A rapid preparation of Mg 3.2-y A x Sb z Bi 2-z Methods for thermoelectric materials

Abstract

The present invention discloses a method for rapidly preparing Mg 3.2‑ y A x Sb z Bi 2‑z The method of preparing thermoelectric materials belongs to the field of preparing thermoelectric energy conversion materials. By using a three-dimensional vibration ball mill, Mg can be converted into 3.2‑y A x Sb z Bi 2‑z The bulk source material of the base is ground into high performance Mg 3.2‑y A x Sb z Bi 2‑z Based on thermoelectric alloy powders. This rapid, high-energy ball milling method can quickly produce thermoelectric materials with a ZT > 1.5 from bulk source materials. The above preparation method is simple to operate, and the resulting materials have high performance and are suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to a method for rapidly preparing Mg 3.2-y A x Sb z Bi 2-z The invention discloses a method for preparing medium- and high-temperature thermoelectric materials, belonging to the field of preparation of temperature difference power generation energy conversion materials. Background Art

[0002] Carbon neutrality and carbon peak have been goals pursued by society in recent years. Reducing the consumption of traditional fossil energy and increasing the use of alternative energy sources is an effective approach. Furthermore, the utilization rate of traditional fossil energy has been low, generally around 30%, with most of the energy released as heat. Effectively utilizing this energy would also help reduce fossil energy consumption.

[0003] Thermoelectric devices are devices that directly convert heat into electricity, finding important applications in waste heat recovery and thermal power generation. Thermoelectric materials are the core component of thermoelectric devices, and their performance directly determines their efficiency and output power. Therefore, high-performance thermoelectric materials are highly sought after. The performance of thermoelectric materials is primarily evaluated by their ZT value; the higher the material's ZT value, the higher the energy conversion efficiency. For thermoelectric materials operating at medium to high temperatures, materials with a ZT greater than 1 are generally considered valuable.

[0004] Mg3Sb2-based thermoelectric materials have been a hot topic of research in recent years. Due to their high performance and low cost of raw materials, they have been favored by many researchers. However, there are still major problems in the synthesis of Mg3Sb2-based thermoelectric materials. Some research groups have prepared high-performance Mg3Sb2-based thermoelectric materials by sealing them with tantalum tubes, but this method is expensive and has a long preparation cycle. Some research groups have also used ball milling to prepare them, but due to the different ball milling methods and the different ratios of balls and materials during ball milling, the ball milling time is generally greater than 10 hours. Therefore, the efficient preparation of Mg3Sb2-based thermoelectric materials must be overcome for their further application. Summary of the Invention

[0005] In view of the above problems, the present invention provides an efficient preparation method for high performance Mg 3.2-y A x Sb z Bi 2-z Methods for producing medium and high temperature thermoelectric materials.

[0006] The technical solutions of the present invention are as follows:

[0007] On the one hand, the present invention can directly prepare n-type thermoelectric material Mg by high energy ball milling. 3.2-y A xSb z Bi 2-z , wherein A is Yb or Tm;

[0008] On the other hand, the n-type thermoelectric material prepared by the preparation method provided by the present invention has a ZT value greater than 1.5.

[0009] An n-type Mg 3.2-y A x Sb z Bi 2-z A method for preparing a thermoelectric material comprises the following steps:

[0010] (1) placing the raw materials in a ball mill according to a molar ratio of Mg:A:Sb:Bi of 3.0-3.2:0-0.1:0-2:2-0; wherein A is Yb or Tm; and the sum of the molar ratios of Sb and Bi is 2;

[0011] (2) The spheres are placed in a ball mill (the volume of the ball mill is 50ml-100ml) in a ratio of 2-5 large spheres to 4-15 small spheres; the mass ratio of the spheres to the raw materials is 2:1 to 8:1

[0012] (3) The ball milling reaction is carried out for 20 min to 100 min under the condition that the ball mill is filled with inert gas (you can set it to 15 min first, open it in the glove box after the ball milling is completed, use a medicine spoon to scrape off the sticking to the wall, cover it and grind it for another 15-20 min);

[0013] (4) After the reaction is completed, the sample is pressed into a tablet under inert gas to obtain the product.

[0014] Furthermore, in the above technical solution, the Mg includes magnesium chips or magnesium particles, and the forms of the A, the Sb, and the Bi include particles or powders.

[0015] Furthermore, in the above technical solution, the thickness of the magnesium chips is 0.1mm-1mm (can be cleaned with dilute hydrochloric acid for 2-5 seconds, with a hydrochloric acid concentration of 1%-5%), and the length is 0.1-30mm; the size of the particles is P<10mm.

[0016] Furthermore, in the above technical solution, the diameter of the large sphere is 10mm-15mm, and the diameter of the small sphere is 5mm-8mm.

[0017] Furthermore, in the above technical solution, the material of the sphere includes stainless steel.

[0018] Furthermore, in the above technical solution, the tablet pressing equipment includes spark plasma hot pressing sintering or hot pressing sintering system.

[0019] Furthermore, in the above technical solution, the tableting conditions are as follows: under 50-70 MPa, first tableting at 300℃-500℃ for 5min-10min, then heating to 750℃-800℃ for tableting for 2min-5min, and finally cooling to room temperature.

[0020] Furthermore, in the above technical solution, the ball mill for the ball milling reaction is a high-energy ball mill with a rotation speed greater than 500 rpm.

[0021] Furthermore, in the above technical solution, the high-energy ball mill with a rotation speed greater than 500 rpm includes a SPEX-8000D high-energy ball mill and a SPEX-8000M high-energy ball mill.

[0022] Furthermore, in the above technical solution, the inert gas includes argon,

[0023] The present invention also provides an n-type thermoelectric material prepared according to the above method, wherein the n-type thermoelectric material is Mg 3.2- y A x Sb z Bi 2-z ; wherein A is Yb or Tm, x=0-0.1, y=0-0.2, z=0-2; the sum of the molar ratios of Sb and Bi is 2.

[0024] Mg prepared by the method provided by the present invention 3.2-y A x Sb z Bi 2-z The base thermoelectric material not only has high preparation efficiency, but also has high performance of the prepared material.

[0025] Beneficial effects

[0026] 1. The present invention provides a method for preparing Mg 3.2-y A x Sb z Bi 2-z The method of preparing thermoelectric materials is fast and efficient, and the prepared materials have high performance.

[0027] 2. The thermoelectric material provided by the present invention can be synthesized quickly and efficiently and is suitable for mass production.

[0028] 3. The high-energy ball milling method provided by the present invention is fast and efficient in preparing medium-temperature thermoelectric materials, and saves more time than traditional preparation methods and ordinary ball milling methods, and the preparation time is shortened by at least 10 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The performance diagram of the thermoelectric material prepared in Example 1. Wherein: (a) is the resistivity of the material, (b) is the Seebeck coefficient of the material, (c) is the thermal conductivity of the material, and (d) is the ZT value of the material. DETAILED DESCRIPTION

[0030] The following are specific embodiments of the present invention, but the present invention is by no means limited to these embodiments.

[0031] Example 1

[0032] Semiconductor thermoelectric material Mg 3.1 Yb 0.1 Sb 1.5 Bi 0.5 .

[0033] The preparation method of the semiconductor thermoelectric power generation device provided by the present invention is as follows:

[0034] (1) Raw material preparation

[0035] Magnesium chips: 2.0671 g, ytterbium powder: 0.0606 g, antimony particles: 4.9313 g, bismuth particles: 2.7648 g.

[0036] (2) Material preparation

[0037] Place the weighed raw materials into a SPEX8007 stainless steel ball milling jar. Add four large balls with a diameter of 12.7 mm, followed by 12 small balls with a diameter of 6.25 mm. The jar is then placed into a glove box, filled with argon, and loaded onto the SPEX ball mill. Set the milling time to 40 minutes. After the milling is complete, open the jar in the glove box and remove the sample.

[0038] The sample was then placed in a graphite mold in a glove box and pressed into a pellet, which was then placed in a hot press sintering furnace for sintering at 50 MPa, 400°C for 10 min, and then 800°C for 2 min.

[0039] Mg prepared by the present invention 3.1 Yb 0.1 Sb 1.5 Bi 0.5 The performance test results of the thermoelectric materials are as follows Figure 1 As shown, Figure 1 (a) is the material resistivity, Figure 1 (b) is the Seebeck coefficient of the material, Figure 1 (c) is the thermal conductivity of the material, Figure 1 (d) is the ZT value of the material. 3.1 Yb 0.1 Sb 1.5 Bi 0.5The ZT value of the thermoelectric material can be maintained above 1.5 above 400℃, and its average output power is high, at 2000μWm -1 K -2 above.

[0040] Comparative Example

[0041]

[0042]

[0043] By comparison, it can be found that the preparation method of the present invention has greatly improved the preparation efficiency.

[0044] Within the technical field of the invention, several equivalent substitutions or obvious modifications may be made without departing from the technical solution of the invention, and all of them should be deemed to fall within the protection scope of the invention.

Claims

1. An n-type Mg 3.2-y A x Sb z Bi 2-z A method for preparing a thermoelectric material, characterized in that: The steps include: (1) The raw materials are placed in a ball mill according to a molar ratio of Mg:A:Sb:Bi of 3.0-3.2:0-0.1:0-2:2-0; the above ranges do not include zero; wherein A is Yb; and the sum of the molar ratios of Sb and Bi is 2; (2) placing the spheres in a ball mill in a ratio of 2-5 large spheres to 4-15 small spheres; the mass ratio of the spheres to the raw material is 2:1 to 8:1; (3) The ball milling reaction is carried out for 20 min to 100 min under the condition that the ball milling tank is filled with inert gas; (4) After the reaction is completed, the sample is pressed into a tablet under an inert gas to obtain; The diameter of the large sphere is 10mm-15mm, and the diameter of the small sphere is 5mm-8mm; The material of the sphere includes stainless steel; The tableting conditions are as follows: under 50-70 MPa, first tableting at 300-500°C for 5-10 minutes, then heating to 750-800°C for 2-5 minutes, and finally cooling to room temperature; The ball mill for the ball milling reaction is a high-energy ball mill with a rotation speed greater than 500 revolutions per minute.

2. The preparation method according to claim 1, characterized in that The Mg includes magnesium chips or magnesium particles, and the forms of the A, Sb, and Bi include particles or powders.

3. The preparation method according to claim 2, characterized in that The thickness of the magnesium chips is 0.1 mm to 1 mm, and the length is 0.1 to 30 mm; the size of the particles is Dp<10 mm.

4. The preparation method according to claim 1, characterized in that The tablet pressing equipment includes spark plasma hot pressing sintering or hot pressing sintering system.

5. The preparation method according to claim 1, characterized in that The high-energy ball mill with a rotation speed greater than 500 rpm includes SPEX-8000D high-energy ball mill and SPEX-8000M high-energy ball mill.

6. The n-type thermoelectric material prepared by the method according to any one of claims 1 to 5, characterized in that: The n-type thermoelectric material is Mg 3.2-y A x Sb z Bi 2-z ; The above ranges do not include zero point; wherein A is Yb, x=0-0.1, y=0-0.2, z=0-2; the sum of the molar ratios of Sb and Bi is 2.

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