P-type bismuth telluride-based material and preparation method and application thereof

Abstract

The invention provides a p-type bismuth telluride-based material and a preparation method and application thereof, and belongs to the technical field of thermoelectric energy conversion materials. The p-type bismuth telluride-based material comprises a base material and a Bi element doped into crystal lattices of the base material; the base material comprises BiaSb1. 45Te3, and a is greater than or equal to 0.55 and less than or equal to 0.58. The thermoelectric performance and the mechanical performance of the material are improved by introducing the Bi element (electronegativity 2.02) which has a small electronegativity difference with the Te element (electronegativity 2.1), and the small electronegativity difference enables the Bi element in a matrix to have higher solubility, so that the carrier concentration (the doping of the Bi element mainly optimizes the carrier concentration) and the density of the material are improved; and the increase of the carrier concentration can improve the conductivity, so that the thermoelectric performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoelectric energy conversion materials, and specifically relates to a p-type bismuth telluride-based material and a preparation method and application thereof. Background Art

[0002] Thermoelectric materials are functional materials that convert heat energy directly into electrical energy. Thermoelectric materials have become an indispensable part of industry due to their characteristics of no mechanical rotating parts, long life, and no pollution. In recent years, the sustainable development strategy has been adhered to and implemented, and thermoelectric materials have also been widely used in aerospace, industrial waste heat, and automobile exhaust waste heat. Its thermoelectric performance mainly depends on the thermoelectric figure of merit ZT, ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity. The larger the ZT value, the better the thermoelectric performance of the material.

[0003] Currently, the only commercial thermoelectric material is bismuth telluride (Bi2Te3). Industrial production of bismuth telluride materials usually adopts the method of melt combined with ball milling and sintering to prepare materials. The materials prepared by this method have good preferred orientation and usually have good thermoelectric properties. The ZT value of p-type bismuth telluride-based materials is ~1.1. At the same time, this method has a long cycle. However, the good preferred orientation makes the layered bismuth telluride materials prone to interlayer cleavage during service, and the mechanical properties are poor. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a p-type bismuth telluride-based material and a preparation method and application thereof. The p-type bismuth telluride-based material provided by the present invention has excellent mechanical properties and thermoelectric properties.

[0005] In order to achieve the above object, the present invention provides the following scheme:

[0006] The present invention provides a p-type bismuth telluride-based material, comprising a base material and a Bi element doped into a lattice of the base material; the base material comprises Bi a Sb 1.45 Te3, wherein 0.55≤a≤0.58.

[0007] Preferably, the doping amount of the Bi element is ≤4wt%.

[0008] Preferably, the p-type bismuth telluride-based material has a density of 95.1-99.5%, a thermoelectric figure of merit of 1.15-1.45, a Vickers hardness of 0.91-1.1 GPa, a compressive strength of 81-94.6 MPa, and a carrier concentration of (1-13.2)×10 19 cm -1 .

[0009] The present invention provides a method for preparing the p-type bismuth telluride-based material according to the above scheme, comprising the following steps:

[0010] Under the protection of inert gas, a Bi single substance, a Sb single substance and a Te single substance are ball-milled to obtain a p-type bismuth telluride-based powder; the rotation speed of the ball mill is 800-1500 rpm; the molar ratio of the Bi single substance to the Sb single substance is (0.55-0.58):1.45; the molar ratio of the Sb single substance to the Te single substance is 1.45:3;

[0011] The p-type bismuth telluride-based powder is hot-pressed and sintered to obtain the p-type bismuth telluride-based material.

[0012] Preferably, the ball milling time is 5 to 8 hours, and the ball-to-material ratio is (1 to 5):1.

[0013] Preferably, the particle size of the p-type bismuth telluride-based powder is 0.1-10 μm.

[0014] Preferably, the hot pressing sintering is performed under a pressure of 60 to 90 MPa, a temperature of 600 to 850° C., and a heat and pressure holding time of 2 to 10 min.

[0015] Preferably, the hot pressing sintering is vacuum hot pressing sintering, and the vacuum degree is ≤1×10 -1 ~1Pa.

[0016] Preferably, the inert gas comprises argon.

[0017] The present invention provides the use of the p-type bismuth telluride-based material described in the above scheme or the p-type bismuth telluride-based material prepared by the preparation method described in the above scheme in a thermoelectric device.

[0018] The present invention provides a p-type bismuth telluride-based material, comprising a base material and a Bi element doped into a lattice of the base material; the base material comprises Bi a Sb 1.45 Te3, wherein 0.55≤a≤0.58. The present invention improves the thermoelectric and mechanical properties of the material by introducing a Bi element (electronegativity 2.02) having a smaller electronegativity difference with the Te element (electronegativity 2.1). The small electronegativity difference can make the Bi element in the matrix have a greater solubility, thereby improving the carrier concentration (Bi element doping mainly optimizes the carrier concentration) and density of the material. The increase in carrier concentration will increase the conductivity, thereby improving the thermoelectric performance.

[0019] The p-type bismuth telluride-based thermoelectric material prepared by the present invention has excellent thermoelectric properties and high electrical properties, and the conductivity σ at room temperature is 12×10 4S / m, the Seebeck coefficient S is 180.1μV / k. The ball milling method and the introduction of additional Bi elements are conducive to the generation of a large number of point defects and line defects. These defects effectively scatter phonons, thereby obtaining extremely low lattice thermal conductivity. This decoupling method allows the material to achieve a final thermoelectric figure of merit of 1.45, and the average ZT in the temperature range of 300-500K can reach 1.24.

[0020] The p-type thermoelectric material prepared by the present invention has good mechanical properties. Ball milling and hot pressing sintering are conducive to reducing the particle size. The introduction of additional Bi elements can effectively increase the density. This optimization increases the compressive strength and Vickers hardness of the material. In addition, hot pressing sintering can make the grains grow more completely, improve the crystallinity, and thus improve the mechanical properties.

[0021] The thermoelectric material prepared by the present invention realizes the combination of excellent mechanical properties and thermoelectric properties, improves the problem of extremely high scrap rate of commercial bismuth telluride materials due to poor mechanical properties, and greatly shortens the preparation process by optimizing ball milling and hot pressing processes. This method has great application potential in subsequent power generation, refrigeration and other fields.

[0022] The method provided by the present invention enables the thermoelectric material to have a wider operating temperature range, and at the same time has better thermoelectric performance and mechanical properties, and can ensure a better yield rate when preparing thermoelectric devices.

[0023] Furthermore, the present invention shortens the ball milling and hot pressing sintering time as much as possible to meet the needs of industrial production. The preparation method provided by the present invention is simple to operate, convenient to prepare, and has good repeatability. It can prepare p-type bismuth telluride-based materials in large quantities, and the required equipment is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 The XRD patterns (left) and the local magnified images (right) of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1;

[0026] Figure 2 The graphs are the temperature dependence of the conductivity of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1;

[0027] Figure 3The graphs are the dependence of the Seebeck coefficient of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1 on temperature;

[0028] Figure 4 The graphs showing the dependence of carrier concentration on temperature of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1;

[0029] Figure 5 The graphs are the dependence of the power factor of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1 on the temperature;

[0030] Figure 6 The graphs are the dependence of the thermal conductivity of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1 on the temperature;

[0031] Figure 7 The graphs are the temperature dependence of the thermoelectric figure of merit of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1;

[0032] Figure 8 The Vickers hardness spectrum of the p-type bismuth telluride-based thermoelectric material prepared in Examples 1 to 5 of the present invention and Comparative Example 1;

[0033] Fig. 9 The compressive strength spectrum of the p-type bismuth telluride-based thermoelectric material prepared in Example 2, Example 5 and Comparative Example 1 of the present invention;

[0034] Fig.10 The p-type bismuth telluride-based thermoelectric material Bi prepared in Example 2 of the present invention 0.55 Sb 1.45 Transmission test spectrum of Te3+2.5wt%Bi. DETAILED DESCRIPTION

[0035] The present invention provides a p-type bismuth telluride-based material, comprising a base material and a Bi element doped into a lattice of the base material; the base material comprises Bi a Sb 1.45 Te3, wherein 0.55≤a≤0.58.

[0036] Unless otherwise specified, the raw materials and equipment used in the present invention are commercially available products.

[0037] In the present invention, the doping amount of the Bi element (i.e., the mass ratio of the Bi element to the matrix material) is ≤4wt%. In an embodiment of the present invention, it can be 1wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt% or 4wt%.

[0038] The present invention improves the thermoelectric and mechanical properties of the material by introducing the Bi element (electronegativity 2.02) with a smaller electronegativity difference from the Te element (electronegativity 2.1). The small electronegativity difference can make the Bi element in the matrix have a greater solubility, thereby improving the carrier concentration (Bi element doping mainly optimizes the carrier concentration) and density of the material. The increase in carrier concentration will increase the electrical conductivity, thereby improving the thermoelectric performance.

[0039] In the present invention, the p-type bismuth telluride-based material has a density of 95.1-99.5%, a thermoelectric figure of merit of 1.15-1.45, a Vickers hardness of 0.91-1.1 GPa, a compressive strength of 81-94.6 MPa, and a carrier concentration of (1-13.2)×10 19 cm -1 .

[0040] The present invention provides a method for preparing the p-type bismuth telluride-based material according to the above scheme, comprising the following steps:

[0041] Under the protection of inert gas, a Bi single substance, a Sb single substance and a Te single substance are ball-milled to obtain a p-type bismuth telluride-based powder; the rotation speed of the ball mill is 800-1500 rpm; the molar ratio of the Bi single substance to the Sb single substance is (0.55-0.58):1.45; the molar ratio of the Sb single substance to the Te single substance is 1.45:3;

[0042] The p-type bismuth telluride-based powder is hot-pressed and sintered to obtain the p-type bismuth telluride-based material.

[0043] The present invention ball-mills Bi, Sb and Te under inert gas protection to obtain p-type bismuth telluride-based powder; the rotation speed of the ball mill is 800-1500 rpm; the molar ratio of the Bi and Sb is (0.55-0.58):1.45; the molar ratio of the Sb and Te is 1.45:3.

[0044] The invention limits the rotation speed of the ball mill to 800-1500 rpm. The high rotation speed can make the collision between the powder and the stainless steel ball more intense during the ball milling process, so that the particle size of the powder is smaller. The finer the powder, the more complete the reaction, and the reaction time can also be shortened.

[0045] In the present invention, the inert gas preferably includes argon. The present invention can prevent oxidation of materials through inert gas protection. In the present invention, the purity of the Bi single substance, Sb single substance and Te single substance is preferably greater than 99.99%.

[0046] In the present invention, the ball milling time is preferably 5 to 8 hours, and in the embodiments of the present invention, it can be 5 hours, 6 hours, 7 hours or 8 hours; the ball-to-material ratio of the ball milling is preferably (1 to 5): 1, and in the embodiments of the present invention, it can be 1: 1, 2: 1, 2.5: 1, 3: 1, 4: 1 or 5: 1. In the present invention, the ball milling is preferably carried out in a stainless steel ball milling tank.

[0047] After the ball milling is completed, the present invention preferably cools the obtained powder, and then takes the obtained powder out of the ball milling jar under the protection of inert gas.

[0048] In the present invention, the particle size of the p-type bismuth telluride-based powder is preferably 0.1-10 μm, and in the embodiment of the present invention, it can be 1 μm, 3 μm, 5 μm, 8 μm or 10 μm.

[0049] In the process of ball milling, Bi, Sb and Te generate Bi 0.55 Sb 1.45 Te3, and then some unreacted Bi is doped into Bi 0.55 Sb 1.45 In the Te3 lattice, specifically, it occupies the Te site.

[0050] The p-type bismuth telluride-based thermoelectric material prepared by the present invention has excellent thermoelectric properties and high electrical properties, and the conductivity σ at room temperature is 12×10 4 S / m, the Seebeck coefficient S is 180.1μV / k. At the same time, the ball milling method and the introduction of additional Bi elements are conducive to the generation of a large number of point defects and line defects. These defects effectively scatter phonons, thereby obtaining extremely low lattice thermal conductivity. This decoupling method allows the material to achieve a final thermoelectric figure of merit of 1.45, and the average ZT in the temperature range of 300-500K can reach 1.24.

[0051] After obtaining the p-type bismuth telluride-based powder, the present invention performs hot pressing and sintering on the p-type bismuth telluride-based powder to obtain the p-type bismuth telluride-based material.

[0052] In the present invention, the p-type bismuth telluride-based powder is preferably placed in a mold under the protection of an inert gas and subjected to hot pressing and sintering.

[0053] In the present invention, the pressure of the hot pressing sintering is preferably 60-90 MPa, and in the embodiment of the present invention, it can be 60 MPa, 70 MPa, 80 MPa or 90 MPa; the temperature of the hot pressing sintering is 600-850°C, and in the embodiment of the present invention, it can be 600°C, 650°C, 700°C, 750°C or 800°C; the heat preservation and pressure holding time of the hot pressing sintering is preferably 2-10 min, and in the embodiment of the present invention, it can be 2 min, 5 min or 10 min; the hot pressing sintering is preferably vacuum hot pressing sintering, and the vacuum degree is preferably 1×10 -1 ~1pa.

[0054] The p-type thermoelectric material prepared by the present invention has good mechanical properties. Ball milling and hot pressing sintering are conducive to reducing the particle size. The introduction of additional Bi elements can effectively increase the density. This optimization increases the compressive strength and Vickers hardness of the material. In addition, hot pressing sintering can make the grains grow more completely, improve the crystallinity, and thus improve the mechanical properties.

[0055] The thermoelectric material prepared by the present invention realizes the combination of excellent mechanical properties and thermoelectric properties, improves the problem of extremely high scrap rate of commercial bismuth telluride materials due to poor mechanical properties, and greatly shortens the preparation process by optimizing ball milling and hot pressing processes. This method has great application potential in subsequent power generation, refrigeration and other fields.

[0056] The method provided by the present invention enables the thermoelectric material to have a wider operating temperature range, and at the same time has better thermoelectric performance and mechanical properties, and can ensure a better yield rate when preparing thermoelectric devices.

[0057] The present invention shortens the ball milling and hot pressing sintering time as much as possible to meet the needs of industrial production. The preparation method provided by the present invention is simple to operate, convenient to prepare, and has good repeatability. It can prepare p-type bismuth telluride-based materials in large quantities, and the required equipment is simple.

[0058] The present invention provides the application of the above-mentioned p-type bismuth telluride-based material in a thermoelectric device. In the present invention, it can be specifically applied to a car refrigerator or a campfire charger.

[0059] In order to further illustrate the present invention, a p-type bismuth telluride-based material provided by the present invention and its preparation method and application are described in detail below in combination with the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] A method for preparing a p-type bismuth telluride-based thermoelectric material is as follows:

[0062] Bi 0.55 Sb 1.45Preparation of Te3+2wt%Bi powder: Under an inert gas Ar atmosphere, 1.7387g Bi element, 2.61883g Sb element and 5.6771g Te element were placed in a stainless steel ball mill with 6 balls (25g balls in total), and the mixture was put into a ball mill for 8h. The ball mill speed was set to 1200rpm and the power was 110W to obtain powder. The powder was cooled and then taken out of the glove box to obtain p-type bismuth telluride-based powder.

[0063] Bi 0.55 Sb 1.45 Preparation of Te3 bulk material: The p-type bismuth telluride-based powder was placed in a graphite mold with a diameter of 12.7 mm in a glove box. After ensuring that the upper and lower surfaces were flat, it was placed in a hot press for hot pressing and sintering at a pressure of 80 MPa, a temperature of 800 °C, a heat and pressure holding time of 5 min, and a vacuum degree of 1×10 -1 ~1pa, and after cooling, the p-type bismuth telluride-based thermoelectric material is obtained.

[0064] Example 2

[0065] Bi 0.55 Sb 1.45 Preparation of Te3+2.5wt%Bi: The preparation method is the same as that in Example 1, except that the added amount of Bi element is 1.7472g.

[0066] Example 3

[0067] Bi 0.55 Sb 1.45 Preparation of Te3+3wt%Bi: The preparation method is the same as that in Example 1, except that the added amount of Bi element is 1.7557g.

[0068] Example 4

[0069] Bi 0.55 Sb 1.45 Preparation of Te3+3.5wt%Bi: The preparation method is the same as that in Example 1, except that the added amount of Bi element is 1.7642g.

[0070] Example 5

[0071] Bi 0.55 Sb 1.45 Preparation of Te3+4wt%Bi: The preparation method is the same as that in Example 1, except that the amount of Bi element added is 1.7728g.

[0072] Comparative Example 1

[0073] Bi 0.55 Sb 1.45Preparation of Te3: The preparation method is the same as that in Example 1, except that the amount of Bi element added is 1.7046 g.

[0074] Performance testing and structural characterization

[0075] Figure 1 The XRD patterns (left) and the local magnified images (right) of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1 are shown. Figure 1 As shown in the middle left figure, the diffraction peaks of all samples correspond to the PDF cards, indicating a high-purity phase. Figure 1 The middle right figure shows that Bi enters the lattice, and the main XRD peak moves to a lower angle, indicating that the lattice is enlarged. It can be seen that the element Bi is doped into the matrix material Bi. 0.55 Sb 1.45 In Te3.

[0076] Figure 2 The graphs are the temperature dependence of the conductivity of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1. Figure 2 As shown in Figure 2, at room temperature 300K, the conductivity increases with the increase of the additional Bi content x, and when x = 0, σ = 4.1 × 10 4 S / m, when x=2,σ=9.6×10 4 S / m, when x = 2.5, σ = 12 × 10 4 S / m, when x=3,σ=14.5×10 4 S / m, when x = 3.5, σ = 16.5 × 10 4 S / m, when x=4,σ=16.8×10 4 S / m, indicating that the p-type bismuth telluride-based thermoelectric material prepared by the present invention has a high conductivity. When the Bi content increases to x=3.5, the conductivity does not increase significantly, indicating that it has reached saturation.

[0077] Figure 3 The temperature dependence of the Seebeck coefficient of the p-type bismuth telluride-based thermoelectric material prepared in Examples 1 to 5 of the present invention and Comparative Example 1 is shown in FIG. Figure 3As shown in the figure, at room temperature 300K, the Seebeck coefficient S decreases with the increase of the additional Bi content x. When x = 0, S = 265.8μV / k, when x = 2, S = 202.9μV / k, when x = 2.5, S = 180.1μV / k, when x = 3, S = 151.2μV / k, when x = 3.5, S = 147.6μV / k, and when x = 4, S = 131.4μV / k. Since the conductivity and the Seebeck coefficient are mutually coupled, the increase in conductivity will inevitably affect the loss of the Seebeck coefficient. However, although the Seebeck coefficient loses a lot at room temperature, with the increase of additional Bi elements, the peak of the Seebeck coefficient gradually moves to high temperature, indicating that the intrinsic excitation is suppressed.

[0078] Figure 4 The graphs are the dependence of the carrier concentration on temperature of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1. Figure 4 As shown in Figure 2, at room temperature 300K, the carrier concentration increases with the increase of the additional Bi content x. When x = 0, n H =(1~1.3)×10 19 cm -1 , when x = 2, n H =(4.2~4.5)×10 19 cm -1 , when x = 2.5, n H =(6~6.3)×10 19 cm -1 (The optimal carrier concentration of bismuth telluride material is usually 5×10 19 cm -1 ), when x=3, n H =(7.8~8.1)×10 19 cm -1 , when x = 3.5 H =(11~11.3)×10 19 cm -1 , when x=4, n H =(13~13.2)×10 19 cm -1 Since the conductivity is positively correlated with the carrier concentration, the increase in carrier concentration will inevitably increase the conductivity. This also corresponds to Figure 2 The conductivity gradually increases with the increase of additional Bi content.

[0079] Figure 5 The power factor of the p-type bismuth telluride-based thermoelectric material prepared in Examples 1 to 5 of the present invention and Comparative Example 1 depends on the temperature. Figure 5As shown, at room temperature of 300K, the power factor PF increases continuously with the increase of Bi content, when x=0, PF=28-30μW / cm*K, when x=2, PF=36-38μW / cm*K, when x=2.5, PF=37-39μW / cm*K, when x=3, PF=33-35μW / cm*K, when x=3.5, PF=35-37μW / cm*K, when x=4, PF=27-29μW / cm*K. With the increase of the additional Bi content x, PF is higher than that of the base material x=0 in the entire temperature range, and the more the additional Bi content, the more the peak of the power factor PF moves toward the higher temperature direction. It shows that the thermoelectric material obtained by the method provided by the present invention has a wide operating temperature range.

[0080] Figure 6 The graphs are the temperature dependence of the thermal conductivity of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1. Figure 6 As shown, at room temperature 300K, the thermal conductivity κ (referring to the total thermal conductivity) increases first and then decreases with the increase of the additional Bi content x. When x = 0, κ = 0.78 W / m*K, when x = 2, κ = 0.94 W / m*K, when x = 2.5, κ = 0.96 W / m*K, when x = 3, κ = 1.26 W / m*K, when x = 3.5, κ = 1.48 W / m*K, and when x = 4, κ = 1.51 W / m*K. Thermal conductivity mainly includes electronic thermal conductivity, lattice thermal conductivity and bipolar thermal conductivity. The increase in thermal conductivity with the increase of Bi content is mainly attributed to the increase in electronic thermal conductivity, because electronic thermal conductivity is mainly proportional to electrical conductivity, and the continuous increase in electrical conductivity has a huge contribution to thermal conductivity.

[0081] Figure 7 The temperature dependence of the thermoelectric figure of merit of the p-type bismuth telluride-based thermoelectric materials prepared in Examples 1 to 5 of the present invention and Comparative Example 1 is shown in the figure. The thermoelectric figure of merit ZT is calculated based on the test results of the above conductivity, Seebeck coefficient and thermal conductivity. The ZT value moves toward the high temperature end with the increase of the additional Bi content until the highest ZT value is no longer within the test temperature range when x=4, and shows a monotonically increasing trend in the entire temperature range. ZT is obtained at a temperature of 360K when x=2.5. max =1.45. This is relative to the ZT of the sample x=0 without the additional introduction of Bi content. max =1.1, which is 32% higher than that of the average value ZT at x = 2.5 in the whole temperature range (300-480K). ave =1.24 compared to ZT when x=0 ave =0.64, which is close to 100%, indicating that the additional Bi element effectively broadens the application range of the material. The specific values ​​are listed in Table 1.

[0082] Figure 8 The Vickers hardness spectrum of the p-type bismuth telluride-based thermoelectric material prepared in Examples 1 to 5 of the present invention and Comparative Example 1; Figure 8 As shown, the Vickers hardness increases first and then decreases with the increase of Bi content. Ten tests were conducted, and when x=0, Hv=0.85~0.95GPa, when x=2, Hv=0.91~1.02GPa, when x=2.5, Hv=0.94~0.99GPa, when x=3, Hv=1.05~1.1GPa, when x=3.5, Hv=1.08~1.18GPa, and when x=4, Hv=1.01~1.08GPa. The test average values ​​are listed in Table 1. The increase in Vickers hardness is mainly attributed to the fact that the introduction of Bi helps to increase the density.

[0083] Fig. 9 The compressive strength spectrum of the p-type bismuth telluride-based thermoelectric material prepared in Example 2, Example 5 and Comparative Example 1 of the present invention is shown in FIG. Fig. 9 As shown, the compressive strength gradually decreases with the increase of Bi content. Three tests were conducted, and the compressive strength was 105-110 MPa when x=0, 90-100 MPa when x=2.5, and 80-85 MPa when x=4. The average values ​​are listed in Table 1. The increase in Vickers hardness is mainly attributed to the increase in density caused by the introduction of Bi, and the density values ​​are listed in Table 1.

[0084] Table 1 Performance test results of materials obtained in Examples and Comparative Examples

[0085]

[0086] Fig.10 The p-type bismuth telluride-based thermoelectric material Bi prepared in Example 2 of the present invention 0.55 Sb 1.45 Transmission test spectrum of Te3+2.5wt%Bi. Fig.10 It can be seen that the three elements are distributed relatively evenly, and a large number of pores are observed in the material.

[0087] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A p-type bismuth telluride-based material, comprising a base material and a Bi element doped into a lattice of the base material; the base material comprises Bi a Sb 1.45 Te3, among which 0.55≤a≤0.58。 2. The p-type bismuth telluride-based material according to claim 1, characterized in that: The doping amount of the Bi element is ≤4wt%.

3. The p-type bismuth telluride-based material according to claim 1 or 2, characterized in that: The p-type bismuth telluride-based material has a density of 95.1-99.5%, a thermoelectric figure of merit of 1.15-1.45, a Vickers hardness of 0.91-1.1 GPa, a compressive strength of 81-94.6 MPa, and a carrier concentration of (1-13.2)×10 19 cm -1 .

4. The method for preparing the p-type bismuth telluride-based material according to any one of claims 1 to 3, comprising the following steps: Under the protection of inert gas, a Bi single substance, a Sb single substance and a Te single substance are ball-milled to obtain a p-type bismuth telluride-based powder; the rotation speed of the ball mill is 800-1500 rpm; the molar ratio of the Bi single substance to the Sb single substance is (0.55-0.58):1.45; the molar ratio of the Sb single substance to the Te single substance is 1.45:3; The p-type bismuth telluride-based powder is hot-pressed and sintered to obtain the p-type bismuth telluride-based material.

5. The preparation method according to claim 4, characterized in that: The ball milling time is 5 to 8 hours, and the ball-to-material ratio is (1 to 5):

1.

6. The preparation method according to claim 4 or 5, characterized in that: The particle size of the p-type bismuth telluride-based powder is 0.1-10 μm.

7. The preparation method according to claim 4, characterized in that: The hot pressing sintering pressure is 60-90 MPa, the temperature is 600-850° C., and the heat preservation and pressure holding time is 2-10 minutes.

8. The preparation method according to claim 4 or 7, characterized in that: The hot pressing sintering is vacuum hot pressing sintering, and the vacuum degree is ≤1×10 -1 ~1Pa.

9. The preparation method according to claim 4, characterized in that: The inert gas includes argon.

10. Use of the p-type bismuth telluride-based material according to any one of claims 1 to 3 or the p-type bismuth telluride-based material prepared by the preparation method according to any one of claims 4 to 9 in thermoelectric devices.

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