Mg3Sb2-based semiconductor material capable of generating n-p conduction transformation along with temperature change and preparation method and application of Mg3Sb2-based semiconductor material

Abstract

The invention discloses an Mg3Sb2-based semiconductor material capable of generating n-p conduction transformation along with temperature change and a preparation method and application thereof, and belongs to the technical field of thermoelectric materials, magnesium powder, bismuth powder and antimony powder are uniformly mixed, and the Mg3Sb2-based semiconductor material is obtained after alloying, cold pressing and sintering. Bi and Sb belong to elements of the same main group and are completely solid solutions, the energy band gap of the material is reduced after Bi is doped at the Sb position, the concentration of the Mg vacancy in the system is excessively reduced through Mg, so that the electron concentration is increased, the energy band gap of the material can be reduced by doping Bi at the Sb position, the material becomes a narrow-band-gap semiconductor, the carrier concentration of the material is improved, and under the combined action of Bi and Sb, the performance of the material is improved. The electron concentration in the material is obviously improved, so that conversion between n-p conduction types can be realized, and the material is a promising material in the thermoelectric field.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoelectric materials, and in particular relates to a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, and a preparation method and application thereof. Background Art

[0002] Fossil fuels emit a large amount of harmful substances when used, which seriously pollutes the atmosphere and water and soil resources, causes global climate change, and directly affects human health and quality of life. Thermoelectric materials are functional materials that can convert heat energy and electrical energy into each other. They are also functional materials that can be used in related fields such as waste heat recovery and semiconductor refrigeration. This material can convert heat energy into electrical energy through thermoelectric conversion, or convert electrical energy into heat energy through reverse conversion. In many fields, the application prospects of thermoelectric materials are very broad.

[0003] Mg3Sb2 is an intrinsic p-type thermoelectric material. Due to its low intrinsic carrier concentration, it has poor electrical properties and low thermoelectric figure of merit. The carrier concentration of the matrix material is usually increased by doping. By doping with suitable elements, thermal stability can be effectively improved. A proper excess of Mg can also improve the thermal stability of the material, but too much Mg may cause oxidation and high thermal conductivity. Mn doping synthesized n-type Mg3Sb2 single crystals for the first time. Although the thermoelectric figure of merit of the first reported n-type Mg3Sb2 is relatively low, this study pointed out the optimization direction for the later discovery of high-performance Mg3Sb2-based thermoelectric materials. In addition, adding excess Mg to suppress intrinsic Mg vacancies can raise the Fermi level to near the conduction band, realizing the transition from p-type to n-type, and the thermoelectric performance of n-type materials is much higher than that of p-type materials.

[0004] Mg3Sb2-based thermoelectric materials have low carrier concentration, insufficient thermal stability and thermoelectric figure of merit that needs to be improved. At the same time, there is a large space for performance optimization of n-type materials, and the research on the np conduction transition phenomenon is still insufficient, which limits the wide application and performance improvement of materials in the field of thermoelectric conversion. Therefore, based on the exploration of the influencing factors of the np conduction transition of Mg3Sb2-based materials, the study found a special Mg3Sb2-based material that can undergo np conduction transition with temperature changes. It is necessary to prepare a semiconductor that undergoes np conduction transition with temperature changes. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature changes, and a preparation method and application thereof, so as to solve the technical problems of low electrical properties and np conduction transition mode of Mg3Sb2-based materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention discloses a method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, wherein magnesium powder, bismuth powder and antimony powder are uniformly mixed, alloyed, cold pressed and sintered to obtain the Mg3Sb2-based semiconductor material;

[0008] The molar ratio of magnesium powder: bismuth powder: antimony powder is 3.2: (2-x): x, wherein x = 0.7.

[0009] Preferably, the alloy is placed in a pure argon environment for 5 minutes and then sealed, and alloyed in a high-energy ball mill.

[0010] Further preferably, the rotation speed of the high energy ball mill is 1200 r / min.

[0011] Further preferably, the ball milling method of the high energy ball mill is to rotate for 30 minutes, pause for 15 minutes, and repeat this process until the effective ball milling time is 8-12 hours.

[0012] Preferably, the cold pressing pressure is 10-50 MPa; the cold pressing dosage is 2.5 g each time.

[0013] Preferably, the sintering temperature is 700°C.

[0014] Preferably, the sintering time is 6 hours.

[0015] Preferably, the heating rate is 5°C / min, the cooling rate is 5°C / min, and the sintering temperature is naturally cooled after it drops to 300°C.

[0016] The present invention also discloses a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, which is prepared by the above-mentioned preparation method. The molecular formula of the Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change is Mg 3.2 Si 2-x Sb x , where x=0.7.

[0017] The invention also discloses the application of the Mg3Sb2-based semiconductor material which undergoes np conduction transition with temperature change and is prepared by the preparation method in the preparation of thermoelectric materials.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention discloses a method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change. Magnesium powder, bismuth powder and antimony powder are uniformly mixed, alloyed and then cold pressed, and then sintered. Finally, a semiconductor that undergoes np conduction transition is obtained according to the temperature change. The electrical properties of the semiconductor are improved by adding an excessive amount of Mg element in the material synthesis process and doping Bi and Te elements in the Sb position. The intrinsic Mg3Sb2-based material is a p-type material. The Mg vacancies in Mg3Sb2 will adsorb electrons in the material, thereby reducing the electrical properties of the material, and the reduction of a large number of electrons will make it difficult for the material to conduct to the n-type. Therefore, an appropriate excess of Mg can fill the Mg vacancies and improve the electrical properties, but excessive Mg will cause oxidation and increase the thermal conductivity. Bi and Sb belong to the same main group elements and are complete solid solutions. Therefore, Bi can be doped in large quantities to replace Sb atoms. After Bi is doped in the Sb position, the energy band gap of the material will be reduced, and the carrier concentration has a certain improvement effect, thereby optimizing the electrical properties. And with the increase of cold pressing pressure, the density of the material increases and the electrical properties are improved. Based on the doping of Mg3Sb2-based materials, np-type conduction conversion and the regulation of ball milling time, the electrical properties of the materials have been improved, and they are promising materials in the field of thermoelectrics.

[0020] Furthermore, excess Mg can reduce the concentration of Mg vacancies in the system, thereby increasing the electron concentration. Sb-doped Bi can reduce the band gap of the material, making it a narrow-bandgap semiconductor, and increase its carrier concentration. The combined effect of the two significantly increases the electron concentration in the material, thereby achieving the transition between np conduction types.

[0021] Furthermore, the higher the speed of the high-speed ball mill, the faster the movement speed of the grinding balls in the cylinder, the stronger the impact force and grinding effect, making the materials easier to crush and mix, the particle size distribution more uniform, and the grinding efficiency significantly improved. The ball mill speed of 1200r / min can achieve the best grinding effect while ensuring that the materials are fully ground.

[0022] Furthermore, appropriate ball milling time can improve the ZT value of thermoelectric materials, because refined particles can reduce the grain size of the material and increase phonon scattering, thereby reducing the lattice thermal conductivity of the material and further improving the performance of the material.

[0023] The present invention also discloses a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, which is obtained by the above-mentioned preparation method. This semiconductor can automatically adjust its conductivity type (n-type or p-type) under different temperature conditions, thereby maintaining relatively stable electrical properties. This makes it more reliable in application scenarios with a wide temperature range, such as electronic devices in extreme environments, and this temperature-dependent semiconductor can adapt to temperature changes by adjusting the conductivity type, reducing the risk of failure caused by temperature fluctuations.

[0024] The present invention also discloses the application of the Mg3Sb2-based semiconductor material which undergoes np conduction transition with temperature change and is prepared by the above-mentioned preparation method in the preparation of thermoelectric materials. Due to its excellent temperature adaptability and stability, this semiconductor has broad application prospects in special environments such as aerospace, deep-sea exploration, polar scientific research, etc., and is expected to develop new electronic devices with unique functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a performance diagram of the Seebeck coefficient of the Mg3Sb2-based semiconductor material prepared in Examples 3-5 of the present invention varying with temperature.

[0026] Figure 2 This is the XRD spectrum of the Mg3Sb2-based semiconductor material prepared in Examples 3-5 of the present invention. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0030] The intrinsic Mg3Sb2-based material behaves as a p-type semiconductor with a low ZT value. Doping is usually used to increase the carrier concentration of the base material. The n-type Mg3Sb2-based material has developed rapidly due to its excellent performance and is a promising material in thermoelectric applications, which has attracted much attention in recent years. The main raw materials of the present invention are magnesium powder, bismuth powder and antimony powder, and the preparation method thereof is through conventional traditional sintering, ball milling alloying, cold pressing and then sintering in a tube furnace. The concentration of Mg vacancies in the system is reduced by excessive Mg, thereby increasing the electron concentration. Sb-doped Bi can reduce the energy band gap of the material, making it a narrow band gap semiconductor, and improve its carrier concentration. Under the joint action of the two, the electron concentration in the material is significantly increased, thereby realizing the transition between np conduction types. As one of the important influencing factors of semiconductors, temperature is also of great significance to study the preparation of semiconductors that undergo np conduction transition with temperature changes.

[0031] The present invention discloses a method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0032] 1) Using magnesium powder, bismuth powder and antimony powder as raw materials, weigh the magnesium powder, bismuth powder and antimony powder in a molar ratio of 3.2:(2-x):x, wherein x=0.7.

[0033] 2) The powders weighed in step 1) are poured into a ball mill in sequence, placed in a pure argon environment for 5 minutes, and then sealed.

[0034] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a rotation speed of 1200 r / min for a ball milling time of 8-12 h.

[0035] 4) Take 2.5 g of the powder ground in step 3) and perform cold pressing at a pressure of 10-50 MPa.

[0036] 5) After cold pressing, the product was placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate were both 5°C / min. After the sintering temperature dropped to 300°C, the product was naturally cooled.

[0037] The method according to step 3) is characterized in that the ball-to-material ratio is 10:1, and the ball milling method is to rotate for 30 minutes, pause for 15 minutes, and repeat this until the effective ball milling time is 8-12 hours.

[0038] Example 1

[0039] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0040] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0041] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0042] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 8 h;

[0043] 4) taking 2.5 g of the powder ground in step 3), and cold pressing at a pressure of 10 MPa;

[0044] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0045] Example 2

[0046] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0047] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0048] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0049] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 8 h;

[0050] 4) taking 2.5 g of the powder ground in step 3), and cold pressing at a pressure of 20 MPa;

[0051] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0052] Example 3

[0053] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0054] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0055] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0056] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 8 h;

[0057] 4) taking 2.5 g of the powder ground in step 3), and cold pressing at a pressure of 30 MPa;

[0058] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0059] Example 4

[0060] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0061] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0062] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0063] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 8 h;

[0064] 4) taking 2.5 g of the powder ground in step 3) and cold pressing at a pressure of 40 MPa;

[0065] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0066] Example 5

[0067] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0068] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0069] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0070] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 8 h;

[0071] 4) taking 2.5 g of the powder ground in step 3) and cold pressing at a pressure of 50 MPa;

[0072] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0073] See also Figure 1 The performance diagram of the Seebeck coefficient of the Mg3Sb2-based semiconductor material prepared by using magnesium powder, bismuth powder and antimony powder in Examples 3-5 of the present invention varies with temperature. 3.2 Si 2-x Sb x Below 500K, the Seebeck coefficient is negative, indicating that the prepared Mg3Sb2-based semiconductor material is n-type. Above 500K, the Seebeck coefficient is positive, indicating that the prepared Mg3Sb2-based semiconductor material is p-type and that the Mg3Sb2-based semiconductor material undergoes an np conduction transition.

[0074] See also Figure 2 The XRD spectrum of the Mg3Sb2-based semiconductor material prepared by using magnesium powder, bismuth powder and antimony powder in Examples 3-5 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.

[0075] Example 6

[0076] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0077] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0078] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0079] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 10 h;

[0080] 4) taking 2.5 g of the powder ground in step 3), and cold pressing at a pressure of 50 MPa;

[0081] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0082] Example 7

[0083] A method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change, comprising the following steps:

[0084] 1) Using magnesium powder, antimony powder and bismuth powder as raw materials, weigh 1.5g of magnesium powder, 5.24g of bismuth powder and 1.64g of antimony powder and put them into a ball mill;

[0085] 2) Vacuum the ball mill and flush it with argon gas. The vacuuming is divided into three times, each time for five minutes, and the argon flushing time is 5 minutes;

[0086] 3) placing the ball mill prepared in step 2) in a ball mill for ball milling at a speed of 1200 r / min for 12 h;

[0087] 4) taking 2.5 g of the powder ground in step 3), and cold pressing at a pressure of 50 MPa;

[0088] 5) After cold pressing, the steel is placed in a tubular furnace for sintering at a temperature of 700°C for 6 hours. The heating rate and cooling rate are both 5°C / min. After the sintering temperature drops to 300°C, the steel is naturally cooled.

[0089] 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 method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature, characterized in that: The magnesium powder, bismuth powder and antimony powder are uniformly mixed, alloyed, cold pressed and sintered to obtain a Mg3Sb2-based semiconductor material; The molar ratio of the magnesium powder: bismuth powder: antimony powder is 3.2: (2-x): x, wherein x=0.

7.

2. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 1, characterized in that: The resulting mixture was placed in a pure argon environment for 5 minutes, sealed, and alloyed in a high-energy ball mill.

3. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 2, characterized in that: The rotation speed of the high energy ball mill is 1200r / min.

4. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 3, characterized in that: The ball milling method of the high energy ball mill is to rotate for 30 minutes, pause for 15 minutes, and repeat this process until the effective ball milling time is 8-12 hours.

5. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 1, characterized in that: The cold pressing pressure is 10-50 MPa; the cold pressing dosage is 2.5 g each time.

6. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 1, characterized in that: The sintering temperature is 700°C.

7. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 1, characterized in that: The sintering time is 6 hours.

8. The method for preparing a Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature change according to claim 1, characterized in that: The heating rate was 5°C / min, the cooling rate was 5°C / min, and the sintering temperature was naturally cooled after it dropped to 300°C.

9. A Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature, characterized in that: The Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature is prepared by the preparation method according to any one of claims 1 to 8. The molecular formula of the Mg3Sb2-based semiconductor material is Mg 3.2 Si 2-x Sb x , where x=0.

7.

10. Use of the Mg3Sb2-based semiconductor material that undergoes np conduction transition with temperature, obtained by the preparation method according to any one of claims 1 to 8, in the preparation of thermoelectric materials.

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