Preparation method of flexible bismuth telluride-based thermoelectric material film
By combining electrophoretic deposition and cold isostatic pressing with low-temperature annealing, the problem of preparing bismuth telluride-based thermoelectric thin films with high ZT values, large thickness, and good flexibility using traditional processes has been solved. This has enabled the preparation of high-performance flexible thin films at low temperatures, which are suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI SHENHE THERMO MAGNETICS ELECTRONICS CO LTD
- Filing Date
- 2025-12-29
- Publication Date
- 2026-05-01
AI Technical Summary
Existing technologies struggle to prepare bismuth telluride-based thermoelectric thin films with high ZT values, large thickness, and good flexibility at low temperatures, and traditional processes are incompatible with flexible substrates and roll-to-roll production.
The preparation process employs electrophoretic deposition combined with cold isostatic pressing and low-temperature annealing. A thick film is formed by electrophoretic deposition, and the particles are aligned vertically along the c-axis by cold isostatic pressing. Finally, high c-axis orientation and densification are achieved by low-temperature annealing.
Flexible bismuth telluride-based thermoelectric thin films with excellent thermoelectric properties were prepared at temperatures below 300°C. These films have a thickness of 50–300 μm and excellent flexibility, with high material utilization and low cost, making them suitable for industrialization.
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Figure CN121969032A_ABST
Abstract
Description
A method for preparing a flexible bismuth telluride-based thermoelectric material film Technical Field
[0001] This invention belongs to the field of thermoelectric materials technology and relates to a method for preparing a flexible bismuth telluride-based thermoelectric material film, specifically a preparation process method that combines electrophoretic deposition with cold isostatic pressing and low-temperature annealing. Background Technology
[0002] Since its discovery, bismuth telluride-based thermoelectric materials have relied on high-temperature bulk processes for commercial products. For example, zone melting can produce single crystals with high c-axis orientation, but the material is prone to cleavage along the planes, resulting in a high scrap rate during machining and difficulty in preparing micron-thick sheets. Although powder metallurgy combined with hot pressing can produce fine-grained bulk materials with higher ZT, it is still a rigid material that needs to be mechanically cut into legs and then manually welded and assembled. This results in low material utilization, limited minimum size of thermoelectric legs, high device cost, and difficulty in miniaturization, flexibility, and surface bonding.
[0003] Furthermore, a common drawback of traditional bulk processes is the requirement for prolonged high-temperature holding, which leads to tellurium volatilization and uncontrolled composition. The process itself cannot directly form films and is incompatible with flexible plastic substrates or roll-to-roll production. While existing thin-film technologies (such as magnetron sputtering and electrochemical deposition) can form films, their thickness is typically less than 10 μm, their output power is too low, or they still require annealing at temperatures above 300°C. This makes it difficult to achieve practical thermoelectric thin films that combine high ZT values (≥1.0), large thicknesses (>50 μm), high flexibility, and low cost. Therefore, there is an urgent need for a new process that can achieve performance comparable to or even better than optimal bulk processes at temperatures below 300°C and can directly form films. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a novel method for preparing flexible bismuth telluride-based thermoelectric material films: by combining electrophoretic deposition with cold isostatic pressing and low-temperature annealing, the bismuth telluride-based thermoelectric thin films can achieve high density and high c-axis orientation, enabling them to reach ZT≥1.1 at temperatures far lower than those of traditional bulk processes, and possessing excellent flexibility and high performance.
[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:
[0006] In a first aspect, the present invention provides a method for preparing a flexible bismuth telluride-based thermoelectric material film, comprising the following steps:
[0007] 1) Preparation of bismuth telluride-based charged suspension: Bismuth telluride-based powder with an average particle size of 100 nm to 1 μm is dispersed in an organic solvent to form a mixed liquid with a solid content of 20 to 80 g / L. A charging agent is added to make the absolute value of the suspension potential ≥ 40 mV. Then, ultrasonic magnetic stirring is used for a sufficient time to ensure long-term stability and no sedimentation.
[0008] 2) Electrophoretic deposition of thick film: Using conductive substrate copper foil as deposition electrode and inert graphite as counter electrode, under the conditions of electrode spacing of 5-30 mm and DC voltage of 40-150 V, the bismuth telluride-based charged suspension in step (1) is deposited to obtain a thick film with a thickness of 10-300 μm and a smooth surface.
[0009] 3) Cold isostatic pressing densification and pre-orientation: The wet film is vacuum sealed and placed in a cold isostatic press at a pressure of 100-400 MPa for 3-30 minutes. The particles are initially aligned perpendicular to the film surface along the c-axis.
[0010] 4) Low-temperature annealing induces highly oriented recrystallization: The film after cold isostatic pressing is placed in a vacuum environment and kept at 180-250℃ for 0.5-5h to achieve stress-induced abnormal grain growth and highly c-axis preferred orientation. After annealing, the film exhibits a metallic luster.
[0011] Preferably, in step (1), the molar ratio of Bi, Sb and Te in the bismuth telluride-based powder is 0.4:1.6:3; and the purity of Bi, Sb and Te is 99.999%.
[0012] The organic solvent is selected from any one of ethanol, n-propanol, isopropanol, acetone, and ethyl acetate.
[0013] The charging agent is selected from iodine; the ultrasonic magnetic stirring time is 2-4 hours.
[0014] Preferably, in step (2), the deposition time is 5 to 60 minutes.
[0015] Preferably, in step (3), the wet film is vacuum sealed using a plastic bag sealing method.
[0016] In a second aspect, the present invention provides a flexible bismuth telluride-based thermoelectric material film, which is prepared by the method described in any of the preceding claims.
[0017] The role and effect of invention
[0018] This invention combines electrophoretic deposition with a synergistic process of cold isostatic pressing and low-temperature annealing to achieve densification and high c-axis orientation recrystallization of bismuth telluride-based thick films in the temperature range of 180–250°C. This achieves excellent thermoelectric figure of merit at a temperature far lower than that of traditional zone melting / SPS bulk processes, while also providing high-performance thermoelectric thin films with a thickness of 50–300 μm and excellent flexibility, breaking the path dependence of traditional high-temperature bulk technology.
[0019] The flexible bismuth telluride-based thermoelectric material film prepared by the method of the present invention has thermoelectric performance reaching the level of commercial bulk materials, while achieving true flexibility and miniaturization, and obtaining a flexible free-supported film with a thickness of 50-300 μm, a bending radius of less than 5 mm, and continuous operation after repeated bending.
[0020] The maximum process temperature of this invention is below 250℃, which significantly improves material utilization and greatly reduces manufacturing costs, making it suitable for industrialization. Attached Figure Description
[0021] Figure 1 shows a process flow chart of the present invention. Detailed Implementation
[0022] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, the following embodiments should not be construed as limiting the scope of the present invention.
[0023] Example 1
[0024] (1) Raw material preparation
[0025] According to the molar ratio of Bi, Sb, and Te as raw materials of 0.4:1.6:3, 3000g of pure tellurium, bismuth, and antimony element particles were weighed as matrix materials and placed in a quartz tube. The tube was then evacuated until the internal pressure was less than 2 Pa and sealed. The quartz tube was then placed in a tube furnace, and the temperature was set to 730℃. Under a vacuum of 0.01 Pa, the temperature was increased to 730℃ at a rate of 10℃ / min and held for at least 6 hours, followed by cooling outside the furnace. The high-temperature synthesized material was ball-milled for 60 minutes under argon protection at a speed of 300 rpm, and after sieving, micron-sized bismuth telluride-based powder was obtained.
[0026] (2) Preparation of bismuth telluride-based charged suspension
[0027] Bismuth telluride-based powder with an average particle size of 100 nm to 1 μm was dispersed in ethanol to form a mixture with a solid content of 20 g / L. Iodine was added as a charging agent to make the absolute value of the suspension potential ≥ 40 mV. Then, ultrasonic magnetic stirring was used for a sufficient time (4 h) to ensure long-term stability and no sedimentation.
[0028] (3) Electrophoretic deposition to form a thick film
[0029] Using a conductive substrate copper foil as the deposition electrode and inert graphite as the counter electrode, with an electrode spacing of 5 mm and a DC voltage of 40 V, the bismuth telluride-based charged suspension in step (1) was deposited for 30-60 min to obtain a thick film with a thickness of about 50 μm and a smooth surface.
[0030] (4) Cold isostatic pressing densification and pre-orientation
[0031] The wet film was vacuum sealed with a plastic film and placed in a cold isostatic press at a pressure of 100 MPa for 30 minutes. The particles were initially arranged perpendicular to the film surface along the c-axis.
[0032] (5) Low-temperature annealing induces highly oriented recrystallization
[0033] The film after cold isostatic pressing is placed in a vacuum environment and kept at 180℃ for 3-4 hours to achieve stress-induced abnormal grain growth and highly c-axis preferred orientation. After annealing, the film exhibits a metallic luster.
[0034] Example 2
[0035] (1) Raw material preparation
[0036] According to the molar ratio of Bi, Sb, and Te as raw materials of 0.4:1.6:3, 3000g of pure tellurium, bismuth, and antimony element particles were weighed as matrix materials and placed in a quartz tube. The tube was then evacuated until the internal pressure was less than 2 Pa and sealed. The quartz tube was then placed in a tube furnace, and the temperature was set to 730℃. Under a vacuum of 0.01 Pa, the temperature was increased to 730℃ at a rate of 10℃ / min and held for at least 6 hours, followed by cooling outside the furnace. The high-temperature synthesized material was ball-milled for 60 minutes under argon protection at a speed of 300 rpm, and after sieving, micron-sized bismuth telluride-based powder was obtained.
[0037] (2) Preparation of bismuth telluride-based charged suspension
[0038] Bismuth telluride-based powder with an average particle size of 100 nm to 1 μm was dispersed in ethanol to form a mixture with a solid content of 50 g / L. Iodine was added as a charging agent to make the absolute value of the suspension potential ≥40 mV. Then, ultrasonic magnetic stirring was used for a sufficient time (4 h) to ensure long-term stability and no sedimentation.
[0039] (3) Electrophoretic deposition to form a thick film
[0040] Using a conductive substrate copper foil as the deposition electrode and inert graphite as the counter electrode, with an electrode spacing of 18 mm and a DC voltage of 100 V, the bismuth telluride-based charged suspension in step (1) was deposited for 30-60 min to obtain a thick film with a thickness of about 200 μm and a smooth surface.
[0041] (4) Cold isostatic pressing densification and pre-orientation
[0042] The wet film was vacuum sealed with a plastic film and placed in a cold isostatic press at a pressure of 250 MPa for 30 minutes. The particles were initially arranged perpendicular to the film surface along the c-axis.
[0043] (5) Low-temperature annealing induces highly oriented recrystallization
[0044] The film after cold isostatic pressing is placed in a vacuum environment and kept at 200℃ for 4-5 hours to achieve stress-induced abnormal grain growth and highly c-axis preferred orientation. After annealing, the film exhibits a metallic luster.
[0045] Example 3
[0046] (1) Raw material preparation
[0047] According to the molar ratio of Bi, Sb, and Te as raw materials of 0.4:1.6:3, 3000g of pure tellurium, bismuth, and antimony element particles were weighed as matrix materials and placed in a quartz tube. The tube was then evacuated until the internal pressure was less than 2 Pa and sealed. The quartz tube was then placed in a tube furnace, and the temperature was set to 730℃. Under a vacuum of 0.01 Pa, the temperature was increased to 730℃ at a rate of 10℃ / min and held for at least 6 hours, followed by cooling outside the furnace. The high-temperature synthesized material was ball-milled for 60 minutes under argon protection at a speed of 300 rpm, and after sieving, micron-sized bismuth telluride-based powder was obtained.
[0048] (2) Preparation of bismuth telluride-based charged suspension
[0049] Bismuth telluride-based powder with an average particle size of 100 nm to 1 μm was dispersed in ethanol to form a mixture with a solid content of 80 g / L. Iodine was added as a charging agent to make the absolute value of the suspension potential ≥40 mV. Then, ultrasonic magnetic stirring was used for a sufficient time (2 to 4 h) to ensure long-term stability and no sedimentation.
[0050] (3) Electrophoretic deposition to form a thick film
[0051] Using a conductive substrate copper foil as the deposition electrode and inert graphite as the counter electrode, with an electrode spacing of 30 mm and a DC voltage of 150 V, the bismuth telluride-based charged suspension in step (1) was deposited for 30-60 min to obtain a thick film with a thickness of about 300 μm and a smooth surface.
[0052] (4) Cold isostatic pressing densification and pre-orientation
[0053] The wet film was vacuum sealed with a plastic film and placed in a cold isostatic press at a pressure of 400 MPa for 30 minutes. The particles were initially arranged perpendicular to the film surface along the c-axis.
[0054] (5) Low-temperature annealing induces highly oriented recrystallization
[0055] The film after cold isostatic pressing is placed in a vacuum environment and kept at 250℃ for 4-5 hours to achieve stress-induced abnormal grain growth and highly c-axis preferred orientation. After annealing, the film exhibits a metallic luster.
[0056] The undescribed parts of this invention are the same as or implemented using existing technology. The applicant declares that this invention is illustrated through the above embodiments, but the invention is not limited to the above detailed methods, i.e., it does not mean that the invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.
Claims
1. A method for preparing a flexible bismuth telluride-based thermoelectric material film, characterized in that, The process includes the following steps: 1) Preparation of bismuth telluride-based charged suspension: Bismuth telluride-based powder with an average particle size of 100 nm to 1 μm is dispersed in an organic solvent to form a mixed liquid with a solid content of 20 to 80 g / L. A charging agent is added to make the absolute value of the suspension potential ≥ 40 mV. Then, ultrasonic magnetic stirring is used for a sufficient time to ensure long-term stability and no sedimentation; 2) Electrophoretic deposition to form a thick film: Using a conductive substrate copper foil as the deposition electrode and inert graphite as the counter electrode, the bismuth telluride-based charged suspension from step (1) is deposited under the condition of an electrode spacing of 5 to 30 mm and a DC voltage of 40 to 150 V to obtain a film with a thickness of 10 to 300 mm. 3) Cold isostatic pressing densification and pre-orientation: The wet film is vacuum sealed and placed in a cold isostatic press at a pressure of 100-400 MPa for 3-30 min. The particles are initially arranged perpendicular to the film surface along the c-axis. 4) Low-temperature annealing-induced high-orientation recrystallization: The film after cold isostatic pressing is placed in a vacuum environment and kept at 180-250℃ for 0.5-5 h to achieve stress-induced abnormal grain growth and highly c-axis preferred orientation. After annealing, the film exhibits a metallic luster.
2. The method for preparing a flexible bismuth telluride-based thermoelectric material film according to claim 1, characterized in that: wherein, In step (1), the molar ratio of Bi, Sb and Te in the bismuth telluride-based powder is 0.4:1.6:3; the purity of Bi, Sb and Te is 99.999%.
3. The method for preparing the flexible bismuth telluride-based thermoelectric material film according to claim 1, characterized in that: in, In step (1), the organic solvent is selected from any one of ethanol, n-propanol, isopropanol, acetone, and ethyl acetate.
4. The method for preparing the flexible bismuth telluride-based thermoelectric material film according to claim 1, characterized in that: in, In step (1), the charging agent is selected from iodine; the ultrasonic magnetic stirring time is 2 to 4 hours.
5. The method for preparing the flexible bismuth telluride-based thermoelectric material film according to claim 4, characterized in that: in, In step (2), the deposition time is 5 to 60 minutes.
6. The method for preparing a flexible bismuth telluride-based thermoelectric material film according to claim 1, characterized in that: in, In step (3), the wet membrane is vacuum sealed using a plastic film sealing method.
7. A flexible bismuth telluride-based thermoelectric material film, characterized in that, It is prepared by the method described in any one of claims 1 to 6.