A bismuth antimony tellurium alloy target material and a method for manufacturing the same

Abstract

The application belongs to the field of target material preparation, and particularly discloses a bismuth-antimony-tellurium alloy target material and a preparation method thereof. x Sb 2‑x Te3, x=0.4-0.7. The bismuth-antimony-tellurium alloy target material is prepared by first preparing a kind of spherical alloy powder through gas atomization, and then sintering the alloy powder through secondary hot pressing, so that the bismuth-antimony-tellurium alloy target material with high density, small and uniform grain size can be finally prepared. The bismuth-antimony-tellurium alloy target material has a density greater than 99.3% and an average grain size less than 10 microns.

Description

Technical Field

[0001] This invention belongs to the field of target material preparation, specifically relating to a bismuth-antimony-tellurium alloy target material and its preparation method. Background Technology

[0002] Thermoelectric materials are functional materials that can convert between electrical energy and thermal energy. Bismuth telluride-based alloys are currently commercially available and are among the most applicable thermoelectric materials near room temperature. They have excellent characteristics such as being pollution-free, lossless, and highly reliable, and are expected to significantly improve energy efficiency and alleviate environmental pollution problems.

[0003] Due to the inability to effectively reduce the thermal conductivity of bulk thermoelectric materials, progress in their performance research has been slow. Since the early 1990s, when Hicks et al. proposed a theory that the dimensionality of materials could significantly improve the performance of thermoelectric materials, thin-film thermoelectric materials have begun to receive widespread attention. Magnetron sputtering utilizes accelerated ions to bombard target atoms and deposit a film. Compared with other preparation methods, bismuth telluride-based thin films prepared by magnetron sputtering have advantages such as low deposition temperature, fast deposition rate, good compositional consistency between the film and the target, and accurate thickness control. It is suitable for preparing multilayer thin films of various materials and is easy to industrialize, making it a commonly used thin film preparation method. Since the performance of the thin film material is closely related to the performance of the sputtering target, the preparation of the target is crucial.

[0004] Sputtering targets are generally polycrystalline, and the finer the grains, the larger the grain boundary area, which has a greater impact on performance. For the same target material, the sputtering rate of a target with fine grains is faster than that of a target with coarse grains; and the thickness distribution of the film deposited by sputtering using a target material with small differences in grain size (uniform grain size) is more uniform. Currently, common target material preparation methods include melting and casting and powder metallurgy. Target materials prepared by melting and casting have coarse grains, and their microstructure, properties, and defects are difficult to control. For example, patent document CN112457013A describes a method for preparing a tellurium-bismuth-based target material, which involves melting an alloy crystal rod in a vacuum melting crucible, casting the tellurium-bismuth-based melt to obtain a tellurium-bismuth-based target blank, and then machining it to obtain the tellurium-bismuth-based target material. Powder metallurgy generally involves first alloying the raw materials to form an ingot, then mechanically crushing it to obtain powder, and finally sintering the powder into a shape. However, impurities and oxygen content are easily introduced during the crushing process, and the resulting powder is usually irregular in shape, which is not conducive to obtaining good microstructure and properties.

[0005] Therefore, in order to further advance the research on improving the performance of thermoelectric materials, there is an urgent need for a fine-grained and uniform bismuth telluride-based alloy target and its preparation method. Summary of the Invention

[0006] In view of the problems of coarse grains, uneven grain size, poor microstructure and performance in the existing technology, the present invention will provide a bismuth-antimony-tellurium alloy target and its preparation method.

[0007] To achieve the above objectives, the following technical solutions are specifically included:

[0008] A method for preparing a bismuth-antimony-tellurium alloy target includes the following steps:

[0009] (1) The tellurium, bismuth, and antimony raw materials are mixed according to Bi x Sb 2-x Te3, x = 0.4 to 0.7 is used as raw material, then smelted, and after cooling, alloyed crystal rods are obtained;

[0010] (2) The alloyed crystal rod is successively melted and atomized to obtain alloy powder; the particle size D50 of the alloy powder is less than 45μm;

[0011] (3) The alloy powder is subjected to a first hot pressing sintering to form a bulk alloy; the temperature of the first hot pressing sintering is 180-360℃, the pressure of the first hot pressing sintering is 15-20MPa, and the time of the first hot pressing sintering is 40-100min.

[0012] (4) The bulk alloy is subjected to a second hot-press sintering to obtain a bismuth-antimony-tellurium alloy target; the temperature of the second hot-press sintering is 320-360℃, the pressure of the second hot-press sintering is 12-15MPa, and the time of the second hot-press sintering is 60-80min.

[0013] This invention first prepares a type of spherical alloy powder through gas atomization. This powder has a uniform composition, small particle size, and a particle size distribution (D50) of less than 45 μm. When this alloy powder is hot-pressed and sintered, the fine particle size leads to problems such as severe powder loss, low density, high brittleness, and susceptibility to cracking during conventional single-stage hot pressing. This invention utilizes a two-stage hot-pressing and sintering technique to prepare bismuth-antimony-tellurium alloy targets with high density and fine, uniform grains. Specifically, the bismuth-antimony-tellurium alloy target of this invention has a density >99.3% and an average grain size <10 μm.

[0014] In a preferred embodiment of the present invention, in step (1), the melting temperature is 680-720℃ and the melting time is 2-30min.

[0015] In a preferred embodiment of the present invention, in step (2), the melting temperature is 680-720℃ and the melting time is 2-30min.

[0016] In a preferred embodiment of the present invention, in step (2), the temperature of the gas atomization is 680-700℃; the heating temperature of the gas atomization nozzle is 400-450℃; the gas atomization pressure is 1.8-2.0MPa; and the diameter of the gas atomization nozzle is 1.0-1.4mm.

[0017] In a preferred embodiment of the present invention, in step (2), the alloy powder is spherical alloy powder.

[0018] In a preferred embodiment of the present invention, in step (3), the time for the first hot pressing sintering is 60 to 80 minutes.

[0019] In a preferred embodiment of the present invention, in step (3), the heating rate from room temperature to the temperature of the first sintering is 5-30℃ / min.

[0020] In a preferred embodiment of the present invention, in step (4), the heating rate from room temperature to the temperature of the second sintering is 5-30℃ / min.

[0021] In a preferred embodiment of the present invention, in step (1), the purity of the tellurium, bismuth and antimony raw materials is ≥4N.

[0022] In a preferred embodiment of the present invention, the melting temperature in step (1) is 500-800°C.

[0023] As a further preferred embodiment of the present invention, in step (1), the melting temperature is 500-700℃.

[0024] This invention also provides a bismuth-antimony-tellurium alloy target prepared by the method described above, wherein the chemical formula is Bi. x Sb 2-x Te3, x = 0.4 to 0.7.

[0025] In a preferred embodiment of the present invention, the chemical formula of the bismuth-antimony-tellurium alloy target is Bi. 0.5 Sb 1.5 Te3.

[0026] Compared with existing technologies, the present invention has the following advantages: The present invention first prepares a type of spherical alloy powder through gas atomization, and then uses a secondary hot-pressing sintering technique to ultimately prepare a bismuth-antimony-tellurium alloy target material with high density and fine, uniform grains. Specifically, the bismuth-antimony-tellurium alloy target material of the present invention has a density >99.3% and an average grain size <10μm. Attached Figure Description

[0027] Figure 1 This is a flowchart of the preparation of bismuth-antimony-tellurium alloy target material in Example 1.

[0028] Figure 2 The image shows the particle size distribution of the alloy powder in Example 1. It can be seen that the particle size distribution of the alloy powder has only one obvious peak, indicating that the particle size distribution of the alloy powder is good and the size is uniform. The particle size D50 of the alloy powder is 3.210 μm.

[0029] Figure 3 The image shown is a microscopic morphology diagram of Example 1. It can be seen that the alloy powder has high sphericity, small particle size, and relatively uniform particle size distribution.

[0030] Figure 4 The images show the partial fracture microstructures of the bismuth-antimony-tellurium alloy target material prepared in Example 1 at 100X (top) and 1000X (bottom).

[0031] Figure 5 This is a partial fracture microstructure of the bismuth-antimony-tellurium alloy target material prepared in Example 2.

[0032] Figure 6 This is a partial fracture microstructure of the bismuth-antimony-tellurium alloy target material prepared in Example 3.

[0033] Figure 7 This is a microscopic image of the local fracture surface of the bismuth-antimony-tellurium alloy target material prepared in Comparative Example 1.

[0034] Figure 8 This is a microscopic image of the local fracture surface of the bismuth-antimony-tellurium alloy target material prepared in Comparative Example 2.

[0035] Figure 9 This is a microscopic image of the local fracture surface of the bismuth-antimony-tellurium alloy target material prepared in Comparative Example 12. Detailed Implementation

[0036] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below through specific embodiments.

[0037] The following are the test methods for the target samples in the examples and comparative examples:

[0038] (1) Target relative density: Specifically, Archimedes' principle is used for detection;

[0039] (2) Powder particle size: tested using a Malvern Mastersizer 2000 laser particle size analyzer;

[0040] (3) Microstructure of the target material: The microstructure was tested using a scanning electron microscope (KYKY-EM3200);

[0041] (4) Component content: The content was tested using an ICP-OES instrument (inductively coupled plasma optical emission spectrometer).

[0042] (5) Impurity content test: The test was conducted using an ICP-OES instrument (inductively coupled plasma optical emission spectrometer).

[0043] Example 1

[0044] (1) Raw materials of tellurium, bismuth, and antimony with a purity ≥4N were prepared according to the stoichiometric ratio Bi 0.5 Sb 1.5 Te3 is used for batching. A total of 1 kg of elemental raw materials is weighed out and placed in a high borosilicate glass tube. The tube is then sealed under vacuum and smelted at 700°C. Specifically, the tube is preheated for 5 minutes, then smelted for 6 minutes and then removed and shaken evenly. It is then placed back into the smelting furnace for 2 minutes of refining. The tube is then removed, placed vertically against an iron frame, and the glass tube wall is gently tapped to remove air bubbles from the melt. After naturally cooling to room temperature, a bismuth-antimony-tellurium alloyed crystal rod is obtained.

[0045] (2) Add 5 kg of alloyed bismuth-antimony-tellurium crystal rods to the melting crucible of the gas atomization equipment, and then evacuate the atomization chamber to 10°C. -3 After Pa, argon gas is introduced and run for 10 minutes to clean the furnace; the temperature is increased to 650℃ at a rate of 12℃ / min for melting. After the alloy is completely melted into a molten body, it is held at the temperature for 6 minutes for refining. When the molten body temperature reaches the atomization temperature of 700℃, the nozzle is heated to 420℃. The nozzle diameter is 1.2mm. The stopper rod is pressed and the argon gas is started. When the gas atomization pressure reaches 2MPa, the stopper rod is pulled up to start atomization. After atomization is completed, the argon gas is turned off and the nozzle heating power is turned off. The argon gas pressure is maintained at 0.02MPa. After cooling to room temperature, the powder in the collection chamber and cyclone separator is cleaned to obtain spherical alloy powder for hot pressing sintering.

[0046] (3) Weigh 500g of spherical alloy powder, place it in a mold, pressurize and heat it under vacuum, and raise it to the temperature of the first hot pressing sintering of 180℃ and pressure of 18MPa in 10min. Then keep it warm and pressurized for 80min to form. When demolding, the block cracks in half along the radial direction (due to its own properties). If there is only one hot pressing sintering in step (3), the sintered product has high target brittleness, is easy to crack, and the powder loss during the sintering process is serious, resulting in low density, which cannot meet the requirements of the target material.

[0047] (4) Crush 490g of the broken piece and place it in the mold. Under vacuum conditions, pressurize and heat it up to the temperature of the second hot pressing sintering of 360℃ and pressure of 15MPa in 20min. Then keep it warm and pressurized for 70min, demold it, and obtain the bismuth antimony tellurium alloy target material.

[0048] The prepared bismuth-antimony-tellurium alloy target was sampled and analyzed. Its relative density was measured to be 99.3%. The composition test results are shown in Table 2, the impurity content in Table 3, and the microstructure of the local fracture surface of the target is shown in Table 4. Figure 4 .from Figure 4 As can be seen, the internal microstructure of the target material is very uniform, with an average grain size of less than 10 μm. The above analytical results indicate that the prepared bismuth-antimony-tellurium alloy target material has high density and very fine and uniform grains.

[0049] Example 2

[0050] Compared with Example 1, the difference in this example is that the temperature of the first hot pressing sintering is 360°C and the time is 60 minutes, and the time to rise from room temperature and atmospheric pressure to the temperature and pressure of the first hot pressing sintering is 30 minutes.

[0051] The prepared target material was sampled and analyzed. Its relative density was 99.6%. The component test results are shown in Table 2, the impurity content is shown in Table 3, and the microstructure of the local fracture surface of the target material is shown in Table 4. Figure 5 ,from Figure 5 As can be seen, the internal microstructure of the target material is very uniform, with an average grain size of less than 10 μm. The above analytical results indicate that the prepared bismuth-antimony-tellurium alloy target material has high density and very fine and uniform grains.

[0052] Example 3

[0053] Compared with Example 1, the difference in this example is that the temperature of the first hot pressing sintering is 360°C, the pressure is 15MPa and the time is 60min, and the time to rise from room temperature and atmospheric pressure to the temperature and pressure of the first hot pressing sintering is 30min; the pressure of the second hot pressing sintering is 12MPa and the time is 60min, and the time to rise from room temperature and atmospheric pressure to the temperature and pressure of the second hot pressing sintering is 30min.

[0054] The prepared target material was sampled and analyzed. Its relative density was 100%. The composition test results are shown in Table 2, the impurity content is shown in Table 3, and the microstructure of the local fracture surface of the target material is shown in Table 4. Figure 6 .from Figure 6 As can be seen, the internal microstructure of the target material is very uniform, with an average grain size of less than 10 μm. The above analytical results indicate that the prepared bismuth-antimony-tellurium alloy target material has high density and very fine and uniform grains.

[0055] Example 4

[0056] Compared with Example 1, the only difference is that the temperature of the first hot pressing sintering is 300°C, and the rest remains the same.

[0057] Example 5

[0058] Compared with Example 1, the only difference is that the temperature of the second hot pressing sintering is 320°C, and the rest remains the same.

[0059] Comparative Example 1

[0060] Compared with Example 1, the difference is that only the first hot pressing sintering is performed, and the hot pressing sintering temperature is 380°C, the pressure is 18MPa, and the time is 90min. After demolding, the shaped target material is obtained.

[0061] The prepared target material was sampled and analyzed. Its relative density was 100%. The microstructure of the local fracture surface of the target material is shown in [the figure]. Figure 7 ,from Figure 7 As can be seen, there are large grains of 40 μm. Compared with Example 1, which was sintered by two hot pressings, the grains of the target material formed by only one hot pressing in this comparative example are larger.

[0062] Comparative Example 2

[0063] Compared with Comparative Example 1, both involve a single hot pressing sintering process, but the difference lies in the hot pressing sintering temperature being 100℃, after which a molded target material is obtained after demolding.

[0064] The prepared target material was sampled and analyzed, and its relative density was 90.5%. The microstructure of the local fracture surface of the target material is shown below. Figure 8 ,from Figure 8 As can be seen, the grains inside the target material have a microstructure of elliptical stacked grains, which is relatively loose and has not fully grown into the grain morphology of bismuth-antimony-tellurium alloy.

[0065] Comparative Example 3

[0066] Compared with Comparative Example 1, both involved a single hot pressing sintering process, but the difference was that the hot pressing sintering temperature was 360℃ and the time was 70 minutes. Upon demolding, the block target material cracked.

[0067] Comparative Example 4

[0068] Compared with Comparative Example 1, both involved a single hot-press sintering process, but the difference was that the hot-press sintering temperature was 360℃, the pressure was 15 MPa, and the time was 70 min. After demolding, a shaped target material was obtained, but it could be easily broken by hand.

[0069] Comparative Example 5

[0070] Compared with Example 1, the difference is that the first hot pressing sintering time in this comparative example is 60 min; the pressure of the second hot pressing sintering is 18 MPa and the time is 50 min, and the time to rise from room temperature and atmospheric pressure to the temperature and pressure of the second hot pressing sintering is 10 min. When demolding, the block target material cracks.

[0071] Comparative Example 6

[0072] Compared with Example 1, the only difference is that the temperature of the first hot pressing sintering is 150°C, and the rest remains the same.

[0073] Comparative Example 7

[0074] Compared with Example 1, the only difference is that the temperature of the first hot pressing sintering is 380°C, and the rest remains the same.

[0075] Comparative Example 8

[0076] Compared with Example 1, the only difference is that the temperature of the second hot pressing sintering is 300°C, and the rest remains the same.

[0077] Comparative Example 9

[0078] Compared with Example 1, the only difference is that the temperature of the second hot pressing sintering is 380°C, and everything else remains the same.

[0079] Comparative Example 10

[0080] Compared with Example 1, the only difference is that the pressure of the second hot pressing sintering is 10 MPa, and the rest remains the same.

[0081] Comparative Example 11

[0082] Compared with Example 1, the only difference is that the pressure of the second hot pressing sintering is 33 MPa, and the rest remains the same.

[0083] Comparative Example 12

[0084] The difference in this comparative example is that: this comparative example is prepared by conventional crushing method (not the gas atomization method of step (2) of this invention) to obtain a non-spherical powder with a particle size D50 of 18 μm; and at the same time, it is prepared by the same method as step (3)-(4) of Example 1.

[0085] The target material in this comparative example has a relative density of 98.3% and relatively large grains.

[0086] Table 1. Sintering process parameters and target material properties of the examples and comparative examples.

[0087]

[0088]

[0089] Table 2. Component content test results of bismuth-antimony-tellurium alloy sputtering targets

[0090]

[0091] Table 3. Test results of impurity content in bismuth-antimony-tellurium alloy sputtering targets.

[0092]

[0093] As can be seen from Examples 1 and Comparative Examples 1-4, even with adjustments to the sintering temperature, pressure, and time, fine alloy powder cannot simultaneously produce a target material with high relative density, fine and uniform grains (average grain size less than 10 μm), and good forming effect. However, the secondary hot-pressing sintering method of the present invention can produce a bismuth-antimony-tellurium alloy target material with high density, very fine and uniform grains, and good forming effect. (See Appendix 1 for details.) Figure 3 It can be seen that the average grain size of the alloy powder is less than 10 μm, but in Comparative Example 1... Figure 7 It can be observed that the grains in the samples are lamellar, and the grain size is generally large, such as the presence of lamellar structures with a size greater than 40 μm.

[0094] Based on the combined results of Example 1 and Comparative Example 5, it can be seen that the first sintering time is short, and after demolding, the block material is relatively loose and porous, with low density and easy to break.

[0095] As can be seen from Example 1 and Comparative Examples 6-11, if the temperature, pressure and other parameters of the first and second hot pressing sintering are not within the range required by the method of the present invention, it is impossible to obtain a bismuth-antimony-tellurium alloy target material with high density, very fine and uniform grains and good forming effect.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing a bismuth antimony tellurium alloy target material, characterized by, Includes the following steps: (1) Te, Bi, Sb raw materials are proportioned according to Bi x Sb 2-x Te3, x=0.4~0.7, then smelting, and after cooling, the alloyed crystal bar is obtained; (2) The alloyed crystal rod is melted and atomized in sequence to obtain alloy powder; the average grain size of the alloy powder is less than 10 μm; (3) The alloy powder is subjected to a first hot pressing sintering to form a bulk alloy; the temperature of the first hot pressing sintering is 180~360℃, the pressure of the first hot pressing sintering is 15~20MPa, and the time of the first hot pressing sintering is 40~100min. (4) The bulk alloy is subjected to a second hot pressing sintering to obtain a bismuth-antimony-tellurium alloy target; the temperature of the second hot pressing sintering is 320~360℃, the pressure of the second hot pressing sintering is 12~15MPa, and the time of the second hot pressing sintering is 60~80min.

2. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (3), the first hot pressing sintering time is 60~80min.

3. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (2), the temperature of the gas atomization is 680-700℃; the heating temperature of the gas atomization nozzle is 400-450℃; the gas atomization pressure is 1.8-2.0MPa; and the diameter of the gas atomization nozzle is 1.0-1.4mm.

4. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (1), the melting temperature is 680-720℃ and the melting time is 2-30min; in step (2), the melting temperature is 680-720℃ and the melting time is 2-30min.

5. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (3), the heating rate from room temperature to the temperature of the first sintering is 5-30℃ / min.

6. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (4), the heating rate from room temperature to the temperature of the second sintering is 5-30℃ / min.

7. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (2), the alloy powder is spherical alloy powder.

8. The method for preparing the bismuth-antimony-tellurium alloy target as described in claim 1, characterized in that, In step (1), the purity of tellurium, bismuth and antimony raw materials is ≥4N.

9. The bismuth-antimony-tellurium alloy target prepared by the method of any one of claims 1-8.

10. The bismuth-antimony-tellurium alloy target as described in claim 9, characterized in that, Bi x Sb 2-x Te3, x = 0.4~0.7.

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