P-type magnesium bismuthide single crystal material, preparation method therefor and use thereof

Abstract

The present invention provides a P-type magnesium bismuthide single crystal material, a preparation method therefor and a use thereof. The preparation method comprises the steps of: weighing magnesium metal and bismuth metal raw materials, placing the raw materials into a crucible, adding a filter piece, and using a cover plate to seal the crucible; placing the crucible in step S1 into a quartz tube, using a stopper to seal the quartz tube, evacuating the quartz tube and backfilling same with an inert gas, and then sealing the quartz tube; heating the sealed quartz tube in step S2 from room temperature to 650-700°C to melt the raw materials, maintaining the temperature for a time period, and slowly cooling to 300-350°C; and inverting the cooled quartz tube, quickly placing same in a low-speed centrifuge, and after centrifugation, performing separation to obtain a magnesium bismuthide single crystal material. The P-type magnesium bismuthide single crystal material prepared by the present invention has excellent electrical properties and extremely low thermal conductivity.

Description

A P-type magnesium bismuthide single crystal material, its preparation method and application Technical Field

[0001] This invention relates to the field of thermoelectric semiconductor materials technology, and in particular to a P-type magnesium bismuthide single crystal material, its preparation method, and its application. Background Technology

[0002] Thermoelectric semiconductor materials can directly convert heat energy into electrical energy through the thermoelectric effect, providing a sustainable development strategy for solving today's energy problems. Thermoelectric energy conversion technology has advantages such as high stability, long service life, no pollution, and no noise, and can achieve rapid and precise temperature control of target objects, showing broad application prospects in the field of solid-state refrigeration. The performance of thermoelectric materials depends on the dimensionless figure of merit zT, which is determined by the intrinsic electrical and thermal properties of the semiconductor material, zT = S. 2 σ / (κ L +κ e )T, where S is the Seebeck coefficient, σ is the conductivity, and κ is the electrical conductivity. L κ is the lattice thermal conductivity. e Here, T represents electronic thermal conductivity, and T is absolute temperature. Generally, high-performance thermoelectric materials typically possess high carrier mobility and low lattice thermal conductivity. Over the past few decades, the performance of thermoelectric materials has been continuously improved. Typical high-performance thermoelectric materials include Bi₂Te₃, MgAgSb, PbTe, and n-type Mg₃(Bi,Sb)₂ alloys. In recent years, with the emergence of new theories and technologies, researchers have explored methods such as nanoscale microstructure control and bandgap engineering to further optimize the electrical and thermal properties of materials, achieving further improvements in thermoelectric performance and thus increasing the energy conversion efficiency of thermoelectric materials.

[0003] Meanwhile, the introduction of new theoretical calculation methods, through the study of multiphysics coupling effects, has provided theoretical support for the design of high-performance thermoelectric materials, accelerating the research and development of new thermoelectric materials. For example, researchers are continuously optimizing the performance of thermoelectric materials through various methods. The Shanghai Institute of Ceramics, Chinese Academy of Sciences, reported that by modulating the antisite defect induction strategy, a high-density microstructure was formed in bismuth telluride-based materials, realizing the transformation of inorganic thermoelectric materials from brittle to ductile, and improving the thermoelectric figure of merit of room-temperature ductile materials to about 1.0. The Institute of Chemistry, Chinese Academy of Sciences, reported that the multi-periodic heterostructure characteristics of polymers significantly improved the thermoelectric performance of polymers, bringing their figure of merit close to the commercially available room-temperature best thermoelectric performance level. With the development of integrated circuits and flexible devices, thermoelectric devices provide energy solutions for applications such as wearable microelectronic devices, and also have important application prospects in low-density waste heat recovery and micro solid-state electronic refrigeration. For example, thermoelectric watches that convert human body heat energy into electrical energy, and high-density heat dissipation of local hot spots in microelectronic devices. In addition, integrating thermoelectric materials with other functional materials can develop functional devices with multiphysics coupling performance, realizing efficient energy utilization and multifunctional application scenarios.

[0004] Magnesium bismuthide alloys are one of the latest research hotspots in the field of thermoelectric materials. Their chemical formula is Mg3Bi2, and they are composed of Mg cations. 2+ and anion exchange layer (Mg2Bi2) 2- Magnesium bismuthide (Mg3Bi2) is a hexagonal layered Zintl phase compound that exists stably in air. It has a simple crystal structure composed of relatively low-mass atoms and is a semi-metallic material with a zero band gap. Studies have reported that the Mg3Bi2 lattice structure exhibits phonon softening and microstructure characteristics, resulting in an exceptionally low lattice thermal conductivity of approximately 2.5 W / m² at room temperature. -1 K -1 Magnesium bismuthide (MgB) is a novel thermoelectric material with broad application prospects near room temperature. Recent research from Harbin Institute of Technology has discovered that the unique crystal structure and bonding mechanism of MgB single crystals give them excellent flexibility at room temperature, preventing fracture under bending and tensile deformation, while also possessing superior thermoelectric properties. This material, combining excellent plastic deformation capability and superior thermoelectric properties, adds a new material system to inorganic plastic thermoelectric materials, providing an ideal choice for applications in flexible electronics and wearable devices. Therefore, the preparation of high-quality MgB single crystals and the optimization of their electrical and thermal transport properties hold promise for further development in the field of flexible electronics, providing significant application value for solving energy and environmental problems. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a P-type magnesium bismuthide single crystal material, its preparation method and application, to solve the problem that the near-room temperature thermoelectric materials in the prior art are limited in their widespread application due to their high lattice thermal conductivity and low electron mobility.

[0006] To achieve the above and other related objectives, this invention provides a method for preparing p-type magnesium bismuthide single crystal material. The method includes the following steps:

[0007] S1. Weigh out the raw materials, magnesium metal and bismuth metal, place the raw materials into a crucible, put in a filter, and seal the crucible with a lid.

[0008] S2. Place the crucible from step S1 into the quartz tube, seal the quartz tube, evacuate and replace the inert gas, and then encapsulate the quartz tube.

[0009] S3. Heat the quartz tube packaged in step S2 from room temperature to 650-700°C to melt the raw material, keep it at that temperature for a period of time, and then slowly cool it down to 300-350°C.

[0010] S4. After cooling, the quartz tube is inverted and quickly placed into a low-speed centrifuge. After centrifugation, magnesium bismuthide single crystal material is obtained.

[0011] The present invention also provides a P-type magnesium bismuthide single crystal material prepared by the preparation method described above, wherein the magnesium bismuthide single crystal is in the form of a sheet.

[0012] Preferably, the magnesium bismuthide single crystal has a length and width of 2-5 mm and a thickness of 0.3-1 mm.

[0013] Preferably, the magnesium bismuthide single crystal material has a carrier mobility of 36.4–300 cm⁻¹ in the temperature range of 2–300 K. 2 V -1 s -1 .

[0014] Preferably, the lattice thermal conductivity of the magnesium bismuthide single crystal material is approximately 0.36–4.13 W / m in the temperature range of 2–300 K. -1 K -1 .

[0015] This invention also provides an application of the above-described P-type magnesium bismuthide single crystal material in near-room temperature low-density waste heat utilization thermoelectric power generation and efficient cooling of local hot spots in microelectronic chips.

[0016] As described above, the P-type magnesium bismuthide single crystal material, its preparation method, and its application of the present invention have the following beneficial effects:

[0017] The preparation method of the p-type magnesium bismuthide single crystal material of the present invention uses simple and abundant raw materials with low cost. The preparation method has a simple process flow, high controllability, good repeatability, and is suitable for large-scale production.

[0018] The p-type magnesium bismuthide single crystal material of the present invention is a thermoelectric material with high carrier mobility and extremely low lattice thermal conductivity, that is, it has excellent electrical properties and extremely low thermal conductivity. Attached Figure Description

[0019] Figure 1 is a schematic flowchart I of the preparation method of the P-type magnesium bismuthide single crystal material of the present invention.

[0020] Figure 2 is a schematic flowchart (II) of the preparation method of the P-type magnesium bismuthide single crystal material of the present invention; wherein, 1. weighing; 2. packaging; 3. melting; 4. slow cooling; 5. centrifugation; 6. obtaining single crystal.

[0021] Figure 3 shows the resistivity of single-crystal magnesium bismuthate in Examples 1 and 2 as a function of temperature.

[0022] Figure 4 shows the thermal conductivity of single-crystal magnesium bismuthide as a function of temperature for Examples 1 and 2.

[0023] Figure 5 shows the lattice thermal conductivity of single-crystal magnesium bismuthide in Examples 1 and 2 as a function of temperature.

[0024] Figure 6 shows the migration curves of single-crystal magnesium bismuthate in Examples 1 and 2 as a function of temperature.

[0025] Figure 7 shows the Seebeck coefficient of single-crystal magnesium bismuthate in Examples 1 and 2 as a function of temperature. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0028] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated; moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of the invention.

[0029] The first aspect of this invention provides a method for preparing p-type magnesium bismuthide single crystal material, as shown in Figures 1 and 2, comprising the following steps:

[0030] S1. Weigh out the raw materials, magnesium metal and bismuth metal, place the raw materials into a crucible, put in a filter, and seal the crucible with a lid.

[0031] S2. Place the crucible from step S1 into the quartz tube, seal the quartz tube, evacuate and replace the inert gas, and then encapsulate the quartz tube.

[0032] S3. The quartz tube packaged in step S2 is heated from room temperature to 650-700℃, 650-660℃, 660-670℃, 670-680℃, 680-690℃, 690-700℃, 700-710℃, 710-720℃, 720-730℃, 730-740℃ or 740-750℃ to melt the raw material. After holding at this temperature for a period of time, the temperature is slowly lowered to 300-350℃, 300-310℃, 310-320℃, 320-330℃, 330-340℃ or 340-350℃.

[0033] S4. After cooling, the quartz tube is inverted and quickly placed into a low-speed centrifuge. After centrifugation, magnesium bismuthide single crystal material is obtained.

[0034] In some embodiments of the present invention, the molar ratio of magnesium to bismuth in step S1 is 3:6 to 14. For example, it is 3:6 to 7, 3:7 to 8, 3:8 to 9, 3:9 to 10, 3:10 to 11, 3:11 to 12, 3:12 to 13, or 3:13 to 14. In a preferred embodiment of the present invention, the molar ratio of magnesium to bismuth is 1:3.

[0035] In some embodiments of the present invention, the purity of the magnesium metal in step S1 is >99.8%.

[0036] In some embodiments of the present invention, the purity of the bismuth metal in step S1 is >99.999%.

[0037] In some embodiments of the present invention, the cover sheet in step S1 is an alumina cover sheet.

[0038] In some embodiments of the present invention, the crucible mentioned in step S1 is an alumina crucible.

[0039] In some embodiments of the present invention, the filter sheet in step S1 is an alumina filter sheet.

[0040] In some embodiments of the present invention, the inert gas in step S2 is argon.

[0041] In some embodiments of the present invention, the internal pressure of the quartz tube during the encapsulation process in step S2 is 1 to 100 Pa. For example, it is 1 to 10 Pa, 10 to 20 Pa, 20 to 30 Pa, 30 to 40 Pa, 40 to 50 Pa, 50 to 60 Pa, 60 to 70 Pa, 70 to 80 Pa, 80 to 90 Pa, or 90 to 100 Pa.

[0042] In some embodiments of the present invention, the encapsulation process in step S2 is performed using high-temperature plasma or a high-temperature flame gun. In a preferred embodiment of the present invention, the encapsulation process is performed using a high-temperature flame gun.

[0043] In some embodiments of the present invention, the heating time in step S3 is 6 to 12 hours. For example, it is 6 to 7 hours, 7 to 8 hours, 8 to 9 hours, 9 to 10 hours, 10 to 11 hours, or 11 to 12 hours.

[0044] In some embodiments of the present invention, the heating rate in step S3 is 1–5 °C / min. For example, it is 1–2 °C / min, 2–3 °C / min, 3–4 °C / min, or 4–5 °C / min.

[0045] In some embodiments of the present invention, the temperature rise from room temperature in step S3 is carried out in a pit-type high-temperature furnace.

[0046] In some embodiments of the present invention, the heat preservation time in step S3 is 12 to 24 hours. For example, it is 12 to 14 hours, 14 to 16 hours, 16 to 18 hours, 18 to 20 hours, 20 to 22 hours, or 22 to 24 hours.

[0047] In some embodiments of the present invention, the cooling rate in step S3 is 1.5–2.5 °C / h. For example, it is 1.5–1.7 °C / h, 1.7–1.9 °C / h, 1.9–2.1 °C / h, 2.1–2.3 °C / h, or 2.3–2.5 °C / h. In a preferred embodiment of the present invention, the cooling rate is 2.5 °C / h.

[0048] In some embodiments of the present invention, the centrifugation rate in step S4 is 500–1000 rpm. For example, it is 500–600 rpm, 600–700 rpm, 700–800 rpm, 800–900 rpm, or 900–1000 rpm.

[0049] A second aspect of the present invention provides a P-type magnesium bismuthide single crystal material prepared by the preparation method described above, wherein the magnesium bismuthide single crystal is in the form of a sheet.

[0050] In some embodiments of the present invention, the length and width of the magnesium bismuthide single crystal are 2-5 mm, 2-2.5 mm, 2.5-3 mm, 3-3.5 mm, 3.5-4 mm, 4-4.5 mm or 4.5-5 mm, and the thickness is 0.3-1 mm, 0.3-0.4 mm, 0.4-0.5 mm, 0.5-0.6 mm, 0.6-0.7 mm, 0.7-0.8 mm, 0.8-0.9 mm or 0.9-1 mm.

[0051] In some embodiments of the present invention, the carrier mobility of the magnesium bismuthide single crystal material is 36.4–300 cm⁻¹ in the temperature ranges of 2–300 K, 2–10 K, 10–20 K, 20–50 K, 50–100 K, 100–150 K, 150–200 K, 200–250 K, or 250–300 K. 2 V -1 s -1 For example, 36.4–40 cm 2 V -1 s -1 40-50cm 2 V -1 s -1 50~54.2cm 2 V -1 s -1 54.2~60cm 2 V -1 s -160-80cm 2 V -1 s -1 80-100cm 2 V -1 s -1 100-140cm 2 V -1 s -1 140-180cm 2 V -1 s -1 180-220cm 2 V -1 s -1 220-260cm 2 V -1 s -1 Or 260-300cm 2 V -1 s -1 In a preferred embodiment of the present invention, the magnesium bismuthide single crystal material has a carrier mobility of 36.4–54.2 cm⁻¹ at a temperature of 300 K. 2 V -1 s -1 .

[0052] In some embodiments of the present invention, the lattice thermal conductivity of the magnesium bismuthide single crystal material is approximately 0.36–4.13 W / m in the temperature ranges of 2–300 K, 2–10 K, 10–20 K, 20–50 K, 50–100 K, 100–150 K, 150–200 K, 200–250 K, or 250–300 K. -1 K -1 For example, 0.36–0.5 W / m². -1 K -1 0.5~0.7W m -1 K -1 0.7~0.9W m -1 K -1 0.9~1.05W m -1 K -1 1.05~1.2W m -1 K -1 1.2~1.5W m -1 K -1 1.5~1.7W m -1 K -1 1.7~2.0W m -1 K -1 2.0~2.5W m -1 K -1 2.5~3.0W m -1 K -13.0~3.5W m -1 K -1 3.5~4.0W m -1 K -1 Or 4.0~4.13W m -1 K -1 In a preferred embodiment of the present invention, the lattice thermal conductivity of the magnesium bismuthide single crystal material at a temperature of 280–300 K is 0.36–1.05 W / m. -1 K -1 .

[0053] The third aspect of this invention provides an application of the p-type magnesium bismuthide single crystal material as described above in the fields of near-room temperature low-density waste heat utilization thermoelectric power generation and efficient cooling of local hot spots in microelectronic chips.

[0054] Example 1

[0055] Preparation of a p-type magnesium bismuthide single crystal material:

[0056] S1. Weigh out pure metallic raw materials magnesium and bismuth in a molar ratio of 1:3, with bismuth in 350% excess. Place the raw materials into an alumina crucible, add an alumina filter, and seal the crucible with an alumina cover.

[0057] S2. Place the alumina crucible into the quartz tube, seal it with a quartz plug, and perform vacuuming and argon gas protection treatment on the quartz tube. Repeat the vacuuming process 3 times to keep a small amount of argon gas in the quartz tube. Use a high-temperature flame gun to melt and seal the quartz tube at high temperature, maintaining the internal pressure of the quartz tube at 10 Pa.

[0058] S3. Place the quartz tube into a pit-type high-temperature furnace and heat it to 650°C at a heating rate of 1°C / min. Hold the temperature for 24 hours and then slowly cool it down to 350°C at a rate of 2.5°C / h. At 350°C, the sample is in a molten state where the liquid phase and the stationary phase coexist.

[0059] S4. Quickly place the cooled quartz tube into a low-speed centrifuge for centrifugation, and obtain magnesium bismuthide single crystal material after centrifugation.

[0060] The physical properties of the single crystal prepared in this invention were characterized using a comprehensive physical property measurement system (PPMS, Quantum Design). Electrical properties were measured using DC resistance and Hall effect measurement options, while thermal properties were measured using a thermal transport option. As shown in Figures 3-7, the electrical properties of the magnesium bismuthide single crystal material prepared in Example 1 at 300 K are as follows: resistivity 6.53 Ohm-m, Seebeck coefficient 45.0 μV / K (confirmed as P-type magnesium bismuthide single crystal), and mobility 54.2 cm²V. -1 s -1 Thermal properties at 285 K: Thermal conductivity is 1.68 W / m.-1 K -1 The lattice thermal conductivity is 0.36 W / m. -1 K -1 .

[0061] Example 2

[0062] S1. Weigh out pure metallic raw materials magnesium and bismuth in a molar ratio of 1:2, with bismuth in 200% excess. Place the raw materials into an alumina crucible, add an alumina filter, and seal the crucible with an alumina cover.

[0063] S2. Place the alumina crucible into the quartz tube, seal it with a quartz plug, and perform vacuuming and argon gas protection treatment on the quartz tube. Repeat the vacuuming process 3 times to keep a small amount of argon gas in the quartz tube. Use a high-temperature flame gun to melt and seal the quartz tube at high temperature, maintaining the internal pressure of the quartz tube at 10 Pa.

[0064] S3. Place the quartz tube into a pit-type high-temperature furnace and heat it to 650°C at a heating rate of 1°C / min. Hold the temperature for 24 hours and then slowly cool it down to 350°C at a rate of 1.5°C / h.

[0065] S4. Quickly place the cooled quartz tube into a low-speed centrifuge for centrifugation, and obtain magnesium bismuthide single crystal material after centrifugation.

[0066] As shown in Figures 3-7, the magnesium bismuthide single crystal material prepared in Example 1 has a resistivity of 8.65 Ohm-m and a mobility of 36.4 cm²V at 300K. -1 s -1 The Seebeck coefficient is 53.8 μV / K (confirmed as p-type magnesium bismuthide single crystal), and the thermal conductivity is 1.89 W / m. -1 K -1 The lattice thermal conductivity is 1.02 W / m. -1 K -1 .

[0067] In summary, the method for preparing P-type magnesium bismuthide single crystal material of the present invention uses magnesium metal and bismuth metal as raw materials. The raw materials are simple, abundant, and low in cost. The prepared P-type magnesium bismuthide single crystal material has excellent electrical properties and extremely low thermal conductivity.

[0068] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0069] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing p-type magnesium bismuthide single crystal material, characterized in that, Includes the following steps: S1. Weigh out the raw materials, magnesium metal and bismuth metal, place the raw materials into a crucible, put in a filter, and seal the crucible with a lid. S2. Place the crucible from step S1 into the quartz tube, seal the quartz tube, evacuate and replace the inert gas, and then encapsulate the quartz tube. S3. Heat the quartz tube packaged in step S2 from room temperature to 650-700°C to melt the raw material, keep it at that temperature for a period of time, and then slowly cool it down to 300-350°C. S4. After cooling, the quartz tube is inverted and quickly placed into a low-speed centrifuge. After centrifugation, magnesium bismuthide single crystal material is obtained.

2. The method for preparing P-type magnesium bismuthide single crystal material according to claim 1, characterized in that, The molar ratio of magnesium metal and bismuth metal in step S1 is 3:6 to 14. And / or, the purity of the magnesium metal in step S1 is >99.8%; And / or, the purity of the bismuth metal in step S1 is >99.999%; And / or, the cover sheet mentioned in step S1 is an alumina cover sheet; And / or, the crucible mentioned in step S1 is an alumina crucible; And / or, the filter sheet mentioned in step S1 is an alumina filter sheet.

3. The method for preparing P-type magnesium bismuthide single crystal material according to claim 1, characterized in that, The inert gas mentioned in step S2 is argon; And / or, the internal pressure of the quartz tube during the encapsulation process described in step S2 is 1 to 100 Pa; And / or, the encapsulation process in step S2 is performed using high-temperature plasma or a high-temperature flame gun.

4. The method for preparing P-type magnesium bismuthide single crystal material according to claim 1, characterized in that, The heating time in step S3 is 6–12 hours; And / or, the heating rate in step S3 is 1 to 5 °C / min; And / or, the temperature rise from room temperature described in step S3 is carried out in a pit-type high-temperature furnace; And / or, the heat preservation time in step S3 is 12 to 24 hours; And / or, the cooling rate in step S3 is 1.5 to 2.5 °C / h.

5. The method for preparing P-type magnesium bismuthide single crystal material according to claim 1, characterized in that, The centrifugation rate in step S4 is 500-1000 rpm.

6. A p-type magnesium bismuthide single crystal material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The magnesium bismuthide single crystal is in the form of flakes.

7. The P-type magnesium bismuthide single crystal material according to claim 6, characterized in that, The magnesium bismuthide single crystal has a length and width of 2-5 mm and a thickness of 0.3-1 mm.

8. The P-type magnesium bismuthide single crystal material according to claim 6, characterized in that, The carrier mobility of the magnesium bismuthide single crystal material is 36.4–300 cm⁻¹ in the temperature range of 2–300 K. 2 V -1 s -1 .

9. The P-type magnesium bismuthide single crystal material according to claim 6, characterized in that, The lattice thermal conductivity of the magnesium bismuthide single crystal material is approximately 0.36–4.13 W / m in the temperature range of 2–300 K. -1 K -1 .

10. The application of the P-type magnesium bismuthide single crystal material according to claims 6 to 9 in the fields of near-room temperature low-density waste heat utilization thermoelectric power generation and efficient cooling of local hot spots in microelectronic chips.

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