A flexible thermoelectric film material of Mg3SbBi and its preparation method

Abstract

The application provides a Mg3SbBi flexible thermoelectric film material and a preparation method thereof, and belongs to the technical field of thermoelectric materials. Single-walled carbon nanotubes which are intertwined with each other are used as a substrate, and flaky Mg3SbBi grains are attached to the single-walled carbon nanotubes to grow, so as to form a two-dimensional network structure; the special structure can provide a conductive channel and improve the carrier mobility, so that the thermoelectric film material has high thermoelectric performance; in addition, the network structure formed by the single-walled carbon nanotubes and the flaky Mg3SbBi grains can effectively buffer stress and strain, so as to endow the material with good deformability.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials technology, and in particular to a Mg3SbBi flexible thermoelectric film material and its preparation method. Background Technology

[0002] In recent years, the miniaturization and integration of electronic devices have strongly promoted the rapid development of wearable electronic devices and implantable electronic devices for medical use. Batteries, as a traditional power source, have inconveniences such as the need for regular replacement and maintenance, while thermoelectric energy conversion technology can provide a green, stable, and sustainable power source, which has profound significance for the development of flexible electronics.

[0003] Thermoelectric energy conversion technology relies on thermoelectric materials / devices for its applications, enabling the direct conversion between thermal and electrical energy. It shows promising prospects in thermoelectric power generation and refrigeration. The performance of thermoelectric materials is typically measured by the dimensionless thermoelectric figure of merit zT, where z represents the comprehensive thermal and electrical properties of the thermoelectric material, and T represents the absolute temperature of the environment in which the material is used. zT = S 2 σT / κ, where S is the Seebeck coefficient of the material, σ is the electrical conductivity, and κ is the thermal conductivity of the material. 2 σ is the power factor.

[0004] Thermoelectric materials have developed rapidly in recent years, with some materials achieving a thermoelectric figure of merit (zT) of 2, demonstrating excellent application potential. However, traditional inorganic thermoelectric materials are inherently brittle and cannot meet the requirements for close contact with heat source surfaces with varying curvatures, resulting in relatively high heat loss between the heat source and the thermoelectric material / device. Flexible thermoelectric materials possess excellent deformability, allowing them to conform well to various complex heat source surfaces, such as the human body, providing not only comfort but also improved power generation efficiency. However, for practical applications, flexible thermoelectric materials still face some challenges, such as poor deformability and the need to improve their thermoelectric performance. Summary of the Invention

[0005] The purpose of this invention is to provide a Mg3SbBi flexible thermoelectric film material and its preparation method. The Mg3SbBi flexible thermoelectric film material provided by this invention not only has good thermoelectric properties, but also exhibits excellent deformability, which is conducive to promoting the application of Mg3SbBi thermoelectric materials in the field of flexible electronics.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a Mg3SbBi flexible thermoelectric film material, comprising intertwined single-walled carbon nanotubes and Mg3SbBi grains attached to the single-walled carbon nanotubes, wherein the single-walled carbon nanotubes and Mg3SbBi grains form a two-dimensional network structure; the Mg3SbBi grains are in the form of sheets.

[0008] Preferably, the planar size of the Mg3SbBi grains is 200–500 nm.

[0009] Preferably, the diameter of the single-walled carbon nanotube is 20-100 nm and the length is in the micrometer range.

[0010] This invention provides a method for preparing the Mg3SbBi flexible thermoelectric film material described above, comprising the following steps:

[0011] A dispersion of single-walled carbon nanotubes was coated onto a substrate and dried to obtain a substrate with attached carbon nanotubes.

[0012] Using Mg3Sb2 alloy target and Mg3Bi2 alloy target as sputtering targets, magnetron sputtering is performed on the surface of the substrate with attached carbon nanotubes to form Mg3SbBi grains on the single-walled carbon nanotubes, thereby obtaining the Mg3SbBi flexible thermoelectric film material.

[0013] Preferably, the conditions for magnetron sputtering include: substrate temperature of 400–600°C, target-substrate distance of 50–90 mm, sputtering power of 50–100 W, and sputtering time of 30–60 min.

[0014] Preferably, the Ar gas pressure during magnetron sputtering is 0.5 to 2 Pa.

[0015] Preferably, the rotational speed of the sample stage during magnetron sputtering is 10–30 r / min.

[0016] Preferably, before the magnetron sputtering, the substrate surface with attached carbon nanotubes is pre-sputtered for 10 to 30 minutes.

[0017] Preferably, the dispersion of the single-walled carbon nanotubes is obtained by dispersing the single-walled carbon nanotubes in ethylene glycol.

[0018] Preferably, the preparation of the Mg3Sb2 alloy target includes: mixing metallic Mg and Sb in a molar ratio of Mg:Sb = 3:2, and sequentially performing ball milling and hot pressing, with a hot pressing temperature of 780-800℃ and a hot pressing time of 5-30 min, to obtain the Mg3Sb2 alloy target; the preparation of the Mg3Bi2 alloy target includes: mixing metallic Mg and Bi in a molar ratio of Mg:Bi = 3:2, and sequentially performing ball milling and hot pressing, with a hot pressing temperature of 720-780℃ and a hot pressing time of 5-30 min, to obtain the Mg3Bi2 alloy target.

[0019] This invention provides a flexible thermoelectric film material of Mg3SbBi, which uses intertwined single-walled carbon nanotubes as a substrate, and grows sheet-like Mg3SbBi grains attached to the single-walled carbon nanotubes to form a two-dimensional network structure. This special structure can provide conductive channels and improve carrier mobility, thereby giving the thermoelectric film material high thermoelectric performance. In addition, the network structure formed by single-walled carbon nanotubes and sheet-like Mg3SbBi grains can effectively buffer stress and strain, thereby giving the material good deformability.

[0020] This discovery provides a method for preparing the Mg3SbBi flexible thermoelectric film material described above. The invention uses single-walled carbon nanotubes as a substrate and employs magnetron sputtering to nucleate and grow Mg3SbBi grains on the surface of the carbon nanotubes, forming a two-dimensional network structure. This unique network structure endows the thermoelectric film material with both excellent thermoelectric properties and superior deformability.

[0021] The process for preparing Mg3SbBi flexible thermoelectric film material according to this invention is simple to operate, low in cost, and easy to industrialize.

[0022] Furthermore, the Mg3Sb2 and Mg3Bi2 alloy targets used in this invention are prepared by ball milling and hot pressing, which are not prone to cracking during magnetron sputtering, and the deposited film has a very uniform composition. Attached Figure Description

[0023] Figure 1 XRD images of the Mg3SbBi flexible thermoelectric film material prepared in Example 1;

[0024] Figure 2 SEM image of the single-walled carbon nanotubes used in the Mg3SbBi flexible thermoelectric film material prepared in Example 1;

[0025] Figure 3 SEM image of the Mg3SbBi flexible thermoelectric film prepared in Example 1;

[0026] Figure 4The Seebeck coefficient curve of the Mg3SbBi flexible thermoelectric film material prepared in Example 1 as a function of temperature is shown.

[0027] Figure 5 The electrical conductivity of the Mg3SbBi flexible thermoelectric film material prepared in Example 1 varies with temperature.

[0028] Figure 6 The Seebeck coefficient curve of the Mg3SbBi flexible thermoelectric film material prepared in Example 2 is shown as a function of temperature.

[0029] Figure 7 The electrical conductivity of the Mg3SbBi flexible thermoelectric film material prepared in Example 2 is shown as a function of temperature.

[0030] Figure 8 The Seebeck coefficient curve of the Mg3SbBi flexible thermoelectric film material prepared in Example 3 varies with temperature.

[0031] Figure 9 The electrical conductivity of the Mg3SbBi flexible thermoelectric film material prepared in Example 3 is shown as a function of temperature.

[0032] Figure 10 The curve showing the change in the conductivity ratio of the Mg3SbBi flexible thermoelectric film material prepared in Example 3 as a function of the number of bends.

[0033] Figure 11 The Seebeck coefficient of the Mg3SbBi thermoelectric film material prepared for Comparative Example 1 as a function of temperature;

[0034] Figure 12 The electrical conductivity of the Mg3SbBi thermoelectric film material prepared for Comparative Example 1 varies with temperature. Detailed Implementation

[0035] This invention provides a Mg3SbBi flexible thermoelectric film material, comprising intertwined single-walled carbon nanotubes and Mg3SbBi grains attached to the single-walled carbon nanotubes, wherein the single-walled carbon nanotubes and Mg3SbBi grains form a two-dimensional network structure; the Mg3SbBi grains are in the form of sheets.

[0036] In this invention, the planar size of the Mg3SbBi grains is preferably 200–500 nm. In this invention, Mg3SbBi is a solid solution of Mg3Sb2 and Mg3Bi2. The use of Mg3SbBi in this invention can effectively improve the band structure and electrical properties of the material.

[0037] In this invention, the diameter of the single-walled carbon nanotube is preferably 20–100 nm, and the length is preferably in the micrometer range. Compared with multi-walled carbon nanotubes, single-walled carbon nanotubes have fewer defects and better mechanical and electrical properties.

[0038] This invention uses intertwined single-walled carbon nanotubes as a substrate, with sheet-like Mg3SbBi grains attached to the single-walled carbon nanotubes and grown to form a two-dimensional network structure. This special structure can provide conductive channels and improve carrier mobility, thereby giving the thermoelectric film material high thermoelectric performance. In addition, the network structure formed by single-walled carbon nanotubes and sheet-like Mg3SbBi grains can effectively buffer stress and strain, thus endowing the material with good deformability.

[0039] This invention provides a method for preparing the Mg3SbBi flexible thermoelectric film material described above, comprising the following steps:

[0040] A dispersion of single-walled carbon nanotubes was coated onto a substrate and dried to obtain a substrate with attached carbon nanotubes.

[0041] Using Mg3Sb2 alloy target and Mg3Bi2 alloy target as sputtering targets, magnetron sputtering is performed on the surface of the substrate with attached carbon nanotubes to form Mg3SbBi grains on the single-walled carbon nanotubes, thereby obtaining the Mg3SbBi flexible thermoelectric film material.

[0042] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0043] In this invention, a dispersion of single-walled carbon nanotubes is coated onto a substrate, and after drying, a substrate with attached carbon nanotubes is obtained.

[0044] In this invention, the dispersion of single-walled carbon nanotubes is preferably obtained by dispersing single-walled carbon nanotubes in ethylene glycol. In this invention, the diameter of the single-walled carbon nanotubes is preferably 20–100 nm, and the length is preferably in the micrometer range. This invention does not have special requirements for the amount of ethylene glycol used, as long as it is sufficient to disperse the single-walled carbon nanotubes uniformly. In this invention, the dispersion is preferably ultrasonic dispersion, and the ultrasonic dispersion time is preferably 30–60 min. In this invention, before dispersing the single-walled carbon nanotubes in ethylene glycol, it is preferable to sequentially place the single-walled carbon nanotubes in dilute hydrochloric acid and ethanol for ultrasonic cleaning for 15–30 min respectively to remove impurities from the single-walled carbon nanotubes. In this invention, the volume fraction of the dilute hydrochloric acid is preferably 5–15%.

[0045] In this invention, the substrate preferably comprises a glass sheet. Before coating the substrate, the substrate is preferably cleaned. The cleaning process preferably includes: ultrasonically cleaning the substrate sequentially in acetone, ethanol, and ultrapure water for 20–40 minutes each, followed by drying with nitrogen gas.

[0046] In this invention, the coating method is preferably spraying. This invention does not have special requirements for the spraying conditions; it is sufficient to ensure that the carbon nanotube dispersion is sprayed evenly.

[0047] In this invention, the drying temperature is preferably 60–100°C, and the drying time is preferably 5–8 hours. In this invention, the thickness of the single-walled carbon nanotube layer formed after coating is preferably 50–200 μm, more preferably 60–180 μm, and even more preferably 80–150 μm.

[0048] After obtaining the substrate with attached carbon nanotubes, the present invention uses Mg3Sb2 alloy target and Mg3Bi2 alloy target as sputtering targets to perform magnetron sputtering on the surface of the substrate with attached carbon nanotubes, forming Mg3SbBi grains on the single-walled carbon nanotubes, and obtaining the Mg3SbBi flexible thermoelectric film material.

[0049] In this invention, the preparation of the Mg3Sb2 alloy target preferably includes: mixing metallic Mg and Sb in a molar ratio of Mg:Sb = 3:2, and then performing ball milling and hot pressing in sequence. The hot pressing temperature is 780-800℃ and the hot pressing time is 5-30 min to obtain the Mg3Sb2 alloy target.

[0050] The preferred preparation method for the Mg3Bi2 alloy target includes: mixing metallic Mg and Bi in a molar ratio of Mg:Bi = 3:2, followed by ball milling and hot pressing. The hot pressing temperature is 720–780°C, and the hot pressing time is 5–30 min, to obtain the Mg3Bi2 alloy target. The Mg3Sb2 and Mg3Bi2 alloy targets used in this invention, prepared by ball milling and hot pressing, are less prone to cracking during magnetron sputtering, and the deposited film has a very uniform composition.

[0051] In this invention, the magnetron sputtering is preferably radio frequency sputtering. The preferred conditions for magnetron sputtering include: a substrate temperature of 400–600°C, a target-substrate distance of 50–90 mm, a sputtering power of 50–100 W, and a sputtering time of 30–60 min. More preferably, the substrate temperature is 450–550°C, the target-substrate distance is 60–80 mm, the sputtering power is 60–80 W, and the sputtering time is 40–50 min.

[0052] In this invention, the Ar gas pressure for magnetron sputtering is preferably 0.5–2 Pa, more preferably 1.0–1.5 Pa. The rotational speed of the sample stage during magnetron sputtering is 10–30 r / min, more preferably 15–25 r / min.

[0053] Before the magnetron sputtering, the present invention preferably further includes pre-sputtering the substrate surface to which the carbon nanotubes are attached, and the pre-sputtering time is preferably 10 to 30 minutes.

[0054] In this invention, the entire magnetic control process is preferably as follows:

[0055] The Mg3Sb2 and Mg3Bi2 alloy targets were fixed in the target positions connected to the RF power supply within the chamber, and the target-substrate distance was adjusted. Simultaneously, the substrate with attached single-walled carbon nanotubes was mounted on the sample stage. The mechanical pump and molecular pump were then sequentially activated to evacuate the chamber until a vacuum range of 4–8 × 10⁻⁶ was achieved. -4 Pa; turn on the heating power supply and heat the substrate to the sputtering temperature; turn on the sample stage rotation button and adjust the sample stage speed; introduce Ar and adjust the gas pressure to 0.5-2 Pa; turn on the baffle and RF power supply in sequence, and pre-sputter for 10-30 min; adjust the RF power supply power to 50-100 W, turn off the baffle, and start sputtering for 30-60 min; turn off the RF power supply and heating power supply; allow it to cool naturally to room temperature to obtain the Mg3SbBi flexible film material.

[0056] This invention uses single-walled carbon nanotubes as a substrate and employs magnetron sputtering to nucleate and grow Mg3SbBi grains on the surface of the carbon nanotubes, forming a two-dimensional network structure. This unique network structure endows the thermoelectric film material with both excellent thermoelectric properties and superior deformability.

[0057] The following detailed description, in conjunction with embodiments, illustrates a Mg3SbBi flexible thermoelectric film material and its preparation method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] (1) Mix Mg and Sb metals in a molar ratio of Mg:Sb = 3:2, and then ball mill and hot press them in sequence. The hot pressing temperature is 800℃ and the hot pressing time is 5min to obtain Mg3Sb2 alloy target.

[0060] Metallic Mg and Bi were mixed in a molar ratio of Mg:Bi = 3:2, and then ball-milled and hot-pressed sequentially. The hot-pressing temperature was 750℃ and the hot-pressing time was 5min to obtain a Mg3Bi2 alloy target.

[0061] (2) Place the glass slide in acetone, ethanol and ultrapure water in sequence and ultrasonically clean for 20 minutes each, then dry it with nitrogen gas.

[0062] (3) Single-walled carbon nanotubes (SWCNTs) were placed in dilute hydrochloric acid and ethanol respectively for ultrasonic cleaning for 20 min to remove impurities from SWCNTs;

[0063] (4) Place the cleaned SWCNTs in an ethylene glycol solution and sonicate for 30 minutes to form a uniformly dispersed solution.

[0064] (5) Use a spray gun to uniformly spray the ethylene glycol solution containing SWCNTs onto a glass slide. The solution volume is 5 mL. Then place the glass slide on a heating table and dry it at 60°C for 5 h. After drying, the thickness of the SWCNTs film formed is 50 μm.

[0065] (6) Fix the Mg3Sb2 and Mg3Bi2 alloy targets in the cavity and connect them to the target position of the RF power supply. The target-to-substrate distance is 60mm. At the same time, install the glass substrate with SWCNTs attached on the sample stage.

[0066] (7) Turn on the mechanical pump and molecular pump in sequence to evacuate the chamber until the vacuum range reaches 8×10⁻⁶. -4 Pa;

[0067] (8) Turn on the heating power supply and heat the substrate to 400°C;

[0068] (9) Turn on the sample stage rotation button and adjust the sample stage speed to 10 r / min;

[0069] (10) Introduce Ar and adjust the gas pressure to 0.5 Pa;

[0070] (11) Turn on the baffle and RF power supply in sequence, and pre-sputter for 10 minutes;

[0071] (12) Adjust the RF power supply to 50W, close the baffle, start sputtering, and the sputtering time is 60min;

[0072] (13) Turn off the radio frequency power supply and heating power supply; allow it to cool naturally to room temperature to obtain the Mg3SbBi flexible film material. The composition and structure of the film are analyzed using an X-ray diffractometer, such as... Figure 1 As shown.

[0073] Depend on Figure 1 It can be seen that the film is a pure Mg3SbBi phase, and no obvious impurity peaks appear. The surface morphology of the single-walled carbon nanotubes used was observed using scanning electron microscopy (SEM), and the results are as follows. Figure 2 As shown, single-walled nanotubes intertwine to form a two-dimensional network structure, which provides support for the growth of Mg3SbBi. Figure 3 SEM images of the Mg3SbBi flexible thermoelectric film prepared in Example 1, by... Figure 3 It can be seen that the carbon nanotubes are covered with sheet-like Mg3SbBi grains with a planar size of 200-500 nm, and the carbon nanotubes are no longer visible. Figure 4 The Seebeck coefficient of the Mg3SbBi flexible thermoelectric film prepared in Example 1 is related to temperature. Figure 4As can be seen, the Seebeck coefficient is positive, indicating that the material exhibits p-type conductivity. The Seebeck coefficient first increases and then decreases, with the maximum Seebeck coefficient being 22 μV / K. Figure 5 The figure shows the relationship between the conductivity and temperature of the Mg3SbBi flexible film material in Example 1. It can be seen that the conductivity increases continuously with increasing temperature, reaching a maximum value of 4 × 10⁻⁶. 4 S / m.

[0074] Example 2

[0075] (1) Mix Mg and Sb metals in a molar ratio of Mg:Sb=3:2, and then ball mill and hot press them in sequence. The hot pressing temperature is 820℃ and the hot pressing time is 10min to obtain Mg3Sb2 alloy target.

[0076] Metallic Mg and Bi were mixed in a molar ratio of Mg:Bi = 3:2, and then ball-milled and hot-pressed sequentially. The hot-pressing temperature was 730℃ and the hot-pressing time was 10 min to obtain a Mg3Bi2 alloy target.

[0077] (2) Place the glass slide in acetone, ethanol and ultrapure water in sequence and ultrasonically clean for 30 minutes each, then dry it with nitrogen gas.

[0078] (3) Place the SWCNTs in dilute hydrochloric acid and ethanol in sequence and ultrasonically clean them for 25 min each to remove impurities from the SWCNTs;

[0079] (4) Place the cleaned SWCNTs in an ethylene glycol solution and sonicate for 40 minutes to form a uniformly dispersed solution.

[0080] (5) Ethylene glycol containing SWCNTs was easily and evenly sprayed onto a glass slide using a spray gun. The glass slide was then placed on a heating table and dried at 70°C for 5 hours. After drying, the thickness of the SWCNTs film formed was 80 μm.

[0081] (6) Fix the Mg3Sb2 and Mg3Bi2 alloy targets in the cavity and connect them to the target position of the RF power supply. The target-to-substrate distance is 70mm. At the same time, install the glass substrate with SWCNTs attached on the sample stage.

[0082] (7) Turn on the mechanical pump and molecular pump in sequence to evacuate the chamber until the vacuum range reaches 6×10⁻⁶. -4 Pa;

[0083] (8) Turn on the heating power supply and heat the substrate to 500°C;

[0084] (9) Turn on the sample stage rotation button and adjust the sample stage speed to 20 r / min;

[0085] (10) Introduce Ar and adjust the gas pressure to 1 Pa;

[0086] (11) Turn on the baffle and RF power supply in sequence, and pre-sputter for 20 minutes;

[0087] (12) Adjust the RF power supply to 80W, close the baffle, start sputtering, and the sputtering time is 50min;

[0088] (13) Turn off the radio frequency power supply and heating power supply; allow it to cool naturally to room temperature to obtain Mg3SbBi flexible film material.

[0089] XRD tests were performed on the Mg3SbBi flexible film material of Example 2, which showed that the film was a pure Mg3SbBi phase and no obvious impurity peaks appeared. The SEM results showed that it was similar to that of Example 1, except that the size of the sheet-like Mg3SbBi grains was slightly different, ranging from 250 to 500 nm. Figure 6 The Seebeck coefficient of the Mg3SbBi flexible thermoelectric film prepared in Example 2 is related to temperature. Figure 6 As can be seen, the Seebeck coefficient is positive, indicating that the material exhibits p-type conductivity. The Seebeck coefficient first increases and then decreases, with the maximum Seebeck coefficient being 32 μV / K. Figure 7 The figure shows the relationship between the conductivity and temperature of the Mg3SbBi flexible film material in Example 2. It can be seen that the conductivity increases continuously with increasing temperature, reaching a maximum value of 3.6 × 10⁻⁶. 4 S / m.

[0090] Example 3

[0091] (1) Mix Mg and Sb metals in a molar ratio of Mg:Sb = 3:2, and then ball mill and hot press them in sequence. The hot pressing temperature is 800℃ and the hot pressing time is 20min to obtain Mg3Sb2 alloy target.

[0092] Metallic Mg and Bi were mixed in a molar ratio of Mg:Bi = 3:2, and then ball-milled and hot-pressed sequentially. The hot-pressing temperature was 750℃ and the hot-pressing time was 20 min to obtain a Mg3Bi2 alloy target.

[0093] (2) Place the glass slide in acetone, ethanol and ultrapure water in sequence and ultrasonically clean for 40 min each, then dry it with nitrogen gas.

[0094] (3) Place the SWCNTs in dilute hydrochloric acid and ethanol in sequence and ultrasonically clean them for 30 min each to remove impurities from the SWCNTs;

[0095] (4) Place the cleaned SWCNTs in an ethylene glycol solution and sonicate for 60 minutes to form a uniformly dispersed solution.

[0096] (5) Ethylene glycol containing SWCNTs was easily and evenly sprayed onto a glass slide using a spray gun. The glass slide was then placed on a heating table and dried at 90°C for 6 hours. After drying, the thickness of the SWCNTs film formed was 100 μm.

[0097] (6) Fix the Mg3Sb2 and Mg3Bi2 alloy targets in the cavity and connect them to the target position of the RF power supply. The target-to-substrate distance is 80mm. At the same time, install the glass substrate with SWCNTs attached on the sample stage.

[0098] (7) Turn on the mechanical pump and molecular pump in sequence to evacuate the chamber until the vacuum range reaches 4×10⁻⁶. -4 Pa;

[0099] (8) Turn on the heating power supply and heat the substrate to 600°C;

[0100] (9) Turn on the sample stage rotation button and adjust the sample stage speed to 30 r / min;

[0101] (10) Introduce Ar and adjust the gas pressure to 2 Pa;

[0102] (11) Turn on the baffle and RF power supply in sequence, and pre-sputter for 30 minutes;

[0103] (12) Adjust the RF power supply to 100W, close the baffle, start sputtering, and the sputtering time is 30min;

[0104] (13) Turn off the radio frequency power supply and heating power supply; allow it to cool naturally to room temperature to obtain Mg3SbBi flexible film material.

[0105] XRD tests were performed on the Mg3SbBi flexible film material of Example 3, which showed that the film was a pure Mg3SbBi phase and no obvious impurity peaks appeared. SEM results showed that it was similar to that of Example 1, except that the size of the sheet-like Mg3SbBi grains was different, ranging from 300 to 500 nm.

[0106] Figure 8 The Seebeck coefficient of the Mg3SbBi flexible thermoelectric film prepared in Example 3 is related to temperature. Figure 8 As can be seen, the Seebeck coefficient is positive, indicating that the material has p-type semiconductor conductivity. The Seebeck coefficient first increases and then decreases, with the maximum Seebeck coefficient being 33 μV / K. Figure 9 The figure shows the relationship between the conductivity and temperature of the Mg3SbBi flexible film material in Example 3. It can be seen that the conductivity increases continuously with increasing temperature, reaching a maximum value of 3.6 × 10⁻⁶. 4 S / m, the material's electrical conductivity at room temperature is 2×10⁻⁶. 4S / m. To characterize the deformability of the material, the relationship between the material's electrical conductivity and the number of bending cycles was tested, such as... Figure 10 As shown, σ0 is the initial conductivity, and σ is the conductivity of the material after bending. It can be seen that when the bending radius is 5 mm, the conductivity after the first bend is 2 × 10⁻⁶. 4 When the bending cycle reaches 500 times, the material conductivity is 1.95 × 10⁻⁶ S / m. 4 The S / m ratio shows almost no attenuation, indicating that the Mg3SbBi flexible film material has good deformability.

[0107] Comparative Example 1

[0108] (1) Mix Mg and Sb metals in a molar ratio of Mg:Sb = 3:2, and then ball mill and hot press them in sequence. The hot pressing temperature is 800℃ and the hot pressing time is 20min to obtain Mg3Sb2 alloy target.

[0109] Metallic Mg and Bi were mixed in a molar ratio of Mg:Bi = 3:2, and then ball-milled and hot-pressed sequentially. The hot-pressing temperature was 750℃ and the hot-pressing time was 20 min to obtain a Mg3Bi2 alloy target.

[0110] (2) Place the glass slide in acetone, ethanol and ultrapure water in sequence and ultrasonically clean for 40 min each, then dry it with nitrogen gas.

[0111] (3) Fix the Mg3Sb2 and Mg3Bi2 alloy targets in the cavity and connect them to the RF power supply. The target-to-substrate distance is 80mm. At the same time, the glass substrate is installed on the sample stage.

[0112] (4) Turn on the mechanical pump and molecular pump in sequence to evacuate the chamber until the vacuum range reaches 4×10⁻⁶. -4 Pa;

[0113] (5) Turn on the heating power supply and heat the substrate to 600°C;

[0114] (6) Turn on the sample stage rotation button and adjust the sample stage speed to 30r / min;

[0115] (7) Introduce Ar and adjust the gas pressure to 2 Pa;

[0116] (8) Turn on the baffle and RF power supply in sequence, and pre-sputter for 30 minutes;

[0117] (9) Adjust the RF power supply to 100W, close the baffle, and start sputtering for 30 minutes.

[0118] (10) Turn off the radio frequency power supply and heating power supply; allow it to cool naturally to room temperature to obtain Mg3SbBi film material.

[0119] XRD tests were performed on the Mg3SbBi flexible film material of Comparative Example 1, which showed that the film was a pure Mg3SbBi phase with no obvious impurity peaks. SEM results showed that it was similar to that of Example 3, with the size of the sheet-like Mg3SbBi grains being 300-500 nm.

[0120] Figure 11 To illustrate the relationship between the Seebeck coefficient and temperature of the Mg3SbBi thermoelectric film prepared in Comparative Example 1, the following data was collected. Figure 11 It can be seen that the Seebeck coefficient is positive, and the Seebeck coefficient first increases and then decreases, with the maximum Seebeck coefficient being 43 μV / K. Figure 12 The figure shows the relationship between the conductivity of the Mg3SbBi film material and temperature, which is a comparative example. It can be seen that the conductivity increases continuously with increasing temperature, reaching a maximum value of approximately 1.7 × 10⁻⁶. 2 The S / m value is much lower than that of film materials prepared on carbon nanotube substrates. Furthermore, glass is a rigid substrate, and the film cannot detach from the substrate. Therefore, the Mg3SbBi thermoelectric film prepared on a glass substrate does not have deformability.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible thermoelectric film material of Mg3SbBi, characterized in that, It includes intertwined single-walled carbon nanotubes and Mg3SbBi grains attached to the single-walled carbon nanotubes, wherein the single-walled carbon nanotubes and Mg3SbBi grains form a two-dimensional network structure; the Mg3SbBi grains are plate-shaped. The preparation method of the Mg3SbBi flexible thermoelectric film material includes the following steps: A dispersion of single-walled carbon nanotubes was coated onto a substrate and dried to obtain a substrate with attached carbon nanotubes. Using Mg3Sb2 alloy target and Mg3Bi2 alloy target as sputtering targets, magnetron sputtering is performed on the surface of the substrate with attached carbon nanotubes to form Mg3SbBi grains on single-walled carbon nanotubes, thereby obtaining the Mg3SbBi flexible thermoelectric film material. The preparation of the Mg3Sb2 alloy target includes: mixing metallic Mg and Sb in a molar ratio of Mg:Sb=3:2, and then sequentially ball-milling and hot-pressing. The hot-pressing temperature is 780~800℃ and the hot-pressing time is 5~30min to obtain the Mg3Sb2 alloy target. The preparation of the Mg3Bi2 alloy target includes: mixing metallic Mg and Bi in a molar ratio of Mg:Bi=3:2, and then sequentially ball-milling and hot-pressing. The hot-pressing temperature is 720~780℃ and the hot-pressing time is 5~30min to obtain the Mg3Bi2 alloy target.

2. The Mg3SbBi flexible thermoelectric film material according to claim 1, characterized in that, The planar size of the Mg3SbBi grains is 200~500nm.

3. The Mg3SbBi flexible thermoelectric film material according to claim 1, characterized in that, The single-walled carbon nanotubes have a diameter of 20-100 nm and a length in the micrometer range.

4. The method for preparing the Mg3SbBi flexible thermoelectric film material according to any one of claims 1 to 3, characterized in that, Includes the following steps: A dispersion of single-walled carbon nanotubes was coated onto a substrate and dried to obtain a substrate with attached carbon nanotubes. Using Mg3Sb2 alloy target and Mg3Bi2 alloy target as sputtering targets, magnetron sputtering is performed on the surface of the substrate with attached carbon nanotubes to form Mg3SbBi grains on single-walled carbon nanotubes, thereby obtaining the Mg3SbBi flexible thermoelectric film material. The preparation of the Mg3Sb2 alloy target includes: mixing metallic Mg and Sb in a molar ratio of Mg:Sb=3:2, and then sequentially ball-milling and hot-pressing. The hot-pressing temperature is 780~800℃ and the hot-pressing time is 5~30min to obtain the Mg3Sb2 alloy target. The preparation of the Mg3Bi2 alloy target includes: mixing metallic Mg and Bi in a molar ratio of Mg:Bi=3:2, and then sequentially ball-milling and hot-pressing. The hot-pressing temperature is 720~780℃ and the hot-pressing time is 5~30min to obtain the Mg3Bi2 alloy target.

5. The preparation method according to claim 4, characterized in that, The conditions for magnetron sputtering include: substrate temperature of 400~600℃, target-substrate distance of 50~90mm, sputtering power of 50~100W, and sputtering time of 30~60min.

6. The preparation method according to claim 5, characterized in that, The Ar gas pressure during magnetron sputtering is 0.5~2 Pa.

7. The preparation method according to claim 5, characterized in that, The sample stage rotates at a speed of 10-30 r / min during magnetron sputtering.

8. The preparation method according to claim 4, characterized in that, Before the magnetron sputtering, the substrate surface with attached carbon nanotubes is pre-sputtered for 10-30 minutes.

9. The preparation method according to claim 4, characterized in that, The dispersion of the single-walled carbon nanotubes was obtained by dispersing the single-walled carbon nanotubes in ethylene glycol.

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