High-thermoelectric-performance p-type Bi2Te3-based thermoelectric material and preparation method thereof
By combining non-equilibrium rapid solidification with mechanical alloying and spark plasma sintering, a p-type Bi2Te3-based thermoelectric material with high thermoelectric performance was prepared, solving the preparation problem of Sn/Ce/Sb multi-doped bismuth telluride-based thermoelectric materials and achieving a synergistic improvement in high thermoelectric figure of merit and high mechanical properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-07
AI Technical Summary
The existing technology lacks the application of rapid solidification method to the preparation of Sn/Ce/Sb multi-doped bismuth telluride-based thermoelectric materials, especially in achieving uniform elemental distribution, nanostructure control and metastable structure synergistic optimization, which still needs further exploration.
A high-thermoelectric-performance p-type Bi2Te3-based thermoelectric material was prepared by combining non-equilibrium rapid solidification process with mechanical alloying, melt spinning and spark plasma sintering. By synergistic doping of Sn and Ce, a nanostructure with uniform composition and fine grains was constructed. Ce was used as a phonon scattering center and Sn as an electron control center to achieve decoupling of electroacoustic transport and high mechanical properties of the material.
The thermoelectric figure of merit (ZT) of the material was significantly improved to 1.45, the lattice thermal conductivity was reduced, and the mechanical and electrical transport properties of the material were enhanced, enabling the large-scale preparation of high-performance thermoelectric materials.
Smart Images
Figure CN121815947A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of thermoelectric materials, in particular to a p-type thermoelectric material with high thermoelectric performance and a preparation method thereof. BACKGROUND
[0002] Under the background of accelerating transformation of global energy structure and deepening of the "double carbon" strategy, the innovation of new energy technology has become the core driving force to ensure national energy security and achieve sustainable development. As a green energy approach that can realize the direct conversion of heat and electricity, thermoelectric technology has shown important application value in industrial waste heat recovery, space power, solid-state refrigeration and precision temperature control, etc. due to its advantages of full solid-state operation, high reliability and environmental friendliness.
[0003] Among various thermoelectric materials, p-type Bi-Te-based materials are the most mature commercialized system with the best performance in the near room temperature region, which has been widely used in solid-state refrigeration and temperature control equipment. However, this material system still faces two major technical bottlenecks: first, the difficulty in improving the thermoelectric figure of merit (ZT value), which is limited by the strong coupling relationship between the electrical and acoustic transport parameters; second, the poor mechanical properties and difficult processing due to the intrinsic layered structure, which mainly originates from the crystal characteristics prone to fracture along the cleavage plane.
[0004] Traditional preparation methods such as zone melting and Bridgman method have obvious technical limitations. These methods have low cooling rate, and element segregation and second phase precipitation are easy to occur during the preparation process, resulting in uneven material composition and decreased phase purity; at the same time, the grain size is large, and the scattering ability of phonons is limited, which is difficult to effectively reduce the lattice thermal conductivity. Although current researches have tried to improve the material performance by doping and nanocrystallization, it is difficult to achieve uniform distribution of multi-element doping elements and precise control of microstructure by traditional methods. Especially in the multi-element doping system, due to the difference in segregation coefficient, composition segregation is easy to occur in the equilibrium solidification process, which not only reduces the carrier mobility, but also affects the electrical transport performance of the material.
[0005] To break through the above limitations, researches point out that constructing multi-level heterogeneous structure at atomic and nanometer scale is the key path to realize the decoupling of electrical and acoustic transport. Nanostructure engineering can effectively block the propagation of phonons, reduce the lattice thermal conductivity, while maintaining efficient transport of electrons, approaching the ideal state of "phonon glass-electron crystal" by constructing high-density grain boundaries, nano-precipitates and point defects, etc. In addition, fine nanostructure can also inhibit crack propagation and enhance the mechanical properties and service stability of the material.
[0006] In view of the above problems, non-equilibrium rapid solidification process shows unique advantages. This process can effectively control the microstructure of the material by extremely high cooling rate (usually up to 10<6>~10<9> K / s), which can effectively suppress the formation of second phase and composition segregation, and can also effectively reduce the lattice thermal conductivity by constructing high-density grain boundaries and nano-precipitates. This breakthrough overcomes the thermodynamic equilibrium limitations of traditional solidification processes, providing a new technical approach for the preparation of high-performance thermoelectric materials. However, there are no reports in the current technology on the application of non-equilibrium rapid solidification methods to the research of Sn / Ce / Sb multi-doped bismuth telluride-based thermoelectric materials systems. In particular, further exploration is needed on how to achieve uniform elemental distribution, nanostructure control, and synergistic optimization of metastable structures through this process.
[0007] Therefore, developing a method for preparing multi-doped bismuth telluride-based thermoelectric materials based on rapid solidification is of great significance for breaking through existing technological bottlenecks and promoting the development of thermoelectric materials. Summary of the Invention
[0008] The technical problem to be solved by this invention is:
[0009] The existing technology lacks the ability to apply rapid solidification methods to the preparation of Sn / Ce / Sb multi-doped bismuth telluride-based thermoelectric materials.
[0010] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:
[0011] This invention provides a high thermoelectric performance p-type Bi2Te3-based thermoelectric material, which has the following composition: (1) The base material is the matrix, and the P-type is obtained by synergistic doping of Sn and Ce. Bulk materials;
[0012] The Ce doping concentration is 0.5% of the total material mass. 2.0%;
[0013] The Sn doping concentration is 0.02% of the total material mass. 0.1%.
[0014] This invention provides a method for preparing a high-thermoelectric-performance p-type Bi2Te3-based thermoelectric material, comprising the following steps:
[0015] S1. Based on the molar ratio of Bi, Sb, and Te elements in the composition formula (1) of claim 1, a mixture of elemental Bi, elemental Sb, and elemental Te is packaged into a container; the mixture is then melted by heating the container to obtain... Oriented crystals;
[0016] S2, the above The oriented crystal is broken, and elemental Ce and elemental Sn of claim 1 are added to it to obtain mixture two. Mixture two is then pulverized, and the pulverized mixture two is placed in a can under a protective gas atmosphere and mechanically ground to prepare Ce / Sn co-doped P-type crystal. Material powder;
[0017] S3, the Ce and Sn co-doped P-type The material powder is cold-pressed into blocks and broken into small pieces to prepare nanocrystalline ribbons by a melt-spinning process;
[0018] S4, the nanocrystalline ribbons are subjected to a spark plasma sintering treatment to prepare a high-density Sn / Ce co-doped P-type material;
[0019] S5, the high-density Sn / Ce co-doped P-type material is packaged into a container, annealed, cut, and a Sn / Ce co-doped P-type bulk material is obtained.
[0020] Further, the melting in step S1 is vacuum melting at a temperature of 700°C to synthesize the powder oriented crystal.
[0021] Further, the mechanical grinding in step S2 adopts ball milling, uses a hard alloy ball mill tank and grinding balls, and uses petroleum ether as the ball milling medium, under the conditions of a rotation speed of 410 r / min and a ball-to-material ratio of 10:1, the mechanical ball milling is performed for 20 hours.
[0022] Further, the melt-spinning in step S3 is performed under the following conditions: the copper roller linear speed is set to 47.1 m / s, the roller nozzle spacing is 4.5 mm, and the spraying gas pressure is 60 kPa.
[0023] Further, the spark plasma sintering in S4 is as follows: the nanocrystalline ribbons are placed in a mold and put into a spark plasma sintering system, vacuum is drawn to a vacuum degree of less than 4 Pa, and then sintering is started, the sintering program is as follows: the heating rate is 80 K / min, the internal sintering pressure is 8.8 kN, the sintering pressure is 60 MPa, the pressure is applied within 1 min, then the temperature is raised from room temperature to 750 K within 5 min under pressure, the temperature is kept for 5 min, and finally the furnace is cooled to obtain a high-density Sn / Ce co-doped P-type Bi 0.48 Sb 1.52 Te3 material.
[0024] Further, the annealing in step S5 is as follows: the high-density Sn / Ce co-doped P-type Bi 0.48 Sb 1.52 Te3 material is sealed in a quartz tube with a vacuum degree of not higher than 1×10⁻³ Pa, and annealing treatment is performed at a temperature of 720 K for 24 h.
[0025] Further, the cutting in S5 obtains a Sn / Ce co-doped P-type The bulk material is a cuboid material with a size of 4mm*4mm*10mm.
[0026] Compared with the prior art, the application has the following beneficial effects:
[0027] 1. The application combines mechanical alloying with melt-spinning rapid solidification process to synergistically construct a nanostructure with uniform composition and fine grains. This structure can effectively enhance phonon scattering, significantly reduce the lattice thermal conductivity of the material, and optimize the electrical transport performance (Seebeck coefficient and electrical conductivity) by maintaining a high carrier mobility and band control, thereby significantly improving the thermoelectric figure of merit of the material. In addition, the ultra-fine grain structure also significantly enhances the hardness, strength and toughness of the material through grain refinement strengthening, improving its mechanical reliability.
[0028] 2. The application combines spark plasma sintering (SPS) with subsequent annealing treatment. The non-equilibrium rapid densification of SPS effectively preserves the metastable structures (such as nanocrystals and supersaturated solid solutions) in the powder, and the severe lattice distortion and high-density grain boundaries introduced by the high-entropy strategy significantly enhance phonon scattering, greatly reducing the thermal conductivity of the material. The subsequent annealing treatment further controls the precipitates and grain boundary states while eliminating internal stress and repairing crystal defects to improve carrier mobility, thereby optimizing electrical transport performance while reducing thermal conductivity and synergistically enhancing the strength and toughness of the material, ultimately achieving a synergistic improvement in high-entropy thermoelectric materials in terms of high thermoelectric figure of merit and high mechanical performance. This results in a significant increase in the power factor of the material (optimal value ), and a reduction in thermal conductivity, thereby significantly improving the thermoelectric performance of the material.
[0029] 3. The application realizes the synergistic optimization and effective decoupling of the electrical and thermal transport parameters of the material through the co-doping of Sn and Ce. Specifically, Sn doping mainly serves as an electron control center, precisely controlling the carrier concentration and inducing band convergence to increase electrical conductivity while maintaining or increasing the Seebeck coefficient, thereby significantly improving the power factor. Ce doping mainly serves as a phonon scattering center, introducing strong point defects (due to mass and radius differences) and nanoscale precipitates to achieve multi-scale scattering of full-band phonons, thereby reducing the lattice thermal conductivity to near the glass limit. The two functions are clear and synergistic, and together they significantly improve the thermoelectric figure of merit (ZT) to 1.45.
[0030] 4. The preparation process of the application is simple, controllable and easy to operate, with low requirements for preparation conditions, which can effectively reduce production costs and is suitable for large-scale production of high-performance thermoelectric materials. BRIEF DESCRIPTION OF DRAWINGS
[0031] Figure 1 SEM image of the nanocrystalline band in the embodiment of the application;
[0032] Figure 2 Ce / Sn co-doped P-type material conductivity graph;
[0033] Figure 3 Ce / Sn co-doped P-type material Seebeck coefficient graph;
[0034] Figure 4 Ce / Sn co-doped P-type material thermal conductivity graph;
[0035] Figure 5 Ce / Sn co-doped P-type material thermoelectric figure of merit (ZT) graph. DETAILED DESCRIPTION
[0036] In order to make the person skilled in the art better understand the present application, in the following will be described in conjunction with the accompanying drawings of the exemplary embodiments or embodiments of the present application. Obviously, the described embodiments or embodiments are only a part of the embodiments or embodiments of the present application, rather than all. Based on the embodiments or embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts should belong to the scope of protection of the present application.
[0037] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.
[0038] The present application provides a P-type bismuth telluride-based thermoelectric material, which is based on the base material of the composition formula (1), and the P-type bulk material obtained by the synergistic doping of Sn and Ce;
[0039] The Ce doping amount is 0.5% of the total mass of the material 2.0%;
[0040] The Sn doping amount is 0.02% of the total mass of the material 0.1%.
[0041] It should be noted that in the P-type Bi0. 48 Sb1. 52 Sn x Ce y Te3 bulk material lattice, The substitution sites in the lattice introduce a positively charged hole to maintain charge balance and increase hole concentration. As a rare earth element, Ce has a much larger atomic radius than Bi and Sb. When Ce substitutes for Bi / Sb sites in the lattice, it introduces strong lattice distortion and strain field, generating a powerful point defect scattering effect to effectively reduce short-wavelength phonon scattering and lower thermal conductivity. In addition, when Ce exceeds its solid solubility, it may form nanoscale Ce-Te precipitates, which further scatter low-frequency phonons, achieving effective suppression of phonons across the entire frequency band.
[0042] Example 1
[0043] Ce / Sn co-doped p-type electron microstructures were tested using a comprehensive thermoelectric property testing system. The material is systematically characterized by its Seebeck coefficient, electrical conductivity, and thermal conductivity, such as... Figure 2 and Figure 3 As shown in the figure. Test results show that both the conductivity and Seebeck coefficient of the doped sample are significantly improved. The increase in conductivity is mainly attributed to the lattice substitution of Bi³⁺ by Sn²⁺: since Sn has one less outermost electron than Bi, each Sn²⁺ ion introducing a positively charged hole when substituting a Bi³⁺ site introduces a positively charged hole to maintain charge balance, thus effectively increasing the hole concentration. With the gradual increase of Sn concentration, the conductivity of the material gradually increases, reaching a maximum value of 1.644 × 10⁻⁶ when the Sn doping concentration is 0.1%. 5 The increase in the Seebeck coefficient is mainly due to the bandgap modulation effect of Sn doping. The introduction of Sn increases the effective mass of the material, and the decrease in carrier mobility due to increased temperature further enhances the Seebeck coefficient. At a Sn doping concentration of 0.02% and a temperature of 500°C... At that time, the Seebeck coefficient reached its maximum value of 265. .
[0044] Ce / Sn co-doped p-type thermoelectric performance was tested using a comprehensive thermoelectric performance testing system. The thermal conductivity of the material was systematically measured, and the results are as follows: Figure 4 As shown in the figure. Tests show that the thermal conductivity of the doped sample decreases significantly. When the Ce doping concentration is 2.0% and the Sn doping concentration is 0.02%, the thermal conductivity of the material reaches its lowest value at 450 K. The decrease of thermal conductivity is mainly attributed to the following mechanisms: first, as a rare earth element, the atomic radius of Ce is much larger than that of Bi and Sb. When Ce replaces the Bi / Sb sites in the lattice, it will introduce strong lattice distortion and strain field, resulting in strong point defect scattering effect. These defects are expected to effectively reduce the scattering of short-wave phonons, thereby reducing the thermal conductivity. In addition, when Ce exceeds the solid solubility, nano-sized Ce-Te precipitates may be formed, which can further scatter low-frequency phonons, thereby achieving effective suppression of full-band phonons. At the same time, the ultra-fine grain structure obtained by the mechanical alloying-melt spinning process introduces a high density of grain boundaries, which provides additional scattering centers for phonon transmission, further reducing the lattice thermal conductivity. The synergistic effect of multiple scattering mechanisms is the key reason for achieving low thermal conductivity of the material.
[0045] According to the measured Seebeck coefficient, electrical conductivity and thermal conductivity values in Figure 2 , Figure 3 and Figure 4 , the dimensionless thermoelectric figure of merit (ZT value) is calculated as shown in Figure 5 . In the measured temperature range, the thermoelectric figure of merit of all samples after doping is higher than 1, and reaches a peak value of 1.45 at 400K. This indicates that doping and the preparation process adopted can improve the thermoelectric performance of the material, and therefore has strong application prospects.
[0046] The Ce / Sn co-doped P-type material of Example 1 can be manufactured by the following steps, and for materials with different elements in the material composition of Example 1, as long as the material or proportioning ratio is adjusted arbitrarily, the same method can be used to manufacture.
[0047] S1, take the elemental Bi, Sb and Te in a molar ratio of 12:38:75, and seal the weighed raw materials in a glass tube. Vacuum melting is carried out at a temperature of 700℃, and the powder is synthesized oriented crystal;
[0048] S2, the The oriented crystal is broken into powder, and rare earth element Ce and semi-metal element Sn are added to obtain a mixture, wherein the doping amount of the rare earth element Ce is 2% of the total mass of the material, and the incorporation amount of the semi-metal Sn is 0, 0.02%, 0.05%, 0.07%, and 0.1% of the total mass of the material, respectively. The mixture is crushed to a particle size of about 1 mm, and mixing and canning are completed in an argon glove box to effectively prevent oxidation. A planetary high-energy ball mill and a hard alloy ball mill tank and grinding balls are used, and petroleum ether is used as the ball milling medium. The mechanical ball milling is performed at a rotation speed of 410 r / min and a ball-to-material ratio of 10:1 for 20 hours to obtain a P-type A thermoelectric material mechanical alloy powder;
[0049] S3, the P-type The thermoelectric material mechanical alloy powder is cold-pressed into a block and broken into small pieces. The block is loaded into a quartz crucible with a nozzle aperture of 0.5 mm and placed in a spinning belt furnace. A copper roller line speed of 47.1 m / s, a roller nozzle spacing of 4.5 mm, and a spraying gas pressure of 60 kPa are set to prepare a nanocrystalline ribbon. Subsequently, the collected ribbon is ground into powder in a glove box and sieved through a 200-mesh screen.
[0050] S4, the ribbon powder obtained in step S3 is placed in a graphite mill coated with carbon paper, and the mill is inserted into a spark plasma sintering system and a thermocouple for vacuum pumping. When the vacuum degree reaches below 4 Pa, sintering is started. The sintering program is as follows: the heating rate is 80 K / min, the internal sintering pressure is 8.8 kN, the sintering pressure is 60 MPa, the pressure is applied within 1 min, then the temperature is raised from room temperature to 750 K within 5 min under pressure, then the temperature is kept at 750 K for 5 min, and finally the furnace is cooled to obtain a high-density Sn / Ce co-doped P-type Bulk material.
[0051] S5, the high-density Sn / Ce co-doped P-type Bulk material. Bulk material.
[0052] Figure 1The scanning electron microscope (SEM) image (magnification: 600x) of the nanocrystalline ribbon obtained in step S3 is shown. It can be seen that the sample as a whole presents a typical lamellar morphology, the structure is interlaced with a network-like distribution, and clear melt flow and shear marks can be seen, reflecting the strong deformation characteristics in the rapid solidification process. The material is composed of irregular sheet units of micron to sub-micron scale, the grain size distribution is uneven, and there is an obvious size gradient, indicating that there is a difference in cooling rate at different positions. The surface of the sheet layer is relatively smooth, the overall morphology is uniform, and no obvious second phase clusters or composition segregation are observed, indicating that the melt spinning process effectively promotes the uniform distribution and solid solution of the doping elements, providing a uniform precursor for the preparation of the subsequent bulk material.
[0053] Although the present application discloses as above, the protection scope of the present application is not limited to this. The person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and these changes and modifications will fall within the protection scope of the present application.
Claims
1. A high thermoelectric performance p-type Bi2Te3-based thermoelectric material, characterized in that, Its composition formula is (1) The base material is the matrix, and the P-type is obtained by synergistic doping of Sn and Ce. Bulk materials; The Ce doping concentration accounts for 0.5% of the total material mass. 2.0%; The Sn doping concentration is 0.02% of the total material mass. 0.1%.
2. A method for preparing a high thermoelectric performance p-type Bi2Te3-based thermoelectric material, characterized in that, Includes the following steps: S1. Based on the molar ratio of Bi, Sb, and Te elements in the composition formula (1) of claim 1, a mixture of elemental Bi, elemental Sb, and elemental Te is packaged into a container; Bi is prepared by melting the mixture by heating the container. 0.48 Sb 1.52 Te3 oriented crystal; S2, the Bi 0.48 Sb 1.52 Te3 oriented crystals were broken up, and elemental Ce and Sn of the doping amounts described in claim 1 were added to obtain mixture two. Mixture two was then pulverized, and under a protective gas atmosphere, the pulverized mixture two was placed in a can and mechanically ground to prepare Ce / Sn co-doped P-type Bi. 0.48 Sb 1.52 Te3 material powder; S3, the p-type Bi co-doped with Ce and Sn is then... 0.48 Sb 1.52 Te3 material powder is cold-pressed into blocks and broken into small pieces, and nanocrystalline ribbons are prepared by melt spinning process; S4. The nanocrystalline strips are subjected to spark plasma sintering to prepare highly dense Sn / Ce co-doped P-type Bi. 0.48 Sb 1.52 Te3 materials; S5, the highly dense Sn / Ce co-doped p-type Bi 0.48 Sb 1.52 Te3 material is encapsulated in a container, annealed, and cut to obtain Sn / Ce co-doped P-type Bi0. 48 Sb1. 52 Sn x Ce y Te3 bulk material.
3. The method according to claim 2, characterized in that, The melting process described in step S1 involves vacuum melting at a temperature of 700°C to synthesize Bi from the powder. 0.48 Sb 1.52 Te3 oriented crystal.
4. The method according to claim 3, characterized in that, The mechanical grinding described in step S2 is performed by ball milling, using a cemented carbide ball milling jar and grinding balls, with petroleum ether as the ball milling medium, and mechanical ball milling for 20 hours at a rotation speed of 410 r / min and a ball-to-material ratio of 10:
1.
5. The method according to claim 4, characterized in that, The conditions for melting and spinning in step S3 are as follows: the linear speed of the copper roller is set to 47.1 m / s, the distance between the roller nozzles is 4.5 mm, and the injection air pressure is 60 kPa.
6. The method according to claim 5, characterized in that, The spark plasma sintering described in S4 specifically involves: placing the nanocrystalline ribbon into a mold, placing it in a spark plasma sintering system, and evacuating the system until the vacuum level reaches below 4 Pa before starting sintering. The sintering procedure is as follows: a heating rate of 80 K / min, an internal sintering pressure of 8.8 kN, and a sintering pressure of 60 MPa. The pressure is first applied within 1 minute, and then the temperature is increased from room temperature to 750 K within 5 minutes under pressure, held for 5 minutes, and finally cooled in the furnace to obtain highly dense Sn / Ce co-doped P-type Bi. 0.48 Sb 1.52 Te3 material.
7. The method according to claim 6, characterized in that, The annealing in step S5 is: annealing the highly dense Sn / Ce co-doped P-type Bi 0.48 Sb 1.52 The Te3 material was sealed in a quartz tube with a vacuum level not exceeding 1×10⁻³ Pa and annealed at 720 K for 24 h.
8. The method according to claim 7, characterized in that, Sn / Ce co-doped P-type cells were obtained by cutting S5. The block material is a rectangular prism with dimensions of 4mm × 4mm × 10mm.