前記基材と反対側の温度を前記基材側の温度と異なる温度に付与する第二温度付与手段と、を備え、
    　前記熱電変換膜は、ＦｅｘとＳｎ１－ｘ（０．４ ≦ｘ≦ ０．９）を含む組成物からなるアモルファス構造を有することを特徴とする熱電変換装置。     A substrate;
    A thermoelectric conversion film formed on one surface of the base material;
    a first temperature applying means for applying a temperature to the substrate side of the thermoelectric conversion film;
    a second temperature applying means for applying a temperature to a side of the thermoelectric conversion film opposite to the base material, the second temperature applying means ...
    The thermoelectric conversion device is characterized in that the thermoelectric conversion film has an amorphous structure made of a composition containing Fe x and Sn 1-x (0.4≦x≦0.9).
  2. 　前記アモルファス構造は、前記熱電変換膜の全体積の５０％以上を占めることを特徴とする請求項１に記載の熱電変換装置。 The thermoelectric conversion device according to claim 1, characterized in that the amorphous structure occupies 50% or more of the total volume of the thermoelectric conversion film.
  3. 　前記熱電変換膜は、複数の結晶構造を有する部分を有し、それらの合計体積が、前記全体積の５％以上、５０％以下であることを特徴とする請求項２に記載の熱電変換装置。 The thermoelectric conversion device according to claim 2, characterized in that the thermoelectric conversion film has portions having multiple crystal structures, the total volume of which is 5% or more and 50% or less of the total volume.
  4. 　前記組成物は、組成式ＦｅｘＳｎ１－ｘ、０．７≦ｘ≦０．９で表されることを特徴とする請求項１に記載の熱電変換装置。 2. The thermoelectric conversion device according to claim 1, wherein the composition is represented by a composition formula Fe x Sn 1-x , where 0.7≦x≦0.9.
  5. 　前記アモルファス構造は、Ｘ線回折パターンにおいて、ブラッグ反射に伴うピーク値のノイズに対する比が、３０以下であることを特徴とする請求項１に記載の熱電変換装置。 The thermoelectric conversion device of claim 1, characterized in that the amorphous structure has an X-ray diffraction pattern in which the ratio of peak values associated with Bragg reflection to noise is 30 or less.
  6. 　前記組成物は、さらにＴａ、Ｗ、Ｐｔ、Ｍｏ、Ｍｎ、Ｉｎ、Ａｌ、Ｇｅ、Ｓｉ、Ｇａから選択される元素Ａを含み、
    　組成式Ｆｅｘ―ｙＳｎ１－ｘ－ｚＡｙ＋ｚ、０．４≦ｘ≦０．９、０．０５≦ｙ≦０．６、０．０５≦ｚ≦０．４で表されることを特徴とする請求項１に記載の熱電変換装置。     The composition further comprises an element A selected from Ta, W, Pt, Mo, Mn, In, Al, Ge, Si, Ga;
    2. The thermoelectric conversion device according to claim 1, characterized in that it is represented by a composition formula Fe x-y Sn 1-x-z A y+z , where 0.4≦x≦0.9, 0.05≦y≦0.6, and 0.05≦z≦0.4.
  7. 　前記組成物は、さらにＳｎ以外の典型元素から選択される元素Ｂを含み、
    　組成式Ｆｅｘ―ｙＳｎ１－ｘ－ｚＢｙ＋ｚ、０．４≦ｘ≦０．９、０．０５≦ｙ≦０．６、０．０５≦ｚ≦０．４で表されることを特徴とする請求項１に記載の熱電変換装置。     The composition further includes an element B selected from the main group elements other than Sn,
    2. The thermoelectric conversion device according to claim 1, characterized in that it is represented by a composition formula Fe x-y Sn 1-x-z B y+z , where 0.4≦x≦0.9, 0.05≦y≦0.6, and 0.05≦z≦0.4.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020040264A1 (en) * 2018-08-24 2020-02-27 国立大学法人東北大学 Hall element
WO2020218613A1 (en) * 2019-04-26 2020-10-29 国立大学法人東京大学 Thermoelectric conversion element and thermoelectric conversion device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020040264A1 (en) * 2018-08-24 2020-02-27 国立大学法人東北大学 Hall element
WO2020218613A1 (en) * 2019-04-26 2020-10-29 国立大学法人東京大学 Thermoelectric conversion element and thermoelectric conversion device

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