A single-crystal zrcosb semi-hassler alloy and a preparation method and application thereof
Large-size single-crystal ZrCoSb semi-Hassler alloys were prepared by controlling the pulling rate using the Bridgman method, solving the preparation difficulties in existing technologies and achieving optimized thermoelectric properties of single-crystal alloys.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2023-03-22
- Publication Date
- 2026-07-07
AI Technical Summary
Existing technologies make it difficult to prepare large-size single-crystal ZrCoSb semi-Hasler alloys, and polycrystalline samples present challenges in device fabrication and applications.
Large-size single-crystal ZrCoSb semi-Hassler alloys were prepared by using the Bridgman process for crystal growth, controlling the pulling rate to 0.5–2 mm/h, combined with high-purity argon protection and multiple melting processes.
Large-size single-crystal ZrCoSb semi-Hassler alloys with a length exceeding 40 mm were successfully prepared, eliminating the influence of grain boundaries on carrier scattering and optimizing thermoelectric properties.
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Figure CN116356415B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of alloy materials technology, and in particular to a single-crystal ZrCoSb semi-Hassler alloy, its preparation method, and its application. Background Technology
[0002] Currently, approximately two-thirds of energy is wasted as waste heat, making the improvement of energy utilization an urgent problem to be solved. Thermoelectric materials offer a reliable solution, primarily because they can effectively convert waste heat into electrical energy through the energy difference carried by internal charge carriers. Semi-Hassler alloys, with their excellent thermoelectric properties, are among the most promising medium- and high-temperature materials.
[0003] ZrCoSb alloy, as an excellent p-type semi-Hassler alloy, has seen significant development and optimization of its thermoelectric properties. These properties primarily depend on the thermoelectric figure of merit ZT, where ZT = S. 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. According to the definition of ZT, low κ and high S and σ are beneficial to improving thermoelectric performance. Since these three thermoelectric parameters are coupled, achieving independent control of these parameters is key to improving thermoelectric performance. Analysis shows that the coupling between thermoelectric parameters is based on carrier concentration, and all three vary with the carrier concentration. For electrical conductivity, it is mainly determined by carrier concentration and carrier mobility. Therefore, unilaterally optimizing carrier mobility is one effective direction for decoupling thermoelectric parameters. It is well known that in ZrCoSb semi-Hassler alloys, grain boundaries are the main medium for carrier scattering, thus hindering the optimization of electrical conductivity. Although researchers have used a series of strategies to increase carrier mobility, most of these studies are based on polycrystalline samples. Therefore, it is necessary to prepare single-crystal ZrCoSb semi-Hassler alloys to eliminate the influence of grain boundaries on carrier scattering in order to further optimize the thermoelectric performance of semi-Hassler alloys. Due to the high melting point of semi-Hasler alloys, domestic and foreign scholars mainly use the Sn flux method to grow single-crystal ZrNiSn semi-Hasler alloys. However, the product is an irregular plate-like crystal, which is difficult to process and apply in devices.
[0004] Therefore, how to prepare large-size single-crystal ZrCoSb semi-Hasler alloys has become an urgent problem to be solved. Summary of the Invention
[0005] The purpose of this invention is to provide a single-crystal ZrCoSb semi-Hassler alloy, its preparation method, and its applications. The preparation method provided by this invention can produce large-size single-crystal ZrCoSb semi-Hassler alloys.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] This invention provides a method for preparing single-crystal ZrCoSb semi-Hassler alloy, comprising the following steps:
[0008] (1) The alloy raw materials are smelted to obtain polycrystalline ZrCoSb ingots;
[0009] (2) The polycrystalline ZrCoSb ingot obtained in step (1) is grown by the Bridgman method to obtain a single crystal ZrCoSb semi-Hasler alloy; the pulling rate during crystal growth is 0.5 to 2 mm / h.
[0010] Preferably, the melting process in step (1) is performed ≥ 3 times.
[0011] Preferably, the time spent in the molten state during each melting process is at least 40 seconds.
[0012] Preferably, the crystal growth in step (2) includes preheating, melting, crystal growth and cooling in sequence.
[0013] Preferably, the preheating temperature is 200–400°C, and the preheating holding time is 10–30 minutes.
[0014] Preferably, the melting temperature is 1570–1600°C.
[0015] Preferably, the holding time for melting is ≥3h.
[0016] Preferably, the temperature at which the crystal growth begins is 1540–1560°C.
[0017] Preferably, the pressure during crystal growth in step (2) is 115000 to 135000 Pa.
[0018] This invention also provides the application of the single-crystal ZrCoSb semi-Hassler alloy prepared by the preparation method described above as a thermoelectric material.
[0019] This invention provides a method for preparing a single-crystal ZrCoSb semi-Hassler alloy, comprising the following steps: (1) melting alloy raw materials to obtain a polycrystalline ZrCoSb ingot; (2) growing the polycrystalline ZrCoSb ingot obtained in step (1) using the Bridgman process to obtain a single-crystal ZrCoSb semi-Hassler alloy; the pulling rate during crystal growth is 0.5–2 mm / h. This invention first obtains a polycrystalline ingot through melting, then grows it using the Bridgman process, controlling the pulling rate during growth, and slowly growing a large-size single-crystal ZrCoSb semi-Hassler alloy using a temperature gradient. The results of the embodiments show that the length of the single-crystal ZrCoSb semi-Hassler alloy prepared by the method of this invention can reach more than 40 mm. Attached Figure Description
[0020] Figure 1 A photograph of the single-crystal ZrCoSb semi-Hassler alloy prepared in Example 1 of this invention;
[0021] Figure 2 The XRD pattern of the single-crystal ZrCoSb semi-Hassler alloy prepared in Example 1 of this invention;
[0022] Figure 3 The XRD pattern of the single-crystal ZrCoSb semi-Hassler alloy prepared in Example 2 of this invention;
[0023] Figure 4 The image shows the XRD pattern of the ZrCoSb semi-Hassler alloy prepared in Comparative Example 1 of this invention. Detailed Implementation
[0024] This invention provides a method for preparing single-crystal ZrCoSb semi-Hassler alloy, comprising the following steps:
[0025] (1) The alloy raw materials are smelted to obtain polycrystalline ZrCoSb ingots;
[0026] (2) The polycrystalline ZrCoSb ingot obtained in step (1) is grown by the Bridgman method to obtain a single crystal ZrCoSb semi-Hasler alloy; the pulling rate during crystal growth is 0.5 to 2 mm / h.
[0027] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.
[0028] This invention involves melting alloy raw materials to obtain polycrystalline ZrCoSb ingots.
[0029] In this invention, the alloy raw materials preferably include pure Zr, pure Co, and pure Sb; the mass fractions of Zr in pure Zr, Co in pure Co, and Sb in pure Sb are preferably >99.99%.
[0030] This invention does not impose a specific limitation on the melting temperature, as long as it ensures that the alloy raw materials are fully melted. In this invention, the number of melting operations is preferably ≥3 times; the time spent maintaining the molten state during each melting operation is preferably at least 40 seconds. This invention preferably involves cooling to room temperature after each melting operation before proceeding to the next melting operation. In this invention, the melting is preferably performed using magnetic levitation induction melting. By limiting the melting time and number of operations within the above-mentioned ranges, this invention ensures that the raw materials are fully melted, resulting in an ingot with a uniform composition distribution.
[0031] In this invention, the smelting is preferably carried out in a high-purity argon atmosphere. This high-purity argon atmosphere prevents air residue from forming impurities in the ingot, thus improving the ingot quality.
[0032] After obtaining a polycrystalline ZrCoSb ingot, the present invention uses the Bridgman process to grow a single-crystal ZrCoSb semi-Hassler alloy from the polycrystalline ZrCoSb ingot.
[0033] In this invention, the polycrystalline ZrCoSb ingot is preferably crushed before use. The crushing operation is not particularly limited; any crushing technique well-known to those skilled in the art can be used. In this invention, the crushed ingot can be more easily added to subsequent equipment and facilitates ingot melting.
[0034] In this invention, the crystal growth preferably includes preheating, melting, crystal growth and cooling in sequence.
[0035] In this invention, the preheating temperature is preferably 200–400°C, more preferably 250–350°C; the preheating holding time is preferably 10–30 min, more preferably 15–25 min. In this invention, the preheating is used to remove moisture from the equipment and ingot, preventing the formation of impurities in the melt.
[0036] In this invention, the melting temperature is preferably 1570–1600℃, more preferably 1570–1590℃; the holding time for melting is preferably ≥3 hours. In this invention, the process of heating to the melting temperature is preferably as follows:
[0037] Heat to the first intermediate temperature at the first rate;
[0038] The temperature is increased from the first intermediate temperature to the second intermediate temperature at a second rate;
[0039] The temperature is increased from the second intermediate temperature to the melting temperature at a third rate;
[0040] The first rate is preferably 3-10℃ / min, more preferably 5-8℃ / min; the first intermediate temperature is preferably 1000-1200℃, more preferably 1050-1150℃; the second rate is preferably 2-5℃ / min, more preferably 3-4℃ / min; the second intermediate temperature is preferably 1480-1510℃, more preferably 1500℃; the third rate is preferably 1-3℃ / min, more preferably 1.5-2℃ / min; no heat preservation is performed after heating to the first and second intermediate temperatures.
[0041] The heating method described above in this invention enables better melting of the ingot. In this invention, during the melting process, the sample stage preferably rotates counterclockwise or clockwise at a rate of 1–3 mm / min. This rotation ensures uniform heating, which is more conducive to the melting of the ingot.
[0042] After melting is complete, the present invention preferably cools the melt to the temperature at which crystal growth begins at a rate of 1 to 3 °C / min.
[0043] In this invention, the initial temperature for crystal growth is preferably 1540–1560°C, more preferably 1550°C. Limiting the initial temperature for crystal growth to this range is beneficial for subsequent crystal growth, resulting in large-size single crystals.
[0044] In this invention, the crystal growing rate is 0.5–2 mm / h, preferably 1–1.5 mm / h. By limiting the growing rate to the above range, this invention enables the crystal to grow into a large-sized single crystal.
[0045] In this invention, the crystal growth is preferably performed by moving the heating furnace cavity upwards; the pulling rate is the upward movement rate of the heating furnace cavity. In this invention, the temperature change of the heating furnace cavity is preferably 18–22 °C / cm, more preferably 20 °C / cm; the endpoint of the upward movement of the heating furnace cavity is preferably beyond the crucible.
[0046] In this invention, the cooling is preferably:
[0047] Cool to a first cooling temperature at a first cooling rate;
[0048] Cooled from the first cooling temperature to room temperature at a second cooling rate.
[0049] The first cooling rate is preferably 2-5℃ / min, more preferably 3-4℃ / min; the first cooling temperature is preferably 990-1100℃, more preferably 1000℃; the second cooling rate is preferably 3-10℃, more preferably 5-8℃.
[0050] This invention employs a two-stage cooling process. The first stage of cooling acts similarly to annealing, thereby improving the overall performance of the single crystal.
[0051] In this invention, the crystal growth is preferably carried out in a Bridgman furnace. In an embodiment of this invention, the Bridgman furnace is preferably the SKJ-BG1650 from Hefei Kejing Materials Technology Co., Ltd. In this invention, the growth furnace is preferably cleaned with high-purity argon gas before preheating; the number of cleansing cycles is preferably ≥4; and after each cleansing, the vacuum level is preferably reduced to below 20 Pa.
[0052] In this invention, high-purity argon gas is preferably introduced throughout the entire Bridgman crystal growth process. The pressure during the Bridgman crystal growth process is preferably 115,000–135,000 Pa, more preferably 120,000–130,000 Pa. By limiting the pressure within the above range, this invention enables in-furnace gas circulation and maintains melt purity.
[0053] In this invention, during the Bridgman crystal growth process, the bottom of the crucible is preferably triangular pyramidal, and the cone angle of the crucible is preferably <40°. Controlling the cone angle of the crucible in this invention is more conducive to growing large-sized single crystals.
[0054] In this invention, the size of the single-crystal ZrCoSb semi-Hassler alloy is preferably >10mm.
[0055] This invention also provides the application of the single-crystal ZrCoSb semi-Hassler alloy prepared by the preparation method described above as a thermoelectric material.
[0056] The present invention does not impose any special limitations on the operation of the single-crystal ZrCoSb semi-Hassler alloy as a thermoelectric material, and any technical solution for the application of semi-Hassler alloy as a thermoelectric material that is well known to those skilled in the art can be used.
[0057] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0058] Example 1
[0059] (1) Using pure Zr, Co, and Sb particles with a mass fraction greater than 99.99% as raw materials, weigh and batch according to the nominal composition of ZrCoSb, put them into a crucible and pass high-purity argon gas through for magnetic levitation induction melting 3 times. During each melting process, the time to maintain the molten state is 40s, and finally a polycrystalline ZrCoSb semi-Hasler alloy ingot with uniform composition distribution is obtained.
[0060] (2) Using the SKJ-BG1650 Bridgman crystal growth furnace from Hefei Kejing Materials Technology Co., Ltd., the polycrystalline ZrCoSb semi-Hasler alloy ingot was crushed and placed into a graphite crucible with a bottom cone angle of 30°. The furnace was cleaned four times with high-purity argon gas, with the vacuum level reduced to below 20 Pa each time. It was then preheated at 300°C for 30 min, while the sample stage rotated clockwise at a rate of 1 mm / min. The temperature was then increased to 1000°C at a rate of 10°C / min, followed by increases to 1500°C at a rate of 5°C / min, and then further increased at a rate of 3°C / min. The temperature was increased to 1600℃ at a rate of min, and held at this temperature for 3 hours to ensure that the polycrystalline ingot was completely melted. Then, the temperature was decreased to 1550℃ at a rate of 3℃ / min, and the furnace chamber was moved upward at a rate of 0.5 mm / h. The temperature change of the furnace chamber was 20℃ / cm. After the pulling was completed, the temperature was decreased to 1000℃ at a rate of 5℃ / min, and then decreased to room temperature at a rate of 10℃ / min. Throughout the process, high-purity argon gas was introduced to maintain the furnace pressure at 115000~125000Pa, and a single-crystal ZrCoSb semi-Hasler alloy was obtained.
[0061] Example 2
[0062] Replace the upward movement rate of the heating furnace cavity in step (2) of Example 1 with 2 mm / h, and keep all other parameters the same as in Example 1.
[0063] Comparative Example 1
[0064] Replace the upward movement rate of the heating furnace cavity in step (2) of Example 1 with 3 mm / h, and keep all other parameters the same as in Example 1.
[0065] A physical image of the single-crystal ZrCoSb semi-Hassler alloy prepared in Example 1 is shown below. Figure 1 As shown. From Figure 1 As can be seen from the above, the single-crystal ZrCoSb semi-Hassler alloy prepared by this invention has a large size, with a size > 40 mm.
[0066] The XRD patterns (parallel to the lifting direction) of the products prepared in Example 1, Example 2, and Comparative Example 1 are shown below. Figures 2-4 As shown. From Figure 2 As can be seen from the XRD analysis, although weak stray peaks appear, they are negligible compared to the (111) diffraction peak. Combined with... Figure 1The physical image shown confirms that Example 1 prepared a large-size ZrCoSb single-crystal semi-Hasler alloy grown along (111).
[0067] from Figure 3 As can be seen from the XRD analysis, although weak impurity peaks appear, they are negligible compared to the (l20) diffraction peaks. The analysis confirms that Example 2 successfully prepared a ZrCoSb single-crystal semi-Hassler alloy grown along (l20).
[0068] from Figure 4 As can be seen from the XRD analysis, when the pulling rate is 3 mm / h, strong impurity peaks appear in Comparative Example 1, and the orientation of the ZrCoSb matrix exhibits multi-orientation. The analysis indicates that Comparative Example 1 does not belong to a ZrCoSb single-crystal semi-Hassler alloy.
[0069] In summary, this invention prepares large-size single-crystal ZrCoSb single-crystal semi-Hasler alloy by controlling the pulling rate during the growth process.
[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a single-crystal ZrCoSb semi-Hassler alloy, comprising the following steps: (1) The alloy raw materials are smelted to obtain polycrystalline ZrCoSb ingots; (2) The polycrystalline ZrCoSb ingot obtained in step (1) is crystal grown by the Bridgman method to obtain a single crystal ZrCoSb semi-Hassler alloy; the pulling rate during crystal growth is 0.5~2mm / h. The crystal growth in step (2) includes preheating, melting, crystal growth and cooling in sequence; the temperature at the beginning of the crystal growth is 1540~1560℃; the pressure during the crystal growth process is 115000~135000Pa.
2. The preparation method according to claim 1, characterized in that, The number of melting operations in step (1) is ≥3 times.
3. The preparation method according to claim 2, characterized in that, The time spent in the molten state during each melting process must be at least 40 seconds.
4. The preparation method according to claim 1, characterized in that, The preheating temperature is 200~400℃, and the preheating holding time is 10~30min.
5. The preparation method according to claim 1, characterized in that, The melting temperature is 1570~1600℃.
6. The preparation method according to claim 1 or 5, characterized in that, The holding time for melting is ≥3h.
7. The application of the single-crystal ZrCoSb semi-Hassler alloy prepared by the preparation method according to any one of claims 1 to 6 as a thermoelectric material.