Thermoelectric alloy thin film materials, their preparation methods and applications

Abstract

This invention provides a thermoelectric alloy thin film material formed from a material having the following chemical formula: CrPt x Where 2.0≤x≤2.8. This invention also provides a method for preparing the thermoelectric alloy thin film material of this invention, comprising the following steps: (1) periodically depositing Cr and Pt films sequentially on a substrate using magnetron sputtering; (2) annealing the structure formed in step (1) under vacuum. This invention also provides the use of the thermoelectric alloy thin film material of this invention in thermoelectric conversion devices. This invention also provides a thermoelectric conversion device. The thermoelectric alloy thin film material of this invention has a large anomalous Nernst coefficient and still has a large voltage signal output under zero field.

Description

Technical Field

[0001] This invention belongs to the field of materials. Specifically, this invention relates to thermoelectric alloy thin film materials, their preparation methods, and applications. Background Technology

[0002] Low-carbon and environmentally friendly development is a crucial strategy for China, and waste heat recovery technology is an important part of it. Thermoelectric materials, which enable the conversion of heat energy into electrical energy, have attracted considerable attention. Traditional thermoelectric materials utilize the Seebeck effect, which states that when heat flows through a material and creates a temperature difference, a voltage is generated in the direction of the temperature gradient. In recent years, a thermoelectric conversion device utilizing the anomalous Nernst effect has emerged. When heat flows through a magnetic material and creates a temperature difference, a voltage is generated in the direction perpendicular to both the magnetic moment and the temperature gradient.

[0003] Compared to the relatively complex three-dimensional structure of thermoelectric devices based on the Seebeck effect, devices based on the anomalous Nernst effect have a simpler structure and can achieve larger area devices. However, the anomalous Nernst effect of traditional magnetic materials is still very small and far from meeting application requirements; for example, the anomalous Nernst coefficient of Fe at room temperature is only 0.3 μV / K.

[0004] Patent application CN116200831A discloses a type of cobalt-based all-Hessler alloy material, its preparation method, and polycrystalline devices. The patent application includes Co2MnGa... 0.95 Si 0.05 It is a material with the largest anomalous Nernst, with a maximum anomalous Nernst coefficient of 7.46 μV / K. However, the anomalous Nernst signal of this material is close to 0 under zero field, making it unable to operate under zero field.

[0005] Therefore, there is an urgent need for a material with a large anomalous Nernst coefficient and a large voltage signal output even under zero field conditions. Summary of the Invention

[0006] The anomalous Nernst effect of traditional ferromagnetic materials is very small, which severely limits their application in thermoelectric materials. Moreover, among the existing materials with relatively large anomalous Nernst, such as CoMnGa, the anomalous Nernst coefficient is close to 0 under zero field, which is not conducive to practical applications.

[0007] Therefore, the object of the present invention is to provide a thermoelectric alloy thin film material that has a large anomalous Nernst coefficient and still has a large voltage signal output under zero field.

[0008] Another object of the present invention is to provide a method for preparing the thermoelectric alloy thin film material of the present invention.

[0009] Another object of the present invention is to provide the use of the thermoelectric alloy thin film material of the present invention in thermoelectric conversion devices.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0011] In a first aspect, the present invention provides a thermoelectric alloy thin film material formed from a material having the following chemical formula: CrPt x , where 2.0≤x≤2.8.

[0012] Preferably, in the thermoelectric alloy thin film material of the present invention, the thermoelectric alloy thin film material has an anomalous Nernst coefficient greater than or equal to 4.6 μV / K at 300 K.

[0013] In a second aspect, the present invention provides a method for preparing the thermoelectric alloy thin film material of the present invention, comprising the following steps:

[0014] (1) Cr and Pt films are periodically deposited sequentially on the substrate using magnetron sputtering.

[0015] (2) Anneal the structure formed in step (1) under vacuum.

[0016] Preferably, in the method described in this invention, the thickness of the Cr film is 0.44nm-0.55nm, and the thickness of the Pt film is 1.50nm-1.65nm.

[0017] Preferably, in the method described in this invention, the annealing is carried out under the following conditions: the annealing temperature is 600-800℃, preferably 650-800℃; and the annealing time is greater than 2 hours, preferably 4-8 hours.

[0018] In this invention, there are no special requirements for the substrate in step (1), and some substrates known in the art, such as Si wafers, MgO, glass, and SrTiO3, can be used.

[0019] In this invention, there are no special requirements for the vacuum conditions in step (2), which can be better than 5 × 10⁻⁶. -5 Annealing was performed under vacuum at Pa.

[0020] Thirdly, the present invention provides the use of the thermoelectric alloy thin film material of the present invention in thermoelectric conversion devices.

[0021] Fourthly, the present invention provides a thermoelectric conversion device, which comprises, from bottom to top, a substrate, a thermoelectric alloy thin film material, and a protective layer; wherein the thermoelectric alloy thin film material is formed of a material having the following chemical formula: CrPt x , where 2.0≤x≤2.8.

[0022] Preferably, in the thermoelectric conversion device of the present invention, the thermoelectric alloy thin film material has an anomalous Nernst coefficient of greater than or equal to 4.6 μV / K at 300 K.

[0023] In this invention, the substrate is a chemically stable material with a smooth surface. Preferably, in the thermoelectric conversion device of this invention, the substrate is selected from one or more of silicon, glass, MgO, and SrTiO3.

[0024] Preferably, in the thermoelectric conversion device of the present invention, the protective layer is formed of SiO2 and / or Ta. The thickness of the protective layer is about 2-10 nm.

[0025] The present invention has the following beneficial effects:

[0026] The thermoelectric alloy thin film material of the present invention exhibits a large anomalous Nernst effect, reaching 8.8 μV / K. Furthermore, the thermoelectric alloy thin film material of the present invention possesses excellent vertical anisotropy, with the easy axis almost completely perpendicular to the film surface, enabling a large voltage signal output even without an external field when an in-plane temperature gradient is applied. Attached Figure Description

[0027] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0028] Figure 1 This is a schematic diagram of the structure of a thermoelectric conversion device according to a specific embodiment of the present invention;

[0029] Figure 2 These are the XRD patterns of the thermoelectric alloy thin film materials prepared in Examples 1-3 and Comparative Examples 1-2 of this invention;

[0030] Figure 3 These are anomalous Hall resistance measurement diagrams of the thermoelectric alloy thin film materials prepared in Examples 1-3 and Comparative Examples 1-2 of this invention;

[0031] Figure 4 These are anomalous Nernst coefficient diagrams of the thermoelectric alloy thin film materials prepared in Examples 1-3 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] In this embodiment, the thermoelectric conversion device is fabricated in the following order from bottom to top: a thermally oxidized silicon substrate with a thickness of 0.5 mm; and a thermoelectric alloy thin film material CrPt.x The thickness is 35nm; the silicon dioxide protective layer is 5nm thick.

[0035] The preparation method of the thermoelectric alloy thin film material with a large anomalous Nernst effect in this embodiment is as follows:

[0036] The magnetron sputtering method is employed, where the background vacuum is better than 5 × 10⁻⁶. -5 Using high-purity Ar gas as the sputtering gas at a pressure of 0.35 Pa, multi-period [Cr (0.47 nm)\Pt (1.62 nm)] was deposited on an oxide-coated Si wafer. n Where n is the number of periods, and in this embodiment, n is 15. Cr (0.47nm) indicates that the thickness of the Cr film in a single period is 0.47nm, and Pt (1.62nm) indicates that the thickness of the Pt film in a single period is 1.62nm. After deposition, the thin film material is subjected to vacuum at 800 degrees Celsius (better than 5×10⁻⁶). - 5 The final sample was obtained by annealing at 800 degrees Celsius for 5 hours under no external field conditions (Pa). The final chemical formula of the obtained thermoelectric alloy thin film material was calculated to be CrPt. 2.70 .

[0037] Phase analysis of the thermoelectric alloy thin film material prepared in this embodiment was performed using a Rigaku X-ray diffractometer (XRD). Figure 2 As shown, the film after annealing is confirmed to have a CrPt3 structure and is preferentially oriented in the (111) plane.

[0038] Using Quantum Design's comprehensive property measurement system, the anomalous Hall resistance of thermoelectric alloy thin film materials at 300K as a function of out-of-plane magnetic field was measured. Figure 3 As shown. Figure 3 This demonstrates that the thermoelectric alloy thin film material exhibits excellent perpendicular anisotropy. Furthermore, using a Kethely 2182A nanovoltmeter and a 2611B DC meter, the anomalous Nernst thermoelectric potential coefficient of the thin film at 300 K, as a function of the out-of-plane magnetic field, was measured as follows: Figure 4 As shown. Figure 4 The anomalous Nernst coefficient of the thermoelectric alloy thin film material prepared in this embodiment is shown to be 4.6 μV / K. Furthermore, Figure 4 This demonstrates that even when the external magnetic field is zero, almost the entire voltage signal can still be output. Specifically, Figure 4 The results show that when the external magnetic field H = 0, the anomalous Nernst coefficient is still approximately 4.4V (thin film magnetic moment in the +Z direction) or -4.4V (thin film magnetic moment in the -Z direction), which is very close to the total signal of 4.6V.

[0039] Example 2

[0040] In this embodiment, the thermoelectric conversion device is fabricated in the following order from bottom to top: a thermally oxidized silicon substrate with a thickness of 0.5 mm; and a thermoelectric alloy thin film material CrPt. x The thickness is 35nm; the silicon dioxide protective layer is 5nm thick.

[0041] The preparation method of the thermoelectric alloy thin film material with a large anomalous Nernst effect in this embodiment is as follows:

[0042] The magnetron sputtering method is employed, where the background vacuum is better than 5 × 10⁻⁶. -5 Using high-purity Ar gas as the sputtering gas at a sputtering pressure of 0.35 Pa, multi-period [Cr (0.47 nm)\Pt (1.53 nm)] was deposited on an oxide-coated Si wafer. n Where n is the number of periods, and in this embodiment, n is 15. Cr (0.47nm) indicates that the thickness of the Cr film in a single period is 0.47nm, and Pt (1.53nm) indicates that the thickness of the Pt film in a single period is 1.53nm. After deposition, the thin film material is subjected to vacuum at 800 degrees Celsius (better than 5 × 10⁻⁶). - 5 The final sample was obtained by annealing at 800 degrees Celsius for 5 hours under no external field conditions (Pa). The final chemical formula of the obtained thermoelectric alloy thin film material was calculated to be CrPt. 2.53 .

[0043] Phase analysis of the thermoelectric alloy thin film material prepared in this embodiment was performed using a Rigaku X-ray diffractometer (XRD). Figure 2 As shown, the film after annealing is confirmed to have a CrPt3 structure and is preferentially oriented in the (111) plane.

[0044] Using Quantum Design's comprehensive property measurement system, the anomalous Hall resistance of thermoelectric alloy thin film materials at 300K as a function of out-of-plane magnetic field was measured. Figure 3 As shown. Figure 3 This demonstrates that the thin film exhibits excellent vertical anisotropy. Furthermore, using a Kethely 2182A nanovoltmeter and a 2611B DC meter, the anomalous Nernst thermoelectric potential coefficient of the thin film at 300 K, as a function of the out-of-plane magnetic field, was measured as follows: Figure 4 As shown. Figure 4 The anomalous Nernst coefficient of the thermoelectric alloy thin film material prepared in this embodiment is shown to be 8.8 μV / K. Furthermore, Figure 4 This demonstrates that even when the external magnetic field is zero, almost the entire voltage signal can still be output. Specifically, Figure 4 The results show that when the external magnetic field H = 0, the anomalous Nernst coefficient is still about 8.6V (thin film magnetic moment in the +Z direction) or -8.6V (thin film magnetic moment in the -Z direction), which is very close to the total signal of 8.8V.

[0045] Example 3

[0046] In this embodiment, the thermoelectric conversion device is fabricated in the following order from bottom to top: a thermally oxidized silicon substrate with a thickness of 0.5 mm; and a thermoelectric alloy thin film material CrPt. x The thickness is 35nm; the silicon dioxide protective layer is 5nm thick.

[0047] The preparation method of the thermoelectric alloy thin film material with a large anomalous Nernst effect in this embodiment is as follows:

[0048] The magnetron sputtering method is employed, where the background vacuum is better than 5 × 10⁻⁶. -5 Using high-purity Ar gas as the sputtering gas at a pressure of 0.35 Pa, multi-period [Cr (0.53 nm)\Pt (1.59 nm)] was deposited on an oxide-coated Si wafer. n Where n is the number of periods, and in this embodiment, n is 15. Cr (0.53nm) indicates that the thickness of the Cr film in a single period is 0.53nm, and Pt (1.59nm) indicates that the thickness of the Pt film in a single period is 1.59nm. After deposition, the thin film material is subjected to high vacuum (better than 5×10⁻⁶) at 800 degrees Celsius. -5 The final sample was obtained by annealing at 800 degrees Celsius for 5 hours under no external field conditions (Pa). The final chemical formula of the obtained thermoelectric alloy thin film material was calculated to be CrPt. 2.37 .

[0049] Phase analysis of the thermoelectric alloy thin film material prepared in this embodiment was performed using a Rigaku X-ray diffractometer (XRD). Figure 2 As shown, the film after annealing is confirmed to have a CrPt3 structure and is preferentially oriented in the (111) plane.

[0050] Using Quantum Design's comprehensive property measurement system, the anomalous Hall resistance of thermoelectric alloy thin film materials at 300K as a function of out-of-plane magnetic field was measured. Figure 3 As shown. Figure 3 This demonstrates that the thermoelectric alloy thin film material exhibits excellent perpendicular anisotropy. Furthermore, using a Kethely 2182A nanovoltmeter and a 2611B DC meter, the anomalous Nernst thermoelectric potential coefficient of the thin film at 300 K, as a function of the out-of-plane magnetic field, was measured as follows: Figure 4 As shown. Figure 4 The anomalous Nernst coefficient of the thermoelectric alloy thin film material prepared in this embodiment is shown to be 4.7 μV / K. Furthermore, Figure 4 This demonstrates that even when the external magnetic field is zero, almost the entire voltage signal can still be output. Specifically, Figure 4The results show that when the external magnetic field H = 0, the anomalous Nernst coefficient is still about 4.3V (thin film magnetic moment in the +Z direction) or -4.3V (thin film magnetic moment in the -Z direction), which is very close to the total signal of 4.7V.

[0051] Comparative Example 1

[0052] In this embodiment, the thermoelectric conversion device is fabricated in the following order from bottom to top: a thermally oxidized silicon substrate with a thickness of 0.5 mm; and a thermoelectric alloy thin film material CrPt. x The thickness is 35nm; the silicon dioxide protective layer is 5nm thick.

[0053] The preparation method of the thermoelectric alloy thin film material with a large anomalous Nernst effect in this embodiment is as follows:

[0054] The magnetron sputtering method is employed, where the background vacuum is better than 5 × 10⁻⁶. -5 Using high-purity Ar gas as the sputtering gas at a pressure of 0.35 Pa, multi-period [Cr (0.48 nm)\Pt (1.56 nm)] was deposited on an oxide-coated Si wafer. n Where n is the number of periods, and in this embodiment, n is 16. Cr (0.48nm) indicates that the thickness of the Cr film in a single period is 0.48nm, and Pt (1.56nm) indicates that the thickness of the Pt film in a single period is 1.56nm. After deposition, the thin film material is subjected to high vacuum (better than 5×10⁻⁶) at 800 degrees Celsius. -5 The final sample was obtained by annealing at 800 degrees Celsius for 5 hours under no external field conditions (Pa). The final chemical formula of the obtained thermoelectric alloy thin film material was calculated to be CrPt. 1.78 .

[0055] Phase analysis of the thermoelectric alloy thin film material prepared in this embodiment was performed using a Rigaku X-ray diffractometer (XRD). Figure 2 As shown, the film after annealing is confirmed to have a CrPt3 structure and is preferentially oriented in the (111) plane.

[0056] Using Quantum Design's comprehensive property measurement system, the anomalous Hall resistance of thermoelectric alloy thin film materials at 300K as a function of out-of-plane magnetic field was measured. Figure 3 As shown. Figure 3 This demonstrates that the thermoelectric alloy thin film material exhibits excellent perpendicular anisotropy. Furthermore, using a Kethely 2182A nanovoltmeter and a 2611B DC meter, the anomalous Nernst thermoelectric potential coefficient of the thin film at 300 K, as a function of the out-of-plane magnetic field, was measured as follows: Figure 4 As shown. Figure 4 The anomalous Nernst coefficient of the thermoelectric alloy thin film material prepared in this embodiment is shown to be 1.4 μV / K, which is much smaller than that of CrPt.2.70 4.4 μV / K.

[0057] Comparative Example 2

[0058] In this embodiment, the thermoelectric conversion device is fabricated in the following order from bottom to top: a thermally oxidized silicon substrate with a thickness of 0.5 mm; and a thermoelectric alloy thin film material CrPt. x The thickness is 35nm; the silicon dioxide protective layer is 5nm thick.

[0059] The preparation method of the thermoelectric alloy thin film material with a large anomalous Nernst effect in this embodiment is as follows:

[0060] The magnetron sputtering method is employed, where the background vacuum is better than 5 × 10⁻⁶. -5 Using high-purity Ar gas as the sputtering gas at a pressure of 0.35 Pa, multi-period [Cr (0.37 nm)\Pt (1.36 nm)] was deposited on an oxide-coated Si wafer. n Where n is the number of periods, and in this embodiment, n is 20. Cr (0.37nm) indicates that the thickness of the Cr film in a single period is 0.37nm, and Pt (1.36nm) indicates that the thickness of the Pt film in a single period is 1.36nm. After deposition, the thin film material is subjected to high vacuum (better than 5×10⁻⁶) at 800 degrees Celsius. -5 The final sample was obtained by annealing at 800 degrees Celsius for 5 hours under no external field conditions (Pa). The final chemical formula of the obtained thermoelectric alloy thin film material was calculated to be CrPt. 2.92 .

[0061] Phase analysis of the thermoelectric alloy thin film material prepared in this embodiment was performed using a Rigaku X-ray diffractometer (XRD). Figure 2 As shown, the film after annealing is confirmed to have a CrPt3 structure and is preferentially oriented in the (111) plane.

[0062] Using Quantum Design's comprehensive property measurement system, the anomalous Hall resistance of thermoelectric alloy thin film materials at 300K as a function of out-of-plane magnetic field was measured. Figure 3 As shown. Figure 3 This demonstrates that the thermoelectric alloy thin film material exhibits excellent perpendicular anisotropy. Furthermore, using a Kethely 2182A nanovoltmeter and a 2611B DC meter, the anomalous Nernst thermoelectric potential coefficient of the thin film at 300 K, as a function of the out-of-plane magnetic field, was measured as follows: Figure 4 As shown. Figure 4 The anomalous Nernst coefficient of the thermoelectric alloy thin film material prepared in this embodiment is shown to be 0.6 μV / K. When the external magnetic field H = 0, the anomalous Nernst coefficient is close to 0.

Claims

1. A thermoelectric alloy thin film material formed from a material having the following chemical formula: CrPt x Where 2.0 ≤ x ≤ 2.8; The thermoelectric alloy thin film material is prepared by a method comprising the following steps: (1) Cr and Pt films are periodically deposited sequentially on the substrate using magnetron sputtering. (2) Anneal the structure formed in step (1) under vacuum; The thickness of the Cr film is 0.1 nm-3 nm, and the thickness of the Pt film is 0.2 nm-5 nm. The annealing is carried out under the following conditions: annealing temperature is 600-800℃, and annealing time is greater than 2 hours.

2. The thermoelectric alloy thin film material according to claim 1, wherein, The thermoelectric alloy thin film material has an anomalous Nernst coefficient greater than or equal to 4.6 μV / K at 300K.

3. Use of the thermoelectric alloy thin film material of claim 1 or 2 in thermoelectric conversion devices.

4. A thermoelectric conversion device, comprising, from bottom to top, a substrate, a thermoelectric alloy thin film material, and a protective layer; wherein the thermoelectric alloy thin film material is formed of a material having the following chemical formula: CrPt x Where 2.0 ≤ x ≤ 2.8; The thermoelectric alloy thin film material is prepared by a method comprising the following steps: (1) Cr and Pt films are periodically deposited sequentially on the substrate using magnetron sputtering. (2) Anneal the structure formed in step (1) under vacuum; The thickness of the Cr film is 0.1 nm-3 nm, and the thickness of the Pt film is 0.2 nm-5 nm. The annealing is carried out under the following conditions: annealing temperature is 600-800℃, and annealing time is greater than 2 hours.

5. The thermoelectric conversion device according to claim 4, wherein, The thermoelectric alloy thin film material has an anomalous Nernst coefficient greater than or equal to 4.6 μV / K at 300K.

6. The thermoelectric conversion device according to claim 4, wherein, The substrate is selected from one or more of silicon, glass, MgO and SrTiO3.

7. The thermoelectric conversion device according to claim 4, wherein, The protective layer is formed of SiO2 and / or Ta.

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