Half-Heusler thermoelectric material, preparation method and application thereof
By using a step-by-step powdering process involving high-melting-point and low-melting-point metals and vacuum heat treatment, combined with discharge plasma sintering, the problems of compositional imbalance and impurity phase formation in Half-Heusler thermoelectric materials were solved, achieving the preparation of a high-purity single-phase structure and improving the thermoelectric properties and density of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-26
- Publication Date
- 2026-03-17
AI Technical Summary
In existing methods for preparing Half-Heusler thermoelectric materials, the volatilization of low-melting-point metals during the smelting process leads to an imbalance in the composition ratio and the formation of impurity phases. Furthermore, the loss of low-melting-point metals is severe, making it difficult to prepare materials with high-purity single-phase structures.
High-melting-point metals are first melted and then powdered separately with low-melting-point metals. After being mixed evenly by ball milling, they are subjected to vacuum heat treatment and annealing, combined with discharge plasma sintering. This process avoids uneven diffusion and loss of metal elements, achieves grain refinement, and optimizes the thermoelectric properties of the material.
High-purity, single-phase Half-Heusler thermoelectric materials were prepared, which improved the thermoelectric properties and density of the materials and avoided the loss of low-melting-point metals and the problem of imbalance in composition ratio.
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Figure CN117265309B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of alloy materials technology, and in particular to a Half-Heusler thermoelectric material, its preparation method, and its application. Background Technology
[0002] In recent years, energy and environmental issues have become increasingly prominent, and the development of diverse energy structures and upgraded energy technologies is urgently needed. Currently, energy utilization efficiency remains low, with most consumed energy being emitted into the atmosphere as industrial waste heat. To effectively improve energy efficiency and reduce carbon emissions, industrial waste heat can be reused, primarily involving thermoelectric conversion technology. This technology relies on thermoelectric materials and achieves the conversion of heat energy into electrical energy through internal charge carrier transport, mainly including the Seebeck effect, Peltier effect, and Thomson effect.
[0003] In thermoelectric material systems, Half-Heusler thermoelectric materials possess characteristics such as high ZT values, high mechanical properties, low cost, and environmental friendliness, thus attracting widespread attention and research from the academic community. Due to the significant differences in melting points among elements in Half-Heusler alloys, alloy preparation often employs compensation methods using low-melting-point elements, such as N-type Zr. 0.5 Hf 0.5 NiSn, P-type Nb 0.86 Hf 0.14 FeSb, etc.
[0004] Among common preparation methods, p-type Nb 0.8 TiFe 1.02 Taking Sb thermoelectric materials as an example, Nb, Ti, Fe, and Sb are first weighed in a certain proportion and then subjected to suspension melting. After melting 3-5 times, annealing is performed, and finally, the materials are crushed into powder and sintered using SPS. In the above preparation method, because the low-melting-point metal Sb volatilizes during the melting process, an additional amount of Sb needs to be added, resulting in excessive consumption of the low-melting-point metal. Moreover, the prepared thermoelectric materials have problems such as impurity phases and imbalanced composition ratios. Therefore, there is an urgent need to develop a method for preparing single-phase Half-Heusler thermoelectric materials. Summary of the Invention
[0005] To address the aforementioned technical problems, this disclosure provides a Half-Heusler thermoelectric material, its preparation method, and its applications. The preparation method provided by this disclosure first involves melting a high-melting-point metal, then separately pulverizing it with a low-melting-point metal and mixing them under vacuum heat treatment. This ensures thorough and uniform mixing of the metal elements while maintaining a constant proportion, avoiding the problems of uneven and slow diffusion of metal elements during a single melting process. Furthermore, it avoids the loss of low-melting-point metals or alloys. Combined with cooling and annealing treatments, grain refinement is achieved, optimizing the thermoelectric properties of the material and yielding a high-purity Half-Heusler thermoelectric material with a single-phase structure.
[0006] In a first aspect, this disclosure provides a method for preparing a Half-Heusler thermoelectric material, the method comprising the following steps:
[0007] (1) Melt high-melting-point metals to obtain high-melting-point alloys;
[0008] (2) Mixing high-melting-point alloy powder and low-melting-point metal powder;
[0009] (3) The mixed powders are subjected to vacuum heat treatment and annealing to obtain pretreated materials;
[0010] (4) The pretreated material is subjected to discharge plasma sintering to obtain the Half-Heusler thermoelectric material;
[0011] The high-melting-point metal has a melting point above 1500℃, and the low-melting-point metal has a melting point below 400℃. That is, a high-melting-point metal refers to a metal with a melting point higher than that of Fe, and a low-melting-point metal is a metal with a low evaporation temperature (below 400℃).
[0012] The preparation method provided in this disclosure enables uniform mixing of various metal element components and maintains a constant ratio, avoiding the problems of uneven and slow diffusion of metal elements during one-time melting, and does not cause loss of low-melting-point metals or alloys. It achieves grain refinement, optimizes the thermoelectric properties of the material, and prepares a high-purity Half-Heusler thermoelectric material with a single-phase structure. Specifically:
[0013] In the preparation method provided in this disclosure, a high-melting-point metal is first melted, and then powdered separately from a low-melting-point metal. The low-melting-point metal powder and the high-melting-point alloy powder are then mixed evenly. This disclosure ensures that the metal elements are evenly distributed and the element ratio is constant by mixing the powders. Then, vacuum heat treatment is performed, which can avoid the problem of component ratio imbalance and impurity phase formation caused by the volatilization of low-melting-point metals or alloys during one-time melting (arc melting, suspension melting, induction melting). Moreover, it does not cause the loss of low-melting-point metals or alloys. Combined with annealing treatment, grain refinement is achieved, and the thermoelectric properties of the material are optimized. This allows the powder to have the characteristics of the Half-Heusler phase structure before the sintering step, and can improve the phase purity, thus preparing a Half-Heusler thermoelectric material with a single phase structure.
[0014] As a preferred technical solution of this disclosure, the mixing method in step (2) is ball milling, and the particle size after ball milling is preferably 300-500 mesh, such as 325 mesh, 350 mesh, 380 mesh, 400 mesh, 420 mesh, 440 mesh, 460 mesh, 480 mesh, etc.
[0015] This disclosure utilizes ball milling to thoroughly and uniformly mix high-melting-point alloys and low-melting-point metals, achieving preliminary alloying and increasing the surface energy of the powder. The powder is then passed through a 300-500 mesh sieve to obtain a mixed metal powder with uniform particle size.
[0016] As a preferred technical solution of this disclosure, the mixing in step (2) is carried out under a protective gas atmosphere, preferably argon.
[0017] As a preferred technical solution of this disclosure, step (2) further includes grinding the high melting point alloy and the low melting point metal into powders, and then mixing them by ball milling.
[0018] This disclosure involves separately pulverizing high-melting-point alloys and low-melting-point metals, and then using ball milling to mix them thoroughly and evenly. This avoids the problem of impurity phases formed due to the imbalance of thermoelectric material composition caused by the volatilization of low-melting-point metals during one-time melting (arc melting, suspension melting, induction melting).
[0019] This disclosure does not impose too many limitations on the method of powder preparation. As a specific embodiment of this disclosure, mechanical crushing can be used for powder preparation.
[0020] As a preferred embodiment of this disclosure, the particle size of the high melting point alloy powder and the low melting point metal powder are each independently selected from 300-500 mesh.
[0021] The high-melting-point alloy powder and the low-melting-point metal powder disclosed herein both have a particle size of 300-500 mesh, which ensures that the two are mixed more thoroughly and evenly.
[0022] As a preferred technical solution of this disclosure, the vacuum heat treatment temperature is 900-950℃, such as 910℃, 920℃, 930℃, 940℃, etc.
[0023] As a preferred technical solution of this disclosure, the vacuum heat treatment time is 16-18 hours, such as 16.5 hours, 17 hours, 17.5 hours, etc.
[0024] This disclosure involves vacuum heat treatment of uniformly mixed powders, with control of the treatment temperature and time within the scope of this disclosure. This allows for easier and more uniform diffusion of metal elements between the powders, enabling atomic diffusion between high-melting-point alloy powders and low-melting-point metal powders to form a single-phase structure. This results in a powder with a single Half-Heusler phase structure and high phase purity, avoiding the problems of uneven and slow diffusion of metal elements during one-time melting.
[0025] As a preferred technical solution of this disclosure, the annealing temperature is 800-850℃, such as 810℃, 820℃, 830℃, 840℃, etc.
[0026] As a preferred technical solution of this disclosure, the annealing process takes 3-5 days.
[0027] This disclosure, by controlling the annealing temperature and annealing time within the scope of this disclosure, can avoid the formation of impurity phases caused by insufficient diffusion of metal elements, and achieve a single Half-Heusler phase structure in the mixed powder before sintering, thereby improving phase purity.
[0028] As a preferred technical solution of this disclosure, in step (3), after completing the vacuum heat treatment, the temperature is cooled down to the annealing temperature in the treatment environment for annealing treatment.
[0029] The cooling and temperature reduction in the processing environment described in this disclosure refers to stopping heating after vacuum heat treatment is completed, without removing the mixed powder, and cooling it directly in the furnace environment where the heat treatment was performed.
[0030] The present invention discloses a method that, after vacuum heat treatment of mixed metal powders, followed by furnace cooling, can achieve grain refinement and optimize the thermoelectric properties of the material.
[0031] As a preferred technical solution of this disclosure, the pressure of the discharge plasma sintering is 28.2-28.7kN, such as 28.3kN, 28.4kN, 28.5kN, 28.6kN, etc.
[0032] As a preferred technical solution of this disclosure, the temperature of the discharge plasma sintering is 880-930℃, such as 890℃, 900℃, 910℃, 920℃, etc.
[0033] As a preferred technical solution of this disclosure, step (4) further includes pre-pressing at 600-700 Pa before sintering, wherein 600-700 Pa can be 620 Pa, 640 Pa, 660 Pa, 680 Pa, etc.
[0034] As a preferred embodiment of this disclosure, the preparation method includes the following steps:
[0035] (1) Under an argon atmosphere, high-melting-point metals are subjected to electric arc melting 3-5 times to obtain high-melting-point alloys;
[0036] (2) The high melting point alloy and the low melting point metal are respectively powdered and passed through a 300-500 mesh sieve. Then the powder is ball-milled at 160-200 r / min for 2-4 h and passed through a 300-500 mesh sieve.
[0037] (3) The sieved mixed powder is subjected to vacuum heat treatment at 900-950℃ for 16-18h, cooled to 800-850℃ in the treatment environment and annealed for 3-5 days, and then passed through a 300-500 mesh sieve to obtain the pretreated material.
[0038] (4) The pretreated material is pre-pressed at 600-700 Pa and then subjected to discharge plasma sintering at 28.2-28.7 kN and 880-930 °C to obtain the Half-Heusler thermoelectric material.
[0039] As a preferred technical solution of this disclosure, the time for arc melting in step (1) is 4-5 min, such as 4.2 min, 4.3 min, 4.5 min, 4.8 min, etc.
[0040] This disclosure first prepares high-melting-point alloys and low-melting-point metals into powders, then mixes and alloys the two powders by ball milling, followed by vacuum heat treatment and annealing. This facilitates uniform and rapid diffusion of metal elements, thereby achieving the construction of a high-purity, single-phase Half-Heusler structure. Furthermore, the furnace cooling method after vacuum heat treatment of the mixed powders is beneficial for grain refinement and optimization of the thermoelectric properties of the material.
[0041] Secondly, this disclosure provides a Half-Heusler thermoelectric material prepared by the preparation method described in the first aspect.
[0042] The Half-Heusler thermoelectric material disclosed herein does not produce any impurity phases, the powder has a single-phase structure, and high purity.
[0043] As a preferred embodiment of this disclosure, the Half-Heusler thermoelectric material is selected from P-type Half-Heusler thermoelectric materials, preferably Nb. 0.86 Hf 0.14 FeSb.
[0044] Thirdly, this disclosure provides the application of the Half-Heusler thermoelectric material described in the second aspect in space probes and industrial waste heat utilization.
[0045] The technical solution provided in this disclosure has the following advantages compared with the prior art:
[0046] (1) The preparation method provided in this disclosure first melts the high melting point metal, then mixes it with the low melting point metal after powdering, and then performs vacuum heat treatment. This can ensure that the metal element components are fully and evenly mixed and the proportion remains constant, avoiding the problem of uneven and slow diffusion of metal elements during one-time melting, and will not cause the loss of low melting point metal or alloy.
[0047] (2) The present invention discloses a mixed metal powder that is vacuum heat treated and then cooled in the furnace, which can achieve grain refinement and optimize the thermoelectric properties of the material.
[0048] (3) The preparation method provided in this disclosure can obtain high-purity single-phase Half-Heusler thermoelectric materials, effectively improving phase purity. Attached Figure Description
[0049] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.
[0050] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0051] Figure 1 Nb obtained in Embodiment 1 of this disclosure 0.86 Hf 0.14 XRD pattern of FeSb thermoelectric material;
[0052] Figure 2 Here is a SEM image of the thermoelectric material obtained in Embodiment 1 of this disclosure;
[0053] Figure 3 Here is a SEM image of the thermoelectric material obtained in Comparative Example 1 of this disclosure;
[0054] Figure 4 ZT performance diagrams of the thermoelectric materials obtained in Embodiment 1 and Comparative Example 1 of this disclosure;
[0055] Figure 5 ZT performance diagrams of the thermoelectric materials obtained in Examples 1, 4 and 5 of this disclosure;
[0056] Figure 6 The resistivity of the thermoelectric materials obtained in Embodiments 1, 4 and 5 of this disclosure varies with temperature.
[0057] Figure 7 The graphs show the thermal conductivity of the thermoelectric materials obtained in Examples 1, 4, and 5 of this disclosure as a function of temperature.
[0058] Figure 8 The graph shows the Seebeck coefficient of the thermoelectric materials obtained in Examples 1, 4 and 5 of this disclosure as a function of temperature.
[0059] Figure 9 SEM image of the thermoelectric material obtained in Example 1 Figure 1 ;
[0060] Figure 10 SEM image of the thermoelectric material obtained in Example 1 Figure 2 ;
[0061] Figure 11 SEM image of the thermoelectric material obtained in Example 1 Figure 3 ;
[0062] Figure 12 SEM image of the thermoelectric material obtained in Example 4 Figure 1 ;
[0063] Figure 13 SEM image of the thermoelectric material obtained in Example 4 Figure 2 ;
[0064] Figure 14 SEM image of the thermoelectric material obtained in Example 4 Figure 3 ;
[0065] Figure 15 SEM image of the thermoelectric material obtained in Example 5 Figure 1 ;
[0066] Figure 16 SEM image of the thermoelectric material obtained in Example 5 Figure 2 ;
[0067] Figure 17SEM image of the thermoelectric material obtained in Example 5 Figure 3 . Detailed Implementation
[0068] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.
[0069] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.
[0070] Example 1
[0071] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method includes the following steps:
[0072] (1) Weigh each metal according to the mass ratio of Nb, Hf, Fe and Sb of 0.86:0.14:1:1;
[0073] (2) Under an argon atmosphere, Nb, Hf and Fe were subjected to arc melting 4 times under electromagnetic stirring, each time for 5 minutes, to obtain a high melting point alloy (Nb, Hf, Fe);
[0074] (3) The high melting point alloy and Sb were respectively crushed into powder by mechanical crushing and passed through a 400-mesh sieve. Then, in a glove box, the obtained high melting point alloy (Nb, Hf, Fe) powder and Sb powder were placed in a planetary ball mill and ball milled at 180 r / min for 3 h. The ball-milled powder was passed through a 400-mesh sieve to obtain a mixed powder with uniform particle size.
[0075] (4) Place the mixed powder in a graphite tube, vacuum seal it in a quartz tube, place it in a muffle furnace for vacuum heat treatment at 930°C for 17 hours. After completion, stop heating and cool it with the furnace. Then perform annealing treatment at 820°C for 3 days. After annealing, pass the powder through a 400-mesh sieve to obtain a pretreated material with uniform particle size.
[0076] (5) After weighing the pretreated material, place it in a graphite mold and pre-press it with a force of 650Pa. Then, perform discharge plasma sintering with a process pressure of 28.5KN and a sintering temperature of 930℃.
[0077] Example 2
[0078] This embodiment provides an Nb 0.86Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method includes the following steps:
[0079] (1) Weigh each metal according to the mass ratio of Nb, Hf, Fe and Sb of 0.86:0.14:1:1;
[0080] (2) Under an argon atmosphere, Nb, Hf and Fe were subjected to arc melting three times with electromagnetic stirring, each time for 4 minutes, to obtain a high melting point alloy (Nb, Hf, Fe);
[0081] (3) The high melting point alloy and Sb were respectively crushed into powder by mechanical crushing and passed through a 300-mesh sieve. Then, in a glove box, the obtained high melting point alloy (Nb, Hf, Fe) powder and Sb powder were placed in a planetary ball mill and ball milled at 160 r / min for 2 h. The ball-milled powder was passed through a 300-mesh sieve to obtain a mixed powder with uniform particle size.
[0082] (4) Place the mixed powder in a graphite tube, vacuum seal it in a quartz tube, place it in a muffle furnace for vacuum heat treatment at 900°C for 16 hours. After completion, stop heating and cool with the furnace. Then perform annealing at 800°C for 3 days. After annealing, pass the powder through a 300-mesh sieve to obtain a pretreated material with uniform particle size.
[0083] (5) After weighing the pretreated material, place it in a graphite mold and pre-press it with a force of 600Pa. Then, perform discharge plasma sintering with a process pressure of 28.2KN and a sintering temperature of 880℃.
[0084] Example 3
[0085] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method includes the following steps:
[0086] (1) Weigh each metal according to the mass ratio of Nb, Hf, Fe and Sb of 0.86:0.14:1:1;
[0087] (2) Under an argon atmosphere, Nb, Hf and Fe were subjected to electric arc melting 5 times under electromagnetic stirring, each time for 5 minutes, to obtain a high melting point alloy (Nb, Hf, Fe);
[0088] (3) The high melting point alloy and Sb were respectively crushed into powder by mechanical crushing and passed through a 500-mesh sieve. Then, in a glove box, the obtained high melting point alloy (Nb, Hf, Fe) powder and Sb powder were placed in a planetary ball mill and ball milled at 200 r / min for 4 h. The ball-milled powder was passed through a 500-mesh sieve to obtain a mixed powder with uniform particle size.
[0089] (4) Place the mixed powder in a graphite tube, vacuum seal it in a quartz tube, place it in a muffle furnace for vacuum heat treatment at 950°C for 18 hours. After completion, stop heating and cool it with the furnace. Then perform annealing treatment at 850°C for 3 days. After annealing, pass the powder through a 500-mesh sieve to obtain a pretreated material with uniform particle size.
[0090] (5) After weighing the pretreated material, place it in a graphite mold and pre-press it with a force of 700Pa. Then, perform discharge plasma sintering with a process pressure of 28.7KN and a sintering temperature of 900℃.
[0091] Examples 4-5
[0092] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0093] The difference between this embodiment and embodiment 1 is that the annealing time in step (4) is 4 days (embodiment 4) and 5 days (embodiment 5).
[0094] Example 6
[0095] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0096] The difference between this embodiment and Embodiment 1 is that the powder sieve mesh size in each step is replaced with 200 mesh.
[0097] Examples 7-8
[0098] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0099] The difference between this embodiment and Embodiment 1 is that the temperature of the vacuum heat treatment in step (4) is replaced with 800℃ (Embodiment 7) and 1100℃ (Embodiment 8), respectively.
[0100] Examples 9-10
[0101] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0102] The difference between this embodiment and Embodiment 1 is that the annealing temperature in step (4) is replaced with 700℃ (Embodiment 9) and 900℃ (Embodiment 10), respectively.
[0103] Examples 11-12
[0104] This embodiment provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0105] The difference between this embodiment and Embodiment 1 is that the annealing time in step (4) is replaced with 2 days (Embodiment 11) and 6 days (Embodiment 12), respectively.
[0106] Comparative Example 1
[0107] This comparative example provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method is the same as in Example 1;
[0108] The difference between this comparative example and Example 1 is that the furnace cooling in step (4) is replaced by taking out the powder after vacuum heat treatment and cooling it in the air (air cooling).
[0109] Comparative Example 2
[0110] This comparative example provides an Nb 0.86 Hf 0.14 FeSb thermoelectric material and its preparation method, wherein the preparation method includes the following steps:
[0111] (1) Weigh each metal according to the mass ratio of Nb, Hf, Fe and Sb of 0.86:0.14:1:1.05 and perform electric arc melting 3 times.
[0112] It was discovered that a large amount of dust formed by the volatilization of Sb was deposited on the inner wall of the chamber, making subsequent annealing and sintering processes impossible. This is because in NbFeSb series thermoelectric materials, Sb has a melting point of 630℃. If this element is added to the electric arc melting process, it will cause severe volatilization of Sb, thus making it impossible to form a P-type Half-Heusler material with a consistent elemental ratio and complete structure.
[0113] Performance Test 1
[0114] The Nb obtained in Example 1 0.86 Hf 0.14 XRD tests were performed on the FeSb thermoelectric material, and the results are as follows: Figure 1 As shown.
[0115] Depend on Figure 1It can be seen that the preparation method provided in this disclosure has prepared P-type HH material with high purity single-phase structure, effectively improving phase purity.
[0116] Performance Test 2
[0117] (1) SEM tests were performed on the thermoelectric materials obtained in Example 1 and Comparative Example 1, and the results are as follows: Figure 2 and Figure 3 As shown; Figure 2 The image shows the SEM image of the thermoelectric material obtained in Example 1. Figure 3 The image shows the SEM image of the thermoelectric material obtained in Comparative Example 1.
[0118] Depend on Figure 2 and Figure 3 It can be seen that, compared with air cooling, the microstructure of thermoelectric materials obtained by furnace cooling is more uniform and the porosity is relatively smaller.
[0119] (2) The density of the thermoelectric materials obtained in Examples 1-12 and Comparative Example 1 was tested using the water displacement method. The test results are shown in Table 1.
[0120] (3) The thermoelectric properties of the thermoelectric materials obtained in Examples 1-12 and Comparative Example 1 were tested, and the calculation formula is shown in Equation 1:
[0121] ZT=(σS 2 T) / k Formula 1
[0122] Where S: Seebeck coefficient, unit μV / K; σ: electrical conductivity of the material, inversely proportional to resistivity, unit S / m; k: thermal conductivity of the material, unit W / mK. The test results are shown in Table 1.
[0123] The ZT properties of the thermoelectric materials obtained in Example 1 and Comparative Example 1 are as follows: Figure 4 As shown, the ZT properties of the thermoelectric materials obtained in Examples 1, 4, and 5 are as follows: Figure 5 As shown in the figure, the resistivity of the thermoelectric materials obtained in Examples 1, 4, and 5 changes with temperature. Figure 6 As shown in the figure, the thermal conductivity of the thermoelectric materials obtained in Examples 1, 4, and 5 varies with temperature. Figure 7 As shown in the figure, the Seebeck coefficient of the thermoelectric materials obtained in Examples 1, 4, and 5 varies with temperature. Figure 8 As shown.
[0124] The density and thermoelectric properties of the thermoelectric materials obtained in Examples 1-12 and Comparative Example 1 are shown in Table 1:
[0125] Table 1
[0126]
[0127]
[0128] Referring to the accompanying drawings and Table 1, it can be seen that the Half-Heusler thermoelectric material prepared in this application exhibits excellent thermoelectric properties and good density. From Examples 1, 4, and 5, it can be observed that with increasing annealing time, ZT... max and ZT ave All gradually decreased; a comparison between Example 1 and Examples 6-12 revealed that the sieve mesh size was too small (Example 6), ZT max Reduced; the vacuum heat treatment temperature is too low (Example 7) or too high (Example 8), ZT max and ZT ave Both decrease; annealing temperature too low (Example 9) or too high (Example 10), ZT max and ZT ave Both decrease; annealing time is too short (Example 11) or too long (Example 12), ZT max and ZT ave Both decrease. A comparison between Example 1 and Comparative Example 1 reveals that the ZT value of the thermoelectric material obtained by furnace cooling is higher than that of the thermoelectric material obtained by air cooling.
[0129] (4) The thermoelectric materials obtained in Examples 1, 4, and 5 were subjected to SEM testing, and the results are as follows: Figure 9-17 As shown, where,
[0130] Figure 9 SEM image of the thermoelectric material obtained in Example 1 Figure 1 , Figure 10 SEM image of the thermoelectric material obtained in Example 1 Figure 2 , Figure 11 SEM image of the thermoelectric material obtained in Example 1 Figure 3 ;
[0131] Figure 12 SEM image of the thermoelectric material obtained in Example 4 Figure 1 , Figure 13 SEM image of the thermoelectric material obtained in Example 4 Figure 2 , Figure 14 SEM image of the thermoelectric material obtained in Example 4 Figure 3 ;
[0132] Figure 15 SEM image of the thermoelectric material obtained in Example 5 Figure 1 , Figure 16 SEM image of the thermoelectric material obtained in Example 5 Figure 2 , Figure 17 SEM image of the thermoelectric material obtained in Example 5 Figure 3 ;
[0133] in, Figure 10 and Figure 11 , Figure 13 and Figure 14 , Figure 16 and Figure 17 These are SEM images of different locations on the thermoelectric material.
[0134] The preparation method disclosed herein yields ZT thermoelectric materials with increasing annealing time. max and ZT ave All gradually decrease, combined Figure 9-17 It can be seen that this is due to the appearance of macroscopic large pores inside the thermoelectric material, which reduces the density, increases the resistivity, decreases the thermal conductivity and reduces the Seebeck coefficient. The appearance of macroscopic large pores is due to the release of powder surface energy during long-term annealing, and the sintering of dense structures requires a high temperature.
[0135] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0136] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method of producing a Half-Heusler thermoelectric material, characterized by, The preparation method comprises the following steps: (1) melting a high melting point metal to obtain a high melting point alloy; (2) mixing high melting point alloy powder and low melting point metal powder; (3) vacuum heat treating the mixed powder, and after the vacuum heat treatment, cooling the mixed powder to an annealing temperature in the treatment environment to obtain a pretreated material; the annealing temperature is 800-850 DEG C, and the annealing time is 3-5 days; (4) pre-treating the material to perform discharge plasma sintering to obtain the Half-Heusler thermoelectric material; the Half-Heusler thermoelectric material is a P-type Half-Heusler thermoelectric material Nb 0.86 Hf 0.14 FeSb; wherein the melting point of the high melting point metal is higher than 1500 DEG C, and the melting point of the low melting point metal is lower than 400 DEG C.
2. The production method according to claim 1, characterized by, The mixing method in step (2) is ball milling, and the particle size after ball milling is 300-500 mesh.
3. The production method according to claim 2, characterized by, In step (2), the high melting point alloy and the low melting point metal are separately powdered and then ball milled; The particle size of the high melting point alloy powder and the low melting point metal powder is independently selected from 300-500 mesh.
4. The method of claim 1, wherein, The treatment temperature of the vacuum heat treatment is 900-950 DEG C, and the treatment time is 16-18 h.
5. The preparation method according to claim 1, characterized in that, The pressure of the spark plasma sintering is 28.2-28.7 kN; And / or, the temperature of the spark plasma sintering is 880-930 DEG C.
6. The method of claim 1, wherein, In step (4), before sintering, pre-pressing is performed at 600-700 Pa.
7. The production method according to any one of claims 1 to 6, characterized by, In step (1), the high melting point metal is arc melted 3-5 times in an argon atmosphere to obtain the high melting point alloy; In step (2), the high melting point alloy and the low melting point metal are separately powdered and then sieved through a 300-500 mesh sieve, and then the obtained powder is ball milled at 160-200 r / min for 2-4 h and sieved through a 300-500 mesh sieve; In step (3), the sieved mixed powder is vacuum heat treated at 900-950 DEG C for 16-18 h; In step (4), the pretreated material is spark plasma sintered to obtain the Half-Heusler thermoelectric material, which further comprises: pre-pressing the pretreated material at 600-700 Pa, and performing spark plasma sintering at 28.2-28.7 kN and 880-930 DEG C to obtain the Half-Heusler thermoelectric material.
8. The Half-Heusler thermoelectric material prepared by the preparation method of any one of claims 1-7, The Half-Heusler thermoelectric material is selected from a P-type Half-Heusler thermoelectric material, the P-type Half-Heusler thermoelectric material being Nb 0.86 Hf 0.14 FeSb.
9. The Half-Heusler thermoelectric material of claim 8 is used in space probes and industrial waste heat utilization.
Citation Information
Patent Citations
High-merit figure P-type FeNbHfSb thermoelectric material and preparation method thereof
CN104681706A