A Mg3(Sb,Bi)2-based thermoelectric material and a Mg3(Sb,Bi)2-based thermoelectric arm material and their preparation method

Abstract

This invention discloses a Mg3(Sb,Bi)2-based thermoelectric material and a Mg3(Sb,Bi)2-based thermoelectric arm material, as well as their preparation method, belonging to the field of thermoelectric materials technology. The chemical composition of the Mg3(Sb,Bi)2-based thermoelectric material is Mg... 3.5‑x Co x Sb 2‑y‑z Bi y Te z The Mg3(Sb,Bi)2-based thermoelectric arm material sequentially comprises a first Cu layer, a first Mg-Co interface layer, a Mg3(Sb,Bi)2-based thermoelectric material layer, a second Mg-Co interface layer, and a second Cu layer. The Co element introduced into the Mg3(Sb,Bi)2-based thermoelectric material of this invention can, on the one hand, enter the crystal lattice to form Co-Mg bonds, which helps to increase the overall melting point of the matrix material; on the other hand, some Co elements exist at the grain boundaries to form a Mg-Co second phase, which can promote grain growth, reduce grain boundary scattering, and improve the thermoelectric performance of the material in the near-room temperature range.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials technology, and in particular to a Mg3(Sb,Bi)2-based thermoelectric material and a Mg3(Sb,Bi)2-based thermoelectric arm material and their preparation method. Background Technology

[0002] Thermoelectric materials are functional materials capable of directly converting heat energy into electrical energy. Based on the Seebeck and Peltier thermoelectric effects, they can generate electricity and provide electrothermal cooling without the need for moving mechanical parts. Their core advantages lie in their compact, noiseless structure, lack of mechanical wear, high operational reliability, and environmental friendliness, allowing for direct energy recovery from various types of medium- and low-temperature waste heat. In the field of energy utilization, thermoelectric materials can be widely used in waste heat power generation scenarios such as industrial waste heat, vehicle exhaust, and steel and chemical flue gas, realizing the resource utilization of low-grade thermal energy. Their applications are particularly prominent in thermal management, where, based on the Peltier effect, they can achieve precise temperature control, localized point cooling, and uniform heat dissipation, adapting to the constant-temperature thermal management needs of precision electronic devices, laser equipment, sensors, and vehicle batteries.

[0003] Currently, Bi2Te3-based compounds remain the mainstream commercial room-temperature thermoelectric materials. These materials have mature processes, a high degree of industrialization, and dimensionless thermoelectric figure of merit (ZT) of 0.8–1 in the room-temperature range, making them the core materials for low-temperature waste heat recovery, precision instrument refrigeration, and commercial thermoelectric devices. However, the Bi2Te3-based system has inherent drawbacks that are difficult to avoid. Its crystal structure exhibits significant anisotropy, resulting in high mechanical brittleness and susceptibility to cracking and failure under complex conditions such as industrial vibration and vehicle exhaust. Furthermore, the limited reserves and high market prices of rare elements such as tellurium in the material composition increase the cost of raw materials, raising the investment in the manufacturing and maintenance of thermoelectric devices. In addition, the difficulty in processing and molding, and the high cost of large-scale packaging, all contribute to the limited widespread application of Bi2Te3-based thermoelectric technology in fields such as industrial waste heat recovery and automotive energy recovery.

[0004] In contrast, novel Mg3(Sb,Bi)2-based thermoelectric materials have emerged as a popular candidate to replace traditional bismuth telluride systems due to their outstanding comprehensive advantages. This system possesses intrinsically high thermoelectric transport properties, strong controllability of crystal structure and microstructure, and superior mechanical toughness and structural stability compared to Bi2Te3 alloys, making it suitable for harsh industrial service environments. Furthermore, the abundant and inexpensive reserves of raw materials such as magnesium, antimony, and bismuth provide inherent conditions for low-cost, large-scale mass production, indicating significant potential for industrial application. However, two key bottlenecks remain to be overcome: firstly, its room-temperature thermoelectric performance is slightly lower than that of commercially available Bi2Te3-based materials, and it suffers from thermoelectric performance degradation during long-term high-temperature service, affecting device output stability and lifespan; secondly, the Mg3(Sb,Bi)2 matrix has high chemical reactivity, readily undergoing interfacial diffusion and chemical reactions with commonly used copper-based metal electrodes, leading to increased contact resistance and interfacial bonding failure, severely weakening the long-term reliability of thermoelectric devices. Therefore, optimizing room-temperature performance, suppressing high-temperature degradation, and improving electrode interfacial stability are the core research directions for promoting the industrialization of this material. Summary of the Invention

[0005] The purpose of this invention is to address the problems of low near-room temperature thermoelectric performance, decreased high-temperature stability, and unstable thermoelectric arm interface of existing Mg3(Sb,Bi)2-based thermoelectric materials, and to provide a Mg3(Sb,Bi)2-based thermoelectric arm material with both high thermoelectric performance and high stability, as well as its preparation method, so as to promote the large-scale application of Mg3(Sb,Bi)2-based thermoelectric materials.

[0006] A further technical problem to be solved by the present invention is to provide a Mg3(Sb,Bi)2-based thermoelectric arm material and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A Mg3(Sb,Bi)2-based thermoelectric material with the chemical composition Mg 3.5-x Co x Sb 2-y-z Bi y Te z , where 0≤x≤0.3, 0<y≤1.8, 0<z≤0.05.

[0009] The chemical composition of the Mg3(Sb,Bi)2-based thermoelectric material is Mg 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Mg 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03or Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 .

[0010] Some Co elements enter the crystal lattice to form Co-Mg bonds, while some Co elements exist at the grain boundaries to form the Mg-Co second phase.

[0011] The preparation method of the above-mentioned Mg3(Sb,Bi)2-based thermoelectric material includes the following steps:

[0012] (1) Weigh the metals Mg, Co, Sb, Bi and Te in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=(3.5-x):x:(2-yz):y:z, and ball mill the weighed metals; where 0≤x≤0.3, 0<y≤1.8, 0<z≤0.05; the ball milling time in this step is 2~10h;

[0013] (2) The uniformly ground powder is placed in a graphite mold in an inert atmosphere and subjected to hot pressing treatment; the temperature of hot pressing treatment is 720~840℃, the pressure of hot pressing treatment is 10-20MPa, and the temperature is maintained for 5-40 minutes under pressure.

[0014] (3) After hot pressing, the material is naturally cooled to room temperature to obtain a dense Mg. 3.5-x Co x Sb 2-y-z Bi y Te z Material.

[0015] The heating current during hot pressing is 150-350mA.

[0016] The hot pressing process is carried out under a vacuum of 1-15 Pa.

[0017] A Mg3(Sb,Bi)2-based thermoelectric arm material has an overall sandwich structure; the Mg3(Sb,Bi)2-based thermoelectric arm material sequentially includes a first Cu layer, a first Mg-Co interface layer, a Mg3(Sb,Bi)2-based thermoelectric material layer, a second Mg-Co interface layer, and a second Cu layer.

[0018] The thickness of the first Cu layer is 50-200 μm; the thickness of the first Mg-Co interface layer is 20-80 μm; the thickness of the second Mg-Co interface layer is 20-80 μm; and the thickness of the second Cu layer is 50-200 μm. The thickness of the Mg3(Sb,Bi)2-based thermoelectric material layer is designed according to requirements.

[0019] The preparation method of the above-mentioned Mg3(Sb,Bi)2-based thermoelectric arm material includes the following steps:

[0020] (1) Prepare Cu powder, Mg-Co nanopowder and the above-mentioned Mg3(Sb,Bi)2-based thermoelectric material after surface treatment;

[0021] (2) The Cu powder / Mg-Co nanopowder / Mg3(Sb,Bi)2-based thermoelectric material / Mg-Co nanopowder / Cu powder sandwich structure is placed in a graphite mold and hot-pressed; the hot-pressing temperature is 400-520℃, the pressure is 2-10MPa, and the holding time is 10-50min.

[0022] (3) After the hot pressing treatment is completed, the pressure is unloaded and the temperature is adjusted to 350-450℃ for in-situ annealing for 8-20h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material.

[0023] The Mg-Co nanopowder is prepared as follows: Mg and Co metal powders are weighed according to the ratio of Mg:Co=1:(2+a) and then ground or ball-milled (preferably for 2-8 hours); where 0≤a≤0.5.

[0024] Among them, the surface-treated Mg3(Sb,Bi)2-based thermoelectric material is the Mg3(Sb,Bi)2-based thermoelectric material mentioned above, which undergoes a process to remove surface impurities. Surface treatment refers to mechanical grinding to remove the surface oxide layer or impurities.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) The Mg3(Sb,Bi)2-based thermoelectric material of the present invention has high thermoelectric performance and high stability. The Co element introduced into the material can enter the crystal lattice and form Co-Mg bonds with a stronger strength than Mg-Mg bonds (the melting point of Co is much higher than that of Mg), which helps to increase the overall melting point of the matrix material and thus improve the stability. On the other hand, some Co elements exist at the grain boundaries to form a Mg-Co second phase, which can promote grain growth, reduce grain boundary scattering, and improve the thermoelectric performance of the material in the near-room temperature range.

[0027] (2) In the Mg3(Sb,Bi)2-based thermoelectric arm material of the present invention, the Mg-Co phase is used as the interface layer material to prepare the thermoelectric arm, which effectively avoids the chemical reaction between the Mg element in Mg3(Sb,Bi)2 and the metal electrode, resulting in a decrease in interface stability. Moreover, the Mg-Co as the interface layer effectively avoids the generation of impurity phases by other new elements, thereby reducing the thermoelectric performance of the material.

[0028] (3) The Mg3(Sb,Bi)2-based thermoelectric arm material of the present invention is hot-pressed again, which not only ensures the high thermoelectric performance and high stability of the Mg3(Sb,Bi)2 matrix material, but also makes the Mg-Co interface layer and the Mg3(Sb,Bi)2 matrix material well bonded, with low contact resistance and stable interface; the in-situ low-temperature annealing further reduces crystal defects such as Mg vacancies in the Mg3(Sb,Bi)2 matrix material and improves the thermal stability of the material.

[0029] (4) The Mg3(Sb,Bi)2-based thermoelectric materials and Mg3(Sb,Bi)2-based thermoelectric arm materials of the present invention effectively solve the problems that existing Mg3(Sb,Bi)2-based thermoelectric materials cannot simultaneously possess high thermoelectric performance and high stability, and have poor interfacial stability of thermoelectric arms, which helps to promote the industrial application of Mg3(Sb,Bi)2-based thermoelectric materials. Attached Figure Description

[0030] Figure 1 The Mg prepared in Example 1 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Material conductivity and Seebeck coefficient as a function of temperature;

[0031] Figure 2 The Mg prepared in Example 2 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 Material conductivity and Seebeck coefficient as a function of temperature;

[0032] Figure 3 The Mg prepared in Example 3 3.2 Co 0.3 SbBi 0.99 Te 0.01 Mg prepared in Comparative Example 1 3.5 SbBi 0.99 Te 0.01 Grain size analysis diagram. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1:

[0035] Part 1: Preparation of Mg 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Thermoelectric materials.

[0036] (1) Weigh out Mg, Co, Sb, Bi and Te with a purity of 99.99% in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=3.4:0.1:1.65:0.3:0.05, put them into a ball mill jar, and mix and grind them on a high-energy ball mill for 2 hours.

[0037] (2) Place the evenly ground powder into a graphite mold in an inert atmosphere and quickly transfer it to a hot press for hot pressing.

[0038] (3) Turn on the hot press, place the graphite mold on the sample stage, ensure that the mold is not tilted, and close the hot press chamber door;

[0039] (4) Turn on the mechanical pump and evacuate to 1 Pa;

[0040] (5) Under the vacuum conditions formed in step (4) above, turn on the heating button, adjust the current to 150mA, heat to 840℃, and apply a pressure of 10MPa;

[0041] (6) Turn off the mechanical pump and maintain the temperature for 40 minutes under pressure.

[0042] (7) Turn off the heating power supply and the mechanical pump, and allow it to cool naturally to room temperature to obtain a dense Mg. 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Thermoelectric materials.

[0043] Part 2: Preparation of Mg3(Sb,Bi)2-based thermoelectric arm materials.

[0044] (8) Weigh high-purity metal powders Mg and Co according to the ratio of Mg:Co=1:2, grind them in a high-energy ball mill for 4 hours to obtain Mg-Co nanopowder;

[0045] (9) Mg 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Impurities on the material surface are removed by mechanical grinding, using Cu powder with a purity ≥99.9%, according to Cu / Mg-Co / Mg ratio. 3.4 Co 0.1 Sb1.65 Bi 0.3 Te 0.05 The / Mg-Co / Cu sandwich structure is placed in a graphite mold and subjected to secondary hot pressing;

[0046] (10) The hot pressing temperature is 400℃, the pressure is 2MPa, and the holding time is 50min;

[0047] (11) Unload the pressure and adjust the temperature to 450℃ for in-situ annealing for 8 hours to obtain Mg3(Sb,Bi)2-based thermoelectric arm material. In the Mg3(Sb,Bi)2-based thermoelectric arm material obtained in this embodiment, the thickness of the first Mg-Co interface layer and the second Mg-Co interface layer are both 20μm; the thickness of the first Cu layer and the second Cu layer are both 50μm; and the thickness of the Mg3(Sb,Bi)2-based thermoelectric material layer is 2mm.

[0048] Figure 1 Mg prepared in Example 1 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Curves showing the relationship between the electrical conductivity and Seebeck coefficient of thermoelectric materials and temperature. Figure 1 The results show that the room temperature conductivity and Seebeck coefficient are 8.7 × 10⁻⁶. 4 The conductivity is 172 μV / K and S / m; moreover, the conductivity decreases with increasing temperature, exhibiting metallic conductivity behavior.

[0049] Example 2:

[0050] Part 1: Preparation of Mg 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 Thermoelectric materials.

[0051] (1) Weigh out Mg, Co, Sb, Bi and Te with a purity of 99.99% in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=3.3:0.2:1.47:0.5:0.03, put them into a ball mill jar, and mix and grind them on a high-energy ball mill for 6 hours.

[0052] (2) Place the evenly ground powder into a graphite mold in an inert atmosphere and quickly transfer it to a hot press for hot pressing.

[0053] (3) Turn on the hot press, place the graphite mold on the sample stage, ensure that the mold is not tilted, and close the hot press chamber door;

[0054] (4) Turn on the mechanical pump and evacuate to 8 Pa;

[0055] (5) Under the vacuum conditions formed in step (4) above, turn on the heating button, adjust the current to 350mA, heat to 800℃, and apply a pressure of 15MPa;

[0056] (6) Turn off the mechanical pump and maintain the temperature for 20 minutes under pressure.

[0057] (7) Turn off the heating power supply and the mechanical pump, and allow it to cool naturally to room temperature to obtain a dense Mg. 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 Thermoelectric materials.

[0058] Part 2: Preparation of Mg3(Sb,Bi)2-based thermoelectric arm materials.

[0059] (8) Weigh high-purity metal powders Mg and Co according to the ratio of Mg:Co=1:2.1, grind them in a high-energy ball mill for 5 hours to obtain Mg-Co nanopowder;

[0060] (9) Mg 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 Impurities on the material surface are removed by mechanical grinding, followed by processing according to Cu / Mg-Co / Mg 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 The Mg-Co / Cu sandwich structure is placed in a graphite mold and subjected to secondary hot pressing;

[0061] (10) The hot pressing temperature is 450℃, the pressure is 6MPa, and the holding time is 25min;

[0062] (11) Unload the pressure, adjust the temperature to 400℃ and perform in-situ annealing for 14h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material. In the Mg3(Sb,Bi)2-based thermoelectric arm material obtained in this embodiment, the thickness of the first Mg-Co interface layer and the second Mg-Co interface layer are both 50μm; the thickness of the first Cu layer and the second Cu layer are both 200μm; and the thickness of the Mg3(Sb,Bi)2-based thermoelectric material layer is 10mm.

[0063] Figure 2 Mg prepared in Example 2 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03Curves showing the relationship between the electrical conductivity and Seebeck coefficient of thermoelectric materials and temperature. Figure 2 As can be seen from Example 2, the Mg prepared 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 The room temperature conductivity and Seebeck coefficient of the thermoelectric material are 8.2 × 10⁻⁶. 4 S / m and 168 μV / K; and the relationship between conductivity and Seebeck coefficient with temperature is similar to that of the material in Example 1.

[0064] Example 3:

[0065] Part 1: Preparation of Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 Thermoelectric materials.

[0066] (1) Weigh out Mg, Co, Sb, Bi and Te with a purity of 99.99% in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=3.2:0.3:1:0.99:0.01, put them into a ball mill jar, and place them on a high-energy ball mill for 10 hours to mix and grind.

[0067] (2) Place the evenly ground powder into a graphite mold in an inert atmosphere and quickly transfer it to a hot press for hot pressing.

[0068] (3) Turn on the hot press, place the graphite mold on the sample stage, ensure that the mold is not tilted, and close the hot press chamber door;

[0069] (4) Turn on the mechanical pump and evacuate to 15 Pa;

[0070] (5) Under the vacuum conditions formed in step (4) above, turn on the heating button, adjust the current to 350mA, heat to 720℃, and apply a pressure of 15MPa;

[0071] (6) Turn off the mechanical pump and maintain the temperature for 5 minutes under pressure.

[0072] (7) Turn off the heating power supply and the mechanical pump, and allow it to cool naturally to room temperature to obtain a dense Mg. 3.2 Co 0.3 SbBi 0.99 Te 0.01 Thermoelectric materials.

[0073] Part 2: Preparation of Mg3(Sb,Bi)2-based thermoelectric arm materials.

[0074] (8) Weigh high-purity metal powders Mg and Co according to the ratio of Mg:Co=1:2.5, grind them in a high-energy ball mill for 8 hours to obtain Mg-Co nanopowder;

[0075] (9) Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 Impurities on the material surface are removed by mechanical grinding, followed by processing according to Cu / Mg-Co / Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 The Mg-Co / Cu sandwich structure is placed in a graphite mold and subjected to secondary hot pressing;

[0076] (10) The hot pressing temperature is 520℃, the pressure is 10MPa, and the holding time is 15min;

[0077] (11) Unload the pressure, adjust the temperature to 350℃ and perform in-situ annealing for 20h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material. In the Mg3(Sb,Bi)2-based thermoelectric arm material obtained in this embodiment, the thickness of the first Mg-Co interface layer and the second Mg-Co interface layer are both 80μm; the thickness of the first Cu layer and the second Cu layer are both 100μm; and the thickness of the Mg3(Sb,Bi)2-based thermoelectric material layer is 5mm.

[0078] Comparative Example 1:

[0079] Comparative Example 1: Preparation of Co-free Mg3(Sb,Bi)2-based thermoelectric materials.

[0080] Part 1: Preparation of Mg 3.5 SbBi 0.99 Te 0.01 Thermoelectric materials.

[0081] (1) Weigh out Mg, Sb, Bi and Te with a purity of 99.99% in an inert atmosphere according to the stoichiometric ratio of Mg:Sb:Bi:Te=3.5:1:0.99:0.01, put them into a ball mill jar, and mix and grind them on a high-energy ball mill for 10 hours.

[0082] (2) Place the evenly ground powder into a graphite mold in an inert atmosphere and quickly transfer it to a hot press for hot pressing.

[0083] (3) Turn on the hot press, place the graphite mold on the sample stage, ensure that the mold is not tilted, and close the hot press chamber door;

[0084] (4) Turn on the mechanical pump and evacuate to 15 Pa;

[0085] (5) Under the vacuum conditions formed in step (4) above, turn on the heating button, adjust the current to 350mA, heat to 720℃, and apply a pressure of 15MPa;

[0086] (6) Turn off the mechanical pump and maintain the temperature for 5 minutes under pressure.

[0087] (7) Turn off the heating power supply and the mechanical pump, and allow it to cool naturally to room temperature to obtain a dense Mg. 3.5 SbBi 0.99 Te 0.01 Thermoelectric materials;

[0088] Part 2: Preparation of Mg3(Sb,Bi)2-based thermoelectric arm materials.

[0089] (8) Weigh high-purity metal powders Mg and Co according to the ratio of Mg:Co=1:2.5, grind them in a high-energy ball mill for 8 hours to obtain Mg-Co nanopowder;

[0090] (9) Mg 3.5 SbBi 0.99 Te 0.01 Impurities on the material surface are removed by mechanical grinding, followed by processing according to Cu / Mg-Co / Mg 3.5 SbBi 0.99 Te 0.01 The Mg-Co / Cu sandwich structure is placed in a graphite mold and subjected to secondary hot pressing;

[0091] (10) The hot pressing temperature is 520℃, the pressure is 10MPa, the holding time is 15min, and the thickness of the Mg-Co interface layer is 80μm;

[0092] (11) Unload the pressure and adjust the temperature to 350℃ for in-situ annealing for 20h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material.

[0093] The grain size of the thermoelectric material samples prepared in Example 3 and Comparative Example 1 was analyzed using backscattered electron diffraction (BSED). The results are as follows: Figure 3 As shown. Figure 3 The Mg prepared in Example 3 3.2 Co 0.3 SbBi 0.99 Te 0.01 Mg prepared in Comparative Example 1 3.5 SbBi 0.99 Te 0.01 Grain size analysis diagram. From Figure 3 As can be seen from the data, the Mg prepared in Example 3... 3.2 Co 0.3 SbBi 0.99 Te 0.01Mg prepared in Comparative Example 1 3.5 SbBi 0.99 Te 0.01 In comparison, the grain size is significantly larger, indicating that Co doping can promote grain growth.

[0094] Table 1 Mg prepared in Example 3 3.2 Co 0.3 SbBi 0.99 Te 0.01 Mg prepared in Comparative Example 1 3.5 SbBi 0.99 Te 0.01 Comparative analysis of room temperature conductivity and Seebeck coefficient

[0095]

[0096] Table 1 shows that the Mg prepared in Example 3... 3.2 Co 0.3 SbBi 0.99 Te 0.01 The electrical conductivity of the thermoelectric material is significantly higher than that of the Mg prepared in Comparative Example 1. 3.5 SbBi 0.99 Te 0.01 Furthermore, the Seebeck coefficient remains essentially unchanged, mainly because Co doping increases the grain size and reduces grain boundaries, thus decreasing electron scattering. The power factor (power factor = conductivity × Seebeck coefficient × Seebeck coefficient) is a parameter for evaluating the overall electrical performance of a material. The power factors of the materials in Example 3 and Comparative Example 1 are 27.5 μW / cmK, respectively. 2 and 17.6 μW / cmK 2 This further illustrates that the Mg3(Sb,Bi)2-based thermoelectric material of this application has high thermoelectric performance and high stability.

[0097] Table 2 Mg prepared in Example 3 3.2 Co 0.3 SbBi 0.99 Te 0.01 Mg prepared in Comparative Example 1 3.5 SbBi 0.99 Te 0.01 Test results of conductivity change before and after 100 hours of in-situ testing at 400℃.

[0098]

[0099] As can be seen from Table 2, the Mg prepared in Example 3 3.2 Co 0.3 SbBi 0.99 Te 0.01 The conductivity of Mg prepared in Comparative Example 1 decreased by only 2%; while the conductivity of Mg prepared in Comparative Example 1 decreased by only 2%.3.5 SbBi 0.99 Te 0.01 Under the same operating conditions, the conductivity decreased by 28%, indicating that the Mg prepared in Example 3... 3.2 Co 0.3 SbBi 0.99 Te 0.01 It has good stability.

[0100] Comparative Example 2:

[0101] Comparative Example 2: Preparation of a thermoelectric arm material without a Mg-Co interface layer. The specific steps include the following:

[0102] (1) Weigh out Mg, Co, Sb, Bi and Te with a purity of 99.99% in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=3.2:0.3:1:0.99:0.01, put them into a ball mill jar, and place them on a high-energy ball mill for 10 hours to mix and grind.

[0103] (2) Place the evenly ground powder into a graphite mold in an inert atmosphere and quickly transfer it to a hot press for hot pressing.

[0104] (3) Turn on the hot press, place the graphite mold on the sample stage, ensure that the mold is not tilted, and close the hot press chamber door;

[0105] (4) Turn on the mechanical pump and evacuate to 15 Pa;

[0106] (5) Under the vacuum conditions formed in step (4) above, turn on the heating button, adjust the current to 350mA, heat to 720℃, and apply a pressure of 15MPa;

[0107] (6) Turn off the mechanical pump and maintain the temperature for 5 minutes under pressure.

[0108] (7) Turn off the heating power supply and the mechanical pump, and allow it to cool naturally to room temperature to obtain a dense Mg. 3.2 Co 0.3 SbBi 0.99 Te 0.01 Material;

[0109] (8) Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 Impurities on the material surface are removed by mechanical grinding, followed by secondary hot pressing, according to Cu / Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 The / Cu sandwich structure is placed in a graphite mold and subjected to secondary hot pressing;

[0110] (9) The hot pressing temperature is 520℃, the pressure is 10MPa, and the holding time is 15min;

[0111] (10) Unload the pressure and adjust the temperature to 350℃ for in-situ annealing for 20h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material.

[0112] Table 3. Interfacial comparison analysis of Mg3(Sb,Bi)2-based thermoelectric arm materials prepared in Example 3 and Comparative Example 2.

[0113]

[0114] As shown in Table 3, compared to Comparative Example 2, Example 3 added a Mg-Co interface layer, with an interface resistance of 25 μΩ / cm. 2 Comparative Example 2, lacking the Mg-Co interface layer, exhibited an interface resistance of 265 μΩ / cm. 2 Furthermore, in Example 3, the contact interface maintained a metallic luster before and after welding, while in Comparative Example 2, the thermoelectric arm underwent a chemical reaction after welding, and the interface changed from a metallic luster to a dark gray color. This indicates that the use of the Mg-Co phase as the interface layer material in the thermoelectric arm fabrication of this invention effectively avoids the chemical reaction between the Mg element in Mg3(Sb,Bi)2 and the metal electrode, which would lead to a decrease in interface stability. Moreover, the Mg-Co interface layer effectively prevents the formation of impurity phases from other new elements, thus reducing the thermoelectric performance of the material.

[0115] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A Mg3(Sb,Bi)2-based thermoelectric material, characterized in that, The chemical composition of the Mg3(Sb,Bi)2-based thermoelectric material is Mg 3.5-x Co x Sb 2-y-z Bi y Te z , where 0≤x≤0.3, 0<y≤1.8, 0<z≤0.

05.

2. The Mg3(Sb,Bi)2-based thermoelectric material according to claim 1, characterized in that, The chemical composition of the Mg3(Sb,Bi)2-based thermoelectric material is Mg 3.4 Co 0.1 Sb 1.65 Bi 0.3 Te 0.05 Mg 3.3 Co 0.2 Sb 1.47 Bi 0.5 Te 0.03 or Mg 3.2 Co 0.3 SbBi 0.99 Te 0.01 .

3. The Mg3(Sb,Bi)2-based thermoelectric material according to claim 1, characterized in that, Some Co elements enter the crystal lattice to form Co-Mg bonds, while some Co elements exist at the grain boundaries to form a Mg-Co second phase.

4. The method for preparing the Mg3(Sb,Bi)2-based thermoelectric material according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Weigh the metals Mg, Co, Sb, Bi and Te in an inert atmosphere according to the stoichiometric ratio of Mg:Co:Sb:Bi:Te=(3.5-x):x:(2-yz):y:z, and ball mill the metals accordingly; where 0≤x≤0.3, 0<y≤1.8, and 0<z≤0.05; (2) The uniformly ground powder is placed in a graphite mold in an inert atmosphere and subjected to hot pressing treatment; the temperature of hot pressing treatment is 720~840℃, the pressure of hot pressing treatment is 10-20MPa, and the temperature is maintained for 5-40 minutes under pressure. (3) After hot pressing, the material is naturally cooled to room temperature to obtain a dense Mg. 3.5-x Co x Sb 2-y-z Bi y Te z Material.

5. The method for preparing the Mg3(Sb,Bi)2-based thermoelectric material according to claim 4, characterized in that, The heating current during hot pressing is 150-350mA.

6. The method for preparing the Mg3(Sb,Bi)2-based thermoelectric material according to claim 4, characterized in that, The hot pressing process is carried out under a vacuum of 1-15 Pa.

7. A Mg3(Sb,Bi)2-based thermoelectric arm material, characterized in that, The Mg3(Sb,Bi)2-based thermoelectric arm material has an overall sandwich structure; the Mg3(Sb,Bi)2-based thermoelectric arm material sequentially includes a first Cu layer, a first Mg-Co interface layer, a Mg3(Sb,Bi)2-based thermoelectric material layer, a second Mg-Co interface layer, and a second Cu layer.

8. The Mg3(Sb,Bi)2-based thermoelectric arm material according to claim 7, characterized in that, The thickness of the first Cu layer is 50-200 μm; the thickness of the first Mg-Co interface layer is 20-80 μm; the thickness of the second Mg-Co interface layer is 20-80 μm; and the thickness of the second Cu layer is 50-200 μm.

9. The method for preparing the Mg3(Sb,Bi)2-based thermoelectric arm material according to claim 7 or 8, characterized in that, Includes the following steps: (1) Prepare Cu powder, Mg-Co nanopowder and the Mg3(Sb,Bi)2-based thermoelectric material according to any one of claims 1 to 3 after surface treatment; (2) The Cu powder / Mg-Co nanopowder / Mg3(Sb,Bi)2-based thermoelectric material / Mg-Co nanopowder / Cu powder sandwich structure is placed in a graphite mold and hot-pressed; the hot-pressing temperature is 400-520℃, the pressure is 2-10MPa, and the holding time is 10-50min. (3) After the hot pressing treatment is completed, the pressure is unloaded and the temperature is adjusted to 350-450℃ for in-situ annealing for 8-20h to obtain Mg3(Sb,Bi)2-based thermoelectric arm material.

10. The method for preparing the Mg3(Sb,Bi)2-based thermoelectric arm material according to claim 9, characterized in that, Mg-Co nanopowder is prepared by the following method: Mg and Co metal powders are weighed according to the ratio of Mg:Co=1:(2+a) and then ground or ball-milled; where 0≤a≤0.5.

Images