Thermoelectric conversion material, thermoelectric conversion element, thermoelectric conversion module, optical sensor, and method for producing thermoelectric conversion material

Abstract

To provide a thermoelectric conversion material capable of improving the efficiency of thermoelectric conversion.SOLUTION: A thermoelectric conversion material contains, as base materials, iron, vanadium and aluminum. The thermoelectric conversion material further contains oxygen. A signal intensity of a vanadium-oxygen bond that is a positive ion with a mass number of 67 is 5.2% or more with respect to a signal intensity of aluminum that is a positive ion with a mass number of 27, based on time-of-flight secondary ion mass spectrometry measured by sputtering 100 nm from the surface while using Bi3++ as a primary ion and argon as a sputter ion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a thermoelectric conversion material, a thermoelectric conversion element, a thermoelectric conversion module, an optical sensor, and a method for manufacturing a thermoelectric conversion material. [Background technology]

[0002] A technique relating to an Fe (iron)-V (vanadium)-Al (aluminum) based thermoelectric conversion material has been disclosed (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] B. Hinterleitner et al., “Thermoelectric performance of a metastable thin-film Heusler alloy”, Nature, Vol. 576,85-90(2019) Summary of the Invention [Problem to be solved by the invention]

[0004] Thermoelectric conversion materials are materials that convert temperature differences (thermal energy) into electricity. The power factor (hereinafter sometimes abbreviated as "PF"), which corresponds to the amount of power generated per unit temperature difference, is expressed by the following formula (1): In formula (1), S is the Seebeck coefficient, and σ is the electrical conductivity.

[0005] PF=S 2 ×σ (1)

[0006] In order to perform efficient thermoelectric conversion, it is important to increase the PF. If the PF can be increased, the efficiency of thermoelectric conversion can be improved.

[0007] Therefore, one of the objects is to provide a thermoelectric conversion material that can improve the efficiency of thermoelectric conversion. [Means for solving the problem]

[0008] The thermoelectric conversion material according to the present disclosure includes iron, vanadium, and aluminum as a matrix material. The thermoelectric conversion material further includes oxygen. The primary ions are Bi3 ++ Using a time-of-flight secondary ion mass spectrometry (TSMS) method, the signal intensity of the vanadium-oxygen bond, a positive ion with a mass number of 67, was measured by sputtering 100 nm from the surface using argon as the sputter ion, and the signal intensity of the aluminum bond, a positive ion with a mass number of 27, was found to be 5.2% or more. [Effects of the Invention]

[0009] In such a thermoelectric conversion material, thermoelectric conversion is efficient. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of a part of a thermoelectric conversion material according to the first embodiment. [Figure 2] FIG. 2 is a flowchart showing typical steps of a method for producing a thermoelectric conversion material according to the first embodiment. [Figure 3] FIG. 3 is a graph showing the relationship between the ratio of the signal intensity of a vanadium-oxygen bond, which is a positive ion with a mass number of 67, to the signal intensity of aluminum, which is a positive ion with a mass number of 27, and the ZT value. [Figure 4] FIG. 4 is a graph showing the relationship between the ratio of the signal intensity of an aluminum-oxygen bond, which is a negative ion with a mass number of 43, to the signal intensity of oxygen, which is a negative ion with a mass number of 16, and the ZT value. [Figure 5] FIG. 5 is a graph showing the relationship between the ratio of the signal intensity of an oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, to the signal intensity of aluminum, which is a positive ion with a mass number of 27, and the ZT value. [Figure 6]FIG. 6 is a schematic diagram showing the structure of a π-type thermoelectric conversion element (power generation element) which is a thermoelectric conversion element. [Figure 7] FIG. 7 is a diagram showing an example of the structure of a power generation module. [Figure 8] FIG. 8 is a diagram showing an example of the structure of an infrared sensor. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Description of the embodiments of the present disclosure] (1) The thermoelectric conversion material according to the present disclosure includes iron, vanadium, and aluminum as a base material. The thermoelectric conversion material further includes oxygen. The primary ions are Bi3 ++ Using argon as the sputtering ion, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was performed by sputtering 100 nm from the surface, and the signal intensity of the vanadium-oxygen bond, which is a positive ion with a mass number of 67, was found to be 5.2% or more of the signal intensity of aluminum, which is a positive ion with a mass number of 27.

[0012] The thermoelectric conversion material contains iron, vanadium, and aluminum as the base material, so although it is a metal, it has a pseudogap near the Fermi level in its band structure. The energy gradient of the density of states in this pseudogap region is steep, making it easy to achieve high thermoelectric properties. Furthermore, Bi3 ++ Using a time-of-flight secondary ion mass spectrometry (TSMS) method, the material was sputtered 100 nm from the surface using argon as the sputter ion, and the signal intensity of the vanadium-oxygen bond, which is a positive ion with a mass number of 67, was measured at 5.2% or more of the signal intensity of the aluminum ion, which is a positive ion with a mass number of 27. This prevents excessive crystallinity and promotes amorphization. Therefore, the thermal conductivity can be prevented from increasing. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material is improved.

[0013] (2) The thermoelectric conversion material according to the present disclosure includes iron, vanadium, and aluminum as a base material. The thermoelectric conversion material further includes oxygen. The primary ions are Bi3 ++ Using argon as the sputtering ion, time-of-flight secondary ion mass spectrometry was performed by sputtering 100 nm from the surface, and the signal intensity of the aluminum-oxygen bond, which is a negative ion with a mass number of 43, was found to be 26.1% or less of the signal intensity of oxygen, which is a negative ion with a mass number of 16.

[0014] The thermoelectric conversion material contains iron, vanadium, and aluminum as the base material, so although it is a metal, it has a pseudogap near the Fermi level in its band structure. The energy gradient of the density of states in this pseudogap region is steep, making it easy to achieve high thermoelectric properties. Furthermore, Bi3 ++ Using argon as sputter ions, the material was sputtered 100 nm from the surface, and time-of-flight secondary ion mass spectrometry was performed. The signal intensity of the aluminum-oxygen bond, which is a negative ion with a mass number of 43, was 26.1% or less of the signal intensity of the oxygen, which is a negative ion with a mass number of 16. This prevents excessive crystallinity and promotes amorphization. Therefore, the thermal conductivity can be prevented from increasing. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material is improved.

[0015] (3) The thermoelectric conversion material according to the present disclosure includes iron, vanadium, and aluminum as a base material. The thermoelectric conversion material further includes oxygen. The primary ions are Bi3 ++ Using argon as the sputtering ion, time-of-flight secondary ion mass spectrometry was performed by sputtering 100 nm from the surface, and the signal intensity of the oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, was found to be 0.67% or more of the signal intensity of aluminum, which is a positive ion with a mass number of 27.

[0016] The thermoelectric conversion material contains iron, vanadium, and aluminum as the base material, so although it is a metal, it has a pseudogap near the Fermi level in its band structure. The energy gradient of the density of states in this pseudogap region is steep, making it easy to achieve high thermoelectric properties. Furthermore, Bi3 ++ Using argon as sputter ions, the material was sputtered 100 nm from the surface, and time-of-flight secondary ion mass spectrometry was performed. The signal intensity of the oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, was 0.67% or more of the signal intensity of the aluminum ion, which is a positive ion with a mass number of 27. This prevents excessive crystallinity and promotes amorphization. Therefore, the thermal conductivity can be prevented from increasing. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material is improved.

[0017] (4) In any of the above (1) to (3), the thermoelectric conversion material may further contain tungsten. By doing so, the tungsten content can be adjusted appropriately, and the amorphization can be promoted while suppressing the collapse of the band structure. Therefore, the thermoelectric conversion efficiency of the thermoelectric conversion material can be more reliably improved.

[0018] (5) In any of the above (1) to (4), the base material may contain an amorphous phase. The thermoelectric conversion material has a high amorphous property. Therefore, the thermoelectric conversion efficiency of the thermoelectric conversion material is reliably improved.

[0019] (6) In any of the above (1) to (5), the thermoelectric conversion material may further include a silicon substrate. The base material may be disposed on the silicon substrate. By doing so, the silicon substrate is disposed as a base substrate for the Fe-V-Al-based base material, which is the base material, and the base material can be easily made amorphous. Therefore, the thermal conductivity of the thermoelectric conversion material is reduced, thereby further improving the thermoelectric conversion efficiency.

[0020] (7) A thermoelectric conversion element according to the present disclosure includes a thermoelectric conversion material section, a first electrode arranged in contact with the thermoelectric conversion material section, and a second electrode arranged in contact with the thermoelectric conversion material section and spaced apart from the first electrode. The material constituting the thermoelectric conversion material section is any one of the thermoelectric conversion materials (1) to (6) above, which has a p-type or n-type conductivity. In the thermoelectric conversion element according to the present disclosure, the material constituting the thermoelectric conversion material section is the thermoelectric conversion material described above. Therefore, the thermoelectric conversion element according to the present disclosure can achieve high thermoelectric conversion efficiency.

[0021] (8) The thermoelectric conversion module of the present disclosure includes the thermoelectric conversion element of the present disclosure (7). According to the thermoelectric conversion module of the present disclosure, by including the thermoelectric conversion element of the present disclosure that can achieve high thermoelectric conversion efficiency, it is possible to obtain a thermoelectric conversion module that can achieve high thermoelectric conversion efficiency.

[0022] (9) An optical sensor according to the present disclosure includes an absorber that absorbs light energy and a thermoelectric conversion material section connected to the absorber. The material constituting the thermoelectric conversion material section is any one of the thermoelectric conversion materials (1) to (6) above, which has a p-type or n-type conductivity. In the optical sensor according to the present disclosure, the material constituting the thermoelectric conversion material section is the thermoelectric conversion material described above. Therefore, a highly sensitive optical sensor can be provided.

[0023] (10) A method for producing a thermoelectric conversion material according to the present disclosure includes the steps of preparing a silicon substrate, preparing raw materials of iron, vanadium, and aluminum, and adjusting the oxygen concentration in a deposition chamber to 1.0×10 -1 Pa or more 1.0×10 -3 and forming a film on the silicon substrate by vapor deposition using the raw material while maintaining the silicon substrate at a temperature of 300°C or higher and 1000°C or lower.

[0024] By the above-described method for producing a thermoelectric conversion material, a thermoelectric conversion material with improved thermoelectric conversion efficiency can be easily produced.

[0025] [Details of the embodiments of the present disclosure] Next, embodiments of the thermoelectric conversion material of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0026] (Embodiment 1) A thermoelectric conversion material according to a first embodiment of the present disclosure will be described below. Fig. 1 is a schematic diagram showing a cross section of a portion of the thermoelectric conversion material according to the first embodiment.

[0027] Referring to FIG. 1, thermoelectric conversion material 11 in embodiment 1 includes base material 12 and silicon substrate 13. FIG. 1 is a cross-sectional view of silicon substrate 13 cut in the thickness direction. Base material 12 is disposed on silicon substrate 13. Base material 12 includes Fe (iron), V (vanadium), and Al (aluminum). Base material 12 is an Fe-V-Al-based material. Base material 12 is formed as a film on Si (silicon) substrate 13.

[0028] In this embodiment, the thermoelectric conversion material 11 contains oxygen and tungsten as a base material. O (oxygen) is contained in the base material 12. The oxygen content is 4 at % or more and 27 at % or less with respect to the entire thermoelectric conversion material 11. The W (tungsten) content is 1.5 at % or more and 16.5 at % or less with respect to the entire thermoelectric conversion material 11. The base material 12 also contains an amorphous phase.

[0029] Here, in the thermoelectric conversion material 11, Bi3 ++ Using argon as the sputtering ion, the signal intensity of the vanadium-oxygen bond, which is a positive ion with a mass number of 67, measured at 100 nm from the surface, was 5.2% or more of the signal intensity of the aluminum ion, which is a positive ion with a mass number of 27. In addition, Bi3 ++Using argon as the sputtering ion, the signal intensity of the aluminum-oxygen bond, which is a negative ion with a mass number of 43, was measured at 100 nm from the surface. The signal intensity of the oxygen, which is a negative ion with a mass number of 16, was 26.1% or less. In addition, Bi3 ++ Using argon as the sputtering ion, time-of-flight secondary ion mass spectrometry was performed by sputtering 100 nm from the surface, and the signal intensity of the oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, was 0.67% or more of the signal intensity of the aluminum, which is a positive ion with a mass number of 27. These will be described in detail later.

[0030] The thermoelectric conversion material 11 according to the first embodiment can be manufactured, for example, by the following manufacturing method. FIG. 2 is a flowchart showing typical steps in the manufacturing method for the thermoelectric conversion material 11 according to the first embodiment. Referring to FIG. 2, in the manufacturing method for the thermoelectric conversion material 11 according to the first embodiment, a raw material preparation step is performed as step (S10). In this step (S10), a silicon substrate 13, specifically an n-type Si(100) substrate, is prepared. In addition, Fe, Al, V, and W, which are used to form a base material film, are prepared. The Fe, Al, V, and W elements may be prepared as a bulk substance of each element, or may be prepared as a compound containing any of Fe, Al, V, and W, such as Fe2VAl. Of course, both may be prepared. The amount of each element to be prepared is adjusted so that the desired composition of the thermoelectric conversion material 11 is finally achieved. In this embodiment, Fe2VAl and W are prepared as simple substances.

[0031] Next, a film formation step is carried out as step (S20). In this step (S20), the silicon substrate 13 is heated at 700°C for 30 minutes or more, and then, while maintaining the heating, a W-containing Fe-V-Al film is formed by RF (Radio Frequency) magnetron sputtering. The film formation rate is 5 nm / min, and in this embodiment, a film of 230 nm is formed. Ar (argon) gas is used for sputtering. In addition, the background oxygen concentration (oxygen partial pressure) is adjusted to 1.0 x 10 to achieve the desired oxygen content. -1 Pa (Pascal) or more 1.0 x 10 -3 The oxygen concentration in the deposition chamber is adjusted to a range of 1.0×10 Pa or less. -1 Pa or more 1.0×10 -3 With the temperature of silicon substrate 13 maintained at 300° C. or higher and 1000° C. or lower, a film is formed by vapor deposition using raw materials on silicon substrate 13. In this manner, base material 12 is formed on silicon substrate 13. In this manner, thermoelectric conversion material 11 in embodiment 1 is obtained.

[0032] Since the Gibbs free energy of VO2 is greater than that of Al2O3, it is generally easier for Al2O3 to form. However, taking into account temperature dependence, at high temperatures the difference in energy between VO2 and Al2O3 becomes smaller, so the proportion of VO2 can be increased when the film is formed at high temperatures.

[0033] The thermoelectric conversion material 11 is a metal because it contains iron, vanadium, and aluminum as the base material 12. However, it has a pseudogap near the Fermi level as a band structure. The energy gradient of the density of states in this pseudogap portion is steep, which makes it easy to achieve high thermoelectric properties.

[0034] Bi3 as the primary ion ++Time-of-flight secondary ion mass spectrometry (TSMS) was performed using argon as sputter ions and sputtering 100 nm from the surface. The signal intensity of the vanadium-oxygen bond, a positive ion with a mass number of 67, was 5.2% or more of the signal intensity of the aluminum ion, a positive ion with a mass number of 27. This prevents excessive crystallinity and promotes amorphization. Therefore, the thermal conductivity is prevented from increasing. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material 11 is improved.

[0035] In addition, Bi3 ++ Using argon as sputter ions, time-of-flight secondary ion mass spectrometry was performed by sputtering 100 nm from the surface, and the signal intensity of the aluminum-oxygen bond, which is a negative ion with a mass number of 43, was 26.1% or less of the signal intensity of the oxygen, which is a negative ion with a mass number of 16. By doing so, it is possible to prevent the crystallinity from becoming too high and promote amorphization. Therefore, it is possible to prevent the thermal conductivity from becoming too high. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material 11 is improved.

[0036] In addition, Bi3 ++ Using argon as sputter ions, time-of-flight secondary ion mass spectrometry was performed by sputtering 100 nm from the surface, and the signal intensity of the oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, was 0.67% or more of the signal intensity of the aluminum, which is a positive ion with a mass number of 27. This prevents excessive crystallinity and promotes amorphization. Therefore, it is possible to prevent the thermal conductivity from increasing. As a result, the thermoelectric conversion efficiency of the thermoelectric conversion material 11 is improved.

[0037] Furthermore, by the above-described method for producing a thermoelectric conversion material, a thermoelectric conversion material with improved thermoelectric conversion efficiency can be easily produced.

[0038] In this embodiment, the thermoelectric conversion material 11 contains oxygen and tungsten as a base material. When the thermoelectric conversion material 11 contains oxygen and tungsten, the crystalline structure is easily broken down and the material is easily made amorphous. This reduces the thermal conductivity of the thermoelectric conversion material 11, making it easier to improve its thermoelectric properties. This further improves the efficiency of thermoelectric conversion.

[0039] In this embodiment, the base material 12 includes an amorphous phase. Such a thermoelectric conversion material 11 has a high degree of amorphousness. Therefore, in such a thermoelectric conversion material 11, the efficiency of thermoelectric conversion is reliably improved.

[0040] In this embodiment, the thermoelectric conversion material 11 includes a silicon substrate 13. The base material 12 is disposed on the silicon substrate 13. Therefore, by disposing the silicon substrate 13 as a substrate underlying the Fe-V-Al-based base material, the base material 12 can be easily made amorphous. Therefore, the thermal conductivity of the thermoelectric conversion material 11 is reduced, thereby further improving the thermoelectric conversion efficiency.

[0041] The physical properties of the obtained thermoelectric conversion material 11 are measured, for example, by the following method. The content ratio of elements greater than 0.1 at% can be measured, for example, by EDX (Energy Dispersive X-ray spectrometry). EDX was measured by taking a TEM (Transmission Electron Microscope) image of a portion of the thermoelectric conversion material 11. The TEM image was taken using a JEM-2800 (manufactured by JEOL Ltd.). The measurement conditions were an acceleration voltage of 200 kV, a probe size of 0.5 nm, and a CL aperture of 3. The conditions for detecting atoms by EDX were an EDX (manufactured by Thermo Fisher Scientific K.K.). The measurement conditions were a spot size of 0.5 nm, a CL aperture of 3, a mapping analysis mode, and a 20-minute analysis time. The content ratio of elements less than 0.1 at% can be measured, for example, by SIMS (Secondary Ion Mass Spectroscopy). Specifically, the measurement was performed using ADEPT-1010 manufactured by ULVAC, Inc., and the ion source used for the measurement was CsR + ions for the element R.

[0042] Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was performed using a PHInanoTOFII instrument. Bi3 ++ The acceleration voltage was 30 kV, the measurement area was 100 μm × 100 μm, the detected ions were both positive and negative ions, cleaning was performed (Ar ion sputtering), and the mass number analysis range was 1 to 500. + The negative ions are normalized by the amount of O detected. - The measurement was performed by sputtering 100 nm from the surface.

[0043] The electrical conductivity and Seebeck coefficient were measured using a thermoelectric property measurement device (RZ2001i, manufactured by Ozawa Scientific Co., Ltd.). The measurement method is as follows: First, the thermoelectric conversion material is fixed to a pair of quartz jigs so as to bridge the gap, and the atmosphere is heated in a resistance heating furnace. One end of the quartz jigs is left hollow, and nitrogen gas is passed through it to cool one end of the thermoelectric conversion material. This creates a temperature difference in the thermoelectric conversion material. The temperature difference between two points on the surface of the thermoelectric conversion material is measured using a platinum-platinum-rhodium thermocouple (R thermocouple). A voltmeter is connected to the thermocouple to measure the voltage generated by the temperature difference between the two points. This allows the generated voltage relative to the temperature difference to be measured, which can then be used to estimate the Seebeck coefficient of the material. Resistance is measured using the four-terminal method. That is, two electric wires are connected to the outside of two platinum wires connected to a voltmeter. A current is passed through the wire, and the voltage drop is measured using the internal voltmeter. In this way, the resistance value of the thermoelectric conversion material is measured using the four-terminal method. The conductivity is derived from the measured resistance value. The PF is then calculated based on the obtained conductivity and Seebeck coefficient using the above formula (1).

[0044] Here, the conversion efficiency η of the temperature difference (thermal energy) into electrical energy using a thermoelectric conversion material is given by the following equation (2):

[0045] η=ΔT / T h (M-1) / (M+T c / T h )···(2)

[0046] η is the conversion efficiency, ΔT is T h and T c The difference between T h is the temperature on the hot side, T c is the temperature on the lower side, and M is (1+ZT) 1 / 2 , ZT=α 2ST / κ and ZT are dimensionless figures of merit, α is the Seebeck coefficient, S is the electrical conductivity, and κ is the thermal conductivity. The conversion efficiency is a monotonically increasing function of ZT. If the ZT value of the thermoelectric conversion material 11 is high, it can be said that the thermoelectric conversion efficiency is high. Specifically, a ZT value of 3 or more can be said to be a high thermoelectric conversion efficiency.

[0047] (Example) Here, thermoelectric conversion materials were prepared. The results are shown in Figures 3, 4, 5, Tables 1 and 2. Figure 3 is a graph showing the relationship between the ratio of the signal intensity of a vanadium-oxygen bond (a positive ion with a mass number of 67) to the signal intensity of an aluminum ion (a positive ion with a mass number of 27) and the ZT value. In Figure 3, the horizontal axis represents the signal intensity ratio, and the vertical axis represents the ZT value. The same applies to the horizontal and vertical axes of the graphs shown below. Figure 4 is a graph showing the relationship between the ratio of the signal intensity of an aluminum-oxygen bond (a negative ion with a mass number of 43) to the signal intensity of an oxygen ion (a negative ion with a mass number of 16) and the ZT value. Figure 5 is a graph showing the relationship between the ratio of the signal intensity of an oxygen-iron-vanadium bond (a positive ion with a mass number of 123) to the signal intensity of an aluminum ion (a positive ion with a mass number of 27) and the ZT value. Table 1 shows the signal intensity ratios and ZT values ​​shown in Figures 3, 4, and 5. In Table 1, "(O+V) / Al" indicates the ratio of the signal intensity of the vanadium-oxygen bond, a positive ion with a mass number of 67, to the signal intensity of aluminum, a positive ion with a mass number of 27. "(O+Al) / O" indicates the ratio of the signal intensity of the aluminum-oxygen bond, a negative ion with a mass number of 43, to the signal intensity of oxygen, a negative ion with a mass number of 16. "(O+Fe+V) / Al" indicates the ratio of the signal intensity of the oxygen-iron-vanadium bond, a positive ion with a mass number of 123, to the signal intensity of aluminum, a positive ion with a mass number of 27. Table 2 shows the results of calculating the intersections of each graph in Figures 3, 4, and 5 with ZT = 3 and ZT = 3.5. In each figure, two horizontal thick lines 14 and 15 indicate plots where ZT is 3 and 3.5, respectively. The composition of the thermoelectric conversion material is (FeV 0.96 Al1W 0.04 ) 0.94 O 0.06 It is as follows.

[0048] [Table 1]

[0049] [Table 2]

[0050] With reference to Tables 1, 2, and FIG. 3, for "(O+V) / Al," ZT is 3 or greater at 5.2% (0.052) or greater, which is the intersection point between bold line 14 and the graph. Furthermore, for "(O+V) / Al," ZT is 3.5 or greater at 5.5% (0.055) or greater, which is the intersection point between bold line 15 and the graph. With reference to Tables 1, 2, and FIG. 4, for "(O+Al) / O," ZT is 3 or greater at 26.1% (0.261) or less, which is the intersection point between bold line 14 and the graph. Furthermore, for "(O+Al) / O," ZT is 3.5 or greater at 25.2% (0.252) or less, which is the intersection point between bold line 15 and the graph. 5, for "(O+Fe+V) / Al", ZT is 3 or more at 0.67% (0.0067) or more, which is the intersection point between thick line 14 and the graph. Also, for "(O+Fe+V) / Al", ZT is 3.5 or more at 0.074% (0.0074) or more, which is the intersection point between thick line 15 and the graph.

[0051] (Embodiment 2) Next, a power generating element will be described as one embodiment of a thermoelectric conversion element using the thermoelectric conversion material according to the present disclosure.

[0052] 6 is a schematic diagram showing the structure of a π-type thermoelectric conversion element (power generation element) 21, which is a thermoelectric conversion element in this embodiment. Referring to Fig. 6, the π-type thermoelectric conversion element 21 includes a p-type thermoelectric conversion material part 22, which is a first thermoelectric conversion material part, an n-type thermoelectric conversion material part 23, which is a second thermoelectric conversion material part, a high-temperature side electrode 24, a first low-temperature side electrode 25, a second low-temperature side electrode 26, and wiring 27.

[0053] The material constituting the p-type thermoelectric conversion material section 22 is the thermoelectric conversion material of the first embodiment, whose composition has been adjusted to have a p-type conductivity. Examples of p-type dopants (acceptors) include Ti (titanium) and Zr (zirconium). The thermoelectric conversion material constituting the n-type thermoelectric conversion material section 23 is the thermoelectric conversion material of the first embodiment, whose composition has been adjusted to have an n-type conductivity. Examples of n-type dopants (donors) include Si (silicon), Ge (germanium), Mo (molybdenum), Co (cobalt), and Pt (platinum).

[0054] The p-type thermoelectric conversion material section 22 and the n-type thermoelectric conversion material section 23 are arranged side by side with a gap between them. The high-temperature side electrode 24 is arranged so as to extend from one end 31 of the p-type thermoelectric conversion material section 22 to one end 32 of the n-type thermoelectric conversion material section 23. The high-temperature side electrode 24 is arranged so as to contact both one end 31 of the p-type thermoelectric conversion material section 22 and one end 32 of the n-type thermoelectric conversion material section 23. The high-temperature side electrode 24 is arranged so as to connect one end 31 of the p-type thermoelectric conversion material section 22 to one end 32 of the n-type thermoelectric conversion material section 23. The high-temperature side electrode 24 is made of a conductive material, for example, a metal. The high-temperature side electrode 24 is in ohmic contact with the p-type thermoelectric conversion material section 22 and the n-type thermoelectric conversion material section 23.

[0055] The first low-temperature side electrode 25 is arranged in contact with the other end 33 of the p-type thermoelectric conversion material part 22. The first low-temperature side electrode 25 is arranged apart from the high-temperature side electrode 24. The first low-temperature side electrode 25 is made of a conductive material, for example, a metal. The first low-temperature side electrode 25 is in ohmic contact with the p-type thermoelectric conversion material part 22.

[0056] The second low-temperature side electrode 26 is arranged in contact with the other end 34 of the n-type thermoelectric conversion material part 23. The second low-temperature side electrode 26 is arranged apart from the high-temperature side electrode 24 and the first low-temperature side electrode 25. The second low-temperature side electrode 26 is made of a conductive material, for example, a metal. The second low-temperature side electrode 26 is in ohmic contact with the n-type thermoelectric conversion material part 23.

[0057] The wiring 27 is made of a conductor such as metal, etc. The wiring 27 electrically connects the first low-temperature side electrode 25 and the second low-temperature side electrode 26 together.

[0058] In the π-type thermoelectric conversion element 21, for example, when a temperature difference is created such that one end 31 of the p-type thermoelectric conversion material section 22 and one end 32 of the n-type thermoelectric conversion material section 23 are at a high temperature, and the other end 33 of the p-type thermoelectric conversion material section 22 and the other end 34 of the n-type thermoelectric conversion material section 23 are at a low temperature, p-type carriers (holes) move from one end 31 to the other end 33 in the p-type thermoelectric conversion material section 22. At this time, n-type carriers (electrons) move from one end 32 to the other end 34 in the n-type thermoelectric conversion material section 23. As a result, a current flows through the wiring 27 in the direction of arrow I. In this way, the π-type thermoelectric conversion element 21 generates electricity through thermoelectric conversion using the temperature difference. That is, the π-type thermoelectric conversion element 21 is a power generation element.

[0059] The thermoelectric conversion material of the first embodiment, which can achieve a high ZT, is used as the material for forming the n-type thermoelectric conversion material portion 23. As a result, the π-type thermoelectric conversion element 21 is a highly efficient power generating element.

[0060] In the above embodiment, a π-type thermoelectric conversion element has been described as an example of the thermoelectric conversion element of the present disclosure, but the thermoelectric conversion element of the present disclosure is not limited to this. The thermoelectric conversion element of the present disclosure may be a thermoelectric conversion element having another structure, such as an I-type (uni-leg) thermoelectric conversion element.

[0061] (Embodiment 3) A power generation module serving as a thermoelectric conversion module can be obtained by electrically connecting a plurality of π-type thermoelectric conversion elements 21. The power generation module 41, which is a thermoelectric conversion module of this embodiment, has a structure in which a plurality of π-type thermoelectric conversion elements 21 are connected in series.

[0062] FIG. 7 is a diagram illustrating an example of the structure of a power generation module. Referring to FIG. 7, a power generation module 41 according to this embodiment includes a p-type thermoelectric conversion material portion 22, an n-type thermoelectric conversion material portion 23, low-temperature-side electrodes 25 and 26 corresponding to the first low-temperature-side electrode 25 and the second low-temperature-side electrode 26, a high-temperature-side electrode 24, a low-temperature-side insulator substrate 28, and a high-temperature-side insulator substrate 29. The low-temperature-side insulator substrate 28 and the high-temperature-side insulator substrate 29 are made of ceramic such as alumina. The p-type thermoelectric conversion material portion 22 and the n-type thermoelectric conversion material portion 23 are arranged alternately. The low-temperature-side electrodes 25 and 26 are arranged in contact with the p-type thermoelectric conversion material portion 22 and the n-type thermoelectric conversion material portion 23, similar to the π-type thermoelectric conversion element 21 described above. The high-temperature-side electrode 24 is arranged in contact with the p-type thermoelectric conversion material portion 22 and the n-type thermoelectric conversion material portion 23, similar to the π-type thermoelectric conversion element 21 described above. The p-type thermoelectric conversion material section 22 is connected to the adjacent n-type thermoelectric conversion material section 23 on one side by a common high-temperature electrode 24. The p-type thermoelectric conversion material section 22 is also connected to the adjacent n-type thermoelectric conversion material section 23 on a side different from the one side by common low-temperature electrodes 25, 26. In this way, all of the p-type thermoelectric conversion material sections 22 and n-type thermoelectric conversion material sections 23 are connected in series.

[0063] The low-temperature-side insulator substrate 28 is arranged on the main surface side opposite to the side in contact with the p-type thermoelectric conversion material section 22 and the n-type thermoelectric conversion material section 23 of the plate-shaped low-temperature-side electrodes 25, 26. One low-temperature-side insulator substrate 28 is arranged for each of the plurality (all) of low-temperature-side electrodes 25, 26. The high-temperature-side insulator substrate 29 is arranged on the side opposite to the side in contact with the p-type thermoelectric conversion material section 22 and the n-type thermoelectric conversion material section 23 of the plate-shaped high-temperature-side electrode 24. One high-temperature-side insulator substrate 29 is arranged for each of the plurality (all) of high-temperature-side electrodes 24.

[0064] Wiring 27 is connected to high-temperature side electrode 24 or low-temperature side electrodes 25, 26 that contact p-type thermoelectric conversion material section 22 or n-type thermoelectric conversion material section 23 located at both ends of p-type thermoelectric conversion material section 22 and n-type thermoelectric conversion material section 23 connected in series. When a temperature difference is created such that high-temperature side insulator substrate 29 side is high temperature and low-temperature side insulator substrate 28 side is low temperature, current flows in the direction of arrow I through p-type thermoelectric conversion material section 22 and n-type thermoelectric conversion material section 23 connected in series, as in the case of above-mentioned π-type thermoelectric conversion element 21. In this way, power generation is achieved in power generation module 41 by thermoelectric conversion utilizing the temperature difference.

[0065] (Fourth embodiment) Next, an infrared sensor, which is an optical sensor, will be described as another embodiment of a thermoelectric conversion element using the thermoelectric conversion material according to the present disclosure.

[0066] Fig. 8 is a diagram showing an example of the structure of infrared sensor 51. Referring to Fig. 8, infrared sensor 51 includes a p-type thermoelectric conversion material part 52 and an n-type thermoelectric conversion material part 53 arranged adjacent to each other. P-type thermoelectric conversion material part 52 and n-type thermoelectric conversion material part 53 are formed on substrate 54.

[0067] The infrared sensor 51 includes a substrate 54, an etching stop layer 55, an n-type thermoelectric conversion material layer 56, and an n + The semiconductor device includes an n-side ohmic contact layer 57, an insulator layer 58, a p-type thermoelectric conversion material layer 59, an n-side ohmic contact electrode 61, a p-side ohmic contact electrode 62, a heat absorption pad 63, an absorber 64, and a protective film 65.

[0068] The substrate 54 is made of an insulator such as silicon dioxide. A recess 66 is formed in the substrate 54. The etching stop layer 55 is formed to cover the surface of the substrate 54. The etching stop layer 55 is made of an insulator such as silicon nitride. A gap is formed between the etching stop layer 55 and the recess 66 of the substrate 54.

[0069] The n-type thermoelectric conversion material layer 56 is formed on the main surface of the etching stop layer 55 opposite to the substrate 54. The thermoelectric conversion material constituting the n-type thermoelectric conversion material layer 56 is the thermoelectric conversion material of the first embodiment. + The n-type ohmic contact layer 57 is formed on the main surface of the n-type thermoelectric conversion material layer 56 opposite to the etching stop layer 55. + The n-type ohmic contact layer 57 is doped with n-type impurities that generate n-type carriers (electrons), which are majority carriers. + The conductivity type of the ohmic contact layer 57 is n-type.

[0070] n + An n-side ohmic contact electrode 61 is disposed so as to be in contact with the center of the main surface of the n-type ohmic contact layer 57 opposite to the n-type thermoelectric conversion material layer 56. The n-side ohmic contact electrode 61 is + The n-type ohmic contact layer 57 is made of a material that can make ohmic contact with the n-type ohmic contact layer 57, such as a metal. + An insulator layer 58 made of an insulator such as silicon dioxide is disposed on the main surface of the n-type ohmic contact layer 57 opposite to the n-type thermoelectric conversion material layer 56. The insulator layer 58 is disposed on the n-side ohmic contact electrode 61 on the p-type thermoelectric conversion material portion 52 side. + The ohmic contact layer 57 is disposed on the major surface of the ohmic contact layer 57 .

[0071] n + A protective film 65 is further disposed on the main surface of the n-type ohmic contact layer 57 opposite the n-type thermoelectric conversion material layer 56. The protective film 65 is disposed on the n-side ohmic contact electrode 61 opposite the p-type thermoelectric conversion material layer 52. + The n-type ohmic contact layer 57 is disposed on the main surface of the n-type ohmic contact layer 57. + On the main surface of the n-type ohmic contact layer 57 opposite to the n-type thermoelectric conversion material layer 56, another n-side ohmic contact electrode 61 is arranged on the opposite side to the n-side ohmic contact electrode 61 with a protective film 65 sandwiched therebetween.

[0072] n of the insulator layer 58 +A p-type thermoelectric conversion material layer 59 is disposed on the main surface opposite to the p-type ohmic contact layer 57 .

[0073] A protective film 65 is disposed in the center of the main surface of the p-type thermoelectric conversion material layer 59 opposite the insulator layer 58. A pair of p-side ohmic contact electrodes 62 are disposed on the main surface of the p-type thermoelectric conversion material layer 59 opposite the insulator layer 58, sandwiching the protective film 65 therebetween. The p-side ohmic contact electrodes 62 are made of a material, such as a metal, that can make ohmic contact with the p-type thermoelectric conversion material layer 59. Of the pair of p-side ohmic contact electrodes 62, the p-side ohmic contact electrode 62 on the n-type thermoelectric conversion material portion 53 side is connected to the n-side ohmic contact electrode 61.

[0074] The p-side ohmic contact electrode 62 and the n-side ohmic contact electrode 61 are connected to each other. + An absorber 64 is disposed so as to cover the main surface opposite the n-type ohmic contact layer 57. The absorber 64 is made of, for example, titanium. A heat absorption pad 63 is disposed so as to be in contact with the p-side ohmic contact electrode 62 on the side not connected to the n-side ohmic contact electrode 61. In addition, a heat absorption pad 63 is disposed so as to be in contact with the n-side ohmic contact electrode 61 on the side not connected to the p-side ohmic contact electrode 62. Au (gold) / Ti (titanium), for example, is used as a material for forming the heat absorption pad 63. That is, the absorber 64 and the n-type thermoelectric conversion material layer 56 are thermally connected. The absorber 64 and the p-type thermoelectric conversion material layer 59 are thermally connected.

[0075] When infrared rays are irradiated onto the infrared sensor 51, the absorber 64 absorbs the infrared energy. As a result, the temperature of the absorber 64 rises. Meanwhile, the temperature rise of the heat absorption pad 63 is suppressed. Therefore, a temperature difference is generated between the absorber 64 and the heat absorption pad 63. Then, in the p-type thermoelectric conversion material layer 59, p-type carriers (holes) move from the absorber 64 side toward the heat absorption pad 63 side. Meanwhile, in the n-type thermoelectric conversion material layer 56, n-type carriers (electrons) move from the absorber 64 side toward the heat absorption pad 63 side. Then, the infrared rays are detected by extracting a current generated as a result of the carrier movement from the n-side ohmic contact electrode 61 and the p-side ohmic contact electrode 62.

[0076] In infrared sensor 51 of the present embodiment, the thermoelectric conversion material of embodiment 1 is used as the thermoelectric conversion material that constitutes n-type thermoelectric conversion material layer 56. As a result, infrared sensor 51 is a highly sensitive infrared sensor.

[0077] (Other embodiments) In the above embodiment, the thermoelectric conversion material is manufactured by depositing a base material on a silicon substrate, but this is not limited to this. The thermoelectric conversion material may be manufactured by depositing a base material on another substrate, or the thermoelectric conversion material may not include a silicon substrate.

[0078] In the above-described embodiment, the thermoelectric conversion material may be configured to contain neither oxygen nor tungsten.

[0079] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above description but by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0080] 11 Thermoelectric conversion materials 12 Base material 13 Silicon substrate 14,15 thick line 21 π-type thermoelectric conversion element 22,52 p-type Thermoelectric Materials Department 23,53 n-Type Thermoelectric Materials Department 24 High temperature side electrode 25 1st low temperature side electrode (low temperature side electrode) 26 2nd low temperature side electrode (low temperature side electrode) 27, 42, 43 Wiring 28 Low temperature side insulator substrate 29 High temperature side insulator substrate 31, 32, 33, 34 End 41 Thermoelectric conversion module 51 Infrared sensor 54 PCB 55 Etching stop layer 56 n-type thermoelectric conversion material layer 57n + Ohmic contact layer 58 Insulator Layer 59 p-type thermoelectric conversion material layer 61 n-side ohmic contact electrode 62 p-side ohmic contact electrode 63 Heat absorption pad 64 Absorber 65 Protective film 66 Recess I arrow.

Claims

1. The base material includes iron, vanadium, and aluminum, It also contains oxygen, Bi as the primary ion ３ ＋＋ and a time-of-flight secondary ion mass spectrometry (TSMS) measurement performed by sputtering a region 100 nm from the surface using argon as sputter ions, wherein the signal intensity of a vanadium-oxygen bond, which is a positive ion having a mass number of 67, is 5.2% or more of the signal intensity of an aluminum ion, which is a positive ion having a mass number of 27.

2. The base material includes iron, vanadium, and aluminum, It also contains oxygen, Bi as the primary ion ３ ＋＋ a thermoelectric conversion material, wherein, when time-of-flight secondary ion mass spectrometry is performed by sputtering a region 100 nm from the surface using argon as sputter ions, the signal intensity of an aluminum-oxygen bond, which is a negative ion having a mass number of 43, is 26.1% or less of the signal intensity of oxygen, which is a negative ion having a mass number of 16.

3. The base material includes iron, vanadium, and aluminum, It also contains oxygen, Bi as the primary ion ３ ＋＋ and a time-of-flight secondary ion mass spectrometry (TSMS) measurement performed by sputtering a region 100 nm from the surface using argon as sputter ions, in which the signal intensity of an oxygen-iron-aluminum bond, which is a positive ion with a mass number of 123, is 0.67% or more of the signal intensity of aluminum, which is a positive ion with a mass number of 27.

4. The thermoelectric conversion material according to claim 1 , further comprising tungsten.

5. The thermoelectric conversion material according to claim 1 , wherein the base material includes an amorphous phase.

6. further comprising a silicon substrate; The thermoelectric conversion material according to claim 1 , wherein the base material is disposed on the silicon substrate.

7. Thermoelectric Materials Department, a first electrode disposed in contact with the thermoelectric conversion material portion; a second electrode in contact with the thermoelectric conversion material portion and disposed apart from the first electrode, A thermoelectric conversion element, wherein the material constituting the thermoelectric conversion material section is the thermoelectric conversion material according to any one of claims 1 to 3, and the conductivity type of the material is p-type or n-type.

8. A thermoelectric conversion module comprising the thermoelectric conversion element according to claim 7 .

9. an absorber that absorbs light energy; a thermoelectric conversion material portion connected to the absorber, 4. An optical sensor comprising the thermoelectric conversion material according to claim 1, wherein the material constituting the thermoelectric conversion material section has a conductivity type of p-type or n-type.

10. providing a silicon substrate; preparing raw materials for iron, vanadium, and aluminum; The oxygen concentration in the deposition chamber was set to 1.0 x 10 －１ Pa or more 1.0×10 －３ and forming a film on the silicon substrate by vapor deposition using the raw material while maintaining the silicon substrate at a temperature of 300°C or higher and 1000°C or lower.

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