A method for improving the performance and thermal stability of a Te-based thermoelectric arm by using a topological dense packing

Abstract

The application belongs to the technical field of thermoelectric device preparation and connectors, and aims to solve the problem of Te 0.985 Sb 0.015 During the connection of thermoelectric materials and Ni electrodes, a large number of aggregated pores and segregation of doped elements Sb are generated at the interface, which seriously weakens the electrical transport performance and thermal stability at the interface. A method for improving the performance and thermal stability of Te-based thermoelectric arms by using topological dense packing is provided. A topological dense packing NiTe 2‑x , 0≤ x ≤0.9 is synthesized by a solid phase reaction method, which is introduced into the Ni and Te 0.985 Sb 0.015 between them to form a Ni / NiTe 2‑x / Te 0.985 Sb 0.015 / NiTe 2‑x / Ni gradient connection structure. The problem of a large number of aggregated pores and segregation of doped elements Sb due to the severe diffusion of Ni into Te 0.985 Sb 0.015 and reaction at the interface is successfully eliminated, and the performance and service life of the thermoelectric connector are improved.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric device fabrication and connector technology, and relates to a method for improving the performance and thermal stability of Te-based thermoelectric arms using topologically close-packed phases, more specifically, for improving Ni / Te... 0.985 Sb 0.015 Methods for studying the performance and thermal stability of / Ni thermoelectric arms. Through Te... 0.985 Sb 0.015 A Ni-Te alloy with a topologically dense structure is introduced between Ni and Te as a barrier layer to form a gradient connection interface. This effectively eliminates the aggregated pores caused by the intense elemental cross-diffusion and reaction between Ni and Te at the interface, as well as the segregation of the dopant element Sb, thereby improving the performance and thermal stability of the Te-based thermoelectric material / Ni electrode thermoelectric arm. Background Technology

[0002] Te 0.985 Sb 0.015 Thermoelectric materials have zT With excellent thermoelectric performance reaching around 1, as a single-element thermoelectric material, its thermoelectric properties do not fluctuate drastically due to the loss of matrix elements during service, making it more stable than other multi-component materials. This gives it great application potential in the field of thermoelectric power generation, especially in the medium and low temperature range. However, Te... 0.985 Sb 0.015 During the connection with the Ni electrode, the interface will be affected by Ni flowing towards Te. 0.985 Sb 0.015 The intense diffusion and reaction on one side produce a large number of aggregated pores and the segregation of dopant element Sb, which severely weakens the electrical transport performance and thermal stability at the interface. Summary of the Invention

[0003] This invention aims to solve the current Te 0.985 Sb 0.015 During the connection between the thermoelectric material and the Ni electrode, the interface will be affected by Ni-to-Te. 0.985 Sb 0.015 The intense diffusion and reaction on one side generate numerous aggregated pores and Sb segregation, severely weakening the electrical transport performance and thermal stability at the interface. This invention provides a method to improve the performance and thermal stability of Te-based thermoelectric arms using a topologically close-packed phase. The invention introduces a Ni-Te alloy with a topologically close-packed structure as a barrier layer, forming a gradient connection interface, thereby effectively eliminating the aggregated pores and Sb segregation caused by the intense inter-elemental diffusion and reaction between Ni and Te at the interface (e.g., ...). Figure 1 As shown in a) and e), this improves the performance and thermal stability of the Te-based thermoelectric material / Ni electrode thermoelectric arm.

[0004] This invention is achieved by the following technical solution: a method for improving the performance and thermal stability of Te-based thermoelectric arms using a topologically close-packed phase, wherein a topologically close-packed phase NiTe is synthesized via a solid-state reaction method. 2-x , 0≤ x ≤0.9, introduce it into Ni and Te 0.985 Sb 0.015 Ni / NiTe forms between 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient connection structure to replace traditional Ni / Te 0.985 Sb 0.015 / Ni structure.

[0005] The Ni / NiTe 2-x / Te 0.985 Sb 0.015 / NiTe 2-x The / Ni gradient connection structure is densified and connected using a spark plasma sintering (SPS) system.

[0006] The specific steps are as follows:

[0007] (1) Powder preparation: Bulk Te with a purity ≥99.99% and granular Sb were weighed according to the stoichiometric ratio and packaged in a vacuum carbon-plated quartz tube. The quartz tube was placed in a pit furnace and melted at 550℃ for 8 hours. After quenching, it was placed in a pit furnace again and annealed at 400℃ for 24 hours to obtain bulk Te. 0.985 Sb 0.015 After being manually ground, it is used as powder 1;

[0008] Ni powder with a particle size less than 45 μm and a purity ≥ 99.9% was weighed according to stoichiometric ratio and placed in a polytetrafluoroethylene ball mill jar. The mixture was intermittently ball-milled at 1250 rpm for 4 hours, with a 30-minute rest period followed by a 15-minute rest period. The entire process was carried out under an argon protective atmosphere. The resulting powder was cold-pressed into blocks at 15 MPa, then encapsulated in a vacuum quartz tube and placed in a pit furnace for solid-state reaction at 550℃ for 8 hours. The mixture was then cooled with the furnace to obtain blocky NiTe. 2-x , 0≤ x ≤0.9, the resulting block was ball-milled again at 1250 rpm for 1 hour to obtain powder 2;

[0009] Ni powder with a particle size of less than 45μm and a purity of ≥99.9% is used as powder 3;

[0010] (2) Powder loading into the mold: under argon environment, after laying two layers of graphite paper, 0.4g of powder 3 is loaded into a graphite mold with a diameter of 17mm and cold-pressed to 50-60% density; 0.5g of powder 2 is placed above powder 3 and cold-pressed to 50-60% density; 8.5g of powder 1 is placed above powder 2 and cold-pressed to 50-60% density; then 0.5g of powder 2 is placed above powder 1 and cold-pressed to 50-60% density; finally, 0.4g of powder 3 is placed above powder 2 and cold-pressed to 50-60% density, and finally two layers of graphite paper are covered, and the mold is from bottom to top: two layers of graphite paper-powder 3-powder 2-powder 1-powder 2-powder 3-two layers of graphite paper;

[0011] (3) Sintering connection: the graphite mold loaded with powder is placed in the SPS furnace for sintering connection, first pre-pressing 2.5-5MPa, after the vacuum degree in the furnace is extracted to <25Pa, filling 99.999% argon to 0.05MPa, then pulse current is introduced to make the powder uniformly heated to 250℃ at a heating rate of 50-60℃ / min, while the pressure is increased to 55MPa, and the powder is heated to 385-390℃ at a heating rate of 70℃ / min, and the temperature is kept for 10min, then the pressure is quickly released to 2.5-5MPa in 30s, the temperature is unchanged during the pressure release, then the temperature is slowly reduced to 280℃ at a rate of 15-20℃ / min, and then the furnace is naturally cooled, forming a Ni / NiTe 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient structure thermoelectric joint.

[0012] Compared with the prior art, the present application introduces a NiTe x with a composition range of 0≤x≤0.9 between the Te-based thermoelectric material and the electrode material Ni. 2-x As a barrier layer, the formed Ni / NiTe 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient connection structure successfully eliminates the problem of a large number of aggregated pores and the segregation of the doping element Sb at the interface, greatly improving the performance and service life of the thermoelectric joint. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 Fig. 2 is the microstructure and EDS area scanning results of the interface after aging at 200℃ for 6d and 12d; in the figure: a) is the microstructure and EDS area scanning results of the Ni / Te 0.985 Sb 0.015Interface micro-morphology and EDS area scan results of Ni / NiTe2 after aging at 200℃ for 6d / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 6d 1.8 / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 12d 1.5 / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 12d 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe2 after aging at 200℃ for 6d / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 12d 1.8 / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 12d 1.5 / Te 0.985 Sb 0.015 Interface micro-morphology and EDS area scan results of Ni / NiTe after aging at 200℃ for 12d

[0014] Figure 2 Output power density and interface contact resistivity of each joint during aging process; in the figure: a) is output power density; b) is interface contact resistivity. DETAILED DESCRIPTION

[0015] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, and the materials cited and referred to herein are incorporated by reference in their entirety.

[0017] The equivalents of the described specific embodiments that would be apparent to those skilled in the art and that are realized by routine experimentation are intended to be included in the present application.

[0018] The experimental methods in the following examples are all conventional methods unless otherwise specified. The instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0019] Example 1: A method for improving the performance and thermal stability of a Sb / Ni thermoelectric arm 0.985 Sb 0.015 The specific steps of the method for improving the performance and thermal stability of a Sb / Ni thermoelectric arm are as follows:

[0020] Bulk Te with a purity of ≥99.99% and granular Sb were weighed according to the stoichiometric ratio and packaged in a vacuum carbon-coated quartz tube. The quartz tube was placed in a muffle furnace and melted at 550°C for 8h. After quenching, it was again placed in a muffle furnace and annealed at 400°C for 24h to obtain bulk Te 0.985 Sb 0.015 After manual grinding, it was used as powder 1;

[0021] Ni powder with a particle size of less than 45μm and a purity of ≥99.9% and Te powder were weighed according to the stoichiometric ratio of NiTe2, placed in a polytetrafluoroethylene ball mill jar, and intermittently mixed for 4h at 1250rpm with 15min rest after each 30min of ball milling. The whole process was carried out in an argon protective atmosphere. The obtained powder was cold-pressed into a block at 15MPa, then packaged in a vacuum quartz tube, and placed in a muffle furnace for solid-phase reaction at 550°C for 8h, then cooled in the furnace to obtain bulk NiTe2. The obtained bulk was again intermittently ball-milled at 1250rpm for 1h to obtain powder 2.

[0022] Ni powder with a particle size of less than 45μm and a purity of ≥99.9% was used as powder 3.

[0023] Under an argon environment, 0.4g of powder 3 was loaded into a graphite mold and cold-pressed to a density of 50-60%. Then 0.5g of powder 2 was placed on top of the powder 3 and cold-pressed to a density of 50-60%. Then 8.5g of powder 1 was placed on top of the powder 2 and cold-pressed to a density of 50-60%. Then 0.5g of powder 2 was placed on top of the powder 1 and cold-pressed to a density of 50-60%. Then 0.4g of powder 3 was placed on top of the powder 2 and cold-pressed to a density of 50-60%. Finally, two layers of graphite paper were placed on top.

[0024] A graphite mold containing powder is placed in an SPS furnace for sintering and bonding. First, a pre-pressure of 2.5-5 MPa is applied. After the vacuum level in the furnace is reduced to below 25 Pa, 99.999% argon gas is introduced to a pressure of 0.05 MPa. Then, a pulsed current is applied at a heating rate of 50-60 °C / min to uniformly heat the powder to 250 °C. Simultaneously, the pressure is increased to 55 MPa and held. While holding the pressure, the powder is heated at a rate of 70 °C / min to 385-390 °C and held for 10 min. Then, the pressure is rapidly released to 2.5-5 MPa over 30 seconds, maintaining a constant temperature during the release. The temperature is then slowly reduced to 280 °C at a rate of 15-20 °C / min, and subsequently cooled in the furnace to form Ni / NiTe2. / Te 0.985 Sb 0.015 / NiTe2 / Ni gradient structure thermoelectric joint.

[0025] Ni / NiTe2 / Te 0.985 Sb 0.015 Typical microstructures of the interface after aging at 200℃ for 6 days and 12 days, and EDS surface scanning results are as follows: Figure 1 As shown in (b) and (f), the results indicate that the introduction of NiTe2 significantly inhibits the migration of Ni into Te, and does not affect the migration of Ni into Te. 0.985 Sb 0.015 A distinct reaction layer and diffusion layer were found, effectively solving the Ni / Te problem. 0.985 Sb 0.015 The interface exhibits aggregated pores and Sb enrichment due to the intense diffusion of Ni and the loss of Te, and is compared with... Figure 1 As shown in (b) and (f), no thickening of the reaction layer or diffusion layer, nor the appearance of pores or Sb enrichment was observed during the aging process; the electrical transport performance and thermal stability of the joint were thus effectively improved, such as Figure 2 As shown by the purple line group in (a), after aging at 200℃ for 6 days, Ni / NiTe2 / Te 0.985 Sb 0.015 The output power density of the / NiTe2 / Ni connector can still reach 181mW / cm². 2 Around, much higher than Ni / Te 0.985 Sb 0.015 / Ni's 167mW / cm 2 ,like Figure 2 (a) The black line group, and Ni / NiTe2 / Te 0.985 Sb 0.015 The output power density of the / NiTe2 / Ni connector remains almost unchanged during aging; the corresponding contact resistivity of the former is only 9.31 μΩ·cm.2 , far less than Ni / Te 0.985 Sb 0.015 21 μΩ·cm at the interface 2 , and also almost unchanged during aging process Figure 2 (b); which proves that the introduction of topological dense phase NiTe2 is an effective method to improve the performance of Te-based thermoelectric junction.

[0026] Example 2: A method for improving the performance and thermal stability of Ni / Te 0.985 Sb 0.015 / Ni thermoelectric arm by using topological dense phase. The specific method is as follows:

[0027] The preparation method of powder 1 is the same as that of example 1; powder 2: Ni powder and Te powder with purity ≥99.9% are weighed according to the stoichiometric ratio of NiTe 1.8 , and the bulk NiTe 1.8 is obtained by cooling in the furnace, and the obtained bulk is intermittently ball milled at 1250 r / min for 1 h to obtain powder 2, and the remaining method is the same as that described in example 1; and the Ni / NiTe 1.8 / Te 0.985 Sb 0.015 / NiTe 1.8 / Ni gradient structure thermoelectric junction.

[0028] Ni / NiTe 1.8 / Te 0.985 Sb 0.015 The typical microstructure and EDS area scanning results of the interface after aging for 6d and 12d at 200℃ are shown in Figure 1 (c) and (g). The results show that the introduction of NiTe 1.8 also effectively solves the problems of aggregation type holes and enrichment of Sb element existing at the interface of Ni / Te 0.985 Sb 0.015 / Ni junction, and it can be known from the comparison of Figure 1 (c) and (g) that no thickening of reaction layer and diffusion layer and appearance of holes and Sb enrichment are observed during the aging process; the electrical transport performance and stability of the junction are also effectively improved, as shown by the green line group in Figure 2 (a), after aging for 6d at 200℃, the output power density of the Ni / NiTe 1.8 / Te 0.985 Sb 0.015 / NiTe 1.8 / Ni junction can still reach 191 mW / cm 2 , which is much higher than that of Ni / Te 0.985 Sb 0.015 / Ni's 167mW / cm 2 , and Ni / NiTe 1.8 / Te 0.985 Sb 0.015 / NiTe 1.8 The output power density of the / Ni connector remains almost unchanged during aging; the corresponding contact resistivity of the former is only 12.1 μΩ·cm. 2 Much smaller than Ni / Te 0.985 Sb 0.015 21 μΩ·cm at the interface 2 And similarly, it remained almost unchanged during the validity period. Figure 2 (b)); The above proof introduces the topologically dense NiTe phase. 1.8 This is an effective method to improve the performance of Te-based thermoelectric connectors.

[0029] Example 3: A method for improving Ni / Te ratio using topological close-packed phases 0.985 Sb 0.015 Methods for determining the performance and thermal stability of / Ni thermoelectric arms. Specific methods are as follows:

[0030] The preparation method of powder 1 is the same as in Example 1; powder 2: Ni powder with a purity ≥99.9% and Te powder are prepared according to NiTe 1.5 The stoichiometric weights were weighed and cooled in the furnace to obtain bulk NiTe. 1.5 The resulting block was then intermittently ball-milled at 1250 rpm for 1 hour to obtain powder 2. The remaining methods were the same as those described in Example 1; forming Ni / NiTe 1.5 / Te 0.985 Sb 0.015 / NiTe 1.5 / Ni gradient structure thermoelectric joint.

[0031] Ni / NiTe 1.5 / Te 0.985 Sb 0.015 Typical interface microstructures and EDS surface scan results after aging at 200℃ for 6 and 12 days are shown below. Figure 1 As shown in (d) and (h). The results indicate that NiTe 1.5 The introduction of this also effectively solved the Ni / Te problem. 0.985 Sb 0.015 The presence of clustered voids and Sb element enrichment at the / Ni interface, and a comparison Figure 1 As shown in (d) and (h), no thickening of the reaction layer or diffusion layer, nor the appearance of pores or Sb enrichment was observed during the aging process; the electrical transport performance and stability of the joint were also effectively improved, such as Figure 2(a) shows the blue line group, Ni / NiTe 1.5 / Te 0.985 Sb 0.015 / NiTe 1.5 The output power density of the / Ni connector is 169 mW / cm² after 6 days of aging. 2 Higher than Ni / Te 0.985 Sb 0.015 / Ni's 167mW / cm 2 The corresponding contact resistivity of the former is only 15.1 μΩ·cm. 2 Much smaller than Ni / Te 0.985 Sb 0.015 21 μΩ·cm at the interface 2 And similarly, it remained almost unchanged during the validity period. Figure 2 (b)); The above proof introduces the topologically dense NiTe phase. 1.5 Phase 1 is an effective method to improve the performance of Te-based thermoelectric joints.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the performance and thermal stability of Te-based thermoelectric arms using topologically close-packed phases, characterized in that: Topologically close-packed NiTe was synthesized via a solid-state reaction method. 2-x , 0≤x≤0.9, introduce this into Ni and Te 0.985 Sb 0.015 Ni / NiTe forms between 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient connection structure to replace traditional Ni / Te 0.985 Sb 0.015 / Ni structure; The Ni / NiTe 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient connection structure is sintered and densified and connected using a spark plasma sintering (SPS) device. The specific steps are as follows: (1) Powder preparation: Bulk Te with a purity ≥99.99% and granular Sb were weighed according to the stoichiometric ratio and packaged in a vacuum carbon-plated quartz tube. The quartz tube was placed in a pit furnace and melted at 550℃ for 8 hours. After quenching, it was placed in a pit furnace again and annealed at 400℃ for 24 hours to obtain bulk Te. 0.985 Sb 0.015 After being manually ground, it is used as powder 1; Ni powder with a particle size of less than 45 μm and a purity of ≥99.9% was weighed with Te powder according to stoichiometric ratio and placed in a polytetrafluoroethylene ball mill jar for intermittent ball milling for 4 hours. The entire process was carried out under an argon protective atmosphere. The resulting powder was cold-pressed into blocks at 15 MPa, then sealed in a vacuum quartz tube and placed in a pit furnace for solid-phase reaction at 550 °C for 8 hours. The mixture was then cooled with the furnace to obtain blocky NiTe. 2-χ , 0≤ x ≤0.9, the resulting block was intermittently ball-milled for 1 hour to obtain powder 2; Ni powder with a particle size of less than 45μm and a purity of ≥99.9% is used as powder 3; (2) Powder loading into the mold: Under argon atmosphere, after laying two layers of graphite paper, 0.4g of powder 3 is loaded into a graphite mold with a diameter of 17mm and cold-pressed to a density of 50-60%; 0.5g of powder 2 is placed on top of powder 3 and cold-pressed to a density of 50-60%; then 8.5g of powder 1 is placed on top of powder 2 and cold-pressed to a density of 50-60%; then 0.5g of powder 2 is placed on top of powder 1 and cold-pressed to a density of 50-60%; finally, 0.4g of powder 3 is placed on top of powder 2 and cold-pressed to a density of 50-60%, and finally two layers of graphite paper are covered. The order from bottom to top in the mold is two layers of graphite paper - powder 3 - powder 2 - powder 1 - powder 2 - powder 3 - two layers of graphite paper; (3) Sintering connection: The graphite mold containing the powder is placed in the SPS furnace for sintering connection. First, the pre-pressure is 2.5-5 MPa. After the vacuum degree in the furnace is reduced to <25 Pa, 99.999% argon gas is introduced to 0.05 MPa. Then, a pulse current is introduced to heat the powder at a rate of 50-60℃ / min to 250℃. While heating, the pressure is increased to 55 MPa and held. While holding the pressure, the powder is heated to 385-390℃ at a rate of 70℃ / min and held for 10 min. Then, the pressure is quickly released to 2.5-5 MPa in 30 s. The temperature remains unchanged during the pressure release. Then, the temperature is slowly reduced to 280℃ at a rate of 15-20℃ / min. After that, the furnace is allowed to cool naturally to form Ni / NiTe. 2-x / Te 0.985 Sb 0.015 / NiTe 2-x / Ni gradient structure thermoelectric joint.

2. The method for improving the performance and thermal stability of Te-based thermoelectric arms using topologically close-packed phases according to claim 1, characterized in that: The intermittent ball milling method in step (1) is as follows: ball mill for 30 minutes and then rest for 15 minutes, and mix at 1250 rpm.

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