High-performance out-of-plane orientation polycrystalline bismuth telluride and rapid preparation method thereof

Abstract

The invention discloses a rapid preparation method of high-performance out-of-plane orientation polycrystalline bismuth telluride, which comprises the following steps: n-type bismuth telluride has a chemical formula of Bi2Te3-xSex, and x is more than or equal to 0 and less than or equal to xlt; the chemical formula of the p-type bismuth telluride is Bi < 0.4 > Sb < 1.6 > Te3, or the chemical formula of the p-type bismuth telluride is Bi < 0.4 > Sb < 1.6 > Te3; carrying out electromagnetic smelting on the raw materials in the step (1), and cooling to obtain a cast ingot; and powdering the cast ingot in the step (2), and carrying out hot extrusion forming to obtain the n-type or p-type polycrystalline bismuth telluride. By means of the preparation method, the polycrystalline bismuth telluride with the high zT value can be efficiently prepared.

Description

Technical Field

[0001] The invention belongs to the field of thermoelectric materials, and in particular relates to a polycrystalline bismuth telluride-based bulk material and a rapid preparation method thereof. Background Art

[0002] Thermoelectric materials are functional materials that realize the mutual conversion of thermal energy and electrical energy through the directional movement of carriers based on the Seebeck effect and the Peltier effect. Compared with traditional power generation or refrigeration equipment, thermoelectric devices constructed using thermoelectric materials have the characteristics of small size, no moving parts, and high reliability. They play an irreplaceable role in deep space exploration, self-powered modules, and 5G optical communication temperature control. The energy conversion efficiency of thermoelectric materials is nonlinearly proportional to the dimensionless constant zT value, and the zT value can be calculated by formula (1): zT = S 2 σT / κ(1) Where S is the Seebeck coefficient of the material, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. From equation (1), it can be simply deduced that high-performance thermoelectric materials can be obtained by simply increasing the Seebeck coefficient and electrical conductivity of the material and reducing the thermal conductivity. However, the actual situation is not so simple. The mutual coupling of electron and phonon transport will limit the independent regulation of the above parameters. This is the main factor limiting the development of high-performance thermoelectric materials and devices.

[0003] Bismuth telluride (Bi, Sb) 2 (Te, Se) 3 ) is currently the only material that can be used commercially on a large scale in the field of thermoelectrics. The biggest advantage of this material is that its application temperature range is near room temperature (~300K), and it can be used in both ambient temperature difference self-powered equipment and room temperature refrigeration equipment; secondly, the conduction band and valence band in the energy band structure of bismuth telluride have high degeneracy, which ensures its excellent electrical properties; Bi and Te are both heavy elements, and the large molecular weight of bismuth telluride ensures its extremely low thermal conductivity. However, bismuth telluride has a distinct layered crystal structure, and the thermoelectric properties along the layered direction or perpendicular to the layered direction vary greatly, which to a certain extent limits the development of polycrystalline bismuth telluride. The currently commonly used commercial production method for bismuth telluride is the zone melting method. The preferred direction of thermoelectric transport of the bismuth telluride crystal rods produced by this method is the axial direction of the rod, which also facilitates the subsequent attachment of the electroplating barrier layer and the cutting of the thermoelectric arm.

[0004] However, bismuth telluride itself is a semiconductor with brittle mechanical properties. The zone melting crystal rod is a quasi-single crystal with coarse grains, resulting in extremely poor mechanical properties. The minimum processing size is only about 1mm, which cannot meet the processing requirements of micro thermoelectric devices in current 5G optical communication modules (thermoelectric arm size <300μm).

[0005] Polycrystalline highly oriented bismuth telluride represents the current high-end manufacturing direction of thermoelectric materials. Although there are many literature reports on the use of ball milling to obtain bismuth telluride fine powder, followed by hot pressing or plasma discharge sintering to prepare polycrystalline bismuth telluride bulk materials, the process has acceptable performance when preparing p-type bismuth telluride, but when preparing n-type bismuth telluride with more obvious preferred orientation, a single hot pressing is not enough to reverse its orientation, which will lead to a decrease in the final thermoelectric performance. If highly oriented n-type bismuth telluride is to be obtained, multiple rolling processes are required, which increases the production cost on the one hand, and on the other hand, the bismuth telluride polycrystalline crystal orientation produced by this method yields under the action of axial pressure, resulting in the preferred orientation of thermoelectric transport of bismuth telluride in this method being radial, which is not conducive to subsequent electroplating and cutting processes.

[0006] In summary, both the zone melting process and the powder metallurgy process have obvious defects in the preparation of micro thermoelectric devices. The hot extrusion technology derived from these two processes has the advantages of axial preferential orientation and high mechanical properties. It is the preferred process for bismuth telluride materials in micro thermoelectric devices. The raw material used in this process is bismuth telluride fine powder. Although some literature reports that ball milling, liquid phase synthesis, self-propagating high temperature synthesis and other methods can be used to obtain bismuth telluride fine powder with uniform composition, the ball milling method has high requirements for equipment, long working time, and gas protection is required during the process; the amount of powder obtained by the liquid phase synthesis method is small, the cost performance is extremely low, and it is not suitable for large-scale production; and the self-propagating high temperature synthesis itself requires a single substance of less than 200 mesh fine powder, which is expensive, and the donor-like effect of bismuth telluride itself will affect the powder raw material, increase the electronic carrier concentration of the product, and the optimal use temperature zone is significantly shifted. Obtaining a simple, efficient, low-cost, and high-quality synthesis method for bismuth telluride powder is the key to preparing high-performance bismuth telluride polycrystalline rods. Summary of the invention

[0007] The present invention provides a rapid preparation method for high-performance out-of-plane oriented polycrystalline bismuth telluride, through which polycrystalline bismuth telluride with a higher zT value can be efficiently prepared.

[0008] The present invention provides a rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride, comprising:

[0009] (1) According to the chemical formula of n-type bismuth telluride, Bi 2 Te 3-x Se x , where 0≤x<0.6, or the chemical formula of p-type bismuth telluride is Bi 0.4 Sb 1.6 Te 3 Carry out raw material batching, place the single-element raw materials in a quartz tube and then seal the tube in vacuum;

[0010] (2) electromagnetically melting and cooling the single-element raw material in step (1) to obtain an ingot;

[0011] (3) Powdering the ingot in step (2) and hot extruding it to obtain n-type or p-type polycrystalline bismuth telluride.

[0012] The present invention adopts electromagnetic smelting to complete the smelting of bismuth telluride raw materials within an extremely short time. Compared with the method of smelting bismuth telluride raw materials disclosed in the prior art, the efficiency is significantly improved.

[0013] The present invention can obtain polycrystalline bismuth telluride with better grain size and better out-of-plane orientation by directly hot extruding the ingot after powdering, without the need for powder screening and with lower requirements on particle size, and is therefore suitable for large-scale production.

[0014] Preferably, the total amount of the single substance raw material added is 150g to 1000g, the power of the electromagnetic smelting is 1-10kw, and the heating time is 3 to 5min.

[0015] The present invention controls the amount of raw materials added and the parameters of electromagnetic smelting, so that the raw materials of bismuth telluride can be fully melted in a shorter time.

[0016] Preferably, oscillation is performed during the electromagnetic smelting process, and the oscillation time is 10 to 120 seconds. By controlling the oscillation time, the raw materials can be melted more evenly.

[0017] Preferably, the cooling method is quenching, and the quenching medium is water.

[0018] Preferably, the raw materials are at least two of Bi, Sb, Te and Se blocks.

[0019] Preferably, the ingot is mechanically crushed or air flow crushed to obtain ingot powder. The power of the mechanical crushing or air flow crushing is 2.3kw and the speed is 25000r / min. In the process of hot extrusion, under the action of huge pressure and high temperature, elastic and plastic deformation and brittle fracture occur between particles of micron-sized powder, and mechanical meshing is performed, and gravity is created between atoms on the contact surface, resulting in a certain bonding strength of the polycrystalline block after hot extrusion.

[0020] Preferably, the temperature of the hot extrusion molding is 300-500°C, the pressure is 500-1200Mpa, and the hot extrusion time is 10-60min. The present invention can obtain a suitable grain size under a suitable temperature and hot extrusion time, and the grains of polycrystalline bismuth telluride tend to have the same orientation in the out-of-plane direction and are densely arranged through pressure, so that a higher zT value can be obtained.

[0021] The present invention also provides a high-performance out-of-plane oriented polycrystalline bismuth telluride, which is prepared by the rapid preparation method of the high-performance out-of-plane oriented polycrystalline bismuth telluride;

[0022] The grain size of the high-performance out-of-plane oriented polycrystalline bismuth telluride is 2 to 10 μm;

[0023] The high-performance out-of-plane oriented polycrystalline bismuth telluride is n-type bismuth telluride or p-type bismuth telluride. At 30-523K, the dimensionless thermoelectric figure of merit of the n-type bismuth telluride is 0.33-0.88, and the dimensionless thermoelectric figure of merit of the p-type bismuth telluride is 0.39-1.1.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The commonly used method for preparing polycrystalline bismuth telluride on the market is usually high-temperature smelting, ball milling and subsequent powder metallurgy process. High-temperature smelting and ball milling generally take dozens of hours, while the electromagnetic smelting synthesis reaction provided by the present invention only takes 3 to 5 minutes in total, and the subsequent powdering process only takes 15 to 180 seconds. The powder preparation time is short, the synthesis process is simple to operate, and the equipment requirements are low, which is completely suitable for large-scale production.

[0026] The polycrystalline n-type and p-type bismuth telluride provided by the present invention have thermoelectric merits of 0.87 and 1.1 at 300K, respectively, which are comparable to the thermoelectric performance of the bismuth telluride comparison sample obtained by long-term smelting. Compared with the currently reported rapid synthesis of polycrystalline bismuth telluride, the present invention not only has no requirements on the initial morphology of the raw materials (the currently reported self-propagating methods require the use of raw material powders below 200 mesh, which further increases the cost of synthesis), but also has relatively high performance at 300K. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Bi prepared in Comparative Example 1 2 Te 2.7 Se 0.3 Seebeck coefficient S, electrical conductivity σ, thermal conductivity κ and zT value curves of the samples;

[0028] Figure 2 Bi prepared in Comparative Example 2 0.5 Sb 1.5 Te 3 Seebeck coefficient S, electrical conductivity σ, thermal conductivity κ and zT value curves of the samples;

[0029] Figure 3 Bi prepared in Comparative Example 3 0.5 Sb 1.5 Te 3 Seebeck coefficient S, electrical conductivity σ, thermal conductivity κ and zT value curves of the samples;

[0030] Figure 4 The n-type polycrystalline Bi prepared in Example 1 2Te 2.7 Se 0.3 XRD pattern of the bulk in the out-of-plane direction;

[0031] Figure 5 The n-type polycrystalline Bi prepared in Example 1 2 Te 2.7 Se 0.3 SEM images of the block in different directions, among which, Figure 5 (a) is the in-plane SEM image. Figure 5 (b) is the out-of-plane SEM image. Figure 5 (c) is the SEM image of the powder;

[0032] Figure 6 The n-type polycrystalline Bi prepared in Example 1 2 Te 2.7 Se 0.3 Thermoelectric performance diagram of the bulk in the out-of-plane direction;

[0033] Figure 7 The n-type polycrystalline Bi prepared in Example 2 2 Te 3 XRD pattern of the bulk in the out-of-plane direction;

[0034] Figure 8 The n-type polycrystalline Bi prepared in Example 2 2 Te 3 Thermoelectric performance diagram of the bulk in the out-of-plane direction;

[0035] Fig. 9 The n-type polycrystalline Bi prepared in Example 3 2 Te 2.4 Se 0.6 XRD pattern of the bulk in the out-of-plane direction;

[0036] Fig.10 The n-type polycrystalline Bi prepared in Example 3 2 Te 2.4 Se 0.6 Thermoelectric performance diagram of the bulk in the out-of-plane direction;

[0037] Fig.11 The p-type polycrystalline Bi prepared in Example 4 0.4 Sb 1.6 Te 3 XRD pattern of the bulk in the out-of-plane direction;

[0038] Fig.12 The p-type polycrystalline Bi prepared in Example 4 0.4 Sb 1.6 Te 3 Plot of the thermoelectric performance of the bulk in the out-of-plane direction. DETAILED DESCRIPTION

[0039] For a better understanding of the present invention, the present invention is further described below in conjunction with comparative examples and embodiments, but the present invention is not limited to the following embodiments.

[0040] Comparative Example 1

[0041] Bi, Se, Te powders below 200 mesh are used as raw materials. 2 Te 3-x Se x (n-type, 0≤x≤3) was manually ground and mixed in a molar ratio, and n-type Bi was prepared by high-temperature self-propagating combined with plasma activated sintering. 2 Te 3-x Se x Bulk material, room temperature zT value is 0.69, the specific preparation process is as follows:

[0042] (1) According to the stoichiometric ratio of n-type Bi 2 Te 3-x Se x (0≤x≤3) Weigh Bi, Te, and Se powders with a mesh size below 200, grind them manually in a mortar for 10 minutes, and then cold-press them into blocks. Vacuum seal the tube in a quartz tube, and perform ignition self-propagation induced single-substance reaction.

[0043] (2) The product after the reaction was characterized by XRD as Bi 2 Te 3-x Se x (0≤x≤3) single phase; the above product is loaded into a graphite mold and sintered for 10 min under 753K, 20Mpa conditions for plasma activation to obtain Bi 2 Te 3-x Se x (0≤x≤3) bulk material. Among them, Bi at 300K 2 Te 3-x Se x The room temperature zT value of the sample is the highest, about 0.69.

[0044] Figure 1 The given is Bi 2 Te 2.7 Se 0.3 The Seebeck coefficient S of the sample ( Figure 1 (a)), conductivity σ( Figure 1 (b)) and thermal conductivity κ( Figure 1 (c)), and the zT value of the material can be obtained by calculation ( Figure 1 (d)).

[0045] Comparative Example 2

[0046] Bi, Sb, Te powders below 200 mesh are used as raw materials. 2-x Sb x Te 3 (p-type, 0≤x≤2) was manually ground and mixed in a molar ratio, and p-type Bi was prepared by high-temperature self-propagating combined with plasma activated sintering. 0.5 Sb 1.5 Te 3 The bulk material has a room temperature zT value of 1.0. The specific preparation process is as follows:

[0047] (1) According to the stoichiometric ratio Bi 2-x Sb x Te 3 (0≤x≤3) Weigh Bi, Sb, and Te powders with a mesh size below 200, grind them manually in a mortar for 10 minutes, and then cold press them into blocks. Vacuum seal the tube in a quartz tube. Place the sealed quartz tube together with the materials in a high-temperature muffle furnace preheated to 823K and conduct a self-propagating reaction for 3 minutes. The product after the reaction is characterized by XRD as Bi 2-x Sb x Te 3 (0≤x≤3) single phase.

[0048] (2) The above product is placed in a graphite mold and sintered at 753K, 20Mpa for 10 minutes by plasma activation to obtain Bi 2-x Sb x Te 3 (0≤x≤2) bulk material.

[0049] Among them, at 300K, Bi 0.5 Sb 1.5 Te 3 The room temperature zT value of the sample is the highest, about 1.0. Figure 2 The given is Bi 0.5 Sb 1.5 Te 3 The Seebeck coefficient S of the sample ( Figure 2 (a)), conductivity σ( Figure 2 (b)) and thermal conductivity κ( Figure 2 (c)), and the zT value of the material can be obtained by calculation ( Figure 2 (d)).

[0050] Comparative Example 3

[0051] Bi in Comparative Example 2 0.5 Sb 1.5 Te 3 is the ratio of the highest zT value at room temperature obtained by powder self-propagation method, while the ratio used in the embodiment of the present invention is Bi 0.4 Sb1.6 Te 3 For the convenience of comparison, the ratio used in this embodiment is also added to Comparative Example 3 for the convenience of comparison.

[0052] Bi, Sb, Te powders below 200 mesh are used as raw materials. 2-x Sb x Te 3 (p-type, 0≤x≤2) was manually ground and mixed in a molar ratio, and p-type Bi was prepared by high-temperature self-propagating combined with plasma activated sintering. 0.4 Sb 1.6 Te 3 The bulk material has a room temperature zT value of 1.0. The specific preparation process is as follows:

[0053] (1) According to the stoichiometric ratio Bi 0.4 Sb 1.6 Te 3 Weigh Bi, Sb, and Te powders with a mesh size below 200, grind them manually in a mortar for 10 minutes, and then cold press them into blocks. Vacuum seal the tube in a quartz tube. Place the sealed quartz tube together with the materials in a high-temperature muffle furnace preheated to 823K and perform self-propagating reaction for 3 minutes. The product after the reaction is characterized by XRD as Bi 0.4 Sb 1.6 Te 3 Single phase.

[0054] (2) The above product is placed in a graphite mold and sintered at 753K, 20Mpa for 10 minutes by plasma activation to obtain Bi 2-x Sb x Te 3 (0≤x≤2) bulk material. Among them, Bi at 300K 0.4 Sb 1.6 Te 3 The room temperature zT value of the sample is the highest, about 1.0. Figure 2 The given is Bi 0.5 Sb 1.5 Te 3 The Seebeck coefficient S of the sample ( Figure 3 (a)), conductivity σ( Figure 3 (b)) and thermal conductivity κ( Figure 3 (c)), and the zT value of the material can be obtained by calculation ( Figure 3 (d)).

[0055] Example 1

[0056] A method for rapidly preparing high-performance out-of-plane oriented polycrystalline bismuth telluride, which adopts electromagnetic melting for rapid compounding, powderizes with a powder pulverizer, and then prepares n-type bismuth telluride blocks by high-temperature hot extrusion, mainly comprising the following steps:

[0057] (1) Using Bi, Te, and Se blocks as raw materials, weigh a total of 150 g and a molar ratio of 2:2.7:0.3, place them in a pre-cleaned quartz tube, and vacuum seal the tube after the air in the tube is evacuated to below 1 Pa.

[0058] (2) The vacuum quartz tube containing Bi, Te, and Se blocks is placed in an electromagnetic melting crucible with a power of 1 kW. After heating for 3 minutes, the tube is oscillated for about 1 minute and quenched with pure water.

[0059] (3) The obtained ingot is put into a hot extrusion mold after being pulverized, wherein the powder particle size is 1 to 10 μm, and hot extrusion molding is performed at 733K and 1200 MPa for 10 to 60 minutes to obtain a columnar block with a length of 200 cm and a diameter of 12.7 mm, which is n-type polycrystalline Bi 2 Te 2.7 Se 0.3 Bulk thermoelectric materials.

[0060] The above-mentioned reduced diameter n-type polycrystalline Bi 2 Te 2.7 Se 0.3 The rod is cut into pieces with a thickness of 1.2 mm and a diameter of The thermoelectric properties of sheets and 3*3*15mm (15mm corresponds to the axial direction) cuboids are tested respectively; the remaining materials after cutting will be used for the characterization of phase composition and microstructure.

[0061] Figure 4 The n-type polycrystalline Bi prepared in Example 1 2 Te 2.7 Se 0.3 The XRD pattern of the bulk in the out-of-plane direction shows that all peaks are related to Bi 2 Te 3 The standard peaks are consistent, proving that the sample prepared in Example 1 is Bi 2 Te 2.7 Se 0.3 Single phase.

[0062] Figure 5 (a) Figure 5 (b) is the n-type polycrystalline Bi prepared in Example 1 2 Te 2.7 Se 0.3The SEM images of the block in different directions show that the block is an obvious polycrystalline sample, and the grains tend to have the same orientation in the out-of-plane direction and are densely arranged, which is consistent with the density test results. Figure 5 (c) It can be seen that the powder particle size is 1 to 10 μm.

[0063] The entire preparation process of this embodiment takes less than 15 minutes, which is comparable to the self-propagating reaction comparative example for rapid production of bismuth telluride. Figure 6 (a)-(d) show the n-type polycrystalline Bi prepared in Example 1 2 Te 2.7 Se 0.3 Thermoelectric performance of bulk in out-of-plane direction, n-type polycrystalline Bi in this example 2 Te 2.7 Se 0.3 At 300K, the zT value is 0.87, which is 26% higher than the 0.69 of the self-propagating n-type bismuth telluride in comparative example 1.

[0064] Example 2

[0065] A method for rapidly preparing high-performance out-of-plane oriented polycrystalline bismuth telluride, which adopts electromagnetic melting for rapid compounding, powderizes with a powder pulverizer, and then prepares n-type bismuth telluride blocks by high-temperature hot extrusion, mainly comprising the following steps:

[0066] (1) Using Bi and Te blocks as raw materials, weigh a total of 150 g and a molar ratio of 2:3, place them in a pre-cleaned quartz tube, and vacuum seal the tube after the air in the quartz tube is evacuated to below 1 Pa;

[0067] (2) The vacuum quartz tube containing Bi and Te blocks is placed in an electromagnetic melting crucible with an electromagnetic melting power of 5 kW. After heating for 3 minutes, the ingot is oscillated for about 1 minute and quenched with pure water. (3) The obtained ingot is powdered and placed in a hot extrusion mold. The powder particle size is 1 to 10 μm. The ingot is hot extruded at 733 K and 1200 MPa for 10 minutes to obtain a columnar block with a length of 200 cm and a diameter of 12.7 mm, which is n-type polycrystalline Bi. 2 Te 3 Bulk thermoelectric materials.

[0068] The above-mentioned reduced diameter n-type polycrystalline Bi 2 Te 3 The rod is cut into pieces with a thickness of 1.2 mm and a diameter of The thermoelectric properties of sheets and 3*3*15mm (15mm corresponds to the axial direction) cuboids are tested respectively; the remaining materials after cutting will be used for the characterization of phase composition and microstructure.

[0069] Figure 7 The n-type polycrystalline Bi prepared in Example 2 2 Te 3 The XRD pattern of the bulk in the out-of-plane direction shows that all peaks are related to Bi 2 Te 3 The standard peaks are consistent, proving that the sample prepared in Example 2 is Bi 2 Te 3 Single phase.

[0070] Figure 8 (a)-(b) are n-type polycrystalline Bi prepared in Example 2 2 Te 3 Thermoelectric performance of bulk in out-of-plane direction, n-type polycrystalline Bi in this example 2 Te 3 At 300K, the zT value is 0.78, which is 13% higher than the 0.69 of the self-propagating n-type bismuth telluride in comparative example 1.

[0071] Example 3

[0072] A method for rapidly preparing high-performance out-of-plane oriented polycrystalline bismuth telluride, which adopts electromagnetic melting for rapid compounding, powderizes with a powder pulverizer, and then prepares n-type bismuth telluride blocks by high-temperature hot extrusion, mainly comprising the following steps:

[0073] (1) Using Bi, Te, and Se blocks as raw materials, weigh a total of 150 g and a molar ratio of 2:2.4:06, place them in a pre-cleaned quartz tube, and vacuum seal the tube after the air in the quartz tube is evacuated to below 1 Pa;

[0074] (2) placing the vacuum quartz tube containing Bi, Te, and Se blocks in an electromagnetic melting crucible with an electromagnetic melting power of 10 kW, heating the reaction for 3 minutes, oscillating for about 1 minute, and quenching with pure water;

[0075] (3) The obtained ingot is put into a hot extrusion mold after being pulverized. The powder particle size is 1 to 10 μm. The hot extrusion molding is carried out at 733K and 1200 MPa for 10 minutes to obtain a columnar block with a length of 200 cm and a diameter of 12.7 mm, which is n-type polycrystalline Bi 2 Te 2.4 Se 0.6 Bulk thermoelectric materials.

[0076] The above-mentioned reduced diameter n-type polycrystalline Bi 2 Te 2.4 Se 0.6 The rod is cut into pieces with a thickness of 1.2 mm and a diameter of The thermoelectric properties of sheets and 3*3*15mm (15mm corresponds to the axial direction) cuboids are tested respectively; the remaining materials after cutting will be used for the characterization of phase composition and microstructure.

[0077] Fig. 9 The XRD spectrum of the block in Example 3 in the out-of-plane direction, all peaks are consistent with the standard peaks of Bi2Te3, proving that the sample prepared in Example 3 is Bi 2 Te 2.4 Se 0.6 Single phase.

[0078] Fig.10 (a)-(b) are the thermoelectric properties of the middle block prepared in Example 3 in the out-of-plane direction. The n-type polycrystalline Bi 2 Te 3 The zT value is 0.73 at 300K, which is 5.8% higher than the 0.69 of the self-propagating n-type bismuth telluride in comparative example 1.

[0079] Example 4

[0080] A method for rapidly preparing high-performance out-of-plane oriented polycrystalline bismuth telluride, which adopts electromagnetic melting for rapid compounding, powderizes with a powder pulverizer, and then prepares a p-type bismuth telluride block by high-temperature hot extrusion, mainly comprising the following steps:

[0081] (1) Using Bi, Te, and Sb blocks as raw materials, weigh them with a total amount of 150 g and a molar ratio of 0.4:3:1.6, place them in a pre-cleaned quartz tube, and wait until the air in the quartz tube is evacuated to below 1 Pa, and then vacuum seal the tube.

[0082] (2) The vacuum quartz tube containing Bi, Te, and Sb blocks is placed in an electromagnetic melting crucible with an electromagnetic melting power of 3 kW. After heating for 3 minutes, the tube is oscillated for about 1 minute and quenched with pure water.

[0083] (3) The obtained ingot is put into a hot extrusion mold after being pulverized. The powder particle size is 1 to 10 μm. The hot extrusion molding is carried out at 733K and 1200 MPa for 10 minutes to obtain a columnar block with a length of 200 cm and a diameter of 12.7 mm, which is p-type polycrystalline Bi 0.4 Sb 1.6 Te 3 Bulk thermoelectric materials.

[0084] The above-mentioned diameter-shrink p-type polycrystalline Bi 0.4 Sb 1.6 Te 3 The rod is cut into pieces with a thickness of 1.2 mm and a diameter of The thermoelectric properties of sheets and 3*3*15mm (15mm corresponds to the axial direction) cuboids are tested respectively; the remaining materials after cutting will be used for the characterization of phase composition and microstructure.

[0085] Fig.11 The XRD pattern of the block in Example 4 in the out-of-plane direction, all peaks are related to Bi 0.5 Sb 1.5 Te 3 The standard peaks are consistent, proving that the sample prepared in Example 4 is Bi 0.4 Sb 1.6 Te 3 Single phase.

[0086] Fig.12 The thermoelectric performance of the bulk in the out-of-plane direction in Example 4 is shown in Table 1. 0.4 Sb 1.6 Te 3 The zT value is 1.1 at 300K, which is 10% higher than the 1.0 performance of the self-propagating p-type bismuth telluride in Comparative Example 2.

[0087] The present invention adopts a rapid electromagnetic melting process, combined with high-speed powderization technology and hot extrusion molding, to quickly prepare polycrystalline bismuth telluride rods, wherein n-type Bi 2 Te 2.7 Se 0.3 At 300K, the zT value is about 0.87; p-type Bi 0.4 Sb 1.6 Te 3 The zT value is about 1.1 at 300 K. As shown in Table 1, compared with the traditional method, this method has a simple process, a short preparation cycle, and is energy-saving and environmentally friendly, and is suitable for large-scale industrial production of the material.

[0088] Table 1: Room temperature performance comparison between comparative examples and examples

[0089]

[0090]

Claims

1. A rapid preparation method for high-performance out-of-plane oriented polycrystalline bismuth telluride, characterized in that: include: (1) According to the chemical formula of n-type bismuth telluride, Bi2Te 3-x Se x , where 0≤x<0.6, or the chemical formula of p-type bismuth telluride is Bi 0.4 Sb 1.6 Te3 is used to prepare raw materials, and the single-element raw materials are placed in a quartz tube and then sealed in vacuum; (2) electromagnetically melting and cooling the single-element raw material in step (1) to obtain an ingot; (3) Powdering the ingot in step (2) and hot extruding it to obtain n-type or p-type polycrystalline bismuth telluride.

2. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: The amount of the raw material added is 150-1000 g, the power of the electromagnetic smelting is 1-10 kW, and the heating time is 3-5 min.

3. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: Oscillation is performed during the electromagnetic smelting process, and the oscillation time is 10 to 120 seconds.

4. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: The cooling method is quenching, and the quenching medium is water.

5. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: The raw materials are at least two of Bi, Sb, Te and Se blocks.

6. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: The ingot is mechanically pulverized or air flow pulverized to obtain ingot powder.

7. The rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to claim 1, characterized in that: The temperature of the hot extrusion molding is 300-500° C., the pressure is 500-1200 MPa, and the hot extrusion time is 10-60 minutes.

8. A high-performance out-of-plane oriented polycrystalline bismuth telluride, characterized in that: Prepared by the rapid preparation method of high-performance out-of-plane oriented polycrystalline bismuth telluride according to any one of claims 1 to 7; The grain size of the high-performance out-of-plane oriented polycrystalline bismuth telluride is 1 to 10 μm; The high-performance out-of-plane oriented polycrystalline bismuth telluride is n-type bismuth telluride or p-type bismuth telluride. At 300-527KK, the dimensionless thermoelectric figure of merit of the n-type bismuth telluride is 0.33-0.88, and the dimensionless thermoelectric figure of merit of the p-type bismuth telluride is 0.39-1.1.

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