Preparation method and application of bismuth telluride-based thermoelectric material for flattening induced crystal lattice

Abstract

The invention belongs to the field of thermoelectric materials and devices, and particularly discloses a preparation method and application of a bismuth telluride-based thermoelectric material for inducing lattice leveling. PbxBi0. 5Sb1. 5Te3 is synthesized through a one-step hydrothermal method, and then original powder is pre-pressed by adopting a rapid annealing process so as to promote a spark plasma sintering process. Results show that a small amount of Pb atoms induce the lattice leveling phenomenon in the process of a hydrothermal synthesis method, a flexible thermoelectric device (F-TED) is constructed based on the material, 16.8 mW high power is output under the temperature difference of 50 K, and human skin heat can be directly collected to supply power to an electronic device; and when the hot end is kept at 29.51 DEG C, the maximum refrigeration temperature difference delta Tmax is equal to 60K.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric material preparation, specifically relating to a method for preparing bismuth telluride-based thermoelectric materials with induced lattice flattening and its application. Background Technology

[0002] Thermoelectric (TE) materials have attracted much attention due to their ability to directly convert heat energy into electrical energy, providing a promising pathway for sustainable energy conversion. They have been extensively studied for applications such as low-grade waste heat recovery in the temperature range of 300-573 K. The performance of thermoelectric materials is quantified using a dimensionless quality factor (ZT), defined as ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. To achieve a high ZT value, the key is to maximize the Seebeck coefficient and electrical conductivity while minimizing the thermal conductivity. Glen Slack proposed the concept of phonon glass-electron crystals (PGECs). Since the transport of charge carriers and phonons jointly determines thermoelectric performance, lattice integrity plays a crucial role. For phonon transport, lattice vibrations dominate heat conduction; any lattice disorder can effectively scatter phonons and reduce κ. Conversely, efficient electron transport requires an ordered lattice structure. Therefore, balancing the mean free path of electrons and phonons has become a core strategy for improving thermoelectric performance. Element doping has been proven to be an effective method for optimizing the balance of the mean free path of electrons and phonons in thermoelectric materials. Among them, bismuth telluride (Bi2Te3)-based compounds are the most mature and commercially available systems, and their performance can be finely tuned through selective doping. Previous studies have shown that introducing suitable dopants can suppress intrinsic bipolar excitation, thereby broadening the effective operating temperature range. Xiong Rui et al. found that in p-type Bi... 0.5 Sb 1.5 Replacing bismuth / antimony with tin in Te3 nanosheets generates a large number of vacancies, increases carrier concentration, and reduces bipolar thermal conductivity at high temperatures. The optimized power factor (PF) reaches 3.11 mW / m² at room temperature. -1 K -2 Zhao Lidong et al. proposed a "lattice flattening" doping strategy—introducing trace amounts of foreign atoms to fill intrinsic vacancies to promote carrier transport, thereby obtaining high-performance thermoelectric materials with a flatter and more ordered lattice structure. Lead has the characteristics of low solid solubility and heavy atomic weight, and even at trace doping concentrations, it can significantly change electronic and heat transport properties. Therefore, it is possible to try introducing trace amounts of Pb into thermoelectric materials to induce lattice flattening. However, current research on Pb-doped Bi... 0.5 Sb 1.5Most methods for preparing Te3 materials rely on traditional high-temperature melting, which is uneconomical, energy-intensive, and unsuitable for large-scale industrial application. Furthermore, current methods for preparing thermoelectric materials that induce lattice flattening are also energy-intensive and have long preparation cycles. Therefore, there is an urgent need to develop a low-energy-consumption, short-cycle method for preparing thermoelectric materials that induce lattice flattening. Summary of the Invention

[0003] In order to overcome the problems of high energy consumption and long cycle in the preparation of thermoelectric materials with lattice flattening characteristics by existing technologies, this invention induces lattice flattening in bismuth telluride thermoelectric materials through hydrothermal synthesis.

[0004] To achieve the above objectives, this invention selects lead as the p-type Bi. 0.5 Sb 1.5 Dopants in Te3 thermoelectric materials induce a lattice flattening effect to improve the thermoelectric properties of the material.

[0005] A method for preparing a bismuth telluride-based thermoelectric material with induced lattice flattening, comprising the following specific steps: (1) Using water as a solvent, PbCl2, BiCl3, SbCl3 and Te nanopowder (preferably with a particle size of 100-500 nm) are mixed evenly in a certain molar ratio under alkaline conditions; (2) Under stirring, a reducing agent and a complexing agent were added to the solution after (1) was mixed evenly. Then, the solution was sealed and pressurized to ensure that the chemical reaction proceeded fully. The reaction product was washed with acetone and ethanol in sequence and then dried to obtain PbBST nanosheets. (3) Place the PbBST nanosheets in a graphite mold, introduce nitrogen gas and seal the mold, then place it in an SPS discharge plasma activation sintering equipment for annealing. (4) The annealed sample is densified again by SPS discharge plasma sintering to obtain a lattice-flattened bismuth telluride-based thermoelectric material.

[0006] Furthermore, the molar ratio of the PbCl2, BiCl3, SbCl3 and Te nanopowders is 0.005-0.01:0.5:1.5:3, preferably 0.009:0.5:1.5:3.

[0007] Furthermore, the reducing agent is sodium borohydride; and / or The complexing agent is disodium ethylenediaminetetraacetate; Furthermore, the mass ratio of sodium borohydride to disodium ethylenediaminetetraacetate is 10:1, and the molar ratio of sodium borohydride to PbCl2 is 3g:0.005-0.01mol, preferably 3g:0.009mol; The alkaline environment in (1) is achieved by adding sodium hydroxide; Furthermore, the specific operation of the pressurization treatment in (2) is as follows: react at room temperature and 10-30 MPa for 8-15 hours, and then heat to 150-200℃ to continue the reaction for 1-5 hours, preferably react at room temperature and 10 MPa for 12 hours, and then heat to 180℃ to continue the reaction for 3 hours. Furthermore, the drying in (2) is performed at 70°C for 6 hours; Furthermore, in step (3), the annealing temperature is 350°C and the holding time is 10 min; Furthermore, the densification sintering conditions in (4) are: sintering at 50 MPa pressure and 410 °C for 10 min.

[0008] This invention also uses geometric strain analysis, relative atomic column displacement, and contrast calculation to normalize the HAADF-STEM atomic phase diagram of the obtained bismuth telluride-based thermoelectric material (processing software: DigitalMicrograph). Combined with the unit cell diagram (calculation software: VESTA) and defect formation energy calculation diagram, it theoretically proves that the introduction of Pb atoms effectively fills the intrinsic bismuth vacancies in the lattice, achieving lattice flattening.

[0009] In addition, this application also provides the application of the bismuth telluride-based thermoelectric material obtained by the above preparation method in the preparation of flexible wearable thermoelectric devices.

[0010] Furthermore, the application is as follows: using bismuth telluride-based thermoelectric materials as p-type Pb... x Bi 0.5 Sb 1.5 Te3 thermoelectric particles, combined with commercially available N-type Bi2Te 2.7 Se 0.3 Thermoelectric particles and flexible substrates are used to fabricate flexible self-powered wearable thermoelectric devices that can be fixed to the fingers with Velcro and use the heat of human skin to power a small light bulb in a boost circuit. When a current of 1.5A is applied and the hot end is kept at 29.51℃, the maximum cooling temperature difference of the device can reach 60 K.

[0011] Compared with the prior art, the beneficial effects and advantages of the present invention are as follows: This invention discloses for the first time a method for preparing thermoelectric materials that induces lattice flattening. Specifically, lattice flattening is induced in bismuth telluride thermoelectric materials via hydrothermal synthesis. This method has a short preparation cycle, low energy consumption, and is more environmentally friendly. Furthermore, due to the uncertainties and difficulties in imaging and preparing polycrystalline samples using transmission electron microscopy (TEM), this invention combines geometric strain analysis, relative atomic column displacement calculation, and atomic column contrast analysis using TEM to demonstrate the lattice flattening phenomenon from a new perspective. This method is applicable to polycrystalline thermoelectric materials and has the advantages of low sample preparation difficulty and universality. Inducing lattice flattening in bismuth telluride thermoelectric materials via hydrothermal synthesis optimizes electrical conductivity. Simultaneously, Pb filling of intrinsic Bi vacancies effectively regulates the crystal structure, promoting multiband synglisis and further optimizing the Seebeck coefficient and electrical conductivity. Moreover, processing the lattice-flattened material into flexible wearable thermoelectric devices greatly promotes the development of wearable electronic devices in the fields of power generation and cooling. Attached Figure Description

[0012] Figure 1 For Pb 0.009 Comparison of transmission electron microscopy images of BST and BST samples.

[0013] Figure 2 Pb with different Pb contents x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between the conductivity of a bulk Te3 sample and temperature. Figure 3 Pb with different Pb contents x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between the Seebeck coefficient and temperature for bulk Te3 samples; Figure 4 Pb with different Pb contents x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between the power factor of the bulk Te3 sample and temperature. Figure 5 Pb with different Pb contents x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between the thermal conductivity of the bulk Te3 sample and temperature. Figure 6 Pb with different Pb contents x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between the thermoelectric figure of merit of a bulk Te3 sample and temperature.

[0014] Figure 7 For Pb 0.009 A schematic diagram of the BST unit cell structure and a calculation diagram of the formation energy of related defects.

[0015] Figure 8 For Pb 0.009 Performance and physical images of flexible thermoelectric devices fabricated from BST materials. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention is not limited to the following embodiments; specific implementation methods can be determined based on the technical solutions of the present invention and according to actual circumstances.

[0017] Example 1 This invention selects lead as the p-type Bi 0.5 Sb 1.5 Pb was synthesized as a dopant for Te3 thermoelectric materials via a hydrothermal method. 0.009 BST thermoelectric materials, the specific steps are as follows: Step (1) Pour PbCl2, BiCl3, SbCl3 and Te nanoparticles (particle size 100-200 nm) with molar amounts (unit: mol, the same below, not repeated) of 0.009, 0.5, 1.5 and 3 respectively into a 100 mL polytetrafluoroethylene cup, and then add 30 mL of deionized water.

[0018] Step (2) Add 2.5 g of sodium hydroxide to maintain the alkaline environment of the solution, and stir the sample at 600 rpm for 30 minutes until completely dissolved.

[0019] Step (3) Add 3 grams of reducing agent sodium borohydride NaBH4 and 0.3 grams of complexing agent disodium ethylenediaminetetraacetate (EDTA-2Na) to the polytetrafluoroethylene container in sequence.

[0020] Step (4) After sealing the stainless steel reactor containing the polytetrafluoroethylene cup, it was subjected to room temperature and pressure treatment (room temperature was 25°C and pressure was 10 MPa) for 12 hours. Then, the temperature was raised to 180°C and reacted for 3 hours (while maintaining the pressure of 10 MPa) to ensure the chemical reaction proceeded fully. The reaction product was washed sequentially with acetone and anhydrous ethanol to reduce byproducts. Finally, the washed product was dried at 70°C for 6 hours to obtain Pb. 0.009 BST nanosheets.

[0021] Step (5) Pb 0.009 BST nanosheets were placed in a cylindrical graphite mold with a diameter of 12.7 mm, and Pb was coated with carbon paper. 0.009The BST nanosheets were sealed and nitrogen (N2) was introduced. The mold containing the nanosheets was then placed in an SPS (spark plasma sintering) annealing apparatus (annealing temperature 350℃, holding time 10min).

[0022] Step (6) The annealed sample was placed under a pressure of 50 MPa and a temperature of 410 °C and then subjected to SPS discharge plasma sintering for 10 min to obtain Pb. 0.009 BST Thermoelectric Materials.

[0023] Step (7) Cut the sintered cylinder into rectangular strips of 3×3×11 cubic millimeters and square pieces of 6×6×2 cubic millimeters along the direction of vertical pressure.

[0024] Step (8) involves testing the electrical properties of the cut rectangular strips, the thermal properties of the square pieces, and characterization analysis using transmission electron microscopy. The electrical properties are tested using the four-probe method to measure the Seebeck coefficient and conductivity of the thermoelectric material, using the CTA-3S thermoelectric material testing system. The thermal properties are tested using the laser perturbation method to measure the thermal diffusivity of the material, and then the thermal conductivity is calculated. The formula for thermal conductivity is κ = D×C. P ×ρ, where D is the thermal diffusivity, C P ρ is the specific heat of the material, and ρ is the density of the material; both are constants. The testing equipment was an LFA 467 HyperFlash. The transmission electron microscope used was a JEM-F200.

[0025] Example 2 This invention synthesizes BST thermoelectric material using a hydrothermal method, and the specific steps are as follows: Step (1) Pour BiCl3, SbCl3 and Te nanopowders with molar amounts of 0.5, 1.5 and 3 respectively into a 100 mL polytetrafluoroethylene cup, and then add 30 mL of deionized water.

[0026] Step (2) Add 2.5 g of sodium hydroxide (NaOH) to maintain the alkaline environment of the solution, and stir the sample at 600 rpm for 30 minutes using a magnetic stirrer until it is completely dissolved.

[0027] Step (3) Add 3 grams of reducing agent NaBH4 and 0.3 grams of EDTA-2Na to the polytetrafluoroethylene container in sequence.

[0028] Step (4) involves sealing the stainless steel reactor containing the polytetrafluoroethylene cup and then pressurizing it at room temperature (10 MPa) for 12 hours. The temperature is then raised to 180°C and the reaction continues for 3 hours to ensure the chemical reaction proceeds fully. The resulting reaction product is washed sequentially with acetone and anhydrous ethanol to reduce the formation of byproducts. Finally, the obtained powder is dried at 70°C for 6 hours to obtain BST nanosheets.

[0029] Step (5) Place the BST nanosheets in a cylindrical graphite mold with a diameter of 12.7 mm, and seal the BST nanosheets with carbon paper. Then, introduce nitrogen (N2) gas. Place the mold containing the nanosheets in an SPS discharge plasma sintering equipment for annealing (annealing temperature is 350℃, holding time is 10 min).

[0030] Step (6) The annealed sample is placed under a pressure of 50 MPa and a temperature of 410 °C and then subjected to spark plasma sintering for 10 min to obtain BST thermoelectric material.

[0031] Step (7) Cut the sintered cylinder into rectangular strips of 3×3×11 cubic millimeters and square pieces of 6×6×2 cubic millimeters along the direction of vertical pressure.

[0032] Step (8) involves testing the electrical properties of the cut rectangular strips, the thermal properties of the square pieces, and characterization analysis using transmission electron microscopy. The electrical properties are tested using the four-probe method to measure the Seebeck coefficient and conductivity of the thermoelectric material, using the CTA-3S thermoelectric material testing system. The thermal properties are tested using the laser perturbation method to measure the thermal diffusivity of the material, and then the thermal conductivity is calculated. The formula for thermal conductivity is κ = D×C. P ×ρ, where D is the thermal diffusivity, C P ρ is the specific heat of the material, and ρ is the density of the material; both are constants. The testing equipment was an LFA 467 HyperFlash. The transmission electron microscope used was a JEM-F200.

[0033] Fourier transform and geometric strain analysis were performed on the HAADF-STEM atomic phase diagrams (processing software was DigitalMicrograph).

[0034] Referring to the HAADF-STEM atomic phase diagram, the displacement of the atomic pillars was calculated based on the overall periodic structure information (the processing software was DigitalMicrograph).

[0035] The HAADF-STEM atomic phase diagrams were analyzed for contrast, and the contrast calculation data were normalized (processing software was DigitalMicrograph).

[0036] Figure 1 For Pb 0.009 Comparison of transmission electron microscopy images of BST and BST samples, specifically including Figure 1 (ae) represents Pb 0.009 The surface distribution diagrams of Bi, Sb, Te and Pb elements in the BST sample under a transmission electron microscope show that Pb atoms have been successfully incorporated into the BST lattice. Figure 1 (f) and (g) are BST and Pb, respectively. 0.009 High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of the BST samples, along with corresponding Fast Fourier Transform (FFT) images, clearly show that both belong to the

[0001] band axis, and their crystal plane orientations also belong to (11). 0) and (1) 10) These two crystal plane families. Figure 1 (h) and (i) are respectively Figure 1 (f) and (g) are geometric phase analysis diagrams on the

[0001] band axis. Comparing the two, it can be found that the overall strain of the BST sample is slightly higher, with some areas even reaching about 30% strain. However, in Pb 0.009 In some regions of the BST sample, the strain value is as high as 1.4%. This phenomenon can be explained by the presence of a large number of intrinsic vacancies in the BST sample, leading to locally high strain. When a large number of vacancies accumulate, dislocation domains or crystalline damage in some areas can occur, resulting in an increase in the strain value in those areas. Correspondingly, Figure 1 (i) The strain value is very small, which indicates that Pb doping can effectively mitigate the strain problem caused by vacancies. This also proves that the BST lattice is flattened after Pb doping. Figure 1 (j) and (k) are Figure 1 (f) and (g) are high-magnification HAADF-STEM images and corresponding atomic column displacement distribution maps. It can be observed that in the BST sample, except for the central region which is the original reference point, there are significant atomic displacements around the perimeter. In Pb... 0.009 In the BST sample, most atoms exhibit an initial state without displacement. Only in the lower left corner do some atomic displacement begins to appear. This demonstrates that Pb doping can effectively fill vacancies, thus effectively suppressing the influence of vacancies on the overall periodic structure of the material. Figure 1 (l) and (m) respectively give BST and Pb 0.009High-resolution HAADF-STEM contrast analysis of the BST samples reveals a sharp drop in contrast for some atomic columns compared to others. This is because STEM imaging operates on a Z-contrast basis; the higher the sum of the atomic numbers in a column, the brighter it is, meaning higher its contrast. Columns with significantly lower-than-average contrast are likely due to vacancies. Therefore, it's certain that vacancies are present in the lower-contrast samples. In the Pb-doped samples, while the contrast values ​​fluctuate, there is no sharp drop. This is because the Te / Sb / Bi / Pb ratios differ within different columns, causing these fluctuations. For example, a higher Pb and Bi ratio results in higher contrast, while a higher Te and Sb ratio results in lower contrast. Figure 1 (n) and Figure 1 (p) shows the relative contrast calculation diagram and three-dimensional contrast diagram of the BST sample, respectively. It can be observed that the contrast is relatively uniform in the lower part of the image, while the upper half shows a large number of atomic pillars containing vacancies. Combined with... Figure 1 (p) This provides a more intuitive demonstration that vacancies have a certain degree of fluidity and will exhibit certain enrichment regions. When this vacancies enrichment region reaches an extreme level, the large strain region seen in the previous strain analysis diagram will appear. Figure 1 (o) and Figure 1 (q) represent the BST sample (left) and Pb, respectively. 0.009 The contrast-normalized image of BST (right) and the two-dimensional contrast comparison image show that there is no extreme cool-toned contrast in the Pb-doped sample; most of the contrast fluctuations are due to the relative atomic percentages. This confirms that Pb doping effectively fills the intrinsic vacancies of Bi, achieving lattice flattening.

[0037] By changing the molar amounts of PbCl2 in step (1) of Example 1 to "0.009:0.5:1.5:3", the values ​​of "0.009" were changed to "0", "0.005", "0.007", and "0.01" respectively, Pb with different Pb contents were prepared. x Bi 0.5 Sb 1.5 The schematic diagram showing the relationship between the conductivity of each bulk Te3 sample and temperature is shown below. Figure 2 It is not difficult to observe that as the Pb content increases, the conductivity of the sample also increases, where Pb... 0.01 Bi 0.5 Sb 1.5 Te3 and Pb 0.009 Bi 0.5 Sb 1.5 The Te3 sample has relatively high electrical conductivity. Figure 3For the above-mentioned Pb contents of different Pb, x Bi 0.5 Sb 1.5 The schematic diagram of the Seebeck coefficient of the Te3 bulk sample as a function of temperature shows that below 400 K, the Seebeck coefficient decreases with increasing Pb content, where Pb... 0.01 Bi 0.5 Sb 1.5 The Te3 sample had the lowest Seebeck coefficient, while the Pb sample had the lowest. 0.009 Bi 0.5 Sb 1.5 The Seebeck coefficient of the Te3 sample is in a moderate range. Figure 4 For the above-mentioned Pb contents of different Pb, x Bi 0.5 Sb 1.5 The schematic diagram of the power factor of the bulk Te3 sample as a function of temperature shows that Pb 0.009 Bi 0.5 Sb 1.5 The Te3 sample had the highest power factor value. Figure 5 For the above-mentioned Pb contents of different Pb, x Bi 0.5 Sb 1.5 A schematic diagram showing the relationship between thermal conductivity and temperature for bulk Te3 samples reveals that below 400 K, the thermal conductivity of all samples increases with increasing Pb content, where Pb... 0.01 Bi 0.5 Sb 1.5 The Te3 sample had the highest thermal conductivity. Figure 6 For the above-mentioned Pb contents of different Pb, x Bi 0.5 Sb 1.5 The schematic diagram of the thermoelectric figure of merit (TFP) of the bulk Te3 samples as a function of temperature shows that the peak value of the TFP for all samples first increases and then decreases with increasing Pb content, ultimately decreasing to the lowest value. 0.009 Bi 0.5 Sb 1.5 The Te3 sample had the highest thermoelectric figure of merit.

[0038] Geometric strain analysis, relative atomic column displacement calculation, and atomic column contrast analysis using transmission electron microscopy revealed that the introduction of Pb effectively filled intrinsic bismuth vacancies in the crystal lattice, achieving lattice flattening and thus significantly improving electrical conductivity. Furthermore, through… Figure 7Theoretical calculations (using VESTA software) revealed that, under Bi enrichment conditions, the Bi vacancy formation energy and the energy required for Pb atoms to occupy Bi vacancies are lowest. This indicates that when Pb atoms are introduced into the BST material, the probability of Pb atoms filling Bi vacancies is highest. Simultaneously, this structural modulation also promotes multi-band synergy, further optimizing the Seebeck coefficient and electrical conductivity of the material. Therefore, Pb... 0.009 The BST sample exhibited 3.86 mWm at 400 K. -1 K -2 The sample exhibited an excellent power factor. Ultimately, the maximum ZT value reached 1.38 at 400 K, and the average ZT value in the 300-500 K temperature range was 1.24, nearly double that of the original sample. Furthermore, using Pb... 0.009 BST's flexible thermoelectric device (F-TED) exhibits outstanding performance: it outputs a high power of 16.8 mW at a temperature difference of 50 K, and the maximum cooling temperature difference ΔT max It reached 60K.

[0039] The thermoelectric properties of the bulk sample were tested at 400 K, including Pb. 0.009 The conductivity σ of the BST bulk sample is 8.64*10. 4 S / m, Seebeck S coefficient is 211.55 μVK -1 The power factor PF is 3.86 mWm. -1 K -2 The thermal conductivity κ is 1.12 W / m². -1 K -1 The thermoelectric figure of merit (ZT) is 1.38, which is 1.98 times higher than that of the BST sample.

[0040] Example 3: A method for fabricating a flexible wearable thermoelectric device, comprising the following steps: Step (1): Sinter the Pb after step (6) of Example 1 0.009 BST uses a sliding cutter to cut several 1.4 mm × 1.4 mm × 2.5 mm thermoelectric legs along the vertical pressure direction as P-type thermoelectric legs for electrical devices. Then, nickel is electroplated on their surface (thickness is 0.3 mm).

[0041] Step (2): Use screen printing technology to print a low-temperature solder (Sn) layer with a thickness of approximately 0.1 mm onto the copper electrode. 42 Bi 58 (melting point is 138℃), then 49 pairs of electroplated P-type and N-type thermocouples (purchased commercial N-type Bi2Te) 2.7 Se 0.3The thermoelectric legs are arranged in an array between the electrodes and welded at 470 K for 10 minutes to form a semi-finished F-TED.

[0042] Step (3) The blade cuts along the straight line between the bottom electrodes to create a foldable, fully functional flexible thermoelectric device, with an appearance like... Figure 8 (d).

[0043] Figure 8 For Pb 0.009 Performance and physical images of flexible thermoelectric devices fabricated from BST materials, specifically including... Figure 8 (a) and (b) Power-voltage (PV) curves and current-voltage (IV) curves at different temperature differences. Figure 8 (c) shows the relationship between the maximum output voltage and power and the temperature difference. Figure 8 (d) is a photo of the assembled F-TED. Figure 8 (e) is a schematic diagram of the bending radius of F-TED. Figure 8 (f) Demonstration of wearable flexibility: In an environment of 27.9°C, the device collects heat from different parts of the human body and directly drives the LED to emit light through a boost converter. Figure 8 (gi) represents infrared thermal images recorded under different input currents.

[0044] Based on Pb 0.009 BST has constructed a flexible thermoelectric device (F-TED) that can directly collect heat from human skin to power electronic devices; it outputs a high power of 16.8 mW at a temperature difference of 50 K, and the maximum cooling temperature difference ΔTmax = 60 K when the hot end is kept at 29.51℃.

[0045] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a bismuth telluride-based thermoelectric material with induced lattice flattening, comprising the following specific steps: (1) Using water as a solvent, PbCl2, BiCl3, SbCl3 and Te nanopowders were mixed evenly in a certain molar ratio under alkaline conditions; (2) Under stirring, add reducing agent and complexing agent to the solution after (1) is mixed evenly, then seal and pressurize to allow the chemical reaction to proceed fully; the reaction product is washed with acetone and ethanol in sequence and then dried to obtain PbBST nanosheets; (3) Place the PbBST nanosheets in a graphite mold, introduce nitrogen gas and seal the mold, then place it in an SPS discharge plasma activation sintering equipment for annealing. (4) The annealed sample is placed in a densification sintering process by SPS discharge plasma sintering to obtain a lattice-flattened bismuth telluride-based thermoelectric material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the PbCl2, BiCl3, SbCl3 and Te nanopowders is 0.005-0.01:0.5:1.5:

3.

3. The preparation method according to claim 1, characterized in that, The reducing agent is sodium borohydride; and / or The complexing agent is disodium ethylenediaminetetraacetate.

4. The preparation method according to claim 3, characterized in that, The mass ratio of sodium borohydride to disodium ethylenediaminetetraacetate is 10:1, and the molar ratio of sodium borohydride to PbCl2 is 3g:0.005-0.01mol.

5. The preparation method according to claim 1, characterized in that, The specific procedure for pressurization is as follows: react at room temperature and 10-30 MPa for 8-15 hours, then raise the temperature to 150-200℃ and continue the reaction for 1-5 hours.

6. The preparation method according to claim 1, characterized in that, The drying process in (2) involves drying at 70°C for 6 hours.

7. The preparation method according to claim 1, characterized in that, In step (3), the annealing temperature is 350℃ and the holding time is 10min.

8. The preparation method according to claim 1, characterized in that, The densification sintering conditions in (4) are: sintering at 50 MPa pressure and 410 °C for 10 min.

9. The application of the bismuth telluride-based thermoelectric material obtained by the preparation method according to any one of claims 1-8 in the preparation of flexible wearable thermoelectric devices.

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