Bi2Te3-based material with high thermoelectric performance and preparation method thereof

Abstract

The invention discloses a Bi2Te3-based material with high thermoelectric performance and a preparation method of the Bi2Te3-based material. The method comprises the following steps: firstly, synthesizing Bi2Te3-based nanocrystalline powder by adopting a hydrothermal method, then uniformly introducing an X-type zeolite molecular sieve with high ionic conductivity electrical property and a nano porous structure into the Bi2Te3-based powder, and rapidly sintering and compacting the powder by utilizing a spark plasma sintering technology so as to obtain a Bi2Te3 / Na-LSX nano composite material block. The X-type zeolite molecular sieve is introduced as a nano second phase, so that the electrical property of the Bi2Te3-based material is improved, meanwhile, phonon scattering is enhanced by nanopores, the heat conductivity of the material is reduced, and finally, the thermoelectric property of the Bi2Te3-based material is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials and relates to a Bi2Te3-based material with high thermoelectric performance and its preparation method. Background Technology

[0002] Thermoelectric materials are considered a promising solution to environmental and energy crises. Generally, the thermoelectric properties and conversion efficiency of thermoelectric materials are determined by the dimensionless thermoelectric figure of merit zT = S. 2 σT / κ tot The molecular part reflects the electron transport capacity and can be determined by the power factor PF = S. 2 σ represents the result, where S is the Seebeck coefficient, σ is the conductivity, and T is the absolute operating temperature; κ in the denominator tot The total thermal conductivity (zT) reflects the material's ability to conduct heat. However, the transport of phonons and electron carriers determines the aforementioned thermoelectric parameters, leading to complex coupling relationships among these parameters and severely limiting the improvement of zT values. Therefore, the key to improving the thermoelectric performance of materials lies in how to significantly reduce κ and increase S by controlling the transport of electron carriers and phonons within the material without severely sacrificing σ.

[0003] Bi₂Te₃-based thermoelectric materials, as the most commercially viable thermoelectric system currently available, exhibit excellent thermoelectric conversion performance at room temperature due to their superior Seebeck coefficient and electrical conductivity. However, this system suffers from two fundamental limitations: firstly, its intrinsic band gap is too narrow (0.13-0.15 eV), leading to a significant enhancement of the bipolar conductivity effect in the high-temperature region and causing a sharp decline in the Seebeck coefficient; secondly, the material's intrinsic thermal conductivity remains relatively high, significantly falling short of the low thermal conductivity requirements of ideal thermoelectric materials. These inherent defects severely restrict the potential for improving the material's zT value, making it difficult to break through existing bottlenecks in energy conversion efficiency in the mid-to-high temperature range.

[0004] In the research of Bi2Te3-based thermoelectric materials, researchers have adopted a variety of innovative methods to improve performance. Reference 1 introduces Bi2Te3 nanowires synthesized by hydrothermal method when preparing Bi2Te3 matrix by zone melting method, which effectively reduces the lattice thermal conductivity of the material and thus improves thermoelectric conversion efficiency (Xie W, Tang X, Yan Y, et al. Unique nanostructures and enhanced thermoelectric performance of melt-spun BiSbTe alloys[J]. Appliedphysics letters,2009,94(10):102111-1-102111-3.). Reference 2 successfully prepared a graphene / Bi2Te3 composite thermoelectric material with a higher zT value by uniformly distributing Bi2Te3 particles on the surface of graphene sheets using spark plasma sintering technology (Xu Z, Wu H, Zhu T, et al. Attaining high mid-temperature performance in (Bi,Sb)2Te3 thermoelectric materials via synergistic optimization[J]. NPGAsia Materials, 2016, 8(9): e302-e302.). Reference 3 combined hot pressing and coating technology to significantly optimize the thermoelectric performance of the material by introducing carbon materials such as carbon fibers and multi-walled carbon nanotubes into the Bi2Te3 matrix (Shyni P, Pradyumnan P P. Fermi level tuning in modified Bi2Te3 system for thermoelectric applications[J]. RSC advances, 2021, 11(8): 4539-4546.).

[0005] Among Bi2Te3-based materials, p-type BiSbTe materials based on Sb alloys have improved the room temperature zT value from 1.0 to 1.2, but still lag significantly behind other high zT thermoelectric materials. Therefore, it is urgent to find a strategy that can effectively reduce κ while improving the electrical properties of thermoelectric materials, thereby achieving further performance enhancements in Bi2Te3-based thermoelectric materials. Summary of the Invention

[0006] The purpose of this invention is to provide a Bi2Te3-based material with high thermoelectric properties and its preparation method.

[0007] The technical solution for achieving the objective of this invention is as follows:

[0008] A method for preparing Bi2Te3-based materials with high thermoelectric properties includes the following steps:

[0009] Step 1: Disodium ethylenediaminetetraacetate, bismuth trichloride (BiCl3), antimony trichloride (SbCl3), tellurium (Te) powder, sodium hydroxide (NaOH), and sodium borohydride (NaBH4) are mixed and dissolved in water at a mass ratio of 0.5–0.8:0.7–0.8:2–2.4:2.5–3:4–6:1.5–3. The mixture is then subjected to a hydrothermal reaction at 180–220°C. After the reaction is completed, the mixture is cooled to room temperature, centrifuged to remove impurities, vacuum dried, and ground to obtain p-type Bi. 0.4 Sb 1.6 Te3 nanopowder;

[0010] Step 2, p-type Bi 0.4 Sb 1.6 Te3 nanoparticles were ultrasonically dispersed in ethanol, then Na-LSX zeolite molecular sieve powder was added, and the mixture was ultrasonically stirred until uniformly dispersed. The mixture was then vacuum dried and ground to obtain Bi. 0.4 Sb 1.6 Te3 / Na-LSX composite nanopowder;

[0011] Step 3, Bi 0.4 Sb 1.6 Te3 / Na-LSX composite nanoparticles were subjected to discharge plasma sintering at 420±20℃ to obtain Bi 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite bulk.

[0012] Preferably, in step 1, the mass ratio of disodium ethylenediaminetetraacetate, bismuth trichloride, antimony trichloride, tellurium powder, sodium hydroxide, and sodium borohydride is 0.6:0.75:2.2:2.7:5:2.

[0013] Preferably, in step 1, the mass-to-volume ratio of disodium ethylenediaminetetraacetate and water is 0.5–0.8 g: 80–140 mL, more preferably 0.6 g: 120 mL.

[0014] Preferably, in step 1, the hydrothermal reaction time is 10–15 h.

[0015] Preferably, in step 1, the centrifugation speed is 11000-12000 r / min and the centrifugation time is 3-5 min.

[0016] Preferably, in step 1, the washing method is to first wash three times with ultrapure water by centrifugation, and then wash three times with anhydrous ethanol by centrifugation.

[0017] Preferably, in step 1 or 2, the vacuum drying temperature is 40–60°C and the drying time is 12–18 h.

[0018] Preferably, in step 2, the mass of the Na-LSX powder is Bi. 0.4 Sb 1.6 0.5–1.0 wt% of the total mass of the Te3 / Na-LSX composite powder.

[0019] Preferably, in step 3, the holding time is 5 to 15 minutes and the sintering pressure is 50 to 70 MPa.

[0020] This invention provides Bi prepared by the above method. 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite material.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) This invention synthesizes p-type Bi using a hydrothermal method. 0.4 Sb 1.6 Te3 nanocrystalline powder was synthesized using a convenient method that allowed for easy control of chemical composition and grain size. Furthermore, the synthesis of Bi... 0.4 Sb 1.6 The Te3 / Na-LSX nanocomposite powder is prepared using spark plasma sintering technology. Compared with traditional hot pressing technology, this preparation process not only has a lower process temperature range and a simpler preparation process, but also endows the material with better mechanical properties, making it more suitable for industrial production. This significantly reduces the preparation cost while improving the material performance.

[0023] (2) This invention introduces X-type zeolite molecular sieve as a nano-second phase to enhance the performance of p-type Bi. 0.4 Sb 1.6 While enhancing the electrical properties of Te3 materials, the nanopores also improve phonon scattering and reduce the thermal conductivity of the material. Ultimately, this significantly improves the p-type Bi... 0.4 Sb 1.6 Thermoelectric properties of Te3 materials, including Bi 0.4 Sb 1.6 The zT peak value of Te3 / 0.5wt%Na-LSX reached 1.42 at 373K. Attached Figure Description

[0024] Figure 1 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The relationship between conductivity (σ) and temperature (T) of Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples.

[0025] Figure 2 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The Seebeck coefficient (S) versus temperature (T) for Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples.

[0026] Figure 3 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 Power factor (S) of Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples 2 Graph showing the relationship between σ and temperature (T).

[0027] Figure 4 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 Total thermal conductivity (κ) of Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples tot The relationship between temperature (T) and temperature (T).

[0028] Figure 5 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The relationship between the thermoelectric figure of merit (zT) and temperature (T) of Te3 / x wt% Na-LSX samples (x = 0, 0.5 and 1.0). Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0030] Example 1

[0031] 0.6 g of disodium ethylenediaminetetraacetate was dissolved in a 200 mL hydrothermal reactor liner containing 120 mL of deionized water to form a uniform dispersion. Then, 0.75 g of BiCl3, 2.2 g of SbCl3, 2.7 g of Te powder, and 5 g of NaOH were added sequentially. Finally, the mixture was magnetically stirred for 15 min at room temperature, followed by the addition of 2 g of NaBH4. After stirring at room temperature for 1 h, the mixture was transferred to a stainless steel autoclave and heated in a 200 °C oven for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and the product was separated by high-speed centrifugation (11000 r / min, 3.5 min). The product was washed three times with alternating centrifugation using ultrapure water and anhydrous ethanol. The washed powder was dried in a vacuum drying oven at 50 °C for 12 h, and then ground to obtain p-type Bi. 0.4 Sb 1.6 Te3 nanopowder.

[0032] 1.592gp type Bi 0.4Sb 1.6 Te3 nanoparticles were ultrasonically dispersed in ethanol, then 0.008 g (0.5 wt%) of Na-LSX powder was added. The mixture was ultrasonically stirred for 1 h until uniformly dispersed, and then the solution was vacuum dried. The sample was removed, ground into powder, and placed in a graphite mold with an inner diameter of 10 mm for discharge plasma sintering at 420 °C for 5 min and 60 MPa to obtain Bi. 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite bulk material. The thermoelectric properties of the bulk material were tested after cutting and polishing, with the direction parallel to the sintering pressure.

[0033] Example 2

[0034] 0.6 g of disodium ethylenediaminetetraacetate was dissolved in a 200 mL hydrothermal reactor liner containing 120 mL of deionized water to form a uniform dispersion. Then, 0.75 g of BiCl3, 2.2 g of SbCl3, 2.7 g of Te powder, and 5 g of NaOH were added sequentially. Finally, the mixture was magnetically stirred for 15 min at room temperature, followed by the addition of 2 g of NaBH4. After stirring at room temperature for 1 h, the mixture was transferred to a stainless steel autoclave and heated in a 200 °C oven for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and the product was separated by high-speed centrifugation (11000 r / min, 3.5 min). The product was washed three times with alternating centrifugation using ultrapure water and anhydrous ethanol. The washed powder was dried in a vacuum drying oven at 50 °C for 12 h, and then ground to obtain p-type Bi. 0.4 Sb 1.6 Te3 nanopowder.

[0035] 1.584gp type Bi 0.4 Sb 1.6 Te3 nanoparticles were ultrasonically dispersed in ethanol, then 0.016 g (1.0 wt%) of Na-LSX powder was added. The mixture was ultrasonically stirred for 1 h until uniformly dispersed, and then the solution was vacuum dried. The sample was removed, ground into powder, and placed in a graphite mold with an inner diameter of 10 mm for discharge plasma sintering at 420 °C for 5 min and 60 MPa to obtain Bi. 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite bulk material. The thermoelectric properties of the bulk material were tested after cutting and polishing, with the direction parallel to the sintering pressure.

[0036] Comparative Example 1

[0037] 0.6 g of disodium ethylenediaminetetraacetate was dissolved in a 200 mL hydrothermal reactor liner containing 120 mL of deionized water to form a uniform dispersion. Then, 0.75 g of BiCl3, 2.2 g of SbCl3, 2.7 g of Te powder, and 5 g of NaOH were added sequentially. Finally, the mixture was magnetically stirred for 15 min at room temperature, followed by the addition of 2 g of NaBH4. After stirring at room temperature for 1 h, the mixture was transferred to a stainless steel autoclave and heated in a 200 °C oven for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and the product was separated by high-speed centrifugation (11000 r / min, 3.5 min). The product was washed three times alternately by centrifugation with ultrapure water and anhydrous ethanol. The washed powder was then dried in a vacuum drying oven at 50 °C for 12 h. The p-type Bi... 0.4 Sb 1.6 Te3 nanopowder samples were ground into powder and then placed in a graphite mold with an inner diameter of 10 mm for discharge plasma sintering. The sintering temperature was 420℃, the holding time was 5 min, and the sintering pressure was 60 MPa, yielding pure Bi. 0.4 Sb 1.6 Te3 nanomaterial bulk. The thermoelectric properties of the bulk material were tested after cutting and polishing, with the direction parallel to the sintering pressure.

[0038] Figure 1 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The graph showing the relationship between conductivity (σ) and temperature (T) of Te3 / x wt% Na-LSX (x = 0, 0.5, and 1.0) samples reveals that conductivity decreases with increasing temperature, a typical characteristic of degenerate semiconductors. The introduction of Na-LSX reduces the conductivity of the nanocomposite material across the entire temperature range, a result of the reduced carrier concentration.

[0039] Figure 2 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The graph showing the Seebeck coefficient (S) versus temperature (T) for Te3 / x wt% Na-LSX samples (x = 0, 0.5, and 1.0) reveals that the Seebeck coefficient is positive in all cases, confirming its p-type conductivity. Within the range of 298–423 K, the Seebeck coefficient initially increases and then decreases with temperature, primarily due to the intrinsic excitation of charge carriers at high temperatures. 0.4 Sb 1.6 Te3 / 0.5wt% Na-LSX and Bi 0.4 Sb 1.6 Te3 / 1.0wt% Na-LSX composite sample relative to Bi 0.4 Sb 1.6Te3 significantly improves the Seebeck coefficient. When the Na-LSX composite content is 1.0 wt%, the Seebeck coefficient of the composite material reaches a maximum of 240.5 μV K at 373 K. -1 .

[0040] Figure 3 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 Power factor (S) of Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples 2 The graph showing the relationship between σ and temperature (T) reveals that the power factor of the composite material is significantly improved across the entire temperature range after the introduction of 0.5 wt% Na-LSX, reaching a maximum of 3.6 mW / m² at 298 K. -1 K -2 The power factor of the composite material decreased slightly after incorporating 1.0 wt% Na-LSX.

[0041] Figure 4 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 Total thermal conductivity (κ) of Te3 / x wt% Na-LSX (x = 0, 0.5 and 1.0) samples tot The graph showing the relationship between Na-LSX and temperature (T) shows that the introduction of Na-LSX significantly reduced the Bi content. 0.4 Sb 1.6 The overall thermal conductivity of Te3 is mainly due to the intrinsic low thermal conductivity and abundant sub-nanopores of Na-LSX, which enable effective phonon engineering.

[0042] Figure 5 Bi prepared for each embodiment and comparative example 0.4 Sb 1.6 The graph showing the relationship between the thermoelectric figure of merit (zT) and temperature (T) of Te3 / x wt% Na-LSX (x = 0, 0.5, and 1.0) samples shows that when the Na-LSX composite content is 0.5 wt%, Bi 0.4 Sb 1.6 Te3 / 0.5wt%Na-LSX achieved a peak zT value of 1.42 at 373 K, compared to Bi 0.4 Sb 1.6 The Te3 substrate improved by 16.4%.

Claims

1. A method for preparing Bi2Te3-based materials with high thermoelectric properties, characterized in that, Includes the following steps: Step 1: Disodium ethylenediaminetetraacetate (EDTA), BiCl3, SbCl3, Te powder, NaOH, and NaBH4 are mixed in water at a mass ratio of 0.5~0.8:0.7~0.8:2~2.4:2.5~3:4~6:1.5~3. The mixture is then subjected to a hydrothermal reaction at 180~220 °C. After the reaction is completed, the mixture is cooled to room temperature, centrifuged to remove impurities, vacuum dried, and ground to obtain p-type Bi. 0.4 Sb 1.6 Te3 nanopowder; Step 2, p-type Bi 0.4 Sb 1.6 Te3 nanoparticles were ultrasonically dispersed in ethanol, then X-type zeolite molecular sieve powder was added, and the mixture was ultrasonically stirred until uniformly dispersed. The mixture was then vacuum dried and ground to obtain Bi. 0.4 Sb 1.6 Te3 / Na-LSX composite nanopowder; Step 3, Bi 0.4 Sb 1.6 Te3 / Na-LSX composite nanopowder was subjected to discharge plasma sintering at 420±20 ℃ to obtain Bi 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite bulk.

2. The preparation method according to claim 1, characterized in that, In step 1, the mass-to-volume ratio of disodium ethylenediaminetetraacetate (EDTA) to water is 0.5-0.8 g: 80-140 mL.

3. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of disodium ethylenediaminetetraacetate, BiCl3, SbCl3, Te powder, NaOH and NaBH4 is 0.6:0.75:2.2:2.7:5:2, and the mass-volume ratio of disodium ethylenediaminetetraacetate and water is 0.6g:120mL.

4. The preparation method according to claim 1, characterized in that, In step 1, the hydrothermal reaction time is 10-15 hours.

5. The preparation method according to claim 1, characterized in that, In step 1, the centrifugation speed is 11000~12000 r / min and the centrifugation time is 3~5 min.

6. The preparation method according to claim 1, characterized in that, In step 1, the washing method is to first centrifuge with ultrapure water 3 times, and then centrifuge with anhydrous ethanol 3 times.

7. The preparation method according to claim 1, characterized in that, In step 1 or 2, the vacuum drying temperature is 40~60℃ and the drying time is 12~18 h.

8. The preparation method according to claim 1, characterized in that, In step 2, the mass of the X-type zeolite molecular sieve powder is Bi. 0.4 Sb 1.6 0.5~1.0 wt% of the total mass of Te3 / Na-LSX composite powder.

9. The preparation method according to claim 1, characterized in that, In step 3, the holding time is 5~15 min and the sintering pressure is 50~70 MPa.

10. Bi prepared by any one of claims 1 to 9 0.4 Sb 1.6 Te3 / Na-LSX nanocomposite material.

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