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

Abstract

The invention belongs to the technical field of thermoelectric materials, and provides a composite P-type bismuth telluride-based material and a preparation method thereof in order to improve the thermoelectric performance of the thermoelectric materials, the composite P-type bismuth telluride-based material comprises a P-type bismuth telluride matrix with the chemical formula being Bi < 0.5 > Sb < 1.5 > Te < 3.2 > and a compound used for compounding, the chemical formula of the composite compound is selected from one or more of Cu2GeSe3, Ag8GeTe6 and Ag5Te3, and the chemical formula of the P-type bismuth telluride matrix is Bi < 0.5 > Sb < 1.5 > Te < 3.2 >. And the usage amount of the composite compound is 0.04-0.1% of the mass of the P-type bismuth telluride matrix. According to the P-type bismuth telluride-based composite material provided by the invention, crystal boundary, second phase and other defects are introduced after compounding to enhance phonon scattering, so that the lattice thermal conductivity is effectively reduced, and finally, the improvement of the material performance is realized by optimizing the carrier concentration and reducing the lattice thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, specifically relating to a composite P-type bismuth telluride-based material and its preparation method. Background Technology

[0002] p-type bismuth telluride (Bi2Te3)-based materials are among the most commercially mature thermoelectric materials currently available, possessing excellent thermoelectric properties and primarily used for thermoelectric power generation and refrigeration. The advantages of p-type materials lie in their high Seebeck coefficient and electrical conductivity, while their low thermal conductivity makes them outstanding in thermoelectric power generation. Thermoelectric materials can utilize the Seebeck and Peltier effects to achieve the interconversion of thermal and electrical energy. Thermoelectric devices fabricated using these materials offer advantages such as being pollution-free, noise-free, compact in structure, requiring no moving parts, and maintenance-free, playing an irreplaceable role in fields such as deep space exploration power supplies, precise temperature control, and efficient refrigeration.

[0003] The performance evaluation index for thermoelectric materials is the dimensionless thermoelectric figure of merit zT. A higher zT value indicates better thermoelectric performance. The calculation formula is zT = S 2 σ / (κ L +κ e ), where S is the Seebeck coefficient, σ is the conductivity, and κ is the electrical conductivity. L It is the lattice thermal conductivity, κ e It refers to electronic thermal conductivity. S, σ, and κ e The carrier concentration n is closely related to the material's carrier concentration n, and there exists an optimal carrier concentration n. opt This allows the zT value to reach its maximum. Furthermore, reducing the κ of the material... L This is also an effective optimization strategy to improve the zT value.

[0004] Bismuth telluride-based alloys are currently the best-performing thermoelectric materials in the room temperature range. The carrier concentration and lattice thermal conductivity can be controlled by combining them with other compounds. For example, CN102339946B discloses a high-performance thermoelectric composite material and its preparation method. This composite material consists of two phases: the first phase is n-type Bi₂Te₃-Bi₂Se₃ or p-type Bi₂Te₃-Sb₂Te₃, and the second phase is metal oxide nanoparticles; the metal oxide nanoparticles account for 0.05% to 10% of the total weight of the thermoelectric composite material. The n-type Bi₂Te₃-Bi₂Se₃ or p-type Bi₂Te₃-Sb₂Te₃ powder is ultrasonically mixed with the nano-oxide, and then subjected to discharge plasma sintering to obtain a dense bulk material. This invention improves material performance by combining it with alumina, titanium oxide, etc. Compared with bismuth telluride-based thermoelectric matrix materials, while maintaining the basic conductivity of the matrix thermoelectric material, the lattice thermal conductivity of the material can be significantly reduced and the Seeback coefficient of the material can be increased, thereby significantly improving the thermoelectric performance of the material.

[0005] However, when a relatively conductive metal nanophase is used as the second phase, the poor thermal stability of the metal itself may affect the chemical stability of the matrix material. These problems will limit further improvement of the thermoelectric properties of the material. Furthermore, the choice of which compound to use for composite formation and the amount of composite are closely related to the material preparation process. Therefore, selecting the optimal composite compound based on a specific preparation process is one of the key research areas for optimizing material properties. Summary of the Invention

[0006] To improve the thermoelectric performance of thermoelectric materials, this invention provides a composite P-type bismuth telluride-based material and its preparation method. The provided P-type bismuth telluride-based composite material introduces defects such as grain boundaries and second phases after compositing to enhance phonon scattering, effectively reducing lattice thermal conductivity. Ultimately, the material performance is improved by optimizing the carrier concentration and reducing the lattice thermal conductivity.

[0007] This invention is achieved through the following technical solution: A composite p-type bismuth telluride-based material, comprising a p-type bismuth telluride matrix with the chemical formula Bi. 0.5 Sb 1.5 Te 3.2 , And compounds used for composites, wherein the amount of composite compound used is 0.04% to 0.1% of the mass of the p-type bismuth telluride matrix.

[0008] Preferably, the chemical formula of the composite compound is selected from one or more of Cu2GeSe3, Ag8GeTe6, and Ag5Te3. On the one hand, the presence of elements such as Ag, Cu, and Ge in the composite compound can increase the hole concentration of the material, suppress intrinsic excitation, and improve the Seebeck coefficient and electrical conductivity. On the other hand, it can enhance phonon scattering through grain boundaries and nanophases, thereby reducing lattice thermal conductivity. Ultimately, the material performance is improved by optimizing the carrier concentration and reducing the lattice thermal conductivity.

[0009] The above-mentioned composite p-type bismuth telluride-based material was prepared by powder metallurgy, and the preparation method includes the following steps: (1) Weigh the raw materials according to the chemical formula of the composite compound, put them into a quartz tube, and seal the tube under vacuum; As a preferred embodiment, Cu, Ge, and Se are weighed out as raw materials with the chemical formula Cu2GeSe3, Ag and Te are weighed out as raw materials with the chemical formula Ag5Te3, and Ag2Te, GeTe, and Te are weighed out as raw materials with the chemical formula Ag8GeTe6.

[0010] (2) The quartz tube was smelted and annealed at high temperature in a muffle furnace, and after cooling, a composite compound was obtained. The composite compound powder was obtained by ball milling in an inert gas-protected ball mill jar with a particle size of <20μm. Preferably, the melting temperature is 850-1050℃, the annealing temperature is 420-700℃, and the annealing time is 48-96h. More preferably, the melting temperature of Cu2GeSe3 is 900-950℃, the annealing temperature is 500-550℃, and the annealing time is 72-96h; the melting temperature of Ag5Te3 is 850-900℃, the annealing temperature is 420-500℃, and the annealing time is 72-96h; and the melting temperature of Ag8GeTe6 is 970-1050℃, the annealing temperature is 620-700℃, and the annealing time is 48-72h.

[0011] Preferably, the ball milling speed is 400-600 r / min and the ball milling time is 30-50 min.

[0012] (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out the elemental Bi, Sb, and Te, and pack them together with the composite compound powder into a quartz tube, then seal the tube under vacuum. Preferably, the mass of the composite compound powder is 0.04% to 0.1% of the mass of the matrix.

[0013] (4) Melt the quartz tube by heating and swinging it in a swing furnace, and then cool it to obtain an ingot; Preferably, the melting temperature is 800-1000℃.

[0014] (5) The ingot is crushed and powdered in a glove box protected by inert gas, and the powder is loaded into a metal mold; (6) The mold is placed in a hot press furnace, vacuumed and then hot-pressed and sintered. After cooling, P-type bismuth telluride-based composite material is obtained.

[0015] Preferably, the hot pressing temperature is 450-480℃, the pressure is 50-80MPa, and the sintering time is 30-60min.

[0016] Preferably, the inert gas mentioned above includes either argon or nitrogen.

[0017] The composite compound used in this invention can effectively increase hole concentration, suppress intrinsic excitation, and improve Seebeck coefficient and electrical conductivity. At the same time, the composite compound itself has low lattice thermal conductivity, and the introduction of defects such as grain boundaries and second phases after compositing enhances phonon scattering, effectively reducing lattice thermal conductivity. Thus, the material performance is improved by optimizing carrier concentration and reducing lattice thermal conductivity.

[0018] Compared with the prior art, the beneficial effects of the present invention are: by optimizing the carrier concentration and reducing the lattice thermal conductivity, the present invention significantly improves the thermoelectric performance of the p-type bismuth telluride-based composite material, with the zT peak value being nearly 30% higher than that of the matrix material. Attached Figure Description

[0019] Figure 1 Powder X-ray diffraction patterns of Ag8GeTe6, Ag5Te3, and Cu2GeSe3; Figure 2 The Seebeck coefficient of the samples prepared in Comparative Example 1 and Examples 1 to 10 varies with temperature. Figure 3 The graph shows the change in electrical conductivity as a function of temperature for the samples prepared in Comparative Example 1 and Examples 1 to 10. Figure 4 The power factor of the samples prepared in Comparative Example 1 and Examples 1 to 10 varies with temperature. Figure 5 The graph shows the change in total thermal conductivity as a function of temperature for the samples prepared in Comparative Example 1 and Examples 1 to 10. Figure 6 The lattice thermal conductivity of the samples prepared in Comparative Example 1 and Examples 1 to 10 varies with temperature. Figure 7 The graph shows the zT value as a function of temperature for the samples prepared in Comparative Example 1 and Examples 1 to 10. Detailed Implementation

[0020] To facilitate understanding of the present invention, the following embodiments further illustrate the content of the present invention. However, the content of the present invention is not limited to the following embodiments. All raw materials used in the embodiments can be commercially available or prepared using conventional methods.

[0021] Comparative Example 1: (1) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elemental raw materials and encapsulate them in a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (3) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is then loaded into a metal mold; (4) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, obtain the uncomposite P-type bismuth telluride-based material, which is denoted as sample 1.

[0022] Example 1: (1) Weigh out Cu, Ge, and Se elemental raw materials according to the chemical formula Cu2GeSe3, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 900℃ in a muffle furnace, then annealed at 500℃ for 72h, and after cooling, Cu2GeSe3 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.2g of Cu₂GeSe₃ powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Cu2GeSe3 is obtained and is referred to as sample 2.

[0023] The XRD diffraction pattern of the prepared Cu2GeSe3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Cu2GeSe3 is a pure phase.

[0024] Example 2: The difference from Example 1 is that the mass of Cu2GeSe3 is 0.05% of the total mass of the p-type bismuth telluride matrix material.

[0025] (1) Weigh out Cu, Ge, and Se elemental raw materials according to the chemical formula Cu2GeSe3, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 900℃ in a muffle furnace, then annealed at 500℃ for 72h, and after cooling, Cu2GeSe3 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the matrix chemical formula Bi 0.5Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.1g of Cu₂GeSe₃ powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Cu2GeSe3 is obtained and is referred to as sample 3.

[0026] The XRD diffraction pattern of the prepared Cu2GeSe3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Cu2GeSe3 is a pure phase.

[0027] Example 3: The difference from Example 1 is that the mass of Cu2GeSe3 is 0.08% of the total mass of the p-type bismuth telluride matrix material.

[0028] (1) Weigh out Cu, Ge, and Se elemental raw materials according to the chemical formula Cu2GeSe3, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 950°C in a muffle furnace, then annealed at 550°C for 96 hours. After cooling, Cu2GeSe3 compound was obtained and then high-energy ball milling was performed in an argon-protected ball mill jar to obtain powder with a particle size <20μm, a ball milling speed of 600r / min, and a ball milling time of 40min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.16g of Cu₂GeSe₃ powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a 900°C swing furnace for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 40min at 480℃ and 80MPa. After cooling, the P-type bismuth telluride composite material of Cu2GeSe3 is obtained and is referred to as sample 4.

[0029] The XRD diffraction pattern of the prepared Cu2GeSe3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Cu2GeSe3 is a pure phase.

[0030] Example 4: (1) Weigh out Ag and Te raw materials according to the chemical formula Ag5Te3, put them into a clean quartz tube, and evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 850°C in a muffle furnace, then annealed at 420°C for 72 hours. After cooling, Ag5Te3 compound was obtained and powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.2g of Ag5Te3 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Ag5Te3 is obtained and is referred to as sample 5.

[0031] The XRD diffraction pattern of the prepared Ag5Te3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag5Te3 is a pure phase.

[0032] Example 5: The difference from Example 4 is that the mass of Ag5Te3 is 0.04% of the total mass of the p-type bismuth telluride matrix material.

[0033] (1) Weigh out Ag and Te raw materials according to the chemical formula Ag5Te3, put them into a clean quartz tube, and evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 850°C in a muffle furnace, then annealed at 420°C for 72 hours. After cooling, Ag5Te3 compound was obtained and powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.08g of Ag5Te3 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Ag5Te3 is obtained and is referred to as sample 6.

[0034] The XRD diffraction pattern of the prepared Ag5Te3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag5Te3 is a pure phase.

[0035] Example 6: The difference from Example 4 is that the mass of Ag5Te3 is 0.08% of the total mass of the p-type bismuth telluride matrix material.

[0036] (1) Weigh out Ag and Te raw materials according to the chemical formula Ag5Te3, put them into a clean quartz tube, and evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 900°C in a muffle furnace, then annealed at 500°C for 96 hours. After cooling, Ag5Te3 compound was obtained and powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 400r / min, and the ball milling time was 50min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.16g of Ag5Te3 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a 900°C swing furnace for 5 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 50min at 460℃ and 70MPa. After cooling, the P-type bismuth telluride composite material of Ag5Te3 is obtained and is referred to as sample 7.

[0037] The XRD diffraction pattern of the prepared Ag5Te3 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag5Te3 is a pure phase.

[0038] Example 7: (1) Weigh Ag2Te, GeTe, and Te raw materials according to the chemical formula Ag8GeTe6, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 970℃ in a muffle furnace, then annealed at 620℃ for 48h, and after cooling, Ag8GeTe6 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.2g of Ag8GeTe6 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Ag8GeTe6 is obtained and is referred to as sample 8.

[0039] The XRD diffraction pattern of the prepared Ag8GeTe6 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag8GeTe6 is a pure phase.

[0040] Example 8: The difference from Example 7 is that the mass of Ag8GeTe6 is 0.05% of the total mass of the p-type bismuth telluride matrix material.

[0041] (1) Weigh Ag2Te, GeTe, and Te raw materials according to the chemical formula Ag8GeTe6, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 970℃ in a muffle furnace, then annealed at 620℃ for 48h, and after cooling, Ag8GeTe6 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.1g of Ag8GeTe6 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Ag8GeTe6 is obtained and is referred to as sample 9.

[0042] The XRD diffraction pattern of the prepared Ag8GeTe6 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag8GeTe6 is a pure phase.

[0043] Example 9: The difference from Example 7 is that the mass of Ag8GeTe6 is 0.08% of the total mass of the p-type bismuth telluride matrix material.

[0044] (1) Weigh Ag2Te, GeTe, and Te raw materials according to the chemical formula Ag8GeTe6, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 1050℃ in a muffle furnace, then annealed at 700℃ for 72h, and after cooling, Ag8GeTe6 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 550r / min, and the ball milling time was 40min. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements and 0.16g of Ag8GeTe6 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) Place the quartz tube containing the raw material in a 1000℃ swing furnace for 6 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (5) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (6) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 60min at 470℃ and 70MPa. After cooling, the P-type bismuth telluride composite material of Ag8GeTe6 is obtained and is referred to as sample 10.

[0045] The XRD diffraction pattern of the prepared Ag8GeTe6 powder corresponds to the standard card, such as... Figure 1 As shown, this indicates that the compound Ag8GeTe6 is a pure phase.

[0046] Example 10: (1) Weigh Ag2Te, GeTe, and Te raw materials according to the chemical formula Ag8GeTe6, and put them into a clean quartz tube. Evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (2) The quartz tube was melted at 970℃ in a muffle furnace, then annealed at 620℃ for 48h, and after cooling, Ag8GeTe6 compound was obtained. The powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (3) Weigh out Cu, Ge, and Se elemental raw materials according to the chemical formula Cu2GeSe3, put them into a clean quartz tube, and evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (4) The quartz tube was melted at 900°C in a muffle furnace, then annealed at 500°C for 72 hours. After cooling, Cu2GeSe3 compound was obtained and then ball-milled in an argon-protected ball mill jar to obtain powder with a particle size of <20μm, a ball milling speed of 500r / min, and a ball milling time of 30min. (5) Weigh out Ag and Te elemental raw materials according to the chemical formula Ag5Te3, put them into a clean quartz tube, and evacuate the quartz tube to 10°C. -3 Pa, the tube was sealed using an oxyhydrogen flame; (6) The quartz tube was melted at 850°C in a muffle furnace, then annealed at 420°C for 72 hours. After cooling, Ag5Te3 compound was obtained and powder was obtained by high-energy ball milling in an argon-protected ball mill jar. The powder particle size was <20μm, the ball milling speed was 500r / min, and the ball milling time was 30min. (7) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out 200g of Bi, Sb, and Te elements, along with 0.03g each of Ag8GeTe6 powder, Ag5Te3 powder, and Cu2GeSe3 powder, and place them into a clean quartz tube. Evacuate the quartz tube to 10°C. - 3 Pa, the tube was sealed using an oxyhydrogen flame; (8) Place the quartz tube containing the raw material in a swing furnace at 800°C for 4 hours. Swing the furnace during the melting process to ensure that the melt is uniform and the reaction is complete. After cooling, the ingot is obtained. (9) The ingot is crushed for 1 minute in an argon-protected glove box using a crusher, and the powder is loaded into a metal mold; (10) Transfer the mold to the hot press furnace, evacuate to ≤2Pa, and hot press for 30min at 450℃ and 50MPa. After cooling, the P-type bismuth telluride composite material of Ag8GeTe6 is obtained and is referred to as sample 11.

[0047] The XRD diffraction patterns of the prepared Ag5Te3, Cu2GeSe3, and Ag8GeTe6 powders correspond to the standard cards, such as... Figure 1 As shown, this indicates that compounds Ag5Te3, Cu2GeSe3, and Ag8GeTe6 are pure phases.

[0048] like Figure 2The Seebeck coefficient versus temperature graph shows that after being composited with Cu2GeSe3, Ag5Te3, and Ag8GeTe6, the high-temperature Seebeck coefficients of samples 2 to 11 are all higher than that of sample 1. This indicates that the composite compounds effectively doped the samples, increasing the hole concentration and suppressing the decrease in the high-temperature Seebeck coefficient caused by intrinsic excitation. Furthermore, samples 2, 5, and 8, with higher mass percentages of composite compounds, have lower room-temperature Seebeck coefficients than samples 3, 6, 9, and 11, indicating higher hole concentrations. This demonstrates a positive correlation between the mass percentage of the composite compound and the hole concentration.

[0049] like Figure 3 The graph shows the change in conductivity with temperature. It can be seen that after being compounded with Cu2GeSe3, Ag5Te3, and Ag8GeTe6, respectively, the conductivity of samples 2 to 11 is higher than that of sample 1. Furthermore, samples 2, 5, and 8, which have a higher mass percentage, have even higher conductivity, which is correlated with the increase in hole concentration.

[0050] like Figure 4 The graph shows the power factor as a function of temperature. It can be seen that due to the increase in hole concentration, the power factors of samples 2 to 11 are all higher than those of sample 1. Furthermore, the intrinsic excitation of samples 2, 5, and 8, which have higher hole concentrations, is significantly suppressed, and the power factors at higher temperatures are higher than those of samples 3, 6, 9, and 11.

[0051] like Figure 5 and Figure 6 As shown, the graphs depict the changes in total thermal conductivity and lattice thermal conductivity with temperature. It can be seen that due to the suppression of intrinsic excitation, the bipolar thermal conductivity decreases at high temperatures, and the total thermal conductivity of samples 2 to 11 at high temperatures is lower than that of sample 1. At room temperature, the total thermal conductivity mainly originates from electronic thermal conductivity, while samples 2, 5, and 8 have higher electrical conductivity, resulting in higher total thermal conductivity. Simultaneously, it can be seen that the composite compounds introduce more defects, enhancing phonon scattering, leading to significantly lower lattice thermal conductivity for samples 2 to 11 compared to sample 1. Furthermore, the lattice thermal conductivity is even lower when the mass percentage of the composite compound is higher. Samples 3, 6, 9, and 11 have lower composite compound mass percentages, and although their electrical conductivity is improved, the decrease in lattice thermal conductivity offsets the increase in electronic thermal conductivity, resulting in total thermal conductivity at room temperature that is essentially the same as that of sample 1.

[0052] like Figure 7 As shown in the figure, the zT value changes with temperature. Finally, samples 3, 6, 9, and 11 have the highest zT values ​​at room temperature, while samples 2, 5, and 8 have better zT values ​​at high temperatures. The peak zT values ​​of samples 2 to 11 are nearly 30% higher than those of sample 1, which is a significant improvement.

[0053] In summary, the p-type bismuth telluride-based materials composed of Cu2GeSe3, Ag5Te3, and Ag8GeTe6 can effectively increase the hole concentration, suppress intrinsic excitation, and increase the Seebeck coefficient and electrical conductivity. At the same time, the abundant defects introduced enhance phonon scattering and reduce lattice thermal conductivity, ultimately resulting in a significant increase in zT value.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any modifications or alterations made by those skilled in the art without departing from the scope of the present invention using the disclosed technical content are equivalent to equivalent embodiments and still fall within the scope of the present invention.

Claims

1. A composite p-type bismuth telluride-based material, characterized in that, The composite P-type bismuth telluride-based material includes a P-type bismuth telluride matrix with the chemical formula Bi. 0.5 Sb 1.5 Te 3.2 And compounds used for composites, wherein the amount of composite compound used is 0.04% to 0.1% of the mass of the p-type bismuth telluride matrix.

2. The composite p-type bismuth telluride-based material according to claim 1, characterized in that, The chemical formula of the composite compound is selected from one or more of Cu2GeSe3, Ag8GeTe6, and Ag5Te3.

3. A preparation method as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the chemical formula of the composite compound, put them into a quartz tube, and seal the tube under vacuum; (2) The quartz tube is subjected to high-temperature melting and annealing, and after cooling, a composite compound is obtained. The composite compound powder is obtained by ball milling under an inert gas. (3) According to the matrix chemical formula Bi 0.5 Sb 1.5 Te 3.2 Weigh out the elemental Bi, Sb, and Te, and pack them together with the composite compound powder into a quartz tube, then seal the tube under vacuum. (4) Heat and melt the material in a swing furnace, and then cool it to obtain an ingot; (5) The ingot is crushed and powdered under the protection of inert gas, and the powder is loaded into a metal mold; (6) The mold is placed in a hot press furnace, vacuumed and then hot-pressed. After cooling, P-type bismuth telluride-based composite material is obtained.

4. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, In step (1), Cu, Ge, and Se are weighed out of the composite compound with chemical formula Cu2GeSe3, Ag and Te are weighed out of the composite compound with chemical formula Ag5Te3, and Ag2Te, GeTe, and Te are weighed out of the composite compound with chemical formula Ag8GeTe6.

5. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, In step (2), the melting temperature is 850-1050℃, the annealing temperature is 420-700℃, and the annealing time is 48-96h.

6. The method for preparing the composite p-type bismuth telluride-based material according to claim 5, characterized in that, The melting temperature of Cu2GeSe3 is 900-950℃, the annealing temperature is 500-550℃, and the annealing time is 72-96h; the melting temperature of Ag5Te3 is 850-900℃, the annealing temperature is 420-500℃, and the annealing time is 72-96h; the melting temperature of Ag8GeTe6 is 970-1050℃, the annealing temperature is 620-700℃, and the annealing time is 48-72h.

7. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, Step (2) The ball milling speed is 400-600 r / min and the ball milling time is 30-50 min.

8. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, In step (2), the powder particle size is <20μm.

9. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, The melting temperature in step (4) is 800-1000℃.

10. The method for preparing the composite p-type bismuth telluride-based material according to claim 3, characterized in that, Step (6) The hot pressing temperature is 450-480℃, the pressure is 50-80MPa, and the sintering time is 30-60min.

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