Preparation method and application of high-performance semiconductor thermoelectric crystal bar

Abstract

The invention provides a preparation method and application of a high-performance semiconductor thermoelectric crystal bar, and relates to the field of thermoelectric materials. The high-performance semiconductor thermoelectric crystal bar is obtained by additionally adding 10-15% of Te, smelting in a mixed gas environment of Ar and H2 in a volume ratio of (3-5): 1, swinging, cooling, zone-melting and post-processing. Additionally added Te compensates for the actual component loss caused by Te element volatilization in the high-temperature smelting process, the volatilized Te is captured by H2 to generate H2Te gas, the H2Te gas is re-deposited into the melt through gas phase diffusion, dynamic circulation is formed, and the Te component deviation is reduced; te agglomeration holes are avoided, and the density of the material is improved; the composition uniformity of the material is improved, lattice scattering is further reduced, the conductivity and the Seebeck coefficient are improved, and the thermoelectric figure of merit is further improved.

Description

Technical Field

[0001] The present invention relates to the field of thermoelectric materials, and in particular to a preparation method of a high-performance semiconductor thermoelectric crystal rod and its application. Background Art

[0002] With the widespread application of thermoelectric ingot materials in cutting-edge fields such as energy recovery, semiconductor thermoelectric power generation, and refrigeration, the demand for their high performance and stability has become increasingly urgent. However, the entire preparation process currently faces numerous technical bottlenecks, which seriously restrict the performance improvement and industrial development of thermoelectric ingot materials. During material synthesis, the high-temperature volatilization of chalcogens (Te / Se) remains a persistent challenge. Traditional synthesis methods, whether melting in a pure vacuum environment or filling the material with an inert gas (such as argon), are unable to effectively suppress the volatilization of chalcogens. This leads to an imbalance in the material's stoichiometric ratio, directly affecting the core performance parameters of thermoelectric materials, such as the Seebeck coefficient, electrical conductivity, and thermal conductivity, thereby reducing thermoelectric conversion efficiency. Even with the traditional compensation method of excessive Te addition (5-8%), problems such as excessive Te agglomeration and low compensation efficiency can still occur, resulting in poor material composition uniformity and insufficient crystal density, which in turn reduces the material's thermoelectric figure of merit. As the application scenarios of thermoelectric materials continue to expand, such as in fields such as aerospace and high-end electronic equipment, which require extremely high performance stability, traditional preparation processes for thermoelectric crystal rods have become difficult to meet actual needs due to problems such as large performance fluctuations and poor quality consistency. Therefore, it is urgent to develop new preparation processes and parameter control methods to effectively solve problems such as chalcogen volatilization, poor material composition uniformity, and low crystal rod density, achieve breakthroughs in the high performance and high stability of thermoelectric crystal rod materials, and promote the high-quality development of the thermoelectric materials industry. Summary of the Invention

[0003] In view of the technical problems existing in the prior art, the present invention aims to provide a method for preparing a high-performance semiconductor thermoelectric crystal rod and its application.

[0004] One of the purposes of the present invention is to provide a method for preparing a high-performance semiconductor thermoelectric crystal rod, comprising the following steps: First, Bi raw material, Sb raw material, Te raw material and Se raw material are mixed according to a set ratio, and then Te is additionally added in an amount of 10-15% of the total mass of Te in the set ratio to obtain a reaction material; The reaction material is placed in an Ar and H2 mixed gas environment and smelted to obtain a molten material body; wherein the volume ratio of Ar to H2 is 3~5:1; The molten material is swung, cooled, zone-melted and post-processed to obtain a high-performance semiconductor thermoelectric crystal rod.

[0005] Preferably, the pressure of the Ar and H2 mixed gas is 0.05-0.15 MPa.

[0006] Preferably, the setting ratio includes: the molar ratio of the Bi raw material, the Sb raw material, the Te raw material and the Se raw material is 2-y:y:3-x:x, 0≤x≤1, 0≤y≤2.

[0007] Preferably, the reaction material is placed in an Ar and H2 mixed gas environment for smelting, and a molten material body is obtained, which includes: First smelting: the reaction material is kept at 550-650℃ for 25-35 min to obtain a first molten material body; Second smelting: the first molten material body is kept at 750-850℃ for 0.8-1.2 h to obtain a second molten material body; Third smelting: the molten material body is kept at 700-800℃ for 1.5-2.5 h.

[0008] Preferably, the heating rate of the first smelting is 8-12℃ / min, the heating rate of the second smelting is 3-6℃ / min, and the cooling rate of the third smelting is 1-3℃ / min.

[0009] Preferably, the swinging rate is 12-18 rpm.

[0010] Preferably, the cooling includes first cooling at 3-6℃ / min to 450-550℃ and keeping for 1-2 h, and then naturally cooling the molten material body to 20-30℃.

[0011] Preferably, the temperature gradient of the melting zone of the zone melting is 55-65℃ / cm, the moving speed of the melting zone is 2.5-3.5 cm / h, and the rotating speed of the crystal is 4-6 rpm.

[0012] The second object of the present application is to provide a high-performance semiconductor thermoelectric crystal rod prepared by the preparation method.

[0013] The third object of the present application is to provide an application of the thermoelectric crystal rod in a thermoelectric device, a micro refrigeration device or a temperature sensing device.

[0014] The present application has the following advantages: The application provides a preparation method of a high-performance semiconductor thermoelectric crystal rod. Bi raw materials, Sb raw materials, Te raw materials and Se raw materials are proportioned according to a set proportion, and 10-15% of Te in the total mass of Te in the set proportion is additionally added to obtain a reaction material; the reaction material is placed in an Ar and H2 mixed gas environment for smelting to obtain a molten material body; the volume ratio of Ar to H2 is 3-5:1; the molten material body is subjected to swinging, cooling, zone melting and post-processing to obtain the high-performance semiconductor thermoelectric crystal rod. The additional addition of 10-15% of Te in the total mass of Te in the set proportion in combination with the smelting in the Ar and H2 mixed gas environment can compensate for the actual composition loss caused by the volatilization of Te elements in the high-temperature smelting process, and ensure that the chemical composition of the final crystal rod is consistent with the target formula. The vapor pressure of Te is significantly increased, which causes continuous volatilization of Te from the melt. The volatilized Te is captured by H2 to generate H2Te gas, which is redeposited into the melt through gas phase diffusion, forming a dynamic cycle rather than a static accumulation, improving the element compensation efficiency, reducing the Te composition deviation, and realizing precise composition control. The eddy current generated by swinging accelerates the penetration of H2Te gas into the melt. At the same time, Ar as a carrier gas further promotes the uniform diffusion of H2Te gas in the melt, avoids Te agglomeration holes, and improves the density of the material; the excess Te uniformly compensates for each region of the melt through gas phase circulation, avoids the local enrichment and agglomeration caused by the direct mixing of excess Te powder in the traditional process, improves the composition uniformity of the material, and further reduces the lattice scattering, improves the electrical conductivity and Seebeck coefficient, and further improves the thermoelectric figure of merit (ZT value). DETAILED DESCRIPTION

[0015] According to a first aspect of the application, a preparation method of a high-performance semiconductor thermoelectric crystal rod is provided, comprising the following steps: First, Bi raw materials, Sb raw materials, Te raw materials and Se raw materials are proportioned according to a set proportion, and 10-15% of Te in the total mass of Te in the set proportion is additionally added to obtain a reaction material; The reaction material is placed in an Ar and H2 mixed gas environment for smelting to obtain a molten material body; wherein the volume ratio of Ar to H2 is 3-5:1; The molten material body is subjected to swinging, cooling, zone melting and post-processing to obtain the high-performance semiconductor thermoelectric crystal rod.

[0016] In the present invention, an additional amount of Te accounting for 10-15% of the total mass of Te in the set ratio is added and smelted in a mixed gas environment of Ar and H2. During the smelting process, 10-15% of Te can compensate for the actual component loss caused by the volatilization of Te elements during the high-temperature smelting process, ensuring that the chemical composition of the final crystal rod is consistent with the target formula. The vapor pressure of Te increases significantly, causing it to continue to volatilize from the melt. The volatilized Te is captured by H2 to generate H2Te gas, which is redeposited into the melt through gas phase diffusion, forming a dynamic cycle rather than static accumulation, thereby improving the element compensation efficiency and achieving precise composition control. Excess Te is evenly compensated for various regions of the melt through gas phase circulation, avoiding local enrichment and agglomeration caused by direct mixing of excess Te powder in traditional processes, improving the composition uniformity of the material, and thus reducing lattice scattering and improving electrical conductivity. The eddy currents generated by the swing accelerate the penetration of H2Te gas into the melt. At the same time, Ar acts as a carrier gas to further promote the uniform diffusion of H2Te gas in the melt, avoiding Te agglomeration holes and improving the density of the material.

[0017] In the present invention, to ensure process safety, the H2 concentration needs to be controlled at ≤25%. However, if the H2 ratio is lower than 17%, the reaction rate drops to 70%, and volatilization cannot be effectively compensated.

[0018] In the present invention, the additionally added Te accounts for 10%, 11%, 12%, 13%, 14% or 15% of the total mass of Te in the set formula, for example.

[0019] In the present invention, the volume ratio of Ar to H 2 is, for example, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0020] In a preferred embodiment of the present invention, the pressure of the Ar and H2 mixed gas is 0.05~0.15MPa.

[0021] In the present invention, a suitable mixed gas pressure can provide a suitable environment for the volatilization of Te. When the pressure is between 0.05 and 0.15 MPa, the volatilization of Te will not be suppressed due to the high pressure, nor will it be too violent and difficult to control due to the low pressure. Within this pressure range, the volatilized Te can be captured by H2 in time to generate H2Te gas, providing a basis for subsequent gas phase circulation. If the pressure is greater than 0.15 MPa, the rate of Te volatilization will decrease, resulting in a reduction in the amount of H2Te gas generated, which is not conducive to component compensation; if the pressure is less than 0.05 MPa, Te will volatilize rapidly in large quantities, exceeding the capture capacity of H2, resulting in waste of Te and instability of the composition.

[0022] Ar as a carrier gas can effectively promote the uniform diffusion of H2Te gas in the melt when the mixed gas pressure is 0.05-0.15 MPa. This pressure range allows Ar and H2Te gas to form a stable mixed gas phase environment, and Ar can drive H2Te gas to be uniformly distributed in the melt, avoiding Te aggregation to form holes. If the pressure exceeds this range, the carrying and diffusion of Ar to H2Te gas will be affected, causing Te to aggregate in local areas, reducing the density of the material. Within this pressure range, the compensation efficiency of Te is the highest, and the composition uniformity and thermoelectric performance of the crystal bar are optimal. When the pressure exceeds this range, the material performance decreases due to composition deviation or structural defects.

[0023] In addition, excessively high pressure will increase the pressure load of the smelting equipment, posing a safety hazard, leading to equipment seal failure, explosion and other dangerous situations. Controlling the pressure in the relatively low range of 0.05-0.15 MPa can reduce these safety risks and ensure the safety of operators and equipment.

[0024] In the present application, the pressure of the Ar and H2 mixed gas is, for example, 0.05 MPa, 0.06 MPa, 0.07 MPa, 0.08 MPa, 0.09 MPa, 0.10 MPa, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.14 MPa or 0.15 MPa.

[0025] In the present application, the set ratio includes: the molar ratio of Bi raw material, Sb raw material, Te raw material and Se raw material is 2-y:y:3-x:x, 0≤x≤1, 0≤y≤2.

[0026] In a preferred embodiment of the present application, the reaction material is placed in an Ar and H2 mixed gas environment for smelting to obtain a molten material body, which includes: First stage smelting: the reaction material is kept at 550-650℃ for 25-35 min to obtain a first stage molten material body; Second stage smelting: the first stage molten material body is kept at 750-850℃ for 0.8-1.2 h to obtain a second stage molten material body; Third stage smelting: keeping at 700-800℃ for 1.5-2.5 h to obtain a molten material body.

[0027] In the present invention, the first melting stage is a low-temperature pre-melting phase. Te has a melting point of 450°C, while the Bi, Sb, and Se components of the semiconductor thermoelectric material have higher melting points. The temperature of 550-650°C, between the melting point of Te and the main phase, preferentially melts Te and low-melting-point additives, forming a liquid "solvent" that encapsulates unmelted solid particles and accelerates mass transfer. Low temperatures result in a low Te vapor pressure, which suppresses unnecessary losses of excess Te in the initial phase and reduces early Te volatilization, ensuring that it is primarily available for the subsequent dynamic compensation cycle. The Ar-H2 gas mixture is stable at low temperatures, and H2 begins to form H2Te gas with trace amounts of volatilized Te, pre-starting the second, higher-temperature gas-phase cycle. This low-temperature pre-melting avoids "crusting" or localized agglomeration associated with direct high-temperature melting, improves initial melt uniformity, and provides a good mass transfer foundation for subsequent stages.

[0028] In this invention, the second melting stage is a high-temperature homogenization phase, enabling full component melting, sufficient reaction, and efficient operation of the gas-phase compensation mechanism. At temperatures above 750-850°C, which is above the melting point of the main phase, all solid components are completely melted, forming a homogeneous liquid melt, which provides conditions for element diffusion. At high temperatures, the Te vapor pressure increases significantly, causing excess Te to continuously volatilize and react with H2 to form H2Te gas. Under the influence of Ar carrier gas, H2Te diffuses to the melt surface, decomposes, and redeposits Te, compensating for Te losses in the main melt. Holding time is controlled between 0.8 and 1.2 hours, balancing "sufficient reaction" with "avoiding excessive volatilization"—excessive holding times increase net Te losses, while shorter holding times result in inadequate mixing. The second melting stage achieves dynamic Te equilibrium through gas-phase circulation, ensuring a stable melt composition. High-temperature homogenization reduces macrosegregation and provides a uniform initial feedstock for subsequent zone melting.

[0029] In the present invention, the third stage of smelting is a low-temperature, steady-state stage. The third stage of smelting has a lower temperature than the second stage, which reduces the intensity of melt convection and switches to microscopic homogenization dominated by molecular diffusion. The 1.5-2.5h heat preservation allows solute atoms to fully diffuse in the liquid, reducing dendritic segregation or composition gradients. At lower temperatures, the melt viscosity increases, the bubble rise rate slows down, and the vortex generated by the swinging process promotes bubble rupture and discharge, while dissolving unmelted particles and improving melt density. The temperature is between the Te melting point and the melting point of the main phase, the Te volatilization rate is moderate, and the H2Te gas phase circulation continues but with reduced intensity, ensuring that the Te content in the final melt is close to the target formula, resulting in significantly improved microscopic composition uniformity and a melt density of >99.5%. This reduces composition mutations or pore defects during crystallization and lays the foundation for subsequent zone melting growth of high-quality single crystals.

[0030] In the present invention, a segmented design of low-temperature pre-melting, high-temperature reaction, and finally low-temperature stabilization is adopted to avoid the vicious cycle of "volatilization-loss-segregation" caused by traditional single high-temperature melting, thereby achieving precise control of composition. The holding time of each segment is coupled with the temperature. The high-temperature segment improves mass transfer efficiency, while the low-temperature and long holding segment improves diffusion sufficiency, achieving a balance between mass transfer efficiency and diffusion sufficiency, ensuring macroscopic uniformity and microscopic crystal structure optimization. At the same time, the low-temperature segment establishes a stable gas phase environment, the high-temperature segment strengthens H2Te circulation compensation, and the low-temperature segment stabilizes the final composition. The combination of the three melting stages maximizes the "dynamic compensation" efficiency of excess Te, while suppressing Te agglomeration or pore formation.

[0031] In a preferred embodiment of the present invention, the heating rate of the first melting stage is 8-12°C / min, the heating rate of the second melting stage is 3-6°C / min, and the cooling rate of the third melting stage is 1-3°C / min.

[0032] In the present invention, different heating or cooling rates are set for each melting stage in order to balance multiple factors such as reaction rate, element volatilization, crystal structure formation and defect elimination at different stages, thereby preparing high-performance semiconductor thermoelectric crystal rods.

[0033] In the present invention, in the first stage of smelting, the reaction materials need to be rapidly heated from room temperature to a pre-melting temperature range of 550-650°C. A relatively high heating rate of 8-12°C / min enables the reaction materials to quickly reach the target temperature and reduce the residence time in the low-temperature stage. Because the chemical reaction rate of the reaction materials is slow at low temperatures, too long a period of time at low temperatures may cause some unnecessary side reactions to occur or cause certain components in the reaction materials to undergo adverse changes such as oxidation. Te begins to melt at a relatively low temperature, and rapid heating can melt Te as quickly as possible, forming a liquid "solvent" that encapsulates the unmelted solid particles, accelerating the mass transfer process and laying a good foundation for subsequent reactions and mixing. At the same time, this heating rate will not be too fast to cause excessive volatilization of elements such as Te, because the temperature has not yet reached a level where Te can significantly volatilize.

[0034] The second melting stage involves heating from the pre-melting temperature in the first stage to a high-temperature homogenization stage of 750-850°C. At this point, all solid components must be completely melted and fully reacted. A slow heating rate of 3-6°C / min allows the reactants ample time to react during the heating process, avoiding overly rapid heating that could lead to excessively violent reactions, resulting in a smoother and more complete reaction. This promotes uniform mixing of the elements and the progression of chemical reactions, ensuring the formation of a uniform liquid melt. During this stage, the vapor pressure of Te increases significantly with increasing temperature, increasing the risk of volatilization. A slower heating rate ensures a relatively controlled volatilization of Te, allowing the volatilized Te to be captured by H2 to form H2Te gas, which is then redeposited into the melt through gas phase circulation, achieving dynamic elemental compensation and ensuring that the final ingot's chemical composition is consistent with the target formulation. Furthermore, a slower heating rate promotes the orderly formation of the crystal structure. During the heating process, atoms have ample time to rearrange and recombine, reducing the generation of crystal defects and laying a good foundation for subsequent melt-zone growth of high-quality single crystals.

[0035] During the cooling process of the third melting stage, the temperature is lower than that of the second stage, the convection intensity of the melt decreases, and the microscopic homogenization process dominated by molecular diffusion becomes more important. A slower cooling rate of 1-3°C / min provides sufficient time for solute atoms to fully diffuse in the liquid, reducing dendritic segregation or composition gradients, and making the material's microscopic composition more uniform. A lower cooling rate can gradually increase the melt viscosity and slow the rate of bubble rise. The vortex generated by the rocking process facilitates the rupture and discharge of bubbles, while allowing time for unmelted particles to dissolve, thereby increasing the density of the melt and avoiding the formation of defects such as pores. During the cooling process, crystals gradually form and grow. A slower cooling rate can achieve more orderly crystal growth, reduce stress and defects in the crystals, and improve the quality and performance of the crystal ingot.

[0036] In a preferred embodiment of the present invention, the rocking speed is 12-18 rpm, and the rocking time is 10-30 min.

[0037] In the present invention, during the rocking process, the melt forms a periodic rotating flow in the container, generating a vortex.

[0038] When the swing rate is less than 12 rpm, the eddy current intensity is insufficient to effectively break the surface tension and viscous resistance of the melt, resulting in H2Te gas retention on the melt surface and slow penetration into the interior, making it difficult to achieve uniform gas phase diffusion compensation, which may cause local Te enrichment or depletion. When the swing rate is greater than 18 rpm, excessive turbulence will form, causing melt splashing or violent disturbance, destroying the stability of the molten material, and may even introduce bubbles or impurities, while increasing the mechanical load of the equipment and detrimental to process stability. A rate of 12-18 rpm can form moderate eddy currents, ensuring rapid penetration and diffusion of H2Te gas in the melt while avoiding system instability caused by excessive disturbance.

[0039] In the present invention, the vortex generated by the swing can promote mass transfer within the melt, promoting the uniform distribution of excess Te to various areas of the melt through gas phase circulation, and avoiding Te agglomeration or local enrichment agglomeration caused by static melting in traditional processes. Within the rotation speed range of 12 to 18 rpm, the melt components are ensured to be fully mixed before cooling, reducing segregation caused by density differences or uneven solidification rates, thereby reducing pores, increasing the density of the material, improving the uniformity of crystal growth, and ultimately improving thermoelectric performance.

[0040] The rate of 12~18rpm matches the environmental parameters of the Ar and H2 mixed gas, forming a dual homogenization effect of vortex stirring and gas phase diffusion, ensuring efficient and uniform redistribution of the Te element in the melt.

[0041] In a preferred embodiment of the present invention, cooling comprises firstly cooling the temperature to 450-550°C at a rate of 3-6°C / min and keeping the temperature for 1-2 hours; and then naturally cooling the molten material to 20-30°C.

[0042] In the present invention, a cooling rate of 3-6°C / min is considered a moderate cooling rate. At this cooling rate, non-uniform nucleation caused by rapid cooling is avoided. A cooling rate greater than 6°C / min causes the melt to quickly cross the solidus, forming a large number of small, randomly oriented nuclei. This leads to uneven grain size and increased grain boundary defects, affecting electrical conductivity. The solubility of Te in the melt decreases with decreasing temperature. Slow cooling allows the excess Te compensated by gas phase circulation to precipitate or redissolve uniformly, avoiding localized Te-rich phase agglomeration or pore formation.

[0043] The temperature range of 450~550℃ is close to the eutectic temperature or solid-liquid coexistence zone of the material. During the holding process, the liquid phase can continue to dissolve Te atoms or other alloying elements that have not been fully diffused, reducing dendrite segregation and ensuring the uniformity of solid composition. Thermal stress may exist in the melt during melting and shaking. During holding, the stress is relaxed by atomic diffusion, avoiding cracking of the crystal rod due to stress concentration after cooling to room temperature.

[0044] Zone melting requires the material to have a certain initial density and a solid substrate with few defects. The uniform primary crystal structure formed during the first stage of cooling can provide a stable "starting point" for zone melting, reducing melting zone fluctuations or crystal growth interruptions caused by local compositional inhomogeneities during the zone melting process.

[0045] The core function of natural cooling is to allow slow grain growth. Bismuth telluride-based materials have a layered structure. Slow cooling can make the crystal grow preferentially along the c-axis, forming a complete layered lattice and reducing grain boundary scattering. Rapid cooling will lead to atomic coordination imbalance, forming defects such as vacancies and interstitial atoms, while natural cooling gives atoms sufficient time to migrate to equilibrium positions, reducing defect concentration and optimizing electrical properties.

[0046] In a preferred embodiment of the present invention, the melting zone temperature gradient of the zone melting is 55-65° C. / cm, the melting zone moving speed is 2.5-3.5 cm / h, and the crystal rotation rate is 4-6 rpm.

[0047] In this invention, directional solidification of bismuth telluride-based materials relies on a temperature gradient at the solid-liquid interface. A gradient of 55-65°C / cm ensures sufficient solute expulsion from the melt into the liquid phase, improving crystal purity. It also provides sufficient driving force for the growth of layered structures along the c-axis, suppressing lateral grain competition and forming highly oriented columnar crystals. This avoids component overcooling caused by an insufficient gradient or thermal stress concentration at the solid-liquid interface caused by an excessive gradient. This gradient ensures that the heat transfer efficiency during solid-liquid interface movement matches the crystal growth rate, maintaining a stable interface morphology. The diffusion coefficients of atoms such as Te and Bi in bismuth telluride melts are low. A velocity of 2.5-3.5 cm / h ensures sufficient time for solutes in the melt to distribute evenly, reducing axial segregation. Slow motion allows sufficient time for atoms at the crystal growth interface to achieve regular alignment, suppressing the formation of crystal defects such as vacancies and dislocations, and particularly preventing interlaminar dislocations caused by rapid solidification. This velocity matches the material's minimum defect-free growth rate, ensuring the high carrier mobility required for thermoelectric performance. The crystal rotation rate is 4~6 rpm to optimize the melt homogeneity and crystal symmetry.

[0048] In a preferred embodiment of the present invention, the post-treatment includes annealing in an Ar atmosphere at 500°C for 24 hours, cutting the slices into 3×3×10 cm along the growth direction, and then performing the post-treatment. 3 Square bars; hot pressed at 450°C, 50 MPa for 1 hour.

[0049] According to a second aspect of the present invention, a high-performance semiconductor thermoelectric crystal rod prepared by the preparation method described above is provided.

[0050] A third object of the present invention is to provide an application of the thermoelectric crystal rod as described above in a thermoelectric power generation component, a micro refrigeration component or a temperature sensing component.

[0051] Example 1 First, the Bi raw material, the Sb raw material, the Te raw material and the Se raw material are prepared according to the molar ratio of the Bi raw material, the Sb raw material, the Te raw material and the Se raw material of 1.8:0.2:2.7:0.3, and then Te accounting for 10% of the total mass of Te in the set ratio is additionally added to obtain a reaction material; The reaction material was placed in an Ar and H2 mixed gas environment with a volume ratio of Ar to H2 of 5:1 and a pressure of 0.05 MPa. The first stage of melting was carried out: the reaction material was heated to 600°C at a rate of 10°C / min and kept at this temperature for 30 minutes to obtain the first stage of molten material. The second stage of melting was then carried out: the first stage of molten material was heated to 800°C at a rate of 5°C / min and kept at this temperature for 1 hour to obtain the second stage of molten material. Finally, the third stage of melting was carried out: the reaction material was cooled to 750°C at a rate of 2°C / min and kept at this temperature for 2 hours to obtain the molten material. The molten material was shaken at a speed of 15 rpm for 20 minutes, then cooled to 500 °C at a speed of 4 °C / min, kept at this temperature for 1.5 hours, and then naturally cooled to 25 °C. Then, a zone melting treatment was performed with a melting zone temperature gradient of 60 °C / cm, a melting zone movement speed of 3 cm / h, and a crystal rotation rate of 5 rpm. Finally, the material was annealed in an Ar atmosphere at 500 °C for 24 hours and cut into 3 × 3 × 10 cm sections along the growth direction. 3 square rod; high-performance semiconductor thermoelectric crystal rod was obtained by hot pressing at 450°C and 50 MPa for 1 hour.

[0052] Example 2 In this embodiment, Te accounting for 12% of the total mass of Te in the set proportion is additionally added in an Ar and H2 mixed gas environment with a volume ratio of Ar to H2 of 4:1. Other steps and parameters are consistent with those in Example 1.

[0053] Example 3 In this embodiment, Te accounting for 15% of the total mass of Te in the set proportion is additionally added, and the volume ratio of Ar and H2 is 3:1 in an Ar and H2 mixed gas environment. Other steps and parameters are consistent with those in Example 1.

[0054] Example 4 In this embodiment, the pressure of the Ar and H2 mixed gas is 0.1 MPa, and the other steps and parameters are consistent with those in Example 2.

[0055] Example 5 In this embodiment, the pressure of the Ar and H2 mixed gas is 0.15 MPa, and the other steps and parameters are consistent with those in Example 2.

[0056] Example 6 In this embodiment, the first melting stage is as follows: the reaction material is heated to 600°C at a rate of 8°C / min and held at this temperature for 30 minutes to obtain a first molten material. The second melting stage is as follows: the first molten material is heated to 800°C at a rate of 3°C / min and held at this temperature for 1 hour to obtain a second molten material. Finally, the third melting stage is as follows: the reaction material is cooled to 750°C at a rate of 1°C / min and held at this temperature for 2 hours to obtain a molten material. Other steps and parameters are the same as those in Example 4.

[0057] Example 7 In this embodiment, the first melting stage is as follows: the reaction material is heated to 600°C at a rate of 12°C / min and held at this temperature for 30 minutes to obtain a first molten material. The second melting stage is as follows: the first molten material is heated to 800°C at a rate of 6°C / min and held at this temperature for 1 hour to obtain a second molten material. Finally, the third melting stage is as follows: the reaction material is cooled to 750°C at a rate of 3°C / min and held at this temperature for 2 hours to obtain a molten material. Other steps and parameters are the same as those in Example 4.

[0058] Example 8 In this embodiment, the first stage of smelting is heated to 550°C, the second stage of smelting is heated to 750°C, and the third stage of smelting is cooled to 700°C. Other steps and parameters are the same as those in Example 4.

[0059] Example 9 In this embodiment, the first stage of smelting is heated to 650°C, the second stage of smelting is heated to 850°C, and the third stage of smelting is cooled to 800°C. Other steps and parameters are the same as those in Example 4.

[0060] Example 10 In this embodiment, the first stage of melting and holding is 25 minutes, the second stage of melting and holding is 0.8 hours, and the third stage of melting and holding is 1.5 hours. Other steps and parameters are the same as those in Example 4.

[0061] Example 11 In this embodiment, the first stage of melting and holding is 35 minutes, the second stage of melting and holding is 1.2 hours, and the third stage of melting and holding is 2.5 hours. Other steps and parameters are the same as those in Example 4.

[0062] Example 12 In this embodiment, the rocking speed is 12 rpm, and the other steps and parameters are consistent with those in Example 4.

[0063] Example 13 In this embodiment, the rocking speed is 18 rpm, and the other steps and parameters are consistent with those in Example 4.

[0064] Example 14 In this embodiment, the temperature is first lowered to 500° C. at a rate of 3° C. / min, kept at this temperature for 1.5 h, and then naturally cooled to 25° C. The other steps and parameters are the same as those in Example 4.

[0065] Example 15 In this embodiment, the temperature is first lowered to 500° C. at a rate of 6° C. / min, kept at this temperature for 1.5 h, and then naturally cooled to 25° C. The other steps and parameters are the same as those in Example 4.

[0066] Comparative Example 1 In this comparative example, Te accounting for 6% of the total mass of Te in the set ratio is additionally added, and the reaction material is placed in a vacuum environment for melting. Other steps and parameters are consistent with those in Example 1.

[0067] Comparative Example 2 In this comparative example, Te was additionally added in an amount of 6% by mass of the total Te in the set ratio, and other steps and parameters were consistent with those in Example 1.

[0068] Comparative Example 3 In this comparative example, Te accounting for 20% of the total mass of Te in the set proportion was additionally added, and other steps and parameters were consistent with those in Example 1.

[0069] Comparative Example 4 The volume ratio of Ar to H2 was 7:1, and the other steps and parameters were the same as those in Example 1.

[0070] Performance Testing Test method: Te composition deviation is tested according to GB / T 23607-2009 standard method; Density is tested using the GB / T 30455-2013 standard method; Thermoelectric figure of merit (ZT value): The ZT value calculation formula is ZT = α 2 σT / κ, where α represents the Seebeck coefficient of the material, σ represents the electrical conductivity, κ represents the total thermal conductivity of the material, and T represents the absolute temperature; total thermal conductivity κ = DCpρ, where D represents the thermal diffusivity, Cp represents the specific heat capacity, and ρ represents the density; the thermal diffusivity D is obtained by laser thermal conductivity measurement; the specific heat capacity Cp is calculated by the Dulong-Petit equation; and the density ρ is measured by the Archimedean displacement method.

[0071] The performance test results are shown in Table 1 and Table 2: Table 1 Performance test results of the embodiment

[0072] Table 2 Comparative Example Performance Test Results

[0073] In the examples, the mass of additional Te added is in the range of 10%-15%, and the smelting process is carried out under Ar / H2 protection, which effectively suppresses the volatilization of Te and controls the composition deviation within 0.1%-0.3%. The density reaches 97.5%-97.8%. The composition uniformity and dense structure optimize the carrier concentration and thermal conductivity, and the ZT value is between 0.85-1.2. Among them, Examples 2, 4, and 15 have higher ZT values ​​due to better parameter matching.

[0074] In comparative example 1, in vacuum melting, due to the lack of H2 reduction protection, Te oxidation loss leads to a significant increase in deviation; in comparative example 2, Te.

[0075] Insufficient Te addition and excess Te in Comparative Example 3 resulted in a compositional imbalance. Comparative Example 4 exhibited an unbalanced gas ratio due to insufficient H₂ and poor Te volatilization control, resulting in a slight deviation from the specified range. In Comparative Examples 1-4, improper melting conditions or compositional control led to increased porosity, impurities, and precipitated phases, resulting in a density below 97.5%. Comparative Example 1 achieved the lowest density due to the vacuum environment's tendency to introduce oxidative impurities. Compositional deviations, structural defects, or oxidative impurities reduced carrier mobility and thermal conductivity in the comparative examples, resulting in ZT values ​​below 0.85. Comparative Example 1 had the lowest density due to severe lattice defects caused by oxidation.

[0076] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a high-performance semiconductor thermoelectric crystal rod, characterized in that: The following steps are involved: The Bi raw material, the Sb raw material, the Te raw material and the Se raw material are mixed according to a set ratio, and Te is additionally added in an amount of 10-15% of the total mass of Te in the set ratio to obtain a reaction material; The reaction material is placed in an Ar and H2 mixed gas environment and smelted to obtain a molten material body; wherein the volume ratio of Ar to H2 is 3~5:1; The molten material is swung, cooled, zone-melted and post-processed to obtain a high-performance semiconductor thermoelectric crystal rod.

2. The preparation method according to claim 1, wherein The pressure of the Ar and H2 mixed gas is 0.05~0.15MPa.

3. The preparation method according to claim 1, wherein The set ratio includes: the molar ratio of Bi raw material, Sb raw material, Te raw material and Se raw material is 2-y:y:3-x:x, 0≤x≤1, 0≤y≤2.

4. The preparation method according to claim 1, wherein The step of placing the reaction material in an Ar and H2 mixed gas environment and smelting the reaction material to obtain a molten material body comprises: First stage smelting: keep the reaction material at 550~650℃ for 25-35min to obtain the first stage molten material; Second stage smelting: keep the first stage molten material at 750-850℃ for 0.8-1.2h to obtain the second stage molten material; The third smelting stage: keep warm at 700~800℃ for 1.5~2.5h to obtain molten material.

5. The preparation method according to claim 4, wherein The heating rate of the first melting stage is 8-12°C / min, the heating rate of the second melting stage is 3-6°C / min, and the cooling rate of the third melting stage is 1-3°C / min.

6. The preparation method according to claim 1, wherein The rocking speed is 12-18 rpm.

7. The preparation method according to claim 1, wherein The cooling comprises firstly cooling the temperature to 450-550° C. at a rate of 3-6° C. / min, keeping the temperature for 1-2 hours, and then naturally cooling the temperature to 20-30° C.

8. The preparation method according to claim 1, wherein The melting zone temperature gradient of the zone melting is 55-65° C. / cm, the melting zone moving speed is 2.5-3.5 cm / h, and the crystal rotation rate is 4-6 rpm.

9. A high-performance semiconductor thermoelectric crystal rod produced by the production method according to any one of claims 1 to 8.

10. Use of the thermoelectric crystal rod according to claim 9 in a thermoelectric power generation component, a micro refrigeration component or a temperature sensor component.

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