Iodide doped N-type bismuth telluride crystal bar and preparation method thereof

Abstract

The invention discloses a preparation method of an iodide doped N-type bismuth telluride crystal bar, and belongs to the technical field of thermoelectric materials. According to the preparation method, the iodide solution is sprayed on the inner wall of the glass according to a certain single spraying amount to be dried for multiple times, then the N-type bismuth telluride raw material is added, and zone melting is performed under a certain condition, so that the iodide-doped N-type bismuth telluride crystal bar which is uniform and controllable in doping amount can be obtained; meanwhile, the iodide-doped N-type bismuth telluride crystal bar provided by the invention is simple in pretreatment operation on the inner wall of the glass, high in efficiency and beneficial to industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoelectric materials, and in particular relates to an iodide-doped N-type bismuth telluride crystal rod and a preparation method thereof. Background Art

[0002] Thermoelectric materials can realize the effective conversion between thermal energy and electrical energy. Compared with the shortcomings of traditional energy conversion such as high pollution, low reliability and high noise, most thermoelectric energy conversion devices have the advantages of simple structure and controllable size. They are a kind of green energy material with very broad application prospects. Among them, the most commercially mature one is bismuth telluride-based thermoelectric material.

[0003] In the current research, patent CN112342618B prepares doped bismuth telluride by crushing elemental tellurium, elemental bismuth and doping element raw materials, adding them into a glass tube for swing melting, and its performance stable area is only greater than 70%. Patent CN114920563B also obtains P-type bismuth telluride raw materials by crushing-sealing tube-swing melting-zone melting of elemental tellurium, bismuth, antimony and silver raw materials, and then obtains P-type bismuth telluride sintered materials by further crushing and sintering. The steps are extremely cumbersome and the energy consumption is high.

[0004] Obviously, in the prior art, the doping of the zone melting crystal rod is mainly carried out by adding compounds of doping elements in the swing melting stage, but the melting temperature is usually above 500°C. For low-boiling point, easily decomposable, and volatile doping element compounds, such as tellurium iodide, bismuth iodide, etc., the doping element compounds will be enriched in the crystal rod due to volatilization, gasification, etc., resulting in uneven distribution of the doping components of the overall zone melting crystal rod, which leads to large differences in thermoelectric properties of different parts of the crystal rod, making it difficult to meet the needs of commercial, large-scale production of stable high thermoelectric performance N-type zone melting bismuth telluride crystal rods. Summary of the invention

[0005] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide an iodide-doped N-type bismuth telluride crystal rod with controllable and uniform doping and a preparation method thereof.

[0006] To achieve the above object, in a first aspect of the present invention, the present invention provides a method for preparing an iodide-doped N-type bismuth telluride crystal rod, the preparation method comprising the following steps:

[0007] (1) spraying an iodide solution on the inner wall of a glass tube and then drying it, repeating this process multiple times to obtain a glass tube with a pretreated inner surface;

[0008] (2) adding N-type bismuth telluride raw material into the glass tube with the inner surface pretreated in step (1), sealing the tube and performing zone melting treatment, and cooling after the zone melting treatment to obtain iodide-doped N-type bismuth telluride crystal rod;

[0009] In the step (1), the amount of a single spray is less than or equal to 250 mL per square meter of inner tube area;

[0010] In the step (2), the zone melting temperature is 650-800°C, the zone melting speed is 1-3 mm / min, and the zone melting width is 3-6 mm.

[0011] The present invention sprays an iodide solution on the inner wall of glass with a certain single spraying amount, dries the solution and repeats the process for multiple times, then adds an N-type bismuth telluride raw material and performs zone melting under certain conditions. Since the zone melting process moves along with the temperature zone, the crystal rod is partially heated, and only the crystal rod in the heated area reacts with the iodide of the glass tube wall, thereby avoiding the aggregation of iodide caused by large-scale melting and heating, thereby obtaining a uniformly doped iodide-doped N-type bismuth telluride crystal rod, and the doping amount is controllable. At the same time, the operation method for pre-treating the iodide-doped N-type bismuth telluride crystal rod on the glass inner tube provided by the present invention is simple and is conducive to actual production.

[0012] Exemplarily, the spraying amount is any point value or any two point range value less than or equal to 250mL per square meter of inner tube area, for example, it can be 10mL, 20mL, 30mL, 40mL, 50mL, 60mL, 70mL, 80mL, 90mL, 100mL, 120mL, 140mL, 160mL, 180mL, 200mL, 220mL, 240mL, 250mL, etc.

[0013] Preferably, the spraying amount is greater than or equal to 10 mL and less than or equal to 250 mL per square meter of inner tube area.

[0014] The present invention has found that the amount of a single spray not only affects the work efficiency, but also has a certain impact on the uniformity of the product. When the spraying amount is further selected to be greater than or equal to 10 mL and less than or equal to 250 mL per square meter of inner tube area, the overall effect is more excellent.

[0015] Exemplarily, the zone melting temperature can be any point value or any two point range value between 650-800℃, for example, it can be 650℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃, 800℃, etc.; the zone melting speed can be any point value or any two point range value between 1-3mm / min, for example, it can be 1mm / min, 1.5mm / min, 2mm / min, 2.5mm / min, 3mm / min, etc.; the zone melting width can be any point value or any two point range value between 3-6mm, for example, it can be 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, etc.

[0016] Exemplarily, the present invention has no special limitation on the spraying equipment, such as conventional air spray guns, low-pressure high-flow spray guns, electrostatic spray guns, air-assisted airless spray guns, special spray guns, etc. can be used; as long as the spraying amount is within the range given by the present invention.

[0017] As a preferred embodiment of the preparation method of the present invention, in the iodide solution, the mass volume ratio of iodide to solvent is 1g: (100-1000)mL.

[0018] The iodide solution provided by the present invention can be determined according to the required iodide doping mass ratio, the type of doped iodide and the type of selected solvent. When it is within the mass volume ratio range of iodide and solvent given by the present invention, a good spraying effect can be achieved during the subsequent spraying process while obtaining the target doping amount of iodide-doped N-type bismuth telluride crystal rods, thereby helping to improve the uniformity of doping.

[0019] As a preferred embodiment of the preparation method of the present invention, the iodide includes at least one of bismuth iodide, tellurium iodide and antimony iodide.

[0020] As a preferred embodiment of the preparation method of the present invention, the solvent includes at least one of ethanol, ammonia water, acetone and pentanol.

[0021] Preferably, the iodide solution comprises any one of the following: 1) an ethanol solution of tellurium iodide, 2) an acetone solution of tellurium iodide, 3) an ethanol solution of bismuth iodide, 4) an ammonia solution of bismuth iodide, 5) a pentanol solution of bismuth iodide.

[0022] The present invention has found that when the combination of the above iodide solutions is used, uniform doping can be better achieved.

[0023] As a preferred embodiment of the preparation method of the present invention, in the step (1), the drying temperature is greater than or equal to the volatilization temperature of the solvent in the iodide solution and less than or equal to the sublimation temperature of the iodide.

[0024] The present invention has found that when the drying temperature is further selected to be greater than or equal to the volatilization temperature of the solvent in the iodide solution and less than or equal to the sublimation temperature of the iodide, the solvent can be effectively evaporated and removed without affecting the iodide, thereby avoiding excessive fluctuations in the doping mass percentage caused by iodide sublimation or uneven iodide doping.

[0025] As a preferred embodiment of the preparation method of the present invention, the inner diameter of the glass tube is 20-60 mm, and the length of the glass tube is 90-180 cm.

[0026] As a preferred embodiment of the preparation method of the present invention, in the N-type bismuth telluride, the atomic mass of bismuth is 30-60%, the atomic mass of tellurium is 30-50%, and the remainder is selenium.

[0027] As a preferred embodiment of the preparation method of the present invention, in the step (2), the amount of N-type bismuth telluride added is 30-75% of the volume of the glass tube.

[0028] As a preferred embodiment of the preparation method of the present invention, in the step (2), the sealing point is 20-30 mm away from the edge of the iodide spraying along the direction of the glass tube mouth.

[0029] In a second aspect of the present invention, the present invention provides an iodide-doped N-type bismuth telluride crystal rod, wherein the iodide-doped N-type bismuth telluride crystal rod is prepared by the preparation method of the present invention.

[0030] As a preferred embodiment of the iodide-doped N-type bismuth telluride crystal rod of the present invention, the doping amount of iodide is 0.1-1 wt % based on the iodide-doped N-type bismuth telluride crystal rod.

[0031] As a preferred embodiment of the iodide-doped N-type bismuth telluride crystal rod of the present invention, the length of the iodide-doped N-type bismuth telluride crystal rod is 150-500 mm.

[0032] As a preferred embodiment of the preparation method of the present invention,

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention sprays an iodide solution on the inner wall of a glass with a certain single spraying amount, dries it and repeats the process for multiple times, then adds an N-type bismuth telluride raw material and performs zone melting under certain conditions, thereby obtaining a uniformly doped iodide-doped N-type bismuth telluride crystal rod, and the doping amount is controllable; meanwhile, the operation method of the iodide-doped N-type bismuth telluride crystal rod provided by the present invention is simple and is conducive to actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of sampling and testing of iodide-doped N-type bismuth telluride crystal rods in the effect example. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] Unless otherwise specified, the reagents, methods and equipment used in the present invention are all conventional reagents, methods and equipment in the art; and unless otherwise specified, the raw materials used in parallel experiments are from the same batch of raw materials.

[0038] Example 1

[0039] An embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The preparation method of the iodide-doped N-type bismuth telluride crystal rod comprises the following steps:

[0040] (1) dissolving 0.75 g of tellurium iodide in ammonia water at a solid-liquid ratio of tellurium iodide: ammonia water = 1 g: 100 mL, and stirring to obtain a uniformly dissolved tellurium iodide solution;

[0041] (2) spraying the tellurium iodide solution onto the inner wall of a glass tube with an inner diameter of 30 mm and a length of 150 cm by a low-pressure, high-flow spray gun, with the amount of each spraying being 20 mL per square meter of the inner tube area, ensuring that the liquid adheres to the inner wall of the glass tube without converging. After the spraying is completed, hot air drying is performed at 80° C. The spraying-drying operation is repeated multiple times until the tellurium iodide solution in step (1) is sprayed completely, thereby obtaining a glass tube with a pretreated inner surface;

[0042] (3) 1.5 kg of N-type bismuth telluride compound raw material (in N-type bismuth telluride, the atomic mass of bismuth is 45%, the atomic mass of tellurium is 40%, and the remainder is selenium) is added to the glass tube with the inner surface pretreated in the previous step (the amount of N-type bismuth telluride added is 50% of the volume of the glass tube), and then the tube is sealed (the sealing point is 25 mm away from the edge of the iodide spraying along the direction of the glass tube mouth), and finally placed in a zone melting furnace with a zone melting temperature of 700° C., a zone melting speed of 2 mm / min, and a zone melting width of 5 mm. After the zone melting is completed and the temperature is cooled, an iodide-doped N-type bismuth telluride crystal rod is obtained.

[0043] Example 2

[0044] An embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The preparation method of the iodide-doped N-type bismuth telluride crystal rod comprises the following steps:

[0045] (1) dissolving 1.2 g of bismuth iodide in ethanol at a solid-liquid ratio of bismuth iodide:ethanol=1 g:500 mL, and stirring to obtain a uniformly dissolved bismuth iodide solution;

[0046] (2) spraying the tellurium iodide solution onto the inner wall of a glass tube having an inner diameter of 30 mm and a length of 150 cm by a conventional air spray gun, with the amount of each spraying being 50 mL per square meter of the inner tube area, ensuring that the liquid adheres to the inner wall of the glass tube and does not gather. After the spraying is completed, hot air drying is performed at 80° C. The spraying-drying operation is repeated multiple times until the tellurium iodide solution in step (1) is sprayed completely, thereby obtaining a glass tube with a pretreated inner surface;

[0047] (3) 1.5 kg of N-type bismuth telluride compound raw material (in N-type bismuth telluride, the atomic mass of bismuth is 40%, the atomic mass of tellurium is 50%, and the remainder is selenium) is added to the glass tube with the inner surface pretreated in the previous step (the amount of N-type bismuth telluride added is 35% of the volume of the glass tube), and then the tube is sealed (the sealing point is 20 mm away from the edge of the iodide spraying along the direction of the glass tube mouth), and finally placed in a zone melting furnace with a zone melting temperature of 650° C., a zone melting speed of 3 mm / min, and a zone melting width of 4 mm. After the zone melting is completed and the temperature is cooled, an iodide-doped N-type bismuth telluride crystal rod is obtained.

[0048] Example 3

[0049] An embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The preparation method of the iodide-doped N-type bismuth telluride crystal rod comprises the following steps:

[0050] (1) dissolving 1.2 g of bismuth iodide in ethanol at a solid-liquid ratio of bismuth iodide:ethanol=1 g:1000 mL, and stirring to obtain a uniformly dissolved bismuth iodide solution;

[0051] (2) spraying the tellurium iodide solution onto the inner wall of a glass tube having an inner diameter of 30 mm and a length of 150 cm by a conventional air spray gun, with the amount of each spraying being 100 mL per square meter of the inner tube area, ensuring that the liquid adheres to the inner wall of the glass tube without converging. After the spraying is completed, hot air drying is performed at 80° C. The spraying-drying operation is repeated multiple times until the tellurium iodide solution in step (1) is sprayed completely, thereby obtaining a glass tube with a pretreated inner surface;

[0052] (3) 1.5 kg of N-type bismuth telluride compound raw material (in N-type bismuth telluride, the atomic mass of bismuth is 60%, the atomic mass of tellurium is 30%, and the remainder is selenium) is added to the glass tube with the inner surface pretreated in the previous step (the amount of N-type bismuth telluride added is 75% of the volume of the glass tube), and then the tube is sealed (the sealing point is 30 mm away from the edge of the iodide spraying along the direction of the glass tube mouth), and finally placed in a zone melting furnace with a zone melting temperature of 800° C., a zone melting speed of 1 mm / min, and a zone melting width of 6 mm. After the zone melting is completed and the temperature is cooled, an iodide-doped N-type bismuth telluride crystal rod is obtained.

[0053] Example 4

[0054] The embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that the solid-liquid ratio in step (1) is tellurium iodide: ammonia water = 1 g: 50 mL.

[0055] Example 5

[0056] The embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that the solid-liquid ratio in step (1) is tellurium iodide: ammonia water = 1 g: 1500 mL.

[0057] Example 6

[0058] The embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that in step (3), the sealing tube is 10 mm away from the edge of the iodide spraying along the direction of the glass tube mouth.

[0059] Example 7

[0060] The embodiment of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that in step (3), the sealing tube is 40 mm away from the edge of the iodide spraying along the direction of the glass tube mouth.

[0061] Comparative Example 1

[0062] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod, and the preparation method of the iodide-doped N-type bismuth telluride crystal rod comprises the following steps:

[0063] 0.75 g of tellurium iodide is added to an ordinary untreated glass tube with an inner diameter of 30 mm and a length of 150 cm, and then 1.5 kg of N-type bismuth telluride compound raw material is added (in N-type bismuth telluride, the atomic mass of bismuth is 45%, the atomic mass of tellurium is 40%, and the remainder is selenium. The amount of N-type bismuth telluride added is 50% of the volume in the glass tube), and then the tube is sealed and finally placed in a zone melting furnace with a zone melting temperature of 700° C., a zone melting travel speed of 2 mm / min, and a zone melting width of 5 mm. After the zone melting is completed and the temperature is cooled, an iodide-doped N-type bismuth telluride crystal rod is obtained.

[0064] Comparative Example 2

[0065] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that the amount of each spraying in step (2) is 300 mL per square meter of inner tube area.

[0066] Comparative Example 3

[0067] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that in step (3), the zone melting temperature is 600° C., the zone melting speed is 2 mm / min, and the zone melting width is 5 mm.

[0068] Comparative Example 4

[0069] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that in step (3), the zone melting temperature is 700° C., the zone melting speed is 4 mm / min, and the zone melting width is 5 mm.

[0070] Comparative Example 5

[0071] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and Example 1 is that in step (3), the zone melting temperature is 700° C., the zone melting speed is 2 mm / min, and the zone melting width is 8 mm.

[0072] Comparative Example 6

[0073] The comparative example of the present invention provides an iodide-doped N-type bismuth telluride crystal rod. The only difference between the preparation method of the iodide-doped N-type bismuth telluride crystal rod and that of Example 1 is that in step (3), the zone melting temperature is 700° C., the zone melting speed is 2 mm / min, and the zone melting width is 1 mm.

[0074] Effect example

[0075] Effect Example of the Invention The doping uniformity of the iodide-doped N-type bismuth telluride crystal rods prepared in the embodiments and comparative examples and the difference from the theoretical doping amount are explored, specifically: the iodine content of the upper, middle and lower parts of the crystal rod is tested by ICP-MS; the upper sampling point is 5 cm away from the top, the middle sampling point is in the middle of the crystal rod, and the lower sampling point is 5 cm away from the bottom; the results are shown in Table 1;

[0076] Among them, the measured values ​​in Table 1 are the mass percentages of iodine elements measured by ICP-MS in the upper, middle and lower parts, and the deviations are the differences between the measured values ​​and the theoretical values ​​in the upper, middle and lower parts;

[0077] Table 1

[0078]

[0079] It can be seen from Table 1 that when the preparation method provided by the present invention is adopted, the doping deviation of the obtained iodide-doped N-type bismuth telluride crystal rod is small and the uniformity is high.

[0080] It can be seen from Example 1 and Comparative Example 2 that when the spraying amount is too high during the preparation process, the doping deviation of the obtained crystal rod becomes larger and the uniformity decreases; it can be seen from Example 1 and Comparative Examples 3-6 that the zone melting parameters will also affect the doping uniformity of the product.

[0081] Finally, it should be noted that the above embodiments are intended to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing an iodide-doped N-type bismuth telluride crystal rod, characterized in that: The preparation method comprises the following steps: (1) spraying an iodide solution on the inner wall of a glass tube and then drying it, repeating this process multiple times to obtain a glass tube with a pretreated inner surface; (2) adding N-type bismuth telluride raw material into the glass tube with the inner surface pretreated in step (1), sealing the tube and performing zone melting treatment, and cooling after the zone melting treatment to obtain iodide-doped N-type bismuth telluride crystal rod; In the step (1), the amount of a single spray is less than or equal to 250 mL per square meter of inner tube area; In the step (2), the zone melting temperature is 650-800°C, the zone melting speed is 1-3 mm / min, and the zone melting width is 3-6 mm.

2. The preparation method according to claim 1, characterized in that: In the iodide solution, the mass volume ratio of iodide to solvent is 1 g: (100-1000) mL.

3. The preparation method according to claim 2, characterized in that: The iodide includes at least one of bismuth iodide, tellurium iodide, and antimony iodide; And / or, the solvent includes at least one of ethanol, ammonia, acetone and pentanol.

4. The preparation method according to claim 1, characterized in that: In the step (1), the drying temperature is greater than or equal to the volatilization temperature of the solvent in the iodide solution and less than or equal to the sublimation temperature of the iodide.

5. The preparation method according to claim 1, characterized in that: The inner diameter of the glass tube is 20-60 mm, and the length of the glass tube is 90-180 cm.

6. The preparation method according to claim 1, characterized in that: In the N-type bismuth telluride, the atomic mass of bismuth is 30-60%, the atomic mass of tellurium is 30-50%, and the remainder is selenium.

7. The preparation method according to claim 1, characterized in that: In the step (2), the amount of N-type bismuth telluride added is 30-75% of the volume of the glass tube.

8. The preparation method according to claim 1, characterized in that: In the step (2), the sealing point is 20-30 mm away from the edge of the iodide spraying along the direction of the glass tube opening.

9. An iodide-doped N-type bismuth telluride crystal rod, characterized in that: The iodide-doped N-type bismuth telluride crystal rod is prepared by the preparation method according to any one of claims 1 to 8.

10. The iodide-doped N-type bismuth telluride crystal rod according to claim 9, characterized in that: The doping amount of iodide is 0.1-1wt% based on the iodide-doped N-type bismuth telluride crystal rod; And / or, the length of the iodide-doped N-type bismuth telluride crystal rod is 150-500 mm.

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