Mg3Sb2-based semiconductor material for energy conversion and preparation method thereof

Abstract

The invention discloses an Mg3Sb2-based semiconductor material for energy conversion and a preparation method thereof, and belongs to the technical field of energy conversion, and the molecular formula of the Mg3Sb2-based semiconductor material is Mg < 3.2 > Bi < 1.3 > Sb < 0.7 >. Mg < 3.2 > Bi < 1.3 > Sb < 0.7 > can generate n-p conduction transformation; when the K is less than 500 K, Mg < 3.2 > Bi < 1.3 > Sb < 0.7 > is an n-type semiconductor; when the voltage is greater than 500 K, Mg < 3.2 > Bi < 1.3 > Sb < 0.7 > is a p-type semiconductor. The preparation method comprises the following steps: uniformly mixing magnesium powder, bismuth powder and antimony powder according to a molar ratio of 3.2: 1.3: 0.7, sealing in a pure argon environment, and carrying out alloying, cold pressing and sintering to obtain the Mg3.2 Bi1. 3Sb0.7. When Bi is doped into the Sb position, the Mg vacancy concentration in the material can be effectively reduced, and the electron concentration can be improved at the same time. The doping not only enables the energy band gap of the material to be narrowed and converted into a narrow-band-gap semiconductor, but also improves the carrier concentration of the material. Under the combined action of the two factors, the electron concentration in the material is remarkably enhanced, and then conversion from an n-type conduction type to a p-type conduction type can be achieved. Therefore, the material has huge application potential in the technical field of energy conversion.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy conversion, and in particular relates to a Mg3Sb2-based semiconductor material for energy conversion and a preparation method thereof. Background Art

[0002] With the growing global demand for clean energy and efficient energy utilization technology, thermoelectric materials have attracted much attention due to their ability to achieve direct conversion between thermal energy and electrical energy. Among the many thermoelectric materials, Mg3Sb2-based materials are considered to be one of the most promising thermoelectric conversion materials due to their unique physical and chemical properties. However, although Mg3Sb2-based materials have high thermoelectric conversion potential in theory, their practical application is severely limited by their low energy conversion efficiency.

[0003] Mg3Sb2 as an intrinsic p Type thermoelectric semiconductors have a relatively low intrinsic carrier concentration, which directly leads to a decrease in the material's electrical conductivity, which in turn affects the thermoelectric conversion efficiency. In order to increase its carrier concentration, researchers have tried a variety of doping strategies, such as introducing other elements to replace Mg or Sb atoms, in order to improve the material's electrical properties and thermoelectric figure of merit. However, these doping strategies are often accompanied by a decrease in thermal stability or an increase in thermal conductivity, resulting in limited improvement in overall thermoelectric performance. In addition, Mg3Sb2-based materials also have deficiencies in thermal stability. Under high-temperature working conditions, the material is prone to structural changes or phase changes, resulting in a significant decrease in thermoelectric performance. At the same time, the thermoelectric figure of merit (a key indicator of thermoelectric conversion efficiency) of Mg3Sb2-based materials also needs to be improved to meet the needs of efficient energy conversion in practical applications. On the other hand, although n The thermoelectric performance of Mg3Sb2 materials is superior to that of p However, there is still much room for performance optimization. n The preparation process and performance research of Mg3Sb2 type materials are still insufficient, which limits their wide application in the field of energy conversion.

[0004] The challenges faced by Mg3Sb2-based materials in terms of energy conversion efficiency mainly include low intrinsic carrier concentration, insufficient thermal stability, and the need to improve the thermoelectric figure of merit. n There are many problems such as large room for material performance optimization. These problems jointly restrict the practical application and development of Mg3Sb2-based materials in the field of efficient energy conversion. Therefore, exploring new methods and technologies to improve the energy conversion efficiency of Mg3Sb2-based materials has become an important topic in the current research field of thermoelectric materials. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a Mg3Sb2-based semiconductor material for energy conversion and a preparation method thereof, so as to solve the technical problem of low energy conversion efficiency of Mg3Sb2-based materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a Mg3Sb2-based semiconductor material for energy conversion. The molecular formula of the Mg3Sb2-based semiconductor material is Mg 3.2 Bi 1.3 Sb 0.7 Mg 3.2 Bi 1.3 Sb 0.7 Can happen np conduction transition; below 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for n type semiconductor; above 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for p Type semiconductor.

[0007] The present invention also discloses a method for preparing the Mg3Sb2-based semiconductor material for energy conversion, comprising: uniformly mixing magnesium powder, bismuth powder and antimony powder in a molar ratio of 3.2:1.3:0.7, sealing in a pure argon environment, alloying, cold pressing and sintering to obtain Mg3Sb2-based semiconductor material. 3.2 Bi 1.3 Sb 0.7 .

[0008] Preferably, the alloying is carried out in a high-energy ball mill, the ball milling method of the high-energy ball mill is intermittent rotary ball milling, and the ball-to-material ratio is (8-10):1.

[0009] More preferably, the conditions for intermittent rotary ball milling are: first rotate for 30 min, pause for 15 min, and repeat multiple times until the ball milling time is 8-12 h.

[0010] Further preferably, the rotation speed of the high energy ball mill is 1100-1300 r / min.

[0011] Preferably, the cold pressing pressure is 10-50 MPa.

[0012] Preferably, the amount of cold pressing is 2-3 g / time.

[0013] Preferably, the sintering temperature is 600-800°C.

[0014] Preferably, the sintering time is 5-7 h.

[0015] Preferably, the heating rate of sintering is 5-10°C / min, the cooling rate is 5-10°C / min, and the sintering temperature is reduced to 280-320°C and then cooled naturally.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a Mg3Sb2-based semiconductor material for energy conversion. The Mg3Sb2-based semiconductor material for energy conversion can automatically convert its conductivity type under different temperature conditions. This feature provides a new solution for improving energy conversion efficiency. Traditional semiconductor materials often cause unstable electrical properties due to temperature changes. Especially at extreme temperatures, they may not be able to maintain efficient energy conversion capabilities. However, the Mg3Sb2-based semiconductor material disclosed in the present invention effectively meets this challenge through its adaptive conductivity type conversion mechanism. When the ambient temperature changes, it can automatically adjust its conductivity type (in n Type and p This adaptive ability has a significant effect on improving energy conversion efficiency. First, it reduces energy losses in the energy conversion process caused by temperature fluctuations. In traditional semiconductor materials, temperature changes may lead to changes in carrier concentration, changes in band structure, or intensification of lattice vibrations, which will reduce energy conversion efficiency. However, Mg3Sb2-based materials can maintain effective carrier transmission and efficient energy conversion by adjusting the conductivity type, thereby reducing these losses. Secondly, this adaptive conductivity type conversion feature also enhances the stability and reliability of the material over a wide temperature range. Whether in high or low temperature environments, Mg3Sb2-based semiconductors can maintain stable electrical properties, making it an ideal choice for electronic devices in extreme environments. In such environments, traditional semiconductor materials may fail due to unstable performance, but Mg3Sb2-based materials can work continuously and efficiently. Mg3Sb2-based semiconductor materials effectively solve the problem of low energy conversion efficiency through their unique adaptive conductivity type conversion mechanism. It not only improves the efficiency of the energy conversion process, but also enhances the stability and reliability of the material in a wide temperature range, providing new solutions for energy conversion applications in extreme environments. Due to its excellent temperature adaptability and stability, this semiconductor has broad application prospects in energy conversion devices, cruise missiles, and ballistic missile defense systems, and is expected to develop new electronic devices with unique functions.

[0017] The present invention also discloses a method for preparing the Mg3Sb2-based semiconductor material for energy conversion, wherein magnesium powder, bismuth powder and antimony powder in a molar ratio of 3.2:1.3:0.7 are uniformly mixed, sealed in a pure argon environment, alloyed, cold pressed and sintered to obtain Mg3Sb2-based semiconductor material. 3.2 Bi 1.3 Sb 0.7 In order to significantly improve the electrical properties of the material, an excess of Mg was added, and Bi was introduced into the Sb lattice position for doping. Excessive Mg can reduce the concentration of Mg vacancies in the system, thereby increasing the electron concentration. Sb doping with Bi can reduce the energy band gap of the material, making it a narrow band gap semiconductor, and increase its carrier concentration. Under the combined effect of the two, the electron concentration in the material is significantly increased, which can achieve np Transition between conduction types. Originally, Mg3Sb2-based semiconductor materials exhibit p The Mg vacancies in the material can capture electrons, which in turn weakens the electrical performance of the material and hinders its transfer to n type conduction. In order to deal with this problem, the amount of Mg is increased to effectively fill these vacancies, thereby improving the electrical properties. However, excessive addition of Mg should also be cautious, because too much Mg may lead to increased oxidation of the material and increased thermal conductivity. On the other hand, since Bi and Sb belong to the same group of elements, a complete solid solution can be formed between the two. This feature allows Bi to replace Sb atoms in large quantities. Doping at the Sb position not only reduces the band gap of the material, but also significantly increases the concentration of carriers, further optimizing the electrical properties. In addition, as the pressure increases during the cold pressing process, the density of the material also increases, which plays a positive role in enhancing the electrical properties. By finely controlling the doping ratio of Mg3Sb2-based materials and achieving np The flexible conversion of type conduction successfully improved the overall electrical properties of the material, thereby improving its energy conversion efficiency. Therefore, this Mg3Sb2-based semiconductor material has shown great application in the field of thermoelectric conversion technology.

[0018] Furthermore, the increase in the speed of the ball mill directly drives the high-speed movement of the grinding balls in the cylinder, which not only enhances the impact force of the grinding balls on the materials, but also greatly improves the fineness of the grinding. This high-intensity mechanical action effectively promotes the crushing and mixing of the materials, making the particle size distribution of the final product more uniform and significantly improving the grinding efficiency. The microstructure of the Mg3Sb2-based material was optimized by carefully controlling the ball milling time. The appropriate ball milling time refines the particles of the material and reduces the grain size accordingly. This change in microstructure is crucial for thermoelectric materials, which can significantly enhance the scattering effect of phonons and effectively reduce the lattice thermal conductivity of the material. In the application context of Mg3Sb2-based materials, the optimization of this microstructure is directly related to the improvement of its energy conversion efficiency. Due to the reduction in lattice thermal conductivity, the material can more effectively maintain the temperature gradient during the thermoelectric conversion process, thereby improving the efficiency of thermoelectric conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a performance diagram of the Seebeck coefficient of the Mg3Sb2-based semiconductor material for energy conversion prepared in Examples 2-5 of the present invention as a function of temperature.

[0020] Figure 2 This is the XRD spectrum of the Mg3Sb2-based semiconductor material for energy conversion prepared in Examples 2-5 of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: The eigenstate of Mg3Sb2-based compounds is p The ZT value of the thermoelectric performance evaluation index is relatively low, which limits its application potential in the field of efficient energy conversion. Doping technology is usually used to regulate and increase the carrier density of the matrix material. n Mg3Sb2-based materials have become a research hotspot in the field of thermoelectric conversion materials due to their excellent thermoelectric properties and rapid development momentum. The present invention proposes a method for preparing Mg3Sb2-based semiconductor materials for energy conversion, using magnesium powder, bismuth powder and antimony powder as raw materials, and optimizing the microstructure and electrical properties of the material through a series of fine processing steps. Including the steps of ball milling alloying, cold pressing and high-temperature sintering. The concentration of Mg vacancies inside the material is reduced by excessive addition of Mg element, thereby effectively improving the carrier density of electrons. At the same time, Bi element is doped on the lattice site of Sb, which not only successfully reduces the energy band gap of the material and transforms it into a narrow bandgap semiconductor, but also further promotes the increase of carrier concentration. The synergistic effect of these two modification strategies significantly improves the electron concentration in Mg3Sb2-based materials and achieves the goal of... n Type to p This transformation has a profound positive impact on the thermoelectric conversion efficiency of the material and provides a new opportunity to optimize the thermoelectric performance of the material. In addition, we have also systematically explored the effect of temperature on the thermoelectric properties of Mg3Sb2-based materials, which is of vital scientific significance for a deep understanding of the thermal transport mechanism of the material and further optimization of its thermoelectric conversion efficiency.

[0024] The present invention discloses a Mg3Sb2-based semiconductor material for energy conversion, the molecular formula of which is Mg 3.2 Bi 1.3 Sb 0.7 Mg 3.2 Bi 1.3 Sb 0.7 Can happen np conduction transition; below 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for n type semiconductor; above 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for pBy doping Bi at the Sb position, the energy band gap of the material is effectively reduced, turning it into a narrow band gap semiconductor, thereby significantly increasing the carrier concentration. This change directly enhances the electrical properties of the material and lays an electrical foundation for improving energy conversion efficiency. By precisely controlling the raw material ratio, the Mg3Sb2-based material has been successfully transformed from n Type to p This conversion enables the material to more flexibly adapt to different working environments and requirements during the energy conversion process, thereby improving the overall efficiency of energy conversion.

[0025] The present invention discloses a method for preparing a Mg3Sb2-based semiconductor material for energy conversion, comprising the following steps: 1) Using magnesium powder, bismuth powder and antimony powder as raw materials, weigh the molar ratio of magnesium powder, bismuth powder and antimony powder to be 3.2: (2-x): x, where x = 0.7.

[0026] 2) Pour the powders weighed in step 1) into the ball mill in sequence, place them in a pure argon environment for 5 minutes, and then seal them.

[0027] 3) Place the ball mill jar prepared in step 2) in a ball mill for ball milling. The speed of the ball mill is 1100-1300 r / min and the ball milling time is 8-12 h.

[0028] 4) Take 2-3 g of the powder ground in step 3) and cold press it at a pressure of 10-50 MPa.

[0029] 5) After cold pressing, the product is placed in a tubular furnace for sintering at a sintering temperature of 600-800 °C for 5-7 h. The heating rate and cooling rate are both 5-10 °C / min. After the sintering temperature drops to 280-320 °C, the product is naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0030] According to the method in step 3), the ball-to-material ratio is (8-10):1, and the ball milling method is to rotate for 30 minutes, pause for 15 minutes, and repeat this process until the effective ball milling time is 8-12 hours.

[0031] The invention discloses a method for preparing a Mg3Sb2-based semiconductor material for energy conversion. The method comprises mixing magnesium powder, bismuth powder and antimony powder in a molar ratio of 3.2:1.3:0.7, sealing the mixture in a pure argon environment, alloying, cold pressing and sintering the mixture to obtain Mg3Sb2-based semiconductor material. 3.2 Bi 1.3 Sb 0.7. Effective regulation and optimization of material properties are achieved. By accurately setting the molar ratio of magnesium powder, bismuth powder and antimony powder, especially the ratio of bismuth and antimony (x=0.7), a basis is provided for the preparation of Mg3Sb2-based materials with specific structures and properties, which helps to optimize material properties. Ball milling is carried out in a pure argon protection environment to avoid oxidation of the material during the ball milling process. At the same time, the use of a specific ball-to-material ratio and intermittent ball milling method effectively improves the alloying degree of the powder, promotes the uniform mixing of the raw materials and the refinement of the microstructure, and lays a good foundation for the subsequent sintering process. By setting reasonable cold pressing pressure and sintering parameters (including sintering temperature, time, heating and cooling rates, etc.), the densification of the material and the proper growth of the grains are ensured, while cracks or structural defects that may be caused by excessively rapid heating and cooling are avoided, thereby improving the overall performance and stability of the material. Through the implementation of the above-mentioned preparation method, especially the optimization of the raw material ratio and sintering process, the Mg3Sb2-based material has been successfully achieved from n Type to p The conversion of the conduction characteristics of the semiconductor is of great significance for broadening the application range of materials and improving energy conversion efficiency. The prepared Mg3Sb2-based semiconductor material shows higher efficiency in energy conversion. The improvement of the material microstructure, the increase of carrier concentration and the enhancement of thermoelectric performance provide broad prospects for the application of the material in the fields of thermoelectric conversion, energy collection and storage.

[0032] Example 1 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 8:1, a rotation speed of 1100 r / min, and a ball milling time of 8 h; 4) Take 2 g of the powder ground in step 3) and cold press it at a pressure of 10 MPa; 5) After cold pressing, the product is placed in a tubular furnace for sintering at a temperature of 600 °C for 7 h. The heating rate and cooling rate are both 10 °C / min. After the sintering temperature drops to 280 °C, the product is naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0033] Example 2 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 10:1, a ball mill speed of 1200 r / min, and a ball milling time of 8 h; 4) Take 2.5 g of the powder ground in step 3) and cold press it at a pressure of 20 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700 °C for 6 h, with a heating rate and a cooling rate of 5 °C / min. After the sintering temperature dropped to 300 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0034] Example 3 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 10:1, a ball mill speed of 1200 r / min, and a ball milling time of 8 h; 4) Take 2.5 g of the powder ground in step 3) and cold press it at a pressure of 30 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700 °C for 6 h, with a heating rate and a cooling rate of 5 °C / min. After the sintering temperature dropped to 300 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0035] Example 4 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 10:1, a ball mill speed of 1200 r / min, and a ball milling time of 8 h; 4) Take 2.5 g of the powder ground in step 3) and cold press it at a pressure of 40 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700 °C for 6 h, with a heating rate and a cooling rate of 5 °C / min. After the sintering temperature dropped to 300 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0036] Example 5 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 10:1, a ball mill speed of 1200 r / min, and a ball milling time of 8 h; 4) Take 2.5 g of the powder ground in step 3) and cold press it at a pressure of 50 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700 °C for 6 h, with a heating rate and a cooling rate of 5 °C / min. After the sintering temperature dropped to 300 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0037] See also Figure 1 The performance diagram of the Seebeck coefficient of the Mg3Sb2-based semiconductor material for energy conversion prepared by using magnesium powder, bismuth powder and antimony powder in Examples 2-5 of the present invention varies with temperature. 3.2 Si 2-x Sb x Below 500 K, the Seebeck coefficient is negative, indicating that the prepared Mg3Sb2-based semiconductor material is n type ， The Seebeck coefficient is positive after exceeding 500 K, indicating that the prepared Mg3Sb2-based semiconductor material is p Type, Mg3Sb2-based semiconductor materials np Transmission transformation. npThe existence of conduction transition has a significant impact on energy conversion efficiency. During the energy conversion process, the conduction type of the material directly affects its electrical properties and thermoelectric conversion efficiency. np Conductive transition, the Mg3Sb2-based semiconductor material for energy conversion prepared by the present invention can maintain a higher energy conversion efficiency in a wider temperature range.

[0038] See also Figure 2 The XRD spectrum of the Mg3Sb2-based semiconductor material for energy conversion prepared by using magnesium powder, bismuth powder and antimony powder in Examples 2-5 of the present invention. The XRD spectrum of the Mg3Sb2-based semiconductor material is compared with the Mg3Sb2 standard card, and it can be found that all peaks match the standard card well, indicating that it is feasible to prepare the Mg3Sb2-based semiconductor material using the traditional sintering method.

[0039] Example 6 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 10:1, a rotation speed of 1300 r / min, and a ball milling time of 12 h; 4) Take 3 g of the powder ground in step 3) and cold press it at a pressure of 50 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 800 °C for 5 h, with a heating rate and a cooling rate of 8 °C / min. After the sintering temperature dropped to 320 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0040] Example 7 A method for preparing a Mg3Sb2-based semiconductor material for energy conversion comprises the following steps: 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5 g magnesium powder, 5.24 g bismuth powder and 1.64 g antimony powder and put them into a ball mill; 2) Vacuum the ball mill and flush it with argon. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes; 3) Place the ball mill prepared in step 2) in a ball mill for ball milling, with a ball-to-material ratio of 9:1, a rotation speed of 1200 r / min, and a ball milling time of 12 h; 4) Take 2.5 g of the powder ground in step 3) and cold press it at a pressure of 50 MPa; 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700 °C for 6 h, with a heating rate and a cooling rate of 5 °C / min. After the sintering temperature dropped to 300 °C, the product was naturally cooled to obtain a Mg3Sb2-based semiconductor material for energy conversion.

[0041] The present invention discloses a Mg3Sb2-based semiconductor material for energy conversion and a preparation method thereof. When Bi is doped into the Sb position, the Mg vacancy concentration in the material can be effectively reduced and the electron concentration can be increased at the same time. This doping not only narrows the energy band gap of the material and transforms it into a narrow band gap semiconductor, but also increases its carrier concentration. Under the combined effect of these two factors, the electron concentration inside the material is significantly enhanced, thereby being able to achieve n Type to p Therefore, this material shows great application potential in the field of energy conversion technology.

[0042] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A Mg3Sb2-based semiconductor material for energy conversion, characterized in that: The molecular formula of the Mg3Sb2-based semiconductor material is Mg 3.2 Bi 1.3 Sb 0.7 ; The Mg 3.2 Bi 1.3 Sb 0.7 Can happen np conduction transition; below 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for n type semiconductor; above 500 K, Mg 3.2 Bi 1.3 Sb 0.7 for p Type semiconductor.

2. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 1, characterized in that: include: Magnesium powder, bismuth powder and antimony powder with a molar ratio of 3.2:1.3:0.7 were mixed evenly, sealed in a pure argon environment, alloyed, cold pressed and sintered to obtain Mg 3.2 Bi 1.3 Sb 0.7 .

3. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The alloying is carried out in a high-energy ball mill, the ball milling mode of the high-energy ball mill is intermittent rotary ball milling, and the ball-to-material ratio is (8-10):

1.

4. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 3, characterized in that: The conditions of the intermittent rotary ball milling are: first rotate for 30 minutes, pause for 15 minutes, and repeat several times until the ball milling time is 8-12 hours.

5. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 3, characterized in that: The rotation speed of the high energy ball mill is 1100-1300 r / min.

6. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The cold pressing pressure is 10-50 MPa.

7. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The amount of cold pressing is 2-3 g / time.

8. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The sintering temperature is 600-800°C.

9. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The sintering time is 5-7 h.

10. The method for preparing the Mg3Sb2-based semiconductor material for energy conversion according to claim 2, characterized in that: The heating rate of the sintering is 5-10°C / min, the cooling rate is 5-10°C / min, and the sintering temperature is naturally cooled down to 280-320°C.

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