Antimony telluride-based thermoelectric material, thermoelectric module and preparation method and application thereof

Abstract

The invention provides an antimony telluride-based thermoelectric material, a thermoelectric module and a preparation method and application thereof, and relates to the technical field of thermoelectric materials. The antimony telluride-based thermoelectric material is a P-type homogeneous double-section thermoelectric material, can greatly reduce high-temperature-low-temperature interface contact resistance, low thermal expansion coefficient difference and low interface element diffusion caused by the same structure, and overcomes the problem of poor stability caused by mismatching of thermal expansion coefficients of different thermoelectric materials; through the co-doping of Cd and S, the band gap of the thermoelectric material in a high-temperature section (more than 500K) is expanded, the introduction of high-density twin boundaries and dislocation is promoted, the bipolar effect is inhibited, the thermoelectric conversion efficiency and mechanical strength of the thermoelectric material are improved, and the prepared antimony telluride-based thermoelectric material has excellent mechanical properties and thermoelectric properties.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, and in particular to an antimony telluride-based thermoelectric material, a thermoelectric module, and a preparation method and application thereof. Background Art

[0002] Modern industry consumes a large amount of energy, and more than 60% of the energy is lost in the form of waste heat. High-temperature waste heat is easy to recycle and reuse, but the recovery of low-grade waste heat (<650 K), which accounts for more than 50% of the total waste heat, faces many challenges. The energy conversion efficiency of thermoelectric generators used for waste heat recovery is mainly determined by the figure of merit (ZT value) of the thermoelectric material, ZT = σS²T / κtot, where σ, S, T, and κtot are electrical conductivity, Seebeck coefficient, absolute temperature, and total thermal conductivity, respectively. Obviously, it is more challenging to achieve high ZT and high energy conversion efficiency at low temperatures.

[0003] High-performance thermoelectric materials for low-grade waste heat recovery (<650 K) have long been limited to Bi2Te3 materials, but the typical energy conversion efficiency of thermoelectric generators based on Bi2Te3 materials is only ~7% or lower, and is only suitable for operation below 500 K. Therefore, how to improve the energy conversion efficiency of thermoelectric generators and broaden their operating temperature range is an urgent problem to be solved in the field of low-grade waste heat recovery.

[0004] In order to improve the energy conversion efficiency of thermoelectric generators and broaden their operating temperature range, segmented thermoelectric generator structures and Bi2Te3's analogue Sb2Te3 are currently used. However, in segmented thermoelectric generators, due to the mismatch in thermal expansion coefficients between different thermoelectric materials, it is difficult for thermoelectric power generation modules to achieve high operating stability; and Sb2Te3 materials not only have a low ZT value, but also their mechanical strength decreases under high temperature conditions. Therefore, how to make thermoelectric materials have excellent thermoelectric performance, operating stability and mechanical strength is the main challenge facing the field of thermoelectric materials. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an antimony telluride-based thermoelectric material, a thermoelectric module, and a preparation method and application thereof. The antimony telluride-based thermoelectric material and the thermoelectric module have excellent thermoelectric conversion efficiency, good operating stability and excellent mechanical properties.

[0006] The specific technical scheme of the present invention is: In a first aspect, the present invention provides an antimony telluride-based thermoelectric material, wherein the antimony telluride-based thermoelectric material is a P-type homogeneous double-stage thermoelectric material, which sequentially comprises a first-stage material, an intermediate metal bonding layer, and a second-stage material; The first stage material is selected from at least one of the compounds shown in Formula I: Cd x Sb 2-x Te 3-y S y Formula I, Among them, 0<x≤1.0, 0≤y≤1.0; The second stage material is selected from at least one of the compounds shown in Formula II: Bi z Sb 2-z Te3 formula II, Among them, 0<z≤1.0.

[0007] The present invention provides an antimony telluride-based thermoelectric material, which is a P-type homogeneous double-stage thermoelectric material, wherein the main components of the compounds in the first-stage material and the second-stage material are both antimony telluride, and the first-stage material and the second-stage material having the same main components are connected together through a metal bonding layer to form a homogeneous double-stage material, thereby overcoming the problem of poor stability caused by the mismatch of thermal expansion coefficients between different thermoelectric materials; the first-stage material is a thermoelectric material suitable for the high-temperature stage (above 500K), and Cd is further selected as an electron acceptor to be doped in the antimony telluride to suppress the formation energy of antisite defects, thereby controlling the increase of carrier concentration and expanding the band gap, and promoting the introduction of high-density twin boundaries and dislocations, which is helpful to suppress the bipolar effect and improve the thermoelectric conversion efficiency of the high-temperature stage, thereby achieving simultaneous improvement of the thermoelectric conversion efficiency and mechanical properties of the thermoelectric material; at the same time, the second-stage material is a thermoelectric material suitable for the low-temperature stage (below 500K), which combines antimony telluride and bismuth telluride, and while matching the performance of the first-stage material, it also ensures the high thermoelectric conversion efficiency of the low-temperature stage.

[0008] In a possible implementation, the material of the intermediate metal bonding layer includes metal nickel. Using metal nickel as the material of the intermediate metal bonding layer can provide better adhesion and better charge transfer performance.

[0009] In a possible implementation, the thickness of the intermediate metal bonding layer is 10-50 μm. When the thickness of the intermediate metal bonding layer is 10-50 μm, sufficient bonding force is provided while preventing the intermediate metal bonding layer from being too thick to reduce the thermoelectric conversion efficiency.

[0010] In a second aspect, the present invention also provides a method for preparing the antimony telluride-based thermoelectric material, comprising the following steps: S1. Weighing a first mixed raw material including antimony, tellurium, cadmium and sulfur according to a stoichiometric ratio, and melting and quenching the first mixed raw material to obtain a first-stage crystal material; Weighing a second mixed raw material including antimony, tellurium and bismuth according to a stoichiometric ratio, and melting and quenching the second mixed raw material to obtain a second-stage crystal material; S2, the first-stage crystal material and the second-stage crystal material in step S1 are respectively subjected to grinding treatment to obtain first-stage material powder and second-stage material powder respectively; S3, the first-stage material powder and the second-stage material powder and the bonding metal powder in step S2 are sequentially loaded into a mold in the order of second-stage material powder-bonding metal powder-first-stage material powder, and a sintered block is formed through a one-step sintering treatment to obtain an antimony telluride-based thermoelectric material.

[0011] The method for preparing antimony telluride-based thermoelectric materials provided by the present invention first obtains material powder by smelting, quenching and grinding, and then adopts a one-step sintering method to sinter the first-stage material powder and the second-stage material powder into a homogeneous two-stage thermoelectric material by stacking sintering technology, which can greatly reduce the high-temperature-low-temperature interface contact resistance. Due to the low thermal expansion coefficient difference and low interface element diffusion brought by the same structure, the thermoelectric material will hardly fail and decay during long-term service. Therefore, long-term cyclic service can be maintained while ensuring thermoelectric performance. At the same time, in the one-step sintering process, high-density twins and high-density microscopic dislocations are induced to form, so that the prepared antimony telluride-based thermoelectric material has both high mechanical strength and excellent thermoelectric performance.

[0012] In a possible implementation manner, the smelting device in step S1 is a box furnace or a swing smelting furnace.

[0013] In a possible implementation manner, the vacuum degree of the smelting in step S1 is less than 10 Pa, the smelting temperature is 700-1000° C., and the smelting time is 60-480 min.

[0014] In a possible implementation, the particle size of the first-stage material powder and the second-stage material powder in step S2 is 1-50 μm. By controlling the particle size of the first-stage material powder and the second-stage material powder within the above range, it is beneficial to improve the mechanical properties and stability of antimony telluride-based thermoelectric materials.

[0015] In a possible implementation manner, the one-step sintering process in step S3 adopts vacuum hot pressing sintering or plasma spark sintering.

[0016] In a possible implementation, the temperature of the one-step sintering process in step S3 is 400-600°C, the pressure of the one-step sintering process is 40-80 MPa, and the time of the one-step sintering process is 5-30 min. By controlling the process parameters of the one-step sintering within the above range, the antimony telluride-based thermoelectric material can have better thermoelectric performance.

[0017] In a third aspect, the present invention further provides a thermoelectric module, comprising a P-type thermoelectric material and an N-type thermoelectric material, wherein the P-type thermoelectric material is connected to the N-type thermoelectric material via a conductive metal, the P-type thermoelectric material is the antimony telluride-based thermoelectric material, and the N-type thermoelectric material is a bismuth telluride material.

[0018] In a fourth aspect, the present invention also provides a method for preparing the above-mentioned thermoelectric module, comprising the following steps: T1, the antimony telluride-based thermoelectric material is cut to obtain an antimony telluride-based sheet; T2, the antimony telluride-based sheet described in step T1 is electroplated and then cut to obtain antimony telluride-based particles; T3. The antimony telluride-based particles and bismuth telluride materials described in step T2 are assembled and welded with conductive metal to obtain a thermoelectric module.

[0019] In a possible implementation manner, the cutting process in step T1 adopts multi-wire cutting.

[0020] In a possible implementation manner, the electroplating treatment in step T2 is chemical plating.

[0021] In a possible implementation manner, the cutting in step T2 is performed by wire electric discharge cutting.

[0022] In a possible implementation manner, the antimony telluride-based particles in step T2 have a length of 2-5 mm, a width of 2-5 mm, and a height of 8-14 mm.

[0023] In a fifth aspect, the present invention also provides the application of the above antimony telluride-based thermoelectric material in the field of waste heat recovery.

[0024] Based on the common knowledge in this field, the above-mentioned implementation modes can be combined arbitrarily.

[0025] The reagents and raw materials used in the present invention are commercially available.

[0026] The positive and progressive effects of the present invention are: The antimony telluride-based thermoelectric material provided by the present invention achieves an excellent balance among the mechanical strength, stability and thermoelectric performance of the antimony telluride material through element doping and a one-step sintering process. By using the antimony telluride-based thermoelectric material, an antimony telluride-based homogeneous double-stage thermoelectric module having high thermoelectric conversion efficiency, good stability and high mechanical properties is further obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the preparation process of antimony telluride-based thermoelectric materials and thermoelectric modules in Example 1.

[0028] Figure 2The figure of merit of the thermoelectric modules prepared in Examples 1-3 and Comparative Examples 1-5 varies with temperature.

[0029] Figure 3 The data graph of the thermoelectric conversion efficiency obtained in Examples 1-3 and Comparative Examples 1-5 changing with temperature. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0031] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0032] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0033] Example 1

[0034] This embodiment provides an antimony telluride-based thermoelectric material and a thermoelectric module. The antimony telluride-based thermoelectric material is a P-type homogeneous double-stage thermoelectric material, which includes Cd 0.04 Sb 1.96 Te 2.94 S 0.06 High temperature thermoelectric materials, metal Ni layer and Bi 0.2 Sb 1.8 Te3 low-temperature thermoelectric material, the thickness of the metal Ni layer is 25 μm. The thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material. The P-type thermoelectric material is an antimony telluride-based thermoelectric material in this embodiment, and the N-type thermoelectric material is a bismuth telluride material. The P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0035] It is prepared by the following steps: (1) Weighing high-purity cadmium powder, high-purity antimony particles, high-purity tellurium bulk and high-purity sulfur powder according to a stoichiometric ratio and mixing them to obtain a first mixed raw material; weighing high-purity antimony particles, high-purity tellurium bulk and high-purity bismuth particles according to a stoichiometric ratio and mixing them to obtain a second mixed raw material; smelting the first mixed raw material and the second mixed raw material in a box furnace respectively, at a vacuum degree of 5 Pa and a temperature of 1000 ° C for 90 min, and obtaining a first-stage crystal material and a second-stage crystal material after the smelting is completed; (2) grinding the first-stage crystal material and the second-stage crystal material in step (1) respectively by ball milling, and then sieving to obtain first-stage material powder and second-stage material powder with a particle size in the range of 1-50 μm; (3) The first-stage material powder and the second-stage material powder and the nickel powder in step (2) are sequentially loaded into a Φ20 mm graphite mold in the order of the second-stage material powder-nickel powder-first-stage material powder, and a plasma spark sintering furnace is used to perform a one-step sintering treatment at a temperature of 520 °C and a pressure of 60 MPa to form a sintered block to obtain an antimony telluride-based thermoelectric material, which is recorded as sample D1; (4) using a multi-wire cutting machine, cutting the sintered block in step (3) into a thin slice with a thickness of 12 mm along the pressure direction, and after the thin slice is treated by chemical plating and electroplating, it is electrospark cut to form antimony telluride particles, and the antimony telluride particles are 4 mm in length, 4 mm in width, and 12 mm in height; (5) In step (4), the antimony telluride particles and bismuth telluride particles are assembled and welded with the metal copper sheet to obtain a thermoelectric module, which is recorded as sample S1.

[0036] Figure 1 Schematic diagram of the preparation process of antimony telluride-based thermoelectric materials and thermoelectric modules in Example 1.

[0037] Example 2

[0038] This embodiment provides an antimony telluride-based thermoelectric material and a thermoelectric module. The antimony telluride-based thermoelectric material is a P-type homogeneous double-stage thermoelectric material, which includes Cd 0.04 Sb 1.96 Te3 high temperature thermoelectric material, metal Ni layer and Bi 0.2 Sb 1.8 Te3 low-temperature thermoelectric material, the thickness of the metal Ni layer is 50μm. The thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material. The P-type thermoelectric material is an antimony telluride-based thermoelectric material in this embodiment, and the N-type thermoelectric material is a bismuth telluride material. The P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0039] It is prepared by the following steps: (1) Weighing high-purity cadmium powder, high-purity antimony particles and high-purity tellurium blocks according to a stoichiometric ratio and mixing them to obtain a first mixed raw material; weighing high-purity antimony particles, high-purity tellurium blocks and high-purity bismuth particles according to a stoichiometric ratio and mixing them to obtain a second mixed raw material; smelting the first mixed raw material and the second mixed raw material in a swing smelting furnace respectively, at a vacuum degree of 9 Pa and a temperature of 700 ° C for 480 min, and after the smelting is completed, a first-stage crystal material and a second-stage crystal material are obtained; (2) grinding the first-stage crystal material and the second-stage crystal material in step (1) respectively by ball milling, and then sieving to obtain first-stage material powder and second-stage material powder with a particle size in the range of 1-50 μm; (3) The first-stage material powder and the second-stage material powder and the nickel powder in step (2) are sequentially loaded into a Φ20 mm graphite mold in the order of the second-stage material powder-nickel powder-first-stage material powder, and a plasma spark sintering furnace is used to perform a one-step sintering treatment at a temperature of 520 °C and a pressure of 60 MPa to form a sintered block to obtain an antimony telluride-based thermoelectric material, which is recorded as sample D2; (4) using a multi-wire cutting machine, cutting the sintered block in step (3) into a thin slice with a thickness of 12 mm along the pressure direction, and cutting the thin slice into antimony telluride particles after chemical plating and electroplating. The antimony telluride particles have a length of 5 mm, a width of 5 mm, and a height of 14 mm; (5) In step (4), the antimony telluride particles and bismuth telluride particles are assembled and welded with the metal copper sheet to obtain a thermoelectric module, which is recorded as sample S2.

[0040] Example 3

[0041] This embodiment provides an antimony telluride-based thermoelectric material and a thermoelectric module. The antimony telluride-based thermoelectric material is a P-type homogeneous double-stage thermoelectric material, which includes Cd 0.06 Sb 1.94 Te 2.94 S 0.06 High temperature thermoelectric materials, metal Ni layer and Bi 0.2 Sb 1.8 Te3 low-temperature thermoelectric material, the thickness of the metal Ni layer is 10 μm. The thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material. The P-type thermoelectric material is an antimony telluride-based thermoelectric material in this embodiment, and the N-type thermoelectric material is a bismuth telluride material. The P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0042] It is prepared by the following steps: (1) Weighing high-purity cadmium powder, high-purity antimony particles, high-purity tellurium bulk and high-purity sulfur powder according to a stoichiometric ratio and mixing them to obtain a first mixed raw material; weighing high-purity antimony particles, high-purity tellurium bulk and high-purity bismuth particles according to a stoichiometric ratio and mixing them to form a second mixed raw material; smelting the first mixed raw material and the second mixed raw material in a box furnace respectively, at a vacuum degree of 6 Pa and a temperature of 800 ° C for 200 min, and after the smelting is completed, a first-stage crystal material and a second-stage crystal material are obtained; (2) grinding the first-stage crystal material and the second-stage crystal material in step (1) respectively by ball milling, and then sieving to obtain first-stage material powder and second-stage material powder with a particle size in the range of 1-50 μm; (3) The first-stage material powder and the second-stage material powder and the nickel powder in step (2) are sequentially loaded into a Φ20 mm graphite mold in the order of the second-stage material powder-nickel powder-first-stage material powder, and a plasma spark sintering furnace is used to perform a one-step sintering treatment at a temperature of 520 °C and a pressure of 60 MPa to form a sintered block to obtain an antimony telluride-based thermoelectric material, which is recorded as sample D1; (4) using a multi-wire cutting machine, cutting the sintered block in step (3) into a thin slice with a thickness of 12 mm along the pressure direction, and cutting the thin slice into antimony telluride particles after chemical plating and electroplating. The antimony telluride particles have a length of 2 mm, a width of 2 mm, and a height of 8 mm; (5) In step (4), the antimony telluride particles and bismuth telluride particles are assembled and welded with the metal copper sheet to obtain a thermoelectric module, which is recorded as sample S1.

[0043] Comparative Example 1 This comparative example provides a heterogeneous dual-stage thermoelectric material and a thermoelectric module. The heterogeneous dual-stage thermoelectric material is a P-type heterogeneous dual-stage material, which is composed of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) single crystal thin sheets stacked together; the thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, the P-type thermoelectric material is the heterogeneous dual-stage thermoelectric material in this comparative example, and the N-type thermoelectric material is a bismuth telluride material, and the P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0044] It is prepared by the following steps: Weighing high-purity antimony particles and high-purity tellurium blocks according to a stoichiometric ratio, and mixing them to obtain a first mixed raw material; weighing high-purity tellurium blocks and high-purity bismuth particles according to a stoichiometric ratio, and mixing them to form a second mixed raw material; the first mixed raw material and the second mixed raw material are respectively smelted in a swing smelting furnace, under the conditions of a vacuum degree of 5 Pa and a temperature of 1000 ° C, for 90 minutes, and after the smelting is completed, crystal pulling growth is carried out, and the crystal pulling growth temperature is 800 ° C and the speed is 20 mm / h; after the crystal pulling growth is completed, bismuth telluride (Bi2Te3) crystal rods and antimony telluride (Sb2Te3) crystal rods are obtained; The bismuth telluride and antimony telluride crystal rods prepared in step (1) are cut into bismuth telluride and antimony telluride single crystal sheets of equal length and thickness of 6 mm respectively along the direction of crystal pulling growth, and are stacked to form a heterogeneous dual-segment thermoelectric material, which is recorded as sample D4; The thermoelectric material in step (2) is electroplated and cut, and assembled with bismuth telluride material and metal copper sheet into a thermoelectric module, which is recorded as sample S4.

[0045] Comparative Example 2 This comparative example provides a single-stage thermoelectric material and a thermoelectric module. The single-stage thermoelectric material is a P-type antimony telluride (Sb2Te3) single crystal thin sheet; the thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, the P-type thermoelectric material is the single-stage thermoelectric material in this comparative example, the N-type thermoelectric material is a bismuth telluride material, and the P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0046] It is prepared by the following steps: (1) Weighing high-purity antimony particles and high-purity tellurium blocks according to the stoichiometric ratio, mixing them to obtain a mixed raw material; smelting the mixed raw material in a swing smelting furnace under the conditions of a vacuum degree of 5 Pa and a temperature of 1000 °C for 90 min, and after the smelting is completed, performing crystal pulling growth at a temperature of 800 °C and a speed of 20 mm / h; after the crystal pulling growth is completed, an antimony telluride (Sb2Te3) crystal rod is obtained; (2) Cutting the antimony telluride crystal rod in step (1) into antimony telluride single crystal slices of equal length and thickness of 6 mm along the crystal pulling growth direction, recorded as sample D4; (3) The antimony telluride single crystal sheet prepared in step (2) is electroplated and cut, and assembled with bismuth telluride material and metal copper sheet into a thermoelectric module, which is recorded as sample S4.

[0047] Comparative Example 3 This comparative example provides a single-stage thermoelectric material and a thermoelectric module. The single-stage thermoelectric material is a P-type bismuth telluride single crystal sheet; the thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, the P-type thermoelectric material is the single-stage thermoelectric material in this comparative example, the N-type thermoelectric material is a bismuth telluride material, and the P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0048] It is prepared by the following steps: (1) Weighing high-purity bismuth particles and high-purity tellurium blocks according to the stoichiometric ratio, mixing them to obtain a mixed raw material; smelting the mixed raw material in a swing smelting furnace under the conditions of a vacuum degree of 5 Pa and a temperature of 1000 °C for 90 min, and after the smelting is completed, performing crystal pulling growth at a temperature of 800 °C and a speed of 20 mm / h; after the crystal pulling growth is completed, a bismuth telluride crystal rod is obtained; (2) Cutting the bismuth telluride crystal rod in step (1) into bismuth telluride single crystal sheets of equal length and thickness of 6 mm along the direction of crystal pulling growth, recorded as sample D4; (3) The bismuth telluride single crystal sheet prepared in step (2) is electroplated and cut, and assembled with bismuth telluride material and metal copper sheet into a thermoelectric module, which is recorded as sample S4.

[0049] Comparative Example 4 This comparative example provides a single-stage thermoelectric material and a thermoelectric module. The single-stage thermoelectric material is a P-type antimony telluride (Bi2Te3) single crystal thin sheet; the thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, the P-type thermoelectric material is the single-stage thermoelectric material in this comparative example, the N-type thermoelectric material is a bismuth telluride material, and the P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0050] It is prepared by the following steps: (1) Weighing high-purity antimony particles and high-purity tellurium blocks according to the stoichiometric ratio to form a mixed raw material; smelting the mixed raw materials in a box furnace for 90 min under the conditions of a vacuum degree of 5 Pa and a temperature of 1000 °C. After the smelting is completed, an antimony telluride crystal material is obtained; (2) grinding the antimony telluride material crystal material in step (1) by ball milling, and then sieving to obtain antimony telluride powder with a powder particle size in the range of 1-50 μm; (3) The antimony telluride powder in step (2) was loaded into a Φ20 mm graphite mold and subjected to a one-step sintering treatment at a temperature of 520 °C and a pressure of 60 MPa in a plasma spark sintering furnace to form a sintered block, thereby obtaining a single-stage thermoelectric material, which was recorded as sample D7; (4) using a multi-wire cutting machine, cutting the sintered block in step (3) into thin slices with a thickness of 12 mm along the pressure direction, and cutting the thin slices to form antimony telluride particles after chemical plating and electroplating; (5) In step (4), the antimony telluride particles and bismuth telluride particles are assembled and welded with the metal copper sheet to obtain a thermoelectric module, which is recorded as sample S7.

[0051] Comparative Example 5 This comparative example provides a single-stage thermoelectric material and a thermoelectric module. The single-stage thermoelectric material is a bismuth telluride (Bi2Te3) single crystal sheet; the thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, the P-type thermoelectric material is the single-stage thermoelectric material in this comparative example, the N-type thermoelectric material is a bismuth telluride material, and the P-type thermoelectric material and the N-type thermoelectric material are connected by a metal copper sheet.

[0052] It is prepared by the following steps: (1) Weighing high-purity antimony particles and high-purity bismuth particles according to a stoichiometric ratio to form a mixed raw material; smelting the mixed raw materials in a box furnace for 90 min under a vacuum degree of 5 Pa and a temperature of 1000 °C. After the smelting is completed, bismuth telluride crystal material is obtained; (2) grinding the bismuth telluride material ingot in step (1) by ball milling, and then sieving to obtain bismuth telluride powder with a particle size in the range of 1-50 μm; (3) The bismuth telluride powder in step (2) was loaded into a Φ20 mm graphite mold and subjected to a one-step sintering treatment at a temperature of 520 °C and a pressure of 60 MPa in a plasma spark sintering furnace to form a sintered block, thereby obtaining a single-stage thermoelectric material, which was recorded as sample D8; (4) using a multi-wire cutting machine, cutting the sintered block in step (3) into a thin slice with a thickness of 12 mm along the pressure direction, and then electroplating the thin slice and then performing electric spark cutting to form bismuth telluride particles; (5) The bismuth telluride particles and n-type bismuth telluride particles in step (4) are assembled and welded with the metal copper sheet to obtain a thermoelectric module, which is recorded as sample S8.

[0053] Test Method Description Thermoelectric figure of merit (ZT) test method: The sintered p / n-type antimony telluride / bismuth telluride bulk thermoelectric material was cut into 3×3×12 mm conductivity test strips and 10×10×1.2 mm or Φ12.7×1.2 mm thermal conductivity test slices. The ZEM-3 instrument (ULVAC, Japan) was used to measure the conductivity and Seebeck coefficient of the sample in a low-pressure helium atmosphere at a temperature range of 300~500 K. The total thermal conductivity was obtained using the expression ktot = CpρD, where the density ρ was measured using the Archimedean method, Cp was calculated using the Dulong-Petit law, and the thermal diffusion coefficient D was measured using a laser thermal conductivity meter (Netzsch, LFA-467, Germany) in a nitrogen atmosphere.

[0054] Thermoelectric conversion efficiency test method: The thermoelectric conversion efficiency of the thermoelectric module was measured using 17 pairs of p / n thermoelectric arms, and the test parameters were as follows: the sintered antimony telluride-based thermoelectric materials and bismuth telluride bulk thermoelectric materials were cut into 12 mm sheets, chemically plated, and then cut into 3×3×12 mm particles. Subsequently, 40×40 mm ceramic plates, 10×4 mm copper electrodes, and particles were assembled and welded at 400 °C for 10 min, and then the thermoelectric conversion efficiency was tested at temperature differences of ΔT = 50, 100, 150, 200, 250, 300, and 350 K.

[0055] Test results description: Samples D1-D8 and S1-S8 were tested and analyzed, and the test results are shown in Table 1, Table 2, Figure 2 and Figure 3 As shown, Table 1 shows the compressive strength of samples D1-D8, and Table 2 shows the Vickers hardness of samples D1-D8. Figure 2 The thermoelectric figure of merit of the samples obtained in Examples 1 to 3 and Comparative Examples 1 to 5 varies with temperature; Figure 3 The figure is a graph showing the thermoelectric conversion efficiency of the thermoelectric modules obtained in Examples 1 to 3 and Comparative Examples 1 to 5 as a function of temperature.

[0056] Table 1: Compressive strength of samples D1−D8 Sample No. D1 D2 D3 D4 D5 D6 D7 D8 Compressive strength (MPa) 197 184 169 154 86 112 128 157 Table 2: Vickers hardness of samples D1−D8 Sample No. D1 D2 D3 D4 D5 D6 D7 D8 Vickers hardness(GPa) 0.55 0.49 0.41 0.31 0.14 0.17 0.22 0.34 It can be seen from the data in Table 1 and Table 2 that the compressive strength and Vickers hardness of samples D1-D3 are significantly higher than those of samples D7 and D8. Relative to the single-stage thermoelectric material samples D7 and D8 prepared in Comparative Examples 4 and 5, the homogeneous double-stage antimony telluride-based thermoelectric material samples D1-D3 prepared in Examples 1-3 of the present invention have higher mechanical strength; at the same time, compared with the thermoelectric material samples D4-D6 prepared in Comparative Examples 1-3, the compressive strength and Vickers hardness of samples D1-D3 are also significantly improved, and the mechanical strength of the antimony telluride-based thermoelectric material samples prepared by the present invention is significantly improved.

[0057] from Figure 2 and Figure 3 It can be seen from the data that compared with the thermoelectric modules S4-S6 prepared in comparative examples 1-3, the thermoelectric modules S1-S3 prepared by the sintering process in Examples 1-3 have higher thermoelectric merits. At the same time, compared with the thermoelectric modules S7 and S8 prepared by single-stage thermoelectric materials in comparative examples 4 and 5, the thermoelectric materials with homogeneous double-stage structures in Examples 1-3 maintain a very high thermoelectric merit ZT in the entire temperature range.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An antimony telluride-based thermoelectric material, characterized in that: The antimony telluride-based thermoelectric material is a P-type homogeneous double-stage thermoelectric material, which includes a first-stage material, an intermediate metal bonding layer and a second-stage material in sequence; The first stage material is selected from at least one of the compounds shown in Formula I: Cd x Sb 2-x Te 3-y S y Formula I, Among them, 0<x≤1.0, 0≤y≤1.0; The second stage material is selected from at least one of the compounds shown in Formula II: Bi z Sb 2-z Te3 of formula II, Among them, 0<z≤1.

0.

2. The antimony telluride-based thermoelectric material according to claim 1, characterized in that: The material of the intermediate metal bonding layer includes metal nickel; And / or, the thickness of the intermediate metal bonding layer is 10-50 μm.

3. The method for preparing antimony telluride-based thermoelectric material according to claim 1, characterized in that: The following steps are involved: S1. Weighing a first mixed raw material including antimony, tellurium, cadmium and sulfur according to a stoichiometric ratio, and melting and quenching the first mixed raw material to obtain a first-stage crystal material; Weighing a second mixed raw material including antimony, tellurium and bismuth according to a stoichiometric ratio, and melting and quenching the second mixed raw material to obtain a second-stage crystal material; S2, the first-stage crystal material and the second-stage crystal material in step S1 are respectively subjected to grinding treatment to obtain first-stage material powder and second-stage material powder respectively; S3, the first-stage material powder and the second-stage material powder and the bonding metal powder in step S2 are sequentially loaded into a mold in the order of second-stage material powder-bonding metal powder-first-stage material powder, and a sintered block is formed through a one-step sintering treatment to obtain an antimony telluride-based thermoelectric material.

4. The method for preparing antimony telluride-based thermoelectric material according to claim 3, characterized in that: The smelting device in step S1 is a box furnace or a swing smelting furnace; And / or, the vacuum degree of the smelting in step S1 is less than 10 Pa, the smelting temperature is 700-1000° C., and the smelting time is 60-480 min.

5. The method for preparing antimony telluride-based thermoelectric material according to claim 3, characterized in that: The particle size of the first-stage material powder and the second-stage material powder in step S2 is 1-50 μm.

6. The method for preparing antimony telluride-based thermoelectric material according to claim 3, characterized in that: The one-step sintering process in step S3 adopts vacuum hot pressing sintering or plasma spark sintering; And / or, the temperature of the one-step sintering treatment in step S3 is 400-500° C., the pressure of the one-step sintering treatment is 40-50 Mpa, and the time of the one-step sintering treatment is 5-30 min.

7. A thermoelectric module, characterized in that: The thermoelectric module includes a P-type thermoelectric material and an N-type thermoelectric material, wherein the P-type thermoelectric material is connected to the N-type thermoelectric material via a conductive metal, the P-type thermoelectric material is the antimony telluride-based thermoelectric material according to claim 1 or 2, and the N-type thermoelectric material is a bismuth telluride material.

8. The method for preparing a thermoelectric module according to claim 7, characterized in that: The following steps are involved: T1, the antimony telluride-based thermoelectric material is cut to obtain an antimony telluride-based sheet; T2, the antimony telluride-based sheet described in step T1 is electroplated and then cut to obtain antimony telluride-based particles; T3. The antimony telluride-based particles and bismuth telluride materials described in step T2 are assembled and welded with conductive metal to obtain a thermoelectric module.

9. The method for preparing a thermoelectric module according to claim 8, characterized in that: The cutting process in step T1 adopts multi-wire cutting; And / or, the electroplating treatment in step T2 adopts chemical plating; And / or, the cutting in step T2 is performed by wire electric discharge cutting; And / or, the antimony telluride-based particles in step T2 have a length of 2-5 mm, a width of 2-5 mm, and a height of 8-14 mm.

10. Use of the antimony telluride-based thermoelectric material according to claim 1 or 2 in the field of waste heat recovery.

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